Revisiting parallel catadioptric goniophotometers

Boris Karamata; Marilyne Andersen

doi:10.1117/12.2020561

13 May 2013 Revisiting parallel catadioptric goniophotometers

Boris Karamata, Marilyne Andersen

Proceedings Volume 8788, Optical Measurement Systems for Industrial Inspection VIII; 87881Q (2013) https://doi.org/10.1117/12.2020561
Event: SPIE Optical Metrology 2013, 2013, Munich, Germany

Abstract

A thorough knowledge of the angular distribution of light scattered by an illuminated surface under different angles is essential in numerous industrial and research applications. Traditionally, the angular distribution of a reflected or transmitted light flux as function of the illumination angle, described by the Bidirectional Scattering Distribution Function (BSDF), is measured with a point-by-point scanning goniophotometer yielding impractically long acquisition times. Significantly faster measurements can be achieved by a device capable of simultaneously imaging the far-field distribution of light scattered by a sample onto a two-dimensional sensor array. Such an angular-to-spatial mapping function can be realized with a parallel catadioptric mapping goniophotometer (CMG). In this contribution, we formally establish the design requirement for a reliable CMG. Based on heuristic considerations we show that, to avoid degrading the angular-to-spatial function, the acceptance angle of the lens system inherent to a CMG must be smaller than 60°. By means of a parametric study, we investigate the practical design limitations of a CMG caused by the constraints imposed by the properties of a real lens system. Our study reveals that the values of the key design parameters of a CMG fall within a relatively small range. This imposes the shape of the ellipsoidal reflector and drastically restricts the room for a design trade-off between the sample size and the angular resolution. We provide a quantitative analysis for the key parameters of a CMG for two relevant cases.

Citation Download Citation

Boris Karamata and Marilyne Andersen "Revisiting parallel catadioptric goniophotometers", Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 87881Q (13 May 2013); https://doi.org/10.1117/12.2020561

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