JPH0792587B2 - Projection liquid crystal display - Google Patents

Description

TECHNICAL FIELD The present invention relates to a projection type liquid crystal display device.

[Prior Art] Conventionally, as a projection type liquid crystal display device, there is one disclosed in JP-A-60-2916. This uses three liquid crystal panels with R, G, and B pixels formed, each liquid crystal panel is provided with a light source, and the light transmitted through each liquid crystal panel is combined using a dichroic mirror to be displayed on the screen. The image is displayed.

[Problems to be Solved by the Invention] In the above, three light sources are required, the light utilization efficiency is poor, and variations occur due to deterioration of the lamps, and there is a drawback that the image quality deteriorates. Moreover, since three lamps and three liquid crystal panels are used, the overall configuration is large. Further, different dichroic mirrors must be used, which causes an increase in manufacturing cost.

The present invention provides a projection type liquid crystal display device which requires only one light source and can be downsized.

[Means for Solving the Problem] According to the present invention, the light from one lamp is split into two systems of light rays at right angles to each other by two lenses, and a reflector is provided in the rear of the lamp corresponding to the lens, The two systems of light rays are reflected by the two reflection optical systems in the directions orthogonal to each other, and a dichroic mirror is provided at the orthogonal position of the reflected light beams, and a red and blue liquid crystal panel corresponding to one of the paths of the two systems of light rays. Is provided with a liquid crystal panel corresponding to green in the path of the other light beam, and a lens for converging light is provided between each liquid crystal panel and the dichroic mirror.

[Embodiment] In FIG. 1, 1 is a light source such as a halogen lamp or xenon lamp, 2 and 2 are cold mirrors that constitute a reflector, and 3 and 3 are split light from a light source into parallel light beams in two directions orthogonal to each other. Condenser lens, 4 and 4 are heat-proof filters. Reference numerals 5 and 5 are reflection mirrors, 6 is a liquid crystal panel compatible with R (red) and B (blue), and 7 is a liquid crystal panel compatible with G (green). In this example, as the liquid crystal panels 6 and 7, positive type TN
Type liquid crystal is used, and two polarizing plates 8 and 9 having polarization axes orthogonal to each other as shown in FIG. 2 are used, and P-polarized light is made incident on the dichroic mirror 10. is there. Reference numerals 11 and 11 denote convex lenses that converge parallel rays by θ (θ ≦ θ ≦ 5 °), and 12 denotes a projection lens system.

In the above configuration, the light from the light source 1 is reflected directly or by the cold mirrors 2, 2 and the condenser lens
It is incident on 3, 3 and becomes parallel rays. The parallel rays are reflected by the reflection mirrors 5, 5 via the heat insulating filters 4, 4 and supplied to the liquid crystal panels 6, 7. The light transmitted through the polarizing plate 8, the liquid crystal panel 7, and the polarizing plate 9 and the light transmitted through the polarizing plate 8, the liquid crystal panel 6, and the polarizing plate 9 are P-wave polarized light, which is θ by the convex lenses 11 and 11. It is converged and supplied to the dichroic mirror 10. By converging the parallel rays by the convex lens in this way, the aperture of the projection lens system can be made small and the aberration can be made small.

However, if θ is set to 5 ° or more, color shading is likely to occur on the screen and the image quality is deteriorated.

The dichroic mirror 10 uses a G-reflecting mirror. G light transmitted through the liquid crystal panel 7 is reflected and R and B light transmitted through the liquid crystal panel 6 are transmitted and combined to form a projection lens system. Projected by 12.

In this example, the P-polarized light is incident on the dichroic mirror 10, but this is for the following reason. According to an experiment by the applicant, TN is displayed on the liquid crystal panel.
In the case of linearly polarized light using a (twisted nematic) type liquid crystal, a ghost image due to multiple reflection may occur depending on the optical axis of the light incident on the dichroic mirror, and the image may have poor color purity. found. That is, there is no problem if the light is incident with P-wave polarization, but the above-mentioned drawbacks occur if the light is incident with S-wave polarization. This is because the surface reflectance of the glass is different between the P wave and the S wave as shown in FIG. 3 and the spectral characteristic of the dichroic mirror is different between the P wave and the S wave as shown in FIG. To do.

As can be seen from FIG. 3, near the incident angle of 45 °, the P wave is hardly reflected, but the S wave is reflected. This means that, in FIG. 5, when the S-wave is incident on the dichroic mirror 13, the light k having an unnecessary wavelength that is transmitted through the multilayer thin film 14 and then reflected at the boundary surface between the glass and the air is k. It means big. This also applies to transmitted light j, reflected light K and k and transmitted light J and j.
However, when the plate thickness of the glass is t, it is laterally displaced by 2t and enters the projection lens system. Since the projection lens magnifies about 10 to 100 times, if a normal mirror with a thickness of about 3 mm is used, the above deviation will be noticed and a ghost image will be projected.

In addition, FIG. 4 shows the spectral characteristics of the G reflection dichroic mirror at 45 ° incidence. The wavelength range of the reflected light is narrow for the P wave, whereas it is wide for the S wave. Recognize. In other words, when an S wave is input,
Not only G, but also light in the range close to R and B is reflected, and the color purity deteriorates.

Therefore, in this example, the dichroic mirror 10 has a P
It is configured such that wave-polarized light is incident. Therefore, there is almost no reflection of light having an unnecessary wavelength, and the reflected lights j and k in FIG. Therefore, a ghost does not appear on the screen, and the reflection of light of an unnecessary wavelength is eliminated, so that an image with good color purity can be obtained.

By the way, the light source 1 needs to be air-cooled because it has heat. However, according to the configuration of this example, the wind can be removed by rotating the fan from the front or rear of the drawing to efficiently cool the light. is there.

By the way, when a stereoscopic image display device is constructed by using two sets of the example shown in FIG. 1, as shown in FIG.
In front of the projection lenses 15 and 16, each set of G reflection dichroic mirrors 1 corresponding to the dichroic mirror 10 in FIG.
7 and 18 may be provided as shown in the figure. In this case, R and B lights are incident from the front of the projection lenses 15 and 16 and transmitted through the dichroic mirrors 17 and 18, and G light is incident from the side of the dichroic mirror 17 and above the dichroic mirror 18. It is a thing. This allows the dichroic mirrors 17 and 18 to make R,
The G and B lights are combined and supplied to the projection lenses 15 and 16 to project a stereoscopic image.

However, the light incident on the dichroic mirrors 17 and 18 is only P waves.

The position of the polarizing plate need not be on both sides of the liquid crystal panel, and the same effect can be obtained by arranging the polarizing plate in front of the projection lens or in front of the screen.

Further, in the above embodiment, the positive type is used as the TN type liquid crystal panel, but the negative type may be used. In this case, two polarizing plates whose polarization axes are parallel to each other are used.

According to the present invention, the light of one lamp is split into two light beams in the directions perpendicular to each other by the two lenses, and the reflector is provided in the rear of the lamp so as to correspond to the lens.
Light is used efficiently and a single lamp can provide high illuminance. Moreover, even if the lamp deteriorates, color unevenness does not occur, which is advantageous in terms of configuration and cost, and adjustment is easy. Moreover, only one expensive dichroic mirror is required and only two liquid crystal panels are required, which is inexpensive and structurally compact, which is advantageous in the assembly process. Furthermore, since a lens for converging light is provided between each liquid crystal panel and the dichroic mirror, the converged light is incident on the dichroic mirror, which can reduce the aperture of the projection lens system and also reduce aberration. You can

[Brief description of drawings]

1 is an explanatory view showing an embodiment of the present invention, FIG. 2 is a perspective view showing a part of FIG. 1 extracted, and FIG. 3 is a characteristic view showing surface reflectance of glass, FIG. 4 is a characteristic diagram showing the spectral characteristics of the G reflection dichroic mirror at 45 ° incidence.
FIG. 6 is an explanatory view showing the light reflected by the dichroic mirror, and FIG. 6 is an explanatory view showing the projection lens and the dichroic mirror in front of it when forming the stereoscopic image display device. 1 …… Light source 2,2 …… Cold mirror 3,3 …… Condenser lens 5,5 …… Reflecting mirror 6,7 …… LCD panel 10 …… Dichroic mirror 12 …… Projection lens system 15,16 …… Projection lens System 17,18 …… Dichroic mirror

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shingo Takahashi 4-1-1 Taihei, Sumida-ku, Tokyo Inside the stock company Seikosha (72) Inventor Tomoaki Takahashi 4-1-1 Taihei, Sumida-ku, Tokyo Stocks (56) References JP-A-60-179723 (JP, A) JP-A-58-117534 (JP, A) Actually open 59-41348 (JP, U) Actual-open Sho-58-67325 ( JP, U) JP-B-48-32124 (JP, B1) JP-B-55-49292 (JP, B1)

Claims (1)

[Claims] 1. A lamp, two lenses for splitting light from the lamp into two substantially parallel rays of light in directions orthogonal to each other, and a lamp provided behind the lamp corresponding to the lens. And a reflection plate, two reflection optical systems that reflect the two systems of light rays at right angles in a direction in which they are orthogonal to each other, and a light beam from one reflection optical system that is provided at a position orthogonal to the two systems of light rays. The light rays transmitted from the other reflection optical system are reflected to combine the light rays from the respective reflection optical systems, and 1
Dichroic mirror to be a system light beam, one red and blue liquid crystal panel provided on one of the two system light path, and one green corresponding liquid crystal panel provided on the other two system light path. A liquid crystal panel, a lens for converging light provided between each of the liquid crystal panels and the dichroic mirror, and a projection lens system for projecting one system of light rays from the dichroic mirror.