12. Reconnaissance sensors. IR reconnaissance sensors have been developed to detect
invisible IR emissions. Unlike aerial cameras which use lenses to expose photographic film to
light reflected from the subject, the IR sensors employ a combination of optics, electronics,
and mechanical devices to produce the image. The three basic units in an IR reconnaissance
set are (Figure 1-4):
The scanner receives or collects a portion of the IR energy radiated from the area
being scanned. This collected energy is focused onto a detector that is sensitive to the IR
region of the electromagnetic spectrum.