Novel Vertical Scanning Algorithm with Advanced Control to Increase Range and Accuracy of Differential Confocal Microscopy

Differential confocal microscopy (DCM) is a powerful tool for mapping the 3-D topography of samples at micrometer and submicrometer scales. However, the limited vertical scanning range of conventional DCM makes it challenging to obtain 3-D profiles precisely. This study sought to mitigate this restriction by developing a novel vertical scanning algorithm as well as an adaptive sliding mode controller based on the internal model principle to precisely track the step scanning trajectory to deal with uncertainties in system parameters, external disturbances, and the hysteresis effect of the piezoelectric scanner in the $Z$ -axis. In experiments, our proprietary DCM system proved highly effective in terms of scanning range, imaging accuracy, and reliability.