Local dimming driving method and device of liquid crystal display device

• US 8,670,006 B2
• Filed: 09/16/2010
• Issued: 03/11/2014
• Est. Priority Date: 12/14/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Hong, Hee-Jung, Oh, Eui-Yeol, Lee, Si-Hoon, Ahn, Hee-Won
• Primary Examiner(s): Mingistu, Amare
• Assistant Examiner(s): Figueroa-Gibson, Gloryvid
• Application Number:
  US12/883,321
• Publication Number:
  US 20110141090A1
• Time in Patent Office: 1,272 Days
• Field of Search: 345/690, 345/102, 345/211, 345/204, 345/87
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• 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 local dimming driving method of the LCD device includes divisionally driving all of a plurality of blocks of a backlight unit using a maximum luminance signal and measuring luminance per block, setting one of the plurality of blocks as a reference block, detecting luminance deviations between the reference block and the residual blocks, and setting an offset value per block for compensating for the detected luminance deviations per block, analyzing an input image in units of blocks corresponding to the plurality of blocks of a backlight unit respectively, detecting a representative value per block, and determining a dimming value per block according to the representative value per block, correcting the dimming value per block using the offset value per block, and controlling the luminance of the backlight unit on a block-by-block basis using the corrected dimming value per block.

Claims

1. A local dimming driving method of a liquid crystal display device, the local dimming driving method comprising:

divisionally driving all of a plurality of blocks of a backlight unit using a maximum luminance signal and measuring luminance per block;

setting one of the plurality of blocks as a reference block, detecting luminance deviations between the reference block and the residual blocks, setting an offset value per block for compensating for the detected luminance deviations per block, and storing the offset value per block in a memory;

analyzing input image data in units of blocks corresponding to the plurality of blocks of the backlight unit respectively, detecting a representative value per block, and determining a dimming value per block according to the representative value per block;

correcting the dimming value per block using the offset value per block to output a corrected diming value per block;

controlling the luminance of the backlight unit on a block-by-block basis using the corrected dimming value per block;

analyzing light quantity of a light source of a block of the backlight unit and storing light profile data in the memory;

calculating a gain value using the light profile data from the memory and the dimming value per block; and

compensating the input image data using the gain value,

wherein;

the gain value is calculated as a ratio between a first total light quantity per pixel when maximum luminance of the backlight unit and a second total light quantity per pixel when luminance of the backlight unit controlled by local dimming,

the first total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data, when the luminance of the backlight unit has a maximum value, and

the second total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data and the dimming value per block, when the luminance of the backlight unit is controlled on the block-by-block basis according to the dimming value per block, thereby multiplying the light quantities reaching each pixel from the light sources of blocks neighboring the each pixel by the local dimming value per block to sum multiplied values.

2. The local dimming driving method according to claim 1, wherein the reference block is a block with a lowest luminance value of the plurality of blocks driven using the maximum luminance signal.

3. The local dimming driving method according to claim 2, wherein:

the offset value per block is a duty ratio of a Pulse Width Modulation (PWM) signal in correspondence with a difference between the luminance value of the reference block and the luminance value of each block, and

the offset value per block is subtracted from the dimming value per block so as to correct the dimming value per block.

4. The local dimming driving method according to claim 2, wherein:

the offset value per block is a ratio of the luminance value of the reference block to the luminance value of each block, and

the dimming value per block is multiplied by the offset value per block so as to correct the dimming value per block.

5. A method of driving a liquid crystal display device, the method comprising:

divisionally driving all of a plurality of blocks of a backlight unit using a maximum luminance signal and measuring luminance per block;

setting one of the plurality of blocks as a reference block, detecting luminance deviations between the reference block and the residual blocks, setting an offset value per block for compensating for the detected luminance deviations per block, and storing the offset value per block in a memory;

analyzing input image data in units of blocks corresponding to the plurality of blocks of the backlight unit respectively, detecting a representative value per block, and determining a dimming value per block according to the representative value per block;

correcting the dimming value per block using the offset value per block to output a corrected diming value per block;

controlling the luminance of the backlight unit on a block-by-block basis using the corrected dimming value per block;

analyzing light quantity of a light source of a block of the backlight unit and storing light profile data in the memory;

calculating a gain value using the light profile data and the dimming value per block;

compensating the input image data using the calculated gain value to output a compensated image data;

supplying the compensated image data to a liquid crystal panel; and

displaying the input image data by a combination of the luminance of the backlight unit controlled on the block-by-block basis and light transmittance controlled by the compensated image data on the liquid crystal panel,

wherein;

the gain value is calculated as a ratio between a first total light quantity per pixel when maximum luminance of the backlight unit and a second total light quantity per pixel when luminance of the backlight unit controlled by local dimming,

the first total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data, when the luminance of the backlight unit has a maximum value, and

the second total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data and the dimming value per block, when the luminance of the backlight unit is controlled on the block-by-block basis according to the dimming value per block, thereby multiplying the light quantities reaching each pixel from the light sources of blocks neighboring the each pixel by the local dimming value per block to sum multiplied values.

6. The method of driving the liquid crystal display device according to claim 5, wherein the reference block is a block with a lowest luminance value of the plurality of blocks driven using the maximum luminance signal.

