Movement control by a metrological instrument

• US 6,594,532 B2
• Filed: 11/26/2001
• Issued: 07/15/2003
• Est. Priority Date: 05/28/1999
• Status: Active Grant

• Current Assignee: Taylor Hobson Limited (Ametek Incorporated)
• Original Assignee: Taylor Hobson Limited (Ametek Incorporated)
• Inventors: Mills, Michael
• Primary Examiner(s): Follansbee, John
• Assistant Examiner(s): BARNES-BULLOCK, CRYSTAL JOY
• Application Number:
  US09/991,919
• Publication Number:
  US 20020059041A1
• Time in Patent Office: 596 Days
• Field of Search: 700/56, 700/195, 702/127, 702/95, 702/167, 702/168, 738/658, 738/665, 335/49, 335/72, 335/59, 335/55, 335/56
• US Class Current: 700/56
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 7/008 using coordinate measuring machines
• CPC Class Codes: G01B 7/28 for measuring contours or curvatures
• CPC Class Codes: G01B 7/34 for measuring roughness or irregularity of surfaces

Abstract

A measurement probe is carried by a carriage movable in a first direction to cause the measurement probe to traverse a measurement path across a surface of an object received by a support surface to provide measurement data representing variations in a second direction different from the first direction of surface features along the measurement path. The support surface is movable in a third direction different from the first and second directions. Measurement of a surface area is effected by controlling the carriage to cause the measurement probe to traverse a plurality of measurement paths across an area of the surface of an object mounted on the support surface and by controlling the support surface to move in the third direction after each measurement path traverse. Measurement data thus obtained for a reference sphere of previously known radius is used to determine the relative orientation of the first and third directions. Measurement data provided by the measurement probe may then be corrected in accordance with any error in the determined relative orientations of the first and third directions.

Claims

1. An instrument, comprising:

means for receiving a measurement probe;

first moving means for effecting relative movement in a first direction between a support for receiving a reference object of known form and the measurement probe receiving means so as to cause the measurement probe to traverse a measurement path across a surface of the reference object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features of the reference object surface along the measurement path;

second moving means for effecting relative movement between the support and the measurement probe receiving means in a third direction different from the first and second directions;

control means for causing the first moving means to effect said relative movement in said first direction a plurality of times and for causing the second moving means to effect said relative movement in said third direction between movements in said first direction for causing the measurement probe to traverse a plurality of said measurement paths across an area of the surface of the reference object mounted on the support and to provide measurement data representing variations in the surface along each measurement path; and

processor means comprising determining means for using measurement data provided by the measurement probe and representing variations across the area of the surface of the reference object to determine the relative orientations of the first and third directions.

2. An instrument according to claim 1, wherein the receiving means is arranged to receive a measurement probe or a machine tool component such that the instrument is operable as a metrological instrument when the measurement probe is received by the receiving means and is operable as a machine tool when the machine tool component is received by the receiving means.

3. An instrument according to claim 2, further comprising a machine tool component comprising a cutting or polishing device.

4. An instrument according to claim 1, further comprising means for correcting measurement data provided by the measurement probe in accordance with any error in the determined relative orientations of the first and third directions.

5. An instrument according to claim 4, wherein the determining means is arranged to use the measurement data provided by the measurement probe and representing variations across the surface area of the reference object of known form to determine the relative orientations of the first and third directions and the relative orientations of the second and third directions, and wherein the correcting means is operable to correct measurement data provided by the measurement probe in accordance with any error in the relative orientations of the first and third directions and any error in the relative orientations of the second and third directions.

6. An instrument according to claim 4, further comprising means for correcting measurement data in accordance with the determined value and means for storing calibration data corresponding to corrections made by the correcting means.

7. An instrument according to claim 1, wherein the reference object is such that each measurement path forms an arc and the determining means comprises first determining means for determining a central focus or axis of each arc and second determining means for using the determined central foci or axes to determine the relative orientations of the first and third directions.

8. An instrument according to claim 7, wherein the second determining means comprises means for fitting a line through the centers of the arcs to determine the orientation of the third direction to the first direction.

9. An instrument according to claim 7, wherein the second determining means comprises means for fitting a line through the centers of the arcs in the plane containing the first and third directions to determine the orientation of the third direction to the first direction.

10. An instrument according to claim 1, wherein the determining means is arranged to use the measurement data provided by the measurement probe and representing variations across the surface area of the reference object of known form to determine the relative orientations of the first and third directions and the relative orientations of the second and third directions.

