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Infrared detectors: Past, present and future

The author provides a thumbnail sketch of the historical development of infrared detectors and related technology. IR detectors are characterized by the shape of their spectral response, their speed of response and the detectivity at a particular wavelength, usually at the spectral peak. In addition, such data as temperature of operation, magnitude and frequency dependance of detector noise, detector impedance, angular field of view and detector area may distinguish one type of detector from another and even detectors of the same type. Detectors may be placed into two categories with vastly different properties: Thermal and Photon detectors. Thermal detectors have been in use since the early 1800's.