Abstract
This paper introduces an optical 2-axis Micro Electro-Mechanical System (MEMS) micromirror actuated by a pair of electrothermal actuators and a set of passive torsion bars. The actuated element is a dual-reflective circular mirror plate of 1 in diameter. This inner mirror plate is connected to a rigid frame via a pair of torsion bars in two diametrically opposite ends located on the rotation axis. A pair of electrothermal bimorphs generates a force onto the perpendicular free ends of the mirror plate in the same angular direction. An array of electrothermal bimorph cantilevers deflects the rigid frame around a working angle of 45 for side-view scan. The performed scans reach large mechanical angles of 32 for the frame and 22 for the in-frame mirror. We denote three resonant main modes, pure flexion of the frame at 205 , a pure torsion of the mirror plate at 1.286 and coupled mode of combined flexion and torsion at 1.588 . The micro device was fabricated through successive stacks of materials onto a silicon-on-insulator wafer and the patterned deposition on the back-side of the dual-reflective mirror is achieved through a dry film photoresist photolithography process.
Highlights
Optical Micro Electro-Mechanical System (MEMS) micro-scanners are exploited by a large variety of applications that usually require large displacement range, high operating frequencies, miniaturization, simplicity of packaging and integration
The micro-scanner proposed in this paper was designed and fabricated in order to be, in a future perspective, embedded into a Swept-Source Optical Coherence Tomography (OCT) (SS-OCT) endomicroscopic probe (Figure 1b) based on a Mirau micro-interferometer [4]
The mirror plate is tilted inside the frame using the pair of Meshed Inverted-Series-Connected (MISC) electrothermal actuators located on both sides of the plate
Summary
Optical Micro Electro-Mechanical System (MEMS) micro-scanners are exploited by a large variety of applications that usually require large displacement range, high operating frequencies, miniaturization, simplicity of packaging and integration. Various methods, such as piezoelectric, electrostatic, electromagnetic and electrothermal technologies [1] have been used to develop devices able to measure each application’s requirements. The mirror plate is still subject to fluctuation with surrounding temperature and to uncontrolled changes due to vibrations or disturbances In addition to these flaws, angular sensing mechanisms are usually unavailable, so that they are left uncontrolled [8] or with mere open-loop controls [9]. Once the micro-scanning device is embedded on top of it, two additional B-scan axes can be realized so that a 3D image can be obtained
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