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B6 - Endoscopic Geometry Inspection

Endoscopic Geometry Inspection by Modular Fibre-optic Sensors

Project Status: Active

Last Update: 14.02.2019


The aim of subproject B6 Endoscopic Geometry Inspection is to develop a measuring system based on the principle of fringe projection in combination with flexible optical fibres. The usage of optical fibres allows a spatial separation of the measuring head and the camera-projector unit. Therefore, a measuring head of small dimensions can perform measurements in forming plants. The main task of subproject B6 is the design of the optical setup, the construction of appropriate measuring heads within in the context of the measuring task and the development of algorithms processing the fringe pattern by including the transmission properties of the used optics.

The first phase lead to the principle design of the endoscopic fringe projection system allowing first measurements of gear geometries of a tool for sheet-bulk metal forming. The second phase prepared the system for automated in-situ inspections, thus the measuring-time was reduced by extending the system capabilities by implementing the model-based invers fringe projection technique. Furthermore, a multi-stage positioning unit was developed, allowing flexible positioning of the measuring head. The range of functions has been expanded by the integration of liquid lenses, being able to enlarge the depth of field and extend the size of the measuring volume.

Within the third phase all aspects of the previous work will be combined in one portable device being able to perform in field measurements. To enhance its usability, the system should come with an assistant system. Implying all critical process parameters to be wide-ranging assessed and if possible, being predefined within the context of the measuring task. The influence of the fringe frequencies in the context of different geometries with varyingly oriented surfaces shall particularly be analysed. According to that, the measurement uncertainty shall be reduced by the integration of the adaptive projection of local frequency-modulated patterns.

Working Groups



    • Matthias, S.: A flexible endoscopic structured light 3-D sensor: Design, models, and image processing(2018), Garbsen: PZH-Verlag, published
    • Matthias, S.; Kästner, M.; Reithmeier, E.: A 3D measuring endoscope for hand-guided operation. In: Measurement Science and Technology, 29(2018), pp. 094001


    • Matthias, S.; Schlobohm, J.; Kästner, M.; Reithmeier, E.: Fringe projection profilometry using rigid and flexible endoscopes. In: tm-Technisches Messen, 84(2017), pp. 123-129
    • Matthias, S.; Schlobohm, J.; Kästner, M.; Reithmeier, E.: Fiber-optic fringe projection with crosstalk reduction by adaptive pattern masking. In: Proc. Of SPIE , 10117(2017), pp. A-1-A-8
    • Matthias, S.; Kästner, M.; Reithmeier, E.: Pattern sequences for fast absolute phase retrieval with application in the handheld operation of structured light sensors. In: Engineering for a Changing World, (2017)59, pp. H.1.1.11