Abstract:
The present laser barcode scanner employs (i) a simplified scan mechanism made from a semi-flexible substrate that eliminates complicated optical assemblies, (ii) a layout with location features eliminating the need for special alignment, and (iii) a layout with all surface mounted devices on a single layer eliminating the need for extra soldering. Together these strategies, when used with a method of mitigating stray-light by separating light paths with a circuit board, combine to achieve a laser barcode scanner of unique simplicity and performance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of Chinese Application No. 201320813885.8 filed Dec. 12, 2013 at the State Intellectual Property Office of the People&#39;s Republic of China. The foregoing patent application is hereby incorporated by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to indicia readers, such as laser barcode scanners. 
       BACKGROUND 
       [0003]    Over the past few decades, the use of code symbol readers, such as barcode scanners, has dramatically increased. Businesses have particularly gravitated toward the use of code symbol readers in the inventory management and point-of-sale contexts. Scanning barcode readers are particularly popular because of their long and adjustable working distances. 
         [0004]    Traditional scanner designs are limited by complexity constraints. Such designs may require time consuming alignment of complicated folded optical paths to mitigate stray light and ensure proper performance. Multiple circuit boards are commonly used and connected with flexible circuits, each adding to the cost and assembly time. 
         [0005]    Thus, a need exists for a laser barcode scanner solution that uses a variety of techniques to simplify the design, to achieve good performance, and to remain cost-effective to produce. 
       SUMMARY 
       [0006]    Accordingly, in one aspect, the invention embraces a system for reading indicia, such as barcodes. The indicia-reading system includes an indicia-capturing subsystem for optically acquiring information about indicia within the indicia-capturing subsystem&#39;s field of view. An indicia-decoding subsystem is configured for decoding the indicia information acquired by the indicia-capturing subsystem, and an interface subsystem translates this information into a communication protocol and communicates with a peripheral host device (e.g., an external computer). 
         [0007]    The indicia-capturing subsystem itself includes a transmission module (e.g., a transmission subsystem), which transmits electromagnetic radiation, and a reception module (e.g., a reception subsystem), which collects and detects the electromagnetic radiation reflected or scattered from the indicia. 
         [0008]    More particularly, the indicia-capturing subsystem may include one circuit board (i.e., exactly one, two-sided circuit board) that itself includes (i) a light source for projecting electromagnetic radiation (e.g., laser light) toward indicia, (ii) a light-deflecting assembly for scanning the radiation, and (iii) a photodiode or other sensor for collecting the electromagnetic radiation reflected from the indicia (e.g., reflected laser light). 
         [0009]    The light source and the photodiode are typically positioned on the circuit board such that the electromagnetic radiation projected from the light source to the indicia and the electromagnetic radiation reflected from the indicia to the photodiode may trace different paths (i.e., “non-retro”). For instance, the light source may be positioned on the first side of the circuit board and the photodiode may be positioned on a second side of the circuit board. 
         [0010]    In another aspect, the invention embraces a method for reading indicia (e.g., employing the foregoing system). In this regard, the method employs a non-retro electromagnetic-radiation path to facilitate the selective mitigation of stray light. 
         [0011]    The foregoing illustrative summary, as well as other exemplary objectives and/or advantages of the invention, and the manner in which the same are accomplished, are further explained within the following detailed description and its accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  depicts an exemplary handheld indicia reader according to the present invention. 
           [0013]      FIG. 2  depicts a block diagram showing the indicia reader&#39;s primary subsystems. 
           [0014]      FIG. 3  depicts a first (top) side of an exemplary circuit board, illustrating the transmission module of the indicia-capturing subsystem. 
           [0015]      FIG. 4  depicts a second (bottom) side of an exemplary circuit board, illustrating the reception module of the indicia-capturing subsystem. 
           [0016]      FIG. 5  depicts the positioning of the window associated with an exemplary circuit board. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    As noted, the present invention embraces a system and associated method for reading indicia. 
         [0018]    The system, which typically is embodied in a simplified handheld indicia reader (e.g., laser scanner or scanner)  100  as depicted in  FIG. 1 , facilitates the reading of indicia  102 , such as barcodes, QR codes, matrix codes, or other computer-readable indicia. 
