Fizeau interferometer
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A Fizeau interferometer[1] is similar to a Fabry–Pérot interferometer in that they both consist of two reflecting surfaces. In a Fizeau interferometer, however, the two surfaces are usually much less than totally reflecting (4–30%), so that secondary reflections don't contribute greatly to the fringe contrast. An angled beam splitter captures the reference and measurement beams.
Fizeau interferometers are commonly used for measuring the shape of an optical surface: Typically, a fabricated lens or mirror is compared to a reference piece with the same shape or a flat. The reference piece is sometimes realized by a diffractive optical element, as this can be manufactured by lithographic methods, which inherently warrant for high precision. Fizeau interferometers are also used in fiber optic sensors for measuring pressure, temperature, strain, etc.
Fizeau used his interferometer to measure the effect of movement of a medium upon the speed of light, as seen the second figure. Light reflected from the tilted beam splitter is made parallel using a lens and split by slits into two beams, which traverse a tube carrying water moving with velocity v. Each beam travels a different leg of the tube, is reflected at the mirror at left, and returns through the opposite leg of the tube. Thus, both beams travel the same path, but one in the direction of flow of the water, and the other opposing the flow. The two beams are recombined at the detector, forming an interference pattern that depends upon any difference in time traveling the two paths.[2]
[edit] See also
[edit] References
- ^ Lawson, Peter R. "Principles of Long Baseline Stellar Interferometry." Course notes from the 1999 Michelson Summer School, held August 15–19, 1999. Editied by Peter R. Lawson. Published by National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 2000.
- ^ Robert Williams Wood (1905). Physical Optics. The Macmillan Company. p. 514. http://books.google.com/books?id=Ohp5AAAAIAAJ&pg=PA514.
[edit] External links
- Some typical measurement setups from the booklet of interferometer manufacturer Zygo Corp.
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