KR20210070719A - Holographic display device and method of manufacturing the same for extending viewing angle using transmissive phase mask - Google Patents

Abstract

Disclosed are a holographic display device and a method with an extended viewing angle using a transmissive phase mask. The holographic display device includes: a spatial light modulator (SLM) for modulating and outputting incident light according to a hologram pattern; and the transmissive phase mask which modulates and outputs the light output from the spatial light modulator. The transmissive phase mask may have a smaller pixel pitch than the spatial light modulator. Therefore, it is possible to extend the viewing angle compared to a conventional holographic display.

Description

HOLOGRAPHIC DISPLAY DEVICE AND METHOD OF MANUFACTURING THE SAME FOR EXTENDING VIEWING ANGLE USING TRANSMISSIVE PHASE MASK

The present invention relates to a holographic display apparatus and method, and more particularly, to an apparatus and method for extending a viewing angle of a holographic display using a transmissive phase mask.

Holography is a technology that uses the diffraction and interference of light. Unlike the existing 2D image that records only the amplitude information of light, it also utilizes the phase information of light to provide a perfect 3D image like seeing the real thing.

Holographic displays typically optically reproduce holographic data through a spatial light modulator (SLM). In this case, the viewing angle of the holographic display has a characteristic inversely proportional to the physical pixel pitch of the SLM. That is, a smaller pixel pitch provides a wider viewing angle.

However, in order to provide a viewing angle close to 180 degrees provided by a 2D display, a pixel size of several hundred nm corresponding to a half-wavelength of a light source is required, so a holographic display has a narrower viewing angle than a 2D display.

In addition, when the pixel pitch is reduced while maintaining the physical size of the display, the resolution of the image to be processed by the display increases, which may put a load on data processing and transmission.

Accordingly, a technology for adding a diffuser between the light source and the spatial light modulator has been developed, such as Digital 3D holographic display using scattering layers for enhanced viewing angle and image size (Proc. SPIE vol. 10219, 2017). However, since the transmittance of the diffuser is not high and the characteristic information of the diffuser cannot be accurately known, there is a disadvantage that it takes a lot of time to optimize the holographic image.

Accordingly, there is a demand for a method capable of extending the viewing angle of a holographic display without increasing the size of data or increasing the optimization time.

The present invention provides an apparatus in which a viewing angle is extended by combining a transmissive phase mask with a pixel pitch smaller than that of the spatial light modulator with the spatial light modulator.

In addition, the present invention provides an apparatus and method for selectively reproducing a 2D display and a holographic display by using a transmissive phase mask that transparently transmits light output from a spatial light modulator.

A holographic display apparatus according to an embodiment of the present invention includes a spatial light modulator (SLM) for modulating and outputting incident light according to a hologram pattern; and a transmissive phase mask for modulating and outputting the light output from the spatial light modulator. Including, the transmissive phase mask may have a smaller pixel pitch than that of the spatial light modulator.

The transmissive phase mask of the holographic display device according to an embodiment of the present invention may be formed such that pixels are arranged in a random pattern to output a random phase.

The holographic pattern of the holographic display device according to an embodiment of the present invention is formed by a value of an input field output from pixels of the spatial light modulator and input to the transmissive phase mask and light output from the transmissive phase mask. It can be calculated according to the transmission matrix between the values of the output fields.

The value of the output field of the holographic display device according to an embodiment of the present invention may be a representative value selected based on information of each of a plurality of pixels of a transmissive phase mask matched to one of the pixels of the spatial light modulator. .

The holographic pattern of the holographic display device according to an embodiment of the present invention is a 2D matrix obtained by converting a Hadamard vector corresponding to each pixel of the spatial light modulator and a uniform matrix corresponding to the reference beam. can be calculated using

The transmissive phase mask of the holographic display device according to an embodiment of the present invention may be attached in a direction in which light is output from the spatial light modulator.

