Ranger HRC™ operator´s manual – History of Infrared technology
Publ. No. TM 614 006 699 Rev B – ENGLISH (EN) – Oct 30. 2008
greatest attention by the military, because it enabled an observer for the
first time in history to literally ‘see in the dark’. However, the sensitivity
of the image converter was limited to the near infrared wavelengths, and
the most interesting military targets (i.e. enemy soldiers) had to be illu
-
minated by infrared search beams. Since this involved the risk of giving
away the observer’s position to a similarly-equipped enemy observer, it is
understandable that military interest in the image converter eventually
faded.
The tactical military disadvantages of so-called ‘active’ (i.e. search beam-
equipped) thermal imaging systems provided impetus following the
1939–45 war for extensive secret military infrared-research programs
into the possibilities of developing ‘passive’ (no search beam) systems
around the extremely sensitive photon detector. During this period, mili-
tary secrecy regulations completely prevented disclosure of the status of
infrared-imaging technology. This secrecy only began to be lifted in the
middle of the 1950’s, and from that time adequate thermal-imaging devi-
ces finally began to be available to civilian science and industry.
