JPH0736066B2 - LCD projector - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present 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 projects a display image of the liquid crystal display panel on a screen surface in an enlarged manner. A structure shown in FIG. 4 is known.

The structure of this liquid crystal projector will be described. In the figure, reference numeral 1 denotes a transmissive dot matrix liquid crystal display panel. Behind the liquid crystal display panel 1, a light source lamp 2 and light from the light source lamp 2 are directed to the liquid crystal display panel. A reflector 3 for reflecting the light is provided. The light source lamp 2
Generally, a high-luminance lamp such as a xenon lamp is used. The reflector 3 is composed of a spheroidal mirror having a focal point, and the light reflected by the reflector 3 passes through the focal point of the reflector 3 and enters a condenser lens (aspherical lens) 4, The condenser lens 4 collimates the light and makes it enter the liquid crystal display panel 1. Further, 5 is a liquid crystal display panel 1
The light (image light) which is a projection lens provided in front of the liquid crystal display panel is magnified by the projection lens 5 and projected on the screen 6 surface.

That is, this liquid crystal projector is provided with the liquid crystal display panel 1.
The light transmitted through the projection lens 5 is projected onto the screen 6 surface by the projection lens 5 to form an image on the screen 6 surface. According to this liquid crystal projector, a display image on a small liquid crystal display panel can be greatly enlarged and viewed. it can.

However, in the above liquid crystal projector, since the light source lamp 2 is located in the central portion of the reflector 3, the central portion of the light flux a reflected by the reflector 3 behind the light source lamp 2 is shown in FIGS. 5 and 6. As shown in FIG. 4, the liquid crystal display panel 1 has a problem that the amount of light passing through the central portion thereof is insufficient and the central portion of the screen projection image becomes dark like a shadow. In addition to the light reflected by the reflector 3, the light emitted from the light source is directly emitted from the light source lamp 2 to the condenser lens 4 as shown by the broken line in FIG.
Although there is also light that goes to the side, the direct light from the light source lamp 2 has a lower brightness than the reflected light from the reflector 3 and the direct light spreads almost uniformly over the whole, so that the central part (first The shaded portions in FIGS. 5 and 6 are much darker than their surroundings. Furthermore, the light source lamp 2
The direct light from is incident on the liquid crystal display panel 1 in a certain direction without becoming parallel light even if it passes through the condenser lens 4, so that there is also a problem that a ghost is generated in a projected image from the liquid crystal display panel. is there.

[Object of the Invention]

The present invention has been made in view of the above situation, and an object thereof is to provide a liquid crystal display panel even if the central portion of the light flux reflected by the reflector becomes dark due to the shadow of the light source lamp. In order to provide a liquid crystal projector capable of projecting a bright, high-quality image on the screen surface without any shadow in the central portion, it is possible to allow a sufficient amount of light to enter the central portion. is there.

[Outline of Invention]

That is, according to the present invention, a light diffusing plate is provided near the focal point of the reflector to allow light passing through the focal point of the reflector to pass therethrough and to diffuse and transmit light that does not pass through the focal point. Then, since the direct light from the light source lamp that does not pass through the focal point of the reflector is diffused by the light diffusing plate, the amount of light in the central portion of the light flux reflected by the reflector is compensated by the diffused light passing through the light diffusing plate. As a result, a sufficient amount of light can be incident on the liquid crystal display panel, and bright and excellent display can be performed.

Example of Invention

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

In FIG. 1 and FIG. 2, 1 is a TN type transmissive dot matrix liquid crystal display panel, 2 is a light source lamp such as a xenon lamp, 3 is a focused reflector consisting of a spheroidal mirror, 4 is a condenser lens, 5 Is a projection lens, 6
Are screens, which are the same as those provided in a conventional liquid crystal projector. The liquid crystal display panel 1 is provided so as to be inclined by a predetermined angle with respect to the optical axis O in order to most efficiently enter the light made into the parallel light by the condenser lens 4, and the projection lens 5 and the screen. 6 is provided so as to be inclined parallel to the liquid crystal display panel 1.

