Classifications

• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
  • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
  • G06K7/14—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation using light without selection of wavelength, e.g. sensing reflected white light
  • G06K7/1404—Methods for optical code recognition
  • G06K7/146—Methods for optical code recognition the method including quality enhancement steps
  • G06K7/1465—Methods for optical code recognition the method including quality enhancement steps using several successive scans of the optical code
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
  • G02B26/10—Scanning systems
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
  • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
  • G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
  • G06K7/10792—Special measures in relation to the object to be scanned
• • G—PHYSICS
  • G06—COMPUTING OR CALCULATING; COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
  • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
  • G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
  • G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
  • G06K7/10851—Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device

Definitions

• the present invention relates to barcode reading techniques, and more particularly, to a method and system for sensing a barcode, especially when the resolution of the signal is low and/or the noise is large.
• an analog optical signal obtained by a barcode reader or scanner is usually digitized by a digitizer into a digital signal, e.g., into a square wave form.
• a proper threshold (gate level) of the digitizer is adopted so as to effectively separate the signal from the noise, as shown in Figs. Ib-If in which various scenarios are schematically illustrated.
• the digitized results 3 and 4 correspond to the higher and lower thresholds 2 and 1 respectively.
• both higher and lower thresholds 2 and 1 can generate correct result 3, 4 (see Fig. Ib).
• a lower threshold 1 shall be used so as not to miss some of the signal elements, e.g., 20a and 20b (see Fig. Ic).
• a higher threshold 2 shall be used so as not to generate false results from the noise (see Fig. Id).
• the signal can be effectively separated from the noise by selecting a proper threshold.
• the amplitudes of some signal elements 20a, 20b may be close to that of the noise 30, as illustrated in Fig. If, thus the signal 20 cannot be effectively separated from the noise by either a higher or a lower threshold 2 or 1.
• a method of sensing a barcode comprises the steps of scanning the barcode at least twice at different times so as to obtain at least two instances of an optical signal, digitizing the at least two instances of the optical signal into at least two results, and generating an output using both of the at least two results.
• the noise is usually random in nature and fluctuates more than the real barcode signal
• the noise can be eliminated by applying a proper algorithm to the digitized results created from original signals obtained in different time.
• the output is generated by applying an AND algorithm to the at least two digitized results.
• the method comprises a step o f synchronizing the timing in the at least two digitized results.
• each instance of the optical signal obtained in different time is digitized with at least a first threshold and a second threshold.
• the results from the first threshold are used to generate the output, while the outcomes from the second threshold are used to synchronize the timing of the first results.
• the second threshold is larger than the first threshold, because the noise is usually smaller than the signal.
• the present invention also provides a system for sensing a barcode, which comprises detecting means adapted for obtaining at least two instances of an optical signal in at least two scanning operations applied to the barcode at different times, digitizing means for digitizing the at least two instances of the optical signal into at least two results, and means for generating an output by using both of the at least two results.
• the means for generating the output comprises means for applying an AND algorithm to the at least two results so as to eliminate noise that is usually random and fluctuating.
• means for synchronizing the timing in the at least two results is provided.
• the system comprises a first digitizer with a first threshold to create the above results from the instances of the optical signal, and a second digitizer for digitizing the instances of the optical signal simultaneously with the first digitizer.
• the outcomes of the second digitizer are used for synchronizing the timing between or among the results from the first digitizer.
• Figs. Ia - If schematically illustrate different resolution/noise scenarios in the prior art;
• Figs. 2a-2d schematically illustrate digitized results from three different instances of the original signal obtained from the same barcode;
• Fig. 2f illustrates an output generated by applying an AND algorithm to the digitized results in Figs. 2a-2d according to the teaching of the present invention
• Figs. 3a and 3b illustrate two embodiments of the system according to the present invention
• Fig. 4 is a flow chat schematically illustrates the method of the present invention.
• Figs. 2a-2d illustrate the same scenario as in Fig. 2f in which amplitudes of some signal elements 20a, 20b in the signal 20 may be at the same level as that of the noise 30, and no proper threshold can be found to effectively separate the signal 20 and the noise 30 from each other.
