A microscope includes an objective lens and a pair of zoom lenses arranged in series along an optical path from the objective lens to a video camera, which converts the output of the second zoom lens to a video signal for display of a magnified first image on an associated monitor. A portion of the output...http://www.google.co.uk/patents/US5668660?utm_source=gb-gplus-sharePatent US5668660 - Microscope with plural zoom lens assemblies in series
