Method for measuring the geometry of an object by means of a co-ordination measuring device

• US 7,064,845 B2
• Filed: 09/20/2001
• Issued: 06/20/2006
• Est. Priority Date: 09/22/2000
• Status: Expired due to Fees

• Current Assignee: Werth Messtechnik GmbH
• Original Assignee: Werth Messtechnik GmbH
• Inventors: Christoph, Ralf
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): Nguyen, Sang H.
• Application Number:
  US10/297,624
• Publication Number:
  US 20040264758A1
• Time in Patent Office: 1,734 Days
• Field of Search: 356600-625, 335/03, 335/56, 340/576, 345/427, 345441-442, 345/356, 364/578, 250/559.22, 250/559.05, 382/149, 382/147, 382/150, 395/143
• US Class Current: 356/601
• CPC Class Codes: G01B 11/005 coordinate measuring machines
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G05B 19/40937 concerning programming of machining or material parameters, pocket machining
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A process for measuring of an object geometry is disclosed using a coordinate measuring device wherein the object geometry is recorded by an optical sensor and represented as an image content, wherein within the image content, geometric structures suitable for the measurement of the object are subsequently selected and evaluated.

Claims

1. Process for the measurement of an object geometry (12) by means of a coordinate measuring device (10), the object geometry (12) is recorded by means of an image processing sensor (14) movable along the x-, y-, and z-axes by means of a positioning system of the coordinate measuring device, and said object geometry is represented by an image content (32), and whereby, within the image content, geometric structures (60–

70) suitable for the measurement of the object are selected and subsequently evaluated, characterized in that at the time of any modification of the image content (32) on the basis of a modification of a value of the coordinate measuring device effected by operation of the coordinate measuring device, said image content is automatically searched for the geometric structures (60–

70) suitable for the measurement of the object (12), and the suitable structures are marked and made available for further evaluation.

2. Process according to claim 1, characterized in that the modification of the image content (32) takes place when modification of the optical magnification and/or of the position of mechanical axes of the coordinate measuring device (10) and/or of the light intensity is implemented.

3. Process according to claim 1, characterized in that the modification of the image content (32) is represented by a signal.

4. Process according to claim 1, characterized in that the signal representing the modification of the image content (32) is produced by a control unit (22) of a zoom lens of the coordinate measuring device (10) at the time of modification of the optical magnification.

5. Process according to claim 1, characterized in that the signal representing the modification of the image content (32) is produced by a replacement unit (56) when the modification of the optical magnification is produced by replacement of the objective.

6. Process according to claim 1, characterized in that the signal representing the modification of the image content (32) is produced by an actuation control (18) when the state of a counter on at least one axis of the coordinate measuring device (10) remains constant, following a position change, for longer than a predetermined interval of “

dead time”

.

7. Process according to claim 1, characterized in that the signal representing the modification of the image content (32) is produced by a lighting control (24), when a nominal lighting value, following a modification of lighting, remains within a tolerance range for longer than a predetermined interval of “

dead time”

.

8. Process according to claim 1, characterized in that the signal representing the modification of the image content (32) is produced by an additional optical sensor, when the constancy of the light ratios gives rise to an inference with regard to the modification of the image content.

9. Process according to claim 1, characterized in that the signal representing the modification of the image content (32) is manually produced by an operator by pressing a button.

10. Process according to claim 1, characterized in that the image content (32) is automatically searched for at least one regular geometric element.

11. Process according to claim 1, characterized in that the automatically proposed geometric structures contours and geometric elements (60–

70) are manually selected by an operator through the control of a monitor by means of an input device.

12. Process according to claim 1, characterized in that the automatically selected geometric structures can be automatically incorporated into a characteristic list at the time of a new modification of the image content (32).

13. Process according to claim 1, characterized in that the automatically preselected elements (60–

70) are manually deleted and modified by the operator, whereby, especially, an area of interest from the represented object geometry can be defined by the operator him/herself.

14. Process for the measurement of an object geometry according to claim 1, characterized in that for identification of the relevant geometric structures (60–

70) suitable for the measurement of the object (12), a comparison of the recorded geometric structures of the object geometry with at least one regular geometric element is performed, and characterized in that the geometric structures of the object geometry which show the least deviation in shape, relative to the regular geometric element, are marked.

15. Process for the measurement of an object geometry according to claim 1, characterized in that the marking of the geometric structure suitable for the measurement of the object takes place in a manner whereby an image processing window (72, 74, 76, 78) is automatically adjusted to the marked geometric structure.

16. Process according to claim 15, characterized in that an optimized adjustment takes place by means of a predetermined part tolerance.

17. Process according to claim 15, characterized in that the automatic adjustment is performed with respect to the direction and proportion of the marked geometric structure (64, 66).

18. Process for the measurement of an object geometry according to claim 1, characterized in that out of the quantity of preselected geometric structures (60–

70, 82, 84), the structure located closest to the middle of a represented image section (88)is automatically selected.

19. Process for the measurement of an object geometry according to claim 1, characterized in that as a function of an object class to be measured and/or the mode of operation of the coordinate measuring device (10), strategies for the marking of the geometric structures (60–

70) suitable for the measurement of the object (12) are selected and/or determined.

20. Process for the measurement of an object geometry according to claim 1, characterized in that the strategies for the marking of the geometric structures (60–

70) suitable for the measurement of the object (12) are dependent upon the type of object.

21. Process for the measurement of an object geometry according to claim 1, characterized in that the strategies for the marking of the geometric structures (60–

70) suitable for the measurement of the object (12) are dependent upon a property of reflection of the surface of the object (12).

22. Process according to claim 1, characterized in that as a strategy for contour and feature extraction, image filters and/or contour filters.

23. Process for the measurement of an object geometry according to claim 1, characterized in that in the course of an automatic sweep of several objects (12) of the same type, both an image processing algorithm and the image processing window (74, 76, 78) are allocated to an average value of the respective geometric structures.

24. Process for the measurement of a geometric structure, according to claim 1, characterized in that as a function of the geometric structures suitable for the measurement of the object, scanning or point-by-point measurement are accessed for the purpose of evaluation of a shape for the purpose of evaluation of a diameter, distance, or angle dimensions.

25. Process for the measurement of a geometric structure, according to claim 1, characterized in that for the selection of the geometric structures available nominal files are used for comparison.

26. Process for the measurement of workpiece geometries by means of coordinate measuring devices with image processing sensors, according to claim 1, characterized in that image processing contours (108) are provided, within a pixel raster (106), with additional information with regard to subpixel coordinates within the pixel.

27. Process according to claim 26, characterized in that the contours (108) are described by so-called Freeman Chains and that corresponding subpixel bytes (114) are added to each byte of the Freeman Chain.

28. Process according to claim 26, characterized in that in image processing operations both the Freeman code and the subpixel information are processed.

29. Process according to claim 1, characterized in that absolute coordinates calculated from the Freeman code (112) and the subpixel information (114) can be generated in subpixel resolution.

30. Process according to claim 1, characterized in that the subpixel information (114) can be represented as separate vectors, in the x and y directions.