Apparatus and method for calibrating a scanning head
First Claim
1. A method of calibrating a measurement scale in a scanning head using a reference artefact, the method comprising the steps of;
- (i) rotating a surface sensing device mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a plurality of different angular orientations relative to the reference artefact, the scanning head comprising at least one scale that provides a measure of a rotational position of the scanning head about the at least one axis;
(ii) measuring, with the surface sensing device, at least one property of the reference artefact at each of the different angular orientations of step (i); and
(iii) creating an error map or function relating measurements of the at least one measurement scale to angular orientations of the scanning head using the properties of the reference artefact measured in step (ii).
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Accused Products
Abstract
A method of calibrating a measurement scale in a motorized scanning head using a reference artefact is described. The method comprises the step of rotating a surface sensing device, such as a scanning probe, mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a plurality of different angular orientations relative to the reference artefact. A step is then performed of measuring, with the surface sensing device, at least one property of the reference artefact at each of the different angular orientations. An error map or function is then created for at least one measurement scale of the scanning head using the properties of the reference artefact measured and optionally known or calibrated properties of that reference artefact. The method may comprise use of co-ordinate positioning apparatus, such as a co-ordinate measuring machine, to move the scanning head. The reference artefact may comprise a single feature or an array of features.
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Citations
24 Claims
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1. A method of calibrating a measurement scale in a scanning head using a reference artefact, the method comprising the steps of;
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(i) rotating a surface sensing device mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a plurality of different angular orientations relative to the reference artefact, the scanning head comprising at least one scale that provides a measure of a rotational position of the scanning head about the at least one axis; (ii) measuring, with the surface sensing device, at least one property of the reference artefact at each of the different angular orientations of step (i); and (iii) creating an error map or function relating measurements of the at least one measurement scale to angular orientations of the scanning head using the properties of the reference artefact measured in step (ii). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of calibrating a scanning head using a calibration artefact comprising a plurality of calibrated features, the method comprising the steps of
(i) rotating a surface sensing device mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a surface sensing relationship with a selected calibrated feature of the plurality of calibrated features, the scanning head comprising at least one scale that provides a measure of a rotational position of the scanning head about the at least one axis; -
(ii) measuring, with the surface sensing device, at least one property of the selected calibrated feature of the calibration artefact; (iii) repeating steps (i) and (ii) with at least one further selected calibrated feature; and (iv) creating an error map or function relating measurements from the for at least one measurement scale to angular orientations of the scanning head from the difference between the properties of the calibration artefact measured in step (ii) and the calibrated properties of the calibration artefact. - View Dependent Claims (18)
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19. A method of calibrating a scanning head using a reference artefact comprising a first feature, the method comprising the steps of;
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(i) placing a surface sensing device mounted on the scanning head in a first angular orientation relative to the first feature, (ii) measuring, with the surface sensing device, a property of the first feature of the reference artefact; (iii) using the scanning head to rotate the surface sensing device about at least one axis of the scanning head such that the surface sensing device adopts a different angular orientation relative to the first feature of the reference artefact, the scanning head comprising at least one scale that provides a measure of a rotational position of the scanning head about the at least one axis; (iv) remeasuring, with the surface sensing device, the property of the first feature of the reference artefact; and (v) creating an error map or function relating measurements from the at least one measurement scale to angular orientations of the scanning head from the measured properties of the first feature of the reference artefact that are acquired during steps (ii) and (iv). - View Dependent Claims (20)
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21. A method for calibrating a scanning head, comprising the steps of;
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(i) using a surface sensing device mounted on the scanning head to measure a property of a reference artefact; (ii) repeating the measurement of step (i) with one or more rotational axes of the scanning head rotated through a different angular range, the scanning head comprising one or more measurement scales that provides a measure of a rotational position of the scanning head about the one or more rotational axes; and (iii) creating an error map or function relating measurements from the one or more measurement scales to angular orientations of the scanning head from the measured properties of the reference artefact acquired in step (i).
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22. A method of calibrating a measurement scale in a scanning head using a calibrated artefact, the method comprising the steps of;
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(i) rotating a surface sensing device mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a plurality of different angular orientations relative to the calibrated artefact, the scanning head comprising at least one scale that provides a measure of a rotational position of the scanning head about the at least one axis; (ii) measuring, with the surface sensing device, a plurality of points on the calibrated artefact at each of the different angular orientations of step (i); (iii) rotating the calibrated artefact to different positions and repeating steps (i) and (ii); and (iv) creating an error map or function relating measurements from the at least one measurement scale of the scanning head (16) to an angular orientation of the scanning head from the plurality of points measured in step (ii) for each position of the calibrated artefact.
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23. A method of calibrating a measurement scale in a scanning head using a calibrated artefact, the method comprising the steps of;
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(i) rotating a surface sensing device mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a plurality of different angular orientations relative to the calibrated artefact, the scanning head comprising at least one scale that provides a measure of an angular orientation of the scanning head about the at least one axis; (ii) measuring, with the surface sensing device, a plurality of points on the calibrated artefact at each of the different angular orientations of step (i); and (iii) creating an error map or function correcting the measure of angular orientation measured from the at least one measurement scale from a comparison of the plurality of points measured in step (ii) and at least one calibrated dimension of the calibrated artefact.
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24. A method of calibrating a measurement scale in a scanning head using a calibrated artefact, the method comprising the steps of;
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(i) rotating a surface sensing device mounted on the scanning head about at least one axis of the scanning head to move the surface sensing device into a plurality of different angular orientations relative to the calibrated artefact, the scanning head comprising at least one scale that provides a measure of an angular orientation of the scanning head about the at least one axis; (ii) measuring, with the surface sensing device, a plurality of points on the calibrated artefact at each of the different angular orientations of step (i); (iii) rotating the calibrated artefact to different positions and repeating steps (i) and (ii); and (iv) creating an error map or function correcting the measure of angular orientation measured from the at least one measurement scale from the plurality of points measured in step (ii) for each position of the calibrated artefact.
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Specification