Method and apparatus for locating patterns in an optical image
First Claim
1. An apparatus for identifying a linear pattern, having an expected radius less than or equal to a value r, in an image signal, I, said apparatus comprising:
- A. projection means for generating a projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of said linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along said axis,B. mirror symmetry filter means, coupled with said projection means, responsive to said radius and said projection signal for filtering that projection signal to generate a mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein,wherein said mirror symmetry filter means includes means for filtering said projection signal P to generate two mirror symmetry signals, S1 and S2, wherein each signal S1, S2 is representative of the degree of symmetry of the projection signal P about each point therein, and wherein each signal S1, S2 is out of phase with the other,C. notch detection means, coupled with said mirror symmetry filter means, for operating on said mirror symmetry signal with a selected mask to generate a peak location signal emphasizing a peak in said mirror symmetry signal corresponding to a location of a center of said linear pattern, andD. peak locating means, coupled with said notch detection means, for identifying a peak in said peak location signal, and for estimating from a location of that peak a location of a center of said linear pattern.
0 Assignments
0 Petitions
Accused Products
Abstract
The invention provides methods and apparatus for processing an image to identify the position of a linear pattern--for example, a line or a cross-hair comprising a plurality of intersecting lines. The system performs a first processing step for generating a projection of the image along axes aligned with an expected position of the linear patterns. A second processing step performs a mirror symmetry filtering on the projection to bring out a single peak corresponding to the center of the linear pattern. To further isolate that peak, the system performs a further filtering operation to remove peaks of lesser slope angle, so that only a highly sloped spike corresponding to the linear pattern will remain. The position of the center that peak corresponds to the center of the linear pattern in the original input signal.
-
Citations
16 Claims
-
1. An apparatus for identifying a linear pattern, having an expected radius less than or equal to a value r, in an image signal, I, said apparatus comprising:
-
A. projection means for generating a projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of said linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along said axis, B. mirror symmetry filter means, coupled with said projection means, responsive to said radius and said projection signal for filtering that projection signal to generate a mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, wherein said mirror symmetry filter means includes means for filtering said projection signal P to generate two mirror symmetry signals, S1 and S2, wherein each signal S1, S2 is representative of the degree of symmetry of the projection signal P about each point therein, and wherein each signal S1, S2 is out of phase with the other, C. notch detection means, coupled with said mirror symmetry filter means, for operating on said mirror symmetry signal with a selected mask to generate a peak location signal emphasizing a peak in said mirror symmetry signal corresponding to a location of a center of said linear pattern, and D. peak locating means, coupled with said notch detection means, for identifying a peak in said peak location signal, and for estimating from a location of that peak a location of a center of said linear pattern. - View Dependent Claims (3, 4)
-
-
2. An apparatus for identifying a cross-hair comprising a plurality of intersecting linear patterns, having expected radii less than or equal to a value r, in an image signal, I, said apparatus comprising:
-
A. projection means for a generating, for each of said linear patterns, a corresponding projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of that linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along the respective axis, B. mirror symmetry filter means, coupled with said projection means, and responsive to said radius and each said projection signal, for filtering that projection signal to generate a corresponding mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, wherein said mirror symmetry filter means includes means for filtering said projection signal P to generate two mirror symmetry signals, S1 and S2, wherein each signal S1, S2 is representative of the degree of symmetry of the projection signal P about each point therein, and wherein each signal S1, S2 is out of phase with the other, C. notch detection means, coupled with said mirror symmetry filter means, for operating on each said mirror symmetry signal with a selected mask to generate a corresponding peak location signal emphasizing a peak in each said mirror symmetry signal corresponding to a location of a center of the corresponding linear pattern, D. peak locating means, coupled with said notch detection means, for identifying a peak in each said peak location signal, and for estimating from a location of that peak a location of a center of the corresponding linear pattern, and E. center point locating means, coupled with said peak locating means, for determining the center of said cross-hair pattern to lie at an intersection of the estimated locations of said linear patterns.
-
-
5. An apparatus for identifying a linear pattern, having an expected radius less than or equal to a value r, in an image signal, I, said apparatus comprising:
-
A. projection means for generating a projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of said linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along said axis, B. mirror symmetry filter means, coupled with said projection means, responsive to said radius and said projection signal for filtering that projection signal to generate a mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, C. notch detection means, coupled with said mirror symmetry filter means, for operating on said mirror symmetry signal with a selected mask to generate a peak location signal emphasizing a peak in said mirror symmetry signal corresponding to a location of a center of said linear pattern, wherein said notch detection means includes means for operating on said mirror symmetry signal S with a selected mask in accord with the mathematical function ##EQU8## where N, P and Z are elements of said mask, each of respective lengths n, p and z, and D. peak locating means, coupled with said notch detection means, for identifying a peak in said peak location signal, and for estimating from a location of that peak a location of a center of said linear pattern. - View Dependent Claims (7, 8)
-
-
6. An apparatus for identifying a cross-hair comprising a plurality of intersecting linear patterns, having expected radii less than or equal to a value r, in an image signal, I, said apparatus comprising:
-
A. projection means for a generating, for each of said linear patterns, a corresponding projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of that linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along the respective axis, B. mirror symmetry filter means, coupled with said projection means, and responsive to said radius and each said projection signal, for filtering that projection signal to generate a corresponding mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, C. notch detection means, coupled with said mirror symmetry filter means, for operating on each said mirror symmetry signal with a selected mask to generate a corresponding peak location signal emphasizing a peak in each said mirror symmetry signal corresponding to a location of a center of the corresponding linear pattern, wherein said notch detection means includes means for operating on said mirror symmetry signal S with a selected mask in accord with the mathematical function ##EQU9## where N, P and Z are elements of said mask, each of respective lengths n, p and z, and D. peak locating means, coupled with said notch detection means, for identifying a peak in each said peak location signal, and for estimating from a location of that peak a location of a center of the corresponding linear pattern, and E. center point locating means, coupled with said peak locating means, for determining the center of said cross-hair pattern to lie at an intersection of the estimated locations of said linear patterns.
