Imaging lens assembly

The present invention relates to an imaging lens assembly, and more particularly to an imaging lens assembly which is suitable for installation into an image input device of a portable telephone or personal computer, a digital camera, a CCD camera used for monitoring purposes, a surveying device, or similar.

Imaging apparatuses using solid-state image sensing devices such as CCD (Charge-Coupled Device) type image sensors and CMOS (Complementary Metal-Oxide Semiconductor) type image sensors include digital still cameras, digital video cameras, and the like. Imaging apparatuses using such solid-state image sensing devices are suitable for miniaturization, and hence have recently been mounted in compact information terminals such as cellular phone sets.

With increases in the miniaturization and pixel density of solid-state image sensing devices, demands have arisen for smaller and higher-performance imaging lenses assembly to be mounted in these imaging apparatuses. The imaging lenses assembly used for such an application includes, in order from an object side to an image side: a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens having a negative refractive power.

The imaging lens assembly disclosed in Japanese Patent Application Unexamined Publication (Kokai) No. 2014-098896 has four lenses as set forth. However, the distribution of the refractive powers of the first and second lenses and the shape thereof are unsuitable, thus it is worse for miniaturization and wide-angle of the imaging lens assembly.

The imaging lens assembly disclosed in Japanese Patent No. 5370619 has four lenses as set forth. Among these lenses, the distribution of the refractive power of the second lens and the shapes of the first and second lenses are unsuitable, which makes it difficult to miniaturize the imaging lens assembly.

Accordingly, an improved imaging lens assembly which can overcome the disadvantages described above is desired.

Many aspects of the embodiment can be better understood with reference to the following drawings. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an illustrative structure of an imaging lens assembly related to the present disclosure.

FIG. 2 is an illustrative structure of an imaging lens assembly related to a first embodiment of the present disclosure.

FIG. 3 is an aberration curve showing spherical aberration (on-axis chromatic aberration) of the imaging lens assembly of the first embodiment.

FIG. 4 is an aberration curve showing the ratio chromatic aberration of the imaging lens assembly of the first embodiment.

FIG. 5 is an aberration curve showing the curvature of field and the distortion of the imaging lens assembly of the first embodiment.

FIG. 6 is an illustrative structure of an imaging lens assembly related to a second embodiment of the present disclosure.

FIG. 7 is an aberration curve showing spherical aberration (on-axis chromatic aberration) of the imaging lens assembly of the second embodiment.

FIG. 8 is an aberration curve showing the ratio chromatic aberration of the imaging lens assembly of the second embodiment.

FIG. 9 is an aberration curve showing the curvature of field and the distortion of the imaging lens assembly of the second embodiment.

FIG. 10 is an illustrative structure of an imaging lens assembly related to a third embodiment of the present disclosure.

FIG. 11 is an aberration curve showing spherical aberration (on-axis chromatic aberration) of the imaging lens assembly of the third embodiment.

FIG. 12 is an aberration curve showing the ratio chromatic aberration of the imaging lens assembly of the third embodiment.

FIG. 13 is an aberration curve showing the curvature of field and the distortion of the imaging lens assembly of the third embodiment.

FIG. 14 is an illustrative structure of an imaging lens assembly related to a fourth embodiment of the present disclosure.

FIG. 15 is an aberration curve showing spherical aberration (on-axis chromatic aberration) of the imaging lens assembly of the fourth embodiment.

FIG. 16 is an aberration curve showing the ratio chromatic aberration of the imaging lens assembly of the fourth embodiment.

FIG. 17 is an aberration curve showing the curvature of field and the distortion of the imaging lens assembly of the fourth embodiment.

The present invention will hereinafter be described in detail with reference to several embodiments.

Referring to FIG. 1 , an imaging lens assembly LA related to the present disclosure includes, in order from an object side to an image side: an aperture stop S 1 , a first lens L 1 , a second lens L 2 , a third lens L 3 , and a fourth lens L 4 . A glass plate GF is arranged between the fourth lens L 4 and an image plane. The glass plate GF may be a cover glass, an IR filter, or a low frequency filter. Alternatively, the glass plate may be arranged at other position.

