Bar code online scanner/verifier

• US 6,354,503 B1
• Filed: 06/21/2000
• Issued: 03/12/2002
• Est. Priority Date: 06/21/2000
• Status: Expired due to Term

• Current Assignee: TSC Auto ID Technology Co., Ltd.
• Original Assignee: RJS Systems International
• Inventors: Chiu, Lihu
• Primary Examiner(s): Frech, Karl D.
• Assistant Examiner(s): Kim, Ahshik
• Application Number:
  US09/598,928
• Time in Patent Office: 629 Days
• Field of Search: 235/462.19, 235/462.25, 235/462.08
• US Class Current: 235/462.18
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1443 locating of the code in an image
• CPC Class Codes: G06K 7/1478 adapting the threshold for pixels in a CMOS or CCD pixel sensor for black and white recognition
• CPC Class Codes: G06K 7/1486 Setting the threshold-width for bar codes to be decoded

Abstract

A bar code scanner/verifier rapidly analyzes reflections of a scanning laser beam to determine whether or not a scanned line portion contains a bar code, so analysis of a bar code begins only when a legitimate bar code is present. The apparatus reads transitions in reflectance and indicates that a bar code is not present when the transitions are not large enough to qualify for a bar code, and when there are not enough transitions per unit distance. The circuit does this by generating MAX minus MIN, where MAX continually decreases over time but is raised every time a high reflectance is encountered, and MIN continually increases over time but is lowered every time a low reflectance is encountered. When MAX minus MIN drops below a programmable predetermined noise level, the circuit indicates that there is no bar code. Another circuit counts the number of transitions in a region where MAX minus MIN is above the noise level, and indicates that a bar code is present only if at least a certain number of transitions, e.g. 17, are found within a predetermined scan distance such as 2 cm. The circuit for detecting the presence or absence of a bar code can be implemented in analog, or in software using sparse data, e.g. every 4 or 8 samples.

Claims

1. Apparatus for scanning for a bar code on a surface that moves past the apparatus, where the apparatus includes a scanning laser beam source which scans along a predetermined distance and a detector for detecting reflections of the laser beam and for generating analog signals representing the magnitude of the detected reflections, comprising:

an analog circuit that records transitions, of at least a predetermined magnitude, of the light amplitude detected by said detector, and that generates a signal indicating that a bar code is not present in an area that includes a first transition and an area immediately following said first transition, when a second transition fails to be detected within a predetermined distance following said first transition,said analog circuit being constructed to generate a signal representing MAX minus MIN, wherein;

said MAX value continuously decreases in value at a controlled MAX rate, from a magnitude representing substantially complete reflection until the magnitude of a bright reflection is detected with a reflection magnitude greater than the instantaneous MAX value and with the MAX value then immediately increasing to said value of said bright reflection and then continuously decreasing again at said controlled MAX rate;

said MIN value continuously increases in value at a controlled MIN rate from a magnitude representing substantially no reflection until a low detected reflection is detected with a brightness level less than the instantaneous MIN value and with the MIN value then immediately decreasing to the value of said low detected reflection and then continually increasing again at said controlled MIN rate;

said analog circuit includes a circuit part that generates said signal indicating that a bar code is not present in said area that includes said first transition when the signal representing MAX minus MIN decreases below a predetermined level.

2. Apparatus for scanning for a bar code on a surface that moves past the apparatus, where the apparatus includes a scanning laser beam source and a detector that detects reflections, comprising:

a first circuit that begins a digital analysis of a possible bar code at a predetermined location after said laser beam has scanned past said location;

a second circuit connected to said detector, said second circuit constructed to generate a difference signal representing MAX minus MIN wherein;

MAX can vary from substantially 0% to 100% and is raised to a level representing the present reflection of a bright reflection when the percent reflection of the bright reflection exceeds the immediately preceding level of MAX, and with MAX thereafter decaying at a controlled rate;

MIN can vary from substantially 0% to 100% and is lowered to a level representing the percent reflection of a dim reflection when the percent reflection of the dim reflection is less than the immediately preceding level of MIN, and with MIN thereafter increasing at a controlled rate;

said second circuit is constructed to control said first circuit to begin a digital analysis of a possible bar code that begins at said predetermined location only when said difference signal exceeds a predetermined noise level signal along at least a predetermined minimum scanning distance.

3. The apparatus described in claim 2 wherein:

said second circuit is constructed so said controlled rates of MAX and MIN are asymptotically to substantially 0% and 100%, respectively.

