JPH0219889A - Projection image display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a projection type image display device that uses a liquid crystal display element as an optical shutter and can project a bright image.

[Prior Art] Currently, cathode ray tubes are very often used in image display devices, but when trying to obtain a large image, the weight of the cathode ray tube increases rapidly. For this reason, projection image display devices are used that use a cathode ray tube that can display images with very high brightness and an enlarged projection optical system. I can't get it. Therefore, devices have begun to be developed that separate the light source and the display area and combine a bright light source, an optical shutter using a liquid crystal display element, and an enlarged projection optical system.

A projection type image display device using the above-mentioned liquid crystal display element as an optical shutter is described, for example, in Nis.I.D.87 Digest, Session 6 (SID) in 1987.
87 DIGEST, 5ession 6) No. 75~
Page 78, 21ro Display, '87 (EUR
ODISPLAY'87), pages 115 and 116, disclose a method using a halogen lamp or a xenon lamp as a light source, respectively. In either case, the liquid crystal in a portion corresponding to each pixel of the matrix is driven by a thin film transistor (TPT) to reliably operate a matrix type liquid crystal display element made up of a large number of pixels. In addition, since liquid crystals generally become an isotropic liquid when heated to high temperatures, care must be taken when cooling them.In addition to forced air cooling of the light source itself, a filter is used to filter out the large amount of infrared rays generated by the light source. It is being removed.

[Problems to be Solved by the Invention] In order to achieve miniaturization, the above-mentioned conventional device uses a halogen lamp or xenon lamp that generates a relatively large amount of heat, so it requires a cooling fan and an infrared cutoff filter. Even if you use a liquid crystal display, it is difficult to avoid temperature rise in the liquid crystal display element, and you are limited by the output of the light source, resulting in problems such as not being able to make the displayed image bright enough or making the image large enough. Ta. Due to the use of powerful cooling fans,
In some cases, they became a source of noise and caused other problems.

If liquid cooling is used to improve cooling capacity, the equipment will become complicated.

Since it becomes large, there is no point in selecting the above type of light source.

The present invention provides a display that is sufficiently bright and large enough to be displayed without being bothered by heat generated by the light source, and that is relatively small.
An object of the present invention is to provide a projection type image display device.

[Means to solve the problem] In order to achieve the above object, the present invention.

In a projection type image display device equipped with a light source, an optical shutter using a liquid crystal display element, and an enlarged projection optical system, an electrodeless microwave discharge light source is used as the light source.

[Function] Regarding the electrodeless microwave discharge light source device, it is described, for example, in Illuminating Engineering Society Study Group Material L3-86-1-6, pages 17 to 21, but the light source itself has a high luminous efficiency; Since there is no need to provide electrodes in the envelope that encloses the plasma generation medium, there is a wide degree of freedom in selecting the medium, and therefore there is a wide degree of freedom in selecting the color tone of the light source. It has the advantage of a long life, less change in color tone even when the amount of light is changed, and faster rise in color tone, brightness, and light output compared to ordinary high-pressure discharge light sources. Since the light source itself has good luminous efficiency, even when taking into account the loss on the microwave generator side, the efficiency is equal to or higher than that of incandescent lamps, halogen lamps, xenon lamps, etc. Even if the distance between the optical shutter made of a liquid crystal display element and the electrodeless light source is not long, the heat generated by the light source itself is small, so it is sufficient to install an ultraviolet blocking filter to prevent the polarizing plate from deteriorating due to ultraviolet rays, and the amount of heat generated can be reduced. There is no need for an infrared cutoff filter or a forced air cooling device as in the case of the above-mentioned conventional light source, which has a large amount of light.

[Example] FIG. 1 is a schematic diagram of an embodiment of the present invention.

From an electrodeless discharge lamp 2 (in this example, a spherical envelope made of transparent quartz is filled with a substance similar to that of metal halide lamps or multi-halogen lamps) excited by an excitation device 1. Light is uniformly irradiated by a lens 3 onto a liquid crystal plate 4 (in this example, a simple TN type plate (Okano et al., "Liquid Crystal Applications", Baifukan, p. 16)). The liquid crystal plate 4 is driven by a drive circuit 5, and a desired image is displayed on the liquid crystal plate. The light transmitted through the liquid crystal plate 4, that is, the image displayed by the liquid crystal plate 4, is magnified by a lens 6 and projected onto a screen 7. FIG. 2 is a sectional view of the liquid crystal plate 4. The liquid crystal plate 4 has an X-direction electrode, and
Y-direction electrodes are formed perpendicular to these, and a liquid crystal material 9 is sandwiched between two glass substrates 8 facing each other across a narrow gap. A desired image is displayed by inputting a scanning signal and a display signal. Note that, as is well known, the X electrode and Y electrode are formed of a film of a transparent conductive material, and are not shown in the figure.
An alignment film is formed on the side of the glass substrate that contacts the liquid crystal, and a polarizing plate is attached to the outside of the substrate.

In the configuration shown in this figure, since the liquid crystal plate is a transmissive type, both the upper and lower glass substrates are transparent (if used as a reflective type).

The substrate on the side through which light enters and exits is transparent, and a reflective plate using an aluminum vapor-deposited film is placed on the outside of the substrate on the other side.

In this case, the electrodeless discharge lamp is of course placed on the screen side of the liquid crystal panel)6 FIG. 3 shows an electrodeless microwave discharge light source. Microwaves are generated by a magnetron 10, passed through a waveguide 11, and radiated into a cavity resonator 12 from a feed port. The cavity resonator 12 is composed of a metal mesh 13 that reflects microwaves but transmits light. The reflector 14 can be designed independently of the microwave so that a light distribution suitable for the purpose can be obtained. A cooling fan 15 is used to cool the waveguide and magnetron. In this example, the magnetron has a power of 750W.
By inputting information, we were able to display a black and white image that could be viewed for one minute in a bright room on a screen with a diagonal length of 5 meters. Only one cooling fan was needed for the magnetron, and it was sufficiently quiet. In addition, the magnetron and its power supply, etc.
It was possible to use one developed for microwave ovens, and a good performance-price ratio was obtained.

In this example, the displayed image was monochrome, but it is easy to make it color using an optical system such as that described on page 78 of the Niss I Day 87 Digest, Session 6. In this case, since a light source having the same color tone as a metal halide lamp can be used, the color tone of the displayed image is also very good.

[Effects of the Invention] As explained above, according to the present invention, it is possible to display a bright image on a large screen while keeping the optical shutter made of a liquid crystal display element at a sufficiently low temperature with a relatively simple and compact configuration. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an 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.

Claims (1)

[Claims] 1. In a projection type image display device equipped with an optical shutter using a liquid crystal display element, a light source that illuminates the optical shutter, and an optical system that enlarges and projects an image formed by the shutter, an electrodeless microwave discharge is used as a light source. A projection type image display device characterized by using a light source.