The first lens L 1 has a positive refractive power, the second lens L 2 has a negative refractive power, the third lens L 3 has a positive refractive power, and the fourth lens L 4 has a negative refractive power. With the configuration of the refractive powers of the lenses, the imaging lens assembly LA may be miniaturized. Further, for correcting aberrations appropriately, these four lenses are configured to be aspherical.

The imaging lens assembly LA satisfies the following conditions (1)˜(4):

1.08≦ f 1/ f≦ 1.20  (1)

−4.00≦ f 2/ f≦− 2.50  (2)

−1.50≦( R 1+ R 2)/( R 1− R 2)≦−1.25  (3)

1.30≦( R 3+ R 4)/( R 3− R 4)≦5.00  (4)

Wherein: f is a focal length of the imaging lens assembly LA; f 1 is a focal length of the first lens L 1 ; f 2 is a focal length of the second lens L 2 ; R 1 is a curvature radius of the object side surface of the first lens L 1 ; R 2 is a curvature radius of the image side surface of the first lens L 1 ; R 3 is a curvature radius of the object side surface of the second lens L 2 ; R 4 is a curvature radius of the image side surface of the second lens L 2 .

Condition (1) prescribes the positive refractive power of the first lens L 1 . If the value excesses the minimum limit, the positive refractive power of the first lens L 1 is too powerful to correct image aberration, and it is worse for wide-angle of the imaging lens assembly LA. If the value excesses the maximum limit, it weakens the positive refraction power of the first lens L 1 and makes it difficult to miniaturize the imaging lens assembly LA.

Condition (2) prescribed the negative refractive power of the second lens L 2 . If the value excesses the minimum limit, it weakens the negative refractive power of the second lens L 2 , and makes it difficult to correct the on-axis and off-axis chromatic aberration. If the value excesses the maximum limit, the negative refractive power of the second lens L 2 is too powerful to correct image aberrations. Meanwhile, high level image aberration causes axial eccentricity of the second lens L 2 , which further results in image distortion.

Condition (3) prescribes the shape of the first lens L 1 . If the value does not satisfy this condition, it is difficult to correct the high level image aberration, such as the spherical aberration, and so on, with the miniaturization and wide-angle development of the imaging lens assembly LA.

Condition (4) prescribes the shape of the second lens L 2 . If the value does not satisfy this condition, it is difficult to correct the on-axis chromatic aberration, with the miniaturization and wide-angle development of the imaging lens assembly LA.

The third lens L 3 has a positive refractive power, and the imaging lens assembly LA satisfies the following conditions (5)-(6):

0.5 f 3/ f 0.75  (5)

1.40 ( R 5+ R 6)/( R 5− R 6) 2.00  (6)

Wherein: f is the focal length of the imaging lens assembly LA; f 3 is a focal length of the third lens L 3 ; R 5 is a curvature radius of the object side surface of the third lens L 3 ; R 6 is a curvature radius of the image side surface of the third lens L 3 .

Condition (5) prescribes the positive refractive power of the third lens L 3 . If the value excesses the minimum limit, the positive refractive power of the third lens L 3 is too powerful to correct image aberrations. Meanwhile, high level image aberration causes axial eccentricity of the third lens L 3 , which further results in image distortion. If the value excesses the maximum limit, the positive refractive power of the third lens L 3 is weakened and it is difficult to miniaturize the imaging lens assembly LA.

Condition (6) prescribes the shape of the third lens L 3 . If the value does not satisfy this condition, it is worse for correcting image aberrations. Meanwhile, high level image aberration causes axial eccentricity of the third lens L 3 , which further results in image distortion.

The fourth lens L 4 has a negative refractive power, and the imaging lens assembly LA satisfies the following conditions (7)-(8):

− 0 . 80 f 4/ f − 0.60  (7)

1.20 ( R 7+ R 8)/( R 7− R 8) 2.50  (8)

Wherein: f is the focal length of the imaging lens assembly LA; f 4 is a focal length of the fourth lens L 4 ; R 7 is a curvature radius of the object side surface of the fourth lens L 4 ; R 8 is a curvature radius of the image side surface of the fourth lens L 4 .

