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Proceedings Paper

Illumination system development using design and analysis of computer experiments
Author(s): Janos C. Keresztes; Bart De Ketelaere; Jan Audenaert; R. John Koshel; Wouter Saeys
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Paper Abstract

Computer assisted optimal illumination design is crucial when developing cost-effective machine vision systems. Standard local optimization methods, such as downhill simplex optimization (DHSO), often result in an optimal solution that is influenced by the starting point by converging to a local minimum, especially when dealing with high dimensional illumination designs or nonlinear merit spaces. This work presents a novel nonlinear optimization approach, based on design and analysis of computer experiments (DACE). The methodology is first illustrated with a 2D case study of four light sources symmetrically positioned along a fixed arc in order to obtain optimal irradiance uniformity on a flat Lambertian reflecting target at the arc center. The first step consists of choosing angular positions with no overlap between sources using a fast, flexible space filling design. Ray-tracing simulations are then performed at the design points and a merit function is used for each configuration to quantify the homogeneity of the irradiance at the target. The obtained homogeneities at the design points are further used as input to a Gaussian Process (GP), which develops a preliminary distribution for the expected merit space. Global optimization is then performed on the GP more likely providing optimal parameters. Next, the light positioning case study is further investigated by varying the radius of the arc, and by adding two spots symmetrically positioned along an arc diametrically opposed to the first one. The added value of using DACE with regard to the performance in convergence is 6 times faster than the standard simplex method for equal uniformity of 97%. The obtained results were successfully validated experimentally using a short-wavelength infrared (SWIR) hyperspectral imager monitoring a Spectralon panel illuminated by tungsten halogen sources with 10% of relative error.

Paper Details

Date Published: 3 September 2015
PDF: 15 pages
Proc. SPIE 9579, Novel Optical Systems Design and Optimization XVIII, 95790I (3 September 2015); doi: 10.1117/12.2191082
Show Author Affiliations
Janos C. Keresztes, KU Leuven (Belgium)
Bart De Ketelaere, KU Leuven (Belgium)
Jan Audenaert, KU Leuven (Belgium)
R. John Koshel, The Univ. of Arizona (United States)
Wouter Saeys, KU Leuven (Belgium)

Published in SPIE Proceedings Vol. 9579:
Novel Optical Systems Design and Optimization XVIII
G. Groot Gregory; Arthur J. Davis; Cornelius F. Hahlweg, Editor(s)

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