Presentation + Paper
20 June 2021 The effects of pattern screen surface deformation on deflectometric measurements: a simulation study
Author Affiliations +
Abstract
Phase-measuring deflectometry (PMD) is an optical inspection technique for full-field topography measurements of reflective sample surfaces. The measurement principle relies on the analysis of specific patterns, reflected at the sample surface. Evaluation algorithms often model the respective pattern screen as a planar light source. However, the 3200 pattern screen in our inspection setup exhibits a central bulge of its surface of about 2–3mm. This paper presents a simulation framework for PMD to evaluate the effects of a deformed screen surface. The idea is to simulate image data acquired with screen surface deformations and to examine the effects on the PMD evaluation results. The simulated setup consists of a 3200 pattern screen with an adjustable central bulge height of 0–3mm and two cameras with a field of view (FOV) of approximately 225mm by 172mm on the sample surface. A first experiment examines the reconstruction errors for a planar sample surface if the reconstruction algorithm uses perfect calibration data (i.e. the same parameters used for the simulated image acquisition). The reconstructed surfaces exhibit a tilt with a maximum height difference of 174 μm across the FOV. A second experiment repeats the reconstruction process of the same sample surface, using camera parameters determined in a simulated calibration process. The resulting surfaces possess irregular, wave-like errors with amplitudes of up to 9 μm in the FOV. The presented simulation results reveal the accuracy limits if a deformation model of the pattern screen is not explicitly included in the reconstruction process.
Conference Presentation
© (2021) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stephan Allgeier, Ulrich Gengenbach, Bernd Köhler, Klaus-Martin Reichert, and Veit Hagenmeyer "The effects of pattern screen surface deformation on deflectometric measurements: a simulation study", Proc. SPIE 11787, Automated Visual Inspection and Machine Vision IV, 1178708 (20 June 2021); https://doi.org/10.1117/12.2591877
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