Methods and Systems for Image Tonescale Adjustment to Compensate for a Reduced Source Light Power Level

• US 20070092139A1
• Filed: 11/28/2006
• Published: 04/26/2007
• Est. Priority Date: 12/02/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott
• Granted Patent: US 7,768,496 B2
• Time in Patent Office: Days
• US Class Current: 382/169
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

Embodiments of the present invention comprise systems, methods and devices for increasing the perceived brightness of an image. In some embodiments this increase compensates for a decrease in display light-source illumination.

Claims

1. A method for adjusting an image for display with a reduced source light power level, said method comprising:

a) creating an input image histogram for an input image;

b) locating a histogram feature on said input image histogram;

c) finding an input image histogram feature code value corresponding to said histogram feature;

d) determining an enhanced feature code value based on said input image histogram feature code value and a reduced source light power level;

e) establishing a tonescale correction curve fitted to said enhanced feature code value; and

f) processing at least a portion of said input image with said tonescale correction curve.

2. A method as described in claim 1 wherein said histogram feature is a histogram peak.

3. A method as described in claim 1 wherein said determining comprises calculating a simulated, reduced-power histogram, finding the difference between the code value of the input image histogram feature and the simulated, reduced-power histogram feature and adding said difference to the input image histogram feature code value.

4. A method as described in claim 1 wherein said determining comprises mapping said input image histogram feature code value to an enhanced code value with a display luminance model.

5. A method as described in claim 1 wherein said determining comprises finding a code value that will emit substantially the same luminance from a display using a reduced source light power level as said image histogram feature code value would emit from said display using a full power source light.

6. A method as described in claim 1 wherein said processing at least a portion of said image comprises applying said tonescale correction curve to specific frequency range of said image.

7. A method as described in claim 1 wherein said establishing a tonescale correction curve comprises fitting a power curve to said enhanced feature code value and a point that maps a zero input code value to zero output code value.

8. A method as described in claim 1 wherein said establishing a tonescale correction curve comprises fitting a power curve to said enhanced feature code value, a point that maps a zero input code value to zero output code value and a point that maps a maximum input code value to a maximum output code value.

9. A method for adjusting an image for display with a reduced source light power level, said method comprising:

a) creating an input image histogram for an input image;

b) locating an input image histogram peak on said input image histogram;

c) finding an input image histogram peak code value corresponding to said histogram peak;

d) determining an enhanced peak code value that will cause a display to emit a substantially similar amount of light at a reduced source light power level to what the input image histogram peak code value would cause said display to emit with a full power source light; and

e) calculating a tonescale correction curve that intersects said enhanced peak code value.

10. A method as described in claim 9 wherein said determining an enhanced peak code value comprises calculating a simulated, reduced-power histogram, finding the difference between the code value of the input image histogram peak and the simulated, reduced-power histogram peak and adding said difference to the input image histogram peak code value.

11. A method as described in claim 9 wherein said determining an enhanced peak code value comprises mapping said input image histogram peak code value to an enhanced peak code value with a display luminance model.

12. A method as described in claim 9 further comprising applying said tonescale correction curve to a specific frequency range of said image.

13. A method as described in claim 9 wherein said calculating a tonescale correction curve comprises fitting a power curve to said enhanced peak code value and a point that maps a zero input code value to a zero output code value.

14. A method as described in claim 9 wherein said calculating a tonescale correction curve comprises fitting a power curve to said enhanced peak code value, a point that maps a zero input code value to a zero output code value and a point that maps a maximum input code value to a maximum output code value.

15. A system for adjusting an image for display with a reduced source light power level, said system comprising:

a) a histogram generator for creating an input image histogram for an input image;

b) a peak detector for locating an input image histogram peak on said input image histogram and a code value corresponding to said histogram peak;

c) a processor for determining an enhanced peak code value that will cause a display to emit a substantially similar amount of light at a reduced source light power level to what the input image histogram peak code value would cause said display to emit with a full power source light; and

d) a tonescale correction calculator for calculating a tonescale correction curve that intersects said enhanced peak code value.

16. A system as described in claim 15 wherein said processor for determining an enhanced peak code value calculates a simulated, reduced-power histogram, finds the difference between the code value of the input image histogram peak and the simulated, reduced-power histogram peak and adds said difference to the input image histogram peak code value.

17. A system as described in claim 15 wherein said processor for determining an enhanced peak code value maps said input image histogram peak code value to an enhanced peak code value with a display luminance model.

18. A system as described in claim 15 wherein said calculator for calculating a tonescale correction curve fits a power curve to said enhanced peak code value.

19. A system as described in claim 15 wherein said calculator for calculating a tonescale correction curve fits a power curve to said enhanced peak code value and a point that maps a zero input code value to a zero output code value.

20. A system as described in claim 15 wherein said calculator for calculating a tonescale correction curve fits a power curve to said enhanced peak code value, a point that maps a zero input code value to a zero output code value and a point that maps a maximum input code value to a maximum output code value.