Method and apparatus to enable the high speed evaluation of bar code indicia

• US 5,633,488 A
• Filed: 12/19/1995
• Issued: 05/27/1997
• Est. Priority Date: 12/19/1995
• Status: Expired due to Term

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: Webscan, Inc. (Cognex Corporation)
• Inventors: Spitz, Glenn S.
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): LEE, MICHAEL GUNYOUNG
• Application Number:
  US08/575,097
• Time in Patent Office: 525 Days
• Field of Search: 235/462, 235/463
• US Class Current: 235/462.27
• 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 7/1452 detecting bar code edges

Abstract

A method and apparatus to enable the high speed evaluation of the quality of a bar code indicia by processing a scan reflectance profile signal generated by a scanner unit. The scan reflectance profile signal is sampled by an analog-to-digital converter, with the sample values from the converter processed as they are produced in real-time to determine a highest positive peak sample value and a lowest negative peak sample value for each element of the bar code indicia. The lowest negative and highest positive peak sample values for each element being accessible for post-processing to determine at least one figure of merit indicative of the quality of the bar code indicia being evaluated. The samples produced by the a/d converter are processed as they are generated to filter and reduce the total collection of sample values stored and/or considered, while still providing the critical highest and lowest peak sample values for the scanned elements to enable high speed verification.

Claims

1. A method for evaluating the quality of a bar code indicia by processing a scan reflectance profile signal representative of elements of the bar code indicia, the scan reflectance profile signal generated by scanning the bar code indicia, said method comprising the steps of:

a) detecting a first edge of the scan reflectance signal as the bar code indicia is being scanned, the first edge indicating the beginning of a first element of the bar code indicia;

b) sampling a portion of the scan reflectance signal representative of said element to produce a sequence of sample values;

c) processing said sequence of sample values of step b) as each sample value is produced to determine a highest positive peak sample value and a lowest negative peak sample value provided by said sequence of sample values associated with said element being scanned and sampled;

d) detecting a next edge of the scan reflectance signal indicating the end of said element and the start of the scanning and sampling of an adjacent element;

e) storing into a peak sample buffer memory said highest positive and lowest negative peak sample values determined in step c); and

f) repeating steps b), c), d) and e) for a plurality of adjacent elements that along with the first processed element form the bar code indicia;

said highest positive peak and lowest negative peak sample values stored in step e) for each element scanned being accessible in said peak sample buffer memory for post-processing to determine at least one figure of merit associated with the quality of the bar code indicia.

2. The method of claim 1 further comprising the step of post-processing said highest positive and lowest negative peak sample values for each element comprising the bar code indicia to determine at least one figure of merit indicative of the quality of the bar code indicia being evaluated.

3. The method of claim 1 wherein a plurality of scan reflectance profile signals generated by scanning the bar code indicia at spaced locations along the height of the elements of the bar code indicia are processed in succession to determine said highest positive and lowest negative peak sample values for each element comprising the bar code indicia for each said scan reflectance profile signal generated.

4. The method of claim 3 further comprising the step of post-processing said highest positive and lowest negative peak sample values determined for each element of each scan reflectance profile signal processed to determine at least one figure of merit indicative of the overall quality of the bar code indicia being evaluated.

5. The method of claim 1 wherein detecting an edge within the scan reflectance signal in step d), causes an element width count to be stored in an element width buffer memory at step d);

said storing of element width counts continuing until all portions of the scan reflectance profile signal representative of the elements of the bar code indicia are processed.

6. The method of claim 5 further comprising the step of post-processing said highest positive peak sample value, said lowest negative peak sample value, and said element width count value determined for each element to determine at least one figure of merit indicative of the quality of the bar code indicia being evaluated.

7. A method for evaluating the quality of a bar code indicia by processing a scan reflectance profile signal representative of the elements of the bar code indicia, the scan reflectance profile signal generated by scanning the bar code indicia, said method comprising the steps of:

a) sampling the scan reflectance signal to provide a sequence of sample values representative of each element of the bar code indicia; and

b) processing each sample value of said sequence of sample values as each sample is produced in step a) to determine a highest positive peak sample value and a lowest negative peak sample value associated with each element of the bar code indicia;

thereby determining a plurality of pairs of peak sample values, each pair consisting of said highest positive and lowest negative peak sample values for each scanned element, each of said pairs of peak sample values being accessible for post-processing to determine at least one figure of merit indicative of the quality of the bar code indicia.

