Display devices with ambient light sensing

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

using a light sensor arrangement in the display device to generate a first signal based on an ambient light level with a first illumination source drive condition, wherein the step of generating the first signal comprises:

detecting a light level with a first light sensor exposed to ambient light at an output of the display to generate a third signal;

detecting a light level with a second light sensor more shielded from the same ambient light than the first light sensor to generate a fourth signal; and

processing the third and fourth signals generated by the first and second sensors to derive the first signal;

using the light sensor arrangement in the display device to generate a second signal based on the same 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, and wherein the second illumination source drive condition and the first illumination source drive condition are implemented at different times, wherein the step of generating the second signal comprises:

detecting a light level with the first light sensor exposed to the same ambient light at the display output to generate a fifth signal;

detecting a light level with the second light sensor more shielded from the same ambient light than the first light sensor to generate a sixth signal; and

processing the fifth and sixth signals generated by the first and second sensors to derive the second signal;

processing the first and second signals to generate a first correction parameter and correcting the first signal using the first correction parameter to generate a corrected signal; and

controlling the display device based on the corrected signal.

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 processing the third and fourth signals generated by the first and second sensors comprises subtracting the fourth signal generated by the second sensor from the third signal generated by the first sensor to derive the first signal.

6. The method as claimed in claim 1 , wherein the step of processing the fifth and sixth signals generated by the first and second sensors comprises subtracting the sixth signal generated by the second sensor from the fifth signal generated by the first sensor to derive the second signal.

7. 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 first and second illumination source drive conditions to remove discontinuity between the light sensor arrangement response characteristics for the first and second illumination source drive conditions.

8. The method as claimed in claim 7 , wherein the step of processing the first and second signals comprises linearly shifting and changing the gradient of a light sensor arrangement response characteristic in one of the illumination source drive conditions to remove discontinuity and change in gradient between light sensor arrangement response characteristics for the two illumination source drive conditions.

9. 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 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.

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

11. A display device comprising:

an illumination source;

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

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

a processor 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, wherein the second illumination source drive condition and the first second illumination source drive condition are implemented at different times;

process the first and second signals to generate a first correction parameter and correcting the first signal using the first correction parameter to generate a corrected signal; and

control the illumination source based on the corrected signal,

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 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. A method as claimed in claim 1 , wherein the first correction parameter is a difference between the first and second signals and the corrected signal is a sum of the first correction parameter and the first signal.

13. A method as claimed in claim 1 , wherein the first signal and the second signal are generated at different times.

14. A method as claimed in claim 1 , wherein the display device comprises a display pixel array.

15. The display device as claimed in claim 11 , wherein the first correction parameter is a difference between the first and second signals and the corrected signal is a sum of the first correction parameter and the first signal.

16. The display device as claimed in claim 11 , wherein the first signal and the second signal are generated at different times.

17. The display device as claimed in claim 11 , wherein the display device comprises a display pixel array.