JP2970762B2 - Projection image display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device that can project a bright image by using a liquid crystal display element as an optical shutter.

[Related Art] At present, a cathode ray tube is very often used in an image display device. However, when a large image is to be obtained, the weight of the cathode ray tube rapidly increases. Therefore, a cathode ray tube capable of displaying an image with extremely high brightness and a projection type image display device using an enlarged projection optical system are used, but this method is limited by the cathode ray tube itself and an image larger than a certain size is used. Cannot be obtained.
Therefore, an apparatus has been developed in which a light source and a display portion are separated from each other, and a bright light source, an optical shutter using a liquid crystal display element, and an enlarged projection optical system are combined.

A projection type image display device using the above liquid crystal display element as an optical shutter is described in, for example, 1987, S.I.D.87 Digest, Session 6 (SID 87 DIGES).
T, Session 6) Pages 75-78, Euro Display, '
87 (EURO DISPLAY '87), pp. 115-116, describes the use of a halogen lamp or a xenon lamp as a light source, respectively. Both are thin film transistors (TF
By T), the liquid crystal in the portion corresponding to each pixel of the matrix is driven to reliably operate the matrix type liquid crystal display element including a large number of pixels. In addition, liquid crystals generally become isotropic liquids at high temperatures, so care is taken in cooling any of them.Forcibly air-cooling the light source itself, and a large amount of infrared light generated from the light source can also be filtered using a filter. Has been removed.

[Problems to be Solved by the Invention] The above-described conventional apparatus uses a halogen lamp or a xenon lamp that generates a relatively large amount of heat, also for the purpose of downsizing, so that a cooling fan or an infrared cutoff filter is used. Even if is used, the temperature rise of the liquid crystal display element is inevitable,
The output of the light source is limited, and the brightness of the displayed image cannot be increased sufficiently, and the image cannot be enlarged sufficiently. In some cases, the use of a powerful cooling fan resulted in noise and other problems. If liquid cooling is used to improve the cooling capacity, the equipment will be complicated,
Since it becomes large, there is no point in selecting a light source of the kind described above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a projection-type image display device which can display a sufficiently bright and sufficiently large image without being bothered by heat generated by a light source and is relatively small.

[Means for Solving the Problems] In order to achieve the above object, an invention according to claim 1 of the present invention provides an optical shutter using a liquid crystal display element, a light source for irradiating the optical shutter, and a shutter formed by the shutter. A projection type image display device having an optical system for enlarging and projecting an image to be projected, an electrodeless discharge lamp, a magnetron for generating microwaves, and a microwave from the magnetron as the electrodeless discharge lamp as the light source. And an electrodeless microwave discharge light source having a waveguide leading to the light source.

According to a second aspect of the present invention, there is provided a projection type image display apparatus according to the first aspect, wherein the light from the electrodeless discharge lamp is effectively used. A projection type image display device, wherein the electrode discharge lamp is arranged in a cavity resonator made of a metal mesh that reflects microwaves but transmits light.

In order to further achieve the above object, claim 3 of the present invention
The invention according to claim 1, wherein in the projection type image display device according to claim 1 or 2, even if a polarizing plate is used for the liquid crystal display element, the electrodeless discharge lamp and the polarizing plate are not deteriorated by ultraviolet rays. A projection-type image display device characterized in that an ultraviolet cutoff filter is provided between optical shutters of a liquid crystal display element.

In order to further achieve the above object, claim 4 of the present invention
In the projection type image display device according to any one of claims 1 to 3, the light from the electrodeless discharge lamp is so irradiated that the light from the electrodeless discharge lamp uniformly irradiates the liquid crystal display element. A projection type image display device, wherein an optical shutter by the liquid crystal display element is irradiated through a lens.

[Operation] Regarding the electrodeless microwave discharge light source device, for example,
As described in the Institute of Illuminating Materials, L3-86-1-6, pp. 17-21, the light source itself has a high luminous efficiency, and the electrodes are placed in an envelope enclosing the plasma generating medium. Since there is no need to provide, the degree of freedom of selection of the medium and therefore the degree of color tone selection of the light source is wide, the life of the light source itself consisting of the envelope and the plasma generation medium is long, and the color tone changes little even if the light amount is changed. In addition, there are advantages such as quick rise of color tone, brightness and light output as compared with a normal high-pressure discharge light source or the like.
Since the luminous efficiency of the light source itself is good, an efficiency equal to or higher than that of an incandescent lamp, a halogen lamp, a xenon lamp, or the like can be obtained even in consideration of the loss on the microwave generator side. Even if the distance between the optical shutter composed of the liquid crystal display element and the electrodeless light source is not long, the light source itself generates little heat, so it is sufficient to provide an ultraviolet blocking filter so that the polarizing plate is not deteriorated by ultraviolet light. As in the case of the above-mentioned conventional light source having a large size, there is no need for an infrared cutoff filter or a forced air cooling device.

