Profile Measurement With A Phase-Shifting Common-Path Polarization Interferometer

A common-path polarization interferometer is constructed for measuring microscopic surface profile. A double-focus lens made of birefringent material is used to divide the wave. To detect phase difference smaller than unit fringe, phase-shifting technique is adopted. This optical system is expected to be insensitive to vibration, temperature variation and air draft because of its common-path geometry. With this system microscopic surface profiles of some samples are measured. The measurements confirm its insensitiveness to vibration. On the basis of the results of the experiment, some problems for this type of an interferometer are discussed.