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Three Sensor Bar Code Scanner Using Sensor Spacing as a Reference

IP.com Disclosure Number: IPCOM000082475D
Original Publication Date: 1974-Dec-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Kulikowski, RJ: AUTHOR [+2]

Abstract

Retrospective pulse modulated bars and spaces of width d and 2d, which represent a binary "1" if an adjacent bar and space are of the same width and a binary "0" if an adjacent bar and space are of different widths, can be scanned by a hand-held scanner having three sensor apertures of negligible width which are spaced d and 2.5d apart from each other.

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Three Sensor Bar Code Scanner Using Sensor Spacing as a Reference

Retrospective pulse modulated bars and spaces of width d and 2d, which represent a binary "1" if an adjacent bar and space are of the same width and a binary "0" if an adjacent bar and space are of different widths, can be scanned by a hand-held scanner having three sensor apertures of negligible width which are spaced d and 2.5d apart from each other.

Fig. 1 shows circuitry for implementing a three-sensor method of decoding this form of retrospective pulse modulation. Bar and space edge detectors 11 through 21 detect leading edge transitions as bars and spaces pass under sensors A, B, and C which are located in scanner 10, as shown in Fig. 2.

Fig. 2 also shows waveforms in time relationship with the signals generated at sensor A for the other sensors B and C, and the outputs of the edge detectors AB through CS as well as bar flip-flop 23 and space flip-flop 25.

Bar flip-flop 23 is toggled by the output of OR gate 27 whenever the leading edge of a bar is detected at sensor B or at sensor C. Likewise, space flip-flop 25 is toggled by the output of OR gate 29 whenever the leading edge of a space is detected at sensor B or at sensor C.

Sensor A provides properly timed reference signals to OR gate 31 to generate a data clock signal and to AND gates 33 through 39, which sample the contents of bar and space flip-flops 23 and 25 to determine whether a 1 or a 0 has been encoded.

AND gates 33 and 35 detect...