According to an embodiment of the present invention, a holographic display device setting method for setting a holographic display device including a spatial light modulator and a transmissive phase mask for modulating an output of the spatial light modulator includes input of a transmissive phase mask according to a sample hologram pattern. determining the value of the field, and determining the value of the output field of the transmissive phase mask according to the sample three-dimensional image generated according to the sample hologram pattern; determining a transmission matrix based on the value of the input field and the value of the output field; and storing the transmission matrix in a processor or a storage medium of the holographic display device, wherein the processor of the holographic display inputs a three-dimensional image to be displayed in an output field of the transmission matrix, and a holographic pattern , and input the calculated hologram pattern to the spatial light modulator to display a three-dimensional image.

The transmissive phase mask of the holographic display setting method according to an embodiment of the present invention may have a smaller pixel pitch than the spatial light modulator.

A holographic display setting method according to an embodiment of the present invention includes the steps of grouping pixels of a transmissive phase mask corresponding to each pixel of a spatial light modulator, and determining a representative value using values of an output field of the grouped pixels. The method may further include determining the transmission matrix by matching the value of the input field with the representative value to determine the transmission matrix.

According to an embodiment of the present invention, by combining a transmissive phase mask having a smaller pixel pitch than the spatial light modulator with the spatial light modulator, the viewing angle can be extended compared to the conventional holographic display.

In addition, according to an embodiment of the present invention, a 2D display and a holographic display can be selectively reproduced by using a transmissive phase mask that transparently transmits light output from the spatial light modulator.

1 is a view showing a holographic display device according to an embodiment of the present invention.
2 is an example of a process in which the holographic display device according to an embodiment of the present invention expands a viewing angle using a pixel pitch of a transmissive phase mask.
3 is a flowchart illustrating a hologram pattern optimization method according to an embodiment of the present invention.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, since various changes may be made to the embodiments, the scope of the patent application is not limited or limited by these embodiments. It should be understood that all modifications, equivalents and substitutes for the embodiments are included in the scope of the rights.

The terms used in the examples are used for description purposes only, and should not be construed as limiting. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

In addition, in the description with reference to the accompanying drawings, the same components are assigned the same reference numerals regardless of the reference numerals, and the overlapping description thereof will be omitted. In the description of the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted.

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

1 is a view showing a holographic display device according to an embodiment of the present invention.

The holographic display apparatus 100 may include a spatial light modulator 110 and a transmissive phase mask 120 as shown in FIG. 1 .

A spatial light modulator (SLM) 110 may modulate and output light incident from a light source according to a hologram pattern.

The distance between the spatial light modulator 110 and the transmissive phase mask 120 may be determined differently according to embodiments or may be adjusted according to conditions. In addition, the transmissive phase mask 120 may be attached in a direction in which the spatial light modulator 120 outputs light.

The transmissive phase mask 120 modulates and outputs the light output from the spatial light modulator 110 , thereby generating a 3D image 101 as shown in FIG. 1 . In this case, a pixel pitch of pixels included in the transmissive phase mask 120 may be smaller than a pixel pitch of pixels included in the spatial light modulator 110 .

In addition, since the pixel pitch of pixels included in the transmissive phase mask 120 is smaller than the pixel pitch of the pixels of the spatial light modulator 110 , a plurality of pixels of the transmissive phase mask 120 per pixel of the spatial light modulator 110 . may be matched.

That is, lights output from a plurality of pixels of the transmissive phase mask 120 may correspond to an input field output from one pixel of the spatial light modulator 110 . Accordingly, a representative value selected based on information on each of the plurality of pixels of the transmissive phase mask 120 matched to one of the pixels of the spatial light modulator 110 may be defined as the value of the output field corresponding to the input field. can For example, at least one of phase averaging, vector averaging, median, and strong information selection may be used as a method of determining the representative value.

And, the transmissive phase mask 120, Pixels may be arranged in a random pattern to output a random phase. In this case, the hologram pattern used by the spatial light modulator 110 to modulate the light source may be determined in consideration of the random pattern of the transmissive phase mask 120 .

