Machine vision methods for determining characteristics of three-dimensional objects

• US 5,978,502 A
• Filed: 04/01/1996
• Issued: 11/02/1999
• Est. Priority Date: 04/01/1996
• Status: Expired due to Term

• Current Assignee: Cognex Corporation
• Original Assignee: Cognex Corporation
• Inventors: Ohashi, Yoshikazu
• Primary Examiner(s): Boudreau, Leo H.
• Assistant Examiner(s): MEHTA, BHAVESH M
• Application Number:
  US08/626,041
• Time in Patent Office: 1,310 Days
• Field of Search: 382/145-147, 382/149, 382/150, 382/154, 382/168, 382/170, 382/203, 382/286, 356/237, 356/374, 348/87, 348/126, 348/130, 702/150, 702/155, 702/82, 702/113
• US Class Current: 382/147
• CPC Class Codes: G06T 2207/30152 Solder
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06V 20/64 Three-dimensional objects

Abstract

A method for determining spatial characteristics of a selected object in an image that has pixel values representing heights of corresponding portions thereof is characterized by the steps of finding one or more heights of portions of the object, determining a volume of the object at and above (or below) a selected height by summing a count representing a cross-sectional area of the object at that height with a count representing a volume of the object at a greater (or lesser) height, and outputting the volume so determined. A related method determines a cross-sectional area of an object in such a "height" image by finding one or more heights of portions of the object and summing a count of pixels in the object at the selected height with a count representing a cross-sectional area of the object above that height.

Claims

1. A method for determining spatial characteristics of a selected object in an image that has pixel values representing heights of corresponding portions of the object, the method comprising the steps of

A. identifying, from the image, heights of portions of the selected object;

B. performing the following steps to determine a spatial characteristic of the selected object;

i. determining a value of a cross-sectional area of the object above a selected height by summing a count of pixels in the object at the selected height and a count representing a cross-sectional area of the object above that height;

ii. determining a value of a volume of the object above the selected height by summing a count representing the cross-sectional area of the object at the selected height and a count representing the volume of the object above that height;

C. outputting at least one of the cross-sectional area and volume so determined.

2. A method according to claim 1, wherein at least one of the determining steps are made with respect to each of at least selected heights in the selected object, beginning with the maximum height and progressing through lesser heights.

3. A method according to claim 1, wherein the step of identifying heights of the image includes the step of generating a histogram of the heights of the selected object.

4. A method according to claim 1, including the steps of

determining a base height of one or more objects in the image;

performing connectivity analysis to identify one or more objects in the image portions of which are at heights at or above the base height;

selecting one of those objects as the selected object.

5. A method for determining spatial characteristics of one or more objects in an image that has pixel values representing heights of corresponding portions of the objects, the method comprising the steps of

A. determining a base height of one or more objects in the image;

B. performing connectivity analysis to identify one or more objects in the image having heights at or above the base height;

C. for each of one or more objects in the image, performing the following steps;

i. identifying, from the image, heights of portions of the object;

ii. for each of at least selected heights in the object, beginning with the maximum height and progressing through lesser heights, performing the following steps;

a. determining a value of a cross-sectional area of the object at the selected height by summing a count of pixels in the object at the selected height and a count, if any, representing the cross-sectional area of the object above that height;

b. determining a value of a volume of the object at the selected height by summing a count representing the cross-sectional area of the object at the selected height and a count, if any, representing the volume of the object above that height;

iii. outputting at least one of the cross-sectional area and volume so determined.

6. A method according to claim 5, wherein the determining steps of steps C.ii.a and C.ii.b are made with respect to each height in the object, beginning with the maximum height and progressing successively through each of the lesser heights.

