Development of an ultra precision aspherical profiler for synchrotron radiation mirror. Calibration of the angle positioning for the goniometer

A new ultra-precision profiler has been developed in order to measure such as asymmetric and aspheric profiles. In the present study, the normal vectors at each points on the surface are determined by the reflected light beam goes back exactly on the same path as the incident beam. The surface gradients at each point are calculated from the normal vector and the surface profile is obtained by integrating the gradient. The measuring instrument was designed according to the above principle of the measuring method. In the design, four ultra-precision goniometers were applied to adjust of the light axis for the normal vector measurement. In the present measuring, the most important item is the measuring accuracy of the normal vectors by the goniometers. Therefore, the rotating angle positioning errors were measured and calibrated. In this paper, the calibration method is described. And evaluate the results of the measuring accuracy. (author)