JPH0436745A - Projection display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a projection type display device that irradiates an image formed on a light valve with illumination light and projects the image onto a screen using a projection lens.

Conventional technology In order to obtain a large-screen image, light from a light source is irradiated onto a small light valve that forms an optical image according to the video signal.
A method of projecting and enlarging the optical image onto a screen is known. In this type of projection display device, the resolution of the projected image is almost determined by the resolution of the light valve, and increasing the luminous flux of the light source increases the light output, so if a high-resolution light valve is used, the display area can be reduced. It is possible to realize a projection type display device that is small but has high resolution and large light output. Furthermore, recently, a method using liquid crystal for a light valve has been attracting attention (for example, see page 375 of 5ID86 Digest).

A conventional projection display device using a liquid crystal panel as a light valve will be described.

FIG. 8 shows an example of the configuration of a conventional projection display device using a liquid crystal panel as a light valve.

Light from a light source 3 consisting of a lamp 1 and a parabolic mirror 2 that converts the white light emitted from the lamp 1 into approximately parallel light passes through an ultraviolet and heat ray cutting filter 4, and then passes through a blue-reflecting dichroic filter. The color light is separated into blue, green, and red color light by a color separation optical means 8 composed of a mirror 5, a green-reflecting dichroic mirror 6, and a red-reflecting dichroic ink mirror 7. After the blue-green and red color lights pass through the field lens 9, they are respectively displayed on an active matrix liquid crystal panel 10B.
, IOG, and IOR. LCD panel l0B10G
, An optical image is formed on the IOR according to the video signal.

The blue, green, and red color lights output from the liquid crystal panels IOB, IOC, and IOR, respectively, are transmitted through three channels whose optical axes are arranged in parallel.
Book projection lens IIB, IIG, 11. The image is enlarged and projected onto the screen 12 by R. Images of each color light are synthesized on the screen 12 by slightly changing the position and tilt of the liquid crystal panel.

Problems to be Solved by the Invention In FIG. 8, the illuminance distribution of illumination light has a property of rapidly attenuating on a plane perpendicular to the optical axis according to the distance from the optical axis. Therefore, the difference in brightness between the center and the periphery of the projected image becomes large. Also, from the light source to the light valve surface (liquid crystal panel IOB, IOC).

If the optical path lengths up to 10R) are different, the illuminance distribution on each light valve surface will change, and the brightness of the projected image will change.

This has the problem of causing color unevenness. Furthermore, in the system using three projection lenses, since the optical axes of each projection lens are arranged in parallel, the blue and green of the projected image are determined by the law of cos' θ of the projection lenses.

The problem is that the illuminance ratio of red changes depending on the location on the screen, resulting in uneven brightness of one color.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a projection display device in which a projected image has less unevenness in brightness and color.

Means for Solving the Problems In order to solve the above-mentioned problems, a projection display device of the present invention includes a light source and a blue light source that emits white light from the light source.

a color separation optical means that separates light into green and red color components; three light valves that receive the light emitted from the color separation optical means and form an optical image according to a video signal; a screen; It is equipped with three projection lenses that receive the light emitted from the light valve and project the optical image onto a screen, and a light attenuator having a transmittance distribution.

Further, the projection type display device of the present invention includes a light source, a color separation optical means for separating white light from the light source into light of blue, green, and red color components, and receiving light emitted from the color separation optical means. Three light valves that form an optical image according to the video signal,
a color synthesis optical means for synthesizing light of blue, green and red color components emitted from the light valve; a projection lens for receiving the light emitted from the light valve and projecting the optical image onto a screen; The light attenuating means has a distribution.

Operation The present invention has the above-described configuration, and by providing a light attenuation means having a transmittance distribution, the illuminance distribution of the illumination light irradiated onto the light valve is made uniform. Also, from the light source
The blue color depends on the location on the screen, which is caused by the difference in the optical path length to the surface of the two light valves and the difference in the optical axis position of the three projection lenses.

Changes in the illuminance ratio of green and red can be made uniform over the entire screen, and unevenness in two colors of brightness can be reduced.

EXAMPLE A first example of the projection type display device of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a projection type display device in this embodiment, in which a liquid crystal panel is used as a light valve. In FIG. 1, 20 is a lamp, 21 is a parabolic mirror, 22 is a light source composed of the lamp 20 and the parabolic mirror 21, 23 is an ultraviolet ray/heat ray cutting filter, 24.32
．． 33 is a film thickness distribution type ND filter, 25 is a blue-reflecting dichroic mirror, 26 is a green-reflecting dichroic mirror, 27 is a red-reflecting dichroic mirror, and 28 is a color separation optical means consisting of a dichroic mirror 25.26°27. , 29B, 29G.

