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The first edition was published in September 1993. Typographical errors were corrected and material was updated for the second edition published in June 1998 with two re-printings. So what prompted this third edition? Nearly every test performed today captures the data with a frame grabber for computer analysis. Viewing lines traces on an oscilloscope is relic of the past. Test procedures throughout the book have been changed to reflect current test methodologies. Staring arrays produce phasing artifacts that affect nearly every measurement. The test procedures clearly state when phasing may affect results. Several chapters have been substantially reorganized. References have been updated to include 2008 material. Below are the major changes.
The concept of target/background ΔT (delta-T) with its dependence on background temperature is clarified in Chapter 3. Ambient temperature drift affects test results for MWIR and LWIR systems differently. Although the community uses ΔT to describe the target-background difference, sensor output is proportional to photon flux differences. For fixed ΔT, the flux difference depends upon the background temperature. Therefore all measurements that are a function of ΔT (e.g., MRT and NEDT) will be a function of the background temperature.
Chapter 7, Noise, has been revised. Old measurement techniques that were developed for scanning arrays (pre-1990) have been separated from current methods (staring arrays). In the second edition, the two test techniques were interwoven and therefore somewhat confusing. Description of the three-dimensional noise model has been expanded with test methods clarified. While often overlooked, 1/f noise can easily affect noise statistics.
MTF measurements (Chapter 8) are a major update. Scanning and staring array methodologies have been delineated. Test techniques evolved from periodic targets to a tilted slit and tilted edge (knife edge) with the tilted edge being the most common. Sample test results for each method are provided as well as the advantages and disadvantages of each method. Although MRT test procedures have not changed very much over the years, observer variability is now well-documented (Chapter 10).
All figures and graphs have been redrawn. Doug Marks provided all of the illustrations.
Gerald C. Holst
March 2008
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