# US 11,979,688 B2 · Spatial light modulator

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- Number: US 11,979,688 B2
- Document ID: US11979688B2
- Status: Granted
- Kind: B2
- Application number: 17/408,012
- Filed: 2021-08-20
- Published: 2022-02-24
- Granted: 2024-05-07
- Earliest claimed: 2020-08-21
- Assignees: Dualitas Ltd
- Applicants: Dualitas Ltd
- Inventors: Jamieson Christmas
- Web page: https://patentgrep.com/patent/US11979688B2

## CPC

- H04N 9/312: {Driving therefor (driving of electronic spatial light modulators in displays other than projection devices G09G3/34, G09G3/36; control of liquid crystal elements G02F1/133; control of micromechanical modulators G02B26/08)}
- G03H 1/0005: {Adaptation of holography to specific applications (holographic optical element G02B5/32; holographic scanner G02B26/106; recognition using holographic mask G06V10/88; holographic memories G11B7/0065, G11C13/042)}
- G03H 1/2294: {Addressing the hologram to an active spatial light modulator}
- G09G 3/003: {to produce spatial visual effects}
- G09G 3/2022: {using sub-frames}
- G09G 3/3607: {for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels (display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127)}
- G09G 3/3648: {using an active matrix (G09G3/367 - G09G3/3696 take precedence)}
- H04N 9/3108: {by using a single electronic spatial light modulator}
- G02F 1/134345: {Subdivided pixels, e.g. for grey scale or redundancy}
- G03H 2001/0088: {for video-holography, i.e. integrating hologram acquisition, transmission and display}
- G03H 2001/2271: {RGB holobject}
- G03H 2001/2297: {using frame sequential, e.g. for reducing speckle noise}
- G03H 2225/22: Electrically addressed SLM [EA-SLM]
- G03H 2226/02: Computing or processing means, e.g. digital signal processor [DSP]
- G03H 2240/61: SLM related parameters, e.g. pixel size
- G03H 2240/62: Sampling aspect applied to sensor or display
- G09G 2300/0426: Layout of electrodes and connections
- G09G 2300/0857: Static memory circuit, e.g. flip-flop
- G09G 2310/0286: Details of a shift registers arranged for use in a driving circuit
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- G03H: HOLOGRAPHIC PROCESSES OR APPARATUS (holograms, e.g. point holograms, used as ordinary optical elements G02B5/32; producing stereoscopic or other three-dimensional effects G02B30/00; diffraction-grating systems G02B27/44; systems using moiré fringes G02B27/60; optical logic elements G02F3/00; stereo-photography G03B35/00; photosensitive materials or processes for photographic purposes G03C; {stereo-photographic or similar processes G03C9/00}; apparatus for processing exposed photographic materials G03D; analogue computers performing mathematical operations with the aid of optical elements G06E3/00; authentication by radiation, of concealed information carried by holograms or diffraction gratings G06K19/16; holographic storage G11B7/0065, G11C13/04; {stereoscopic or other three dimensional effects in television systems H04N13/00})
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

A liquid crystal on silicon spatial light modulator comprising an array of light-modulating pixels and a controller are disclosed. Each light-modulating pixel of the array comprises liquid crystal and is associated with a respective flip-flop. The controller receives a hologram of an image comprising a plurality of hologram pixels. Each hologram pixel comprises a respective n-bit hologram pixel value. The controller drives each light-modulating pixel in accordance with a respective hologram pixel value of the hologram. There is a one-to-n pixel correlation between the hologram and the light-modulating pixels. The flip-flops of each contiguous group of n light-modulating pixels are connected in series to form a shift register. During operation of the shift register, the n-bit hologram pixel value associated with each contiguous group of n light-modulating pixels is provided to each light-modulating pixel one bit at a time over the course of at least n clock cycles.

## Claims

### Claim 1

A liquid crystal on silicon spatial light modulator comprising:
an array of light-modulating pixels each comprising liquid crystal, wherein each light-modulating pixel is associated with a respective flip-flop;
a controller arranged to: receive a hologram of an image, wherein the hologram comprising a plurality of hologram pixels each comprising a respective n-bit hologram pixel value; and drive each light-modulating pixel of a contiguous group of n light-modulating pixels in accordance with a respective hologram pixel value of the hologram such that there is a one-to-n pixel correlation between the hologram and the light-modulating pixels,
wherein the flip-flops of each contiguous group of n light-modulating pixels are connected in series to form a shift register such that, during operation of the shift register, the n-bit hologram pixel value associated with each contiguous group of n light-modulating pixels is provided to each light-modulating pixel of the contiguous group one bit at a time over the course of at least n clock cycles.

