Bar code symbol scanning system employing time-division multiplexed laser scanning and signal processing to avoid optical cross-talk and other unwanted light interference

• US 6,969,004 B2
• Filed: 07/26/2002
• Issued: 11/29/2005
• Est. Priority Date: 01/11/2002
• Status: Expired due to Term

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Lucera, Mark, Ralph, Joseph
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US10/207,731
• Publication Number:
  US 20030136843A1
• Time in Patent Office: 1,222 Days
• Field of Search: 23546201-46248, 235/472.01, 235/472.02, 235/472.03, 235/470, 235/454, 235/455, 250/223.R
• US Class Current: 235/462.25
• CPC Class Codes: A47F 9/04 Check-out counters, e.g. for self-service stores
• CPC Class Codes: G06K 7/10623 Constructional details
• CPC Class Codes: G06K 7/10693 for omnidirectional scanning
• CPC Class Codes: G06Q 20/20 Point-of-sale [POS] network systems
• CPC Class Codes: G06Q 20/201 Price look-up processing, e.g. updating
• CPC Class Codes: G06Q 20/202 Interconnection or interaction of plural electronic cash registers [ECR] or to host computer, e.g. network details, transfer of information from host to ECR or from ECR to ECR
• CPC Class Codes: G06Q 20/203 Inventory monitoring
• CPC Class Codes: G06Q 20/204 comprising interface for record bearing medium or carrier for electronic funds transfer or payment credit
• CPC Class Codes: G06Q 30/02 Marketing; Price estimation or determination; Fundraising
• CPC Class Codes: G07G 1/0045 with a code reader for reading of an identifying code of the article to be registered, e.g. barcode reader or radio-frequency identity [RFID] reader
• CPC Class Codes: G07G 1/0054 with control of supplementary check-parameters, e.g. weight or number of articles

Abstract

A laser scanning system that employs synchronous time-division-multiplexed laser scanning operations and signal processing operations. A plurality of successive non-overlapping time slots are defined and logically assigned to a unique laser scanning beam and corresponding photosensor. During a given time slot, the laser scanning beam logically assigned thereto is selectively generated (or selectively projected) into the scanning volume while generation (or projection) of the other laser scanning beam is disabled. During the given time slot, the photosensor logically assigned thereto is operably coupled to signal processing circuitry that performs bar code detection operations on the data signals derived therefrom while the other photosensor is operably decoupled from such signal processing circuitry. The frequency of time slots logically assigned to a given laser scanning beam and corresponding photosensor is preferably greater than at least two times the highest frequency component expected in the scan data signal received at the photosensor.

Claims

1. A method of scanning bar code symbols on objects within a 3-D volume with a plurality of multidirectional laser scanning beams, said method comprising the steps of:

providing a plurality of photosensors corresponding to said plurality of multidirectional laser scanning beams;

generating timing signals that represent success non-overlapping time slots each logically assigned to a unique laser scanning beam and corresponding photosensor; and

in response to said timing signals, controlling generation of said plurality of laser multidirectional scanning beams and synchronously controlling signal processing operations that perform bar code detection and decoding operations on data signals derived from output of said plurality of photosensors.

2. The method of claim 1, wherein the step of controlling generation of said plurality of multidirectional laser scanning beams operates, during a given time slot, to:

turn on the corresponding one laser scanning beam which is logically assigned to the given time slot; and

turn substantially off any other laser scanning beam of said plurality of multidirectional laser scanning beams.

3. The method of claim 2, wherein a given laser scanning beam is turned on by operating the visible laser diode module that produces such laser scanning beam at an optical power level much greater than its threshold optical power level.

4. The method of claim 2, wherein a given laser scanning beam is turned substantially off by operating the visible laser diode module that produces such laser scanning beam at an optical power level less than its threshold optical power level.

5. The method of claim 2, wherein a given laser scanning beam is turned substantially off by operating the visible laser diode module that produces such laser scanning beam at an optical power level near its threshold optical power level, thereby enabling quick turn on of the visible laser diode module.

6. The method of claim 2, wherein a given laser scanning beam is turned on by supplying current to a visible laser diode module that produces such laser scanning beam at a current level much greater than threshold current for said visible laser diode module.

7. The method of claim 6, further comprising the step of controlling said current level provided to said visible laser diode module by modulating a dynamic current source.

8. The method of claim 7, wherein said dynamic current source is directly coupled to said visible laser diode module.

9. The method of claim 2, wherein a given laser scanning beam is turned substantially off by supplying current to a visible laser diode module that produces such laser scanning beam at a current level near or less than threshold current for said visible laser diode module.

