Profiler tip characterization using a precision sphere

摘要

To achieve high precision form measurements by a tactile profiler, besides a stable coordinate system and a constant velocity of motion the form of the probing tip is a decisive factor. For reliable form measurements the form of the profiler tip has to be removed from the measured profiles. Therefore, the mean tip radius and the 3 d tip shape have to be investigated. As a nearly ideal sample for 3 d tip characterization a calibrated precision sphere is measured by the metrological profiler instrument HRTS at the PTB. The instrument is equipped with a linear moving stylus and an interferometer on the z-axis. The construction of the measurement head allows equivalent profile measurements in x- and y-direction of the instrument. Therefore, mean tip radius values are determined for x- and y-scanning for the full opening angle of the tip. Topographical measurements are used for imaging the tip within a limited opening angle. After characterisation of the tip for both scanning directions a conventional two dimensional tip characteriser sample is investigated by x- and y-scanning. The radii of the test specimen are calibrated with an expanded uncertainty of 0.11 μm with excellent agreement for both scanning directions.