Bar code reader using scanned memory array

• US 5,396,054 A
• Filed: 05/09/1994
• Issued: 03/07/1995
• Est. Priority Date: 03/01/1989
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Metlitsky, Boris, Krichever, Mark J.
• Primary Examiner(s): Weinhardt, Robert A.
• Application Number:
  US08/240,299
• Time in Patent Office: 302 Days
• Field of Search: 235/462, 235/472, 235/470, 235/467, 235/456, 235/454, 235/466
• US Class Current: 235/462.1
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/1092 sensing by means of TV-scanning
• 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 7/1456 determining the orientation of the optical code with respect to the reader and correcting therefore

Abstract

In a bar code reader, a field of view which includes a symbol to be read is imaged upon a light-responsive array such as a CCD imager device. The output of this array is transferred to a memory array to provide a bit-mapped type of binary representation of the image including the symbol. The memory is scanned (instead of the field of view itself being mechanically scanned) to recognize and decode the symbol. Because the angular orientation of the symbol is variable, this binary representation may be interpreted to determine how the memory array is to be scanned to recognize the bar code symbol. For example, the distinctive patterns of characters used in bar codes may be found by scanning the memory and the relative positions of these patterns interpreted to determine the position, size and shape of the symbol in the memory, thereby defining at what angular displacement the memory array need be addressed to traverse the rows of the bar code symbol. Or, the memory array may be simply scanned using preselected scan lines (beginning with a raster-type scan) until code recognition is obtained.

Claims

1. A method of reading a bar code symbol comprising the steps of:

(a) optically imaging upon a light-detector array a field of view including a symbol to be read;

(b) directly transferring serially only to a serial port of a memory array a binary representation of light impinging upon the light-detector array;

(c) during said transferring, scanning said binary representation in the memory array via a parallel port of said memory array to produce electrical data output to processing means; and

(d) evaluating said electrical data output including finding the presence of bar code symbol information by said processing means to thereby determine orientation of the bar code symbol.

2. A method according to claim 1 wherein said step of optically imaging includes directing light onto said field of view and focusing reflected light onto said light-detector array.

3. A method according to claim 1 wherein said light-detector array is a CCD device, and said step of transferring includes serially accessing the light-detector array.

4. A method according to claim 1 wherein said step of scanning the memory array includes addressing rows and columns of an array of memory cells of the memory array in a sequence of linear patterns including at least two linear patterns angularly positioned with respect to the rows and columns.

5. A method according to claim 1 wherein the symbol includes a plurality of rows of bar code patterns in a two-dimensional array.

6. A method according to claim 1 wherein said light-detector array is in a stationary unit aimed toward said field of view.

7. A method according to claim 1 wherein said light-detector array is in a hand-held unit adapted to be aimed toward the bar code symbol, and the hand-held unit includes a manually-activated trigger;

and wherein said method includes responding to activation of said trigger to initiate said steps of transferring and scanning.

8. A method according to claim 1 wherein the angular orientation of the symbol within the field of view is nonparallel to the rows or columns of the light-detector array.

9. A method according to claim 1 including the step of determining the orientation of a symbol included within said representation and then scanning said array based upon said determination.

10. A method according to claim 1 including the step of identifying patterns in said binary representation corresponding to bar code symbols.

11. A method according to claim 10 wherein said step of identifying includes the step of counting transitions from one type of binary data to the other.

12. A method of operating a bar code scanner for reading bar code symbols, comprising the steps of:

(a) generating directly in a light-responsive array a binary representation of a two-dimensional field of view, the field of view including a symbol to be read;

said generating including the step of optically imaging said field of view onto said light-responsive array to generate said binary representation of said field of view;

then serially transferring said binary representation to a memory array by a direct serial-only coupling;

(b) during said step of serially transferring, scanning said memory array by parallel accessing said memory array by processing means, said scanning including generating an effective scan line or lines having an angular orientation corresponding to that of a representation of the symbol included within said binary representation, said scanning including determining the angular orientation of at least part of said representation of the symbol, said scanning being effective to produce electrical data output; and

said scanning including finding bar code information by said processing means in the electrical data output to thereby determine said angular orientation.

13. A method according to claim 12 wherein said generating includes reading said memory in a regular pattern and checking for recognizable bar code characters, then reading said memory using a sequence of addresses determined from the location of said recognizable bar code characters.

14. A method according to claim 12 wherein said step of scanning the memory array includes addressing rows and columns of an array of memory cells of the memory array in a sequence of linear patterns at a plurality of different angles with respect to the rows and columns.

15. A method according to claim 12 wherein the symbol includes at least one row of bar code patterns.

16. A method according to claim 15 wherein the symbol includes a plurality of rows of bar code patterns in a two-dimensional array.

17. A method according to claim 12 wherein the light-responsive array is in a hand-held unit which includes a manually-activated trigger, and the method includes activating said trigger to initiate said step of generating.

18. A method according to claim 12 wherein the angular orientation of bar code symbol is variable, and the lines of said scanning of the memory array are at variable angles.

19. A method according to claim 12 wherein said light-responsive array is in a stationary unit aimed toward a fixed field of view.

20. A method according to claim 12 including, prior to said step of generating a scan line, performing the step of identifying patterns in said binary representation corresponding to the bar code symbol by reading out said binary representation and evaluating said read out in a CPU.

21. A method according to claim 20 wherein said step of identifying includes the step of counting transitions from one type of binary data to the other.

