JPH04362622A - Rear type 4-sided multi-LCD projection device - Google Patents

Abstract

PURPOSE:To provide the rear type four-surface multiple liquid crystal projection device which is superior in portability while reduced in thickness and size, by reducing a projection distance. CONSTITUTION:This device is equipped with a rear projection type screen 13 which has four divided projection areas 14A-14D and four liquid crystal projection devices 20 in total which are arranged by two each above and below behind the screen while projection lenses 30 face forward; and image light 28 from those liquid crystal projection devices 20 is refracted and reflected forward and backward twice by a reflecting mirror 22 and projected on the corresponding projection areas.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention uses four liquid crystal projection devices, uses the light source light of each liquid crystal projection device that passes through a transmissive liquid crystal panel as image light, and expands the image light onto a screen from the back side. This invention relates to a rear type four-sided multi-LCD projection device that displays images by projecting images.

0002

[Background Art] In recent years, the progress of liquid crystal display technology has been remarkable, and with the advent of liquid crystal plates with excellent contrast and color reproducibility, liquid crystal color projection devices that use color liquid crystal plates as image display carriers and enlarge and project images onto large screens have been developed. It has been put into practical use. This type of device converges light from a light source into a substantially parallel beam using a converging optical system, irradiates it onto a transmissive color liquid crystal panel, and enlarges and projects the transmitted light onto a screen via a projection optical system. The projection device is usually arranged in front of the screen so that its optical axis is perpendicular to the screen surface. 5 and 6 are schematic diagrams showing the arrangement of such a liquid crystal color projection device and a screen. FIG. 5 shows the case where the liquid crystal color projection device 1 is installed on the floor of the room, and FIG. 6 shows the case where the liquid crystal color projection device 1 is hung from the ceiling. Indicates when to use it. Note that 2 is a screen arranged substantially perpendicularly along the wall surface.

0003

[Problems to be Solved by the Invention] By the way, if a rear projection type multi-LCD projection device is constructed using a plurality of conventional liquid crystal color projection devices 1 as described above, the projection screen obtained by one liquid crystal projection device will be When L=100 inches, the projection distance D needs to be about 350 cm, making it impossible to realize a portable rear projection type multi-liquid crystal projection device.

On the other hand, the present applicant previously filed Japanese Patent Application No. 2-2998.
No. 57, even if a conventional LCD projection device such as the one described above is installed on the floor or suspended from the ceiling, and the entire device is tilted to project toward a screen placed parallel to the wall, the top or bottom edge of the screen We have proposed a liquid crystal projection device that does not cause trapezoidal distortion or out-of-focus in the projected image due to the difference in distance between the projector and the projection lens, and can obtain a 100-inch projection screen with a relatively short projection distance of about 250 cm. .

[0005] This liquid crystal projection device makes light source light incident on the liquid crystal panel at a predetermined angle with respect to an axis perpendicular to the panel surface of the liquid crystal panel, and uses a mirror provided in a projection lens to capture the image light transmitted through the liquid crystal panel. In the same incident plane, a predetermined tilt angle is given to the inclination angle of the optical axis of the light source light, and the light is reflected toward the light source, and the optical axis is incident on the optical axis of this reflected light at the predetermined angle. In this way, the projection lens is tilted by the tilt angle and the center is positioned to project onto a screen placed parallel to the projection lens, so the LCD projection device can be installed on the floor, or Even if the screen is hung from a screen and the image is projected from below or above, it is possible to obtain an image without uneven lighting, trapezoidal distortion, out-of-focus, etc.

Furthermore, since the baseline or upper line of the projected image can be made horizontal, it is not only easy to adjust the installation, but also to configure the direction of the incident light and the projected light to face each other. Since the mirror for this purpose is disposed within the projection lens, the entire device can be downsized and the projection distance can be shortened. but,
This liquid crystal projection device also has the problem that the projection distance is still too long and the device is too large to constitute a portable rear projection type multi-liquid crystal projection device, making it impractical.

[0007] Therefore, the present invention has been made in view of the above-mentioned conventional problems, and its purpose is to shorten the projection distance, realize a thinner and smaller size, and have excellent versatility. An object of the present invention is to provide a rear type four-sided multi-liquid crystal projection device.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a rear projection type screen having a projection area divided into four parts, and a rear projection type screen having a projection area divided into four parts, and
A total of four liquid crystal projection devices each having two projection lenses facing forward are provided, and the image light from these liquid crystal projection devices is refracted and reflected twice by a reflecting mirror to form each of the corresponding projection areas. It is designed so that each of them is projected on the other side.

