JPH03146941A - Liquid crystal projection type display device - Google Patents

Abstract

PURPOSE:To eliminate an irregularity in contrast due to a difference in incidence angle, to reproduce and display an image of good quality, and to reduce the diameter of a projection lens by setting the angle of incidence of light on an optical control means equally to '0 deg.' over the entire plane. CONSTITUTION:The light from a light source 21 is diffracted spectrally into the three primary colors by dichroic mirrors 231 - 233 and the primary color light beams are controlled by liquid crystal light valves 241 - 243, passed through an optical multiplexing means consisting of dichroic mirrors 234 - 236, and projected and display by a lens 25. In this case, convex lenses 261 - 263 are set at the light incidence parts of the respective valves and convex lenses 271 - 273 are set at their light projection parts. Therefore, the optical axes of incidence of the respective valves are all made parallel through the convex lenses and projection light beams are refracted by the convex lenses toward the optical axes to set a uniform contrast in an image from the center part to the peripheral part.

Description

[Detailed description of the invention] (Objective of the invention) [Industrial application field] This invention controls light separated by a dichroic mirror through a light valve configured using a liquid crystal,
The present invention relates to a liquid crystal projection type display device that performs projection display.

[Prior Art] FIG. 3 shows an example of a conventional projection type display device using a liquid crystal. Light generated by a light source 11 is reflected by a spherical reflector 12, and is reflected by a condenser lens 13. make them parallel rays. The output light from this condensing lens 13 is supplied to a first dichroic mirror 141,
The light transmitted through the first dichroic mirror 141 is supplied to the second dichroic mirror 142, and the reflected light is supplied to the third dichroic mirror 143. The third dichroic mirror 143 reflects a part of the supplied light and supplies it to the fourth dichroic mirror 144 , while the other part passes through and supplies it to the fifth dichroic mirror 145 .

That is, the output light from the condenser lens 13 is split into three primary color lights of red (R), green (G), and blue (B) by the first to third dichroic mirrors 141 to 143, and these split lights are Liquid crystal light valves 151 to 153 corresponding to each of the three primary colors are set in the paths of the three primary colors. The three primary color lights respectively controlled by the liquid crystal light valves 151 to 153 are collected by the projection lens 16 via the sixth dichroic mirror 148, and are projected and displayed.

In the liquid crystal display device configured in this way, the light source 11
The lights are condensed by the condensing lens 13, and
The dichroic mirrors 141-143 separate the light into three primary color wavelengths, and the liquid crystal light valves 151-1
53 and are optically controlled. The light that has passed through the liquid crystal light valves 151 to 153 is transmitted to the fourth to sixth dichroic mirrors 144 to 14.
The images are combined again by B, and enlarged and projected onto the projection screen by the projection lens 16.

Here, the first to sixth dichroic mirrors 141-
146 is composed of a mirror that is specially coated so as to reflect only the wavelength range of the specified primary color light.

In such a projection display device, the positional relationship between the light source 11, the spherical reflecting mirror 12, and the condensing lens 13 is as follows.
Light can be collected most efficiently in the state shown in the figure. The solid angle Φ in this state is expressed by the following formula.

Φ−2π(1−cosθl) However, “0°≦θl≦900” Therefore, if the reflectance of the reflecting mirror I2 is R, then the fourth
The light collection rate Ω in the state shown in the figure is expressed by the following formula.

Ω−[(2π(1−cosθ1) ) /4π]x(
1+Rf) Then, assuming that the reflectance Rf of the reflecting mirror 12 is approximately "1", the condensing rate Ω is as follows.

Ω-1-eosθ1 As is clear from this equation, increasing θl increases the light collection efficiency, but in order to increase θ1, the reflector 12 or condensing lens 13 should be brought closer to the light source 11. Either the diameter must be increased or the diameter must be increased. However, the light source 11 emits high heat, and there is a limit to how close it can be.

Further, the reflected light from the reflecting mirror 12 is focused at the position of the light source 11, but the light source 11 is composed of, for example, a metal halide lamp, and since this metal halide lamp is opaque, the light collection rate is reduced. .

