ANALOG WAVEFORM DECODER
UTILIZING HISTOGRAM OF EDGE SIZES
 Inventors: Eugene B. Joseph; Theodosios Pavlidis, both of Setauket, N.Y.
 Assignee: Symbol Technologies, Inc., Bohemia, N.Y.
 Appl. No.: 96,579
 Filed: Jul. 23, 1993
Related U.S. Application Data
 Continuation of Ser. No. 759,332, Sep. 13, 1991, abandoned.
 Int. CI.* G06K 7/10
 U.S. CI 235/462; 235/463
 Field of Search 235/462, 454, 463, 470
 References Cited
U.S. PATENT DOCUMENTS
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Primary Examiner—Donald Hajec
Assistant Examiner—Jeffrey R. Filipek
A method for decoding information contained in an analog waveform representative of a bar code symbol comprising the steps of identifying a decodable portion of an analog waveform; processing said decodable portion to obtain a plurality of waveform descriptors; and performing a high and low density decoding process to one or more of said plurality of waveform descriptors for decoding information contained in either a high or low density symbol respectively, is disclosed. The high density decoder used for decoding high density symbols utilizes extrema extents, i.e., areas of the peaks and valleys of the analog waveform which directly correlate to the size of the bars/spaces of a high density bar code. After locating the seed point of the waveform, each extrema extent is generated and thresholded at each peak/valley location to decide its size. The high density decoder is adaptive in that the thresholding extent value is updated as the solution grows away from the seed point. The low density decoder used for decoding low density symbols utilizes the widths of the peaks/valleys for decoding purposes and utilizes a histogramming and backtracking technique for removing noise levels from the analog waveform. Backtracking allows another decode attempt to be made if one is unsuccessful.
38 Claims, 11 Drawing Sheets