White-light interferometric measurement of spherical and aspherical surfaces

White-light interferometric techniques and image processing techniques have been widely applied in measurement of surface profiles. A new method based on two technologies to achieve the optical non-contact shape measurement for spherical and aspherical surfaces is presented in this paper. This method utilizes the pixels of the image to locate the points of surface and obtains the surface height information by a vertical scanning white-light interferometric system. A set of a three-dimensional stage composed of a fine and coarse two-step vertical driver, and a two-dimensional horizontal driver is designed to enlarge the measurement area and the vertical scanning range. The measurement precision depends on the the performance of the interference microscope and the three-dimensional stage, so the influence of the interference microscope on the measurement result and the precision of the stage are analyzed. In the stage, a grating sensor is used to monitor the scanning process and the scanning information is fed to driving circuit to compensate for the errors. Additionally, experiments are carried out and correlative results are also shown.