Bar code reader to read different bar code formats

• US 5,051,567 A
• Filed: 06/13/1989
• Issued: 09/24/1991
• Est. Priority Date: 06/13/1989
• Status: Expired due to Term

• Current Assignee: George L. Harwood of Printronix Inc.
• Original Assignee: RJS, Inc. (Zebra Technologies Corporation)
• Inventors: Tedesco, Jack
• Primary Examiner(s): Levy, Stuart S.
• Assistant Examiner(s): Weinberg, Richard M.
• Application Number:
  US07/365,544
• Time in Patent Office: 833 Days
• Field of Search: 235/462, 235/454, 235/439, 235/435, 235/465, 235/472, 250/553, 250/208.1, 250/208.3, 250/211 R, 250/568
• US Class Current: 235/462.17
• CPC Class Codes: G06K 2207/1013 Multi-focal
• CPC Class Codes: G06K 7/10841 Particularities of the light-sensitive elements semiconductor devices H01L

Abstract

A bar code reader is described which can accurately read bar codes with different minimum widths of dark and light elements. The reader includes a lens that forms an image of a portion of a bar code onto a detector assembly which includes a photocell. The photocell output is delivered to a detection circuit that detects the passage of images of light and dark elements across the photodetector. In one arrangement, the detector assembly defines a plurality of photocell devices have photosensitive regions of different areas, and a switch assembly connects a selected one of the photocell devices to the detector circuit. The detector assembly can include several independent cells (52-58, FIG. 4) of different diameters, with one at a time connected to the detection circuit. The detector assembly can instead include several closely adjacent photocells (82-88, FIG. 5), with selected groups connected in parallel to the detection circuit. In another arrangement, a mask is provided, with holes (142-148, FIG. 7) of different diameters, and the mask can be moved so a selected one of the holes lies in front of a large photocell. In another arrangement, a zoom lens (112, FIG. 6) varies the magnification of the bar code image formed on a photocell. In another arrangement, a camera-type iris (162, FIG. 9) lies over a photocell.

Claims

1. In a bar code reader for reading bar codes having dark and light bar shaped elements of different densities, wherein some bar code formats have bars of different widths than those of other bar code formats, which includes a detector assembly that detects light incident thereon, optic means for forming an image of a portion of a bar code lying at a particular position onto said detector assembly and where the image moves relative to the detector assembly, and a detector circuit for indicating the presence of different bar code elements, the improvement wherein:

said detector assembly defines a plurality of photocell devices each having a photosensitive region of predetermined area, each photocell device generating an electrical signal of a magnitude dependent upon the amount of light incident on its photosensitive region;

switch means for connecting a selected one, but not other, of said photocell devices to said detector circuit, which optimizes reading of a particular bar code format, during the entire reading of at least one bar code having a plurality of said elements;

said photocell devices having photosensitive regions of different areas, and said optic means being constructed to form an image of said bar code portion onto all of said photocell devices during said relative movement.

2. The improvement described in claim 1 wherein:

said plurality of photocell devices includes a plurality of substantially coplanar and closely spaced but separate photocells having light sensitive regions of different areas, with each photocell device having an outer edge and being constructed to detect substantially all light within said outer edge.

3. The improvement described in claim 1 wherein:

said plurality of photocell devices includes a plurality of closely spaced individual photocells, and said switch means is constructed to deliver a signal to said detector circuit equal to the sum of the amplitudes of the outputs of a plurality of said photocells.

4. The improvement described in claim 3 wherein:

said photocells have substantially circular peripheries of different diameters and lie concentric to each other, with small gaps between adjacent photocells, so the sum of the amplitudes of the outputs of the innermost and a plurality of adjacent photocells substantially equals the output of a circular photocell having the same diameter as the largest photocell.

5. The improvement described in claim 1 including:

a plurality of light emitting devices which each emits light of a different spectrum, each positioned to illuminate said portion of said bar code; and

means for energizing a selected one of said light emitting devices during the entire reading of at least one bar code having a plurality of said elements.

