Additional Metrics

doi:10.1117/3.2588947.ch18

Additional Metrics

Book: Electro-Optical Imaging System Performance, Sixth Edition

Author(s): Gerald C. Holst

Published: 2017

https://doi.org/10.1117/3.2588947.ch18

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Abstract

Range predictions (discussed in Chapter 20, Range predictions) are based upon cycles on the target. The conversion from spatial frequency (cycles/mrad) to cycles on the target is a function of the TTP (NVThermIP/NVIPM) or the MRT/MRC (older models) and the target angular subtense, θ_TGT. While the TTP/MTF/MRC spatial frequency is limited by the optics cutoff or the Nyquist frequency, θTGT is not and can approach zero at long ranges. This is reasonable for a linear shift invariant (LSI) system. Spatially, the detector array is not a LSI system, suggesting that the smallest target that an observer can distinguish must be at least one IFOV. As θ_TGT further decreases, it may be useful to consider hotspot detection.