Lateral scanning confocal microscopy for the determination of in-plane displacements of microelectromechanical systems devices

A method named lateral scanning confocal microscopy (LtSCM) is proposed with the aim of determining the in-plane displacement of microstructures, especially of those moving components within microelectromechanical systems (MEMS) actuators and sensors, which feature high aspect ratio and limited geometrical size in one or two dimensions within the surface plane. The principle of the LtSCM is presented and theoretically analyzed, which indicates that the LtSCM has the potential to determine with high resolution the in-plane displacement, position, and even the geometrical size of the object. Furthermore, in the case of in-plane displacement measurement, the measurement resolution of the LtSCM should be insensitive to the dynamic performance of the movable microstructures, i.e., from quasi-static to ultrahigh speed. In a proof-of-principle experiment, the voltage-displacement response of an electrostatic comb-drive actuator has been obtained with nanometric resolution.