Development of a Stepping Piezoelectric Actuator for an Autofocus Microscopic Observation System

Microscope is an indispensable instrument for biomedical and semiconductor manufacturing fields. However, the existing focusing mechanisms suffer from problems of low resolution and poor adaptability in the microscopes with small focus depth, high resolution, and multiple lenses. In this work, we propose a stepping piezoelectric actuator (SPEA) using two bending-bending hybrid actuating units (AUs), which has the characteristics of high resolution (9 nm), large motion stroke (centimeter level), and fast-moving speed (1.73 mm/s). Furthermore, a piezoelectric autofocus system (PEAFS) that used the SPEA as a focusing mechanism is established based on the visual feedback algorithm, and a microscopic observation demonstration of onion epidermal cells is displayed, which proves that the SPEA has the ability of being a novel focusing mechanism, and the focusing principle of adjusting the image distance is feasible. This work provides a new idea and scheme for the design of focusing mechanism and focusing principle in various microscopes, such as scanning electron microscope, super-resolution microscope, and confocal laser scanning microscope.