11. An instrument according to claim 10, wherein the reference object is such that each measurement path forms an arc and the determining means comprises first determining means for determining a central focus or axis of each arc and second determining means for using the determined central foci or axes to determine the relative orientations of the first and third directions and of the second and third directions.

12. An instrument according to claim 11, wherein the second determining means comprises means for fitting a line through the centres of the arcs to determine the relative orientations of the first and third directions.

13. An instrument according to claim 11 wherein the second determining means comprises means for fitting a first line through the centers of the arcs in the plane containing the first and third directions to determine the orientation of the third direction to the first direction and for fitting a second line through the centers of the arcs in the plane containing the second and third directions to determine the orientation of the third direction to the second direction.

14. An instrument according to claim 1, further comprising means for pivotally supporting the measurement probe so that the measurement probe pivots about a pivot axis in response to surface variations.

15. An instrument according to claim 14, wherein the reference object is such that each measurement path forms an arc and the determining means comprises first determining means for determining a central focus or axis of each arc and second determining means for using the determined central foci or axes to determine the relative orientations of the first and third directions, and further comprising means for correcting start and end points of each measurement path for arcuate errors in the movement of the measurement probe.

16. An instrument according to claim 1, further comprising means for correcting start and end points of each measurement path for errors in the movement of the measurement probe.

17. An instrument according to claim 1, wherein the processor means further comprises means for fitting a three-dimensional form to the reference object measurement data, means for comparing a characteristic of the fitted three-dimensional form to the corresponding characteristic of the reference object, and means for adjusting a value representing the distance of relative movement in the third direction between measurement paths to determine the value for that distance for which the characteristic of the fitted form most closely corresponds to the characteristic of reference object.

18. An instrument according to claim 17, further comprising means for correcting measurement data in accordance with the determined value.

19. An instrument according to claim 1, further comprising output means for removing surface form data from measurement data provided by the measurement probe.

25. An instrument according to claim 1 or 20, wherein the first, second and third directions are mutually orthogonal.

71. A storage medium carrying processor instructions for configuring computing apparatus to provide the processor means set out in claim 1, 20, 26, 27, 28, 66, 67, or 68.

72. A signal carrying processor instructions for configuring computing apparatus to provide the processor means set out in claim 1, 20, 26, 27, 28, 66, 67, or 68.

20. A metrological instrument for determining surface features comprising at least one of surface form and texture, comprising:

first moving means for effecting relative movement in a first direction between a support for receiving a reference object of known form and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of the reference object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features of the reference object along the measurement path;

second moving means for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions;

control means for causing the first moving means to effect said relative movement in said first direction a plurality of times and for causing the second moving means to effect said relative movement in said third direction between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of the reference object mounted on the support and to provide measurement data representing variations in the surface along each measurement path; and

processor means for processing the measurement data provided by the measurement probe to produce data representing features of at least one of surface form and texture of the surface, the processor means further comprising determining means for using measurement data provided by the measurement probe and representing variations across a surface area of a reference object of known form to determine the relative orientations of the first and third directions.

21. An instrument according to claim 20, further comprising means for outputting measurement data to a user.

22. An instrument according to claim 21, wherein the output means is arranged to provide a topographical or perspective representation of the measured surface area.

23. An instrument according to claim 21, further comprising means for correcting measurement data in accordance with the determined value and means for removing surface form data from measurement data provided by the measurement probe and wherein the processor means is arranged to output measurement data to the output means after correction and surface form removal.

24. An instrument according to claim 21, wherein the output means comprises a display.

26. A metrological instrument for determining surface features comprising at least one of surface form and texture, comprising:

first moving means for effecting relative movement in a first direction between a support for receiving an object and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path;

second moving means for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions;

control means for causing the first moving means to effect said relative movement in said first direction a plurality of times and for causing the second moving means to effect said relative movement in said third direction after each movement in said first direction to cause the measurement probe to traverse a plurality of measurement paths across an area of the surface of an object mounted on the support and to provide measurement data representing variations in the surface along each measurement path; and

processor means for processing the measurement data provided by the measurement probe to produce data representing features of at least one of surface form and texture of the surface;

wherein the processor means further comprises determining means for using measurement data provided by the measurement probe and representing variations across a surface area of a reference object of known form to determine any difference between a measured value of a characteristic representing the form of the reference object and the actual value of that characteristic, means for adjusting a value representing the distance moved in the third direction between measurement paths to determine the distance value for which the measured value of the characteristic most closely matches the actual value and means for using the determined distance to correct or adjust measurement data.

