High-speed 3D shape measurement of transparent objects by sequential thermal fringe projection and image acquisition in the long-wave infrared

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

doi:10.1117/12.2663331

12 June 2023 High-speed 3D shape measurement of transparent objects by sequential thermal fringe projection and image acquisition in the long-wave infrared

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

Author Affiliations +

Proceedings Volume 12536, Thermosense: Thermal Infrared Applications XLV; 125360P (2023) https://doi.org/10.1117/12.2663331
Event: SPIE Defense + Commercial Sensing, 2023, Orlando, Florida, United States

Abstract

Recently, we have successfully tackled the challenge of measuring the 3D shape of uncooperative materials, i.e., materials with optical properties such as being glossy, transparent, absorbent, or translucent. By projecting sequential thermal fringes in the long-wave infrared (LWIR) combined with a stereo camera setup in the midwave infrared (MWIR), we were able to three-dimensionally record object shapes within one second. However, in many applications, e.g., for 100 % quality assurance, even shorter measurement times are required. To achieve camera frame rates higher than 125 fps at room temperature, Max Planck’s law of thermal emission teaches us a change in the camera spectral range from MWIR to LWIR. If irradiation and image acquisition have to run in parallel, the camera chips must therefore be protected against the radiation projected by the CO₂ laser at a wavelength of 10.6 µm. Appropriate filters have been available only recently. In this contribution, we present our high-speed LWIR 3D sensor. The work includes a characterization of our setup regarding its measurement accuracy and speed. The results are compared to the performance of previous thermal 3D sensors. We show 3D measurement results of static objects as well as of a dynamic measurement situation of a transparent object. Furthermore, we demonstrate that our setup enables us to extend the measurability of material classes towards objects with high thermal conductivities.

Conference Presentation

Citation Download Citation

Martin Landmann, Henri Speck, Zengyang Gao, Stefan Heist, Peter Kühmstedt, and Gunther Notni "High-speed 3D shape measurement of transparent objects by sequential thermal fringe projection and image acquisition in the long-wave infrared", Proc. SPIE 12536, Thermosense: Thermal Infrared Applications XLV, 125360P (12 June 2023); https://doi.org/10.1117/12.2663331

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