A miniaturized low-power VCM actuator for auto-focusing applications.

In keeping with consumer preferences for ever smaller electronic products, a requirement exists for compact, high-performance auto-focusing actuators for the camera modules deployed in cell phones. Accordingly, the present study proposes a miniaturized electromagnetic-based actuator comprising a voice coil motor (VCM) and a closed-loop position control system in which an auto-focusing capability is achieved by using a position feedback signal generated by a Hall element to dynamically adjust the position of the lens module. The experimental results show that the holding current required to maintain a lens module weighing 200 mgw in the vertical position is 17 mA +/- 2 mA. Compared to conventional VCM actuators deployed in cell phone camera applications, the actuator presented in this study has a smaller size (6.5 mm x 6.5 mm x 4 mm) and an improved power efficiency. In particular, the miniaturized actuator reduces the holding current required to maintain the lens module in the focusing position by around 75% of that required in a traditional actuator.