JPH08292498A - Image display device - Google Patents

Abstract

PURPOSE: To increase the degree of freedom in mirror arrangement and to lessen depth by using a hologram which allows the free setting of incident and exit angles as a mirror for turning back a projection optical system. CONSTITUTION: A CRT is used as a light emitting display means 2 and a projecting lens is disposed on the front surface of the light emitting display means 2 in such a manner that the image information emitted therefrom is cast via the projecting optical system to the hologram 1. The hologram 1 is formed by exposing a hologram photosensitive material with two parallel beams. The hologram is thus so formed by exposing that incident angle attains 50 deg. and the exit angle 9 attains 30 deg.. The hologram 1 is disposed between a transmission type screen 4 consisting of ground glass and the projecting lens system in such a manner that the incident angle from the projecting lens system attains 50 deg. and the exit angle reflected and diffracted toward the transmission type screen 4 attains 30 deg.. The shape of the image emitted from the CRT is used by distorting the shape reverse in order to negate the distortion of the trapezoidal shape in the hologram.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for projecting an image from behind on a transmissive screen and displaying the transmitted image, such as a rear projection type television receiver.

[0002]

2. Description of the Related Art Recently, a television receiver having a large display surface has been demanded. In particular, for a large-screen display device of 40 inches or more, it is difficult to manufacture a display device of 40 inches or more with a CRT. Therefore, a rear projection type television receiver has been proposed in which an image of a small CRT or a liquid crystal display device is projected from the back on a transmissive screen using a magnifying projection lens and the transmitted image is displayed.

However, since the display surface is large, the optical path length of the projection system also becomes long. Therefore, in order to reduce the size of the entire image receiver, a conventional plane mirror has conventionally been used to bend the optical path.

Further, in order to efficiently scatter light forward from the transmissive screen, it is necessary to project the light almost perpendicularly to the screen. According to the conventional methods, the large mirror 10 needs to be placed at a relatively slanted angle as shown in FIG. 3, so that the depth cannot be made very thin.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide a rear projection type image display device which has not been known so far. To provide.

[0006]

The present invention has been made in view of the above-mentioned problems, and includes a light emitting display unit that emits light containing image information, and a transmissive screen that is irradiated with the light. An image display device is provided, in which a projection means and a hologram are arranged in this order from the light emitting display means side between the light emitting display means and the transmissive screen.

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

FIG. 1 is a schematic sectional view showing an example of an image display device according to the present invention. The light emitting display means 2 such as a CRT or a liquid crystal display element emits image information. This image information is applied to the hologram 1 via the projection means 3 including a projection lens. Thus, the image display device 2
0 indicates that the light emitted from the light emitting display means 2 is applied to the hologram 1 via the projection means 3 and is diffracted and applied to the transmissive screen 4, so that the light emitting display means 2, the projection means 3 and the hologram 1 are displayed. The transmissive screen 4 is arranged in this order in the optical axis direction.

Since the hologram 1 is a reflection type hologram and can reflect incident light in a non-regular reflection direction, even if the hologram 1 is arranged at a rising angle as shown in the figure, it is substantially perpendicular to the screen 4. You can illuminate it.
As a result, the depth of the image display device can be reduced by the amount by which the hologram 1 rises.

FIG. 2 shows a hologram exposure method. Laser light beams 6 and 7 are incident on the hologram photosensitive material 5.
If the radii of curvature of the wavefronts of both light fluxes are made substantially the same, a hologram having no lens effect can be produced. Both light fluxes may be parallel light rays, or if it is desired to have a lens effect, light fluxes having different wavefront radii of curvature may be used. If the hologram has a magnification by this lens action, the size of the display device itself can be further reduced. The projection lens may have the function of doing so. Therefore, a toric surface, a cylindrical surface, an off-axis surface, or the like may be used as part of the projection lens. Further, a lens or the like having a correction function independent of the projection lens may be used. Further, a second hologram can be used as a projection means other than this projection lens. In this case, the chromatic aberration of the hologram, which is essential to the present invention, can be canceled by the second hologram.

Since the full width at half maximum of the diffraction spectrum of a hologram is generally narrow, a plurality of holograms having different diffraction wavelengths may be superposed or one hologram photosensitive material may be subjected to multiple exposure for full-color display.

When the non-regular reflection performance of the hologram is used, the image is distorted into a trapezoidal shape. Therefore, it is preferable to deform the image shape of the light emitting display means in advance so as to cancel this distortion.

As a light source used for the light emitting display means,
A cold cathode tube, a hot cathode tube, etc. are exemplified, but the present invention is not limited to this, and various light sources can be used. In order to suppress the chromatic aberration generated in the hologram, it is preferable to use a light source having a bright line-shaped wavelength characteristic such as a cold cathode tube. Further, by arranging a narrow band wavelength filter on the front surface of a halogen lamp or the like, it is possible to generate bright line light.

In the above example, the reflection hologram was used as the hologram. However, a transmission hologram can be appropriately used in consideration of the arrangement of the light emitting display means, the transmission screen and the like, the size of the entire apparatus and the like.

[0015]

Embodiments of the present invention will be described below.

As shown in FIG. 1, a high-brightness CRT is used as the light emitting and displaying means 2, and a projection lens system is provided on the front surface of the light emitting and displaying means 2 so that image information emitted from the CRT is irradiated onto the hologram 1 through the projection lens system. Arranged. Hologram 1
Is produced by exposing the hologram photosensitive material with two parallel lights, and is so exposed that the incident angle 8 is 50 ° and the outgoing angle (reflection diffraction angle) 9 is 30 °.

The incident angle from the projection lens system is 50
And the hologram 1 so that the outgoing angle for reflection and diffraction toward the transmissive screen 4 made of frosted glass is 30 °.
Was placed between the transmissive screen 4 and the projection lens system.
The shape of the image emitted from the CRT was reversed in advance in order to cancel the trapezoidal distortion in the hologram. As a result, a clear image with little distortion could be observed.

[0018]

According to the present invention, since a hologram whose input / output angle can be freely set is used as the folding mirror of the projection optical system, the degree of freedom in arranging the mirror is increased, and the large-screen rear projection type with a small depth is used. An image display device such as a television receiver could be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a rear projection type image display device according to the present invention.

FIG. 2 is a schematic sectional view showing an example of a method of exposing a hologram in the present invention.

FIG. 3 is a schematic sectional view showing an example of a conventional rear projection type image display device.

[Explanation of symbols]

 1: Hologram 2: Light emitting display means 3: Projection means 4: Screen 5: Holographic photosensitive material 6: Laser light flux 7: Laser light flux 8: Incidence angle 9: Emission angle 10: Mirror

Claims (4)

[Claims] 1. A light emitting display means for emitting light including image information, and a transmissive screen irradiated with the light, wherein a projection means and a hologram emit light between the light emitting display means and the transmissive screen. An image display device, which is arranged in this order from the display means side. 2. The image display device according to claim 1, wherein the hologram is a hologram laminate in which a plurality of holograms having different diffraction wavelengths are superposed. 3. The projection means for canceling the aberration of the hologram.
Image display device. 4. The image display device according to claim 1, wherein the image shape of the light emitting display means is deformed in advance so as to cancel the image distortion of the hologram.