Calibration of piezo actuators and systems by dynamic interferometry

To achieve precise measurements of small displacements in non-contact atomic force microscopy, it is crucial to control the position of moving parts with high accuracy. This is commonly accomplished by piezo actuators, for instance, in the form of tube piezos for positioning the tip or optics. For their calibration, we propose an approach based on the dynamic response signal from a fiber interferometer used for cantilever displacement detection. The fine-positioning z-piezo of the fiber is calibrated by the analysis of measurements of the dynamic interferometer response signal recorded for various cantilever oscillation amplitudes and varied distances between the cantilever and the fiber end. Furthermore, we demonstrate the cantilever oscillation amplitude calibration under conditions of various amounts of tube piezo contraction and extension. The merits and limits of accuracy for such type of calibration are discussed.