My understanding of night vision goggles is that they amplify existing light; so ferinstance, a soldier patrolling the desert at night can get by with the light cast by the stars & moon thanks to his goggles.
Would these work in absolute darkness, like in a photographer’s darkroom or something?
My video camera paints the surroundings with infrared in absolute darkness if there is no ambient light at all; it occurs to me the same technology could be (and probably is) applied to night vision devices when there is no light to amplify.
See here, for instance:
*Imaging results with and without active-infrared.Active infrared night vision combines infrared illumination of spectral range 700nm–1000nm – just below the visible spectrum of the human eye – with CCD cameras sensitive to this light. The resulting scene, which is apparently dark to a human observer, appears as a monochrome image on a normal display device.
Because active infrared night vision systems can incorporate illuminators that produce high levels of infrared light, the resulting images are typically higher resolution than other night vision technologies. Active infrared night vision is now commonly found in commercial, residential and government security applications, where it enables effective night time imaging under low light conditions. However, since active infrared light can be detected by night vision goggles, it is generally not used in tactical military operations.*"
I can tell you that the NVG-7Bs that I used in the Army did not work in really dark nights (starless/cloudy/no moon) out in the woods/desert. As beowulff said, however, they did have a setting for infrared and with the use an infrared light they would work for a very short distance.
This is called FLIR and is a much more complicated and expensive device. In order to “see” the long-wave IR emitted by people, the sensors usually need to be cooled well below room temperature (often to cryogenic temperatures), which make these systems impractical to mount on goggles (with current technology).
I work for Cobham who have a contract to provide aircraft and crews for Australia’s Border Protection Command (BPC). We do maritime surveillance and the sensor suite in our Dash 8s includes a Wescam FLIR and Raytheon search Radar.