JPH02187740A - Projecting type color display device - Google Patents

Abstract

PURPOSE:To excellently decrease the color unevenness of a synthetic picture by adjusting difference in brightness distribution caused by difference in the optical path length of each color, etc., with a correcting mirror, i.e., a concave mirror or a convex mirror. CONSTITUTION:Light is transmitted through a filter 40 and made incident on a blue dichroic mirror 42, and thereby splitting blue color light. This splitted blue color light is reflected by a reflecting mirror 44 and made incident on a light value 46, and a blue color image is formed. Next, the light transmitted through the dichroic mirror 42 is made incident on a green color dichroic mirror 48, and thereby splitting green color light. This green color light is made incident on a liquid crystal light valve for the green color 50, and a green color image is formed. And then, the red light transmitted through the mirror 48 is reflected by a concave mirror 64 and a reflecting mirror 54 in this order, and made incident on a liquid crystal light valve for the red color 56. In this time, the red light is converged to an image center by a concave area 64, and a red image is formed by a valve 56. Each color image is synthesized by a dichroic prism for synthesizing colors 58, and the picture with less color unevenness can thus be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a projection type color display device using a plurality of image forming light valves, and particularly relates to color unevenness correction of the projected image. It is something.

[Conventional technology] The light from a predetermined light source is red (R) and green (G).

It separates the light into the three primary colors of blue (B), and forms an image by inputting these path lights into each liquid crystal light valve for red, green, and blue, and then combines and projects the red, green, and blue images. Compared to CRT projectors such as televisions, projection type color display devices (liquid crystal projectors) have the following features: 1) The unit can be made smaller and lighter.

2) Screen size can be freely selected.

3) Clear color images can be obtained.

4) High brightness images can be obtained.

5. Prices can be reduced.

It has favorable advantages such as:

By the way, as such a conventional projection type color display device, there is one shown in FIG. 6 or FIG. 7, for example. Among these, the one shown in Fig. 6 is
This is disclosed in Japanese Patent No. 791.

In the same figure, a halogen lamp 1 with a reflector lO
The light emitted from the mirror 2 is collimated by the condenser lens 14, and parallel light enters the dichroic mirror 16. This dichroic mirror 16 separates the incident light into three primary color lights: red, green, and blue.

Among these separated lights, the red light is reflected by the reflection mirror 18.20.
The light is sequentially reflected by the light and enters the liquid crystal light valve 22 for red color. Then, a red image is formed here. Next, the green light directly enters the green liquid crystal light valve 24, where a green image is formed. Also, blue light is
The light is sequentially reflected by the reflection mirrors 26 and 28 and enters the blue liquid crystal light valve 30. And here a blue image is formed.

Next, red, green and blue liquid crystal light bulbs 22°24.30
The red, green, and blue images respectively formed by the above are combined by a color compositing gicchroic prism 32, and the combined color image is projected onto a screen 36 by a projection lens 34.

Next, a conventional example shown in FIG. 7 will be explained.

In the figure, infrared rays of light emitted from a light source 38 such as a halogen lamp are filtered out by a filter 40 . This makes it difficult for the heat from the light source 38 to be transmitted to the front surface.

The light transmitted through the filter 40 enters the blue dichroic mirror 42, where the blue light is separated. The separated blue light is reflected by a reflecting mirror 44 and enters a blue liquid crystal light valve 46 . And here, a blue image is formed.

Next, the light transmitted through the blue dichroic mirror 42 is
The green light is incident on a green chromic mirror 48, where the green light is separated. The separated green light enters the green liquid crystal light valve 50.

Here, a green image is formed.

Next, the red light that has passed through the green glaucroic mirror 48 is sequentially reflected by reflection mirrors 52 and 54 and enters the liquid crystal light valve 56 for red. And here,
A red image is formed.

Next, blue, green, and red liquid crystal light bulbs 4q.

The blue, green, and red images respectively formed by 50 and 56 are combined by a color compositing gicchroic prism 58, and the combined color image is projected onto a screen 62 by a projection lens 60.

[Problems to be Solved by the Invention] In the conventional projection type color display device as described above, the following relationship exists regarding the optical path lengths of the red, green, and blue lights. Note that the distance between the dichroic mirror and the reflecting mirror is equal.

First, in the conventional example shown in FIG. 6, the optical path of the light path differs between the condenser lens 14 and the liquid crystal light valves 22, 24, and 30. After the red and blue lights are color-separated by the dichroic mirror 16, they are both reflected by two reflective mirrors and enter the liquid crystal light valve 22.30, and the optical path lengths of both are as follows. equal. On the other hand, after the green light passes through the dichroic mirror 16,
The light enters the liquid crystal light valve 24 directly.

Therefore, the optical path lengths of red, green, and presound light have a relationship of red=blue, red>green, and blue>green.

