JPH02187739A - Projecting type color display device - Google Patents

Abstract

PURPOSE:To preferably 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 with a transmitting light amount adjusting member. CONSTITUTION:Light is transmitted through a filter 40 and made incident on a blue color 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 liquid crystal light valve for the blue color 46, and a blue color image is formed. Next, the light transmitted through a mirror 42 is made incident on a green color dichroic mirror 48, and thereby splitting green color light. The splitted light is made incident on a liquid crystal light valve for the green color 50, and a green color image is formed. And then, red color light transmitted through the mirror 48 is reflected by mirrors 52 and 54 and made incident on a liquid crystal light valve for the red color 56. In this time, the red color light is decreased in the light amount of an image peripheral part by a transmit light amount adjusting member 46, and a red color image is formed by a value 56. Each color image is synthesized by a dichroic prism for synthesizing colors 58, and the color unevenness of the synthesized picture can be decreased.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a projection type color display device using a plurality of image forming light valves. It concerns correction.

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

Separates the light into the three primary colors of blue (B), forms an image by entering each of these lights into red, green, and blue liquid crystal light valves, and then combines and projects the red, green, and blue images. Compared to CRT projectors such as televisions, projection color display devices (liquid crystal projectors) can achieve the following: (1) A smaller and lighter unit.

(2) Screen size can be freely selected.

(3) Clear color images can be obtained.

(4) High brightness images can be obtained.

(5) Lower prices can be achieved.

It has favorable advantages such as:

By the way, as such a conventional projection type color display device, there is one shown in FIG. 4 or FIG. 5, for example. Among these, the one shown in Fig. 4 is
This is disclosed in Japanese Patent No. 791.

In the figure, a halogen lamp 1 with a reflector 10 is shown.
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 18.2.
0, the red liquid crystal light valve 22
incident on . 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. Further, the blue light is sequentially reflected by the reflecting mirrors 26 and 28 and enters the blue liquid crystal light valve 30. A blue image is then formed here.

Next [This red, green, and blue LCD light bulb 22° 24.3
The red, green, and blue images respectively formed by 0 are synthesized by a color compositing guide 32,
The combined color image is projected onto a screen 36 by a projection lens 34.

Next, a conventional example shown in FIG. 5 will be explained.

In FIG. 2, the infrared light emitted from a light source 38 such as a halogen lamp is filtered 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 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.

[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.
The optical path of each light is different between the liquid crystal light valves 22, 24, and 30. The red and blue lights (1) are color-separated by the dichroic mirror 16 and then reflected by two reflective mirrors before entering the liquid crystal light valve 22 and 30. The optical path lengths are equal. On the other hand, green light passes through the dichroic mirror 16 and then directly enters the liquid crystal light valve 24 .

Therefore, the optical path lengths of red, green, and blue lights have the following relationship: red=blue, red>green, and blue>green.

Next, in the conventional example shown in FIG. 5, the optical path of each 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 passed through the liquid crystal rad valve 46. '50, and the optical path lengths of both are almost equal. On the other hand, the red light passes through the green glaucroic mirror 48, is further reflected by two reflective mirrors 52 and 54, and enters the liquid crystal light valve 56. Therefore, the optical path lengths of red, green, and blue light have the following relationships: blue=green, blue and red, and green and red.

Let us consider once again the brightness 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 6 (
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 brightness distribution near the light source, and brightness in the center (dark peripheral areas) away 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 composite of La and Lb, as shown in Figure (C). becomes. 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. 4, the graph La is the luminance distribution of green light, and the graph Lb is the luminance distribution of red and blue lights. Therefore, in the periphery of the projected image, the red and blue lights are stronger than the green light, and this uneven brightness distribution results in color unevenness. In the example, the graph La is the edge, the brightness distribution of blue light, and the graph Lb is the brightness distribution of red light.Therefore,
In the periphery of the projected image, red light is stronger than green and blue light, and similarly, color unevenness occurs due to the non-uniformity of the brightness distribution.

The present invention has been made in view of these points, and is intended to reduce the occurrence of color unevenness in the peripheral areas of images caused by uneven brightness distribution due to differences in the optical path length of light from the light source to the light valve. It is an object of the present invention to provide a projection type color display device that can effectively prevent such problems.

[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 transmitted light amount adjusting member is provided in the optical path of the separated primary color light and has a transmission characteristic set in accordance with the brightness distribution difference between the images of each primary color light. It is characterized in that it is provided as necessary.

[For A] According to the present invention, each separated primary color light is transmitted by the transmitted light amount adjusting member provided as necessary.
Receive 8. The amount of adjustment 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 example is
This invention is applied to the conventional example shown in FIG. 5 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, a filter 40 for cutting infrared rays is arranged on the light emission side of the light source 38.

A blue dichroic mirror 42 is provided on the light transmission side of this filter 40, and a reflection mirror 44 is provided on the light reflection side of this blue dichroic mirror 42 and on the incident side of the blue liquid crystal light valve 46. ing.

