Two-dimension lateral shearing interferometry with dual-mode

Abstract

Lateral shearing interferometry is an attractive technique to measure the wavefront aberration of high numerical aperture optical systems, of which using two-dimensional grating can divide and shear the wavefront in two-dimension simultaneously. A two-dimension lateral shearing interferometer based on chessboard grating was designed, which can work in dual-mode: the phase shifting mode and the Fourier transform mode. In the phase shifting mode, the phase shifting was realized by moving chessboard grating along the shearing direction in the image plane. In the Fourier transform mode, the spatial carrier frequency was realized by positioning the grating at the Talbot distance of the objective image plane. An experimental setup was designed to measure a 10×, NA0.25 microscope objective at 632.8nm wavelength. The objective was measured by the experimental setup in dual-mode, the results showed that the wavefront of the objective was 0.172λ RMS; in the phase shifting mode, the repeatability (3σ) of RMS was 1.1mλ; in the Fourier transform mode, the repeatability (3σ) of RMS was 2.7mλ; after correcting the coordinates of the wavefront, the differences of Z5 to Z36 between phase shifting mode and the Fourier transform mode were better than 8mλ.