Embodiment FIG. 1 is a schematic configuration diagram of an embodiment of the present invention. An electrodeless discharge lamp 2 excited by an excitation device 1 (in this embodiment, a transparent quartz spherical envelope is filled with a substance similar to that of a metal halide lamp or a multi-halogen lamp). The light is uniformly radiated by the lens 3 onto the liquid crystal plate 4 (in this embodiment, a simple TN type ("Liquid Crystal-Application", page 16 of Baifukan, edited by Okano et al.)). The liquid crystal plate 4 is driven by a drive circuit 5, and a desired image is displayed on the liquid crystal plate. Light transmitted through the liquid crystal plate 4, that is, the liquid crystal plate 4
Is enlarged by the lens 6 and projected on the screen 7. FIG. 2 is a sectional view of the liquid crystal plate 4. The liquid crystal plate 4 has a structure in which an X direction electrode and a Y direction electrode orthogonal thereto are formed, and a liquid crystal material 9 is sandwiched between two glass substrates 8 facing each other with a narrow gap. A desired image is displayed by inputting appropriate scanning signals and display signals from the circuit 5 to the X and Y electrodes. As is well known, the X electrode and the Y electrode are formed of a film of a transparent conductive material, and are not shown. However, an alignment film is formed on the side of the glass substrate which is in contact with the liquid crystal. Is attached with a polarizing plate. In the configuration shown in this figure, since the liquid crystal plate is of a transmissive type, both the upper and lower glass substrates are transparent (if used as a reflective type, the substrate on which light enters and exits is transparent and the other side is transparent. A reflector using an aluminum vapor-deposited film is arranged outside the substrate, in which case the electrodeless discharge lamp is, of course, placed on the screen side of the liquid crystal plate).

FIG. 3 shows an electrodeless microwave discharge light source. Microwaves are generated by a magnetron 10 and radiated through a waveguide 11 from a feed port into a cavity resonator 12. Cavity resonator
Reference numeral 12 denotes a metal mesh 13 that reflects microwaves but transmits light. The reflector 14 can be designed irrespective of microwaves so as to obtain a light distribution according to the application. A cooling fan 15 is used for cooling the waveguide and the magnetron. In this embodiment, a 750 W power was input to the magnetron, and a black-and-white image enough to be viewed in a bright room could be displayed on a screen having a diagonal length of 5 m. Only one cooling fan was needed for the magnetron, and it was quiet enough. As the magnetron and its power supply, those developed for a microwave oven can be used, and a good performance / price ratio was obtained.

In the present embodiment, the display image is monochrome, but the SDI 87 digest, the
It is easy to colorize using an optical system such as that described on page 78. At that time, a color tone similar to that of a metal halide lamp can be used as a light source. is there.

[Effects of the Invention] As described above, the present invention adopts a configuration having no electrode in the lamp, so that the restrictions on the luminous enclosure are greatly expanded and a luminous material with high efficiency and high color rendering can be selected. Therefore, a brighter light source can be obtained, and a decrease in screen brightness due to enlarged projection can be prevented as much as possible.

It is possible to reduce the output in the infrared region,
The influence of heat on the liquid crystal display element can be reduced, thereby improving the reliability of the liquid crystal display element and stabilizing the operation characteristics.

The forced cooling of the liquid crystal display element can be omitted, or the size of the forced cooling mechanism can be reduced.

Furthermore, by arranging the electrodeless discharge lamp in a cavity resonator made of a metal mesh that reflects microwaves but transmits light, light from the electrodeless discharge lamp can be effectively used.

Further, by disposing an ultraviolet blocking filter between the electrodeless discharge lamp and the optical shutter of the liquid crystal display element, even if the polarizer is used for the liquid crystal display element, the polarizer may be deteriorated by the ultraviolet light. Can be prevented.

Further, by configuring the light from the electrodeless discharge lamp to irradiate the optical shutter by the liquid crystal display element through the lens, the light from the electrodeless discharge lamp uniformly irradiates the liquid crystal display element. I can do it.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment of the present invention, FIG. 2 is a sectional view of a liquid crystal plate used as an optical shutter, and FIG. 3 is a diagram showing an electrodeless microwave discharge light source according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Exciter, 2 ... Electrodeless discharge lamp, 3 ... Lens, 4 ... Liquid crystal plate, 5 ... Drive circuit, 6 ... Lens, 7
... screen, 8 ... glass substrate, 9 ... liquid crystal material,
10 ... magnetron, 11 ... waveguide, 12 ... cavity resonator, 13 ... metal mesh, 14 ... reflector, 15 ... cooling fan.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-235352 (JP, A) JP-A-60-158543 (JP, A) Jpn.

Claims (4)

(57) [Claims] 1. A projection type image display device comprising: an optical shutter by a liquid crystal display element; a light source for irradiating the optical shutter; and an optical system for enlarging and projecting an image formed by the shutter. A projection type image characterized by being an electrodeless microwave discharge light source having an electrodeless discharge lamp, a magnetron for generating microwaves, and a waveguide for guiding microwaves from the magnetron to the electrodeless discharge lamp. Display device. 2. The electrodeless microwave discharge light source according to claim 1, wherein the electrodeless discharge lamp in the electrodeless microwave discharge light source is disposed in a cavity resonator made of a metal mesh that reflects microwaves. Projection image display device. 3. The projection type image display device according to claim 1, wherein an ultraviolet cutoff filter is provided between the electrodeless discharge lamp and an optical shutter formed by the liquid crystal display element. 4. The projection type image display device according to claim 1, wherein light from said electrodeless discharge lamp irradiates an optical shutter of said liquid crystal display element via a lens.