Optical EngineeringComputer simulation of fixed-pattern-noise-limited noise-equivalent-temperature differences in mercury cadmium telluride focal-plane arrays
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The noise-equivalent-temperature difference (NETD) is calculated in fixed-pattern-noise-limited mercury cadmium telluride (MCT) focal-plane arrays (FPA5) for both 3- to 5-μm and 8- to 14-μm terrestrial imaging applications, on the basis of a model for MCT in which a linear two-point compensation scheme is considered. The contributions to the NETD from the fixed-pattern noise of an array-in terms of gain, offset, and residual error-are calculated and taken in quadrature to obtain the NETD of the FPA. The effect of stability of the focal-plane temperature is included, but the contribution of readout is not considered. The largest contribution to the NETD is from the residual error in the compensation scheme. Decreasing the intrascene temperature difference and including a sharp-cutoff filter are shown to decrease the NETD. The composition has been varied so as to obtain the lowest NETD in each band: at x = 0.31 in the 3- to 5-μm band, and at x = 0.22 to 0.23 in the 8- to 14- μm band (where x is the composition in the alloy Hg1-xCdxTe).