JP2012185728A - Image recognition system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence frequency of identification error to be low if the state of an imaging surface is different.SOLUTION: A camera 15 images a mark 42 put on the surface of a connecting rod 41 and outputs image data. An auxiliary illumination 13 irradiates the surface of the connecting rod 41 with irradiation light of which light quantity is changeable. An image processing determination unit 25 detects and identifies the mark 42 from the image data output by the camera 15. A light quantity control unit 27 changes light quantity of the auxiliary illumination 13 when the image processing determination unit 25 does not identify the mark 42 from the image data.

Description

  The present invention relates to an image recognition system.

  In JP-A-64-36387, in various production processes such as automobiles, a stamped character attached to the surface of each part constituting a vehicle body is imaged by a camera, and character image data is cut out from the captured image data. Character recognition apparatus for converting each pixel information of cut out image data into binary data, detecting a character pattern from the binary data, and identifying the character by matching the detected character pattern with a previously registered character pattern Is described.

JP-A 64-36387

  In the above character recognition device, each pixel information of image data captured by the camera is converted into binary data to detect a character pattern, so that the character pattern detection accuracy is affected by the imaging environment of the camera. In particular, since the state (for example, reflectance) of the imaging surface with the engraved characters is not necessarily uniform, it is easily affected by the brightness (illuminance) of the imaging surface. For this reason, depending on the brightness of the imaging surface, the detection accuracy of the character pattern is deteriorated, and there is a possibility that the frequency of occurrence of identification errors increases when a plurality of components are continuously detected.

  Therefore, an object of the present invention is to provide an image recognition system that can suppress the occurrence frequency of identification errors even when the state of the imaging surface is different.

  In order to achieve the above object, an image recognition system according to the present invention includes an imaging unit, an irradiation unit, a symbol identification unit, and a light amount control unit.

  The imaging means images a symbol attached to the surface of the target object and outputs the image data. The irradiation unit irradiates the surface of the target object with irradiation light whose light quantity can be changed. The symbol identifying unit detects and identifies the symbol from the image data output by the imaging unit. The light quantity control means changes the light quantity of the irradiation means when the symbol identification means cannot identify the symbol from the image data.

  Symbols include letters, numbers and figures. The method of attaching a symbol to the surface of the target object includes not only printing and engraving but also sticking of a seal on which the symbol is printed. Further, the light quantity control means may gradually increase the light quantity of the irradiating means from the lower limit light quantity or gradually decrease from the upper limit light quantity.

  In the above configuration, when the symbol identifying unit cannot identify the symbol from the image data, the light amount of the irradiating unit is changed. Therefore, the reflectance of the imaging surface is different among a plurality of target objects that are continuously detected. However, symbols can be identified using image data captured with an appropriate amount of light for each imaging surface, and the frequency of occurrence of identification errors can be kept low.

  In addition, the image recognition determination system controls the imaging direction changing unit when the imaging direction changing unit that changes the imaging direction of the imaging unit with respect to the surface of the target object and the symbol identifying unit cannot identify the symbol from the image data. Imaging direction control means for changing the imaging direction of the means.

  The imaging direction control means may change the imaging direction of the imaging means when the symbol identification means cannot identify the symbol from the image data even if the light quantity control means changes the light quantity of the irradiation means. When changing the light quantity of the means, the imaging direction of the imaging means may be changed.

  In the above configuration, since the imaging direction can be changed in addition to the amount of light, the frequency of occurrence of identification errors can be further reduced.

  According to the present invention, the occurrence frequency of identification errors can be kept low even when the state of the imaging surface is different.

It is a schematic structure figure showing typically an image recognition system of one embodiment of the present invention. It is a top view which shows typically the connecting rod of the state accommodated in the conveyance box. It is a perspective view which shows an imaging unit typically. It is a flowchart which shows the test | inspection process which a controller performs.

