Locating shapes in two-dimensional space curves

Details Locating shapes in two-dimensional space curves Locating shapes in two-dimensional space curves

1996-01-02

1998-05-12

Couso, Jose L.

Image analysis

Pattern recognition

Feature extraction

G06K 748

Patent

active

057518530

ABSTRACT:
A method is provided for finding a feature of an object by finding at least one instance of a model two-dimensional space curve that represents the feature within a target two-dimensional space curve that represents at least a portion of the object. Unlike previous methods for finding a two-dimensional space curve within another two-dimensional space curve, the method of the invention is able to find any shape at any orientation or position in the two-dimensional space curve. The model and target two-dimensional space curves each include a plurality of points. Each point is characterized by a position in two dimensions, where the position is a function of distance S along the two-dimensional space curve. For each of the plurality of points of the two-dimensional space curve, the position in two dimensions as a function of distance S is converted into an angle as a function of distance S to provide an angle-based space curve. Then, at run-time, the angle-based model space curve is used to find at least one position along the angle-based target space curve that results in a match metric value that exceeds a match threshold. To provide invariance with respect to rotation, translation, and scaling, it is preferred to use normalized correlation as the match metric. The method of the invention can be used to find the notch or flat on the perimeter of a semiconductor wafer.

REFERENCES:
patent: 4183013 (1980-01-01), Agrawala et al.
patent: 4712248 (1987-12-01), Hongo
patent: 4731858 (1988-03-01), Grasmueller et al.
patent: 4910786 (1990-03-01), Eichel

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