Reference free nonuniformity correction for mercury cadmium telluride infrared focal plane arrays

Multi-detector HgCdTe infrared focal plane arrays suffer from inherent low frequency and fixed pattern noise. They are thus limited by their inability to calibrate out individual detector variations. These variations are due to detector to detector dark current (offset) as well as responsivity (gain) variations which completely mask useful thermal signatures in infra-red scenes. Conventional detector compensatory techniques require uniform temperature references. previously special calibration images were used to calibrate systems at start up with off board digital calibration techniques used to correct nonuniformities in the detector array. However, calibration only at start up fails to take into account other operating points as well as any drift In the parameters. This paper describes a real time offset and responsivity (gain) compensation technique for a 3 - 5 mu m HgCdTe infrared focal plane array. The method presented employs a real time scene based correction technique and dispenses with temperature references using the infrared scene itself for calibration. This method allows for the continuous update of the compensation coefficients using statistical assumptions of the scene under view without interrupting the scene with a temperature reference.