Interferometria

Interferometria is a measurement technique that relies on the superposition of waves to extract information about differences in optical path length, wavelength, or surface topography. When waves from a coherent source are split and later recombined, they interfere, producing an interference pattern whose intensity depends on the phase difference between the two paths. Small changes in distance, index of refraction, or surface geometry can shift the fringes, enabling precise metrology.

A typical interferometer uses a coherent light source, a beam splitter, mirrors or arms, and a detector or camera to observe the fringes. Common designs include the Michelson interferometer, which splits and recombines light along two perpendicular arms; the Mach-Zehnder interferometer, which has two separate paths; and the Fabry-Pérot interferometer, which uses multiple reflections in a cavity. Variants such as the Sagnac interferometer or Lloyd’s mirror are also employed. Interferometry can operate with optical, infrared, or radio waves and generally requires stable optical paths and sufficient coherence.

Applications span scientific and industrial domains. In metrology, it enables high-precision surface profiling, flatness measurements, and refractive-index determinations. In astronomy, interferometry combines signals from multiple telescopes to increase angular resolution (stellar interferometry, aperture synthesis, very long baseline interferometry). Gravitational wave detectors (for example, LIGO and Virgo) use laser interferometry to measure tiny spacetime distortions. Fourier transform spectroscopy and fiber-optic sensing are additional important uses.

Limitations include sensitivity to vibrations, temperature and air fluctuations, and the need for precise alignment and optical stability. The technique relies on coherent sources and careful data analysis to extract phase information.