JPH06118437A - Projection type display device - Google Patents

Abstract

PURPOSE:To obtain a projection type display device provided with an optical system capable of preventing resolution from being lowered due to aberration. CONSTITUTION:This device is a projection type display device including a polarizing beam splitter 6 which transmits a flux of beams emitted from a light source and a photoconductive liquid crystal light bulb 1 which reflects the beam while attaching a projection image on the bundle of beams, and it is provided with at least two dichroic mirrors 10 arranged obliquely plane- symmetrically against a plane setting the center optical axis of the flux of beam while a normal between the polarizing beam splitter 6 and the photoconductive liquid crystal light bulb 1 and which divide the flux of beams into wavelength components, and an astigmatism correction means arranged on the incident or emitting plane of the polarizing beam splitter 6, or between the polarizing beams splitter 6 and the photoconductive liquid crystal light bulb 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a polarizing element such as a polarizing plate or a polarizing beam splitter through which a light beam emitted from a light source is transmitted, and a projection image is formed on the light beam of the S or P polarization component in the light beam. The present invention relates to a projection type display device which has a photoconductive liquid crystal light valve that reflects the light while imparting it, and projects the reflected light by a projection lens system.

[0002]

2. Description of the Related Art Such a projection type display device uses a photoconductive type liquid crystal light valve (LCLV element). Such a photoconductive liquid crystal light valve is of a reflective type in which a reflective layer or the like is provided between the liquid crystal layer and the photoconductive layer. FIG. 1 shows an example of a monochrome type configuration of such a projection type liquid crystal display device. In the figure, the photoconductive layer side of the photoconductive liquid crystal light valve 1 is coupled to the front face of the CRT 2. The CRT writes the image displayed on its front face into the photoconductive layer of the conductive type liquid crystal light valve 1 via the optical fiber layer. The grayscale of the projected image of the liquid crystal layer is formed according to the potential of the photoconductive layer. On the other hand, the luminous flux emitted from the light source 3 such as a metal halide lamp is received by the cold mirror 4,
After passing through optical elements such as the condenser lens 5 and the polarizing plate 7,
It is incident on the polarization beam splitter 6. The P-polarized component of this incident light passes through the polarization beam splitter 6. S
The polarization component has its traveling direction bent by the polarization beam splitter 6 and enters the photoconductive liquid crystal light valve 1.

Here, when a projected image is drawn on the liquid crystal layer of the photoconductive liquid crystal light valve 1, the reflected light reflected by the photoconductive liquid crystal light valve 1 depends on the light and shade of the image of the liquid crystal layer. The P-polarized component will be locally included.
Then, only the P-polarized component in the reflected light passes through the polarization beam splitter 6 as it is, so that the image of the P-polarized component is projected on the screen 9 through the projection lens 8.

In a projection type liquid crystal display device using such a photoconductive type liquid crystal light valve, a light beam bundle RGB is provided between the polarization beam splitter and the photoconductive type liquid crystal light valve.
A color projection type liquid crystal display device is known in which a dichroic mirror that divides into (red, green and blue) wavelength components is arranged and three CRTs that emit RGB light are used.

[0005]

In such a color projection type liquid crystal display device, a light source such as a metal halide lamp emits a bundle of parallel rays by a reflector of a concave reflecting mirror arranged so as to surround the metal halide lamp, but in a diverging or converging state. Also emits a ray bundle of. In the color projection type liquid crystal display device, since a plurality of dichroic mirrors are arranged in the optical system that shares the incident / reflecting path of the light flux emitted from the metal halide lamp, the divergent or convergent light flux passes through the dichroic mirror. At that time, aberration occurs, which becomes a problem. Since the dichroic mirror has parallel entrance and exit surfaces and is arranged so that its entrance and exit surfaces are inclined with respect to the optical axis of the ray bundle, the dichroic mirror has a divergent or convergent ray bundle passing through it. Gives astigmatism. Furthermore, the dichroic mirror not only produces astigmatism but also coma that cannot be ignored. Therefore,
In a color projection display device using a photoconductive liquid crystal light valve, astigmatism and coma also cause a reduction in resolution and contrast.

An object of the present invention is to provide a projection type display device having an optical system which prevents a reduction in resolution due to aberration.

