Principle and simulation of correlation steered scanning for SPM to overcome thermal drift

A new scanning strategy named correlation steered scanning for Scanning Probe Microscopy (SPM) is proposed in this paper. Different from the traditional raster scanning, this method adopts scanning band by band. A narrow band of the sample is scanned at first, and then a band with a partial overlap to the first one is scanned reversely. Each band is composed of several blocks. The overlap between blocks in the corresponding position of two adjacent bands is utilized to estimate the relative drift speed in real-time based on the digital image correlation technique. Estimated results are employed to steer the following block scanning in order to keep the bands overlapped and parallel to one another. A large area can be scanned completely by repeating this process, without missing any information of the sample. When all the bands are scanned, a data processing program is applied to calibrate the thermal drift with the estimated drift speed, and the redundant areas caused by the overlap is corrected using a bilinear interpolation, then a very large area and drift-free image can be obtained. An arbitrarily large area can be scanned theoretically, because the drift within a small block can be estimated and compensated using the correlation steered scanning method in real-time. Experiments by simulating with a gray scale image were conducted and excellent result had been achieved. This method will be very useful for SPMs aimed at ultrahigh precision and large scan area.