Local circular scanning for autonomous feature tracking in AFM

The atomic force microscope (AFM) is a powerful imaging tool able to measure surface topology at the nanometer scale that is particularly well-suited to biological applications. Despite advances that have pushed imaging speeds of the fastest instruments to on the order of 10 frames/second, there remains a need for even faster speeds. In addition, there is a large installed base of standard, slower instruments and techniques that can increase imaging rate without signifiant alterations to the equipment can have a large impact on the scientific capabilities of many labs. In this paper we describe and demonstrate the local circular scan, a novel feature-tracking procedure that uses the imaging data in real time to steer the probe of the AFM. Imaging rates are increased by reducing the total imaging area, focusing on the features of interest. The technique simplifies an earlier algorithm of one of the authors by reducing overall computational complexity and improving overall robustness. The technique is demonstrated through experimental results on calibration gratings.