System and method for stress detection in a molded container

• US 5,926,268 A
• Filed: 06/04/1997
• Issued: 07/20/1999
• Est. Priority Date: 06/04/1996
• Status: Expired due to Term

• Current Assignee: Emhart Glass SA (Bucher Industries AG)
• Original Assignee: INEX, Inc. (BWI Plc)
• Inventors: Parniawski, Richard, Kosta, Bozidar, Bonewitz, Manuel
• Primary Examiner(s): KIM, ROBERT H
• Application Number:
  US08/868,715
• Time in Patent Office: 776 Days
• Field of Search: 356/237, 356/240, 356/390, 356/32-34, 356/364, 356/366-367, 356/370, 356/428, 356/72, 250/223 B, 382/142, 348/127, 209/526, 209/576-577, 209/579, 209/938-939
• US Class Current: 356/240.1
• CPC Class Codes: B07C 5/3416 according to radiation transmissivity, e.g. for light, x-rays, particle radiation detecting hidden objects G01V
• CPC Class Codes: B07C 5/365 using a single separation means
• CPC Class Codes: G01N 2021/9063 Hot-end container inspection
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/9036 using arrays of emitters or receivers

Abstract

System and method for inspecting a container for defects. A first polarizer positioned between a light source and the container polarizes light provided by the light source for illuminating the container. A second polarizer positioned between the container and a camera polarizes the light transmitted through the container to the camera. As positioned, the axes of transmission of the first and second polarizers are non-parallel relative to each other. An image processor processes an image generated by the camera as a function of an optical characteristic of the image to detect defects in the container.

Claims

1. A system for inspecting a container for stress defects comprising:

a light source for providing light to illuminate the container;

a camera for generating an image of the illuminated container, said image including a plurality of pixels, said pixels each having a value representative of an optical characteristic of the image;

a first polarizer positioned between the light source and the container for polarizing the light illuminating the container;

a second polarizer positioned between the container and the camera for polarizing the light transmitted through the container to the camera, said first and second polarizers each having an axis of transmission, said axes of transmission being non-parallel relative to each other; and

an image processor for processing the image generated by the camera, said image processor;

scanning the image as a function of the pixel values to acquire edge data by which a portion of the container is identified in the image;

defining at least one region of interest in the image, said defined region having a size, shape and position based on the container portion identified in the image; and

inspecting the image as a function of the pixel values within the defined region to detect edges in the image which correspond to defects in the container.

2. The system of claim 1 wherein the axis of transmission of the first polarizer is approximately perpendicular to the axis of transmission of the second polarizer.

3. The system of claim 1 further comprising a diffuser for diffusing the light provided by the light source.

4. The system of claim 1 further comprising a light control filter for filtering the light provided by the light source to reduce glare from the illuminated container.

5. The system of claim 1 wherein the camera comprises a first camera and further comprising a second camera for generating another image of the illuminated container, a third polarizer for polarizing the light illuminating the container and a fourth polarizer for polarizing the light transmitted through the container to the second camera, said third and fourth polarizers each having an axis of transmission, said axes of transmission being non-parallel relative to each other.

6. The system of claim 5 wherein the first and second cameras each have an optical axis, said optical axes being non-parallel relative to each other.

7. The system of claim 6 wherein the optical axis of the first camera is generally perpendicular to an axis of symmetry of the container and wherein the optical axis of the second camera is generally parallel to the axis of symmetry of the container.

8. The system of claim 5 further comprising a container rotator for rotating the container before the second camera generates the other image of the illuminated container.

9. The system of claim 1 wherein the image processor groups the detected edges as a function of their locations in the image to define objects in the image, said defined objects each including one or more pixels, and wherein the image processor includes a memory storing information regarding defects as a function of the defined objects.

10. The system of claim 1 wherein the pixel values correspond to the intensity of the pixels and wherein the optical characteristic of the image detected by the image processor is a gradient of the pixel values.

11. The system of claim 10 wherein the image generated by the camera includes an image of the bottom of the container and the defined region is approximately centered on the image of the bottom of the container.

12. The system of claim 11 wherein the defined region has a generally circular periphery and an outer radius corresponding to the size of the container.

13. The system of claim 1 wherein the container has an axis of symmetry and the camera has an optical axis and further comprising a position sensor for detecting the position of the container relative to the camera, said camera being responsive to the position sensor for generating the image of the container approximately when the axis of symmetry of the container intersects the optical axis of the camera.

14. The system of claim 13 wherein the camera is responsive to the position sensor for generating the image of the container when the axis of symmetry of the container is generally coaxial with the optical axis of the camera.

15. The system of claim 1 for use with a lehr for annealing the container before inspection by the system, further comprising a feedback circuit for providing information representative of the detected defects, said lehr being controlled as a function of the information provided by the feedback circuit so that the defects may be corrected in containers subsequently annealed in the lehr.

