Hand-supportable imaging-based bar code symbol reader having a multi-mode bar code symbol image processor dynamically reconfigurable in response to real-time image processing operations carried out on captured images

• US 7,273,180 B2
• Filed: 07/16/2004
• Issued: 09/25/2007
• 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, Schmidt, Mark, Kotlarsky, Anatoly, Tao, Xi, Russell, Garrett, Bonanno, John
• Primary Examiner(s): Kim; Ahshik
• Application Number:
  US10/893,800
• Publication Number:
  US 20050103865A1
• Time in Patent Office: 1,166 Days
• Field of Search: 235/472.01, 235/472.02, 235/462.1, 235/462.11, 235/472.09, 235/462.22, 235/462.24, 235/462.25
• US Class Current: 235/472.01
• 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; a System Mode Configuration Parameter Table; 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 image processor that is dynamically reconfigurable in response to real-time image processing operations carried out on captured digital images.

Claims

1. A hand-supportable digital imaging-based bar code symbol reading device supporting narrow-area and wide-area modes of illumination and image capture, said hand-supportable digital imaging-based bar code symbol reading device comprising:

a hand-supportable housing;

a multi-mode area-type image formation and detection subsystem having image formation optics for producing a field of view (FOV) upon an object to be imaged and an area-type 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 said area-type image sensing array are enabled, or (ii) a wide-area image capture mode in which substantially all rows of said area-type image sensing array are enabled;

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

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

a multimode image-processing based bar code symbol reading subsystem for automatically processing images captured and buffered by said image capturing and buffering subsystem and reading 1D and 2D bar code symbols represented therein;

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 and coordinating each said subsystem component described above in accordance with a method of controlled subsystem operation including the steps of,

(i) said multi-mode LED-based illumination subsystem producing the narrow-area field of narrow-band illumination within the FOV of said multi-mode area-type image formation and detection subsystem,

(ii) said multi-mode area-type image capturing and buffering subsystem automatically capturing and buffering a 1D digital image during the narrow-area image capture mode of said multi-mode area-type image capturing and buffering subsystem,

(iii) said multi-mode image processing bar code symbol reading subsystem processing said 1D digital image to read a 1D bar code symbol represented in said 1D digital image, but upon said multi-mode image-processing bar code symbol reading subsystem failing to successfully read a 1D bar code symbol represented in said 1D digital image,

(iv) said multi-mode LED-based illumination subsystem automatically producing the wide-area field of narrow-band illumination within the FOV of said multi-mode area-type image formation and detection subsystem,

(v) said image capturing and buffering subsystem capturing and buffering a 2D digital image during the wide-area image capture mode of said image capturing and buffering subsystem, and

(vi) said multi-mode image processing bar code symbol reading subsystem being dynamically reconfigured in real-time to process said 2D digital image to read a 1D or 2D bar code symbol represented in said 2D digital image.

2. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, which further comprises:

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

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

3. The hand-supportable digital imaging-based bar code symbol reading device of claim 1, wherein said multi-mode image-processing bar code symbol reading subsystem can be programmed to operate in two or more modes of operation selected from the group consisting of:

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

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

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

a fourth mode, wherein said multi-mode image-processing 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 the second mode, so as to read one or more bar code symbols represented in said captured narrow-area frame of digital image data; and

a fifth mode, wherein said multi-mode image-processing 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 the second mode, to read one or more bar code symbols represented in said captured frame of digital image data.

4. The hand-supportable digital imaging-based bar code symbol reading device of claim 3, wherein the steps involved in said decode process carried out by the multi-mode image-processing based bar code symbol reading subsystem during said first mode of operation, comprising:

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

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

5. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein the first stage of processing within the multi-mode image-processing based bar code symbol reading subsystem configured in said first mode of operation, involves the generation of a low-resolution image of a package label from an original high-resolution image thereof.

6. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein said first stage of processing further involves partitioning of said low-resolution image of a package label, calculating feature vectors using the same, and examining these feature vectors for parallel lines.

7. The hand-supportable digital imaging-based bar code symbol reading device of claim 6, wherein during said second stage of processing, the calculation of feature vectors within each block of low-resolution image data involves using gradient vectors, edge density measures, the number of parallel edge vectors, centroids of edges, intensity variance, and the histogram of intensities captured from said low-resolution image.

8. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein during said second stage of processing, the examination of feature vectors involves looking for high edge density, large number of parallel edge vectors and large intensity variance.

9. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein while calculating bar code orientation during said second stage of processing, for each feature vector block, the bar code is traversed at different angles, 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.

10. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein during said second stage of processing, the marking of the four corners of detected bar code symbol involves performing the following operations on a full high-resolution image of the package label, namely:

(i) traversing the bar code symbol in either direction starting from the center of the block,

(ii) detecting the extent of modulation using the intensity variance, and

(iii) detecting the x,y coordinates of the four corners of the bar code symbol, and defining the ROI by the detected four corners of the bar code symbol within said high-resolution image.

11. The hand-supportable digital imaging-based bar code symbol reading device of claim 5, wherein while updating the feature vectors during said third stage of processing, the histogram component of the feature vector Fv is updated while traversing the bar code symbol, the estimate of the black-to-white transition is calculated, and an estimate of narrow and wide elements of the bar code symbol are calculated.

12. The hand-supportable digital imaging-based bar code symbol reading device of claim 11, wherein while searching for zero crossings during said third stage of processing, the high-resolution image is median filtered in a direction perpendicular to bar code orientation, the second derivative zero crossings are used to define edge crossings, the zero-crossing data is used only for detecting edge transitions, and the black/white transition estimates are used to put upper and lower bounds on the grey levels of the bars and spaces of the bar code symbol represented within the captured image.

13. The hand-supportable digital imaging-based bar code symbol reading device of claim 12, wherein while creating bar and space pattern during said third stage of processing, the edge transition is modeled as a ramp function, the edge transition is assumed to be 1 pixel wide, the edge transition location is determined at the subpixel level, and the bar and space counts are gathered using edge transition data.

14. The hand-supportable digital imaging-based bar code symbol reading device of claim 13, wherein while decoding bar and space patterns during said third stage of processing, the bar and space data is framed with borders, and the bar and space data is decoded using laser scanning bar code decoding algorithms.

15. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein the image-processing method carried out by the multi-mode image-processing based bar code symbol reading subsystem during said second mode of operation comprises the sequence of steps:

(1) during a first stage of processing, 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 blocks of image data, and creating a feature vector for the middle block using spatial-derivative based image processing techniques;

(2) during a 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 symbol 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.

16. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein the image processing method carried out by the multi-mode image-processing based bar code symbol reading subsystem during said fourth mode of operation, comprises the sequence of steps:

(i) directly processing a narrow-area portion of a captured high-resolution image, starting from the middle thereof,

(ii) examining the zero-crossings of the filtered image,

(iii) creating bar and space patterns therefrom, and

(iv) decoding the bar and space patterns using conventional decoding algorithms.

17. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein the image-processing method carried out by the multi-mode image-processing based bar code symbol reading subsystem during said fifth mode of operation, comprises the sequence of steps:

(i) assuming 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 directly processing the high-resolution image along a set of parallel spaced-apart virtual scan lines,

(ii) examining the zero-crossings along the virtual scan lines,

(iii) creating bar and space patterns therefrom, and

(iv) decoding the bar and space patterns,

(v) optionally, reprocessing 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.

18. The hand-supportable digital imaging-based bar code symbol reading device of claim 17, wherein said different angle is selected from the group consisting of 0, 30, 60, 90, 120 or 150 degrees.

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

20. The hand-supportable digital imaging-based bar code symbol reading device of claim 4, wherein the image-processing based bar code reading method carried out by the multi-mode image-processing based bar code symbol reading subsystem during said third mode of operation designed for use in combination with said fifth mode of operation, and comprises the sequence of steps:

(i) the first stage of processing involves receiving region of interest (ROI) coordinates obtained during said fifth mode of operation after the occurrence of a failure to decode, re-partitioning the captured low-resolution image from said fifth mode into blocks of image data, and creating a feature vector for the ROI-specified block(s) using spatial-derivative based image processing techniques,

(ii) 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

(iii) 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.