High Resolution Optical Displacement Measurements of a Piezo Scanner

This application note details the use of the PICOSCALE Interferometer for high-resolution optical displacement measurements of a piezo scanner. It demonstrates how the interferometer provides sub-nanometer precision for validating the performance of piezo scanners in closed-loop configurations.

Problem: Positioning systems using piezo technology require high precision for applications where slip behavior or resolution limitations could impact accuracy. Verifying the performance of piezo scanners at sub-nanometer scales is challenging without appropriate metrology tools.

Solution: The PICOSCALE Interferometer provides precise out-of-loop displacement measurements with a resolution well beyond conventional optical encoders. This ensures accurate characterization of the piezo scanner's motion.

Implementation

• A SmarAct piezo scanner was equipped with an internal optical encoder and controlled by an MCS2 motion controller.
• A PICOSCALE sensor head was aligned to measure the displacement of a mirror mounted on the scanner.
• Displacement signals were processed to verify the motion sequence commanded by the MCS2.
• Steps of 1 nm and 2 nm were executed and measured for validation.

Result: The PICOSCALE Interferometer confirmed the piezo scanner's ability to achieve sub-nanometer motion steps with high accuracy:

• 1 nm steps resulted in mean displacements of -1.01 nm (backward) and 0.97 nm (forward).
• 2 nm steps resulted in mean displacements of -2.00 nm (backward) and 1.96 nm (forward). The results validate the scanner's performance and the interferometer's capability for high-resolution measurements, suitable for quality control and advanced research applications.