DISPLAY BRIGHTNESS CONTROL TEMPORAL RESPONSE

• US 20120019493A1
• Filed: 09/30/2010
• Published: 01/26/2012
• Est. Priority Date: 07/26/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Barnhoefer, Ulrich T., Chen, Wei
• Granted Patent: US 9,119,261 B2
• Time in Patent Office: Days
• US Class Current: 345/207
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• 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: H05B 41/3922 and measurement of the incident light
• CPC Class Codes: H05B 45/12 using optical feedback

Abstract

Methods and devices are provided for controlling the brightness of a display for an electronic device based on ambient light conditions. In one embodiment, an electronic device may employ one or more brightness adjustment profiles that define response rates for changing brightness levels based on ambient light levels. The response rates may vary depending on the magnitude and/or direction of change in the ambient light levels. In certain embodiments, the response rates may be designed to approximate the physical response of the human vision system. Further, in certain embodiments, noise reduction techniques may be employed by adjusting the response rates based on the magnitude of the change in the ambient light level and/or based on whether the display is operating at steady state or executing a brightness adjustment.

Claims

1. An electronic device, comprising:

a display comprising a backlight;

one or more ambient light sensors configured to detect an ambient light level; and

a display controller configured to determine a new brightness level for the backlight based on the detected ambient light level, and configured to adjust the backlight to the new brightness level at a rate determined based on a change between the new brightness level and a current brightness level.

2. The electronic device of claim 1, wherein the display controller is configured to increase the brightness at a first rate and to decrease the brightness at a second rate less than the first rate.

3. The electronic device of claim 1, wherein the display controller is configured to adjust the backlight to the new brightness level at a rate that approximates a physiological response of the human eye.

4. The electronic device of claim 1, wherein the display controller is configured to determine an amount of the change and a direction of the change between the new brightness level and a current brightness level.

5. The electronic device of claim 4, wherein the display controller is configured to determine the rate based on the amount of change and the direction of change when the amount of change is greater than a specified amount, and to determine the rate based solely on the amount of change when the amount of change is less than or equal to the specified amount.

6. The electronic device of claim 5, wherein the specified amount comprises approximately one-third of the current brightness level.

7. A method, comprising:

detecting an ambient light level;

determining a new brightness level for a backlight based on the detected ambient light level;

determining a brightness change between the new brightness level and a current brightness level; and

adjusting the backlight to the new brightness level at a rate determined based on the brightness change.

8. The method of claim 7, comprising determining the rate based on a direction of the brightness change.

9. The method of claim 7, comprising determining the rate based on an adjustment profile that specifies a faster adjustment rate for an increase in the ambient light level and a slower adjustment rate for a decrease in the ambient light level.

10. The method of claim 9, wherein the adjustment profile specifies a relatively constant rate when the brightness change is less than approximately one-third of the current brightness level.

11. The method of claim 7, comprising determining the rate by selecting a time constant that corresponds to the brightness change.

12. The method of claim 7, comprising determining an ambient light change between the detected ambient light level and a previous ambient light level and verifying that a duration of the ambient light change has been exceeded prior to adjusting the backlight to the new brightness level.

13. The method of claim 7, comprising determining an ambient light change between the detected ambient light level and a previous ambient light level and verifying that an amount of the ambient light change exceeds a threshold amount prior to adjusting the backlight to the new brightness level.

14. The method of claim 13, wherein the threshold amount comprises approximately 5 to 10 percent of the previous ambient light level.

15. An electronic device, comprising:

a display comprising a backlight;

one or more ambient light sensors configured to detect an ambient light level; and

a display controller configured to determine whether an amount of change between the detected ambient light level and a previous ambient light level or between a current display brightness and a previous display brightness exceeds a threshold, and configured to select the threshold based on a brightness adjustment state of the backlight, wherein the display controller is configured to select a first value as the threshold when the backlight is transitioning to a new brightness level and a second value as the threshold when the backlight is operating at a steady brightness level.

16. The electronic device of claim 15, wherein the first value specifies an ambient light level change, and wherein the second value specifies a brightness change.

17. The electronic device of claim 15, wherein the display controller is configured to adjust a brightness of the backlight to a new brightness level corresponding to the detected ambient light level in response to determining that the amount of change exceeds the threshold.

18. A method, comprising:

determining a brightness adjustment state of a backlight by determining whether the backlight is transitioning to a new brightness level or operating at a steady brightness level;

selecting between an ambient light threshold and a brightness threshold based on the brightness adjustment state; and

determining whether a change in an ambient light level or a display brightness exceeds a threshold amount corresponding to the selected ambient light threshold or the selected brightness threshold.

19. The method of claim 18, wherein selecting between an ambient light threshold and a brightness threshold comprises selecting the brightness threshold when the backlight is transitioning to a new brightness level and selecting the ambient light threshold when the backlight is operating at a steady brightness level.

20. The method of claim 19, wherein the ambient light threshold comprises approximately 15 to 20 percent of a current ambient light level, and wherein the brightness threshold comprises approximately 5 to 10 percent of a current display brightness.

21. The method of claim 18, wherein determining whether a change in the ambient light level exceeds the threshold amount comprises determining a first amount of change between a detected ambient light level and a previous ambient light level, and wherein determining whether a change in the display brightness exceeds the threshold amount comprises determining a second amount of change between a current brightness and a target brightness.

22. The method of claim 18, comprising adjusting the backlight to a new brightness level in response to determining that the change exceeds the threshold amount.

23. The method of claim 18, comprising detecting an ambient light level and determining whether an amount of change between the detected ambient light level and a previous ambient light level exceeds the threshold amount.

24. The method of claim 18, comprising determining a new brightness level for the backlight based on a detected ambient light level and determining whether an amount of change between the new brightness level and a current brightness level exceeds the threshold amount.