In the configuration of the condensing system using the spherical reflector 12 in this way,
There is a limit to increasing the light collection efficiency, and in order to further improve the light collection efficiency, a light collection system in which the reflecting mirror has an aspherical surface such as an ellipsoid or a paraboloid can be considered.

FIG. 5 shows an example using an aspherical reflecting mirror 121. If such a reflecting mirror 121 is used, the reflected light from the light source 11 will not be focused at the light source, but will be focused at the light source. There is no decrease in light rate. Furthermore, since the solid angle can be large, the light can be focused more highly than when using a spherical reflector.

In the aspherical reflecting mirror 121 used in this manner, under ideal circumstances, the reflected light is parallel to the optical axis. However, since the actual light source 11 has an arc length, the main optical axis at the center of the luminous flux is located at the liquid crystal light valve 1 as shown in FIG.
The end portion of 5 is in a widened state. Therefore, if light is allowed to pass through the liquid crystal light valve 15 in this state, a lens with a large diameter will be required. Therefore, as shown in FIG.
It is conceivable that a projection lens with a small diameter can be used by arranging the lens and bending the main optical axis in the direction of the optical axis.

When the convex lens 17 is installed in front of the liquid crystal light valve 15 in this way, the main optical axis of the light passing through this lens 17 is
As shown in FIG. 7A, the incident angle is large at the periphery of the liquid crystal light valve 15. (B) in Figure 7 is the same figure (
This is an enlarged view of the area indicated by the broken line in A), where the incident angle of the optical axis a at the center of the liquid crystal light valve 15 is set to 00, but the angle of incidence of the optical axis a to the peripheral area is The angle of incidence is set to θ.

In general, a liquid crystal light valve has an incident angle versus contrast characteristic as shown in FIG. Therefore, the contrast of the projected image differs between when the incident angle of the principal optical axis is 08 and when the incident angle is θ. In other words, images with different contrasts are projected between the center and the periphery.

[Problems to be Solved by the Invention] This invention has been made in view of the above points, and provides an object to project and display images using a liquid crystal light valve without using a particularly large-diameter projection lens or the like. At the same time, it is an object of the present invention to provide a liquid crystal projection type display device that can display a high-quality image in which the contrast between the center portion and the peripheral portion of the projected image is set to be uniform.

(Structure of the Invention) [Means for Solving the Problems] In the liquid crystal projection display device according to the present invention, the light emitted from the light source is divided into three parts by dichroic mirrors.
The three primary color lights are separated into primary colors, each of which is controlled by a liquid crystal light valve, and further combined by a light combining means constituted by a dichroic mirror for projection display. In this case, a first convex lens is set at the light incidence part of the liquid crystal light valve, and the output light from the liquid crystal light valve is guided to the projection means via the second convex lens.

[Function] In the liquid crystal projection display device configured in this way,
The optical axes of the light entering the liquid crystal light valve are all set in a parallel state by the first convex lens, and the light passing through this liquid crystal light valve is bent in the optical axis direction by the second convex lens. . Therefore, in the projected image, uniform contrast is set from the center to the periphery, and it is possible to use a small-diameter projection lens.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the overall configuration. Light from a light source 21 is reflected by a reflecting mirror 22 having a parabolic reflecting surface, for example, and is supplied to a first dichroic mirror 231. A part of the light supplied to this dichroic mirror 231 passes through this dichroic mirror 231 and is supplied to the second dichroic mirror 232.
A portion is reflected and supplied to the third dichroic mirror 233.

These first to third dichroic mirrors 211 to 23
Reference numeral 3 constitutes a spectroscopic means, in which the light wavelengths transmitted by each of the dichroic mirrors 231 to 233 are set corresponding to the three primary color lights of red, green, and blue, and the second and third dichroic mirrors The first and second primary color lights reflected by 232.213 and the third dichroic mirror 2
The third primary color light transmitted through 33 causes the three primary color lights to be output.

In the path of the output light from the second and third dichroic mirrors 232 and 233 constituting this spectroscopic means,
Liquid crystal light valves 241 to each control three primary color lights
243 is set. These LCD light valves 241
-243 are driven and controlled by signals corresponding to the three primary colors, respectively, and constitute a light control means.

