WO2022179186A1 - 频闪阶梯照明缺陷检测系统 - Google Patents

频闪阶梯照明缺陷检测系统 Download PDF

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Publication number
WO2022179186A1
WO2022179186A1 PCT/CN2021/129951 CN2021129951W WO2022179186A1 WO 2022179186 A1 WO2022179186 A1 WO 2022179186A1 CN 2021129951 W CN2021129951 W CN 2021129951W WO 2022179186 A1 WO2022179186 A1 WO 2022179186A1
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Prior art keywords
light source
stroboscopic
camera
control unit
frequency
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PCT/CN2021/129951
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English (en)
French (fr)
Inventor
胡肖松
骈冰
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中科慧远视觉技术（洛阳）有限公司
中科慧远视觉技术(北京)有限公司
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Priority to US18/276,242 priority Critical patent/US20240118218A1/en
Publication of WO2022179186A1 publication Critical patent/WO2022179186A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8806—Specially adapted optical and illumination features
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B15/00—Special procedures for taking photographs; Apparatus therefor
    • G03B15/02—Illuminating scene
    • G03B15/03—Combinations of cameras with lighting apparatus; Flash units
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8806—Specially adapted optical and illumination features
    • G01N2021/8838—Stroboscopic illumination; synchronised illumination

Definitions

  • the present application relates to the technical field of machine vision defect detection, and in particular, to a machine vision appearance defect detection system and implementation method with multiple cameras and stroboscopic staircase lighting.
  • the machine vision system converts the captured target into an image signal through an image capture device (two types of CMOS and CCD sensors), and transmits it to a dedicated image processing system.
  • the image system performs various operations on these signals to extract the characteristics of the target. Its basic components usually include cameras, lenses, light sources, frame grabbers, image processors, image processing software and algorithms.
  • machine vision systems have been deeply used in industrial inspection systems, which are used to identify product information, measure product dimensions, and detect product defects.
  • industrial inspection systems which are used to identify product information, measure product dimensions, and detect product defects.
  • users have very high requirements on the appearance of 3C consumer electronic products, it is particularly important to detect the appearance defects of products in the production of products.
  • the existing image acquisition techniques for product appearance defect detection can be divided into three categories.
  • One is to use a high-precision area scan camera and light source to obtain reflection or transmission, bright field or dark field pictures of the product through appropriate shooting angles and light intensity, and then process the information of the target.
  • This solution can obtain most product features and is widely used.
  • the disadvantage is that the industrial pipeline is often moving, and the influence of motion needs to be eliminated in the image.
  • due to the resolution limitation of the existing area scan camera it often cannot reach 3C
  • the identification of micron-level defects in consumer products, or the extremely high requirements for image processing algorithms at this time, are currently difficult to meet.
  • 3D vision technologies include binocular vision, structured light, TOF (time-of-flight), triangular ranging, lidar, etc. These technologies are currently widely used in the identification, measurement and positioning of three-dimensional physics, but are rarely used in defect detection. And it is also difficult to meet the micron-level high-precision requirements of 3C products.
  • the third is to use a line scan camera and light source to obtain the reflected bright field, reflected dark field, transmitted bright field and transmitted dark field images of the target object and then provide them to the computer system for processing.
  • the advantage of this solution is that the resolution of the line scan camera is high, which can achieve the identification of micron-level defects, and the combination of the line scan camera and the light source, combined with the encoder of the motion system, is especially suitable for applications in industrial pipelines, so the current high Precision defect detection systems generally use this scheme.
  • the defects reflected in the pictures of the four scenarios (reflected bright field, reflected dark field, transmitted bright field, and transmitted dark field) obtained by the detected object through the detection system of the line scan camera are often limited, because the linear scan The speed of the camera taking pictures is fixed, and the driving current of the light source corresponding to the shooting angle is fixed. Therefore, when shooting different defects, it is often necessary to change the pulse width of the corresponding light source, and the maximum pulse width of the light source is the exposure of the line scan camera. Time, and the wider pulse width has no effect on the line scan camera, so this greatly limits the number of photos and the types of defect detection.
  • the current of the driving circuit corresponding to a single light source is fixed, when changing the illumination angle to take photos of different bright fields or dark fields, this light source is often not used in each defect at the same time, so the utilization rate of the light source is very high. Low, with fewer kinds of defects in simultaneous shots. At this time, the number of light sources and cameras can only be increased to take the required photos or more types of defects, which increases the cost and complexity of the system.
