KR101462330B1 - A device for displaying image in an electro-holographic display - Google Patents

Abstract

The present invention relates to an image display apparatus for an electronic holographic display, and more particularly, to a holographic stereoscopic image display apparatus which forms a reproduced image of a hologram in upper and lower or left and right spaces of a hologram, separates images of the hologram reproduction image and the hologram display surface using a phase optical system, A hologram reproduced image is displayed by covering an image of the hologram display surface and a diffusing plate having a low diffusing degree is arranged to reduce the risk of damage to the viewer's eyes by increasing the contrast of the reproduced image, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an image display apparatus for an electronic holographic display,

The present invention relates to an image display apparatus for an electronic holographic display, and more particularly, to a holographic stereoscopic image display apparatus which forms a reproduced image of a hologram in upper and lower or left and right spaces of a hologram, separates images of the hologram reproduction image and the hologram display surface using a phase optical system, An image display device of an electronic holographic display which displays only a hologram reproduction image by covering an image of the hologram display surface and disposing a diffusion plate having a low diffusing degree to increase the contrast of the hologram reproduction image and reduce the risk of damage to the viewer's eyes .

A holographic display electronically displays a hologram to realize a reconstructed spatial image of a hologram through a display.
Since the hologram reproduction phase makes use of all the recognition mechanisms of the viewer's eyes, such as volumetric imaging methods, the holographic display is different from the conventional three-dimensional image display device which relies only on parallax, Eye Fatigue) is regarded as the most natural way to display three-dimensional images.
Both the holographic display and the volumetric imaging device are capable of generating a three-dimensional image having a volume in space, but in particular, the holographic display advantageously does not require a rotation or movement mechanism unlike the volumetric imaging method.
However, existing holographic displays suffer from two representative problems, namely, the absence of suitable display devices for electronically displaying the hologram and the safety of the viewer's eye to the laser beam that must be used for image reconstruction.

The Acousto-Optic Modulator (AOM), which has been used in the past, is a phase-shift type optical modulator that displays a hologram using a refractive index change of a modulator medium proportional to the amplitude of an applied acoustic wave. It is possible to display a line hologram with a type device and display a frame-by-frame hologram by time-multiplexing.
In addition, the device can enlarge the size of the displayable hologram to several tens of centimeters through time multiplexing using a fast acoustic wave velocity in the medium. However, if the period of the interference fringe is approximately 12 mu m or less, display is impossible.
Due to such a problem, the angle at which the spatial reproduction image can be seen becomes narrower than that of the water. Therefore, an image reduction optical system for enlarging the viewing angle is required, and the volume occupied by the peripheral device for driving is very large, It has the disadvantage of becoming bulky.
In addition, the AOM having a large aperture width is difficult to implement, and the number of simultaneously visible line holograms is in inverse proportion to the width of the aperture, so that it is rarely used recently. Instead, a spatial light modulator (SLM) is used to display the hologram. Currently available SLMs are still small in size and their pixel size is somewhat larger than AOM, but they are capable of displaying full parallax holograms, being easy to use, and rapidly developing in terms of pixel size and resolution, It is expected to become a hologram.
In general, the hologram reproduced image itself is reproduced through one space or the hologram display surface, so that it is impossible to view the reproduced image separately from the display surface. Therefore, it is very difficult to view the picture on the display screen having a relatively low brightness compared to the brightness of the display screen.
In order to separate the hologram reproduction image from the hologram display surface, it is necessary to newly develop an optical system capable of separating the hologram reproduction image and the hologram display surface, or to use a screen for diffusing light such as a diffusing plate, It is necessary to prevent the hologram display surface from being seen by spreading.
The use of the diffuser reduces the risk of damage to the eye by scattering the image by focusing only the reproduced hologram image on the diffuser without viewing the hologram display surface. However, it is possible to view the reproduced image only in a space in which the hologram reproduced image is realized, Other parts of the reproduction image to be displayed in addition to the plate position are also diffused, making it difficult to display the part other than the focal point.
Therefore, when the diffuser plate is used, only the portion corresponding to the diffuser plate position on the reproduced image is displayed, so that the reproduced image becomes a plane having only the position of the space, and the display on the space having the volume becomes impossible.