Specifically, when a command to display the three-dimensional image 101 on the holographic display is input, the processor of the holographic display device inputs the three-dimensional image 101 into the output field of the transmission matrix, and the three-dimensional image 101 ), a hologram pattern can be calculated according to the value of the input field of the transmission matrix. At this time, the transmission matrix is between the value of the input field output from the pixels of the spatial light modulator 110 and input to the transmissive phase mask 120 and the value of the output field formed by the light output from the transmissive phase mask 120 . may be a matrix of

The random pattern of the transmissive phase mask 120 may have a pixel pitch and a random phase value determined in consideration of a viewing angle extension required for the holographic display apparatus 100 . In this case, the degree of randomness of the random pattern may mean the degree to which energy distribution for extending the viewing angle is possible. Accordingly, the transmissive phase mask may include a pattern having regularity that satisfies the condition that energy distribution for extending the viewing angle is possible.

That is, the pattern included in the transmissive phase mask 120 may mean a pattern having a pixel pitch sufficient to extend the viewing angle and sufficiently dispersing energy within the corresponding viewing angle. And, in general, the random pattern may satisfy the characteristics of the pattern included in the transmissive phase mask 120 .

The hologram pattern of the spatial light modulator 110 is to be determined by first propagating the 3D image information of the object to be reproduced to the transmissive phase mask 120 and then propagating it to the spatial light modulator 110 again. can For example, propagation may be performed using Rayleigh-Sommerfeld diffraction, Fresnel diffraction, or Fraunhofer diffraction.

Then, it can be checked whether the 3D image 101 is reproduced by propagating the hologram of the spatial light modulator 110 to the 3D image information plane. Then, when the 3D image 101 is not reproduced, the hologram pattern of the spatial light modulator 110 is optimized by updating the 3D image information of the object and repeating the above process using the updated 3D image information. can do.

For example, the optimization process of the hologram pattern may be an Iterative Fourier Transform Algorithm (IFTA).

In addition, the transmissive phase mask 120 can selectively reproduce a 2D display and a holographic display. In addition, the transmissive phase mask 120 can be designed and applied from a binary phase to a multi-level, and the ratio with the SLM can also be adjusted with various values.

In addition, the viewing angle extension of the transmissive phase mask 120 can be applied in all directions horizontally and vertically, or only in horizontal or vertical directions.

In addition, although not shown in FIG. 1 , the holographic display apparatus 100 is disposed before and after the spatial light modulator 110 and the transmissive phase mask 120 , or between the spatial light modulator 110 and the transmissive phase mask 120 . Lenses can also be placed. In this case, the random pattern of the transmissive phase mask 120 may be calculated by further considering the characteristics of the lens.

The holographic display apparatus 100 may extend a viewing angle compared to a conventional holographic display by combining the transmissive phase mask 120 having a smaller pixel pitch than the spatial light modulator 110 with the spatial light modulator 110 .

In addition, the holographic display apparatus 100 uses a transmissive phase mask 120 that transparently transmits the light output from the spatial light modulator 110, thereby displaying a 2D display displaying a 2D image and a 3D image. A holographic display can be selectively reproduced.

2 is an example of a process in which the holographic display device according to an embodiment of the present invention expands a viewing angle using a pixel pitch of a transmissive phase mask.

Since the holographic display is based on optical reproduction through the spatial light modulator, the viewing angle that a user can observe in the holographic display device may be determined according to the pixel pitch of the spatial light modulator and the wavelength of the light source.

For example, as shown in Case 1, the conventional holographic display in which the size of the pixel pitch of the spatial light modulator (SLM) 200 is 8 μm and the wavelength of the light source is 660 nm is diffracted according to Equation 1 The angle θ may be about 2.36 degrees, and the viewing angle may be 4.7 degrees.

On the other hand, in the holographic display device according to an embodiment of the present invention, a transmission phase mask 120 having a pixel pitch of 4 μm is disposed behind a spatial light modulator (SLM) 110 having a pixel pitch of 8 μm, According to Equation 2, as shown in Case 2, the diffraction angle θ can be extended to 4.3 degrees.

