An optical element to be arranged in an optical pickup apparatus for conducting information recording and/or reproducing and to converge light fluxes with a plurality of wavelengths including a wavelength of Î» 1 and a wavelength of Î» 2 onto information recording media, comprises one or more optical main bodies; and an antireflective film which is arranged on a surface of the optical element main bodies and on which at least one optical functional surface is formed, wherein a reflectivity of an incident light flux perpendicular to the optical functional surface has a local maximum value of 1% or more between the wavelength Î» 1 and the wavelength Î» 2.

Description

43 parts

›BACKGROUND OF THE INVENTION

The present invention relates to an optical pick-up device by which recording and/or reproducing of the information is conducted, and to an optical element provided in the optical pick-up device.

Conventionally, as information recording media, there are CD using a light flux of wavelength of about 780 nm, DVD using a light flux of wavelength of 635-650 nm, and AOD (Advanced Optical Disc) using the light flux having wavelength of about 405 nm or blu-ray disc, and an optical pick-up device which can correspond also to any information recording medium such as AOD or blu-ray disc, DVD and/or CD is developed. On an optical functional surface of the optical element such as an objective lens provided in this optical pick-up device, a antireflective film to prevent the reflection of the light flux is provided.

Generally, the antireflective film has the reflection prevention function for each light flux of the wavelength of a broad band, and corresponding to the breadth of the wavelength region (hereinafter, it is denoted as the reflection prevention wavelength region) in which the reflection is to be prevented, or the magnitude of the refractive index of the optical element main body, the reflection factor for a target (hereinafter, it is denoted as a target reflection factor), it is structured by various layer numbers. Specifically, in the optical pick-up device which can correspond to AOD or blu-ray disc and DVD, for example, in the case where the reflection prevention wavelength region is 400-650 nm, the refractive index of the optical element main body is about 1.5-1.6, and the magnitude of the target reflection factor is not larger than 1%, the antireflective film of the optical element is generally structured by 5-7 layers. Further, in the optical pick-up device which can correspond to AOD or blu-ray disc, DVD and CD, when the reflection prevention wavelength region is 400-800 nm, the antireflective film is structured by 9 layers or more (for example, refer to Patent Document 1).

Hereupon, when the antireflective film number is increased, there is a problem that the production cost is increased, or water enters between layers and the spectral characteristic is changed. Further, particularly when the optical element main body is formed of optical plastic, there is problem that the environmental resistance is lowered such as a case where a crack is generated on the antireflective film by the stress of the antireflective film itself, or the adhesion between the antireflective film and optical element main body is lowered.

Therefore, in order to solve such a problem, there is a technology by which, by limiting the wavelength whose reflection factor is not larger than 1% to only two kinds of wavelengths, the antireflective film is structured by few layer numbers of 3-7 (for example, refer to Patent Document 2).

(Patent Document 1)

Tokkai 2000-111702

(Patent Document 2)

Tokkaihei 11-167003

However, the technology disclosed in the above Patent Document 2 is a technology by which the reflection of the light flux having wavelength 150-300 nm or the light flux having wavelength 400-800 nm is prevented, and is not a technology by which the reflection of the light flux of wavelength 390-430 nm or the light flux of wavelength of 630-800 nm is prevented.

The object of the present invention is to provide an optical element by which the reflection of the light flux of wavelength of 390-430 nm or the light flux of wavelength of 630-800 nm can be prevented using the antireflective film with fewer layer numbers than conventional devices, and an optical pick-up device provided with this optical element.

A structure written in item 1 is an optical element which is provided in an optical pick-up device which conducts the recording and/or reproducing of the information, and which light-converges light fluxes of a plurality of wavelengths including wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and wavelength λ 2 (630≦λ 2 ≦800 nm) on the information recording medium, and there are provided with one or more optical element main bodies, and the antireflective film which is provided on the surface of the optical element main body and on which at least one optical functional surface is formed, and the reflection factor of the light flux incident perpendicularly on the optical functional surface shows the local maximal value not smaller than 1% between the wavelength λ 1 and the wavelength λ 2 . Furthermore, it is preferable that the local maximal value is not smaller than 2%.

Herein, the plurality of wavelengths means the wavelengths of 2 kinds or more. Further, “between the wavelength λ 1 and the wavelength λ 2 ” means a range which is longer than the wavelength λ 1 , and shorter than the wavelength λ 2 .

According to the above-described structure, because the reflection factor of the light flux incident perpendicularly on the optical functional surface shows the local maximal value not smaller than 1% between the wavelength λ 1 and the wavelength λ 2 , the reflection factor is relatively low to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 , and is in the situation in which the reflection is prevented. Accordingly, by reducing the reflection prevention function between the wavelength λ 1 and the wavelength λ 2 , the layer numbers of the antireflective film can be reduced without losing the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 against the conventional antireflective film by which the reflection is prevented to the whole of light fluxes of the broad wavelength region of wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by entering of water between layers of the antireflective film can be suppressed.

Further, even when the optical element main body is made of plastic, a case where a crack is generated in the antireflective film by the stress of the antireflective film, or the adherence of the antireflective film and the optical element main body is lowered, can be prevented, that is, the environmental resistance can be improved.

›BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an outline structure of an optical pick-up device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing an objective lens according to an embodiment of the present invention.

FIG. 3 is a view showing an outline structure of another embodiment of the optical pick-up device according to an embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing another embodiment of the objective lens according to an embodiment of the present invention.

FIG. 5 is a view showing a spectral reflection factor curve on the optical functional surface formed of an antireflective film of Table 1.

FIG. 6 is a view showing a spectral reflection factor curve on the optical functional surface formed of an antireflective film of Table 2.

FIG. 7 is a view showing a spectral reflection factor curve on the optical functional surface formed of an antireflective film of Table 3.

FIG. 8 is a view showing a spectral reflection factor curve on the optical functional surface formed of an antireflective film of Table 4.

FIG. 9 is a view showing a spectral reflection factor curve on the optical functional surface formed of an antireflective film of Table 6.

FIG. 10 is a view showing a spectral reflection factor curve on the optical functional surface formed of a antireflective film of Table 7.

FIG. 11 is a view showing a spectral reflection factor curve on the optical functional surface formed of a antireflective film of Table 8.

FIG. 12 is a view showing a spectral reflection factor curve on the optical functional surface formed of a antireflective film of Table 11.

FIG. 13 is a view showing a spectral reflection factor curve on the optical functional surface formed of a antireflective film of Table 12.

FIG. 14 is a view showing a spectral reflection factor curve on the optical functional surface formed of a antireflective film of Table 13.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 1 of 22

A preferred embodiment of the present invention will be described below.

According to a structure written in item 2 , in the optical element written in item 1 , the plurality of wavelengths includes a wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and a wavelength λ 2 is 630 nm≦λ 2 ≦670 nm.

According to the structure written in item 2 , the reflection of the light flux of using wavelength λ 1 of AOD or blu-ray disc, the light flux of using wavelength λ 2 of DVD, and the light flux of using wavelength λ 3 can be prevented by the antireflective film of few layer numbers.

According to the structure written in item 3 , in the optical element written in item 1 or 2 , the maximum incidence and projection angle θmax of the light flux of wavelength λ 1 on the optical functional surface is 0°≦θmax≦40°.

According to the structure written in item 3 , by using the light flux of 0°≦θmax≦40°, the accurate recording or reproducing of the information can be conducted.

According to a structure written in item 4 , in the optical element written in any one of items 1 - 3 , the refractive index n 0 of the optical element main body is 1.45≦n 0 ≦1.65, and in a layer included in the antireflective film, in the first layer positioned on the most optical element main body side, the refractive index n 1 , is 1.7≦n 1 , ≦2.5, and the optical film thickness nd, is 225 nm≦nd 1 ≦275 nm, and in the second layer secondly positioned on the optical element main body side, the refractive index n 2 is 1.3≦n 2 ≦1.55, and the optical film thickness nd 2 is 100 nm≦nd 2 ≦150 nm.

Herein, the optical film thickness is a value expressed by the film thickness×refractive index (nm), and the film thickness means the thickness in the normal direction of the surface of the optical element main body.

According to the invention written in item 4 , because the first layer and the second layer can prevent the reflection of the light flux of each wavelength, without deteriorating the reflection prevention function, the number of layers of the antireflective film can be reduced.

According to the structure written in item 5 , in the optical element written in any one of items 1 - 3 , the refractive index n 0 of the optical element main body is 1.45≦n 0 ≦1.65, and in the layer included in the antireflective film, as to the first layer positioned on the most optical element main body side, the refractive index n 1 is 1.7≦n 1 ≦2.5, and the optical film thickness nd 1 is 125 nm≦nd 1 ≦175 nm, and as to the second layer positioned secondly on the optical element main body side, the refractive index n 2 is 1.55≦n 2 ≦1.7, and the optical film thickness nd 2 is 75 nm≦nd 2 ≦125 nm, and as to the third layer positioned thirdly on the optical element main body side, the refractive index n 3 is 1.3≦n 3 <1.55, and the optical film thickness nd 3 is 100 nm≦nd 3 ≦150 nm.

According to a structure written in item 5 , because the first layer, second layer, and third layer can prevent the reflection of the light flux of each wavelength, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function.

According to the structure written in item 6 , in the optical element written in any one of items 1 - 3 , the refractive index n 0 of the optical element main body is 1.45≦n 0 ≦1.65, and in the layer included in the antireflective film, as to the first layer positioned on the most optical element main body side, the refractive index n 1 is 1.7≦n 1 ≦2.5, and the optical film thickness nd 1 is 25 nm≦nd 1 ≦75 nm, as to the second layer positioned secondly on the optical element main body side, the refractive index n 2 is 1.3≦n 2 ≦1.55, and the optical film thickness nd 2 is 25 nm≦nd 2 ≦75 nm, as to the third layer positioned thirdly on the optical element main body side, the refractive index n 3 is 1.7≦n 3 ≦2.5, and the optical film thickness nd 3 is 225 nm≦nd 3 ≦275 nm, and as to the fourth layer positioned fourthly on the optical element main body side, the refractive index n 4 is 1.3≦n 4 <1.55, and the optical film thickness nd 4 is 135 nm≦nd 4 ≦185 nm.

According to the structure written in item 6 , because the reflection of the light flux of each wavelength can be prevented by the first layer, second layer, third layer, and fourth layer, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function.

A structure written in item 7 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and is an optical element by which the light flux of a plurality of wavelengths including wavelength λ 1 (390 nm≦λ 1 ≦430 nm), and the light flux of a plurality of wavelengths including wavelength λ 2 (630 nm≦λ 2 ≦λ670 nm), are light-converged onto the information recording medium, and it has one or more optical element main bodies, and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed in such a manner that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum film thickness in the effective diameter))/average film thickness, is not larger than 5%, and at least 2 optical functional surfaces in which the maximum incidence and projection angle θmax in the effective diameter is 0° θmax≦40°, are formed, and in these optical functional surfaces, in the case where the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm or λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is not larger than 1%, and in the case where the wavelength λ is a wavelength within the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

According to the structure written in item 7 , in the case where the wavelength λ of the light flux perpendicularly incident on the optical functional surface is λ 1 ≦λ≦λ 1 +15 nm, and in the case where λ 2 ≦λ≦λ 2 +15 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection for the wavelength in these zones can be prevented. Further, in the case where wavelength λ is a wavelength in the area λ 1 +15 nm≦λ≦λ 2 , because the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered, different from the conventional antireflective film which prevents the reflection for the whole light fluxes in the broad wavelength region of wavelength λ 1 -λ 2 , the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function for the light flux of the wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by the entering of water between layers of the antireflective film can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 2 of 22

Further, even when the optical element main body is made of optical plastic, a case where a crack is generated in antireflective film by the stress of the antireflective film, or the adherence of the antireflective film to the optical element main body is reduced, can be prevented, that is, the environmental resistance can be increased.

Hereupon, as a method by which the reflection film is formed in such a manner that a value of ((the maximum film thickness in the effective diameter to the light flux of wavelength λ 1 )−(the minimum film thickness in the effective diameter))/average film thickness is not larger than 5%, there is a method by which a rotation revolution tool is fitted to an evaporating machine by which the antireflective film is evaporated, or when the film is formed by a CVD (Chemical Vapor Deposition) method, a method by which the pressure of an atmosphere is adjusted to a little high condition. Further, in the case where the antireflective film is formed in this manner, when the optical film thickness of the antireflective film is larger than the using wavelength, an incident angle of the light flux can be changed and the spherical aberration is deteriorated. Therefore, it is preferable that the transmission wave-front of the optical element after the film is formed, is measured, a metallic mold to mold the optical element main body is corrected, and the design work of the optical element main body is conducted so that the spherical aberration of the antireflective film is previously cancelled.

