minimize Header

Prof. Dr.-Ing. Jochen Hiller

Faculty of Mechanical Engineering and Mechatronics

Professors

Professor

C 224

0991/3615-375

publications

Sortierung:

Contribution

Jochen Hiller
S. Kasperl

Analyse von Einflussgrößen beim dimensionellen Messen mittels Röntgencomputertomographie.

In: Berichtsband BB 104, DGZfP Jahrestagung (Fürth).

(2007)

Contribution

S. Kasperl
Jochen Hiller

Modellierung und Messung von Kenn- und Einflussgrößen in der CT.

In: Berichtsband F-54, 229. PTB-Seminar Geometriebestimmung mit industrieller Computertomographie (Braunschweig). pg. 137-152

(2007)

Journal article

Jochen Hiller
S. Kasperl
U. Hilpert
M. Bartscher

Koordinatenmessung mit industrieller Röntgen-Computertomografie.

In: tm - Technisches Messen pg. 553-564

(2007)

DOI: 10.1524/teme.2007.74.11.553

show abstract

Die industrielle Computertomografie (CT) hat in der letzten Zeit eine deutliche Weiterentwicklung in Richtung Koordinatenmesstechnik erfahren. Zahlreiche Messaufgaben können bereits sinnvoll und konkurrenzfähig gegenüber anderer Messtechnik gelöst werden. Dieser Beitrag beschreibt anhand eines speziellen Prüfkörpers und ausgewählter Mess- und Kenngrößen dimensionelle Messeigenschaften industrieller CT-Anlagen. Es wird gezeigt, wie sich unterschiedliche physikalische Effekte auf diese dimensionellen Messgrößen auswirken können. Darüber hinaus wird ein Korrekturverfahren vorgestellt, mit dem die Genauigkeit der mit CT ermittelten Geometriedaten erhöht werden kann. Industrial computed tomography (CT) has lately experienced a distinct development with respect to the coordinate measuring technique. Numerous measuring tasks can already be solved reasonably and in competition with other measuring techniques. This article describes - by means of a Special test body and selected measurands and characteristics - the dimensional measuring properties of industrial CT Systems. The possible influence of different physical effects on these dimensional measurands is demonstrated. In addition, a correction method to improve the accuracy of the geometric data determined by CT is presented.

Contribution

Jochen Hiller
S. Schindler
T. Fuchs
F. Porsch

Bestimmung des lokalen räumlichen Auflösungsvermögens eines industriellen Mikro-Computertomographie-Systems (μCT) mit Hilfe einer Modulationsübertragungsfunktion.

In: VDI-Berichte 2011 - Sensoren und Messsysteme (Ludwigsburg). pg. 507-520

(2008)

Contribution

Jochen Hiller
R. Hanke
M. Maisl
A. Weckenmann
P. Krämer

Computed Tomography - A new oppurtunity to measure complete volumes.

In: Proceedings of NCSL International Workshop and Symposium (Orlando, FL, USA).

(2008)

Contribution

Jochen Hiller
S. Kasperl

Messunsicherheitsbetrachtungen in der industriellen Computertomographie (CT) mittels Simulation.

In: Berichtsband GMA-Fachtagung: Messunsicherheit praxisgerecht bestimmen (Erfurt).

(2008)

Contribution

Jochen Hiller
C. Funk
S. Kasperl

Vergleich von Fächerstrahl- und Kegelstrahl Computertomographie-Messungen am Beispiel eines Zylinderkopfsegmentes.

In: Berichtsband BB-115 zur DGZfP-Jahrestagung (Münster).

(2009)

Journal article

S. Kasperl
Jochen Hiller

Artefaktkorrekturen beim dimensionellen Messen mit industrieller Röntgen-Computertomographie.

In: tm - Technisches Messen pg. 401-409

(2009)

DOI: 10.1524/teme.2009.0918

show abstract

Die zerstörungsfreie Untersuchung komplexer Bauteile ist eine wichtige Prüfaufgabe in der industriellen Fertigung. Die dabei gestellten Anforderungen umfassen eine schnelle Verifikation der Maßhaltigkeit sowie die Analyse von Soll-Ist-Vergleichen. Für diese Erfordernisse ist die Computertomographie (CT) als zerstörungsfreie Prüfmethode bestens geeignet. Allerdings äußern sich physikalische Effekte wie Strahlaufhärtung und Streustrahlung in den rekonstruierten Schichten als Artefakte, die die Bildqualität verschlechtern und die Erfüllung der genannten Prüfaufgaben erschweren oder verhindern. Dieser Beitrag beschreibt, wie mit Hilfe der Iterativen Artefakt-Reduktion (IAR) die Qualität der Rekonstruktionen verbessert werden kann. Am Beispiel eines speziellen Referenzkörpers und eines Aluminiumtestkörpers werden ausgewählte Kenn- und Messgrößen ermittelt und die erzielten Genauigkeitssteigerungen quantifiziert. Abstract

Journal article

S. Kasperl
Jochen Hiller
M. Krumm

Computed Tomography Metrology in Industrial Research and Development.

In: MP - Materials Testing vol. 51 pg. 405-411

(2009)

DOI: 10.3139/120.110053

show abstract

Beim zerstörungsfreien Prüfen wird die Computertomographie (CT) zunehmend für dimensionelle Messaufgaben eingesetzt, wie beispielsweise in der industriellen Werkstückprüfung. Neben der Bestimmung der Messunsicherheit ist die Verbesserung der Bildqualität Gegenstand aktueller Forschungen, um die CT als Koordinatenmessgerät zu etablieren.

Contribution

T. Schön
I. Bauscher
T. Fuchs
U. Hassler
Jochen Hiller
S. Kasperl
S. Oeckl
S. Schröpfer
V. Weizel

Dimensionelles Messen mit Helix-Computertomographie.

In: Berichtsband BB-115 zur DGZfP-Jahrestagung (Münster).

(2009)

Contribution

M. Franz
C. Funk
Jochen Hiller
S. Kasperl
M. Krumm
S. Schröpfer

Reliability of Dimensional Measurements by Computed Tomography for Industrial Applications.

In: Proceedings of the 4th European-American Workshop on Reliability of NDT (Berlin).

(2009)

Contribution

S. Kasperl
Jochen Hiller

Dimensionelles Messen mit Helix-Computertomographie.

In: Leitfaden zur industriellen Computertomographie. pg. 12-14

(2010)

Contribution

Jochen Hiller
S. Kasperl
L. Reindl

Charakterisierung und Modellierung eines μCT-Systems.

