Ward D Vision 800 Review
Most people like to think of spy movies and army films when they consider night vision goggles, but my love affair with the technology reaches back to the cartoonishly large Night Vision Devices used by young Tim Murphy in Jurassic Park. They made for the coolest toy in the series of vertically integrated products released by Universal, but I never did get a pair from my parents.
The Ward-D-Vision 800 series digital night vision add on system is designed to be coupled behind a normal day telescopic sight to give it night vision capabilities. The system will work with most day telescopic sights, providing they have an adjustable objective, or preferably (for ease of use) a sidewheel focus system.
Ward 800s
Looking back, the toys would never have done the job you saw in the movie. They were essentially just giant pairs of green-tinted glasses that made the world around you look vaguely like the images produced by a pair of night vision goggles. Why green? Well, we'll get to that. But first, a lesson in light.
Human beings only see a certain portion of available light along what we call the visible spectrum. Above that spectrum is ultraviolet light (the stuff that gives you sunburn), and below it is infrared light (the light your remote control uses). NVDs are sensitive to infrared light as well as visible light, so they can collect light the wavelengths of which are too long for our eyes to detect.
When that light passes through the objective lens or lenses on a pair of night vision goggles, it meets a series of plates that enhances its power. The first of these is called a photocathode, which is a negatively charged plate that ejects an electron further down the tube in exact correspondence to any photons of light that hit it.
The next element is called a microchannel plate. When the electrons from the photocathode pass through the MCP, 5,000-volt bursts of electricity accelerate them through microscopic channels in the glass. On their way through these channels, the MCP emits thousands of electrons that, again, correspond to the position and intensity of the original photons. This is due to a phenomenon called cascaded secondary emission.
Finally, these newly multiplied electrons pass through a screen coated with phosphors. The energy of the electrons excites the phosphors, the electrons of which release photon particles as they descend from an excited state. Those phosphorescent photons are what cast the green color on your night vision image, the light from which then travels through the goggles' ocular lens and into your eye.
In short, these goggles take in all available light from the infrared spectrum up through the spectrum of visible light, convert its photons to electrons, exponentially multiply those electrons, and revert all those new electrons back into photons that your goggles then focus into a clear, night vision image.