Dynamic focus-tracking MEMS scanning micromirror for an endoscopic, optical coherence tomography based imaging system

Abstract

We demonstrate a 3-dimensional scanning micromirror device using micro-electromechanical systems (MEMS) technology to integrate 2-dimesional spatial scanning with dynamic focal control. The electrostatically actuated devices employ a biaxial gimbal structure, to allow 2-dimensional beam scanning, and a deformable mirror membrane, for focal tunability. The 800 micrometer diameter mirrors are designed to fit inside an imaging probe sufficiently compact for use in the working channel of a standard endoscope. Large optical scanning ranges of more than 20 degrees with low actuation voltages have been achieved with these micromirror devices. Additionally, tunable mirror curvature allows dynamic control of the focal length between infinite and 25 mm with less than 100 V. High mechanical resonant frequencies, of up to 500 Hz, allow faster repositioning of the optical beam and a higher frame rate for the imaging system. These MEMS micromirror devices are used in an optical coherence tomography (OCT) imaging system. 2-dimensional, cross-sectional and spatial, images have been obtained using spectral-domain and time-domain OCT systems.