A Fizeau interferometer 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

Optical fiber

An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...

 sensors for measuring pressure

Pressure

Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

, temperature

Temperature

Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

, strain

Strain (materials science)

In continuum mechanics, the infinitesimal strain theory, sometimes called small deformation theory, small displacement theory, or small displacement-gradient theory, deals with infinitesimal deformations of a continuum body...

, 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

Beam splitter

A beam splitter is an optical device that splits a beam of light in two. It is the crucial part of most interferometers.In its most common form, a rectangle, it is made from two triangular glass prisms which are glued together at their base using Canada balsam...

 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.

See also

• Hippolyte Fizeau
  Hippolyte Fizeau
  Armand Hippolyte Louis Fizeau was a French physicist.-Biography:Fizeau was born in Paris. His earliest work was concerned with improvements in photographic processes. Following suggestions by François Arago, Léon Foucault and Fizeau collaborated in a series of investigations on the interference of...
  
  
• List of types of interferometers
• Fizeau–Foucault apparatus

External links

• Some typical measurement setups from the booklet of interferometer manufacturer Zygo Corp.