Patent Publication Number: US-2021182519-A1

Title: Code reader device and method for online verification of a code

Description:
The invention relates to a code reader device according to the preamble of claim  1  as well as a method for automatic verification of a code according to the preamble of claim  10 . Moreover, the invention relates to a modular code reading apparatus. 
     A code reader device and a method for online verification of a code is known from EP 2 677 492 A1. 
     A camera-based code reader takes pictures of the objects with the code located on them by means of a pixel-resolving image sensor, instead of scanning code regions. An image evaluation software then extracts the code information from these pictures. Camera-based code readers can also easily handle types of code other than one-dimensional bar codes, which are constructed in two dimensions such as a matrix code and which provide more information. 
     In order to assure high reading rates, the quality control of codes is also important. The judging of the code quality is also known as code verification. In this process, certain code properties are checked, such as are required for a reading of the code. This process may involve a decoding, the outcome of which may also be known in advance, and it then only needs to be confirmed. Standards have been agreed upon for code quality, such as those in ISO16022, ISO15415, ISO15416 or ISO29158. 
     In EP 2 677 492 A1 it is stated that a code verification traditionally takes place in an offline mode, in which certain physical boundary conditions are dictated. The code verification should assess the test object in a reproducible and reliable manner, rather than artifacts of the camera setup such as angle of detection, selected image magnification, or light exposure time. Instructions are given for this regarding the reading situation during the verification. 
     For example, a code verification is recommended at the center of the image, in order to avoid the margin region of the lens, and for this a target marking is specified, where the test object should be placed. 
     The boundary conditions to be satisfied furthermore include a known standard illumination without interference light from one or more known light sources, multiple and periodically recurring calibration cycles, an unchanging reading distance between test object and lens, and generally the dictating of a defined detection position both as regards the position of the code reader and that of the code being checked. 
     Such boundary conditions cannot be met in practice under actual conditions of online use. 
     The handling of such verification systems requires high skill on the part of the operator. In EP 2 677 492 A1, to simplify the code verification, a code reader is proposed having an image sensor for generating of images of a detection zone resolved in pixels, a decoding unit for identifying code regions in the images and reading of their encoded information, and a verification unit for judging the code quality according to predefined criteria. 
     The verification unit here is designed to generate at first a normalized verification image of the code from the code regions by means of an image processing for the verification. 
     The teaching disclosed in EP 2 677 492 A1 starts from the notion of circumventing the usual techniques for code verification. Instead of ensuring fixed, standardized physical boundary conditions, the circumstances on site are utilized. The standardized conditions are then produced afterwards by image processing. This produces a normalized verification image, which is used to judge the code quality. 
     But in this method a calibrating must be done before every changing of the code, the object, or the reading distance, which in turn requires high skill on the part of the operator. 
     Starting from this, the problem which the present invention proposes to solve is to modify a code reader device and a method for automatic verification of a code of the aforementioned kind so that both the calibrating and the verification are simplified. 
     The problem is solved according to the invention by a code reader device having the features of claim  1  and by a method for online verification of a code having the features of claim  10 . 
    
    
     
       Further details, benefits and features of the invention will emerge not only from the claims and the features found therein, both alone and in combination, but also from the following description of a preferred exemplary embodiment shown in the drawing. 
       There are shown: 
         FIG. 1  a schematic sectional representation of a camera-based code reader device, 
         FIG. 2  a perspective representation of the code reader device, 
         FIG. 3  a schematic representation of a device for automatic verification of a code, 
         FIG. 4  a perspective representation of a scanning device, especially a hand scanner 
         FIG. 5   a )- d ) modules of the hand scanner of  FIG. 4   
     
    
    
