"When you see the little green pictures on CNN of people ...at night, think of Professor Spicer."
Piero Pianetta
In early World War II, U.S. engineer William Spicer (1929-2004) was aware of the visibility problem of conducting military operations at night and was looking into a solution based on photoemission. In photoemission, light is treated as packages of energy called photons, which strike a material to bounce out electrons. In 1942 Spicer developed the first night vision goggles using image enhancement.
At night, light is present in small quantities from various sources, but our eyes may not detect it. The photons from this light enter the goggle lens and strike a light-sensitive surface called a photocathode, releasing electrons. The electrons are accelerated toward a microchannel plate that releases thousands more electrons through a cascade reaction. These electrons hit a screen coated with phosphor chemicals to emit visible light. As thousands of electrons are generated from the small quantity of original photons, a much brighter corresponding image is produced.
When light enters the goggles it can be of any color, but once the photons transfer their energy to the electrons this information is lost. The image should therefore be black and white but it is actually green. Green phosphors are used in the screen because the eye can differentiate more shades of green than any other color, gaining as much detail as possible.