In: Berichtsband ITG/GMA-Fachtagung Sensoren und Messsysteme (Nürnberg). pg. 400-405

(2010)

Contribution

Jochen Hiller
S. Kasperl

Zum Verhältnis von Bildqualität und Messgenauigkeit in der CT-Metrologie.

In: Berichtsband Industrielle Computertomografie Tagung (Wels, Österreich). pg. 155-162

(2010)

Lecture

Jochen Hiller

Seminar on industrial CT.

Technical University of Denmark, Department of Mechanical Engineering Kgs. Lyngby, Dänemark

2010 (2010)

Contribution

Jochen Hiller
S. Kasperl
D. Weiss

Comparison of Probing Error in Dimensional Measurement by Means of 3D Computed Tomography.

In: Proceedings of the 2nd International Symposium on NDT in Aerospace (Hamburg).

(2010)

Contribution

P. Müller
Jochen Hiller
A. Cantatore
L. Chiffre

Investigation of measuring strategies in computed tomography.

In: Proceedings of the International Conference on Advanced Manufacturing Engineering (Newstech, Brno, Tschechische Republik).

(2011)

Lecture

Jochen Hiller

Estimation of uncertainties in CT metrology by simulation.

In: International Workshop on Computed Tomography for Dimensional Metrology

Università di Padova Padua, Italien

2011 (2011)

Journal article

Jochen Hiller
T. Fuchs
S. Kasperl
L. Reindl

Einfluss der Bildqualität röntgentomographischer Abbildungen auf Koordinatenmessungen. Grundlagen, Messungen und Simulationen.

In: tm - Technisches Messen pg. 334-347

(2011)

DOI: 10.1524/teme.2011.0137

show abstract

Die industrielle Computertomographie (CT) findet in der dimensionellen Messtechnik zunehmend Akzeptanz. Allerdings ist noch wenig über den konkreten Einfluss verschiedener Systemkomponenten, physikalischer Störgrößen oder Bildverarbeitungsschritte auf dimensionelle CT-Messungen bekannt. In diesem Beitrag werden physikalische Bildgütemerkmale zur Beurteilung der Bildqualität in der CT vorgestellt und mittels Computersimulationen der Einfluss der Rekonstruktionsbildgüte auf Koordinatenmessungen untersucht.

Lecture

Jochen Hiller

CT scanning strategy - Prediction of image quality.

In: Conference on Application of CT Scanning in Industry

Danish Technological Institute Taastrup, Dänemark

31.05.2011 (2011)

Lecture

S. Reisinger
S. Kasperl
M. Franz
Jochen Hiller
U. Schmid

Simulation-Based Planning of Optimal Conditions for Industrial Computed Tomography.

In: International Symposium on Digital Industrial Radiology and Computed Tomography

Berlin

20.-22.06.2011 (2011)

Contribution

P. Müller
Jochen Hiller
A. Cantatore
M. Bartscher
L. Chiffre

New reference object for Metrological performance testing of industrial CT systems.

In: Proceedings of the 12th euspen International Conference (Juni 2012, Stockholm, Schweden).

(2012)

Journal article

Jochen Hiller
M. Maisl
L. Reindl

Physical characterization and performance evaluation of an x-ray micro-computed tomography system for dimensional metrology applications.

In: Measurement Science and Technology vol. 23 pg. 085404

(2012)

DOI: 10.1088/0957-0233/23/8/085404

show abstract

This paper presents physical and metrological characterization measurements conducted for an industrial x-ray micro-computed tomography (CT) system. As is well known in CT metrology, many factors, e.g., in the scanning and reconstruction process, the image processing, and the 3D data evaluation, influence the dimensional measurement properties of the system as a whole. Therefore, it is important to know what leads to, and what are the consequences of, e.g., a geometrical misalignment of the scanner system, image unsharpness (blurring), or noise or image artefacts. In our study, the two main components of a CT scanner, i.e. the x-ray tube and the flat-panel detector, are characterized. The contrast and noise transfer property of the scanner is obtained using image-processing methods based on linear systems theory. A long-term temperature measurement in the scanner cabinet has been carried out. The dimensional measurement property has been quantified by using a calibrated ball-bar and uncertainty budgeting. Information about the performance of a CT scanner system in terms of contrast and noise transmission and sources of geometrical errors will help plan CT scans more efficiently. In particular, it will minimize the user's influence by a systematic line of action, taking into account the physical and technical limitations and influences on dimensional measurements.

Contribution

K. Poulios
G. Svendsen
Jochen Hiller
P. Klit

Coefficient of Friction Measurements for Thermoplastics and Fiber Composites under Low Sliding Velocity and High Pressure.

In: Proceedings of the 15th Nordic Symposium on Tribology 2012 (NordTrib, Trondheim, Norwegen).

(2012)

Journal article

Jochen Hiller
L. Reindl

A computer simulation platform for the estimation of measurement uncertainties in dimensional X-ray computed tomography.

In: Measurement vol. 45 pg. 2166-2182

(2012)

DOI: 10.1016/j.measurement.2012.05.030

Lecture

Jochen Hiller

Systematic Errors in Dimensional X-ray Computed Tomography.

In: Maletekniske Dage

Taastrup, Dänemark

2012 (2012)

Journal article

Jochen Hiller
L. Reindl

A computer simulation for the estimation of measurement uncertainties in dimensional X-ray computed tomography.

In: Measurement pg. 2166-2182

(2012)

Journal article

P. Müller
Jochen Hiller
A. Cantatore
L. Chiffre

A study on evaluation strategies in Dimensional X-ray computed tomography by estimation of measurement uncertainties.

In: International Journal of Metrology and Quality Engineering vol. 3 pg. 107-115

(2012)

DOI: 10.1051/ijmqe/2012011

show abstract

Computed tomography has entered the industrial world in 1980’s as a technique for non-destructive testing and has nowadays become a revolutionary tool for dimensional metrology, suitable for actual/nominal comparison and verification of geometrical and dimensional tolerances. This paper evaluates measurement results using different measuring strategies applied in different inspection software packages for volume and surface data analysis. The strategy influence is determined by calculating the measurement uncertainty. This investigation includes measurements of two industrial items, an aluminium pipe connector and a plastic toggle, a hearing aid component. These are measured using a commercial CT scanner. Traceability is transferred using tactile and optical coordinate measuring machines, which are used to produce reference measurements. Results show that measurements of diameter for both parts resulted in smaller systematic errors compared to distance and height measurements. It was found that uncertainties of all measurands evaluated on surface data were generally greater compared to measurements performed on volume data.

