Methods and systems for motion adaptive backlight driving for LCD displays with area adaptive backlight

• US 8,026,894 B2
• Filed: 08/22/2007
• Issued: 09/27/2011
• Est. Priority Date: 10/15/2004
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Feng, Xiao-Fan
• Primary Examiner(s): Beck; Alexander S
• Assistant Examiner(s): HICKS, CHARLES V
• Application Number:
  US11/843,529
• Publication Number:
  US 20070285382A1
• Time in Patent Office: 1,497 Days
• Field of Search: 345/102
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• 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 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2320/106 Determination of movement vectors or equivalent parameters within the image
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• 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

Elements of the present invention relate to systems and methods for generating, modifying and applying backlight array driving values.

Claims

1. A method for generating a backlight image for a display backlight array, said method comprising:

a) receiving an input image comprising an array of pixel values representing an image at a first resolution;

b) subsampling said input image to create an intermediate resolution image, wherein said intermediate resolution image has a resolution that is lower than said first resolution and wherein said intermediate resolution image comprises sub-block values, each of which correspond to a different plurality of input image pixel values;

c) determining a current-frame sub-block characteristic for each of said pluralities of input image pixel values;

d) determining a previous-frame sub-block characteristic for pluralities of input image pixel values in a previous frame;

e) creating a motion map with motion elements for each backlight element, wherein the resolution of said backlight elements is less than said intermediate resolution and a plurality of said sub-blocks corresponds to one of said motion elements, said creating occurring by comparing said previous-frame sub-block characteristics to said current-frame sub-block characteristics, wherein one of said motion elements, indicates motion when one of said previous-frame sub-block characteristics, for a particular sub-block corresponding to said motion element, is substantially different than the current-frame sub-block characteristic corresponding to said particular sub-block;

f) creating a motion status map, wherein said motion status map comprises motion status elements corresponding to each of said motion elements, wherein the value of said motion status elements increases incrementally with each successive frame to a maximum motion status value when a corresponding motion status element of a previous frame indicates motion and the value of said motion status elements decreases incrementally with each successive frame to a minimum motion status value when a corresponding motion status element of a previous frame does not indicate motion;

g) calculating a local LED maximum value within a window containing a current LED driving value;

h) calculating, based on a corresponding one of said motion status elements, an updated LED driving value that is a weighted combination of said current LED driving value and said LED maximum value.

2. A method as described in claim 1 further comprising low-pass filtering said input image to create said intermediate-resolution image.

3. A method as described in claim 1 wherein said previous-frame sub-block characteristic and said current-frame sub-block characteristic are average pixel values for pixels corresponding to said sub-blocks.

4. A method as described in claim 1 wherein said maximum motion status value is 4.

5. A method as described in claim 1 wherein said minimum motion status value is 0.

6. A method as described in claim 1 wherein said creating a motion status map comprises assigning a value to a motion status element that is the minimum of 4 and one more than the motion status element of a corresponding motion status element in a previous frame when said motion status element corresponds to a motion element that indicates motion.

7. A method as described in claim 1 wherein said creating a motion status map comprises assigning a value to a motion status element that is the maximum of zero and one less than the value of a corresponding motion status element in a previous frame when said motion status element corresponds to a motion element that does not indicate motion.

8. A method as described in claim 1 wherein said updated LED driving value is calculated with the following equation:

9. A method as described in claim 1 wherein said LED maximum value window is a square window centered on said current LED driving value.

10. A method as described in claim 1 wherein said LED maximum value window is a one-dimensional window aligned with a motion vector corresponding to said current LED driving value.

11. A method for generating a backlight image for a display backlight array, said method comprising:

a) receiving an input image comprising an array of pixel values representing an image at a first resolution;

b) low-pass filtering said input image to create a low-pass filtered (LPF) image;

c) subsampling said LPF image to create an LED resolution image, wherein said LED resolution image has a resolution that is lower than said first resolution and wherein said LED resolution image comprises backlight elements, each of which correspond to a different plurality of input image pixel values;

d) creating a motion map with motion elements for each backlight element, wherein the resolution of said backlight elements is the same as said LED resolution, and wherein said motion elements indicate motion based on a comparison of current frame characteristics and previous frame characteristics;

e) creating a motion status map, wherein said motion status map comprises motion status elements corresponding to each of said motion elements, wherein the value of said motion status elements increases incrementally with each successive frame to a maximum motion status value when a corresponding motion status element of a previous frame indicates motion and the value of said motion status elements decreases incrementally with each successive frame to a minimum motion status value when a corresponding motion status element of a previous frame does not indicate motion;

f) calculating a local LED maximum value within a window containing a current LED driving value;

g) calculating, based on a corresponding one of said motion status elements, an updated LED driving value that is a weighted combination of said current LED driving value and said LED maximum value.