8. The method of claim 7 further comprising the step of storing said highest positive and lowest negative peak sample values in a peak sample buffer memory as they are determined in step b).

9. The method of claim 7 wherein a plurality of scan reflectance profile signals generated at spaced locations along the height of the elements comprising the bar code indicia are processed in succession to determine said highest positive and lowest negative peak sample values for each element comprising said bar code indicia for each scan reflectance profile signal generated;

said highest positive and lowest negative peak sample values being accessible to determine at least one figure of merit indicative of the overall quality of the bar code indicia being evaluated.

10. The method of claim 9 further comprising the step of post-processing said highest positive and lowest negative peak sample values determined for each element of each scan reflectance profile signal processed to determine at least one figure of merit indicative of the overall quality of the bar code indicia being evaluated.

11. An apparatus for evaluating the quality of a bar code indicia by processing a scan reflectance profile signal representative of elements of the bar code indicia, the scan reflectance profile signal processed as it is generated by a scanner unit arranged to scan the bar code indicia, said apparatus comprising:

an analog-to-digital converter to sample the scan reflectance profile signal as it is generated by said scanner unit, said analog-to-digital converter producing a sequence of samples, each sample having a value representative of the analog value of the scan reflectance signal;

an edge detection unit to detect edges within the scan reflectance profile signal, the edges indicating the start of each element within the bar code indicia; and

a peak sample determining unit that is coupled to the analog-to-digital converter, said peak sample determining unit provided to determine a highest positive peak sample value and a lowest negative peak sample value for each element from the sample values produced by said analog-to-digital converter as each element within the bar code indicia is scanned;

said highest positive and lowest negative peak sample values determined for each element already scanned being immediately accessible to begin post-processing to determine at least one figure of merit indicative of the quality of the bar code indicia being evaluated.

12. The apparatus of claim 11, further comprising a peak sample buffer memory to store said highest positive and lowest negative peak sample values as said values are determined by said peak sample determining unit for each scanned element of the bar code indicia.

13. The apparatus of claim 12, further comprising a post-processing computer to read and post-process said peak sample values stored in said peak sample buffer memory to determine at least one figure of merit indicative of the quality of the bar code indicia.

14. An apparatus for evaluating the quality of a bar code indicia by processing a scan reflectance profile signal representative of elements within the bar code indicia, the scan reflectance profile signal generated by a scanner unit and sampled by an analog-to-digital converter to produce a sequence of samples, each sample representative of the analog value of the scan reflectance signal, said apparatus comprising:

an edge detection unit to detect edges within the scan reflectance profile signal, the edges indicating the start of each of the elements of the bar code indicia; and

a peak sample determining unit coupled to the analog-to-digital converter, said peak sample determining unit provided to determine, for each element a highest positive peak sample value and a lowest negative peak sample value from the sample values produced by said analog-to-digital converter as each element within the bar code indicia is scanned;

wherein said highest positive and lowest negative peak sample values determined for already processed elements are accessible to begin post-processing to determine at least one figure of merit indicative of the quality of the bar code indicia.

15. The apparatus of claim 14, further comprising a peak sample buffer memory to store said highest positive and lowest negative peak sample values determined for each element of said bar code indicia until said peak sample values are needed for post-processing.

16. The apparatus of claim 15, further comprising a post-processing computer to post-process said peak sample values stored in said peak sample buffer memory to determine at least one figure of merit indicative of the quality of the bar code indicia.

17. An apparatus to enable the evaluation of the quality of a bar code indicia by processing a scan reflectance profile signal representative of the elements within the bar code indicia as the scan reflectance profile is generated to determine a highest positive peak sample value and a lowest negative peak sample value of each element, the scan reflectance profile signal generated by a scanner unit arranged to scan the bar code indicia, said apparatus comprising:

an analog-to-digital converter, to sample the scan reflectance signal as it is generated by said scanner unit, to produce a sequence of sample values representative of the analog value of the scan reflectance signal;

an edge detection unit to detect edges within the scan reflectance profile signal, the edges indicating the beginning of elements of the bar code indicia and further indicative of the end of each of said elements and when said highest positive and lowest negative peak sample values have been determined for each scanned element;

a polarity indicator to indicate a polarity of a peak sample value to next be determined, said polarity being indicated by a first logic level when determining a positive peak sample value or a second logic level when determining a negative peak sample value; and

