Bar code reader

• US 5,591,952 A
• Filed: 01/26/1995
• Issued: 01/07/1997
• 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): SHEPPERD, JOHN W
• Application Number:
  US08/378,596
• Time in Patent Office: 712 Days
• Field of Search: 235/462, 235/470
• US Class Current: 235/462.11
• 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 two-dimensional bar code symbol having a plurality of linearly arranged indicia patterns of encoded information having a reading direction corresponding to said linear direction, said method comprising the steps of:

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

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

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

(d) evaluating said electrical output including finding the presence of bar code symbol information by said processing means to thereby determine orientation of said linearly arranged pattern of bar code data in said bar code symbol; and

(e) thereafter scanning said binary representation in the memory array via said parallel port of said memory array using addressing based on said determined orientation to produce electrical bar code data to said processing means, and decoding said electrical bar code data using said processing means.

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 may be non-parallel to the rows or columns of the light-detector array.

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

10. A method according to claim 1 further comprising 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 two-dimensional bar code symbols of the type having a plurality of rows of bar code data, said method comprising the steps of:

(a) generating directly in a light-responsive array a binary representation of a two-dimensional field of view, said 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 direct serial only coupling;

(b) scanning said memory array via a parallel port to said memory array, said scanning including generating an effective scan line having an angular orientation corresponding to that of a representation of said symbol included within said binary representation, said scanning being effective to produce electrical data output; and

scanning including using said processing means to read the electrical data output to locate a portion of the bar code information and determine said angular orientation of said bar code information, and thereafter addressing said memory based on said angular orientation to produce electrical data output corresponding to complete rows of said symbol.

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 said memory array includes addressing rows and columns of an array of memory cells of that 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. Apparatus according to claim 15 wherein said processing means accessing the memory array evaluates data read from said memory array to identify bar code patterns by detecting the ratio of data representing bars to data representing space between bars.

18. 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.

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

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

21. 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.

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

23. Apparatus according to claim 21 wherein said optical means directs a light beam onto said field of view and focuses reflected light onto said light-responsive array.

24. Apparatus for reading a two-dimensional bar code symbol having plurality of rows of bar code information, comprising:

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

(b) a memory array having a serial port receiving 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, 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 orientation, and said processing means including means for finding bar code information in said binary representation for one row of said symbol to determine said orientation of said symbol for accessing said memory array to scan complete rows of said symbol.

25. Apparatus according to claim 24 wherein said processing 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.

26. Apparatus according to claim 24 wherein said light responsive array is in a hand-held unit aimed toward the bar code symbol.

27. Apparatus according to claim 26 wherein the hand-held unit includes a manually activated trigger, said trigger being actuated to initiate said accessing of the light-responsive array.

28. Apparatus according to claim 24 wherein said means accessing the memory array evaluates data from the memory array to identify bar code patterns by counting transitions between data representing bar and data representing space between bars.

29. A method of reading a two-dimensional symbol, said symbol having a plurality of different linearly arranged indicia patterns of encoded information, each pattern having a reading direction corresponding to said linearly arranged patterns, said method comprising the steps of:

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

(b) transferring to a port of a memory a binary representation of light impinging upon the light-detector device;

(c) scanning said binary representation in said memory using a plurality of scan paths, via a port of said memory, to produce electrical output to processing means;

(d) evaluating said electrical data output including finding the presence of a part of said encoded information by said processing means and further including determining the orientation of one of said plurality of said linearly arranged patterns in said symbol; and

(e) thereafter scanning said binary representation in the memory using scan paths based on said determined orientation to produce encoded information to said processing means.

30. A method according to claim 29 wherein said light-detector device is a two-dimensional array.

31. A method according to claim 29 wherein said symbol is a plurality of parallel rows of differing bar code data and said linearly arranged patterns are said rows.

32. A method according to claim 29 wherein said memory has a serial port for receiving said binary representation from said light-detector device, and has a second port for access by said processing means.

33. A method of operating a scanner for reading a two-dimensional symbol, said symbol having differing pattern s in vertical versus horizontal directions and having preferred directional paths for reading data therein, said method comprising the steps of:

(a) generating with a light-responsive device a representation of a two-dimensional field of view, the field of view including said symbol to be read;

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

then transferring said representation in binary form to a memory array;

(b) scanning said memory by accessing said memory array by processing means, said scanning including generating a scan line by addressing said memory and evaluating data accessed by said addressing to find indications of valid data for a complete row of said symbol to thereby develop a scan line for a first readable path, and thereafter generating additional scan lines oriented to said scan line for a first readable row, to read additional paths of said symbol.

34. A method of reading a two-dimensional symbol, said symbol having a plurality of different linearly arranged indicia patterns of encoded information, each pattern having a preferred reading direction corresponding to said linearly arranged patterns, said method comprising the steps of:

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

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

(c) scanning said binary representation in the memory using a plurality of scan paths, via a port of said memory to produce electrical data output to processing means;

(d) evaluating said electrical data output including finding said symbol by detecting characteristics of a portion of said symbol, then orienting said scan paths until a full pattern is found in a given scan path, then continuing to scan said memory using further scan paths oriented according to said given scan path.

35. A method according to claim 34 wherein further scan paths are linear and parallel.

36. A method according to claim 34 wherein said light-detector device is a two-dimensional array.

37. A method according to claim 34 wherein said symbol is a plurality of parallel rows of differing bar code data and said linearly arranged patterns are said arrays.

38. A method according to claim 34 wherein said memory has a serial port for receiving said binary representation from said light-detector device, and has a second port for access by said processing means.

39. A method of reading a bar code symbol or the like comprising the steps of:

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

(b) transferring to a memory array a binary representation of light impinging upon the light-detector array;

(c) scanning said memory array along a sequence of scan paths to produce electrical data output to at least a corresponding segment of a row including bar code information;

(d) changing said sequence of scan paths if a partial row of bar code information is detected within a single scan line of said scan paths; and

(e) repeating steps (c) and (d) until the data represented in the complete symbol has been recognized.