27. Control apparatus for controlling an instrument, comprising:

means for causing first moving means to effect relative movement a plurality of times in a first direction between a support for receiving a reference object of known form and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of the reference object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path;

means for causing second moving means to effect relative movement between the support and the measurement probe in a third direction different from the first and second directions between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of the reference object and to provide measurement data representing variations in the surface along each measurement path; and

processor means comprising determining means for using measurement data provided by the measurement probe and representing variations across the surface area of the reference object to determine the relative orientations of the first and third directions.

29. Apparatus according to claim 27 or 28, further comprising means for correcting measurement data provided by the measurement probe in accordance with any error in the relative orientations of the first and third directions.

30. Apparatus according to claim 27 or 28, wherein the reference object is such that each measurement path forms an arc and the determining means comprises first determining means for determining a central focus or axis of each arc and second determining means for using the determined central foci or axes to determine the relative orientations of the first and third directions.

31. Apparatus according to claim 30, wherein the second determining means comprises means for fitting a line through the centers of the arcs to determine the orientation of the third direction to the first direction.

32. Apparatus according to claim 30, wherein the second determining means comprises means for fitting a line through the centers of the arcs in the plane containing the first and third directions to determine the orientation of the third direction to the first direction.

33. Apparatus according to claim 27 or 28, wherein the determining means is arranged to use the measurement data provided by the measurement probe and representing variations across the surface area of the reference object of known form to determine the relative orientations of the first and third directions and the relative orientations of the second and third directions.

34. Apparatus according to claim 33, further comprising means for correcting measurement data provided by the measurement probe in accordance with any error in the relative orientations of the first and third directions, wherein the correcting means is operable to correct measurement data provided by the measurement probe in accordance with any error in the relative orientations of the first and third directions and any error in the relative orientations of the second and third directions.

35. Apparatus according to claim 33, wherein the reference object is such that each measurement path forms an arc and the determining means comprises first determining means for determining a central focus or axis of each arc and second determining means for using the determined central foci or axes to determine the relative orientations of the first and third directions and the second and third directions.

36. Apparatus according to claim 35, wherein the second determining means comprises means for fitting a line through the centers of the arcs to determine the orientation of the first and third directions and the second and third directions.

37. Apparatus according to claim 35, wherein the second determining means comprises means for fitting a first line through the centers of the arcs in the plane containing the first and third directions to determine the orientation of the third direction to the first direction and for fitting a second line through the centers of the arcs in the plane containing the second and third directions to determine the orientation of the third direction to the second direction.

38. Apparatus according to claim 27 or 28, further comprising means for correcting start and end points of each measurement path for errors in the movement of the measurement probe.

39. Apparatus according to claim 27 or 28, further comprising means for correcting start and end points of each measurement path for arcuate errors in the movement of the measurement probe.

40. Apparatus according to claim 27 or 28, wherein the processor means further comprises means for fitting a three-dimensional form to the reference object measurement data, means for comparing a characteristic of the fitted three-dimensional form to the corresponding characteristic of the reference object and means for adjusting a value representing the distance of relative movement in the third direction between measurement paths to determine the value for that distance for which the characteristic of the fitted form most closely corresponds to the characteristic of reference object and means for correcting measurement data in accordance with the determined value.

41. An instrument according to claim 27 or 28, further comprising means for removing surface form data from measurement data provided by the measurement probe.

42. Apparatus according to claim 27 or 28, further comprising output means for providing a topographical or perspective representation of the measured surface area.

28. Control apparatus for a metrological instrument for determining surface features comprising at least one of surface form and texture, comprising:

means for causing first moving means to effect relative movement a plurality of times in a first direction between a support for receiving an object and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path;

means for causing second moving means to effect relative movement between the support and the measurement probe in a third direction different from the first and second directions between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of an object mounted on the support and to provide measurement data representing variations in the surface along each measurement path; and

processor means for processing the measurement data provided by the measurement probe to produce data representing features of at least one of surface form and texture of the surface of the object, wherein the processor means further comprises determining means for using measurement data provided by the measurement probe and representing variations across a surface area of a surface of a reference object of known form to determine the relative orientations of the first and third directions.

43. A method of determining the relative orientation of axes of an instrument having a first mover for effecting relative movement along a first axis in a first direction between a support for receiving an object, a receiver for receiving a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path, and a second mover for effecting relative movement between the support and the receiver along another axis in a third direction different from the first and second directions, the method comprising the steps of:

causing the first mover to effect said relative movement in said first direction a plurality of times and causing the second mover to effect said relative movement in said third direction between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of a reference object of known form mounted on the support and to provide measurement data representing variations in the reference object surface along each measurement path; and

determining the relative orientations of the first and third directions using measurement data provided by the measurement probe and representing variations across said surface area of said reference object.

