BAR CODE READING CIRCUITRY

• US 3,790,756 A
• Filed: 11/08/1972
• Issued: 02/05/1974
• Est. Priority Date: 11/08/1972
• Status: Expired due to Term

• Current Assignee: Kay Madsen, Kenneth E. Graves, Warren J. Schmidt
• Original Assignee: Kay Madsen, Kenneth E. Graves, Warren J. Schmidt
• Inventors: Graves, Kenneth E., Madsen, Kay, Schmidt, Warren J.
• Primary Examiner(s): Cook, Daryl W.
• Application Number:
  US05/304,870
• Time in Patent Office: 454 Days
• Field of Search: 235/61.11E,61.11D,61.12R,61.12M,61.12N 340/146.3K 250/219R,219D,219DC,219DD
• US Class Current: 235/462.02
• CPC Class Codes: B07C 3/14 using light-responsive detecting means for information carriers G06K7/14
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48

Abstract

Circuitry for a bar/half bar code reader which includes a stationary array of photodetectors aligned to scan over a relatively large scan width to detect and decode a data line which occupies only a fraction of the area of the scan width. The circuitry includes counting means for locating the relative position of the bottom of the first bar in the data line with respect to the scan width. The remaining bars in the data line are then tracked by interrogating only the information from those photodetectors which located and analyzed the first bar. Means are also provided for continuously determining the relative position of the bottom of each bar in the data line and for incrementally adjusting the tracking circuitry so that codes which are skewed with respect to the scan width can be successfully tracked.

Claims

1. In an apparatus for reading bar code data printed on an article which apparatus includes means for continuously scanning over a predetermined scan width on the article that includes an area through which the bar code data is arranged to be passed, said scan width being generally in alignment with but significantly greater than the length of any of the bars in said bar code data, and logic circuit means for interrogating the successive scans to determine the presence of long and short bars and for producing signals in response thereto;

the improvement comprising circuitry including means for registering the presence or absence of code marking data within a plurality of incremental areas aligned across said scan width, means for counting the number of incremental areas from one end of said scan width to determine the location of a tracking incremental area as established by the first incremental area which indicates the presence of code marking data to thereby indicate the location of the bottom of the first bar of a line of data with respect to said scan width, logic circuit means for monitoring the incremental areas adjacent to said tracking incremental area to determine whether or not a bar is present, means for interrogating subsequent scans by monitoring the incremental area corresponding to the position of said tracking incremental area and monitoring a sufficient number of adjacent incremental areas to determine the presence of and the height of a bar, and means for altering the corresponding position of said tracking incremental area with respect to said scan width if the bottoms of the bars in the line of data are not aligned with the terminal incremental areas of said scan width whereby said means for interrogating the scan after the presence and location of the first bar of a line of data have been established will be limited to operation over an area significantly smaller than the area of said scan width which smaller area generally corresponds to the location of the line of data within the scan width.

2. In an apparatus for reading bar code data as set forth in claim 1 wherein said circuitry includes a shift register having a plurality of serially connected cells arranged to receive data representative of the presence or absence of code marking data in said incremental areas, means for producing a series of shift pulses for serially shifting the data in said shift register, a counter for counting the number of shift pulses required to shift the code marking data indicative of the bottom of the first bar of said line of data to the output end of the register, memory means for recording said required number of shift pulses, and means responsive to said memory means for initiating said means for interrogating the subsequent scans of said line of data.

3. In an apparatus for reading bar code data as set forth in claim 2 wherein said means responsive to said memory means includes a comparator for comparing the number recorded in said memory means with the number in said counter for counting the shift pulses.

4. In an apparatus for reading bar code data as set forth in claim 1 wherein said means for altering the corresponding position of said tracking incremental area coMprises means for monitoring the incremental areas on both sides of said tracking incremental area during said subsequent scans.

5. In an apparatus for reading bar code data as set forth in claim 1 wherein said registering means comprises a shift register including a plurality of serially connected cells, and said logic circuit means for monitoring the incremental areas adjacent to said tracking incremental area includes an analog circuit arranged to measure the logic level outputs of a plurality of said cells at the output end of the register.

