---
res:
  bibo_abstract:
  - "<jats:title>Abstract</jats:title>\r\n               <jats:p>Industrial x-ray
    computed tomography (CT) systems with high geometric flexibility are increasingly
    utilized for large-scale measurement objects or challenging measurement tasks.
    To maintain high accuracy when deviating from the established circular scan trajectory,
    trajectory calibration methods using multi-sphere reference objects with known
    marker positions are commonly employed. These multi-sphere objects can either
    be scanned together with the measurement object (online trajectory calibration)
    or in a separate scan (offline trajectory calibration). While offline calibration
    increases machine time, it generally results in higher scan quality. However,
    a sufficient pose repeatability is necessary to ensure comparable or even superior
    accuracy to online calibration. In this contribution, we present a straightforward
    procedure to compare both types of trajectory calibration in a way that the differences
    of the results can directly be traced back to the influence of the pose repeatability.
    The multi-sphere reference object is not only used for trajectory calibration,
    but simultaneously as a measurement object for repeated measurements. The methodology
    is tested on both a twin robotic CT system and a conventional CT system that is
    additionally equipped with a hexapod manipulator for adaptive object tilting.
    Results showed, independent from the type of trajectory calibration, systematic
    measurement errors in the order of 10<jats:sup>−5</jats:sup>–10<jats:sup>−4</jats:sup>
    of measured sphere distances and sphericity values below 50 <jats:inline-formula>\r\n
    \                    <jats:tex-math/>\r\n                     <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"
    overflow=\"scroll\">\r\n                        <mml:mrow>\r\n                           <mml:mrow>\r\n
    \                             <mml:mtext>μ</mml:mtext>\r\n                           </mml:mrow>\r\n
    \                          <mml:mrow>\r\n                              <mml:mi
    mathvariant=\"normal\">m</mml:mi>\r\n                           </mml:mrow>\r\n
    \                       </mml:mrow>\r\n                     </mml:math>\r\n                  </jats:inline-formula>.
    For sphere distances, random errors were increased by a factor of 5 due to the
    offline trajectory calibration, but were still low (<jats:inline-formula>\r\n
    \                    <jats:tex-math/>\r\n                     <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\"
    overflow=\"scroll\">\r\n                        <mml:mrow>\r\n                           <mml:mrow>\r\n
    \                             <mml:mo>&lt;</mml:mo>\r\n                           </mml:mrow>\r\n
    \                          <mml:mrow>\r\n                              <mml:mn>1</mml:mn>\r\n
    \                          </mml:mrow>\r\n                           <mml:mstyle
    scriptlevel=\"0\"/>\r\n                           <mml:mrow>\r\n                              <mml:mtext>μ</mml:mtext>\r\n
    \                          </mml:mrow>\r\n                           <mml:mrow>\r\n
    \                             <mml:mi mathvariant=\"normal\">m</mml:mi>\r\n                           </mml:mrow>\r\n
    \                       </mml:mrow>\r\n                     </mml:math>\r\n                  </jats:inline-formula>)
    in comparison to systematic errors and the spread of different measurement features.
    Overall, both investigated systems demonstrated sufficient positioning repeatability
    for offline trajectory calibration. The method is in general also applicable to
    any other types of manipulator systems used for CT devices. It provides a workflow
    for the decision which type of trajectory calibration is preferable for a given
    CT system.</jats:p>@eng"
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: Lorenz
      foaf_name: Butzhammer, Lorenz
      foaf_surname: Butzhammer
  - foaf_Person:
      foaf_givenName: Niklas
      foaf_name: Handke, Niklas
      foaf_surname: Handke
  - foaf_Person:
      foaf_givenName: Simon
      foaf_name: Wittl, Simon
      foaf_surname: Wittl
  - foaf_Person:
      foaf_givenName: Gabriel
      foaf_name: Herl, Gabriel
      foaf_surname: Herl
  - foaf_Person:
      foaf_givenName: Tino
      foaf_name: Hausotte, Tino
      foaf_surname: Hausotte
  bibo_doi: 10.1088/1361-6501/ada05a
  bibo_issue: '2'
  bibo_volume: 36
  dct_date: 2025^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/0957-0233
  - http://id.crossref.org/issn/1361-6501
  dct_language: eng
  dct_publisher: IOP Publishing@
  dct_title: Direct assessment of the influence of pose repeatability on the accuracy
    of dimensional measurements for computed tomography systems with high degrees
    of freedom@
...