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 7,510,118 B2
• Filed: 11/21/2005
• Issued: 03/31/2009
• 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:
  US11/285,752
• Publication Number:
  US 20060283954A1
• Time in Patent Office: 1,226 Days
• Field of Search: 23546201-46245, 235/472.01, 235/472.02, 235/472.03, 235/454, 235/455, 235/494
• 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 (for bar code detection). 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. Moreover, 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. In other embodiments, the time slots logically assigned to a given laser scanning beam and corresponding photosensor correspond to scanning planes (or scanning plane groups) generated by the given laser scanning beam during revolution of at least one rotating polygonal mirror. In the preferred embodiment, such synchronous time-division-multiplexed laser scanning operations and signal processing operations (for bar code detection) are embodied in a bioptical laser scanning system comprising a plurality of laser scanning stations, each of which produces a plurality of groups of quasi-orthogonal laser scanning planes that are projected within predetermined regions of space contained within a 3-D scanning volume defined between the bottom and side-scanning windows of the system.

Claims

1. A bar code symbol scanning system comprising:

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

optical elements for projecting said plurality of laser scanning beams into a scanning volume at different orientations for scanning one or more bar code symbols on objects within the scanning volume, collecting light reflections from said laser scanning beams, and directing these light reflections to a plurality of photosensors corresponding in number to the plurality of laser scanning beams and producing electrical signals corresponding to light reflections from the scanned bar code symbols;

signal processing circuitry operably, coupled to the output of said photosensors, for processing said electrical signals and detecting and decoding the bar code symbols scanned by the laser scanning beams;

timing signal generation circuitry for generating timing signals that correspond to successive non-overlapping time slots,

wherein each said laser scanning beam and corresponding photosensor is logically assigned to one of said successive non-overlapping time slots;

a laser light source control mechanism for operating, during a given time slot, in response to the timing signals generated by said timing signal generation circuitry, so as to selectively enable one said 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 for operating, during the given time slot, in response to the timing signals generated by said timing signal generation circuitry, so as to selectively enable one said photosensor, logically assigned to the given time slot, to be operably coupled to said signal processing circuitry.

2. The bar code symbol scanning system of claim 1, wherein a subset of said multiple scanning beams are substantially coincident to one another.

3. The bar code symbol scanning system of claim 1, 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.

4. The bar code symbol scanning system of claim 1,

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, so as to operably decouple said plurality of photosensors from said signal processing circuitry during each null period.

5. The bar code symbol scanning system of claim 1, 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.

6. The bar code symbol scanning system of claim 1, 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.

7. The bar code symbol scanning system of claim 1, wherein said timing signal generator includes an oscillator and multi-state counter.

8. The bar code symbol scanning system of claim 1, 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.

9. The bar code symbol scanning system of claim 1, 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.

10. The bar code symbol scanning system of claim 1, 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.

11. The bar code symbol scanning system of claim 1, 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.

12. The bar code symbol scanning system of claim 11, 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 to said signal processing circuitry via said multiplexing circuitry.

13. The bar code symbol scanning system of claim 12, 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 to said signal processing circuitry via said multiplexing circuitry.

14. The bar code symbol scanning system of claim 1, 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.

15. The bar code symbol scanning system of claim 1, 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.

16. The bar code symbol scanning system of claim 1, 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.

17. The bar code symbol scanning system of claim 1, 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.

18. The bar code symbol scanning system of claim 1, 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.

19. The bar code symbol scanning system of claim 18, wherein said laser light source control mechanism controls said current level provided to said visible laser diode module by modulating a dynamic current source.

20. The bar code symbol scanning system of claim 19, wherein said dynamic current source is directly coupled to said visible laser diode module.

21. The bar code symbol scanning system of claim 1, 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.

22. The bar code symbol scanning system of claim 21, wherein said laser light source control mechanism controls current level provided to said visible laser diode module by modulating a dynamic current source.

23. The bar code symbol scanning system of claim 22, wherein said dynamic current source is directly coupled to said visible laser diode module.

24. The bar code symbol scanning system 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.

25. The bar code symbol scanning system 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.

26. The bar code symbol scanning system 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.