a peak sample determining unit to determine said highest positive peak sample value and said lowest negative peak sample value from the sample values provided by said analog-to-digital converter as each element within the bar code indicia is scanned, said peak sample determining unit having;

a peak sample storage unit responsive to a first comparator, said first comparator producing a first control signal to enable said peak sample storage unit to store a current sample produced by said analog-to-digital converter if said current sample value is of the proper relative magnitude so as to represent a possible new peak value with respect to the polarity indicated by said polarity indicator;

a second comparator for comparing the relative magnitude of said current sample to the relative magnitude of a value being equal to a sum of the sample value currently stored in said peak sample storage unit and an offset value, said second comparator indicating when a peak value has been determined and providing a second control signal to said polarity indicator to configure said peak sample determining unit to determine a peak of opposite polarity to the peak just determined; and

a highest peak sample storage unit to store said highest positive peak sample value and a lowest peak sample storage unit to store said lowest negative peak sample value, each of said peak sample value stored being determined from the sequence of sample values produced by said analog-to-digital converter as each element of the bar code indicia is scanned and sampled;

said highest and lowest peak sample storage units being responsive to a third comparator in combination with said second control signal, said third comparator included to compare the relative magnitudes of said value stored in said peak sample storage unit and said value currently stored in said highest peak sample storage unit or said lowest peak sample storage unit as determined by said polarity indicator, and storing said value of said peak sample storage unit in said highest peak sample storage unit or said lowest peak sample storage unit when said third comparator determines that a new highest positive or lowest negative peak sample value has been determined;

said polarity indicator configuring the peak sample determining unit to alternately determine opposite polarity peak sample values until the edge detection unit detects an edge of the scan reflectance profile signal indicating that said highest positive and lowest negative peak sample values have been determined for the element currently being scanned and processed.

18. The apparatus of claim 17, further comprising a peak sample buffer memory to hold said highest positive and lowest negative peak sample values determined for each scanned element of said bar code indicia until said peak sample values are needed for post-processing.

19. The apparatus of claim 18, further comprising a post-processing computer to receive and post-process said peak sample values stored in said peak sample buffer memory to determine at least one figure of merit indicative of the quality of the bar code indicia.

20. An apparatus to process a sequence of sample values representative of a portion of a scan reflectance profile signal generated by a scanner unit scanning elements of a bar code indicia, said sample values produced by an analog-to-digital converter arranged to sample the scan reflectance signal as it is generated, said apparatus processing each sample of said sequence of sample values as each sample is produced to determine a highest positive peak sample value and a lowest negative peak sample value for each element as each element is scanned, said apparatus comprising:

a polarity indicator to indicate a polarity of a peak sample value to be determined, said polarity being indicated by a first logic level when determining a positive peak sample value and a second logic level when determining a negative peak sample value;

a peak sample storage unit responsive to a first comparator, said first comparator producing a first control signal to enable said peak sample storage unit to store a current sample produced by said analog-to-digital converter if said current sample is of the proper relative magnitude so as to represent a possible new peak sample value with respect to the polarity indicated by said polarity indicator;

a second comparator for comparing the relative magnitude of said current sample to the relative magnitude of a value being equal to a sum of the sample value currently stored in said peak sample storage unit and an offset value, said second comparator indicating when a peak value has been determined and providing a second control signal to said polarity indicator to configure said apparatus to determine a peak of opposite polarity to the peak just determined; and

a highest peak sample storage unit to store said highest positive peak sample value and a lowest peak sample storage unit to store said lowest negative peak sample value, each of said highest positive and lowest negative peak sample values stored being determined from the sequence of sample values produced by the analog-to-digital converter as each element of the bar code indicia is scanned;

said highest and lowest peak sample storage units being responsive to a third comparator in combination with said second control signal, said third comparator included to compare the relative magnitudes of said value stored in said peak sample storage unit and said value currently stored in said highest peak sample storage unit or said lowest peak sample storage unit as determined by said polarity indicator, and storing said value of said peak sample storage unit in said highest peak sample storage unit or said lowest peak sample storage unit when said third comparator determines that a new highest positive or lowest negative peak sample value has been determined by the processing of said sequence of sample values produced as each element is scanned and sampled;

said polarity indicator configuring the apparatus to alternately determine opposite polarity peak values until the sequence of sample values representative of each element has been processed and said highest positive and lowest negative peak sample values for each element scanned has been determined.