KR101842753B1 - Holographic Display Method and Apparatus according to Time Angular Multiplexing - Google Patents

Abstract

A method and an apparatus for holographic display by visual multiplexing are also provided. A holographic display device according to an embodiment of the present invention includes: an SLM that diffracts incident plane waves to display a holographic interference pattern; an optical system that expands the diffracted wave front in the SLM; And a second mirror for changing the second mirror. Through such multiplexed holographic display, it is possible to enlarge the size in the holographic display plane and to increase the viewing angle while using one SLM, and natural hologram display is possible.

Description

Technical Field [0001] The present invention relates to a holographic display method and an apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic technique, and more particularly, to a holographic display method and apparatus by multiplexing.

Holographic display technology has a great advantage in that it can provide a nearly perfect three-dimensional shape as a technique of recording and reproducing a diffused wavefront from an object.

However, due to the limitations of current scientific and industrial development, there is no hologram display panel which can express hologram perfectly, and there is no hologram display panel which has LCD (Liquid Crystal Display), Liquid Crystal on Silicon (LCoS) and DMD Device) is used as a spatial light modulator (SLM) as a holographic display device.

Conventional SLMs provide a narrow field of view due to pixel spacing that is not sufficient to display a hologram, which makes it difficult to enlarge the hologram image or to increase the viewing angle.

Even if the viewing angle is increased by using the reducing optical system, the spatial bandwidth product is unchanged, and thus the hologram image is reduced. To increase the space-time product, a space is enlarged using a plurality of SLMs and a bandwidth is increased using a reduction optical system. However, due to the problem of using a plurality of SLMs and the use of a reduction optical system, There is a limit to increasing the size.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a holographic storage medium capable of increasing a hologram image or ensuring a sufficient viewing angle even when one SLM is used, And a viewing angle is increased by temporally and spatially multiplexing the wavefronts that are generated by the viewing angle multiplexing.

According to an aspect of the present invention, there is provided a holographic display device including a spatial light modulator (SLM) for displaying a holographic interference pattern and diffracting an incident plane wave; An optical system for magnifying a wavefront diffracted by the SLM; And a first mirror for changing the traveling path of the wave front in the optical system in a first direction.

The holographic display device according to an embodiment of the present invention may further include a second mirror for changing the traveling path of the wavefront in the optical system to a second direction.

In addition, the first direction and the second direction may be vertical.

The first mirror may be located in the focal plane of the first optical system constituting the optical system.

Further, the first optical system may include lens-1 and lens-2.

The holographic display device according to an embodiment of the present invention further includes a filter disposed between the lens-1 and the lens-2 and transmitting only a first-order diffraction component at a wavefront diffracted by the SLM .

Further, the second mirror may be located in the focal plane of the second optical system constituting the optical system.

The second optical system may include a lens-3 and a lens-4.

According to another aspect of the present invention, there is provided a holographic display device, wherein the optical system further includes a third optical system for re-imaging the wavefront, which has been redirected by the second mirror, onto the holographic display plane.

The third optical system may include a lens-5 and a lens-6.

In addition, the holographic display plane may be located in the focal plane of the third optical system.

The 'size on the wavefront that is re-imaged on the holographic display plane' with respect to 'the size of the SLM' may be a product of the magnification of the first optical system, the magnification of the second optical system, and the magnification of the third optical system .

According to another embodiment of the present invention, there is provided a holographic display method comprising: displaying a holographic interference pattern; Diffracting an incident plane wave; A diffuse system for expanding the diffracted wavefront; And changing a traveling path of the wave front to a first direction.

The holographic display method according to another embodiment of the present invention may further include changing a traveling path of the wave front to a second direction.

According to another embodiment of the present invention, a holographic display system includes a spatial light modulator (SLM) for displaying a holographic interference pattern and diffracting incident plane waves, an optical system for magnifying the wavefront diffracted by the SLM, And a first mirror for changing the traveling path of the wavefront in a first direction within the first direction; And a computing device for generating a holographic interference pattern displayed on the SLM with reference to the first direction.

