JP2809912B2 - Hologram display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram display device for displaying a three-dimensional image by a holographic stereogram.

[0002]

2. Description of the Related Art A holographic stereogram, which is a hologram synthesized from a large number of two-dimensional images having parallax, is used as a means for recording and reproducing a three-dimensional image because a natural three-dimensional effect can be obtained.

A holographic stereogram is basically created through two steps as described below.

That is, in the first step, as shown in FIG. 4, a subject 31 is photographed from multiple directions, and a large number of two-dimensional images (original images) having parallax are recorded. Specifically, at a position separated from the subject 31 by the distance L, the camera 32 is moved to the position No. .. Are moved in parallel as in 1, 2, 3,... And the subject 31 is photographed at regular intervals P while the camera 32 is panned. Here, panning the camera refers to an operation of always pointing the camera toward the subject and focusing the camera on the center of the subject.
Note that a similar image can be recorded by moving the subject 31 instead of moving the camera.

[0005] Instead of actually photographing a subject, a fictitious object created by a computer may be displayed on a CRT and photographed by a camera.

Next, in a second step, a holographic stereogram is synthesized. There are a laser beam regeneration type and a white light regeneration type depending on the optical system used in the synthesizing device, but since these are basically the same configuration, here,
The laser beam reproduction type will be described. An example of this type of holographic stereogram synthesizing device is shown in FIG.

In FIG. 5, a laser beam emitted from a laser light source 41 is divided by a beam splitter 42 into a reference beam 43 and an original film irradiation beam 44. The original film irradiation light 44 is reflected by a mirror 45 and is
6, the original film 49 is illuminated through the pinhole 47 and the condenser lens 48. As a result, an image of the original film is projected onto the diffusion plate 51 through the projection lens 50.

The hologram dry plate 53 is located at a distance 1 from the diffusion plate 51, and a slit 52 having a vertically long opening is provided on the front surface thereof. on the other hand,
The reference light 43 from the beam splitter 42 is reflected by a mirror 54 and diffused by a beam diffusion lens 55 to illuminate a hologram dry plate 53. The slit 52 is moved in accordance with the advance of the original film, that is, the movement of the interval P between the cameras. As a result, the light from the diffusion plate 51 corresponding to the projected image and the reference light 43 cause the opening of the slit to be opened. A hologram having parallax is recorded for each part.

Here, assuming that the magnification of the image projected on the diffusion plate 51 with respect to the real object is m and the shooting distance between the subject and the camera is L, the distance 1 between the diffusion plate 51 and the hologram dry plate 53 is ,

[0010]

Satisfies l = mL. Further, the total number of frames K of the original photograph is represented by S (= mP) for the slit width and W for the moving distance of the camera.

[0011]

K = mW / nS (n is a positive integer) must be satisfied.

In the holographic stereogram synthesizing apparatus shown in FIG. 5, the original film 49 is used. Instead of using the film, a computer graphics image is displayed by using an electric address type spatial light modulator such as a liquid crystal display. In this case, the step of photographing the original image (the first step described above) can be simplified.

FIG. 6 shows a principle diagram of a TN (twisted nematic) type liquid crystal display which is a kind of an electric address type spatial light modulator.

In FIG. 6, the TN type liquid crystal display is composed of pixels arranged in rows and columns. Each pixel forms liquid crystal molecules 56 in which the arrangement of molecules is twisted by 90 degrees, and an alignment film and transparent electrodes 57 and 58 are formed. Glass substrates 59, 60
And the deflection filters 61 and 62. In the state (a) where no voltage is applied, the light passes, and in the state (b) where the voltage is applied, the light is cut off. Then, an image is displayed by controlling the applied voltage for each pixel.

FIG. 7 shows a method of reproducing an image using a holographic stereogram. In FIG. 7, a holographic dry plate 53 on which a hologram is recorded is developed to obtain a holographic stereogram 63, and a holographic stereogram 63 is reproduced from the same position as the reference light 43 through a beam diffusing lens 64.
By illuminating, the observer 70 can observe the stereoscopic image (virtual image) 66 at the position where the diffusion plate 51 was located.

[0016]

In general, it is desirable to display a three-dimensional image using a hologram of this kind as simply and quickly as possible.

However, in the display of a stereoscopic image using the conventional holographic stereogram as described above,
It is possible to simplify the above-mentioned first step by using an electric address type spatial light modulator, but in the subsequent second step, a process such as development of a photographic plate on which a hologram is recorded is required. It is time-consuming, difficult to display quickly, and it is virtually impossible to display a stereoscopic image in real time.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a hologram display device capable of displaying a three-dimensional image in real time.

