Laser display apparatus

This application claims priority from Korean Patent Application No. 10-2005-0104932, filed on Nov. 3, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

1. Field of the Invention

The present invention relates to a display apparatus using a laser as a light source, and more particularly, to a laser display apparatus designed to limit the excessive intensity of laser light.

2. Description of the Related Art

A laser display apparatus with excellent directionality allows simple and easy arrangement of optical components. Further, because laser light has higher intensity than that of light emitted from other kinds of light sources, a laser display apparatus provides a large screen having high resolution.

FIG. 1 illustrates an optical arrangement of a conventional laser display apparatus. Referring to FIG. 1 , the conventional laser display apparatus includes a laser 11 , a condenser lens 13 , an acousto-optic modulator (AOM) 15 , and an optical scanning unit 20 .

The laser 11 continuously emits laser light during driving of the display, which is converged by the condenser lens 13 . The AOM 15 is disposed between the condenser lens 13 and the optical scanning unit 20 and controls the transmittance of incident light according to an input image signal so that light corresponding to an image to be displayed on a screen 17 is incident on the optical scanning unit 20 . The optical scanning unit 20 includes a rotating polygonal mirror 21 primarily scanning incident light to produce scan lines A, and a galvanometer 25 secondarily scanning the scan lines A produced by the rotating polygonal mirror 21 so that a planar image B can be focused on the screen 17 .

The laser display apparatus having the above-described construction can provide high contrast and clear images by using a laser emitting high-intensity light as a light source.

However, because the laser 11 adjusts the amount and intensity of light it emits based on the amount of current being supplied, the intensity of light emitted by the laser 11 may exceed the maximum value of an allowable range when too much current is supplied. Further, when light is incident on a specific region of the screen 17 for more than a predetermined time, the amount and intensity of light may be excessively high. When the amount and intensity of laser light are excessively high, exposing the laser beam directly to human eyes may cause significant damage to the viewer's eyesight.

An aspect of the present invention provides a laser display apparatus that can prevent excessive intensity of laser light.

According to an aspect of the present invention, there is provided a laser display apparatus for displaying an image by scanning laser light onto a screen including: a laser emitting the laser light; an optical scanning unit scanning light emitted by the laser and providing a planar image to the screen; a laser light intensity adjusting unit limiting the intensity of laser light being scanned onto the screen; and a projection lens unit that is disposed between the laser and the screen and enlarges and projects laser light onto the screen.

The laser light intensity adjusting unit includes an optical limiter that is disposed between the laser and the optical scanning unit and nonlinearly increases the intensity of exit laser light propagating toward the optical scanning unit with increasing intensity of incident laser light emitted by the laser, limits the intensity of the exit laser light when the intensity of the incident laser light exceeds a predetermined value so that exit laser light with intensity not exceeding the predetermined value is incident on the optical scanning unit.

In another exemplary embodiment, the laser light intensity adjusting unit includes: a shutter that is disposed in the propagation path of laser light emitted by the laser and selectively blocks laser light propagating toward the screen; an error detector detecting the malfunction of the optical scanning unit; and a shutter controller controlling the shutter to block the propagation of the laser light emitted by the laser when the error detector determines that the optical scanning unit malfunctions.

In yet another exemplary embodiment, the laser light intensity adjusting unit includes: an error detector detecting the malfunction of the optical scanning unit; and a laser switching controller intercepting a driving power of the laser when the error detector determines that the malfunction of the optical scanning unit occurs.

The above and other features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIG. 1 illustrates an optical arrangement of a conventional laser display apparatus;

FIG. 2 illustrates an optical arrangement of a laser display apparatus according to an exemplary embodiment of the present invention;

FIG. 3 is a graph illustrating a change in intensity of light irradiated on a screen with respect to the intensity of light emitted by a laser when an optical limiter of the laser display apparatus illustrated in FIG. 2 is used;

FIG. 4 illustrates an optical arrangement of a laser display apparatus according to another exemplary embodiment of the present invention; and

FIG. 5 illustrates an optical arrangement of a laser display apparatus according to another exemplary embodiment of the present invention.

Hereinafter, the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings.

FIG. 2 illustrates an optical arrangement of a laser display apparatus according to an exemplary embodiment of the present invention. Referring to FIG. 2 , the laser display apparatus includes a laser 31 emitting laser light of a predetermined wavelength, an optical scanning unit, a light intensity adjusting unit, and a projection lens unit 39 that is disposed between the laser 31 and the screen 50 and enlarges and projects light onto the screen 50 .

The laser 31 continuously emits laser light during a driving operation. The laser 31 includes first through third lasers 31 a through 31 c emitting red, blue, and green laser beams of three different wavelengths, respectively, to implement a color display. Although FIG. 2 illustrates that the first through third lasers 31 a through 31 c are arranged from top to bottom, they may be arranged in a different order. Further, although in the above description, the first through third lasers 31 a through 31 c emit red, blue, and green laser beams, the laser 31 may include a different number of lasers emitting other colors.

The optical scanning unit scans light emitted by the laser 31 and provides an image to the screen 50 . To achieve this function, the optical scanning unit includes a cylindrical lens 33 , a linear reflective panel 35 , and a scanning mirror 41 .

The cylindrical lens 33 shapes incident light emitted by the laser 31 into light having a linear cross-section. As illustrated in FIG. 2 , when the first through third lasers 31 a through 31 c are used as light sources, the cylindrical lens 33 includes first through third cylindrical lenses 33 a through 33 c that are disposed in the propagation paths of laser beams emitted by the first through third lasers 31 a through 31 c and shape the corresponding laser beams.

