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Saturday, August 3, 2019

IR (Infrared) sensors

What is IR (Infrared) sensors?

Infrared sensors are the sensors which can detect infrared radiation . Infrared waves are not visible to human eye. It has wavelength greater then visible light, visible light has the wavelength in the range of 0.4 to 0.7 micro meter. Infrared ray has wavelength greater than 0.7 micro meter.

The IR sensors are the reverse biased diode made up of suitable band gap material, when infrared radiation falls on the detector electron hole pairs are generated in the depletion region which is swept by the large electrical field available in the depletion region. Thus a current gets established. Since infrared radiation has less energy compare to visible light ( because it has low frequency compare to visible light and the energy of incident photon =hv where v is the frequency , h is Planck constant ) so material with suitable band gap should be chosen. Silicon which is widely used in electronics is not a choice because it has band gap of 1.2eV, and the incident infrared radiation do not have this much of energy . So for infrared detector the material of suitable bandwidth is Mercury Cadmium Telluride (MCT).
Infrared detectors are widely used in thermal imaging . A body when heated radiates infrared light which can be detected by infrared detector and a thermal image can be formed.

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