Locally Adaptive Backlight Control

• US 20180247609A1
• Filed: 02/24/2017
• Published: 08/30/2018
• Est. Priority Date: 02/24/2017
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Joshi, Ameya, Albrecht, Marc, Chang, Sean, Jung, Tobias
• Granted Patent: US 10,803,828 B2
• Time in Patent Office: Days
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

Systems, methods, and computer readable media to improve the operation of display systems are disclosed. In general, techniques are disclosed for dynamically adjusting backlight elements based on image content. More particularly, a backlight element'"'"'s intensity may be targeted for boosting (i.e., increasing) based on content of the backlight element'"'"'s corresponding image region, where after a check may be made to determine if the proposed increase is likely to risk generation of a halo. If the proposed intensity increase would risk a halo, the backlight element'"'"'s proposed intensity may be dimmed. Repeating the boost/dim cycle in an iterative fashion permits an image to be displayed with brighter highlights and deeper blacks.

Claims

1. A display method, comprising:

obtaining an image, the image comprising pixels wherein each pixel has a value;

determining an initial brightness value for each of a plurality of backlight elements, wherein each of the backlight elements is associated with a corresponding plurality of image pixels;

determining a first proposed brightness value for each of the backlight elements, each first proposed brightness value based on a backlight element'"'"'s initial brightness value and corresponding image pixel values;

determining a second proposed brightness value for each of the backlight elements, each second proposed brightness value based on a backlight element'"'"'s first proposed brightness value and a halo risk value;

setting each backlight element'"'"'s brightness value based the backlight element'"'"'s second proposed brightness value; and

displaying the image in conjunction with setting each backlight element'"'"'s brightness value.

2. The method of claim 1, wherein obtaining an image comprises:

obtaining a color image; and

converting the color image to a grayscale image.

3. The method of claim 2, wherein determining an initial brightness value for each of a plurality of backlight elements comprises:

selecting a first initial brightness value for each of the backlight elements;

applying a point-spread-function to each backlight element'"'"'s first initial brightness value to generate a first value; and

determining the initial brightness value for each backlight element based on the backlight element'"'"'s first value.

4. The method of claim 1, wherein determining a first proposed brightness value for each of the backlight elements comprises determining one or more statistical values for each backlight element, wherein each of a backlight element'"'"'s one or more statistical values are based on the backlight element'"'"'s corresponding image pixel values.

5. The method of claim 4, further comprising:

increasing the proposed brightness value of a first backlight element based on the first backlight element'"'"'s statistical values; and

not adjusting the proposed brightness value of a second backlight element based on the second backlight element'"'"'s statistical values.

6. The method of claim 1, wherein determining a second proposed brightness value for each of the plurality of backlight elements comprises:

determining a likelihood that a backlight element'"'"'s first proposed brightness value would generate a halo effect when the image is displayed; and

reducing the brightness of a backlight element based on the backlight element'"'"'s halo likelihood.

7. The method of claim 1, further comprising:

determining, for each of the backlight elements, a second initial brightness value based on the second proposed brightness value; and

repeating determining, for each of the backlight elements, first and second proposed brightness values based on the second initial brightness value.

8. The method of claim 7, wherein repeating is performed a specified number of times before each backlight element'"'"'s brightness value is set, wherein each backlight element'"'"'s brightness value is based on the last determined second proposed brightness value.

9. A non-transitory programmable storage device having instructions configured to cause one or more processors to:

obtain an image, the image comprising pixels wherein each pixel has a value;

determine an initial brightness value for each of a plurality of backlight elements, wherein each of the backlight elements is associated with a corresponding plurality of image pixels;

determine a first proposed brightness value for each of the backlight elements, each first proposed brightness value based on a backlight element'"'"'s initial brightness value and corresponding image pixel values;

determine a second proposed brightness value for each of the backlight elements, each second proposed brightness value based on a backlight element'"'"'s first proposed brightness value and a halo risk value;

set each backlight element'"'"'s brightness value based the backlight element'"'"'s second proposed brightness value; and

display the image in conjunction with setting each backlight element'"'"'s brightness value.

10. The non-transitory programmable storage device of claim 9, wherein the instructions to obtain comprise instructions to:

obtain a color image; and

convert the color image to a grayscale image.

