JPH0756134A - Liquid crystal projection type display device - Google Patents

Abstract

PURPOSE:To obtain high brightness and high resolution by reducing the number of optical elements on an optical path to the utmost when a full-color liquid crystal projection type display device is used as a monochromatic display. CONSTITUTION:In a full-color display mode, a light beam emitted from a light source lamp 201 is separated to green, blue and red by dichroic mirrors for separating 204 and 206 and the light of respective components is passed through liquid crystal light valves 223, 222 and 221 changing transmissivity by a video signal. Besides, it is synthesized by dichroic morrors for synthesizing 207 and 209 and projected by a projection lens 231. Specially, the mirror 204, a condenser lens 212, the valve 223 and the mirror 209 are arranged in the course of the optical path on a straight line connecting the lamp 201 and the lens 231. Then, the movable mirrors 204 and 209 are eliminated from the optical path in a monochromatic display mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projection display device for projecting a color moving image or a still image on a screen by using a liquid crystal. Is separated into three primary color components of green, blue, and red with a dichroic mirror having, an optical shutter (light valve) that changes the transmittance of the liquid crystal according to the luminance information of the video signal is passed through each of the separated light rays, and the light is combined with the dichroic mirror. The present invention relates to a liquid crystal projection display device, which is also called a liquid crystal projector, which is a display type device that forms an image on a screen via a lens.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a conventional liquid crystal projection display device of this type.

As shown in FIG. 1, a light beam emitted from a light source lamp 101 (usually a metal halide lamp is used) becomes a parallel light beam by a reflecting plate 102, and a G (green) light beam is separated by a separating dichroic mirror 104. ) And B (blue) components are reflected, and R (red)
The component is transmitted. The UV / IR filter 103 placed in front of the mirror 104 serves to absorb ultraviolet rays harmful to the human body. The optical path is shown by a thin broken line.

The R component light beam is bent at a right angle by the total reflection mirror 105 and is condensed by the condenser lens 110 so as to be focus-coupled by the projection lens 131. A liquid crystal light valve 121, which expresses the brightness and darkness of an image by modulating the transmittance of the R component light according to the R image signal level, is arranged at a position very close to the condenser lens 110.

On the other hand, the G component and the B component reflected by the separating dichroic mirror 104 are reflected by the separating dichroic mirror 106 and the B component is transmitted. The rays of the G component and the B component thus separated are respectively separated by the condenser lens 1 as in the case of the R component.
The liquid crystal light valve 12 is focused by 11, 112.
2, 123, light of each component is modulated in its transmittance according to each video signal level to express the brightness of the image. The G component ray modulated by the liquid crystal light valve 122 is the dichroic mirror for synthesis 1.
At 07, it is combined with the above-mentioned R component ray. The combining dichroic mirror 107 is basically the same as the other separating dichroic mirrors, and controls transmission / reflection with a predetermined light spectrum as a boundary.

The B component light beam is bent at a right angle by the total reflection mirror 108, and the dichroic mirror 109 for synthesis is used.
All the rays of RGB components are combined by the screen, and the combined rays are projected onto the screen (not shown) by the projection lens 131.
An image is formed on the screen and the function as a display is exhibited.

[0007]

However, in the prior art as described above, in order to display a black and white screen on a full color display device which generally uses the three primary colors of red, green and blue,
It suffices to apply exactly the same level of red, green, and blue video signals to each liquid crystal light valve and modulate the amount of light with the liquid crystal light valve. As shown in, it will pass through at least three mirrors. Passing through these mirrors reduces the amount of light each time, causing a decrease in brightness. This leads to deterioration of the degree of recognition of characters in the function of transmitting information to the user, which is the maximum purpose as a display of OA (office automation) equipment,
It can be fatal.

Furthermore, in the conventional device, red, green, and blue are used.
Since the primary color light passes through different routes, when combining them,
Although it is necessary to match the pixel information on the screen (referred to as registration registration), the registration is simple in the liquid crystal projection display device as compared with a projection display using a CRT (cathode ray tube). The adjustment process exists as an indispensable problem.