Another problem with the holographic display is the problem of eye damage to the viewer due to the use of the laser beam as a light source. Since the laser light used for reproducing the hologram has a high coherent characteristic, the size of the laser light is much smaller than that of the white light when focused by a lens / spherical reflector.
In addition, the hologram reproduced image appearing in the space is formed by convergence of the reconstruction light. The intensity of the light forming the reproduced image depends on the diffraction efficiency of the hologram So that it will have a considerable size.
Therefore, since most of the light involved in the formation of the hologram reproduction image may be incident on the viewer's eyes, the brighter the reproduction image, the greater the probability of damaging the viewer's eyes.
In addition, the hologram display surface that appears together with the hologram reproduction image is very bright due to the reproduction laser beam diffracted by the diffraction and the laser beam scattered by the nonuniformity of the display surface, thereby making it difficult to view the hologram reproduction, It is not a good way to directly view the reproduction image of the hologram.
Therefore, in order to view the holographic display more safely, and to display a spatial volume image, which is a characteristic of the hologram reproduction image, it is necessary to first separate the reproduction image from the hologram display plane so that only the reproduction image is displayed. It is necessary to have a transmission or reflection type diffuser plate having a low diffusing degree which does not detract from the volume of the regenerated image while recognizing it.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a hologram display device, And does not damage the volume of the regenerated image.

According to another aspect of the present invention, there is provided an image display apparatus for an electronic holographic display, including: a hologram; Hologram reproduction phase; A phase optical system, an opaque plate, and a low-diffusing transparent plate.

The hologram reproduction image can be generated in the reproduction space, and the hologram reproduction image can be increased in size as the distance in the hologram increases.

The hologram reconstructed image may be further away from the phase optical system than the rear focal plane of the phase optical system.

The reproduced image of the hologram and the hologram display surface may be opposite to each other with respect to the optical axis of the image optical system.

The opaque plate can be used to cover the image of the hologram display surface.

The position of the bottom of the opaque plate may be between the top of the top of the reproduction image of the hologram and the bottom of the hologram display surface.

The position of the bottom of the opaque plate may be located between the image of the reproduction image of the hologram and the space where the image of the hologram display surface appears.

The position of the bottom of the opaque plate can be such that the ray passing through the display surface of the hologram and the bottom of the reproduced image does not invade the path of the ray traveling in the direction changing by the phase optical system.

The position of the bottom of the opaque plate can be such that the light rays passing through the top of the display surface of the hologram and the bottom of the reproduced image do not invade the path of the light beam which is deflected by the phase optical system.

The low diffusion transparent plate can be superimposed on the hologram reproduction image.

Further, the low-diffusing transparent plate and the surface coating-coated reflector may be laminated and used as a reflection type.

Also, the low diffusion transparent plate may be made of a material having characteristics similar to PDLC.

Further, the low haze transparent plate having a total haze ratio of not more than 20% can be used.

In addition, the low-diffusing transparent plate may be formed by arranging a low-diffusing transparent plate such that the volume is sliced at regular intervals so as to cover the volume possessed by the reproduced image using a plurality of PDLC-type low-diffusing transparent plates Lt; / RTI >

It is preferable to simultaneously apply a voltage to the PDLC-type low-diffusing transparent plate arranged at the time of display on the reproduction surface so that these transparent plates always remain transparent.

At this time, the PDLC type low diffusion transparent plate can be used without overlapping.

At this time, the overlapped transparent plate can be placed at any position in the volume space of the reproduced image.

In addition, it is preferable to repeatedly turn on / off the driving voltage 43 at a speed not lower than 30 Hz per second sequentially in order of the arranged PDLC type low-diffusing transparent plates so that the volume of the reproduced image can be viewed by spatial positions.

At this time, when one PDLC type low diffusion transparent plate is off, it is preferable that the remaining transparent plate is in the ON state.

The size of the image by the phase image optical system of the reproduction phase is smaller than that of the reproduction image or the size of the image by the phase image system of the reproduction phase is the same as the reproduction image or the size of the image by the reproduction image phase system is larger than the reproduction image have.

