Computed Tomography and Metrology

Fraunhofer Institute for Integrated Circuits

Data Evaluation

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Error correction and further treatment are the main factors of data evaluation.








Evaluation on the Specimen

Depending on measurement task dimension, form and position are determined within the CT data set:

  • Measurement of single dimensions (distances, angles, etc.)
  • Fitting of regular geometries (cylinders, spheres, planes)
  • Actual/nominal value comparison using CAD or reference data
By fitting regular geometries the diameter and geometry deviations can be determined up to an entire actual/nominal value comparison of the CT data set with reference data.
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Scaling

For the correction of systematic errors that can arise from insufficiently known mappings a scaling of voxel size is conducted. Using parameters known from tactile measurements (e.g. sphere distance deviations) of reference bodies (e.g. sphere rod) that are acquired alongside the measurement volume, the true voxel size can be determined and adapted. The measuring accuracy can be increased by 40% in certain cases.

Determination of Characteristics in Metrology

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Using real or virtual test blocks like sphere calotte cubes or plates it is possible to characterize or optimize the global and local measurement properties of CT systems the same way it is done in tactile coordinate measurement.





Reverse Engineering in Modern Dental Laboratories

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Point cloud measured tactilely (top) and actual/nominal value comparison at a casting (bottom). The devoations between the CT-reconstruction an the tactile date is shown in different colours.

Production Process

Data Evaluation Production Process
By performing a CT scan of the impression of the dentition a digital model of the primed teeth is generated. The generated restaurations (inlays, coronas) are modeled in real-time. After computing the complete inlay or corona geometry the data sets are reproduced on a very precise dental drill before they are submitted to quality control (Biodentis GmbH, Leipzig).

Inspection of Material Thickness

For the determination of reliability and stability of the restaurations material thickness is checked throughout the manufacturing process in order to cope with the high quality standards.