Large scale atomic force microscopy for characterisation of optical surfaces and coatings

Abstract

A variety of SPM techniques allow measuring different local physical properties of the surface investigated. One of the key properties of interest in production and development of micro- and nano-optics is a high local resolution of diffractive as well as refractive optical elements. By integrating an atomic force microscope into a coordinate measuring machine with subnanometre resolution and nanometre uncertainty a large scale atomic-force microscope is realised which enables a simultaneous investigation of form and roughness of specimens with sizes up to 25 mm × 25 mm × 5 mm along x, y and z-axes. The calibration of the AFM-sensor is performed with different silicon gratings. Each grating is specially designed for investigating the lateral and axial resolution as well as the accuracy in slope measurement. Different modes of scanning strategies have been analysed and error compensated for micro and nanostructured optical components with a surface diameter up to 25 mm.