Self-sensing Piezoelectric Micro-lens Actuator

The fast micro-lens actuator used in portable micro-optics devices needs an integrated sensing mechanism for feedback control. This paper presents the design and implementation of a readout circuit using a charge amplifier for the piezoelectric micro-lens actuator. The designed circuit captures the small vibration of the piezoelectric actuator by measuring the charge generated due to the mechanical motion of the piezoelectric beam. The performance of the designed readout circuit is evaluated by comparing the measured readout circuit output with an optical sensor. The obtained open-loop settling time and signal-to-noise ratio for the piezoelectric micro-lens actuator are 120 ms and 30 dB, respectively, similar to the optical sensors. Experimentally measured results demonstrate that the on-chip self-sensing piezoelectric layer can replace the off-chip bulky optical sensor to provide a feedback signal for the closed-loop control of the piezoelectric micro-lens actuator, which is necessary for compact, handheld, and portable devices.