Phase-shifting interferometric profilometry with a wavelength-tunable diode source

A phase-shifting interferometer with a tunable external-cavity laser diode has been constructed for forming three-dimensional (3-D) phase profiles. The interference phase is shifted equally in four steps by varying the source wavelength. Profilometry is achieved by measuring the phase shifts that are extracted by the Carré algorithm. The linear regression of the distance measurement from 40 μm to 13mm has been experimentally demonstrated by phase-shifting interferometry. A laser-diode interferometer has been applied to 3-D profile measurement for a step-mirror object at a deep depth.