JPH08248514A - Back projection type projector - Google Patents

Abstract

PURPOSE: To provide a thin and light weight back projection type projector. CONSTITUTION: Projected light 2 from a projector 7 is made obliquely incident on the back 8a of a light transmission type hologram sheet 8. The light made incident on the back 8a of the hologram sheet 8 is bent (diffracted) by the hologram sheet 8 so that it enters nearly perpendicularly to the surface of a screen 4. An observer 6 views a video projected from the back 4a of the screen 4 from the front of the screen 4. The projector 7 has a swing correction function, and it can secure the incident angle of the projected light 2 to the surface 8a of the hologram sheet 8 to be large, then the projector is thinned.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rear projection type projection device for displaying an image by projecting it from the rear surface of a screen, and particularly, to reduce the depth dimension of a housing to make the device thinner. The present invention relates to a rear projection type projection device.

[0002]

2. Description of the Related Art FIG. 3 is a schematic side view of a conventional rear projection type projection apparatus, in which a projector 1, a mirror -3 and a screen 4 are housed in a casing 5 and emitted from the projector 1. The light 2 is reflected by the mirror 3 and projected on the screen 4, and the observer 6 can see the image projected on the screen 4. Hereinafter, components having the same function even if they are slightly different in shape and size are denoted by the same reference numerals.

[0003]

By the way, in the conventional example shown in FIG. 3, since the exit light 2 from the projector 1 has the same incident angle and exit angle with respect to the mirror-3, the arrangement of the mirror-3 is different. There are restrictions, and there is a limit in reducing the depth dimension of the housing 5 to achieve a thin structure. Further, when the screen 4 is made large, naturally, the mirror 3 also needs a large area, and a thick mirror is required to have mechanical strength.
As a result, there is a problem that the weight of the entire device becomes very heavy.

[0004]

In order to solve the above-mentioned problems, the present invention provides a rear projection type projection apparatus comprising a projector and a screen for projecting an image projected from the projector from the rear, In the optical path between the projector and the screen, there is provided a hologram sheet for deflecting light emitted from the projector so as to be substantially perpendicular to the screen surface. Provided is a rear projection type projection device.

[0005]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic side view of a rear projection type projector according to an embodiment of the present invention. In the figure,
The light 2 emitted from the projector 7 is obliquely incident on the back surface 8a of the light transmission hologram sheet 8. The light incident on the back surface 8a of the light transmissive hologram sheet 8 is bent (diffracted) by the light transmissive hologram sheet 8 so as to be incident substantially perpendicularly to the surface of the screen 4. . Observer 6
Can see the image projected from the rear surface 4a of the screen 4 from the front surface of the screen 4. Screen 4
For example, a diffusion type such as beads can be used. The light 2 emitted from the projector 7 is obliquely incident on the light-transmitting hologram sheet 8 and projected on the screen 4, so that a normal tilt correction is performed. Here, the projector 7
Since it has a tilt correction function, the incident angle of the emitted light 2 with respect to the surface 8a of the light transmission hologram sheet 8 can be made large, and the device can be made thin. The transmissive hologram sheet 8 may be in contact with the back surface 4 a of the screen 4 or may be formed integrally with the screen 4.

As described above, the light-transmitting hologram sheet 8 having the characteristic of bending and transmitting light is arranged between the projector 7 having a tilt correction function and the screen 4. Thus, a thin and lightweight rear projection type projection device can be realized.

FIG. 2 is a schematic side view of a rear projection type projection apparatus according to another embodiment of the present invention. In the figure, the light 2 emitted from the projector 7 having the tilt correction function is obliquely incident on the surface 9a of the light reflection hologram sheet 9. The light incident on the surface 9 a of the light reflection hologram sheet 9 is reflected (diffracted) by the light reflection hologram sheet 9 so as to be incident substantially perpendicular to the surface of the screen 4. It enters the rear surface 4a of the lamp 4. The observer 6 can see the image projected from the rear surface 4 a of the screen 4 from the front of the screen 4. As the screen 4, for example, a diffusion type such as beads can be used. Projector 7
The emitted light 2 from is obliquely incident on the light reflection hologram sheet 9 and is projected on the screen 4, so that a normal tilt correction is performed. Here, the projector 7 has a tilt correction function and is provided on the surface 9a of the light reflection hologram sheet 9.
The incident angle of the emitted light 2 with respect to can be made large, and the device can be made thin.

As described above, the light-transmitting hologram sheet 9 having the characteristic of bending and reflecting light is arranged between the projector 7 having the tilt correction function and the screen 4. Thus, a thin and lightweight rear projection type projection device can be realized.

The hologram sheet (light transmitting hologram sheet 8 or light reflecting hologram sheet 9) used in the rear projection type projection apparatus of the present invention is a mirror of the conventional rear projection type projection apparatus shown in FIG. It is much thinner and lighter than No. 3. It is also possible to use a prism array that incorporates a number of small prisms instead of this hologram sheet. However, with a prism array, moire may occur, and stripe-shaped brightness at joints or folded portions of small prisms. The unevenness occurs. On the other hand, in the rear projection type projection device of the present invention using the hologram sheet, it is possible to display a natural image without distortion without causing moire or striped luminance unevenness. Further, this hologram sheet may have a Fresnel lens effect together, and for example, the spread of the light emitted from the projector 7 can be reduced. Further, the optical path in the housing of the rear projection type projection device is not limited to the above embodiment, but can be variously configured by using, for example, a small mirror or the like between the projector and the hologram sheet. Even in a device having a small size, a larger projection image can be obtained by effectively using the space in the housing and increasing the optical path length.

[0010]

As described above, according to the rear projection type projection apparatus of the present invention, the depth dimension of the housing can be reduced, and it is thin and lightweight, and moire and striped luminance unevenness are not generated. Instead, it can display a natural image without distortion.

[Brief description of drawings]

FIG. 1 is a schematic side view of a rear projection type projector according to an embodiment of the present invention.

FIG. 2 is a schematic side view of a rear projection type projector according to another embodiment of the present invention.

FIG. 3 is a schematic side view of a conventional rear projection type projector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projector 2 Emitting light 3 Mirror 4 Screen 4a Rear surface of screen 4 5 Housing 6 Observer 7 Projector 8 Light-transmitting hologram sheet 8a Light-transmitting hologram sheet 8 rear surface 9 Light Reflective hologram sheet 9a Surface of light reflective hologram sheet 9

Claims (5)

[Claims] 1. A rear projection type projection device comprising a projector and a screen for projecting an image emitted from the projector from the rear surface, in a light path between the projector and the screen. A rear projection type projection apparatus having a hologram sheet for deflecting light emitted from the projector so as to be substantially perpendicular to the screen surface. 2. The rear projection type projection apparatus according to claim 1, wherein the projector has a tilt correction function for correcting the tilt of the projection image on the screen surface. 3. The rear projection type projection apparatus according to claim 1, wherein the hologram sheet has a Fresnel lens effect. 4. The rear projection type projection apparatus according to claim 1, wherein the hologram sheet is a light transmission type. 5. The rear projection type projection apparatus according to claim 1, wherein the hologram sheet is a light reflection type.