Modeling and design of piezoelectrically actuated MEMS tunable lenses

Autofocus is a crucial feature in cameras, especially when photographing objects at different distances and having them in sharp focus without any quality loss in the captured image. Over the last decade, several research efforts have been made to incorporate tunable focus for mobile-device cameras using micro-scale components. Qualitatively, this would enable miniaturized cameras with lower power consumption, much faster response in scanning focus range and higher reliability. The microelectromechanical-systems-(MEMS)-based tunable focus lenses are promising alternatives as autofocus mechanisms when compared to the conventional macro-scale approaches such as the Voice Coil Motor (VCM) or ultrasonic motors. Moreover, such MEMS autofocus lenses would achieve higher resolution smartphone cameras without having any moving parts within the camera housing, which consumes power during focus adjustment and causes a loss in the Field-of-View (FoV) as for the VCM. The research reported in this thesis is to construct a modeling framework for the piezoelectrically actuated MEMS tunable lenses on the electromechanical domain by finding an approximation for the lens displacement, and using it afterwards in the optical domain to find the lens' optical performance. Given the modeling framework, two design concepts have been proposed. The first one is to achieve larger lens apertures while having a tradeoff between focal length and RMS-wavefront error (RMSWFE), while the second is to increase lens' tunable range of focal lengths by controlling layers' stresses during fabrication.