# US 12,003,896 B2 · Projection display device

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- Number: US 12,003,896 B2
- Document ID: US12003896B2
- Status: Granted
- Kind: B2
- Application number: 17/588,146
- Filed: 2022-01-28
- Published: 2022-07-14
- Granted: 2024-06-04
- Earliest claimed: 2019-07-29
- Assignees: Appotronics Corporation Limited
- Applicants: Appotronics Corporation Limited
- Inventors: Fei Hu; Chen Chen; Xin Yu; Zuqiang Guo; Yi Li
- Web page: https://patentgrep.com/patent/US12003896B2

## CPC

- H04N 9/3155: {for controlling the light source (light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406)}
- 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)}
- H04N 9/317: {Convergence or focusing systems (electronic adjustment of convergence H04N9/3185; convergence or focusing arrangements for cathode ray tubes H04N9/28; means for automatic focusing of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/53)}
- H04N 13/339: using spatial multiplexing (H04N13/337 takes precedence)
- H04N 13/363: using image projection screens (volumetric display H04N13/388)
- H04N 13/398: Synchronisation thereof; Control thereof
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Provided is a projection display device for displaying a time period of one frame of stereo image as a first modulation period. The projection display device includes: a light source for emitting illumination light; a spatial light modulator for modulating the illumination light according to a plurality of frames of two-dimensional images corresponding to a stereo image to be displayed, and sequentially emitting, within the first modulation period, image light corresponding to the plurality of frames of the two-dimensional images; an angle deflection apparatus arranged in an emergent optical path of the image light and used for deflecting the image light corresponding to the plurality of frames of two-dimensional images to different angles for emission; and a projection screen for displaying the image light deflected by the angle deflection apparatus.

## Claims

### Claim 1

A projection display device, wherein a period in which one frame of stereo image is displayed is referred to as a first modulation cycle, and the projection display device comprises:
a light source, configured to emit illumination light;
a spatial light modulator, configured to modulate the illumination light based on a plurality of frames of 2D images corresponding to a stereo image to-be-displayed, and sequentially emit, in the first modulation cycle, image light corresponding to the plurality of frames of 2D images;
an angle deflection apparatus, disposed on an emergent optical path of the image light, and configured to deflect the image light corresponding to the plurality of frames of 2D images to different angles for emission; and
a projection screen, configured to display the image light deflected by the angle deflection apparatus.

### Claim 2 (depends on 1)

The projection display device according to claim 1, wherein
the first modulation cycle comprises a plurality of second modulation cycles, and the spatial light modulator emits image light of one frame of 2D image in the second modulation cycle;
the projection display device further comprises a control apparatus, which is configured to control the light source to emit illumination light with varying brightness in the second modulation cycle; and
the control apparatus is further configured to control a time length corresponding to a least significant bit (LSB) of the spatial light modulator in the second modulation cycle and an ON status or OFF status of a modulation unit of the spatial light modulator in a time length corresponding to each of the LSB, such that the spatial light modulator is capable of obtaining a specified illumination brightness set through modulation in the second modulation cycle.

### Claim 3 (depends on 2)

The projection display device according to claim 2, wherein
the second modulation cycle comprises a low-brightness period and a high-brightness period, the light source emits light with first-level brightness in the low-brightness period and emits light with second-level brightness in the high-brightness period, and the first-level brightness is less than the second-level brightness.

### Claim 4 (depends on 3)

The projection display device according to claim 3, wherein
each of the first-level brightness and the second-level brightness is range brightness; and any brightness of the first-level brightness is less than any brightness of the second-level brightness; or
average brightness of the first-level brightness is less than rated brightness of the second-level brightness; or
light brightness of the light source when the light source is continuously driven at its rated current is rated brightness, any brightness of the first-level brightness is less than the rated brightness, any brightness of the second-level brightness is not less than the rated brightness, and a difference value between the rated brightness and average brightness of the first-level brightness and the second-level brightness is less than a specified threshold.

### Claim 5 (depends on 3)

The projection display device according to claim 3, wherein
at least one of the first-level brightness or the second-level brightness changes in a step-like manner, and brightness in each step corresponds to a time length corresponding to at least one LSB.

### Claim 6 (depends on 5)

The projection display device according to claim 5, wherein the low-brightness period comprises m LSBs, the high-brightness period comprises n LSBs, m and n are positive integers, and brightness of the illumination light in the low-brightness period satisfies the following formula:
L1i=L/2m+1−i, wherein 1≤i≤m, where i is an integer, and L1i represents brightness of the illumination light corresponding to an ith LSB;
brightness of the illumination light in the high-brightness period satisfies the following formula:
L2j=L*2j−1, wherein 1≤j≤n, where j is an integer, and L2j represents brightness of the illumination light corresponding to a jth LSB; and
if the time length corresponding to the LSB is denoted as tLSB, then the second modulation cycle satisfies the following formula: T=(m+n)*tLSB, where T represents the second modulation cycle.

### Claim 7 (depends on 6)

The projection display device according to claim 6, wherein 2n−n≈m+(½m).

### Claim 8 (depends on 2)

The projection display device according to claim 2, wherein
the control apparatus is configured to generate a stereo image from a plurality of frames of images of different image formation planes, and then split the stereo image based on an algorithm to obtain 2D images corresponding to different spatial angles; and
the angle deflection apparatus is configured to deflect, to a corresponding spatial angle, image light corresponding to any 2D image and emitted by the spatial light modulator.

### Claim 9 (depends on 8)

The projection display device according to claim 8, wherein
the control apparatus controls, based on a correspondence between the spatial angle and a steady state of the modulation unit, the modulation unit to perform deflection in different steady states when the spatial light modulator modulates different frames of 2D images.

### Claim 10 (depends on 8)

The projection display device according to claim 8, wherein
the angle deflection apparatus comprises a plurality of guide portions sequentially located on the optical path of the image light in the first modulation cycle, each of the plurality of guide portions is configured to deflect the image light of the 2D image to its associated spatial angle, and each of the plurality of guide portions stays in the optical path for a period of time corresponding to the second modulation cycle.

### Claim 11 (depends on 1)

The projection display device according to claim 1, wherein the projection screen is an angle-spreading screen.

### Claim 12 (depends on 4)

The projection display device according to claim 4, wherein
at least one of the first-level brightness or the second-level brightness changes in a step-like manner, and brightness in each step corresponds to a time length corresponding to at least one LSB.