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Optical detectors are devices used to detect the electromagnetic radiation near of or from the
visible spectrum
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All of the optical detectors are based on the external or
internal photoelectric effect, which means that a photon incident at the surface or that enters in
the bulk of the material is able to expel an electron (if it has enough energy) and leave in place a
hole (if the material is semiconductor)
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The CCD are in fact FET transistors that are connected
in series (coupled one after the other)
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This
charge is then transferred from one FET to another by applying a suitable changing potential to
successive FETs
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Another type of optical detectors (which are made using vacuum tubes not from solid state
devices) are the phototubes
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These electrons emitted are then collected
at the anode of the tube by applying a suitable potential
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The maximum sensible
wavelength is in ultraviolet and they found applications is reading the sound tracks from movies
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The third type of optical detectors are the semiconductor detectors used to detect the X and
gamma rays
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They have applications just in X and
gamma ray scientific spectrometry and they are usually made of Silicon or Germanium
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There are also many other optical detectors on the market, and each of them has its particular
application and detection sensitivity
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Each of them has a special
construction that is suitable for its particular applications
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