Why Security system uses Infrared Camera? Fact File 37

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.

The generated electrons are now accelerated to another closely located Phosphor layer. This layer act as the Anode layer. When the accelerated electrons hit on the phosphor anode layer, light emission takes place through luminescence. Each electron from the photocathode can generate many electrons from the phosphor layer. This will create the visible image in the camera.

Image Source : Spy Infrared

Modern infrared vision systems have charged channels to accelerate the speed of electrons. The electrons release millions of electrons from the charged channels so that image from far located objects can be easily obtained.