Further, in the prior art, since the design of the optical system is easy (for example, only one type of imaging lens is required), the light valves 121, 122, 1 as shown in FIG.
An arrangement method has been adopted in which the distance from 23 to the projection lens 131 is constant. However, at this time, the light valves are not on the same plane as is apparent in FIG. This greatly hinders downsizing and cost reduction of the device. In other words, it is necessary to have three sets of divided liquid crystal light valves.

Further, one or more of the three light valves are arranged horizontally with respect to the ground. This suggests the possibility of image quality deterioration due to the adhesion of dust, and can be a fatal defect of the display device. Depending on the arrangement of the light valve and the projection lens, it is possible to solve the problem that these three light valves are not arranged horizontally with respect to the ground. In this case, however, the physical shape of the optical device and thus the entire device is significantly restricted. Therefore, it becomes inferior in practicality.

The present invention has been made in view of the above-mentioned points, and its main purpose is, when it is used as a monochrome OA device display, to minimize the number of optical elements on the optical path through which a light beam passes to achieve high brightness and high resolution. Another object of the present invention is to provide a liquid crystal projection display device capable of obtaining

Another object of the present invention is to provide a liquid crystal projection display device which does not require registration in addition to the above-mentioned objects, can be made compact and inexpensive, and can prevent dust from adhering thereto. .

[0013]

In order to achieve the above object, the present invention uses a light beam generated from a light source to generate green, blue and red light.
A plurality of separation dichroic mirrors that are separated into primary color components, and the transmittance of the liquid crystal is changed according to the luminance information of the video signal for each of the three primary color components of green, blue, and red separated by each of the separation dichroic mirrors. A plurality of liquid crystal light valves, a plurality of combining dichroic mirrors that combine the light beams of the three primary color components that have passed through the liquid crystal light valves, and the light beams combined by the combining dichroic mirrors are imaged on the screen. And a lens system that allows the separation of one of the separation dichroic mirrors, one of the liquid crystal light valves, and one of the combining dichroic mirrors on an optical path connecting the light source and the lens system. When the separation dichroic mirror and the combining dichroic mirror that have been separated are set to the optical path in the monochrome display mode. Characterized by comprising means for removing or retracted from.

Further, according to one aspect of the present invention, preferably, the optical path excluding the separating dichroic mirror and the combining dichroic mirror removed or retracted from the optical path in the monochrome display mode is linear. Arrange the total reflection mirror by the arrangement of the light source and the lens system,
It is characterized in that the optical path is refracted.

The present invention can be preferably characterized in that the plurality of liquid crystal light valves are arranged on the same plane.

[0016]

According to the present invention, the separation dichroic mirror and the composition dichroic mirror in the light path of at least one of green, blue and red are detachably or movably constructed in order to display a single color (for example, black and white). Since this monochromatic liquid crystal light valve is used to enable monochromatic display, it is necessary to compensate for the decrease in brightness and resolution that are lost due to the trade-off due to full color. When applied to the case, it exerts the maximum effect and can display a very bright single color. Therefore, among the fields of use of display devices, particularly when used as a display device of OA equipment represented by a personal computer, when many characters are displayed, the purpose of identifying the characters is sufficiently achieved even in black and white. Therefore, the present invention is extremely practical, and character identification becomes very easy.

Further, in the present invention, by disposing the light valves on the same surface and treating them as an integrated unit, it is possible to reduce the number of parts (and eventually cost). For example, a high-definition direct-viewing type liquid crystal display panel can be applied to a projection type display, the range of use for one liquid crystal is expanded, and the cost can be reduced. Further, from the viewpoint of dust prevention, it is not necessary to dispose the light valve on the horizontal plane, so that the selection range of the optical device shape can be widened.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 shows a schematic configuration of a liquid crystal projection display device according to an embodiment of the present invention. In FIG. 2, 201 is a light source lamp, 202 is a reflector, and 203 is a UV / IR filter. Reference numeral 204 is a detachable or movable separation dichroic mirror, 206 is a fixed separation dichroic mirror, 208 and 205 are total reflection mirrors, 207 is a fixed combining dichroic mirror, and 209 is a removable or movable combining dichroic mirror. is there.
210, 211 and 212 are condenser lenses, and 221, 222 and 223 are R, G and B respectively.
231 is a projection lens.