Lecture

Jochen Hiller

Evaluation strategies in CT scanning.

In: CT Conference

Kgs. Lyngby, Dänemark

12.06.2012 (2012)

Lecture

P. Müller
Jochen Hiller
A. Cantatore
M. Bartscher
L. Chiffre

Investigation on the influence of image quality in X-ray CT metrology.

In: Conference on Industrial Computed Tomography (ICT)

Wels, Österreich

19.-21.09.2012 (2012)

Journal article

P. Müller
A. Cantatore
J. Andreasen
Jochen Hiller
L. Chiffre

Computed Tomography as a Tool for Tolerance Verification of Industrial Parts.

In: Procedia CIRP vol. 10 pg. 125-132

(2013)

DOI: 10.1016/j.procir.2013.08.022

show abstract

Computed tomography (CT) is becoming an important technology for industrial applications, enabling fast and accurate control of manufactured parts. In only a few minutes, a complete 3D model of a part may be obtained, allowing measurements of external and internal features. This paper presents results of tolerance verification of a plastic housing for an insulin pen manufactured by Novo Nordisk A/S. Calculation of measurement uncertainties was taken into account in decision making regarding the specified tolerance limits. Variables in terms of CT systems, data sets, and evaluation software are considered in this study.

Journal article

K. Poulios
G. Svendsen
Jochen Hiller
P. Klit

Coefficient of Friction Measurements for Thermophastics and Fibre Composites Under Low Sliding Velocity and High Pressure.

In: Tribology Letters vol. 51 pg. 191-198

(2013)

DOI: 10.1007/s11249-013-0107-0

show abstract

Friction materials for typical brake applications are normally designed considering thermal stability as the major performance criterion. There are, however, brake applications with very limited sliding velocities, where the generated heat is insignificant. In such cases it is possible that friction materials which are untypical for brake applications, like thermoplastics and fibre composites, can offer superior performance in terms of braking torque, wear resistance and cost than typical brake linings. In this paper coefficient of friction measurements for various thermoplastic and fibre composite materials running against a steel surface are presented. All tests were carried out on a pin-on-disc test-rig in reciprocating operation at a fixed sliding speed and various pressure levels for both dry and grease lubricated conditions. Moreover, a generic theoretical framework is introduced in order to interpret the changes of friction observed during the running-in phase.

Journal article

P. Müller
Jochen Hiller
Y. Dai
J. Andreasen
H. Hansen
L. Chiffre

Estimation of measurement uncertainties in X-ray computed tomography metrology using the substitution method.

In: CIRP Journal of Manufacturing Science and Technology vol. 7 pg. 222-232

(2014)

DOI: 10.1016/j.cirpj.2014.04.002

show abstract

This paper presents the application of the substitution method for the estimation of measurement uncertainties using calibrated workpieces in X-ray computed tomography (CT) metrology. We have shown that this, well accepted method for uncertainty estimation using tactile coordinate measuring machines, can be applied to dimensional CT measurements. The method is based on repeated measurements carried out on a calibrated master piece. The master piece is a component of a dose engine from an insulin pen. Measurement uncertainties estimated from the repeated measurements of the master piece were transferred on to additionally scanned uncalibrated workpieces which provided the necessary link for achieving traceable measurements.

Contribution

D. Schmid
J. Merz
Jochen Hiller

New Method for Master Pattern Tool Correction Based on Computed Tomography Data and Intelligent Reverse Engineering.

In: iCT 2014 5th Conference on Industrial Computed Tomography (iCT) 2014.

(2014)

Journal article

A. Tissen
Peter Hornberger
Jochen Hiller
Simon Zabler
B. Baudrit
S. Horlemann

Dimensionelles Messen und Materialprüfung an belasteten Bauteilen mit In-situ-CT.

In: inspect vol. 15 pg. 54-56

(2014)

show abstract

Die Anwendung der Röntgen-Computertomographie (CT) als zerstörungsfreie Prüfung (zfP) entwickelt sich zunehmend zu einem unverzichtbaren bildgebenden Verfahren in der Qualitätssicherung. Seit dem letzten Jahrzehnt wird diese Technologie verstärkt auch in der dimensionellen Messtechnik eingesetzt.

Journal article

Jochen Hiller
G. Genta
G. Barbato
L. Chiffre
R. Levi

Measurement Uncertainty Evaluation in Dimensional X-ray Computed Tomography Using the Bootstrap Method.

In: International Journal of Precision Engineering and Manufacturing vol. 15 pg. 617-622

(2014)

DOI: 10.1007/s12541-014-0379-9

show abstract

Industrial applications of computed tomography (CT) for dimensional metrology on various components are fast increasing, owing to a number of favorable properties such as capability of non-destructive internal measurements. Uncertainty evaluation is however more complex than in conventional measurement processes, e.g., with tactile systems, also due to factors related to systematic errors, mainly caused by specific CT image characteristics. In this paper we propose a simulation-based framework for measurement uncertainty evaluation in dimensional CT using the bootstrap method. In a case study the problem concerning measurement uncertainties was addressed with bootstrap and successfully applied to ball-bar CT measurements. Results obtained enabled extension to more complex shapes such as actual industrial components as we show by tests on a hollow cylinder workpiece.

Lecture

D. Schmid
J. Merz
Jochen Hiller

New Method for Master Pattern Tool Correction Based on Computed Tomography Data and Intelligent Reverse Engineering.

In: iCT Conference 2014 (Conference on Industrial Computed Tomography)

Wels, Österreich

25.-28.02.2014 (2014)

Journal article

P. Müller
Jochen Hiller
Y. Dai
J. Andreasen
H. Hansen
L. Chiffre

Quantitative analysis of scaling error compensation methods in dimensional X-ray computed tomography.

In: CIRP Journal of Manufacturing Science and Technology vol. 10 pg. 68-76

https://www.sciencedirect.com/science/article/pii/S1755581715000279 (2015)

DOI: 10.1016/j.cirpj.2015.04.004

show abstract

X-ray Computed Tomography (CT) has become an important technology for quality control of industrial components. As with other technologies, e.g., tactile coordinate measurements or optical measurements, CT is influenced by numerous quantities which may have negative impact on the accuracy and repeatability of dimensional and geometrical measurements. The aim of this paper is to discuss different methods for the correction of scaling errors and to quantify their influence on dimensional measurements. Scaling errors occur first and foremost in CT systems with no built-in compensation of positioning errors of the manipulator system (magnification axis). This article also introduces a new compensation method for scaling errors using a database of reference scaling factors and discusses its advantages and disadvantages. In total, three methods for the correction of scaling errors – using the CT ball plate, using calibrated features measured by CMM and using a database of reference values – are presented and applied within a case study. The investigation was performed on a dose engine component of an insulin pen, for which several dimensional measurands were defined. The component has a complex geometry and is made of brass, which makes its measurements with CT challenging. It is shown that each scaling error correction method results in different deviations between CT measurements and reference measurements from a CMM. Measurement uncertainties were estimated for each method, taking into consideration the contributions related to the applied correction method. The newly suggested approach using the database appeared to work well, indicating, that if the properties of a CT system under investigation are monitored using a reference object (ball bar in our case), a correction factor based on individual selected magnification factors can be applied for scaling error correction of any object, and thus no additional scanning of a reference object is needed.

