Patent ID: 8242430

Claim:
A light measurement apparatus, comprising: a first sensor that senses light and generates a first current indicative of the light sensed by the first sensor; a second sensor that senses light and generates a second current indicative of the light sensed by the second sensor; an analog circuit that subtracts the first current from the second current to produce a third current that is equal to the first current minus the second current +/− an error resulting from a mismatch error associated with the analog circuit; an analog-to-digital converter that converts the third current to a digitized version of the third current; and a calibration circuit that produces an adjustment signal in dependence on the digitized version of the third current; wherein the adjustment signal produced by the calibration circuit is used to reduce the mismatch error associated with the analog circuit that subtracts the first current from the second current to produce the third current.