  • the present application discloses a stroboscopic staircase lighting defect detection system.
  • the defect detection system of the present application controls the stroboscopic step of the light source, that is, simultaneously changes the turn-on pulse width and the working current value of the light source, and uses multiple light sources to work together to achieve multi-directional detection of various defects. imaging purpose.
  • the preferred embodiment scheme of the present application using dual cameras can take more photos of objects in the bright and dark fields in one assembly line work, improve the utilization rate of the light source, and increase the types of detectable defects and The number of images achieved in the prior art can only be achieved by 4-8 cameras.
  • the present application provides a stroboscopic ladder lighting defect detection system, the system is used for product appearance defect detection, comprising: an image extraction unit (101), a light and shade adjustment unit (102), a data processing unit (103) and a strobe control unit (104).
  • the image extraction unit (101), connected to the stroboscopic control unit (104), is used for obtaining stable and clear images in various transmission/reflection vision brightfield/darkfield;
  • the light-dark adjustment unit (102) is connected to the stroboscopic control unit (104), and is used for setting various transmission/reflection visual brightfield/darkfield, and in various transmission/reflection visual brightfield/darkfield convert;
  • the data processing unit (103), connected with the strobe control unit (104), is used to generate a pulse code signal, generate an enable signal after detecting the product under test, and transmit the enable signal to the strobe control unit (104);
  • the stroboscopic control unit (104) is respectively connected with the image extraction unit (101), the shading adjustment unit (102) and the data processing unit (103), and is used for real-time recording of the signal transmitted by the data processing unit (103), frequency-doubling and/or dividing the signal; controlling the image extraction unit (101) to obtain an image using the frequency-doubling and/or frequency-dividing signal; controlling the shading adjustment using the frequency-doubling and/or frequency-dividing signal.
  • the unit (102) sets the transmissive/reflective visual brightfield/darkfield and switches between various transmissive/reflective visual brightfield/darkfield.
  • the image extraction unit (101) further includes a plurality of cameras; the light and shade adjustment unit (102) further includes a plurality of light sources.
  • the data processing unit (103) further includes an encoder and a PLC controller;
  • the stroboscopic control unit (104) further includes: a stroboscopic control circuit, a drive circuit, an input interface circuit and an output interface circuit.
  • the image extraction unit (101) further includes two cameras; the cameras are line scan cameras; the light and shade adjustment unit (102) further includes a plurality of light sources.
  • the camera is a line scan camera; the encoder generates a corresponding pulse code signal according to the rotational speed of the mechanical rotation system; the PLC controller is a programmable controller, which generates an enabling signal after detecting the object to be measured provided to the strobe control unit (104).
  • the driving circuit outputs a constant current signal for driving the shading adjustment unit (102); the pulse width and period of the output current can be set under PWM control; the pulse width can be set in each period It can be set to any different value; it can realize that the output current of each PWM modulated pulse width can be set to any different value.
  • the first camera is located in the reflected bright field of the first light source, and the second camera is located in the transmitted bright field of the first light source; at the same time, the first camera is located in the second light source In the reflection dark field of the light source, the second camera is located in the transmission dark field of the second light source.
  • the stroboscopic control unit (104) is further configured to record the signal of the encoder in real time, and obtain a rising edge and a period;
  • the stroboscopic control unit (104) is further configured to perform frequency multiplication and/or frequency division on the signal of the encoder according to the running speed, the number of pictures or defect types, and camera parameters;
  • the stroboscopic control unit (104) is further configured to judge whether the PLC controller is enabled or not, return to the previous step if it is invalid, and perform subsequent signal output if it is valid;
  • the stroboscopic control unit (104) is further configured to control the driving circuit of the reflected brightfield light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform strobe step lighting and Photograph;
  • the stroboscopic control unit (104) is further used to control the driving circuit of the reflected dark field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform strobe step lighting and Photograph;
  • the stroboscopic control unit (104) is further configured to control the drive circuit of the transmitted brightfield light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform stroboscopic step lighting and Photograph;
  • the stroboscopic control unit (104) is further used to control the driving circuit of the transmission dark field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform stroboscopic step lighting and Photograph;
  • the stroboscopic control unit (104) is further configured to control the driving circuits of each camera and the corresponding light source according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing.