It is possible to separate the display surface of the hologram from the reproduced image through the present invention so that only the reproduced image can be seen, thereby making it possible for the viewer to recognize the presence of the reproduced image more clearly and also not to damage the volume of the reproduced image.

Also, it is possible to increase the contrast ratio of the reproduction image and reduce the risk of damage to the viewer's eyes.

1 is a conceptual diagram showing a principle of recording and reproducing a general hologram,
FIG. 2 is a diagram showing a phase display apparatus of an electron holographic display according to the present invention,
3 is a configuration diagram showing a method of arranging a low-diffusing transparent plate in the present invention.

According to the present invention, the hologram reproduction image is focused on the upper and lower or left and right spaces of the hologram, and the phase of the hologram reproduction image and the hologram display surface are formed opposite to each other with respect to the optical axis of the phase optical system using a phase optical system The image of the hologram display surface is hidden invisible to the viewer's eyes, so that only the image on the hologram reproduction image is visible. In the upper position of this hologram image, diffusion similar to or similar to PDLC (Polymer Dispersed Liquid Crystal) And the electronic holographic display system which reduces the risk of damage to the viewer's eyes while increasing the contrast ratio of the reproduction image.

PDLC is a type of liquid crystal cell used in a liquid crystal display (LCD), and has characteristics in which the transmission of light is controlled according to the scattering intensity of light and a polarizing plate is not required. Several types of structures have been proposed, including a large number of liquid crystal molecules (liquid crystal molecular grains) of several millimeters dispersed in a polymer, or a liquid crystal in a net-like polymer.
Without the applied voltage, the liquid crystal molecules become irregular and scatter at the interface (interface) where the refractive index with the medium is different. When a voltage is applied, the directions of the liquid crystals are aligned and the refractive indices of both are aligned to become a transmissive state. The display becomes bright, but if the thickness of the liquid crystal cell is not increased, the contrast is not ensured, and consequently, the driving voltage is increased.

FIG. 1 is a conceptual diagram showing a principle of recording and reproducing a general hologram, and shows a conventional principle of recording and reproducing holograms. In order to record the hologram 1, the reference wave 4 incident on the hologram display surface 2 at an angle of intersection 3 not greater than? And the object wave 6 from the object 5 And the reproduction wave 7 in the same direction as the reference wave 4 is irradiated on the hologram display surface 2 so that the hologram 1 is displayed on a DMD (Digital Micro-Mirror Device) The reproduced image 8 is generated at the same position as the original object 5. In this case,
At this time, if the hologram 1 is a transmissive element instead of a reflective element, the reproduction wave 9 should be moved in a direction opposite to the reference wave 4. [ When the intersection angle 3 between the reference wave 4 and the object wave 6 is not larger than?, The reproducing space 10 in which the reproducing image 8 can be formed is formed in the hologram 1 as d = h a volume corresponding to the hologram 1 at the center thereof in the form of a square duct Du whose width is increased by an angle? formed by intersection of the line 12 and the line 13 by a distance of / tan? 16) is subtracted.
Here, h represents a height / width when the display surface 2 of the hologram 1 is a square. Therefore, the size of the object 5 and the reproduction image 8 can be increased as the distance from the hologram 1 increases. The reproduction space 10 is the same as the object space, and the object 5 must also be in the reproduction space 10.
However, since the width 14 of the reproduction space 10 increases as the distance from the hologram 1 increases, the height 15 of the reproduction image 8 and the object can not be greater than the width 14 .

