ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
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Articles | Volume V-1-2022
ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., V-1-2022, 179–186, 2022
https://doi.org/10.5194/isprs-annals-V-1-2022-179-2022
ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., V-1-2022, 179–186, 2022
https://doi.org/10.5194/isprs-annals-V-1-2022-179-2022
 
17 May 2022
17 May 2022

CALIBRATION AND VALIDATION OF A STEREO CAMERA SYSTEM AUGMENTED WITH A LONG-WAVE INFRARED MODULE TO MONITOR ULTRASONIC WELDING OF THERMOPLASTICS

M. Wischow1, D. Dahlke1, H. Meißner1, I. Ernst1, S. Jarka2, and R. Glück2 M. Wischow et al.
  • 1Institute of Optical Sensor Systems, German Aerospace Center, 12489 Berlin, Germany
  • 2Center for Lightweight Production Technology, German Aerospace Center, 86159 Augsburg, Germany

Keywords: Stereo-Camera, Infrared, Co-Registration, DoF, Ultrasonic Welding, Quality Assessment

Abstract. Ultrasonic welding of thermoplastics has become an important industrial manufacturing process in the fields of aerospace and transportation. High quality standards are demanded and a reliable quality assessment routine is fundamental. Most on-site and off-site approaches are time consuming or require additional active illumination. Especially temperature models have proven to be good indicators for welding quality. We present a methodology to measure the surface temperature in real-time and visualize it simultaneously as a 3D model. Through augmenting a stereo camera system with an additional passive thermal infrared camera, we are able to map the heat data of multiple successive welds of large, free-form structures into a common 3D data representation. A challenging calibration approach is used to derive the inner and exterior orientation for the trifocal camera system. Geometric and radiometric improvements for an aluminium chessboard allow the usage of wide-angle optics for the thermal infrared camera. Consequently, we verify the quality of each camera by means of their resolving power. Therefore, a Siemens star test pattern is used for the thermal camera as well. We demonstrate the effectiveness of our methodology on a robot-guided ultrasonic welding tool.