         [0019]    As depicted in  FIG. 2 , the indicia reading system  10  includes an indicia-capturing subsystem  11  for acquiring optical information about indicia. The indicia-capturing subsystem  11  includes a transmission module  13  and reception module  14 . The transmission module  13  is responsible for scanning the electromagnetic radiation  15  (e.g., light from a visible laser diode or VLD  31 ) back and forth across the indicia  102  while the reception module  14  collects and detects the reflected radiation  16  and converts it into an analog, electronic signal  17 . This analog signal is input into the indicia-decoding subsystem  20 . There, the analog signal is processed and converted into a digital signal  19 , which is then sent to the interface subsystem  12 . The interface subsystem  12  communicates the decoded indicia information to the output  18  via a communication protocol (e.g., USB). 
         [0020]      FIG. 3  and  FIG. 4  depict opposite sides of an exemplary circuit board.  FIG. 3  illustrates the indicia-capturing subsystem&#39;s transmission module.  FIG. 4  illustrates the indicia-capturing subsystem&#39;s reception module, as well as the surface mounted parts that include the indicia-decoding and the interface subsystems. 
         [0021]    Referring to the top side of the circuit board  26  in  FIG. 3 , the details of the transmission module  13  are shown. The indicia-capturing subsystem&#39;s transmission module is assembled on an optic holder  30 , which contains a VLD  31 , a scanning mirror (“flipper mirror”)  32 , and a coil  35 . Assembling these items onto a single holder  30  allows for easy assembly, robust alignment, and simple repair. Light from the VLD  31  is focused at a set working distance  101  from the scanner along a folded imaging path  36 . The flipper mirror  32  scans the light to sweep an angular range  103 . 
         [0022]    In other words, the light-deflecting assembly includes a hinged mirror  32  (i.e., the flipper mirror), a magnet  34 , and a coil  35 . The flipper mirror  32  is affixed to one side of a flexible substrate  33  (e.g., a copper-clad polyimide sheet) with a magnet  34  affixed to the opposite side of the flexible substrate  33 . The flexible substrate  33  is clamped to the optic holder  30  at one edge so that it is free to move about this hinged edge. The magnet  34  affixed opposite the mirror  32  interacts with the coil&#39;s magnetic field in such a way as to reciprocate the mirror  32  (i.e., actuate the flipper mirror  32  back and forth) about the hinged edge. The coil&#39;s magnetic field is produced by driving the coil  35  with an alternating electric current. Typically, the frequency of this alternating signal is adjusted to be near the mechanical resonance of the flipper mirror  32  in order to minimize the current amplitude necessary for sufficient scanning. 
         [0023]    The laser scanner  100  includes location features (e.g., location holes) that facilitate permanent alignment of the indicia-capturing subsystem. Such location features, along with the optic holder module  30 , secure the light source  31  (e.g., a laser diode) and the light-deflecting assembly to facilitate permanent alignment of the indicia-capturing subsystem (e.g., the mechanical tolerances are selected to maintain alignment suitable for scanning operations). There is no need for additional alignment of these subassemblies. This optic holder  30  is affixed to the top side of the circuit board  26  so that the emitted light is transmitted through the top half of scanner window  46  and onto the barcode  102  at the proper working distance  101 . The laser scanner includes a collimator lens for projecting the emitted laser light with a nearly constant spot-size over a range of distances, including the working distance  101 . The size of the light spot at the working distance depends on the particular application, but the light spot should, in general, be smaller than either a bar or space of the barcode in order to prevent reading errors. The light source  31 , which should operate at wavelength suitable for efficient detection, should be situated in the pass-band of any reception-module filtering. 
         [0024]    When the laser scanner&#39;s trigger  105  is pressed, transmitted light  15  is scanned across its scanning range  103 . During a scan the transmitted light  15  encounters a barcode  102  and the reflected light  16  is directed back toward the indicia reader  10 . The reflected signal&#39;s amplitude is modulated because of the different reflectivities of the barcode along the scanned direction. The barcode&#39;s light areas reflect more light than do the barcode&#39;s dark areas. Thus, the modulation of the reflected light  16  represents the barcode&#39;s coded information. The reception module gathers this reflected light  16  and converts it into an electronic signal suitable for decoding. 
