JPH0787427A - Projection type picture display device - Google Patents

Abstract

PURPOSE:To obtain a projected picture with a stable and high contrast by providing an incident angle regulation means between a light source and a polarized beam splitter in the projection picture display device using the polarized beam splitter so as to set the dispersion in the incident angle of a light made incident on the polarized beam splitter within an optional range. CONSTITUTION:An inclination of a light made incident on a polarized beam splitter 7 and a reflection type liquid crystal display panel 8 is set within an optional range by an incident angle regulation means 6 which is provided between a light source 1 and the polarized beam splitter 7. A picture with high luminance and high resolution is obtained without deteriorated contrast even when a light source is not necessarily close to a point light source by setting the range of the incident angle in a range to warrant the contrast of a projected picture obtained finally by the performance of the polarized beam splitter 7. The incident angle regulation means 6 is preferably a fiber assembly made of a material whose refractive index differs in the middle part and the surrounding parts or a fiber optical plate of the similar configuration thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a projection type image display device which forms an image by decomposing and combining lights according to polarization directions by using a polarization beam splitter.

[0002]

2. Description of the Related Art With the increase in size of televisions, the demand for projection-type image display devices is increasing because they can more easily accommodate larger screens than conventional direct-view image display devices.

Particularly in the field of business use requiring a screen of 100 inches or more, the demand is growing steadily not only for conventional events and monitoring applications but also for presentation applications by connecting to a computer. .

In such a projection type image display device, the conventional structure is such that an image on a cathode ray tube (hereinafter referred to as a CRT) is enlarged and projected by a projection lens arranged in front of the cathode ray tube. In order to achieve both high resolution and high brightness, it was not practical due to the large size and high cost of the device. In order to solve this problem, a light source and a light valve are separately provided so that both high resolution and high brightness are compatible with each other in the market.

When roughly classified, a device comprising a light source and a light valve has a light valve comprising an oil film or an elastomer and a schlieren optical system, a light valve using a transmissive liquid crystal panel, and a light valve reflecting liquid crystal panel. There is a thing using.

However, there is also a problem in the above-mentioned device composed of the light source and the light valve, one of which is a decrease in contrast, in particular, "black floating" caused by light leakage to the black display portion.

These causes differ depending on the respective configurations. Although the degree of influence is large and small, a common cause is that if the incident angle of light from the light source is large, the light valve cannot shield the light completely (hereinafter referred to as incident angle dependency). A xenon light source whose discharge arc is sufficiently short is used to obtain high-luminance and high-contrast in a commercially available device, and thus a light beam that is nearly parallel (small incident angle to the light valve) is obtained. However, the xenon light source has a short life of about 500 hours and may explode at the end of its life.

Therefore, in a projection type image display device comprising a light source and a light valve which enables high brightness and high resolution, a device having a high contrast equivalent to that of an image projection device using a conventional CRT is commercially available. It was difficult to get it into the market.

Conventional examples devised to solve this problem,
Japanese Patent Laid-Open No. 56-155924 is shown in FIG. In this embodiment, a fiber optic plate is provided on the surface of the light valve to regulate the incident angle of light incident on the light valve, and the purpose is to improve the above-mentioned dependency of the light valve on the incident angle.

[0010]

According to this, the deterioration of the contrast due to the incident angle dependency of the light valve can be suppressed. However, considering the case where a reflective liquid crystal panel is used as a light valve, the factors that influence the contrast are the incident angle dependency of the polarization beam splitter as well as the incident angle dependency of the light valve, and in the conventional example shown in FIG. No effect can be obtained, so it cannot be said that sufficient contrast can be obtained.

[0011]

In order to solve the above-mentioned problems, the projection type image display apparatus of the present invention is a polarized light beam for branching and combining of optical paths among projection type image display apparatuses comprising a light source and a light valve. In a device using a splitter, as a means for solving the above problems, a light source provided with a reflection mirror in a light emitting body, an image display element functioning as a light valve by converting the polarization state of incident light, A projection lens provided so as to magnify and project an image on the image display element, and a polarization beam splitter that branches the optical path depending on the polarization direction of incident light,
Between the polarization beam splitter and the light source, an incident angle regulating means for limiting an incident angle of incident light is provided.

Further, the incident angle regulating means has its optical axis parallel to the optical axis direction connecting the polarization beam splitter and the light source, and an assembly of fibers made of materials having different refractive indexes in the central portion and the peripheral portion, or A projection type image display device having the above-mentioned means characterized in that it is a fiber optic plate having a similar structure and the above-mentioned means characterized in that the image display element is a reflection type liquid crystal panel has been devised.

