Novel design for a confocal endoscope

A tapered-array confocal endoscope (TACE) was developed that does not depend on scanning hardware for image development. Instead, the system relies on tapers formed at the distal ends of each fiber within a coherent image guide bundle to simultaneously form multiple point sources of light and to act as a pin-hole aperture for in-focus reflected or fluorescent light. For center-to-center fiber spacing to remain unchanged during taper formation, mechanical isolation of individual optical fibers is achieved by acid etching. Image guides are thermally drawn to form biconical tapers within each fiber. Re-strengthening of tapers is accomplished using opaque, low-viscosity epoxy and steel tubing. Finally, reinforced image guides are transected near the center of the tapers and each half-guide is polished back to desired aperture diameters.; Adjustment of aperture size is a fundamental step in fine tuning the sectioning performance of the TACE imaging system. A grinding and polishing process was developed and has been shown to remove small amounts of material from the TACE array which facilitates fine control of aperture size. We have shown that selection of array aperture size directly leads to control of optical section thickness. Fiber diameters of fabricated arrays were reduced from 100 mum to apertures smaller than 20 mum. The confocal sectioning thicknesses of image guides were reduced from 150 mum to less than 25 mum. We have formed arrays with taper angles of 1.0° plus or minus a tenth of a degree. In the range of taper geometries achieved, section thickness has a nearly one-to-one relationship to aperture size and shows little dependence on taper length and angle. Previous research has shown that tapers in this range may perform nearly lossless.; To develop additional understanding of the complex elements required for non-scanning, full-frame confocal imaging, a computerized TACE numerical model was produced. Results of numerical simulations demonstrate that taper angle affects both efficiency of the system as well as the magnitude of signal returning from non-focal planes. The model predicted that the number of pinholes in the TACE array does not affect section thickness. The direct relationship between pinhole size and section thickness seen at the optical bench was verified by simulations. Agreement between TACE model data and bench experiments suggest the model can be used to predict optical performance.