JPS6271919A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To project the image of good quality removing a shadow from its center part to a screen surface by arranging a light diffusing plate for passing light passed through the focus of a reflector as it is and diffusibly transmitting light which is not passed through the focus near the focus of the reflector. CONSTITUTION:The light diffusing plate 7 arranged between a light source and a condenser lens 4 is constituted by forming a light transmitting hole 7a on the center of a transparent plate consisting of transparent resin such as glass or acrylic resin and executing a rough surface processing over the whole surface of the transparent plate. The light diffusing plate 7 is arranged on the focal position of a reflector 3 so that the center of the light transmitting hole 7a coincides with the optical axis 0. The light transmitting hole 7a is formed as small as possible so as to transmit only the light reflected by the reflector 3 and transmitted to the condenser lens 4 through the focus of the reflector 3. Namely, the light diffusing plate 7 passes the light passed through the focus of the reflector 3 as it is and diffusibly transmitting the light which is not passed through the focus.

Description

[Detailed description of the invention] (Technical field of invention) This invention relates to a liquid crystal projector.

(Technical background of the invention and its problems) A liquid crystal projector displays an image (for example, a television image) using a transmissive dot matrix liquid crystal display panel, and enlarges the displayed image on the liquid crystal display panel onto the screen surface. A liquid crystal projector having a configuration as shown in FIG. 4 is conventionally known.

To explain the configuration of this liquid crystal projector, reference numeral 1 in the figure is a transmissive dot matrix liquid crystal display panel, and behind the liquid crystal display panel 1 is a light source lamp 2 and a liquid crystal display panel that transmits light from the light source lamp 2. A reflector 3 is provided to reflect the light toward. Note that as the light source lamp 2, a high-intensity lamp such as a xenon lamp is generally used. In addition, the reflector 3 is made of a spheroidal mirror with dots and dots, and the light reflected by this reflector 3 passes through the focus of this reflector 3, enters a condenser lens (aspherical lens) 4, and enters the condenser lens (aspherical lens) 4. The condenser lens 4 converts the light into parallel light, which then enters the liquid crystal display panel 1. Further, 5 is a projection lens provided in front of the liquid crystal display panel 1, and the light (image light) transmitted through the liquid crystal display panel is magnified by the projection lens 5 and projected onto the screen 6.

That is, this liquid crystal projector has a liquid crystal display panel 1.
The light that has passed through the screen is projected onto the screen 6 using the projection lens 5, and an image is formed on the screen 6. According to this liquid crystal projector, the displayed image on the small liquid crystal display panel can be greatly enlarged and viewed. can.

However, in the liquid crystal projector described above, since the light source lamp 2 is located at the center of the reflector 3, the light source lamp 2 provides a shadow, and the central portion of the luminous flux a reflected by the reflector 3 is shown in FIGS. 5 and 6. As a result, the amount of light passing through the center of the liquid crystal display panel 1 is insufficient, resulting in a problem that the center of the image projected on the screen becomes dark as if it were a shadow. Note that, in addition to the light reflected by the reflector 3, the light from the light source is transmitted directly from the light source lamp 2 to the condenser lens 4 as shown by the broken line in FIG.
There is also light that goes to the side, but the direct light from the light source lamp 2 has lower brightness than the reflected light from the reflector 3.
Moreover, since this direct light is spread almost uniformly over the entire area, the central part of the light beam (the shaded part in FIGS. 5 and 6) is considerably darker than the surrounding area.

[Purpose of the invention]

This invention was developed in view of the above-mentioned circumstances, and its purpose is to prevent the liquid crystal display from being damaged even if the light source lamp is in the shadow and the central part of the light beam reflected by the reflector becomes dark. To provide a liquid crystal projector capable of projecting a high-quality image without a shadow in the central part onto a screen surface by allowing a sufficient amount of light to enter the central part of a display panel. It is in.

[Summary of the invention]

That is, in the present invention, a light diffusing plate is provided near the focal point of the reflector, allowing light that passes through the focal point of the reflector to pass through as is, while light that does not pass through the focal point is diffused and transmitted. In this case, direct light from the light source lamp that does not pass through the focus of the reflector is diffused by the light diffusing plate, so the amount of light in the center of the light beam reflected by the reflector is supplemented by the diffused light passing through the light diffusing plate. Therefore, there is sufficient light even in the center of the LCD panel]
of light can be incident.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIGS. 1 and 2, 1 is a TN type transmission type dot matrix liquid crystal display panel, 2 is a light source lamp such as a xenon lamp, 3 is a focal reflector made of a spheroidal mirror, 4 is a condenser lens, and 5 is a condenser lens. is a projection lens,
6 is a screen, which is the same as that provided in a conventional liquid crystal display. The liquid crystal display panel 1 is tilted at a predetermined angle with respect to the optical axis 0 in order to most efficiently input the light parallelized by the condenser lens 4, and the projection lens 5 and the screen 6 is also provided to be inclined parallel to the liquid crystal display panel 1.

