DISPLAY DEVICES WITH AMBIENT LIGHT SENSING

• US 20090167676A1
• Filed: 12/23/2008
• Published: 07/02/2009
• Est. Priority Date: 12/26/2007
• Status: Active Grant

• Current Assignee: InnoLux Corporation
• Original Assignee: TPO Displays Corporation (InnoLux Corporation)
• Inventors: Edwards, Martin John, Ayres, John Richard
• Granted Patent: US 8,319,721 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• 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

A method is provided of controlling an illumination source for a display device which comprises a display modulator for modulating the light provided by the illumination source. The method comprises using a light sensor arrangement to generate a first signal based on an ambient light level with first illumination source drive condition, and using the light sensor arrangement to generate a second signal based on the same ambient light level but with second illumination source drive condition different to the first drive condition. The first and second signals are processed to compensate for differences in the light sensor arrangement response characteristics when operating with the first and second illumination source drive conditions thereby to derive a compensated light sensor arrangement characteristic covering both the first and second illumination source drive conditions. Ambient light levels detected using this model of the characteristic are used to control the display device.

Claims

1. A method of controlling a display device, the display device comprising a display modulator for modulating the light provided by the illumination source, the method comprising:

using a light sensor arrangement to generate a first signal based on an ambient light level with a first illumination source drive condition;

using the light sensor arrangement to generate a second signal based on the ambient light level but with a second illumination source drive condition wherein the second illumination source drive condition is different to the first illumination source drive condition;

processing the first and second signals to compensate for differences in the light sensor arrangement response characteristics when operating with the first and second illumination source drive conditions thereby to derive a compensated light sensor arrangement characteristic covering both the first and second illumination source drive conditions; and

controlling the display device using a detected light level based on the light level as detected by the light sensor arrangement based on the compensated light sensor arrangement characteristic.

2. The method as claimed in claim 1, wherein the step of controlling the display device comprises controlling the illumination source.

3. The method as claimed in claim 2, wherein the first illumination source drive condition comprises the illumination source on, and the second illumination source drive condition comprises the illumination source off.

4. The method as claimed in claim 1, wherein the first illumination source drive condition comprises the illumination source on, and the second illumination source drive condition comprises the illumination source off.

5. The method as claimed in claim 1, wherein the step of generating a signal with first drive condition comprises:

detecting a light level with a first light sensor exposed to ambient light at the display output;

detecting a light level with a second light sensor more shielded from ambient light than the first light sensor; and

processing the signals generated by the first and second sensors to derive an ambient light level.

6. The method as claimed in claim 5, wherein the step of processing the signals generated by the first and second sensors comprises subtracting the signal generated by the second sensor from the signal generated by the first sensor to derive an ambient light level.

7. The method as claimed claim 1, wherein the step of generating a signal with second drive condition comprises:

detecting a light level with a first light sensor exposed to ambient light at the display output;

detecting a light level with a second light sensor more shielded from ambient light than the first light sensor; and

processing the signals generated by the first and second sensors to derive an ambient light level.

8. The method as claimed in claim 7, wherein the step of processing the signals generated by the first and second sensors comprises subtracting the signal generated by the second sensor from the signal generated by the first sensor to derive an ambient light level.

9. The method as claimed in claim 1, wherein the step of processing the first and second signals comprises linearly shifting the light sensor arrangement response characteristic in one of the illumination source drive conditions to remove discontinuity between the light sensor arrangement response characteristics for the two illumination source drive conditions.

10. The method as claimed in claim 9, wherein the step of processing the first and second signals comprises linearly shifting and changing the gradient of the light sensor arrangement response characteristic in one of the illumination source drive conditions to remove discontinuity and change in gradient between the light sensor arrangement response characteristics for the two illumination source drive conditions.

11. The method as claimed in claim 1, further comprising:

using the light sensor arrangement to generate a third signal based on a second ambient light level with the first illumination source drive conditions

using the light sensor arrangement to generate a fourth signal based on the same second ambient light level but with the second illumination source drive condition; and

processing the first to fourth signals to compensate for differences in the light sensor arrangement response characteristics when operating with the first and second illumination source drive conditions thereby to derive a compensated light sensor arrangement characteristic covering both the first and second illumination source drive conditions.

12. The method as claimed in claim 1, wherein the illumination source is controlled to provide a desired output level using pulse width modulation control.

13. A computer program comprising computer program code means adapted to perform all of the steps of claim 1 when said program is run on a computer.

14. The computer program as claimed in claim 13 embodied on a computer readable medium.

15. A display device comprising:

an illumination source;

a display modulator for modulating the light provided by the illumination source;

a light sensor arrangement for generating signals based on an ambient light level and the illumination source; and

a processor for processing the signals received from the light sensor arrangement, wherein the processor is adapted to;

use the light sensor arrangement to generate a first signal based on an ambient light level with first illumination source drive condition;

use the light sensor arrangement to generate a second signal based on the same ambient light level but with second illumination source drive condition different to the first drive condition;

process the first and second signals to compensate for differences in the light sensor arrangement response characteristics when operating with the first and second illumination source drive conditions thereby to derive a compensated light sensor arrangement characteristic covering both the first and second illumination source drive conditions; and

control the display device using a detected light level based on the light level as detected by the light sensor arrangement based on the compensated light sensor arrangement characteristic.

16. The display device as claimed in claim 15, wherein the processor is further adapted to:

use the light sensor arrangement to generate a third signal based on a second ambient light level with the first illumination source drive condition;

use the light sensor arrangement to generate a fourth signal based on the same second ambient light level but with the second illumination source drive condition; and

process the first to fourth signals to compensate for differences in the light sensor arrangement response characteristics when operating with the first and second illumination source drive conditions thereby to derive a compensated light sensor arrangement characteristic covering both the first and second illumination source drive conditions.