  • the present application provides a method for detecting stroboscopic staircase lighting defects, comprising the following steps:
  • Step 1 select the camera light source: according to the defect type to be detected by the system and/or the number of photos taken, select the first camera, the second camera and the first light source and the second light source suitable for it;
  • Step 2 install the imaging system: according to the defects to be imaged, the angles and positions of the light source, the first camera, and the second camera are initially determined structurally, and the angles of the first camera and the second camera are respectively adjusted for each defect to be tested. and position, when imaging data needs to be added, add a third camera and a fourth camera until the Mth camera is added, where M is a positive integer greater than 3; the position of the device is initially fixed according to the brightfield and darkfield requirements;
  • Step 3 set the encoder parameters: according to the speed of the system detection product, set the speed of the motion system, and obtain the cycle of the encoder accordingly;
  • Step 4 setting the stroboscopic control unit: according to the encoder cycle, the number of photos taken, and the camera parameters, the frequency multiplication and frequency division parameters of the stroboscopic control unit are set, and the parameters of the stroboscopic ladder lighting are initially set;
  • Step 5 adjust the optical parameters: for each defect to be tested, adjust the angles of the first light source and the second light source respectively.
  • N is a positive integer greater than 3; after debugging, fix the position of each component so that there is no relative displacement and angular rotation between them;
  • Step 6 debug the stroboscopic control unit: for each defect to be tested, debug the stroboscopic and step parameters respectively, correct the pulse width and working current value of the corresponding light source, and ensure that the gray value of the captured image falls within the acceptable setting. within the range;
  • Step 7 image dismantling: using a computer system to dismantle the multi-line images captured by the line scan camera;
  • Step 8 determine the imaging clarity: determine whether the imaging clarity of the image defect reaches the set threshold; if the clarity does not reach the set threshold, return to step 5, and the clarity reaches the set threshold and proceed to the next step;
  • Step 9 data analysis: use the computer system debugging software and algorithm defects to perform data analysis to complete the detection.
  • the present application also provides a dual-camera strobe step lighting defect detection method, the number of cameras used in the method is only two, and the following steps are included:
  • Step 1 select the camera light source: according to the defect type to be detected by the system and/or the number of photos taken, select the first camera, the second camera and the first light source and the second light source suitable for it;
  • Step 2 install the imaging system: according to the defects to be imaged, the angles and positions of the light source, the first camera, and the second camera are initially determined structurally, and the positions of the devices are preliminarily fixed according to the requirements of the bright field and the dark field;
  • Step 3 set the encoder parameters: according to the speed of the system detection product, set the speed of the motion system, and obtain the cycle of the encoder accordingly;
  • Step 4 setting the stroboscopic control unit: according to the encoder cycle, the number of photos taken, and the camera parameters, the frequency multiplication and frequency division parameters of the stroboscopic control unit are set, and the parameters of the stroboscopic ladder lighting are initially set;
  • Step 5 adjust the optical parameters: for each defect to be tested, adjust the angles of the first light source and the second light source respectively.
  • N is a positive integer greater than 3; after debugging, fix the position of each component so that there is no relative displacement and angular rotation between them;
  • Step 6 debug the stroboscopic control unit: for each defect to be tested, debug the stroboscopic and step parameters respectively, correct the pulse width and working current value of the corresponding light source, and ensure that the gray value of the captured image falls within the acceptable setting. within the range;
  • Step 7 image dismantling: using a computer system to dismantle the multi-line images captured by the line scan camera;
  • Step 8 determine the imaging clarity: determine whether the imaging clarity of the image defect reaches the set threshold; if the clarity does not reach the set threshold, return to step 5, and the clarity reaches the set threshold and proceed to the next step;
  • Step 9 data analysis: use the computer system debugging software and algorithm defects to perform data analysis to complete the detection.
  • the stroboscopic control unit is used to record the signal of the encoder in real time, and obtain the rising edge and period;
  • the stroboscopic control unit is configured to perform frequency doubling and/or frequency division on the signal of the encoder according to the running speed, the number of pictures or defect types, and camera parameters;
  • the stroboscopic control unit is used for judging whether the enabling of the PLC controller is valid, returning to the previous step if it is invalid, and performing subsequent signal output if it is valid;
  • the stroboscopic control unit is used to control the driving circuit of the reflected bright-field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuit of the reflective dark field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuit of the transmitted bright field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuit of the transmission dark-field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuits of each camera and the corresponding light source according to the frequency multiplied and/or divided signal as the output line trigger signal to perform strobe lighting and photographing.
  • the combination scheme of line scan camera, encoder and PLC controller can ensure the detection of micron-level defects in consumer 3C products, and is very suitable for installation in the production line.