16. The system of claim 1 for use with a container molding apparatus for forming the container, further comprising a feedback circuit for providing information representative of the detected defects, said container molding apparatus being controlled as a function of the information provided by the feedback circuit so that the defects may be corrected in containers subsequently formed by the container molding apparatus.

17. The system of claim 1 for use with another inspection apparatus for inspecting the container for defects, further comprising a feedback circuit for providing information representative of the detected defects from the system to the other inspection apparatus, said other inspection apparatus being controlled as a function of the information provided by the feedback circuit.

18. The system of claim 1 wherein the image processor defines a plurality of regions of interest in the image based on the size and shape of the container and wherein the image processor executes an edge detection routine for detecting edges in the image within one region of interest and executes a different edge detection routine for detecting edges in the image within another region of interest.

19. A method of inspecting a container for stress defects comprising:

positioning the container between a light source and a camera;

positioning a first polarizer between the light source and the container;

positioning a second polarizer between the container and the camera, said first and second polarizers each having an axis of transmission, said axes of transmission being non-parallel relative to each other;

illuminating the container with light provided by the light source;

polarizing the light illuminating the container with the first polarizer;

polarizing the light transmitted through the container to the camera with the second polarizer;

generating an image of the container with the camera, said image including a plurality of pixels, said pixels each having a value representative of an optical characteristic of the image;

scanning the image as a function of the pixel values to acquire edge data by which a portion of the container is identified in the image;

defining at least one region of interest in the image, said defined region having a size, shape and position based on the container portion identified in the image; and

processing the image as a function of the pixel values within the defined region to detect edges in the image which correspond to defects in the container.

20. The method of claim 19 wherein the steps of positioning the first and second polarizers includes positioning the axis of transmission of the first polarizer approximately perpendicular to the axis of transmission of the second polarizer.

21. The method of claim 19 further comprising the step of diffusing the light provided by the light source.

22. The method of claim 19 further comprising the step of filtering the light provided by the light source to reduce glare from the illuminated container.

23. The method of claim 19 further comprising the steps of polarizing the light illuminating the container with a third polarizer, polarizing the light transmitted through the container to a second camera with a fourth polarizer, and generating another image of the illuminated container with the second camera.

24. The method of claim 23 wherein each of the cameras has an optical axis and further comprising the step of positioning the cameras so that the optical axes are non-parallel relative to each other.

25. The method of claim 24 further comprising the step of positioning the cameras so that the optical axis of one of the cameras is generally perpendicular to an axis of symmetry of the container and the optical axis of the other camera is generally parallel to the axis of symmetry of the container.

26. The method of claim 23 further comprising the step of rotating the container before generating the other image of the illuminated container with the second camera.

27. The method of claim 19 further comprising the step of grouping the detected edges as a function of their locations in the image to define objects in the image, said defined objects each including one or more pixels, and the steps of storing information regarding defects in a memory and retrieving the stored information from the memory as a function of the defined objects.

28. The method of claim 19 wherein the pixel values correspond to the intensity of the pixels and wherein the step of detecting an optical characteristic of the image comprises detecting a gradient of the pixel values.

29. The method of claim 19 wherein the image generated by the camera includes an image of the bottom of the container and further comprising the step of approximately centering the defined region on the image of the bottom of the container.

30. The method of claim 29 wherein the step of defining the region includes defining a region having a generally circular periphery and an outer radius corresponding to the size of the container.

31. The method of claim 19 wherein the container has an axis of symmetry and the camera has an optical axis and further comprising the step of detecting the position of the container relative to the camera, said camera being responsive to the detected position for generating the image of the container approximately when the axis of symmetry of the container intersects the optical axis of the camera.

32. The method of claim 31 wherein the step of generating the image includes generating the image when the axis of symmetry of the container is generally coaxial with the optical axis of the camera.

33. The method of claim 19 for use with a lehr for annealing the container before inspection, further comprising the steps of providing information representative of the detected defects in the container and controlling the lehr as a function of the information so that the defects may be corrected in containers subsequently annealed in the lehr.

34. The method of claim 19 for use with a container molding apparatus for forming the container, further comprising the steps of providing information representative of the detected defects in the container and controlling the container molding apparatus as a function of the information so that the defects may be corrected in containers subsequently formed by the container molding apparatus.

35. The method of claim 19 for use with another inspection apparatus for inspecting the container for defects, further comprising the steps of providing information representative of the detected defects in the container to the other inspection apparatus and controlling the other inspection apparatus as a function of the information.

36. The method of claim 19 wherein the defining step comprises defining a plurality of regions of interest in the image based on the size and shape of the container and further comprising the step of executing an edge detection routine for detecting edges in the image within one region of interest and executing a different edge detection routine for detecting edges in the image within another region of interest.