# US 11,308,895 B2 · Liquid crystal display device, image displaying method thereof, and backlight control device for local dimming

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- Number: US 11,308,895 B2
- Document ID: US11308895B2
- Status: Granted
- Kind: B2
- Application number: 16/625,715
- Filed: 2019-11-12
- Published: 2021-10-28
- Granted: 2022-04-19
- Earliest claimed: 2019-08-06
- Applicants: Tcl China Star Optoelectronics Technology Co., Ltd.
- Inventors: Jiang Zhu
- Web page: https://patentgrep.com/patent/US11308895B2

## CPC

- G09G 3/3406: {Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336)}
- G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines}
- G09G 3/36: using liquid crystals
- G09G 3/3611: {Control of matrices with row and column drivers}
- G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other
- G09G 2320/066: for control of contrast
- G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data
- 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)

## Abstract

The present disclosure provides a liquid crystal display device, an image displaying method thereof, and a backlight control device by disposing the backlight control device between a backlight module and a liquid crystal display panel, wherein the backlight control device divides an image into a plurality of pixel units, calculates corresponding dimming coefficients of the pixel units, and adjusts a first optical signal output by the backlight module according to a plurality of dimming coefficients to output a plurality of second optical signals, thereby achieving local dimming and improving display contrast of the liquid crystal display device.

## Claims

### Claim 1

A liquid crystal display device, comprising a backlight module, a backlight control device, and a liquid crystal display panel, wherein the backlight control device is disposed between the backlight module and the liquid crystal display panel;
the backlight module is used to output a first optical signal;
the backlight control device is used to receive an image signal and the first optical signal, to divide an image into a plurality of pixel units (j, i), to analyze pixel information of the pixel units (j, i) to correspondingly output a plurality of dimming coefficients, and to adjust the first optical signal according to the dimming coefficients to output a plurality of second optical signals; and
the liquid crystal display panel is used to receive the second optical signals to display the image corresponding to the image signal;
wherein each of the pixel units (j, i) comprises at least one pixel, each of the pixel units (j, i) corresponds to each of the dimming coefficients, j represents a row where the pixel unit (j, i) is located, and i represents a column where the pixel unit (j, i) is located,
wherein the backlight control device comprises a processor and a plurality of backlight control units, the processor is used to receive the image signal, to divide the image into the plurality of pixel units (j, i), and to analyze the pixel information of the pixel units (j, i) to correspondingly output the plurality of dimming coefficients, and each of the backlight control units is used to adjust the first optical signal according to each of the dimming coefficients to correspondingly output each of the second optical signals, and
wherein the processor comprises a first dimming coefficient output unit used to receive the image signal, to divide the image into the plurality of pixel units (j, i), to calculate a maximum grayscale value Ymax and an average brightness value Yav each of the pixel units (j, i), and then to calculate a first dimming coefficient L(j, i) corresponding to each of the pixel units (j, i) according to a following formula (1):
L(j,i)=(1−α)×Yav+αYmax (1),
wherein α is a weighting coefficient, when a value of Ymax is less than or equal to a first threshold, α is 0; when the value of Ymax is greater than or equal to a second threshold, α is 1; and when the value of Ymax is greater than the first threshold and less than the second threshold, α=kYmax, wherein k is a constant greater than 0; and
the first dimming coefficient L(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).

### Claim 2 (depends on 1)

The liquid crystal display device according to claim 1, wherein the processor comprises a first dimming coefficient output unit and a spatial filter, the first dimming coefficient output unit is used to receive the image signal, to divide the image into the plurality of pixel units (j, i), to calculate a maximum grayscale value Ymax and an average brightness value Yav of each of the pixel units (j, i), and then to calculate a first dimming coefficient L(j, i) corresponding to each of the pixel units (j, i) according to a following formula (1):
L(j,i)=(1−α)×Yav+αYmax (1),
wherein α is a weighting coefficient, when a value of Ymax is less than or equal to a first threshold, α is 0; when the value of Ymax is greater than or equal to a second threshold, α is 1; and when the value of Ymax is greater than the first threshold and less than the second threshold, α=kYmax, wherein k is a constant greater than 0; and
the spatial filter is used to spatial filter the first dimming coefficient L(j, i) corresponding to each of the pixel units(j, i) to output a second dimming coefficient Lfin(j, i) corresponding to each of the pixel units(j, i), and the second dimming coefficient Lfin(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).