       FIG. 1  shows a schematic sectional representation of a camera-based code reader  10 . The code reader  10  comprises a camera  12  with integrated image sensor  14  having an upstream auto focus device  16 . The camera  12  takes pictures of a detection zone  18  in which a desired object is located, having a code  20 , which may have different sizes and different reading distances from the camera  12 . 
     The code reader  10  furthermore comprises multiple illumination devices, a first illumination device being a coaxial illumination  22 , providing a diffuse bright field  24  running parallel to an optical axis  26 . The optical axis  26  passes through the image sensor  14  at right angles and likewise stands at right angles to the code  20 . The coaxial illumination  22  emits light onto a translucent mirror  28 , which reflects the diffuse bright field  24  in the direction of the inspection zone  18  or the code  20 . 
     Furthermore, there is provided a second, preferably ring-shaped illumination  30  in the form of a dome illumination, which emits a diffuse stray field  32  toward a dome-shaped reflector  34 , from which a diffuse stray field is reflected onto the code  20  with light beams oriented not parallel to the optical axis  26 . 
     Moreover, a third illumination device is provided in the form of a dark field illumination  38 , which his designed as a ring-shaped illumination at an end-face margin of the code reader  10  and which emits light beams  40  at a small angle a of around 30° onto the code  20 . 
     The light beams  42  reflected from the inspection zone  18  are received by the auto focus unit  16  and brought into focus on the image sensor  14 . The image sensor, such as a CCD or CMOS chip with a plurality of pixel elements arranged in a row or a matrix, generates image data of the inspection zone  18  and relays this to an evaluation unit  44 . The evaluation unit  44  in the exemplary embodiment shown is integrated in the code reader  10 , but it may also be connected externally across an interface  47 . The evaluation unit  44  comprises a calibrating unit  46 , a decoding unit  48 , a verification unit  50 , a camera controller  52  and an illumination controller  54 . 
     For the display of measurement results and for operator control of the code reader  10 , the evaluation unit  44  is coupled to a display and control unit  56 , which is integrated in a housing  58  of the code reader  10  or which can be connected externally across the interface  47 . 
     The calibrating unit  46  serves for an automatic normalized calibrating of the code reader in dependence on the type of code, the placement of the code on the object, and the focusing, i.e., the distance of the code  20  from the sensor  14 . 
     For this, it is provided that norm-specific and distance-specific calibrating data are stored in the calibrating unit for each focus position of the auto focus unit  16 . The calibrating data encompass settings for the illuminations  22 ,  30 ,  38  such as the illumination type, the illumination brightness and/or the illumination angle, as well as settings for the camera  14 , such as aperture and/or light exposure time, which are provided to the camera controller  52  and/or the illumination controller  53  for adjusting a normalized illumination or normalized conditions. 
     The decoding unit  48  is adapted to decoding the code  20 , i.e., to reading out the information contained in the code  20 . 
     The verification unit  50  is able to evaluate the incoming image from an incoming image by various processing steps and to show the parameters of the verification on the display  56 , such as the cell contrast, the cell modulation, the reflection marg. and minimum reflection. 
     The camera controller  52  is adapted to set the light exposure time and the aperture of the camera  14  according to the calibrating data provided by the calibrating unit  46 . 
     The illumination controller is adapted to set the normalized illumination according to the calibrating data provided by the calibrating unit  46 . 
       FIG. 2  shows in perspective representation one possible configuration of the code reader  10 , having a cylindrical housing  58 , the display and control unit  56  being integrated in the wall of the housing  58 . The cylindrical housing has a light exit opening  60  at its end face, which is surrounded by the ring-shaped illumination unit  38 . The camera  14 , the optics and auto focus unit  16 , and the illuminations  22 ,  30  are arranged in the interior of the housing  58 . 
     The code reader  10  represented in  FIG. 2  can alternatively be configured as a desktop device, a handheld device, or be integrated in a process metering device  62 , as is represented in  FIG. 3 . 
     With respect to  FIG. 3 , the function of the code reader  10  shall be explained for the fully automatic online verification of codes  20  of different sizes and at different distances from the camera  12 . 
     An object  64  with the code  20  being checked is placed automatically or manually by an attendant in the inspection zone  18  of the code reader  10 . A standard for the verification of the code  20  is selected on the external display and control unit  56  or via a digital input. After this, the following steps are performed fully automatically:
         initial image recording   checking of the focus   further image recording until the focus has been set properly (auto focus)   selection of norm-specific and distance-specific calibrating data on the basis of a distance value of the correct focus from a memory   checking of the illumination settings with the aid of standard benchmarks obtained from the calibrating data   further image recording until the illumination of the object  60  or the code  20  conforms to the standard criteria   evaluations of the image recorded under the standard criteria by means of the verification unit   displaying of verification parameters such as cell constant, cell modulation, reflection mag. and minimum reflection by the display and control unit   saving of the values, preferably in an internal memory or on a USB storage medium   printing out of a protocol       

