JPH0540311A - Back projection type display device - Google Patents

Abstract

PURPOSE:To provide the thin back projection type display device which has small aberrations and high picture quality and is sharp by increasing a space assigned for a projection optical means and reducing the load upon a projection lens. CONSTITUTION:The back projection type display device has an optical unit 2 which projects an image, formed by a light source and an optical modulating means, on a screen, and the screen 3; and the center optical axis of projection light projected from the projection optical unit slants to the normal of the screen in a vertical plane and also slants even in a horizontal plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for enlarging and projecting a video image, a computer image or the like from the rear side.

[0002]

2. Description of the Related Art Recently, a magnified projection display device has been attracting attention, which is capable of magnifying and projecting a display image of a CRT or a liquid crystal on a screen to display it as a large screen.

This is because there is a limit to the size of image display by a cathode ray tube (CRT), and the size of the cathode ray tube itself becomes large in order to enlarge the screen, and the size of about 40 inches is practically limited. Therefore, this is to meet the demand for obtaining more images.

Therefore, using a CRT or liquid crystal, an optical system for enlarging and projecting an image displayed on the CRT or liquid crystal is housed in a cabinet, and a rear projection is performed on a screen provided on the front of the cabinet to display an enlarged image from the front of the cabinet. A display device that can be viewed has been provided.

In this type of conventional rear projection display device, for example, as seen in Japanese Utility Model Application Laid-Open No. 1-85778, a transmissive liquid crystal panel is illuminated by a light source and an image displayed on the liquid crystal panel is displayed. Magnify with the projection lens,
It is a structure that changes the optical path by a reflection mirror and guides it to the back of the screen. By doing so, the projection optical system is housed in the cabinet, can be moved to any place, and the image on the screen can be viewed even in a bright room.

However, in the above-mentioned rear projection display device, in order to guide the light flux transmitted through the light valve to the screen by changing the optical path by the reflection mirror, keystone distortion occurs unless projection is performed with an optical axis perpendicular to the screen. Therefore, the installation condition of the reflection mirror is greatly restricted, which increases the volume occupied by the projection optical system, especially the dimension in the depth direction with respect to the screen (cabinet thickness). There is a problem that the rear projection type display device cannot be used. In view of this, the rear projection type display device of the oblique projection system shown in Japanese Patent Publication No. 2-1243 has been invented, and the present invention is an improvement thereof.

[0007]

In the projection optical display device described above, as shown in FIG. 8, the space allocated to the projection optical unit is small, and the projection distance for bending and storing the reflection mirror is also limited. This places a heavy burden on the projection lens included in the projection optical unit,
There is a problem that it is difficult to reduce the aberration.

In view of this, the present invention uses a light valve and rear-projects the image on the screen in the front of the cabinet to obtain an enlarged image. The purpose of the invention is to provide a rear projection display device.

[0009]

Rear projection having projection means for projecting an image generated by a light source and light modulation means on a screen, a reflection mirror for changing the optical path of projection light, and a screen in a cabinet. In the flat-panel display device, the central optical axis of the projection light projected by the projection means is oblique in the plane perpendicular to the normal to the screen and also in the horizontal plane. Characterize.

[0010]

【Example】

(Embodiment 1) FIG. 1 is an embodiment of the present invention, FIG. 2 is a side view thereof, and FIG. 3 is a front view thereof. In this embodiment, a box-shaped cabinet 1 is provided, and a projection optical unit 2 including a display body, a rear projection type screen 3 provided on the front surface of the cabinet 1, and the projection optical unit are provided in the cabinet 1. First, second and third reflection mirrors 4 for guiding the projected light flux from the second screen to the back surface of the screen 3.
5 and 6 are provided. In FIG. 1, the projection light emitted from the projection optical unit 2 including the display body is reflected by the first reflection mirror 4, is reflected by the second reflection mirror 5, and is then reflected by the third reflection mirror 5.
The light is reflected by the reflection mirror 6 and enters the screen 3.
At this time, the projection light is oblique with respect to the normal line of the screen 3 in a vertical plane and also in a horizontal plane.