### Claim 2 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 wherein each light-modulating pixel is further associated with a respective one-bit of memory and the controller is arranged to provide each light-modulating pixel of a contiguous group with a different bit of the respective n-bit hologram pixel value prior to operation of the shift register.

### Claim 3 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 wherein the shift register is operated such that the liquid crystal of each light-modulating pixel responds to an RMS voltage corresponding to the respective n-bit hologram pixel value.

### Claim 4 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 wherein n is dependent on wavelength and the controller is arranged to select n based on a wavelength associated with the hologram.

### Claim 5 (depends on 4)

A liquid crystal on silicon spatial light modulator as claimed in claim 4 wherein n increases with wavelength.

### Claim 6 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 wherein each flip-flop comprises a first output, “Q”, and a second output, “Q-bar”, wherein the first output is opposite to the second output, and the controller is arranged drive each light-modulating pixel of each contiguous group using the first outputs of the flip-flops for at least n clock cycles and then drive each light-modulating pixel of each contiguous group using the second output of the flip-flops for at least n clock cycles in order to achieve frame inversion.

### Claim 7 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 wherein each contiguous group of pixels form a substantially square array or a substantially rectangular array.

### Claim 8 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 wherein the clock of the shift register is operated at greater than 25 KHz such as greater than 50 KHz.

### Claim 9 (depends on 1)

A liquid crystal on silicon spatial light modulator as claimed in claim 1 comprising at least 10,000×10,000 light modulating pixels, wherein the size of each pixel is less than 2×2 μm such as no more than 1×1 μm.

### Claim 10 (depends on 1)

A holographic projector comprising the liquid crystal on silicon spatial light modulator of claim 1 and a light source, wherein the light source is arranged to illuminate the spatial light modulator such that a holographic reconstruction of the image is projected onto a replay plane.

### Claim 11 (depends on 10)

A holographic projector as claimed in claim 10 wherein a first holographic reconstruction comprising light of a first wavelength and a second holographic reconstruction comprising light of a second wavelength are formed on a replay plane and the value of n associated with the first holographic reconstruction is different to the value of n associated with the second holographic reconstruction.

### Claim 12 (depends on 11)

A holographic projector as claimed in claim 11 wherein the first wavelength is greater than the second wavelength and the value of n associated with the first holographic reconstruction is greater than the value of n associated with the second holographic reconstruction.

### Claim 13 (depends on 1, 10)

A holographic projector as claimed in claim 10 wherein the first holographic reconstruction is formed using a first liquid crystal on silicon spatial light modulator as claimed in claim 1 operating using a value of n=n1 and the second holographic reconstruction is formed using a second liquid crystal on silicon spatial light modulator as claimed in claim 1 operating using a value of n=n2, wherein n1 is not equal to n2.

### Claim 14 (depends on 1, 10)

A holographic projector as claimed in claim 10 wherein the first holographic reconstruction and second holographic reconstruction are formed using the same liquid crystal on silicon spatial light modulator a claimed in claim 1, wherein the controller is arranged to reconfigure the light modulating pixels such that the first holographic reconstruction is formed using a value of n=n1 and the second holographic reconstruction is formed using a value of n=n2, wherein n1 is not equal to n2.

### Claim 15

A method of operating a liquid crystal on silicon spatial light modulator comprising liquid crystal, wherein each light-modulating pixel is associated with a respective flip-flop, the method comprising:
receiving a hologram of an image, wherein the hologram comprising a plurality of hologram pixels each comprising a respective n-bit hologram pixel value;
driving each light-modulating pixel of a contiguous group of n light-modulating pixels in accordance with a respective hologram pixel value of the hologram such that there is a one-to-n pixel correlation between the hologram and the light-modulating pixels,
wherein the flip-flops of each contiguous group of n light-modulating pixels are connected in series to form a shift register, wherein the method further comprises:
operating the shift register such that the n-bit hologram pixel value associated with each contiguous group of n light-modulating pixels is provided to each light-modulating pixel of the contiguous group one bit at a time over the course of at least n clock cycles.