FIRST-ORDER ANALYSIS OF A 3-LENS AFOCAL ZOOM SYSTEM

A general analysis for the first-order design of a three-lens afocal z oom system with one lens fixed is presented. The reasonable solution a reas in the focal length diagrams with positive or negative magnificat ion are derived and shown graphically. The relation between the two se parations of the three lenses in zooming is found to be a hyperbola. A ccording to the different locations of hyperbola centers, four cases a re analyzed. From the four hyperbolic graphs, we get five different ty pes of zoom systems. For each zoom type, we find the maximum range of magnification and the position where the maximum or minimum system len gth occurs during zooming. The zoom loci for the first or second lens fixed are also discussed. (C) 1997 Society of Photo-Optical Instrument ation Engineers.