An interferometer is an instrument used to measure waves through interference patterns. Interferometry is the process by which two waves are combined so they can be studied for differences in their patterns. The fields of study where interferometry is used are astronomy, physics, optics, and oceanography.
In astronomy, interferometers are actually two or more telescopes and mirrors working together to provide high resolution of images of objects in space. The telescopes are generally located thousands of miles apart. The process works by spacing the mirrored lenses of the telescope at planned intervals. The light from outside the Earth's atmosphere bounces off the lenses as in a reflecting telescope and is combined into an interferometer as radio waves. The radio waves are then measured to produce a high resolution image.
A special observatory known as the Laser Interferometer Gravitational-Wave Observatory (LIGO) is devoted solely to detecting gravitational waves. This observatory uses its research to detect astronomical events such as gamma-ray bursts and possible collisions to Earth. Gravitational waves from supernovas, black holes, and neutron stars are observed and measured for research and understanding of how and when they formed.
In physics and optical interferometry, as well as astronomy, the Michelson interferometer is used to detect gravitational waves and to generate an optical differential-phase shift keying (DPSK) demodulator. A DPSK converts the phase-coded signal into an intensity-coded signal. This allows the signal to be amplified and increases both the quality and the amount of data that can be transmitted.
The Michelson interferometer works by having two mirrors set at a 90 degree angle. A third, partially-silvered mirror is set between them at a 45 degree angle. As light moves through the partially silvered mirror, it splits the beam of light and each beam takes a different path. This interference due to separate wavelengths is converted to a wavelength path which is detected by the interferometer. The signal is amplified as it comes back together, which increases the quality of the transmission.
Interferometric data is used in oceanography to determine the state of oceanic activity. The interferometer detects wavelengths using an algorithm known as parametric retrieval algorithm (PRA). PRA is able to use information gathered from Along-Track Interferometric Synthetic Aperture Radar (AT-InSAR) with wind data and converts it to information useful for weather centers. Information such as the height of waves, length of waves, and wave directions is helpful in determining weather patterns and possible ocean floor activities.