JP3328821B2 - Image display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, and more particularly, to a rear projection type image display device.

[0002]

2. Description of the Related Art In recent years, a projection lens and a plurality of projection mirrors are provided in a main body case, and image light transmitted through the projection lens is sequentially reflected by the projection mirror to form a light transmission type provided in a display window of the main body case. 2. Description of the Related Art A rear projection type image display device that projects onto a screen from the rear side has been developed.

[0003] Such an image display device can be used as a large-screen image display device, but directs image light from a plurality of projection mirrors provided in a main body case to a light transmission screen. It is necessary to arrange the reflecting projection mirror obliquely at a relatively large angle with respect to the light transmission screen.

For this reason, in the above-described image display device, since the projection mirror protrudes greatly toward the rear side of the main body case, the depth of the main body case becomes longer, which is a major obstacle in making the device thinner. .

In order to solve such a problem, a prism plate having a prism surface for totally reflecting the image light from the projection mirror, and the image light reflected by the prism plate being larger than the critical angle of the prism surface. An image display apparatus in which a reflector that reflects an angle toward a light-transmitting screen is provided in a main body case is described in Japanese Utility Model Laid-Open No. 1-97686.

According to such an image display device, the image light reflected by the projection mirror is reflected by the prism surface of the prism plate and enters the light transmission screen through the reflector and the prism plate. The image light can be made incident on the light-transmitting screen without being disposed at a large inclination angle, and the projection mirror does not protrude greatly to the rear side of the main body case, so that the device can be made thinner. Have advantages.

[0007]

However, in the above-described image display device, since the prism plate is composed of a large number of prism elements formed linearly along the width direction of the main body case, the prism plate is formed from the reflector. The incident angle of the image light incident on the plate differs depending on the position of the prism plate, and surface reflection of the image light occurs on the prism plate depending on the incident angle of the image light incident on the prism plate from the reflector. For this reason, in the above-described image display device, the amount of incident light varies on the light incident surface of the light transmission screen, and the unevenness in the amount of incident light causes unevenness in brightness of an image projected and displayed on the light transmission screen.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and has as its object to prevent brightness unevenness occurring in a projected image on a light-transmitting screen due to an incident angle of image light incident on a prism plate from a reflector. It is an object of the present invention to provide an image display device capable of performing the following.

[0009]

In order to solve the above-mentioned problems, an image display device according to the present invention comprises a prism plate formed by a large number of prism elements formed in an arc around the exit pupil position of a projection lens. It is characterized by having done.

[0010]

In the image display device having the above structure, the incident angles of the image light from the reflector to the prism plate are all equal.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the figure, reference numeral 11 denotes a main body case of an image display device according to one embodiment of the present invention, and a display window 12 formed on the front of the main body case 11 is provided with a light transmission type screen 13 for forming a display screen. Have been. In the figure, reference numeral 14 denotes a projection image creation unit that is provided in the main body case 11 and creates an image projected and displayed on the light transmission type screen 13.
Is composed of a liquid crystal display panel 15 and an illumination light source 17 for irradiating the liquid crystal display panel 15 with illumination light via a mirror 16.

In the figure, reference numeral 18 denotes a projection lens for projecting the image light emitted from the projection image forming means 14 onto the light transmitting screen 13. The image light transmitted through the projection lens 18 is provided in the main body case 11. The light enters the prism plate 21 through the projection mirror 19 and the projection mirror 20, and is totally reflected by the prism surface 21 a of the prism plate 21 so as to irradiate the reflector 22.

The reflector 22 is accommodated in the main body case 11 with its reflection surface facing the prism plate 21, and the image light reflected by the reflector 22 is prism-shaped at an angle larger than the critical angle of the prism surface 21a. The light is incident on the plate 21.

The prism plate 21 is housed in the main body case 11 with the prism surface 21a facing the light transmission screen 13, and as shown in FIGS. 2 and 3, the exit pupil position of the projection lens 18 (front side). It is composed of a number of prism elements 23 formed in an arc with the focus (O) as the center.

In such a configuration, the image light emitted from the projection image creating means 14 enters the prism plate 21 via the projection lens 18, the projection mirror 19 and the projection mirror 20, and is incident on the prism surface 21a of the prism plate 21. The light is totally reflected and applied to the reflector 22. And the prism plate 2
The image light applied to the reflector 22 from 1 is reflected by the reflection surface of the reflector 22, re-enters the prism plate 21 at an angle larger than the critical angle of the prism surface 21a, passes through the prism surface 21a, and transmits light. The light enters the mold screen 13.

Here, since the prism plate 21 is composed of a large number of prism elements 23 formed in an arc around the exit pupil position O of the projection lens 18 as described above, FIG. 4 and FIG. As shown, the incident angles θ of the image light incident on the prism plate 21 from the reflector 22 are all equal. As a result, the image light that has entered the prism plate 21 from the reflector 22 passes through the prism surface 21a and enters the light-transmitting screen 13, so that the light is transmitted depending on the incident angle of the image light that enters the prism plate 21 from the reflector 22. It is possible to prevent uneven brightness occurring in the projected image of the mold screen 13.

In the above-described embodiment, the projection image creating means 14 is composed of the liquid crystal display panel 15 and the illumination light source 17 for irradiating the liquid crystal display panel 15 with illumination light via the mirror 16. A luminance CRT or the like may be used.

[0018]

As described above, according to the present invention, since the incident angles of the image light entering the prism plate from the reflector are all equal, the incident angle of the image light entering the prism plate from the reflector depends on the incident angle. It is possible to provide an image display device capable of preventing brightness unevenness occurring in a projected image of a light transmission screen.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image display device according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a configuration of a prism plate according to the embodiment.

FIG. 3 is a front view of a prism plate.

FIG. 4 is a sectional view taken along the line AA of FIG. 3;

FIG. 5 is a sectional view taken along the line BB in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Main body case 12 ... Display window 13 ... Light transmission type screen 14 ... Image light emission means 18 ... Projection lens 20 ... Projection mirror 21 ... Prism plate 22 ... Reflector 23 ... Prism element

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03B 21/28 G02B 27/02 G03B 21/10

Claims (1)

(57) [Claims] 1. A projection lens in a main body case, and a plurality of projection mirrors for reflecting image light transmitted through the projection lens and projecting the reflected image light on a light transmission screen provided in a display window of the main body case. And a prism surface that totally reflects the image light from the projection mirror that reflects the image light toward the light-transmitting screen among the projection mirrors. A prism plate and a reflector that reflects the image light from the prism plate toward the light transmission screen at an angle larger than the critical angle of the prism surface are provided, and the prism plate is provided with a projection lens. An image display device comprising a large number of prism elements formed in an arc shape with an exit pupil position as a center.