JP2000019641A - Lighting device for projector device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly irradiate only an original image part with light emitted from an illumination light source and to enhance the utilizing efficiency of the illumination light. SOLUTION: This illumination device for a projector is constituted of a hologram 9, a grating 8 and the illumination light source 7. The hologram 9 is an off-axis transmission type hologram on which a diffusion body having almost identical size to the original image of a projector device and uniform brightness is recorded. The grating 8 is the transmission type grating formed so that an interval between the fringes of the surface is set to be an almost identical angle to an interval between the interference fringes of the surface of the hologram 9. Then, they are arranged so that the white light whose diffusivity is small is emitted by the light source 7, the light emitted from the light source 7 is made incident on the grating 8, the light diffracted from the grating 8 is made incident on the hologram 9 and the original image of the projector is illuminated with the light diffracted from the hologram 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device used for a projector device such as a projector, a slide projector, a liquid crystal video projector, etc., which projects a transmission type original image on a screen with a lens. In particular, the present invention relates to a technique for uniformly and efficiently illuminating an original image with light from an illumination light source to obtain a bright projected image.

[0002]

2. Description of the Related Art As shown in FIG. 1, a projector device illuminates an original image 3 by passing light from an illuminating device 1 through a condenser lens 2, and after illuminating an original image 3 with the light passing through a projection lens 4. The projection image of the original image 3 is formed on a screen (not shown). Conventionally, illumination devices used in such projector devices include, for example,
It is as shown in FIG. This device has a configuration in which a miniature bulb 6 is placed at a focal position of a concave reflector 5 having a slightly diffusive property. The light emitted from the miniature bulb 6 is reflected by the reflecting plate 5, becomes slightly diffused light slightly wider than the parallel light, and illuminates an original image (not shown). Here, the reason why the reflecting plate 5 is provided with a diffusing property is that if the light is completely collimated, the illumination on the original image becomes non-uniform due to the shadow of the miniature bulb or the like. This is to make the uniformity. As shown in the schematic diagram of FIG. 3, the intensity of the illuminating light in such an illuminating device has a distribution in which the central portion is bright and becomes darker toward the periphery, but the change in the illumination intensity is small in the central portion. Therefore, the original image is used so that the original image is almost uniformly illuminated by illuminating the original image with light that is wider than the original image.

[0003]

As described above, in the conventional illuminating device, it is necessary to illuminate a considerably wider area than the original image in order to uniformly illuminate the original image. For this reason, there has been a problem that the illumination light hitting other than the original image is wasted, which is disadvantageous in obtaining a bright projected image. The present invention has been made in order to solve such a problem, and irradiates light from an illumination light source as uniform light only to an original image portion, thereby increasing the efficiency of use of illumination light and producing a bright image. The purpose is to get.

[0004]

According to the present invention, there is provided a lighting device for a projector comprising a hologram, a grating, and an illumination light source. An off-axis transmission hologram in which a diffuse object having substantially the same size and uniform brightness as the original image of the apparatus is recorded, wherein the grating has a fringe interval on the surface thereof, and A transmission type grating having an angle substantially equal to the interference fringe interval, wherein the illumination light source is a light source that emits white light with low diffusivity, and light from the illumination light source is incident on the grating. The diffracted light from the grating is incident on the hologram, and the diffracted light from the hologram illuminates the original image of the projector. Characterized in that it is a lighting device for a projector is arranged so that.

[0005]