  • the special stroboscopic control unit is used to realize the acquisition of the encoder and PLC controller signals, as well as the control of the light source and the camera, which can realize the flexible adjustment and upgrading of the system.
  • FIG. 1 is a block diagram of the structure of a stroboscopic ladder lighting defect detection system according to an embodiment of the present application.
  • FIG. 2 is a schematic structural diagram of a stroboscopic ladder lighting defect detection system according to an embodiment of the present application.
  • FIG. 3 is a schematic structural diagram of a stroboscopic ladder lighting defect detection system for adding a third light source to an Nth light source for supplementary light according to an embodiment of the present application.
  • FIG. 4 is a timing chart of strobe lighting imaging in the prior art.
  • FIG. 5 is a time sequence diagram of stroboscopic staircase illumination imaging performed by the defect detection method according to the embodiment of the present application.
  • FIG. 6 is a timing diagram of multi-light source coordinated stroboscopic step lighting imaging in the defect detection method according to the embodiment of the present application.
  • FIG. 7 is a flowchart of a working method of a strobe control unit according to an embodiment of the present application.
  • FIG. 8 is a flowchart of a method for detecting a defect in stroboscopic staircase lighting according to an embodiment of the present application.
  • the appearance defect detection system of the multi-camera and stroboscopic staircase lighting of the present application belongs to the field of machine vision.
  • the system consists of a first camera, a second camera, a light source, an encoder, a PLC controller, and a stroboscopic control unit;
  • the first camera and the second camera are line scan cameras;
  • the light source includes at least a first light source and a second light source;
  • the encoder generates corresponding pulse coding signals according to the rotational speed of the mechanical rotation system;
  • the PLC controller is The programmable controller generates an enabling signal after detecting the measured object and provides it to the stroboscopic control unit;
  • the stroboscopic control unit includes an input interface circuit, an output interface circuit, a stroboscopic control circuit, and a plurality of light sources.
  • the application uses multiple light sources to work together to achieve the purpose of lighting and imaging various defects in multiple directions, increasing the types of detectable defects, and improving the detection of machine vision appearance defects. system efficiency.
  • Appearance defect detection system with dual cameras and strobe step lighting including a first camera, a second camera, a light source, an encoder, a PLC controller, and a strobe control unit; the first camera and the second camera are line scan cameras
  • the described light source includes at least a first light source and a second light source;
  • the encoder generates a corresponding pulse coding signal according to the rotational speed of the mechanical rotating system;
  • the PLC controller is a programmable controller, which detects the After the object is detected, an enabling signal is generated and provided to the stroboscopic control unit;
  • the stroboscopic control unit includes an input interface circuit, an output interface circuit, a stroboscopic control circuit, and a drive circuit for a plurality of light sources.
  • the various light sources in the light source are LED light sources, which can be line light sources, flat light sources, ring light sources, square light sources, bar light sources, dome light sources, flat shadowless light sources, coaxial light sources, ultraviolet light sources, infrared light sources, point light sources, etc. one or a combination of several.
  • the light source may also include a third light source, or a fourth light source, or the third light source to the Nth light source,
  • N is any natural number greater than "3"; in principle, the positions of the third light source to the Nth light source can be at any point in the XYZ three-dimensional coordinates, as long as it does not affect the imaging line of the first camera, the second camera and the third light source.
  • Strobe control unit in which the characteristics of the driving circuit are: the output is a constant current signal, which is used to drive the light source; it supports strobe adjustment, that is, the pulse width and period of the output current under PWM control can be set, especially the pulse width It can be different in each cycle; it supports step current regulation, that is, in each PWM modulation pulse width, the output current value can be set to be different, and the output current value can be arbitrarily set between 0A and the maximum output current.
  • the machine vision appearance defect detection system with dual cameras and strobe ladder control, the positional relationship of each component in the system is: the object to be measured is placed in the mechanical rotation system to move in a straight line at a uniform speed, with the movement direction as the X axis, the first light source and the second light source
  • the center point of the two light sources is the origin O
  • the center line of the strip area of the object to be photographed is the Y axis
  • the upward origin is the Z axis
  • the first camera, the second camera, the first light source and the second light source in the light source The centers of all are in the XOZ plane, where the first light source forms an angle a with the X axis, and the second light source forms an angle b with the X axis;
  • the first camera is in the reflected bright field of the first light source, and the second camera is in the second light source.
