Methods and systems for color preservation with a color-modulated backlight

• US 8,416,179 B2
• Filed: 07/10/2008
• Issued: 04/09/2013
• Est. Priority Date: 07/10/2008
• 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 Joseph
• Primary Examiner(s): Lao, Lun-Yi
• Assistant Examiner(s): Abebe, Sosina
• Application Number:
  US12/170,660
• Publication Number:
  US 20100007599A1
• Time in Patent Office: 1,734 Days
• Field of Search: 345/102, 345/77, 345/204, 345/390, 345/690, 345/82, 345/214, 345/88, 345/89, 345/207, 362 971- 973
• US Class Current: 345/102
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• 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 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• 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 2340/0435 Change or adaptation of the frame rate of the video stream
• 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 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• 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 compensating an image for backlight color variation. Some embodiments comprise compensation for color variation in RGB backlights when backlight color channels use differing gain functions.

Claims

1. A tangible, non-transitory, computer-readable medium comprising computer-readable instructions for instructing a processor to implement a method for adjusting image code values for backlight variations, said method comprising:

a) determining a first backlight intensity value for a first color channel of a backlight element corresponding to a pixel;

b) determining a first ideal gain value to compensate for said first backlight intensity value in said first color channel;

c) determining a first gain equivalent value to compensate for said first backlight intensity value in said first color channel;

d) calculating a first gain reduction factor based on said first ideal gain value and said first gain equivalent value for said first color channel;

e) determining a second backlight intensity value for a second color channel of said pixel;

f) determining a second ideal gain value to compensate for said second backlight intensity value in said second color channel;

g) determining a second gain equivalent value to compensate for said second backlight intensity value in said second color channel;

h) calculating a second gain reduction factor based on said second ideal gain value and said second gain equivalent value for said second color channel;

i) selecting one of said first gain reduction factor related to said first color channel and said second gain reduction factor related to said second color channel as a selected gain reduction factor to be applied to both said first color channel and said second color channel, said selecting being based on color preservation; and

j) determining an adjusted image color channel code value using an original image code value for a color channel of said pixel, said ideal gain and said selected gain reduction factor.

2. A tangible, non-transitory, computer-readable medium as described in claim 1 where in said first ideal gain value is determined with the relationship,

3. A tangible, non-transitory, computer-readable medium as described in claim 1 wherein said second ideal gain value is determined with the relationship,

4. A tangible, non-transitory, computer-readable medium as described in claim 1 wherein said first gain equivalent value is determined with the relationship,

5. A tangible, non-transitory, computer-readable medium as described in claim 1 wherein said first gain reduction factor is determined with the relationship,

6. A method for adjusting image code values for backlight variations, said method comprising:

a) determining a first backlight intensity value for a first color channel of a backlight element corresponding to a pixel;

b) determining a first ideal gain value to compensate for said first backlight intensity value in said first color channel;

c) determining a first gain equivalent value to compensate for said first backlight intensity value in said first color channel;

d) calculating a first gain reduction factor based on said first ideal gain value and said first gain equivalent value for said first color channel;

e) determining a second backlight intensity value for a second color channel of said pixel;

f) determining a second ideal gain value to compensate for said second backlight intensity value in said second color channel;

g) determining a second gain equivalent value to compensate for said second backlight intensity value in said second color channel;

h) calculating a second gain reduction factor based on said second ideal gain value and said second gain equivalent value for said second color channel;

i) selecting one of said first gain reduction factor related to said first color channel and said second gain reduction factor related to said second color channel as a selected gain reduction factor to be applied to both said first color channel and said second color channel, said selecting being based on color preservation; and

j) determining an adjusted image color channel code value using an original image code value for a color channel of said pixel, said ideal gain and said selected gain reduction factor.

7. A method as described in claim 6 wherein said first ideal gain value is determined with the relationship,

8. A method as described in claim 6 wherein said second ideal gain value is determined with the relationship,

9. A method as described in claim 6 wherein said first gain equivalent value is determined with the relationship,

10. A method as described in claim 6 wherein said second gain equivalent value is determined with the relationship,

11. A method as described in claim 6 wherein said first gain reduction factor is determined with the relationship,

12. A method as described in claim 6 wherein said second gain reduction factor is determined with the relationship,

13. A method as described in claim 6 wherein said selecting one of said first gain reduction factor and said second gain reduction factor as a selected gain reduction factor comprises selecting a minimum gain reduction factor that reduces clipping.

14. A method as described in claim 6 wherein said first ideal gain value is determined using a backlight crosstalk matrix.

15. A method as described in claim 6 wherein said second ideal gain value is determined using a backlight crosstalk matrix.

16. A method as described in claim 6 wherein said first gain equivalent value is determined using a backlight crosstalk matrix.

17. A method as described in claim 6 wherein said second gain equivalent value is determined using a backlight crosstalk matrix.

18. A method for adjusting image code values for backlight variations, said method comprising:

a) determining a first backlight intensity value for a first color channel of a pixel;

b) determining a first ideal gain value to compensate for said first backlight intensity value, wherein said first ideal gain value is determined with the relationship,