COLOR CORRECTION TO COMPENSATE FOR DISPLAYS' LUMINANCE AND CHROMINANCE TRANSFER CHARACTERISTICS

• US 20110149166A1
• Filed: 12/23/2009
• Published: 06/23/2011
• Est. Priority Date: 12/23/2009
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Higgins, Michael Francis, Brown Elliott, Candice Hellen, Botzas, Anthony
• Granted Patent: US 9,049,410 B2
• Time in Patent Office: Days
• US Class Current: 348/649
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/2044 using dithering
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82
• CPC Class Codes: H04N 9/69 for modifying the colour signals by gamma correction controlling camera response for colour signals H04N23/83
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

Displays are provided with circuitry performing color correction to compensate for the displays'"'"' luminance and chrominance transfer characteristics. Some techniques are suitable for RGBW displays and for subpixel-rendered displays. Some displays include an external light source (e.g. a backlight unit in LCDs), and the color correction is coordinated with dynamic control of the light source.

Claims

1. A method for processing image data for displaying an image by using a plurality of primary colors, the primary colors comprising a plurality of first primary colors and one or more second primary colors, the method comprising:

obtaining a color signal representing one or more colors in the image, the color signal comprising a representation of an amount of each said primary color in the one or more colors;

obtaining a first signal incorporating a first correction of the color signal, the first correction being to correct for a display'"'"'s transfer characteristic, the first signal being dependent on the amount of each of one or more of the first primary colors in said representation;

obtaining a second signal incorporating a second correction of the color signal, the first correction being to correct for the display'"'"'s transfer characteristic, the second signal being independent of the amounts of the first primary colors in said representation but being dependent on one or more of the amounts of the one or more second primary colors in said representation;

obtaining a relative-amount signal which represents an indication as to a relative amount, in said representation, of at least one of the one or more second primary colors relative to at least one of the first primary colors;

from the first and second signals and the relative-amount signal, obtaining a combined-correction signal representing a combined correction which depends on the first and second corrections and on the relative amount.

2. The method of claim 1 wherein the first signal is independent of the amounts of the one or more second primary colors in said representation.

3. The method of claim 1 wherein depending on the relative amount, the combined correction is equal to the first correction, to the second correction, or to a value between the first and second corrections, the combined correction being closer to the first correction if the relative amount is smaller.

4. The method of claim 1 wherein the combined correction is a result of linear interpolation of the first and second corrections.

5. The method of claim 1 wherein the relative amount is an increasing function of one or more of the amounts of the one or more second primary colors and is a decreasing function of one or more of the amounts of the first primary colors.

6. The method of claim 1 further comprising using the combined correction signal to display the image.

7. The method of claim 1 wherein the combined-correction signal defines the combined correction as one or more grey values in a non-linear color space.

8. The method of claim 5 wherein the amounts of each color are values of color coordinates in a linear color space.

9. The method of claim 1 wherein at least some corrections of each second primary color to correct for the display'"'"'s transfer characteristic are operable to be performed by correcting two or more of the first primary colors.

16. The apparatus of claim 1 wherein each second primary color is representable as a mixture of two or more of the first primary colors.

10. An apparatus for displaying an image, the apparatus comprising circuitry for correcting, for a display'"'"'s transfer characteristic, a color signal representing one or more colors in the image, the color signal comprising values of color coordinates of each said color, the color coordinates being associated with a plurality of primary colors, the primary colors comprising a plurality of first primary colors and one or more second primary colors, the color coordinates of each color comprising first coordinates associated with the first primary colors and comprising one or more second coordinates associated with the one or more second primary colors, the circuitry comprising:

a first circuit for generating a first signal incorporating a first correction of the color signal, the first correction being to correct for the display'"'"'s transfer characteristic, the first signal being dependent on values of one or more of the first coordinates in the color signal;

a second circuit for generating a second signal incorporating a second correction of the color signal, the second correction being to correct for the display'"'"'s transfer characteristic, the second signal being independent of values of the first coordinates in the color signal but being dependent on values of one or more of the one or more second coordinates in the color signal;

an interpolation circuit for generating a combined-correction signal by interpolation from the first and second signals based on an indication of a relative amount of at least one of the one or more second primary colors relative to at least one of the first primary colors.

11. The apparatus of claim 10 wherein the first signal is independent of the values of the one or more second coordinates in the color signal.

12. The apparatus of claim 10 wherein the interpolation is linear.

13. The apparatus of claim 10 wherein the relative amount is an increasing function of values of one or more of the one or more second coordinates and is a decreasing function of values of one or more of the first coordinates.

14. The apparatus of claim 10 wherein the combined-correction signal defines the combined correction as one or more grey values in a non-linear color space.

15. The apparatus of claim 10 wherein the color coordinates of each color are in a linear color space.

17. An apparatus for displaying an image by using a plurality of primary colors, the primary colors comprising a plurality of first primary colors and one or more second primary colors, the apparatus comprising circuitry for correcting, for a display'"'"'s transfer characteristic, a color signal representing one or more colors in the image, the color signal comprising values of one or more color coordinates of each color, the circuitry comprising:

a first data path for processing the color signal; and

a second data path for processing the color signal;

wherein the first and second data paths comprise shared circuitry;

wherein the first data path comprises a first color correction circuit comprising a separate color correction circuit for correcting, for the transfer characteristic, each value of a color coordinate of a plurality of first sets of the color coordinates, each first set comprising one or more but less than all of the color coordinates of each color, the separate color correction circuits of the first data path being operable to correct, for the transfer characteristic, the color signal representing any one of the first primary colors to a predefined display quality;

wherein the second data path comprises a second color correction circuit comprising a separate color correction circuit for correcting, for the transfer characteristic, each value of a color coordinate of a plurality of second sets of the color coordinates, each second set comprising one or more but less than all of the color coordinates of each color, the second data path being operable to correct, for the transfer characteristic, the color signal representing at least one second primary color to a predefined display quality;

wherein the shared circuitry comprises an interpolation circuit for generating a combined-correction signal by interpolation from a signal obtained using the first color correction circuit and a signal obtained using the second color correction circuit, the interpolation being based on an indication of a relative amount of at least one of the one or more second primary colors relative to at least one of the first primary colors in the one or more colors.

18. The apparatus of claim 17 wherein each of said first and second sets consists of a single color coordinate.

19. The apparatus of claim 17 wherein the shared circuitry comprises a third color correction circuit connected downstream of the interpolation circuit, the shared circuit being for correcting amounts of the primary colors for the transfer characteristic.

20. The apparatus of claim 19 wherein the shared circuitry further comprises a subpixel rendering circuit connected between the interpolation circuit and the third color correction circuit.

21. The apparatus of claim 19 wherein the shared circuitry further comprises a control circuit connected between the interpolation circuit and the third color correction circuit for determining an output power of a light source used to display an image, the output power in displaying the image being dynamically determined from one or more images displayed by the apparatus, the light source being for providing light to subpixels controlled by signals which are generated by the first and second data paths and which depend on the output power.

22. The apparatus of claim 17 wherein the shared circuitry further comprises a subpixel rendering circuit connected downstream of the interpolation circuit.

23. The apparatus of claim 17 wherein the shared circuitry further comprises a control circuit connected downstream of the interpolation circuit for determining an output power of a light source used to display an image, the output power in displaying the image being dynamically determined from one or more images displayed by the apparatus, the light source being for providing light to subpixels controlled by signals which are generated by the first and second data paths and which depend on the output power.