Contribution

Peter Landstorfer
Thomas Miller
Jochen Hiller

Automatisierung von Mess- und Prüfprozessen mit Computertomographie.

In: Leitfaden zur industriellen Röntgentechnik. Zerstörungsfreie Prüfung mit Bildverarbeitung (Vision)

(2015)

Contribution

Peter Hornberger
Christian Aichinger
Jochen Hiller

Dimensionelles Messen mit Computertomographie.

In: Leitfaden zur industriellen Röntgentechnik. Zerstörungsfreie Prüfung mit Bildverarbeitung (Vision)

(2015)

Contribution

Simon Rettenberger
Peter Hornberger
A. Tissen
Jochen Hiller
Simon Zabler

Messtechnik und Materialprüfung an belasteten Bauteilen mit In-situ-Computertomographie.

In: Leitfaden zur industriellen Röntgentechnik. Zerstörungsfreie Prüfung mit Bildverarbeitung (Vision)

(2015)

Journal article

A. Gameros
L. Chiffre
H. Siller
Jochen Hiller
G. Genta

A reverse engineering methodology for nickel alloy turbine blades with internal features.

In: CIRP Journal of Manufacturing Science and Technology vol. 9 pg. 116-124

(2015)

DOI: 10.1016/j.cirpj.2014.12.001

show abstract

The scope of this work is to present a reverse engineering (RE) methodology for freeform surfaces, based on a case study of a turbine blade made of Inconel, including the reconstruction of its internal cooling system. The methodology uses an optical scanner and X-ray computed tomography (CT) equipment. Traceability of the measurements was obtained through the use of a Modular Freeform Gage (MFG). An uncertainty budget is presented for both measuring technologies and results show that the RE methodology presented is promising when comparing uncertainty values against common industrial tolerances.

Journal article

Peter Landstorfer
Jochen Hiller

Präzision in drei Freiheitsgraden - Exakte Bauteilpositionierung bei CT-Messungen ohne zusätzliche Antriebe.

In: inspect

(2015)

show abstract

Die präzise und reproduzierbare Ausrichtung von Messobjekten im CT ist eine wesentliche Voraussetzung für die Erzeugung vollständiger und genauer Datensätze. Mit einer universellen Positioniereinheit für industrielle Computertomographen (CT), die vollständig von den im Gerät vorhandenen Achsen angetrieben wird und dabei eine Ausrichtung von Messobjekten in drei Freiheitsgraden ermöglicht, wird dies in Zukunft einfacher zu realisieren sein.

Journal article

S. Horlemann
E. Kraus
B. Baudrit
M. Bastian
A. Tissen
Jochen Hiller
Simon Zabler

In-situ-Prüfungen von Kunststoff-Klebeverbindungen mit Computertomographie.

In: KGK Rubber Point - Kautschuk Gummi Kunststoffe

(2015)

show abstract

Das mechanische Verhalten von geklebten PEEK-Verbindungen wurde unter Belastung mittels Computertomographie in-situ untersucht. Hierbei wurden für eine Zugscher-Probe die Dehnungsverteilungen in der gesamten Klebeverbindung sowie in der Klebeebene lokal bei einem mehraxialen Zustand analysiert.

Contribution

Jochen Hiller
Peter Hornberger
Mario Salzinger

Bewertung technischer Oberflächen mit Röntgen-Computertomographie.

In: Leitfaden zur Inspektion und Charakterisierung von Oberflächen mit Bildverarbeitung. (Vision-Leitfaden)

Eds.:
M. Sackewitz
Fraunhofer-Allianz Vision

Fraunhofer Verlag Stuttgart

(2016)

Journal article

A. Detterbeck
M. Hofmeister
D. Haddad
D. Weber
M. Schmid
A. Hölzing
Simon Zabler
E. Hofmann
K.-H. Hiller
P. Jakob
J. Engel
Jochen Hiller
U. Hirschenfelder

Determination of the mesio-distal tooth width via 3D imaging techniques with and without ionizing radiation: CBCT, MSCT, and μCT versus MRI.

In: European Journal of Orthodontics vol. 39 pg. 310-319

(2016)

DOI: 10.1093/ejo/cjw047

show abstract

Objective: The purpose of this study was to estimate the feasibility and accuracy of mesio-distal width measurements with magnetic resonance imaging (MRI) in comparison to conventional 3D imaging techniques [multi-slice CT (MSCT), cone-beam CT (CBCT), and µCT]. The measured values of the tooth widths were compared to each other to estimate the amount of radiation necessary to enable orthodontic diagnostics. Material and Methods: Two pig skulls were measured with MSCT, CBCT, µCT, and MRI. Three different judges were asked to determine the mesio-distal tooth width of 14 teeth in 2D tomographic images and in 3D segmented images via a virtual ruler in every imaging dataset. Results: Approximately 19% (27/140) of all test points in 2D tomographic slice images and 12% (17/140) of the test points in 3D segmented images showed a significant difference (P ≤ 0.05). The largest significant difference was 1.6mm (P < 0.001). There were fewer significant differences in the measurement of the tooth germs than in erupted teeth. Conclusions: Measurement of tooth width by MRI seems to be clinically equivalent to the conventional techniques (CBCT and MSCT). Tooth germs are better illustrated than erupted teeth on MRI. Three-dimensional segmented images offer only a slight advantage over 2D tomographic slice images. MRI, which avoids radiation, is particularly appealing in adolescents if these data can be corroborated in further studies.

Journal article

Jochen Hiller
Peter Hornberger

Measurement accuracy in X-ray computed tomography metrology: Toward a systematic analysis of interference effects in tomographic imaging.

