Design and control of a novel non-raster scan pattern for fast scanning probe microscopy

A significant difficulty associated with achieving high scan speeds in scanning probe microscopes is that the probe is required to scan the sample in a zig-zag (raster) pattern. The fast axis of the scanner is required to track a non-smooth signal that contains frequency components beyond its mechanical bandwidth. Therefore, fast raster scans lead to distortions in the obtained image. This paper proposes analysis and design methods for a nonlinear but smooth scan pattern, known as Lissajous pattern, which enables us to achieve high-quality images at very high scan speeds where raster scanning typically leads to significant image distortions. Criteria are also proposed and formulated for constructing Lissajous trajectory and calculating the parameters and resolution. Together with the implementation of an internal model controller for high precision tracking, the proposed method is successfully employed to scan images in high speeds using a low resonance frequency SPM platform of only 825 Hz.