10. The method of claim 9, further comprising the step of controlling current level provided to said visible laser diode module by modulating a dynamic current source.

11. The method of claim 10, wherein said dynamic current source is directly coupled to said visible laser diode module.

12. The method of claim 2, wherein a given laser scanning beam is selectively turned on and turned substantially off by modulating a dynamic current source that directly supplies current to a visible laser diode module that produces such laser scanning beam.

13. The method of claim 12, further comprising the step of providing a current source that operates independent from said dynamic current source to directly supply current to said visible laser diode module at a current level at or near threshold current for said visible laser diode module, thereby enabling quick turn on of said visible laser diode module.

14. The method of claim 2, wherein a given laser scanning beam is selectively turned on and turned substantially off by modulating a switchable current source that directly supplies current to a visible laser diode module that produces such laser scanning beam.

15. The method of claim 1, wherein each pair of non-overlapping time slots is bounded by a null period, and wherein the step of controlling generation of said plurality of multidirectional laser scanning beams operates during each null period to disable generation of said plurality of multidirectional laser scanning beams.

16. The method of claim 1, further comprising the steps of:

providing signal processing circuitry that, when operably coupled to the output of said photosensors, detects and decoded bar code symbols therein; and

in response to said timing signals, selectively enabling only one of said plurality of photosensors to be operably coupled to said signal processing circuitry during a given time slot.

17. The method of claim 16, further comprising the step of:

controlling multiplexing circuitry coupled between said plurality of photosensors and said signal processing circuitry to selectively couple signal processing circuitry to one photosensor during a time slot corresponding to said one photosensor.

18. The method of claim 17, wherein said signal processing circuitry includes shared analog to digital signal conversion circuitry that processes signals derived from any one of said plurality of photosensors when operably coupled thereto via said multiplexing circuitry.

19. The method of claim 18, further comprising the step of selectively enabling said shared analog to digital signal conversion circuitry during time slots when any one of said plurality of photosensors is operably coupled thereto via said multiplexing circuitry.

20. The method of claim 16, wherein said signal processing circuitry includes a plurality of analog to digital signal converters each processing signals derived from a unique one of said plurality of photosensors.

21. The method of claim 20, further comprising the step of selectively enabling one of said plurality of analog to digital signal converters during a time slot corresponding thereto.

22. The method of claim 1, wherein frequency of time slots logically assigned to a given laser scanning beam and corresponding photosensor is greater than at least two times the highest frequency component expected in the scan data signal received at said photosensor.

23. The method of claim 1, wherein time slots logically assigned to a given laser scanning beam and corresponding photosensor correspond to scanning planes generated by the given laser scanning beam during revolution of at least one rotating polygonal mirror.

24. The method of claim 1, wherein time slots logically assigned to a given laser scanning beam and corresponding photosensor correspond to scanning plane groups generated by the given laser scanning beam during revolution of at least one rotating polygonal mirror.

25. An optical scanner comprising:

at least one laser light source for generating a plurality of laser scanning beams;

optical elements for projecting multiple laser scanning beams into a scanning volume at different orientations, collecting reflection from such multiple laser scanning beams, and directing such reflection to a plurality of photosensors corresponding in number to said plurality of laser scanning beams;

signal processing circuitry that, when operably coupled to the output of said photosensors, detects and decoded bar code symbols therein;

timing signal generation circuitry that generates timing signals that correspond to successive non-overlapping time slots each logically assigned to a unique laser scanning beam and corresponding photosensor;

a laser light source control mechanism that operates during a given time slot, in response to the timing signals generated by said timing signal generation circuitry, to selectively enable the one laser scanning beam logically assigned to the given time slot to be generated and/or projected into said scanning volume; and

a signal processing control mechanism that operates during the given time slot, in response to the timing signals generated by said timing signal generation circuitry, to selectively enable the one photosensor logically assigned to the given time slot to be operably coupled to said signal processing circuitry.

26. The optical of claim 25, wherein a subset of said multiple scanning beams are substantially coincident to one another.

27. The optical scanner of claim 25, wherein said at least one light source comprises a plurality of visible laser diodes, and wherein said laser light source control mechanism selectively disables generation of the scanning laser beam by a given visible laser diode by controlling power supplied to the given visible laser diode.

28. The optical scanner of claim 25,

wherein each pair of non-overlapping time slots in bounded by a null period;

wherein said laser light source control mechanism that operates, in response to the timing signals generated by said timing signal generation circuitry, to disable generation and/or projection of said plurality of laser scanning beams into said scanning volume during each null period; and

wherein the signal processing control mechanism operates, in response to the timing signals generated by said timing signal generation circuitry, to operably decouple said plurality of photosensors from said signal processing circuitry diving each null period.

