JP2973594B2 - Projection image 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 projection type image display apparatus for brightly enlarging and projecting an image on a light valve for forming an image by controlling light transmittance by an electric signal.

[0002]

2. Description of the Related Art As a large-screen display device, there is a video projector, of which a high-intensity CRT is projected on a screen by a projection lens, and a type in which a liquid crystal panel is used as a light valve to project the image. There is. In recent years, attention has been paid to those using liquid crystals that can be expected to be smaller and lighter in set size with the progress of liquid crystal technology. FIG. 5 shows a principle diagram of a projection type image display device using a liquid crystal panel as a light valve. In FIG. 5, 1 is a light source lamp, 2 is a concave reflecting mirror, 3 is a field lens, 4
Denotes a liquid crystal light valve, 5 denotes a projection lens, and 6 denotes a screen. Light from a light source 1 is condensed by a concave reflecting mirror 2 and enters a liquid crystal light valve 4 through a field lens 3. The liquid crystal light valve 4 controls the transmittance of the pixel according to the video signal, and enlarges and projects the image on the screen 6 by the projection lens 5.

As a means for forming a large screen without lowering the resolution and brightness, there is a multi-vision system in which a plurality of projection type image display units are stacked to form one large screen.

[0004]

The problem of the multi-vision system is how to make joints between units less noticeable. If the luminance difference near the seam of the adjacent projection type image display unit is large, the seam becomes more conspicuous.

[0005] The liquid crystal light valve includes a normally black system in which the liquid crystal displays black when no voltage is applied and a normally white system in which the liquid crystal displays white when no voltage is applied. Normally
The white liquid crystal panel can display a higher contrast than the normally black liquid crystal panel, but has a large viewing angle dependence, and the viewing angle direction that provides the best contrast is slightly inclined from the normal direction of the liquid crystal panel. . Therefore, in order to project an image so that the contrast becomes the best, it is necessary to project the illumination light from the direction in which the contrast of the liquid crystal panel 4 becomes the best as shown in FIG.
The projection lens 5 is arranged so that the optical axis is substantially perpendicular to the screen 6 and the liquid crystal panel 4 is substantially parallel to the screen 6 so that there is no defocus and large keystone distortion does not occur. In this case, in the vertical direction of FIG.
The angle of view used by the projection lens is different. Generally, when the angle of view of the projection lens becomes large, the amount of peripheral light becomes small, so that uneven brightness of the projected image occurs in the vertical direction of the screen. Therefore, if this image projection device is simply combined as a single unit in the middle and lower two stages, there is a problem that the screen luminance difference between the upper and lower units is large at the joint portion of the units, and the seams are easily noticeable.

In view of the above-mentioned problems, the present invention provides a normally white liquid crystal panel which forms an image by controlling light transmittance by an electric signal as a light valve, and forms an image with a high contrast and a bright large screen. An object of the present invention is to provide a multi-vision projection type image display device.

[0007]

In order to achieve this object, a projection type image display device according to the present invention comprises a normally white liquid crystal panel which controls a light transmittance in accordance with a high-luminance light source and a video signal. An image forming unit to be a light valve;
One large screen is formed by combining two projection-type image display units each having a projection lens for enlarging and projecting the image on a screen in the vertical direction and two or more in the horizontal direction. Are arranged so that the direction of the viewing angle at which the contrast of the liquid crystal display element of the projection image display unit becomes the best is opposite to the vertical direction.

[0008]

According to the present invention, the above problem is solved by this configuration. That is, in a multi-vision system in which a plurality of upper and lower stages and a plurality of right and left units are stacked, each of the upper and lower liquid crystal projection image display units projects illumination light from a direction in which the contrast of the liquid crystal panel becomes the best. At this time, if the direction of the viewing angle at which the contrast of the liquid crystal display elements of the upper and lower projection image display units is the best is opposite to the vertical direction, the direction of illumination and the angle of view of the projection lens Is symmetric with respect to the seam between the upper and lower units, and therefore, the luminance distribution of the multi-vision composite screen is also almost symmetrical with respect to the seam between the upper and lower units. It is possible to obtain a projection-type image display device with no significant luminance difference and with less noticeable seams.