In addition, in the holographic display device according to an embodiment of the present invention, a transmissive phase mask 120 having a pixel pitch of 2 μm is disposed behind a spatial light modulator (SLM) 110 having a pixel pitch of 8 μm, According to Equation 3, as shown in Case 2, the diffraction angle θ may be further extended to 9.5 degrees.

3 is a flowchart illustrating a hologram pattern optimization method according to an embodiment of the present invention.

In step 310 , the apparatus for optimizing the hologram pattern may propagate the 3D image information of the object to be reproduced as the 3D image 101 to the transmissive phase mask 120 . In this case, the hologram pattern optimization apparatus may propagate 3D image information using one of Rayleigh-Sommerfeld diffraction, Fresnel diffraction, and Fraunhofer diffraction.

In operation 320 , the hologram pattern optimization apparatus may propagate the 3D image information propagated to the transmissive phase mask 120 in operation 310 to the spatial light modulator 110 .

In operation 330 , the hologram pattern optimization apparatus may determine a representative value of a plurality of pixels of the transmissive phase mask 120 corresponding to one pixel of the spatial light modulator 110 . In this case, the hologram pattern optimization apparatus corresponds to one pixel of the spatial light modulator 110 by using at least one method of phase averaging, vector averaging, median, and strong information selection for a plurality of pixels of the transmissive phase mask 120 . A representative value of a plurality of pixels of the transmissive phase mask 120 may be determined.

In operation 340 , the hologram pattern optimization apparatus may propagate the hologram pattern of the spatial light modulator 110 back to the 3D image information plane.

In operation 350 , the apparatus for optimizing the hologram pattern may determine whether the hologram pattern propagated to the 3D image information plane in operation 340 reproduces the 3D image 101 . When the 3D image 101 is reproduced, the apparatus for optimizing the hologram pattern may determine that the hologram pattern is optimized and end the optimization method. If the 3D image 301 cannot be reproduced, the hologram pattern optimization apparatus may perform step 360 .

In operation 360 , the hologram pattern optimization apparatus may update 3D information of the object. Next, in operation 310 , the apparatus for optimizing the hologram pattern may propagate the 3D information updated in operation 360 to the transmissive phase mask 120 .

That is, the hologram pattern optimization device generates a hologram pattern through the process of propagating the 3D image information to the transmissive phase mask 120 and the spatial light modulator 110, and the generated hologram pattern cannot reproduce the 3D image. In this case, the hologram pattern may be optimized by repeating the process of generating the hologram pattern again by updating the 3D image information.

In the present invention, by combining the transmissive phase mask 120 having a smaller pixel pitch than the spatial light modulator 110 with the spatial light modulator 110, the viewing angle can be extended compared to the conventional holographic display.

In addition, the present invention can selectively reproduce a 2D display and a holographic display by using the transmissive phase mask 120 that transparently transmits the light output from the spatial light modulator 110 .

Meanwhile, the method for manufacturing a holographic display according to the present invention is written as a program that can be executed on a computer and can be implemented in various recording media such as magnetic storage media, optical reading media, and digital storage media.

Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or combinations thereof. Implementations may be implemented for processing by, or controlling the operation of, a data processing device, eg, a programmable processor, computer, or number of computers, in a computer program product, eg, a machine-readable storage device (computer-readable available medium) as a computer program tangibly embodied in it. A computer program, such as the computer program(s) described above, may be written in any form of programming language, including compiled or interpreted languages, as a standalone program or in a module, component, subroutine, or computing environment. It can be deployed in any form, including as other units suitable for use in A computer program may be deployed to be processed on one computer or multiple computers at one site or to be distributed across multiple sites and interconnected by a communications network.

