MEASUREMENT APPARATUS AND METHOD
First Claim
1. A computer implemented method of determining the surface shape of an aspheric object using a metrological apparatus, the method comprising:
- positioning the object on a support surface of a turntable of the metrological apparatus so that an axis of the object is tilted with respect to the axis of rotation of the turntable by a tilt angle, α
;
using a measurement probe to make a first measurement of the object to provide first measurement data;
rotating the turntable;
after rotation of the turntable, using a measurement probe to make a second measurement of the object, diametrically opposite the first measurement, to provide second measurement data,estimating a first angle, γ
1, based on fitting the first measurement data using a surface model comprising;
a dependency on the axis tilt angle, α
, anda dependency on the radius, R, of the base of the object;
estimating a second angle, γ
2, based on fitting the second measurement data to the surface model; and
determining the axis tilt angle based on the first angle and the second angle.
1 Assignment
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Accused Products
Abstract
A computer implemented method of determining the surface shape of an aspheric object using a metrological apparatus includes positioning the object on a support surface of a turntable so that an axis of the object is tilted with respect to the axis of rotation of the turntable; using a measurement probe to make a first measurement of the object; rotating the turntable; after rotation of the turntable, using a measurement probe to make a second measurement of the object, diametrically opposite the first measurement, estimating a first angle based on fitting the first measurement data using a surface model including: a dependency on the axis tilt angle and a dependency on the radius of the base of the object; estimating a second angle based on fitting the second measurement data to the surface model; and determining the tilt angle based on the first angle and the second angle.
16 Citations
33 Claims
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1. A computer implemented method of determining the surface shape of an aspheric object using a metrological apparatus, the method comprising:
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positioning the object on a support surface of a turntable of the metrological apparatus so that an axis of the object is tilted with respect to the axis of rotation of the turntable by a tilt angle, α
;using a measurement probe to make a first measurement of the object to provide first measurement data;
rotating the turntable;after rotation of the turntable, using a measurement probe to make a second measurement of the object, diametrically opposite the first measurement, to provide second measurement data, estimating a first angle, γ
1, based on fitting the first measurement data using a surface model comprising;a dependency on the axis tilt angle, α
, anda dependency on the radius, R, of the base of the object; estimating a second angle, γ
2, based on fitting the second measurement data to the surface model; anddetermining the axis tilt angle based on the first angle and the second angle. - View Dependent Claims (2, 3, 4, 5, 6, 8, 10, 13, 14, 17, 19, 21, 22)
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7. (canceled)
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9. (canceled)
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11. (canceled)
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12. (canceled)
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15. (canceled)
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16. (canceled)
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18. (canceled)
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20. (canceled)
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23. (canceled)
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24. A metrological apparatus for determining the surface shape of an aspheric object, the apparatus comprising;
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a turntable having a support surface for supporting an object to be measured, wherein the turntable is operable to rotate about a rotation axis; a measurement probe operable to traverse a measurement path across the surface of the object to be measured to provide measurement data; a controller operable to control the measurement probe to traverse a first measurement path to provide first measurement data and to rotate the turntable and, after rotation of the turntable, to control the measurement probe to traverse a second measurement path to provide second measurement data, wherein the first measurement path and the second measurement path are diametrically opposite each other on the surface of the object, and a data processor configured to; estimate a first angle, γ
1, based on fitting the first measurement data using a surface model comprising;
a dependency on the axis tilt angle, α
, and a dependency on the radius, R, of the base of the object;estimate a second angle, γ
2, based on fitting the second measurement data to the surface model; and
todetermine the axis tilt angle based on at least one of the first angle and the second angle. - View Dependent Claims (25)
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26. A data processor for a metrological instrument, wherein the processor is configured to:
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receive first measurement data and second measurement data, wherein the first and second measurement data each provide a part of a measurement of the profile of the surface of an aspheric object to be measured; estimate a first angle, γ
1, based on fitting the first measurement data using a surface model comprising;
a dependency on the axis tilt angle, α
, and a dependency on the radius, R, of the base of the object;estimate a second angle, γ
2, based on fitting the second measurement data to the surface model; and
todetermine the axis tilt angle based on the tilt angle of the probe and at least one of the first angle and the second angle. - View Dependent Claims (27, 28)
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29. (canceled)
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30. A non-transitory computer readable medium storing program instructions operable to program a processor to perform a method comprising the steps of:
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positioning the object on a support surface of a turntable of the metrological apparatus so that an axis of the object is tilted with respect to the axis of rotation of the turntable by a tilt angle, α
;using a measurement probe to make a first measurement of the object to provide first measurement data;
rotating the turntable;after rotation of the turntable, using a measurement probe to make a second measurement of the object, diametrically opposite the first measurement, to provide second measurement data, estimating a first angle, γ
1, based on fitting the first measurement data using a surface model comprising;a dependency on the axis tilt angle, α
, anda dependency on the radius, R, of the base of the object; estimating a second angle, γ
2, based on fitting the second measurement data to the surface model; anddetermining the axis tilt angle based on the first angle and the second angle.
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31. (canceled)
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32. (canceled)
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33. (canceled)
Specification