  • the first camera is in the reflection dark field of the second light source, and the second camera is in the
  • a machine vision appearance defect detection system with dual cameras and stroboscopic ladder control the working method of the stroboscopic control unit is as follows: firstly, recording the encoder signal in real time to obtain the rising edge and period; Quantity (type of defect), camera parameters, etc., frequency multiplication and frequency division of the encoder signal; thirdly, to judge whether the PLC controller enable is valid, if it is invalid, return to step 2, and if it is valid, the subsequent signal output is performed;
  • the frequency-divided signal is used as the output line trigger signal to control the driving circuit of the reflected brightfield light source corresponding to the first camera and the second camera to perform strobe lighting and photographing;
  • the fifth is the same, use the line trigger signal to control
  • the driving circuit of the reflected dark field light source corresponding to the first camera and the second camera performs strobe lighting and photographing;
  • the sixth is the same, using the line trigger signal to control the transmitted bright field light source corresponding to the second camera and the second camera
  • the driving circuit of the second camera is used
  • the machine vision appearance defect detection system with dual cameras and stroboscopic ladder control the process of the detection method is as follows: First, select the camera and light source: According to the type of defects to be detected by the system or the number of photos taken, select the appropriate first camera, The second camera, the first light source, the second light source, up to the Nth light source; the second is, the installation system: according to the defects to be imaged, the angles and positions of the light source, the first camera, and the second camera are preliminarily determined structurally.
  • Field and dark field require preliminary fixation of the position of the device; third, set the encoder parameters: according to the speed of the system to detect the product, set the rate of the motion system, and obtain the cycle of the encoder accordingly; fourth, set the strobe control unit: according to the The encoder cycle, the number of photos taken, the parameters of the camera, etc., set the frequency multiplication and frequency division parameters of the strobe control unit, and initially set the parameters of the strobe staircase lighting; the fifth is to debug the optical parameters: for each defect, debug the first The angle of the light source and the second light source. When the supplementary light is needed, the third light source is added to fill the Nth light source, and the position of the device is fixed after the debugging is completed.
  • debugging the stroboscopic control unit for each defect, debug separately Strobe and step parameters, that is, correct the pulse width and working current value of the corresponding light source, so that the gray value of the captured image is within an acceptable range; the seventh is to disassemble the multi-line image captured by the line scan camera in the computer. Figure (if there is a problem with dismantling the image, such as wrong or overlapping images, go back to step 4 to modify the parameters); eighth, judge whether the defect image is clear or not, if it is not clear, go back to step five, and if it is clear, run down; nine Yes, in computers, debugging software and analyzing algorithm flaws.
  • the stroboscopic staircase lighting defect detection system is used for the appearance defect detection of products, including: an image extraction unit (101), a light and shade adjustment unit (102), a data processing unit (103) and a stroboscopic control unit (104).
  • the image extraction unit (101), connected to the stroboscopic control unit (104), is used for obtaining stable and clear images in various transmission/reflection vision brightfield/darkfield;
  • the light-dark adjustment unit (102) is connected to the stroboscopic control unit (104), and is used for setting various transmission/reflection visual brightfield/darkfield, and in various transmission/reflection visual brightfield/darkfield convert;
  • the data processing unit (103), connected with the strobe control unit (104), is used to generate a pulse code signal, generate an enable signal after detecting the product under test, and transmit the enable signal to the strobe control unit (104);
  • the stroboscopic control unit (104) is respectively connected with the image extraction unit (101), the shading adjustment unit (102) and the data processing unit (103), and is used for real-time recording of the signal transmitted by the data processing unit (103), frequency-doubling and/or dividing the signal; controlling the image extraction unit (101) to obtain an image using the frequency-doubling and/or frequency-dividing signal; controlling the shading adjustment using the frequency-doubling and/or frequency-dividing signal.
  • the unit (102) sets the transmissive/reflective visual brightfield/darkfield and switches between various transmissive/reflective visual brightfield/darkfield.
  • the image extraction unit (101) further includes a plurality of cameras; the light and shade adjustment unit (102) further includes a plurality of light sources.
  • the data processing unit (103) further includes an encoder and a PLC controller;
  • the stroboscopic control unit (104) further includes: a stroboscopic control circuit, a drive circuit, an input interface circuit and an output interface circuit.
  • the image extraction unit (101) further includes two cameras; the cameras are line scan cameras; the light and shade adjustment unit (102) further includes a plurality of light sources.
  • the camera is a line scan camera; the encoder generates a corresponding pulse code signal according to the rotational speed of the mechanical rotation system; the PLC controller is a programmable controller, which generates an enabling signal after detecting the object to be measured provided to the strobe control unit (104).
