JPH04267231A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a projection type liquid crystal display device having a high brightness by separately focusing a light beam having a circular cross-sectional shape at the emission from a light source in both directions vertical and lateral of a liquid crystal light valve so that the efficiency of incidence upon a rectangular aperture of the liquid crystal light valve may be increased since the light beam can be radiated to the rectangular aperture with an elliptic shape. CONSTITUTION:A parallel light ray beam emitted from a light source 1 is focused by a convex lens 2 and is subjected to color-separation by dichroic mirrors 4, 5 and a reflection mirror 6. The separated beams are refocused only in the vertical direction by a cylindrical lens 7 and is optically modulated by liquid crystal light valves 8R, 8G, 8B. Thus optically modulated separated light beams are color-synthesized by dichroic mirrors 10, 11 and a reflection mirror 6, and is then enlarged and projected onto a screen 13 by a projection lens 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type liquid crystal display device in which an image formed by a liquid crystal light valve is enlarged and projected by a projection lens.

0002

2. Description of the Related Art Conventionally, a convex lens is disposed between a light source and a liquid crystal light valve, and a light beam from the light source is condensed near the entrance pupil of a projection lens.

0003

[Problems to be Solved by the Invention] A light source used in a projection type liquid crystal display device generally has a configuration in which a light beam diverging radially from a lamp is converted into a parallel light beam by a reflector having a circular cross section in the direction perpendicular to the optical axis. It is true. Further, the aperture of a liquid crystal light valve is generally rectangular. Therefore, the emitted light beam from the light source has a circular cross-sectional shape, and even after passing through a convex lens that is rotationally symmetrical with respect to the optical axis and is arranged on the optical path leading to the liquid crystal light valve, the cross-sectional shape is circular. That is, since the light flux that illuminates the aperture of the liquid crystal light valve also has a circular cross-sectional shape, a large amount of light flux is lost without entering the rectangular aperture. This loss increases as the aperture of the liquid crystal light valve becomes horizontally elongated, so this is an extremely important issue for high-definition liquid crystal light valves, that is, liquid crystal light valves with an aperture aspect ratio of 16:9. Become.

The projection type liquid crystal display device of the present invention solves the above problems, and its purpose is to provide a high brightness projection type liquid crystal display device that has high efficiency in utilizing the emitted light flux from the light source. There is a particular thing.

[0005]

[Means for Solving the Problems] In order to solve the above problems, a projection type liquid crystal display device of the present invention includes a light source, a light separation means for separating light from the light source, and a light separation means for modulating the light from the light separation means. In a projection type liquid crystal display device having a liquid crystal light valve that combines light modulated by the liquid crystal light valve, a light combining means that combines light modulated by the liquid crystal light valve, and a projection lens that projects the light from the light combining means, between the light source and the liquid crystal light valve, It is characterized by a convex lens and a cylindrical lens arranged in series. Another feature is that a toric lens is placed between the light source and the liquid crystal light valve.

[0006]

Embodiment 1 FIG. 1 is a block diagram of an optical system in an embodiment of the present invention. The light source 1 includes a lamp filled with halogen, xenon, metal halide gas, etc., and a reflector that reflects divergent light emitted from the lamp as parallel light. The light emitted from the light source 1 is condensed by a convex lens 2 and enters a light separating means 3. The light separating means 3 includes dichroic mirrors 4 and 5.
For example, by providing the dichroic mirror 4 with wavelength characteristics for red reflection, and providing the dichroic mirror 5 with wavelength characteristics for blue transmission, the incident light can be converted into the three primary colors of red, green, and blue. To separate. Each color light separated by the light separation means 3 is refocused only in the vertical direction by a cylindrical lens 7 disposed on each optical path, and is incident on liquid crystal light valves 8R, 8G, and 8B corresponding to each color. do. Here, each color light is subjected to light modulation corresponding to each color by the liquid crystal light valves 8R, 8G, 8B, that is, a transmittance variable operation according to a signal voltage, and an image is formed for each color. 9. LCD light bulb 8R, 8G,
8B generally has a configuration in which polarizing plates are placed before and after an active matrix liquid crystal panel. The light combining means 9 is composed of dichroic mirrors 10 and 11 and a reflecting mirror 6. For example, the dichroic mirror 10 is provided with a wavelength characteristic for transmitting red, and the dichroic mirror 11 is provided with a wavelength characteristic for reflecting blue. are synthesized as full-color image light. The light emitted from the light combining means 9 is enlarged and projected by the projection lens 12 to form a full color image on the screen 13 in front. In addition, the dichroic mirrors 4 and 5 and the dichroic mirror 10,
By manipulating the wavelength characteristics of the liquid crystal light valves 11, the arrangement of the liquid crystal light valves 8R, 8G, and 8B can be changed as appropriate.

