20 April 1998 Variable-focal-length microelectromechanical lens
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Abstract
We discuss the characteristics of a novel microelectromechanical cylindrical focusing mirror having a focal length which is controlled by active and intrinsic stresses in the thin films composing it. The unactuated mechanical state of the mirror is determined by intrinsic stress levels in a SiN structural layer and a piezoelectric PZT actuator layer which are part of a doubly clamped cantilever beam. The stresses are controlled by the sputter- deposition parameters and annealing conditions. The stresses concentrate curvature in the thin central mirror portion of the beam and can give the mirror a minimum focal length of as little as 100 micrometers . The focal length is increased during actuation of the PZT layer by inducing a differential tensile stress which reduces the curvature. Theoretical results are presented which predict the maximum focal length range and operating speed for a given device design. They indicate that operating frequencies of greater than 100 kHz can be achieved for a device with a focal length range of 100 micrometers to infinity. Experimental results will verify the operating principal of the proposed device.
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Mark J. Mescher, Mark J. Mescher, Michael L. Reed, Michael L. Reed, Tuviah E. Schlesinger, Tuviah E. Schlesinger, } "Variable-focal-length microelectromechanical lens", Proc. SPIE 3289, Micro-Optics Integration and Assemblies, (20 April 1998); doi: 10.1117/12.305482; https://doi.org/10.1117/12.305482
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