  • the driving circuit outputs a constant current signal for driving the shading adjustment unit (102); the pulse width and period of the output current can be set under PWM control; the pulse width can be set in each period It can be set to any different value; it can realize that the output current of each PWM modulated pulse width can be set to any different value.
  • the first camera is located in the reflected bright field of the first light source, and the second camera is located in the transmitted bright field of the first light source; at the same time, the first camera is located in the second light source In the reflection dark field of the light source, the second camera is located in the transmission dark field of the second light source.
  • the stroboscopic control unit (104) is further configured to record the signal of the encoder in real time, and obtain a rising edge and a period;
  • the stroboscopic control unit (104) is further configured to perform frequency doubling and/or frequency division on the signal of the encoder according to the running speed, the number of pictures or defect types, and camera parameters;
  • the stroboscopic control unit (104) is further configured to judge whether the PLC controller is enabled or not, return to the previous step if it is invalid, and perform subsequent signal output if it is valid;
  • the stroboscopic control unit (104) is further configured to control the driving circuit of the reflected brightfield light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform strobe step lighting and Photograph;
  • the stroboscopic control unit (104) is further used to control the driving circuit of the reflected dark field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform strobe step lighting and Photograph;
  • the stroboscopic control unit (104) is further configured to control the drive circuit of the transmitted brightfield light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform stroboscopic step lighting and Photograph;
  • the stroboscopic control unit (104) is further used to control the driving circuit of the transmission dark field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal, to perform stroboscopic step lighting and Photograph;
  • the stroboscopic control unit (104) is further configured to control the driving circuits of each camera and the corresponding light source according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing.
  • Step 1 select the camera light source: according to the defect type to be detected by the system and/or the number of photos taken, select the first camera, the second camera and the first light source and the second light source suitable for it;
  • Step 2 install the imaging system: according to the defects to be imaged, the angles and positions of the light source, the first camera, and the second camera are initially determined structurally, and the angles of the first camera and the second camera are respectively adjusted for each defect to be tested. and position, when imaging data needs to be added, add a third camera and a fourth camera until the Mth camera is added, where M is a positive integer greater than 3; the position of the device is initially fixed according to the brightfield and darkfield requirements;
  • Step 3 set the encoder parameters: according to the speed of the system detection product, set the speed of the motion system, and obtain the cycle of the encoder accordingly;
  • Step 4 setting the stroboscopic control unit: according to the encoder cycle, the number of photos taken, and the camera parameters, the frequency multiplication and frequency division parameters of the stroboscopic control unit are set, and the parameters of the stroboscopic ladder lighting are initially set;
  • Step 5 adjust the optical parameters: for each defect to be tested, adjust the angles of the first light source and the second light source respectively.
  • N is a positive integer greater than 3; after debugging, fix the position of each component so that there is no relative displacement and angular rotation between them;
  • Step 6 debug the stroboscopic control unit: for each defect to be tested, debug the stroboscopic and step parameters respectively, correct the pulse width and working current value of the corresponding light source, and ensure that the gray value of the captured image falls within the acceptable setting. within the range;
  • Step 7 image dismantling: using a computer system to dismantle the multi-line images captured by the line scan camera;
  • Step 8 determine the imaging clarity: determine whether the imaging clarity of the image defect reaches the set threshold; if the clarity does not reach the set threshold, return to step 5, and the clarity reaches the set threshold and proceed to the next step;
  • Step 9 data analysis: use the computer system debugging software and algorithm defects to perform data analysis to complete the detection.
  • the number of cameras used in the method is only two, including the following steps:
  • Step 1 select the camera light source: according to the defect type to be detected by the system and/or the number of photos taken, select the first camera, the second camera and the first light source and the second light source suitable for it;
  • Step 2 install the imaging system: according to the defects to be imaged, the angles and positions of the light source, the first camera, and the second camera are initially determined structurally, and the positions of the devices are preliminarily fixed according to the requirements of the bright field and the dark field;
  • Step 3 set the encoder parameters: according to the speed of the system detection product, set the speed of the motion system, and obtain the cycle of the encoder accordingly;
  • Step 4 setting the stroboscopic control unit: according to the encoder cycle, the number of photos taken, and the camera parameters, the frequency multiplication and frequency division parameters of the stroboscopic control unit are set, and the parameters of the stroboscopic ladder lighting are initially set;
  • Step 5 adjust the optical parameters: for each defect to be tested, adjust the angles of the first light source and the second light source respectively.