In: Precision Engineering vol. 45 pg. 18-32

https://www.sciencedirect.com/science/article/pii/S0141635915002238 (2016)

DOI: 10.1016/j.precisioneng.2015.12.003

show abstract

In this paper an investigation of interference effects leading to limitations of metrological performance of X-ray computed tomography (CT) used as a coordinate measuring technique is presented. Using reconstruction data, image quality metrics, and calculations of artifact formation, a deeper understanding and explanation of the physical and technical limitations of CT used in dimensional metrology is given. This is demonstrated in a case study using a simple hollow cylinder made of steel as a test object and calibration measurements from a tactile coordinate measuring machine (CMM). Two different threshold determination strategies for surface computation are applied. Within the study it is also shown that CT image properties, threshold determination strategies, and systematic and random measurement errors must have a definite correlation. As a conclusion it is recommended to focus more strongly on the correlation of local CT image quality and data evaluation operations in order to reduce systematic errors in surface computation and to increase repeatability of dimensional CT measurements.

Contribution

Mario Salzinger
Peter Hornberger
Jochen Hiller

Analysis and comparison of the surface filtering characteristics of computed tomography and tactile measurements.

In: iCT 2016 6th Conference on Industrial Computed Tomography (iCT) 2016.

(2016)

show abstract

Analysis and comparison of the surface filtering characteristics of computed tomography and tactile measurementsMario Salzinger, Peter Hornberger, Jochen HillerFraunhofer Application Center for Computed Tomography in Metrology CTMT, Deggendorf, Germany, e-mail: mario.salzinger@iis.fraunhofer.de, peter.hornberger@iis.fraunhofer.de, jochen.hiller@iis.fraunhofer.deAbstractThe use of industrial computed tomography for dimensional measurements is still met with considerable suspicion because of the numerous factors that influence the measurement uncertainty, which thus is hardly describable by a mathematical model. As a consequence, reference measurements with a tactile coordinate measuring machine (CMM) are usually performed. Image unsharpness when using computed tomography (CT) can be seen as low pass filter and therefore is one among many factors that influence the metrological performance of a CT system. However, it is also known that the geometry of the probe tip acts as a mechanical filter when using tactile CMMs. The studies in this work are performed with the help of a simple specimen which includes a number of surfaces of different waviness and roughness. Capturing the surfaces using both systems and comparing the results allows a deeper analysis and understanding of the filtering effects. The measurements are performed with probe balls of different diameters on a CMM. TheCT measurements are performed using various spatial resolution settings, resulting in different surface filtering characteristics. Additionally, surface measurements using a stylus instrument are performed. The comparison of these measurements shows that the CMM is more accurate when measuring form deviations of higher order. However, it also shows that the metrological performance, when measuring dimensional and geometrical measurands using the two systems, is comparable in many cases. Keywords: CMM, CT, metrology, roughness, surface, waviness

Lecture

Mario Salzinger
Peter Hornberger
Jochen Hiller

Analysis and comparison of the surface filtering characteristics of computed tomography and tactile measurements.

In: 6th Conference on Industrial Computed Tomography (iCT 2016)

Wels, Österreich

09.-12.02.2016 (2016)

Contribution

Jochen Hiller
Peter Hornberger
Thomas Miller

Dimensional Metrology for Industrial Computed Tomography.

In: Handbook of X-ray Imaging - Physics and Technology. (Series in medical physics and biomedical engineering) pg. 949-958

Eds.:
P. Russo

CRC Press Boca Raton, FL, USA

(2017)

Journal article

Jochen Hiller
N. Sawczyn
D. Imkamp
E. Uhlmann

Untersuchungen zur Messunsicherheit und Wirtschaftlichkeit dimensioneller Computertomographie-Messungen an ausgewählten Beispielen.

In: tm - Technisches Messen vol. 84 pg. 336-347

(2017)

show abstract

Die industrielle Computertomographie (CT) wird zunehmend für die zerstörungsfreie Prüfung von Bauteilen als Instrument der fertigungsbegleitenden Qualitätssicherung eingesetzt. Ein Vorteil gegenüber taktilen oder optischen Messverfahren ist insbesondere die Möglichkeit, sowohl außen- als auch innenliegende Geometriemerkmale zerstörungsfrei zu erfassen. In diesem Beitrag werden anhand ausgewählter Bauteile Möglichkeiten zur Steigerung der Wirtschaftlichkeit von CT-Messungen durch gleichzeitige tomographische Erfassung mehrerer Bauteile im Messvolumen untersucht und die Messunsicherheit für die einzelnen Aufnahmeszenarien experimentell ermittelt.

Contribution

Gabriel Herl
Simon Rettenberger
Jochen Hiller

Fusion mehrerer Computertomographie-Aufnahmen zur Verbesserung der Bildqualität.

In: Forschungsbericht 2016/2017 der Technischen Hochschule Deggendorf. pg. 29-32

(2017)

Journal article

Thomas Fischer
Mario Salzinger
Daniel Heinz
Jochen Hiller

Quantitative Untersuchung zur Reduzierung der Messzeit in der dimensionellen Computertomographie.

In: Bavarian Journal of Applied Sciences vol. 3 pg. 282-296

(2017)

DOI: 10.25929/jy3v-pm72

show abstract

Einer der häufig genannten Nachteile für Computertomographie-(CT-)Anwender in der industriellen Praxis ist der Zeitfaktor. Für einen messtechnisch auswertbaren CT-Scan ist das System in den meisten Fällen mindestens 30 Minuten lang ausgelastet, je nach Prüfobjekt und Genauigkeitsanforderungen oft auch deutlich länger. Ziel dieser Untersuchung ist es, mit derzeitig möglichen Methoden herauszufinden, wie die Scanzeiten verringert werden können und wie sich diese Reduzierung auf die Qualität der Messung bezüglich Messgenauigkeit und Wiederholgenauigkeit auswirkt. Nach Auswahl und taktiler Referenzmessung eines Prüfkörpers werden mit dem 360° Stop&Go-Verfahren sowie mit zwei weiteren Scanstrategien, der 180° CT und der FlyBy-CT, Messdaten erzeugt. Es folgt ein Vergleich der Messergebnisse und der Messzeiten. Bei der 180°-Messung wird das Objekt intermittierend um die Hälfte rotiert, wohingegen beim FlyBy-Modus eine kontinuierliche Objektbewegung ohne Abbremsung erfolgt. Beide Messverfahren haben sich für diverse Anwendungsszenarien bewährt. Die größte Messzeitreduzierung ist beim Einsatz des FlyBy-Modus zu erwarten. Im Vergleich dazu bietet der 180°-Modus ebenfalls Vorteile, auch wenn die erwartete Scanzeit gegenüber dem FlyBy-Modus länger ist. Mit diesem lässt sich trotz der Möglichkeit zur Bildmittelung Scanzeit einsparen, gegenüber dem herkömmlichen 360°-Scanverfahren lässt sich aber zudem bei gleichbleibender Zeit eine erhöhte Rauschreduzierung erzielen. One of the biggest disadvantages operators complain about in the field of industrial computed tomography is the time factor. CT scans for measuring purposes will usually take at least 30 minutes, yet often noticeably longer, depending on the specimen and accuracy requirements. The purpose of this research is to determine how scan times can be reduced by applying the currently available methods and to assess in which way this reduction influences measurement quality with regards to measurement accuracy and repeatability. After choosing a test specimen and performing tactile measurements to determine the nominal values, measurement data is generated by using the 360° Stop&Go procedure, the 180° CT and the FlyBy-CT. Then the measurement results and durations are compared with each other. Measurements using the 180° procedure are performed by intermittently rotating the object by 180 degrees, whereas the FlyBy mode involves a continuous object movement without deceleration. Both CT modes are well proven in various applications. Out of all three methods, the FlyBy mode has the greatest potential for reducing overall scan times. In comparison, the 180° mode also has its advantages, although the expected scan times are longer compared to the FlyBy mode. This CT mode offers the opportunity to reduce scan times despite the option of image averaging. In addition, compared to the conventional 360° scan procedures, it is possible to achieve a higher level of noise reduction within a constant time.

