JPH0572651A - Projection type picture display device - Google Patents

Abstract

PURPOSE:To enable a large screen to be projected by a short projecting distance, to make a projection type picture display device inexpensive by setting only one liquid crystal panel for displaying a picture and to obtain a projected picture with high resolution in the projection type picture display device using the liquid crystal panel. CONSTITUTION:Liquid crystal panel units 12, 24 and 27 are respectively placed on the optical paths of blue, red and green. They are actuated as a shutter. By opening and closing them without superposing the plural color of light, the image of the color of the transmitted light is displayed on a liquid crystal panel unit for forming an image 18 and enlarged and projected by a projection lens 20. By such constitution, the large screen is realized by the short projecting distance by making the back focus of the lens 20 short. Besides, the device is made inexpensive by setting only one liquid crystal panel and the projected picture with high resolution is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a projection type image display device using a liquid crystal panel as an image display element, particularly to cost reduction and short focus of a projection lens.

[0002]

2. Description of the Related Art With the increase in size of televisions, the demand for projection-type image display devices is increasing because they can more easily cope with larger sizes than conventional direct-view type image display devices.

Among them, a projection type image display device using a liquid crystal as a light valve is on the market because it is easy to operate in order to obtain a large screen at home, the device itself is not large, and no installation work is required. Accepted by.

Projection type image display devices using liquid crystal as a light valve can be roughly classified into the following two types in the current market. One uses only one liquid crystal panel, and this liquid crystal panel is provided with three color filters of red, green, and blue. The other is a projection type image display device for enlarging and projecting this image with a projection lens, and the other is This is a projection-type image display device in which light from a light source is separated into three colors of red, green, and blue, liquid crystal panels are arranged on the respective optical paths, and the images here are combined and enlarged and projected by a projection lens.

[0005]

Of these, the former is significantly inferior in image quality to the latter, but the optical system is simple in construction and only one liquid crystal panel is required, so that it can be provided at a relatively low cost. I can.

The image quality of the latter is greatly improved as compared with the former, but the configuration of the optical system is complicated, the set itself is large because three liquid crystal panels are required, and the image of three liquid crystal panels is large. It becomes expensive because of the need for convergence adjustment to overlap with each other, and because the color combining optical system exists between the projection lens and the liquid crystal panel, the focal length of the projection lens becomes long and you can enjoy a large screen. Has a problem that a long projection distance is required.

In view of the above problems, the present invention intends to provide a projection-type image display device when a high-resolution image can be obtained even though the optical system has a simple structure.

[0008]

According to the present invention, at least a liquid crystal panel which is an image display element, a projection lens which is provided to project an image of the liquid crystal panel which is the image display element, a light source, and a light of the light source are provided. Optical means for decomposing and combining the three primary colors of red, green, and blue, and a shutter provided during the decomposition and combining of the optical paths of red, green, and blue of the optical means, where the shutter is one of the optical paths of red, green, and blue. One of the optical paths is set to be open, and at this time, the liquid crystal panel, which is an image display element, displays an image in the color of the open optical path. A large screen can be realized with high resolution image quality at low cost and a short projection distance.

[0009]

In the present invention, one of the red, green, and blue optical paths of the shutter is set to be open, and at this time, the liquid crystal panel, which is the image display element, is set to the color of the open optical path. An image is displayed, and this image is enlarged and projected by the projection lens. Next, the shutter that was transmitting the light is blocked, and at the same time as this, the shutter on the optical path of one of the other colors transmits the light. At this time, the display is switched to the image of the color that has just been transmitted on the liquid crystal panel. This is also enlarged and projected by the projection lens as described above. After that, the remaining one color is similarly guided to the liquid crystal panel and an image of that color is projected. By repeating this operation at high speed, it is as if the images of red, green, and blue are overlapped and displayed on the eyes of the observer of the projected image. In this way, with the configuration of the present invention, only one liquid crystal panel for displaying an image is required. Since there is only one image display unit, no convergence adjustment is required. Because the surface accuracy of the mirror used in the display device is unnecessary, it is possible to obtain a projection image with high resolution equivalent to that of the liquid crystal projection type image display device using the above-mentioned three liquid crystal panel, but at a low price. Can be provided.

Further, since no space is particularly required between the liquid crystal panel and the projection lens, the focal length of the projection lens can be set short, so that a large screen can be provided with a short projection distance.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of a two-body projection type image display device using a liquid crystal panel. 1 indicates a light source,
The light source drive circuit 3 operated by the power supplied from the power supply circuit 2 drives and emits light. The light emitted from this is sent to the ultraviolet / infrared cut mirror 7 supported by the inner wall 5 of the first housing 6 by the reflector 4. Of the light incident on the ultraviolet / infrared cut mirror 7, only the visible light component is incident on the blue transmission dichroic mirror 8. At this time, only the light of the blue wavelength is transmitted through the condenser lens 10 by the surface mirror 9 and then is incident on the incident side polarization plate 11a. Only the light of the necessary polarization component is incident on the liquid crystal panel unit 12 by the incident side polarization plate 11a. The liquid crystal drive circuit provided in the liquid crystal panel unit 12 is connected to the signal processing circuit 13. The signal processing circuit 13 is supplied with power from the power supply circuit 2 and has an input terminal 14 for receiving a signal from the outside. When the liquid crystal panel unit 12 is opened to transmit light, the blue light transmitted through the emission side polarization plate 11b is transmitted through the red reflection dichroic mirror 15 and after being reflected by the green transmission dichroic mirror 16. , The polarization axis of which is the exit side polarization plate 1
The incident side polarization plate 17a is set to the same angle as 1b. After that, light is incident on the liquid crystal panel unit 18, but the liquid crystal drive circuit provided in the liquid crystal panel unit 18 is connected to the signal processing circuit 13, and an image in the color of the transmitted light is displayed on the panel portion. Showing up.
An image emitted from the emission side polarization plate 17b is enlarged and projected by the projection lens 20 supported by the lens barrel 19.