7. The method of driving the liquid crystal display device according to claim 6, wherein:

the offset value per block is a duty ratio of a Pulse Width Modulation (PWM) signal in correspondence with a difference between the luminance value of the reference block and the luminance value of each block, and

the offset value per block is subtracted from the dimming value per block so as to correct the dimming value per block.

8. The method of driving the liquid crystal display device according to claim 6, wherein:

the offset value per block is a ratio of the luminance value of the reference block to the luminance value of each block, and

the dimming value per block is multiplied by the offset value per block so as to correct the dimming value per block.

9. A local dimming driving device of a liquid crystal display device, the local dimming driving device comprising:

a memory storing an offset value per block and light profile data, wherein the offset value per block is set as a value to compensate for luminance deviations between a reference block and the residual blocks when all of the plurality of blocks of the backlight unit are driven with maximum luminance, and the light profile data are obtained by analyzing the quantity of light of a light source of a block of the backlight unit;

an image analyzer analyzing input image data in units of blocks corresponding to the plurality of blocks of the backlight unit and detecting a representative value per block;

a dimming value decider determining the dimming value per block according to the representative value per block from the image analyzer;

a dimming value corrector correcting the dimming value per block from the dimming value decider using the offset value per block from the memory;

a gain value calculator calculating a gain value using the light profile data from the memory and the dimming value per block from the dimming value decider; and

a data compensator compensating the input image data using the gain value,

wherein;

the gain value is calculated as a ratio between a first total light quantity per pixel when maximum luminance of the backlight unit and a second total light quantity per pixel when luminance of the backlight unit controlled by local dimming,

the first total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data, when the luminance of the backlight unit has a maximum value, and

the second total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data and the dimming value per block, when the luminance of the backlight unit is controlled on the block-by-block basis according to the dimming value per block, thereby multiplying the light quantities reaching each pixel from the light sources of blocks neighboring the each pixel by the local dimming value per block to sum multiplied values.

10. The local dimming driving device according to claim 9, wherein the reference block is a block with a lowest luminance value of the plurality of blocks driven using the maximum luminance signal.

11. The local dimming driving device according to claim 10, wherein:

the offset value per block is a duty ratio of a Pulse Width Modulation (PWM) signal in correspondence with a difference between the luminance value of the reference block and the luminance value of each block, and

the dimming value corrector subtracts the offset value per block from the dimming value per block so as to correct the dimming value per block.

12. The local dimming driving device according to claim 10, wherein:

the offset value per block is a ratio of the luminance value of the reference block to the luminance value of each block, and

the dimming value corrector multiplies the dimming value per block by the offset value per block so as to correct the dimming value per block.

13. A liquid crystal display device comprising:

a local dimming driver analyzing input image data, generating a dimming value per block and compensating the input image data;

a panel driver supplying a compensated image data from the local dimming driver to a liquid crystal panel;

a timing controller outputting the compensated image data from the local dimming driver to the panel driver and controlling driving timing of the panel driver;

a backlight unit including a plurality of blocks to irradiate light to the liquid crystal panel; and

a backlight driver driving the plurality of blocks using the dimming value per block from the local dimming driver,

wherein the local dimming driver comprises;

a memory storing an offset value per block and light profile data, wherein the offset value per block is set as a value to compensate for luminance deviations between a reference block and the residual blocks when all of the plurality of blocks of the backlight unit are driven with maximum luminance, and the light profile data are obtained by analyzing the quantity of light of a light source of a block of the backlight unit;

an image analyzer analyzing the input image data in units of blocks corresponding to the plurality of blocks of the backlight unit and detecting a representative value per block;

a dimming value decider determining the dimming value per block according to the representative value per block from the image analyzer;

a dimming value corrector correcting the dimming value per block from the dimming value decider using the offset value per block from the memory;

a gain value calculator calculating a gain value using the light profile data from the memory and the dimming value per block from the dimming value decider; and

a data compensator compensating the input image data using the gain value,

wherein;

the gain value is calculated as a ratio between a first total light quantity per pixel when maximum luminance of the backlight unit and a second total light quantity per pixel when luminance of the backlight unit controlled by local dimming,

the first total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data, when the luminance of the backlight unit has a maximum value, and

the second total light quantity per pixel is calculated as a sum of light quantities reaching each pixel from the light sources of blocks neighboring the each pixel using the light profile data and the dimming value per block, when the luminance of the backlight unit is controlled on the block-by-block basis according to the dimming value per block, thereby multiplying the light quantities reaching each pixel from the light sources of blocks neighboring the each pixel by the local dimming value per block to sum multiplied values.

14. The liquid crystal display device according to claim 13, wherein the reference block is a block with a lowest luminance value of the plurality of blocks driven using the maximum luminance signal.

15. The liquid crystal display device according to claim 14, wherein:

the offset value per block is a duty ratio of a Pulse Width Modulation (PWM) signal in correspondence with a difference between the luminance value of the reference block and the luminance value of each block, and

the dimming value corrector subtracts the offset value per block from the dimming value per block so as to correct the dimming value per block.

16. The liquid crystal display device according to claim 14, wherein:

the offset value per block is a ratio of the luminance value of the reference block to the luminance value of each block, and

the dimming value corrector multiplies the dimming value per block by the offset value per block so as to correct the dimming value per block.

17. The liquid crystal display device according to claim 13, wherein the backlight unit is a direct or edge type backlight unit.

18. The liquid crystal display device according to claim 13, wherein the local dimming driver is built in the timing controller.