Method of optimizing target quantities for optical precision measurement and apparatus therefor

• US 20040131244A1
• Filed: 10/20/2003
• Published: 07/08/2004
• Est. Priority Date: 04/18/2001
• Status: Active Grant

• Current Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Inventors: Kuhn, Olaf, Nehse, Uwe, Linss, Gerhard
• Granted Patent: US 7,254,262 B2
• Time in Patent Office: Days
• US Class Current: 382/141
• CPC Class Codes: G01B 11/024 by means of diode-array scanning
• CPC Class Codes: G01B 11/028 by measuring lateral position of a boundary of the object G01B11/022, G01B11/024, G01B11/04 take precedence
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals

Abstract

A method for optimizing target quantities for optical precision measuring includes obtaining ancillary parameters from image data of a workpiece which is to be measured. Control data for influence quantities of the target quantities are derived from the ancillary parameters. The control data is derived as follows: by determining the courses of the ancillary parameters depending on at least one influence quantity and the courses of the ancillary parameters are determined in such a way that the courses have a like extremum of the functional dependence from the influence quantities. An overall course of the ancillary parameters is determined and an extremum of the overall course of the ancillary parameters is determined. Corresponding values of the influence quantities are determined at the site of the determined extremum as control data for the influence quantity.

Claims

1. A method for optimizing target quantities for optical precision measuring, the method comprising the steps of:

obtaining ancillary parameters from image data and deriving control data for influence quantities;

determining a weighted summation of the individual ones of said ancillary parameters for the target function to be optimized; and

,

determining all ancillary parameters in such a manner that they have a like extremum of the functional dependency of the influence quantities.

2. The method of claim 1, wherein the following are used as said ancillary parameters:

contrast, homogeneity, mean brightness and/or gradient.

3. The method of claim 2, wherein the computation of the ancillary parameters takes place based on simulated images which are generated with illumination models of computer graphics.

4. The method of claim 1, wherein the determination of the ancillary parameters takes place via difference forming with an input value with the objective of obtaining a like extremum.

5. The method of claim 1, wherein the weighting factors for the optimization criteria are so computed that a standardization of the individual parameters takes place.

6. The method of claim 1, wherein the determination of the ancillary parameters takes place from each type of color images or gray value images.

7. The method of claim 1, wherein the target quantities of the optimization define 2D structure sites.

8. The method of claim 1, wherein the target quantities of the optimization define the focus site.

9. The method of claim 7, wherein the target quantities of the optimization define the 2D structure site and focus site.

10. The method of claim 1, wherein the target quantities of the optimization define the 3D structure site.

11. The method of claim 1, wherein at least one influence quantity relates to the illumination.

12. The method of claim 11, wherein a parameter set of the reflection characteristics and transmission characteristic p_bdfr is first determined for determining the ancillary parameters.

13. The method of claim 1, wherein an image sequence is recorded by a camera with a synchronized controllable illuminating source and the illumination adjustment is changed between the images.

14. A precision measuring apparatus for measuring workpieces, the precision measuring apparatus comprising:

means for obtaining ancillary parameters from image data and deriving control data for influence quantities;

means for determining a weighted summation of the individual ones of said ancillary parameters for the target function to be optimized; and

,

means for determining all ancillary parameters in such a manner that they have a like extreme of the functional dependency of the influence quantities.

15. The precision measuring apparatus of claim 14, wherein said precision measuring apparatus is a coordinate measuring apparatus.

16. A method for optimizing target quantities for optical precision measuring wherein ancillary parameters are obtained from image data of a workpiece to be measured and wherein control data is derived from said ancillary parameters for influence quantities of these target quantities, the method comprising deriving the control data with the steps of:

determining the courses of the ancillary parameters in dependence upon at least one influence quantity and determining the courses of the ancillary parameters so that the courses have a like extremum of the functional dependency of the influence quantity;

determining a total course of the ancillary parameters in dependence upon the influence quantity via weighted summation of the courses of the ancillary parameters;

determining an extremum of the total course of the ancillary parameters; and

,

determining the corresponding value of the influence quantity at the site of the specific extremum as control datum for the influence quantity.