  • N is a positive integer greater than 3; after debugging, fix the position of each component so that there is no relative displacement and angular rotation between them;
  • Step 6 debug the stroboscopic control unit: for each defect to be tested, debug the stroboscopic and step parameters respectively, correct the pulse width and working current value of the corresponding light source, and ensure that the gray value of the captured image falls within the acceptable setting. within the range;
  • Step 7 image dismantling: using a computer system to dismantle the multi-line images captured by the line scan camera;
  • Step 8 determine the imaging clarity: determine whether the imaging clarity of the image defect reaches the set threshold; if the clarity does not reach the set threshold, return to step 5, and the clarity reaches the set threshold and proceed to the next step;
  • Step 9 data analysis: use the computer system debugging software and algorithm defects to perform data analysis to complete the detection.
  • the stroboscopic control unit is used to record the signal of the encoder in real time, and obtain the rising edge and period;
  • the stroboscopic control unit is configured to perform frequency doubling and/or frequency division on the signal of the encoder according to the running speed, the number of pictures or defect types, and camera parameters;
  • the stroboscopic control unit is used for judging whether the enabling of the PLC controller is valid, returning to the previous step if it is invalid, and performing subsequent signal output if it is valid;
  • the stroboscopic control unit is used to control the driving circuit of the reflected bright-field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuit of the reflective dark field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuit of the transmitted bright field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuit of the transmission dark-field light source corresponding to each camera according to the frequency-doubling and/or frequency-dividing signal as the output line trigger signal to perform strobe lighting and photographing ;
  • the stroboscopic control unit is used to control the driving circuits of each camera and the corresponding light source according to the frequency multiplied and/or divided signal as the output line trigger signal to perform strobe lighting and photographing.
  • the defect detection system includes: an image extraction unit (101), a light and shade adjustment unit (102), a data processing unit (103) and a strobe control unit (104).
  • the image extraction unit (101) includes a plurality of cameras; the shading adjustment unit (102) further includes a plurality of light sources.
  • the data processing unit (103) further includes an encoder and a PLC controller; the stroboscopic control unit (104) further includes: a stroboscopic control circuit, a drive circuit, an input interface circuit and an output interface circuit.
  • the encoder generates a corresponding pulse code signal according to the rotational speed of the mechanical rotating system;
  • the PLC controller is a programmable controller, which generates an enabling signal after detecting the object to be measured and provides it to the stroboscopic control unit;
  • the stroboscopic control unit (104) It includes an input interface circuit, an output interface circuit, a stroboscopic control circuit, and a drive circuit for multiple light sources.
  • the various light sources in the light source are LED light sources, which can be line light sources, plane light sources, ring light sources, square light sources, strip light sources, dome light sources, plane shadowless light sources, coaxial light sources, ultraviolet light sources, infrared light sources, One or a combination of point light sources, etc.
  • the characteristics of the driving circuit are: the output is a constant current signal, which is used to drive the light source; it supports stroboscopic adjustment, that is, the pulse width and period of the output current under PWM control can be set, especially The pulse width can be different in each cycle; it supports step current adjustment, that is, in each PWM modulation pulse width, the output current value can be set to be different, and the output current value can be arbitrarily set between 0A and the maximum output current .
  • FIG. 2 it is a schematic structural diagram of the stroboscopic staircase lighting defect detection system according to the embodiment of the present application.
  • the components are: a first camera 201 , a second camera 202 , a first light source 203 , a second light source 204 , a measured object 205 , an encoder 206 , a PLC controller 207 , and a strobe control unit 104 .
  • each component in the system is as follows: the object to be measured is placed in the mechanical rotating system to move in a straight line at a uniform speed, with the movement direction as the X axis, the center point of the first light source and the second light source as the origin O, the object to be photographed
  • the center line of the bar-shaped area is the Y axis, and the upward origin is the Z axis; then the centers of the first camera, the second camera, and the first light source and the second light source in the light source are all on the XOZ plane.
  • the first camera is in the reflected bright field of the first light source, and the second camera is in the transmitted bright field of the first light source , meanwhile, the first camera is in the reflection dark field of the second light source, and the second camera is in the transmission dark field of the second light source.
  • FIG. 7 it is a flowchart of the working method of the strobe control unit according to the embodiment of the present application.
