Hydraulic controlled polyester-based micro adaptive mirror with adjustable focal length

Currently micro-electromechanical systems (MEMS) technology is creating micro-mirrors for applications such as scanning and adaptive optics. A 0.5 μm thin, reflective polyester sheet is used to create a 950 μm diameter flexible mirror that is capable of changing its concavity. A system that consists of electrical circuits and LabVIEW interfaces were used to control the mirror. This paper presents a micro-mirror that is fabricated from a 0.5 μm thin, reflective polyester sheet clamped with aluminum disks. An electromagnetic plunge actuator controls the pressure beneath the mirror to change the curvature of the mirror. The focal point of the micro-mirror ranges from approximately infinity to 3.5 mm. This range is much wider than the ranges that are typical of MEMS mirrors. The curvature of the micro-mirror can be altered at a maximum observable frequency of about 15 Hz. The micro-mirror center depth movement is at increments of approximately 2 μm and the focal length increment of change is approximately 5 mm. The mirror is capable of dynamically focusing on objects at a distance of 6 cm to longer than 7 m away from the mirror.