Abstract: A system for decoding a bar code symbol receives a signal representative of the symbol and searches the signal in one dimension to locate two adjacent critical points corresponding to an element of the symbol. The system also computes a value representative of the signal energy between the two critical points and determines the width of the element in accordance with the value.A bar code symbol decoding system receives a signal representative of a bar code symbol having a plurality of characters, one of which is a checksum character. The system determines a first choice for each of the characters and a second choice for at least one of the characters from the signal. The system performs checksum analysis in accordance with the first choice for each of the characters. If that checksum analysis is not satisfied, then the system performs checksum analysis using the second choice.

Abstract: A system for detecting a bar code symbol receives a two-dimensional image containing the symbol, where the system has no a priori knowledge of the orientation of the symbol in the image. The system scans the image in one dimension to locate a quiet zone for the symbol and searches the image in one dimension to identify a start/stop character of the symbol. A system for decoding a bar code symbol having a plurality of elements receives a signal representative of the symbol. The system searches the signal along a first search step to characterize the width of one of the elements. The system then selects a second search step by projecting from the first search step onto a reference line, where the reference line is not parallel to either the first or second search steps. The system then searches the signal along the second search step to characterize the width of another of the elements. A system for decoding a bar code symbol having at least three elements receives a signal representative of the symbol.

Abstract: A system for finding a corner of an artifact in a two-dimensional pixel image selects an original seed pixel and generates a reference vector using the original seed pixel. The system selects a next seed pixel using the original seed pixel and generates a current vector using the next seed pixel. The system compares the current vector to the reference vector and selects a corner based on that comparison. Also a system for finding a corner of a bar code symbol in a two-dimensional pixel image selects a sequence of seed pixels, having a first seed pixel and a plurality of successive seed pixels, where each successive seed pixel is selected in accordance with the previous seed pixel in the sequence. The system generates a reference vector in accordance with the first seed pixel and generates a plurality of successive vectors, each in accordance with a successive seed pixel. The system compares the reference vector to each of the successive vectors and selects a corner in accordance with the comparison.

Abstract: A bar code reader decodes a bar code symbol, one character at a time, by analyzing the spaces of each character independently from the bars of each character. The reader determines the widths of each space and each bar. The reader then determines a space-width threshold based on the widths of the spaces and a bar-width threshold based on the widths of the bars. The reader then classifies each space as being either narrow or wide by comparing each space to the space-width threshold. The reader also classifies each bar as being either narrow or wide by comparing each bar to the bar-width threshold. The reader then decodes the character according to the narrow/wide classifications.

Abstract: A system for detecting a bar code symbol receives a two-dimensional image containing the symbol, where the system has no a priori knowledge of the orientation of the symbol in the image. The system scans the image in one dimension to locate a quiet zone for the symbol and searches the image in one dimension to identify a start/stop character of the symbol.

Abstract: A system for decoding a bar code symbol receives a signal representative of the symbol and searches the signal in one dimension to locate two adjacent critical points corresponding to an element of the symbol. The system also computes a value representative of the signal energy between the two critical points and determines the width of the element in accordance with the value.