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Proceedings Paper

Large-volume NIR pattern projection sensor for continuous low-latency 3D measurements
Author(s): Christoph Munkelt; Matthias Heinze; Christian Bräuer-Burchardt; Shantanu P. Kodgirwar; Peter Kühmstedt; Gunther Notni
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Paper Abstract

For continuous, low-latency, irritation-free 3D measurements in large-volumes, dot-pattern- or time-of-flight-based sensors have been traditionally used. However, measurement accuracy and temporal stability limits the application in demanding medical or industrial contexts. Practical solutions also need to remain cost-effective. To meet these requirements, we started from a simple GOBO-based, aperiodic sinusoidal pattern projection (using a near-infrared (NIR) LED) 3D sensor for medium-sized measurement volumes. By tuning the system for large-volume operation, we were able to obtain a reasonable combination of measurement accuracy and speed. The current realization covers a volume of up to 4.0 m x 2.2 m x 1.5 m (width x height x depth). The 3D data is acquired at < 20 fps at resolutions of < 1000 x 500 px and true end-to-end latencies of < 140 ms. We present the system architecture consisting of GigE Vision cameras, a high-power LED-driven projection unit using a GOBO wheel, and the compute backend for the online GPU-based, temporal pattern correlation 3D calculation and filtering. To compensate for the low pattern intensity due to the short exposure time, we operate the cameras in 2x2 binning. Furthermore, the optics are tuned for large apertures to maximize light throughput. We characterize the sensor system with respect to measurement quality by quantitative evaluations including probing error, sphere-spacing error, and flatness measurement error. By comparison with another 3D sensor as a baseline, we show the benefits of our approach. Finally, we present measurement examples from human-machine interface (HMI).

Paper Details

Date Published: 13 May 2019
PDF: 7 pages
Proc. SPIE 10991, Dimensional Optical Metrology and Inspection for Practical Applications VIII, 109910K (13 May 2019); doi: 10.1117/12.2518636
Show Author Affiliations
Christoph Munkelt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Matthias Heinze, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Christian Bräuer-Burchardt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Shantanu P. Kodgirwar, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Peter Kühmstedt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Gunther Notni, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Technische Univ. Ilmenau (Germany)


Published in SPIE Proceedings Vol. 10991:
Dimensional Optical Metrology and Inspection for Practical Applications VIII
Kevin G. Harding; Song Zhang, Editor(s)

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