Readout for Fast IR Imaging With Large Detector Capacitance

A methodology for designing highly accurate readout circuits for infrared (IR) image detectors that have large pixel detector capacitances (of the order of tens of picofarads) and are required to operate with short exposure times (<100 µs) has been devised. In this context, "highly accurate" signifies capable of (1) nearly linear response over a wide dynamic range with (2) little or no image lag ("ghost" image readout attributable to capacitive retention of charge from preceding image frames), and (3) low readout noise. The methodology has been used to enhance the performance of NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), and is expected to satisfy an increasing need for highly accurate readout circuits in other applications, including other imaging spectrometers and infrared video cameras now undergoing development.