Contribution

Peter Hornberger
Christian Aichinger
Jochen Hiller

Dimensionelles Messen mit Computertomographie.

In: Handbuch zur industriellen Bildverarbeitung. Qualitätssicherung in der Praxis. pg. 285-291

Eds.:
M. Sackewitz
Fraunhofer-Allianz Vision

Fraunhofer Verlag

(2017)

Journal article

Simon Rettenberger
F. Bittner
H.-J. Endres
Jochen Hiller

Blick in belastete Composite-Bauteile.

In: Konstruktion (Zeitschrift für Produktentwicklung und Ingenieur-Werkstoffe) pg. IW10-IW13

(2017)

Contribution

A. Stock
Gabriel Herl
T. Sauer
Jochen Hiller

Metal artifact reduction by fusion of CT scans from different positions using the unfiltered backprojection.

In: iCT 2018 8th Conference on Industrial Computed Tomography (iCT) 2018, 6-9 Feb, Wels, Austria.

(2018)

show abstract

Metal objects or metal parts in an object are still a major problem of X-ray computed tomography (CT) because of so called metal artifacts. We propose a new method – a multipositional data fusion – for automatically fusing multiple CT volumes from different positions to reduce these metal artifacts. After scanning a specimen several times at different positions and reconstruction of every scan (e.g. by the filtered backprojection), we also perform an unfiltered backprojection. Based on the assumption that metal artifacts occur the most wherever X-rays are attenuated a lot, the unfiltered backprojection is used to autonomously estimate the likelihood of metal artifacts in every voxel of every scan. The different volumes are registered and then fused by weighted sum preferring the voxels with low values in the unfiltered backprojection results. In our tests on real objects, our method fully automatically created optimized volumes with significantly less metal artifacts. The multipositional data fusion was compared to the commercially multi spectra fusion of Werth Messtechnik GmbH and outperformed it in one of the use cases.

Contribution

A. Stock
Gabriel Herl
T. Sauer
Jochen Hiller

Edge preserving compression of CT scans using wavelets.

In: SHM-NDT 2018 International Symposium on Structural Health Monitoring and Nondestructive Testing 4-5 Oct 2018, Saarbrücken – Germany.

(2018)

show abstract

This work addresses the subject of efficient storage of computed tomography (CT) data with an emphasis on the quality of surfaces. Industrial dimensional metrology often requires high measurement accuracy and we show that this is retained using wavelet-based compression methods. The applied techniques include a tensor product wavelet transform and soft wavelet shrinkage. In our tests on real objects, we compared dimensional CT measurements of compressed and uncompressed volumes. We were able to reduce the necessary storage space significantly with a minimal loss of accuracy. For a multi sphere phantom, we decreased the storage space to 4.7% (from 638 MB to 30 MB) with an average deviation below 1 µm from the original volume.

Lecture

Gabriel Herl
Simon Rettenberger
Jochen Hiller
T. Sauer

Metal artifact reduction by fusion of CT scans from different positions using the unfiltered backprojection.

In: 8th Conference on Industrial Computed Tomography (iCT 2018)

Wels, Österreich

06.-09.02.2018 (2018)

show abstract

Lecture

A. Stock
Gabriel Herl
T. Sauer
Jochen Hiller

Edge preserving compression of CT scans using wavelets.

In: International Symposium on Structural Health Monitoring and Nondestructive Testing

Saarbrücken

04.-05.10.2018 (2018)

show abstract

Contribution

Borges de Oliveira, F.
M. Bartscher
U. Neuschaefer-Rube
R. Tutsch
Jochen Hiller

Multi-Material Acceptance Testing for CT-Based Coordinate Measurement Systems.

In: Proceedings of the 12th International Conference on Measurement and Quality Control. Cyber Physical Issue : IMEKO TC 14 2019 (Lecture Notes in Mechanical Engineering) pg. 131 ff.

Eds.:
N. Durakbasa
V. Majstorović

Springer Verlag GmbH

(2019)

Contribution

Gabriel Herl
Jochen Hiller
T. Sauer

Artifact reduction in X-ray computed tomography by multipositional data fusion using local image quality measures.

In: iCT 2019 9th Conference on Industrial Computed Tomography (iCT) [13-15 February, 2019; Padua, Italy].

(2019)

show abstract

Metal artifacts are still a major problem in X-ray industrial computed tomography. In order to reduce metal artifacts and increase the image quality of X-ray CT-scans, we suggest using projection data from multiple scans with differently positioned object orientations. We present two different approaches for multipositional CT, which are especially effective for multimaterial objects with high absorbing metal parts. On one hand, we reconstruct the different scans separatly, estimate the local quality of the resulting volumes and then fuse these volumes to an optimized volume. On the other hand, we introduce smART (shrinking merged Algebraic Reconstruction Technique) and merge sinograms of different scans, estimate the reliability of each projection pixel and then reconstruct the merged sinogram with an adapted SART reconstruction method. We demonstrate our approaches on simulations and on measurement data and are able to show a significant reduction of image artifacts qualitatively and quantitatively with the help of dimensional measurement results.

Contribution

Peter Landstorfer
Gabriel Herl
Jochen Hiller

Investigation of Non-circular Scanning Trajectories in Robot-based Industrial X-ray Computed Tomography of Multi-material Objects.

