The conventional auto-focus and zoom image systems were made by a set of motor-moved lenses. Because of mechanical moving parts, it is not easy to miniaturize their sizes. In this paper, we propose a thin autofocus system using a large stroke MEMS (micro-electro-mechanical systems) deformable mirror which has the potential to downscale the size and to minimize chromatic aberration. The large stroke MEMS deformable mirror is made by a polyimide membrane that has a maximum 12 microm displacement over a 3 mm aperture. The module size is 5.4 mm thick in optical design layout and 6.7 mm after packaging. This autofocus system is designed with the f-number=4.13, on-axis MTF=0.28 at full frequency of 230 cycles/mm, and incident light within+/-26 degree. The position of clear image can vary from 4 cm to 50 cm achieved by controlling the surface curvature of the MEMS deformable mirror.

Adaptive optics is a technology that improves the performance of optical systems by reducing wavefront distortion. Currently, it is playing a more important role in astronomy, laser physics, nonlinear optics, medicine, vision and the defense industry. In this paper, we demonstrate a microelectromechanical system (MEMS) deformable mirror that is made of a 2.15 µm thick polyimide film and is actuated by electrostatic force. We made a large-stroke MEMS deformable mirror with a 20 mm diameter circular opening and 67 hexagonal actuation electrodes. We also used modeling software, ANSYS, to simulate the deformation behavior of the membrane and discussed the device parameter tuning for versatile applications. The maximum stroke was 39 µm as 195 V was applied. Because of the large stroke of the device, the resonant frequency was approximately 40 Hz. The resonant frequency can be increased by thickening the polyimide membrane. The polymer deformable mirror is a strong candidate for active wavefront control, based on our experimental results.

This paper discusses the design, fabrication, and test results of electromagnetically actuated two-dimensional (2-D) microelectromechanical systems (MEMS) optical switches. The switching element consists of a 20 µm × 500 µm × 1200 µm vertical micromirror, which is monolithically integrated with an actuation flap. The micromirror is made by anisotropic tetramethyl-ammonium-hydroxide wet etching with an optical insertion loss of about 0.2 dB. A maximum insertion loss of 2.1 dB has been experimentally demonstrated for a 10 × 10 2-D optical crossconnect switch. The actuation flap has double layers of spiral metal coils to generate a large actuation force with the permanent magnets placed at the bottom of the MEMS chip. The magnetic flux is created on the surface of a pair of opposite polarized magnets to precisely control the moving direction of the vertical mirror. The required voltage is less than 0.5 V, and the power consumption is about 3.5 mW for a switching element. Due to the center symmetric design and the stress-free characteristic of the micromirror, the temperature dependence loss is demonstrated to be as low as 0.05 dB. A switching time of 5 ms is achieved by applying the proper driving waveform.

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In this paper, we report spring corner designs and driving waveforms to improve the reliability for a MEMS (Micro-Electro-Mechanical System) actuator. In order to prevent the stiction problems, no stopper or damping absorber is adopted. Therefore, an actuator could travel long distance by electromagnetic force without any object in moving path to absorb excess momentum. Due to long displacement and large mass, springs of MEMS actuators tend to crack from weak points with high stress concentration and this situation degrades reliability performance. Stress distribution over different spring designs were simulated and a serpentine spring with circular and wide corner design was chosen due to its low stress concentration. This design has smaller stress concentration versus displacement. Furthermore, the resonant frequencies are removed from the driving waveform based on the analysis of discrete Fourier transfer function. The reshaped waveform not only shortens actuator switching time, but also ensures that the spring is in a small displacement region without overshooting so that the maximum stress is kept below 200 MPa. The experimental results show that the MEMS device designed by theses principles can survive 500 g (gravity acceleration) shock test and pass 150 million switching cycles without failure.