6. In an apparatus for reading bar code data printed on an article, a shift register including a plurality of serially connected cells adapted to provide logic levels outputs representative of the presence or absence of code marking in a plurality of segmental areas aligned across a scan width on the article through which the bar code data is arranged to be passed, means for serially shifting the data within said register, means for monitoring the outputs of at least two spaced cells of said register for a predetermined number of shifts, means for initiating said monitoring means when one of said two cells contains a signal from a segmental area indicative of the position of the bottom of the previously scanned bar, said monitoring means including means for counting the number of positive code marking indications from each of the associated cells during said predetermined number of shifts to establish the validity of said data, and logic circuitry for comparing the outputs of the monitoring means associated with each of said cells for determining the presence of and the nature of the bar being scanned.

7. In an apparatus for reading bar code data as set forth in claim 6 wherein said monitoring means includes means for monitoring the output of a third cell of said register for said predetermined number of shifts, said third cell being spaced equally between said other two monitored cells of the register.

8. In an apparatus for reading bar code data as set forth in claim 6 wherein said logic circuitry includes means for producing a first output pulse when the counting means associated with the cell of said two cells which is closest to the output end of the register establishes the validity of said data, said logic circuitry further including means for producing a second output pulse when the counting means associated with both of said two cells simultaneously establish the validity of said data whereby said first output pulse indicates the presence of a bar and whereby the second output pulse indicates the presence of a tall bar.

9. In an apparatus for reading bar code data as set forth in claim 7 wherein said logic circuitry includes means for producing a first output pulse when the counting means associated with the cell of said three cells which is closest to the output end of the register establishes the validity of said data, said logic circuitry further including means for producing a second output pulse when the counting means associated with each of said three cells simultaneously establish the validity of said data whereby said first output pulse indicates the presence of a bar and whereby the second output pulse indicates the presence of a tall bar.

10. In an apparatus for reading bar code data as set forth in claim 6 including a shift pulse counter for counting the number of shifts required from the time data is placed in said register until the bottom of the first bar of a line of data is indicated by the logic level output of the cell of said two cells in said register which is closest to the output end of the register, memory means for storing the number obtained by said shift pulse counter, means for causing said shift pulse counter to count the number of shifts required to serially shift data out of said register during scans of the remaining bars in said line of data, and comparator means for comparing the number in said shift pulse counter with the number in said memory means during scans of subsequent bars in said line of data in order to initiate said monitoring means.

11. In an apparatus for reading bar code data as set forth in claim 10 including means for incrementing the number in said memory means either upwardly or downwardly after the scanning of each bar in said line of data when the bars are skewed with respect to said scan width.

12. In an apparatus for reading bar code data printed on an article, a first shift register including a plurality of serially connected cells, a second shift register including a plurality of serially connected cells, said second shift register being connected to receive data serially shifted from said first shift register, means operative during a first scan for transferring data in parallel into said first shift register representative of the presence or absence of code marking in a plurality of segmented areas aligned across a scan width on the article through which scan width the bar code data is arranged to be passed, means for serially shifting said first register so that the cells at the output end of the register indicate the presence in said scan width bar in a line of bar code data, means for serially shifting information from said first register into said second register when said output end of the first register indicates the presence of a bar, means for comparing corresponding cells of said first and second registers after the first register has received information from a second scan and such information has been shifted the same number of times as the previously scanned information before it was transferred into said second register, and means responsive to said last named means for determining the presence of a bar and its position relative to the previously scanned bar.

13. In an apparatus for reading bar code data printed on an article, a shift register including a plurality of serially connected cells, means for transferring data in parallel into said shift register representative of the presence or absence of code marking data in a plurality of segmented areas aligned across a scan width on the article through which scan width the bar code data is arranged to be passed, means for serially shifting said register so that the cells at the output end of the register indicate the presence in said scan width of the first bar in a line of bar code data, means for recording the number of shift pulses required to thus shift said register, an analog network to monitor certain of the cells at the output end of the register to establish the validity of said first bar, and means operative to serially shift said register by the same number of shift pulses on subsequent scans of said line of data prior to the interrogation of said cells for establishing the presence or absence of the remaining bars in said line of data.

14. In an apparatus for reading bar code data as set forth in claim 13 including means for incrementally altering said recorded number of pulses if the line of data is skewed with respect to said scan width.