Charge transfer devices for infrared imaging

A great number of infrared photodetectors has been developed for use in thermal imaging systems operating in either the 3-5 micrometer or 8-12 micrometer atmospheric windows. At present the number of detectors used in IR imaging systems is limited by the requirement to connect each detector to its own preamplifier. It is hoped that the use of charge transfer devices (principally charge coupled devices, CCDs, and charge injection devices, CIDs) at or near the focal plane for multiplexing and signal processing will make practical IR focal planes with thousands of IR detectors. There exists a wide variety of approaches to the use of charge transfer devices in infrared focal planes. Five high packing density, high quantum efficiency, approaches appropriate for series-parallel scan are discussed. Attention is given to IR sensitive CCD, direct injection (hybrid), direct injection (extrinsic silicon), the accumulation mode (extrinsic silicon), and infrared sensitive CID with silicon CCD signal processing.