Abstract:
A matrix code reader comprises a camera-on-a-chip CMOS image sensor with a global-shutter and window-of-interest constraints. The CMOS image code reader is mounted in a handheld or stationary unit that also include a local display screen, a microprocessor, and a serial communications interface. A trigger allows a user to signal the microprocessor to capture the visual scene being imaged by the CMOS image sensor when the local display screen indicates a properly framed image.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to electronic imaging devices, and more particularly to cameras that efficiently capture matrix code images.  
         DESCRIPTION OF THE PRIOR ART  
         [0002]    Bar codes on products and bar-code code readers at the check-out stands are now ubiquitous in American retail stores. These familiar systems use a one-dimension code format that looks like a group of parallel lines with small variations in the line thickness and spacing. The bar codes have only to encode a relatively small amount of data, e.g., the universal product code (UPC) or store “SKU” number. Typical bar-code readers sweep a single laser beam across the printed bar code and read the digital variations that occur in the reflected light.  
           [0003]    Much more data can be encoded in two-dimension “matrix” code formats. Symbol Technologies (Bohemia, N.Y.) has developed and markets an extensive product offering related to two-dimensional bar-code symbols. U.S. Pat. No. 5,243,655, issued Sep. 7, 1993, to Ynjiun Wang, describes a system for encoding and decoding data in machine-readable graphics. Optical scanning is used to read the two-dimensional bar-code symbols, for example a laser light beam is swept in a raster pattern. The trouble with this is if the object and the code reader are moving relative to one another, the raster return signal will have spatially generated distortions. These distortions can confuse and interfere with the decoders.  
           [0004]    Only the actual two-dimensional bar-code symbol in the field of view of the code reader is of interest. Such symbol can have a variety of orientations, sizes, and distortions in the overall field of view that depend on the relative positions of the object and code reader, and also the optical system involved. U.S. Pat. No. 5,304,787, issued Apr. 19, 1994, to Ynjian Wang, describes methods for locating such two-dimensional bar codes. Once the bar code image is parsed, the decoding can proceed. An image buffer is used to store the whole image scanned. The bar code image is included somewhere within this whole image. Sampling, analysis, and correlating processes are used to draw a bounding box that minimally comprises all of the bar code image.  
           [0005]    Frederick Schuessler, et al., suggest using CCD imaging cameras to scan bar codes in U.S. Pat. No. 6,047,892, issued Apr. 11, 2000. Such Patent reviews prior art one-dimension and two-dimension bar code formats that are in widespread use.  
           [0006]    Jerome Drexler describes a method and system for laser writing microscopic data spots on cards and labels readable with a linear CCD array, in U.S. Pat. No. 6,145,742, issued Nov. 14, 2000. Such system is said to be able to store as much as 500 times what the widely adopted PDF417 two-dimensional bar code can store. Optical storage media is used to host an array of microscopic data spots. The storage media is moved orthogonal to the linear CCD array so the whole field of data storage can be read in. This requires that the orientation and optics be tightly controlled, and a free-hand use of such system with a handheld code reader is probably not practical.  
           [0007]    Prior art bar-code scanning technologies suffer from not being fast enough to “stop” all movement in an image exposure. The faster the relative movement between the object and the camera, and the finer the image resolution required, the quicker the shutter speed must be. Once the image is captured, conventional techniques seem to be up to the job of parsing the region-of-interest and resolving random image orientations.  
           [0008]    Many of the commercial units being marketed do not provide any means of displaying the area being scanned or for showing any data that has been interpreted from the scan. They instead have sounders that beep different tones depending on whether a snapshot has captured the bar code or data matrix properly. Sometimes several attempts are needed because the image got blocked or was blurred by relative velocities, vibration, or optics.  
         SUMMARY OF THE INVENTION  
         [0009]    It is therefore an object of the present invention to provide a matrix code reader that can capture a video image with a two-dimensional optical bar code.  
           [0010]    It is another object of the present invention to provide a matrix code reader with a fast enough shutter to stop relative motion and prevent image distortions.  
           [0011]    Briefly, a matrix code reader embodiment of the present invention comprises a camera-on-a-chip CMOS image sensor with a global-shutter and window-of-interest constraints. The CMOS image code reader is mounted in a handheld or stationary unit that also includes a local display screen, a microprocessor, and a serial communications interface. A trigger allows a user to signal the microprocessor to capture the visual scene being imaged by the CMOS image sensor when the local display screen indicates a properly framed image.  
           [0012]    An advantage of the present invention is that a matrix code reader is provided that can scan two-dimensional bar codes.  
           [0013]    Another advantage of the present invention is that a matrix code reader is provided that captures the desired information quickly and reliably.  
