THIRD GENERATION PASSIVE VIEWERS
Because photo-emission has normally a cut-off wavelength of about
1.2 microns, to make use of the 1.6 micron emission from the night sky, a photoconductor
material was used for the cathode material with a photoemitter deposited on the rear
surface of the photoconductor. Others used solid state techniques principally based on
gallium arsenide with the electrical output coupled to a electroluminescent display. The
other method was the Quantum Counter
using specially prepared crystals which emitted visible light when a local source of
infra-red light was added to the infra-red emission from the scene.
Another night viewer was based on a solid state technique using
Silicon or Germanium. The elemental detector was integrated with a high gain
microminiature solid state amplifier. Versions were constructed with an electroluminescent
display for imaging.