On the other hand, 7 is a light diffusing plate provided between the light source and the condenser lens 4. As shown in FIG. 3, this light diffusing plate 7 has a light transmitting hole 7a in the center of a transparent plate made of glass or a transparent resin such as acrylic resin, and has a rough surface that diffuses light over the entire surface of the transparent plate. The light diffusing plate 7 is provided at the focal point of the reflector 3 with the center of the light transmission hole 7a aligned with the optical axis O. Further, the light transmitting holes 7a of the light diffusing plate 7 are reflected by the reflector 3, and the light transmitting holes 7a of the light diffusing plate 7 are
It is made as small as possible so as to transmit only the light directed toward the condenser lens 4 through the focal point of the lens. In other words,
This light diffusing plate 7 allows the light that passes through the focal point of the reflector 3 to pass through as is, and diffuses and transmits the light that does not pass through the focal point.

In this liquid crystal projector, the light beam a reflected by the reflector 3 passes through the light transmission hole 7a of the light diffusion plate 7, but the direct light from the light source lamp 2 spreads as shown by the broken line in FIG. Of this direct light, most of the light other than the light directed toward the light transmission holes 7a of the light diffusing plate 7 is transmitted through the light diffusing plate 7.
The light is diffused by the light diffusing plate 7 through the part other than the light transmitting hole 7a, and this diffused light also goes to the center of the condenser lens 4, so the light transmitting hole 7a of the light diffusing plate 7 The amount of light at the center of the luminous flux a passing through increases.

That is, this liquid crystal projector diffuses direct light from the light source lamp 2 that does not pass through the focal point of the reflector 3 using the navigation light diffusion plate 7, thereby reducing the amount of light in the central portion of the luminous flux a reflected by the reflector 3. This is supplemented by the diffused light that has passed through the plate 7. In this way, a sufficient amount of light 1 can be incident on the liquid crystal display panel 1 at the center thereof, so that the light source Even if the central part of the luminous flux a reflected by the reflector 3 becomes dark due to the lamp 2 being in the shade, a sufficient amount of light will be incident on the central part of the liquid crystal display panel 1, and the central part will be illuminated. A high-quality image without shadows can be projected onto the screen.

In the above embodiment, the light diffusing plate 7 is provided at the focal point of the reflector 3;
It may be provided at a position that is shifted to some extent from the focal position.

〔Effect of the invention〕

In this invention, a light diffusing plate is provided near the focal point of the reflector, allowing light that passes through the focal point of the reflector to pass through as is, and light that does not pass through the focal point to be diffused and transmitted, so that the light source lamp is shaded. Even if the central part of the luminous flux reflected by the reflector becomes dark, the direct light from the light source lamp that does not pass through the focus of the reflector is diffused by the light diffusing plate, so that it does not reach the central part of the liquid crystal display panel. A sufficient optical layer of light can be incident, and therefore,
A high-quality image with no shadow in the center can be projected onto the screen.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of this invention.
FIG. 1 is a basic configuration diagram of a liquid crystal projector, FIG. 2 is an enlarged view of the light source side, and FIG. 3 is a perspective view of a light diffusing plate. 4 and 5 are diagrams showing the basic structure of a conventional liquid crystal projector and an enlarged view of the light source side thereof, and FIG. 6 is a sectional view of a light beam taken along line A--A in FIG. 5. DESCRIPTION OF SYMBOLS 1... Liquid crystal display panel, 2... Light source lamps, 3... Reflector, 4... Condenser lens, 5... Projection lens 6... Screen, 7... Light diffusing plate. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 3

Claims (1)

[Claims] A transmissive liquid crystal display panel, a light source lamp disposed behind the liquid crystal display panel, a focal reflector that reflects light from the light source lamp toward the liquid crystal display panel, and light reflected by the reflector. a condenser lens that guides the light as parallel light to the liquid crystal display panel;
In a liquid crystal projector comprising a projection lens disposed in front of the liquid crystal display panel to enlarge and project a display image of the liquid crystal display panel onto a screen surface, the light passing through the focus of the reflector remains unchanged in the vicinity of the focus of the reflector. A liquid crystal projector comprising a light diffusing plate that diffuses and transmits light that does not pass through the focal point.