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: Expired due to Term

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Zhu, Xiaoxun, Au, Ka Man, Liu, Yong, Liu, Liang, Kotlarsky, Anatoly, Tao, Xi, Zhang, Wenhua, Hou, Rui, Yu, Hongpeng
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US11/607,114
• Publication Number:
  US 20070145144A1
• Time in Patent Office: 887 Days
• Field of Search: 235/462.27, 235/462.11, 235/462.25, 235/462.42
• US Class Current: 235/462.27
• CPC Class Codes: G06F 9/44526 Plug-ins; Add-ons
• CPC Class Codes: G06K 2207/1012 Special detection of object
• CPC Class Codes: G06K 7/10712 Fixed beam scanning
• CPC Class Codes: G06K 7/10732 Light sources
• CPC Class Codes: G06K 7/10831 Arrangement of optical elements, e.g. lenses, mirrors, prisms optical elements per se G02B
• 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 7/10881 constructional details of hand-held scanners
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

Abstract

A digital-imaging based code symbol reading system comprising an image sensing array with a field of view (FOV), an illumination subsystem with an LED illumination array, an automatic illumination measurement subsystem, an illumination control subsystem, and programmed imager processor supporting an image-processing based illumination metering program. The automatic illumination measurement subsystem automatically measures the illumination level at a particular region of the FOV and determines the illumination duration necessary to achieve a desired spatial intensity in the detected digital image. The illumination metering program automatically analyzes and measures, in real-time, the spatial intensity distribution of the digital image and determines whether or not a corrected illumination duration is required or desired when detecting the next or subsequent digital images, during the current or subsequent object illumination and imaging cycle. The previously determined illumination duration is over-written with the corrected illumination duration, which is used to drive the illumination subsystem and form and detect one or more subsequent digital images of the illuminated object.

Claims

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.

2. The method of claim 1, which further comprises:

(j) repeating steps (c) through (i) one or more additional times during each object illumination and imaging operation, so as to produce a digital image having a spatial intensity level with high image contrast.

3. The method of claim 1, wherein said particular region is a central region of said FOV.

4. The method of claim 1, wherein said image sensing array is an area-type image sensing array.

5. The method of claim 1, wherein said illumination duration is a time count stored in memory within said digital-imaging based code symbol reader.

6. The method of claim 1, wherein said digital-imaging based code symbol reader comprises a hand-supportable housing.

7. The method of claim 1, wherein said code symbol is a bar code symbol.

8. The method of claim 7, wherein said bar code symbol is selected from the group consisting of 1D bar code symbols, 2D bar code symbols and data matrix symbols.

9. The method of claim 1, wherein step (b), said trigger event is generated by an automatic object presence detector disposed in said digital-imaging based code symbol reader.

10. The method of claim 1, wherein step (b), said trigger event is generated by the operator manually-actuating a trigger switch integrated with said digital-imaging based code symbol reader.

11. A digital-imaging-based code symbol reading system comprising:

a housing having a light transmission window;

an image formation and detection subsystem having an image sensing array and image formation optics having a field of view (FOV) defined relative to said light transmission window;

an automatic object presence detection subsystem, disposed in said housing, for automatically detecting the presence of an object within said FOV;

an illumination subsystem, disposed in said housing, and having an LED-based illumination array for producing a field of illumination with said FOV during object illumination and imaging operations;

an illumination measurement subsystem, disposed in said housing, for automatically measuring the level of illumination at a particular region of said FOV during object illumination and imaging operations, 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;

an illumination control subsystem, disposed in said housing, and using said illumination duration determined by said illumination measurement subsystem so as to control the time duration that said LED-based illumination array is driven during object illumination and imaging operations; and

a programmed image processor, disposed in said housing, and supporting an image-processing based illumination metering program, and decode processing of one or more digital images formed and detected by said image formation and detection subsystem so as to read one or more 1D and/or 2D code symbols represented in said one or more digital images; and

a system control subsystem, disposed in said housing, for controlling and/or coordinating the operations of one or more of said subsystems and components identified above.

12. The digital-imaging-based code symbol reading system of claim 11, wherein, in response to an object being moved into said FOV, said automatic object presence detection subsystem automatically generates a trigger event within said digital-imaging based code symbol reader;

and

wherein, in response to the generation of said trigger event, the following sequence of operations are carried out under the control and/or coordination of said system control subsystem;

(1) said illumination subsystem produces and projects said field of illumination within said FOV and onto said detected object;

(2) said illumination measurement subsystem automatically measures the level of illumination at said particular portion of said FOV, and determines and storing the illumination duration necessary to achieve the desired spatial intensity in a digital image to be formed and detected by said information and detection subsystem;

(3) said illumination control subsystem uses said determined illumination duration to control the time duration that said LED-based illumination array is driven during object illumination and imaging operations;

(4) said image formation and detection subsystem forms and detects a digital image of the illuminated object within said FOV;

(5) said programmed image processor uses said image-processing based illumination metering program to analyze and measure, in real-time, the spatial intensity distribution of the detected digital image, and determines 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;

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

(7) said illumination control subsystem uses 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.