  Hereinafter, an embodiment in which an image recognition system of the present invention is applied to an inspection system will be described with reference to the drawings. In this inspection system, a connecting rod (connecting rod) 41 used in an automobile engine is a target object, and a combination of a plurality of (four in this embodiment) connecting rods 41 used in one engine is appropriate (four It is inspected whether or not the connecting rods 41 are all the same standard). The target object is not limited to the connecting rod, and the image recognition system of the present invention can be applied to various parts.

  As shown in FIG. 1, the inspection system 1 controls the robot arm (imaging direction changing means) 2, the imaging unit 10 fixed to the robot arm 2, the conveyor 40 that conveys the connecting rod 41, and the entire inspection process. A controller 20 and a display device 3 are provided.

  As shown in FIG. 2, the side surface (surface) of one end of the connecting rod 41 is marked (symbol) 42 and twelve (three sets) so that the marking 42 of each connecting rod 41 is exposed upward. Connecting rods 41 are accommodated side by side in one transport box 43. The conveyor 40 conveys the conveyance box 43 so as to sequentially stop at a predetermined inspection position. In one transport box 43, three sets (12) of connecting rods 41A, 41B, 41C are arranged side by side along the transport direction. Four common rods 41 of the same standard used for one engine are marked with one common letter (alphabet, number, etc.) as an engraved mark 42, and the inspection system 1 has four connecting rods in the same set. It is inspected whether or not a desired common marking 42 is attached to all 41.

  As shown in FIGS. 1 and 3, the imaging unit 10 has a base plate 11 fixed to the tip of the robot arm 2, a camera unit 12 fixed to the base plate 11, and auxiliary illumination (irradiation means) 13. The camera unit 12 includes a main illumination 14 and a camera (imaging means) 15.

  The robot arm 2 is a device that can move the imaging unit 10 to an arbitrary position and direction, and moves the imaging unit 10 to a predetermined imaging position and stops. The imaging position of the imaging unit 10 is set in advance for each of the 12 connecting rods 41 in the transport box 43 stopped at the inspection position. The robot arm 2 moves the imaging unit 10 to the imaging position at the foremost end corresponding to the connecting rod 41 at the foremost end in the transport direction among the 12 imaging positions corresponding to the 12 connecting rods 41, and then transports it. The imaging unit 10 is moved backward in the direction, and the imaging unit 10 is sequentially stopped at each imaging position until the imaging position at the rearmost end corresponding to the connecting rod 41 at the rearmost end in the transport direction is reached. The attitude of the imaging unit 10 (camera 15) when stopping at each imaging position (imaging direction of the camera 15 with respect to the imaging surface) is set to a predetermined basic attitude. The robot arm 2 can change the posture of the camera 15 stepwise from the basic posture within a predetermined movable range. Note that a known robot arm such as a multi-joint robot or a robot combined with a linear drive device can be arbitrarily employed as long as necessary conditions are satisfied.

  The camera 15 is, for example, a CCD camera, and in the state where the imaging unit 10 is stopped at the imaging position, the engraving 42 is imaged using the surface of one end of the connecting rod 41 corresponding to the imaging position as an imaging surface, and the image data is transferred to the controller. 20 output.

  The main illumination 14 has a ring shape and is arranged so as to cover the periphery of the camera 15. The main illumination 14 and the auxiliary illumination 13 are fixed to the base plate 11 so that each irradiation light irradiates the imaging surface with the imaging direction of the camera 15 facing the imaging surface. The main illumination 14 is an illumination device whose light amount is fixed to a predetermined amount, and the auxiliary illumination 13 is an illumination device whose light amount can be changed. The method of changing the light quantity of the auxiliary illumination 13 is not particularly limited, but for example, it is possible to connect a variable constant current power supply circuit inside and control the current value of the variable constant current power supply circuit. The light amount of the auxiliary illumination 13 is set to zero (light-off state) in the initial state, and gradually increases step by step in response to an instruction from the controller 20.

  The controller 20 includes a CPU (Central Processing Unit) 21 and a storage unit 22. The controller 20 may be a general-purpose personal computer or a dedicated device. The storage unit 22 includes a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and stores various programs and various data for the CPU 21 to execute various processes. The various programs include an inspection program for the CPU 21 to execute an inspection process.