In this embodiment, each liquid crystal light valve 22
1, 222, and 223 are, for example, arranged on the same substrate (not shown) and on the same plane, and the planes are arranged substantially perpendicular to the ground. The substrate is a mounting substrate, for example, a transparent plate or a frame having a plurality of mounting windows. Furthermore, the liquid crystal light valves 221, 222, 2
23 may be of a type in which one large liquid crystal panel (liquid crystal light valve) is divided and used.

These liquid crystal light valves 221, 222,
The condenser lenses 210 and 21
One of the mirrors 208, 206 and 204 is attached to one of the light source side mirrors 208, 206 and 204 and the projection lens side mirror groups 205 and 207, which are arranged side by side in the same direction. , 209.

Incidentally, each condenser lens 210, 21
The focal lengths of 1 and 212 are determined corresponding to the difference in optical distance between the corresponding liquid crystal light valve and the projection lens 231, for example.

In particular, the light source lamp 201 and the projection lens 23
1 are arranged in the same direction so that the separation dichroic mirror 204 and the combining dichroic mirror 209 arranged between them can be attached to and detached from the apparatus or can be moved to positions retracted from the optical path indicated by the broken line. Is configured. For example, by providing a pair of parallel rail-shaped mirror holders (not shown) having slide grooves,
The mirrors 204 and 209 are placed in the grooves of the mirror holder.
Can be detached or moved freely. For this, it is possible to use a well-known hold mechanism for slide photographs, a photographing filter exchange mechanism, or the like. Or again.
A common arm or link (not shown) may be attached to the mirrors 204 and 209, and the arms or links may be rotated to retract the mirrors 204 and 209 from the optical path and return them to the optical path.
The above attachment / detachment or movement may be performed manually, but it is more preferable to use an actuator such as a micromotor or a solenoid that works in conjunction with a push button switch or an input key.

Next, the operation of this embodiment will be described.

First, the case of displaying a normal full-color television image will be described.

Light rays emitted from the light source lamp 201 (usually a metal halide lamp is used) are reflected by the reflection plate 202.
To make parallel rays, and separate dichroic mirror 2
By 04, the B component of the light ray is transmitted, and the G and R components are reflected. The UV / IR filter 203 functions to absorb ultraviolet rays harmful to the human body.

The component B component passes through the separation dichroic mirror 204 and is condensed by the condenser lens 212 so as to be focus-coupled by the projection lens 231. A liquid crystal light valve 223 for B, which expresses the brightness of the image by modulating the transmittance of the B component light according to the B video signal level, is arranged at a position very close to the condenser lens 212.

On the other hand, the G component and R component rays reflected by the separating dichroic mirror 204 are reflected by the separating dichroic mirror 206, and the R component is transmitted. The G and R component rays separated in this way are condensed by the condenser lenses 211 and 210, respectively, as in the case of the B component described above, and the respective component light components are separated by the liquid crystal light valves 222 and 221. The lightness and darkness of the image is expressed by modulating the transmittance according to the video signal level. The light rays modulated by the liquid crystal light valve 222 are combined dichroic mirror 20.
7 is combined with the R component ray described above. The combining dichroic mirror 207 is basically the same as the other separating dichroic mirrors, and controls transmission / reflection with a predetermined light spectrum as a boundary.

Further, the R component ray is a total reflection mirror 208,
The optical path is bent at a right angle by 205, and after being combined with the G component by the G component combining dichroic mirror 207, all of the RGB component light beams are combined by the B component combining dichroic mirror 209, and the combined light beam is the projection lens. 231
An image is formed on a screen (not shown) by the above, and the function as a display is exhibited.

Next, the case of displaying a black and white screen of the OA equipment will be described. In this case, both the separating dichroic mirror 204 and the combining dichroic mirror 209 are removed from the optical path. As a mechanism for this removal, as described above, attachment / detachment or parallel movement, rotation movement with one side as a fulcrum, and the like are conceivable, but any mechanism may be adopted.