7. A method for determining spatial characteristics of a selected object in an image that has pixel values representing heights of corresponding portions of the object, the method comprising the steps of

A. identifying, from the image, heights of portions of the selected object;

B. performing the following steps in order to determine one or more spatial characteristics of the selected object;

i. for each of at least selected heights in the selected object, beginning with the greater height and progressing through lesser heights, determining a value of a cross-sectional area of the object at the selected height by summing a count of pixels in the object at the selected height and a count, if any, representing the cross-sectional area of the object at a greater height;

ii. for each of at least selected heights in the selected object, beginning with the lesser height and progressing through greater heights, determining a value of a volume of the object below the selected height by summing a count representing the cross-sectional area of the object at the selected height and a count representing the volume of the object below that height;

C. outputting at least one of the cross-sectional area and volume so determined.

8. A method according to claim 7, wherein at least one of the steps of identifying heights of the image includes the step of generating a histogram of the heights of the selected object.

9. A method according to claim 8, including the steps of

determining a base height of one or more objects in the image;

performing connectivity analysis to identify one or more objects in the image portions of which are at heights at or above the base height; and

selecting one of those objects as the selected object.

10. A method for determining spatial characteristics of a solder bump in an image that has pixel values representing heights of corresponding portions of the solder bump, the method comprising the steps of

A. identifying, from the image, heights of portions of the solder bump;

B. performing the following steps in order to determine one or more spatial characteristics of the solder bump;

i. determining, from the image, a value of a cross-sectional area of the solder bump at a selected height by summing a count of pixels in the solder bump at the selected height and a count representing a cross-sectional area of the solder bump at a greater height;

ii. determining a value of a volume of the solder bump at the selected height by summing a count representing a cross-sectional area of the solder bump at the selected height and a count representing of the volume of the solder bump above that height;

C. outputting at least one of the cross-sectional area and volume so determined.

11. A method for determining spatial characteristics of one or more solder bumps in an image that has pixel values representing heights of corresponding portions of the solder bumps, the method comprising the steps of

A. determining a base height of one or more solder bumps in the image;

B. performing connectivity analysis to identify one or more solder bumps in the image having heights at or above the base height;

C. for each of one or more solder bumps in the image, performing the following steps;

i. identifying, from the image, heights of portions of the solder bump;

ii. for each of at least selected heights in the solder bump, beginning with the maximum height and progressing through lesser heights, performing the following steps;

a. determining a value of a cross-sectional area of the solder bump at the selected height by summing a count of pixels in the solder bump at the selected height and a count, if any, representing the cross-sectional area of the solder bump at a greater height;

b. determining a value of a volume of the solder bump at the selected height by summing a count representing the cross-sectional area of the solder bump at the selected height and a count, if any, representing the volume of the solder bump above that height;

iii. outputting at least one of the cross-sectional area and volume so determined.

12. A method for determining spatial characteristics of a selected solder bump in an image that has pixel values representing heights of corresponding portions of the solder bump, the method comprising the steps of

A. identifying, from the image, heights of portions of the solder bump;

B. performing the following steps in order to determine one or more spatial characteristics of the selected solder bump;

i. for each of at least selected heights in the solder bump, beginning with the greater height and progressing through lesser heights, determining a value of a cross-sectional area of the solder bump at the selected height by summing a count of pixels in the solder bump at the selected height and a count, if any, representing the cross-sectional area of the solder bump above that height;

ii. for each of at least selected heights in the solder bump, beginning with the lesser height and progressing through greater heights, determining a value of a volume of the solder bump below the selected height by summing a count representing the cross-sectional area of the solder bump at the selected height and a count representing the volume of the solder bump below a lesser height;

C. outputting at least one of the cross-sectional area and volume so determined.

13. A method for determining spatial characteristics of a selected object in an image that has pixel values representing heights of corresponding portions of the object, the method comprising the steps of

A. identifying, from the image, heights of portions of the selected object;

B. determining a value of a cross-sectional area of the object above a selected height by summing a count of pixels in the object at the selected height and a count representing a cross-sectional area of the object above that height;

C. outputting the cross-sectional area so determined.

14. A method according to claim 13, wherein the determining step is made with respect to each of at least selected heights in the selected object, beginning with the maximum height and progressing through lesser heights.

