A full-color scanning fiber endoscope

Abstract

Minimally invasive medical procedures will benefit from flexible endoscopes that are extremely thin yet produce high quality images. Current devices use fiber bundles or silicon image sensors placed in the distal tip where each pixel in the image is derived from an element in the distal tip, such that improving resolution requires increasing distal tip diameter. The University of Washington has developed the scanning fiber endoscope (SFE) to provide full color, high resolution images from a flexible endoscope with a small distal tip diameter. The SFE uses a single mode fiber vibrating in resonance to scan a focused laser spot over the tissue and a detector to record the time-multiplexed backscatter signal. The SFE contains a 400 micron diameter piezoelectric tube through which a length of singlemode optical fiber is placed. The tube drives the fiber tip at its resonant frequency (currently 5 KHz) in an expanding pattern of 250 spirals (500 pixel diameter image) at a frame rate of 15 Hertz. Imaging parameters are determined by the lens system placed in the 1.06 mm diameter distal tip. Prototype systems with 70 degree field-of-view and 10 micron resolution have been developed. Color images are created with red, green, and blue laser sources coupled into the single scanning fiber. Backscattered light is collected with twelve 250 micron multimode fibers placed around the periphery of the microscanner resulting in a total distal tip diameter of 1.6 mm. Frame sequential color, fluorescence, and continuous color imaging modes have been demonstrated in the non-confocal geometry.