CLASSIFICATION METHOD AND APPARATUS FOR PATTERN RECOGNITION SYSTEMS

• US 3,638,188 A
• Filed: 10/17/1969
• Issued: 01/25/1972
• Est. Priority Date: 10/17/1969
• Status: Expired due to Term

• Current Assignee: Glenn E. Tisdale, Peter H. Pincoffs
• Original Assignee: Glenn E. Tisdale, Peter H. Pincoffs
• Inventors: Pincoffs, Peter H., Tisdale, Glenn E.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US04/867,247
• Time in Patent Office: 830 Days
• Field of Search: 340/146.3,172.5 235/15R
• US Class Current: 382/225
• CPC Class Codes: G06V 10/40 Extraction of image or video features

Abstract

Features are extracted from a two-dimensional image for subsequent classification of patterns within the image according to correspondence between the extracted features and reference features in a set extracted previously from known patterns. In extracting the features, measurements are first taken of observed characteristics of the image about two or more predefined points in the image, these measurements being chosen to be invariant regardless of orientation, scale, and position of the pattern in the image. The measurements, along with data regarding relative positions of the selected points, constitute the features from which eventual pattern recognition may be achieved. In the classification procedure, the features extracted from the image are compared with reference features for a set of known pattern classes, in order to classify any unknown pattern that may be present within the image and that is associated with at least some of the extracted features.

Claims

1. A method of classifying unknown patterns that may be present in an image according to features extracted from the image wherein points of substantial information contained within the image are accepted as image points and the geometric relationship of the accepted image points is measured, and further measurements are made which are invariant with respect to orientation, scale and position of any unknown pattern that may be associated with the image, with regard to said accepted image points, comprising:

comparing said invariant measurements with reference invariant values similarly extracted from each of a plurality of known patterns and determining if correspondence within allowable tolerances exists between said invariant measurements and the reference invariant values of a given reference pattern, and, if said correspondence exists, normalizing the measurements indicative of the geometrical relationship of said image points of the unknown pattern with respect to the reference values indicative of the geometrical relationship of points in the given reference pattern for determining if correspondence exists with regard to orientation and scale, within allowable tolerances, between the measurements of the unknown pattern and the corresponding values of the given reference pattern, and classifying any such unknown pattern in the image under consideration on the basis of the greatest acceptable degree of correspondence between a plurality of extracted features of said image and reference features of said known patterns.

2. The method of claim 1 wherein said image points are chosen as occurring at positions of marked contrast to the remainder of the image.

3. The method of claim 1 wherein at least some of said invariant measurements correspond to the orientation of lines emanating from accepted image points relative to the geometrical relationships of said image points.

4. The method of claim 1 wherein at least some of said invariant measurements correspond to the color or intensity of color at some of said accepted image points.

5. The method of claim 1 wherein at least some of said measurements correspond to the gradients of gray scale intensity relative to some of said accepted image points.

6. The method of claim 1 wherein said invariant measurements correspond to the orientation of line segments in said image emanating from said accepted image points relative to the geometrical relationships of said accepted image points.

7. The method of claim 1 wherein said step of classifying is performed by preparing clusters representative of the degree of correspondence between the extracted features of said image and reference features for each known pattern class.

8. Apparatus for classifying unknown patterns that may be present in an image according to features extracted from the image wherein points of substantial information contained within the image are accepted as image points and the geometric relationship of the accepted image points is measured, and further measurements are made which are invariant with respect to orientation, scale and position of any unknown pattern that may be associated with the image, with regard to said accepted image points, comprising:

means storing reference invariant values extracted from reference features of classes of known patterns, means responsive to said invariant measurements for comparison with said reference invariant values, means responsive to correspondence within allowable tolerances between said invariant measurements and said reference invariant values of a given reference pattern to normalize the measurements indicative of the geometrical relationship of said image points of the unknown pattern with respect to the reference values indicative of the geometrical relationship of points in the given reference pattern, and means responsive to said normalization and to said comparison for forming a cluster indicative of the number of matches including at least an acceptable number thereof, between the reference features for a particular class of known patterns and said features extracted from said image, and indicative of the scale and orientation of an associated unknown pattern, relative to said particular class of known patterns, as a basis for comparison with other such clusters indicative of respective number of matches relative to other classes of known patterns.

9. The apparatus according to claim 8 further comprising:

means responsive to all of said clusters for comparison thereof to determine the class of known patterns with which the extracted features of the image show the greatest degree of match.

10. The apparatus according to claim 8 wherein at least some of said invariant measurements correspond to the orientation of lines emanating from accepted image points relative to the geometrical relationships of said image points.

11. The apparatus according to claim 8 wherein at least some of said invariant measurements correspond to the color or intensity of color at some of said accepted image points.

12. The apparatus according to claim 8 wherein at least some of said measurements correspond to the gradients of gray scale intensity relative to some of said accepted image points.

13. The apparatus according to claim 8 wherein said invariant measurements correspond to the orientation of line segments in said image emanating from said accepted image points relative to the geometrical relationships of said accepted image points.