Next, the light reflected by the blue transmission dichroic mirror 8 is separated by the red reflection dichroic mirror 21 into light in the red wavelength range and light in the green wavelength range. Of these, the red light is reflected, passes through the condenser lens 22 in the same manner as the blue light, and then enters the incident side polarization plate 23a, so that only the light of the necessary polarization component is emitted.
It is incident on 4. The liquid crystal panel unit 24 contains a liquid crystal drive circuit (not shown). This liquid crystal drive circuit is connected to the signal processing circuit 13. When the liquid crystal panel unit 24 is opened so as to transmit light, the red light transmitted through the emission side polarization plate 23b is reflected by the red reflection dichroic mirror 15 and after being reflected by the green transmission dichroic mirror 16. The incident side polarization plate 17 whose polarization axis is set to the same angle as that of the emission side polarization plate 23b.
It is incident on a. After that, the light enters the liquid crystal panel unit 18, and the image emitted from the emission side polarizing plate 17b is the lens barrel 1.
It is enlarged and projected as a projection image by the projection lens 20 supported by 9.

Regarding the remaining green light, the transmitted light becomes blue and green by the red reflection dichroic mirror 21, but the blue light has already been removed by the blue transmission dichroic mirror 8, so only the green light is transmitted through the condenser lens 25. , Is incident on the incident side polarization plate 26 a, and only the light of the necessary polarization component is incident on the liquid crystal panel unit 27. The liquid crystal panel unit 27 contains a liquid crystal drive circuit (not shown).
This liquid crystal drive circuit is connected to the signal processing circuit 13. When the liquid crystal panel unit 27 is opened so as to transmit light, the light transmitted through the emission side polarization plate 26b is reflected by the surface mirror 28, and the green transmission dichroic mirror 16 is provided.
And enters the incident side polarization plate 17a whose polarization axis is set to the same angle as the emission side polarization plate 26b. After that, the light enters the liquid crystal panel unit 18, and the image emitted from the emission side polarization plate 17b is enlarged and projected as a projection image by the projection lens 20 supported by the lens barrel 19.

The liquid crystal panel units 12, 24, 27
Unlike the liquid crystal panel unit 18, it is not an object for displaying an image but an optical shutter, so that it is not necessary to drive each pixel. Also, these are controlled so that they do not simultaneously transmit light.

By adopting the above-mentioned structure, compared with the structure in which the conventional dichroic mirror or prism is interposed between the projection lens and the liquid crystal panel which is the image display device,
Since the back focus of the projection lens can be shortened, a large screen can be realized with a short projection distance. Also, since there is only one image display device, no convergence adjustment is required. The surface precision of the optical part of the color synthesis system is not necessary compared to the conventional one. Since the liquid crystal panel units 12, 24 and 27 are mere optical shutters, it is possible to realize cost reduction as compared with the conventional structure because control is not required for each pixel.

In this embodiment, the liquid crystal panel is used as the optical shutter, but the optical shutter is not limited to this, and a mechanical shutter can be used.

Needless to say, the color separation for dividing the light source into red, green and blue lights and the structure of the color combining system for combining these are not limited to the structure of this embodiment.

[0018]

In the conventional structure, three sets of liquid crystal panels are required, so that the set itself becomes large, and convergence adjustment for superimposing the images of the three liquid crystal panels is also required, which is expensive. Since the color synthesizing optical system exists between the projection lens and the liquid crystal panel, the projection lens has a long focal length, which requires a long projection distance to enjoy a large screen. According to the above, at least a liquid crystal panel which is an image display device,
A projection lens provided so as to project an image of the liquid crystal panel which is the image display element, a light source, an optical means for decomposing and combining light of the light source into three primary colors of red, green and blue, and red, green and blue of the optical means. It comprises a shutter provided during the disassembly and synthesis of the respective optical paths, of which the shutter is set so that one of the optical paths of red, green and blue is opened, and at this time, it is an image display element. By adopting a configuration in which an image of the color of the open optical path is displayed on the liquid crystal panel, high resolution image quality can be realized at low cost and on a large screen with a short projection distance.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a two-body projection type image display device according to the present invention.

[Explanation of symbols]

 1 Light Source 2 Power Supply Circuit 3 Light Source Driving Circuit 4 Reflector 5 Inner Wall of First Housing 6 First Housing 7 UV / Infrared Cut Mirror 8 Blue Transmission Dichroic Mirror 9 28 Surface Mirror 10 22 25 Condenser Lens 11a 17a 21a 26a Incident Side Polarizing plate 11b 17b 21b 26b Emitting side polarizing plate 12 24 27 Liquid crystal panel unit 13 Signal processing circuit 14 External signal input terminal 15 21 Red reflection dichroic mirror 16 Green transmission dichroic mirror 18 Image display liquid crystal panel unit 19 Lens barrel 20 Projection lens

Claims (1)

[Claims] 1. A liquid crystal panel that is at least an image display element, a projection lens that is provided to project an image on the liquid crystal panel that is an image display element, a light source, and light from the light source into three primary colors of red, green, and blue. It is composed of optical means for disassembling and synthesizing, and a shutter provided during the disassembling and synthesizing of the red, green and blue optical paths of the optical means, and the shutter is such that one of the red, green and blue optical paths is open. The projection-type image display device is characterized in that the liquid crystal panel displays an image of the color of the open optical path.