[0009]

[Operation] In the present invention, the reflecting mirror enlarges and projects the image light emitted from the liquid crystal projection device twice onto the projection area corresponding to the liquid crystal projection device from the back side of the screen, thereby reducing the projection distance. Shorten.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on embodiments shown in the drawings. FIG. 1 is an external perspective view showing an embodiment of a rear type four-sided multi-LCD projection device according to the present invention, and FIG.
3 is a sectional view taken along line II-II of FIG.
A line sectional view, FIG. 4 is a schematic diagram showing an optical system of a liquid crystal projection device. In these figures, the rear type four-sided multi-LCD projection device 1
0 has a longitudinally thin box-shaped housing 11 whose front center and entire back are open, and a rear projection screen 13 is attached to the front opening 12.

The rear projection type screen 13 is made of acrylic resin or the like, and when the projection size L is 80 inches, it has a width of 160 cm and a height of 120 cm, and is divided into four by vertical and horizontal lines that intersect with each other at the center. , has four projection areas 14A to 14D. Further, on the surface of the screen 13, a lenticular lens (cylindrical lens) 15 consisting of a large number of semi-cylindrical protrusions extending vertically over the entire length in the width direction and closely spaced in the left-right direction is disposed on the entire surface. On the other hand, Fresnel lenses 16A to 16D are integrally formed on the back surface for each of the projection areas 14A to 14D. The Fresnel lenses 16A to 16D convert transmitted image light emitted from a liquid crystal projection device 20 (described later) and transmitted through the screen 13 into parallel light, and each has a substantially triangular cross-sectional shape and a plurality of annular protrusions protruding concentrically. The inclination angle of the inner slope of each protrusion is larger toward the center and gradually decreases as it moves away from the center. The lenticular lens 15 focuses the transmitted image light transmitted through the screen 13 in front of the screen,
It works to enhance the light distribution characteristics toward the front. A light-shielding band 17 is provided at the boundary of each of the projection areas 14A to 14D. When the screen 13 is composed of a single plate, the light-shielding band 17 is formed on the projection area 1 on the back side of the screen.
4A to 14D protruding perpendicularly to the screen surface, and is manufactured by integrally joining four divided screens formed separately for each projection area 14A to 14D, the joining A light-shielding paint or a light-shielding film may be interposed on the surface to form a light-shielding band, or a thin light-shielding plate may be interposed on the joint surface and a portion thereof may protrude toward the back side. In this case, in this embodiment, four projection areas 14A to 14D each have the same structure and are divided into four parts.
An example is shown in which two split screens are integrally joined to form one rear projection type screen 13, and a thin light shielding plate as a light shielding band 17 is interposed on the joint surface so that a part of it protrudes to the back side of the screen. . Note that the rear projection screen 13 is not limited to the above configuration and can be modified in various ways. For example, a lenticular lens 15 may be provided on the front surface and the back surface may be made flat, or the front surface may be made rough like ground glass. It may be formed so that the back surface is a flat surface. The rear projection screen 13 configured in this manner is held at its peripheral edge by a frame 19 made of aluminum or the like, and is fitted and fixed into the front opening 12 of the housing 11.

Inside the housing 11, a total of four liquid crystal projection devices 20 are disposed, two each at the upper and lower rear of the screen, corresponding to each of the projection areas 14A to 14D. Four sets of two reflecting mirrors 22 are arranged to refract and reflect the image light 28 emitted from the device 20 twice and project it onto the projection areas 14A to 14D corresponding to the liquid crystal projection device. As shown in FIG. 4, the liquid crystal projection device 20 includes a light source 25 such as a xenon lamp, a condenser lens 26 that converts the emitted light from the light source 25 into substantially parallel light, and an image by transmitting the obtained substantially parallel light source light 27. A transmissive liquid crystal panel 29 is used as light 28, and the image light 28 transmitted through the liquid crystal panel 29 is enlarged and displayed on the screen 1.
It is composed of an L-shaped projection lens 30 and the like for projecting images onto the screen. The liquid crystal panel 29 has TN mode liquid crystal cells arranged, and if the voltage applied to the liquid crystal panel is changed according to the video signal of the television, the liquid crystal panel 29
9 displays a television image. The L-type projection lens 30 is composed of two lenses 31A and 31B and a mirror 32 disposed between these lenses 31A and 31B, and the lens 31B faces the first reflection mirror 22A of the reflection mirror 22. It is placed facing forward.

