Cassini Oval Scanning for High-Speed AFM Imaging

Atomic force microscopy (AFM) generally scans the sample surface following a raster pattern signal, which contains discontinuities at turning points and frequencies beyond mechanical bandwidth of scanning stage. Consequently, raster scanning at high speed brings distortions to the resulting image. This paper describes a non-raster scanning method based on Cassini oval pattern. In this method, by adopting Cassini oval pattern, the input control signals of the two axes of scanner are replaced by sinusoid-like smooth signals, thereby reducing the harmonic vibration and improving scanning bandwidth. In addition, details on how to formulate the scanning pattern and generate the Cassini oval signals are analyzed. Experimental results of implementing this method in a commercial AFM and a compensated piezoelectric scanner indicate its feasibility on imaging.