11. The non-transitory programmable storage device of claim 10, wherein the instructions to determine an initial brightness value for each of a plurality of backlight elements comprise instructions to:

select a first initial brightness value for each of the backlight elements;

apply a point-spread-function to each backlight element'"'"'s first initial brightness value to generate a first value; and

determine the initial brightness value for each backlight element based on the backlight element'"'"'s first value.

12. The non-transitory programmable storage device of claim 9, wherein the instructions to determine a first proposed brightness value for each of the backlight elements comprise instructions to determine one or more statistical values for each backlight element, wherein each of a backlight element'"'"'s one or more statistical values are based on the backlight element'"'"'s corresponding image pixel values.

13. The non-transitory programmable storage device of claim 12, further comprising instructions to:

increase the proposed brightness value of a first backlight element based on the first backlight element'"'"'s statistical values; and

not adjust the proposed brightness value of a second backlight element based on the second backlight element'"'"'s statistical values.

14. The non-transitory programmable storage device of claim 9, wherein the instructions to determine a second proposed brightness value for each of the plurality of backlight elements comprise instructions to:

determine a likelihood that a backlight element'"'"'s first proposed brightness value would generate a halo effect when the image is displayed; and

reduce the brightness of a backlight element based on the backlight element'"'"'s halo likelihood.

15. The non-transitory programmable storage device of claim 9, further comprising instructions to:

determine, for each of the backlight elements, a second initial brightness value based on the second proposed brightness value; and

repeat determining, for each of the backlight elements, first and second proposed brightness values based on the second initial brightness value.

16. The non-transitory programmable storage device of claim 15, wherein the instructions to repeat is performed a specified number of times before each backlight element'"'"'s brightness value is set, wherein each backlight element'"'"'s brightness value is based on the last determined second proposed brightness value.

17. An electronic system, comprising:

a memory;

a display having a plurality of backlight elements and operatively coupled to the memory; and

one or more processors operatively coupled to the memory and display and configured to execute program code stored in the memory to—

obtain an image from the memory, the image comprising pixels wherein each pixel has a value;

determine an initial brightness value for each of a plurality of the display'"'"'s backlight elements, wherein each of the backlight elements is associated with a corresponding plurality of image pixels;

determine a first proposed brightness value for each of the backlight elements, each first proposed brightness value based on a backlight element'"'"'s initial brightness value and corresponding image pixel values;

determine a second proposed brightness value for each of the backlight elements, each second proposed brightness value based on a backlight element'"'"'s first proposed brightness value and a halo risk value;

set each backlight element'"'"'s brightness value based the backlight element'"'"'s second proposed brightness value; and

display, on the display, the image in conjunction with setting each backlight element'"'"'s brightness value.

18. The electronic system of claim 17, wherein the instructions to obtain comprise instructions to:

obtain a color image; and

convert the color image to a grayscale image.

19. The electronic system of claim 18, wherein the instructions to determine an initial brightness value for each of a plurality of backlight elements comprise instructions to:

select a first initial brightness value for each of the backlight elements;

apply a point-spread-function to each backlight element'"'"'s first initial brightness value to generate a first value; and

determine the initial brightness value for each backlight element based on the backlight element'"'"'s first value.

20. The electronic system of claim 17, wherein the instructions to determine a first proposed brightness value for each of the backlight elements comprise instructions to determine one or more statistical values for each backlight element, wherein each of a backlight element'"'"'s one or more statistical values are based on the backlight element'"'"'s corresponding image pixel values.

21. The electronic system of claim 20, wherein the memory further comprises instructions to:

increase the proposed brightness value of a first backlight element based on the first backlight element'"'"'s statistical values; and

not adjust the proposed brightness value of a second backlight element based on the second backlight element'"'"'s statistical values.

22. The electronic system of claim 17, wherein the instructions to determine a second proposed brightness value for each of the plurality of backlight elements comprise instructions to:

determine a likelihood that a backlight element'"'"'s first proposed brightness value would generate a halo effect when the image is displayed; and

reduce the brightness of a backlight element based on the backlight element'"'"'s halo likelihood.

23. The electronic system of claim 17, wherein the memory further comprises instructions to:

determine, for each of the backlight elements, a second initial brightness value based on the second proposed brightness value; and

repeat determining, for each of the backlight elements, first and second proposed brightness values based on the second initial brightness value.

24. The electronic system of claim 23, wherein the instructions to repeat is performed a specified number of times before each backlight element'"'"'s brightness value is set, wherein each backlight element'"'"'s brightness value is based on the last determined second proposed brightness value.