Planar laser illumination and imaging device employing laser current modulation to generate spectral components and reduce temporal coherence of laser beam, so as to achieve a reduction in speckle-pattern noise during time-averaged detection of images of objects illuminated thereby during imaging operations

• US 7,513,428 B2
• Filed: 11/21/2006
• Issued: 04/07/2009
• Est. Priority Date: 11/21/2001
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Colavito, Stephen, Good, Timothy A., Knowles, C. Harry, Giordano, Patrick, Jankevics, Andrew, Tsikos, Constantine J., Wirth, Allan, Svedas, William
• Primary Examiner(s): Lee; Michael G
• Assistant Examiner(s): Haupt; Kristy A
• Application Number:
  US11/603,349
• Publication Number:
  US 20070138284A1
• Time in Patent Office: 868 Days
• Field of Search: 235/454, 235/455, 235/462.01, 235/462.22, 235/462.23, 235/462.24, 235/462.25, 235/462.41, 235/462.42
• US Class Current: 235/455
• CPC Class Codes: G06K 7/10 by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
• CPC Class Codes: H04N 1/02865 using an array of light sources or a combination of such arrays, e.g. an LED bar
• CPC Class Codes: H04N 1/03 with photodetectors arranged in a substantially linear array

Abstract

An imaging device including at least one imaging array and image formation optics that provide a field of view corresponding to the imaging array. At least one illumination module (which includes at least one source of coherent illumination) produces planar light illumination that substantially overlaps the field of view corresponding to the imaging array. Illumination control circuitry modulates the power level of illumination produced by the source of coherent illumination during each photo-integration time period of the imaging array to thereby reduce speckle noise in images captured by the imaging array. The illumination control circuitry preferably modulates the power level of illumination by controlling the number and/or duration of time periods corresponding to different power levels of illumination produced by the source of coherent illumination during each photo-integration time period of the imaging array.

Claims

1. An imaging device capable of detecting an image of a target object with reduced speckle-pattern noise, said imaging device comprising:

at least one image detection array and image formation optics that provide a field of view corresponding to said at least one image detection array;

at least one illumination module that produces planar light illumination that substantially overlaps the field of view corresponding to said image detection array, said at least one illumination module including at least one source of laser illumination producing laser illumination having a characteristic wavelength and being driven by a current level supplied to said source of laser illumination; and

illumination control circuitry that modulates a current level supplied to said source of laser illumination so as to generate spectral components other than said characteristic wavelength so as to reduce the temporal coherence of laser illumination produced by said source of laser illumination so that, during each photo-integration time period of said image detection array, said target object is illuminated with a temporally coherent-reduced laser illumination and numerous substantially different time-varying speckle-noise patterns are produced at said image detection array over the photo-integration time period thereof;

whereby said numerous substantially different time-varying speckle-noise patterns are detected at said image detection array over said photo-integration time period, and said detected speckle-noise patterns are temporally averaged at said image detection array during said photo-integration time period thereof,

thereby reducing the power of speckle-pattern noise at said at least one image detection array.

2. The imaging device of claim 1, wherein said at least one source of laser illumination comprises at least one visible laser diode.

3. The imaging device of claim 1, wherein said at least one source of laser illumination comprises a plurality of visible laser diodes.

4. The imaging device of claim 1, wherein said at least one illumination module comprises a laser illumination source, at least one focusing lens element, and at least one cylindrical lens element integrated into a modular housing.

5. The imaging device of claim 1, comprising a plurality of illumination modules each comprising a laser illumination source, at least one focusing lens element, and at least one cylindrical lens element integrated into a modular housing.

6. The imaging device of claim 1, wherein said image detection array comprises a linear image detection array.

7. The imaging device of claim 1, wherein said image detection array comprises an area image detection array.

8. The imaging device of claim 1, wherein said illumination control circuitry includes feedback circuitry operably coupled between a monitor photodiode and a dynamic current source, said dynamic current source providing current to said source of laser illumination, and said feedback circuitry controlling said current level supplied to said source of laser illumination during each photo-integration time period of said image detection array in response to timing signals and an output of said monitor photodiode provided thereto.

9. A method of illuminating at least one imaging array and reducing speckle noise in images captured by said at least one image detection array, the method comprising the steps of:

providing said at least one image detection array and image formation optics that provide a field of view corresponding to said at least one image detection array;

providing at least one illumination module that produces planar light illumination that substantially overlaps the field of view corresponding to said image detection array, said at least one illumination module including at least one source of laser illumination producing laser illumination having a characteristic wavelength and being driven by a current level supplied to said source of coherent illumination; and

modulating a current level said source of laser illumination during each photo-integration time period of said image detection array so as to generate spectral components other than said characteristic wavelength and reduce the temporal coherence of laser illumination produced by said source of laser illumination,

so that said target object is illuminated with temporally coherent-reduced laser illumination and numerous substantially different time-varying speckle-noise patterns are produced at said image detection array over the photo-integration time period thereof,

whereby said numerous substantially different time-varying speckle-noise patterns are detected at said image detection array over said photo-integration time period, and said detected speckle-noise patterns are temporally averaged at said image detection array during said photo-integration time period thereof,

thereby reducing the power of speckle-pattern noise at said at least one image detection array.

10. The method of claim 9, wherein said at least one source comprises at least one visible laser diode.

11. The method of claim 9, wherein said at least one source of laser illumination comprises a plurality of visible laser diodes.

12. The method of claim 9, wherein said at least one illumination module comprises a laser illumination source, at least one focusing lens element, and at least one cylindrical lens element integrated into a modular housing.

13. The method of claim 9, wherein said at least one illumination module comprises a plurality of illumination modules each comprising a laser illumination source, at least one focusing lens element, and at least one cylindrical lens element integrated into a modular housing.

14. The method of claim 9, wherein said image detection array comprises a linear image detection array.

15. The method of claim 9, wherein said image detection array comprises an area image detection array.

16. The method of claim 9, further comprising the step of:

providing a monitor photodiode and a dynamic current source, said dynamic current source providing current to said source of laser illumination;

controlling said dynamic current source to vary the current level of illumination produced by said source of laser illumination during each photo-integration time period of said image detection array in response to timing signals and an output of said monitor photodiode.