AMBIENT LIGHT COLOR COMPENSATION SYSTEMS AND METHODS FOR ELECTRONIC DEVICE DISPLAYS

• US 20190318696A1
• Filed: 07/24/2018
• Published: 10/17/2019
• Est. Priority Date: 04/13/2018
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: IMAI, Francisco H., ZHANG, Chi, FORES HERRANZ, Adria, WU, Jiaying, SPENCE, Arthur L., ALBRECHT, Marc
• Granted Patent: US 10,733,942 B2
• Time in Patent Office: Days
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 2360/144 the light being ambient light
• 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 3/3607 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

Abstract

Aspects of the subject technology relate to electronic devices with displays and ambient light sensors. An electronic device modifies the color of images to be displayed based on measured ambient light color. The modification is performed in a perceptually uniform color space and includes a determination of a bleaching effect of reflected ambient light, and a determination of a color correction factor to be applied within the perceptually uniform color space,7 based on the determined bleaching effect. The modification may also include an application of a strength factor that mitigates out-of-gamut colors in color compensated images.

Claims

1. An electronic device, comprising:

a display having an array of display pixels configured to emit colored display light;

an ambient light sensor; and

processing circuitry configured to;

transform an image to be displayed with the display to a perceptually uniform color space;

obtain an ambient light measurement from the ambient light sensor;

determine a color compensation factor based on the transformed image and the ambient light measurement;

apply the color compensation factor to the transformed image;

perform an inverse transform of the transformed image with the color compensation applied to obtain a compensated image; and

provide the compensated image to the display, for display by the array of display pixels.

2. The electronic device of claim 1, wherein the processing circuitry is further configured to determine a spectral power distribution of ambient light in an environment of the electronic device based on the ambient light measurement.

3. The electronic device of claim 2, wherein the processing circuitry is further configured to determine reflected light tristimulus values for a reflected portion of the ambient light based on the spectral power distribution, and based on display spectral reflectance data and color matching data stored in memory of the electronic device.

4. The electronic device of claim 3, wherein the processing circuitry is further configured to determine image tristimulus values for the image.

5. The electronic device of claim 4, wherein the processing circuitry is further configured to determine bleached image tristimulus values by combining the reflected light tristimulus values and the image tristimulus values.

6. The electronic device of claim 5, wherein the processing circuitry is further configured to transform the bleached image tristimulus values to bleached image perceptually uniform color space values.

7. The electronic device of claim 6, wherein the processing circuitry is further configured to:

transform the image to be displayed with the display to the perceptually uniform color space, at least in part by transforming the image tristimulus values to image perceptually uniform color space values; and

determine the color compensation factor by combining the bleached image perceptually uniform color space values with the image perceptually uniform color space values.

8. The electronic device of claim 7, wherein the processing circuitry is further configured to:

determine a color compensation strength based on the ambient light measurement; and

apply the color compensation strength to the transformed image with the color compensation applied, prior to performing the inverse transform.

9. The electronic device of claim 7, wherein the image perceptually uniform color space values comprise a brightness value, a redness-greenness value, and a yellowness-blueness value for the image, and wherein the color compensation factor comprises a first compensation factor for the redness-greenness value and a second compensation factor for the yellowness-blueness value.

10. An electronic device, comprising:

a display having an array of display pixels configured to emit colored display light;

an ambient light sensor; and

processing circuitry configured to;

obtain an ambient light measurement from the ambient light sensor;

obtain an input image to be displayed by the display;

determine expected reflection data based on the ambient light measurement and display spectral reflectance data;

determine color bleaching data based on the expected reflection data and a transformation of the input image;

determine a color correction factor based on the color bleaching data and the transformation of the input image;

apply the color correction factor to the transformation of the input image; and

generate a compensated output image for display based on the transformation of the input image with the color correction factor applied.

11. The electronic device of claim 10, wherein the display spectral reflectance data comprises a plurality of spectral reflectances of the display under a corresponding plurality of ambient light types.

12. The electronic device of claim 11, wherein the ambient light measurement comprises a brightness and a color of ambient light detected by the ambient light sensor.

13. The electronic device of claim 12, wherein the input image is a red-green-blue image, and wherein the processing circuitry is further configured to:

determine tristimulus values for the red-green-blue image;

determine image cone responses from the determined tristimulus values; and

determine perceptually uniform color space values from the image cone responses to obtain the transformation of the input image.

14. The electronic device of claim 13, wherein the perceptually uniform color space values comprise a redness-greenness value and yellowness-blueness value for the input image.

15. The electronic device of claim 14, wherein the color correction factor comprises a first color correction factor for the redness-greenness value and a second color correction factor for the yellowness-blueness value.

16. A method for operating an electronic device having a display, the method comprising:

obtaining an image to be displayed by the display;

obtaining a measurement of ambient light in an environment around the electronic device;

transforming the image to a perceptually uniform color space;

determining a color correction for the image based on the measurement of the ambient light and the transformed image; and

generating a compensated image based on the transformed image and the color correction.

17. The method of claim 16, further comprising obtaining tristimulus values for a reflected portion of the ambient light.

18. A method for operating an electronic device having a display, the method comprising:

obtaining an image to be displayed by the display;

obtaining a measurement of ambient light in an environment around the electronic device;

obtaining reflected light tristimulus values;

determining a color correction for the image based on the reflected light tristimulus values and a color transformation of the image; and

generating a compensated image based on the color transformation of the image and the color correction.

19. The method of claim 18, wherein obtaining the reflected light tristimulus values comprises computing the reflected light tristimulus values directly from one or more channel readings of an ambient light sensor of the electronic device.

20. The method of claim 18, wherein obtaining the reflected light tristimulus values comprises determining a spectral power distribution of the ambient light based on the measurement of the ambient light.

21. The method of claim 20, wherein obtaining the reflected light tristimulus values further comprises integrating the spectral power distribution with a display spectral reflectance of the display and a color matching function.