Machine vision system for identifying and assessing features of an article

• US 6,408,429 B1
• Filed: 03/10/2000
• Issued: 06/18/2002
• Est. Priority Date: 01/17/1997
• Status: Expired due to Term

• Current Assignee: Cognex Corporation
• Original Assignee: Cognex Corporation
• Inventors: Nadabar, Sateesh G., Collins, Edward A. Jr., Kawata, Masayoki, Marrion, Cyril C. Jr., Bachelder, Ivan A.
• Primary Examiner(s): Dam, Tuan Q.
• Assistant Examiner(s): Chavis, John Q.
• Application Number:
  US09/522,885
• Time in Patent Office: 830 Days
• Field of Search: 717/1
• US Class Current: 717/100
• CPC Class Codes: G06T 2207/30121 CRT, LCD or plasma display
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

An improved vision system is provided for identifying and assessing features of an article. Systems are provided for developing feature assessment programs, which, when deployed, may inspect parts and/or provide position information for guiding automated manipulation of such parts. The improved system is easy to use and facilitates the development of versatile and flexible article assessment programs. In one aspect, the system comprises a set of step tools from which a set of step objects is instantiated. The set of step tools may comprise machine vision step objects that comprise routines for processing an image of the article to provide article feature information. A control flow data structure and a data flow data structure may each be provided. The control flow data structure charts a flow of control among the step objects. The data flow data structure includes a data flow connection providing access to portions of the data flow data structure for at least one of individual accessing and individual defining of a data source for a given step object.

Claims

1. A computer-readable medium encoded with a program, said program comprising:

a set of step tools from which a set of step objects is instantiated, said set of step objects comprising machine vision step objects that comprise routines for processing an image of an article to provide article feature information;

a control flow data structure for charting a flow of control among said step objects, said control flow data structure comprising a control flow connection, said control flow connection providing access to portions of said control flow data structure for at least one of individual accessing and individual defining of a following step object specified to follow a given step object; and

a data flow data structure for charting a flow of data among said step objects, said data flow data structure comprising a data flow connection, said data flow connection providing access to portions of said data flow data structure for at least one of individual accessing and individual defining of a data source for a given step object.

2. A computer system for developing on a computer-readable medium an article assessment program that identifies and assesses features of an article, said computer system comprising:

a user interface;

a class definer for defining on said computer-readable medium a class of objects based upon geometric features of said article;

a computer-readable step tool library, said step tool library comprising step tools from which step objects are instantiated, said step objects comprising machine vision step objects comprising routines for processing an image of said article to provide article feature information, respective ones of said step objects comprising at least one routine defining and controlling execution of said article assessment program;

an instantiator for instantiating said step object;

a control flow data structure and means for interfacing said user interface to said control flow data structure to chart a flow of control among said step objects, by a user specifying for a given individual step object a following step object that will next define and control execution of the article assessment program; and

a data flow data structure and means for interfacing said user interface to said data flow data structure to chart a flow of data among said step objects, by a user specifying a data source for a given step object.

3. The computer system according to claim 2, wherein said step tools comprise machine vision step tools from which machine vision step objects are instantiated and program flow step tools from which program flow step objects are instantiated, said machine vision step objects comprising routines for processing an image of said article to provide article feature information, and said program flow step objects comprising routines for managing transitions to or from said machine vision step objects.

4. The computer system according to claim 2, wherein said flow of control is specified by separately specifying for a given individual step object a first following step object for one type of result of a routine of said given step object and a second following step object for another type of result of the routine of said given step object.

5. The computer system according to claim 2, wherein said computer system comprises a program loaded in memory.

6. The computer system according to claim 2, wherein said article comprises a part, and said assessing of features comprises inspecting said part for defects in certain features of said part.

7. The computer system according to claim 2, wherein said article comprises a surface mount device, and said assessing of features comprises inspecting said surface mount device for defects in certain features of said surface mount device.

8. The computer system according to claim 2, wherein said article comprises a surface mount device, and said assessing of features comprises determining a position of said surface mount device in relation to a mounting system for mounting said surface mount device to a circuit board.

9. The computer system according to claim 8, wherein said assessing of features further comprises determining a position of said surface mount device in relation to a mounting system for mounting said surface mount device to a circuit board.

10. The computer system according to claim 2, wherein said step objects comprise at least two output statuses, including a PASS status and a FAIL status, said control flow data structure comprising a structure for designating that the following step object comprises a first following step when the given step object comprises a PASS status and that the following step object comprises a second following step when the given step object comprises a FAIL status.

