This paper reports preliminary results from the development and application of a two-dimensional MEMS endoscopic scanner for OCT imaging. A 1 mm diameter mirror provides high aperture over large scan angle and can scan at rates of hundreds of Hz in both axes. The mirror is integrated with focusing optics and a fiber-optic collimator into a package of ~5 mm diameter. Using a broadband femtosecond laser light source, ultrahigh axial image resolution of < 5 um in tissue is achieved at 1.06 um center wavelength. Ultrahigh resolution cross-sectional and three-dimensional OCT imaging is demonstrated with the endoscope with ~12 um transverse resolution and < 5 um axial resolution.
Three-dimensional imaging is achieved by optical coherence tomography (OCT) integrated with a two-axis MEMS scanner to enable noninvasive volume imaging of biological tissues. The longitudinal scan is obtained by optical coherence interferometry. The transverse scan is obtained by tilting the two-axis MEMS mirror to scan the optical beam across the target. High-resolution OCT imaging has enabled in vivo observation of tissue architectural layers and differentiation of normal from tumor lesions within the human gastrointestinal tract. MEMS scanner based catheters with distal beam scanning can image with higher speed, precision, and repeatability than conventional linear scanning catheters. In this work, a 1-mm diameter MEMS scanning mirror with collimator and focusing optics is integrated into a compact 5-mm diameter package that is compatible with limited space in the endoscope. A large fill factor mirror provides high aperture over large scan angle and frequencies of hundreds of Hz in both axes. Using a broadband femtosecond laser light source, high axial image resolution of ~5 um is achieved at 1.06 um wavelength. Transverse resolution of ~ 12-um is demonstrated for cross-sectional image with the endoscope.
Silicon micromachining technology has opened up many new possibilities in implementing optical and optoelectronic systems in micro scale. It offers unparalleled capabilities in extending the functionality of optical devices and the miniaturization of optical systems. Movable structures, microactuators, micropositioners and micro-optical elements can be monolithically integrated on the same substrate-using batch processing technologies. In this paper, we report the recent progresses in developing of MEMS actuators and micropositioners based on silicon surface micromachining technology. In particular, free-space fiber optic switches and micro-XYZ stages will be discussed. A 2 X 2 free- space fiber optic switch consist of an out-of-plane micromirror driven by integrated scratch device actuators (SDA), and a build-in balancing spring. A fall time and a rise time of 15 ms and 6 ms have been achieved, respectively. In addition, a self-assembled micro-XYZ stage, hybrid-integrated with a 300 micrometers micro-ball lens has been demonstrated for active alignment in the free-space Si micro-optical bench. We have achieved up to 100 micrometers in all three independent axes for the micro ball lens with integrated SDAs that have a step resolution of 27 nm. This novel device can be used for dynamic tracking and alignment between fiber/fiber and fiber/laser free-space optical interconnects, with increased efficiency and vibration stability.