  The inspection program includes a transfer control program for executing the transfer control process, an arm control program for executing the arm control process, a symbol identification program for executing the symbol identification process, and a determination for executing the combination determination process. A program is included. The conveyance control process is a process for controlling the conveyor 40 and conveying the conveyance box 43. The arm control process is a process for controlling the robot arm 2 to move and stop the imaging unit 10. The symbol identification process is a process of imaging the imaging surface of the connecting rod 41 with the camera 15 and identifying the marking 42 included in the image data. The combination determination process is a process of determining whether or not the combination of the connecting rods 41 is appropriate based on the identified marking 42. These programs may be read from an external storage medium such as various CD media (Compact Disc Media) and stored in the storage unit 22, or may be acquired via a network such as the Internet and stored in the storage unit 22. May be. The various data includes data defining the stop position of the transport box 43, data defining the stop position of the imaging unit 10, and the like.

  In the storage unit 22, an area for temporarily storing image data, marking information, and the like is set. The storage area for the stamp information is set for each transport box 43.

  The CPU 21 functions as the conveyor control unit 23 by executing the conveyance control process, and functions as the arm control unit (imaging direction control means) 24 by executing the arm control process, and executes the symbol identification process and the combination determination process. As a result, the imaging control unit 25, the image processing determination unit (symbol identification unit) 26, the light amount control unit (light amount control unit) 27, and the display control unit 28 function. Note that a part of the function of the CPU 21 may be extracted and provided in another information processing apparatus, for example, by providing a sequencer for performing the conveyance process and the arm control process separately from the controller.

  The conveyor control unit 23 controls the conveyor 40 so that the transport box 43 moves to the inspection position and sequentially stops.

  The arm control unit 24 drives the robot arm 2 so that the imaging unit 10 sequentially moves to 12 imaging positions corresponding to the connecting rods 41 and stops at the basic posture with the transport box 43 stopped at the inspection position. Control.

  In the symbol identification process, the light quantity control unit 27 turns on the main illumination 14. Further, the light quantity control unit 27 maintains the auxiliary illumination 13 in the initial state (light-off state) at the start of the symbol identification process for one connecting rod 41.

  In the symbol identification process, the imaging control unit 25 outputs an imaging instruction signal to the camera 15 after the imaging unit 10 moves to the imaging position and stops. The camera 15 that has received the imaging instruction signal images the imaging surface of the connecting rod 41 and outputs the image data to the controller 20.

  When image data is input from the camera 15 to the controller 20, the image processing determination unit 26 performs image processing and pattern determination. In the image processing, image data including the marking 42 is cut out from the image data captured by the camera 15, each pixel information of the cut-out image data is converted into binary data, and a character pattern is detected from the binary data. In the pattern determination, the detected character pattern is matched with a pre-stored character pattern, the stamp 42 is identified (determining which symbol the stamp 42 represents), and the symbol represented by the stamp 42 is used as stamp information. The data is sequentially stored in the storage unit 22.

  When the image processing determination unit 26 cannot identify the marking 42, the light amount control unit 27 controls the auxiliary illumination 13 so that the light amount increases stepwise. The imaging control unit 25 outputs an imaging instruction signal to the camera 15 every time the light amount of the auxiliary illumination 13 increases stepwise. The camera 15 that has received the imaging instruction signal images the imaging surface of the connecting rod 41 and outputs the image data to the controller 20. When image data is input from the camera 15 to the controller 20, the image processing determination unit 26 performs image processing and pattern determination. The light amount control unit 27 continues to increase the light amount of the auxiliary illumination 13 until the image processing determination unit 26 identifies the marking 42 or until the auxiliary illumination 13 reaches the maximum light amount (upper limit value).