The reflection mirrors 4, 5 and 6 are mounted on the cabinet 1.
The projection optical unit 2 has a large space which can be occupied by the projection optical unit 2 because the projection optical unit 2 has a large space.

On the back surface of the screen 3, there is used a prism total reflection type screen in which a large number of prisms are arranged in an ellipse having a projection lens and a projected image observer as two focal points, or an arc approximated by an ellipse. .. As a result, the projection light obliquely incident on the screen 3 is totally reflected by the prism surface of the screen 3 and then moved from the front surface of the screen 3 to the front of the screen 3 as shown in a partially enlarged view in FIG. Since the light is condensed by the observer who is present, the observer can observe a bright display image that is an enlarged projection image of the display body even in a bright room under indoor illumination light.

(Embodiment 2) FIG. 4 shows a second embodiment of the present invention, FIG. 5 is a side view thereof, and FIG. 6 is a front view thereof. Similar to the first embodiment, the present embodiment has a box-shaped cabinet 1 in which a projection optical unit 2 including a display body and a rear projection type screen provided on the front surface of the cabinet 1 are provided. 3 and first, second, third reflection mirrors 4, 5, 6 and a fourth mirror 7 for guiding the projection light beam from the projection optical unit 2 to the back surface of the screen 3.

In FIG. 4, the projection light emitted from the projection optical unit 2 including the display body is reflected by the first reflection mirror 4, the second reflection mirror 5, and then the third reflection mirror 6. After being reflected by, and reflected by the fourth reflecting mirror 7, it is incident on the screen 3. At this time, the projection light is oblique with respect to the normal line of the screen 3 in the vertical plane and also in the horizontal plane.

The reflection mirror 4 is installed on one side of the cabinet 1 and the reflection mirrors 5, 6 and 7 are installed on the other side of the cabinet 1 in a biased manner, so that the projection optical unit 2 can occupy the space. Is greatly taken. Further, in this example, the projection distance is set to be larger than that in the first embodiment, so that the load on the projection lens can be further reduced.

[0016]

As described above, in the cabinet,
In a rear projection display device having a projection means for projecting an image generated by a light source and a light modulation means on a screen, a reflection mirror for changing the optical path of projection light, and a screen, the projection means projects the image. Since the central optical axis of the projected light is inclined in the plane perpendicular to the normal of the screen and also in the horizontal plane, the space allocated to the projection optical system can be increased. The load on the projection lens is reduced, the depth of the cabinet is thin, and a clear and bright high-quality rear projection display device can be provided.

[Brief description of drawings]

FIG. 1 is a diagram of an oblique rear projection display device according to a first embodiment of the present invention.

FIG. 2 is a side view of an oblique rear projection display device according to the first embodiment of the present invention.

FIG. 3 is a front view of the oblique rear projection display device according to the first embodiment of the present invention.

FIG. 4 is a diagram of an oblique rear projection display device according to a second embodiment of the present invention.

FIG. 5 is a side view of an oblique rear projection display device according to a second embodiment of the present invention.

FIG. 6 is a front view of an oblique rear projection display device according to a second embodiment of the present invention.

FIG. 7 is a partially enlarged view of a vertical cross section of a screen used in a diagonal rear projection display device according to an embodiment of the present invention.

FIG. 8 is a diagram of an oblique rear projection display device according to a conventional example.

[Explanation of symbols]

 1 Cabinet 2 Projection Optical Unit 3 Screen 4 First Reflection Mirror 5 Second Reflection Mirror 6 Third Reflection Mirror 7 Fourth Reflection Mirror

Claims (1)

[Claims] 1. A rear projection display device having a projection means for projecting an image generated by a light source and a light modulation means on a screen, a reflection mirror for changing an optical path of projection light, and a screen in a cabinet. In the above, the central optical axis of the projection light projected by the projection means is oblique in a plane perpendicular to the normal of the screen and also in a horizontal plane. , Rear projection display device.