Patent ID: 8581891

Claim:
A sensor arrangement for use in sensing light from either a light source that is respectively operation at a first power supply frequency or a light source that is operated at a second power supply frequency which is different from said first power supply frequency, the sensor arrangement comprising: a light detector configured to generate an output in response to light incident upon the detector; and an averaging circuit configured to sample the output during each of a plurality of overlapping and equally spaced time intervals, each interval being about equal in time to an oscillatory period of the first power supply frequency and the combined time of the intervals being about equal to the combined time of an integer number of oscillatory periods of the second power supply frequency, and to integrate the output sampled for each of the overlapping time intervals and to combine the integrated output to form a new output; wherein the light detector is a photo-element, the averaging circuit is a digital averaging circuit that samples a continuous output of the photo-element over a time interval including all of the overlapping intervals, and the digital averaging circuit integrates the output sampled for each of the overlapping time intervals and combines the integrated output to form the new output by weighting portions of the output according to the number of time intervals that overlap in each portion, and combining weighted portions of the output to form the new output.