[0019]

In order to achieve the above object, a hologram display device according to the present invention comprises: a projection unit for sequentially projecting a large number of two-dimensional hologram original images having parallax at a predetermined period; A diffuser to be projected, an optically addressed spatial light modulator arranged opposite to the diffuser so that light from the diffuser is irradiated, and light from the diffuser to the optically addressed spatial light modulator. Irradiating means for irradiating the reference light in a superposed manner, and provided on the side of the optical address type spatial light modulator facing the light from the diffusion plate and the reference light so that the light from the diffusion plate and the reference light can be moved A liquid crystal shutter for selectively reaching the optically addressed spatial light modulator through a slit, and control means for controlling the liquid crystal shutter to move the slit in synchronization with the original image.

[0020]

According to the hologram display device of the present invention, when the projection means projects the original image onto the diffusion plate, light from the diffusion plate is applied to the light-addressed spatial light modulator through the slit of the liquid crystal shutter. You. On the other hand, the irradiating means irradiates the light addressed spatial light modulator with reference light through the slit of the liquid crystal shutter so as to overlap the light from the diffusion plate. Here, under the control of the control means, the slit of the liquid crystal shutter moves in synchronization with the original image sequentially projected at a predetermined cycle, so that the light from the diffusion plate reaching the optically addressed spatial light modulator through the slit is transmitted. The holographic stereogram corresponding to the original image, that is, a large number of two-dimensional original images for holograms having parallax, can be created in the optically addressed spatial light modulator due to the interference between this light and the reference light.

As a result, a holographic stereogram can be recorded in real time on the optically-addressed spatial light modulator, and if appropriate reproduction light is applied to the optically-addressed spatial light modulator simultaneously with recording, Such a holographic stereogram can be reproduced in real time, and can be erased in real time. Therefore, the hologram display device of the present invention can display a three-dimensional image in real time, and can display a three-dimensional image as a moving image.

The operation of the present invention will be more apparent from the following examples of the present invention, and further other effects of the present invention will be apparent.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a hologram display device according to an embodiment of the present invention. FIG. 1 is a schematic side view showing a schematic configuration of an optical system and an electric circuit portion of the device, and FIG. 2 is a schematic plan view showing a schematic configuration of an optical system of the device.

In FIGS. 1 and 2, a hologram display device 1 includes a laser light source 2, a beam diffusion lens 3, a pinhole 4, a liquid crystal display 5, which is an example of an electric address type spatial light modulator for displaying an original image, and a diffusion plate. 6, a half mirror 7, a liquid crystal shutter 8, an optical address type spatial light modulator 9, a deflection beam splitter 10, a reproduction light source 11, an image memory 12, and a control device 13. The control device 13 as an example of the control means is constituted by, for example, a computer.

The laser light emitted from the laser light source 2 illuminates the liquid crystal display 5 driven according to the information in the image memory 12 through the beam diffusion lens 3 and the pinhole 4, and as a result, is displayed on the liquid crystal display 5. The original images are sequentially projected on the diffusion plate 6. The liquid crystal display 5
Is, for example, the known liquid crystal display described above. The original image displayed on the liquid crystal display 5 is created by the same method as in the related art. That is, the original image is photographed by moving the camera parallel to the subject (or moving the subject parallel to the camera) and panning the camera so as to always face the subject. Also, instead of using the original pictures actually taken, a computer
Of course, it is also possible to use an image created by graphics or the like. A large number of hologram two-dimensional original images having parallax created in this way are stored in an image memory 12 such as a VTR or a frame buffer. 5 is displayed.

As described above, in this embodiment, an example of the projection means is constituted by the laser light source 2, the beam diffusion lens 3, the pinhole 4, and the liquid crystal display 5, which are examples of the light source.

The optical address type spatial light modulator 9 includes a diffuser 6
At a distance l from the camera. The optical address type spatial light modulator 9 is illuminated by light from the diffusion plate 6 on which the original image is projected via the half mirror 7 and the liquid crystal shutter 8, and at the same time, a predetermined optical system (FIG. (Not shown), and is illuminated by the reference light 14 of a substantially parallel light beam branched from the laser light source 2. As described above, in the present embodiment, the laser light source 2 constitutes a part of the projection unit and a part of the irradiation unit.