45. A method according to claim 43 or 44, further comprising correcting measurement data provided by the measurement probe in accordance with any error in the determined relative orientations of the first and third directions.

46. A method according to claim 43 or 44, wherein the reference object is such that each measurement path forms an arc and the determining step comprises determining a central focus or axis of each arc and using the determined central foci or axes to determine the relative orientations of the first and third directions.

47. A method according to claim 46, which comprises determining the orientation of the third direction to the first direction by fitting a line through the centers of the arcs.

48. A method according to claim 46, which comprises determining the orientation of the third direction to the first direction by fitting a line through the centers of the arcs in the plane containing the first and third directions.

49. A method according to claim 43 or 44, wherein the determining step comprises using the measurement data provided by the measurement probe and representing variations across the surface area of the reference object of known form to determine the relative orientations of the first and third directions and the relative orientations of the second and third directions.

50. A method according to claim 49, further comprising correcting measurement data provided by the measurement probe in accordance with any error in the determined relative orientations of the first and third directions and correcting measurement data provided by the measurement probe in accordance with any error in the relative orientations of the first and third directions and any error in the relative orientations of the second and third directions.

51. A method according to claim 49, wherein the reference object is such that each measurement path forms an arc and the determining step comprises determining a central focus or axis of each arc and using the determined central foci or axes to determine the relative orientations of the first and third directions and the second and third directions.

52. A method according to claim 51, which comprises fitting a line through the centres of the arcs to determine the relative orientations of the first and third directions and the second and third directions.

53. A method according to claim 51, which comprises fitting a first line through the centers of the arcs in the plane containing the first and third directions to determine the orientation of the third direction to the first direction and fitting a second line through the centers of the arcs in the plane containing the second and third directions to determine the orientation of the third direction to the second direction.

54. A method according to claim 43 or 44, further comprising correcting start and end points of each measurement path for errors in the movement of the measurement probe.

55. A method according to claim 43 or 44, further comprising fitting a three-dimensional form to the reference object measurement data, comparing a characteristic of the fitted three-dimensional form to the corresponding characteristic of the reference object, adjusting a value representing the distance of relative movement in the third direction between measurement paths to determine the value for that distance for which the characteristic of the fitted form most closely corresponds to the characteristic of reference object and correcting measurement data in accordance with the determined value.

56. A method according to claim 43 or 44, further comprising removing surface form data from measurement data provided by the measurement probe.

57. A method according to claim 43 or 44, further comprising outputting measurement data to a user as a topographical or perspective representation of the measured surface area.

59. A method according to claim 43, 44, or 58, further comprising supplying a signal carrying measurement data correction data.

60. A method according to claim 43, 44, or 58, further comprising storing measurement data correction data as calibration data on a storage medium.

61. A method of obtaining data representing surface features comprising at least one of surface form and texture using a metrological instrument having

a first mover for effecting relative movement in a first direction between a support for receiving an object and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path, and

a second mover for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions,

the method comprising the steps of:

causing the first mover to effect said relative movement in said first direction a plurality of times and causing the second mover to effect said relative movement in said third direction between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of an object mounted on the support and to provide measurement data representing variations in the surface along each measurement path; and

correcting the measurement data using correction data obtained using a method in accordance with claim 43 or 44.

62. A storage medium carrying processor instructions for causing processing means to carry out a method in accordance with claim 61.

63. A signal carrying processor instructions for causing processing means to carry out a method in accordance with claim 61.

64. A storage medium carrying processor instructions for causing processing means to carry out a method in accordance with claim 43, 44, or 58.

65. A signal carrying processor instructions for causing processing means to carry out a method in accordance with claim 43, 44, or 58.

44. A method of obtaining calibration data using a metrological instrument having a first mover for effecting relative movement in a first direction between a support for receiving an object and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path, and a second mover for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions, the method comprising the steps of:

causing the first mover to effect said relative movement in said first direction a plurality of times and causing the second mover to effect said relative movement in said third direction between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of a reference object mounted on the support and to provide measurement data representing variations in the surface of known form along each measurement path; and

determining the relative orientations of the first and third directions using measurement data provided by the measurement probe and representing variations across said surface area of said reference object.

