Back to results
US 10,478,147 B2Granted
Calibration apparatus and method for computed tomography
AssigneeNikon Metrology NV
InventorsSam Hawker, Gemma Fardell, Patrick Blankaert
Life of this patent
Estimating the term…
Abstract
A calibration object is imaged in a radiographic system such as a CT system. The images are processed to calibrate the system, without prior measurement of the calibration object. Initial estimates are refined to improve accuracy.
Claims28
A method of calibrating a radiographic system comprising a source and a detector, the method comprising:
- providing a calibration object comprising a plurality of markers,
- rotating the calibration object relative to the source and/or detector,
- acquiring a plurality of radiographic images of the calibration object,
- identifying the plurality of markers in the plurality of images,
- deriving an elliptical path for each of the plurality of markers using said plurality of images by
- assigning a nominal value representing a distance between the source and an axis of rotation of each said marker, and
- determining complete geometrical parameters of the system apart from said nominal distance value using the radiographic images and said nominal distance value,
- where said complete geometrical parameters are seven parameters including two parameters specifying a principal point, one parameter specifying a focal length, two parameters specifying the orientation of the axis of rotation and two parameters specifying the position of the axis of rotation, and using said elliptical paths to determine geometrical parameters of the system.
5 more elements
A method of calibrating a radiographic system comprising a source and a detector, the method comprising:
- providing an object equipped with a marker,
- rotating the object relative to the source and/or detector,
- acquiring a plurality of radiographic images of the object,
- identifying a position of an image of the marker in each of a plurality of images, deriving a path for the marker using said plurality of images by
- assigning a nominal value representing a distance between the source and an axis of rotation of said marker, and
- determining complete geometrical parameters of the system apart from said nominal distance value using the radiographic images and said nominal distance value,
- where said complete geometrical parameters are seven parameters including two parameters specifying a principal point, one parameter specifying a focal length, two parameters specifying the orientation of the axis of rotation and two parameters specifying the position of the axis of rotation, and
- using said path to determine geometrical parameters of the system.
5 more elements
A radiographic system having a source and a detector, the radiographic system configured to:
- rotate a calibration object comprising a plurality of markers relative to the source and/or detector,
- acquire a plurality of radiographic images of the calibration object,
- identify the plurality of markers in the plurality of images,
- derive an elliptical path for each of the plurality of markers using said plurality of images by
- assigning a nominal value representing a distance between the source and an axis of rotation of each said marker, and
- determining complete geometrical parameters of the system apart from said nominal distance value using the radiographic images and said nominal distance value,
- where said complete geometrical parameters are seven parameters including two parameters specifying a principal point, one parameter specifying a focal length, two parameters specifying the orientation of the axis of rotation and two parameters specifying the position of the axis of rotation, and
- use said elliptical paths to determine geometrical parameters of the system.
5 more elements
Dependencies are inferred from the claim text.