Laser scanner for reading two dimensional bar codes

• US 5,637,851 A
• Filed: 02/14/1995
• Issued: 06/10/1997
• 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: Swartz, Jerome, Metlitsky, Boris
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): LEE, MICHAEL GUNYOUNG
• Application Number:
  US08/388,480
• Time in Patent Office: 847 Days
• Field of Search: 235/462, 235/470
• US Class Current: 235/462.2
• CPC Class Codes: G06K 19/06037 multi-dimensional coding
• CPC Class Codes: G06K 2019/06262 with target- or other orientation-indicating feature
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners
• CPC Class Codes: G06K 7/1093 sensing, after transfer of the image of the data-field to an intermediate store, e.g. storage with cathode ray tube
• CPC Class Codes: G06K 7/1456 determining the orientation of the optical code with respect to the reader and correcting therefore

Abstract

An apparatus and method for reading data in the form of indicia on a surface of a target, the indicia having a preferred reading direction, including a light source for illuminating a portion of the surface to be read with a laser beam in a scanning pattern at a predetermined scanning angle so as to scan spatially adjacent portions of the surface. A detector and a processor is provided that is operative for detecting at least a portion of the light reflected from the indicia and storing representations thereof, and further determining the angular difference between the preferred reading direction and the scanning angle. An optical component disposed adjacent the light source is provided for optically directing the laser beam along a path toward the surface and is capable of controlling and setting the predetermined scanning angle. Furthermore, the optical component may be automatically rotated so as to align the direction of scan with the preferred reading direction of the indicia.

Claims

1. A system for reading a bar code symbol, said symbol having at least one group of elements, comprising a hand-held scanning unit in a lightweight, portable housing comprising:

(a) a light source for generating light beam directed toward a target area including a symbol to be read;

(b) means for optically modifying and directing the light beam along an optical path toward said symbol located in the vicinity of a reference plane exterior to said scanning unit and for scanning spatially adjacent portions of said reference plane;

(c) a photo detector component having a field of view and operative for detecting light of variable intensity reflected off said target area and for generating electrical signals indicative of the detected intensity;

(d) means for converting said electrical signals into digital representations thereof, the digital representations embodying a bit map image of said target area;

(e) means for storing said digital representations in addressable storage medium;

(f) means for accessing said storage medium in an address sequence corresponding to a linear scan through the bit map image and processing each pixel in such linear scan to determine the presence in the bit map image of at least one group of elements of said symbol included within the field of view of said photo detector component; and

(g) means for automatically changing said address sequence to a second linear scan if said linear scan results in recognizing only a portion of a group of elements of said symbol.

2. The system of claim 1 wherein said group is a row.

3. The system of claim 1 wherein said light source comprises a laser diode.

4. The system of claim 1 wherein said addressable storage medium is a memory array.

5. An apparatus for detecting indicia including a plurality of groups of elements of different light reflectivity, comprising:

(a) a light source for emitting a light beam;

(b) an optical component disposed in the path of said beam for optically modifying and directing the light beam along an optical path toward a target located in the vicinity of a reference plane lying in said optical path so as to scan spatially adjacent elements of groups in said reference plane in a first scan direction;

(c) sensor means having a field of view operative for detecting light of variable intensity reflected off said target, and for generating an electrical image of said field of view of said sensor means;

(d) means for storing said electrical image in an addressable storage medium;

(e) means for performing a linear scan of said electrical image in said addressable storage medium; and

(f) means for changing said linear scan of said electrical image to a different linear scan if a partial but not complete group of elements is recognized by the linear scan of step (e).

6. The apparatus of claim 5 wherein said groups are rows.

7. The apparatus of claim 5 wherein said light source comprises a laser diode.

8. The apparatus of claim 5 wherein said optical component comprises a scanning mirror.

9. The apparatus of claim 8 wherein said scanning mirror is connected to mechanical means for moving said scanning mirror so as to direct said light beam along said optical path.

10. The apparatus of claim 5 wherein said means for processing said electrical signal comprises a microprocessor.

11. A system for reading a bar code symbol, said symbol having at least one row, comprising:

a hand-held scanning unit in a lightweight, portable housing including

(i) a light source for generating a light beam directed toward a symbol to be read;

(ii) means for optically modifying and directing the light beam along an optical path toward said symbol located in the vicinity of a reference plane exteriorly of the scanning trait and for scanning spatially adjacent portions of said reference plane;

(iii) a photodetector component having a field of view and operative for detecting at least a portion of light of variable intensity reflected off the symbol and for generating electrical signals indicative of the detected intensity;

(iv) means for converting said electrical signals into digital representations thereof, the digital representations embodying a bit-map image of the field of view of said photodetector component;

(v) means for storing said digital representations in an addressable storage medium; and

(vi) means for accessing said storage means in an address sequence corresponding to a linear scan through the bit-map image and determining if a row of the bit-map image corresponds to a row of the symbol; and

(vii) means responsive to said determining for automatically changing said accessing to a second address sequence if said linear scan recognizes a partial row of said symbol.

