Fiber point diffraction interferometer in measurement of spherical lens

An advanced fiber point diffraction interferometer (FPDI) is built for measuring spherical mirror surface and spherical lens wave front aberration with high precision. This new interferometer is based on point diffraction technique. Using short coherence length laser as light source, the perfect spherical wave diffracts from fiber point resource as reference wave. And the spherical wave is interfered with object wave to achieve higher accuracy. A phase shifting point diffraction interferometer with one single-mode-optical-fiber is built for measuring concave spherical mirror surface. A concave spherical mirror is measured by the experimental facility. The interferograms are collected by CCD and analyzed by computer. The PV values and RMS values of resulted surface error are compared with the result acquired by digital wave front interferometer. The measured surface is fitted and represented by Zernike polynomials. The results compared with Zygo GPI interferometer are proximately the same. Finally the differences between them are discussed in detail. To measure the aberration of spherical lens, a two single-mode-optical-fibers point diffraction interferometer is built by adding another single mode optical fiber. A convex lens is measured. The interferograms is presented.