Since the magnification m of the image projected on the diffusion plate 6 with respect to the real object is 1, the photographing distance L from the subject and the distance 1 between the diffusion plate 6 and the optically addressable spatial light modulator 9 are determined. Are equal. That is,

[0029]

## EQU3 ## where l = L. Assuming that the slit width is S and the moving distance of the camera is W, the total number of frames K of the photographed original image must satisfy the equation (2) described above. Moving distance W = 50 mm, n = 1 and slit width S
= 0.5 mm. Therefore, the total number K of original pictures is 10
It becomes zero.

Next, the liquid crystal shutter 8 forming a slit will be described. The liquid crystal shutter 8 can be composed of, for example, an electric address type spatial light modulator like the liquid crystal display 5. The liquid crystal shutter 8 displays a slit on its display under the control of the control device 13, and moves the slit in synchronization with the original image.
The slit movement pitch is 0.5mm, the same as the slit width
And

As described above, the display of the slit on the liquid crystal shutter 8 and the movement synchronized with the original image are controlled by the control device 13. As a result, the light of the original image from the diffuser 6 and the reference light 14 selectively reach the spatial light modulator 9 through the slit displayed on the liquid crystal shutter 8 and move to the slit. An interference fringe is formed on the optical address type spatial light modulator 9 for each position.

FIG. 3 shows a specific structure of the optical address type spatial light modulator 9.

In FIG. 3, the optical modulator 9 includes glass substrates 21 and 22, transparent electrode layers 23 and 24, a photoelectric layer 25 composed of, for example, an amorphous silicon layer, a dielectric layer (mirror layer) 26, and a ferroelectric layer. The liquid crystal layer 27 is composed of the liquid crystal layer 27. The molecules of the liquid crystal layer 27 are aligned in two alignment states according to the polarity of the applied voltage, and maintain the state even when the application of the voltage is stopped. The photoelectric layer 25 has such a property that the resistance of the portion irradiated with light is extremely small.
When the optical input information is input to the fifth side, the resistance of the photoelectric layer 25 changes according to the pattern of the optical input information, and the same electric field distribution as the optical input information pattern is applied to the liquid crystal layer 27. Therefore, the liquid crystal molecules rotate in a portion where the light intensity is high, and are aligned in a different alignment state from the first, while in a portion where the light intensity is low, the initial alignment state is maintained. Therefore, when linearly polarized light is incident from the liquid crystal layer 27 side, the polarized light is reflected as it is in the initial alignment state portion, but is reflected by rotating the polarization plane by 90 degrees in the portion where the liquid crystal molecules are rotated. You.

Therefore, in this embodiment, FIGS.
As shown in FIG. 3, the reproduction light 1 of S-polarized light (polarized light whose electric field oscillates perpendicular to the paper) from a plane symmetrical direction to the reference light 14.
5 is radiated to the liquid crystal layer 27 side of the optically addressed spatial modulator 9 via the polarization beam splitter 10, the reflected light is diffracted by each polarization component in accordance with the recorded information on the interference fringes,
Only the light whose polarization plane is rotated passes through the polarization beam splitter 10 and reproduces the wavefront from the original image. The component of the reflected light whose polarization plane does not rotate is the polarization beam splitter 1
Reflected at 0. The 0th-order diffracted light of the reproduction light is removed by a condenser lens system and a spatial filter (not shown).

As described above, an image is reproduced in real time from the holographic stereogram recorded in the optical address type spatial light modulator 9. In this case, the optical address type spatial light modulator 9 and the polarization beam splitter 10 function as an amplitude modulation type hologram.

Also, if a half mirror is used instead of the polarization beam splitter 10 and the zero-order diffracted light is removed by a condenser lens system and a spatial filter, the light reflected and diffracted by the optical address type spatial light modulator 9 becomes orthogonal. Since the polarized light components do not interfere with each other, light of each polarized light component forms a reproduced image. In that case, the light modulator 9 functions as a phase modulation hologram. Further, the reproduction light at that time may be polarized light or non-polarized light, which is advantageous.

In this embodiment, the reason why the reference light 14 and the reproduction light 15 are irradiated on the optical modulator 9 by using the half mirror 7 and the polarization beam splitter 10 is that the spatial resolution of the optical modulator 9 is based on the spatial frequency. As low as 100 lp / mm,
This is because light cannot be diffracted at a large angle. If a high-resolution spatial light modulator is used, the irradiation angle of the reference light and the reproduction light can be increased as in the conventional case, and the half mirror 7 and the polarization beam splitter 10 are not required. As a result, a condenser lens system and a spatial filter for eliminating the zero-order diffracted light are inevitably required.

