Single-shot reflective shearing point diffraction interferometer for wavefront measurements

A single-shot reflective shearing point diffraction interferometer (S-SRSPDI) is designed for large-aperture dynamic wavefront measurements. The PDI is integrated on the small substrate with properly designed thin film. The wavefront under test is reflected by the front and rear surfaces of the substrate respectively to generate an interferogram with high linear-carrier frequency, which is used to reconstruct the wavefront by means of the Fourier transform algorithm. In this paper, the analytic formula of intensity distribution of the interferogram is derived. The parameters related with the carrier frequency of fringes are discussed. The method to optimize the contrast of the interferogram is proposed by analyzing the reflective polarization effects. In addition, the spurious fringes of the interferogram are removed by the proper designed blocking film. S-SRSPDI was applied to detect the dynamic wavefront with a diameter of 400 mm. The measured aberrations are in good agreement with those obtained by the shearing method, which verifies that the proposed S-SRSPDI is a powerful tool for large-aperture dynamic wavefront measurements.