  If the image processing determination unit 26 cannot identify the marking 42 even if the auxiliary illumination 13 reaches the maximum light amount, the arm control unit 24 controls the driving of the robot arm 2 so that the posture of the camera 15 changes stepwise from the basic posture. To do. The imaging control unit 25 outputs an imaging instruction signal to the camera 15 every time the posture of the camera 15 is changed stepwise. The camera 15 that has received the imaging instruction signal images the imaging surface of the connecting rod 41 and outputs the image data to the controller 20. When image data is input from the camera 15 to the controller 20, the image processing determination unit 26 performs image processing and pattern determination. The arm control unit 24 continues to change the posture of the camera 15 until the image processing determination unit 26 identifies the marking 42 or until the posture of the camera 15 reaches the limit of the movable range.

  If the image processing determination unit 26 cannot identify the stamp 42 even when the posture of the camera 15 reaches the limit of the changeable range, the display control unit 28 displays an error display on the display device 3 indicating that the stamp 42 cannot be identified. indicate.

  When the image processing determination unit 26 identifies the markings 42 of all (12) connecting rods 41 accommodated in one transport box 43, whether or not the combination of the connecting rods 41 of each set (4) is appropriate. A combination determination process for determining is executed based on the identified marking 42. Specifically, the marking information stored in the storage unit 22 is read for each set, and when the read four marking information is all predetermined common information, it is determined to be appropriate, and the four marking information is predetermined. If information other than this information is included, it is determined to be inappropriate.

  The display control unit 28 displays the result of the combination determination of the connecting rod 41 by the image processing determination unit 26 on the display device 3.

  Next, one cycle of the inspection process executed by the controller 20 will be described with reference to the flowchart of FIG. This process is started when the controller 20 receives a predetermined start instruction from the inspection worker (for example, pressing a start button), and the light amount control unit 27 maintains the extinguishing of the auxiliary illumination 13 and the main illumination 14. Lights up. When one transport box 43 corresponds to one cycle and inspection of all the connecting rods 41 in one transport box 43 is completed, inspection cycles corresponding to the next transport box 43 are continuously started.

  When this process is started, the conveyor control unit 23 controls the conveyor 40, and the transport box 43 moves to the inspection position and stops (step S1).

  When the transport box 43 stops at the inspection position, the arm control unit 24 controls the robot arm 2, and the camera 15 moves to the foremost imaging position corresponding to the connecting rod 41 at the front end in the transport direction and stops at the basic posture. (Step S2).

  When the imaging unit 10 stops at the imaging position, the imaging control unit 25 outputs an imaging instruction signal to the camera 15, and the camera 15 that has received the imaging instruction signal images the imaging surface of the connecting rod 41 and uses the image data as a controller. 20 (step S3).

  When image data is input from the camera 15 to the controller 20, the image processing determination unit 26 performs image processing and pattern determination (step S4).

  If the marking 42 cannot be identified in the pattern determination (step S5: NO), the light amount control unit 27 determines whether or not the light amount of the auxiliary illumination 13 has reached the upper limit value (step S6). If the light amount has not reached the upper limit (step S6: NO), the light amount of the auxiliary illumination 13 is increased by one step (step S7).

  When the light amount of the auxiliary illumination 13 increases by one step, the imaging surface imaging (step S3), image processing, and pattern determination (step S4) are executed again. If the marking 42 cannot be identified even if the amount of light from the auxiliary illumination 13 increases (step S5: NO), the imaging surface is imaged (step S3), image processing, and pattern determination until the amount of light from the auxiliary illumination 13 reaches the upper limit. (Step S4) is repeatedly executed.

  When the amount of light of the auxiliary illumination 13 reaches the upper limit (step S6: YES), the arm control unit 24 determines whether or not the posture of the camera 15 can be changed (whether or not the limit of the movable range has been reached) ( In step S8), if changeable (step S8: YES), the posture of the camera 15 is changed by one step (step S9).

  When the posture of the camera 15 is changed by one step, the imaging surface imaging (step S3), image processing, and pattern determination (step S4) are executed again. If the marking 42 cannot be identified even if the posture of the camera 15 is changed (step S5: NO), the imaging surface is imaged (step S3), image processing, and pattern determination until the posture of the camera 15 reaches the limit of the movable range. (Step S4) is repeatedly executed.

  When the posture of the camera 15 reaches the limit of the movable range (step S8: NO), the display control unit 28 displays an error display indicating that the stamp 42 cannot be identified on the display device 3 (step S10). The process ends.