In: 16th International Conference on Informatics in Control, Automation and Robotics (ICINCO) [29-31 July, 2019; Prague, Czech Republic].

Eds.:
IEEE Robotics & Automation Society

(2019)

Journal article

Gabriel Herl
Jochen Hiller
S. Kasperl
A. Maier

Reduktion von Metallartefakten durch multipositionale Datenfusion in der industriellen Röntgen-Computertomographie.

In: tm - Technisches Messen vol. 87

(2019)

DOI: 10.1515/teme-2019-0137

show abstract

Metallartefakte stellen eine große Herausforderung für das Messen mit Röntgen-Computertomographie dar. Dieser Beitrag stellt die Methode der multipositionalen Datenfusion zur Reduktion von Metallartefakten vor. Dazu werden mehrere Scans desselben Objekts bei unterschiedlicher Objekt-positionierung durchgeführt, aufeinander registriert und zur Fusion gemeinsam unter Betrachtung eines lokalen Gütemaßes rekonstruiert. In praxisnahen Experimenten wird der Mehrwert der Methode gezeigt. Insbesondere wird dargestellt, wie mit wenig Aufwand und ohne Vorwissen Kunststoffstrukturen trotz starker Metallartefakte sichtbar gemacht werden können, womit das Verfahren ein Alleinstellungsmerkmal gegenüber den existierenden Metallartefaktreduktionsverfahren aufweist.

Contribution

Peter Landstorfer
Jochen Hiller
Matthias Herbst

Investigation of positioning accuracy of industrial robots for robotic-based X-ray computed tomography.

In: iCT 2019 9th Conference on Industrial Computed Tomography (iCT) [13-15 February, 2019; Padua, Italy].

(2019)

show abstract

In this research work we investigated the accuracy of a standard industrial robot. We wanted to find out, how accurate an X-RayComputed Tomography (CT) scan can be performed when using such a robot as a manipulator. The accuracy was measuredusing a laser-interferometer. The measured deviations were used to run an X-Ray simulation via Fraunhofer EZRT’s ScorpiusX-Lab. Metrological analysis was performed as a measure for the quality of the simulated CT-scan. The metrological deviationsreflect the feasible accuracy of a CT-scan in a real CT-setup.

Journal article

Peter Hornberger
A. Sigl
Jochen Hiller
Simon Zabler

Kleiner als ein Mikrometer: Entwicklung einer kompakten, hochauflösenden 3D-Röntgen-CT für die Materialanalyse.

In: VDI-Z (Sonderteil Additive Fertigung) pg. 52 ff.

(2019)

Journal article

F. Heilmeier
R. Koos
M. Singer
C. Bauer
Peter Hornberger
Jochen Hiller
W. Volk

Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining.

In: Sensors vol. 20 pg. 6276

(2020)

DOI: 10.3390/s20216276

show abstract

Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development.

Journal article

Jochen Hiller

Computertomographie (CT) senkt Kosten bei der Retourenbearbeitung.

In: Sensorik-Magazin des Clusters Sensorik Strategische Partnerschaft Sensorik e.V. vol. 99 pg. 3-5

(2020)

Journal article

A. Stock
Gabriel Herl
T. Sauer
Jochen Hiller

Edge-preserving compression of CT scans using wavelets.

In: Insight - Non-Destructive Testing and Condition Monitoring (The British Institute of Non-Destructive Testing) vol. 62 pg. 345-351

(2020)

DOI: 10.1784/insi.2020.62.6.345

show abstract

This work addresses the subject of efficient storage of computed tomography (CT) data with an emphasis on the quality of surfaces. Industrial dimensional metrology often requires high measurement accuracy and it is shown that this is retained using wavelet-based compression methods. The applied techniques include a tensor product wavelet transform and soft wavelet shrinkage. In these tests, performed on real objects, dimensional CT measurements of compressed and uncompressed volumes were compared. The necessary storage space was reduced significantly with a negligible loss of accuracy. The storage space required for a multi-sphere phantom was decreased to 4.7% (from 638 MB to 30 MB), with an average deviation below 1 μm from the original volume.

Journal article

Jochen Hiller
Peter Landstorfer
Philipp Marx
Matthias Herbst

Evaluation of the impact of faulty scanning trajectories in robot-based x-ray computed tomography.

In: Measurement Science and Technology vol. 32 pg. 015401

(2020)

DOI: 10.1088/1361-6501/abaf2a

show abstract

X-ray computed tomography (CT) imaging for industrial applications is limited to certain physical conditions to be fulfilled. The size of the measuring object and the accumulated wall thickness are two fundamental conditions. An omission of these conditions by not capturing object attenuation information by the x-ray detector leads to missing data in the 3D reconstruction process and results as a consequence in image degradation and artifacts. Conventional industrial x-ray CT is based on cone-beam projections and circular or helical scanning trajectories using linear axis and a rotary (lift) table. For many inspection tasks on big-sized or unusually shaped objects the physical limits for obtaining a sufficient high image quality are reached very quickly when using conventional CT systems. Industrial six-axis robots offer much more flexibility with respect to the conditions mentioned earlier and can overcome the limitations of conventional scanners. In the present work we characterized an industrial six-axis robot in its working space following ISO 9283 in terms of pose accuracy and pose repeatability. These results are then used to simulate faulty scanning trajectories in terms of pose deviations where a single robot is used as an object manipulator to rotate virtual specimens on a circular trajectory resulting in different (faulty) reconstruction datasets. These datasets are evaluated visually and by using performance parameters and geometrical features in order to determine the reproduction fidelity (performance) of a one arm robot-based CT system depending on different pose errors. With the results obtained it was shown that a robot-based CT system of type B (in our classification scheme) using one robot as object manipulator should be able to reach a spatial resolution power in the range of the voxel size (in our case 200 µm) and smaller (neglecting effects from focal spot size, detector unsharpness from x-ray to light conversation and scatter radiation) if systematic pose errors are compensated using appropriate calibration methods.

Journal article

Simon Zabler
M. Maisl
Peter Hornberger
Jochen Hiller
C. Fella
R. Hanke

X-ray imaging and computed tomography for engineering applications. Röntgenbildgebung und Computertomografie für technische Anwendungen.