[0007]

A projection type display device of the present invention comprises a polarizing beam splitter which transmits a light beam emitted from a light source, and a photoconductive liquid crystal which imparts a projected image to the light beam while reflecting it. A projection display device including a light valve, which is tilted symmetrically with respect to a plane having a center optical axis of the light flux as a normal line between the polarization beam splitter and the photoconductive liquid crystal light valve. At least two dichroic mirrors that are arranged and divide the light flux into its wavelength components, and are arranged on the entrance or exit surface of the polarization beam splitter or between the polarization beam splitter and the photoconductive liquid crystal light valve. And astigmatism correction means.

[0008]

According to the present invention, it is possible to prevent the resolution from being lowered due to the aberration of the dichroic mirror in the projection type display device.

[0009]

EXAMPLE FIG. 2 shows a projection display device using three CRTs for red (R), green (G) and green (B). The apparatus comprises three CRTs 2R, 2G and 2B for RGB, three LCLV elements 1 mounted for RGB each of which imparts a projected image to an incident ray bundle while reflecting it.
R, 1G and 1B, a total reflection mirror 10, a green reflection dichroic mirror 10G, a blue reflection dichroic mirror 10B, a liquid polarizing prism 6 that transmits a light beam emitted from a light source, a zoom lens 8, a polarizing plate 7, a prepolarizer 20, Infrared (IR) cut filter 31, reflector 3
2, equipped with a metal halide lamp 3. The polarizing plate 7 arranged near the light receiving surface of the polarization beam splitter 6 is provided to increase the degree of polarization. Prepolarizer 20
In order to use the P-polarized component as the projection light, the degree of polarization is increased upstream of the polarization beam splitter 6.

FIG. 3 is a plan view of the apparatus shown in FIG. 2 viewed from the X direction in the figure. As shown, this projection display device
It is suitable for correcting the astigmatism generated on the parallel slant surface of the glass plate of the dichroic mirror composed of the glass plate and the reflection film. That is, in the green optical system including the green reflection dichroic mirror 10G, astigmatism does not occur because the reflection from the green reflection dichroic mirror 10G passes through the reflection of the total reflection mirror 10. In the red optical system for the red color where the light bundle passes through the green reflection dichroic mirror 10G and the blue reflection dichroic mirror 10B, the light bundle passes through the glass flat plate, so that astigmatism occurs in each mirror, but each mirror 10G and Since the reflection directions of 10B are rotated by 90 degrees with respect to the central optical axis of the bundle of rays, the astigmatisms cancel each other out. In the blue optical system, the blue reflective dichroic mirror 10B is formed by laminating the dichroic film 10Bb between two parallel flat plates 10Ba, and the light is reflected by the dichroic film. To cancel.
Therefore, astigmatism can be almost corrected as described above with the configurations shown in FIGS.

However, the coma aberration is as shown in FIGS.
With the configuration shown in (2), the blue and red optical systems cannot be corrected, and they appear as aberrations. Then, the projection type display apparatus of Example 1 according to the present invention shown in FIG. 4 is prepared. Since coma aberration occurs due to the deterioration of the sine condition and the asymmetry of the refraction point coordinates, in the present embodiment, it is arranged in a conjugate manner so as to cancel the coma aberration factors caused by the transmission and refraction of the two dichroic mirrors. The coma aberration is removed by setting the pair of dichroic mirrors.

This projection type display device has the same structure as the projection type display device shown in FIGS. 2 and 3, and FIG. 5 (a) shows a main part showing its characteristics. Green reflective dichroic mirror 10G and blue reflective dichroic mirror 10B
Are arranged between the polarization beam splitter 6 and the photoconductive liquid crystal light valve 1, and are further arranged so as to be plane-symmetrical with respect to a plane P whose normal is the central optical axis of the light beam bundle. As a result, the coma aberrations generated by the dichroic mirrors can be canceled by each other.

On the other hand, astigmatism is caused by each of the mirrors 10G and 1G.
Since the reflection directions of the 0B ray bundles are parallel, they are generated. Therefore, the cylindrical lens 40 is arranged between the green reflective dichroic mirror 10G and the blue reflective dichroic mirror 10B, and the cylindrical lens is extended in a direction to correct the amount of astigmatism generated in the two dichroic mirrors 10G and 10B. Match the directions.

