Optical Path Difference (OPD)
Optical path difference is the phase shift which happens between two previously coherent sources when passed through different mediums. For example a wave passed through glass will appear to travel a greater distance than an identical wave in air. This is because the source in the glass will have experienced a greater number of wavelengths due to the higher refractive index of the glass.
The OPD can be calculated from the following equation:
where d1 and d2 are the distances of the ray passing through medium 1 or 2, n1 is greater refractive index (e.g., glass) and n2 is the smaller refractive index (e.g., air).
Read more about this topic: Optical Path Length
Famous quotes containing the words optical, path and/or difference:
“There is an optical illusion about every person we meet.”
—Ralph Waldo Emerson (1803–1882)
“In the path of an action merely typical
To create the universal, originate a symbol
Out of the impact?”
—T.S. (Thomas Stearns)
“There is a difference between twenty-nine and thirty. When you are twenty-nine it can be the beginning of everything. When you are thirty it can be the end of everything.”
—Gertrude Stein (1874–1946)