In: tm - Technisches Messen vol. 87 pg. 211-226

(2020)

DOI: 10.1515/teme-2019-0151

show abstract

After an incremental development which took place over four decades, X-ray imaging has become an important tool for non-destructive testing and evaluation. Computed Tomography (CT) in particular beholds the power of determining the location of flaws and inclusions (e. g. in castings and composites) in three-dimensional object coordinates. Therefore, and thanks to a speed-up of the measurement, CT is now routinely considered for in-line inspection of electronics, castings and composites. When precision and not speed is important, Micro-CT (μCT) can be employed for Dimensional Measurements (DM, e. g. quality assurance and shape verification), as well as for in situ testing, and for characterizing micro-structures in metals and composites. Using appropriate image processing and analysis μCT can determine the local fibre orientation in composites, the granular morphology of battery cathodes or the inter-connectivity of certain phases in casting alloys. Today, the large variety of X-ray instruments and methods poses an application problem which requires experience and a lot of knowledge for deciding which technique applies best to the task at hand. Application-specific guidelines exist for X-ray radiography testing (RT) only, whereas standardization has been applied to CT, unfortunately leaving out high resolution subμ CT, and nano-CT. For the latter exist an equally high number of NDT applications, however these instruments still necessitate a profound expertise. The task is to identify key industrial applications and push CT from system standardization to application specific automation.

Journal article

F. Heilmeier
R. Koos
Peter Hornberger
Jochen Hiller
K. Weraneck
M. Jakobi
A. Koch
W. Volk

Calibration of cast-in Fibre-Bragg-Gratings for internal strain measurements in cast aluminium by using neutron diffraction.

In: Measurement vol. 163 pg. 107939

(2020)

DOI: 10.1016/j.measurement.2020.107939

show abstract

Fibre Bragg gratings (FBGs) are utilized to function as internal strain sensors during casting, solidification and cooling of two hypoeutectic Al alloys and technically pure Al. In situ neutron diffraction experiments were conducted simultaneously onsite the STRESS-SPEC instrument at the Research-Neutron Source (MLZ) in Garching. The experimental data correlated with structural finite element simulation and X-ray micro tomography (CT) elucidates the mechanisms of this measurement system. The presented work offers a new practical approach to measure in-situ strains during casting of Al alloys by using FBG-based sensors. The FBG strain results correlate with the Al(311) peak obtained by neutron diffraction which is furthermore used for calibration. The examination of interactions between fibres and surrounding cast Al by finite element simulation and CT of the cast specimens enables the application of the sensors for unequivocal strain measurements in castings as well as the characterization of alloys during solidification.

Journal article

Gabriel Herl
Jochen Hiller
A. Maier

Scanning trajectory optimisation using a quantitative Tuybased local quality estimation for robot-based X-ray computed tomography.

In: Nondestructive Testing and Evaluation vol. 35 pg. 287-303

(2021)

DOI: 10.1080/10589759.2020.1774579

show abstract

Robotic CT systems allow complex scanning trajectories. This work presents a workflow to automatically calculate optimised scanning trajectories for robotic CT systems. In particular, as a local quality estimation, this work introduces a quantitative measure to quantify local reconstruction quality based on the Tuy conditions. The proposed method is tested in two summation experiments using an STL model of a motorcycle. In both experiments, a trajectory is calculated using a quantitative Tuy-based local quality estimation and the reconstruction result is then compared to reconstructions using conventional scanning trajectories. The comparison results indicate that the proposed approach automatically finds trajectories that enable 3D reconstructions with high image quality using much less projection data, which allows a significant reduction of scanning time.

Journal article

Julian Wittmann
Gabriel Herl
Jochen Hiller

Generation of a 3D model of the inside volume of shoes for e-commerce applications using industrial x-ray computed tomography.

In: Engineering Research Express vol. 3 pg. 045058

(2021)

DOI: 10.1088/2631-8695/ac43c8

show abstract

In 2018, 47% of global internet users had purchased footwear products through the internet, making it the second most popular online shopping category worldwide right after clothing with 57%. In the same year, on average, about every sixth parcel delivered in Germany (16.3%) was returned. With the effort and costs that are associated with the return of shoes, the objective of reducing the number of returns for shoes promises an enormous economic potential and helps to reduce the CO2 emissions due to a lower traffic volume. This paper presents a workflow for determining the inside volume surface of shoes using industrial x-ray computed tomography (CT). The fundamental idea is based on the Region Growing (RG) method for the segmentation of the shoe's inner volume. Experiments are performed to illustrate the correlation of image quality and segmentation result. After obtaining the 3D surface model of an individual foot, the inner volume surface data of a scanned shoe can then be registered and evaluated in order to provide a reliable feedback for the customer regarding the accuracy of fit of a shoe and the individual foot on the basis of an overall 'metric of comfort' before buying online. This step is not part of the work at hand. Conclusions are drawn and suggestions for improving the robustness and the flexibility of the workflow are given, so it can be adapted to various shoe types and implemented in a fully automated measurement process in the future.

Journal article

Gabriel Herl
Jochen Hiller
M. Thies
J.-N. Zaech
M. Unberath
A. Maier

Task-Specific Trajectory Optimisation for Twin-Robotic X-Ray Tomography.

In: IEEE Transactions on Computational Imaging vol. 7 pg. 894-907

(2021)

DOI: 10.1109/TCI.2021.3102824

show abstract

With the advent of robotic C-arm computed tomography (CT) systems in medicine and twin-robotic CT systems in industry, new possibilities for the realisation of complex trajectories for CT scans are emerging. These trajectories will increase the range of CT applications, enable optimisation of image quality for many applications and open up new possibilities to reduce scan time and radiation dose. In this work, trajectory optimisation methods for optimising both, task-based data quality and data completeness, are presented by combining two different metrics. On the one hand, task-based data quality is optimised with a proven observer model. On the other hand, a Tuy-based metric is utilised to optimise data completeness. Both metrics capture mutually exclusive properties of the trajectory which are necessary, but alone are not sufficient for trajectory optimisation. Hence, existing task-driven trajectory optimisation approaches require additional input to decide on an overall optimal trajectory, e.g. in most cases constraints on the trajectory. Advantages and disadvantages of the presented methods are investigated. It is shown that by combining both metrics, trajectory optimisation for arbitrary geometries becomes possible. In application examples it is shown that this can be used for trajectory optimisation of challenging scanning tasks involving metal parts as well as for trajectory optimisation to reduce the number of projections while ensuring task-dependently high image quality. In total, the results of this work enable new applications for X-ray CT, especially for twin-robotic CT systems which are able to benefit from a high number of degrees of freedom.

labs

Production metrology

Campus Deggendorf

Sustainable Production & Energy Technologies

X-ray computed tomography (CT)

Campus Deggendorf

Quality of Life & Healthcare