According to the structure written in item 8 , in the optical element written in item 7 , the plurality of wavelengths include the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, on the optical functional surface, the reflection factor is not larger than 1%.

According to the structure written in item 8 , when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in this region.

The structure written in item 9 is the optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges the light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and is provided with one or more optical element main bodies and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed in such a manner that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum film thickness in the effective diameter))/average film thickness, is not larger than 5%, and at least 2 optical functional surfaces in which the maximum incidence projection angle θmax in the effective diameter is 40°<θmax<90°, are formed, and in these optical functional surfaces, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength within the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

According to the structure written in item 9 , when the wavelength λ of the light flux incident perpendicularly to the optical functional surface is λ 1 ≦λ≦λ 1 +50 nm and when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function to the light flux of the wavelength λ 1 and the light flux of the wavelength λ 2 against the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetrating of the water between layers of the antireflective film can be suppressed.

Further, even when the optical element main body is made of plastic, it can be prevented that a crack is generated in the antireflective film by the stress of the antireflective film, or the adherence between the antireflective film and the optical element main body is lowered, that is, the environmental resistance can be increased.

According to the structure written in item 10 , in the optical element written in item 9 , the plurality of wavelengths include the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%.

According to the structure written in item 10 , when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in this zone.

The structure written in item 11 is an optical element which is provided in the optical pick-up device which conducts the recording and/or reproducing of the information, and which light-converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and which is provided with an optical element more than 1, and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed in such a manner that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum film thickness in the effective diameter))/average film thickness is not larger than 5%, and at least one of the first optical functional surface in which the maximum incidence projection angle θmax in the effective diameter is 0°≦θmax≦40°, and the second optical functional surface in which the maximum incidence projection angle θmax in the effective diameter is 40°≦θmax≦90°), is formed, and in the first optical functional surface, the reflection factor is not larger than 1% when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, and when it is λ 2 ≦λ≦λ 2 +15 nm, and when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, the reflection factor is not larger than 1% when the wavelength λ is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, and when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 3 of 22

According to the structure written in item 11 , when the wavelength λ of the light flux incident perpendicularly to the first optical functional surface is λ 1 ≦λ≦λ 1 +15 nm, and λ 2 ≦λ≦λ 2 +15 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the second optical functional surface is λ 1 ≦λ≦λ 1 +50 nm, and λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor on the second optical functional surface is not larger than 1%, the reflection can be prevented to the wavelengths in these zones.

Further, in the first optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function for the light flux of wavelength λ 1 and the light flux of wavelength λ 2 against the conventional antireflective film to prevent the reflection to the whole light fluxes of the broad area of wavelengths λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetrating of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 12 , in the optical element written in item 11 , the plurality of wavelengths include the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the first optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is not larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%.

According to the structure written in item 12 , when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor on the second optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in these regions.

The structure written in item 13 is an optical element which is provided in the optical pick-up device which conducts the recording and/or reproducing of the information, and which light-converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and which is provided with an optical element main bodies more than 1, and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed in such a manner that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum film thickness in the effective diameter))/average film thickness is larger than 5%, and at least two optical functional surfaces in which the maximum incidence projection angle θmax in the effective diameter and the maximum surface angle θ⊥max in the effective diameter, are 0°≦θmax≦40°, and 0°≦θ⊥max≦40°, are formed, and in these optical functional surfaces, the reflection factor is not larger than 1% when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, and when it is λ 2 ≦λ≦λ 2 +15 nm, and when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

Herein, the surface angle is an angle formed between the normal line of the optical functional surface and the optical axis.

According to the structure written in item 13 , when the wavelength λ of the light flux incident perpendicularly to the optical functional surface is λ 1 ≦λ≦λ+15 nm, and when it is λ 2 ≦λ≦λ 2 +15 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented to the wavelength in these regions. Further, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 against the conventional antireflective film to prevent the reflection to the whole light fluxes in broad wavelength region of wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 14 , in the optical element written in item 13 , the plurality of wavelengths include wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is not larger than 1%.

According to the structure written in item 14 , when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in these regions.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 4 of 22

The structure written in item 15 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges the light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and it is provided with one or more optical element main bodies and a antireflective film provided on the optical element main body, and the antireflective film is formed so that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum thickness in the effective diameter))/average film thickness is larger than 5%, and the maximum incidence projection angle θmax in the effective diameter and the maximum surface angle θ⊥max in the effective diameter form at least 2 optical functional surfaces in which 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°, and in these optical functional surfaces, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

According to the structure written in item 15 , when the wavelength λ of the light flux incident perpendicularly to the optical functional surface is λ 1 ≦λ≦λ 1 +50 nm, and when λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented to the wavelength in these regions. Further, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor on the optical functional surface shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 against the conventional antireflective film to prevent the reflection to the whole light fluxes in broad wavelength region of wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 16 , in the optical element written in item 15 , the plurality of wavelengths include the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%.

According to the structure written in item 16 , when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, because the reflection factor on the optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in these regions.

The structure written in item 17 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and it is provided with one or more optical element main bodies and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed so that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum thickness in the effective diameter))/average film thickness is larger than 5%, and the maximum incidence projection angle θmax in the effective diameter and the maximum surface angle θ⊥max in the effective diameter form at least one of the first optical functional surface in which 0°≦θmax≦40° and 0°≦θ⊥max≦40°, and at least one of the second optical functional surface in which 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°, and in the first optical functional surface, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, and when λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

According to the structure written in item 17 , when the wavelength λ of the light flux incident perpendicularly to the first optical functional surface is λ 1 ≦λ≦λ 1 +15 nm, and when λ 2 ≦λ≦λ 2 +15 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the second optical functional surface is λ 1 ≦λ≦λ 1 +50 nm, and when λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor on the second optical functional surface is not larger than 1%, the reflection can be prevented to the wavelength in these regions. Further, in the first optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 against the conventional antireflective film to prevent the reflection to the whole light fluxes in broad wavelength region of wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 5 of 22

According to the structure written in item 18 , in the optical element written in item 17 , the wavelength of the plurality of wavelengths includes the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the first optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is not larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%.

According to the structure written in item 18 , when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, because the reflection factor on the second optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in these regions.

The structure written in item 19 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and it is provided with one or more optical element main body and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed so that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum thickness in the effective diameter))/average film thickness is larger than 5%, and the maximum incidence projection angle θmax in the effective diameter and the maximum surface angle θ⊥max in the effective diameter form at least one of the first optical functional surface in which 0°≦θmax≦40° and 0°≦θ⊥max≦40°, and at least one of the second optical functional surface in which 40°<θmax<90° and 40°≦θ⊥max≦90°, and in the first optical functional surface, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +15 nm≦λ≦λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 2 +130 nm, the reflection factor is not larger than 1.5%.

According to the structure written in item 19 , when the wavelength λ of the light flux incident perpendicularly to the first optical functional surface is λ 1 ≦λ≦λ 1 +15 nm, and when λ 2 λ≦ 2 +15 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the second optical functional surface is λ 1 ≦λ≦λ 2 +130 nm, because the reflection factor on the second optical functional surface is not larger than 1.5%, the reflection can be prevented to the wavelength in these regions. Further, in the first optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , because the reflection factor shows the local maximal value larger than 1%, different from the conventional one, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 20 , in the optical element written in item 19 , the wavelength of the plurality of wavelengths includes the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the first optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is not larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +120 nm, the reflection factor is not larger than 1.5%.

According to the structure written in item 20 , when the wavelength λ is λ 3 ≦λ≦λ 3 +15 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ is λ 3 ≦λ≦λ 3 +120 nm, because the reflection factor on the second optical functional surface is not larger than 1.5%, the reflection can be prevented also for the wavelength in these regions.

The structure written in item 21 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and it is provided with one or more optical element main body and the antireflective film provided on the surface of the optical element main body, and the antireflective film is formed so that a value of ((the maximum film thickness in the effective diameter to the light flux of the wavelength λ 1 )−(the minimum thickness in the effective diameter))/average film thickness is larger than 5%, and the maximum incidence projection angle θmax in the effective diameter and the maximum surface angle θ⊥max in the effective diameter form at least one of the first optical functional surface in which 0°≦θmax≦40° and 40°≦θ⊥max≦90°, or 40°≦θmax≦90° and 0°≦θ⊥max≦40°, and at least one of the second optical functional surface in which 40°<θmax<90° and 40°≦θ⊥max≦90°, and in the first optical functional surface, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 2 +130 nm, the reflection factor is not larger than 1.5%.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 6 of 22

According to the structure written in item 21 , when the wavelength λ of the light flux incident perpendicularly to the first optical functional surface is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the second optical functional surface is λ 1 ≦λ≦λ 2 +130 nm, because the reflection factor on the second optical functional surface is not larger than 1.5%, the reflection can be prevented to the wavelength in these regions. Further, in the first optical functional surface, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , because the reflection factor shows the local maximal value larger than 1%, different from the conventional one, the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 22 , in the optical element written in item 21 , the wavelength of the plurality of wavelengths includes the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the first optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 3 +120 nm, the reflection factor is not larger than 1.5%.

According to the structure written in item 22 , when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ is λ 1 λ≦λ 3 +120 nm, because the reflection factor on the second optical functional surface is not larger than 1.5%, the reflection can be prevented also for the wavelength in these regions.

The structure written in item 23 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and it is provided with an optical element main body and the antireflective film provided on the both surfaces of the optical element main body, and which formed the first optical functional surface on the laser light source side of the optical pick-up device and the second optical functional surface on the information recording medium side, and in the first optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

Herein, the laser light source side, and the information recording medium side mean the laser light source side and the information recording medium side in the light path of the using light flux.

According to the structure written in item 23 , when the wavelength λ of the light flux incident perpendicularly to the first optical functional surface is λ 1 ≦λ≦λ 2 +40 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the second optical functional surface is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor on the second optical functional surface is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, when the wavelength is a wavelength in the range of λ 1 +50 nm≦λ≦λ 2 , the reflection factor on the second optical functional surface shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered, different from the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 , the number of layers of antireflective film can be reduced without deteriorating the reflection prevention function for the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by the penetrating of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 24 , in the optical element written in item 23 , the wavelength of the plurality of wavelengths includes the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the first optical functional surface, when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%, and in the second optical functional surface, when the wavelength λ is λ 2 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%.

According to the structure written in item 24 , when the wavelength λ is λ 3 ≦λ≦λ 3 +30 nm, the reflection factor on the first optical functional surface is not larger than 1%, and when the wavelength λ is λ 2 ≦λ≦λ 3 +30 nm, because the reflection factor on the second optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in these regions.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 7 of 22

The structure written in item 25 is an optical element which is provided in the optical pick-up device by which the recording and/or reproducing of the information is conducted, and which light converges light fluxes of a plurality of wavelengths including the wavelength λ 1 (390 nm≦λ 1 ≦430 nm) and the wavelength λ 2 (630 nm≦λ 2 ≦670 nm) on the information recording medium, and it is provided with the first optical element main body arranged on the laser light source side of the optical pick-up device and the second optical element main body arranged on the information recording medium side, and the antireflective film which is provided on the both surfaces of the first optical element main body, and which forms the first optical functional surface on the laser light source side and the second optical functional surface on the information recording medium side, and is provided on both surfaces of the second optical element main body, and the antireflective film which forms the third optical functional surface on the laser light source side and the fourth optical functional surface on the information recording medium side, and in the first optical functional surface and the second optical functional surface, when the wavelength λ of the light flux incident perpendicularly is λ=λ 1 , or λ=λ 2 , the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 <λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the third optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and in the fourth function surface, when the wavelength λ is λ 1 ≦λ≦λ 1 +50 nm, and when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is not larger than 1%, and when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

According to the structure written in item 25 , when the wavelength λ of the light flux incident perpendicularly is λ=λ 1 , and λ=λ 2 , the reflection factor on the first and second optical functional surfaces is not larger than 1%, and when the wavelength λ is λ 1 ≦λ≦λ 2 +40 nm, because the reflection factor on the third optical functional surface is not larger than 1%, and when the wavelength λ is λ 1 ≦λ≦λ 1 +50 nm or when λ 2 ≦λ≦λ 2 +40 nm, the reflection factor on the fourth optical functional surface is not larger than 1%, the reflection can be prevented for the wavelength in these regions. Further, when the wavelength is a wavelength in the range of λ 1 <λ<λ 2 , the reflection factor on the first and second optical functional surfaces shows the local maximal value larger than 1%, and when the wavelength is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor on the fourth optical functional surface shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered, different from the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 , the number of layers of antireflective film can be reduced without deteriorating the reflection prevention function for the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by the penetrating of the water between layers of the antireflective film can be suppressed.

