Miniature Microscope Design And Construction Based On Tilted Rotationally Asymmetric Printed Lenses

Abstract

Successful treatment of many types of cancer is improved when early detection is possible. One method of early detection is microscopic inspection of the tissue at risk. Microscopic inspection can be performed by extracting a biopsy and using traditional microscopes, but biopsy is painful and inconvenient which limits its use. An alternative is in vivo microscopy using an endoscope or microendoscopy. This dissertation describes the design, construction, and evaluation of a miniature microscope or microendoscope based on new microfabrication technologies.All components typically found in a traditional bench-top microscope were designed and built on a miniature scale. The objective was comprised of one planoconvex spherical glass lens and three printed microlenses. The printed lenses were patterned using grayscale lithography in a custom engineered photosensitive hybrid sol-gel glass material. Illumination was delivered by high-brightness Light Emitting Diodes (LEDs) via multimode fiber. The design incorporated a custom imaging detector and a Micro-Electrical-Mechanical-Systems (MEMS) actuator for optical sectioning using structured illumination. The opto-mechanical system is designed using a new concept called "zero alignment assembly" in which the lens elements snap into place and are constrained to a precise position with tolerances tighter than the optical tolerances. This scheme requires no post-assembly alignment or adjustment and simplifies system assembly. The miniature microscope was designed to image in several modes including reflectance, fluorescence, and using structured illumination for optical sectioning. A unique optical design incorporated tilted elements to remove ghost images and internal reflections from the image plane. This design enabled microscopic imaging of extremely low reflectance samples like tissue where the "in-focus" component of the object reflects only 0.04% of the illumination. The miniature microscope was built and tested by imaging a variety of test objects including cancer tissue phantoms and pig tissue. The results demonstrated the successful implementation of many new microfabrication technologies and design concepts to build a working prototype miniature microscope measuring only 3x4x15 mm capable of imaging cellular structure of tissue in reflectance or flourescence.