Apparatus for automatically inspecting objects and identifying or recognizing known and unknown portions thereof, including defects and the like, and method

• US 4,893,346 A
• Filed: 09/02/1987
• Issued: 01/09/1990
• Est. Priority Date: 03/14/1985
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: B.E.L-Tronics, Inc. (Cedar Electronics Holdings Corp.)
• Inventors: Bishop, Robert
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US07/093,114
• Time in Patent Office: 860 Days
• Field of Search: 382/8, 382/55, 382/14, 382/30, 358/101, 358/106
• US Class Current: 382/147
• CPC Class Codes: G06T 2207/20036 Morphological image processing
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 7/001 using an image reference approach

Abstract

Apparatus and method for automatically inspecting objects and identifying or recognizing known and unknown portions thereof, including defects and the like, involving storing digital signal information representing an image of the desired predetermined object shapes to be learned by an image inspecting system and recognized during scanning of objects to be inspected, and modifying the stored digital signal information to create a fictitious image of the object shapes to be learned that incorporates acceptable size or dimension variations and the like in such objects such that during the inspecting of future objects, these acceptable variations will be ignored as defects or unknown elements.

Claims

1. A method of inspection of circuit board conductive shapes wherein digital signal information is stored representing desired shapes to be monitored in future board inspections, the method comprising, originally storing digital signal information representing images of desired predetermined object shapes to be learned;

predetermining at least one of acceptable size or dimension variations in such object shapes;

modifying the stored digital signal information to create a set of fictitious images of said object shapes to be learned that incorporates the acceptable variations therein;

storing the modified digital signal information representing said fictitious images; and

, during circuit board inspections, ignoring said acceptable variations as possible defects by responding to recognition of the acceptable variations in the said fictitious stored images.

2. A method as claimed in claim 1 and in which the said modifying of the originally stored digital signal information as to said size or dimension variations is effected by electronically removing or adding pixel signals to the stored digital signal information to represent a different size or dimension of the object shape.

3. A method as claimed in claim 1 and in which the said originally stored digital signal information includes information as to a conductor pad in which there may be a via hole, and further comprising monitoring the annular nature of a pad detected during said circuit board inspections to insure that a detected hole therein is an acceptable via hole, and, if the detected hole is an acceptable via hole, electronically adding pixel signals to the stored digital signal information in effect to fill in the detected hole to present a fictitious image of a solid conductor pad.

4. A method as claimed in claim 3 and in which said monitoring includes detecting both light reflected from the upper surface of the board and light transmitted through the annular pad from below the board.

5. A method as claimed in claim 4 and in which the light transmitted from below the board is coded to distinguish the same from that reflected from the upper surface of the board.

6. A method as claimed in claim 1 and in which the stored digital signal information includes information representing desired patterns and positions to be monitored in future board inspections, and wherein said method includes inspecting circuit boards to determine the presence of differences from said desired patterns and positions beyond predetermined tolerances, indicating such differences as defects, determining the x-y coordinate locations of such defects, producing separate pictures of local regions of inspected boards at which such defects are located, and producing accompanying recordings of the x-y coordinate locations of such defects.

7. Apparatus for inspection of circuit board conductive shapes wherein digital signal information is stored representing desired shapes to be monitored in future board inspections, the apparatus having, in combination, means for storing digital signal information originally representing images of desired predetermined object shapes to be learned;

means for predetermining at least one of acceptable size or dimension variations in such object shapes;

means for modifying the stored digital signal information to create a set of fictitious images of said object shapes to be learned that incorporates the acceptable variations therein;

means for storing the modified digital signal information representing said fictitious images; and

means operable during circuit board inspections, for ignoring said acceptable variations as possible defects by responding to recognition of the acceptable variations in the said fictitious stored images.

8. Apparatus as claimed in claim 7 and in which the said means for modifying the originally stored digital signal information as to said size or dimension variations is provided with means for electronically removing or adding pixel signals to the stored digital signal information to represent a different size or dimension of the object shape.

9. Apparatus as claimed in claim 7 and in which the said originally stored digital signal information includes information as to a conductor pad in which there may be a via hole, and said apparatus is provided with means for monitoring the annular nature of a pad detected during said circuit board inspections to insure that a detected hole therein is an acceptable via hole, and means for electronically adding pixel signals to the stored digital signal information representing an acceptable via hole in effect to fill in the hole to present a fictitious image of a solid conductor pad.

10. Apparatus as claimed in claim 9 and in which said means for monitoring includes means for detecting both light reflected from the upper surface of the board and light transmitted through the annular pad from below the board.

11. Apparatus as claimed in claim 10 and in which means is provided for coding the light transmitted from below the board to distinguish the same from that reflected from the upper surface of the board.

12. An apparatus as claimed in claim 8, and which the said means for electronically removing or adding pixel signals comprises delay line means connected to receive digital signal information to be stored and delay units connected to the delay line means and to address line inputs of read only memory means to create a matrix of delayed pixel signals, and means for outputting from the read only memory means new computed values representing the removal or adding of pixel signals at a boundary edge of a stored image.