11. A computer-readable medium encoded with an article assessment program for identifying features of an article, said program comprising:

a set of step objects comprising machine vision step objects that comprise routines for processing an image of said article to provide article feature information;

a control flow data structure for charting a flow of control among said step objects, said control flow data structure comprising a control flow connection, said control flow connection providing access to portions of said control flow data structure for at least one of individual accessing and individual defining of a following step object specified to follow a given step object; and

a data flow data structure for charting a flow of data among said step objects, said data flow data structure comprising a data flow connection, said data flow connection providing access to portions of said data flow data structure for at least one of individual accessing and individual defining of a data source for a given step object.

12. A computer system comprising a subsystem for executing from a computer-readable medium a program for identifying and assessing features of an article, said subsystem comprising:

a user interface;

computer-readable calibration data;

a computer-readable article model comprising information representing certain characteristics of said article;

a set of instantiated step objects comprising machine vision step objects that comprise routines for processing an image of said article to provide article feature information;

computer-readable image data representing at least one field of view of a digital image of said article;

a control flow data structure for charting a flow of control among said step objects, said control flow data structure comprising a control flow connection, said control flow connection providing access to portions of said control flow data structure for at least one of individual accessing and individual defining of a following step object specified to follow a given step object; and

a data flow data structure for charting a flow of data among said step objects, said data flow data structure comprising a data flow connection, said data flow connection providing access to portions of said data flow data structure for at least one of individual accessing and individual defining of a data source for a given step object.

13. The computer system according to claim 12, wherein certain ones of said step objects comprise parameters representative of said article in device space.

14. The computer system according to claim 12, wherein said computer-readable article model comprises a data structure shared by multiple ones of said step objects.

15. The computer system according to claim 12, wherein said computer system further comprises a central controller for obtaining and providing FOV data to said subsystem, said subsystem providing guidance information to said central controller to guide the obtention of said FOV data.

16. The computer system according to claim 14, wherein said step objects further comprise program flow step objects, said machine vision step objects comprising routines for processing an image of said article to provide article feature information, and said program flow step objects comprising routines for managing transitions among said machine vision step objects and said central controller, said transitions comprising transferring FOV data between certain ones of said machine vision step objects and said central controller.

17. A computer-readable medium encoded with a program for developing, on at least one of said computer-readable medium and another computer-readable medium, an article assessment program for identifying features of an article, said program comprising:

a class definer for a class of objects based upon geometric features of said article;

a step tool library comprising step tools from which step objects are instantiated, said step objects comprising machine vision step objects comprising routines for processing an image of said article to provide article feature information, respective ones of said step objects comprising at least one routine defining and controlling execution of said article assessment program;

an instantiator for instantiating said step object;

a control flow data structure for charting a flow of control among said step objects, said control flow data structure comprising a control flow connection, said control flow connection providing access to portions of said control flow data structure for at least one of individual accessing and individual defining of a following step object specified to follow a given step object; and

a data flow data structure for charting a flow of data among said step objects, said data flow data structure comprising a data flow connection, said data flow connection providing access to portions of said data flow data structure for at least one of individual accessing and individual defining of a data source for a given step object.

18. A computer-readable medium encoded with a program, said program comprising:

a plurality of step tools configured to instantiate a plurality of step objects, said plurality of step objects comprising machine vision step objects that comprise routines for processing an image of an article to provide article feature information;

a control flow data structure for defining a flow of control between at least two of said plurality of step objects, said control flow data structure comprising a control flow connection, said control flow connection providing access to portions of said control flow data structure for at least one of accessing and defining of a following step object specified to follow a given step object;

a data flow data structure for defining a flow of data between at least two of said plurality of step objects, said data flow data structure comprising a data flow connection, said data flow connection providing access to portions of said data flow data structure for at least one of accessing and defining of a data source for a given step object, and

computer instructions that, when executed by a processor, generate a graphical representation of at least one of the control flow data structure and the data flow data structure.

19. The computer-readable medium of claim 18, wherein the flow of control defined by the control flow data structure defines a flow of control between at least three of said plurality of step objects, said control flow data structure comprising at least two control flow connections comprising a first control flow connection and a second control flow connection, the first control flow connection connecting the given step object and a first following step object and the second control flow connection connecting the given object and a second following step object, said control flow data structure including information indicating that a flow of control from the given step object to the following step object results in a flow of control from the given step object to one of the first and second following step objects based on the results generated by an image processing routine included in the given step object.

