Two-dimensional object recognition using chain codes, histogram normalization and trellis algorithm
First Claim
1. A classification processor for classifying an unknown two-dimensional object having a chain code by correlating an unknown object'"'"'s chain code histogram with stored chain code histograms of known two-dimensional objects comprising:
- means for generating a histogram from the unknown object'"'"'s chain code reflecting size and orientation of the unknown object;
means for correlating the generated histogram with a stored chain code histogram of a known object, comprising;
means for selecting a stored chain code histogram of a known object;
means for comparing the unkown object'"'"'s chain code histogram with the selected known object'"'"'s histogram in a vertical chain code histogram domain;
first means for generating a first correlation factor in the vertical domain to determine scaled size of the unknown object;
means for comparing the unknown object'"'"'s chain code histogram with the selected known object'"'"'s histogram in a horizontal chain code histogram domain;
second means for generating a second correlation factor in the horizontal domain to determine rotational orientation of the unknown object;
means for normalizing the known object'"'"'s chain code hostogram by shifting the known object'"'"'s chain code histogram horizontally and vertically as required to match a scaled size and a rotational orientation of the chain code histogram of a known object; and
means for applying a Viterbi algorithm for resolving a final ambiguity in deciding whether or not the generated histogram and the stored histogram are similar by processing the histograms with a distance function.
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Accused Products
Abstract
A system for classifying a two-dimensional object, the object having a boundary. The system includes a sensor for sensing the boundary of the object, a processor which assigns a chain code to the boundary of the object and memory for storing a plurality of chain code histograms corresponding to known two-dimensional objects. A histogram is generated from the object'"'"'s assigned chain code and correlated in the processor with a chain code histogram from memory. A final ambiguity between the normalized chain code of the object and the chain code of the correlating known object is resolved through application of a Viterbi algorithm.
97 Citations
10 Claims
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1. A classification processor for classifying an unknown two-dimensional object having a chain code by correlating an unknown object'"'"'s chain code histogram with stored chain code histograms of known two-dimensional objects comprising:
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means for generating a histogram from the unknown object'"'"'s chain code reflecting size and orientation of the unknown object; means for correlating the generated histogram with a stored chain code histogram of a known object, comprising; means for selecting a stored chain code histogram of a known object; means for comparing the unkown object'"'"'s chain code histogram with the selected known object'"'"'s histogram in a vertical chain code histogram domain; first means for generating a first correlation factor in the vertical domain to determine scaled size of the unknown object; means for comparing the unknown object'"'"'s chain code histogram with the selected known object'"'"'s histogram in a horizontal chain code histogram domain; second means for generating a second correlation factor in the horizontal domain to determine rotational orientation of the unknown object; means for normalizing the known object'"'"'s chain code hostogram by shifting the known object'"'"'s chain code histogram horizontally and vertically as required to match a scaled size and a rotational orientation of the chain code histogram of a known object; and means for applying a Viterbi algorithm for resolving a final ambiguity in deciding whether or not the generated histogram and the stored histogram are similar by processing the histograms with a distance function. - View Dependent Claims (2, 3)
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4. A method for classifying a two-dimensional object having a chain code by correlating the object'"'"'s chain code histogram with stored chain code histograms of known two-dimensional objects, with steps comprising:
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generating a chain code histogram from the unknown object'"'"'s chain code reflecting size and orientation of the unknown object, wherein the chain code assigned to a boundary of the object is assigned according to a chain code rule containing at least eight directional elements; correlating the generated chain code histogram with a stored chain code histogram of a known object, comprising; comparing the unknown object'"'"'s chain code histogram with a stored histogram of the known object in a vertical chain code histogram domain; generating a first correlation factor in the vertical domain to determine scaled size of the unknown object; comparing the unkown object'"'"'s cahin code histogram with a stored histogram of the known object in a horizontal chain code histogram domain; generating a second correlation factor in the horizontal domain to determine rotational orientation of the unkown object; comparing horizontal and vertical correlation factors with predetermined thresholds; providing results of comparisons of correlation factors, which indicate whether correlating of the unknown object'"'"'s chain code histogram of the known object should continue; and normalizing the unknown object'"'"'s chain code histogram and chain code; and applying a Viterbi algorithm for resolving a final ambiguity in deciding whether or not the generated histogram and the stored histogram are similar by processing the histograms with a distance function. - View Dependent Claims (5, 6)
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7. A system for classifying an unknown two-dimensional object, the object having a boundary, comprising:
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a sensor for sensing the boundary of the object; means for assigning a chain code to the boundary of the object according to a chain code rule containing at least eight directional elements; memory for storing a plurality of chain code histograms of known two-dimensional objects; means for generating a histogram from the assigned chain code reflecting size and orientation of the unknown object; means for correlating the generated histogram with a chain code histogram of a known object, comprising; means for selecting a stored chain code histogram of a known two-dimensional object from the memory; means for comparing the object'"'"'s chain code histogram with the selected histogram in a vertical chain code histogram domain; means for generating a first correlation factor in the vertical domain to determine scaled size of the unknown object; means for comparing the object'"'"'s chain code histogram with the selected histogram in a horizontal chain code histogram domain; a second means for generating a second correlation factor in the horizontal chain code histogram domain to determine rotational orientation of the unknown object; means for comparing first and second correlation factors with predetermined theresholds; and means for normalizing the object'"'"'s chain code histogram and chain code; and means for applying a Viterbi algorithm for resolving a final ambiguity in deciding whether or not the generated histogram and the stored histogram are similar in that the unknown object matches a known object represented by the stored histogram. - View Dependent Claims (8)
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9. A method for classifying an unknown two-dimensional object, the object having a boundary, with steps comprising:
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sensing the boundary of the object; assigning a chain code to the boundary of the object, according to a chain code rule containing at least eight directional elements; storing a plurality of chain code histograms of known two-dimensional objects; generating a chain code histogram from the assigned chain code reflecting size and orientation of the unknown object; correlating the generated histogram with a stored chain code histogram of a known object, comprising; selecting a histogram from the plurality of chain code histograms of known two-dimensional objects; comparing the object'"'"'s chain code histogram with the selected histogram in a vertical chain code histogram domain; generating a correlation factor in the vertical domain; comparing the object'"'"'s chain code histogram with the selected histogram in a horizontal histogram domain; generating a second correlation factor in the horizontal domain; comparing correlation factors with predetermined theresholds; and normalizing the object'"'"'s chain code histogram and chain code; and applying a Viterbi algorithm for resolving a final ambiguity in deciding whether or not the generated histogram and the stored histogram are similar in that the unknown object matches a known object represented by the stored histogram. - View Dependent Claims (10)
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Specification