Further, as shown in FIG. 5B, the cylindrical lens 40 is connected to the blue reflection dichroic mirror 10.
The coma aberration can be removed by arranging between B and the CRT 2 for red in the same manner between the blue reflection dichroic mirror 10B and the CRT 2 for blue. Further, as shown in FIG. 5 (c), the green reflective dichroic mirror 10G is replaced by the same structure as the blue reflective dichroic mirror 10B shown in FIG.
The filter 10Gb is sandwiched between the parallel flat plates 10Ga so that the light is reflected on the filter surface, and the total reflection mirror 10 is back-reflected, that is, the light is transmitted through the glass flat plate and reflected. Further, the coma aberration can be removed even if the green reflection dichroic mirror 10G and the total reflection mirror 10 are arranged so as to be plane-symmetric with respect to the plane P ′ whose normal is the central optical axis of the light bundle. Here, even if the cylindrical lens 40 is arranged at the position indicated by 40a or 40b, that is, on the entrance or exit surface of the polarization beam splitter 6, the same effect as described above can be obtained.

In FIG. 6, the cylindrical lens 40 at the position 40a shown in FIG. 5C is formed into a cylindrical shape 40c as the exit surface of the polarization beam splitter 6, and even if the cylindrical lens and the polarization beam splitter are integrated. An effect similar to the above is produced. As described above, the cylindrical lens, that is, the astigmatism correction means may be arranged on the entrance or exit surface of the polarization beam splitter 6 or between the polarization beam splitter 6 and the photoconductive liquid crystal light valve 1. The present embodiment in which the dichroic mirrors are arranged in one plane and the coma aberrations are mutually canceled so that the coma aberrations are removed and the astigmatism is corrected by another means (for example, a cylindrical lens). As a result, not only astigmatism but also coma can be corrected, and the resolution is further improved. That is, the pair of conjugately arranged dichroic mirrors substantially match the incident angle and the outgoing angle of the bundle of rays, thereby suppressing deterioration of the sine condition. The suppression of the asymmetry of the refraction point coordinates is
In practice, the spot diagramlawm by ray tracing is calculated to be suitable.

[0016]

According to the present invention, a projection type display including a polarizing beam splitter which transmits a light beam emitted from a light source, and a photoconductive liquid crystal light valve which gives a projected image to the light beam while reflecting the projected image. A device, which is arranged between the polarization beam splitter and the photoconductive liquid crystal light valve and is tilted symmetrically with respect to a plane having a center optical axis of the light beam as a normal line, and the light beam having its wavelength component. Since there are at least two dichroic mirrors that are divided into two, and an astigmatism correction unit that is arranged on the entrance or exit surface of the polarization beam splitter or between the polarization beam splitter and the photoconductive liquid crystal light valve, It is possible to prevent a decrease in resolution due to.

[Brief description of drawings]

FIG. 1 is a schematic view of a reflective monochrome projection type liquid crystal display device.

FIG. 2 is a schematic perspective view of a color projection type liquid crystal display device.

FIG. 3 is a schematic plan view of the color projection type liquid crystal display device shown in FIG.

FIG. 4 is a schematic perspective view of a color projection type liquid crystal display device of an example.

FIG. 5 is a schematic plan view of a color projection type liquid crystal display device of an example.

FIG. 6 is a schematic diagram of a polarization beam splitter in this embodiment.

[Explanation of symbols for main parts]

 1 Photoconductive Liquid Crystal Light Valve 2 CRT 3 Metal Halide Lamp 7 Polarizing Plate 6 Polarizing Beam Splitter 8 Projection Lens 9 Screen 20 Prepolarizer 40 Cylindrical Lens

Claims (2)

[Claims] 1. A projection type display device including a polarizing beam splitter which transmits a light beam emitted from a light source, and a photoconductive liquid crystal light valve which reflects a light beam while applying a projected image to the light beam, Between the polarization beam splitter and the photoconductive liquid crystal light valve, the light beam is arranged to be tilted symmetrically with respect to a plane whose normal line is the central optical axis of the light beam, and the light beam is divided into its wavelength components. At least two dichroic mirrors, and astigmatism correction means arranged on the entrance or exit surface of the polarization beam splitter or between the polarization beam splitter and the photoconductive liquid crystal light valve. Characteristic projection display device. 2. The projection display device according to claim 1, wherein the astigmatism correction means is a cylindrical lens.