According to the structure written in item 26 , in the optical element written in item 25 , the plurality of wavelengths include the wavelength λ 3 (760 nm≦λ 3 ≦800 nm), and in the first and second optical functional surfaces, when the wavelength λ is λ=λ 3 , the reflection factor is not larger than 1%, and in the third optical functional surface, when the wavelength λ is λ 1 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%, and in the fourth optical functional surface, when the wavelength λ is λ 2 ≦λ≦λ 3 +30 nm, the reflection factor is not larger than 1%.

According to the structure written in item 26 , because, when the wavelength λ is λ=λ 3 , the reflection factor on the first and second optical functional surfaces is not larger than 1%, and when the wavelength λ is λ 1 ≦λ≦λ 3 +30 nm, the reflection factor on the third optical functional surface is not larger than 1%, and when the wavelength λ is λ 2 ≦λ≦λ 3 +30 nm, the reflection factor on the fourth optical functional surface is not larger than 1%, the reflection can be prevented also for the wavelength in these regions.

The structure written in item 27 is, in the optical element written in any one of items 1 - 26 , an objective lens whose numerical aperture is not smaller than 0.65.

According to the structure written in item 27 , because it is an objective lens whose numerical aperture is not smaller than 0.65, the recording and/or reproducing can be conducted by using AOD as the information recording medium.

According to the structure written in item 28 , in the optical element written in any one of items 1 - 27 , the antireflective film is formed of at least 2 kinds of materials in a low refractive index material whose refractive index n to the light flux of wavelength 500 nm is 1.3≦n≦1.55, and a high refractive index material whose refractive index n to the light flux of wavelength 500 nm is 1.7≦n≦2.5.

According to the structure written in item 28 , the same effect as in the structure written in any one of items 1 - 27 , can be obtained.

According to the structure written in item 29 , in the optical element written in item 28 , the low refractive index material is a material whose main component is MgF 2 or SiO 2 , and the high refractive index material is a material whose main component is TiO 2 , Ta 2 O 5 , CeO 2 , ZrO 2 , HfO 2 or CeF 3 .

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 8 of 22

According to the structure written in item 29 , the same effect as in the structure written in item 28 , can be obtained.

According to the structure written in item 30 , in the optical element written in any one of items 1 - 27 , the antireflective film is formed of at least 3 kinds of materials in a low refractive index material whose refractive index n to the light flux of wavelength 500 nm is 1.3≦n<1.55, a middle refractive index material whose refractive index n to the light flux of wavelength 500 nm is 1.55≦n<1.7, and a high refractive index material whose refractive index n to the light flux of wavelength 500 nm is 1.7≦n<2.5.

According to the structure written in item 30 , the same effect as in the structure written in any one of items 1 - 27 , can be obtained.

According to the structure written in item 31 , in the optical element written in item 30 , the low refractive index material is a material whose main component is MgF 2 or SiO 2 , the middle refractive index material is a material whose main component is Al 2 O 3 , and the high refractive index material is a material whose main component is TiO 2 , Ta 2 O 5 , CeO 2 , ZrO 2 , HfO 2 or CeF 3 .

According to the structure written in item 31 , the same effect as in the structure written in item 30 can be obtained.

According to the structure written in item 32 , in the optical element written in any one of items 1 - 31 , the optical element main body is formed of plastic.

Herein, as the plastic, an optical plastic such as poly carbonate resin or poly methyl methacrylate resin, norbornen resin, alicyclic olefin resin, can be used. Hereupon, as the norbornen resin, it is preferable that poly olefin compound is used.

According to the structure written in item 32 , the same effect as in the structure written in any one of items 1 - 31 , can be obtained.

According to the structure written in item 33 , in the optical element written in any one of items 1 - 31 , the optical element main body is formed of glass.

Herein, as the glass, nitric material for a low melt point glass mold can be used, and specifically, M-BaCD5 (trade name, made by HOYA) can be used.

According to the structure written in item 33 , the same effect as in the structure written in any one of items 1 - 31 , can be obtained.

According to the structure written in item 34 , in the optical system written in any one of items 1 - 33 , a primary coat exists between the optical element main body and the antireflective film, and the refractive index n 0 ′ of the primary coat is, when the refractive index of the optical element main body is n 0 , |n 0 ′−n 0 |≦0.1.

According to the structure written in item 34 , because the primary coat exists between the optical element main body and the antireflective film, the adherence of the antireflective film to the optical element main body can be increased.

Further, because the refractive index n 0 ′ of the primary coat satisfies, to the refractive index n 0 of the optical element main body, |n 0 ′−n 0 |≦0.1, the deterioration of the optical function by providing the primary coat, can be prevented.

The structure written in item 35 is an optical pick-up device and which is provided with the optical element written in any one of items 1 - 34 and the laser light source, and when the light flux projected from the laser light source is light converged on the optical recording medium by the optical element, at least one of the recording of the information in this optical recording medium and the reproducing of the information recorded in the optical recording medium, can be conducted.

According to the structure written in item 35 , the same effect as in the structure written in any one of item 1 - 34 , can be obtained.

Referring to the drawings, embodiments of the present invention will be described below.

The First Embodiment

Initially, an embodiment of the optical pick-up device according to the present invention will be described. FIG. 1 is an outline structural view of an optical pick-up device 1 in the first embodiment. As shown in this view, the optical pick-up device 1 has the first light source 2 a and second light source 2 b , which project the laser light.

The first light source 2 a projects the first light flux of wavelength λ 1 , and the wavelength λ 1 is 380 nm≦λ 1 ≦450 nm, and in the present embodiment, λ 1 =405 nm. This wavelength λ 1 is the using wavelength to AOD (information recording medium) 100 . Hereupon, the thickness t 1 of a protective substrate 101 of AOD 100 is 0.5 mm≦t 1 ≦0.7 mm.

The second light source 2 b projects the second light flux of wavelength λ 2 , and the wavelength λ 2 is 640 nm≦λ 1 ≦680 nm, and in the present embodiment, λ 2 =650 nm. This wavelength λ 2 is the using wavelength to DVD (information recording medium) 200 . Hereupon, the thickness t 1 of a protective substrate 201 of DVD 200 is 0.5 mm≦t 1 ≦0.7 mm.

Each of light fluxes projected from these first light source 2 a and second light source 2 b is light converged on AOD 100 and DVD 200 by a light converging optical system 3 . The light converging optical system 3 has the first and second collimator lenses 30 a and 30 b , the first-third beam splitters 31 a - 31 c , and an objective lens (optical element) 5. The first and second collimator lenses 30 a and 30 b make the light fluxes projected from the first and second light sources 2 a and 2 b , the parallel light.

The beam splitter 31 a makes the first light flux projected from the first light source 2 a transmit toward the direction of the objective lens 5 , and introduces the reflected light from AOD 100 , that is, the returning light to the first detector 4 a.

A sensor lens group 33 a is arranged between the beam splitter 31 a and the first light detector 4 a.

The beam splitter 31 b makes the second light flux projected from the second light source 2 b transmit toward the direction of the beam splitter 31 c , and introduces the reflected light from DVD 200 to the second light detector 4 b . A sensor lens group 33 b is arranged between the beam splitter 31 b and the second light detector 4 b.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 9 of 22

The beam splitter 31 c puts the first light flux from the first light source 2 a and the second light flux from the second light source 2 b on the same light path.

The objective lens 5 is, as shown in FIG. 2 , provided with a lens main body (optical element main body) 50 and a antireflective film 51 , and mounted on the second dimensional actuator (not shown) which can move in a predetermined direction. The numerical aperture NA of the objective lens 5 is 0.65, and the maximum incidence projection angle θmax of the light flux of the wavelength λ 1 on optical functional surfaces 52 and 53 , is 0°≦θmax≦40°.

The lens main body 50 is formed of plastic or glass, and the refractive index n 0 is 1.45≦n 0 ≦1.65. Herein, as the plastic used for the lens main body 50 , the optical plastic such as poly carbonate resin, poly methyl methacrylate resin, norbornen resin, or alicyclic olefin resin, can be used. Hereupon, as the norbornen resin, it is preferable that poly olefin compound is used. Further, as the glass used for the lens main body 50 , a nitric material for a low melt point glass mold can be used, and specifically, M-BaCD5 (trade name, made by HOYA) can be used.

The antireflective film 51 is provided on at least one surface of a lens main body 50 , in the present embodiment, on both surfaces, and forms optical functional surfaces 52 and 53 . The reflection factor of the light flux incident perpendicularly to the optical functional surfaces 52 and 53 , shows the local maximal value not smaller than 1% between the wavelength λ 1 and wavelength λ 2 , and becomes relatively low at the wavelength λ 1 and the wavelength λ 2 . Accordingly, for the first light flux and the second light flux, it is in the situation that the reflection on the optical functional surfaces 52 , 53 , is prevented.

This antireflective film 51 is structured of layers not smaller than 2 and not larger than 30 from at least 2 kinds of materials in the low refractive index material in which the refractive index n to the light flux of wavelength 500 nm, is 1.3≦n≦1.55, and the high refractive index material in which it is 1.7≦n≦2.5. Herein, as the low refractive index material, a material whose main component is MgF 2 or SiO 2 , can be used. Further, as the high refractive index material, a material whose main component is TiO 2 , Ta 2 O 5 , CeO 2 , ZrO 2 , HfO 2 or CeF 3 can be used. Further, for the formation of antireflective film 51 , a method such as evaporation, spattering, CVD, or coating is used.

Further, when the layers included in the antireflective film 51 are defined in the order from the side close to the lens main body 50 , as the first layer, second layer, . . . n-th layer, the refractive index n 1 of the first layer and optical film thickness nd 1 , and the refractive index n 2 of the second layer and optical film thickness nd 2 , are

1.7≦n 1 ≦2.5, 225 nm≦nd 1 , ≦275 nm,

1.3≦n 2 ≦1.55, 100 nm≦nd 2 ≦150 nm.

Hereupon, it is preferable to make the primary coat (not shown) stand between the lens main body 50 and the antireflective film 51 . In this case, the adherence of the antireflective film 51 to the lens main body 50 can be increased. Further, it is preferable that the refractive index n 0 ′ of this primary coat is, to the refractive index n 0 of the lens main body 50 , |n 0 ′−n 0 |≦0.1. In this case, it becomes a situation that the deterioration of the optical function by providing the primary coat is prevented.

Because the operation of the optical pick-up device 1 structured as described above, is well known, the detailed description is neglected, and after the first light flux projected from the first light source 2 a passes the first beam splitter 31 a , it is made parallel light in the first collimator lens 30 a , and passes the third beam splitter 31 c.

Next, the first light flux is light converged on the information recording surface of AOD 100 by the objective lens 5 , and forms a spot on the optical axis L. The first light flux which formed the spot, is modulated by the information pits on the information recording surface and reflected, and passes again the objective lens 5 . Herein, because the reflection of the first light flux on the optical functional surfaces 52 and 53 is prevented by the antireflective film 51 , the first light flux passes the objective lens 5 without lowering the light amount.

Next, the first light flux passes the third beam splitter 31 c , first collimator lens 30 a and is reflected by the first beam splitter 31 a , and branched. Then, the branched first light flux is incident on the first light detector 4 a via sensor lens group 33 a . The first light detector 4 a detects the spot of the incident light and outputs a signal, and the reading signal of the information recorded in AOD 100 is obtained by using the outputted signal.

Further, a shape change of the spot on the first light detector 4 a , or a light amount change by the position change is detected, and the focusing detection or track detection is conducted. According to this detection result, the second dimensional actuator moves the objective lens 5 toward the focus direction and tracking direction so that the first light flux accurately form the spot on the information recording surface.

On the one hand, the second light flux projected from the second light source 2 b is, after passing the second beam splitter 31 b , made parallel light in the second collimator lens 30 b , reflected by the third beam splitter 31 c , and reaches the objective lens 5 .

Next, the second light flux is light converged on the information recording surface of DVD 200 by the objective lens 5 , and forms the spot on the optical axis L. The second light flux which formed the spot, is modulated by the information pits on the information recording surface and reflected, and passes again the objective lens 5 . Herein, because the reflection of the second light flux on the optical functional surfaces 52 , 53 is prevented by the antireflective film 51 , the second light flux passes the objective lens 5 without lowering the light amount.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 10 of 22

Next, the second light flux is reflected by the third beam splitter 31 c , and branched. Then, the branched second light flux passes the second collimator lens 30 b , reflected by the second beam splitter 31 b and branched, and is incident on the second light detector 4 b via sensor lens group 33 a . Hereinafter, it is the same as in the case of the first light flux.

According to the optical pick-up device 1 as described above, different from the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of wavelengths λ 1 -λ 2 , the number of layers of the antireflective film 51 can be reduced without deteriorating the reflection prevention function to the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film 51 can be suppressed.

