JP2581503B2 - LCD projection display - Google Patents

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 type display device for projecting a color moving image or a still image on a screen by using a liquid crystal. Are separated into three primary color components of green, blue, and red by a dichroic mirror having the following. Each of the separated light beams passes through an optical shutter (light valve) that changes the transmittance of liquid crystal according to luminance information of a video signal, and is further synthesized by a dichroic mirror. The present invention relates to a liquid crystal projection display device, which is also called a liquid crystal projector and is a display 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 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) is turned into a parallel light beam by a reflector 102 and is separated by a dichroic mirror 104 into a G (green) light beam. ) And B (blue) components are reflected and R (red)
The components are transmitted. The UV / IR filter 103 placed in front of the mirror 104 functions to absorb ultraviolet rays harmful to the human body. The optical path is shown by a thin broken line.

The light beam of the R component is bent by a total reflection mirror 105 at a right angle, and is condensed by a condenser lens 110 so as to be focus-coupled by a projection lens 131. A liquid crystal light valve 121 that modulates the transmittance of the R component light based on the R video signal level and expresses the brightness of an image is disposed at a location 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 light beams of the G component and the B component separated in this manner are respectively condensed with the condenser lens 1 similarly to the case of the R component described above.
The liquid crystal light valve 12
2 and 123, the light of each component is modulated according to its video signal level to its transmittance to express the brightness of an image. The G component light beam modulated by the liquid crystal light valve 122 passes through the dichroic mirror 1 for synthesis.
07 is combined with the above-described R component light beam. This combining dichroic mirror 107 is basically the same as the other separating dichroic mirror, and controls transmission / reflection at a predetermined light spectrum.

The B-component light beam is bent at a right angle by a total reflection mirror 108 to form a dichroic mirror 109 for synthesis.
, All the rays of the RGB components are combined, and the combined rays are screened by the projection lens 131 (not shown).
An image is formed on the top, 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 generally using three primary colors of red, green and blue,
It is sufficient to apply the same level of red, green and blue video signals to each liquid crystal light valve and modulate the amount of light by the liquid crystal light valve. As shown in the figure, the light passes 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 character recognition 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.

Further, in the conventional device, three colors of red, green and blue are used.
Since the primary color light passes through different paths,
Each piece of pixel information must be matched on a screen (referred to as registration adjustment). Compared with a projection display using a CRT (cathode ray tube), the registration alignment of the liquid crystal projection display device is simple. The adjustment process exists as an indispensable problem.

Conventionally, since the design of the optical system is easy (for example, only one type of imaging lens is required), as shown in FIG. 1, the light valves 121, 122, and 1 are used.
An arrangement method in which the distance from the projection lens 131 to the projection lens 131 is kept constant has been adopted. However, at this time, the light valve is not on the same plane as is apparent from FIG. This has resulted in a great hindrance to downsizing and cost reduction of the device. That is, three sets of divided liquid crystal light valves are required.

Further, at least one of the three light valves is arranged horizontally with the ground. This suggests that the image quality may be degraded due to the adhesion of dust, and may be a fatal defect of the display device. Depending on the arrangement of the light valve and the projection lens, it is not possible to solve the problem that these three light valves are not arranged horizontally with the ground. However, in this case, the physical configuration of the optical device and thus the entire device is significantly restricted. Which is inferior in practicality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a main object of the present invention is to minimize the number of optical elements on an optical path through which light beams pass when using it as a monochrome OA display, thereby achieving high brightness and high resolution. Is to provide a liquid crystal projection display device capable of obtaining the following.

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 achieve a reduction in size and cost, and can prevent dust from adhering. .

[0013]

In order to achieve the above object, the present invention provides a light source which emits light of three colors, green, blue and red.
A plurality of dichroic mirrors for separation into primary color components, and the transmittance of the liquid crystal is changed by the luminance information of the video signal for each of the three primary color components of green, blue and red separated by the respective dichroic mirrors for separation. A plurality of liquid crystal light valves to be combined, a plurality of combining dichroic mirrors for combining respective light beams of the three primary color components passing through each of the liquid crystal light valves, and light beams combined by the combining dichroic mirrors are imaged on a screen. And one of the separating dichroic mirrors, one of the liquid crystal light valves, and one of the synthesizing dichroic mirrors are arranged on an optical path connecting the light source and the lens system. When the dichroic mirror for separation and the dichroic mirror for synthesis are combined in the monochrome display mode, Characterized by comprising means for removing or retracted from.