Next, on the light transmission side of the blue dichroic 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 reflection mirror 52.5 is arranged on the light transmission side of the green guichroic mirror 48.
A liquid crystal light valve 56 for red color is disposed via 4.

Each liquid crystal light valve 46, 50.56 is arranged on the incident side of the color composition guichroic prism 58, and the projection lens 60.56 is arranged on the composite image output side. Screens 62 are arranged respectively.

Next, between the reflecting mirrors 52 and 54, on the optical axis of the red light, a transmitted light amount suppressing member 64 is provided that suppresses the amount of red light in the peripheral area of the image to reduce brightness. The transmitted light amount suppressing member 64 is constructed by, for example, providing a rod-shaped mask plate as shown in FIG. 3 (Al) in a part of a housing (not shown) that constitutes the red light path.

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 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. At this time, the amount of red light at the periphery of the image is reduced by the transmitted light amount adjustment member 64. That is, the distribution of red light changes from graph Lb to graph Lc in FIG. 6(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. 6 fAl, the luminance distribution of the blue and green images is represented by a graph La. Furthermore, the brightness distribution of the red image is represented by the graph Lc, as described above. Comparing these, as shown in the same figure (Ci),
The distribution becomes well approximated even in the periphery of the image. Therefore, color unevenness at the periphery of the image due to non-uniform luminance distribution on the screen 62 is effectively reduced.

Next, with reference to FIG. 3, another configuration of the transmitted light amount adjusting member 64 will be described. First, ``Double series of the same figure (A
In the case shown in l, the border inside the frame is too clear. Therefore, in order to blur the boundaries and give a natural feel,
As shown in the same figure (C1, +D), the inside of the frame has a waveform shape.

Next, the degree of color unevenness around the image gradually changes. Therefore, in order to gradually change the light transmittance of the border inside the frame to make it more natural, the transmittance is gradually decreased from the inside to the outside (Jll), as shown in IEI in the same figure. In this example, if a large number of small holes are made in the frame as shown in the same figure (Fl), the amount of transmission can be easily and effectively adjusted.

Next, in order to more naturally prevent color unevenness in response to the fact that the light source is spherical, the window portion is made into an elliptical or polygonal shape, as shown in the same figure (Gl, [Hl).

Further, instead of having a frame shape, the shape may be a plate shape with a light transmittance of approximately 100% near the center, as shown in fB of the same figure. If this is done, the peripheral portion can be freely configured in any other configuration shown in the figure. Other suitable configurations may be adopted as necessary.

Next, when the present invention is applied to the conventional example shown in FIG. 4 described above, a transmitted light amount adjusting member is provided in both the red light and blue light optical paths.

Furthermore, as mentioned above, depending on the configuration of the light source and flipper, the brightness distribution of each color may be reversed, with a flat distribution across the entire image near the light source, and a distribution where the brightness is higher in the center of the image farther away from the light source. It may happen. In such a case, in the embodiment described above, a transmitted light amount adjusting member is provided in the optical path of the green light and the blue light.

Further, in some cases, the optical path lengths of red, green, and blue may be different from each other. At this time, the light quantity is adjusted in accordance with the difference in optical path length.

In any case, by providing a transmitted light amount adjusting member in the optical path of the colored light having high brightness in the peripheral area of the image, the brightness distribution of each color light may ultimately be made the same on the screen.

Note that the present invention is not limited to the above-mentioned embodiments; for example, the a[! The placement position may be appropriately set as necessary.

Further, the transmitted light amount adjusting member may be formed integrally with other constituent members present in the optical path.

Furthermore, in the embodiments described above, the brightness distribution over the entire image may be adjusted by adjusting the amount of light over the entire image using a suitable filter means or the like.

Further, the light amount adjustment characteristics of the transmitted light amount adjusting member may be determined by taking into consideration the influence on the luminance distribution by optical elements such as reflective mirrors provided in the optical path of each color light.

[Effects of the Invention] As explained above, according to the present invention, the difference in luminance distribution caused by the difference in optical path length of each color light is adjusted by the transmitted light amount adjusting member (-), so that the composite image can be improved. This has the effect of satisfactorily reducing color unevenness.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of an embodiment of the present invention, and FIG.
FIG. 3 is an explanatory diagram showing various examples of the transmitted light amount adjusting member, FIG. 4 and FIG. 5 are configuration diagrams each showing a conventional device, and FIG. It is a graph showing the luminance distribution of each color light that is generated. 38...Light source, 40...Filter, 42.48...
・Blue Guikroic Mirror 44.52.54...
Reflection mirror 46, 50. 56... Liquid crystal light valve (image forming means), 60... Projection lens, 62...
Screen, 64... Transmitted light amount adjustment member. Patent applicant Kunio Kakiki, representative of Victor Japan Co., Ltd. Procedural amendment (method) Date of June 1989

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, a transmitted light amount adjusting member whose transmission characteristics are set corresponding to the luminance distribution of the image of each primary color light is provided as necessary in the optical path of the separated primary color light. A projection color display device featuring: