with surface sensitive tubes, the readout is made by deflection of a beam of electrons; the variations in the current which results are proportional to the energy distribution in the image formed on the sensitive surface: it is electronic image analysis with scanning by an electron beam;
with single element photon detectors which generally remain fixed within the instrument, the image is explored sequentially by virtue of an optomechanical device placed between the objective and the detector: it is optomechanical analysis by deflection of the optical beam;
with arrays of photon detectors able to cover the whole of the focal plane, electromechanical devices are not necessary; the readout is effected sequentially, pixel by pixel, by gathering the electrical charges generated in the elemental detectors under the influence of thermal radiation: it is a new form of electronic analysis but this time by charge transfer.
KeywordsOptical Image Parallel Beam Chromatic Aberration Aspheric Surface Dove Prism
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