Improved illumination system of laparoscopes using an aspherical lens array

摘要

The current fiber-based illumination systems of laparoscopes areudunable to uniformly illuminate a large enough area in abdomen due to theudlimited numerical aperture (NA) of the fiber bundle. Most energy isudconcentrated in a small region at the center of the illumination area. Thisudlimitation becomes problematic in laparoscopes which require capturing audwide field of view. In this paper, we propose an aspherical lens array which isudused to direct the outgoing rays from the fiber bundle of laparoscope toudproduce a more uniformly illuminated, substantially larger field coverageudthan standalone fiber source. An intensity feedback method is developed touddesign the aspherical lens unit for extended non-Lambertian sources, whichudis the key to the design of this lens array. By this method, the lens unit isudobtained after only one iteration, and the lens array is constructed by Booleanudoperation. Then, the ray-tracing technique is used to verify the design.udFurther, the lens array is fabricated and experimental tests are performed. Theudresults clearly show that the well-illuminated area is increased to aboutud0.107m2ud from 0.02m2ud (about 5x larger than a standard fiber illuminationudsource). More details of the internal organs can be clearly observed under thisudimproved illumination condition, which also reflects the significantudimprovement in the optical performance of the laparoscope.