Visibility in Optics
In linear optical interferometers like the Mach-Zehnder interferometer, Michelson interferometer, and Sagnac interferometer interference manifests itself as oscillations in the outgoing intensity, also called "fringes". Under these circumstances, the interferometric visibility is also known as the "Michelson visibility" or the "fringe visibility." For this type of interference, the sum of the intensities (or powers) of the two interfering waves equals the average of the fringes. It follows that the visibility can be written as,
This can also be rewritten as
where max is the maximum of the oscillations and min the minimum of the oscillations. If the two optical fields are ideally monochromatic (consist of only single wavelength) point sources then the predicted visibility will be
where and indicates the intensity of the respective wave. Any dissimilarity between the optical fields will decrease the visibility from the ideal. In this sense, the visibility is a measure of the coherence between two optical fields. A more general formula for this is given by the degree of coherence. This definition of interference directly applies to the interference of water waves and electric signals.
Read more about this topic: Interferometric Visibility
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