Infrared camera is used to capture the image of a moving person in darkness as a measure of security. The surveillance systems used in home, office and commercial establishments uses infrared camera to monitor the premises. The infrared camera utilizes the infrared radiation generating from the body heat. The system senses the infrared and generates a video image of the moving person using the infrared camera. This device is sensitive to only the infrared range of the electromagnetic spectrum.
The system uses a Photocathode sensitive to infrared. The Photocathode consists of a thin layer of metal that can give out electrons by accepting energy from the infrared rays. The thin layer of metal is coated on a flat glass plate. A lens system is provided to focus the infrared light from the source into the photocathode plate. The metal coating in the photocathode is too thin so that when the infrared energy hits the front layer of the metal, electrons will be emitted from its back layer. Thus the photocathode generates an electron pattern based on the infrared photons hitting on the photocathode.