Interferometry

Interferometry uses the overlap of waves to extract extremely precise information about an object — its distance, shape, surface, or motion.

The basic principle

When two or more waves meet, they can reinforce each other (constructive interference) or cancel out (destructive interference) depending on their phase relationship. The resulting pattern is exquisitely sensitive to the smallest changes in the measurement setup.

A classic example

In a Michelson interferometer, a laser beam is split into two paths that travel separately before being recombined. If one of the mirrors shifts even slightly, the interference pattern changes — and that change reveals the shift with extraordinary precision.

Where interferometry is used

• Astronomy: combining signals from multiple telescopes to reveal detail no single telescope could resolve.
• Metrology: micrometer- and nanometer-scale distance and shape measurement in manufacturing.
• Gravitational-wave research: facilities like LIGO use this method to detect minuscule distortions of spacetime.
• Materials science: inspecting surface defects, coating thickness, and deformation.