Comparison of Roughness Measurements Between a Contact Stylus Instrument and an Optical Measurement Device Based on a Color Focus Sensor
R. Danzl, F. Helmli and S. Scherer
Alicona Imaging GmbH, AT
roughness, surface metrology, 3D reconstruction,
The determination of the roughness of technical surfaces plays an important role in scientific and industrial applications. Traditionally, the ISO conform determination of the roughness of a technical surface has been calculated using contact stylus instruments. In contrast to this, we present the optical (and thus non-contact) measurement device InfiniteFocus by Alicona Imaging GmbH, which is able to reconstruct 3D models of technical surfaces with a vertical resolution down to 20nm and allows to measure their roughness. We demonstrate this using a random micro-roughness standard of the company Halle Präzisions - Kalibriernormale GmbH (Germany) with known calibrated roughness parameters Ra and Rz. The basic principle of the InfiniteFocus device is to exploit the small depth of field by vertically scanning a probe using a motorized z-stage. Then, for each point, the height is derived from the position where the point is best in focus. This technology is just about to be included into ISO standards classifying different methods for surface texture extraction. The roughness measurements by InfiniteFoucs are well in the uncertainty range of the calibrated values by Halle which have been performed by a contact stylus instrument approved by the PTB (Physikalisch Technische Bundesanstalt, Germany).
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Nanotech 2006 Conference Program Abstract