Lissajous scanned MEMS endomicroscopes for forward-imaging optical coherence tomography

Abstract

Optical endomicroscopy has raised a great deal of attention for in-vivo clinical applications such as optical biopsy or imaging guided surgery. Current medical endoscopy simply observes a reflected optical image from mucosal surface and it often requires physical biopsies, i.e., resection of some suspicious tissues from a patient body for ex-vivo histological or cytological examination. The main drawback of current endoscopic biopsy is unavailability of on-demand and real-time clinical diagnosis. In other words, microscopic examination after tissue resection not only causes significant time delay for clinical decision but also it may fail to predict tumor-free resection margin. On the other hands, recent development of advanced optical imaging techniques can visualizes the depth of tumor invasion from mucosal resection of intact tissues or organs from characteristic optical signatures with microscopic resolution. The miniaturization of advanced imaging systems and further implementation inside a clinical endoscope can provide new directions for in-vivo optical biopsy. This work presents a fully packaged and compact forward viewing endomicroscope by using a microelectromechanicalsystem (MEMS) lens scanner and a resonant fiber scanner. The MEMS lens scanner enables two dimensional optical scanning of Lissajous patterns by the orthogonal movement of two commercial aspherical glass lenses laterally mounted on two resonating electrostatic MEMS microstages. The MEMS lens scanner was integrated on a printed circuit board and packaged with aluminum housing, a gradient index fiber collimator, and an objective lens. The fiber scanner comprises a single mode fiber implemented inside a piezoelectric tube with quartered electrodes and additional microstructures. The additional structures include both extra masses at the distal end of a scanning fiber and an asymmetric stiffness modulation part with micromachined silicon structures. This additional mass not only shortens t...