System design and error correction for 300 mm aperture vertical Fizeau spatial-temporal phase-shifting interferometer.

ABSTRACT

With the development of high-power lasers for aerospace, electronics, etc., the demand for large-aperture planar optical elements has become more urgent, along with the demand for measurement methods. In this paper, the design of a 300 mm aperture vertical Fizeau spatial-temporal phase-shifting interferometer is discussed. Based on position difference between laser sources, the spatial phase-shifting technique is achieved by generating a laser source array on the focal plane of the collimation lens, and four pairs of coherent beams with different phase shifts are integrated in a vertical Fizeau interference system. Combined with a tunable laser diode, a temporal phase-shifting technique can be realized in any pair of coherent beams through wavelength tuning. The key techniques, which include laser duplication to introduce different phase shifts, conjugate imaging, and separation for interferograms, and assembly for a transmission flat, are demonstrated. The systematic error and position mismatch error of interferograms are eliminated. Comparison experiments are conducted between spatial and temporal phase-shifting techniques. A dynamic water surface is also measured to verify its capacity for detecting dynamic objects.