Method of and an apparatus for measuring surface contour

• US 5,467,289 A
• Filed: 10/12/1993
• Issued: 11/14/1995
• Est. Priority Date: 10/15/1992
• Status: Expired due to Term

• Current Assignee: Mitutoyo Corporation
• Original Assignee: Mitutoyo Corporation
• Inventors: Abe, Makoto, Tokitoh, Hiroyuki, Ohta, Shigekata, Kano, Takahumi, Hidaka, Hiroyuki, Ueda, Morimasa
• Primary Examiner(s): Cosimano, Edward R.
• Assistant Examiner(s): Shah, Kamini S.
• Application Number:
  US08/134,915
• Time in Patent Office: 763 Days
• Field of Search: 364/560, 364/474.03, 364/474.02, 364/474.05, 364/571.01, 364/571.05, 364/167.01, 364/474.36, 356/377, 356/376, 356/72, 356/360, 33/503
• US Class Current: 702/167
• CPC Class Codes: G01B 21/04 by measuring coordinates of points

Abstract

A measurement-datum similar to profile of a measuring object set in a measuring area in which a detector and the measuring object are moved relatively is formed to measure the displacement value between the detector and the measuring object through the relative movement based on the measurement-datum to thereby compute the surface contour of the measuring object from the measured data with reference to the measurement-datum. Since the measurement-datum is set in the spatial area, a precise mechanical processing will not be required for an accurate measurement of the measuring object having a strange profile which was not measured by conventional apparatus.

Claims

1. A method of measuring the surface contour of an object comprising the steps of:

taking a plurality of spaced-apart base measurements of the surface contour of the object with a detector by taking said base measurements along an elongated base datum, wherein said base measurements represent the distance between the object and said base datum;

deriving an elongated measurement datum above the surface of the object based on said base measurements, wherein said measurement datum is at least partially located between said base datum and the object, said derivation of said measurement datum including the step of storing data representative of the distance between said measurement datum and said base datum;

taking a plurality of spaced apart main measurements of the surface contour of the object with said detector, wherein said detector is moved along said measurement datum and said main measurements represent the distance between the surface of the object and the points on said measurement datum at which said main measurements were made; and

generating data representative of the surface contour of the object based on said main measurements and said stored data representing said distance between said measurement datum and said base datum.

2. The method of surface contour measurement of claim 1, wherein said detector is attached to a displacement system for moving said detector relative to the object so that said detector travels along said datums, said displacement system being configured to cause the relative detector/object movement to occur along a mechanical axis, and said method further includes the steps of:

taking a plurality of measurements of a standard object with said detector along said displacement system mechanical axis;

computing compensating data representative of a difference between a spatial axis separate from said displacement system and said displacement system mechanical axis; and

adjusting said measurement datum/base datum distance data with said spatial axis/displacement system mechanical axis compensating data so that said generating data representative of the object surface contour corresponds to contour measurements along said spatial axis.

3. The method of surface contour measurement of claim 2, wherein said detector takes said measurements of the object without contacting the object.

4. The method of surface contour measurement of claim 1, wherein:

said measurement datum is derived so that said measurement datum has at least one section with a circular profile; and

said main measurements are taken along said measurement datum circular section.

5. The method of surface contour measurement of claim 2, wherein:

said measurement datum is derived so that said measurement datum has at least one section with a circular profile; and

said main measurements are at taken along said measurement datum circular section.

6. The method of surface contour measurement of claim 2, wherein said displacement system moves the object relative to said detector along at least one axis to facilitate the taking of said measurements along said datums.

7. The method of surface contour measurement of claim 2, wherein said displacement system moves said detector along at a first axis to facilitate taking said measurements along said datums.

8. The method of surface contour measurement of claim 7, wherein said displacement system is further configured to move the object relative to said detector along a second axis separate from said first axis so that said datums include first sections oriented along said first and second axes.

9. The method of surface contour measurement of claim 8, wherein said displacement is configured to pivot said detector so that said main measurements are along a measurement datum having a curved profile.

10. The method of surface contour measurement of claim 4, wherein:

said displacement system is configured to move the object relative to said detector along a first axis, to move said detector relative to the object along a second axis separate from said first axis and to pivot said detector; and

said base measurements are taken along said first and second axes and said main measurements taken along said measurement datum circular profile section are made by pivoting said detector.

11. The method of surface contour measurement of claim 5, wherein:

said displacement system is configured to move the object relative to said detector along a first axis, to move said detector relative to the object along a second axis separate from said first axis and to pivot said detector; and

said base measurements are taken along said first and second axes and said main measurements taken along said measurement datum circular profile section are made by pivoting said detector.

12. The method of surface contour measurement of claim 11, wherein said detector takes said measurements of the object without contacting the object.

