Local dimming driving method and device of liquid crystal display device

• US 8,427,419 B2
• Filed: 08/10/2010
• Issued: 04/23/2013
• Est. Priority Date: 12/11/2009
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Ahn, Hee-Won, Hong, Hee-Jung, Kwon, Kyung-Joon, Kim, Dong-Woo
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): Trandai, Scott
• Application Number:
  US12/853,811
• Publication Number:
  US 20110141154A1
• Time in Patent Office: 987 Days
• Field of Search: 345/102, 345/690, 345/207, 345/214, 345/694, 362/600, 362 971- 973
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• 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 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

Disclosed herein is a local dimming driving method and device of an LCD device, which is capable of minimizing luminance deviation at the same gray scale due to a dimming difference between blocks. The local dimming driving method of the LCD device includes analyzing input image data in units of blocks and determining a local dimming value per block, performing spatial filtering with respect to the local dimming value per block, repeating spatial filtering by a predetermined repeat count, and controlling luminance of a backlight unit on a block-by-block basis using the local dimming value per block controlled by spatial filtering.

Claims

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

analyzing input image data in units of blocks and determining a local dimming value per block;

performing spatial filtering with respect to the local dimming value per block;

repeating spatial filtering by a predetermined repeat count; and

controlling luminance of a backlight unit on a block-by-block basis using the local dimming value per block controlled by spatial filtering,

wherein the repeat count of spatial filtering is previously set by;

generating a light profile of a light source within the backlight unit, the light profile being obtained by measuring and regulating the quantity of light emitted according to a distance from the light source;

determining a straightness level and a diffusion level of light from the light profile; and

setting the repeat count of spatial filtering in proportion to the straightness level and diffusion level of the light.

2. The local dimming driving method according to claim 1, further comprising:

calculating a gain value using the local dimming value per block; and

compensating the input image data using the gain value.

3. The local dimming driving method according to claim 2, wherein the calculating of the gain value includes:

calculating a first total quantity of light reaching each pixel when the overall luminance of the backlight unit has a maximum value, using the light profile;

calculating a second total quantity of light reaching each pixel when the luminance of the backlight unit is controlled on the block-by-block basis, using the local dimming value per block and the light profile; and

calculating a first gain value on a pixel-by-pixel basis by a ratio of the first total light quantity to the second total light quantity.

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

analyzing input image data in units of blocks and determining a local dimming value per block;

performing spatial filtering with respect to the local dimming value per block;

repeating spatial filtering by a predetermined repeat count;

controlling luminance of a backlight unit on a block-by-block basis using the local dimming value per block controlled by spatial filtering;

calculating a gain value using the local dimming value per block;

compensating the input image data using the gain value;

supplying the compensated 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 data on the liquid crystal panel,

wherein the repeat count of spatial filtering is previously set by;

generating a light profile of a light source within the backlight unit, the light profile being obtained by measuring and regulating the quantity of light emitted according to a distance from the light source;

determining a straightness level and a diffusion level of light from the light profile; and

setting the repeat count of spatial filtering in proportion to the straightness level and diffusion level of the light.

5. The method of driving the liquid crystal display device according to claim 4, wherein the calculating of the gain value includes:

calculating a first total quantity of light reaching each pixel when the overall luminance of the backlight unit has a maximum value, using the light profile;

calculating a second total quantity of light reaching each pixel when the luminance of the backlight unit is controlled on the block-by-block basis, using the local dimming value per block and the light profile; and

calculating a first gain value on a pixel-by-pixel basis by a ratio of the first total light quantity to the second total light quantity.