4. The apparatus described in claim 2 including:

an analog-to-digital converter connected to said detector that produces digital bytes;

a first digital program part that stores all of said bytes and delivers all bytes received within a limited time period to said first circuit;

a second digital program part that is connected to said converter but that takes no more than one-fourth of the bytes produced by said converter and that generates MAX minus MIN from said no more than one-fourth of the bytes.

5. The apparatus described in claim 4 wherein:

said second digital program part takes only the highest and lowest bytes, which represent the highest and lowest values, of each group of at least eight bytes received from said converter, and generates MAX and MIN from said highest and lowest bytes.

6. Apparatus for scanning for a bar code on a surface that moves past the apparatus, where the apparatus includes a scanning laser beam source and a photodetector that detects reflections, comprising:

a first circuit that begins a digital analysis of a possible bar code at a predetermined location where said laser beam has scanned past said location;

a second circuit coupled to said photodetector, said second circuit constructed to generate an edge signal that represents a bar code element edge whenever a rapid change in reflectance is detected, where the change exceeds a predetermined percent of maximum reflection;

a counting circuit which counts the number of said edge signals detected within a predetermined scan distance following a first of said edge signals, and which controls said first circuit to begin a digital analysis of a possible bar code that begins at said first of said edge signals only when the number of said edge signals within said scan distance exceeds a predetermined number;

said first circuit is constructed to convert the output of said photodetector to digital signals that each has one of numerous digital values, while said second circuit is an analog circuit that does not process multiple distinct value digital signals.

7. A method for determining when a bar code is being scanned by an apparatus that scans a laser beam across a line path and that detects reflections and generates analog reflection signals representing the amplitude of reflections of the laser beam, and for indicating when a digital bar code analysis is to begin, comprising:

recording transitions in said reflection signals which exceed a predetermined percent of maximum laser beam reflection and using an analog circuit to generate a signal that indicates that analysis should begin of a bar code lying within a portion of a scan line that begins at a first of said transitions, only when a second of said recorded transitions is detected within a predetermined distance along the scan line following detection of said first transition.

8. A method for determining when a bar code, rather than a non-bar code area, is being scanned by an apparatus that scans a laser beam across a line path and that generates analog reflection signals representing the amplitude of reflections of the laser beam, and for indicating when a digital bar code analysis is to begin, comprising:

generating a signal equal to MAX minus MIN, where MAX and MIN are each variable between substantially 100% reflectivity and 0% reflectivity, by employing transitions in the percent reflectivity of said reflections signals and beginning MAX and MIN at a level of substantially 100% and 0%, respectively, at the beginning of a scan line path portion, to suddenly increase the value of MAX to a level equal to the percent reflectivity of a given upward transition caused by a scanned location of higher reflectivity than the level of MAX signal at the time of detection of said given upward transition, and to suddenly decrease MIN to a level equal to the percent reflectivity of a given downward transition cause by a scanned location of lower reflectivity than the level of MIN at the time of detection of said given downward transition;

continually decreasing MAX and increasing MIN when the level of MAX and MIN is not suddenly increased or decreased, respectively;

when MAX minus MIN is less than a predetermined noise level, indicating that a bar code is not present between said beginning of a scan line path portion and the location along said scan line where MAX minus MIN becomes less than said noise level.

9. A method for determining when a bar code, rather than a non-bar code area, is being scanned by an apparatus that scans a laser beam across a line path and that generates analog reflection signals representing the amplitude of reflections of the laser beam, and for indicating when a digital bar code analysis is to begin, comprising:

counting the number of transitions of said analog reflection signals that exceed a predetermined magnitude within a predetermined minimum scan distance, and indicating that a bar code is not to be analyzed when the number of transitions is less than a predetermined number;

said predetermined number is at least eight.

10. A method for determining when a bar code, rather than a non-bar code area, is being scanned by an apparatus that scans a laser beam across a line path and that generates analog reflection signals representing the amplitude of reflections of the laser beam, and for indicating when a digital bar code analysis is to begin, comprising:

converting said analog reflection signals to digital signals, including generating bytes representing the magnitude of said analog signals at predetermined intervals;

storing said bytes and later using said bytes to perform a bar code analysis;

using only a fraction of said bytes, including using no more than two bytes out of every eight consecutive bytes, to determine whether an area being scanned contains a bar code or does not contain a bar code.

11. The method described in claim 10 wherein:

said step of using only a fraction of said bytes includes determining the bytes of highest and lowest amplitude in each group of at least eight consecutive bytes, and using only said bytes of highest and lowest amplitude in determining whether or not an area contains a bar code.