Scene-Based Nonuniformity Compensation for Imaging Sensors

Multidetector imaging focal plane arrays like CCD TV cameras and infrared arrays possess large detector-to-detector dark current (offset) and responsivity (gain) variations which can completely mask the useful information. Conventional compensation techniques require temperature references of constant radiance over the entire field of view and a mechanical/electrooptical shutter to calibrate the focal plane. This detracts from the mechanical simplicity of multi-detector staring (nonscanning) focal planes. This correspondence describes a real-time offset and responsivity (gain) compensation technique which dispenses with temperature references and shutters in staring focal planes. It makes use of the scene statistics for calibration and continuously updates the compensation coefficients without interrupting the field of view. The results of real-time simulations of this technique with a number of sensors are presented. Real-time LSI/VLSI hardware architectures are addressed. The technique can be implemented with the addition of very little hardware to a conventional compensation technique requiring temperature references. The technique is also suitable for multi-detector scanning focal planes and for the removal of shading in TV sensors as well.