13. A method of determining the surface contour of an object along a spatial axis, said method comprising the steps of:

measuring a standard object with a known contour with a detector that does not contact said standard object, said detector being connected to a displacement system capable of shifting the relationship between said detector and said standard object so that said standard object measurements are taken at a number of selected points along a mechanical axis spaced from a standard object wherein said standard object measurements represent the distance between said standard object and said mechanical axis at the points on said mechanical axis at which said measurements were taken;

comparing said standard object measurements to the known contour of the standard object so as to produce compensation data representative of the difference between said mechanical axis and the spatial axis;

taking a plurality of spaced apart base measurements of the surface contour of the object to be measured with said detector wherein said initial measurements are taken along said mechanical axis;

deriving a measurement datum above the surface of the object based on said base measurements wherein said measurement datum is at least partially located between said mechanical axis datum and the object and has at least one partially curved section, said derivation of said measurement datum including the step of storing data representative of the distance between said measurement datum and said mechanical axis;

taking a plurality of spaced apart main measurements of the surface contour of the object with said detector wherein said main measurements are taken along said measurement datum including said partially curved section thereof, wherein each said main measurement represents the distance between the object and the point on said measurement datum at which the main measurement was taken; and

generating data representative of the object surface contour based on said main measurement data, said data representative of said distance between said measurement datum and said mechanical axis and said compensation data so that said generated data represents the object surface contour relative to the spatial axis.

14. The method of surface contour measurement of claim 13, wherein:

said displacement system is configured to move the object relative to said detector along a first axis, to move said detector relative to the object along a second axis separate from said first axis and to pivot said detector; and

said base measurements are taken along said first and second axes and said main measurements taken along said measurement datum at least one circular profile section are made by pivoting said detector.

15. An apparatus for measuring the surface contour of an object, said apparatus including:

a base;

a table disposed on said base adapted for receiving the object to be measured;

a displacement mechanism attached to said base and to said table for moving said table and the object along a first axis, said displacement mechanism including a drive unit responsive to drive signals for moving said table and a table position encoder for monitoring the position of said table on said base and configured to generate table position signals representative of the position of said table;

a distance measuring detector located above said table, said distance measuring detector being configured to measure the distance between said detector and the object to produce distance measurement signals representative of the distance, said distance measuring detector being configured to perform said measurements without contacting the object;

a detector positioning system connected to said base and said detector for positioning said detector above said table, said detector for moving said detector relative to said table and the object along a second axis separate from said first axis, said detector positioning system including a displacement assembly responsive to detector positioning drive signals for selectively positioning said detector and a position encoder for monitoring the position of said detector relative to said table and configured to generate detector position signals representative of said position of said detector;

a turntable for pivotally securing said detector to said detector positioning unit, said turntable being configured to pivot said detector around a point, said turntable having a turntable drive mechanism for selectively pivoting said detector in response to application of drive signals thereto and having a position detector configured to monitor the pivotal position of said detector that generates turntable position signals representative of the angular position of said detector; and

a control unit connected to said table displacement system for applying said displacement system drive signals thereto and receiving said table position signals therefrom, to said detector positioning system for applying said detector positioning drive signals thereto and receiving said detector position signals therefrom, to said turntable for applying said turntable drive signals thereto and receiving said turntable position signals therefrom and to said detector for receiving said measurement signals therefrom, said control unit being configured to;

generate said table displacement signals, said displacement mechanism drive signals and said turntable displacement signals so as to cause said detector to measure the contour of the object along a base datum, said base datum extending along said first and second axes;

receive a plurality of measurement signals from said detector representative of the distance between said detector and the object along said base datum;

generate a measurement datum based on said initial measurement signals, said measurement datum being at least partially closer to the object than said base datum and having at least one curved portion and to generate data representative of the distance between said base datum and said measurement datum;

generate said table displacement signals, said displacement mechanism drive signals and said turntable displacement signals so as to cause said detector to move along said measurement datum including said at least one curve portion thereof so that said detector makes main measurements representative of distances between said measurement datum and the object;

receive a plurality of main measurement signals from said detector representative of distance between said detector and the object along said measurement datum; and

generate data representative of object surface contour based on the main measurement signals and said data representative of the distance between said base datum and said measurement datum.

16. The apparatus of claim 15, wherein said table displacement mechanism is configured to move said table along a first and third axes wherein said third axis is distinct from said first and second axes.

17. The apparatus of claim 15, wherein the table is configured to move said object along a horizontal axis and said detector positioning system is configured to move said detector along a vertical axis.

18. The apparatus of claim 15, wherein said detector is an optical measuring device.

19. The apparatus of claim 15, wherein said control unit further includes a memory for storing compensating data representative of differences in distance between spatial axes separate from said first and second axes and said base datum and said control unit generates data representative of the surface contour of the object based on said main measurements, said base measurements and said compensation data.