         [0025]    Referring to  FIG. 4 , the reception module (e.g., a reception subsystem or reception circuit) is located on the bottom side of the circuit board  27 . Reflected light  16  is filtered and focused by the integrated lens  48  in the bottom half of the scanner window  47  adjacent to the bottom side of the board, as shown in  FIG. 5 . The transmitted and received laser light beams thus trace different paths through this window  45 . As such, the system is called “non-retro” (e.g., non-retroreflective) to indicate this configuration. The non-retro aspect of this design facilitates its simplicity and helps mitigate stray light. The integrated lens simplifies construction and does not need alignment other than from the scanner housing. 
         [0026]    Satisfactory detection of the reflected light requires that any stray light from the sun, room-lights, or other light sources be minimized. The scanner window is colored so that the transmitted and received laser light may pass with little loss while light of different wavelengths (i.e., colors) is minimized. Additional filtering may be required to supplement this window filtering in cases where the window filter&#39;s suppression is insufficient (e.g., IR filtering in daylight applications). To minimize size and cost, this additional filtering can be integrated with the photodiode detector  40 . 
         [0027]    The lens, which is situated in front of the detector  40 , collects the modulated light and focuses it onto the detector (e.g., a silicon photodiode)  40 . As noted, the detector  40  is located on circuit board opposite the transmission module. In this architecture, the board serves to baffle unmodulated light from the transmission module, which might otherwise leak into the detector. Thus, the non-retro design is an efficient, elegant way to minimize the harmful effects of stray light. 
         [0028]    After the light is detected by the photodiode  40 , the converted electronic analog signal  17  is sent to the first element of the indicia-decoding subsystem, the application specific integrated circuit (i.e., ASIC)  41 . Here, the electronic analog signal is processed to detect modulation. The configurable ASIC  41  performs various functions and has inputs and outputs to drive and monitor other subsystems but is primarily responsible for processing and converting the received signals from the photodiode. The ASIC chip  41  consolidates what would be a large amount of circuitry into a single surface-mounted package, thereby significantly reducing size. The ASIC chip  41  is soldered on the underside of the circuit board  27  along with all the other surface mounted parts. In general, all of the surface-mounted devices are positioned on the underside of the circuit board and no surface-mounted devices are positioned on the top side of the circuit board. By soldering all of the surface mounted parts on one side of the circuit board, the manufacturing complexity is simplified and made more cost effective. 
         [0029]    After processing the raw electronic signal, the ASIC returns a digital signal representing the indicia code  19 . This digital signal is then fed to the microcontroller unit (i.e., the MCU)  42 . The MCU contains a processor core, memory, and programmable input/output peripherals. This unit may be programmed with different codes or different communication protocols. Its job is to verify the digital signal represents a known code, to decode the signal into the information that the barcode represents, and to communicate this data to the output of the indicia-reading system  18  via a communication protocol (e.g., USB). A USB cable may be soldered directly to the laser scanner board via the USB solder pads  43  located on the bottom side of the board  27 . Alternatively, to ease manufacturing, a connector may be used instead of solder pads. 
         [0030]    Thus, the laser barcode scanner solution presented here represents a compact, simple, inexpensive laser scanner that is easy to assemble. A single, two-layer board (i.e., top and bottom) is used. Only one solder reflow run is necessary, and parts such as cables and extra mechanical holders are eliminated. The desired optical paths are aligned by assembly and require no additional alignment (e.g., zero alignment), despite using a flipper mirror assembly made from a flexible substrate. The scan mechanism and the collection subsystems are located on opposite sides of the circuit board to improve performance without adding complexity. 
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         [0032]    In the specification and/or figures, typical embodiments of the invention have been disclosed. The present invention is not limited to such exemplary embodiments. The use of the term “and/or” includes any and all combinations of one or more of the associated listed items. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.