Night vision systems are electronic devices used by military forces to detect and track targets at night. Police officers and hunters also use these devices.
The most advanced night vision system is the Forward-Looking Infrared (FLIR) system, developed in the late 1960’s. The FLIR uses a technique called thermal imaging, which detects and records minute temperature variations. The FLIR converts the temperature readings into electrical signals that generate a clear, black-and-white video image in which hot areas appear bright and cold areas appear dull. FLIR systems cannot be easily detected. When combined with powerful lenses, these systems have an extended range, and they perform relatively well even in bad weather or smoky conditions.
The first night vision systems used special searchlights that sent out infrared rays to illuminate an area. The infrared rays were invisible except when viewed through a special filter. Infrared systems were easily detected. They had a limited range, and they did not work well in bad weather or smoky conditions.
In the early 1960’s, image intensifying systems (sometimes called starlight scopes) were introduced. These systems have special tubes that magnify the starlight and moonlight reflected by objects and then focus the light on a viewing screen to produce an image.