### Claim 3 (depends on 2)

The liquid crystal display device according to claim 2, wherein the spatial filter comprises a maximum neighborhood dimming coefficient computing unit, a smoothing factor computing unit, and a second dimming coefficient output unit,
the maximum neighborhood dimming coefficient computing unit is used to calculate a maximum neighborhood dimming coefficient Nmax of the pixel unit (j, i) according to a following formula (2):
Nmax max(L(j−1,i−1),L(j−1,i),L(j−1,i+1),L(j,i−1),L(j,i+1),L(j+1,i−1),L(j+1,i),L(j+1,i+1)) (2),
wherein the L(j−1, i−1) is a first dimming coefficient of a pixel unit (j−1, i−1), the L(j−1, i) is a first dimming coefficient of a pixel unit (j−1, i), the L(j−1, i+1) is a first dimming coefficient of a pixel unit (j−1, i+1), the L(j, i−1) is a first dimming coefficient of a pixel unit (j, i−1), the L(j, i+1) is a first dimming coefficient of a pixel unit (j, i+1), the L(j+1, i−1) is a first dimming coefficient of a pixel unit (j+1, i−1), the L(j+1, i) is a first dimming coefficient of a pixel unit (j+1, i), and the L(j+1, i+1) is a first dimming coefficient of a pixel unit (j+1, i+1);
the smoothing factor computing unit is used to calculate a smoothing factor sfmax of the pixel unit (j, i) according to a following formula (3):
sfmax=(1−tsf)×Nmax (3),
wherein tsf is a regulation coefficient and is a constant ranging from 0 to 1, and Nmax is the maximum neighborhood dimming coefficient of the pixel unit (j, i); and
the second dimming coefficient output unit is used to calculate the second dimming coefficient Lfin(j, i) of the pixel unit (j, i) according to a following formula (4):
Lfin(j,i)=max(L(j,i),sfmax) (4),
wherein L(j, i) is the first dimming coefficient of the pixel unit (j, i), and sfmax is the smoothing factor of the pixel unit (j, i).

### Claim 4 (depends on 1)

The liquid crystal display device according to claim 1, wherein the liquid crystal display panel comprises a plurality of image display pixel units, each of the image display pixel units comprises at least one image display pixel, the image display pixel units correspond to the backlight control units by one to one and receive the second optical signals output by the corresponding backlight control units, and the at least one image display pixel corresponds to the pixel of the image by one to one.

### Claim 5 (depends on 4)

The liquid crystal display device according to claim 4, wherein each of the image display pixel units comprises four image display pixels, and each of the pixel units (j, i) comprises four pixels.

### Claim 6 (depends on 1)

The liquid crystal display device according to claim 1, wherein the backlight control device comprises a liquid crystal panel, and the liquid crystal panel comprises the plurality of backlight control units.

### Claim 7

An image displaying method of a liquid crystal display device, wherein the liquid crystal display device comprises a backlight module, a backlight control device, and a liquid crystal display panel, the backlight control device is disposed between the backlight module and the liquid crystal display panel, and the method comprises following steps:
the backlight module outputting a first optical signal;
the backlight control device receiving an image signal and the first optical signal, dividing an image into a plurality of pixel units (j, i), analyzing pixel information of the pixel units (j, i) to correspondingly output a plurality of dimming coefficients, and adjusting the first optical signal according to the dimming coefficients to output a plurality of second optical signals; and
the liquid crystal display panel receiving the second optical signals to display the image corresponding to the image signal;
wherein each of the pixel units (j, i) comprises at least one pixel, each of the pixel units (j, i) corresponds to each of the dimming coefficients, j represents a row where the pixel unit (j, i) is located, and i represents a column where the pixel unit (j, i) is located,
wherein the backlight control device comprises a processor and a plurality of backlight control units, the processor receives the image signal, divides the image into the plurality of pixel units (j, i), and analyzes the pixel information of the pixel units (j, i) to correspondingly output the plurality of dimming coefficients, and each of the backlight control units adjusts the first optical signal according to each of the dimming coefficients to correspondingly output each of the second optical signals, and
wherein the processor comprises a first dimming coefficient output unit used to receive the image signal, to divide the image into the plurality of pixel units (j, i), to calculate a maximum grayscale value Ymax and an average brightness value Yav of each of the pixel units (j, i), and then to calculate a first dimming coefficient L(j, i) corresponding to each of the pixel units (j, i) according to a following formula (1):
L(i,i)=(1−α)×Yav+αYmax (1),
wherein α is a weighting coefficient, when a value of Ymax is less than or equal to a first threshold, α is 0; when the value of Ymax is greater than or equal to a second threshold, α is 1; and when the value of Ymax is greater than the first threshold and less than the second threshold, α=kYmax, wherein k is a constant greater than 0; and
the first dimming coefficient L(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).

