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.
An absolute measurement method of spherical lens with Fiber Point Diffraction Interferometer (FPDI) was developed.
To achieve a high accuracy, several key techniques are discussed such as: short coherence length laser, interferogram
collecting, experiment set up, and reconstruction of wave front. Through these techniques an experiment system has been
built. The 5-step phase shifting interferograms are collected. The wave front is fitted by Zernike polynomials and
reconstructed. The repeated measurement result has a good performance compared to a Zygo GPI interferometer.
This paper presents Zernike polynomials fitting wave front which is detected by fiber point diffraction interferometer (FPDI). To confirm that Zernike polynomials are suitable for fitting concave spherical mirror surface, different orders of Zernike polynomials were used to fit several different surfaces which are produced by computer. Fitting result errors were evaluated by residual standard deviation. It is illuminated that Zernike polynomials are suitable for fitting surface which changes smoothly but not suitable for fitting surface with sharp fluctuating. When the shape changes dramatically Zernike polynomials are unable to correctly fit. Choosing appropriate term of polynomials, more terms don't mean higher precision. A metal coated concave spherical mirror, curvature radius 580mm, caliber 70mm, was measured as a sample. The five-step phase shifting interferograms of good quality were detected by an experimental FPDI which was built in lab. Measured wave front was fitted by 36 terms of Zernike polynomials from phase map which were unwrapped from five-step phase shifting interferograms. The measurement result was obtained and compared with that by Zygo interferometer when measured the same mirror. The 2 represented wave fronts have same characters such as centers bulging and marginal trough.