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

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

, terahertz or

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...

portions of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

. It is the amount of incident signal

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

that would be needed to match the internal noise of the detector such that the signal-to-noise ratio 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 Noise-equivalent power (NEP) is a measure of the sensitivity of a photodetector or detector system. It is defined as the signal power that gives a signal-to-noise ratio of one in a one hertz output bandwidth. An output bandwidth of one hertz is equi ...

(NEP). If a relation between intensity and temperature is well defined over the

passband A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenn ...

, as in the case of a

blackbody A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. A black body ...

, then the NET simply scales with the NEP. If a detector is limited by either shot noise or Johnson noise then the NET can be decreased by using an increased integration time. The NET of

flicker noise Flicker noise is a type of electronic noise with a 1/''f'' power spectral density. It is therefore often referred to as 1/''f'' noise or pink noise, though these terms have wider definitions. It occurs in almost all electronic devices and can show ...

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 Hg1−xCdxTe or mercury cadmium telluride (also cadmium mercury telluride, MCT, MerCad Telluride, MerCadTel, MerCaT or CMT) is a chemical compound of cadmium telluride (CdTe) and mercury telluride (HgTe) with a tunable bandgap spanning the shortwav ...

(

LWIR Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

MWIR Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

) or

InSb Indium antimonide (InSb) is a crystalline compound made from the elements indium (In) and antimony (Sb). It is a narrow- gap semiconductor material from the III- V group used in infrared detectors, including thermal imaging cameras, FLIR systems, ...

(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