As Dwarren said- IR goes back to late WW II, uses an IR light source to illuminate target. Also means YOU can be seen by anyone else with an IR scope. Light Amplification (Vietnam era Starlight scope) amplifies existing light, like moonlight, starlight, etc. Useless in a place with no light (tunnel). Passive IR or Thermal Imaging- picks up infrared light given off from targets- body heat, engine heat, etc. Watch the TV night pursuits with a helicopter using FLIR- Forward Looking Infrared. Hot things look bright.
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Used to use a device called an infrared metascope- damned thing used a high voltage battery unlike anything else in the world. Happily, all of you US taxpayers bought those for me.