When the two dichroic mirrors 204 and 209 are removed from the optical path in this way, the light beam emitted from the light source lamp 201 is the condenser lens on the shortest optical path among the plurality of condenser lenses and the liquid crystal light valve. Since only the liquid crystal light valve 212 and the liquid crystal light valve 223 are directly guided to the projection lens 231, by supplying the video signal only to the liquid crystal light valve 223, a monochrome image is projected from the projection lens 231 on the screen. . In this case, since light rays are not passed through the mirror at all, a very bright and high-contrast image is projected on the screen as compared with full-color display, and the recognition of characters can be improved.

For reference, the separation dichroic mirrors 104 and 1 in the conventional configuration shown in FIG.
06 is replaced by a total reflection mirror, and a dichroic mirror for synthesis 107 and 109 can be replaced by a total reflection mirror. A mirror exchange mechanism is provided so that only the liquid crystal light valve 122 for the G component is replaced by the total reflection mirror. It is possible to display a monochrome image similar to that of the present embodiment by using it. However, the number of constituent elements that must be replaced by attachment / detachment or movement is much larger than that of the constituent elements to be removed in this embodiment, and the configuration becomes complicated, so it can be said that it is inferior in practicality.

Further, in FIG. 1, the optical path emitted from the light source exists on a straight line until it reaches the lens, but it is possible to refract the optical path using a total reflection mirror depending on the arrangement of the light source and the lens system. is there.

[0034]

As described above, according to the present invention, the following effects can be obtained.

(1) It is possible to easily realize a monochrome display only mode by changing the arrangement of the constituent elements and by making a part of the mirror a movable mirror without requiring a large change in the components of the conventional structure. Therefore, an effective mechanism can be realized at a relatively low cost in a scene that requires high brightness and high resolution because it may be a single color.

(2) Furthermore, by constructing three liquid crystal light valves on the same substrate, it is possible to realize a wide variety of displays with one type of liquid crystal panel, and also to reduce costs, including the number of parts. Can be expected.

(3) By not forming the light valve on the horizontal plane, the design margin of the optical device provided with the dustproof measure is increased. That is, the fact that the liquid crystal surface is not arranged on the horizontal plane means that the dust influences the transmittance and reflectance of light rays, and the chances of causing image quality deterioration are drastically reduced.

[Brief description of drawings]

FIG. 1 is a layout configuration diagram showing a schematic internal configuration of a conventional liquid crystal projection display device.

FIG. 2 is a layout configuration diagram showing a schematic internal configuration of a liquid crystal projection display device according to an embodiment of the present invention.

[Explanation of symbols]

101, 201 Light source lamp 102, 202 Reflector plate 103, 203 UV, IR filter 104, 106, 206 Separation dichroic mirror 105, 108, 205, 208 Total reflection mirror 107, 109, 207 Synthesis dichroic mirror 110, 111, 112 , 210, 211, 212 Condenser lens 121, 122, 123, 221, 222, 223 Liquid crystal light valve 131, 231 Projection lens 204 Detachable or movable dichroic mirror for separation 209 Detachable or movable dichroic mirror for synthesis

Claims (3)

[Claims] 1. Light rays emitted from a light source are classified into green, blue, and red rays.
A plurality of separation dichroic mirrors that are separated into primary color components, and the green separated by each of the separation dichroic mirrors,
A plurality of liquid crystal light valves that change the transmittance of the liquid crystal according to the luminance information of the video signal for each of the three primary color components of blue and red, and the respective light rays of the three primary color components that have passed through the respective liquid crystal light valves are synthesized. A plurality of combining dichroic mirrors, and a lens system for forming an image of the light rays combined by the combining dichroic mirrors on a screen, and the separating dichroic mirrors on the optical path connecting the light source and the lens system. One of the liquid crystal light valve and one of the combining dichroic mirrors are arranged, and the separating dichroic mirror and the combining dichroic mirror arranged are removed from the optical path in the monochrome display mode. A liquid crystal projection display device comprising means for retracting. 2. The optical path excluding the separating dichroic mirror and the combining dichroic mirror removed or retracted from the optical path in the monochrome display mode is a linear path or a total reflection mirror depending on the arrangement of a light source and a lens system. 2. The liquid crystal projection display device according to claim 1, wherein the liquid crystal projection display device is provided by refracting an optical path. 3. The liquid crystal projection display device according to claim 1, wherein the plurality of liquid crystal light valves are arranged on the same plane.