In this embodiment, the liquid crystal shutter 8 and the light modulator 9 have a different structure. However, a decoded light address type light modulation system in which a liquid crystal shutter is integrated on the photoelectric layer side of the light modulator. A vessel can also be used. In this case, the positional relationship between the liquid crystal shutter and the optical modulator does not shift due to mechanical vibration or the like, and the stability and reliability of the device are improved, and as a result, the quality of a reproduced image can be further improved.

[0039]

As described above in detail, according to the hologram display device of the present invention, the projection means for sequentially projecting the two-dimensional original image for hologram on the diffusion plate at a predetermined period, and the light from the diffusion plate is applied. And the light from the diffusion plate and the reference light reach the optically-addressed spatial light modulator selectively through a movable slit. Holographic stereogram is recorded in real time on the optical address type spatial light modulator, and the liquid crystal shutter is controlled by controlling the liquid crystal shutter to move the slit in synchronization with the original image. Can be reproduced in real time and further deleted, so that a stereoscopic image can be displayed in real time, and moreover, a stereoscopic image can be displayed as a moving image.

Further, since the slit is formed by the liquid crystal shutter, there is no mechanical movable part, so that a high-quality holographic stereogram can be recorded, and the quality of the reproduced image is improved. Furthermore, the absence of mechanically movable parts significantly improves the stability and reliability of the device.

As described above, according to the present invention, it is possible to realize a hologram display device having high stability and reliability capable of displaying a high-quality stereoscopic image as a moving image in real time with a relatively simple structure.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a schematic configuration of an optical system and an electric circuit portion of a hologram display device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing a schematic configuration of an optical system of the hologram display device of FIG.

FIG. 3 is a perspective view showing an optical address type spatial light modulator according to the hologram display device of FIG. 1;

FIG. 4 is a diagram for explaining a method of capturing an original image used for synthesizing a holographic stereogram.

FIG. 5 is a configuration diagram showing a conventional laser reproducing holographic stereogram synthesizing apparatus.

FIG. 6 shows a TN which is a kind of an electric address type spatial light modulator.
FIG. 4 is a view for explaining the operation principle of a liquid crystal display.

FIG. 7 is a diagram for explaining a conventional method of reproducing a stereoscopic image from a holographic stereogram.

[Explanation of symbols]

 Reference Signs List 1 hologram display device 2 laser light source 3 beam diffusion lens 4 pinhole 5 liquid crystal display 6 diffusion plate 7 half mirror 8 liquid crystal shutter 9 optical address type spatial light modulator 11 reproduction light source 10 polarization beam splitter 12 image memory 13 control device 14 reference light 15 Reproduction light 21, 22 Glass substrate 23, 24 Transparent electrode layer 25 Photoelectric layer 26 Dielectric layer 27 Ferroelectric liquid crystal layer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Terutaka Tokumaru 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-1-302376 (JP, A) JP-A-3 -71178 (JP, A) JP-A-4-18587 (JP, A) JP-A-6-43482 (JP, A) JP-A-5-307188 (JP, A) (58) Fields investigated (Int. . ^6, DB name) G03H 1/26 G02F 1/135 G02F 1/13

Claims (4)

(57) [Claims] 1. A projection means for sequentially projecting a large number of two-dimensional hologram original images having a parallax at a predetermined period, a diffusion plate on which the original image is projected, and a light source for irradiating light from the diffusion plate. An optical address type spatial light modulator disposed opposite to the diffuser, an irradiating means for irradiating the optical address type spatial light modulator with reference light by superimposing light from the diffuser on the optical address type spatial light modulator, and The light from the diffusion plate and the reference light are provided on the side of the type spatial light modulator facing the side receiving the light and the reference light, and the light from the diffusion plate and the reference light are selectively passed through a movable slit. A hologram display device comprising: a liquid crystal shutter for reaching an address type spatial light modulator; and control means for controlling the liquid crystal shutter to move the slit in synchronization with the original image. 2. The projector according to claim 1, wherein the projection unit includes an electric address type spatial light modulator on which the original image is displayed, and a light source for irradiating the electric address type spatial light modulator with light for projection. 2. The hologram display device according to claim 1, wherein: 3. An optical address type spatial light modulator, comprising: a photoelectric layer whose impedance is changed by receiving light from the diffusion plate and the reference light; and a liquid crystal on which an image is written by the change of the impedance. The hologram display device according to claim 1, further comprising a layer. 4. The hologram display device according to claim 1, wherein the liquid crystal shutter is integrated with the light addressing type spatial light modulator.