20. The computer-readable medium of claim 18, wherein the graphical representation is configured to serve as a diagnostic feedback to a user by graphically displaying an inspection program.

21. The computer-readable medium of claim 18, wherein the graphical representation is configured as a graphical mechanism for specifying a flow of data or control by allowing a user to graphically connect inspection steps to each other.

22. The computer-readable medium of claim 18, wherein the graphical representation of the control flow data structure illustrates flow of control between at least two step objects of the plurality of step objects.

23. The computer-readable medium of claim 22, wherein the at least two step objects illustrated in the graphical representation of the control flow data structure are represented as nodes.

24. The computer-readable medium of claim 23, wherein the flow of control between the at least two step objects illustrated in the graphical representation is illustrated as a graphical connection between the two nodes corresponding to the two step objects.

25. The computer-readable medium of claim 24, wherein the graphical connection between the two nodes is an arc.

26. The computer-readable medium of claim 18, wherein the graphical representation of the data flow data structure illustrates flow of data between at least two step objects of the plurality of step objects.

27. The computer-readable medium of claim 26, wherein the at least two step objects illustrated in the graphical representation of the data flow data structure are represented as nodes.

28. The computer-readable medium of claim 27, wherein the flow of data between the at least two step objects illustrated in the graphical representation is illustrated as a graphical connection between the two nodes corresponding to the two step objects.

29. The computer-readable medium of claim 28, wherein the graphical connection between the two nodes is an arc.

30. A computer system configured to develop, on a computer-readable medium, an article assessment program that identifies and assesses features of an article, said computer system comprising:

a user interface;

a class definer for defining on said computer-readable medium a class of objects based upon geometric features of said article;

a computer-readable step tool library, said step tool library comprising a plurality of step tools configured to instantiate a plurality of step objects, said plurality of step objects comprising machine vision step objects comprising routines for processing an image of said article to provide article feature information;

a control flow data structure defining a flow of control between at least two step objects of the plurality of step objects by specification for a given step object of at least one following step object that will next define and control execution of the article assessment program, said user interface being operationally coupled to said control flow data structure; and

a data flow data structure defining a flow of data between at least two step objects of the plurality of step objects by specification of a data source for at least one of the two step objects, said user interface being operationally coupled to said data flow data structure; and

wherein the computer system further comprises a graphical user interface that is configured to display a graphical representation of at least one of the control flow data structure and the data flow data structure.

31. The computer system of claim 30, wherein the graphical representation of the control flow data structure illustrates flow of control between at least two step objects of the plurality of step objects.

32. The computer system of claim 30, wherein the graphical representation of the data flow data structure illustrates flow of data between at least two step objects of the plurality of step objects.

33. The computer system of claim 30, wherein the graphical representation is configured to serve as a diagnostic feedback to a user by graphically displaying an inspection program.

34. The computer system of claim 30, wherein the graphical representation is configured as a graphical mechanism for specifying a flow of data or control by allowing a user to graphically connect inspection steps to each other.

35. The computer system of claim 30, wherein each of said step objects comprises at least one routine defining and controlling execution of said article assessment program.

36. The computer system of claim 30, wherein specification of said flow of control separately specifies, for a given step object, a first following step object for one type of result of a routine of said given step object and a second following step object for another type of result of the routine of said given step object.

37. The computer system of claim 30, wherein the graphical representation of the control flow data structure illustrates flow of control between at least two step objects of the plurality of step objects.

38. The computer system of claim 37, wherein the at least two step objects illustrated in the graphical representation of the control flow data structure are represented as nodes.

39. The computer system of claim 38, wherein the flow of control between the at least two step objects illustrated in the graphical representation is illustrated as a graphical connection between the two nodes corresponding to the two step objects.

40. The computer system of claim 39, wherein the graphical connection between the two nodes is an arc.

41. The computer system of claim 40, wherein the graphical representation of the data flow data structure illustrates flow of data between at least two step objects of the plurality of step objects.

42. The computer system of claim 41, wherein the at least two step objects illustrated in the graphical representation of the data flow data structure are represented as nodes.

43. The computer system of claim 42, wherein the flow of data between the at least two step objects illustrated in the graphical representation is illustrated as a graphical connection between the two nodes corresponding to the two step objects.

44. The computer system of claim 43, wherein the graphical connection between the two nodes is an arc.