12. A system as defined in claim 11, wherein said means for accessing said storage means addresses rows and columns of an array of memory cells in a sequence of addresses representing a raster scan of the field of view at a predetermined angle with respect to the axes of the field of view.

13. A system as defined in claim 11, wherein said symbol includes a plurality of rows and bar and space patterns in a two-dimensional array, and further comprises means for processing the data derived from said storing means to determine whether a predetermined pattern is present in the field of view.

14. A system as defined in claim 11, wherein said means for optically modifying and directing the laser beam generates a scan pattern of mutually parallel scan lines.

15. A method for reading a symbol, the symbol comprising at least one recognizable code pattern, comprising the steps of:

(a) directing a light beam from a light source in a scanning pattern over a symbol to be read;

(b) detecting at least a portion of light of variable intensity reflected off the symbol over a field of view and generating digital data representative of the detected light intensity;

(c) transferring the digital data to a memory array such that a digital bitmapped image of the field of view is obtained;

(d) outputting a portion of the digital bitmapped image data from the memory array in such a manner that a scan of the bitmapped image of at least a portion of a scan line is obtained;

(e) processing said outputted portion of said digital bitmapped image data to determine if a code pattern of an entire row of a bar code symbol was scanned; and

(f) changing said outputting of a portion of the digital bitmapped image data if it is determined that a code pattern of a partial row of a bar code symbol was obtained in the output from the memory array.

16. The method of claim 15, wherein the symbol comprises at least two recognizable code patterns wherein steps (d), (e) and (f) further comprise the steps of:

(d) outputting the digital bitmapped image data from the memory array in a first manner such that a rectilinear scan of the bitmapped image is obtained;

(e) processing the output digital bitmapped image data from step (d) to identify a first recognizable code pattern;

(f1) outputting the digital bitmapped image data from the memory array in a second manner such that an angular scan of the bitmapped image is obtained; and

(f2) processing the output digital bitmapped image data from step (f1) to identify a second recognizable code pattern thereby reading the symbol.

17. The method of claim 15, wherein the scanning pattern of step (a) comprises a pattern of mutually parallel lines.

18. A method of reading a symbol containing light variable elements arranged in multiple rows comprising the steps of:

(a) directing a light beam across a target area containing said symbol in a pattern sufficient to capture all elements contained in said target area;

(b) creating an electrical image of reflected light of varying intensity from said target area;

(c) storing said electrical image in an addressable storage medium;

(d) processing said electrical image by performing a linear scan of said addressable storage medium in an effort to read said symbol;

(e) manipulating said linear scan of said addressable storage medium until the entire row of said symbol is recognized; and

(f) continuing the linear scan for which an entire row of said symbol was recognized, until the entire symbol is read.

19. The method as defined in claim 18 wherein said step of directing a light beam includes generating a scan pattern of mutually parallel scan lines.

20. The method of claim 18 wherein the steps are performed using a hand-held unit which includes a manually-activated trigger, and the method further includes the step of manually actuating said trigger to initiate said step of directing said light beam.

21. A method for scanning a bar code symbol having a plurality of discrete groups of information containing elements of different light reflectivity on a target, comprising the steps of:

(a) directing a light beam in a scanning pattern over a target area containing a symbol to be read;

(b) detecting reflected light of variable intensity reflected off said target area;

(c) generating electrical signals indicative of said detected light of variable intensity;

(d) converting said electrical signals into digital representations thereof, said digital representations comprising a bit map image of said target area;

(e) storing said digital representations in an addressable storage medium;

(f) accessing said addressable storage medium in a first address sequence corresponding to a first linear scan through said bit map image;

(g) processing each pixel in said linear scan to determine the presence in said bit map image of at least a portion of one group of elements of said symbol;

(h) changing said address sequence to create a different linear scan through said bit map image if less than all of a group of elements of said symbol was determined to be present;

(i) processing each pixel in said different linear scan to determine the presence in said bit map image of at least a portion of one group of elements of said symbol;

(j) repeating steps (g) and (h) until an entire group of elements of said symbol is recognized; and

(k) continuing the linear scan for which an entire group of elements of said symbol was recognized.

22. A method as defined in claim 21, wherein said step of directing said light beam includes generating a scan pattern of mutually parallel scan lines.

23. A method as defined in claim 21, wherein said step of accessing the addressable storage medium includes addressing the rows and columns of said addressable storage medium in a sequence of addresses that represents a linear traversal of the field of view.

24. The method of claim 21 wherein the steps are performed using a hand-held unit which includes a manually-activated trigger, and the method further includes the step of manually actuating said trigger to initiate said step of directing said light beam.

25. A method for scanning a bar code symbol having a plurality of rows of data comprising the steps of:

(a) scanning a light beam over a target area containing a symbol to be read;

(b) creating a digital representation of reflected light from said target area;

(c) storing said digital representation in memory;

(d) accessing said memory in a linear scan;

(e) determining for each scan line whether a portion of a row of said symbol has been recognized;

(f) changing said linear scan of said memory to a different scan path if only a portion of a row of said symbol was recognized in step (e);

(g) repeating steps (d)-(f) until an entire row of said symbol is recognized; and

continuing said linear scan with which an entire row was recognized.