Compensation methods for display brightness change associated with reduced refresh rate

Patent metadata

Field	Value
Publication number	US-9620064-B2
Application number	US-201314059329-A
Country	US
Kind code	B2
Filing date	Oct 21, 2013
Priority date	Mar 13, 2013
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A method and system are provided for compensating for brightness changes in a display having an array of display pixels. The method includes storing a plurality of look-up tables, where each table has a plurality of brightness signals that provide compensation for a brightness change when the refresh rate is changed during a panel self-refresh. The method also includes using display control circuitry to determine the refresh rate associated with an input signal and to determine a compensation based on the refresh rate. The display control circuitry may, for example, use non-linear interpolation to generate a look-up table for the refresh rate. The display control circuitry may adjust the input signal based on the look-up table to produce an output signal that compensates for a brightness change at the refresh rate. The output signal may be transmitted to the array of display pixels.

First claim

What is claimed is:

1. A method of compensating for brightness change in a display when the display is operated to display a frame of display data at a given refresh rate, wherein the display is controlled using display control circuitry, wherein the display control circuitry is configured to perform compensation using first and second look-up tables, wherein the display control circuitry is configured to impose a limit on an allowable amount of compensation applied to the frame of display data, wherein the first look-up table includes a first plurality of brightness signals that provide compensation for brightness changes at a first refresh rate, and wherein the second look-up table includes a second plurality of brightness signals that provide compensation for brightness changes at a second refresh rate, the method comprising:
with a graphics processing unit, generating an input signal having the given refresh rate;
with a timing controller in the display control circuitry, determining an index value based on the given refresh rate;
with the timing controller in the display control circuitry, generating a third look-up table based on the index value and the first and second look-up tables using interpolation while operating the display to display the frame of display data at the given refresh rate;
with the timing controller in the display control circuitry, applying the third look-up table to the input signal to generate an output signal by adjusting the input signal associated with the frame of display data based on the third look-up table while maintaining the amount of compensation applied to the frame of display data below the limit by applying a portion of a target compensation to the frame of display data; and
with the timing controller in the display control circuitry, transmitting the output signal to a pixel in the display, wherein the output signal adjusts a brightness of the pixel to compensate for the brightness change at the given refresh rate.

2. The method defined in claim 1 wherein the third look-up table includes a third plurality of brightness signals that provide compensation for the brightness change at the given refresh rate and wherein generating the third look-up table based on the index value and the first and second look-up tables comprises using non-linear interpolation to generate the third-look up table.

3. The method defined in claim 1 wherein determining the index value based on the given refresh rate comprises determining the index value based on vertical blanking information.

4. The method defined in claim 3 wherein determining the index value based on vertical blanking information comprises determining the duration of a vertical blanking interval.

5. The method defined in claim 1 wherein the first and second refresh rates correspond respectively to maximum and minimum refresh rates for the display and wherein the given refresh rate is between the maximum and the minimum refresh rates.

6. The method defined in claim 1 wherein the first and second refresh rates correspond respectively to a 60 Hz refresh rate and a 30 Hz refresh rate for the display and wherein the given refresh rate is between 60 Hz and 30 Hz.

7. A display system, comprising:
memory configured to store first and second look-up tables, wherein the first look-up table includes a first plurality of brightness signals that provide compensation for brightness changes at a first refresh rate and wherein the second look-up table includes a second plurality of brightness signals that provide compensation for brightness changes at a second refresh rate;
a display that operates to display a frame of display data at a given refresh rate;
a graphics processing unit that generates an input signal for the frame of display data having the given refresh rate; and
a display control circuitry that imposes a limit on an allowable amount of compensation applied to the frame of display data, wherein the display control circuitry comprises:
a timing controller that receives the input signal from the graphics processing unit, wherein the timing controller:
determines an index value associated with the given refresh rate;
generates a third look-up table based on the index value and the first and second look-up tables using interpolation while operating the display to display the frame of display data at the given refresh rate;
applies the third look-up table to the input signal to produce an output signal while maintaining the amount of compensation applied to the frame of display data below the limit by applying a portion of a target compensation to the frame of display data; and
transmits the output signal to a pixel in the display, wherein the output signal adjusts the brightness of the pixel to compensate for a brightness change while operating the display to display the frame of display data at the given refresh rate.

8. The display system defined in claim 7 wherein the third look-up table includes a third plurality of brightness signals that provide compensation for the brightness change at the given refresh rate and wherein the display control circuitry is configured to generate the third look-up table using non-linear interpolation.

9. The display system defined in claim 7 wherein the first and second refresh rates correspond respectively to maximum and minimum refresh rates and wherein the given refresh rate is between the maximum and minimum refresh rates.

10. The display system defined in claim 7 wherein the first and second refresh rates correspond respectively to a 60 Hz refresh rate and a 30 Hz refresh rate and wherein the given refresh rate is between the 60 Hz refresh rate and the 30 Hz refresh rate.

11. A method of compensating for brightness change in a display when the display is operated at a given refresh rate, wherein the display is controlled using display control circuitry and wherein the display control circuitry is configured to impose a limit on an allowable amount of compensation applied to a given frame of display data, the method comprising:
with the display control circuitry, determining a target compensation index based on the given refresh rate; and
based on the target compensation index, using a current compensation index to compensate an input signal associated with a frame of display data and using an intermediate compensation index to compensate an additional input signal associated with an additional frame of display data while maintaining the amount of compensation applied to the additional frame of display data below the limit, wherein maintaining the amount of compensation applied to the additional frame of display data below the limit comprises applying a portion of the target compensation to the additional frame of display data, and wherein the intermediate compensation index is between the current compensation index and the target compensation index.

12. The method defined in claim 11 wherein the display includes an array of display pixels and wherein compensating the input signal comprises compensating the input signal to produce an output signal, the method further comprising:
transmitting the output signal to the display pixels.

13. The method defined in claim 12 wherein compensating the additional input signal associated with the additional frame of display data comprises compensating for a portion of the brightness change at the given refresh rate, the method further comprising:
using the target compensation index to compensate a subsequent input signal associated with a subsequent frame of display data.

14. The method defined in claim 12 wherein determining the target compensation index based

Assignees

• Apple Inc

Inventors

• Albrecht Marc
• Tann Christopher Philip Alan
• Roland Nicholas G
• Pintz Sandro H
• Kim Taesung

Classifications

• G09G3/3406 Primary

  Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336) · CPC title

• G09G2340/0435

  Change or adaptation of the frame rate of the video stream · CPC title

• G09G3/2007 Primary

  Display of intermediate tones · CPC title

• G09G2320/0626

  for control of overall brightness · CPC title

• G09G2320/0276

  for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction · CPC title