Further, even when the optical element main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 by the stress of the antireflective film 51 , or the adherence between the antireflective film 51 and the optical element main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the above embodiment, description is made as the wavelength of the second light source is not smaller than 640 nm, and not larger than 680 nm, however, it may also be allowable that the wavelength is not smaller than 750 nm and not larger than 850 nm. In this case, as the information recording medium, CD can be used in place of DVD 200 .

The Second Embodiment

Next, the second embodiment of the optical pick-up device according to the present invention will be described. Hereupon, the same component as in the above first embodiment is denoted by the same sign and the description will be neglected.

The optical pick-up device 1 A in the present second embodiment is different from the above first optical pick-up device 1 , and is provided with the objective lens 5 A in place of the objective lens 5 .

The objective lens 5 A is, as shown in FIG. 2 , provided with a lens main body 50 and the antireflective film 51 A. The antireflective film 51 A is provided on at least one surface of a lens main body 50 , in the present embodiment, on both surfaces, and forms optical functional surfaces 52 A, 53 A. The reflection factor of the light flux incident perpendicularly to the optical functional surfaces 52 A, 53 A, shows the local maximal value not smaller than 1% between the wavelength λ 1 and wavelength λ 2 , and becomes-relatively low at the wavelength λ 1 and the wavelength λ 2 . Accordingly, for the first light flux and the second light flux, it is in the situation that the reflection on the optical functional surfaces 52 A, 53 A is prevented.

This antireflective film 51 A is formed of layers not smaller than 3 and not larger than 30 from at least 3 kinds of materials in the low refractive index material in which the refractive index n to the light flux of wavelength 500 nm, is 1.3≦n<1.55, the middle refractive index material in which it is 1.55≦n<1.7, and the high refractive index material in which it is 1.7≦n<2.5. Herein, as the low refractive index material, a material whose main component is MgF 2 or SiO 2 , can be used. Further, as the middle refractive index material, a material whose main component is Al 2 O 3 , can be used. Further, as the high refractive index material, a material whose main component is TiO 2 , Ta 2 O 5 , CeO 2 , ZrO 2 , HfO 2 or CeF 3 can be used.

Further, in layers included in the antireflective film 51 A, the refractive index n, of the first layer and layer thickness nd 1 , the refractive index n 2 of the second layer and layer thickness nd 2 , and the refractive index n 3 of the third layer and layer thickness nd 3 , are

1.7≦n 1 ≦2.5, 125 nm≦nd 1 ≦175 nm,

1.55≦n 2 ≦1.7, 75 nm≦nd 2 ≦125 nm, and

1.3≦n 3 ≦1.55, 100 nm≦nd 3 ≦150 nm.

The operation of the optical pick-up device 1 A as described above is the same as the operation of the optical pick-up device 1 in the above first embodiment. Also by this optical pick-up device 1 A, the same effect as in the above first embodiment can be obtained.

The Third Embodiment

Next, the third embodiment of the optical pick-up device according to the present invention will be described. Hereupon, the same component as in the above first embodiment is denoted by the same sign and the description will be neglected.

FIG. 3 is an outline structural view of an optical pick-up device 1 B in the third embodiment. As shown in this view, the optical pick-up device 1 B is, different from the optical pick-up device 1 in the above first embodiment, further provided with the third light source 2 c , collimator lens 30 c , beam splitter 31 d , and diffraction plate 6 , and an objective lens 5 B in place of the objective lens 5 .

The third light source 2 c projects the third light flux of wavelength λ 3 , and the wavelength λ 3 is 750 nm≦λ 3 ≦850 nm, and in the present embodiment, λ 3 =780 nm. This wavelength λ 3 is the using wavelength for CD (the third optical information recording medium) 300 . Hereupon, the thickness t 3 of a protective substrate 301 of CD 300 is 1.1 mm≦t 3 ≦1.3 mm.

The third collimator lens 30 c makes the light flux projected from the third light source 2 c the parallel light. The beam splitter 31 d puts the third light flux from the third light source 2 c , and the first light flux and the second light flux which transmit the beam splitter 31 c , on the same light path. The diffraction plate 6 to guide the reflected light from CD 300 to the third light detector 4 c is arranged between the beam splitter 31 d and the third light source 2 c.

The objective lens 5 B is, as shown in FIG. 2 , provided with a lens main body (optical element main body) 50 B and the antireflective film 51 B having the reflection prevention function for the first light flux, second light flux, and third light flux.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 11 of 22

The antireflective film 51 B is provided on at least one surface of a lens main body 50 B, in the present embodiment, on both surfaces, and forms optical functional surfaces 52 B, 53 B. The reflection factor of the light flux incident perpendicularly to the optical functional surfaces 52 B, 53 B, shows the local maximal value not smaller than 1% between the wavelength λ 1 and wavelength λ 2 , and becomes relatively low at the wavelength λ 1 and the wavelength λ 2 . Accordingly, for the first light flux and the second light flux, it is in the situation that the reflection on the optical functional surfaces 52 B and 53 B is prevented.

This antireflective film 51 B is formed of layers not smaller than 4 and not larger than 30 from at least 2 kinds of materials in the low refractive index material in which the refractive index n to the light flux of wavelength 500 nm, is 1.3≦n≦1.55, and the high refractive index material in which it is 1.7≦n≦2.5.

Further, in layers included in the antireflective film 51 B, the refractive index n, of the first layer and optical film thickness nd 1 , the refractive index n 2 of the second layer and optical film thickness nd 2 , the refractive index n 3 of the third layer and optical film thickness nd 3 , and the refractive index n 4 of the fourth layer and optical film thickness nd 4 , are

1.7≦n 1 ≦2.5, 25 nm≦nd 1 ≦75 nm,

1.3≦n 2 ≦1.55, 25 nm≦nd 2 ≦75 nm,

1.7≦n 3 ≦2.5, 225 nm≦nd 3 ≦275 nm and

1.3≦n 4 ≦1.55, 135 nm≦nd 4 ≦185 nm.

In the operation of the optical pick-up device 1 B structured as described above, as to the recording and/or reproducing using AOD 100 and DVD 200 , it is the same as the operation of the optical pick-up device 1 in the above first embodiment.

Further, in the operation of the optical pick-up device 1 B, in the recording and/or reproducing using CD 300 , the third light flux projected from the third light source 2 c , after passing the diffraction plate 6 , is made parallel light in the third collimator lens 30 c , reflected by the fourth beam splitter 31 d , and reaches the objective lens 5 .

Next, the third light flux is light converged on the information recording surface of CD 300 by the objective lens 5 , and forms the spot on the optical axis L. The third light flux which formed the spot, is modulated by the information pits on the information recording surface and reflected, and passes again the objective lens 5 . Herein, because the reflection of the second light flux on the optical functional surfaces 52 and 53 is prevented by the antireflective film 51 , the third light flux passes the objective lens 5 without lowering the light amount.

Next, the third light flux is reflected by the fourth beam splitter 31 d , and branched. Then, the branched third light flux passes the third collimator lens 30 c , when passing the diffraction plate 6 , the track is changed, and is incident on the third light detector 4 c . Hereinafter, it is the same as in the case of the first light flux.

According to the optical pick-up device 1 B as described above, different from the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 B can be reduced without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film 51 B can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 B by the stress of the antireflective film 51 B, or the adherence between the antireflective film 51 B and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The Fourth Embodiment

The optical pick-up device 1 C in the present fourth embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 C in place of the objective lens 5 .

The objective lens 5 C is, as shown in FIG. 2 , provided with a lens main body 50 and an antireflective film 51 C.

The antireflective film 51 C is provided on at least one surface of the lens main body 50 , in the present embodiment, both surfaces, and forms the optical functional surfaces 52 C, 53 C. In more detail, the antireflective film 51 C is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is not larger than 5%. That is, the film thickness of the antireflective film 5 C is almost uniform.

In the optical functional surfaces 52 C, 53 C, the maximum incidence projection angle θmax is 0°≦θmax≦40°. Further, in the optical functional surfaces 52 C and 53 C, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 C and 53 C, when the above wavelength λ is a wavelength in the range of λ 1 +15 nm <λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 C described above is the same as the operation of the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 C, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 C and 53 C is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, because the reflection factor in the optical functional surfaces 52 C, 53 C is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered, different from the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 , the number of layers of the antireflective film 51 C can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux. Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film 51 C can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 12 of 22

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 C by the stress of the antireflective film 51 C, or the adherence between the antireflective film 51 C and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The Fifth Embodiment

The optical pick-up device 1 D in the present fifth embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 D in place of the objective lens 5 .

The objective lens 5 D is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 D.

The antireflective film 51 D is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 D, 53 D. In more detail, the antireflective film 51 D is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is not larger than 5%. That is, the film thickness of the antireflective film 5 D is almost uniform.

In the optical functional surfaces 52 D, 53 D, the maximum incidence projection angle θmax in the effective diameter is 40°<θmax<90°. Further, in the optical functional surfaces 52 D and 53 D, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 D and 53 D, when the above wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 D described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 D, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 D and 53 D is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor in the optical functional surfaces 52 D, 53 D is not larger than 1%, the reflection can be prevented for the wavelength in these regions. Further, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therein, the number of layers of the antireflective film 51 D can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux against the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of spectral characteristic by penetration of the water between layers of the antireflective film 51 D can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 D by the stress of the antireflective film 51 D, or the adherence between the antireflective film 51 D and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The Sixth Embodiment

The optical pick-up device 1 E in the present sixth embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 E in place of the objective lens 5 .

The objective lens 5 E is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 E.

The antireflective film 51 E is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 E, 53 E. In more detail, the antireflective film 51 E is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is not larger than 5%. That is, the film thickness of the antireflective film 5 E is almost uniform. In the optical functional surface 52 E, the maximum incidence projection angle θmax in the effective diameter is 40°<θmax<90°. Further, in the optical functional surface 52 E, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 E, when the above wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

In the optical functional surface 53 E, the maximum incidence projection angle θmax in the effective diameter is 0°<θmax<40°. Further, in the optical functional surface 53 E, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 53 E, when the above wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 E described above is the same as the operation of the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 E, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 53 E, is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor in the optical functional surface 53 E is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 E, is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor in the optical functional surface 52 E is not larger than 1%, the reflection can be prevented for the wavelength in these regions. Further, in the optical functional surface 53 E, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film 51 E can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux against the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 E can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 13 of 22

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 E by the stress of the antireflective film 51 E, or the adherence between the antireflective film 51 E and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 E is described as the light incidence surface, and the optical functional surface 53 E is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 E is the light projection surface, and the optical functional surface 53 E is the light incidence surface.

The Seventh Embodiment

The optical pick-up device 1 F in the present seventh embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 F in place of the objective lens 5 .

The objective lens 5 F is, as shown in FIG. 2 , provided with a lens main body 50 and an antireflective film 51 F.

The antireflective film 51 F is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 F, 53 F. In more detail, the antireflective film 51 F is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter)))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 5 F is un-uniform.

In the optical functional surfaces 52 F, 53 F, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max are 0°≦θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surfaces 52 F and 53 F, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 F and 53 F, when the above wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 F described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 F, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 F and 53 F, is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, because the reflection factor in the optical functional surfaces 52 F and 53 F is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered, different from the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 , the number of layers of the antireflective film 51 F can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 F can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 F by the stress of the antireflective film 51 F, or the adherence between the antireflective film 51 F and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The Eighth Embodiment

The optical pick-up device 1 G in the present eighth embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 G in place of the objective lens 5 .

The objective lens 5 G is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 G.

The antireflective film 51 G is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 G, 53 G. In more detail, the antireflective film 51 G is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 5 G is un-uniform.

In the optical functional surfaces 52 G and 53 G, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°. Further, in the optical functional surfaces 52 G and 53 G, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 G and 53 G, when the above wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 G described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 G, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 G and 53 G, is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor in the optical functional surfaces 52 G and 53 G is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film 51 G can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux against the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 G can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 14 of 22

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 G by the stress of the antireflective film 51 G, or the adherence between the antireflective film 51 G and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The Ninth Embodiment

The optical pick-up device 1 I in the present ninth embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 I in place of the objective lens 5 .

The objective lens 5 I is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 I.

The antireflective film 51 I is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 I, 53 I. In more detail, the antireflective film 51 I is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 5 I is un-uniform.

