Noise-equivalent temperature (NET) is a measure of the sensitivity of a detector of thermal radiation in the infrared,

terahertz Terahertz or THz may refer to: * Terahertz (unit), a unit of frequency, defined as one trillion (1012) cycles per second or 1012 hertz * Terahertz radiation, electromagnetic waves within the ITU-designated band of frequencies from 0.3 to 3 terahe ...

or microwave portions of the electromagnetic spectrum. It is the amount of incident signal temperature that would be needed to match the internal noise of the detector such that the

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in deci ...

is equal to one. Often the spectrum of the NET is reported as a temperature ''per root bandwidth''. A detector that measures power is often interested in the analogous noise-equivalent power (NEP). If a relation between intensity and temperature is well defined over the passband, as in the case of a blackbody, then the NET simply scales with the NEP. If a detector is limited by either

shot noise Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge. Shot noise also occurs in photon counting in optical devices, where shot ...

Johnson noise Johnson is a surname of Anglo-Norman origin meaning "Son of John". It is the second most common in the United States and 154th most common in the world. As a common family name in Scotland, Johnson is occasionally a variation of ''Johnston'', a ...

then the NET can be decreased by using an increased integration time. The NET of flicker noise limited detectors can not be reduced by increased integration time. Typically uncooled bolometric detectors have NET figures of 30-200 mK. Cooled photon detecting infrared detectors using materials such as HgCdTe ( LWIR or MWIR) or InSb (MWIR) can approach a NET figure of 10 mK. In the microwave radiation region NET values are typically several hundred millikelvins to several kelvins. For a particular mean signal temperature there is a fundamental limit to NET given by the natural thermodynamic fluctuations of the photon flux from the source under investigation.

External links

Expanding the Vision of Sensor Materials (1995)
{Dead link, date=April 2020 , bot=InternetArchiveBot , fix-attempted=yes National Materials Advisory Board (NMAB) Infrared imaging Equivalent units

See also

External links