4.11.2 Infrared detectors O Devices converting infrared radiations into electric quantities are called infrared detectors 日 Two types: Thermo-sensitive detectors Photosensitive detectors
❑Devices converting infrared radiations into electric quantities are called infrared detectors. ❑Two types: • Thermo-sensitive detectors • Photosensitive detectors 4.11.2 Infrared detectors
4.11.2 Infrared detectors NOnselective infrared detectors Thermo-sensitive detectors take advantage of the heat effect produced by semiconductor films when exposed to infrared radiation The thermo-sensitive device has a relatively long response time of the order of 10-3s Basically, thermo-sensitive detectors have the same response to radiations with different wavelengths They have a flat optical spectrum, and a nearly constant sensitivity over the whole wavelength range of measurement
❑Nonselective infrared detectors : ➢Thermo-sensitive detectors take advantage of the heat effect produced by semiconductor films when exposed to infrared radiation. ➢The thermo-sensitive device has a relatively long response time of the order of 10-3 s. ➢Basically, thermo-sensitive detectors have the same response to radiations with different wavelengths. They have a flat optical spectrum, and a nearly constant sensitivity over the whole wavelength range of measurement. 4.11.2 Infrared detectors
4.11.2 Infrared detectors Oa photoelectrical detector is a semiconductive one When photons are striking on the photosensitive component, electron-hole pairs are decomposed to generate electrical signals. As the photoelectrical effect appears very fast, response of a photoelectrical detector to infrared radiation is much faster than that of a thermo-sensitive detector. usually in the order of or even us
❑ 4.11.2 Infrared detectors A photoelectrical detector is a semiconductive one. When photons are striking on the photosensitive component, electron-hole pairs are decomposed to generate electrical signals. As the photoelectrical effect appears very fast, response of a photoelectrical detector to infrared radiation is much faster than that of a thermo-sensitive detector, usually in the order of ms or even s
4.11.2 Infrared detectors The detector has an unchanged wavelength range, and a peak value at the wavelength, An. The response comes rapidly to stop when the wavelength exceeds (see curve 2 in Fig. 4.108). The reason is that the amount of photons is insufficient to activate the release of electrons within a range of wavelengths larger than a certain wavelength
The detector has an unchanged wavelength range, and a peak value at the wavelength, p . The response comes rapidly to stop when the wavelength exceeds p (see curve 2 in Fig. 4.108). The reason is that the amount of photons is insufficient to activate the release of electrons within a range of wavelengths larger than a certain wavelength. 4.11.2 Infrared detectors
4.11.2 Infrared detectors Photoelectrical detectors operate only in low temperatures R 2 Fig. 4.108 Optical spectrum response of infrared detector
• Photoelectrical detectors operate only in low temperatures 4.11.2 Infrared detectors Fig. 4.108 Optical spectrum response of infrared detector