Patent ID: 6521880
Filing Date: 2003-02-18
Classification: H04N

Abstract:
An imager comprising:one or more detector means comprising a detecting element to produce an output current dependent upon incident flux when biased by a bias voltage, shutter means to open and close periodically to modulate radiation incident upon the detecting element to produce a sequence of alternating open fields in which radiation is incident upon the detecting element and closed fields in which the radiation is at least partially blocked from reaching the detecting element, said detecting element to produce at least a first open output signal Vo1 indicative of the flux incident upon the detector during a first open field, a first closed output signal Vc1 indicative of the flux incident upon the detector during a first closed field, a second open output signal Vo2 indicative of the flux incident upon the detector during a second open field, and a second closed output signal Vc2 indicative of the output of the detecting element during a second closed field, said first output signals Vo1 and Vc1 corresponding to a first pair of fields comprising an open field and a closed field, and said second output signals Vo2 and Vc2 corresponding to a second pair comprising an open and a closed field, reset means to reset the output of the detecting element to a predetermined if voltage, wherein the reset means resets the output after the output signals of Vo1, Vc1, Vo2 and Vc2 have all been obtained, there being no reset of the output of the detecting element between the output signals Vo1, Vc1, Vo2 and Vc2, and processing means to produce a modified ramp value indicative of any ramp increase in the output signals over time by processing pairs of closed field output signals Vc1, Vc2 obtained between resets, the processing means to further process said first and second pairs of output signals together with said modified ramp value to produce a first and second processed image signal from the detecting element, the first processed image signal corresponding to the first pair of fields and the second processed image signal to the second pair of fields.