INFRARED PHYSICS & TECHNOLOGY ELSEVIER Infrared Physics & Technology 36 (1995) 1115-1123 Range formulation for a staring electro-optical and imaging system incorporating the effects of atmospheric trans- mission, focal plane 1/f noise and fixed pattern noise Vikram Dhar, Zafar Khan, S.K. Lomash, K.C. Chhabra Solidstate Physics Laboratory, Lucknow Road, Timarpur, Delhi-110 054, India ~ Received 12 December 1994 Abstract To increase the detection range in staring FPAs, commonly the integration time Ti is increased, as the range is assumed to increase as one-fourth power of T~, (T~/4). It is shown here that the range dependence on T~ is weaker than T~'4, because of the effect of atmosphere. Since the atmospheric transmission coefficient decreases with increasing range, the effect of increasing Ti on the range is considerably reduced. It is also shown that when detector l/f noise dominates over other noise sources, the dependence of range on Ti is much weaker than T~ 4, having a logarithmic dependence. Calculations have been done by integrating equations involving spectral functions--photon flux, atmospheric transmission coefficient, optics transmission coefficient and responsivity--over wavelength, in the spectral range from 8 lam to 12 ~tm. LOWTRAN2 has been used for spectral atmospheric transmission coefficients, for different conditions of ambient temperature (-30°C to 55°C) and relative humidity (50-85%). The range formulation also distinguishes between distant targets (point sources) and nearby targets (extended sources). The analysis is applicable for terrestrial imaging, where the temperature difference of the target and the background is small. The effect of fixed pattern noise (FPN) in mercury cadmium telluride (MCT) FPAs has also been considered by modeling FPN in terms of a composition variation in the MCT. It is seen that range, both in the point source and the extended source cases, is not a sensitive function of FPN. 1. Introduction The maximum detection range is an important parameter characterizing electro-optical imaging systems, including those intended for imaging in the 8-12 lam (LWIR) band, fabricated in mercury ~Phone No. 2916905; Fax No. 91(011)2913609 cadmium telluride (MCT). These systems often use infrared focal plane arrays (FPAs) for thermal imaging of terrestrial scenes. Most analyses of detection range mention the effect of atmospheric transmission, and then proceed to neglect it in the interest of simplicity [1,2]. It is also convenient to assume that the quantum efficiency of the MCT detector is flat through the spectral range, but it is not desirable to do this if a realistic result is 01350-4495/95/$9.00 © 1995 Elsevier Science B.V. All rights reserved SSDI 1350-4495(95)00060-7