Optical measurement procedures respond to slope angles and curvatures in a completely different way to tactile measurement procedures. The aim of PTB's new asphere standard is to enable comparison measurements by means of tactile and optical measurement procedures on surfaces whose form clearly deviates from a sphere. These comparisons can be carried out, for example, for the determination of the lateral resolution of the measuring instrument, with a specimen whose amplitude is modulated in the azimuthal direction by a sequence of sinusoidal profiles in radial direction. This structuring can be applied to spherical basic shapes. The artefact – which a patent has been applied for – allows numerous wavelengths to be determined with diverse amplitudes and, thus, the lateral resolution to be determined by means of only one measurement.
andreas.barthel