  On the other hand, when the marking 42 is identified in the pattern determination (step S5: YES), the image processing determination unit 26 stores the symbol represented by the marking 42 in the storage unit 22 as the marking information (step S11), and the light amount control unit 27. Turns off the auxiliary illumination 13 and sets the amount of light to the minimum (step S12).

  If the camera 15 has not reached the last imaging position and the stamp information stored in the storage unit 22 has not reached the predetermined number (12) (step S13: NO), the process proceeds to step S2, and the camera 15 Is moved to the next imaging position, and the processes in and after step 3 are executed.

  When the camera 15 has reached the last imaging position and the marking information stored in the storage unit 22 has reached a predetermined number (12) (step S13: YES), the image processing determination unit 26 performs combination determination processing. Execute. In the combination determination process, the marking information stored in the storage unit 22 is read for each set, and when the read four marking information is the predetermined common information, it is determined to be appropriate and the four marking information is predetermined. If information other than this information is included, it is determined to be inappropriate.

  When the combination determination process is completed, the display control unit 28 displays the result of the combination determination of the connecting rod 41 by the image processing determination unit 26 on the display device 3, and this process ends.

  As described above, according to the present embodiment, when the image processing determination unit 26 cannot identify the marking 42 from the image data, the amount of light of the auxiliary illumination 13 increases stepwise, and the imaging surface increases every time the amount of light increases. Since the marking 42 is identified from the newly captured image data, even if the reflectance of the imaging surface is different among the plurality of connecting rods 41 that are continuously detected, for each imaging surface The marking 42 can be identified using image data captured with an appropriate amount of light, and the frequency of occurrence of identification errors can be kept low.

  Further, when the image processing determination unit 26 cannot identify the stamp 42 from the image data even when the maximum amount of light is reached, the imaging direction is changed in stages, the imaging surface is imaged every time the imaging direction is changed, and a new image is taken. Since the marking 42 is identified from the image data, the occurrence frequency of identification errors can be further reduced.

  In addition, the said embodiment is an example of this invention and can be changed in the range which does not deviate from this invention.

  For example, instead of the main illumination 14 and the auxiliary illumination 13, a single illumination device that can change the amount of light may be provided. The light quantity of the auxiliary illumination 13 may be decreased stepwise from the predetermined light quantity without increasing from the extinguished state. When changing the imaging direction, the auxiliary illumination 13 may be set to a predetermined light amount without setting the maximum light amount, or the auxiliary illumination 13 may be turned off. The change of the imaging direction of the camera 15 may be performed simultaneously with the decrease of the light amount or may be omitted.

  The present invention is widely applicable to a system for identifying a symbol attached to the surface of a target object.

1: Inspection system 2: Robot arm (imaging direction changing means)
3: Display device 10: Imaging unit 11: Base plate 12: Camera unit 13: Auxiliary illumination (irradiation means)
14: Main illumination 15: Camera (imaging means)
20: Controller 21: CPU
22: Storage unit 23: Conveyor control unit 24: Arm control unit (imaging direction control means)
25: Imaging control unit 26: Image processing determination unit (symbol identification means)
27: Light quantity control unit (light quantity control means)
28: Display control unit 40: Conveyor 41: Connecting rod (target object)
42: Stamp (symbol)
43: Transport box

Claims (2)

An imaging means for imaging the symbol attached to the surface of the target object and outputting the image data;
Irradiating means for irradiating the surface of the target object with irradiation light capable of changing the amount of light;
Symbol identifying means for detecting and identifying the symbol from the image data output by the imaging means;
An image recognition system comprising: a light amount control unit that changes a light amount of the irradiation unit when the symbol identification unit cannot identify the symbol from the image data. The image recognition determination system according to claim 1,
Imaging direction changing means for changing the imaging direction of the imaging means relative to the surface of the target object;
An image direction control unit that controls the image capturing direction changing unit to change the image capturing direction of the image capturing unit when the symbol identifying unit cannot identify the symbol from the image data. system.

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