### Claim 8

A backlight control device, used to receive an image signal and a first optical signal, to divide an image into a plurality of pixel units (j, i), to analyze pixel information of the pixel units (j, i) to correspondingly output a plurality of dimming coefficients, and to adjust the first optical signal according to the dimming coefficients to output a plurality of second optical signals;
wherein each of the pixel units (j, i) comprises at least one pixel, each of the pixel units (j, i) corresponds to each of the dimming coefficients, j represents a row where the pixel unit (j, i) is located, and i represents a column where the pixel unit (j, i) is located,
wherein the backlight control device comprises a processor and a plurality of backlight control units, wherein the processor is used to receive the image signal, to divide the image into the plurality of pixel units (j, i), and to analyze the pixel information of the pixel units (j, i) to correspondingly output the plurality of dimming coefficients, and each of the backlight control units is used to adjust the first optical signal according to each of the dimming coefficients to correspondingly output each of the second optical signals, and
wherein the processor comprises a first dimming coefficient output unit used to receive the image signal, to divide the image into the plurality of pixel units (j, i), to calculate a maximum grayscale value Ymax and an average brightness value Yav of each of the pixel units (j, i), and then to calculate a first dimming coefficient L(j, i) corresponding to each of the pixel units (j, i) according to a following formula (1):
L(j,i)=(1−α)×Yav+αYmax (1),
wherein α is a weighting coefficient, when a value of Ymax is less than or equal to a first threshold, α is 0; when the value of Ymax is greater than or equal to a second threshold, α is 1; and when the value of Ymax is greater than the first threshold and less than the second threshold, α=kYmax, wherein k is a constant greater than 0; and
the first dimming coefficient L(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).

### Claim 9 (depends on 8)

The backlight control device according to claim 8, wherein the processor comprises a spatial filter,
the spatial filter is used to spatial filter the first dimming coefficient L(j, i) corresponding to each of the pixel units(j, i) to output a second dimming coefficient Lfin(j, i) corresponding to each of the pixel units(j, i), and the second dimming coefficient Lfin(j, i) is the dimming coefficient corresponding to each of the pixel units (j, i).

### Claim 10 (depends on 9)

The backlight control device according to claim 9, wherein the spatial filter comprises a maximum neighborhood dimming coefficient computing unit, a smoothing factor computing unit, and a second dimming coefficient output unit,
the maximum neighborhood dimming coefficient computing unit is used to calculate a maximum neighborhood dimming coefficient Nmax of the pixel unit (j, i) according to a following formula (2):
Nmax max(L(j−1,i−1),L(j−1,i),L(j−1,i+1),L(j,i−1),L(j,i+1),L(j+1,i−1),L(j+1,i),L(j+1,i+1)) (2),
wherein the L(j−1, i−1) is a first dimming coefficient of a pixel unit (j−1, i−1), the L(j−1, i) is a first dimming coefficient of a pixel unit (j−1, i), the L(j−1, i+1) is a first dimming coefficient of a pixel unit (j−1, i+1), the L(j, i−1) is a first dimming coefficient of a pixel unit (j, i−1), the L(j, i+1) is a first dimming coefficient of a pixel unit (j, i+1), the L(j+1, i−1) is a first dimming coefficient of a pixel unit (j+1, i−1), the L(j+1, i) is a first dimming coefficient of a pixel unit (j+1, i), and the L(j+1, i+1) is a first dimming coefficient of a pixel unit (j+1, i+1);
the smoothing factor computing unit is used to calculate a smoothing factor sfmax of the pixel unit (j, i) according to a following formula (3):
sfmax=(1−tsf)×Nmax (3),
wherein tsf is a regulation coefficient and is a constant ranging from 0 to 1, and Nmax is the maximum neighborhood dimming coefficient of the pixel unit (j, i);
the second dimming coefficient output unit is used to calculate the second dimming coefficient Lfin(j, i) of the pixel unit (j, i) according to a following formula (4):
Lfin(j,i)=max(L(j,i),sfmax) (4),
wherein L(j, i) is the first dimming coefficient of the pixel unit (j, i), and sfmax is the smoothing factor of the pixel unit (j, i).

### Claim 11 (depends on 8)

The backlight control device according to claim 8, comprising a liquid crystal panel, and the liquid crystal panel comprises a plurality of backlight control units.