29R is a field lens, 30B, 30G, 30R are liquid crystal panels, 31B, 31G, 31R are projection lenses, 3
4 is a screen.

Light emitted from a lamp 20 such as a metal halide lamp, a xenon lamp, or a halogen lamp is converted into substantially parallel light by a parabolic mirror 21. The substantially parallel light from the light source 22 is filtered by the ultraviolet rays and heat rays cut filter 23 so that the ultraviolet rays and heat rays are not transmitted to the front surface, and is then passed through the thickness distribution type ND.
The illumination light is made uniform by the filter 24 and enters the color separation optical means 28 .

The color separation optical means 28 first reflects a blue component using a blue-reflecting dichroic mirror 25 and transmits red and green components. Next, the light transmitted through the dichroic mirror 25 enters the green-reflecting dichroic mirror 26, where only the green component is reflected and the red component is transmitted. Finally, the red component is reflected by a red-reflecting dichroic mirror 27, and unnecessary color components are transmitted. Blue separated by color separation optical means 28.

Field lenses 29B and 29G emit green and red light.

After passing through 29R, the light enters three transmission type liquid crystal panels 30B, 30G, and 30R arranged on the same plane. Field lenses 29B, 29G, 29R are liquid crystal panel 30B
, 30G, 30R, the projection lens 3
1B, 31G, and 31R, and is a plano-convex lens with its flat side facing the liquid crystal panels 30B, 30G, and 30R. The liquid crystal panels 30B, 30G, and 30R are of an active matrix type, and an optical image is formed as a change in transmittance according to a video signal.

The optical image formed by the liquid crystal panels 30B, 30G, and 30R is produced by three projection lenses 31 whose optical axes are arranged parallel to each other.
B, 31G, and 31R are enlarged and projected onto the screen 34, and the projected images of blue, green, and red are combined on the screen 34.

The transmittance of the light emitted from the projection lenses 31B and 31R is controlled by the thickness distribution type ND filters 32 and 33,
The image is enlarged and projected onto the screen 34.

Three liquid crystal panels 30B and 30G on the screen 34.

In order to synthesize images formed by 30R, three liquid crystal panels 30B, 30C; two liquid crystal panels 30B, 30R other than the central part of 30R are connected to projection lenses 31B, 31.
The blue, green, and red projected images are superimposed on the screen 34 by slightly changing the position and inclination on the plane with respect to the R optical axis.

The illuminance distribution of the illumination light is determined by the light distribution characteristics of the lamp 20,
It is determined by the positional relationship between the light emitting part of the lamp and the parabolic mirror 21, and the shape of the light emitting part of the lamp 20, and the illuminance on a plane perpendicular to the optical axis has the property of attenuating rapidly depending on the distance from the optical axis. However, the difference in brightness between the center and the periphery of the projected image increases. Therefore, between the light source 22 and the color separation optical means 28, a thickness distribution type ND filter 24 whose transmittance increases according to the distance from the optical axis is arranged as shown in FIG. Equalize the illuminance between the center and the periphery. Note that the horizontal axis in FIG. 2 is normalized by the maximum distance from the optical axis of the effective luminous flux from the light source. This film thickness distribution type ND filter 24 has Inconel deposited on a glass substrate, and the light absorption concentration is controlled by the film thickness to change the transmittance.

In the imaging optical system, the illuminance E on the screen 34 is expressed as E=-Eo-cos' θ, where K is the aperture efficiency of the projection lens, and θ is the angle of view of the projection lens. Here, Eo is the illuminance on the screen 34 on the optical axis of the projection lens. Therefore, screen 3
The illuminance above 4 decreases as the angle of view θ increases. FIG. 3 shows the illuminance distribution of the projected image on the screen 34 when viewed from the X direction in FIG. Here, the illuminance is standardized by the maximum illuminance on the screen, and the three projection lenses 31B, 31
The case where light of the same wavelength is incident on G and 31R is shown. In the figure, the solid line shows the illuminance distribution of the projection lens 31G, the dashed-dot line shows the projection lens 31B, and the two-dot chain line shows the illuminance distribution of the projection lens 31R, and the horizontal axis is normalized by the maximum horizontal distance of the screen effective display area from the center of the screen. There is.

