CPC G01J 1/4204 (2013.01) [G01J 1/44 (2013.01); H01L 23/585 (2013.01); H01L 27/1443 (2013.01); H01L 27/1446 (2013.01); H01L 31/02019 (2013.01); G01J 2001/446 (2013.01); G01J 2001/448 (2013.01)] | 21 Claims |
1. An ambient light sensor, comprising:
a plurality of pixels;
wherein each pixel comprises a photodetector; and
a readout circuit configured to determine an ambient light level, said readout circuit operating to:
reset a coarse value at the beginning of an exposure time; and
repeat the following steps over the exposure time:
connect the photodetector to a reverse bias voltage supply so that a voltage across the photodetector is reset to a reverse bias voltage level;
disconnect the photodetector from the reverse bias voltage supply so that the voltage across the photodetector decreases in response to absorbed photons and collection of generated carriers;
compare the voltage across the photodetector to a threshold to generate a result having a signal level; and
increment the coarse value when the signal level of the result of the comparison changes;
wherein the coarse value at the end of the exposure time is indicative of the ambient light level.
|