           [0014]    These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the drawing figure. 
       
    
    
     IN THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a functional block diagram of a matrix code reader embodiment of the present invention; and  
         [0016]    [0016]FIG. 2 is a left side diagram of a matrix code reader embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    A matrix code reader embodiment of the present invention is illustrated in FIG. 1 and is referred to herein by the general reference numeral  100 . A matrix code tag  102  is printed on a large object  104  and encodes information about the object, e.g., sales price, serial number, date-of-manufacture, source, destination, airbill, tax ID, contents, materials, warnings, etc. For example, such coding is in two-dimensional bar code, e.g., as popularized by Symbol Technologies (Bohemia, N.Y.), Metanetics (Fort Meyers, Fla.), and others. A CMOS image sensor  105  has the object  104  in a field-of-view  106 . Inside that, is a window-of-interest  108  that spans just the visual image of the matrix code tag  102 .  
         [0018]    The CMOS image sensor  105  must be a type that includes a so-called “global shutter” which exposes and latches all imager pixels instantly in parallel. This is needed to photographically stop any action in the field-of-view  106 . The only such devices known to be acceptable are jointly manufactured by Kodak and Motorola, e.g., Kodak KAC-0310 or KAC-1310, and Motorola SCM20014. It is preferred that such CMOS image sensor  105  also have window-of-interest controls that constrain any video output to just the window-of-interest  108 , and therefore save processing resources from being wasted on other images in the field-of-view  106 . The Kodak and Motorola products mentioned have three registers that are loaded with digital values for the corner position, column-count width, and row-count height.  
         [0019]    A microprocessor  110  provides such global-shutter and window-of-interest controls according to user-supplied operational requirements, e.g., a trigger and user preferences. A video output is received from the CMOS image sensor  105  that is formatted for serial transmission by a serial interface  112 . The video output is also formatted for display on a liquid crystal display (LCD)  114  for local viewing. Such LCD  114  provides feedback to a user so that the CMOS image sensor  105  can be positioned best to capture the matrix code tag  102 . The LCD  114  displays messages from the microprocessor  110  that interpret data that has been decoded from the image obtained from the matrix code tag  102 . Such messages and displays can also be sourced from a remote computer via the serial interface  112 , e.g., to display interpretations that have been remotely decoded.  
         [0020]    The window-of-interest controls are easiest to implement if fixed after brief experimentation, but some applications will benefit if these window-of-interest controls are dynamically generated by continual analyses of the field-of-view  106  by the microprocessor  110  or a remote computer.  
         [0021]    The serial interface  112  comprises standard personal computer (PC) electrical interfaces, cables and connectors, such as DB-9 connectors with RS-232 interfaces, or universal serial bus (USB), etc. Alternatively, the serial interface  112  can comprise IEEE 802.11a wireless local area network (LAN) components.  
         [0022]    The encoding and decoding of the matrix code tag  102  is done using conventional methods and devices. Embodiments of the present invention capture images of the matrix code tag  102  by restricting the image captured and processed to the window-of-interest and using a global shutter. Such embodiments further comprise local video displays to guide the user by providing useful operational feedback.  
         [0023]    [0023]FIG. 2 illustrates a handheld reader embodiment of the present invention, and is referred to herein by the general reference numeral  200 . In general, the reader  200  resembles the Metanetics IR-2000 handheld image reader, e.g., as marketed in the United States by Metanetics, Inc. (Fort Meyers, Fla.). The reader  200  is aimed at a matrix code tag  202  attached to a package  204 . The tag encodes information related to the package. An image sensor  206  is pointed by a user at the tag  202  such that a window-of-interest  208  includes a visual image of the matrix code tag  202 . A trigger  210  on a grip  212  is pulled when the user can see an image of the tag that has been repeated in a small, flat-panel LCD screen  214 . A top end  216  encloses the image sensor  206 . A microcomputer  218  controls both the image sensor  206  and LCD screen  214 . It takes input from the trigger  210 .  
         [0024]    A radio communications transceiver  220  allows for wireless communication over a radio link  222  with a centralized system  224 . For example, a wireless LAN  226  allows ETHERNET-type networking with a microprocessor  228  connected to a database  230 . Measurements obtained from the handheld reader  200  are received, interpreted, and stored by the centralized system  224 . Instructions, information, and/or graphics are returned to the user to be viewed on the LCD screen  214 . These will relate to how the tag  202  has been understood and what is to be done with the package  204 .  
         [0025]    Although the present invention has been described in terms of the presently preferred embodiments, it is to be understood that the disclosure is not to be interpreted as limiting. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all alterations and modifications as fall within the true spirit and scope of the invention.