13. Apparatus as claimed in claim 7 in which said means for storing digital signal information stores digital signal information representing desired patterns and positions to be monitored in future board inspections, and in which said apparatus includes means for inspecting circuit boards to determine the presence of differences from said desired patterns and positions beyond predetermined tolerances and for indicating such differences as defects, means for determining the x-y coordinate locations of said defects, means for producing separate pictures of local regions of inspected boards at which said defects are located, and means for producing accompanying recordings of the x-y coordinate board locations of said defects.

14. A method of inspection of circuit board conductor shapes wherein digital signal information is stored representing shapes to be monitored in future board inspections, the method comprising, storing digital signal information representing an image of a predetermined object shape to be learned;

predetermining size variations in said shape that are acceptable to the inspection;

electronically removing or adding pixel signals to the stored image information to provide modified digital signal information representing a set of images corresponding to different sizes of said object shape, and storing said modified digital signal information.

15. A method as claimed in claim 14 and in which the further steps are performed of scanning further boards to be inspected and detecting signal information at the top of said board corresponding to the object shapes on the board, and recognizing the predetermined shapes within the limits of the stored said different size.

16. A method as claimed in claim 14 and in which said object shape comprises a linear strip and the said electronically removing pixel step provides stored image information of a thinner linear strip acceptable to the inspection process.

17. A method as claimed in claim 14 and in which said object shape is of a curved form and the said electronically adding pixel step provides stored image information of a larger curved form acceptable to the inspection process.

18. A method as claimed in claim 17 and in which said objects comprise discs or pads, one disposed on each side of a translucent or light-transmitting surface in substantial vertical alignment, and the further step is performed of generating a strip of substantially uniform-intensity light beneath said surface, removing infra-red or other spectral energy from said light, and thereafter directing the remaining light through said surface from a position adjacent the rear side of said surface;

said electronically adding pixel step providing stored image information of a larger disc or pad corresponding to acceptable variation in vertical mis-alignment of the discs of pads on opposite sides of said surface.

19. A method as claimed in claim 18 and in which said discs or pads are conductive pads and said translucent surface is a circuit board mounting said pads.

20. A method of inspection of circuit board conductive shapes wherein digital signal information is stored representing desired shapes to be monitored in future board inspections, the method comprising originally storing digital signal information representing images of desired predetermined object shapes, said information including information as to a conductor pad in which there may be a via hole;

and, during the inspecting of boards, monitoring the annular nature of a detected pad to insure that any detected hole therein is an acceptable via hole, and, if the detected hole is an acceptable via hole, electronically adding pixel signals to the stored digital information in effect to fill in the hole to present a fictitious image of a solid conductor pad.

21. A method as claimed in claim 20 and in which said monitoring includes detecting both light reflected from the upper surface of an inspected board and light transmitted through a pad from below the board.

22. A method as claimed in claim 21 and in which the light transmitted from below the board is coded to distinguish the same from that reflected from the upper surface of the board.

23. Apparatus for inspection of circuit board conductive shapes wherein digital signal information is stored representing desired shapes to be monitored in future board inspections, the apparatus having, in combination, means for storing digital signal information representing images of desired predetermined object shapes and including signal information as to a conductor pad in which there may be a via hole, means operable during the inspecting of boards for monitoring the annular nature of a detected pad to insure that any hole detected therein is an acceptable via hole, and means for electronically adding pixel signals to the stored digital signal information representing a detected acceptable via hole in effect to fill in the hole to present a fictitious image of a solid conductor pad.

24. Apparatus as claimed in claim 23 and in which said means for monitoring includes means for detecting both light reflected from the upper surface of an inspected board and light transmitted through a pad from below the board.

25. Apparatus as claimed in claim 24 and in which means is provided for coding the light transmitted from below the inspected board to distinguish that light from light reflected from the upper surface of the inspected board.

26. A method of inspection of circuit board conductive patterns and positions wherein digital signal information is stored representing desired patterns and positions to be monitored in subsequent circuit board inspections, the method comprising, storing digital signal information representing desired patterns and positions, inspecting circuit boards to determine the presence of differences from said desired patterns and positions beyond predetermined tolerances, indicating such differences as defects, determining the x-y coordinate locations of said defects, producing separate pictures of local regions of circuit boards at which said defects are located, and producing accompanying recordings of the x-y coordinate locations of said defects.

27. A method as claimed in claim 26, comprising employing an x-y coordinate table and said pictures to locate said defects.

28. Apparatus for inspection of circuit board conductive patterns and positions wherein digital signal information is stored representing desired patterns and positions to be monitored in subsequent board inspections, the apparatus having, in combination, means for storing digital signal information representing desired patterns and positions, means for inspecting circuit boards to determine the presence of differences from said desired patterns and positions beyond predetermined tolerances and for indicating such differences as defects, means for determining the x-y coordinate locations of said defects, means for producing separate pictures of local regions of circuit boards at which said defects are located, and means for producing accompanying recordings of the x-y coordinate locations of said defects.

29. Apparatus as claimed in claim 28 and in which said apparatus includes an x-y coordinate table employing said pictures to locate said defects.