Condition (7) prescribes the negative refractive power of the fourth lens L 4 . If the value excesses the minimum limit, it is difficult to correct the off-axis chromatic aberration. If the value excesses the maximum limit, high level image aberration causes axial eccentricity of the fourth lens L 4 , which further results in image distortion.

Condition (8) prescribes the shape of the fourth lens L 4 . If the value does not satisfy this condition, it is difficult to correct the off-axis chromatic aberration, with the miniaturization and wide-angle development of the imaging lens assembly LA.

By virtue of the configurations and conditions set forth in the forgoing description, an improved imaging lens assembly LA has the characteristics of miniaturization, wide-angle, TTL/IH 1.5, and 2ω 80°.

Hereinafter, detailed embodiments will be described to test and verify the conditions set forth in the above descriptions.

The parameters of the imaging lens assembly LA are defined as follows, and the unit of each of the distance, radius, and thickness is millimeter (mm).

f: the focal length of the imaging lens assembly LA; f 1 : the focal length of the first lens L 1 ; f 2 : the focal length of the second lens L 2 ; f 3 : the focal length of the third lens L 3 ; f 4 : the focal length of the fourth lens L 4 ; Fno: F number 2ω: full visual angle S 1 : aperture stop R: curvature radius R 1 : the curvature radius of the object side surface of the first lens L 1 ; R 2 : the curvature radius of the image side surface of the first lens L 1 ; R 3 : the curvature radius of the object side surface of the second lens L 2 ; R 4 : the curvature radius of the image side surface of the second lens L 2 ; R 5 : the curvature radius of the object side surface of the third lens L 3 ; R 6 : the curvature radius of the image side surface of the third lens L 3 ; R 7 : the curvature radius of the object side surface of the fourth lens L 4 ; R 8 : the curvature radius of the image side surface of the fourth lens L 4 ; R 9 : the curvature radius of the object side surface of the glass plate GF; R 10 : the curvature radius of the image side surface of the glass plate GF; d: the axial thickness of the lens, or distance between lenses; d 0 : the axial distance between the aperture stop S 1 and the object side surface of the first lens L 1 ; d 1 : the axial thickness of the first lens L 1 ; d 2 : the axial distance between the image side surface of the first lens L 1 and the object side surface of the second lens L 2 ; d 3 : the axial thickness of the second lens L 2 ; d 4 : the axial distance between the image side surface of the second lens L 2 and the object side surface of the third lens L 3 ; d 5 : the axial thickness of the third lens L 3 ; d 6 : the axial distance between the image side surface of the third lens L 3 and the object side surface of the fourth lens L 4 ; d 7 : the axial thickness of the fourth lens L 4 ; d 8 : the axial distance between the image side surface of the fourth lens L 4 and the object side surface of the glass plate GF; d 9 : the axial thickness of the lass plate GF; d 10 : the axial distance between the image side surface of the glass plate GF and the image plane; nd: d line refraction index n 1 : d line refraction index of the first lens L 1 ; n 2 : d line refraction index of the second lens L 2 ; n 3 : d line refraction index of the third lens L 3 ; n 4 : d line refraction index of the fourth lens L 4 ; n 5 : d line refraction index of the glass plate GF; υd: abbe number υ 1 : abbe number of the first lens L 1 ; υ 2 : abbe number of the second lens L 2 ; υ 3 : abbe number of the third lens L 3 ; υ 4 : abbe number of the fourth lens L 4 ; υ 5 : abbe number of the glass plate GF; TTL: the axial distance between the aperture stop and the image plane (total track length); IH: image height.

y =( x 2 /R )/[1+{1−( k+ 1)( x 2 /R 2 )} 1/2 ]+A 4 x 4 +A 6 x 6 +A 8 x 8 ++A 10 x 10 +A 12 x 12 +A 14 A 14   (9)

Wherein, R is axial curvature radius, k is the conic coefficient, A 4 , A 6 , A 8 , A 10 , A 12 , A 14 are the aspherical coefficients.

