A long-range scanning probe microscope for automotive reflector optical quality inspection

A long-range scanning probe microscope (SPM) designed for the measurement of micro- and nanoscale forms, roughness and surface defects was constructed. It is based on commercial crossed roller bearing stages combined with piezoceramic actuators used to compensate the imperfections of the bearing mechanism. Three interferometers are used for all three-axis translation monitoring and feedback. For stage rotation monitoring (axis normal to the sample surface), an autocollimator is used. For nonplanarity compensation and two more axis rotation compensations (axes parallel to sample surface), an optical quality reference plane and a set of tunneling current sensors are used. The developed system enables us to perform large-scale measurements of the surface form with no influence of positioning system non-planarities and piezoceramic component hysteresis. In contrast to specialized metrology systems, e.g. using a six-axis interferometer for stage motion monitoring and feedback, this approach enables a more compact and much cheaper metrology SPM construction.