Noise-equivalent flux density

In optics the noise-equivalent flux density (NEFD) or noise-equivalent irradiance (NEI) of a system is the level of flux density required to be equivalent to the noise present in the system. ^[1] It is a measure used by astronomers in determining the accuracy of observations. ^[2]

The NEFD can be related to a light detector's noise-equivalent power for a collection area A and a photon bandwidth ${\displaystyle \nu }$ by:

${\displaystyle \mathrm {NEFD} =\eta {\frac {\mathrm {NEP} }{A\nu }}}$,

where a factor ${\displaystyle \eta }$ (often 2, in the case of switching between measuring a source and measuring off-source) accounts for the photon statistics for the mode of operation.

See also

External quantum efficiency

References

1. Malacara, Daniel (1988). Physical Optics and Light Measurements. Academic Press. p. 247. ISBN   9780124759718.
2. Benford, D. J.; Hunter, T. R.; Phillips, T. G. (1998). "Noise Equivalent Power of Background Limited Thermal Detectors at Submillimeter Wavelengths". International Journal of Infrared and Millimeter Waves. 19 (7): 931. Bibcode:1998IJIMW..19..931B. doi:10.1023/A:1022671223858. S2CID   9196659.