Obtaining the Transfer Function of optical instruments using large calibrated reference objects

It has been suggested recently that the Transfer Function of instruments such as Coherence Scanning Interferometers could be measured via a single measurement of a large spherical artefact [Appl. Opt. 53(8), 1554–1563 (2014)]. In the current paper we present analytical solutions for the Fourier transform of the ’foil’ model used in this technique, which thus avoids the artefacts resulting from the numerical approach used earlier. The Fourier transform of a partial spherical shell is found to contain points of zero amplitude for spatial frequencies that lie within the Transfer Function. This implies that the Transfer Function is unmeasurable at these points when a single spherical artefact is used, in situations where the foil model is a valid representation of the physical system. We propose extensions to the method to address this issue

Calibration and verification of areal surface texture measuring instruments

In this paper, the calibration and verification infrastructure to support areal surface texture measurement and characterisation will be reviewed. A short historical overview of the subject will be given, along with a discussion of the most common instruments and directions of current international standards. Traceability and uncertainty will be discussed, followed by a presentation of the latest developments in software and material measurement standards. The concept and current infrastructure for determining the metrological characteristics of instruments will be highlighted and future research requirements will be presented