According to a preferred embodiment of the present invention, an optical path excluding a separating dichroic mirror and a combining dichroic mirror removed or retracted from the optical path in the monochrome display mode is linear. The total reflection mirror is arranged by the arrangement of the light source and the lens system,
The optical path is refracted.

[0015] Further, according to a preferred aspect of the present invention, the plurality of liquid crystal light valves are arranged on the same surface.

[0016]

According to the present invention, a separating dichroic mirror and a synthesizing dichroic mirror in a light ray path of at least one of green, blue, and red are detachably or movable in order to display a single color (for example, black and white). Since this single-color liquid crystal light valve enables single-color display, it is necessary to compensate for the reduction in luminance and resolution degradation that was lost due to the trade-off due to full color. When applied to the case, the effect is maximized, and a very bright monochrome display can be achieved. Therefore, in the field of use of display devices, especially when used as a display device of an OA device represented by a personal computer, when displaying many characters and the like, the purpose of identifying the characters in black and white is sufficiently achieved. Therefore, the present invention is extremely practical and makes character identification very easy.

Further, in the present invention, by arranging and configuring the light valve on the same surface and integrally handling the light valve, the number of parts can be reduced (and the cost can be reduced). For example, a high-definition direct-view type liquid crystal display panel can be applied to a projection type display, so that the range of use of one liquid crystal can be widened and cost can be reduced. Further, the light valve does not have to be disposed on a horizontal plane from the viewpoint of dust prevention, so that the range of choice of the optical device shape can be expanded.

[0018]

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

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

In this embodiment, each liquid crystal light valve 22
The reference numerals 1, 222, 223 are arranged on the same surface, for example, on the same substrate (not shown), and the surface is 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. Further, the liquid crystal light valves 221, 222, 2
Reference numeral 23 may be of a type in which one large liquid crystal panel (liquid crystal light valve) is used by dividing the screen.

These liquid crystal light valves 221, 222,
223, condenser lenses 210 and 21 respectively.
One of the mirrors 1 and 212 is mounted and integrated, for example, via a substrate. These mirrors are arranged in the same direction on the light source side, and the mirror groups 208, 206 and 204 on the light source side, and the mirror groups 205 and 207 on the projection lens side. , 209.

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

In particular, the light source lamp 201 and the projection lens 23
1 are arranged in the same direction, and the separating dichroic mirror 204 and the synthesizing dichroic mirror 209 disposed between them are detachable from the apparatus or can be moved to a position retracted from the optical path indicated by a broken line. It is composed. For example, a pair of parallel rail-shaped mirror holders (not shown) having slide grooves are provided,
The mirrors 204 and 209 are provided in the grooves of the mirror holder.
Is stored in a freely detachable or movable manner. For this purpose, it is possible to use a well-known mechanism for holding a slide photograph or a mechanism for replacing a photographing filter. Or again.
A common arm or link (not shown) may be attached to the mirrors 204 and 209, and by rotating this arm or link, the mirrors 204 and 209 may be retracted from the optical path and returned to the optical path.
The above attachment / detachment or movement may be performed manually, but it is more preferable that the attachment / detachment or movement is performed using a micromotor or a solenoid actuator that is linked to a push button switch or an input key.

Next, the operation of this embodiment will be described.

First, a case where a normal full-color television image is displayed will be described.

Light emitted from a light source lamp 201 (usually a metal halide lamp is used) is
Becomes a parallel light beam, and the dichroic mirror for separation 2
Due to 04, the B component of the light beam is transmitted, and the G component and the R component are reflected. The UV / IR filter 203 functions to absorb ultraviolet rays harmful to the human body.

The structure of the B component passes through the dichroic mirror for separation 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 modulates the transmittance of the B component light based on the B video signal level and expresses the brightness of an image, is disposed very close to the condenser lens 212.