Processors suitable for processing a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. In general, a processor will receive instructions and data from read only memory or random access memory or both. Elements of a computer may include at least one processor that executes instructions and one or more memory devices that store instructions and data. In general, a computer may include one or more mass storage devices for storing data, for example magnetic, magneto-optical disks, or optical disks, receiving data from, sending data to, or both. may be combined to become Information carriers suitable for embodying computer program instructions and data are, for example, semiconductor memory devices, for example, magnetic media such as hard disks, floppy disks and magnetic tapes, Compact Disk Read Only Memory (CD-ROM). ), optical recording media such as DVD (Digital Video Disk), magneto-optical media such as optical disk, ROM (Read Only Memory), RAM (RAM) , Random Access Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), and the like. Processors and memories may be supplemented by, or included in, special purpose logic circuitry.

Also, the computer-readable medium may be any available medium that can be accessed by a computer, and may include any computer storage medium.

While this specification contains numerous specific implementation details, they should not be construed as limitations on the scope of any invention or claim, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. should be understood Certain features that are described herein in the context of separate embodiments may be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments, either individually or in any suitable subcombination. Furthermore, although features operate in a particular combination and may be initially depicted as claimed as such, one or more features from a claimed combination may in some cases be excluded from the combination, the claimed combination being a sub-combination. or a variant of a sub-combination.

Likewise, although acts are depicted in the figures in a particular order, it should not be construed that all acts shown must be performed or that such acts must be performed in the specific order or sequential order shown in order to achieve desirable results. In certain cases, multitasking and parallel processing may be advantageous. Further, the separation of the various device components of the above-described embodiments should not be construed as requiring such separation in all embodiments, and the program components and devices described may generally be integrated together into a single software product or packaged into multiple software products. You have to understand that you can.

On the other hand, the embodiments of the present invention disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

110: spatial light modulator (SLM)
120: transmissive phase mask

Claims (10)

a spatial light modulator (SLM) for modulating and outputting incident light according to a hologram pattern; and
Transmissive phase mask modulating and outputting light output from the spatial light modulator
including,
The transmissive phase mask,
A holographic display device with a smaller pixel pitch than a spatial light modulator. According to claim 1,
The transmissive phase mask,
A holographic display device in which pixels are arranged in a random pattern to output a random phase. 3. The method of claim 2,
The hologram pattern is
A holographic display device calculated according to a transmission matrix between a value of an input field output from pixels of the spatial light modulator and input to the transmissive phase mask and a value of an output field formed by light output from the transmissive phase mask . 4. The method of claim 3,
The value of the output field is
A holographic display device that is a representative value selected based on information on each of a plurality of pixels of a transmissive phase mask matched to one of the pixels of the spatial light modulator. 3. The method of claim 2,
The hologram pattern is
A holographic display device that is calculated using a 2D matrix obtained by transforming a Hadamard vector corresponding to each pixel of the spatial light modulator and a uniform matrix corresponding to a reference beam. According to claim 1,
The transmissive phase mask,
A holographic display device attached to a direction in which the spatial light modulator outputs light. A hologram pattern optimization method for optimizing a hologram pattern of a spatial light modulator in a holographic display device including a spatial light modulator and a transmissive phase mask for modulating an output of the spatial light modulator, the method comprising:
propagating 3D image information of an object to be reproduced as a 3D image to a transmissive phase mask;
propagating the 3D image information propagated to the transmissive phase mask to a spatial light modulator;
determining a representative value of a plurality of pixels of a transmissive phase mask corresponding to one pixel of the spatial light modulator;
propagating the hologram pattern of the spatial light modulator 110 to the 3D image information plane; and
When the hologram pattern propagated to the 3D image information plane reproduces the 3D image, determining that the hologram pattern is optimized
A holographic pattern optimization method comprising a. 8. The method of claim 7,
The transmissive phase mask,
A holographic pattern optimization method with a smaller pixel pitch than a spatial light modulator. 9. The method of claim 8,
When the hologram pattern propagated to the 3D image information plane does not reproduce the 3D image, updating 3D information of the object
further comprising,
The step of propagating to the transmissive phase mask,
A hologram pattern optimization method for propagating updated three-dimensional information to the transmissive phase mask. A computer-readable recording medium in which a program for executing the method of any one of claims 7 to 9 is recorded.

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