On the other hand, 7 is a light diffusion plate provided between the light source and the condenser lens 4. As shown in FIG. 3, the light diffusing plate 7 has a light transmitting hole 7a at the center of a transparent plate made of transparent resin such as glass or acrylic resin, and a rough surface for diffusing light over the entire surface of the transparent plate. This light diffusing plate 7 has been subjected to a treatment (not shown).
It is provided at the focal position of the reflector 3 with the center of 7a aligned with the optical axis O. In addition, the light transmission hole 7a of the light diffusion plate 7
Is as small as possible so that only the light reflected by the reflector 3 and passing through the focal point of the reflector 3 toward the condenser lens 4 is transmitted. That is, the light diffusing plate 7 allows the light passing through the focal point of the reflector 3 to pass through as it is and diffuses and transmits the light not passing 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. Most of the direct light other than the light directed to the light transmitting hole 7a of the light diffusing plate 7 is diffused by the light diffusing plate 7 through the part other than the light transmitting hole 7a of the light diffusing plate 7. Since this diffused light also goes to the central portion of the condenser lens 4, the light transmission hole of the light diffusion plate 7
The amount of light in the central portion of the light flux a passing through 7a increases.

That is, in this liquid crystal projector, direct light from the light source lamp 2 that does not pass through the focal point of the reflector 3 is diffused by the light diffusing plate 7, so that the light amount at the central portion of the light flux a reflected by the reflector 3 is diffused by the light diffusing plate. The diffused light that has passed through the light source 7 is used to make up for it. By doing so, a sufficient amount of light can be made incident on the central portion of the liquid crystal display panel 1. Even if the central part of the light flux a reflected by the reflector 3 becomes dark, the liquid crystal display panel 1 is made to enter a sufficient amount of light also in its central part, and the central part is shaded. A good quality image can be projected on the screen surface.

Although the light diffusing plate 7 is provided at the focal position of the reflector 3 in the above embodiment, the light diffusing plate 7 is provided in the reflector 3.
It may be provided at a position that is deviated to some extent from the focal position.

EFFECTS OF THE INVENTION The present invention is provided with a light diffusing plate near the focal point of the reflector, which allows light passing through the focal point of the reflector to pass therethrough and diffuses and transmits light not passing through the focal point. Even if the central part of the light flux reflected by the reflector becomes dark due to the shadow of the lamp, direct light from the light source lamp that does not pass through the focal point of the reflector is diffused by the light diffusion plate, which is sufficient for the liquid crystal display panel. A large amount of light can be incident, and a bright and excellent display in which a ghost does not easily occur in a projected image can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 3 show an embodiment of the present invention.
FIG. 1 is a principle configuration diagram of a liquid crystal projector, FIG. 2 is an enlarged view of a light source side portion, and FIG. 3 is a perspective view of a light diffusion plate. 4 and 5 are principle block diagrams of a conventional liquid crystal projector and an enlarged view of a light source side portion thereof, and FIG.
It is sectional drawing of the light beam which follows the AA line of a figure. 1 ... Liquid crystal display panel, 2 ... Light source lamp, 3 ... Reflector, 4 ... Condenser lens, 5 ... Projection lens,
6 ... Screen, 7 ... Light diffusion plate.

Claims (1)

[Claims] 1. A liquid crystal display panel, a light source lamp, and a focused reflector for reflecting light from the light source lamp toward the liquid crystal display panel, and the light reflected by the reflector as parallel light. And a projection lens for enlarging and projecting the display image of the liquid crystal display panel on the screen surface, and the light passing through the light exit side of the reflector near the focal point on the light exit side of the reflector passes through as it is. And a light diffusing plate for diffusing and transmitting the light that does not pass through the vicinity of the focus.