JPH0384536A - Projection type display device - Google Patents

Abstract

PURPOSE:To eliminate a color irregularity on a display screen and to improve picture quality by interposing filters for in-plane brightness distribution correction in three optical paths penetrating three liquid crystal light valves. CONSTITUTION:The filters 8 for in-plane brightness distribution correction are interposed in the three optical paths penetrating the three liquid crystal light valves 4. Consequently, the filters 8 for in-plane brightness distribution operate so that the transmissivity is high where light incident on the liquid crystal light valves 4 is relatively weak and low where relatively intense. Therefore, the intensity distributions of light projected from the liquid crystal light valves 4 becomes uniform. Consequently, the color irregularity is reduced, the color reproducibility becomes good, and the picture quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection type display device for displaying video images, conbeater images, and the like. In particular, the present invention relates to a projection display device (liquid crystal video projector) using a liquid crystal panel as a light valve, which can realize a large screen with a compact size.

[Prior Art] A projection type display device using a conventional liquid crystal panel as a light valve and having the configuration shown in Fig. 8 has been commercialized by our company (Epson, video projector - VPJ).
-700). Similar projection display devices have also been announced by Sharp and Matsushita Electric (Figure 9).

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, the intensity distribution of the light incident on the six liquid crystal light valves for R, G, and B is different for each of the three liquid crystal light valves. As a result, there were the following issues.

That is, if the incident light intensity distribution is as shown in FIG. 3, for example, the entire image projected onto the screen will be reddish. When an all-white image is displayed, it has a slight reddish tint in the center and becomes more reddish toward the periphery. Even if you use optical means to achieve white balance in the center, normal color reproduction can be achieved in the center, but the peripheral areas will appear reddish.Also, if you try to white balance in the peripheral areas On the contrary, the center part becomes bluish. Therefore, only images with different tones from the original input image can be displayed.
won.

Therefore, the present invention has been made to solve such problems.

[Means for Solving the Problems] A projection type display device of the present invention includes a color separation means for receiving the light from a light source that generates light and separating the light into three colored lights of red, green, and blue, each of which has the three colored lights. 3 modulating one of the three colored lights
In a projection display device comprising two liquid crystal light valves and a projection optical means for projecting the modulated colored light, an in-plane luminance distribution is formed in six optical paths passing through the three liquid crystal light valves. It is characterized by a correction filter inserted.

Further, the filter for in-plane brightness correction is made of a photographic film or a photosensitive plate, and after the photographic film or photosensitive plate is placed in the optical path before exposure, a light source is illuminated and exposed, and then the photographic film or photosensitive plate is exposed. Another feature of the present invention is that the film or photosensitive plate is developed into a negative film or photosensitive plate, which is used as a filter for correcting the in-plane brightness.

[Function] The projection display device configured as described above has high transmittance where the light incident on the liquid crystal light valve is relatively weak, and low transmittance where the light incident on the liquid crystal light valve is relatively strong. The effect of the filter for correcting the in-plane brightness distribution, which has a low rate, makes the intensity distribution of the light emitted from the liquid crystal light valve uniform, improving the image quality on the display screen.

In addition, as mentioned above, the transmittance is high where the light intensity is low, and the transmittance is low where the light intensity is strong, and the transmittance of the surface changes smoothly to correct the light intensity distribution of the light source light. A filter for internal luminance distribution can be created by an extremely simple method of placing a photographic film or a photosensitive plate in the three optical paths and exposing it to light.

[Examples] Hereinafter, the present invention will be explained in detail based on Examples. However, the present invention is not limited to the following examples.

(Example 1) FIG. 1 is a diagram showing the configuration of a projection type display device of the present invention. 1 is a light source unit, 2 is a guichroic mirror 3
is a reflecting mirror; 4 is a liquid crystal light valve; 5 is a dichroic prism; 6 is a projection lens; 7 is a screen; and 8 is a filter for correcting the in-plane brightness distribution.

FIG. 2 shows an external view of the filter for correcting the in-plane luminance distribution of No. 8. In this example, the transmittance in the central part is low and the transmittance in the peripheral part is high. The transmittance distribution is different for the red, line, and blue in-plane brightness distribution correction filters. In this embodiment, the filter for correcting the brightness distribution within the 80-plane plane was placed just before the liquid crystal light valve 4, but it is not limited to this position, and may be placed far in front of the liquid crystal light valve. It can be placed at the back.

The filter for correcting the in-plane luminance distribution of No. 8 was created as follows. First, three photographic photosensitive plates were prepared and placed in a dark room just in front of three liquid crystal light valves. Thereafter, the light source was turned on and each of the three sensitive plates was exposed to light for a predetermined period of time. The light intensity distribution at that time is shown in Figure 3. (
(α) is a distribution map for red, Cb) is a distribution diagram on the periphery, and (C) is a distribution map for blue in the optical path. ) After that, it was removed from the optical system, developed and fixed. The photosensitive plate that has been fixed is in a negative state, so
As shown in FIGS. 4 and 5, respectively, the transmittance was low in the central area where the light intensity was high, and the transmittance was high in the peripheral area where the light intensity was low. The photosensitive plate was used as a filter for correcting the in-plane brightness distribution.

