Presentation + Paper
21 August 2020 Reproducibility of two calibration procedures for phase-measuring deflectometry
Author Affiliations +
Abstract
Phase-measuring deflectometry is an optical inspection technique for reflective surfaces. It enables absolute, quantitative surface measurements, given a calibrated measurement setup. Two general calibration approaches can be found in literature: First, the stepwise approach uses a calibration pattern and determines internal camera parameters and external geometrical parameters in separate, consecutive steps. Second, the holistic approach optimizes all parameters collectively, based on deflectometric measurements of a calibration mirror. Whereas both approaches have been compared regarding the accuracy of subsequent surface measurements, the present contribution focuses on experimental examination of their reproducibility. In experiment E1, we assess the parameter variability by repeating both calibration procedures ten times. In an additional experiment E2, we repeat all calibration measurements related to a mirror/pattern position ten times in a row before rearranging the mirror/pattern, in order to examine the purely noise-related parameter variability. Finally, we calculate the coordinate variability of a set of world points projected onto the image planes of the calibrated cameras. The measured variability is consistently higher in E1 than in E2 (average ratio: 3.2). Unexpectedly, in both experiments, the external parameter variability also turns out to be higher for the holistic approach compared to stepwise calibration (average ratio: 2.3). This is of importance, since the holistic approach is known from literature to be more accurate than the stepwise approach, regarding their respective application to surface measurements. The image coordinate variability is comparable for both calibration approaches with an average of 0.84 and 0.21 camera pixels for E1 and E2, respectively.
Conference Presentation
© (2020) 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 "Reproducibility of two calibration procedures for phase-measuring deflectometry", Proc. SPIE 11490, Interferometry XX, 114900G (21 August 2020); https://doi.org/10.1117/12.2567092
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KEYWORDS
Calibration

Cameras

Mirrors

Imaging systems

Deflectometry

Image processing

Printing

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