Method of setting the time duration of illumination from an LED-based illumination array employed in a digital imaging-based code symbol reader, using an image-processing based illumination metering program executed therewithin

  • US 7,527,206 B2
  • Filed: 11/30/2006
  • Issued: 05/05/2009
  • Est. Priority Date: 11/13/2003
  • Status: Active Grant
First Claim
Patent Images

1. A method of setting the duration that illumination is produced from an LED-based illumination array employed in a digital-imaging based code symbol reader, during object illumination and imaging operations, said method comprising the steps of:

  • (a) bringing said digital-imaging based code symbol reader in proximity with an object bearing a code symbol, wherein said digital-imaging based code symbol reader includes (i) an image formation and detection subsystem having an image sensing array with a field of view (FOV), (ii) an illumination subsystem having said LED-based illumination array, (iii) an illumination measurement subsystem, (iv) an illumination control subsystem, and (v) a programmed image processor supporting an image-processing based illumination metering program;

    (b) in response to an object being moved within said FOV, generating a trigger event within said digital-imaging based code symbol reader;

    (c) in response to said trigger event, producing and projecting a field of illumination within said FOV and onto said detected object;

    (d) said illumination measurement subsystem automatically measuring the level of illumination at a particular region of said FOV during illumination operations initiated in step (c), and determining and storing an illumination duration necessary to achieve a desired spatial intensity in a digital image to be formed and detected by said information and detection subsystem;

    (e) said illumination control subsystem using the illumination duration determined in step (d) to control the time duration that said LED-based illumination array is driven during object illumination and imaging operations;

    (f) said image formation and detection subsystem forming and detecting a digital image of the illuminated object within said FOV;

    (g) said programmed image processor using said image-processing based illumination metering program to analyze and measure, in real-time, the spatial intensity distribution of the detected digital image and determine whether or not a corrected illumination duration is required when forming and detecting a next or subsequent digital image during the current or subsequent object illumination and imaging operation;

    (h) in the event that said programmed image processor determines that a corrected illumination duration is required, then said programmed image processor over-writing the previously determined and stored illumination duration, with the corrected illumination duration determined in step (g); and

    (i) said illumination control subsystem using the corrected illumination duration to control the time duration that said LED-based illumination array is driven during the subsequent object illumination and imaging operations, so that said image formation and detection subsystem forms and detects one or more digital images of the illuminated object.

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