Night vision technology consists of two major types: light amplification or intensification and thermal, which is referred to as infrared imaging. Most consumer night vision products are light amplifying devices. All ITT Night Vision products use light-amplifying technology. This technology takes the small amount of light that's in the surrounding area (such as moonlight or starlight), and converts the light energy (scientists call it photons) into electrical energy (electrons). These electrons pass through a thin disk that's about the size of a quarter and contains more than 10 million channels. As the electrons go through the channels, they strike the channel walls and thousands more electrons are released. These multiplied electrons then bounce off of a phosphor screen which converts the electrons back into photons and lets you see an impressive nighttime view even when it's really dark.
The changes in technology for Night Vision are tracked with Generation designators, so Gen1 is the first generation and Gen2 is the second and so on.
Generation (Gen) 3 is the most sophisticated night vision technology available. The photocathode is coated with sensitive gallium arsenide, which allows for a more efficient conversion of light to electrical energy at extremely low levels of light. Generation 3 provides the clearest, sharpest night vision image available. The units have a higher-performing image intensifier tube with a minimum 51 lp/mm resolution, compared to the 45 lp/mm minimum of a standard Generation 3 unit. Line Pairs per Millimeter (lp/mm) are units used to measure image intensifier resolution; the higher they are, the clearer the image becomes. Generation 2 marked the development of a microchannel plate, which multiplies the number of electrons by the thousands. This produces a clear image in nighttime situations without the distortion of Gen 0 and Gen 1.
Generation 1 has problems with distortion and short-lived intensifier tubes. It uses materials that are better than Gen 0 to convert light to electrons. These units were able to operate at lower light levels than the Gen 0 and became known as "starlight scopes." Imported night vision viewers usually use Gen 1 image intensifiers even though they may be advertised as Gen 2.
Generation 0 technology depended on external light to increase available light energy. After the light was converted to electrons, electrical components focused these electrons through a cone-shaped device (anode) and accelerated them so they hit the phosphor screen with greater energy, creating the visible image. Unfortunately, accelerating the electrons in this manner caused distortion in the image and decreased the tube's life.
There are three important attributes for judging performance. They are: sensitivity, signal and resolution. As the customer, you need to know about these three characteristics to determine the performance level of a night vision system.
Sensitivity, or photoresponse, is the image tube's ability to detect available light. It is usually measured in "uA/lm," or microamperes per lumen. ITT's advanced technology and processing enable us to give our customers products with outstanding sensitivity. That's why many of our products do not come with standard IR illuminators. With many applications, illuminators are not necessary. Our competitors put IR illuminators on their products to obtain acceptable performance under low light conditions.
Signal plays a key role in night vision performance.
Resolution is the third major consideration when purchasing night vision. This is the ability to resolve detail in your image.
