The Navy Precision Optical Interferometer, instead of using a single telescope, combines the light from an array of up to six mirrors spaced tens of meters apart by precisely directing the beams of light from a star to a point. Extraordinary stellar image detail can be derived from the resulting data called an interference pattern.

An optical interferometer works with light that can be best gathered and directed with mirrors and lenses, generally from the visible light through near infrared light. However, an astronomical interferometer is a useful technique for recording extraordinarily high detailed (resolution) images at any wavelength of light (the electromagnetic spectrum) including radio wavelengths. In fact, radio interferometers became practical instruments several decades before optical interferometers (VLA). The technical advantages of longer wavelengths and how radio signals are recorded enabled the early advancement of radio interferometers.

The following discussion pertains to optical interferometry and the Navy Precision Optical Interferometer specifically.