Hand-supportable imaging-based auto-discriminating 1D/2D bar code symbol reader employing a multi-mode image processing bar code symbol reading subsystem having a plurality of modes of operation which are dynamically reconfigurable in response to real-time image analysis

• US 7,360,706 B2
• Filed: 07/19/2004
• Issued: 04/22/2008
• 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, 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:
  US10/894,477
• Publication Number:
  US 20050103856A1
• Time in Patent Office: 1,373 Days
• Field of Search: 235/462.22, 235/462.23, 235/462.24
• 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 IR-based object presence and range detection subsystem; a multi-mode area-type image formation and detection subsystem having narrow-area and wide area image capture modes of operation; a multi-mode LED-based illumination subsystem having narrow-area and wide area illumination modes of operation; an automatic light exposure measurement and illumination control subsystem; an image capturing and buffering subsystem; a multi-mode image-processing bar code symbol reading subsystem; an input/output subsystem; a manually-activatable trigger switch; and a system control subsystem integrated with each of the above-described subsystems. The digital imaging-based bar code reading device employs a multi-mode bar code symbol reading image processor that is dynamically reconfigurable in response to real-time image analysis carried out upon captured narrow and wide area images.

Claims

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

a hand-supportable housing;

a multi-mode area 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 image sensing array for detecting imaged light reflected off the object during illumination operations in either (i) a narrow-area image capture mode in which a few central rows of pixels on the image sensing array are enabled, or (ii) a wide-area image capture mode in which substantially all rows of the CMOS area image sensing array are enabled;

a multi-mode LED-based illumination subsystem for producing narrow and wide area fields of narrow-band illumination within said FOV during narrow-area and wide-area image capture modes, respectively;

an automatic object presence and range detection subsystem for producing an object detection field within the FOV of said multi-mode area image formation and detection subsystem;

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

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

a multi-mode image-processing based bar code symbol reading subsystem having a plurality of modes of operation which are dynamically reconfigurable in response to real-time image analysis, for processing images captured and buffered by said image capturing and buffering subsystem and automatically reading 1D and 2D bar code symbols represented in said captured and buffered images;

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

a system control subsystem for controlling each said subsystem described above;

wherein said plurality of modes of operation of said multi-mode image-processing based bar code symbol reading subsystem are selected from the group consisting of;

a first mode of operation, wherein said multi-mode image-processing based bar code symbol reading subsystem is configured to automatically process a captured frame of digital image data so as to search for one or more bar codes represented therein in an incremental manner, and to continue searching until the entire digital image is processed;

a second mode of operation, wherein said multi-mode image-processing based bar code symbol reading subsystem is configured to automatically process a captured frame of digital image data, starting from the center or sweep spot of the digital image of the object at which the user would have aimed said hand-supportable digital imaging-based bar code in said digital image, so as to search for one or more bar code symbols represented in said digital image, and by searching in a helical manner through frames or blocks of extracted image feature data and marking the same and processing the corresponding raw digital image data until a bar code symbol is recognized/read within the captured frame of digital image data;

a third mode of operation, wherein said multi-mode image-processing based bar code symbol reading subsystem is configured to automatically process a specified region of interest (ROI) in a captured frame of digital image data so as to search for one or more bar codes represented in said capture frame of digital image data, in response to coordinate data specifying the location of the bar code symbol within the FOV of said multi-mode area image formation and detection system;

a fourth mode of operation, wherein said multi-mode image-processing based bar code symbol reading subsystem is configured to automatically process a captured narrow-area frame of digital image data, without feature extraction and marking operations used in said first and second modes, so as read one or more bar code symbols represented in said captured narrow-area frame of digital image data; and

a fifth mode of operation, wherein said multi-mode image-processing based bar code symbol reading subsystem is configured to automatically process a captured frame of digital image data along any one or more predetermined virtual scan line orientations, without feature extraction and marking operations used in said first and second modes, so as to read one or more bar code symbols represented in said captured frame of digital image data.

2. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein during said first mode of operation, said multi-mode image-processing based bar code symbol reading subsystem performs three stages of image processing,

wherein (1) the first stage of processing involves searching for regions of interest (ROIs) by processing a low resolution image of a captured frame of high-resolution digital image data, partitioning the low-resolution image into N×

N blocks, and creating a feature vector for each block using spatial-derivative based image processing techniques,

wherein (2) the second stage of processing involves marking ROIs by examining the feature vectors for regions of high-modulation, calculating bar code element orientation, and marking the four corners of a bar code symbol as a ROI, and

wherein (3) the third stage of processing involves reading any bar code symbols represented within the ROI by traversing the bar code elements and updating the feature vectors, examining the zero-crossings of filtered images, creating bar and space patterns, and decoding the bar and space patterns using decoding algorithms.

3. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, said multi-mode image-processing based bar code symbol reading subsystem performs a first stage of image processing comprising:

(1) generating a low-resolution image of a package label from an original high-resolution image of said package label.

4. The hand-supportable digital imaging-based bar code symbol reading device of claim 3, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, said multi-mode image processing based bar code symbol reading subsystem performs a second stage of image processing further comprising:

(2) partitioning the low-resolution image of the package label;

(3) calculating feature vectors using the same; and

(4) analyzing these feature vectors to detect the presence of parallel lines representative of bars within bar code symbol structures.

5. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, during said second stage of image processing, the step of calculating feature vectors, within each block of low-resolution digital image data, comprises using one or more of the following metrics:

gradient vectors, edge density measures, the number of parallel edge vectors, centroids of edgels, intensity variance, and the histogram of intensities captured from the low-resolution digital image.

6. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein analyzing feature vectors comprises searching for high edge density, a large number of parallel edge vectors and large intensity variance.

7. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, said second stage of image processing further comprises:

(5) calculating bar code element orientation,

wherein for each feature vector block, the bar code symbol is traversed at different angles to produce slices, and, the slices are matched with each other based on least mean square error, and the correct orientation is determined to be that angle which matches the mean square error sense through every slice of the bar code symbol represented within the captured image.

8. The hand-supportable digital imaging-based bar code symbol reading device of claim 6, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, said second stage of image processing further comprises:

(6) marking of the four corners of the detected bar code symbol, and wherein (a) such marking operations are performed on the full high-resolution image of the parcel, (b) the bar code is traversed in either direction starting from the center of the block, (c) the extent of modulation is detected using the intensity variance, and (d) the x,y pixel coordinates of the four corners of the bar code are detected and define the ROI by the detected four corners of the bar code symbol within the high-resolution digital image.

9. The hand-supportable digital imaging-based bar code symbol reading device of claim 2, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, updating the feature vectors during the third stage of processing comprises:

updating the histogram component of the feature vector while traversing the bar code symbol;

calculating the estimate of the black-to-white transitions; and

calculating an estimate of narrow and wide elements of the bar code symbol.

10. The hand-supportable digital imaging-based bar code symbol reading device of claim 9, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, searching for zero crossings during the third stage of processing comprises:

median filtering the high-resolution bar code image in a direction perpendicular to bar code orientation;

estimating black/white edge transitions using only second derivative zero crossings; and

determining the upper and lower bounds on the grey levels of the bars and spaces of the bar code symbol represented within the captured image, using said estimated black/white edge transitions.

11. The hand-supportable digital imaging-based bar code symbol reading device of claim 10, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated in said first mode of operation, creating bar and space patterns during the third stage of processing comprises:

modeling the edge transition as a ramp function;

assuming the edge transition to be 1 pixel wide;

determining the edge transition location at the subpixel level; and

gathering the bar and space counts using edge transition data.

12. The hand-supportable digital imaging-based bar code symbol reading device of claim 11, wherein when said multi-mode image-processing based bar code symbol reading subsystem is operated insaid first mode of operation, said third stage of processing further comprises:

framing the bar and space data with borders; and

decoding the bar and space counts using one or more laser scanning bar code decoding algorithms.

13. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein during said second mode of operation, said multi-mode image-processing based bar code symbol reading subsystem comprises three stages of image processing,

wherein (1) the first stage of processing involves searching for regions of interest (ROIs) by processing a low resolution image of a captured frame of high-resolution image data, partitioning the low-resolution image into N×

N blocks, and creating a feature vector for the middle block using spatial-derivative based image processing techniques;

wherein (2) the second stage of processing involves marking ROIs by examining the feature vectors for regions of high-modulation and returning to the first stage to create feature vectors for other blocks surrounding the middle block in a helical manner, calculating bar code orientation and marking the four corners of a bar code as a ROI; and

(3) the third stage of processing involves reading any bar code symbols represented within the ROI by traversing the bar code and updating the feature vectors, examining the zero-crossings of filtered images, creating bar and space patterns, and decoding the bar and space patterns using conventional decoding algorithms.

14. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein during said third mode of operation, said multi-mode bar code symbol reading subsystem comprises three stages of image processing:

wherein (1) the first stage of processing involves receiving x,y pixel coordinates for the region of interest (ROI) obtained during the fifth mode or after the occurrence of a failure to decode, re-partitioning the captured low-resolution image from the fifth mode into N×

N blocks, and creating a feature vector for the ROI-specified block(s) using spatial-derivative based image processing techniques;

(2) the second stage of processing involves marking additional ROIs by examining the feature vectors for regions of high-modulation and returning to the first stage to create feature vectors for other blocks surrounding the middle block in a helical manner, calculating bar code orientation and marking the four corners of a bar code as a ROI; and

(3) the third stage of processing involves reading any bar code symbols represented within the ROI by traversing the bar code symbol and updating the feature vectors, examining the zero-crossings of filtered images, creating bar and space patterns, and decoding the bar and space patterns using conventional decoding algorithms.

15. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein during said fourth mode of operation, said multi-mode image-processing based bar code symbol reading subsystem comprises one stage of image processing,

wherein a narrow-area portion of a captured high-resolution image, is directly processed starting from the middle thereof;

the zero-crossings of the filtered image are examined and detected;

bar and space patterns are created from examined and detected zero-crossings; and

the bar and space patterns are decoded using conventional decoding algorithms.

16. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein during said fifth mode of operation, said multi-mode image-processing based bar code symbol reading subsystem assumes the imaged bar code symbol resides at the center of the captured wide-area high-resolution image with about a 1:

1 aspect ratio, and

(1) directly processes the high-resolution image along a set of parallel spaced-apart virtual scan lines,

(2) examines the zero-crossings along the virtual scan lines,

(3) creates bar and space patterns therefrom, and

(4) decodes the bar and space patterns, and

(5) optionally, reprocesses the high-resolution image along a different set of parallel spaced-apart virtual scan lines oriented at a different angle from the previously processed set of virtual scan lines.

17. The hand-supportable digital imaging-based bar code symbol reading device of claim 16, wherein said set of parallel spaced-apart virtual scan lines are spaced apart by about 50 pixels.

18. The hand-supportable digital imaging-based bar code symbol reading device of claim 16, wherein said different angle is selected from the group consisting of 0, 30, 60, 90, 120 and 150 degrees.