[0009]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. 1 and 2, the projection type image display unit 7 includes a light source lamp 1, a concave reflecting mirror 2,
It comprises a field lens 3, a liquid crystal light valve 4, and a projection lens 5, each of which is stacked in two stages in the up-down direction and a plurality of stages in the left-right direction, and projects an image on a screen 6 to constitute a large screen. In this way, a large screen with high luminance can be obtained by using multi vision. Here, the liquid crystal light valves 4 of the upper and lower projection type image display units 7 are arranged so that the direction of the viewing angle at which the contrast is best is opposite to the vertical direction. Illumination light is projected and projected.
In the upper projection type image display unit 7, the angle of view of the projection lens 5 on the screen side is small on the lower side, and in the lower projection type image display unit 7, the angle of view of the projection lens 5 on the screen side is small on the upper side. Has been placed. Therefore, in the synthesized multi-vision screen, the vicinity of the upper and lower seams of the projection type image display unit 7 is
Because the small angle of view of the projection lens 5 is used,
Generally, the amount of light is relatively high, and the screen becomes darker as it goes up and down the screen. Otherwise, the brightness near the joint between the upper and lower projection image display units will be low, and the joint will be more noticeable.

The screen 6 may be divided for each projection type image display unit and integrated. In addition, 8 shows the optimal viewing angle.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a rear projection type using a transmission screen 6 so that a projected image can be viewed even in a place where external light exists to some extent. At this time, the center of the Fresnel lens 9 is arranged near the joint of the vertical projection type image display unit 7. For this reason, the luminous flux from the periphery of the transmissive screen can be efficiently bent toward the observer who faces the center of the screen from the vicinity of the vertical line of the screen 6, and the enemy viewing range can be expanded. Here, reference numeral 10 denotes a lenticular lens.

[0012]

As described above, the present invention provides an image forming section using a normally white liquid crystal panel which controls light transmittance according to a high-luminance light source and a video signal as a light valve, and displays the image on a screen. A large screen is formed by combining two projection-type image display units each having a projection lens for enlarging and projecting an image vertically, and a plurality of projection-type image display units in the horizontal direction, and the upper-stage projection image display unit and the lower-stage projection image display. By arranging the liquid crystal display elements of the unit so that the viewing angle direction at which the contrast of the liquid crystal display element is the best is opposite to the vertical direction, there is no extreme brightness difference near the seam between the upper and lower projection image display units, It is possible to obtain a projection-type image display device that is inconspicuous.

Although a normally white liquid crystal panel having a relatively large viewing angle dependency has been described as an image display element, the present invention can be similarly applied to other light valves having a viewing angle dependency.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a projection-type image display device according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view of a projection-type image display device according to a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a projection-type image display device according to a second embodiment of the present invention.

FIG. 4 is a principle diagram of a projection type image display device using a conventional liquid crystal panel as a light valve.

FIG. 5 is a schematic diagram of a projection method for obtaining the best contrast of a normally white liquid crystal panel using a light valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source lamp 2 Concave reflector 3 Field lens 4 Liquid crystal light valve 5 Projection lens 6 Screen 7 Polymer 8 Optimal viewing angle of liquid crystal panel 9 Fresnel lens 10 Lenticular lens

Claims (2)

(57) [Claims] 1. An image forming section having a light valve of a normally white liquid crystal panel for controlling light transmittance according to a high-luminance light source and a video signal, and a projection lens for enlarging and projecting the image on a screen. One large screen is formed by combining two projection image display units in the vertical direction and two or more in the horizontal direction, and the contrast of the liquid crystal display elements of the upper image display unit and the lower image display unit is reduced. A projection-type image display device, wherein the direction of the best viewing angle is arranged to be opposite to the vertical direction. 2. The projection type image display device according to claim 1, wherein a transmission type screen is used, and the center of the Fresnel lens is arranged near a joint between the upper and lower projection image display units.