Thermal single-shot 3D shape measurement of transparent objects by statistical point pattern projection

Martin Landmann; Henri Speck; Zengyang Gao; Stefan Heist; Peter Kühmstedt; Gunther Notni

doi:10.1117/12.3012571

7 June 2024 Thermal single-shot 3D shape measurement of transparent objects by statistical point pattern projection

Martin Landmann, Henri Speck, Zengyang Gao, Stefan Heist, Peter Kühmstedt, Gunther Notni

Proceedings Volume 13038, Dimensional Optical Metrology and Inspection for Practical Applications XIII; 1303803 (2024) https://doi.org/10.1117/12.3012571
Event: SPIE Defense + Commercial Sensing, 2024, National Harbor, Maryland, United States

Abstract

We have recently addressed the challenge of measuring the 3D shapes of uncooperative materials, specifically transparent objects. By sequentially projecting laser lines in the long-wave infrared (LWIR), we generate thermal fringes on the object surface. With a thermal stereo camera setup, we were able to measure the 3D shape of objects in as little as 0.1 seconds. Furthermore, we successfully recorded and reconstructed the dynamic deformation process of transparent objects for the first time at a 3D frame rate of 20 Hz. However, motion blur still exists in these dynamic measurements. To reduce or even eliminate this motion blur and make this thermal 3D method suitable for bin-picking, for example, we have adapted a proven single-shot method from the visible (VIS) and near-infrared (NIR) spectrum to the thermal 3D approach. Instead of using temporal sequences of multi-fringe patterns or scanning single fringes, we now project a statistical point pattern and capture only one thermal stereo image pair. Our new projection system generates a statistical thermal point pattern across the entire measurement field. With a quick single capture from two thermal cameras and a spatial correlation algorithm, we reconstruct the object’s surface in 3D. This significantly reduces the measurement time, leading to a substantial decrease in motion blur during dynamic measurements. In this contribution, we present our single-shot 3D sensor setup, which includes the implementation of our single-shot projection unit, and we showcase the enhanced measurement speed for a transparent object.

Conference Presentation

Citation Download Citation

Martin Landmann, Henri Speck, Zengyang Gao, Stefan Heist, Peter Kühmstedt, and Gunther Notni "Thermal single-shot 3D shape measurement of transparent objects by statistical point pattern projection", Proc. SPIE 13038, Dimensional Optical Metrology and Inspection for Practical Applications XIII, 1303803 (7 June 2024); https://doi.org/10.1117/12.3012571

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