Double-clad fiber for endoscopy.

Endoscopes employing a single optical fiber may have advantages over conventional fiber-bundle or CCD array imaging techniques, including the potential for greater flexibility and miniaturization. Although single-mode fibers can provide superior resolution compared with multimode fibers, they are prone to increased speckle noise and suffer from limited optical throughput and reduced depth of field. We demonstrate the use of a double-clad fiber for single-mode illumination and multimode detection to achieve high-resolution, reduced-speckle imaging with high optical throughput and a large depth of field.