What is a Interferometer?

An interferometer is a device that measures the interference phenomenon that occurs when light is applied to an object. The interference phenomenon depends on the material of the object and the condition of the surface. The surface shape, refractive index, object size, etc. of each object can be measured from the difference in the interference phenomenon. The size that can be measured with an interferometer is at most several to a dozen centimeters. If the measurement sample is large, it is necessary to take some measures such as cutting it out. Interferometers include Michelson interferometers, Mach-Zehnder interferometers, and Fizeau interferometers. Among them, the Fizeau interferometer is a typical one.

Application of Interferometer

Interferometers can measure multiple elements, but are often used to measure refractive index. Specifically, it is a performance evaluation of antireflection films for glass and base films. When light hits the glass or base film, it causes reflection. When reflection occurs, the transmission quality deteriorates due to noise generation and loss of the transmitted signal. Therefore, it is necessary to suppress reflection. The light reflected by the antireflection film is designed to be out of phase with the light reflected by the surface of the substrate. Interference phenomenon occurs due to light with different phases, and each light cancels each other out. By canceling it, all the light will be transmitted. In addition to visible light, anti-reflection filters for ultraviolet and infrared rays are made.

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