The Displacement Measurement Device using a Comb-Drive Actuator

Abstract

The displacement measurement device using a comb-drive actuator is described. The comb-drive actuator is driven in its mechanical resonance by the same manner as the crystal oscillator widely used in modern electronics. The key feature of our comb-drive actuator is to show the clear nonlinear mechanical immitance near its resonance, by which the comb-drive actuator can be vibrated using a simple positive feedback circuit. Since the self-oscillation frequency is changed when a probe formed with the comb-drive actuator contacts with an opposing object, displace mesurement like a stylus meter is possible by measuring the frequency. In our experiment, 0.23 μm step is succesfully measured using the self-oscillated comb-drive actuator.