The three obtained filters for correcting the in-plane luminance distribution were placed precisely at the original exposed positions and fixed.

After fixing the filter for in-plane luminance distribution correction, turn on the light source and set the liquid crystal light valve to the fully transparent state (i.e.
When we measured the intensity distribution of the light passing through each liquid crystal light valve (by inputting an all-white signal), we found that it was uniform within the surface of the liquid crystal light valve for all colors, as shown in Figure 6. In other words, it was shown that the filter for measuring the in-plane luminance distribution according to the present invention 9 can correct the non-uniformity of the light intensity distribution within the plane of the liquid crystal light valve.

When the projection type display device of the present invention (Fig. 1) and the conventional projection type display device (Fig. 8) were arranged side by side and video images were actually displayed, the projection type display device of the present invention was found to be better. The image quality was good, with little color unevenness and good color reproducibility.

In this embodiment, a photosensitive plate made of photographic glass is used as a filter for correcting the in-plane brightness distribution, but the present invention is not limited to this, and a photographic film made of resin such as 70 may also be used.

(Embodiment 2) FIG. 7 is a diagram showing another configuration of the projection type display device of the present invention. (α) is a diagram showing the configuration inside the cabinet,
(b) is a configuration diagram of the projection optical unit.

A filter 8 for correcting the in-plane brightness distribution is placed immediately behind the liquid crystal panel 14.

Even when light with an intensity distribution completely different from that in Example 1 is incident on the three liquid crystal panels as in this example, the filter for correcting the in-plane brightness distribution is adjusted to suit the light intensity distribution. It was possible to make corrections as needed and was effective in improving image quality.

[Effects of the Invention] The projection type display device of the present invention includes a color separation means that receives the light from a light source that generates light and separates the light into three colored lights of red, green, and blue, each of which has a color separation unit that separates the light into three colored lights of red, green, and blue. 3 to modulate one of the
In a projection display device comprising two liquid crystal light valves and a projection optical means for projecting the modulated colored light, an in-plane luminance distribution is formed in three optical paths passing through the three liquid crystal light valves. Since a correction filter is inserted, color unevenness on the display screen is eliminated and the image quality is improved.

Further, the filter for in-plane brightness correction is made of a photographic film or a photosensitive plate, and after the photographic film or photosensitive plate is placed in the optical path before exposure, a light source is illuminated and exposed, and then the photographic film or photosensitive plate is exposed. Since the above effects can be achieved by a simple means of developing a film or photosensitive plate to make a negative film or photosensitive plate and using it as a filter for in-plane brightness correction, the increase in cost is small and it is practical.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a projection type display device in Embodiment 1 of the present invention. FIG. 2 is an external view of a filter for in-plane brightness distribution correction in Embodiment 1 of the present invention. FIG. 3 is a diagram showing the intensity distribution of light incident on each light valve. ((cz) indicates red, (b) indicates green, and (C) indicates blue.) FIG. 4 is an external view of a filter for correcting the in-plane brightness distribution after exposure and development. (α) is red, (b) is green, (base C is blue.) FIG. 5 is a diagram showing the transmittance of a filter for correcting the in-plane brightness distribution after exposure and development. FIG. 6 is a diagram showing the intensity distribution of light emitted from each liquid crystal light valve after a filter for correcting the in-plane brightness distribution is arranged in an all-white state. ((cL) is red, (b) is green,
(C) shows blue. ) FIG. 7 is a diagram showing the configuration of a projection type display device in Embodiment 2 of the present invention. ((α) is a configuration diagram inside the cabinet. (b) is a configuration diagram of the projection optical unit.)
FIG. 8 is a diagram showing the configuration of a conventional projection type display device. FIG. 9 is a diagram showing another configuration of the conventional projection type display device.・・・・・・・・・Light source unit・・・・・・Dichroic mirror °゛3′°°
゛°1″S Fu・・・・・・・Liquid crystal light valve・・・・・Gikuroic prism・・・・・
...Projection lens...Screen...Filter for correcting in-plane brightness distribution
...Filter 0 for red in-plane brightness distribution correction
......Filter 1 for correcting the in-plane brightness distribution for lines...Filter 2 for correcting the in-plane brightness distribution for blue...
...... Field lens 3 ...... Liquid crystal compensation plate 4 ...... Liquid crystal panel 5 ...... Projection lens 6 ... ...Condensing optical system 7...Blue reflection jerky 8...
・・・・Green reflection dichroic 9・・・・・・・Blue reflection dichroic mitsu− Mitsu−

Claims (2)

[Claims] (1) a light source that generates light; a color separation means that receives the light and separates the light into three colored lights of red, green, and blue;
In a projection type display device comprising three liquid crystal light valves that modulate one of two colored lights, and a projection optical means for projecting the modulated colored light, the light passes through the three liquid crystal light valves. A projection type display device characterized in that a filter for correcting in-plane luminance distribution is inserted in three optical paths. (2) The filter for in-plane brightness correction is composed of a photographic film or a photosensitive plate, and after the photographic film or photosensitive plate is placed in the optical path before exposure, a light source is illuminated and the photo is exposed. 2. The projection type display device according to claim 1, wherein the film or photosensitive plate is developed to form a negative film or photosensitive plate, and is used as the filter for correcting the in-plane brightness.