As described above, according to the embodiments of the present invention, it is possible to enlarge the size in the hologram display plane and to increase the viewing angle by using one SLM through holographic display by multiplexing, and to perform natural hologram display Do.

FIG. 1 illustrates a holographic display device according to an embodiment of the present invention. FIG.
2 is a view showing a result of increasing the viewing angle in a hologram display plane in front of an observer,
FIG. 3 is a diagram showing angular multiplexing by GM,
4 is a diagram provided in the description of a method of controlling an SLM of a holographic display device,
5 is a flowchart provided in the description of the holographic display method according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a view illustrating a holographic display device according to an embodiment of the present invention. A holographic display device according to an exemplary embodiment of the present invention performs holographic display by multiplexing visual images.

1, a holographic display device according to an embodiment of the present invention includes a spatial light modulator (SLM) 110, a band pass filter (BPF) 120, and two GM Galvano Mirror (Galvano Mirrors) 131 and 132, and relay optical systems 151 to 156.

The SLM 110 is an element capable of displaying a holographic interference pattern, and is preferably implemented by a DMD (Digital Micromirror Device), but does not preclude implementation by other elements.

The relay optical systems 151 to 156 are composed of six lenses L1 to L6. The BPF 120 is a spatial filter that transmits only the first-order diffraction component in the spatial frequency domain.

The GM1 131 controls the direction of light in the horizontal direction on the reimaging plane and the GM-22 132 controls the direction of light in the vertical direction on the re-imaging plane.

Hereinafter, the operation of the holographic display device shown in FIG. 1 will be described in detail.

First, a computing device (not shown) displays the holographic interference pattern on the SLM 110, which can represent a hologram. Then, a plane wave generated from a light source (not shown) is incident on the SLM 110.

The incident plane wave is diffracted by the holographic interference pattern represented in the SLM 110, where the diffracted wave front is composed of a diffracted zero-order component, a ± first order diffraction component, and a higher order diffraction component of ± second or higher order.

Both the zero-order component and the diffracted component that are not diffracted pass through the lens L1 151 and are evenly distributed by the lens L1 151 in the focal plane, that is, in the spatial frequency domain. However, only the first-order diffraction component necessary for the hologram display is transmitted by the BPF 120. [

The transmitted first-order diffraction component is re-imaged by the lens L2 (152) on the focal plane of the lens L2 (152). The focal plane of L2 152 will be referred to as reimaging plane-1.

In the reimaging plane-1, a holographic interference pattern is formed as a complex field only by the first-order diffraction component diffracted by the SLM 110. [ It can be seen that the wavefront for the three-dimensional object / image to be rendered is displayed in the hologram plane rather than a further holographic interference pattern.

Positioning GM1 131 on reimaging plane-1, and GM1 131 beam steering the beam in a horizontal direction. The wave front reflected by the GM1 131 is re-imaged on the focal plane of the lens L4 154 by the lens L3 153 and the lens L4 154. [ The focal plane of L4 152 will be referred to as reimaging plane-2.

Position GM2 132 on reimaging plane-2, and GM2 132 controls the path of the beam in the vertical direction. The wavefront reflected by the GM2 131 is re-imaged on the focal plane of the lens L6 156 by the lens L5 155 and the lens L6 156. [ The focal plane of L6 156 will be referred to as reimaging plane-3 (140).

The size of the re-imaged wavefront on reimaging plane-1 where GM1 131 is located is determined by the focus ratio of lens L1 151 and lens L2 152. Likewise, the size of the re-imaged wavefront on reimaging plane-2 where GM2 132 is located is determined by the focus ratio of lens L3 153 and lens L4 154, The size of the imaged wavefront is determined by the focus ratio of the lens L5 (155) and the lens L5 (155).

Thus, the magnification M ₁₂ on the wavefront plane at re-imaging plane-1, the magnification M ₃₄ on the wavefront plane at re-imaging plane-2, and the magnification M ₅₆ on the wavefront plane at reimaging plane-3 (140) are as follows.