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

an image analyzer analyzing input image data in units of blocks corresponding to light emitting blocks of a backlight unit;

a dimming value decider determining a local dimming value per block according to the analysis result of the image analyzer;

a spatial filter performing spatial filtering with respect to the local dimming value per block from the dimming value decider, to control the local dimming value per block, and outputting the controlled local dimming value per block; and

a counter counting an output count of the spatial filter and controlling an input/output path of the spatial filter such that the spatial filter repeatedly performs spatial filtering by a predetermined repeat count,

wherein;

a light profile of a light source within the backlight unit is generated,

a straightness level and a diffusion level of light is determined from the light profile, and

the repeat count of spatial filtering is set in proportion to the straightness level and diffusion level of the light, and

wherein the light profile is obtained by measuring and regulating the quantity of light emitted according to a distance from the light source.

7. The local dimming driver according to claim 6, further comprising:

a gain value calculator calculating a gain value using the local dimming value per block from the dimming value decider; and

a data compensator compensating the input image data using the gain value from the gain value calculator.

8. The local dimming driving device according to claim 6, further comprising:

an input selector located at the side of an input terminal of the spatial filter to select and output any one of an output signal from the dimming value decider and a feedback signal from the spatial filter to the spatial filter, under the control of the counter; and

an output selector located at the side of an output terminal of the spatial filter to output the output of the spatial filter in order to drive the backlight unit or to feed back the output of the spatial filter to the input terminal of the spatial filter, under the control of the counter.

9. The local dimming driving device according to claim 7, wherein the gain value calculator:

calculates a first total quantity of light reaching each pixel when the overall luminance of the backlight unit has a maximum value, using the light profile;

calculates a second total quantity of light reaching each pixel when the luminance of the backlight unit is controlled on the block-by-block basis, using the local dimming value per block and the light profile; and

calculates a first gain value on a pixel-by-pixel basis by a ratio of the first total light quantity to the second total light quantity.

10. A liquid crystal display device, comprising:

a local dimming driver analyzing an input image data, generating a local dimming value and compensating an input image data according to the analyzing result;

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

a timing controller outputting the compensated 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 light emitting blocks to irradiate light to the liquid crystal panel; and

a backlight driver driving the light emitting blocks using the dimming value per block from the local dimming driver,

wherein the local dimming driver comprises;

an image analyzer analyzing input image data in units of blocks corresponding to light emitting blocks of a backlight unit,

a dimming value decider determining a local dimming value per block according to the analysis result of the image analyzer,

a spatial filter performing spatial filtering with respect to the local dimming value per block from the dimming value decider, to control the local dimming value per block, and to output the controlled local dimming value per block,

a counter counting an output count of the spatial filter and controlling an input/output path of the spatial filter such that the spatial filter repeatedly performs spatial filtering by a predetermined repeat count,

a gain value calculator calculating a gain value using the local dimming value per block from the dimming value decider, and

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

wherein;

a light profile of a light source within the backlight unit is generated,

a straightness level and a diffusion level of light is determined from the light profile, and

the repeat count of spatial filtering is set in proportion to the straightness level and diffusion level of the light, and

wherein the light profile is obtained by measuring and regulating the quantity of light emitted according to a distance from the light source.

11. The liquid crystal display device according to claim 10, the local dimming driver further comprising:

an input selector located at the side of an input terminal of the spatial filter to select and output any one of an output signal from the dimming value decider and a feedback signal from the spatial filter to the spatial filter, under the control of the counter; and

an output selector located at the side of an output terminal of the spatial filter to output the output of the spatial filter in order to drive the backlight unit or to feed back the output of the spatial filter to the input terminal of the spatial filter, under the control of the counter.

12. The liquid crystal display device according to claim 10, wherein the gain value calculator:

calculates a first total quantity of light reaching each pixel when the overall luminance of the backlight unit has a maximum value, using the light profile;

calculates a second total quantity of light reaching each pixel when the luminance of the backlight unit is controlled on the block-by-block basis, using the local dimming value per block and the light profile; and

calculates a first gain value on a pixel-by-pixel basis by a ratio of the first total light quantity to the second total light quantity.

13. The liquid crystal display device according to claim 10, wherein the local dimming driver is built in the timing controller.