6. A bar code reader which can read bar codes each formed of elongated light and dark elements and wherein different bar code formats have different densities of bar code elements, comprising:

illuminating means for illuminating a bar code lying at a particular position;

a detector assembly which generates an electrical signal;

an optical device which forms an image of a portion of a bar code at said position onto said detector assembly, said optical device being relatively moveable across the bar code to focus portions of all code elements of the bar code onto the detector assembly;

a detector circuit coupled to said detector assembly and constructed to indicate the presence of different code elements;

said optical means being operable to form said image at any of a plurality of different selected magnifications onto said detector assembly, and including means for operating said optical device to select a magnification in accordance with the format of the bar code at said position.

7. A method for reading bar codes that each includes a plurality of dark and light bar code elements, wherein different bar codes may be encountered in which the elements in one bar code may have a greatly different width than the elements in another bar coe, comprising:

establishing a detector assembly which contains at least two photocell devices;

establishing a detector circuit for indicating the presence of differnt bar code elements;

forming an image of a portion of a bar code onto all photocell devices of said detector apparatus and moving the image relative to the detector assembly, until images of portions of all of the elments of the bar code have moved past the detector assembly;

connecting a selected one of said photocell devices, but not the other of said photocell devices, to said detector circuit during a period when images of portions of all the elements of a bar code have moved past the detector assembly. assembly and where the image moves relative to the detector assembly, and a detector circuit for indicating the presence of different bar code elements, the improvement wherein;

said detector assembly defines a plurality of photocell devices each having a photosensitive region of predetermined area, each photocell device generating an electrical signal of a magnitude dependent upon the amount of light incident on its photosensitive region;

switch means for connecting a selected one, but not other, of said photocell devices to said detector circuit, which optimizes reading of a particular bar code format, during the entire reading of at least one bar code having a plurality of said elements;

said photocell devices having photosensitive regions of different areas, and said optic means being constructed to form an image of said bar code portion onto all of said photocell devices during said relative movement.

8. A bar code reader which can read bar codes each formed of elongated light and dark elements and wherein different bar code formats have different densities of bar code elements, comprising:

a source of light positioned to illuminate a bar code lying at a particular position;

a detector assembly which generates an electrical signal;

an optical device positioned to form an image of a portion of a bar code lying at said position onto said detector assembly, said optical device being relatively moveable across the bar code to focus portions of all bar code elements of the bar code onto the detector assembly;

a detector circuit coupled to said detector assembly and constructed to indicate the presence of different code elements;

said detector assembly including a plurality of closely spaced but separate photocells that each have a light sensitive region and that are each constructed to generate an electrical signal of a magnitude dependent on the amount of light incident on the entire light sensitive region of the photocell, said plurality of photocells being closely spaced and lying substantially in a common plane and substantially equally spaced from said optical device, so the bar code image falls on all of said photocells as the optical device moves across the bar code;

said plurality of photocells each having a light sensitive region of a different effective area, and said detector assembly having a switch assembly arranged to connect a selected one of said photocells to said detector circuit so the signal delivered to said detector circuit equals the output from a single one of said photocells.

said source of light includes a plurality of energizable light emitting devices spaced about the path of light extending through said optic means from said portion of a bar code at said position;

said light emitting devices are each constructed to emit light of a different narrow bandwidth;

said switch assembly being constructed to energize only a selected one of said light emitting devices during the reading of an entire bar code containing a plurality of elements.

9. A bar code reader which can read bar codes each formed of elongated light and dark elements and wherein different bar code formats have different densities of bar code elements, comprising:

a source of light positioned to illuminate a bar code lying at a particular position;

a detector assembly which generates an electrical signal;

an optical device positioned to form an image of a portion of a bar code at said position onto said detector assembly, said optical device being relatively moveable across the bar code to focus portions of all code elements of the bar code onto the detector assembly;

a detector circuit coupled to said detector assembly and constructed to indicate the presence of different code elements;

said detector assembly including a plurality of closely spaced but separate concentric photocells that each have a light sensitive region and that are each constructed to generate an electrical signal of a magnitude dependent on the amount of light incident on the light sensitive region thereof, said plurality of photocells being closely spaced and lying substantially in a common plane so the bar code image falls on all of said photocells as the optic means moves across the bar code;

said detector assembly including a switch assembly constructed to deliver to said detector circuit a signal representing the combined outputs of the photocells of any of a plurality of different groups of said photo cells, with each group including a photocell of largest diameter and all photocells lying within it, so the signal delivered to said detector circuit equals the output from a single photocell covering the same areas occupied by said plurality of photocells.