Deflectometric Measurement of Flat and Slightly Curved Optical Surfaces with Improved Lateral Resolution

摘要

At the Physikalisch-Technische Bundesanstalt (PTB), a new Deflectometric Flatness Reference (DFR) for measuring the topography of flat or slightly curved optical surfaces has recently been installed [1-4]. With existing deflectometric procedures like the direct or difference mode, the spot size of the angle measuring system (autocollimator) is the limiting factor for the lateral resolution. To reduce the spot size of the scanning beam, an additional measurement option, called Exact Autocollimation Deflectometric Scanning (EADS) is implemented. The surface under test is tilted at each measuring position to be perpendicular to the incoming light beam, and the tilt is measured by an additional autocollimator. The development of an angle measuring device with reduced spot size is explained. The development of the EADS system is detailed and the system will be compared with the classical deflectometric measurements.