Therefore, the illuminance distribution on the screen 34 differs between blue, green, and red, and the illuminance ratio of blue, green, and red in the composite image changes depending on the location. When the white balance is adjusted at the center of the screen, the blue component is relatively stronger on the left side of the screen compared to the center, resulting in a higher color temperature of the image. On the right side of the screen, the red component is relatively strong and the color temperature of the image decreases.

Further, even when the illuminance distribution of illumination light differs on the blue, green, and red liquid crystal panel surfaces, color unevenness occurs in the projected image.

In order to make this blue, green, and red illuminance ratio uniform across the screen,
Light emitted from the blue and red projection lenses 31B and 31R is controlled by thickness distribution type ND filters 32 and 33. The transmittance distribution of the thickness distribution type ND filters 32 and 33 is set to correct the cos' θ law of the projection lens and illumination non-uniformity due to illumination light. .33 transmittance characteristic diagram is shown. In FIG. 4, the dashed-dotted line is a characteristic diagram of the film thickness distribution type ND filter 32, and the solid line is a characteristic diagram of the film thickness distribution type ND filter 33. Here, the distance from the optical axis on the horizontal axis is the film thickness distribution type ND filter 32, 33 corresponding to the screen horizontal distance in FIG.
It is the distance above, and is standardized by the maximum distance.

The film thickness distribution type ND filters 32 and 33 are arranged between the projection lenses 31B and 31R and the screen 34.
It is placed near the front lens of 1B and 31R. This is because the vicinity of the front lens has a small influence on image formation, and the film thickness distribution type ND filters 32 and 33 are located near the projection lens 31.
This is because it can be made as small as . FIG. 5 shows a chromaticity diagram showing the color unevenness correction effect of the film thickness distribution type ND filter. (a) is before correction, (b) is after correction Screen 3
4 is the chromaticity distribution of the white projected image above. It can be seen from FIG. 5 that color unevenness is well corrected by the film thickness distribution type ND filters 32 and 33.

A polarizing plate may be used as a means for attenuating the light emitted from the projection lenses 31B and 31R. Since the light emitted from the projection lens is linearly polarized light, the light transmittance can also be controlled by a polarizing plate. The polarizing plate is arranged so as to partially attenuate the light emitted from the projection lens. In this case, since the deflection plate is partially arranged, the transmittance changes discretely, but this effect is small if the area has a small effect on imaging.

Similarly, the transmittance characteristics of the film thickness distribution type ND filter shown in FIG. 5 may also be discrete.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 6 shows the configuration of a projection type display device according to a second embodiment of the present invention. In FIG. 6, the light source 221
Color separation optical means 28. Field lens 29B, 29G
, 29R, LCD panel 30B, 30G, 30R1 projection lens 31B, 31C; , 31R, screen 34 is the first
Since the configuration is similar to that shown in the figure, detailed explanation thereof will be omitted.

This embodiment differs from FIG. 1 in a color separation optical means 28 and a liquid crystal panel 30B.

The point is that thickness distribution type h+D filters 35, 36, and 37 are arranged in the optical path between 30G and 30R.

The film thickness distribution type ND filters 35, 36, and 37 uniformly change the illuminance distribution of the illumination light and the illuminance ratio of blue, green, and red of the images projected by the projection lenses 31B, 31G, and 31R over the entire screen, and further, LCD panels 30B and 30G.

It has a transmittance distribution that ensures the white balance of each color light incident on 30R. By configuring like this,
Since the white balance of each color light incident on the liquid crystal panel is ensured, light loss on the liquid crystal panel is minimized, and the reliability of the liquid crystal panel is improved. In addition, the brightness between the center and the periphery of the projected image and the illuminance ratio of blue, green, and red of the projected image are made uniform over the entire screen, and unevenness in one color of brightness is reduced.

A third embodiment of the projection display device of the present invention will be described below with reference to the drawings. FIG. 7 shows the configuration of a projection type display device of the present invention.

Light source 22, color separation optical means 28, field lens 29
B, 29G, 29R1 liquid crystal panel 30B, 30C;, 3
0R.

The film thickness distribution type ND filter 24 is the same as that in the first embodiment. 40 is a dichroic prism which is a color synthesis means;
41 is a projection lens, and 43 and 44 are mirrors.

The substantially parallel light from the light source 22 has ultraviolet rays and heat rays cut by the ultraviolet rays and heat rays cut filter 23, and the thickness distribution type ND
After the illumination light is made uniform by the filter 24, it is separated into blue, green, and red color light by the color separation optical means 28. blue,
The green and red color lights are incident on the liquid crystal panels 30B, 300.3OR, and optical images are formed on the liquid crystal panels 30B, 30G, 30R as changes in transmittance according to the video signal. LCD panels 30B, 30G.

