Instantaneous measurement Fizeau interferometer with high spatial resolution
Modern precision optical manufacturing places high demands on instrument design, both for flexible response to challenging environments and high lateral resolution for measuring both surface form and mid spatial frequency waviness. Here we report on a Fizeau-type interferometer optimized for light-efficient, single-frame carrier fringe acquisition for instantaneous metrology at high lateral resolution. Fully coherent optics and a 1200 x 1200 pixel camera provide high slope acceptance and an instrument transfer function (ITF) above 50% at 250 cycles/aperture for all zoom settings, as demonstrated for an etched phase step and custom periodic artifact. The instrument further provides an ITF of 500 cycles/aperture using optional temporal phase shifting interferometry on the same platform.