22. Apparatus for reading bar code symbols, comprising:

(a) optical means for imaging upon a light-responsive array a field of view which includes a symbol to be read, the array having a serial output;

(b) a memory array having a serial port receiving directly from said serial output a serial binary representation of light impinging upon said light-responsive array, the memory array also having a parallel port;

(c) processing means accessing the memory array via said parallel port, while said serial port is receiving said binary representation, to determine the orientation of a symbol included within said binary representation and producing electrical data output derived from said memory array by scanning based upon said orientation, and said processing means including means for finding bar code information in said binary representation to thereby determine said orientation of said symbol.

23. Apparatus according to claim 22 wherein said optical means directs a light beam onto said field of view and focuses reflected light onto said light-responsive array.

24. Apparatus according to claim 22 wherein said means accessing the memory array addresses rows and columns of an array of memory cells of the memory array in a sequence of linear patterns at a plurality of different angles with respect to the rows and columns.

25. Apparatus according to claim 22 wherein said symbol includes at least one row of bar patterns.

26. Apparatus according to claim 25 wherein said symbol includes a plurality of rows of bar patterns in a two-dimensional array.

27. Apparatus according to claim 22 wherein said light-responsive array is in a hand-held unit aimed toward the bar code symbol.

28. Apparatus according to claim 27 wherein the hand-held unit includes a manually-activated trigger, said trigger being actuated to initiate said accessing of the light-responsive array.

29. Apparatus according to claim 22 wherein said means accessing the memory array evaluates data read from the memory array to identify bar-code patterns by counting transitions between data representing bar and data representing space between bars.

30. Apparatus according to claim 22 wherein said means accessing the memory array evaluates data read from the memory array to identify bar-code patterns by detecting the ratio of data representing bars to data representing space between bars.

31. Apparatus for reading bar code symbols comprising:

(a) a memory array having a serial access port and a parallel access port;

(b) means including optical imaging means generating in said memory array by serial transfer to said serial access port a binary representation of a two-dimensional field of view including a symbol to be read, the optical imaging means including a light-responsive array having a serial output directly coupled to said serial access port;

(c) processing means accessing the memory array via said parallel access port, while said serial transfer is occurring, and producing an electrical data output by scanning said memory array via said parallel access port; and

the processing means including means for finding bar code information in the electrical data output to thereby determine position and angular orientation of said symbol.

32. Apparatus according to claim 31 wherein said memory array is randomly accessible.

33. Apparatus according to claim 32 wherein said optical imaging means includes means for directing a light beam onto said symbol and focusing reflected light onto said memory array.

34. Apparatus according to claim 31 wherein said scanning includes reading a sequence of cells of the memory array extending along a line at an angle to major axes of the memory array corresponding to said angular orientation.

35. Apparatus according to claim 31 wherein said means for accessing the memory array addresses rows and columns of an array of memory cells of the memory array in a sequence of linear patterns at a plurality of different angles with respect to the rows and columns.

36. Apparatus according to claim 31 wherein the symbol includes at least one row of bar and space patterns.

37. Apparatus according to claim 31 wherein the apparatus is in a fixed position and objects having said bar code symbols are moved into range of said means for optically imaging.

38. Apparatus according to claim 31 wherein said apparatus is contained in a hand-held unit aimed toward the bar code symbol, and wherein the hand-held unit includes a manually-activated trigger activated by the user to initiate said generating.

39. Apparatus according to claim 31 wherein said means accessing the memory array evaluates data read from the memory array to identify bar-code patterns by counting transitions between data representing bars and data representing space between bars.

40. Apparatus according to claim 31 wherein said means accessing the memory array evaluates data read from the memory array to identify bar-code patterns by detecting the ratio of data representing bars to data representing space between bars.

41. Apparatus according to claim 31 wherein said means accessing the memory array evaluates data read from the memory array to identify bar-code patterns by comparing data produced by one scan with data produced by a next adjacent scan.

42. A method of scanning a bar code symbol, comprising the steps of:

(a) optically imaging the bar code symbol onto an array of light sensitive elements, each element producing a signal related to light impinging thereon, said array having a serial output;

(b) storing a bit-mapped binary representation of said signals in an array of memory elements, said array having a serial access port and a parallel access port;

wherein said storing includes serially transferring said signals from said serial output of the array of light sensitive elements directly to said array of memory elements only via said serial port;

(c) while said step of storing is occurring, accessing said memory array the by processing means only via said parallel access port for determining the orientation of the representation of said symbol in said array, and for scanning said array of memory elements along selected paths corresponding to said orientation of the binary representation of said symbol to produce an electrical output, and

(d) by said processing means evaluating said electrical output to find bar code symbol information and determine orientation of said bar code symbol.

43. A method according to claim 42 wherein said step of optically imaging includes the step of illuminating a field of view including said symbol with a light beam.

44. A method according to claim 42 wherein the step of scanning includes reading the array of memory elements in a line of elements at an angle to rows or columns of the array.

45. A method according to claim 42 including the step of manually initiating said steps of imaging and storing.

46. A method according to claim 42 wherein said step of scanning includes addressing said array of memory elements from a CPU.

47. A method according to claim 42 including detecting bar code patterns in said binary representation by evaluating the number of transitions between one binary state and the other for a linear sequence of memory cells.

48. A method according to claim 42 including detecting bar code patterns in said binary representation by evaluating the ratio of cells storing one binary state to cells storing the other binary state for a linear sequence of memory cells.

49. A method according to claim 42 including detecting bar code patterns in said binary representation by comparing data produced by one scan with data produced by a next adjacent scan.