29. The optical scanner of claim 25, including at least a horizontal housing portion with a first scanning window disposed therein, wherein said multiple laser scanning beams are projected at different orientations through said first scanning window into a scanning volume disposed above the horizontal window.

30. The optical scanner of claim 25, including at least a horizontal housing portion with a first scanning window disposed therein and a vertical housing portion with a second scanning window disposed therein, wherein said multiple laser scanning beams are projected at different orientations through said first and second scanning windows into a scanning volume disposed adjacent the first and second scanning windows.

31. The optical scanner of claim 25, wherein said timing signal generator includes an oscillator and multi-state counter.

32. The optical scanner of claim 25, wherein said at least one laser light source includes a plurality of visible laser diodes, and said laser light source control mechanism selectively disables said generation of the laser scanning beam by a given visible laser diode by controlling supply of power to the given visible laser diode.

33. The optical scanner of claim 25, wherein said at least one laser light source includes a visible laser diode, and said laser light source control mechanism selectively disables projection of the laser scanning beam generated by the visible laser diode with an optical shutter.

34. The optical scanner of claim 25, wherein said at least one laser light source includes a visible laser diode, and said laser light source control mechanism selectively disables projection of the laser scanning beam generated by the visible laser diode with a beam deflector.

35. The optical scanner of claim 25, wherein said signal processing control mechanism includes multiplexing circuitry coupled between said plurality of photosensors and said signal processing circuitry, and wherein said multiplexing circuitry is controlled to selectively couple signal processing circuitry to a given photosensors during a time slot corresponding thereto.

36. The optical scanner of claim 35, wherein said signal processing circuitry includes shared analog to digital signal conversion circuitry that processes signals derived from any one of said plurality of photosensors when operably coupled thereto via said multiplexing circuitry.

37. The optical scanner of claim 36, wherein said signal processing control mechanism selectively enables said shared analog to digital signal conversion circuitry during time slots when any one of said plurality of photosensors is operably coupled thereto via said multiplexing circuitry.

38. The optical scanner of claim 25, wherein said signal processing circuitry includes a plurality of analog to digital signal converters each processing signals derived from a unique one of said plurality of photosensors, and wherein said signal processing control mechanism selectively enables one of said plurality of analog to digital signal converters during a time slot corresponding thereto.

39. The optical scanner of claim 25, wherein said laser light source control mechanism turns on a given laser scanning beam by operating a visible laser diode module that produces such laser scanning beam at an optical power level much greater than its threshold optical power level.

40. The optical scanner of claim 25, said laser light source control mechanism turns substantially off a given laser scanning beam by operating a visible laser diode module that produces such laser scanning beam at an optical power level less than its threshold optical power level.

41. The optical scanner of claim 25, said laser light source control mechanism turns substantially off a given laser scanning beam by operating a visible laser diode module that produces such laser scanning beam at an optical power level near its threshold optical power level, thereby enabling quick turn on of the visible laser diode module.

42. The optical scanner of claim 25, wherein said laser light source control mechanism turns on a given laser scanning beam by supplying current to a visible laser diode module that produces such laser scanning beam a current level much greater than threshold current for said visible laser diode module.

43. The optical scanner of claim 42, wherein said laser light source control mechanism controls said current level provided to said visible laser diode module by modulating a dynamic current source.

44. The optical scanner of claim 43, wherein said dynamic current source is directly coupled to said visible laser diode module.

45. The optical scanner of claim 25, wherein said laser light source control mechanism turns substantially off a given laser scanning beam by supplying current to a visible laser diode module that produces such laser scanning beam at a current level near or less than threshold current for said visible laser diode module.

46. The optical scanner of claim 45, wherein said laser light source control mechanism controls current level provided to said visible laser diode module by modulating a dynamic current source.

47. The optical scanner of claim 46, wherein said dynamic current source is directly coupled to said visible laser diode module.

48. The optical scanner of claim 25, wherein frequency of time slots logically assigned to a given laser scanning beam and corresponding photosensor is greater than at least two times the highest frequency component expected in the scan data signal received at said photosensor.

49. The optical scanner of claim 25, wherein time slots logically assigned to a given laser scanning beam and corresponding photosensor correspond to scanning planes generated by the given laser scanning beam during revolution of at least one rotating polygonal mirror.

50. The optical scanner of claim 25, wherein time slots logically assigned to a given laser scanning beam and corresponding photosensor correspond to scanning plane groups generated by the given laser scanning beam during revolution of at least one rotating polygonal mirror.