Optical devices generally work by taking a lot of light in at one end, and kind of supplying it to your eye through a small lens at the other end. Years ago, I worked with a guy who had a really expensive pair of binoculars, they were just regular binoculars, not night vision ones, as night vision ones had not been invented at the time, or at least were not available to the public. I remember it was around dusk on a summer evening, and I looked through them, and saw the the sign on a building across the road was appearing to be illuminated. He explained to me how the large lens at the end takes in the light from what is being viewed, and then kind of compresses it down to eyeball size, making it seem brighter. Night vision can work a couple of ways - one is to send out a light beam that is at a frequency that cannot be seen with the naked eye, and then view the object with a lens that is sensitive to the frequency used. The snag is that the range is limited to the range of the invisible light. Modern night vision devices work the same as good binoculars, by taking in a lot of the light that is available, and supplying it to the eye. This is done these days electronically, I suspect that it might be like a digital camera - the light hits the sensitive electronic device that detects light, and then the user actually sees an image of this by looking at a small screen. Anyway, night vision products make really great and unusual gifts, and American Technologies Network make a great line of ATN night vision products.

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