Next, in the conventional example shown in FIG. 7, the optical path of the light is different between the blue dichroic mirror 42 and the liquid crystal light valve 46.50°56. After the blue and green light is reflected or transmitted through the blue dichroic mirror 42, it is reflected once by either the reflecting mirror 44 or the green dichroic mirror 48, and then enters the liquid crystal light valve 46.50. The optical path lengths of both are almost equal. On the other hand, the red light passes through the green guichroic mirror 48, is further reflected by two reflecting mirrors 52 and 54, and enters the liquid crystal light valve 56. Therefore, there is a relationship between the optical path lengths of red, green, and presound light: blue = green, blue = red, and green < red.

Next, let's consider the luminance distribution of the light output from the light source. First of all, in general, in places where the distance from the light source is short, even if you use a reflector to bring the light rays closer to parallel, as shown in Figure 3 (
As shown in the graph La shown in Al, the brightness distribution is bright in the center (dark in the periphery).

On the other hand, as the distance from the light source increases, the parallelism of the light beam improves, resulting in an overall uniform luminance distribution as shown in graph Lb shown in FIG.

Note that depending on the configuration of the light source and flipper, the above relationship may be reversed, resulting in a uniform luminance distribution near the light source, and a luminance distribution that is bright at the center and dark at the periphery at a distance from the light source.

Therefore, as mentioned above, if there is an optical path difference between the red, green, and blue lights, the brightness distribution of the projected image will be the same as the composite of La and Lb, as shown in fc) in the same figure. Become. Note that each color of light may deviate from the predetermined brightness ratio of white light (ratio of red, blue, and green).
This can be easily corrected by adjusting the voltage applied to the liquid crystal light valve.

For example, in the conventional example shown in FIG. 6, the graph La is the brightness distribution of green light, and the graph Lb is the brightness distribution of red and blue lights. Therefore, in the peripheral area of the projected image, the red and blue lights are stronger than the green light, and this uneven brightness distribution results in color unevenness. Further, in the conventional example shown in FIG. 7, the graph La represents the brightness distribution of green and blue lights, and the graph Lb represents the brightness distribution of red light. For this reason,
In the periphery of the projected image, red light is stronger than green and blue light, and this uneven brightness distribution similarly causes color unevenness.

The present invention has been made in view of these points, and effectively prevents the occurrence of color unevenness in images caused by uneven brightness distribution due to differences in the optical path length of light from the light source to the light valve. The object of the present invention is to provide a projection type color display device that can perform the following steps.

[Means for Solving the Problems] The present invention separates light emitted from a predetermined light source into necessary primary color lights, enters each image forming means to form an image of each primary color light, and then In a projection type color display device that combines and projects these images, a mirror provided in the optical path of the separated primary color light is a concave mirror whose characteristics are set corresponding to the luminance distribution of the image of each primary color light. Alternatively, it is characterized in that it is formed as a convex wall as necessary.

[Operation] According to the present invention, the luminance distribution of each separated primary color light is changed by a correction mirror such as a concave mirror or a convex mirror provided as necessary. The degree of change is set according to the difference in brightness distribution of images of each primary color light. Therefore, the luminance distributions of the images of the respective primary color lights to be combined are substantially the same.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings. Note that the same reference numerals are used for the same components as in the conventional example described above. This embodiment is an application of the present invention to the conventional example shown in FIG. 7 mentioned above.

FIG. 1 shows the main parts of an embodiment of the present invention, and FIG. 2 shows a side view. In these figures, an infrared cut filter 40 is arranged on the light emission side of the light source 38.

A blue dichroic mirror 42 is provided on the light transmitting side of the filter 40, and a light reflecting mirror I11 of the blue dichroic mirror 42 is provided on the incident side of the blue liquid crystal light valve 46. 44 are arranged.

Next, on the light transmission side of the blue guichroic mirror 42,
A green glaucroic mirror 48 is provided. A green liquid crystal light valve 50 is arranged on the light reflection side of the green guichroic mirror 48, and a concave mirror 64 (correction mirror) 9 and a reflection mirror 54 are arranged on the light transmission side of the green guichroic mirror 48. A red liquid crystal light valve 56 is arranged through the red color liquid crystal light valve 56. With this concave mirror 64,
Red light is focused in the center.

Each of the liquid crystal light valves 46, 50, 56 is arranged at the entrance I11 of the color composition guichroic prism 58, and the projection lens 60. Screens 62 are arranged respectively.

Next, the overall operation of the above embodiment will be explained. A filter 40 cuts off infrared rays of light emitted from a light source 38 such as a halogen lamp. by this,
Heat from the light source 38 is less likely to be transmitted to the front.

The light transmitted through the filter 40 enters a blue dichroic mirror 42, where the blue light is separated. The separated blue light is reflected by a reflecting mirror 44 and enters a blue liquid crystal light valve 46 . And here, a blue image is formed.