The reflecting mirror 22 is composed of the first reflecting mirror 22A and a second reflecting mirror 22B which is larger than the first reflecting mirror 22A. The first reflection mirror 22A reflects the image light 28 emitted from the liquid crystal projection device 20 backward and diagonally upward or downward, and is configured to reflect the image light 28 emitted from the liquid crystal projection device 20 diagonally upward or downward.
As shown in FIG. 3, in front of the upper liquid crystal projection device 20, the projection area 14C is arranged at a position above the back surface of the screen 13 and tilted rearward at a predetermined angle, and has two lower projection areas 14C, 14D is disposed at a position below the back surface of the screen 13 in front of the lower liquid crystal projection device 20 and tilted forward at a predetermined angle. The second reflection mirror 22B reflects the reflected image light reflected by the first reflection mirror 22A diagonally upward or diagonally downward, and the one corresponding to the two upper projection areas 14A and 14B is shown in FIG. As shown, the upper liquid crystal projection device 20
For those corresponding to the lower two projection areas 14C and 14D, the display is arranged directly below the lower liquid crystal projection device 20 and tilted forward at a predetermined angle. It is arranged.

Here, when each liquid crystal projection device 20 is installed above and below the screen 13, the screen 1
The difference in optical path length between the upper and lower ends of each of the projection areas 14A to 14D of No. 3 and the L-shaped projection lens 30 causes trapezoidal distortion and out-of-focus in the projected image. Therefore, in this embodiment, in order to reduce and prevent the occurrence of such trapezoidal distortion and out-of-focus as much as possible, the liquid crystal panel 29, L-shaped projection lens 30, and The first and second reflecting mirrors 22A and 22B are tilted forward or backward at a predetermined angle, respectively, to correct the optical path length.

[0015] Thus, the rear mold 4 having such a configuration
In the surface multi-LCD projection device 10, four liquid crystal projection devices 20 are disposed at the upper and lower back surfaces of the rear projection screen 13, corresponding to each of the projection areas 14A to 14D. Since it is configured to be refracted and reflected twice, the projection distance (the straight line distance between the screen 13 and the liquid crystal projection device 20) can be significantly shortened, and the screen 13 and the liquid crystal projection device 20 can be installed in the housing 11 with a depth of only 50 cm. can be incorporated. Therefore, it is possible to provide a rear-type four-sided multi-liquid crystal projection device that is thin and compact and has excellent versatility.

In the above embodiment, the case where the image light 28 is formed using one liquid crystal panel 29 has been described, but the present invention is not limited to this.
Three black and white liquid crystal plates are used, and R, G, and B light are incident on these liquid crystal plates through a dichroic mirror that separates the light source of all wavelengths into three color lights of R, G, and B. R, G, and B images are generated and mixed by a dichroic mirror (or dichroic prism), and the color image is enlarged and projected onto a screen 13 via a projection lens 30 and a reflecting mirror 22. Good too.

[0017]

As explained above, according to the rear type four-sided multi-liquid crystal projection device according to the present invention, the image light emitted from each liquid crystal projection device is refracted and reflected twice by the reflecting mirror. A projection distance can be shortened, the device itself can be made thinner and smaller, and a four-rear multi-liquid crystal color projection device can be provided which has excellent versatility.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view showing an embodiment of a rear type four-sided multi-LCD projection device according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is a schematic diagram showing an optical system of a liquid crystal projection device.

FIG. 5 is a projection state diagram when a conventional liquid crystal color projection device is installed on the floor.

FIG. 6 is a projection state diagram when a conventional liquid crystal color projection device is suspended from the ceiling.

[Explanation of symbols]

10 Rear type four-sided multi-LCD projection device 11 Housing 13 Rear projection type screens 14A to 14D Projection area 20 Liquid crystal projection device 22 Reflection mirror 25 Light source 29 Liquid crystal panel 30 Projection lens

Claims (1)

[Claims] 1. A rear projection screen having a projection area divided into four parts, and a total of four liquid crystal projection devices, two each of which are disposed above and below the back of the screen with projection lenses facing forward. A rear type four-sided multi-liquid crystal projection device, characterized in that the image light from these liquid crystal projection devices is refracted and reflected twice by a reflecting mirror and projected onto each of the corresponding projection areas.