58. A method of calibrating a metrological instrument for determining surface features comprising at least one of surface form and texture and having:

first moving means for effecting relative movement in a first direction between a support for receiving an object and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path; and

second moving means for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions, the method comprising the steps of;

causing the first moving means to effect said relative movement in said first direction a plurality of times and causing the second moving means to effect said relative movement in said third direction after each movement in said first direction to cause the measurement probe to traverse a plurality of measurement paths across an area of the surface of a reference object of known form mounted on the support and to provide measurement data representing variations in the surface along each measurement path;

determining using measurement data provided by the measurement probe and representing variations across said surface area of said reference object of known form any difference between a measured value of a characteristic representing the form of the reference object and the actual value of that characteristic; and

adjusting a value representing the distance moved in the third direction between measurement paths to determine the distance value for which the measured value of the characteristic most closely matches the actual value and using the determined distance value to correct or adjust measurement data.

70. A method of obtaining data representing surface features comprising at least one of surface form and texture using a metrological instrument having first moving means for effecting relative movement in a first direction between a support for receiving an object and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of an object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features along the measurement path, and second moving means for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions,

the method comprising the steps of:

causing the first moving means to effect said relative movement in said first direction a plurality of times and causing the second moving means to effect said relative movement in said third direction between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of an object mounted on the support and to provide measurement data representing variations in the surface along each measurement path; and

correcting the measurement data using correction data obtained using a method in accordance with claim 58.

66. A metrological instrument for determining surface features comprising at least one of surface form and texture, comprising:

first moving means for effecting relative movement in a first direction between a support for receiving a reference object of known form and a measurement probe so as to cause the measurement probe to traverse a measurement path across a surface of the reference object received by the support to provide measurement data representing variations, in a second direction different from the first direction, of surface features of the reference object along the measurement path;

second moving means for effecting relative movement between the support and the measurement probe in a third direction different from the first and second directions;

control means for causing the first moving means to effect said relative movement in said first direction a plurality of times and for causing the second moving means to effect said relative movement in said third direction between movements in said first direction to cause the measurement probe to traverse a plurality of said measurement paths across an area of the surface of the reference object mounted on the support and to provide measurement data representing variations in the surface along each measurement path;

processor means for processing the measurement data provided by the measurement probe to produce data representing features of at least one of surface form and texture of the surface, the processor means further comprising determining means for using measurement data provided by the measurement probe and representing variations across a surface area of a reference object of known form to determine the relative orientation of the first and third directions,

wherein the reference object is such that each measurement path forms an arc and the determining means comprises first determining means for determining a central focus or axis of each arc and second determining means for using the determined central foci or axes to determine the relative orientation of the first and third directions,

the instrument further comprising means for pivotally supporting the measurement probe to cause the measurement probe to pivot about a pivot axis in response to surface variations and means for correcting start and end points of each measurement path for errors in the movement of the measurement probe.

67. An instrument, comprising:

means for receiving a measurement probe;

first moving means for effecting relative movement in a first direction between a support for receiving an object and the measurement probe receiving means so as to cause the measurement probe to traverse a measurement path across a surface of a reference object of known form received by the support to provide measurement data representing variations, in a second direction different from the

first direction, of surface features of the object along the measurement path;

second moving means for effecting relative movement between the support and the measurement probe receiving means in a third direction different from the first and second directions;

control means for causing the first moving means to effect said relative movement in said first direction a plurality of times and for causing the second moving means to effect said relative movement in said third direction between movements in said first direction for causing the measurement probe to traverse a plurality of measurement paths across an area of the surface of an object mounted on the support surface and to provide measurement data representing variations in the surface along each measurement path, determining means for using measurement data provided by the measurement probe and representing variations across a surface area of the reference object to determine the relative orientation of the first and third directions; and

means for outputting data to a user to provide a topographical or perspective representation of the measured surface.

68. A control apparatus for a metrological instrument comprising:

a first mover operable to effect relative movement between a measurement probe and a support surface in a first direction so as to cause the measurement probe to traverse and follow changes in a second direction different from the first directions, in a surface of an object mounted to the support surface; and

a second mover operable to effect relative movement between the support surface and the measurement probe in a third direction different from the first and second directions, the control apparatus comprising;

a controller operable to cause the measurement probe to be moved relative to the surface to be measured in the third direction after the measurement probe completes a measurement path in the first direction so that the measurement probe traverses a plurality of parallel measurement paths, and

a processor operable to process measurement data received from the measurement probe as a result of the traversal of the plurality of parallel measurement paths, the processor being operable to process measurement data received as a result of the measurement probe traversing a surface area of known three-dimensional form to determine the orientation of the third direction relative to the first direction and to provide data representing that relative orientation.

69. A metrological instrument having a controller in accordance with claim 68.