FIG. 2 is a schematic diagram of the illumination system in FIG.
A convergence point 14 for light in the vertical direction and a convergence point 15 for light in the horizontal direction
This shows how the light is focused. The focal point 14 is determined by the focal length of the convex lens 2 and the cylindrical lens 7 and the relative position between both lenses, and the focal point 15 is determined by the focal length of the convex lens 2, but is located between the two focal points. In order to improve the light utilization efficiency, it is important to provide the entrance pupil of the projection lens 12 near the point 16 (circle of least confusion) where the cross-sectional area of light is the smallest. Further, FIG. 3 is a diagram showing the relationship between the aperture 17 of the liquid crystal light valve 8 and the irradiation light 18,
When the ellipse that is the cross-sectional shape of the irradiated light 18 circumscribes the aperture 17 and the difference between the cross-sectional area of the irradiated light 18 and the area of the aperture 17 (the shaded area in the figure) is minimized, the light incident on the aperture 17 is Since it increases the maximum, it is important to set the focal length and relative positional relationship of the convex lens 2 and the cylindrical lens 7 so as to be as close as possible to this. The cross-sectional shape of the light beam emitted from the light source 1 is circular, and the difference in area increases as the aperture 17 becomes horizontally longer.
This improvement in light utilization efficiency is particularly effective in high-definition liquid crystal light valves having an aspect ratio of 16:9.

The arrangement and number of the convex lens 2 and the cylindrical lens 7 are not limited to those shown in FIG. 1, and may be arranged on each optical path so that the same light condensing state can be achieved for each liquid crystal light valve. In particular, when both lenses are arranged in series between the light separating means 3 and the liquid crystal light valve 8, the parallelism of the light emitted from the light source 1 is maintained within the light separating means 3, so that the dichroic mirrors 4, 5 There is an advantage that there is no need to consider the angular dependence of the wavelength characteristics of the dichroic mirrors 4 and 5, and the design and manufacture of the dichroic mirrors 4 and 5 become easier.

(Embodiment 2) FIG. 4 is a schematic diagram of an illumination system in another embodiment of the present invention. By disposing a toric lens 19 between the light source 1 and the liquid crystal light valve 8, This embodiment realizes a condensing illumination system similar to the embodiment shown in FIG. Here, the concept of each element other than the illumination system is exactly the same as in the previous embodiment. The toric lens 19 is a lens that has separate refractive powers in the vertical direction and in the horizontal direction, and is a lens that actively generates astigmatism. Therefore, as shown in FIG. 4, for the parallel light flux from the light source 1, there is a convergence point 20 for vertical light and a convergence point 21 for horizontal light of the liquid crystal light valve. A condensing illumination system similar to the illumination system shown in can be formed. The concept of refractive power in the vertical direction and in the horizontal direction is the same as in the above embodiment, and is determined by the relative positional relationship of the light source 1, toric lens 19, liquid crystal light valve 8, and projection lens 12, and the resulting circle of least confusion 22 is It is necessary to arrange the entrance pupil of the projection lens 12 nearby. The arrangement of the toric lens 19 is also the same as in the above-mentioned embodiment, and it may be arranged anywhere on each optical path as long as it can achieve the same light condensing state for each liquid crystal light valve. The advantage of this embodiment is that the number of lenses arranged in series is reduced compared to the previous embodiments, and as a result, the optical system can be made smaller.

0010

Effects of the Invention As explained above, the projection type liquid crystal display device of the present invention can reduce the light source by arranging a convex lens and a cylindrical lens in series or by arranging a toric lens between the light source and the liquid crystal light valve. Since the light beam emitted from the light source has a circular shape, the rectangular aperture of the liquid crystal light valve can be irradiated in an elliptical shape, making it possible to focus the light beam emitted from the light source onto the aperture of the liquid crystal light valve with high efficiency. Yes, it is possible to realize a high-brightness projection type liquid crystal display device. This becomes more effective as the aperture of the liquid crystal light valve becomes more horizontally long, and the effect is particularly large in liquid crystal light valves compatible with high-definition vision.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an optical system in an embodiment of the present invention.

FIG. 2 is a schematic diagram of the illumination system in FIG. 1.

FIG. 3 is a diagram showing the relationship between the aperture of the liquid crystal light valve and irradiation light.

FIG. 4 is a schematic diagram of an illumination system in another embodiment of the invention.

[Explanation of symbols]

1. Light source 2 Convex lens 3. Light separation means 7 Cylindrical lens 8.LCD light bulb 9. Photosynthesis means 12 Projection lens 13 Screen 19 Toric lens

Claims (2)

[Claims] 1. A light source, a light separation means for separating light from the light source, a liquid crystal light valve for modulating the light from the light separation means, and a light synthesis means for combining the light modulated by the liquid crystal light valve. and a projection lens for projecting light from the light combining means, wherein a convex lens and a cylindrical lens are arranged in series between the light source and the liquid crystal light valve. Display device. 2. The projection type liquid crystal display device according to claim 1, further comprising a toric lens disposed between the light source and the liquid crystal light valve.