FIG. 2 is a configuration diagram of an image display apparatus of an electron holographic display according to the present invention, showing a reproduction image separation method in the holographic display of the present invention.
In order to avoid viewing the hologram display surface 2 together with the reconstructed image 8 as in the conventional hologram described in FIG. 1, in the present invention, the reconstructed image 8 is first displayed in the reconstruction space 10 .
The reproduced image 8 and the hologram display surface 2 are positioned so as to be positioned further behind the rear focal plane 18 of the phase optical system 17 using the phase optical system 17 And are positioned opposite to each other with respect to the optical axis (19) of the phase optical system (17).
In this case, the image 20 of the reconstructed image 8 is generated by the phase optical system 17 below the front focal plane 21 of the phase optical system 17 and below the optical axis 19, The image 22 of the image 2 is formed on the upper side of the optical axis 19 in the vicinity of the front focal plane 21 of the phase optical system 17. [
The image 22 of the hologram display surface 2 and the image 20 of the reproduced image 8 are separated from each other and are generated at regular intervals 23 opposite to each other with respect to the optical axis 19, (20) of the reproduction image (8) to the viewer (20) by blocking the image (22) of the hologram display surface (2) So that it can be seen.
The opaque plate 24 may be located at any position of the space 25 within the position where the image 22 of the hologram display surface 2 and the image 20 of the reproduced image 8 are generated. However, a light beam 28 arriving at the phase optical system 17 from the bottom 26 of the hologram display surface 2 and passing through the bottom 27 of the reproduced image 8 passes through the phase optical system 17 It is preferable that the light ray 29 proceeding in the direction of the opaque plate 24 and the foot 30 of the opaque plate 24 are arranged so as to be substantially adjacent to each other and at least the foot 30 of the opaque plate 24 faces the hologram display surface 2 The light beam 32 starting from the upper end 31 of the reproduction image 8 and traveling through the foot 27 of the reproduction image 8 is reflected by the phase optical system 17 so as not to affect the proceeding light ray 33 Should be avoided.
The direction of the light rays forming the image 20 of the hologram reproduction image 8 is determined by using a low diffusion transparent plate 34 such as a PDLC at a position where the image 20 of the hologram reproduction image 8 appears And the contrast ratio of the image 20 of the hologram reproduction image 8 is increased.
At this time, it is required that the haziness ratio of the low diffusion transparent plate 34 does not exceed 20%. When the reflector 35 having a reflective coating on the surface is attached to the low diffusion transparent plate 34, viewing direction of the image 20 of the hologram reproduction image 8 can be reversed.

FIG. 3 shows a method of arranging a low-diffusing transparent plate in the present invention, and shows a method of arranging a low-diffusing transparent plate 34 for increasing the contrast ratio of the image 20 of the reproduced image 8 of the present invention have. In the case of the on / off type low-diffusing transparent plate 34 like the presently available PDLC, since the blurring rate is as low as several% and several layers can be used in a superimposed manner, various methods As shown in FIG.
First, as shown in FIG. 3A, a plurality of PDLC low diffusion transparent plates 36 are used to cover the volume 44 of the image 20 of the hologram reproduction image 8 The volume 44 is arranged so as to be sliced at a constant interval 37. [
Thereafter, the connection wires of each PDLC type low diffusion transparent plate 36 are integrated into one electric wire 45 so that the voltage 38 is simultaneously applied to all the PDLC type low diffusion transparent plates 36, The diffusion transparent plate 36 is allowed to operate in a transparent state.
The amount of the PDLC type low diffusion transparent plate 36 used in this case is in the range where the total blurring rate does not exceed 20% and the range in which the volume 44 of the hologram reproduction image 8 does not distort the volume 44 Should be determined so that the maximum contrast ratio can be obtained.
2, a PDLC 32 is formed at a position 42 between the front 40 and the rear 41 of the volume space 39 occupied by the image 20 of the hologram reproduction image 8, as shown in FIG. 3 (b) Type diffusion diffusion transparent plate 36 to operate. The PDLC type low diffusion transparent plate 36 can be placed at any position in the volume space 39 since it is intended to increase the contrast ratio only, not to allow the hologram reproduction image to be formed.
In the second case described with reference to FIG. 3 (b), the PDLC type low diffusion transparent plates 36 may be used in multiple sheets without overlapping with each other in a range in which the total blurring ratio does not exceed 20%. The number of the PDLC type low diffusion transparent plates 36 to be used at this time is the same as the first method described with reference to Figure 3 (a) except that the volume 44 of the reconstructed image 8 is not distorted The maximum contrast ratio is determined.
3C, the PDLC type low-diffusing transparent plate 36 is arranged as in the first case, and the driving voltage 43 of each PDLC type low-diffusing transparent plate 36 is sequentially And the volume 44 of the image 20 of the hologram reproduction image 8 is repeatedly displayed by spatial positions by repeating Off / On at a speed not lower than 30 Hz per second. This method is somewhat capable of accompanied by flickering of the image but it is the method that can best display the volume 44 possessed by the image 20 of the hologram reproduction image 8. When one PDLC type low diffusion transparent plate 36 is OFF, the rest of the PDLC type low diffusion transparent plate 36 must be in the ON state.

