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Photon noise is the randomness [citation needed] in signal associated with photons arriving at a detector. For a simple black body emitting on an absorber, the noise-equivalent power is given by N E P 2 = 2 h 2 ν 2 Δ ν ( n η + n 2 ) {\displaystyle \mathrm {NEP} ^{2}=2h^{2}\nu ^{2}\Delta \nu \left({\frac {n}{\eta }}+n^{2}\right)}
Image noise is random variation of brightness or color information in images, and is usually an aspect of electronic noise. It can be produced by the image sensor and circuitry of a scanner or digital camera. Image noise can also originate in film grain and in the unavoidable shot noise of an ideal photon detector. Image noise is an undesirable ...
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 noise is associated with the particle nature of light.
Photon counting eliminates gain noise, where the proportionality constant between analog signal out and number of photons varies randomly. Thus, the excess noise factor of a photon-counting detector is unity, and the achievable signal-to-noise ratio for a fixed number of photons is generally higher than the same detector without photon counting.
Due to the exponential reduction of ballistic photons as thickness of the scattering medium increases, the images often have a low number of photons per pixel, resulting in shot noise. Digital image processing and noise reduction are often applied to reduce that noise.
Shot noise as coined by J. Verdeyen [2] is a form of quantum noise related to the statistics of photon counting, the discrete nature of electrons, and intrinsic noise generation in electronics. In contrast to shot noise, [ clarification needed ] the quantum mechanical uncertainty principle sets a lower limit to a measurement.
Many microwave photons can be scattered from a single electron, so the amplitude of the scattering can be increased by increasing the power of the microwave transmitter. The low energy of the microwave photons corresponds to thousands of more photons per unit energy than in the visible region, so shot noise is drastically reduced.
Another method known as interaction-free imaging is used to locate an object without absorbing photons. [10] One more method of quantum imaging is known as ghost imaging. This process uses a photon pair to define an image. The image is created by correlations between the two photons, the stronger the correlations the greater the resolution. [11]