IMAGING SYSTEM PERFORMANCE
FIFTH EDITION by
Gerald C. Holst
This reference contains all of the material needed to design, analyze, and evaluate the performance of imaging systems with recommended inputs to current performance models (NVThermIP). It covers target characterization, atmospheric effects, optics, detectors, displays, sampling, and human perception of image quality. Although emphasis is placed on infrared imaging systems, the principles apply to imaging systems operating in the visible and short wave IR spectrum.
A major design metric is the ratio of the detector cutoff to the optical cutoff (Fλ/d). When the ratio is less than one, the system is detector-limited. This is important to know because if the system is detector-limited, there is no point in changing the optics. The Fλ/d metric is discussed in nearly every chapter and also is a method of describing resolution. The ratio of the Airy disk to the detector size is 2.44Fλ/d.
Nearly all systems manufactured today contain staring arrays. Appropriate material has been added such as integration time as a function of background temperature. The chapter on sampling has been expanded with more imagery and two-dimensional transforms. The amount of aliasing and spurious response is related to Fλ/d. Super resolution reconstruction (SRR) provides maximum range improvement went Fλ/d approaches zero. The SRR algorithm and local area processing is discussed along with modeling methodologies.
Chapter 15 provides more detail on atmospheric effects (e.g., comparing the 1976 standard atmospheric transmission with that for tropical and sub-arctic winter). Chapter 16 contains more information on turbulence with curves that portray the shower curtain effect (It is easier for a sensor in an aircraft to see a ground target than the reverse). Chapter 18 provides the NEDT as a function of background temperature and variable integration time. An extensive list of current target discrimination levels (N50/V50) is found in Chapter 20.
A simplified approach based the Fλ/d metric provides an easy method to quickly estimate system performance. The approach clearly shows when a system is detector-limited or optics-limited. With the advent of two-color systems (MWIR+LWIR), it is shown that the LWIR system tends to be optics-limited whereas the MWIR system tends to be detector-limited.
332 figures, 89 tables, 403 references, 502+xx pages (2008)
IMAGING SYSTEM PERFORMANCE / FIFTH