Fast high-accuracy multi-dimensional pattern inspection
DCFirst Claim
1. A tunable boundary detector for detecting features in a source image, the boundary detector comprising:
- a tunable low-pass filter for filtering the source image to provide a filtered image;
an adjustable image sub-sampler for sub-sampling the filtered image to provide a sub-sampled image; and
an edge detector for detecting edges in the sub-sampled image to provide edges, each edge having an edge position, a gradient magnitude, and a gradient direction wherein the edge detector includes a peak detector configured to use the gradient magnitude and the gradient direction to identify points where the gradient magnitude is a local maximum.
1 Assignment
Litigations
0 Petitions
Reexamination
Accused Products
Abstract
A method and apparatus are provided for identifying differences between a stored pattern and a matching image subset, where variations in pattern position, orientation, and size do not give rise to false differences. The invention is also a system for analyzing an object image with respect to a model pattern so as to detect flaws in the object image. The system includes extracting pattern features from the model pattern; generating a vector-valued function using the pattern features to provide a pattern field; extracting image features from the object image; evaluating each image feature, using the pattern field and an n-dimensional transformation that associates image features with pattern features, so as to determine at least one associated feature characteristic; and using at least one feature characteristic to identify at least one flaw in the object image. The invention can find at least two distinct kinds of flaws: missing features, and extra features. The invention provides pattern inspection that is faster and more accurate than any known prior art method by using a stored pattern that represents an ideal example of the object to be found and inspected, and that can be translated, rotated, and scaled to arbitrary precision much faster than digital image re-sampling, and without pixel grid quantization errors. Furthermore, since the invention does not use digital image re-sampling, there are no pixel quantization errors to cause false differences between the pattern and image that can limit inspection performance.
38 Citations
30 Claims
-
1. A tunable boundary detector for detecting features in a source image, the boundary detector comprising:
-
a tunable low-pass filter for filtering the source image to provide a filtered image; an adjustable image sub-sampler for sub-sampling the filtered image to provide a sub-sampled image; and an edge detector for detecting edges in the sub-sampled image to provide edges, each edge having an edge position, a gradient magnitude, and a gradient direction wherein the edge detector includes a peak detector configured to use the gradient magnitude and the gradient direction to identify points where the gradient magnitude is a local maximum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
-
-
27. A tunable boundary detector for detecting features in a source image, the boundary detector comprising:
-
a tunable low-pass filter for filtering the source image to provide a filtered image; a gradient estimator configured to provide an estimate of horizontal and vertical components of image gradient at each pixel position; a Cartesian-to-polar converter configured to convert each estimate of horizontal and vertical components of image gradient into an estimate of gradient magnitude and gradient direction; a peak detector configured to use each estimate of gradient magnitude and gradient direction to identify points where the gradient magnitude is a local maximum, and to provide for each such point a column number, a row number, a gradient magnitude and a gradient direction; and a sub-pixel interpolator configured to use each column number, row number, gradient magnitude and gradient direction to provide for each such point a vertical component of real valued edge position, a horizontal component of real valued edge position, a gradient magnitude, and a gradient direction. - View Dependent Claims (28)
-
-
29. A tunable boundary detection method for detecting features in a source image, the method comprising:
-
filtering the source image to provide a filtered image; providing an estimate of horizontal and vertical components of image gradient at each pixel position; converting each estimate of horizontal and vertical components of image gradient into an estimate of gradient magnitude and gradient direction; using each estimate of gradient magnitude and gradient direction to identify points where the gradient magnitude is a local maximum, and to provide for each such point a column number, a row number, a gradient magnitude and a gradient direction; and using each column number, row number, gradient magnitude, and gradient direction to provide for each such point a vertical component of real valued sub-pixel edge position, a horizontal component of real valued sub-pixel edge position, a gradient magnitude, and a gradient direction. - View Dependent Claims (30)
-
Specification