     Unlike the prior art, the code reader  10  works entirely independently and needs no further calculating unit such as a personal computer. Only a power supply such as 24 VDC or 230 VAC [is needed]. 
     The quality of the code  20  is marked clearly in color, for example by a red, yellow and green display. In this way, the verification of the code  20  is greatly simplified and can also be performed by untrained personnel. 
     The evaluation unit may have multiple digital outputs, in order to make possible an “inline” operation in addition to the “online” operation. The outputs are designed to be individually programmable. 
     According to the invention, the auto focus unit  16  which is integrated in the code reader  10  focuses the image field on the code  20 , so that verifications can be performed fully automatically with variable distances from the code reader  10 . Moreover, there is an automatic calibrating, so that a repeat calibrating is not needed when the code is changed or the distance (the reading distance) is changed. 
     Another significant feature of the invention worth mentioning is that the code reader  10  can be expanded with external illumination subassemblies, for example, in order to verify with the “low angle” illumination as defined in the standard. 
     For this, the illumination  38  is connected for example to the cylindrical margin of the housing  58 . The illumination may be mounted externally on the margin, for example, and connected by a plug connector to the evaluation unit. The illumination can then be selected appropriately via the software running in the illumination controller  54 . The code reader  10  then verifies the code  20  with the external illumination  38 . The illumination used and further inspection parameters and illumination settings are noted appropriately in an inspection protocol. 
       FIG. 4  shows in perspective representation a modular design of a handheld scanner  68 , comprising a main module  70 , which can be connected across a first electromechanical interface  72  to an intermediate module  74 . The intermediate module  74  can be connected across a second electromechanical interface  76  to a handle module  78 . 
     The handheld scanner  68  is designed as an adaptive system, especially for image processing applications (intelligent camera) or industrial ID applications (1D/2D code reading). 
     Integrated in the main module  70  are an illumination unit, an image unit, an evaluation electronics, and preferably a target marking. Integrated in the intermediate module are a communication unit and optionally a power supply. 
     Adaptively, expansion units can be adapted to a further interface  80  of the main module  70 , such as a diffuser/polar filter unit, a fiberoptic cable for low angle and/or dark field illumination, and various optics. The main module  70  can be adapted at the front end, where an optics unit can be exchanged in purely mechanical manner in order to achieve other image fields and/or focal points. Moreover, there is the option of expanding the internal illumination unit by means of optics in order to generate different light properties, such as direct incident light, diffuse incident light, low angle and/or dark field light. 
     The intermediate module  74  can be connected at the back side by means of the electromechanical interface  76  to the handle module  78 , in order to form a handheld device. Alternatively, the option exists of designing the intermediate module  74  with the main module  70  as an independent unit (fix-mount system). 
     The system becomes functional by means of the communication unit integrated in the intermediate module  74 . The communication unit communicates with the evaluation electronics or with an external controller. By coupling the intermediate module with integrated communication unit, the main module can communicate with any available controller. Furthermore, a power supply unit can be integrated in the intermediate module. Hence, the main module can be retrofitted to a different power supply voltage or adapted to changed power supply voltages. 
     The communication subassembly may also contain multiple communication controllers, in order to communicate in different protocols at the same time. Hence, the option exists of incorporating the scanning unit in a ProfiNet environment and communicating with ProfiNet inside a machine, yet also communicating in parallel with the outside via, for example OPC UA, to an upper-level system or a cloud. 
       FIG. 5 a    shows the intermediate module  74  with adapted handle module  78  and without the main module  70 . 
       FIG. 5 b    shows the intermediate module  74 , where a connector  80  of a cable  82  of a first protocol such as ProfiNet has been connected to the electromechanical interface  76 . The front-side electromechanical interface  72  comprises a U-shaped bracket  84  by means of which the main module  70  can be adapted to the intermediate module  74 . 
       FIG. 5 c    shows the intermediate module  74  with another connector  86 , for a cable  88  of another communication protocol. 
       FIG. 5 d    shows an embodiment in which the intermediate module  74  comprises a wireless radio connection  90  for connecting to a controller (not shown). 
     The intermediate module, the main module and the handle module  70  are designed for industrial use and consist entirely or partly of a robust material, such as a metal. 
     Preferably, the modules are formed as a single piece from a block of material, such as by milling. Alternatively, materials such as stainless steel, die casting, magnesium or carbon can be used. The materials may be machined or fabricated conventionally by lathe turning, milling, stamping, and/or bending, or by an additive manufacturing method (3D printing). 
     When a layout is being enlarged, redesigned, or disassembled, the image processing system (main module) can be easily adapted accordingly to new tasks. 
     In particular, a handheld scanner or handheld ID system can be easily redesigned by dismounting of the handle module  70  and attaching of the connector  80  or  86  of a handheld scanner to form a permanently mounted system. 
     The intermediate module can be powered either by cables  82 ,  88  or by means of an integrated storage battery. Communication protocols can be transmitted by cables or by a radio connection  90 . 
     The data can be transmitted directly to a controller, a computer, or a gateway. 
     In the prior art, scanners in industrial image processing and industrial identification are always equipped with an internal communication interface. Therefore, the scanner basically has a dictated usage: whether it should/must be used as a permanently mounted scanner, the protocol with which it communicates, and so forth. There are scanners in which an internal circuit board can be exchanged. Yet these devices as well (handheld scanners) are designed to be used as handheld scanners. Only the communication protocol can be changed. 
     The scanner according to the invention has an adaptive design. The main module  70  contains the imaging unit, the evaluation unit, the optics unit, the illumination unit and the target marking. Thanks to the adaptive design, the option exists of using the scanner both as a handheld device and as a firmly installed device, wherein the main module can be connected to different power supply and communication subassemblies in order to make possible an adaptation to different communication protocols.