Measuring the phase transfer function of a phase-shifting interferometer

Abstract

In characterizing the performance of a phase-shifting interferometer, the dependence of the measured height on the spatial frequency is rarely considered. We describe a test mirror with a special height relief that can be used to measure the height transfer function for the interferometer in a fashion analogous to the measurement of the modulation transfer function for the optical imaging system. We fabricated the test mirror at the National Institute of Standards and Technology (NIST) using a lithography-based process. The test mirror has several patterns (reminiscent of moth antennae) with variable spacing in radial direction. We describe the fabrication of the test mirror and its application to test the performance of the interferometer.