Methods and systems for image tonescale design

• US 8,169,431 B2
• Filed: 12/26/2007
• Issued: 05/01/2012
• Est. Priority Date: 12/26/2007
• Status: Active Grant

• 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: Kerofsky, Louis J.
• Primary Examiner(s): Lao, Lun-Yi
• Assistant Examiner(s): Abebe, Sosina
• Application Number:
  US11/964,691
• Publication Number:
  US 20090167751A1
• Time in Patent Office: 1,588 Days
• Field of Search: 345 87-102, 345/76, 345/77, 345 82- 83, 345/204, 345/214, 345/690, 362 971- 973
• US Class Current: 345/214
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• 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 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• 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 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

Elements of the present invention relate to systems and methods for generating, a modified process for compensating for a reduced source light illumination level as well as a post-compensation process.

Claims

1. A method for generating an image compensation curve that compensates for a source light illumination level and a post-compensation process, said method comprising:

a) selecting a source light illumination level emitted by a light source and impinging upon at least one light valve, from among a plurality of light source illumination levels, by generating an image histogram and an error metric that;

i) assigns respectively varying nonzero weights to each of a plurality of image code values for each of said plurality of light source illumination levels; and

(ii) multiplies each of said weights by a respectively assigned bin count of each of said image code values in said image histogram;

b) determining post-compensation process output points corresponding to a plurality of image code values input to said post-compensation process;

c) generating a source light illumination level compensation curve based on said source light illumination level selected in said selecting;

d) determining source light illumination level compensation curve output points corresponding to input of said post-compensation process output points;

e) determining the input points for said post-compensation process that will result in output of said source light illumination level compensation curve output points; and

f) defining a modified source light illumination level compensation curve by relating said plurality of image code values to said input points for said post-compensation process.

2. A method as described in claim 1 wherein said post-compensation process is a tonescale curve.

3. A method as described in claim 1 wherein said post-compensation process is implemented with a look-up table (LUT).

4. A method as described in claim 3 wherein said determining the input points for said post-compensation process that will result in output of said source light illumination level compensation curve output points comprises using an inverse LUT.

5. A method as described in claim 1 wherein said selecting a source light illumination level comprises generating a display model.

6. A method as described in claim 1 wherein said selecting a source light illumination level comprises weighting said image histogram with said an error vector.

7. A method for compensating an image for a source light illumination level reduction and a post-compensation process, said method comprising:

a) creating an image histogram for an input image;

b) generating a display model for said image based on said image histogram;

c) determining a performance metric for a plurality of source light illumination levels, emitted by a light source and impinging upon at least one light valve from among a plurality of light source illumination levels, with said display model, said performance metric based on an error metric that;

i) assigns respectively varying nonzero weights to each of a plurality of image code values for each of said plurality of light source illumination levels; and

(ii) multiplies each of said weights by a respectively assigned bin count of each of said image code values in said image histogram;

d) selecting a source light illumination level based on said performance metric;

e) determining post-compensation process output points corresponding to a plurality of image code values input to said post-compensation process;

f) generating a source light illumination level compensation curve based on said source light illumination level selected in said selecting;

g) determining source light illumination level compensation curve output points corresponding to input of said post-compensation process output points;

h) determining the input points for said post-compensation process that will result in output of said source light illumination level compensation curve output points;

i) defining a modified source light illumination level compensation curve by relating said plurality of image code values to said input points for said post-compensation process; and

j) processing said image with said modified source light illumination level compensation curve.

8. A method as described in claim 7 wherein said post-compensation process is a tonescale curve.

9. A method as described in claim 7 wherein said post-compensation process is implemented with a look-up table (LUT).

10. A method as described in claim 9 wherein said determining the input points for said post-compensation process that will result in output of said source light illumination level compensation curve output points comprises using an inverse LUT.

11. A method as described in claim 7 wherein said determining a performance metric further comprises weighting said histogram with said error vectors to obtain a distortion value for each of said source light illumination levels.

12. A method as described in claim 11 wherein said selecting a source light illumination level comprises selecting the source light illumination level corresponding to the lowest distortion value.

13. A system for generating an image compensation curve that compensates for a source light illumination level and a post-compensation process, said system comprising:

a) a selector for selecting a source light illumination level emitted by a light source and impinging upon at least one light valve, from among a plurality of source light illumination levels, where said selector calculates an error metric that;

i) assigns respectively varying nonzero weights to each of a plurality of image code values for each of said plurality of light source illumination levels; and

(ii) multiplies each of said weights by a respectively assigned bin count of each of said image code values in said image histogram;

b) a post-compensation process for determining post-compensation process output points corresponding to a plurality of image code values input to said post-compensation process;

c) a source light illumination level compensation curve based on said source light illumination level selected by said selector, wherein said compensation curve determines source light illumination level compensation curve output points corresponding to input of said post-compensation process output points;

d) an inverse post-compensation process for determining the input points for said post-compensation process that will result in output of said source light illumination level compensation curve output points; and

e) a modified curve generator for generating a modified source light illumination level compensation curve by relating said plurality of image code values to said input points for said post-compensation process.

14. A system as described in claim 13 wherein said modified curve generator defines a modified source light illumination level compensation curve by interpolation between a set of control points.

15. A system as described in claim 13 wherein said post-compensation process is implemented with a look-up table (LUT).

16. A system as described in claim 15 wherein said inverse post-compensation process comprises using an inverse LUT.

17. A system as described in claim 13 wherein said selector for selecting a source light illumination level further comprises a display model.