In the optical functional surface 52 I, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 52 I, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 52 I, when the above wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

In the optical functional surface 53 I, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 0°≦θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 I, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 I, when the above wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 I described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 I, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 I, is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, because the reflection factor in the optical functional surface 53 I is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 I, is λ 1 ≦λ≦ 1 +50 nm or when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor in the optical functional surface 52 I is not larger than 1%, the reflection can be prevented for the wavelength in these regions. Further, in the optical functional surface 53 I, when the wavelength λ is a wavelength in the range of λ 1 +15 nm≦λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the optical functional surface 52 I, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film 51 I can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux against the conventional antireflective film to prevent the reflection for the whole light fluxes in the broad wavelength region of the wavelength λ 1 -λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 I can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 I by the stress of the antireflective film 51 I, or the adherence between the antireflective film 51 I and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 I is described as the light incidence surface, and the optical functional surface 53 I is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 I is the light projection surface, and the optical functional surface 53 I is the light incidence surface.

The Tenth Embodiment

The optical pick-up device 1 J in the present tenth embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 J in place of the objective lens 5 .

The objective lens 5 J is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 J.

The antireflective film 51 J is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 J, 53 J. In more detail, the antireflective film 51 J is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 5 J is un-uniform. In the optical functional surface 52 J, the maximum incidence projection angle. θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 40°<θmax<90° and 40°<θ⊥max<90°. Further, in the optical functional surface 52 J, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 2 +130 nm, the reflection factor is suppressed to not larger than 1.5%. In the optical functional surface 53 J, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 0°θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 J, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 J, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 15 of 22

In the optical functional surface 53 J, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 0°≦θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 J, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 J, when the above wavelength λ is a wavelength in the range of λ 1 +15 nm≦λ≦λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 J described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 J, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 J, is λ 1 ≦λ≦λ 1 +15 nm, or when it is λ 2 ≦λ≦λ 2 +15 nm, because the reflection factor in the optical functional surface 53 J is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 K, is λ 1 ≦λ≦λ 2 +130 nm, because the reflection factor in the optical functional surface 52 K is not larger than 1.5%, the reflection can be prevented for the wavelength in these regions. Further, in the optical functional surface 53 K, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , because the reflection factor shows the local maximal value larger than 1%, different from the conventional one, the number of layers of the antireflective film 51 K can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 K can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 K by the stress of the antireflective film 51 J, or the adherence between the antireflective film 51 K and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 J is described as the light incidence surface, and the optical functional surface 53 J is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 J is the light projection surface, and the optical functional surface 53 J is the light incidence surface.

The 11th Embodiment

The optical pick-up device 1 K in the present 11th embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 K in place of the objective lens 5 .

The objective lens 5 K is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 K.

The antireflective film 51 K is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 K, 53 K. In more detail, the antireflective film 51 K is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 5 K is un-uniform.

In the optical functional surface 52 K, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 40°<θmax<90° and 40°<θ⊥max<90°. Further, in the optical functional surface 52 K, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 2 +130 nm, the reflection factor is suppressed to not larger than 1.5%. In the optical functional surface 53 K, the maximum incidence projection angle θmax in the effective diameter, and the maximum surface angle θ⊥max in the effective diameter, are 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 K, when the wavelength λ of the light-flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 K, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 K described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 K, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 K, is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor in the optical functional surface 53 K is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 K, is λ 1 ≦λ≦λ 2 +130 nm, because the reflection factor in the optical functional surface 52 K is not larger than 1.5%, the reflection can be prevented for the wavelength in these regions. Further, in the optical functional surface 53 K, when the wavelength λ is a wavelength in the range of λ 1 +15 nm≦λ≦λ 2 , because the reflection factor shows the local maximal value larger than 1%, different from the conventional one, the number of layers of the antireflective film 51 K can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 K can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 K by the stress of the antireflective film 51 K, or the adherence between the antireflective film 51 K and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 16 of 22

Hereupon, in the present embodiment, the optical functional surface 52 K is described as the light incidence surface, and the optical functional surface 53 K is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 K is the light projection surface, and the optical functional surface 53 K is the light incidence surface.

The 12th Embodiment

The optical pick-up device 1 L in the present 12th embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 L in place of the objective lens 5 .

The objective lens 5 L is, as shown in FIG. 2 , provided with a lens main body 50 and a antireflective film 51 L.

The antireflective film 51 L is provided on both surfaces of the lens main body 50 , and forms the optical functional surfaces 52 L and 53 L.

The optical functional surface 52 L, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 2 +40 nm, suppresses the reflection factor to not larger than 1%.

The optical functional surface 53 L, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, suppresses the reflection factor to not larger than 1%. Further, in the optical functional surface 53 L, when the wavelength λ is a wavelength in the range of λ 1 +50<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 L described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 L, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 L, is λ 1 ≦λ≦λ 2 +40 nm, because the reflection factor in the optical functional surface 52 L is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 L, is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦ 2 +40 nm, because the reflection factor in the optical functional surface 53 L is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, in the optical functional surface 53 L, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered, different from the conventional one, the number of layers of the antireflective film 51 L can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 L can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 L by the stress of the antireflective film 51 L, or the adherence between the antireflective film 51 L and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 L is described as the light incidence surface, and the optical functional surface 53 L is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 L is the light projection surface, and the optical functional surface 53 L is the light incidence surface.

The 13th Embodiment

The optical pick-up device 1 M in the present 13th embodiment is, different from the above first optical pick-up device 1 , provided with an objective lens 5 M in place of the objective lens 5 .

The objective lens 5 M is, as shown in FIG. 4 , provided with two lens main bodies 501 and 502 , and a antireflective film 51 M.

The lens main body 501 is arranged on the laser light sources 2 a , 2 b side, and the lens main body 502 is arranged on the information recording medium side such as AOD 100 .

The antireflective film 51 M is provided on both surfaces of the lens main bodies 501 and 502 , and forms the optical functional surfaces 54 - 57 .

The optical functional surface 54 on laser light sources 2 a , 2 b side and the optical functional surface 55 on the information recording medium side, when the wavelength λ of the light flux incident perpendicularly to the lens main body 501 is λ=λ 1 , and when λ=λ 2 , suppresses the reflection factor to not larger than 1%.

The optical functional surface 56 on the laser light sources 2 a , 2 b side, when the wavelength λ of the light flux incident perpendicularly to the lens main body 502 is λ 1 ≦λ≦λ 2 +40 nm, suppresses the reflection factor to not larger than 1%. The optical functional surface 57 on the information recording medium side, when the wavelength λ of the light flux incident perpendicularly to the lens main body 502 is λ 1 ≦λ≦λ 1 +50 rm, and when λ 2 ≦λ≦λ 1 +40 nm, suppresses the reflection factor to not larger than 1%. Further, when the wavelength λ is a wavelength in the range of λ 1 +50<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 M described above is the same as in the optical pick-up device 1 in the above first embodiment.

According to this optical pick-up device 1 M, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 54 , 55 , when λ=λ 1 , and when λ=λ 2 , the reflection factor on the optical functional surfaces 54 , 55 , is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 56 , is λ 1 ≦λ≦λ 2 +40 nm, the reflection factor on the optical functional surface 56 is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 57 , is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 2 +40 nm, because the reflection factor on the optical functional surface 7 is not larger than 1%, the reflection can be prevented for the wavelength in these zones. Further, in the optical functional surface 57 , when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, the number of layers of the antireflective film 51 M can be reduced, without deteriorating the reflection prevention function for the first light flux and the second light flux against the conventional one. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 M can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 17 of 22

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 M by the stress of the antireflective film 51 M, or the adherence between the antireflective film 51 M and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The 14th Embodiment

The optical pick-up device 1 N in the present 14th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 N in place of the objective lens 5 B.

The objective lens 5 N is, as shown in FIG. 2 , provided with a lens main body 50 , and an antireflective film 51 N.

The antireflective film 51 N is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 N and 53 N. In more detail, the antireflective film 51 N is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is not larger than 5%. That is, the film thickness of the antireflective film 5 N is almost uniform.

In the optical functional surfaces 52 N and 53 N, the maximum incidence projection angle θmax in the effective diameter is 0°≦θmax≦40°. Further, in the optical functional surfaces 52 N and 53 N, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 N and 53 N, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 N described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 N, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 N and 53 N, is λ 1 ≦λ≦λ 2 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor in the optical functional surfaces 52 N, 53 N, is not larger than 1%, the reflection can be prevented for the wavelengths in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, different from the conventional antireflective film to prevent the reflection to whole light fluxes in a broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 N can be reduced, without deteriorating the reflection prevention function for the first light flux, the second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 N can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 L by the stress of the antireflective film 51 N, or the adherence between the antireflective film 51 N and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The 15th Embodiment

The optical pick-up device 1 O in the present 15th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 O in place of the objective lens 5 B.

The objective lens 5 O is, as shown in FIG. 2 , provided with a lens main body 50 , and an antireflective film 51 O.

The antireflective film 51 O is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 O and 53 O. In more detail, the antireflective film 51 O is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is not larger than 5%. That is, the film thickness of the antireflective film 51 O is almost uniform.

In the optical functional surfaces 52 N, 53 N, the maximum incidence projection angle θmax in the effective diameter is 40°<θmax<90°. Further, in the optical functional surfaces 52 O and 53 O, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 O and 53 O, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 O described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 O, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 O and 53 O, is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, because the reflection factor in the optical functional surfaces 52 O and 53 O, is not larger than 1%, the reflection can be prevented for the wavelengths in these regions. Further, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered Therefore, different from the conventional antireflective film to prevent the reflection to whole light fluxes in a broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 O can be reduced, without deteriorating the reflection prevention function for the first light flux, the second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 O can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 18 of 22

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 O by the stress of the antireflective film 51 O, or the adherence between the antireflective film 51 O and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The 16th Embodiment

The optical pick-up device 1 P in the present 16th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 P in place of the objective lens 5 B.

The objective lens 5 P is, as shown in FIG. 2 , provided with a lens main body 50 , and an antireflective film 51 P.

The antireflective film 51 P is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 P and 53 P. In more detail, the antireflective film 51 P is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is not larger than 5%. That is, the film thickness of the antireflective film 5 P is almost uniform.

In the optical functional surface 52 P, the maximum incidence projection angle θmax in the effective diameter is 40°<θmax<90°. Further, in the optical functional surface 52 P, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 52 P, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

In the optical functional surface 53 P, the maximum incidence projection angle θmax in the effective diameter is 0°<θmax<40°. Further, in the optical functional surface 53 P, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 P, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 P described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 P, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 P, is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor in the optical functional surface 52 P, is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 P, is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, because the reflection factor in the optical functional surface 52 P, is not larger than 1%, the reflection can be prevented for the wavelengths in these regions. Further, in the optical functional surface 53 P, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the optical functional surface 52 P, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, different from the conventional antireflective film to prevent the reflection to whole light fluxes in a broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 P can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 P can be suppressed.

Further, even when the lens main body 50 is made of plastic, it can be prevented that a crack is generated in the antireflective film 51 P by the stress of the antireflective film 51 P, or the adherence between the antireflective film 51 P and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 P is described as the light incidence surface, and the optical functional surface 53 P is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 P is the light projection surface, and the optical functional surface 53 P is the light incidence and projection surface.

The 17th Embodiment

The optical pick-up device 1 Q in the present 17th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 Q in place of the objective lens 5 B.

The objective lens 5 Q is, as shown in FIG. 2 , provided with a lens main body 50 , and a antireflective film 51 Q.

The antireflective film 51 Q is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 Q and 53 Q. In more detail, the antireflective film 51 Q is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 51 Q is un-uniform.

In the optical functional surfaces 52 Q and 53 Q, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 0°≦θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surfaces 52 Q and 53 Q, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 Q and 53 Q, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 19 of 22

The operation of the optical pick-up device 1 Q described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 Q, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 Q and 53 Q, is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor in the optical functional surfaces 52 Q and 53 Q, is not larger than 1%, the reflection can be prevented for the wavelengths in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, because the reflection prevention function is lowered, different from the conventional antireflective film to prevent the reflection to whole light fluxes in a broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 Q can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 P can be suppressed.

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 P by the stress of the antireflective film 51 Q, or the adherence between the antireflective film 51 Q and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The 18th Embodiment

The optical pick-up device 1 R in the present 18th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 R in place of the objective lens 5 B.

The objective lens 5 R is, as shown in FIG. 2 , provided with a lens main body 50 , and a antireflective film 51 R.

The antireflective film 51 R is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 R and 53 R. In more detail, the antireflective film 51 R is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 51 R is un-uniform.

In the optical functional surfaces 52 R and 53 R, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<max<90° and 0°≦θ⊥max≦40°. Further, in the optical functional surfaces 52 R, 53 R, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, when λ 3 ≦λ≦λ 3 +15 nm, or when λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surfaces 52 R and 53 R, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 R described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 R, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 52 R, 53 R, is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, because the reflection factor in the optical functional surfaces 52 R and 53 R, is not larger than 1%, the reflection can be prevented for the wavelengths in these zones. Further, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, different from the conventional antireflective film to prevent the reflection to whole light fluxes in a broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 R can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 R can be suppressed.

