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Principle of measuring distance with an interferometer

Two-panel illustration of an interferometer

In an interferometer, two or more waves overlap to produce an “interference pattern,” which can provide detailed information on the waves, such as their wavelengths (the distance between adjacent peaks). In this simple, ideal setup, an individual light wave from a laser hits a beamsplitter, which creates two light waves traveling in different paths. One of the waves hits a moving mirror, which can vary its distance as it travels to the detector. If one wave’s peaks overlap with the other’s valleys (top panel), they cancel out. If the two wave’s peaks overlap, however, they create a bright spot (bottom panel).

May 2019 • NIST • • Tagged: Diagrams