It is to be understood that the present invention is not limited to the above-described embodiments, but is defined by the scope of the appended claims, and that those skilled in the art can make various changes and modifications within the scope of the appended claims. It is obvious.

1: Hologram 2: Display surface of hologram
3: Crossing angle 4: Reference wave
5: Object 6: Object wave
7: Playback wave 8: Playback phase
9: Playback wave 10: Playback space
11: Distance 12: Line
13: Line 14: Regenerated phase width
15: reproduction image height 16: volume
17: phase optical system 18: rear focal plane
19: optical axis 20: reproduction image by optical system
21: front focal plane 22: image of hologram display plane
23: constant interval 24: opaque plate
25: space in the position 26: hem of the hologram display surface
27: Playback skirt 28: Rays through the display screen and the playback skirt
29: ray 28 changed direction 30: hem of opaque plate
31: upper end of hologram display surface 32: ray traveling through the hem of the reproduction surface
33: ray 32 changed by the optical system
34: low-diffusing transparent plate 35: reflecting mirror having a reflective coating on its surface
36: PDLC-type low diffusion transparent plate 37: space between volume cut surfaces
38: low-diffusing transparent plate voltage 39: volumetric space occupied by the reproduced image
40: forward of the volume space 41: rear of the volume space
42: one position between the front and the back 43: drive voltage
44: volume of reproduction image 45: electric wire

Claims (5)

1. An image display apparatus for displaying only a reproduction image in a holographic display,
A spatial phase which is selected as an upper, a lower, a right, and a left through a reproduction wave which is reflected as the reproduction wave is irradiated in the same direction as the reference wave, is formed by forming an interference fringe by irradiating a reference wave and an object wave at crossing angles set on the display surface A hologram (1) for forming a reproduced image (8) on the reproduced image (8);
The display surface 2 and the reproduction image 8 are disposed on the opposite side from the rear focal plane 18 so that the display surface 2 and the reproduction image 8 are located on the opposite sides of the front focal plane 21, A phase optical system (17) for forming an image (20) of the reproduction image (8) and an image (22) of the display surface (2), respectively;
An opaque plate (24) covering the image (22) of the display surface (2) so as not to infringe the image (20) of the reproduction image (8) in front of the phase optical system (17);
A low diffusing transparent plate 34 provided at a position where the image 20 of the reproduced image 8 appears so as to scatter only a part of the direction of a light ray forming the image 20 of the reproduced image 8 to increase the contrast ratio, ; And a second electrode formed on the second electrode.
The method according to claim 1,
Characterized in that a reflector (35) having a reflective coating is attached to the surface of the low diffusion transparent plate (34) to change viewing direction of the image (20) of the reproduction image (8) .
The method according to claim 1,
The low-diffusing transparent plate 34 is composed of a plurality of PDLC-type low-diffusing transparent diffusing plates 36. The PDBS-type low-diffusing diffusing diffusing plate 36 can be connected at the same time with voltage Wherein the first and second electrodes are formed on the substrate.
The method according to claim 1,
Wherein the low diffusion transparent plate (34) is composed of a plurality of PDLC type low diffusion transparent diffusion plates (36), and each PDLC type low diffusion transparent diffusion plate (36) An image display device of a display.
The method according to claim 1,
The low-diffusing transparent plate 34 is composed of a plurality of PDLC-type low-diffusing transparent diffuser plates 36, and each PDLC-type diffusing transparent diffuser plate 36 is sequentially turned on / off at a rate of 30 Hz or less And the remaining PDLC type low-diffusing transparent diffuser plate is in the ON state when one PDLC-type diffusing transparent diffuser plate is in the OFF state.

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