# US 8,570,316 B2 · Liquid crystal display

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- Number: US 8,570,316 B2
- Document ID: US8570316B2
- Status: Granted
- Kind: B2
- Application number: 12/510,207
- Filed: 2009-07-27
- Published: 2010-06-24
- Granted: 2013-10-29
- Earliest claimed: 2008-12-24
- Assignees: LG Display Co., Ltd.
- Applicants: Jiyoung Ahn; Dongwoo Kang
- Inventors: Jiyoung Ahn; Dongwoo Kang
- Web page: https://patentgrep.com/patent/US8570316B2

## CPC

- G09G 3/2003: {Display of colours (specific for liquid crystal displays G09G3/3607)}
- 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 2300/0452: Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
- G09G 2320/0242: Compensation of deficiencies in the appearance of colours
- G09G 2320/0666: for control of colour parameters, e.g. colour temperature
- G09G 2340/06: Colour space transformation
- 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

A liquid crystal display converts white luminance Y of data displaying a white background into a value satisfying a certain equation upon detecting a brightness contrast image including a pure color image with the white background.

## Claims

### Claim 1

A liquid crystal display, comprising:
an RGBW panel having a plurality of data lines, a plurality of gate lines crossing the data lines, a plurality of TFTs connected to crossings between the data lines and the gate lines, and an RGBW pixel structure;
an image conversion unit for converting white luminance Y of data displaying a white background into a value satisfying any one of the following equations upon detecting a brightness contrast image including a pure color image corresponding to any one of a yellow, a cyan, and a magenta image with the white background;
a data driving circuit for converting digital data converted by the image conversion unit into positive/negative analog data voltages; and
a gate driving circuit for supplying gate pulses to the gate lines,
wherein the image conversion unit includes a chromatic analysis part for calculating the luminance of yellow data, cyan data, or magenta data after analyzing pixel data of input RGB digital video data, and determining the pixel data as the yellow data, the cyan data, or the magenta data,
the equations including:
Y
⁡
(
white
)
=
Yref
⁡
(
white
)
×
MIN
⁢
{
Y
⁡
(
yellow
)
Yref
⁡
(
yellow
)
,
Y
⁡
(
cyan
)
Yref
⁡
(
cyan
)
,
Y
⁡
(
magenta
)
Yref
⁡
(
magenta
)
}
,
⁢
Y
⁡
(
white
)
=
Yref
⁡
(
white
)
×
Y
⁡
(
yellow
)
Yref
⁡
(
yellow
)
,
and
Y
⁡
(
white
)
=
Y
⁡
(
yellow
)
wherein Y(X) is a luminance value of color X, Yref(X) is a luminance value of color X of a reference display device having an RGB pixel structure, and MIN Y(X, Y, Z) is the minimum luminance value among X, Y, and Z.

### Claim 2 (depends on 1)

The liquid crystal display of claim 1, further comprising a timing controller for supplying the digital data from the image conversion unit to the data driving circuit and controlling the data driving circuit and the gate driving circuit.

### Claim 3 (depends on 1)

The liquid crystal display of claim 1, wherein the image conversion unit comprises:
a frame buffer for temporarily storing input RGB digital data;
an achromatic analysis part for calculating the luminance of white data after analyzing pixel data of the input RGB digital video data and determining the pixel data as white data;
a chromatic histogram part for analyzing the distribution of gray scales of the luminance values of the pure colors input from the chromatic analysis part;
an achromatic histogram part for analyzing the distribution of gray scales of the luminance values of white input from the achromatic analysis part;
a white/pure color correction part for detecting an image showing a brightness contrast by analyzing pure color histogram information from the chromatic histogram analysis part and achromatic histogram information from the achromatic histogram analysis part and converting the white luminance of the white background into a value satisfying any one of the above equations upon detecting the image having brightness contrast; and
a data conversion part for correcting the white luminance of RGBW pixels displaying the white background of the image having brightness contrast by using the RGB digital data input from the frame buffer and a correction value from the white/pure color correction part.

### Claim 4 (depends on 1)

The liquid crystal display of claim 1, wherein the image conversion unit equalizes the white luminance displaying the white background regardless of a gray scale change when the image having brightness contrast is detected, and increases the white luminance in proportion to a gray scale value when images other than the image having brightness contrast are detected.

### Claim 5

A liquid crystal display, comprising:
an RGBW panel having a plurality of data lines, a plurality of gate lines crossing the data lines, a plurality of TFTs connected to crossings between the data lines and the gate lines, and an RGBW pixel structure;
an image conversion unit for converting one or more of R subpixel data, G subpixel data, B subpixel data, and W subpixel data displaying a pure color image into a value higher than an input value upon detecting a brightness contrast image including a pure color image with a white background;
a data driving circuit for converting digital data converted by the image conversion unit into positive/negative analog data voltages; and
a gate driving circuit for supplying gate pulses to the gate lines,
wherein the image conversion unit equalizes the white luminance displaying the white background regardless of a gray scale change when the image having brightness contrast is detected, and increases the white luminance in proportion to a gray scale value when images other than the image having brightness contrast are detected.

### Claim 6 (depends on 5)

The liquid crystal display of claim 5, wherein, upon detecting a brightness contrast image including a pure color image corresponding to any one of a yellow, a cyan, and a magenta image with the white background, the image conversion unit converts the white luminance Y(white) of data displaying the white background of the brightness contrast image into a value satisfying any one of the following equations:
Y
⁡
(
white
)
=
Yref
⁡
(
white
)
×
MIN
⁢
{
Y
⁡
(
yellow
)
Yref
⁡
(
yellow
)
,
Y
⁡
(
cyan
)
Yref
⁡
(
cyan
)
,
Y
⁡
(
magenta
)
Yref
⁡
(
magenta
)
}
,
⁢
Y
⁡
(
white
)
=
Yref
⁡
(
white
)
×
Y
⁡
(
yellow
)
Yref
⁡
(
yellow
)
,
and
Y
⁡
(
white
)
=
Y
⁡
(
yellow
)
wherein Y(X) is a luminance value of color X, Yref(X) is a luminance value of color X of a reference display device having an RGB pixel structure, and MIN Y(X, Y, Z) is the minimum luminance value among X, Y, and Z.

### Claim 7 (depends on 5)

The liquid crystal display of claim 5, further comprising a timing controller for supplying the digital data from the image conversion unit to the data driving circuit and controlling the data driving circuit and the gate driving circuit.

### Claim 8 (depends on 5)

The liquid crystal display of claim 5, wherein the image conversion unit comprises:
a frame buffer for temporarily storing input RGB digital data;
a chromatic analysis part for calculating the luminance of yellow data, cyan data, or magenta data after analyzing pixel data of the input RGB digital video data, and determining the pixel data as the yellow data, the cyan data, or the magenta;
an achromatic analysis part for calculating the luminance of white data after analyzing pixel data of the input RGB digital video data and determining the pixel data as white data;
a chromatic histogram part for analyzing the distribution of gray scales of the luminance values of the pure colors input from the chromatic analysis part;
an achromatic histogram part for analyzing the distribution of gray scales of the luminance values of white input from the achromatic analysis part;
a white/pure color correction part for detecting an image showing a brightness contrast by analyzing pure color histogram information from the chromatic histogram analysis part and achromatic histogram information from the achromatic histogram analysis part and converting one or more of the subpixel data into a value higher than an input value upon detecting the image having brightness contrast; and
a data conversion part for correcting the white luminance of RGBW pixels displaying the white background of the image having brightness contrast by using the RGB digital data input from the frame buffer and a correction value from the white/pure color correction part.