ABSTRACT
Interferometry is arguably one of the most powerful diagnostic test tools in the optical toolbox. Interferometric techniques are used for a myriad of purposes ranging from the control of CNC machines of nanometer accuracy to the search for dark matter through gravitational lensing on a cosmological scale. Advances in the quality of laser diodes, have made them suitable for long path difference interferometry, though it is often necessary to spatially filter the laser, usually by transmitting it through a single-mode optical fiber. Interferometry is used as a routine test for optical components and systems at wavelengths ranging from the visible to above 10 µm. Infrared interferometry (IR) relies on sensing using an IR camera, either staring array cadmium mercury telluride or a pyroelectric vidicon tube. Double-pass interferometry can provide a confidence test on system performance, but ultimate proof may require a single-pass test, either by interferometry or by noncoherent broadband modulation transfer function testing or similar.
