The IRicon: A passive infrared camera tube

The IRicon is an IR-sensitive photoconductive TV camera tube. Recently declassified, it was developed for the military to whom many tubes were supplied in direct-readout or return-beam form with magnetic or electrostatic focus and deflection. Passive imaging of low-temperature objects such as humans or vehicles was observed with a normal TV speed of response. Resolution varied from about 100 TV lines at very low radiation levels to about 500 at higher levels. Scene temperatures denoting less than 1° C from ambient have been detected using f/1.2 optics.