Radial shearing interferometer for aspheric surface testing

In this paper, aspheric surface testing technique with radial shearing interferometer has been developed. Zone plates are proposed to construct radial shearing interferometer because of its stability and simplicity. Zone plates were designed and fabricated by photographic processing, which is used as radial shearing devices. Radial shearing interferogram are detected by a CCD camera and processed by a PC computer. Fringe phase of shearing interferogram is evaluated by Fast Fourier transform (FFT) algorithm. Wave aberration estimation method of aspheric surface is also presented, which is depended on polynomial expansion fitting. Some errors of interferometer are discussed. Finally, theoretical analysis and experimental results are compared, which shows its accuracy is less than λ/20.