15. A method according to claim 13, wherein the step of identifying heights of the image includes the step of generating a histogram of the heights of the selected object.

16. A method according to claim 13, including the steps of

determining a base height of one or more objects in the image;

performing connectivity analysis to identify one or more objects in the image portions of which are at heights at or above the base height;

selecting one of those objects as the selected object.

17. A method for determining spatial characteristics of one or more objects in an image that has pixel values representing heights of corresponding portions of the objects, the method comprising the steps of

A. determining a base height of one or more objects in the image;

B. performing connectivity analysis to identify one or more objects in the image having heights at or above the base height;

C. for each of one or more objects in the image, performing the following steps;

i. identifying, from the image, heights of portions of the object;

ii. for each of at least selected heights in the object, beginning with the maximum height and progressing through lesser heights, determining a value of a cross-sectional area of the object at the selected height by summing a count of pixels in the object at the selected height and a count, if any, representing the cross-sectional area of the object above that height;

iii. outputting the cross-sectional area so determined.

18. A method according to claim 17, wherein the determining step C.ii is made with respect to each height in the object, beginning with the maximum height and progressing successively through each of the lesser heights.

19. A method for determining spatial characteristics of a selected object in an image that has pixel values representing heights of corresponding portions of the object, the method comprising the steps of

A. identifying, from the image, heights of portions of the selected object;

B. for each of at least selected heights in the selected object, beginning with the greater height and progressing through lesser heights, determining a value of a cross-sectional area of the object at the selected height by summing a count of pixels in the object at the selected height and a count, if any, representing the cross-sectional area of the object at a greater height;

C. outputting the cross-sectional area so determined.

20. A method according to claim 19, wherein the step of identifying heights of portions of the image includes the step of generating a histogram of the heights of the selected object.

21. A method according to claim 20, including the steps of

determining a base height of one or more objects in the image;

performing connectivity analysis to identify one or more objects in the image portions of which are at heights at or above the base height; and

selecting one of those objects as the selected object.

22. A method for determining spatial characteristics of a solder bump in an image that has pixel values representing heights of corresponding portions of the solder bump, the method comprising the steps of

A. identifying, from the image, heights of portions of the solder bump;

B. determining, from the image, a value of a cross-sectional area of the solder bump at a selected height by summing a count of pixels in the solder bump at the selected height and a count representing a cross-sectional area of the solder bump at a greater height;

C. outputting the cross-sectional area so determined.

23. A method for determining spatial characteristics of one or more solder bumps in an image that has pixel values representing heights of corresponding portions of the solder bumps, the method comprising the steps of

A. determining a base height of one or more solder bumps in the image;

B. performing connectivity analysis to identify one or more solder bumps in the image having heights at or above the base height;

C. for each of one or more solder bumps in the image, performing the following steps;

i. identifying, from the image, heights of portions of the solder bump;

ii. for each of at least selected heights in the solder bump, beginning with the maximum height and progressing through lesser heights, determining a value of a cross-sectional area of the solder bump at the selected height by summing a count of pixels in the solder bump at the selected height and a count, if any, representing the cross-sectional area of the solder bump at a greater height;

iii. outputting the cross-sectional area so determined.

24. A method for determining spatial characteristics of a selected solder bump in an image that has pixel values representing heights of corresponding portions of the solder bump, the method comprising the steps of

A. identifying, from the image, heights of portions of the solder bump;

B. for each of at least selected heights in the solder bump, beginning with the greater height and progressing through lesser heights, determining a value of a cross-sectional area of the solder bump at the selected height by summing a count of pixels in the solder bump at the selected height and a count, if any, representing the cross-sectional area of the solder bump above that height;

C. outputting the cross-sectional area so determined.