Accurate topography measurement of large flat surfaces

A new technology for the precise topography measurement of reflecting flat surfaces is presented in this paper. The instrument is capable of scanning large flats of about 500 mm/sup 2/. The instrument consists of a sensor head, which is an angle-measuring device, based on a CCD camera or a position sensitive detector (PSD). The sensor head includes a pentagon prism that reduces the pitch error in scan direction by a factor of about 100.