Hand-supportable imaging-based bar code symbol reader employing a CMOS-type image sensor using global exposure techniques

• US 7,357,325 B2
• Filed: 07/19/2004
• Issued: 04/15/2008
• Est. Priority Date: 11/13/2003
• Status: Active Grant

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Zhu, Xiaoxun, Knowles, C. Harry, Au, Ka Man, Liu, Yong, Liu, Liang, Schmidt, Mark, Ghosh, Sankar, Kotlarsky, Anatoly, Tao, Xi, Zhang, Wenhua, Amundsen, Thomas, Hou, Rui, Russell, Garrett, Byun, Sung, Yu, Hongpeng, Bonanno, John, Schnee, Michael, Spatafore, Pasqual
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US10/894,478
• Publication Number:
  US 20050103851A1
• Time in Patent Office: 1,366 Days
• Field of Search: 235/462.42, 235/462.24, 235/462.22, 235/462.01, 235/462.09
• US Class Current: 235/462.22
• CPC Class Codes: G06K 7/10732 Light sources
• 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

Abstract

A hand-supportable digital imaging-based bar code symbol reading device comprises: an automatic object presence and range detection subsystem; an area-type image formation and detection subsystem having a CMOS area-type image detection array, and narrow-area and wide area image capture modes of operation; an LED-based illumination subsystem having LED arrays, and narrow-area and wide area illumination modes of operation; an automatic light exposure measurement and illumination control subsystem; an image capturing and buffering subsystem; and an image-processing bar code symbol reading subsystem. The LED arrays associated with the LED-based illumination subsystem are automatically driven in a precise manner to globally expose the CMOS area-type image detection array with LED-based illumination only when substantially all of its rows of pixels are in a state of integration and have a common integration time, thereby enabling the image capturing and buffering subsystem to capture high quality images independent of the relative motion between the hand-supportable digital imaging-based bar code symbol reading device and the object.

Claims

1. A hand-supportable digital imaging-based bar code symbol reading device comprising:

an image formation and detection subsystem having image formation optics for producing a field of view (FOV) upon an object to be imaged and a CMOS area-type image sensing array for detecting imaged light reflected off the object during illumination operations in an image capture mode in which rows of pixels on the image sensing array are enabled;

an LED-based illumination subsystem, having an LED-based illumination array, for producing a field of narrow-band illumination within the FOV of said image formation and detection subsystem during the image capture mode;

an automatic light exposure measurement and illumination control subsystem for automatically measuring the light exposure incident upon a portion of said FOV, and controlling the operation of said LED-based illumination subsystem;

an image capturing and buffering subsystem for capturing and buffering 2D images detected by said image formation and detection subsystem;

an image-processing based bar code symbol reading subsystem for processing 2D images captured and buffered by said image capturing and buffering subsystem and reading 1D and/or 2D bar code symbols represented in said 2D images; and

an input/output subsystem for outputting processed image data to an external host system or other information receiving or responding device;

a system control subsystem for activating and controlling said subsystem components described above in response to a triggering event signal;

wherein once said CMOS area-type image sensing array is activated by said system control subsystem, and when substantially all rows in said CMOS area-type image sensing array are in a state of integration, said system control subsystem automatically activates said automatic light exposure measurement and illumination control subsystem which, in response thereto, automatically drives the LED-based illumination array in a precise manner so as to globally expose said CMOS area-type image sensing array with narrow-band illumination when substantially all rows of pixels in said CMOS area-type image sensing array are in a state of integration and have a common integration time, thereby enabling said image capturing and buffering subsystem to capture high quality images independent of the relative motion between the object and said hand-supportable digital imaging-based bar code symbol reading device.

2. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, which further comprises a hand-supportable housing having an imaging window, and wherein said LED-based illumination subsystem comprises a red-wavelength reflecting high-pass lens element positioned at said imaging window, and a low pass filter is disposed before said CMOS area-type image sensing array, so as to form a narrow-band transmission-type optical filter system integrated with said hand-supportable housing, and transmitting only the optical components of light contained within said narrow-band of illumination, while all other components of ambient light are substantially rejected before image detection at said CMOS area-type image sensing array.

3. The hand-supportable digital imaging-based bar code symbol reading device of claim 2, wherein said automatic light exposure measurement and illumination control subsystem comprises a spherical light collecting mirror and photodiode arranged within said hand-supportable housing, and

wherein incident illumination is collected from a selected portion of the center of said FOV using said spherical light collecting mirror, and then focused upon a photodiode for detection of the intensity of reflected illumination and subsequent processing by said automatic light exposure measurement and illumination control subsystem, so as to then control the illumination produced by said LED-based illumination subsystem.

4. The hand-supportable digital imaging-based bar code symbol reading device of claim 3, wherein illumination is collected from a central portion of said FOV and automatically detected so as to generate a control signal for driving, at the proper intensity, said LED-based illumination array, so that the CMOS area-type image sensing array produces digital images of illuminated objects having sufficient brightness.

5. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein said CMOS area-type image sensing array is operated in a single frame shutter mode and employs a global exposure control method which ensure that all rows of pixels in said CMOS area-type image sensing array have a common integration time, thereby enabling said image capturing and buffering subsystem to capture high quality images even when the object is in a state of motion.

6. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein said global exposure control method comprises:

(a) selecting the single frame shutter mode for said CMOS area-type imaging sensing array;

(b) using light collecting optics in said automatic light exposure measurement and illumination control subsystem to continuously collect illumination from a said portion of the FOV, detect the intensity of the collected illumination, and generate an electrical analog signal corresponding to the detected intensity, for subsequent processing;

(c) activating said CMOS area-type image sensing array so that its rows of pixels begin to integrate photonically-generated electrical charge in response to the formation of an optical image onto said CMOS area-type image sensing array by said image formation optics;

(d) using said CMOS image sensing array to automatically (i) generate an electronic rolling shutter (ERS) digital pulse signal when all rows of pixels in said area-type image sensing array are operated in a state of integration, and (ii) provide said ERS pulse signal to said automatic light exposure measurement and illumination control subsystem so as to activate light exposure measurement and illumination control functions and operations therewithin;

(e) upon activation of light exposure measurement and illumination control functions within said light exposure measurement and illumination control subsystem, (i) processing the electrical analog signal being continuously generated therewithin, (ii) measuring the light exposure level within said portion of the FOV by using said light collecting optics, and (iii) generating an auto-exposure control signal for controlling the generation of narrow-band illumination from said LED-based illumination array; and

(f) using the auto-exposure control signal to drive said LED-based illumination array and illuminate the field of view of said CMOS image sensing array in whatever image capture mode it may be configured, precisely when substantially all rows of pixels in said CMOS area-type image sensing array are in a state of integration, thereby ensuring that substantially all rows of pixels in said CMOS area-type image sensing array have a common integration time.

7. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, which further comprises an automatic object presence detection subsystem for producing an object detection field within the FOV of said image formation and detection subsystem, for generating said triggering event signal upon automatic detection of an object in said FOV.

8. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, which further comprises a manually activatable trigger switch integrated with said hand-supportable housing for generating said triggering event signal upon manual activation of said manually-activatable trigger switch.