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Surface measurement errors using commercial scanning white light interferometers.

Geo, F*; Leach, R K; Petzing, J*; Coupland, J M* (2008) Surface measurement errors using commercial scanning white light interferometers. Meas. Sci. Technol., 19 (1). 015303

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The performance of commercial scanning white light interferometers is examined in a range of measurement tasks. A step height artefact is used to investigate the response of the instruments at a discontinuity, while gratings with sinusoidal and rectangular profiles are used to investigate the effects of surface gradient and spatial frequency. Results are compared with measurements made with tapping mode atomic force microscopy and discrepancies are discussed with reference to error mechanisms put forward in the published literature. As expected it is found that most instruments are prone to errors when used in regions close to a discontinuity or those with a surface gradient that is large compared to the acceptance angle of the objective lens. Amongst other findings, however, we report systematic errors that are observed when the surface gradient is considerably smaller than the acceptance angle. Although these errors are typically less than the mean wavelength of the white light source, they are significant compared to the instrument resolution and indicate that current scanning white light interferometers should be used with some caution if sub-wavelength accuracy is required.

Item Type: Article
Keywords: white light interferometry, measurement errors, surface roughness measurement, multiple scattering effect.
Subjects: Engineering Measurements
Engineering Measurements > Dimensional
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4039

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