17. The method of claim 16, wherein the following are used as said ancillary parameters:

contrast, homogeneity, mean brightness and/or gradient.

18. The method of claim 17, wherein the determination of the ancillary parameters takes place from simulated image data which are generated with illumination models of computer graphics.

19. The method of claim 16, wherein at least individual ones of said ancillary parameters are determined via difference forming with an input value with the objective of obtaining a like extremum of the functional dependency of said influence quantity.

20. The method of claim 16, wherein the weighting factors for the weighted summation of the courses of the ancillary parameters are so determined that a standardization of all ancillary parameters takes place.

21. The method of claim 16, wherein the determination of the ancillary parameters takes place from color images or gray value images.

22. The method of claim 16, wherein the target quantities define the 2D structure sites and/or focus sites.

23. The method of claim 16, wherein the target quantities define 3D structure sites.

24. The method of claim 16, wherein at least one influence quantity relates to the illumination.

25. The method of claim 24, wherein first a reflectance function p_bdfr is determined for determining the course of the ancillary parameters.

26. The method of claim 24, wherein, as image data for determining the course of the ancillary parameters, an image sequence is recorded by a camera with a synchronized illuminating source and the illuminating adjustment is changed between the images.

27. An optical precision measuring apparatus comprising:

an image recording device;

an image processing device connected to said image recording device; and

,

said image processing device functioning to obtain ancillary parameters for optimizing target quantities of a measuring sequence of a workpiece to be measured and to derive control data from said ancillary parameters for influence quantities of said target quantities by performing the following steps;

determining the courses of the ancillary parameters in dependence upon at least one influence quantity with the courses of the ancillary parameters being so determined that the courses have a like extremum of the functional dependency from the influence quantity;

determining a total course of the ancillary parameter in dependence upon the influence quantity via a weighted summation of the courses of the ancillary parameters;

determining an extremum of the total course of the ancillary parameters; and

,

determining the corresponding value of the influence quantity at the site of the determined extremum as a control data for the influence quantity.

28. The optical precision measuring apparatus of claim 27, wherein said apparatus is a coordinate measuring apparatus including a movable mechanical assembly and said image recording device is mounted on said mechanical assembly so as to be movable thereby relative to a workpiece in the three coordinate directions (x, y, z).

29. The optical precision measuring apparatus of claim 28, wherein said image processing device uses at least one of the following as one of said ancillary parameters:

contrast, homogeneity, mean brightness and gradient.

30. The apparatus of claim 28, wherein said image processing device determines the ancillary parameters from simulated images which are generated with illumination models of computer graphics.

31. The apparatus of claim 28, wherein said image processing device determines at least individual ones of said ancillary parameters via difference forming with an input value with the objective of obtaining a like extremum of the functional dependency from said influence quantity.

32. The apparatus of claim 28, wherein said image processing device determines the weighting factors for the weighted summation of the courses of the ancillary parameters so that a standardization of all ancillary parameters takes place.

33. The apparatus of claim 28, wherein said image processing device determines the ancillary parameters from each type of color images or gray value images.

34. The apparatus of claim 28, wherein the target quantities define the 2D structure sites and/or focus sites.

35. The apparatus of claim 28, wherein the target quantities define 3D structure sites.

36. The apparatus of claim 28, wherein at least one influence quantity relates to the illumination.

37. The apparatus of claim 36, wherein a bi-directional reflectance function p_bdfr is determined for determining the ancillary parameters.

38. The apparatus of claim 36, wherein, as image data for determining the course of the ancillary parameters, an image sequence is recorded by a camera with a synchronized illuminating source and the illuminating adjustment is changed between the images.