DRIVING METHOD FOR LOCAL DIMMING OF LIQUID CRYSTAL DISPLAY DEVICE AND APPARATUS USING THE SAME

• US 20110148941A1
• Filed: 08/26/2010
• Published: 06/23/2011
• Est. Priority Date: 12/18/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Lee, Si-Hoon, Choo, Kyo-Hyuck, Kim, Dong-Woo
• Granted Patent: US 8,531,385 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A driving method for local dimming of a Liquid Crystal Display (LCD) device and an apparatus using the same are disclosed. The driving method includes determining a dimming value of each of a plurality of local dimming blocks into which a backlight unit is divided to be driven on a block basis by analyzing input image data on a block basis, detecting a high gray area concentrated with high gray levels from each local dimming block based on the analysis of the input image data, and generating position information about the high gray area according to a distance between the high gray area in the block and an adjacent block, and compensating the dimming value of each of the plurality of local dimming blocks by spatial filtering using a spatial filter having a different filter size or different filter coefficients for local dimming blocks according to the position information about the high gray area in the local dimming block.

Claims

1. A driving method for local dimming of a Liquid Crystal Display (LCD) device, comprising:

determining a dimming value of each of a plurality of local dimming blocks into which a backlight unit is divided to be driven on a block basis by analyzing input image data on a block basis;

detecting a high gray area concentrated with high gray levels from each local dimming block based on the analysis of the input image data, and generating position information about the high gray area according to a distance between the high gray area in the block and an adjacent block; and

compensating the dimming value of each of the plurality of local dimming blocks by spatial filtering using a spatial filter having a different filter size or different filter coefficients for local dimming blocks according to the position information about the high gray area in the local dimming block.

2. The driving method according to claim 1, further comprising calculating a first gain value on a pixel basis using the dimming values of the local dimming blocks and an optical profile of a preset light source and compensating the input image data by applying the first gain values of pixels to the input image data.

3. The driving method according to claim 2, further comprising:

calculating a second gain value on a frame basis for use in converting a maximum value of compensated image data of one frame to a maximum gray level representable in the input image data, and secondarily compensating the compensated image data by applying the second gain values of frames to the compensated image data; and

secondarily compensating the compensated local dimming values of the local dimming blocks by applying the second gain values to the compensated local dimming values.

4. The driving method according to claim 3, wherein as the distance between the high gray area in the block and the adjacent block is larger, the spatial filter size used is smaller.

5. The driving method according to claim 3, wherein as the distance between the high gray area in the block and the adjacent block is larger, the filter coefficients for the blocks used are smaller.

6. The driving method according to claim 3, further comprising:

providing the secondarily compensated image data to a liquid crystal panel; and

controlling luminance of the backlight unit on a block basis by driving the backlight unit on a block basis using the secondarily compensated dimming values of the local dimming blocks.

7. A driving apparatus for local dimming of a Liquid Crystal Display (LCD) device, comprising:

an image analyzer that detects a maximum value for each pixel by analyzing input image data over each of a plurality of local dimming blocks into which a backlight unit is divided to be driven on a block basis, and detects a representative gray level for each block using the maximum values of pixels in the block;

a dimming value decider that determines a dimming value on a block basis according to the representative gray level of each block;

a high gray area detector that detects a high gray area concentrated with high gray levels from each block based on the maximum value of each pixel received from the image analyzer, and generates position information about the high gray area according to a distance between the high gray area in the block and an adjacent block; and

a dimming value compensator that compensates the dimming value of each of the plurality of local dimming blocks by spatial filtering using a spatial filter having a different filter size or different filter coefficients for blocks according to the position information about the high gray area in the block.

8. The driving apparatus according to claim 7, further comprising a data compensator that calculates a first gain value on a pixel basis using the dimming values of the local dimming blocks received from the dimming value decider and an optical profile of a preset light source and compensates the input image data by applying the first gain values of pixels to the input image data.

9. The driving apparatus according to claim 8, further comprising:

a second data compensator that calculates a second gain value on a frame basis for use in converting a maximum value of compensated image data of one frame received from the data compensator to a maximum gray level representable in the input image data, and secondarily compensates the compensated image data by applying the second gain values of frames to the compensated image data; and

a second dimming value compensator that secondarily compensates the compensated local dimming values of the local dimming blocks by applying the second gain values received from the second data compensator to the compensated local dimming values.

10. The driving apparatus according to claim 9, wherein as the distance between the high gray area in the block and the adjacent block is larger, the spatial filter size is smaller.

11. The driving apparatus according to claim 9, wherein as the distance between the high gray area in the block and the adjacent block is larger, the filter coefficients for the blocks are smaller.

12. The driving apparatus according to claim 9, further comprising:

a panel driver that provides the secondarily compensated image data to a liquid crystal panel; and

a backlight driver that controls luminance of the backlight unit on a block basis by driving the backlight unit on a block basis using the secondarily compensated dimming values of the local dimming blocks.