The linear reflective panel 35 is located between the cylindrical lens 33 and the scanning mirror 41 and independently reflects linear incident light that falls on each pixel to produce a base image. To achieve this, the linear reflective panel 35 is arranged along a line in which linear light is incident and may include a plurality of digital micro-mirror devices corresponding to pixels of the image.

As illustrated in FIG. 2 , when the first through third lasers 31 a through 31 c are used as light sources, the linear reflective panel 35 includes first through third linear reflective panels 35 a through 35 c disposed in the propagation paths of beams shaped by the first through third cylindrical lenses 33 a through 33 c

In this case, the laser display apparatus further includes a color combining unit 37 that is disposed between the linear reflective panel 35 and the scanning mirror 41 and combines red, blue, and green laser beams emitted by the first through third lasers 31 a through 31 c and allows beams reflected by the first through third linear reflective panels 35 a through 35 c to propagate along the same path. To achieve this, the color combining unit 37 includes a color wheel having red, blue, and green color filters, which is rotatably disposed in the optical path. Thus, the red, blue, and green filters are sequentially disposed in the optical path as the color wheel rotates so that the red, blue, and green laser beams sequentially propagate toward the scanning mirror 41 .

The scanning mirror 41 reciprocatingly rotates to scan a linearly shaped base image C produced by the linear reflective panel 35 onto the screen 50 and produce an image D.

The light intensity adjusting unit limits the intensity of light being scanned onto the screen 50 when the intensity of light emitted by the laser 31 increases excessively due to factors such as overcurrent.

To achieve this, the light intensity adjusting unit includes an optical limiter 40 that is disposed between the laser 31 and the linear reflective panel 35 . FIG. 3 is a graph illustrating a change in intensity I out of exit light propagating toward the optical scanning unit with respect to the intensity I in of light emitted by the laser 31 when the optical limiter 40 is used. Referring to FIG. 3 , the optical limiter 40 non-linearly increases the intensity I out of exit light with increasing intensity I in of incident light. That is, as the intensity I in of incident light increases, the rate of increase in the intensity I out of exit light decreases. When the intensity I out of exit light reaches saturation light intensity I sat — OL of the optical limiter 40 , the intensity I out will not increase any more and remains at the saturation light intensity I sat — OL . Thus, the optical limiter 40 limits the intensity of exit light when the intensity of incident light exceeds a predetermined value so that exit light, with intensity not exceeding the predetermined value, is irradiated toward the optical scanning unit.

Thus, when excessively high laser light is emitted due to a malfunction of a laser, the intensity of exit light is limited to saturation intensity I out — sat by the optical limiter 40 , thereby preventing damage to a viewer's eyesight due to excessively bright laser light.

As illustrated in FIG. 2 , when the first through third lasers 31 a through 31 c are used as light sources, the optical limiter 40 includes first through third optical limiters 40 a through 40 c disposed in the propagation paths of laser beams emitted by the first through third lasers 31 a through 31 c , respectively.

FIG. 4 illustrates an optical arrangement of a laser display apparatus according to another exemplary embodiment of the present invention.

Referring to FIG. 4 , the laser display apparatus includes a laser 31 , an optical scanning unit, a light intensity adjusting unit, and a projection lens unit 39 . Because the laser 31 , the optical scanning unit, and the projection lens unit 39 have substantially the same structures and functions as their counterparts in the laser display apparatus of FIG. 2 , detailed descriptions thereof will not be provided.

The light intensity adjusting unit prevents excessively high intensity laser light from being incident on a portion of a screen 50 due to a malfunction of the optical scanning unit. To achieve this, the light intensity adjusting unit includes a shutter 140 mechanically blocking laser light, an error detector 141 detecting the malfunction of the optical scanning unit, and a shutter controller 145 controlling the shutter 140 . The shutter 140 is disposed in the propagation path of light emitted by the laser 31 and selectively blocks light propagating toward the screen 50 .

When the error detector 141 determines that the optical scanning unit malfunctions, the shutter controller 145 allows the shutter 140 to block the light emitted by the laser 31 . Conversely, when a scanning mirror 41 operates normally, the shutter controller 145 allows the shutter 140 to open so that light emitted by the laser 31 propagates toward the scanning mirror 41 . Thus, the above configuration can prevent abnormally high intensity laser light from being irradiated onto a portion of the screen 50 .

As illustrated in FIG. 4 , when first through third lasers 31 a through 31 c are used as light sources, the shutter 140 includes first through third shutters 40 a through 40 c disposed in the propagation paths of laser beams emitted by the first through third lasers 31 a through 31 c , respectively.

FIG. 5 illustrates an optical arrangement of a laser display apparatus according to another exemplary embodiment of the present invention. Referring to FIG. 5 , the laser display apparatus includes a laser 31 , an optical scanning unit, a light intensity adjusting unit, and a projection lens unit 39 . Because the laser 31 , the optical scanning unit, and the projection lens unit 39 have substantially the same structures and functions as their counterparts in the laser display apparatus of FIG. 2 , detailed descriptions thereof will not be provided.

The light intensity adjusting unit prevents excessively high intensity laser light from being incident on a portion of a screen 50 due to a malfunction of the optical scanning unit. To achieve this, the light intensity adjusting unit includes an error detector 241 detecting the malfunction of the optical scanning unit and a laser switching controller 245 . When the error detector 241 determines that the optical scanning unit malfunctions, the laser switching controller 245 is enabled to prevent irradiation of laser light. Thus, the above configuration can prevent abnormally high intensity laser light from being irradiated onto a portion of the screen 50 due to a malfunction of a scanning mirror 41 .

A laser display apparatus configured as described above controls light emitted by a laser through an optical limiter, a shutter, and a laser switching controller, thus preventing excessively high intensity laser light being irradiated onto a screen while ensuring a viewer's safety.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.