Multiple-wave radial shearing interferometer based on a Fresnel zone plate

A compact multiple-wave radial shearing interferometer (MWRSI) with strong adaptability, which is based on a Fresnel zone plate (FZP), is proposed. The nominally plane beam under test passes through the FZP and diffracts into multiple orders, including nominally plane beam, converging spherical beams, and diverging spherical beams. After propagating a distance, different apertures of diffraction orders cause multiple beams to meet and interfere in the imaging plane and form radial shear. The single interference pattern contains multiple wavefront differences in the overlapping region of beams. Then, a method that is employed in the wavefront difference retrieval from the MWRSI's interferogram has been given. This MWRSI needs only an FZP and a CCD; therefore, it can be made very compact. It is suitable to measure the continuous and transient wavefront. The numerical simulations and experiments validate the proposed method.