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

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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.

Original languageEnglish
Article number045030
Number of pages12
JournalSurface Topography: Metrology and Properties
Volume8
Issue number4
DOIs
Publication statusPublished - 21 Dec 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • Confocal
  • Interferometry
  • Metrology
  • Profilometry
  • Scanning white light interferometer
  • Stitching

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