-
-
9. A method for identifying a linear pattern having an expected radius less than or equal to a value r, in an image signal, I, said method comprising:
-
A. a projection step for generating a projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of said linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along said axis, B. a mirror symmetry filter step responsive to said radius and said projection signal for filtering that projection signal to generate a mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, wherein said mirror symmetry filter step includes a step for filtering said projection signal P to generate two mirror symmetry signals, S1 and S2, wherein each signal S1, S2 is representative of the degree of symmetry of the projection signal P about each point therein, and wherein each signal S1, S2 is out of phase with the other, C. a notch detection step for operating on said mirror symmetry signal with a selected mask to generate a peak location signal emphasizing a peak in said mirror symmetry signal corresponding to a location of a center of said linear pattern, and D. a peak locating step for identifying a peak in said peak location signal, and for estimating from a location of that peak a location of a center of said linear pattern.
-
-
10. A method for identifying a cross-hair comprising a plurality of intersecting linear patterns, having expected radii less than or equal to a value r, in an image signal, I, said method comprising:
-
A. a projection step for a generating, for each of said linear patterns, a corresponding projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of that linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along the respective axis, B. a mirror symmetry filter step for responding to said radius and each said projection signal for filtering that projection signal to generate a corresponding mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, wherein said mirror symmetry filter step includes a step for filtering said projection signal P to generate two mirror symmetry signals, S1 and S2, wherein each signal S1, S2 is representative of the degree of symmetry of the projection signal P about each point therein, and wherein each signal S1, S2 is out of phase with the other, C. a notch detection step for operating on each said mirror symmetry signal with a selected mask to generate a corresponding peak location signal emphasizing a peak in each said mirror symmetry signal corresponding to a location of a center of the corresponding linear pattern, D. a peak locating step for identifying a peak in each said peak location signal, and for estimating from a location of that peak a location of a center of the corresponding linear pattern, and E. a center point locating step for determining the center of said cross-hair pattern to lie at an intersection of the estimated locations of said linear patterns. - View Dependent Claims (11, 12)
-
-
13. A method for identifying a linear pattern, having an expected radius less than or equal to a value r, in an image signal, I, said method comprising:
-
A. a projection step for generating a projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of said linear pattern, where said projection signal, P, is comprised of elements Pi, wherein i is an integer between 1 and a length of said image signal along said axis, B. a mirror symmetry filter step responsive to said radius and said projection signal for filtering that projection signal to generate a mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, C. a notch detection step for operating on said mirror symmetry signal with a selected mask to generate a peak location signal emphasizing a peak in said mirror symmetry signal corresponding to a location of a center of said linear pattern, wherein said notch detection means includes means for operating on said mirror symmetry signal S with a selected mask in accord with the mathematical function ##EQU12## where N, P and Z are elements of said mask, each of respective lengths n, p and z, and D. a peak locating step for identifying a peak in said peak location signal, and for estimating from a location of that peak a location of a center of said linear pattern. - View Dependent Claims (15, 16)
-
-
14. A method for identifying a cross-hair comprising a plurality of intersecting linear patterns, having expected radii less than or equal to a value r, in an image signal, I, said method comprising:
-
A. a projection step for a generating, for each of said linear patterns, a corresponding projection signal, P, representative of a projection of said image signal along an axis substantially aligned with an expected orientation of that linear pattern, where said projection signal, P, is comprised of elements Pi, where i is an integer between 1 and a length of said image signal along the respective axis, B. a mirror symmetry filter step for responding to said radius and each said projection signal for filtering that projection signal to generate a corresponding mirror symmetry signal, S, representative of the degree of symmetry of the projection signal P about each point therein, C. a notch detection step for operating on each said mirror symmetry signal with a selected mask to generate a corresponding peak location signal emphasizing a peak in each said mirror symmetry signal corresponding to a location of a center of the corresponding linear pattern, wherein said notch detection means includes means for operating on said mirror symmetry signal S with a selected mask in accord with the mathematical function ##EQU13## where N, P and Z are elements of said mask, each of respective lengths n, p and z, and D. a peak locating step for identifying a peak in each said peak location signal, and for estimating from a location of that peak a location of a center of the corresponding linear pattern, and E. a center point locating step for determining the center of said cross-hair pattern to lie at an intersection of the estimated locations of said linear patterns.
-
Specification