# US 10,770,029 B2 · Display device and method of controlling display device

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- Number: US 10,770,029 B2
- Document ID: US10770029B2
- Status: Granted
- Kind: B2
- Application number: 15/991,373
- Filed: 2018-05-29
- Published: 2018-09-27
- Granted: 2020-09-08
- Earliest claimed: 2012-11-28
- Assignees: Seiko Epson Corporation
- Applicants: Seiko Epson Corporation
- Inventors: Takashi Toyooka
- Web page: https://patentgrep.com/patent/US10770029B2

## CPC

- G09G 5/10: Intensity circuits
- G03B 21/2053: {Intensity control of illuminating light (controlled by video signal processing H04N5/74 or H04N9/31)}
- 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 9/3161: {using laser light sources (using laser beams scanning the display screen H04N9/3129)}
- H04N 9/3182: {Colour adjustment, e.g. white balance, shading or gamut (white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607)}
- G03B 21/006: {using LCD's}
- 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)
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A display device includes a solid-state light source driven by a PWM signal, a light modulation device that modulates light emitted by the solid-state light source in response to an image signal, and a signal output unit that determines a duty ratio and a current value of the PWM signal in response to brightness of an image represented by the image signal. The signal output unit outputs a PWM signal having a predetermined first current value to the solid-state light source if the duty ratio is equal to or more than a predetermined first threshold value and outputs a PWM signal having a current value less than the first current value to the solid-state light source if the duty ratio is less than the first threshold value.

## Claims

### Claim 1

A display device comprising:
a solid-state light source driven by a PWM signal;
a light modulation device that modulates light emitted by the solid-state light source in response to an image signal; and
a signal output unit that:
determines a duty ratio and a current value of the PWM signal;
outputs a PWM signal having a predetermined current value to the solid-state light source if the duty ratio is less than a predetermined threshold value; and
outputs a PWM signal having a current value more than the predetermined current value and increasing as the duty ratio is increases, to the solid-state light source if the duty ratio is equal to or more than the predetermined threshold value.

### Claim 2 (depends on 1)

The display device according to claim 1, wherein the signal output unit outputs a PWM signal having a second current value larger than the predetermined current value if the duty ratio is equal to or more than a second threshold value larger than the predetermined threshold value, and outputs a PWM signal having a current value less than the second current value and equal to or more than the predetermined current value in response to the duty ratio if the duty ratio is less than the second threshold value and equal to or more than the predetermined threshold value.

### Claim 3 (depends on 1)

The display device according to claim 1, further comprising a photodetector that detects an amount of light emitted by the solid-state light source,
wherein the signal output unit has a table in which a correspondence relationship between image brightness and the duty ratio is specified, updates the table in response to the amount of light detected by the photodetector, and determines the duty ratio of the PWM signal based on the updated table.

### Claim 4 (depends on 3)

The display device according to claim 3, wherein the signal output unit updates the table by changing the brightness corresponding to the duty ratio of the predetermined threshold value in the table.

### Claim 5

A method of controlling a display device including a solid-state light source driven by a PWM signal, and a light modulation device that modulates light emitted by the solid-state light source in response to an image signal, comprising:
determining a duty ratio and a current value of the PWM signal;
outputting a PWM signal having a predetermined current value to the solid-state light source if the duty ratio is less than a predetermined threshold value; and
outputting a PWM signal having a current value more than the predetermined current value and increasing as the duty ratio is increases to the solid-state light source if the duty ratio is equal to or more than the predetermined threshold value.

### Claim 6

A display device comprising:
a solid-state light source driven by a PWM signal;
a light modulation device that modulates light emitted by the solid-state light source in response to an image signal; and
a signal output unit that:
determines a duty ratio and a current value of the PWM signal;
outputs a PWM signal having a predetermined current value to the solid-state light source if the duty ratio is less than a predetermined threshold value;
outputs a PWM signal having a second current value larger than the predetermined current value if the duty ratio is equal to or more than a second threshold value larger than the predetermined threshold value; and
outputs a PWM signal having a current value less than the second current value and equal to or more than the predetermined current value in response to the duty ratio if the duty ratio is less than the second threshold value and equal to or more than the predetermined threshold value.

### Claim 7 (depends on 6)

The display device according to claim 6, further comprising a photodetector that detects an amount of light emitted by the solid-state light source,
wherein the signal output unit has a table in which a correspondence relationship between image brightness and the duty ratio is specified, updates the table in response to the amount of light detected by the photodetector, and determines the duty ratio of the PWM signal based on the updated table.

### Claim 8 (depends on 7)

The display device according to claim 7, wherein the signal output unit updates the table by changing the brightness corresponding to the duty ratio of the predetermined threshold value in the table.