The calibration of our interference microscope is currently performed by an elaborate multi step process. As a result the total uncertainty of a measurement performed with the interference microscope is much larger than the intrinsic repeatability of the microscope which is of the order of 1 nm. A major contribution to the total uncertainty is a length dependent factor, resulting from a calibration step using gauge blocks that finally yields 8 nm uncertainty for a step height of 2 micrometers . In order to reduce the total uncertainty we propose a novel step-height standard and calibration procedure. The standard is adjustable and can be simultaneously measured with the interference microscope and a laser interferometer allowing calibration of the entire dynamic range of the microscope with a single artefact. The new calibration method eliminates the process that contributes most to the total uncertainty budget in the current procedure. A possible implementation of the step-height standard is presented.
Richard Koops, Richard Koops,
"Improved calibration of an interference microscope", Proc. SPIE 4401, Recent Developments in Traceable Dimensional Measurements, (22 October 2001); doi: 10.1117/12.445634; https://doi.org/10.1117/12.445634