Piezoelectric objective positioners are used for fine focus adjustment and high-speed Z-stack image acquisition, compatible with multiphoton microscopes, confocal imaging systems, microscope stages, and third-party microscopes. The positioner bypasses the relatively slow stepper motors integrated into the microscope to achieve fast 3D scanning. The built-in capacitive feedback sensor provides a resolution of 1 nm in open-loop operation and 3 nm in closed-loop operation, while actively compensating for short-term and long-term drift.