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Proceedings Paper

Energy Ray Tracing
Author(s): John F Forkner
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Paper Abstract

A striking similarity is shown between the shapes of focused coherent and non-coherent optical energy beams. This similarity is shown to be an exact analogy under broadly applicable conditions. It is proven that non-coherent beam focusing equations can be obtained from the well known Gaussian beam propagation equations simply by replacing the Rayleigh range with a new parameter, the focal range, equal to the input beam waist radius divided by the beam angular divergence. The adapted beam equations enable calculation of the first order location and radius of the focused waist minimum for non-coherent energy input beams of finite diameter and finite angular extent - a situation not previously amenable to simple calculation and analysis. A fictitious wavelength can be calculated from the input beam parameters, and this wavelength permits the use of standard Gaussian beam propagation programs to analyze non-coherent beam focusing. The effects of aberration on the waist location and radius calculated with the adapted beam equations is investigated with a new energy ray tracing technique that uses standard spot diagram data obtained under special input conditions and by ray tracing backwards through the lens system. Intensities computed with this technique are compared with actual measured values for an example system, and the agreement is found to be very good. The new ray tracing techniques can be used to analyze the focusing of energy from a wide variety of sources, from low divergence multi-mode lasers to the wide divergence beams from arc lamps with ellipsoidal reflectors. The results presented in this paper reveal that there is a continuity in the characteristics of focused energy beams that extends over the entire range of source coherence, from fundamental mode lasers to the ordinary light sources of everyday experience.

Paper Details

Date Published: 13 June 1989
PDF: 25 pages
Proc. SPIE 1049, Recent Trends in Optical Systems Design and Computer Lens Design Workshop II, (13 June 1989); doi: 10.1117/12.951405
Show Author Affiliations
John F Forkner, Consultant (United States)

Published in SPIE Proceedings Vol. 1049:
Recent Trends in Optical Systems Design and Computer Lens Design Workshop II
Robert E. Fischer; Richard C. Juergens, Editor(s)

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