13. The digital-imaging-based code symbol reading system of claim 12, wherein said system control subsystem coordinates system operations so that operations (1) through (7) are repeated one or more additional times during each object illumination and imaging operation, so as to produce a digital image having a spatial intensity level with high image contrast.

14. The digital-imaging-based code symbol reading system of claim 11, wherein said particular region is a central region of said FOV.

15. The digital-imaging-based code symbol reading system of claim 11, wherein said image sensing array is an area-type image sensing array.

16. The digital-imaging-based code symbol reading system of claim 11, wherein said illumination duration is a time count stored in memory within said digital-imaging based code symbol reading system.

17. The digital-imaging-based code symbol reading system of claim 11, wherein said digital-imaging based code symbol reader comprises a hand-supportable housing.

18. The digital-imaging-based code symbol reading system of claim 11, wherein said code symbol is a bar code symbol.

19. The digital-imaging-based code symbol reading system of claim 18, wherein said bar code symbol is selected from the group consisting of 1D bar code symbols, 2D bar code symbols and data matrix symbols.

20. A digital-imaging based code symbol reading system comprising:

a housing having a light transmission window;

an image formation and detection subsystem having an image sensing array and image formation optics having a field of view (FOV) defined relative to said light transmission window;

a trigger switch integrated with said housing, for generating an trigger event in response to an operator manually-actuating said trigger switch when an object is presented within said FOV for digital imaging;

an illumination subsystem, disposed in said housing, and having with an LED-based illumination array for producing a field of illumination with said FOV during object illumination and imaging operations;

an illumination measurement subsystem, disposed in said housing, for automatically measuring the level of illumination at a particular region of said FOV during object illumination and imaging operations, 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;

an illumination control subsystem, disposed in said housing, and using said illumination duration determined by said illumination measurement subsystem so as to control the time duration that said LED-based illumination array is driven during object illumination and imaging operations; and

a programmed image processor, disposed in said housing, and supporting an image-processing based illumination metering program, and decode processing of one or more digital images formed and detected by said image formation and detection subsystem so as to read one or more 1D and/or 2D code symbols represented in said digital images; and

a system control subsystem, disposed in said housing, for controlling and/or coordinating the operations of one or more of said subsystems and components identified above.

21. The digital-imaging-based code symbol reading system of claim 20, wherein, in response to an object being moved into said FOV, the operator generates said trigger event by manually actuating said trigger switch,

wherein, in response to the generation of said trigger event, the following sequence of operations are carried out under the control and/or coordination of said system control subsystem:

(1) said illumination subsystem produces and projects said field of illumination within said FOV and onto said detected object;

(2) said illumination measurement subsystem automatically measures the level of illumination at said particular region of said FOV, and determines and storing the illumination duration necessary to achieve the desired spatial intensity in a digital image to be formed and detected by said information and detection subsystem;

(3) said illumination control subsystem uses said determined illumination duration to control the time duration that said LED-based illumination array is driven during object illumination and imaging operations;

(4) said image formation and detection subsystem forms and detects a digital image of the illuminated object within said FOV;

(5) said programmed image processor uses said image-processing based illumination metering program to analyze and measure, in real-time, the spatial intensity distribution of the detected digital image, and determines 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;

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

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

22. The digital-imaging-based code symbol reading system of claim 21, wherein said system control subsystem coordinates system operations so that operations (1) through (7) are repeated one or more times during each object illumination and imaging operation, so as to produce a digital image having a spatial intensity level with high image contrast.

23. The digital-imaging-based code symbol reading system of claim 20, wherein said particular region is a central region of said FOV.

24. The digital-imaging-based code symbol reading system of claim 20, wherein said image sensing array is an area-type image sensing array.

25. The digital-imaging-based code symbol reading system of claim 20, wherein said illumination duration is a time count stored in memory within said digital-imaging based code symbol reading system.

26. The digital-imaging-based code symbol reading system of claim 20, wherein said housing is a hand-supportable housing.

27. The digital-imaging-based code symbol reading system of claim 20, wherein said code symbol is a bar code symbol.

28. The digital-imaging-based code symbol reading system of claim 27, wherein said bar code symbol is selected from the group consisting of 1D bar code symbols, 2D bar code symbols and data matrix symbols.