Abstract
Certain optical image processing schemes proposed over the years are severely limited in performance because optical intensity distributions produced by the associated processors are characterized by extremely low signal-to-bias ratios (SBR). The available dynamic range of standard image detectors is used up primarily by the bias content of the distributions, with little dynamic range left over for information-bearing signals. Examples arise in connection with incoherent holography, time-integration acousto-optical spectrum analysis and correlation, and OTF synthesis, as well as in other areas. What is needed for the processing of such low SBR image distributions is an imaging device that is essentially 'ac-coupled,' i.e., that rejects background bias components in low-contrast imagery and responds only to the signal components. The pyroelectric imaging camera, used traditionally for thermal imaging, has these characteristics if the bias components are non-time-varying and the signal components are made to change with time. Recent developments in pyroelectric materials and camera technology suggest that image processor outputs with SBRs of 10-3 or less can be detected with 8 to 14 bits of dynamic range going to the signal information alone. Thus, high SNR processing wit low SBR signals appears possible. We describe briefly the operation of pyroelectric detectors and cameras and then introduce a variety of real-time image processing applications.
