Maxicode data extraction using spatial domain features
First Claim
1. A method of extracting data from a dataform having a pattern of rows of similarly aligned dark and light data cells of a regular polygon shape each having the same width between two parallel sides, comprising the steps of:
- (a) providing pixel data for an image area, said pixel data representative of illumination reflected from said data cells of a regular polygon shape; and
(b) sampling said pixel data to identify a traversal line of pixel data characterized by illumination value transitions spaced along said traversal line at integral multiples of said data cell width, said traversal line thereby being nominally normal to sides of a sequence of dark and light data cells.
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Accused Products
Abstract
Prior methods of reading MaxiCode dataforms have been subject to reduced resolution image scaling and processing and speed constraints of Fourier transform computations. Described spatial domain data extraction methods provide bull'"'"'s eye center location by T-sequence pixel pattern analysis, axis identification by moment analysis of data cell pairs, and integral width square wave analysis of illumination transitions to avoid reading-line cell fragmentation. The center and top of a MaxiCode are identified in high-resolution pixel data, without scaling reduction or Fourier type frequency domain processing. Data is extracted serially from rows of data cells by sampling along lines of pixels aligned by fragmentation analysis so as to traverse complete rows of data cells. Dynamic thresholding accurately defines illumination value transitions between adjacent linear groups of data cells, each group consisting of one or more data cells of the same reflectivity. Application of disclosed methods to other types of dataforms is described.
189 Citations
17 Claims
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1. A method of extracting data from a dataform having a pattern of rows of similarly aligned dark and light data cells of a regular polygon shape each having the same width between two parallel sides, comprising the steps of:
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(a) providing pixel data for an image area, said pixel data representative of illumination reflected from said data cells of a regular polygon shape; and (b) sampling said pixel data to identify a traversal line of pixel data characterized by illumination value transitions spaced along said traversal line at integral multiples of said data cell width, said traversal line thereby being nominally normal to sides of a sequence of dark and light data cells. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of extracting data from a dataform having a pattern of rows of similarly aligned polygonal data cells of a regular polygon shape and of differing reflectivity values, comprising the steps of:
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(a) providing pixel data for an image area, said pixel data representative of illumination reflected from said data cells of a regular polygon shape; (b) determining the derived moment of a contiguous group of data cells of the same reflectivity value, by moment analysis of a portion of said pixel data; and (c) determining the orientation of at least one dataform axis, said orientation corresponding to said derived moment. - View Dependent Claims (9, 10)
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11. A method of extracting data from a dataform having a pattern of rows of similarly aligned polygonal data cells of a regular polygon shape and of differing reflectivity values, comprising the steps of:
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(a) providing pixel data for an image area, said pixel data representative of illumination reflected from said data cells; (b) identifying a reference line defined by moment analysis of a portion of said pixel data, based on the derived moment of a contiguous group of data cells of the same reflectivity value; and (c) determining the orientation of at least one dataform axis, said axis aligned with said reference line. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification