BACKLIGHT CONTROL OF ELECTRONIC DEVICE

• US 20120218239A1
• Filed: 05/04/2012
• Published: 08/30/2012
• Est. Priority Date: 06/02/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: CHEN, Wei, YAO, Wei
• Granted Patent: US 8,890,798 B2
• Time in Patent Office: Days
• US Class Current: 345/207
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

Embodiments are provided herein which may be utilized to eliminate stray light emissions from an LED while ambient light is being sensed. As such, dynamic backlight control systems for use with an electronic display are presented including: an ambient light sensor for sensing ambient light intensity; a backlight for illuminating the electronic display; a switch for controlling the backlight, the switch configured to set a backlight condition to ON or OFF in response to a backlight-off frequency such that the ambient light sensor senses the ambient light intensity in the absence of the backlight; a logic module for determining a backlight level in response to the ambient light intensity; and a backlight control circuit for adjusting the backlight to the backlight level in response to the ambient light intensity.

Claims

1. A backlight control system for use in an electronic device including a display having a backlight arranged to illuminate the display, the backlight control system comprising:

a backlight controller arranged to turn the backlight temporarily off and then back on while the backlight is in an illumination state in which the backlight illuminates the display; and

an ambient light sensor adapted to sense an ambient light intensity when the backlight is temporarily off during the illumination state, and to provide an indication thereof to the backlight controller

2. A backlight control system as recited in claim 1 wherein the backlight controller includes a backlight switch configured to set the backlight to an ON or OFF state according to a backlight-off frequency when the backlight is in the illumination state.

3. A backlight control system as recited in claim 2 wherein the backlight-off frequency is determined such that perceptible flicker in the visual display is avoided.

4. A backlight control system as recited in claim 2 wherein the display is arranged to periodically refresh and the backlight is temporarily turned off for a time interval that is shorter than a time period over which the display is refreshed.

5. A backlight control system as recited in claim 1, further comprising:

an analog-to-digital circuit adapted to convert the ambient light intensity into ambient light intensity data; and

a data bus configured to send the ambient light intensity data to the backlight controller.

6. A backlight control system as recited in claim 2 further comprising:

first computer code adapted to determine a periodicity of the visual display,

second computer code for determining the backlight-off frequency based on the periodicity of the visual display such that the backlight-off frequency is at a non-integer ratio with respect to the periodicity of the visual display, and

third computer code for controlling the backlight switch in accordance with the backlight-off frequency.

7. A backlight control system as recited in claim 1, wherein backlight controller is part of a display processor.

8. A portable electronic device that includes a housing, a display having a backlight and the backlight control system as recited in claim 1.

9. A backlight control system as recited in claim 1 wherein the ambient light sensor is adapted to provide an indication of the ambient light intensity to the backlight controller when the ambient light intensity is greater than a threshold value.

10. A backlight control system as recited in claim 1 wherein the backlight controller is arranged to turn the backlight off and set the backlight out of the illumination state when the ambient light level exceeds a threshold value.

11. A method of controlling backlighting of a display in an electronic device, the method comprising:

turning on a backlight to illuminate the display;

temporarily turning the backlight off while the backlight remains in an illumination state;

sensing an ambient light level while the backlight is temporarily turned off and remains in the illumination state;

turning the backlight back on after the ambient light level has been sensed; and

adjusting the backlight based at least in part upon the sensed ambient light level.

12. A method as recited in claim 11 wherein the display is periodically refreshed and backlight is temporarily turned off for a period of time that is shorter than an interval of time required to refresh the display.

13. A method as recited in claim 11 wherein the display has as associated frame refresh interval and the backlight is temporarily turned off for a period of time that is shorter than the frame refresh interval.

14. A method as recited in claim 11 wherein the adjusting of the backlight includes lowering the level of the backlight when the sensed ambient light level exceeds a first threshold to thereby reduce power consumption of the electronic device.

15. A method as recited in claim 11, wherein the adjusting of the backlight includes setting the backlight to an OFF state when the sensed ambient light level exceeds a first threshold.

16. A method as recited in claim 11 further comprising:

determining a refresh periodicity of the display; and

setting a backlight-off frequency of the backlight, wherein the backlight-off frequency is set according to the refresh periodicity such that flicker in the electronic display is avoided.

17. A method as recited in claim 16 wherein the backlight-off frequency is set such that the backlight-off frequency is at a non-integer ratio with respect to the refresh periodicity of the display.

18. A method as recited in claim 11, wherein said electronic device is a battery powered portable electronic device.