The accuracy of an optically supported fast approach solution for scanning probe microscopy (SPM)-measuring devices

Atomic force microscopy is a diagnostic technique offering sub-micron resolution in both lateral and vertical scales due to observation of interactions between a sharp scanning tip and the surface. Before the sample is scanned, the tip must approach the surface and this process is one of the most critical procedures in terms of the risk of damaging the tip and the sample. Automatic approach methods based on only near-interaction detection cannot provide a fully safe procedure when the distance of hundreds of micrometers is reduced to about 10 nm within a reasonable time period. In this paper we present a method of determining the tip-sample distance using advanced processing of the optical picture. The obtained information can be used during the coarse approach procedure. Eventually, the final approach can be done using near-field interaction detection, more carefully than before, due to the small tip-sample distance. The results of the tests of this method proving its efficiency are presented as well.