Digital image capture and processing system employing a multi-mode illumination subsystem adaptable to ambient illumination levels

• US 7,543,752 B2
• Filed: 01/31/2007
• Issued: 06/09/2009
• 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, Kotlarsky, Anatoly
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US11/700,544
• Publication Number:
  US 20070194122A1
• Time in Patent Office: 860 Days
• Field of Search: 235/462.24, 235/462.42, 235/462.23, 235/462.01, 235/462.09
• US Class Current: 235/462.24
• CPC Class Codes: G06K 7/10683 Arrangement of fixed elements
• 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 7/10801 Multidistance reading
• 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

Abstract

A digital image capture and processing system providing a high degree of adaptability to ambient illumination levels and having great dynamic range. The system includes a multi-mode illumination subsystem, having an active illumination mode and a passive illumination mode. During object illumination and image capturing operations, the exposure quality of a captured digital image is analyzed, and based on the results of such exposure quality analysis, system control parameters are automatically reconfigured. In the event that the exposure quality analysis indicates excessive exposure levels in a captured digital image, then a new set of SCPs is reconfigured, controlling the multi-mode illumination subsystem to operate in its passive illumination mode, whereby, ambient illumination flooding the field of view forms digital images in the image detection array during s object illumination and imaging operations.

Claims

1. A digital image capture and processing system adaptable to ambient illumination levels, comprising:

a digital image formation and detection subsystem and having (i) image formation optics for projecting a field of view (FOV) from an area-type image detection array, and upon an object to be imaged during object illumination and imaging operations, and (ii) said area-type image detection array detecting digital images of the object during said object illumination and imaging operations;

a multi-mode illumination subsystem having an active illumination mode and a passive illumination mode, and an illumination array for producing a field of illumination in said FOV,

wherein when said multi-mode illumination subsystem is configured in said active illumination mode, said illumination array is driven so as to produce said field of illumination in said FOV during object illumination and imaging operations, and

wherein when said multi-mode illumination subsystem is configured in said passive illumination mode, said illumination array is not driven and does not produce said field of illumination in said FOV, but rather, ambient illumination is allowed to flood said FOV during said object illumination and imaging operations;

an automatic illumination control subsystem for controlling said illumination array during said object illumination and imaging operations;

an automatic exposure measurement subsystem for measuring the intensity of illumination reflected and/or scattered off the illuminated object during object illumination and imaging operations, and producing an electrical signal representative of said measured intensity;

said automatic illumination control subsystem including circuitry for providing drive signals to said illumination array, in response to said electrical signal produced by said automatic exposure measurement subsystem;

a digital image capturing and buffering subsystem for capturing and buffering said digital images in memory, during said object illumination and imaging operations;

a digital image processing subsystem for processing said digital images and (i) measuring the exposure quality of said digital images, and (ii) reading one or more 1D and/or 2D code symbols graphically represented in said digital images, and producing symbol character data representative of said read one or more 1D and/or 2D code symbols;

an input/output subsystem for transmitting said symbol character data to an external host system or other information receiving or responding device; and

a system control subsystem for managing, in memory, a set of system control parameters (SCPs) as well as a set of exposure quality threshold (EQT) parameters;

wherein the operation of said digital image capture and processing system is characterized by the values of said set of SCPs at any instance in time;

wherein upon being powered up, said system control subsystem sets (i) said set of SCPs to an initial set of SCPs, and (i) said set of EQT parameters to an initial set of EQT parameters, and wherein said initial set of SCPs controls said illumination subsystem to operate in said active illumination mode, and wherein said illumination array is driven to produce said field of illumination in said FOV during object illumination and imaging operations;

wherein during object illumination and imaging operations, said digital image processing subsystem automatically processes at least one captured digital image so as to analyze and measure the exposure quality of said digital image in relation to said set of EQT parameters, and reconfigures said set of initial SCPs into a new set of SCPs, based on the results of said exposure quality analysis; and

wherein upon said exposure quality analysis indicating excessive exposure levels in said digital image, said new set of SCPs controls said illumination subsystem to operate in said passive illumination mode, and wherein said illumination array is not driven to produce said field of illumination in said FOV, but rather, ambient illumination flooding said FOV forms said digital images on said area-type image detection array during said object illumination and imaging operations.

2. The digital image capture and processing system of claim 1, wherein said initial set of SCPs includes a first set of SCPs including:

(i) a shutter mode parameter, (ii) an electronic gain parameter, (iii) a programmable exposure time parameter, for each block of pixels detected in said image detection array, (iv) an image capture mode parameter, and (v) an image capture control parameter.

3. The digital image capture and processing system of claim 2, wherein said initial set of SCPs further includes a second set of SCPs including:

(i) an illumination mode parameter, (ii) an automatic illumination control parameter, and (iii) an illumination field type parameter.

4. The digital image capture and processing system of claim 1, wherein said measured exposure quality of each said digital image is a quantitative measure selected from the group including brightness quality or level, and image saturation of said digital image.

5. The digital image capture and processing system of claim 2, wherein said image capture mode parameter includes a narrow-area image capture parameter and a wide-area image capture parameter.

6. The digital image capture and processing system of claim 2, wherein said image capture control parameter includes a single frame parameter and a video frames parameter.

7. The digital image capture and processing system of claim 3, wherein said illumination mode parameter includes:

(i) off, (ii) continuous and (iii) strobe/flash values.

8. The digital image capture and processing system of claim 3, wherein said automatic illumination control parameter includes ON and OFF values.

9. The digital image capture and processing system of claim 3, wherein said illumination field type parameter includes:

(i) a narrow-area near-field illumination parameter, (ii) a wide-area far-field illumination parameter, (iii) a narrow-area field of illumination parameter, and (iv) a wide-area field of illumination parameter.

10. The digital image capture and processing system of claim 1, which further comprises an automatic object detection subsystem for automatically detecting the presence of the object in said FOV, and in response thereto, generating a trigger signal indicative of a triggering event.

11. The digital image capture and processing system of claim 10, wherein said object presence detection subsystem further comprises an IR-based object presence detection subsystem.

12. The digital image capture and processing system of claim 11, wherein said IR-based object presence detection subsystem further comprises an IR-based light emitting diode (LED) and an IR-based photo-receiving diode.

13. The digital image capture and processing system of claim 1, which further comprises a manually-actuatable trigger switch for generating a trigger signal indicative of a triggering event in response to manual actuation of said trigger switch.

14. The digital image capture and processing system of claim 1, wherein each said code symbol is a bar code symbol selected from the group consisting of:

(i) a 1D bar code symbol, (ii) a 2D bar code symbol, and (iii) a data matrix type code symbol structure.

15. The digital image capture and processing system of claim 1, wherein said image formation optics comprises a lens barrel assembly for supporting a plurality of lenses.

16. The digital image capture and processing system of claim 1, wherein said field of illumination comprises narrow-band illumination produced from said illumination array.

17. The digital image capture and processing system of claim 1, wherein said illumination array comprises a plurality of light emitting diodes (LEDs).

18. The digital image capture and processing system of claim 16, wherein said narrow-band illumination is visible to the human vision system.