JPH0545726A - Optical system of liquid crystal projector - Google Patents

Abstract

PURPOSE:To obtain bright projected images by efficiently condensing the incident illuminating light on a liquid crystal display panel of an image display device of a projection type constituted by using the liquid crystal display panel, thereby effectively utilizing the light. CONSTITUTION:The liquid crystal projector which condenses the illuminating light R to respective plural picture elements 1b formed on the liquid crystal display panel 1 and projects the image on a screen 6 is disposed with holograms 2 produced to reconstruct the image of the same shape as the shape of the plural picture elements 1b so as to correspond to the plural picture elements 1b. The real images by the holograms 2 are reconstructed in the positions of the respective picture elements 1b of the liquid crystal display panel 1 by the irradiation with the illuminating light R.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system of a liquid crystal projector for efficiently focusing illumination light on each pixel of a liquid crystal display panel.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display panel used in a projection type image display device of this type, a minimum display unit called a pixel is regularly arranged, and each pixel has an independent driving voltage. Is applied to change the optical characteristics of the liquid crystal forming each pixel, thereby displaying an image or a character. However, the line that supplies the drive voltage and the TFT
Since the (thin film transistor) must be provided between pixels, the ratio (aperture ratio) occupied by pixels (apertures) in the screen becomes small. Therefore, when the intensity of the illumination light of the liquid crystal display panel is the same, the lower the aperture ratio of the liquid crystal display panel, the light that enters the pixels other than the pixels does not reach the screen, and the screen becomes dark.

Therefore, in order to solve the problem that the liquid crystal display panel has a low aperture ratio and the screen is dark, the liquid crystal display panel is formed in a rotationally symmetrical manner with respect to the optical axis as a means for converging the illumination light for each pixel. It is known that a (circular) flat plate microlens array is arranged so as to face each pixel (see, for example, JP-A-3-136004).

[0004]

The circular flat plate microlens array described in the prior art requires a long manufacturing process (photolithography, sputtering, etching, ion exchange) and requires expensive equipment, resulting in cost reduction. It had the problem of becoming expensive. Further, while the shape of each opening of the liquid crystal display panel is a square or a key, the flat microlens provides a circular light condensing. Therefore, if all the light is focused so as to enter the opening, the pixels are separated, and the resolution appears to be degraded. On the other hand, when the entire opening is covered, there is a problem in that the light-collecting efficiency and the image quality are not compatible, for example, sufficient light-collecting cannot be obtained. The present invention has been made in view of the above problems of the conventional technique, and an object of the present invention is to provide a liquid crystal projector at a low cost, in which the illumination light condensing efficiency and the image quality are compatible with each other. To do.

[0005]

In order to solve the above-mentioned problems, the present invention provides a liquid crystal projector for projecting an image on a screen by focusing illumination light on each of a plurality of pixels formed on a liquid crystal display panel. A hologram produced so that an image is reproduced in the same shape as a pixel is arranged so as to correspond to the plurality of pixels, and a real image by the hologram is reproduced at each pixel position of the liquid crystal display panel by irradiation of the illumination light. It was done like this.

[0006]

When the hologram is illuminated with illumination light, a real image having the same shape as the pixels formed on the liquid crystal display panel is reproduced at the positions of the pixels formed on the liquid crystal display panel, and the illumination light is the same as the pixel aperture of the display panel. Since the light is focused and transmitted in a shape, the utilization efficiency of illumination light is high and a bright image can be obtained.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a configuration diagram of an optical system of a liquid crystal projector according to the present invention, FIG. 2 is a plan view of a mask for producing a hologram, and FIG. 3 is a configuration diagram of an optical system at the time of producing a hologram.

The optical system of the liquid crystal projector is, as shown in FIG. 1, a liquid crystal display panel 1 which is a transmissive display panel, and a hologram 2 which is formed so as to reproduce an image having the same shape as the pixels of the liquid crystal display panel 1. It is composed of a condenser lens 3, a white light source 4 that emits the illumination light R, a reflecting mirror 5 that reflects the light emitted from the white light source 4 toward the liquid crystal display panel 1, and a projection screen 6. In addition, 7 is a projection lens. The liquid crystal display panel 1 includes two transparent substrates 1
A plurality of pixels 1b are formed between a and 1a.

In order to produce a hologram (Lippmann hologram) 2 capable of reproducing white light, first, a high reflection paint is applied to the portion 10 having the same shape as the plurality of pixels 1b of the liquid crystal display panel 1 as shown in FIG. The applied mask 11 is prepared. Next, as shown in FIG. 3, a film (or glass plate) 12 is placed at the position of the hologram 2 so that the hologram 2 and the liquid crystal display panel 1 in the optical system of the liquid crystal projector have the same positional relationship. The masks 11 are arranged at the respective positions, and the laser light 1 is applied from the film 12 side.
3 is unfolded and the film 12 and the mask 11 which is the subject are illuminated.

Then, interference fringes are recorded on the film 12 due to interference between the reference light, which is the laser light 13 applied directly to the film 12, and the object light, which is the reflected light from the mask 11 that is the subject. The hologram 2 can be obtained by developing the film 12.

When reproducing the image by the hologram 2, the liquid crystal display panel 1 is arranged at the position of the mask 11 at the time of recording as shown in FIG. 1, and the illumination light R is white from the same position as the reference light at the time of recording. If illuminated by the light source 4, the hologram 2
A real image having the same shape as that of the pixel 1b is reproduced at the position of each pixel 1b of the liquid crystal display panel 1 immediately after the pixel.

Therefore, by using the hologram 2 instead of the conventional flat plate microlens array, all the light emitted from the white light source 4 as the illumination light R is converted into an image by the hologram 2 at the position of each pixel 1b of the liquid crystal display panel 1. Since it is reproduced in the same shape as the pixel 1b, a bright image can be obtained.

[0013]

As described above, according to the present invention, the cost can be reduced because the process is short and only the exposure and development are required and the equipment is relatively inexpensive as compared with the case of manufacturing the flat plate microlens array. Further, since the light can be condensed in an arbitrary shape, it is possible to achieve both the light condensing efficiency and the image quality without causing pixel separation. Further, since the flat-plate microlens array has one pixel for each lens, if the lens is scratched or chipped, the pixel will be crushed in black. Since it can be maintained, it is not easily affected by scratches and dust.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical system of a liquid crystal projector according to the present invention.

FIG. 2 is a plan view of a mask for producing a hologram.

FIG. 3 is a block diagram of an optical system during hologram production.

[Explanation of symbols]

1 ... Liquid crystal display panel, 1b ... Pixel, 2 ... Hologram, 3
... condenser lens, 4 ... white light source, 5 ... reflecting mirror, 6 ... projection screen, 7 ... projection lens, R ... illumination light.

Claims (1)

[Claims] 1. In a liquid crystal projector for projecting an image on a screen by focusing illumination light on each of a plurality of pixels formed on a liquid crystal display panel, a hologram produced so that an image is reproduced in the same shape as the plurality of pixels. Is arranged so as to correspond to the plurality of pixels, and the image of the hologram is reproduced at the position of each pixel of the liquid crystal display panel by irradiation of the illumination light.