M ₁₂ = f ₂ / f ₁ , M ₃₄ = f ₃ / f ₄ , M ₅₆ = f ₅ / f ₆

Then, the size on the wavefront at the re-imaging plane-3 (140), which is the holographic display plane located in front of the observer, has a magnification of M _total with respect to the SLM (110).

M _total = M ₁₂ M ₃₄ M ₅₆

Therefore, in the holographic display device shown in the embodiment of the present invention, it is possible to enlarge the size in the hologram display plane finally displayed through the magnification of each lens 151 to 156.

The viewing angle of the holographic display is defined by the diffraction angle, [theta] of the SLM 110, and is calculated as follows.

? = sin? ¹ (? / 2? p)

Where? Is the wavelength of the laser used as the display light source, and? P is the pixel spacing of the SLM 110. For example, if the wavelength of the light source is 633 nm and the pixel interval is 7 um, the diffraction angle is about 2.6 degrees. 2.6 degrees represents a viewing angle that is not suitable from a normal display viewpoint.

However, the holographic display device according to the embodiment of the present invention multiplies the diffracted wavefronts by angular tilting in units of a certain angle, thereby increasing the overall viewing angle.

FIG. 2 shows the result of increasing the viewing angle in the reimaging plane-3 (140), which is the holographic display plane in front of the observer. As described above, the diffraction angle is converted by the magnification of the lens, and the magnification thereof is inversely proportional to the _total lens magnification M _total .

FIG. 3 shows the angular multiplexing by the GMs 131 and 132. When the SLM 110 having a high frame rate is used, when the GM1 and the GM1 and the GM1 131 are controlled at a high speed in a predetermined angle unit when constructing one frame, It is also possible to multiplex.

As shown in FIG. 3, although the GMs 131 and 132 are mirrors that reflect light, the GMs 131 and 132 are shown in a form in which light is reflected without being reflected by the GMs 131 and 132 in FIG. 1 for the convenience of understanding. In fact, it should be noted that the optical axis is bent 90 degrees in the GM1 131 and bent 90 degrees in the GM2 132 as well.

4 is a diagram provided in the description of the manner of controlling the SLM 110 of the holographic display device. As shown in FIG. 4, the computing device 200 displays the holographic interference pattern in the SLM 110.

The holographic interference pattern displayed on the SLM 110 by the computing device 200 is controlled in synchronization with the rotation angles of the GM1 131 and the GM2 132. [ The rotation angle of the GM1 131 and GM2 132 determines the portion of the reimaging plane-3 140 where the wavefront is re-imaged.

The computing device 200 refers to the rotation angles of the GM1 131 and the GM2 132 to generate a holographic interference pattern capable of generating a wavefront image to be re-imaged in a corresponding portion of the re- (110).

5 is a flowchart provided in the description of the holographic display method according to another embodiment of the present invention.

5, first, the computing device 200 displays an holographic interference pattern on the SLM 110 (S310), and generates a wavefront for the three-dimensional object / image formed by the diffraction (S320) .

Then, the BPF 120 extracts only the first-order diffraction components constituting the wavefront for the three-dimensional object / image generated in step S320 (S330), and the GM1 131 and the GM2 132 are subjected to high- The wavefronts seen from the angle are multiplexed on the space in units of a predetermined angle (S340).

On the other hand, in this case, the relay optical systems 151 to 156 enlarge the size of the finally displayed hologram display plane to M _total .

This realizes time angular multiplexing for holographic display, thereby increasing the spatial band product. As a result, the hologram image can be increased and the viewing angle can be increased.

Up to now, the present invention has been described in detail with respect to a preferred embodiment of a method and apparatus for holographic display by multiplexing.

In the embodiments of the present invention, by using the SLM having a high frame rate as the holographic display panel, the wavefront diffracted by the SLM can be magnified in the hologram display plane and the viewing angle can be increased, A device and a method capable of hologram display are proposed.

