Display with adjustable direct-lit backlight units

• US 10,643,549 B1
• Filed: 11/05/2019
• Issued: 05/05/2020
• Est. Priority Date: 04/18/2019
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Jung, Tobias, Albrecht, Marc, Petrovich, Duane M., Chang, Sean C., Zalatimo, David S., Emelie, Pierre-Yves, Luthra, Manev, Le, Chengrui, Hong, Lingyu, Yao, Wei H.
• Primary Examiner(s): Pervan, Michael
• Application Number:
  US16/674,674
• Time in Patent Office: 182 Days
• Field of Search: 345102, 345691
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• 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 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A display may have a pixel array such as a liquid crystal pixel array. The pixel array may be illuminated by a backlight unit that includes an array of light-emitting diodes. A backlight brightness selection circuit may select brightness values for the light-emitting diodes. The backlight brightness selection circuit may select the brightness values based on image data, based on brightness values used in previous image frames, based on device information, and/or based on sensor information. The backlight brightness selection circuit may select the backlight brightness levels to mitigate visible artifacts such as flickering and halo. The backlight levels selected by the backlight brightness selection may be modified by a power consumption compensation circuit. The power consumption compensation circuit may estimate the amount of power consumption required to operate the backlight using the target brightness levels and may modify the target brightness levels to meet maximum power consumption requirements.

Claims

1. An electronic device comprising:

a display having a plurality of pixels;

a backlight having a plurality of light-emitting diodes that are configured to produce backlight illumination for the plurality of pixels;

a backlight brightness selection circuit configured to generate initial target brightness values for the plurality of light-emitting diodes based on image data, wherein the backlight brightness selection circuit comprises a halo mitigation circuit that is configured to modify the initial target brightness values into new target brightness values to mitigate halo effect in the display; and

a brightness ramping circuit configured to gradually change the plurality of light-emitting diodes from previous brightness values to the new target brightness values.

2. The electronic device defined in claim 1, wherein the plurality of pixels comprises a plurality of liquid crystal pixels.

3. The electronic device defined in claim 2, wherein the brightness ramping circuit is configured to gradually change the plurality of light-emitting diodes from the previous brightness values to the new target brightness values based on at least on a response time associated with the plurality of liquid crystal pixels.

4. The electronic device defined in claim 2, wherein the brightness ramping circuit is configured to gradually change the plurality of light-emitting diodes from the previous brightness values to the new target brightness values according to a step function.

5. The electronic device defined in claim 1, wherein the backlight brightness selection circuit comprises a content analysis circuit that generates the initial target brightness values based on the image data.

6. The electronic device defined in claim 5, wherein the backlight brightness selection circuit comprises a flicker mitigation circuit that is configured to modify the initial target brightness values to mitigate flickering in the display.

7. The electronic device defined in claim 5, wherein the backlight brightness selection circuit comprises a flash mitigation circuit that is configured to analyze the image data to identify a flash risk and that is configured to take action to prevent a flash from occurring when the flash risk is identified.

8. The electronic device defined in claim 5, wherein the backlight brightness selection circuit comprises a scene change detection circuit that is configured to analyze the image data to identify a scene change and that is configured to modify the initial target brightness values in response to identifying the scene change.

9. The electronic device defined in claim 1, wherein the backlight brightness selection circuit is configured to, during a first frame, generate the new target brightness values for the plurality of light-emitting diodes based on a first set of image data.

10. The electronic device defined in claim 9, wherein the display is configured to, during a second frame that is subsequent to the first frame, display images using a second set of image data while the plurality of light-emitting diodes produces backlight illumination using the new target brightness values.

11. The electronic device defined in claim 10, wherein the control circuitry is configured to:

during the second frame, generate a simulated backlight reconstruction based on the new target brightness values determined during the first frame.

12. An electronic device comprising:

a display having a plurality of pixels;

a backlight having a plurality of light-emitting diodes that are configured to produce backlight illumination for the plurality of pixels;

a backlight brightness selection circuit configured to generate new brightness values for the plurality of light-emitting diodes based on image data; and

a brightness ramping circuit configured to gradually change the plurality of light-emitting diodes from previous brightness values to the new brightness values, wherein the backlight brightness selection circuit is configured to, during a first frame, generate the new brightness values for the plurality of light-emitting diodes based on a first set of image data, and wherein determining the new brightness values for the plurality of light-emitting diodes based on the first set of image data comprises determining initial target brightness values based on content of the first set of image data and modifying the initial target brightness values based at least on additional brightness values used in an additional frame prior to the first frame.

13. The electronic device defined in claim 12, wherein modifying the initial target brightness values based at least on the additional brightness values used in the additional frame comprises modifying the initial target brightness values in response to a comparison between the additional brightness values used in the additional frame and the initial target brightness values indicating a scene change.

14. The electronic device defined in claim 12, wherein modifying the initial target brightness values based at least on the additional brightness values used in the additional frame comprises applying a temporal filter to the initial target brightness values and the additional brightness values.

15. An electronic device comprising:

a display having a plurality of pixels;

a backlight having a plurality of light-emitting diodes that are configured to produce backlight illumination for the plurality of pixels;

a backlight brightness selection circuit configured to generate new brightness values for the plurality of light-emitting diodes based on image data, wherein the backlight brightness selection circuit comprises;

a content analysis circuit that generates initial target brightness values based on the image data; and

an additional circuit that modifies the initial target brightness values into the new brightness values;

a brightness ramping circuit configured to change the plurality of light-emitting diodes from previous brightness values to the new brightness values, wherein the brightness ramping circuit is configured to set the plurality of light-emitting diodes to one or more intermediate brightness values while changing the plurality of light-emitting diodes from the previous brightness values to the new brightness values.

16. The electronic device defined in claim 15, wherein each pixel of the plurality of pixels is formed form a liquid crystal layer having an associated response curve and wherein changing the plurality of light-emitting diodes from the previous brightness values to the new brightness values comprises changing the plurality of light-emitting diodes from the previous brightness values to the new brightness values based at least on the associated response curve.

17. The electronic device defined in claim 15, wherein the additional circuit is a flicker mitigation circuit that is configured to modify the initial target brightness values to mitigate flickering in the display.

18. The electronic device defined in claim 15, wherein the additional circuit is a scene change detection circuit that is configured to analyze the image data to identify a scene change and that is configured to modify the initial target brightness values in response to identifying the scene change.