[0013]

By providing the incident angle regulating means between the light source and the polarization beam splitter as described above, it is possible to keep the variation of the incident angle of the light incident on the polarization beam splitter within an arbitrary range. By setting the range of this incident angle to the range where the performance of the polarizing beam splitter can guarantee the contrast of the projected image finally obtained,
Even if the light source is not necessarily close to a point light source, it is possible to obtain an image with high brightness and high resolution without deterioration of contrast.

Further, the incident angle regulating means is a fiber optical plate in which fibers made of a glass material having different refractive indexes at the center and the periphery are bundled, and the light having a required incident angle is transmitted between the inside glass material and the outside glass material. The reflected light is transmitted through the fiber optic plate, and the light having an unnecessary incident angle beyond that is transmitted through the outer glass material to separate the optical path from the necessary light. At this time, unnecessary light can be removed by providing a light absorption layer between the fibers.

Since the fiber can be made very fine, it is possible to select transmitted light depending on incident light with a thin plate. Further, it is possible to increase the required light transmittance by suppressing the ratio of the light shielding portion to the opening area when viewed from the incident side.

As described above, according to the present invention, since the image quality can be assured without reducing the contrast, it is possible to use a metal halide lamp or a halogen lamp, and it is possible to expand to the consumer market by reducing the size and cost of the device. become.

[0017]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 shows a block diagram of a first embodiment of the present invention using a reflective liquid crystal light valve.

The light source unit 1 includes a metal halide lamp 2
The parabolic mirror 3 is cemented at one end of the metal halide lamp 2 so that at least a part of the inter-electrode discharge arc of the metal halide lamp 2 is at the focal position. A cold mirror 4 and an ultraviolet ray removing filter 5 are provided on the optical axis on the opening side of the parabolic mirror 3 as shown in the figure. At the tip of the optical axis, there are provided an incident angle regulating means 6 and a polarization beam splitter 7, and the polarization beam splitter 7 transmits light having a vibration direction parallel to the paper surface of FIG. Light having a vibrating direction is reflected by the reflecting surface 7a. A reflection type liquid crystal panel 8 is arranged on the optical axis of the light source 1 reflected by the polarization beam splitter 7 such that its incident surface 8a is perpendicular to the optical axis. In the reflection type liquid crystal panel 8, the light incident from the incident surface 8a receives the front glass 8b and the transparent electrode layer 8
After passing through the liquid crystal layer 8d, the light is reflected by the reflective layer 8e and emitted through the same optical path as that of the incident light. At this time, the reflective layer 8e
When an electric charge is applied between the liquid crystal drive circuit layer 8f provided on the back side of and the transparent electrode layer 8c, the alignment of the liquid crystal in the liquid crystal layer 8d changes, and the oscillation direction of the incident light is polarized by 90 degrees and emitted. When no charge is applied between the liquid crystal drive circuit layer 8f and the transparent electrode layer 8c, the incident light is emitted without changing the vibration direction.

A projection lens 9 is arranged on the side opposite to the reflective liquid crystal panel 8 with respect to the polarized beam splitter 7 on the optical axis perpendicularly connecting the reflective surface 7a of the polarized beam splitter 7 and the incident surface 8a of the reflective liquid crystal panel 8. I am doing it. At this time, the optical axis of the projection lens 9 is on the optical axis, and the projection lens 9
The liquid crystal layer 8d of the reflective liquid crystal panel 8 is provided so as to be located on the image surface of the. By adopting such a configuration, the light source 1
The light emitted from the light is transmitted through a light valve composed of a polarization beam splitter 7 and a reflection type liquid crystal panel 8 at some part,
An image is formed by blocking a part of the image, and a large screen image is obtained by enlarging and projecting the image by the projection lens 9.

In the conventional light valve type image projection apparatus, the incident angle of the light from the light source is larger in the periphery than in the center, but as shown in FIG. The degree of polarization deteriorates. Further, in order to obtain high contrast and uniformity, the liquid crystal panel emits only incident light with a small incident angle, that is, light with a large F-number that is close to parallel light, in order to obtain high contrast and uniformity because the polarization performance changes depending on the incident angle. Since a light source was needed, only xenon lamps that were close to point light sources could be used, and the device was expensive and large.

According to the present invention, as described above, by providing the incident angle regulating means 6 between the light source 1 and the polarization beam splitter 7, the inclination of the light incident on the polarization beam splitter 7 and the reflection type liquid crystal panel 8, That is, since the F number is determined by the incident angle control means 6, the degree of freedom in selecting the light source can be increased. At this time, it goes without saying that the latter is smaller in F number and F number of the light source determined by the incident angle regulating means 6.

Here, the incident angle regulating means 6 can regulate the angle of the transmitted light by a structure having a lattice window with a depth as shown in FIG. However, since the material constituting this is a light absorbing material, the light in the hatched portion in FIG. 3 is absorbed by the light absorbing material even though it is incident at an allowable angle, resulting in a large loss. .

