Electronic device display with charge accumulation tracker

• US 10,102,815 B2
• Filed: 02/07/2018
• Issued: 10/16/2018
• Est. Priority Date: 05/27/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Wang, Chaohao, Tripathi, Brijesh, Tann, Christopher Philip Alan, Zalatimo, David S., Cote, Guy, Nan, Hao, Albrecht, Marc, Sacchetto, Paolo, Pintz, Sandro H.
• Primary Examiner(s): Harris, Dorothy
• Application Number:
  US15/890,517
• Publication Number:
  US 20180166032A1
• Time in Patent Office: 251 Days
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2320/046 Dealing with screen burn-in prevention or compensation of the effects thereof
• CPC Class Codes: G09G 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general

Abstract

An electronic device may generate content that is to be displayed on a display. The display may have an array of liquid crystal display pixels for displaying image frames of the content. The image frames may be displayed with positive and negative polarities to help reduce charge accumulation effects. A charge accumulation tracker may analyze the image frames to determine when there is a risk of excess charge accumulation. The charge accumulation tracker may analyze information on gray levels, frame duration, and frame polarity. The charge accumulation tracker may compute a charge accumulation metric for entire image frames or may process subregions of each frame separately. When subregions are processed separately, each subregion may be individually monitored for a risk of excess charge accumulation.

Claims

1. A display comprising:

rows and columns of pixels that display image frames; and

a charge accumulation tracker, wherein the charge accumulation tracker receives inputs for each of the image frames including gray level values and frame duration information, wherein the charge accumulation tracker computes a charge accumulation metric for each of the image frames as a product of the gray level values and the frame duration information, and wherein the charge accumulation tracker takes remedial action when the charge accumulation metric exceeds a predetermined threshold.

2. The display defined in claim 1, wherein the image frames are displayed on the display with positive and negative polarities and wherein the remedial action comprises adjusting frame polarity of the image frames.

3. The display defined in claim 1, wherein the image frames are displayed with a variable refresh rate, and wherein the remedial action comprises adjusting the refresh rate.

4. The display defined in claim 1, wherein the gray level values include an average gray level value for each of the image frames.

5. The display defined in claim 1, wherein each of the image frames includes multiple subregions, and wherein the gray level values comprise an average gray level value for each of the subregions.

6. The display defined in claim 1, wherein the received inputs comprise frame polarity information, and wherein the charge accumulation tracker computes the charge accumulation metric for each of the image frames as a product of the gray level values, the frame duration information, and the frame polarity information.

7. A display comprising:

pixels that display image frames; and

a charge accumulation tracker, wherein the charge accumulation tracker receives inputs for each of the image frames including gray level values, frame duration information, and frame polarity information, wherein the charge accumulation tracker computes a charge accumulation metric for each of the image frames by applying a weighting function to at least one of the received inputs, and wherein the charge accumulation tracker takes remedial action when the charge accumulation metric exceeds a predetermined threshold.

8. The display defined in claim 7, wherein applying the weighting function comprises applying the weighting function to the gray level values.

9. The display defined in claim 8, wherein the gray level values are average gray level values for each of the image frames.

10. The display defined in claim 8, wherein each of the image frames comprises multiple subregions, and wherein the gray level values are average gray level values for each of the subregions.

11. The display defined in claim 7, wherein applying the weighting function comprises applying the weighting function to the frame duration information.

12. The display defined in claim 7, wherein the weighting function is non-linear.

13. An electronic device, comprising:

a display having rows and columns of pixels;

control circuitry that generates image frames that are displayed on the display, wherein each image frame includes multiple subregions, and wherein each of the subregions includes pixels in multiple rows and multiple columns of the display; and

a charge accumulation tracker that computes a charge accumulation metric for each of the subregions, wherein the charge accumulation tracker takes remedial action when the charge accumulation metric for any of the subregions exceeds a predetermined threshold.

14. The electronic device defined in claim 13, wherein each of the subregions is rectangular.

15. The electronic device defined in claim 13, wherein the image frames are displayed on the display with positive and negative polarities and wherein the remedial action comprises adjusting frame polarity of the image frames.

16. The electronic device defined in claim 13, wherein the image frames are displayed with a variable refresh rate, and wherein the remedial action comprises adjusting the refresh rate.

17. The electronic device defined in claim 16, wherein adjusting the refresh rate comprises increasing the refresh rate.

18. The electronic device defined in claim 13, wherein the charge accumulation tracker computes an average gray level for each of the subregions.

19. The electronic device defined in claim 18, wherein the charge accumulation tracker computes the charge accumulation metric for each of the subregions by applying a weighting function to the average gray level for each of the subregions.

20. The electronic device defined in claim 18, wherein the charge accumulation tracker computes the charge accumulation metric for each of the subregions by computing a product of the average gray level for each of the subregions and a frame duration of the image frame.