12. A method as described in claim 11 wherein said maximum motion status value is 4.

13. A method as described in claim 11 wherein said minimum motion status value is 0.

14. A method as described in claim 11 wherein said creating a motion status map comprises assigning a value to a motion status element that is the minimum of 4 and one more than the motion status element of a corresponding motion status element in a previous frame when said motion status element corresponds to a motion element that indicates motion.

15. A method as described in claim 11 wherein said creating a motion status map comprises assigning a value to a motion status element that is the maximum of zero and one less than the value of a corresponding motion status element in a previous frame when said motion status element corresponds to a motion element that does not indicate motion.

16. A method as described in claim 11 wherein said updated LED driving value is calculated with the following equation:

17. A method as described in claim 11 wherein said LED maximum value window is a square window centered on said current LED driving value.

18. A method as described in claim 11 wherein said LED maximum value window is a one-dimensional window aligned with a motion vector corresponding to said current LED driving value.

19. A method for selective isotropic and anisotropic error diffusion of out-of-range display backlight values, said method comprising:

a) determining an out-of-range error in a backlight value for a backlight element;

b) resetting said backlight value to an in-range value;

c) sorting the backlight values of neighboring backlight elements in ascending order;

d) increasing the values of said neighboring backlight elements proportionally when the minimum of a difference threshold and one half said error is greater than the difference between the maximum and the minimum of said neighboring backlight element values; and

e) increasing said neighboring backlight element values in said ascending order by multiplying each of said element values by coefficients of decreasing value such that the lowest of said element values is multiplied by the largest coefficient and the highest of said element values is multiplied by the smallest coefficient.

20. A method for generating a backlight image for a display backlight array, said method comprising:

receiving an input image comprising an array of pixel values representing an image at a first resolution;

subsampling said input image to create an intermediate resolution image, wherein said intermediate resolution image has a resolution that is lower than said first resolution and wherein said intermediate resolution image comprises sub-block values, each of which correspond to a different plurality of input image pixel values;

determining a current-frame sub-block characteristic for each of said pluralities of input image pixel values;

determining a previous-frame sub-block characteristic for pluralities of input image pixel values in a previous frame;

creating a motion map with motion elements for each backlight element, wherein the resolution of said backlight elements is less than said intermediate resolution and a plurality of said sub-blocks corresponds to one of said motion elements, said creating occurring by comparing said previous-frame sub-block characteristics to said current-frame sub-block characteristics, wherein one of said motion elements, indicates motion when one of said previous-frame sub-block characteristics, for a particular sub-block corresponding to said motion element, is substantially different than the current-frame sub-block characteristic corresponding to said particular sub-block;

creating a motion status map, wherein said motion status map comprises motion status elements corresponding to each of said motion elements, wherein the value of said motion status elements increases incrementally with each successive frame to a maximum motion status value when a corresponding motion status element of a previous frame indicates motion and the value of said motion status elements decreases incrementally with each successive frame to a minimum motion status value when a corresponding motion status element of a previous frame does not indicate motion;

calculating a local LED maximum value within a window containing a current LED driving value;

calculating an updated LED driving value wherein said updated LED driving value is calculated with the following equation;

21. A method for generating a backlight image for a display backlight array, said method comprising:

receiving an input image comprising an array of pixel values representing an image at a first resolution;

low-pass filtering said input image to create a low-pass filtered (LPF) image;

subsampling said LPF image to create an LED resolution image, wherein said LED resolution image has a resolution that is lower than said first resolution and wherein said LED resolution image comprises backlight elements, each of which correspond to a different plurality of input image pixel values;

creating a motion map with motion elements for each backlight element, wherein the resolution of said backlight elements is the same as said LED resolution, and wherein said motion elements indicate motion based on a comparison of current frame characteristics and previous frame characteristics;

creating a motion status map, wherein said motion status map comprises motion status elements corresponding to each of said motion elements, wherein the value of said motion status elements increases incrementally with each successive frame to a maximum motion status value when a corresponding motion status element of a previous frame indicates motion and the value of said motion status elements decreases incrementally with each successive frame to a minimum motion status value when a corresponding motion status element of a previous frame does not indicate motion;

calculating a local LED maximum value within a window containing a current LED driving value;

calculating an updated LED driving value, wherein said updated LED driving value is calculated with the following equation;