Coplanar laser illumination and imaging subsystem employing spectral-mixing and despeckling of laser illumination

• US 7,661,597 B2
• Filed: 10/29/2007
• Issued: 02/16/2010
• Est. Priority Date: 11/24/2000
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Zhu, Xiaoxun, Veksland, Michael, Ren, Jie, Knowles, C. Harry, Xian, Tao, Liu, Yong, Good, Timothy, Giordano, Patrick, Schmidt, Mark, Kotlarsky, Anatoly, Furlong, John, Tao, Xi, Liu, JiBin, Essinger, Steven, Gardner, John, Kearney, Sean, Ellis, Duane, Ciarlante, Nicholas, Hernandez, Mark, Zhuo, Ming
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US11/978,521
• Publication Number:
  US 20080121718A1
• Time in Patent Office: 841 Days
• Field of Search: 235/462.42, 235/462.24, 235/462.43, 235/462.01, 235/462.09
• US Class Current: 235/462.42
• CPC Class Codes: A47F 9/046 Arrangement of recording means in or on check-out counters record carriers or readers per se G06K
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G06K 2207/1012 Special detection of object
• CPC Class Codes: G06K 7/10544 by scanning of the records by radiation in the optical part of the electromagnetic spectrum
• CPC Class Codes: G06K 7/10564 Light sources
• CPC Class Codes: G06K 7/10574 Multiple sources
• CPC Class Codes: G06K 7/10613 by rotation, e.g. polygon
• CPC Class Codes: G06K 7/10623 Constructional details
• CPC Class Codes: G06K 7/10693 for omnidirectional scanning
• CPC Class Codes: G06K 7/10712 Fixed beam scanning
• CPC Class Codes: G06K 7/10722 Photodetector array or CCD scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10782 Slot readers
• CPC Class Codes: G06K 7/10792 Special measures in relation to the object to be scanned
• CPC Class Codes: G06K 7/10851 Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/10861 sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48
• CPC Class Codes: G06Q 20/208 Input by product or record sensing, e.g. weighing or scanner processing
• CPC Class Codes: G06Q 30/06 Buying, selling or leasing transactions
• CPC Class Codes: G06V 10/141 Control of illumination
• CPC Class Codes: G07G 1/0036 Checkout procedures
• 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 3/00 : Alarm indicators, e.g. bells
• CPC Class Codes: G07G 3/006 : False operation

Abstract

A coplanar laser illumination and imaging subsystem deployable in an image capturing and processing system, and including an image formation and detection (IFD) subsystem having an image sensing array and optics providing a field of view (FOV) on the image sensing array, and forming an image of an object within the FOV and detecting said image on the image sensing array and producing a digital image thereof. The system includes a spectral-mixing based illumination subsystem having an array of VLDs for producing a visible illumination beam, and an array of infrared (IR) laser diodes (LDs) for producing an invisible illumination beam. The visible and invisible illumination beams spatially overlaps and spatially/temporally intermixes with each other to produce a composite spectrally-mixed illumination beam having a relative power ratio of visible illumination to invisible illumination (VIS/IR), and is substantially coplanar with the FOV of said image sensing array. A laser despeckling mechanism is provided for reducing the coherence of the composite spectrally-mixed illumination beam, and/or its components, so that the digital images produced by the IFD subsystem having substantially reduced levels of speckle-pattern noise when the laser despeckling mechanism is operational.

Claims

1. A coplanar laser illumination and imaging subsystem deployable in a digital image capturing and processing system, said coplanar laser illumination and imaging subsystem comprising:

an image formation and detection (IFD) subsystem having an image sensing array and optics providing a field of view (FOV) on said image sensing array, and forming a digital image of an object within said FOV and detecting said digital image on said image sensing array and producing a digital image of said detected digital image;

a spectral-mixing based illumination subsystem having an array of visible laser diodes (VLDs) for producing a visible illumination beam, and an array of infrared (IR) laser diodes (LDs) for producing an invisible illumination beam, and wherein said visible and invisible illumination beams spatially overlap and spatially/temporally intermix with each other to produce a composite spectrally-mixed illumination beam having a relative power ratio of visible illumination to invisible illumination (VIS/IR), and being substantially coplanar with the FOV of said image sensing array;

a laser despeckling mechanism for reducing the coherence of said composite spectrally-mixed illumination beam, and/or its components, so that said digital images produced by said IFD subsystem have substantially reduced levels of speckle-pattern noise when said laser despeckling mechanism is operational;

an image capturing and buffering subsystem for capturing and buffering digital images produced by said image sensing array; and

a control subsystem for controlling and/or coordinating the operations of said subsystems.

2. The coplanar laser illumination and imaging subsystem of claim 1, which further comprises an image processing subsystem for processing said buffered digital images so as to read code symbols graphically represented in said digital images.

3. The coplanar laser illumination and imaging subsystem of claim 1, wherein said image sensing array is a linear image sensing array, and said linear image sensing array produces 1D digital images.

4. The coplanar laser illumination and imaging subsystem of claim 1, wherein said image sensing array is an area-type image sensing array.

5. The coplanar laser illumination and imaging subsystem of claim 1, which further comprises an automatic object detection subsystem for automatically detecting the object moving through at least a portion of the FOV of said image sensing array.

6. The coplanar laser illumination and imaging subsystem of claim 1, wherein said laser despeckling mechanism employs a high-frequency modulation (HFM) technique, and an optical multiplexing (OMUX) technique.

7. The coplanar laser illumination and imaging subsystem of claim 1, wherein said relative power ratio of visible illumination to invisible illumination (VIS/IR) is preset in an effort to achieve sufficient image contrast in captured digital images to ensure satisfactory image processing.

8. The coplanar laser illumination and imaging subsystem of claim 1, wherein said relative power ratio of visible illumination to invisible illumination (VIS/IR) is adaptively controlled so as to optimize the relative power ratio of visible illumination to invisible illumination (VIS/IR) in an effort to achieve sufficient image contrast in captured digital images to ensure satisfactory image processing.

9. The coplanar laser illumination and imaging subsystem of claim 1, wherein said illumination control subsystem adaptively controls the relative power ratio of visible illumination to invisible illumination (VIS/IR) during object illumination and imaging operations by controlling the drive current supplied to said VLDs and IR LDs during said object illumination and imaging operations.

10. The coplanar laser illumination and imaging subsystem of claim 9, wherein said drive current supplied to said VLDs and IR LDs is controlled, during object illumination and imaging operations, by the following process:

(i) driving the VLDs and IR LDs with a predetermined/default values of drive currents so as to illuminate the object with a spectral mixture of visible and invisible illumination;

(ii) capturing one or more digital images of the illuminated object and measuring image contrast quality so as to generate feedback or control data; and

(iii) using said feedback or control data to dynamically generate the necessary values for the adjusted drive currents that are used to drive said VLDs and IR LDs and produce an optimal mixture of illumination during object illumination and imaging operations.

11. The coplanar laser illumination and imaging subsystem of claim 5, wherein said automatic object detection subsystem comprises an imaging-based object detection subsystem including an area-type image acquisition subsystem and a digital signal processing chip to support digital image capture and processing operations required for real-time object detection.

12. The coplanar laser illumination and imaging subsystem of claim 2, wherein said code symbols are selected from the group consisting of 1D bar code symbols, 2D bar code symbols and 2D data matrix symbols.

13. The coplanar laser illumination and imaging subsystem of claim 10, wherein said capturing one or more digital images of the illuminated object and measuring image contrast quality is carried out within a digital image processing subsystem.