Optionally, each aspherical surface of each lens could be obtained according to condition (9). Of course, the aspherical surface may also be obtained according to other conditions.

FIG. 2 shows an imaging lens assembly LA in accordance with Embodiment 1 of the present disclosure. TABLE 1 shows the detailed optical data of Embodiment 1. The conic coefficient and aspherical coefficient of the surfaces of the lenses of Embodiment 1 are listed in TABLE 2.

The subsequent TABLE 9 shows all the parameters of the imaging lens assembly of the embodiments corresponding to conditions (1)˜(8). As shown in TABLE 9, the imaging lens assembly LA of Embodiment 1 satisfies all of the conditions (1)-(8). The spherical aberration (on-axis chromatic aberration) of the imaging lens assembly LA of Embodiment 1 is shown in FIG. 3 . The ratio chromatic aberration is shown in FIG. 4 . The curvature of field and the distortion aberration are shown in FIG. 5 . Wherein, S shows the curvature of field corresponding to sagittal image surface, and T shows the curvature of field corresponding to tangential image surface. By virtue of the configuration, the imaging lens assembly LA of Embodiment 1 has the characteristics of wide-angle, miniaturization, 2ω=85.1°, and TTL/IH=1.437.

FIG. 6 shows an imaging lens assembly LA in accordance with Embodiment 2 of the present disclosure. TABLE 3 shows the detailed optical data of Embodiment 2. The conic coefficient and aspherical coefficient of the surfaces of the lenses of Embodiment 2 are listed in TABLE 4.

As shown in TABLE 9, the imaging lens assembly LA of Embodiment 2 satisfies all of the conditions (1)-(8). The spherical aberration (on-axis chromatic aberration) of the imaging lens assembly LA of Embodiment 2 is shown in FIG. 7 . The ratio chromatic aberration is shown in FIG. 8 . The curvature of field and the distortion aberration are shown in FIG. 9 . By virtue of the configuration, the imaging lens assembly LA of Embodiment 2 has the characteristics of wide-angle, miniaturization, 2ω=86.7°, and TTL/IH=1.420.

FIG. 10 shows an imaging lens assembly LA in accordance with Embodiment 3 of the present disclosure. TABLE 5 shows the detailed optical data of Embodiment 3. The conic coefficient and aspherical coefficient of the surfaces of the lenses of Embodiment 3 are listed in TABLE 6.

As shown in TABLE 9, the imaging lens assembly LA of Embodiment 3 satisfies all of the conditions (1)-(8). The spherical aberration (on-axis chromatic aberration) of the imaging lens assembly LA of Embodiment 3 is shown in FIG. 11 . The ratio chromatic aberration is shown in FIG. 12 . The curvature of field and the distortion aberration are shown in FIG. 13 . By virtue of the configuration, the imaging lens assembly LA of Embodiment 3 has the characteristics of wide-angle, miniaturization, 2ω=85.1°, and TTL/IH=1.438.

FIG. 14 shows an imaging lens assembly LA in accordance with Embodiment 4 of the present disclosure. TABLE 7 shows the detailed optical data of Embodiment 4. The conic coefficient and aspherical coefficient of the surfaces of the lenses of Embodiment 4 are listed in TABLE 8.

As shown in TABLE 9, the imaging lens assembly LA of Embodiment 4 satisfies all of the conditions (1)-(8). The spherical aberration (on-axis chromatic aberration) of the imaging lens assembly LA of Embodiment 4 is shown in FIG. 15 . The ratio chromatic aberration is shown in FIG. 16 . The curvature of field and the distortion aberration are shown in FIG. 17 . By virtue of the configuration, the imaging lens assembly LA of Embodiment 4 has the characteristics of wide-angle, miniaturization, 2ω=84.5°, and TTL/IH=1.444.

TABLE 9 shows all the parameters of the imaging lens assembly of the embodiments corresponding to conditions (1)˜(8).

It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.