An instrument that employs the interference of lightwaves to measure the accuracy of optical surfaces; it can measure a length in terms of the length of a wave of light by using interference phenomena based on the wave characteristics of light. Interferometers are used extensively for testing optical elements during manufacture. Typical designs include the Michelson, Twyman-Green and Fizeau interferometers.
The basic interferometer components are a light source, a beamsplitter, a
reference surface and a test surface. The beamsplitter creates the
reference and test beams from a single light source.