On the other hand, in the above embodiment, it is possible to omit one of GM1 131 and GM2 132. [ That is, the technical idea of the present invention can be applied to the case of realizing one-dimensional angular multiplexing instead of two-dimensional angular multiplexing.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention.

110: SLM (Spatial Light Modulator)
120: Band Pass Filter (BPF)
131, 132: GM (Galvano Mirror: Galvano Mirror)
151 to 156: Relay optical system
200: computing device

Claims (15)

An SLM (Spatial Light Modulator) for displaying a holographic interference pattern and diffracting incident plane waves;
An optical system for magnifying a wavefront diffracted by the SLM;
A first plane mirror tilting at a first angle in the optical system to change a traveling path of the wavefront to a first direction; And
And a second plane mirror that tilts at a second angle in the optical system to change a traveling path of a wavefront changed in direction by the first plane mirror to a second direction,
The optical system includes:
A first optical system, a second optical system, and a third optical system,
Wherein the first plane mirror comprises:
A second optical system that is located in a focal plane of the first optical system,
Wherein the second plane mirror comprises:
A second optical system that is located in a focal plane of the second optical system,
The third optical system includes:
Re-imaging the wavefront, which is redirected by the second plane mirror, onto the holographic display plane,
Wherein the holographic display plane comprises:
Wherein the third optical system is located at a focal plane of the third optical system.
delete The method according to claim 1,
Wherein the first direction and the second direction are perpendicular to each other.
delete The method according to claim 1,
The first optical system includes:
Lens-1 and Lens-2.
The method of claim 5,
And a filter disposed between the lens-1 and the lens-2 and transmitting only a first-order diffraction component at a wavefront diffracted by the SLM.
delete The method according to claim 1,
The second optical system includes:
Lens-3, and Lens-4.
delete The method according to claim 1,
The third optical system includes:
A lens-5, and a lens-6.
delete The method according to claim 1,
The 'size on the wavefront re-imaged on the holographic display plane' for 'the size of the SLM'
Wherein the first optical system is a product of a magnification of the first optical system, a magnification of the second optical system, and a magnification of the third optical system.
Displaying a holographic interference pattern;
Diffracting an incident plane wave;
Wherein the optical system magnifies the diffracted wavefront;
Tilting a first plane mirror at a first angle within the optical system to change a traveling path of the wave front to a first direction; And
And tilting the second plane mirror at a second angle within the optical system to change the traveling path of the wavefront changed in direction by the first plane mirror to a second direction,
The optical system includes:
A first optical system, a second optical system, and a third optical system,
Wherein the first plane mirror comprises:
A second optical system that is located in a focal plane of the first optical system,
Wherein the second plane mirror comprises:
A second optical system that is located in a focal plane of the second optical system,
The third optical system includes:
Re-imaging the wavefront, which is redirected by the second plane mirror, onto the holographic display plane,
Wherein the holographic display plane comprises:
Wherein the third optical system is located at a focal plane of the third optical system.
delete An SLM (Spatial Light Modulator) for diffracting incident plane waves by displaying a holographic interference pattern, an optical system for magnifying a wavefront diffracted by the SLM, a tilting means for tilting at a first angle in the optical system, And a second plane mirror for changing a traveling path of a wavefront that is tilted at a second angle in the optical system and changed in direction by the first plane mirror to a second direction, ; And
And a computing device for generating a holographic interference pattern displayed on the SLM with reference to the first direction,
The optical system includes:
A first optical system, a second optical system, and a third optical system,
Wherein the first plane mirror comprises:
A second optical system that is located in a focal plane of the first optical system,
Wherein the second plane mirror comprises:
A second optical system that is located in a focal plane of the second optical system,
The third optical system includes:
Re-imaging the wavefront, which is redirected by the second plane mirror, onto the holographic display plane,
Wherein the holographic display plane comprises:
And the third optical system is located at a focal plane of the third optical system.

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