If the incident angle regulating means 6 is the optical fiber plate shown in FIG. 4 as a means for increasing the transmission efficiency, the light shown by hatching corresponding to the light lost in the structure of FIG. Since the refractive index of the material is different from that of the peripheral material, the light having a useful incident angle among the light from the light source can be efficiently guided to the polarization beam splitter by being reflected by the boundary surface.

Further, as shown in FIG. 5, a pin is set so that light is condensed once by a condenser lens and only light having an effective incident angle is transmitted to the light collecting position, and unnecessary light having a large angle is shielded. A light shielding surface 17 having a hole 18 is provided. Further, the same function can be achieved by an optical system including a collimator lens 16b including the same lens as the condenser lens 16a in order to return the light condensed on the exit side to the angle at which the light is incident on the previous condenser lens. However, in order to process all the light fluxes in the optical path with this optical system, a large space is required in the optical axis direction. Become.

As described above, according to the present invention, the performance of the polarization beam splitter can be guaranteed without being limited to the light source close to the point light source. Therefore, it is traditionally large,
The use of a xenon lamp filled with high-pressure gas made it difficult to achieve a projection-type image display device using a polarizing beam splitter, which was difficult in terms of size and safety. Become.

[0026]

According to the present invention, in a projection type image display device comprising a light source and a light valve, in particular, a device using a polarizing beam splitter for branching and combining optical paths, a light source having a reflecting mirror as a light emitter. An image display element that functions as a light valve by converting the state of incident light, a projection lens that is capable of magnifying and projecting an image on the image display element, and A polarization beam splitter for branching the optical path is provided, and an incidence angle regulating means for limiting an incidence angle of incident light is provided between the polarization beam splitter and the light source. In particular, the incident angle regulating means has an optical axis parallel to the optical axis direction connecting the polarization beam splitter and the light source, and is an assembly of fibers made of materials having different refractive indexes in the central portion and the peripheral portion, or a configuration similar to this. Is a fiber optic plate equipped with. In addition, since the image display element is configured to be a reflective liquid crystal panel, the angle of incidence on the polarization beam splitter can be always guaranteed regardless of the light source, so that a stable and high-contrast projected image can be obtained. It is possible to provide a projected image display device.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention using a reflective liquid crystal light valve.

FIG. 2 is a spectral characteristic diagram showing the incident angle dependence of a polarization beam splitter.

FIG. 3 is a view showing an example of an incident angle regulating means provided with a grid-like wall in the present invention.

FIG. 4 is a view showing an example of an incident angle regulating means using an optical fiber in the present invention.

FIG. 5 is a diagram showing an example of an incident angle regulating means using a lens and an aperture in the present invention.

FIG. 6 is a configuration diagram of a conventional projection-type image display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source part 2 ... Metal halide lamp 3 ... Parabolic mirror 4 ... Cold mirror 5 ... Ultraviolet ray removal filter 6 ... Incident angle control means 7 ... Polarization beam splitter 7a. .. Reflective surface 8 ... Reflective liquid crystal panel 8a ... Incident surface 8b ... Front glass 8c ... Transparent electrode layer 8d ... Liquid crystal layer 8e ... Reflective layer 8f ... Liquid crystal drive circuit Layer 9 ... Projection lens 10a ... Transmittance of P-polarized light when incident at the optimum incident angle 10b ... Transmittance of P-polarized light when incident at the optimum incident angle 11a ... Deviation from the optimum incident angle Transmittance of P-polarized light when light is incident 11b ... Transmittance of S-polarized light when light deviates from the optimum incident angle 12, 15 ... Light absorbing material 13 ... Core optical fiber 14. ..Higher refractive index than core optical fibers Glass material 16a ... Condensing lens 16b ... Collimator lens 17 ... Light-shielding surface 18 ... Pinhole 30 ... Reflective liquid crystal light valve 31 ... Fiber light plate 32 ... Polarization Beam splitter 33 ・ ・ ・ Screen

Claims (3)

[Claims] 1. A light source having a light-emitting body equipped with a reflection mirror, an image display element that functions as a light valve by converting the polarization state of incident light, and an image on the image display element can be enlarged and projected. And a polarization beam splitter for branching the optical path according to the polarization direction of the incident light, and an incident angle regulating means for limiting the incident angle of the incident light between the polarization beam splitter and the light source. A projection-type image display device comprising: 2. The incident angle regulating means has its optical axis parallel to the optical axis direction connecting the polarization beam splitter and the light source,
2. A fiber optical plate having an assembly of fibers made of materials having different refractive indexes in the central portion and the peripheral portion, or a fiber optical plate having a similar configuration.
The described projection-type image display device. 3. The projection type image display device according to claim 1, wherein the image display element is a reflection type liquid crystal panel.