How do night vision goggles work?

Answer 1

A beam of infrared light is sent out which is invisible to the human eye. However just like a digital camera the goggles can pick up the infrared light and convert it into the visible spectrum and display it on an small lcd screen inside the goggles. Wearing these on guard duty a couple years ago I found them very strange. First all you have no depth perception and if you look at anything too bright you're gonna get blinded (temporary). Sorry I don't know the technicalities but I would find out by looking for a book at your local library consortium under "how things work". Night Vision Goggles, (NVG), work by amplifying light � moonlight, starlight - in the Near Infra Red, (NIR), region of the spectrum � approx� 600nm to 930nm, (Gen III). NVGs incorporate Automatic Gain Control, (AGC), this controls the amplification, (gain), of the NVG which helps maintains an acceptable level of contrast of the image presented to the viewer. E.g. a scene viewed under illumination from the full moon will cause the NVG amplification / gain to reduce. The same scene viewed with little NIR illumination will cause the NVG amplification / gain to increase and results in a reduction in the quality of the image being viewed due to �spangles�, (flashing pin points of light on the image), which is �noise� from the amplification / gain process. Incandescent bulbs in addition to visible light, release most of the energy produced in the NIR and IR spectrum, (heat). NVGs used by a sentry to view an approaching vehicle which has illuminated headlights, will find the NVG �blinded� by the amount of NIR being produced by the headlights, similarly NVG used by a pilot can be �blinded� by cockpit illumination � the AGC can only cope with a limited range of NIR illumination before the goggle is saturated � �blinded�. The image presented to the viewer using NVG is monochromatic � green. The image is 2 dimensional � no perception of depth. This makes operating a vehicle or aircraft using NVGs very difficult, since distance and closing speeds are very difficult to assess. Most of the NVG sold commercially are � at best - Gen II, which is very poor in comparison to the GEN III - restricted technology � currently used by the military. Passive NVG's work like this: light photons will come it (any tiny bit of light, moonlight, starlight), and come into the goggle, and it turned into electrons. then, it hits a very thin charged disc, with millions of channels in it. the electrons hit this, and going through the channels it will release millions more electrons. then, these electrons hit a phosphor screen and they basically spread the very little bit of light all over the phosphor screen so you can see. it is actually manifactured so it turns out green, because the human eye can decipher many different shades of green than any other color.