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30 August 2004 Calibration method for IR channel of dual-band long-range airborne camera
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A dual band camera for long-range airborne reconnaissance has a large common Cassegrain objective, a beam splitter, VNIR and MWIR channels. Non-uniformity correction (NUC) must be especially accurate in this type of application, due to the low dynamic range of a raw image acquired through tens of kilometers of atmosphere. Accurate calibration of non-uniformity in the MWIR band represents a challenge, because of considerable emissivity of the optics, variable optics temperature, high cos4 effect, vignetting, complex focal plane geometry, residual misalignment between the exit pupil and the dewar's cold stop, and insertion of a blackbody temperature reference source (TRS) directly in front of the dewar window. The paper describes a special calibration method which overcomes the complexities and achieves high NUC accuracy. The method combines in-laboratory transmissibility measurement with two-stage in-flight periodic calibration. The detector non-uniformity is calibrated in wide signal range. The TRS temperature follows a curve giving linear rise of radiance in time. Inner surface of the pod between the optical windows is used as a uniform source for evaluation of a pattern caused by the optics radiation. This method was successfully implemented in the ElOP long-range oblique photography (LOROP) camera.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Vladimir Petrushevsky "Calibration method for IR channel of dual-band long-range airborne camera", Proc. SPIE 5406, Infrared Technology and Applications XXX, (30 August 2004);

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