Interferometry uses the principles of interference to determine properties about waves, their sources, or the wave propagation medium. Acoustic interferometry has been applied to study the velocity of sound in a fluid. Radio astronomers use interferometry to get accurate measurements of the position and properties of stellar radio sources. Optical interferometry is widely used to observe things without touching or otherwise disturbing them. Light beams are sent through various paths, and they combine at one observation region where interference fringes occur. Interpreting the fringes reveals information about optical surfaces, the precise distance between the source and the observer, spectral properties of light, or the visualization of processes such as crystal growth, combustion, diffusion, and shock wave motion.

The observation and explanation of interference fringes dates back to Robert Hooke and Isaac Newton, but the invention of interferometry is generally attributed to American physicist Albert Michelson. The Michelson interferometer...