Objective lens system for imaging instrument

摘要

A retrofocus objective lens system which is conducive for an otoscope includes a first group of optical elements positioned at a distal portion and a second group of optical elements proximally spaced from the first group of optical elements. The first group of optical elements includes at least one negative small diameter lens while the second group of optical elements include a plurality of small diameter lenses having an aggregate optical power which is positive, allowing an image of interest to be transmitted through the system without any intermediate imaging planes, and without the need for rod lenses. The first and second lens groups are retained in a plurality of linearly interconnected lens tubes such that one lens tubes is linearly adjustable in relation to the remaining lens tubes in order to vary the focal length of the lens system.