Method for enhancing an image displayed on an LCD device

• US 8,400,385 B2
• Filed: 12/21/2007
• Issued: 03/19/2013
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Original Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Inventors: Peng, Huajun, Zhang, Wei, Hung, Chun Kit
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): LAM, VINH TANG
• Application Number:
  US11/962,320
• Publication Number:
  US 20090160877A1
• Time in Patent Office: 1,915 Days
• Field of Search: 345/38, 345/50, 345/60, 345/64, 345 87- 90, 345/97, 345/102, 345/104, 345/690, 349/173
• US Class Current: 345/89
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A method and apparatus for image enhancement in a display illuminated by a lighting device. Enhancement is via use of a non-linear mapping function. An illumination level for the lighting device is determined and used with the mapping function to find a compensation factor for each pixel of the image. The brightness property of each pixel is adjusted by its compensation factor.

Claims

1. A method for controlling a display controller to enhance an image displayed on a display that is controlled by the display controller and illuminated by a lighting device, the image comprising a plurality of pixels, each pixel having an individually adjustable property, the display comprising a transmittance level for each pixel of the image, the method comprising:

storing a mapping function in a non-transitory machine readable storage medium of the display controller, wherein the mapping function includes a linearly decreasing mapping portion, a non-linear mapping portion, and a constant portion;

determining an illumination level of the lighting device for each pixel;

determining, by use of the mapping function and the illumination level, a respective compensation factor for each pixel, including

using the linearly decreasing mapping portion to determine the compensation factor when the illumination level is below a first threshold,

using the non-linear mapping portion to determine the compensation factor when the illumination level is above the first threshold and below a second threshold; and

using the constant portion to determine the compensation factor when the illumination level is above the second threshold;

adjusting the property of each pixel by the compensation factor of the respective pixel; and

adjusting the transmittance level of the display for each pixel by the adjusted property of the respective pixel.

2. The method of claim 1 wherein the mapping function relates lighting device illumination levels to compensation factors.

3. The method of claim 1 wherein each compensation factor decreases or remains constant with increasing illumination level.

4. The method of claim 1 including storing the mapping function as a single dimensional look-up table relating lighting device illumination levels to compensation factors.

5. The method of claim 1 including expressing the linearly decreasing mapping portion as an equation of the form

6. The method of claim 5 including determining a based on display characteristics.

7. The method of claim 1 wherein

the lighting device comprises a plurality of illumination regions, each illumination region having an illumination level and illuminating one or more pixels, and

determining the compensation factor of each pixel based on the illumination level of the illumination region illuminating the pixel.

8. The method of claim 7 wherein the mapping function maps illumination levels to corresponding compensation factors.

9. The method of claim 1 when practiced in a liquid crystal display (LCD) panel illuminated by a dynamically illuminated backlight device having a plurality of independently controllable illumination regions.

10. The method of claim 1 wherein the image is a video image in which the plurality of pixels comprise a plurality of sequential video image frames.