Noise equivalent temperature difference

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Noise Equivalent Temperature Difference (NETD) is a measure of the sensitivity of a detector of thermal radiation in the infrared, terahertz radiation or microwave radiation parts of the electromagnetic spectrum.

It is the scene temperature difference equal to either the internal noise of the detector (detector NETD) or the total electronic noise of a measurement system (system NETD). The signal-to-noise ratio is thus equal to one.

If a detector is limited by either shot noise or Johnson noise then the NETD can be decreased by using an increased integration time. The NETD of flicker noise limited detectors can not be reduced by increased integration time.

Typically uncooled bolometric detectors have NETD figures of 80-200 mK. Cooled photon detecting infrared detectors using materials such as HgCdTe (LWIR or MWIR) or InSb (MWIR) can approach a NETD figure of 10 mK. In the microwave radiation region NETD values are typically several hundred millikelvins to several kelvins.

For a particular mean scene temperature there is a fundamental limit to NETD given by the natural thermodynamic fluctuations of the photon flux from the scene.

[edit] See also

• Detectivity
• Noise equivalent power
• MRTD

[edit] External links

• Expanding the Vision of Sensor Materials (1995) National Materials Advisory Board (NMAB)