A liquid crystal light valve 2 constituting this light control means
The light that has passed through each of 41 to 243 passes through or is reflected by the fourth dichroic mirror 234, and also passes through the fifth dichroic mirror 234.
The light is reflected by a dichroic mirror 235, collected by a sixth dichroic mirror 236, and projected as an image onto a projection screen (not shown) via a projection lens 25.

0 Here, first convex lenses 281 to 263 are interposed between the light incident sides of the liquid crystal light valves 241 to 248 and each of the dichroic mirrors in front thereof. Further, second convex lenses 271 to 273 are respectively set between the light output side of the liquid crystal light valves 241 to 243 and each of the subsequent dichroic mirrors.

FIG. 2 shows the light control part taken out, and shows a first convex lens 26, which sandwiches the liquid crystal light valve 24, to which the light emitted from the reflecting mirror 22 is supplied via a dichroic mirror as appropriate, and the liquid crystal light valve. A second convex lens 27 is provided to which the light transmitted through lens 24 is supplied. and,
A light beam with an open optical axis from the reflecting mirror 22 is converted into parallel light by the first convex lens 26 and supplied to the liquid crystal light valve 24. Further, the parallel light passing through the liquid crystal light valve 24 is converged by the second convex lens 27 and guided to the projection lens 25.

In other words, the first
The convex lens 17 (see FIG. 6) bends the light emitted from the condensing system 1 in the optical axis direction. Therefore, in the peripheral portion of the liquid crystal light valve, the incident angle θ was set as explained in FIG.

However, in the device shown in this embodiment, the first convex lens 2B sets the incident light to the liquid crystal light valve 24 to be parallel to the optical axis. That is, the incident light angle to the liquid crystal light valve 24 is "06" on the entire surface of this light valve 24,
There is no contrast difference between the center part and the peripheral part.

Also. If this parallel light is made to enter the projection lens 25 as it is, the diameter of the projection lens 25 must be made sufficiently large, but by arranging the second convex lens 27, the output light from the liquid crystal light valve 24 can be Since the projection lens 25 can be bent in the optical axis direction, the aperture of the projection lens 25 can be made small.

[Effects of the Invention] As described above, according to the liquid crystal projection type display device according to the present invention, the incident angle of light to the liquid crystal light knob constituting the light control means is uniformly “0” over the entire surface. Therefore, contrast non-uniformity due to differences in incidence angles is eliminated.

That is, it becomes possible to reproduce and display a high-quality image without uneven contrast over the entire surface, and at the same time, the projection lens can be made small in diameter.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining a liquid crystal projection type display device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a light control section used in this embodiment device, and FIG. 3 4 is a diagram illustrating the configuration of a conventional projection display device, FIG. 4 is a diagram also illustrating the condensing system, FIG. 5 is a diagram illustrating an example in which the reflecting mirror is changed, and FIG. Figure 7 showing an example
The figure is a diagram explaining the state of the luminous flux in this example, and FIG. 8 is a characteristic diagram showing the relationship between the light incident angle and the contrast with respect to the liquid crystal light valve. 21... Light source, 22... Reflector, 231-233.
...First to third dichroic mirrors (spectroscopy means)
, 234-23B... fourth to sixth dichroic mirrors (light synthesis means), 24.241-243...
Liquid crystal display lens, 25... Projection lens, 81-263... First convex lens, 27, 71-263... Second convex lens.

Claims (1)

[Scope of Claims] A spectroscopic means including a plurality of dichroic mirrors that separates light emitted from a light source into three primary colors; a light control means configured to include a plurality of liquid crystal light valves for controlling the three primary color lights, and combining the three primary color lights controlled by the light control means;
A light combining means including a plurality of dichroic mirrors; a projection display means for projecting light synthesized by the light combining means; dichroic mirrors corresponding to each of the three primary colors constituting the spectroscopic means; and a light control means. a first convex lens interposed between each liquid crystal light valve, and a plurality of liquid crystal light valves constituting the light control means;
A second dichroic mirror is interposed between the dichroic mirror corresponding to each of the three primary colors constituting the photosynthesizing means, respectively.
A liquid crystal projection type display device comprising: a convex lens; and a liquid crystal projection display device.