The light emitted from 30R is combined into each color light by a color combining optical means, which is a dichroic prism 40, and then enlarged and projected by a projection lens 41.

The distances from the light source 22 to the liquid crystal panels 30B, 30G, and 30R are the same for blue and green color lights, but differ only for the red color light. For this reason, the blue and green LCD panels are 30G.

The illuminance distribution of the illumination light on the liquid crystal panel 30B and the liquid crystal panel 30R changes, causing color unevenness in the composite projected image. The transmittance of red component light is suppressed by the film thickness distribution type ND filter 42 so that the illuminance distribution on each liquid crystal panel surface is the same. Therefore, the brightness between the center and the periphery of the projected image and the illuminance ratio of blue, green, and red of the projected image are made uniform over the entire screen, and two-color unevenness in brightness is reduced.

In addition, the above 1. In the second and third embodiments,
Although an example is shown in which a liquid crystal panel is used as a light valve, the same effect can be obtained by using a light valve that forms an optical image according to a video signal as a change in birefringence or optical rotation such as an electro-optic effect.

Effects of the Invention As described above, according to the present invention, the light attenuating means has a transmittance distribution for blue and green.

The illuminance distribution of the illumination light on the red liquid crystal panel surface and the illuminance ratio of blue, green, and red of the projected image can be made uniform across the entire screen, and unevenness in one color of brightness can be reduced, resulting in an outstanding industrial effect.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a projection type display device according to a first embodiment of the present invention, and FIGS. 2 and 4 are transmittance characteristic diagrams of a film thickness distribution type ND filter according to a first embodiment of the present invention. , FIG. 3 is an illuminance distribution diagram of a projected image according to the first embodiment of the present invention, and FIG.
The figure is a chromaticity diagram of a white projection image showing the color unevenness correction effect according to the first embodiment of the present invention, FIG. 6 is a configuration diagram of a projection type display device according to the second embodiment of the present invention, and FIG. 8 is a configuration diagram of a projection type display device according to a third embodiment of the present invention, and FIG. 8 is a configuration diagram of a conventional projection type display device. 20... Lamp, 21... Parabolic mirror,
22... Light source, 23... Ultraviolet/heat ray cut filter, 24.32.33°35, 36.37
．． 42...Film thickness distribution type ND filter, 25...
...Blue reflective dichroic mirror, 26...
...Green reflective dichroic mirror, 27...
Red reflective dichroic mirror, 28... Color separation optical means, 29B. 29G, 29R・・・Field lens, 30B
, 30C;. 30R...LCD panel, 31B, 31G, 31
R, 41...Projection lens, 34...Screen, 40...Dichroic prism,
43.44...Mirror Fig. 2 1.0 Distance from the tip axis Diagram Water from the middle of the screen qL15 Distance 1 Fig. 1.0 O Distance from the tip axis

Claims (10)

[Claims] (1) A light source, a color separation optical means for separating white light from the light source into light of blue, green, and red color components, and an optical image according to a video signal received by the light emitted from the color separation optical means. a screen, three projection lenses that receive light emitted from the light valves and project the optical image onto the screen, and a light attenuator having a transmittance distribution. A projection display device equipped with (2) The projection type display device according to claim (1), further comprising a light attenuation means between the projection lens and the screen. (3) The projection type display device according to claim (1), further comprising a light attenuation means between the light source and the color separation optical means. (4) The projection type display device according to claim (1), further comprising a light attenuation means between the color separation optical means and the light valve. (5) The projection display device according to any one of claims (1) to (4), wherein the light attenuation means is a thickness distribution type ND filter. (6) The projection display device according to any one of claims (1) to (4), wherein the light attenuation means is a polarizing plate. (7) a light source, a color separation optical means for separating white light from the light source into blue, green, and red color component light; and an optical image according to a video signal received by the light emitted from the color separation optical means. a color synthesis optical means for synthesizing light of blue, green, and red color components emitted from the light valves; and a color synthesis optical means for synthesizing the light of blue, green, and red color components emitted from the light valves, and a color synthesis optical means that receives the light emitted from the light valves and forms the optical image. A projection display device includes a projection lens that projects onto a screen and a light attenuator having a transmittance distribution. (8) The projection type display device according to claim (7), further comprising a light attenuation means between the light source and the color separation optical means. (9) The projection type display device according to claim (7), further comprising a light attenuation means between the color separation optical means and the light valve. (10) The projection display device according to any one of claims (7) to (9), wherein the light attenuation means is a thickness distribution type ND filter.