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 R by the stress of the antireflective film 51 R, or the adherence between the antireflective film 51 R and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

The 19th Embodiment

The optical pick-up device 1 T in the present 19th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 T in place of the objective lens 5 B.

The objective lens 5 T is, as shown in FIG. 2 , provided with a lens main body 50 , and a antireflective film 51 T.

The antireflective film 51 T is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 T and 53 T. In more detail, the antireflective film 51 T is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 51 T is un-uniform.

In the optical functional surface 52 G, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 0°≦θmax≦40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 52 G, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 52 G, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 20 of 22

In the optical functional surface 53 G, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 0°≦θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 G, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 G, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 T described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 T, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 T, is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor in the optical functional surfaces 53 T, is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 T, is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, because the reflection factor in the optical functional surface 52 T is not larger than 1%, the reflection can be prevented for the wavelengths in these regions. Further, in the optical functional surface 53 T, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, and in the optical functional surface 52 T, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, different from the conventional antireflective film to prevent the reflection to whole light fluxes in a broad wavelength region of wavelengths λ 1 -λ 3 , the number of layers of the antireflective film 51 T can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 T can be suppressed.

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 T by the stress of the antireflective film 51 T, or the adherence between the antireflective film 51 T and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 T is described as the light incidence surface, and the optical functional surface 53 T is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 T is the light projection surface, and the optical functional surface 53 T is the light incidence and projection surface.

The 20th Embodiment

The optical pick-up device 1 T in the present 20th embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 U in place of the objective lens 5 B.

The objective lens 5 U is, as shown in FIG. 2 , provided with a lens main body 50 , and a antireflective film 51 U.

The antireflective film 51 U is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 U and 53 U. In more detail, the antireflective film 51 U is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 51 U is un-uniform.

In the optical functional surface 52 U, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 40°<θmax<90° and 40°<θ⊥max<90°. Further, in the optical functional surface 52 U, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 3 +120 nm, the reflection factor is suppressed to not larger than 1.5%.

In the optical functional surface 53 U, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 0°≦θmax≦40° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 U, when the wavelength λ of the light flux incident perpendicularly is λ 1 λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 U, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 T described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 U, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 T, is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor in the optical functional surfaces 53 U, is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 U, is λ 1 ≦λ≦λ 3 +120 nm, because the reflection factor in the optical functional surface 52 U is not larger than 1.5%, the reflection can be prevented for the wavelengths in these zones. Further, in the optical functional surface 53 U, when the wavelength λ is a wavelength in the range of λ 1 +15 nm≦λ≦λ 2 , because the reflection factor shows the local maximal value larger than 1%, different from the conventional one, the number of layers of the antireflective film 51 U can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 U can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 21 of 22

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 U by the stress of the antireflective film 51 U, or the adherence between the antireflective film 51 U and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 U is described as the light incidence surface, and the optical functional surface 53 U is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 U is the light projection surface, and the optical functional surface 53 U is the light incidence surface.

The 21st Embodiment

The optical pick-up device 1 V in the present 21st embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 V in place of the objective lens 5 B.

The objective lens 5 V is, as shown in FIG. 2 , provided with a lens main body 50 , and an antireflective film 51 V.

The antireflective film 51 V is provided on at least one surface of the lens main body 50 , in the present embodiment, on both surfaces, and forms the optical functional surfaces 52 V and 53 V. In more detail, the antireflective film 51 V is formed so that a value of ((the maximum film thickness in the effective diameter to the first light flux)−(the minimum film thickness in this effective diameter))/average film thickness is larger than 5%. That is, the film thickness of the antireflective film 51 V is un-uniform.

In the optical functional surface 52 V, the maximum incidence projection angle Emax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, is 40°<θmax<90° and 40°<θ⊥max<90°. Further, in the optical functional surface 52 V, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 3 +120 nm, the reflection factor is suppressed to not larger than 1.5%.

In the optical functional surface 53 V, the maximum incidence projection angle θmax in the effective diameter, and maximum surface angle θ⊥max in the effective diameter, are 0<θmax<40° and 40°<θ⊥max<90°, or 40°<θmax<90° and 0°≦θ⊥max≦40°. Further, in the optical functional surface 53 V, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, when λ 2 ≦λ≦λ 2 +40 nm, or when λ 3 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 V, when the wavelength λ is a wavelength in the range of λ 1 +15 nm≦λ≦λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 V described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 V, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 V, is λ 1 ≦λ≦λ 1 +15 nm, when λ 2 ≦λ≦λ 2 +15 nm, or when λ 3 ≦λ≦λ 3 +15 nm, the reflection factor in the optical functional surfaces 53 V, is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 V, is λ 1 ≦λ≦λ 3 +120 nm, because the reflection factor in the optical functional surface 52 V is not larger than 1.5%, the reflection can be prevented for the wavelengths in these regions. Further, in the optical functional surface 53 V, when the wavelength λ is a wavelength in the range of λ 1 +15 nm<λ<λ 2 , because the reflection factor shows the local maximal value larger than 1%, different from the conventional one, the number of layers of the antireflective film 51 V can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 V can be suppressed.

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 V by the stress of the antireflective film 51 V, or the adherence between the antireflective film 51 V and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 V is described as the light incidence surface, and the optical functional surface 53 V is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 V is the light projection surface, and the optical functional surface 53 V is the light incidence surface.

The 22nd Embodiment

The optical pick-up device 1 W in the present 22nd embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 W in place of the objective lens 5 B.

The objective lens 5 W is, as shown in FIG. 2 , provided with a lens main body 50 , and a antireflective film 51 W.

The antireflective film 51 W is provided on both surfaces of the lens main body 50 , and forms the optical functional surfaces 52 W and 53 W.

In the optical functional surface 52 W, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%.

In the optical functional surface 53 W, when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 2 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 53 W, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 W described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 W, when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 52 W, is λ 1 ≦λ≦λ 3 +30 nm, the reflection factor in the optical functional surfaces 52 W, is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 53 W, is λ 1 ≦λ≦λ 1 +50 nm, or when it is λ 2 ≦λ≦λ 3 +30 nm, because the reflection factor in the optical functional surface 53 W is not larger than 1%, the reflection can be prevented for the wavelengths in these zones. Further, in the optical functional surface 53 W, when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , because the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, different from the conventional one, the number of layers of the antireflective film 51 W can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 W can be suppressed.

›DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT · 22 of 22

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 W by the stress of the antireflective film 51 W, or the adherence between the antireflective film 51 W and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the present embodiment, the optical functional surface 52 W is described as the light incidence surface, and the optical functional surface 53 W is described as the light projection surface, however, it may also be allowable that the optical functional surface 52 W is the light projection surface, and the optical functional surface 53 W is the light incidence surface.

The 23rd Embodiment

The optical pick-up device 1 X in the present 23rd embodiment is, different from the above third optical pick-up device 1 B, provided with an objective lens 5 X in place of the objective lens 5 B.

The objective lens 5 X is, as shown in FIG. 4 , provided with two lens main bodies 501 and 502 and a antireflective film 51 X.

The lens main body 501 is arranged on laser light sources 2 a - 2 c side, and the lens main body 502 is arranged on the information recording medium side such as AOD 100 .

The antireflective film 51 X is provided on both surfaces of each of lens main bodies 501 , 502 , and forms the optical functional surfaces 54 - 57 .

In the optical functional surface 54 on laser light sources 2 a - 2 c side, and the optical functional surface 55 on the information recording medium side, when the wavelength λ of the light flux incident perpendicularly is λ 1 =λ 2 , when λ=λ 2 , and when λ=λ 3 , the reflection factor is suppressed to not larger than 1%.

In the optical functional surface 56 on laser light sources 2 a , 2 b side to the lens main body 502 , when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. In the optical functional surface 57 on the information recording medium side to the lens main body 502 , when the wavelength λ of the light flux incident perpendicularly is λ 1 ≦λ≦λ 1 +50 nm, and when λ 2 ≦λ≦λ 3 +30 nm, the reflection factor is suppressed to not larger than 1%. Further, in the optical functional surface 57 , when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , the reflection factor shows the local maximal value larger than 1%.

The operation of the optical pick-up device 1 X described above is the same as in the optical pick-up device 1 B in the above third embodiment.

According to this optical pick-up device 1 X, when the wavelength λ of the light flux incident perpendicularly to the optical functional surfaces 54 and 55 , is λ=λ 1 , when λ=λ 2 , and when λ=λ 3 , the reflection factor in the optical functional surfaces 54 and 55 , is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 56 , is λ 1 ≦λ≦λ 3 +30 nm, the reflection factor in the optical functional surfaces 56 , is not larger than 1%, and when the wavelength λ of the light flux incident perpendicularly to the optical functional surface 57 , is λ 1 λ≦λ 1 +50 nm, or when λ 2 ≦λ≦λ 3 +30 nm, because the reflection factor in the optical functional surface 57 is not larger than 1%, the reflection can be prevented for the wavelengths in these zones. Further, in the optical functional surface 57 , when the wavelength λ is a wavelength in the range of λ 1 +50 nm<λ<λ 2 , because the reflection factor shows the local maximal value larger than 1%, that is, the reflection prevention function is lowered. Therefore, different from the conventional one, the number of layers of the antireflective film 51 X can be reduced, without deteriorating the reflection prevention function for the first light flux, second light flux, and third light flux. Accordingly, the production cost can be reduced, and a change of the spectral characteristic by penetration of the water between layers of the antireflective film 51 X can be suppressed.

Further, even when the lens main body 50 is made of optical plastic, it can be prevented that a crack is generated in the antireflective film 51 X by the stress of the antireflective film 51 X, or the adherence between the antireflective film 51 X and the lens main body 50 is lowered, that is, the environmental resistance can be increased.

Hereupon, in the 1st-23rd embodiments, the numerical aperture of the objective lenses 5 , 5 A- 5 X, is described as 0.65, however, it may also be 0.85-0.9. In this case, as the information recording medium, the blu-ray disc whose protective substrate thickness is 0.1 mm, can be used in place of AOD 100 .

Further, in the 1st-12th and 14th-22nd embodiments, the objective lens is described as that it is provided with a lens main body and the antireflective film provided on both surfaces of the lens main body, however, it may also be provided with 2 or more lens main bodies and the antireflective films provided on the surfaces of each of lens main bodies.

Further, in the 1st-23rd embodiments, the optical element is described as the objective lens 5 , however, it may also be a beam shrinker, or beam expander.

›EXAMPLE

By listing Examples and comparative Examples, the present invention will be more specifically described below. Hereupon, in the following Examples, it is defined that the wavelength λ 1 is 405 nm, λ 2 is 650 nm, and λ 3 is 780 nm.

›Examples18

›Example 1

In Example 1, the antireflective film 51 of the objective lens 5 in the above 1st Embodiment, is structured by 2 layers as shown in Table 1. Hereupon, the lens main body is formed of BK7 (trade name, made by Shot glass Co.).

As a result of measurement of the relationship of the reflection factor in optical functional surfaces 52 and 53 of the objective lens 5 and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces 52 and 53 shows, as shown in FIG. 5 , the local maximal value larger than 2% between the wavelength λ 1 and wavelength λ 2 , however, shows the minimum value lower than 1% in the vicinity of the wavelengths λ 1 and λ 2 .

From this, the objective lens 5 in the present example 1 has the reflection prevention function for the first light flux of wavelength λ 1 and the second light flux of wavelength λ 2 , and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 2

In Example 2 , the antireflective film 51 A of the objective lens 5 A in the second embodiment is structured by 3 layers as shown in Table 2.

The relationship of the reflection factor in optical functional surfaces 52 A and 53 A of this objective lens 5 A and the wavelength of the incident ray of light is measured.

As a result of the measurement, the reflection factor of the optical functional surfaces 52 A and 53 A of the objective lens 5 A shows, as shown in FIG. 6 , the local maximal value larger than 2% between the wavelength λ 1 and wavelength λ 2 , however, shows that it is not larger than 1% in the wavelength range of a broad region including the wavelength λ 1 and λ 2 .

From this, the objective lens 5 A in the present example 2 has the reflection prevention function for the first light flux wavelength λ 1 and the second light flux of wavelength λ 2 , and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 3

In Example 3 , the antireflective film 51 B of the objective lens 5 B in the third embodiment is structured by 4 layers as shown in Table 3.

As a result of measurement of the relationship of the reflection factor in optical functional surfaces 52 B and 53 B of this objective lens 5 B and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces 52 B, 53 B shows, as shown in FIG. 7 , the local maximal value larger than 2% between the wavelength λ 1 and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 , and λ 3 .

