Multi-sensor optical profilometer for measurement of large freeforms at nm-level uncertainty

Abstract

Optical measurement of large freeform samples is often limited by the resolution, size and slope limits of measurement devices. This trade-off can be solved using stitching—which, however, creates several difficulties often linked to accuracy of movement of the sample or objective. We present a stitching multisensor freeform topography instrument based on scanning white light interferometer, confocal sensor and accurate movements of the sample tracked using laser interferometers. The interferometers track the sample in 2D at an accuracy of a few nm over a 10 cm × 10 cm area. The instrument is thoroughly characterized and uncertainty is estimated to ensure traceable results. Based on the characterization results the instrument allows topography measurement of freeform sample with 54 nm standard uncertainty for datasets of a few hundred sub-images.

Influence of Different Wax Hardening Agents on Surface Roughness of Refractory Cast Investment Materials

“…Ceresin wax melts at a point of 78C° Each specimen is dipping into the liquid melted wax until the surface of it covered entirely to close all the pores on the surface. [15,16].…”

Traceable stitching interferometry for form measurement of moderately curved freeform surfaces

“…6 measuring a specimen with 100 mm in diameter and up to 1300 μm of freeform departure from the best-fit sphere. Reference 7 presents an approach with a combination of subaperture stitching and white-light interferometry. Instead of tilting the specimen or the interferometer for larger slopes, a higher magnification is used to resolve the interferograms.…”