When the hologram is reproduced with light conjugate with the reference light used for recording, the recorded image of the subject is reproduced as a real image. When a diffuse object is recorded as a subject in a hologram, each point on the hologram surface is
All information on the size and brightness distribution of the diffuse object is recorded. Therefore, when a hologram recording a diffused object is reproduced with light conjugate to the reference light, a real image having the same size and the same brightness distribution as the original subject is reproduced from an arbitrary point on the hologram. Therefore, if a diffuse object having the same size and uniform brightness as the original image of the projector device is recorded as a hologram, and the illumination light is made to enter from a direction conjugate with the reference light,
The diffracted light from the hologram proceeds so as to reproduce an image with a uniform brightness distribution in the same size range as the original image of the projector, regardless of the shape and intensity distribution of the illumination light on the hologram surface. Therefore, if the original image of the projector is placed at that position, it is possible to uniformly illuminate only the range of the original image. However, in the case of a hologram, the traveling direction of diffracted light varies depending on the wavelength to be reproduced due to the influence of chromatic dispersion. The grating 8 and the illumination light source 7 having the same fringe interval are arranged as shown in FIG. Therefore, light of a certain wavelength from the illumination light source 7 is
Diffracted by the grating 8, the diffracted light enters the hologram 9 and is further diffracted by the hologram 9,
Proceed as indicated by line 10. Light of another wavelength emitted from the illumination light source 7 is diffracted in another direction by the grating 8, further diffracted by the hologram 9, and proceeds like a polygonal line 11. At this time, since the magnitude of the chromatic dispersion is determined by the interval between the interference fringes on the surface, the same chromatic dispersion occurs between the hologram 9 and the grating 8 having the same fringe interval on the surface. Is the same as the angle at which the diffracted light from the grating is diffracted by the hologram 9. For this reason, the lights 10 and 11 having different wavelengths emitted from the illumination light source travel in the same direction when finally leaving the hologram, though the diffraction angles on the way are different. Therefore, when such an illumination light source is used, it is possible to uniformly illuminate the range of the original image of the projector with white light emitted from the illumination light source.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 is a schematic diagram showing an embodiment of the lighting device according to the present invention. The hologram 12 used in this figure is produced as follows using an optical system as shown in FIG. 5, for example. In FIG. 5, the laser light emitted from the laser light source 13 is the beam splitter 1
4 divides the image in two directions. One light is spread by the lens 15 and illuminates the diffuser 16, and the diffuser 16
Diffused light passes through the mask 17 and reaches the dry plate 18 from almost the front. Here, the mask 17 is a mask with a window corresponding to the size of the original image of the projector device, and the laser light for illuminating the diffusion plate 16 is spread sufficiently so as to be substantially uniform within the window of the mask 17. There is a need. The other light is reflected by the mirrors 19 and 20, is spread by the lens 21, becomes parallel light by the lens 22, and reaches the dry plate 18 at a certain angle θ. Due to the interference between these two lights, a hologram of a diffuse object having the same size and uniform brightness as the original image of the projector device is recorded on the dry plate 18. The grating 23 used in FIG. 4 is recorded as follows using an optical system as shown in FIG. In FIG. 6, a laser beam generated from a laser light source 24 is split by a beam splitter 25 in two directions. One light is spread by the lens 26,
After being converted into parallel light by the lens 27, the dry plate 28
Reaches The other light is reflected by the mirror 29 and the mirror 30, is spread by the lens 31, becomes parallel light by the lens 32, and reaches the dry plate 28 at the same angle as θ in FIG. Due to the interference between these two lights, a grating is recorded on the dry plate 28 such that the fringe interval on the surface becomes almost the same as that of the hologram 13. Next, the operation of the illumination device of the present invention shown in FIG. 4 and configured using the hologram 12 and the grating 23 produced as described above will be described. In FIG. 4, light emitted from the miniature bulb 33 is reflected by the concave reflecting mirror 34, becomes almost parallel light, and illuminates the grating 23. This light is transmitted to the grating 23
And the diffracted light illuminates the hologram 12 as reproduction illumination light. With this light, a reproduced image 35 of a diffuse object having the same size and uniform brightness as the original image of the projector device is reproduced from the hologram. Therefore, if the original image of the projector device is placed at this position, it can be used as a uniform and efficient lighting device for the projector.

[0007]

As described above, according to the present invention, the illuminating device for the projector is constituted by the hologram, the grating and the illuminating light source, and the hologram has substantially the same size as the original image of the projector device. A diffuse object with uniform brightness is recorded.
An off-axis transmission hologram, wherein the grating is a transmission grating such that the fringe spacing on the surface is substantially the same angle as the interference fringe spacing on the surface of the hologram, and the illumination light source is A light source that emits white light with low diffusivity, light from the illumination light source is incident on the grating, diffracted light from the grating is incident on the hologram, and diffracted light from the hologram is By using a device that is arranged so as to illuminate the original image, it is possible to apply the light from the illumination light source as uniform light only to the original image portion, and to improve the utilization efficiency of the illumination light. And a bright image can be obtained.

[0008]

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a projector device.

FIG. 2 is a schematic diagram showing a conventional lighting device for a projector device.

FIG. 3 is a schematic diagram showing an arrangement of a lighting device for the projector device of the present invention.

FIG. 4 is a schematic diagram showing an embodiment of a lighting device for a projector device of the present invention.

FIG. 5 is a schematic diagram showing an example of a hologram manufacturing system used in the illumination device for the projector device of the present invention.

FIG. 6 is a schematic diagram illustrating an example of a grating manufacturing system used in a lighting device for a projector device of the present invention.

[Explanation of symbols]

 7 Illumination light source 8 Grating 9 Hologram 10 Light with different wavelength (polygonal line) 11 Light with different wavelength (polygonal line) 12 Hologram 13 Laser light source 14 Beam splitter 15 Lens 16 Diffusion plate 17 Mask 18 Dry plate 19 Mirror 20 Mirror 21 Lens 22 Lens 23 Grating 24 Laser light source 25 Beam splitter 26 Lens 27 ‥ Lens 28 ‥‥ Dry plate 29 ‥‥ Mirror 30 ‥‥ Mirror 31 ‥‥ Lens 32 ‥‥ Lens 33 ‥‥ Miniature bulb 34 ‥‥ Reflector 35 ‥‥ Reconstructed image

Claims (1)

[Claims] 1. A hologram, a grating, and an illumination light source, wherein the hologram records a diffuse object having substantially the same size and uniform brightness as an original image of a projector device. An off-axis transmission hologram, wherein the grating is a transmission grating such that the fringe spacing on the surface is substantially the same angle as the interference fringe spacing on the surface of the hologram, and the illumination light source is A light source that emits white light with low diffusivity, light from the illumination light source is incident on the grating, diffracted light from the grating is incident on the hologram, and diffracted light from the hologram is A lighting device for a projector device, wherein the lighting device is arranged to illuminate an original image.