From this, the objective lens 5 B in the present example 3 has the reflection prevention function for the first light flux of wavelength λ 1 and the second light flux of wavelength λ 2 , and the third light flux of wavelength λ 3 , and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 4

In Example 4, the antireflective film 51 B of the objective lens 5 B in the third embodiment is structured by 6 layers as shown in Table 4.

As a result of measurement of the relationship of the reflection vector in optical functional surfaces 52 B, 53 B of this objective lens 5 B and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces 52 B and 53 B shows, as shown in FIG. 8 , the local maximal value larger than 2% between the wavelength λ 1 and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 , and λ 3 .

From this, the objective lens 5 B in the present example 4 has the reflection prevention function for the first light flux of wavelength λ 1 , the second light flux of wavelength λ 2 , and the third light flux of wavelength λ 3 , and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 5

In Example 5, the objective lens 5 C in the embodiments 4, 5 and 6, is structured as a lens of so-called 2-lens composition as shown in Table 5. Hereupon, the lens of 2-lens composition means that it is provided with 2 lens main bodies. The focal distance of this objective lens 5 C is 2.2 mm to the light flux of wavelength 408 nm.

Herein, in Table 5, S 1 -S 4 are respectively optical functional surfaces of objective lens 5 C, and they are positioned in order of S 1 -S 4 toward the information recording medium such as AOD 100 from laser light sources 2 a , 2 b.

In more detail, the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 2-layer structure shown in Table 1. Further, the optical functional surfaces S 3 , S 4 are formed of the antireflective film of 7-layer structure shown in Table 6.

As a result of measurement of the transmission factor of the objective lens 5 C, it shows a good value as in the case that the transmission factor to the light flux of the wavelength 408 nm is 98%, and the transmission factor to the light flux of the wavelength 658 nm is 98%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 , of this objective lens 5 C, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 3 and S 4 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelength λ 1 and λ 2 .

From this, the objective lens 5 C in the present example 5 has the reflection prevention function for the first light flux, the second light flux, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 6

In Example 6, the objective lens 50 in the embodiments 14, 15, 16, is structured as a lens of so-called 2-lens composition as shown in Table 5.

In more detail, the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 6-layer structure shown in Table 4. Further, the optical functional surfaces S 3 , S 4 are formed of the antireflective film of 7-layer structure shown in Table 6.

As a result of measurement of the transmission factor of this objective lens 50 , it shows a good value in which the transmission factor to the light flux of the wavelength 408 nm is 98%, the transmission factor to the light flux of the wavelength 658 nm is 98%, and the transmission factor to the light flux of the wavelength 785 nm is 97%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 , S 2 , of this objective lens 50 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 , S 2 shows, as shown in FIG. 8 , the local maximal value larger than 1% between the wavelength λ 1 +15 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 , and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 3 and S 4 , of this objective lens 50 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 3 , S 4 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 , and λ 3 .

From this, the objective lens 50 in the present example 6 has the reflection prevention function for the first-third light fluxes by the antireflective film 510 whose number of layers is small, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased

›Example 7

In Example 7, the objective lenses 5 F, 51 , 5 J and 5 K in the embodiments 7, 9, 10, 11 and 13 are structured as a lens of so-called 2-lens composition as shown in Table 5.

In more detail, the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 2-layer structure shown in Table 1. Further, the optical functional surface S 3 is formed of the antireflective film of 5-layer structure shown in Table 7.

As a result of measurement of the transmission factor of this objective lens, it shows a good value in which the transmission factor to the light flux of the wavelength 408 nm is 98%, and the transmission factor to the light flux of the wavelength 658 nm is 98%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 , S 2 of this objective lens 5 F, 51 , 5 J and 5 K, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 and S 2 shows, as shown in FIG. 5 , the local maximal value larger than 1% between the wavelength λ 1 +15 nm and wavelength λ 2 , however, shows that it is not larger than 1.5% in the vicinity of wavelengths λ 1 and λ 2 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 4 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 4 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 and λ 2 .

From this, the objective lens in the present example 7 has the reflection prevention function for the first light flux, the second light flux, by the antireflective film whose number of layers is small, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 8

In Example 8, the objective lenses 5 Q, 5 T, 5 U and 5 W in the embodiments 17, 19, 20, 21 and 23 are structured as a lens of so-called 2-lens composition as shown in Table 5.

In more detail, the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 6-layer structure shown in Table 4. Further, the optical functional surface S 3 is formed of the antireflective film of 9-layer structure shown in Table 8. Further, the optical functional surface S 4 is formed of the antireflective film of 7-layer structure shown in Table 6.

As a result of measurement of the transmission factor of these objective lenses 5 Q, 5 T, 5 U and 5 W, it shows a good value in which the transmission factor to the light flux of the wavelength 408 nm is 98%, the transmission factor to the light flux of the wavelength 658 nm is 98%, and the transmission factor to the light flux of the wavelength 785 nm is 97%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 of these objective lens 5 Q, 5 T, 5 U and 5 W, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 and S 2 shows, as shown in FIG. 8 , the local maximal value larger than 1% between the wavelength λ 1 +15 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 3 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 3 shows, as shown in FIG. 11 , that it is not larger than 1.5% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 4 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 4 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and the wavelength λ 2 , however, it shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

From this, the objective lenses 5 q , 5 T, 5 U and 5 W in the present example 8 has the reflection prevention function for the first-third light flux, by the antireflective films 51 Q, 51 T, 51 U and 51 W, whose number of layers is small, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 9

In Example 9, the objective lenses 5 D in the embodiment is structured as a lens of so-called 1 -lens composition as shown in Table 9. The focal distance of this objective lens 5 E is 2.0 mm to the light flux of wavelength 405 nm.

Herein, in Table 9, S 1 and S 2 are respectively optical functional surfaces of objective lens 5 D, and S 1 is positioned on laser light sources 2 a and 2 b side, and S 2 is positioned on the information recording medium such as AOD 100 , to the lens main body 50 .

In more detail, the optical functional surfaces S 1 and S 2 are formed of the antireflective film of 7-layer structure shown in Table 6.

As a result of measurement of the transmission factor of this objective lens 5 D, it shows a good value in which the transmission factor to the light flux of the wavelength 408 nm is 98%, and the transmission factor to the light flux of the wavelength 658 nm is 98%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 of this objective lens 5 D, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 and S 2 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 and λ 2 .

From this, the objective lenses 5 D in the present example 9 has the reflection prevention function for the first, second light flux, by the antireflective film 51 D whose number of layers is small, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 10

In Example 10, the objective lens 50 in the embodiment 15 is structured as a lens of so-called 1 -lens composition as shown in Table 9.

In more details, the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 7-layer composition shown in the Table 6.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 , S 2 of this objective lens 50 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 , S 2 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

From this, it can be seen that the objective lens 50 in the present example 10 has the reflection prevention function for the first-third light flux by the antireflective film 510 whose number of layers is small, and that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 11

In Example 11, the objective lens 5 K in the embodiments 11 and 12 is structured as a lens of so-called 1 -lens composition as shown in Table 9.

In more details, the optical functional surfaces S 1 is formed of the antireflective film of 5-layer composition shown in the Table 7 and S 2 is formed of the antireflective film of 7-layer composition shown in the Table 6.

As a result of measurement of the transmission factor of this objective lens 5 K, it shows a good value in which the transmission factor to the light flux of the wavelength 408 nm is 98%, and the transmission factor to the light flux of the wavelength 658 nm is 98%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 1 of this objective lens 5 K, and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 1 shows, as shown in FIG. 10 , the local maximal value larger than 1% between the wavelength λ 1 +15 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 and λ 2 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 2 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 2 shows, as shown in FIG. 9 , the local maximal value larger than 1% between the wavelength λ 1 +15 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 and λ 2 .

From this, it can be seen that the objective lens 5 K in the present example 11 has the reflection prevention function for the first and second light fluxes by the antireflective film 51 K whose number of layers is small, and that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 12

In Example 12, the objective lens 5 V in the embodiments 21, 22 is structured as a lens of so-called 1 -lens composition as shown in Table 9.

In more details, the optical functional surfaces S 1 is formed of the antireflective film of 9-layer composition shown in the Table 8, and S 2 is formed of the antireflective film of 7-layer composition shown in the Table 6.

As a result of measurement of the transmission factor of this objective lens 5 V, it shows a good value in which the transmission factor to the light flux of the wavelength 408 nm is 98%, the transmission factor to the light flux of the wavelength 658 nm is 98%, and the transmission factor to the light flux of the wavelength 785 nm is 97%.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 1 of this objective lens 5 V, and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 1 shows, as shown in FIG. 11 , that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 , and λ 3 .

From this, it can be seen that the objective lens 5 V in the present example 12 has the reflection prevention function for the first-third light fluxes by the antireflective film 51 V whose number of layers is small, and that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 13

In Example 13, the objective lens 5 W in the embodiment 15, is structured as a lens of so-called 1 -lens composition, and the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 10-layer structure shown in Table 11. In the antireflective film, a value of ((the maximum film thickness in the effective diameter)−(the minimum film thickness in the effective diameter))/average film thickness, is made not larger than 5%, and the film thickness distribution is made uniform.

In the optical pick-up device 1 W using this objective lens 5 W, the recording and reproducing can be surely conducted by the first-third light fluxes. When the transmission factor of the P-polarization and S-polarization of the first-third light fluxes is measured, it is almost equal as shown in Table 10.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 , of this objective lens 5 W, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 and S 2 shows, as shown in FIG. 12 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of λ 1 , λ 2 and λ 3 .

From this, the objective lens 5 W in the present example 13 has the reflection prevention function for the first-third light fluxes, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased. Further, because there is not a case where the incident light amount of the light detector is decreased due to the separation of the transmission factor of the P-polarization and S-polarization, it can be seen that the dependability of the recording and reproducing can be more increased.

›Example 14

In Example 14, the objective lens 5 W in the embodiment 22 is structured as a lens of so-called 1 -lens composition, and the optical functional surface S 1 is formed of the antireflective film of 9-layer structure shown in the Table 12, and the optical functional surface S 2 is formed of the antireflective film of 9-layer structure shown in the Table 13. In the antireflective film, a value of)(the maximum film thickness in the effective diameter)−(the minimum film thickness in the effective diameter))/average film thickness, is made not larger than 5%, and the film thickness distribution is made uniform.

In the optical pick-up device 1 W using this objective lens 5 W, the recording and reproducing can be securely conducted by the first-third light fluxes.,

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 1 of this objective lens 5 W, and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 1 shows, as shown in FIG. 13 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 2 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 2 shows, as shown in FIG. 14 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

From this, the objective lens 5 W in the present example 14 has the reflection prevention function for the first-third light fluxes, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 15

In Example 15, the objective lens 5 W in the embodiment 22 is structured as a lens of so-called 1 -lens composition, and the optical functional surface S 1 is formed of the antireflective film of 9-layer structure shown in the Table 12, and the optical functional surface S 2 is formed of the antireflective film of 9-layer structure shown in the Table 13. In the antireflective film, a value of ((the maximum film thickness in the effective diameter)−(the minimum film thickness in the effective diameter))/average film thickness, is made larger than 5%, and the film thickness distribution is made un-uniform.

When the transmission factor of this objective lens 5 W is measured, the transmission factor is a little lower than the objective lens 5 W in the present example 14, however, also in the optical pick-up device 1 W using the objective lens 5 W in the present example 15, the recording and reproducing can be securely conducted by the first-third light fluxes.

From this, the objective lens 5 W in the present example 15 has the reflection prevention function for the first-third light fluxes, and it can be seen that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 16

In Example 16, the objective lens 5 W in the embodiment 15, is structured as a lens of so-called 2-lens composition, and the optical functional surfaces S 1 and S 2 are formed of the antireflective film of 6-layer structure shown in Table 4, and the optical functional surfaces S 3 , S 4 are formed of the antireflective film of 10-layer structure shown in Table 11. In the antireflective film, a value of ((the maximum film thickness in the effective diameter)−(the minimum film thickness in the effective diameter))/average film thickness, is made not larger than 5%, and the film thickness distribution is made uniform.

In the optical pick-up device 1 X using this objective lens 5 X, the recording and reproducing can be securely conducted by the first-third light fluxes. When the transmission factors of the P-polarization and S-polarization of the first-third light fluxes are measured, they are almost equal as shown in Table 14.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 of this objective lens 5 X, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 and S 2 shows, as shown in FIG. 8 , the local maximal value larger than 1% between the wavelength λ 1 +15 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 3 and S 4 and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 3 , S 4 shows, as shown in FIG. 12 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

From this, it can be seen that the objective lens 5 X in the present example 16 has the reflection prevention function for the first-third light fluxes by the antireflective film 51 X whose number of layers is small, and that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased. Further, because there is not a case where the incident light amount of the light detector is decreased due to the separation of the transmission factor of the P-polarization and S-polarization, it can be seen that the dependability of the recording and reproducing can be more increased.

