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Proceedings Paper

High-resolution Czerny-Turner scatterometer for BRDF measurements
Author(s): Felix Koch; Matthias Zilk; Mike Schnabel; Tilman Glaser
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Paper Abstract

Scattered light level of optical components can severely impair SNR and overall performance of optical systems for imaging and spectrometry. It is therefore necessary to directly assess its angular distribution in terms of BRDF measurements which is, due to the extreme dynamics required for high quality optical surfaces, still a challenging task. In our contribution we will present a self-built scatterometer that is based on a Czerny-Turner geometry in conjunction with a CMOS-camera detector and a single mode fiber coupled 405 nm diode laser source. Our setup is, besides simple spherical mirrors, purely based on stock-components and both, cost-effective and simple to build. Considerations on system design for high resolution and minimized instrumental signature as well as a first breadboard experimental setup will be discussed. The scatterometer utilizes the sensor’s pixels for adaptive sub-slit resolution and 2d measurements in the close vicinity of the plane of incidence. It can cover BRDF-values of up to 14 orders of magnitude and reaches resolutions well below 0.01° which allows to gain useful insights about small-angle scattering that has in the past been difficult to experimentally address. First measurements of superpolished mirrors as well as holographic and mechanically ruled diffraction gratings will be presented. Simple formulae can be used to assign rotation angles to spatial frequencies and, for smooth surfaces with negligible particulate contribution of scattering, also to PSD values and band-limited RMS roughness.

Paper Details

Date Published: 21 June 2019
PDF: 12 pages
Proc. SPIE 11056, Optical Measurement Systems for Industrial Inspection XI, 110561C (21 June 2019); doi: 10.1117/12.2524832
Show Author Affiliations
Felix Koch, Carl Zeiss Jena GmbH (Germany)
Matthias Zilk, Carl Zeiss Jena GmbH (Germany)
Mike Schnabel, Carl Zeiss Jena GmbH (Germany)
Tilman Glaser, Carl Zeiss Jena GmbH (Germany)

Published in SPIE Proceedings Vol. 11056:
Optical Measurement Systems for Industrial Inspection XI
Peter Lehmann; Wolfgang Osten; Armando Albertazzi Gonçalves Jr., Editor(s)

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