• the lower amplitudes of signal elements 20a, 20b may be caused by the fact that the barcode elements 11, 12 have a higher density in the locations corresponding to the signal elements 20a, 20b (see Figs. Ia, Ib).
• optical signal 20 is obtained in different time, e.g., by scanning the same barcode 10 several times with a scanner (not shown). Then all the digitized results from each instances of the optical signal are used to generate a final correct output 5 in which the noise has been eliminated.
• Figs. 2b — 2d exemplarily illustrate that three instances of the optical signal have been obtained. It is clearly shown that neither a higher threshold 2 nor a lower threshold 1 can effectively eliminate the noise 30 to generate a correct digitized result. More specifically, none of the digitized results 3, 4 in Figs. 2b-2d is correct.
• all the digitized results 4 created from all the three instances of the optical signal 20 at the first threshold 1 are used to generate a final output 5.
• an AND algorithm is applied to all the three digitized results 4 in Figs. 2b-2d, and a final output 5 is thus generated as illustrated in Fig. 2f.
• the noise 30 is usually random in nature and fluctuates more than the signal 20
• applying AND algorithm to the digitized results 4, which are created from three instances of the optical signal obtained in different time effectively eliminates the false wave elements (e.g., elements 30a and 30b) caused by the noise 30 and generates a correct final output of the signal 20.
• the first threshold 1 should be properly selected so as to be able to reflect all the elements in the signal 20, including the lower-amplitude signal elements 20a, 20b.
• the timing of the three digitized results 4 will be synchronized.
• the signal 20 is usually less fluctuating than the noise 30. Therefore, preferably a digitized result 3 at the second threshold 2 is used for determining the timing in the corresponding digitized result 4.
• the digitization at the first and second thresholds is carried out simultaneously.
• the second threshold 2 shall be properly selected to reflect the relatively stable signal 20. Since the signal 20 is generally larger than the noise 30, the second threshold 2 is preferably larger than the first threshold 1, thus only reflects the elements of the signal 20. It is noted that lower-amplitude signal elements 20a, 20b are preferably not reflected by the second threshold 2 since they are close to the amplitude of the noise 30.
• a dual-digitizer system is used to carry out the digitization process. More specifically, each instance of the optical signal is input to a first digitizer with the first, lower threshold 1 and a digitizer with the second, higher threshold 2, so as to create the digitized results 4 and 3, respectively. Preferably the two digitizers digitize each instance of the optical signal simultaneously for easier timing determination and synchronization.
• Figs. 3a and 3b illustrate two embodiments of the dual-digitizer system according to the present invention.
• the dual digitizers 41 and 42 are included in the digital module in the system, while in the embodiment in Fig. 3b, the dual digitizers 41 and 42 are a part of the analog module of the system. It is noted that the thresholds in the digitizers 41 and 42 are controlled by a CPU 43 through a gate level control.
• digitized results 3, 4 of each instance of the signal is provided from the digitizers 41, 42 to a memory "RAM" 44 for processing, which includes synchronizing the timing among the digitized results and applying a appropriate algorithm (e.g., an AND algorithm) to the digitized results 4 so as to generate a correct digitized output 5.
• Fig. 4 illustrates steps of the method according to the present invention which may be implemented by the system as illustrated in Figs. 3a and 3b.
• the barcode is scanned once to obtain an instance of the optical signal, which is preprocessed by one or more of the units Pre Amp, Differential, AGC, LPF, ADC as illustrated in Figs. 3a and 3b, in step 110.
• the preprocessed signal is then input to both the first digitizer 41 with a first threshold 1 and the second digitizer 42 with a second threshold 2, at step 120.
• Two different digitized results are created by the two digitizers 41, 42 with different thresholds 1, 2, at step 130.
• the digitized result created by digitizer 42 with the second threshold 2 is used to determine the timing of the digitized result created by digitizer 41 with the first threshold 1. If, at block 150, it is decided that more instances are required, the process goes back to block 100 to obtain a next instance.
• the digitized results created by the first digitizer 41 with the first threshold 1 from all the instances of signal obtained in block 100 are synchronized in timing and applied with an AND algorithm, in block 160, whereby generating a final, correct digitized output signal at block 170.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Artificial Intelligence (AREA)
• Toxicology (AREA)
• General Health & Medical Sciences (AREA)
• Computer Vision & Pattern Recognition (AREA)
• Health & Medical Sciences (AREA)
• Theoretical Computer Science (AREA)
• Quality & Reliability (AREA)
• Optics & Photonics (AREA)
• Image Input (AREA)
• Optical Recording Or Reproduction (AREA)
• Character Input (AREA)

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• 2005
  • 2005-05-05 US US11/125,399 patent/US7354000B2/en not_active Expired - Fee Related
• 2006
  • 2006-05-03 DE DE112006001171T patent/DE112006001171T5/de not_active Withdrawn
  • 2006-05-03 WO PCT/US2006/017002 patent/WO2006121730A1/en not_active Ceased
  • 2006-05-03 GB GB0721593A patent/GB2440080B/en not_active Expired - Fee Related
  • 2006-05-03 JP JP2008510172A patent/JP2008541236A/ja active Pending

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