›Example 17

In Example 17, the objective lens 5 X in the embodiment 23, is structured as a lens of so-called 2-lens composition, and the optical functional surfaces S 1 and S 2 are formed of the antireflective film of 6-layer structure shown in Table 4, the optical functional surface S 3 , is formed of the antireflective film of 9-layer structure shown in Table 12, and the optical functional surface S 4 is formed of the antireflective film of 9-layer structure shown in Table 13. In the antireflective film, a value of ((the maximum film thickness in the effective diameter)−(the minimum film thickness in the effective diameter))/average film thickness, is made not larger than 5%, and the film thickness distribution is made uniform.

In the optical pick-up device 1 X using this objective lens 5 X, the recording and reproducing can be securely conducted by the first-third light fluxes.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 of this objective lens 5 X, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 , S 2 shows, as shown in FIG. 8 , the local maximal value larger than 1% between the wavelength λ 1 and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 3 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 3 shows, as shown in FIG. 13 , that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 4 and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 4 shows, as shown in FIG. 14 , the local maximal value larger than 1% between the wavelength λ 1 +50 nm and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

From this, it can be seen that the objective lens 5 X in the present example 17 has the reflection prevention function for the first-third light fluxes by the antireflective film 51 X whose number of layers is small, and that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

›Example 18

In Example 18, the objective lens 5 X in the embodiment 23, is structured as a lens of so-called 2-lens composition, and the optical functional surfaces S 1 , S 2 are formed of the antireflective film of 6-layer structure shown in Table 4, the optical functional surface S 3 , is formed of the antireflective film of 9-layer structure shown in Table 12, and the optical functional surface S 4 is formed of the antireflective film of 9-layer structure shown in Table 13. In the antireflective film, a value of ((the maximum film thickness in the effective diameter)−(the minimum film thickness in the effective diameter))/average film thickness, is made larger than 5%, and the film thickness distribution is made un-uniform.

When the transmission factor of this objective lens 5 X is measured, the transmission factor is a little lower than the objective lens 5 X in the present example 17, however, also in the optical pick-up device 1 X using the objective lens 5 X in the present example 18, the recording and reproducing can be securely conducted by the first-third light fluxes.

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surfaces S 1 and S 2 of this objective lens 5 X, and the wavelength of the incident ray of light, the reflection factor of the optical functional surfaces S 1 and S 2 shows, as shown in FIG. 8 , the local maximal value larger than 1% between the wavelength λ 1 and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 3 , and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 3 shows, as shown in FIG. 13 , that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

Further, as a result of measurement of the relationship between the reflection factor in the optical functional surface S 4 and the wavelength of the incident ray of light, the reflection factor of the optical functional surface S 4 shows, as shown in FIG. 14 , the local maximal value larger than 1% between the wavelength λ 1 +50 rim and wavelength λ 2 , however, shows that it is not larger than 1% in the vicinity of wavelengths λ 1 , λ 2 and λ 3 .

From this, it can be seen that the objective lens 5 X in the present example 18 has the reflection prevention function for the first-third light fluxes by the antireflective film 51 X whose number of layers is small, and that, by preventing the lowering of transmission light amount, the dependability of the recording and reproducing can be increased.

According to the structure written in item 1 , the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function for the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by the penetration of water between layers of the antireflective film can be suppressed.

According to the structure written in item 2 , it is of course that the same effect as the structure written in item 1 can be obtained, and the reflection of the light flux of using wavelength λ 1 of AOD or blu-ray disc, the light flux of using wavelength λ 2 of DVD, and the light flux of using wavelength λ 3 of CD, can be prevented by the antireflective film whose number of layers is small.

According to the structure written in item 3 , it is of course that the same effect as the structure written in item 1 or item 2 can be obtained, and the accurate recording or reproducing of the information can be conducted by using the light flux of 0°≦θmax≦40°.

According to the structure written in items 4 - 6 , it is of course that the same effect as the structure written any one of items 1 - 3 , can be conducted, and the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function.

According to the structures written in 7 , 9 , 11 , 13 , 15 , 17 , 19 , 21 , 23 , and 25 , the number of layers of the antireflective film can be reduced without deteriorating the reflection prevention function for the light flux of wavelength λ 1 and the light flux of wavelength λ 2 . Accordingly, the production cost can be reduced, and a change of the spectral characteristic by the penetration of water between layers of the antireflective film can be suppressed.

According to the structures written in items 8 , 10 , 12 , 14 , 16 , 18 , 20 , 22 , 24 , and 26 , it is of course that the same effect as the structures written in items 7 , 9 , 11 , 13 , 15 , 17 , 19 , 21 , 23 , and 25 , can be obtained, and the reflection can be prevented also for the wavelength λ in the zone near λ 3 (760≦λ 3 ≦800 nm).

According to the structure written in item 27 , the same effect as the structure written in any one of items 1 - 27 can be obtained.

According to the structure written in items 28 and 30 , the same effect as the structure written in any one of items 1 - 27 can be obtained.

According to the structure written in items 29 and 31 , the same effect as the structure written in items 28 and 30 can be obtained.

According to the structure written in items 32 and 33 , the same effect as the structure written in any one of items 1 - 31 can be obtained.

According to the structure written in item 34 , it is of course that the same effect as the structure written in any one of items 1 - 33 can be obtained, and because the primary coat exists between the optical element main body and antireflective film, the adhesion of the antireflective film to the optical element main body can be increased. According to the structure written in item 35 , the same effect as the structure written in any one of items 1 - 34 can be obtained.

›Tables in the description — 14

TABLE 1

Layer	Material	Index	Thickness
Air		1
2	SiO 2	1.46	85.62
1	Ta 2 O 5	2.06	121.34
Lens	BK7	1.52

TABLE 2

Layer	Material	Index	Thickness
Air		1
3	MgF 2	1.38	95.03
2	Al 2 O 3	1.62	61.56
1	CeO 2	1.81	84.62
Lens	BK7	1.52

TABLE 3

Layer	Material	Index	Thickness
Air		1
4	SiO 2	1.46	112.22
3	Ta 2 O 5	2.06	122.1
2	SiO 2	1.46	39.21
1	Ta 2 O 5	2.06	27.26
Lens	Optical	1.51
	plastic

TABLE 4

Layer	Material	Index	Thickness
Air		1
6	SiO 2	1.46	100.00
5	Ta 2 O 5	2.06	26.60
4	SiO 2	1.46	10.00
3	Ta 2 O 5	2.06	94.00
2	SiO 2	1.46	39.00
1	Ta 2 O 5	2.06	19.00
Lens	Optical	1.51
	plastic

TABLE 5 — 2-lens composition Focal distance = 2.2 (mm) (λ = 408 nm)

	λ =	λ =	λ =
Lens composition	405 nm	650 nm	780 nm
NA	0.87	0.67	0.51
S1	S1 maximum surface angle (°)	18	5.3	3.8
	S1 maximum incident angle (°)	18	10.1	9.9
S2	S2 maximum surface angle (°)	7.7	0.9	1.8
	S2 maximum incident angle (°)	12.3	1.6	5.1
S3	S3 maximum surface angle (°)	69.7	58.9	48
	S3 maximum incident angle (°)	65.1	59.6	51.3
S4	S4 maximum surface angle (°)	1.8	1.9	4.5
	S4 maximum incident angle (°)	56.4	44	35.2

TABLE 6

Layer	Material	Index	Thickness
Air		1
7	SiO 2	1.47	98.22
6	Ta 2 O 5	2.12	47.90
5	SiO 2	1.47	15.00
4	Ta 2 O 5	2.12	64.02
3	SiO 2	1.47	35.44
2	Ta 2 O 5	2.12	15.44
1	SiO 2	1.47	239.00
Lens	BK7	1.53

TABLE 7

Layer	Material	Index	Thickness
Air		1
5	SiO 2	1.46	92.43
4	Ta 2 O 5	2.06	137.51
3	SiO 2	1.46	35.21
2	Ta 2 O 5	2.06	16.74
1	SiO 2	1.46	226.48
Lens	Optical	1.55
	plastic

TABLE 8

Layer	Material	Index	Thickness
Air		1
9	SiO 2	1.46	99.27
8	Ta 2 O 5	2.06	40.94
7	SiO 2	1.46	10.01
6	Ta 2 O 5	2.06	80.77
5	SiO 2	1.46	23.92
4	Ta 2 O 5	2.06	18.42
3	SiO 2	1.46	25.27
2	Ta 2 O 5	2.06	6.43
1	SiO 2	1.46	182.83
Lens	BK7	1.52

TABLE 9 — 1-lens composition Focal distance = 2.0 mm (λ = 405 nm) λ =

	Lens composition	λ = 405 nm	λ = 650 nm	780 nm
NA	0.85	0.65	0.5
S1	S1 maximum surface angle (°)	70.6	55	49.2
	S1 maximum ray angle (°)	70.6	56.2	53.1
S2	S2 maximum surface angle (°)	6.6	1.3	2.9
	S2 maximum ray angle (°)	51.6	41.9	33

TABLE 10

Example	Example 13	Example 14	Example 15
	S1	Table 11	Table 12	Table 12
	S2	Table 11	Table 13	Table 13
Film thickness	Uniform	Uniform	Un-uniform
distribution
408 nm	P-wave	98.5	99.0	98.8
	transmission
	factor (%)
	S-wave	98.5	95.8	95.0
	transmission
	factor (%)
	Average	98.3	97.1	96.7
	transmission
	factor (%)
658 nm	P-wave	99.1	99.2	98.9
	transmission
	factor (%)
	S-wave	97.6	94.3	95.9
	transmission
	factor (%)
	Average	98.1	96.5	97.2
	transmission
	factor (%)
785 nm	P-wave	98.4	98.7	98.2
	transmission
	factor (%)
	S-wave	98.4	97.0	96.6
	transmission
	factor (%)
	Average	98.2	97.6	97.1
	transmission
	factor (%)

TABLE 11

Layer	Material	Index	Thickness
Air		1
10	MgF 2	1.39	106.21
9	TiO 2	2.50	18.98
8	Al 2 O 3	1.65	25.44
7	TiO 2	2.50	92.11
6	Al 2 O 3	1.65	30.61
5	TiO 2	2.50	19.32
4	Al 2 O 3	1.65	77.25
3	TiO 2	2.50	10.43
2	MgF 2	1.39	43.24
1	Al 2 O 3	1.65	71.06
Lens	BK7	1.53

TABLE 12

Layer	Material	Index	Thickness
Air		1
9	SiO 2	1.46	106.08
8	Ta 2 O 5	2.06	40.23
7	SiO 2	1.46	10.67
6	Ta 2 O 5	2.06	85.89
5	SiO 2	1.46	26.22
4	Ta 2 O 5	2.06	16.89
3	SiO 2	1.46	15.79
2	Ta 2 O 5	2.06	9.65
1	SiO 2	1.46	190.96
Lens	Optical	1.55
	plastic

TABLE 13

Layer	Material	Index	Thickness
Air		1
9	SiO 2	1.46	100.84
8	Ta 2 O 5	2.06	38.94
7	SiO 2	1.46	11.75
6	Ta 2 O 5	2.06	78.7
5	SiO 2	1.46	34.17
4	Ta 2 O 5	2.06	8.22
3	SiO 2	1.46	15
2	Ta 2 O 5	2.06	5.27
1	SiO 2	1.46	212.21
Lens	Optical	1.55
	plastic

TABLE 14 — Example

	Example 16	Example 17	Example 18
Name of	S1	Table 4	Table 4	Table 4
coats	S2	Table 4	Table 4	Table 4
	S3	Table 11	Table 12	Table 12
	S4	Table 11	Table 13	Table 13
Film thickness	Uniform	Uniform	Un-uniform
distribution
408 nm	P-wave	98.3	98.8	98.6
	transmission
	factor (%)
	S-wave	98.2	95.5	94.9
	transmission
	factor (%)
	Average	98.3	97.1	96.7
	transmission
	factor (%)
658 nm	P-wave	98.8	98.9	98.6
	transmission
	factor (%)
	S-wave	97.4	94.1	95.7
	transmission
	factor (%)
	Average	98.1	96.5	97.2
	transmission
	factor (%)
785 nm	P-wave	98.2	98.5	98.0
	transmission
	factor (%)
	S-wave	98.1	96.7	96.3
	transmission
	factor (%)
	Average	98.2	97.6	97.1
	transmission
	factor (%)

Claims as granted

37 claims

Classifications

4 codes

IPC · International Patent Classification

Section G — Physics

G11B7/135
G11B7/00

USPC · US Patent Classification

369/112.23369/121

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