Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1999-12-16
2002-03-05
Mancuso, Joseph (Department: 2623)
Image analysis
Applications
Manufacturing or product inspection
C382S286000, C382S197000
Reexamination Certificate
active
06353676
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to analyzing an acquired arrangement of object locations.
The usefulness of a product expected to include items or attributes in a predetermined arrangement is diminished by a defect relating to the arrangement. If the product is meant to be a component in another product, this defect may ruin the other product.
For this reason, products incorporating such items or attributes in such predetermined arrangements may be inspected for compliance with some standard. Examples of products appropriate for inspection include ball grid array devices, micro-ball grid arrays, flip chips, and chip-scale packages (together called “BGAs”). The contacts (i.e., electrical terminals) of a BGA are metallic balls that are mounted on one side of the device for forming electrical connections between an integrated circuit within the BGA and a printed circuit board.
The standard used in the inspection is typically created by manual entry of coordinates, by “golden template” sampling, by derivation from computer-aided design (“CAD”) data, or by some combination of these. According to the manual entry technique, a human operator uses a data entry device, such as a mouse or a keyboard, to specify x-y coordinates for the position of each object in the arrangement. Thus, manual entry can require considerable time. In golden template sampling, the positions of the objects in the standard are taken to be the positions found in an actual implementation of an ideal arrangement (e.g., an arrangement of balls of an actual BGA device). Golden template sampling may take less time than manual entry but may provide results that are less accurate. With respect to derivation from CAD data, the positions of the objects may be determined by software that automatically selects the positions in accordance with information about design goals, if such information is available.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention features a method for analyzing an acquired arrangement of object locations that imperfectly conforms to an ideal arrangement of points. The method includes finding sets of vectors in the acquired arrangement of object locations, and deriving a composite set of vectors from the sets of vectors.
Implementations of the invention may include one or more of the following features. At least one of the object locations may represent an electrical terminal. The method may further include deriving an approximation of the ideal arrangement of points from the acquired arrangement of object locations, wherein the approximation includes an indication of whether an intersection specified by the composite set of vectors corresponds to an object location. The method may further include determining vectors between an object location and a number of the object location's nearest neighboring points, or determining whether an object location matches, to an acceptable tolerance, a position specified by the composite set of vectors. The method may further include adjusting at least one of the vectors in the composite set to take into account a difference between the position specified and the actual position of the matching object location. The method may further include, based on the composite set of vectors and the actual position of the matching object location, specifying a location in which to search for another matching object location. The method may further include determining whether a non-matching object location matches, to an acceptable tolerance, another position specified by another composite set of the vectors.
In general, in another aspect, the invention features a system for detecting a pattern of discrete objects represented in an image. The system includes a location producer deriving an arrangement of object locations from the image, each object location representing an electrical terminal; a vectors producer deriving a set of vectors represented in the arrangement; a grid element producer deriving a two-vector grid element from the set of vectors; and a grid producer and grid element refiner testing the two-vector grid element against the arrangement of object locations and refining the two-vector grid element to take into account the actual positions of the object locations.
Among the advantages of the invention are one or more of the following. An effective approximation of an ideal regular pattern can be derived from a single golden template sample. Thus, in a case where direct information about the ideal pattern is unavailable (e.g., because CAD data is non-existent or inaccessible), the sample can be used as indirect information about the ideal pattern. In addition, the effective approximation can provide a standard that is sufficient for use in a quality control inspection system, which renders unnecessary the expense of time and resources involved in creating the standard by direct information. At least a portion of the standard can be stored in abbreviated form (e.g., a grid element to be repeated, and an on-off table), which can significantly reduce data storage requirements, especially in cases of large arrangements.
Other advantages and features will become apparent from the following description and from the claims.
REFERENCES:
patent: 5465152 (1995-11-01), Bilodeau
patent: 5550763 (1996-08-01), Michael
patent: 5574668 (1996-11-01), Beaty
patent: 5574801 (1996-11-01), Collet-Beillon
patent: 5592562 (1997-01-01), Rooks
patent: 5652658 (1997-07-01), Jackson
patent: 5694482 (1997-12-01), Maali et al.
patent: 5828449 (1998-10-01), King et al.
Deley et al., “Accurate Placement of Ball Grid Array Packages,” reprinted fromElectronic Packaging&Production, Apr. 1996, Cahners Publishing Company, Newton, MA, USA.
University of Waterloo Computer Graphics Lab, “Affine Transformations,” http://www.undergrad.math.uwaterloo.ca/~cs488/In.HTML/Affinenode4.html, pp. 1-3.
Thomas, Jr., “Chapter 14 Partial Differentiation,”Calculus and Analytic Geometry, 1953, pp. 481-532, Addison-Wesley Publishing Company, Inc., Cambridge, MA, USA.
Cognex Corporation, Chapter 7 Mathematics, Coordinate Transformation by Pseudoinverse,Cognex 3000/4000/5000 System Software, 1996, pp. 204-210, Revision 7.4 590-0134, Natick, MA.
Cognex Corporation, “Chapter 1 Searching, Correlation Searching,”Cognex 3000/4000/5000 Vision Tools, 1996, pp. 17-25, Revision 7.4 590-0136, Natick, MA.
Ballard, D.H., Generalizing the Hough Transform to Detect Arbitrary Shapes*,Pattern Recognition, 1981, pp. 111-122, vol. 13, No. 2, Pergamon Press Ltd., UK.
Carcappa, “On Improving BGA Reliability and Quality”, Surface Mount Technology, Jun. 1997, pp. 44-46.
Grimson et al., On the Sensitivity of the Hough Transform for Object Recognition,IEEE Transactions on Pattern Analysis and Machine Intelligence, Mar. 1990, pp. 255-274, vol. 12. No. 3.
Silver et al., “Practical Golden Template Comparison,”Cognex Corporation, Jun. 6, 1990, pp. 2-11, Needham, MA, USA.
“RVSI Vanguard VAi 5200/VAi 5300,” http://www.vai.net/products/prod02.htm, pp. 1-4.
“RVSI Vanguard Products,” http://www.vai.net/products/products.htm, pp. 1-2.
Bali Vikkram
Cognex Coporation
Mancuso Joseph
O'Dea Arthur J.
LandOfFree
Analyzing an acquired arrangement of object locations does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Analyzing an acquired arrangement of object locations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Analyzing an acquired arrangement of object locations will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2816531