Next, the light transmitted through the blue dichroic mirror 42 is
The green light enters a green dichroic mirror 48, where the green light is separated. The separated green light enters the green liquid crystal light valve 50.

Here, a green image is formed.

Next, the red light transmitted through the green dichroic mirror 48 is sequentially reflected by the concave mirror 649 and the reflecting mirror 54, and enters the red liquid crystal light valve 56. At this time,
The red light is focused at the center of the image by the concave mirror 64. That is, the distribution of red light changes from graph Lb to graph Lc in FIG. 3(B), and a red image is formed by the red liquid crystal light valve 56 based on this distribution of red light.

Next, blue, green, and red liquid crystal light bulbs 46°50.56
The blue, green, and red images respectively formed by the above are combined by a color compositing gicchroic prism 58, and the combined color image is projected onto a screen 62 by a projection lens 60.

As shown in FIG. 3(A), the luminance distribution of blue and green images is represented by a graph La. Also.

As mentioned above, the brightness distribution of the red image is represented by the graph Lc
It is expressed as When these are compared, the distributions become well approximated, as shown in FIG. Therefore, color unevenness in the image due to non-uniform luminance distribution on the screen 62 is effectively reduced. Further, since only the shape of the reflecting mirror is changed, the cost is low.

In addition, in the above embodiment, the conventional reflecting mirror 5 shown in FIG.
Although the concave mirror 64 is used instead of 2, the reflective mirror 52 may be left as conventional and the reflective mirror 54 may be a concave mirror (or both the reflective mirrors 52 and 54 may be concave mirrors).

Next, other embodiments of the present invention will be described with reference to FIGS. 4 and 5. In this embodiment, as shown in FIG. 4, a convex mirror 66 (correction mirror) is used in place of the reflecting mirror 44 of the conventional example shown in FIG.
This uses a color separation correction mirror).

Of these, the convex mirror 66 scatters blue light, and the convex dichroic mirror 68 scatters green light. Therefore, the luminance distributions of the blue light and the green light are each flattened as shown in the graph Ld of FIG. 5 [Al. As a result, the brightness distribution in the blue and green light images is almost the same as the brightness distribution in the red light image, as shown in the same figure (C1), and the brightness distribution in the blue and green light images is almost the same as the brightness distribution in the red light image. Color unevenness in the image will be reduced.

In the embodiment shown in FIG. 4, the same effect can be obtained even if the convex mirror 66 is a normal reflecting mirror and the blue dichroic mirror 42 is a convex dichroic mirror.

Next, the case where the present invention is applied to the conventional example shown in FIG. 6 will be described. In this case, for red light, at least one of the guichroic mirror 16A and the reflecting mirror 18.20 has a concave surface, and for blue light, the guichroic mirror 16B1 and the reflecting mirror 26.28 have a concave surface. Note that in this example, there is no mirror in the optical path of the green light, so there is no example of using a convex mirror.

The optical characteristics of the correction mirror may be determined in consideration of the influence on the luminance distribution by optical elements such as other mirrors provided in the optical path of each color light.

[Effects of the Invention] As explained above, according to the present invention, the difference occurs due to the difference in optical path length of each color light. Since the brightness distribution difference is adjusted using a concave mirror or a convex mirror for correction, there is an effect that the color unevenness of the composite image is favorably reduced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of an embodiment of the present invention, and FIG.
The figure is a side view of the embodiment, FIG. 3 is a graph showing the luminance distribution of the image of each color light in the embodiment, FIG. 4 is a side view of another embodiment of the present invention, and FIG. 5 is the other embodiment. A graph showing the luminance distribution of the image of each color light in this embodiment, and FIGS. 6 and 7 are configuration diagrams showing the conventional apparatus, respectively. 38...Light source, 40...Filter, 42.48...
-Blue guichroic mirror, 44.52.54...
Reflection mirror, 46.50.56--Liquid crystal light valve (image forming means), 60...-Projection lens, 62...
Screen, 64...-Concave mirror, 66... Convex mirror, 6
8...Convex mirror mirror patent applicant Representative of Victor Japan Co., Ltd. Kunio Kakiki ○q Mishi Heisei Nakum 2017 Ninohe 72nd Special Remarks Office Director Atsushi 1999 Patent Application No. 7417 Projection type color display device 5, all drawings to be corrected

Claims (1)

[Claims] Light emitted from a predetermined light source is separated into necessary primary color lights, which are incident on each image forming means to form an image of each primary color light, and then these images are synthesized. In the projection type color display device, the mirror provided in the optical path of the separated primary color light is formed into a concave mirror or a convex mirror whose characteristics are set corresponding to the luminance distribution of the image of each primary color light. Features a projection type color display device.