On the other hand, the G component and R component light beams reflected by the separating dichroic mirror 204 are reflected by the separating dichroic mirror 206, and the R component is transmitted. The G component and R component light beams thus separated are condensed by condenser lenses 211 and 210, respectively, and the respective component light beams are respectively condensed by liquid crystal light valves 222 and 221 as in the case of the B component described above. The transmittance is modulated by the video signal level to express the brightness of the image. The light beam modulated by the liquid crystal light valve 222 is applied to the combining dichroic mirror 20.
7 is combined with the above-mentioned R component light beam. This combining dichroic mirror 207 is basically the same as the other separating dichroic mirror, and controls transmission / reflection at a predetermined light spectrum.

The R component light beam is reflected by the total reflection mirror 208,
At 205, the optical path is bent at a right angle, 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 projected by the projection lens. 231
Thereby, an image is formed on a screen (not shown), and the function as a display is exhibited.

Next, the case of displaying a black and white screen of an OA device will be described. In this case, the separation dichroic mirror 204 and the synthesizing dichroic mirror 209 are both removed from the optical path, and black-and-white information using means (not shown) for converting separately prepared R, G, and B primary color signals into black-and-white information. (Monochrome luminance signal). This R, G, B
Means for converting the three primary color signals into black and white information is a well-known technique, and a detailed description thereof will be omitted. As a mechanism for this removal, as described above, attachment / detachment or parallel movement, rotation with one side as a fulcrum, or the like is conceivable, but any mechanism may be employed.

When the two dichroic mirrors 204 and 209 are removed from the optical path as described above, the light emitted from the light source lamp 201 becomes 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 223 and the liquid crystal light valve 223 are guided straight to the projection lens 231, by supplying a video signal only to the liquid crystal light valve 223, a monochrome image is projected from the projection lens 231 onto a screen. . In this case, since no light passes through the mirror at all, an image which is very bright and has high contrast as compared with the full color display is displayed on the screen, and the recognition of characters can be improved.

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

Further, in FIG. 1, although the optical path emitted from the light source is straight until it reaches the lens, the optical path can be refracted by 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 not necessary to largely change the components of the conventional configuration, and it is possible to easily realize the monochrome display only mode by changing the arrangement of the components and making a part of the mirror a movable mirror. Therefore, a mechanism which is effective in a case where high luminance and high resolution are required because a single color may be used can be realized relatively inexpensively.

(2) Further, by configuring 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 to reduce costs including reduction in 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 for which dust protection is taken increases. That is, not disposing the liquid crystal surface on the horizontal plane means that dust has an effect on light transmittance and reflectance, and the chance of causing image quality deterioration is drastically reduced.

[Brief description of the drawings]

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

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

[Explanation of symbols]

101, 201 Light source lamp 102, 202 Reflector 103, 203 UV, IR filter 104, 106, 206 Dichroic mirror for separation 105, 108, 205, 208 Total reflection mirror 107, 109, 207 Dichroic mirror for synthesis 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 separating dichroic mirror 209 Detachable or movable separating dichroic mirror

Claims (3)

(57) [Claims] 1. Light rays generated from a light source are classified into green, blue, and red.
A plurality of dichroic mirrors for separation into primary color components, and the green separated by the respective dichroic mirrors for separation;
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 each light beam of the three primary color components passing through each of the liquid crystal light valves is synthesized. A plurality of dichroic mirrors for synthesis, and a lens system for forming an image of a light beam synthesized by the dichroic mirror for synthesis on a screen, wherein the dichroic mirror for separation is provided on an optical path connecting the light source and the lens system. One, one of the liquid crystal light valves, and one of the synthesizing dichroic mirrors. The arranged dichroic mirror for separation and the dichroic mirror for synthesis are disposed or removed from the optical path in the monochrome display mode. A liquid crystal projection display device comprising a retracting means. 2. An optical path excluding a separating dichroic mirror and a synthesizing dichroic mirror removed or retracted from the optical path in the monochrome display mode is linear 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 an optical path is refracted. 3. The liquid crystal projection display according to claim 1, wherein the plurality of liquid crystal light valves are arranged on the same plane.