# US 7,612,757 B2 · Liquid crystal display with modulated black point

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- Number: US 7,612,757 B2
- Document ID: US7612757B2
- Status: Granted
- Kind: B2
- Application number: 10/966,308
- Filed: 2004-10-15
- Published: 2005-11-10
- Granted: 2009-11-03
- Earliest claimed: 2004-05-04
- Assignees: Sharp Laboratories of America, Inc.
- Inventors: Xiao-fan Feng; Scott J. Daly
- Web page: https://patentgrep.com/patent/US7612757B2

## CPC

- G09G 3/3426: {the different display panel areas being distributed in two dimensions, e.g. matrix}
- G09G 3/3413: {Details of control of colour illumination sources}
- G09G 2320/0238: Improving the black level
- G09G 2320/0247: Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
- G09G 2320/0261: in the context of movement of objects on the screen or movement of the observer relative to the screen
- G09G 2320/0276: for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
- G09G 2320/062: Adjustment of illumination source parameters
- G09G 2320/0633: by amplitude modulation of the brightness of the illumination source
- G09G 2320/064: by time modulation of the brightness of the illumination source
- G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other
- G09G 2330/10: Dealing with defective pixels
- 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 backlit display with improved dynamic range. The disclosed display illuminates a pixel of the display at respective non-zero illumination levels during each of a first frame and a second frame and decreases the illumination level of the pixel during the interval between the first frame and the second frame.

## Claims

### Claim 1

A method for displaying an image on a liquid crystal display comprising:
(a) illuminating a first pixel at a first maximum non-zero illumination level during a first frame;
(b) illuminating said first pixel at a second maximum non-zero illumination level during a second frame, wherein said second frame is the next frame immediately following said first frame, wherein said second maximum illumination level is greater than said first maximum illumination level;
(c) wherein said first pixel is decreased in illumination to an intermediate level less than said first maximum illumination level prior to illuminating said first pixel at said second maximum illumination level during said second frame; and
(d) wherein the magnitude and duration of said second maximum non-zero illumination level are automatically calculated as a function of said intermediate level and a target image brightness for said next frame, wherein said function is (Target Brightness−Intermediate level*(frame duration−second maximum illumination level duration))/second maximum illumination level duration and wherein said target image brightness for said second frame is achieved and said duration is as small as can be achieved given the brightest value obtainable by said pixel.