<title>Aberration effects on illumination beams focused by lens systems</title>

Abstract

In previous papers the author has shown that lens systems focusing wide-angle, large diameter illumination beams do not focus the output beam-waist at the location predicted by the standard paraxial lens imaging equations. The paraxial equations fail because they are meant to apply to rays that lie in the plane of the lens system axis of symmetry- meridional rays, whereas illumination beams are composed of skew or out-of-plane rays. The skew-ray equations derived in the author's earlier papers turn out to provide the correct description of the non-imaging optics of focused illumination beams. The skew-ray beam equations allow the basic lens system parameters; focal length and conjugate distances to be determined from the input beam diameter and divergence angle. The lens system parameters calculated from the skew-ray beam equations are optimal in the sense that they define an optical system that theoretically satisfies the fundamental requirement of conservation of E'tendue. Therefore if the appropriate aberrations of this theoretically optimum illumination beam optical system can be corrected the system should approach 100 percent geometric throughput. This paper discusses how certain types of imaging optical systems can be used as models for the design of equivalent non-imaging illumination beam- transformer optical systems. The use of these image system models permits a direct assessment of the importance of the classical image aberrations in the design of highly efficient illumination beam optics. The paper also outlines design methods for optimizing illumination beam optics using existing imaging optics software. The conclusion is that practical illumination optics beam-transformers can be designed with throughputs above 99 percent, even using a single lens.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.