When one will measure the precision profiles of super smooth surfaces using an optical interferometer, a perfect-flat reference mirror should be used. However, it is impossible to obtain such a mirror. For the case using a stylus method, a perfectly-straight-moving slide table should be used. It is impossible to obtain that table too. In this paper, We propose the optical precision profiling method which does not need a perfect-flat plane. This method is developed on the optical skid method previously reported (the 1st report). For the surface data obtained using the optical skid method, the amplitude of low spatial-frequency components were attenuated noticeably and the data were used as the roughness profiles. This paper will make it clear that : (1) One can theoretically calculate the exact attenuation rate of frequency component from the positions and the sizes of the photo-detectors used in the sensor head of the optical skid method. (2) One can completely retrieve the surface profile by the digital filtering using the calculated attenuation rate. In an experiment, a profile of a step height standard is retrieved using the method mentioned above. And a waviness profile of a mirror obtained using this method is compared with the profile measured using Talystep.