  • the working method of the stroboscopic control unit (104) is:
  • step 703 judge whether the PLC controller enable is valid, if invalid, return to step 702, and if valid, perform subsequent signal output;
  • step 709 The number of all photographed lines is output in a loop. If not completed, return to step 703. If completed, the defect detection of one product is completed.
  • FIG. 8 it is a flowchart of the method for detecting the defect of stroboscopic staircase lighting according to the embodiment of the present application.
  • the process of the machine vision appearance defect detection system controlled by dual cameras and strobe steps is as follows:
  • Select a camera and a light source according to the type of defects to be detected by the system or the number of photos taken, select a suitable first camera, a second camera, a first light source, a second light source, up to the Nth light source;
  • Set the strobe control unit according to the encoder cycle, the number of photos taken, the parameters of the camera, etc., set the frequency multiplication and frequency division parameters of the strobe control unit, and initially set the parameters of the strobe ladder lighting;
  • dismantle the multi-line image captured by the line scan camera (if there is a problem with dismantling the image, such as a wrong image or overlapping images, go back to step 4 to modify the parameters);
  • FIG. 3 it is a schematic structural diagram of a stroboscopic ladder lighting defect detection system according to an embodiment of the present application that adds three light sources to light sources N for supplementary light.
  • the components are: first camera 201, second camera 202, first light source 203, second light source 204, measured object 205, encoder 206, PLC controller 207, strobe control unit 104, third light source 209 , a fourth light source 210 , and an Nth light source 211 .
  • the first camera and the second camera are line scan cameras;
  • the light source includes at least a first light source and a second light source;
  • the encoder generates corresponding pulse coding signals according to the rotational speed of the mechanical rotating system;
  • the PLC controller is a programmable controller, which detects After reaching the measured object, an enabling signal is generated and provided to the stroboscopic control unit;
  • the stroboscopic control unit (104) includes an input interface circuit, an output interface circuit, a stroboscopic control circuit, and a drive circuit for a plurality of light sources.
  • the light source in addition to the first light source and the second light source, the light source may also include a third light source, or a third light source and a fourth light source, or the third light source to The Nth light source, where N is any natural number greater than "3"; the position of the third light source to the Nth light source can in principle be at any point in the XYZ three-dimensional coordinates, as long as it does not affect the first camera and the second camera.
  • the imaging circuit and the optical path of the first light source and the second light source; the functions of the third light source to the Nth light source are to cooperate with the first light source and the second light source to illuminate the measured object, so that the first camera and the second camera can shoot Various defects in the appearance of the product are found.
  • the third light source and the fourth light source are illuminated from the side, and the purpose is to fill in the side light when the first light source and the second light source are illuminated; the Nth light source is placed at the bottom of the detected object, and the bottom of the detected object is illuminated.
  • the function of adding the third light source, the fourth light source and the Nth light source is to make the responsible surface defects of the inspected product easier to present; the third light source, the fourth light source and the Nth light source can be illuminated as needed during operation Can also be unlit. The same is true for adding other light sources to the system.
  • the working method of the stroboscopic control unit (104) and the detection method of the stroboscopic step-controlled machine vision appearance defect detection system are the same as those of the previous embodiment.
  • FIG. 4 is a timing chart of stroboscopic illumination imaging in the prior art. Wherein, when the period of the line frequency signal is T, the first light source, the second light source, the first camera, and the second camera are used to detect and photograph the defects of the four tested products.
  • the first light source is turned on for T1, and the current value is I1 (the magnitude of the current value corresponds to the intensity of the LED light source light); in the photo D2C2 of the transmission dark field photo , the second light source is turned on time T2, the current I2; in the photo D1C2 of the transmission bright field, the first light source is turned on for the time T3, the current I1; in the photo D2C1 of the reflection dark field, the second light source is turned on for the time T4, the current I2; It can be seen from the above photos that only the pulse widths T1, T2, T3, and T4 can be changed in conventional stroboscopic lighting, while the first light source corresponds to the working current I1, and the second light source corresponds to the working current I2 is fixed.
  • FIG. 5 it is a time sequence diagram of stroboscopic staircase illumination imaging for the defect detection method according to the embodiment of the present application.
  • the period of the line frequency signal is T
  • the first light source, the second light source, the first camera, and the second camera are used to detect and photograph the defects of the four tested products.
  • the first light source is turned on for T1
  • the current value is I1 (the magnitude of the current value corresponds to the intensity of the LED light source light)
  • the second light source is turned on time T2, the current I2
  • the first light source is turned on for the time T3, the current I3
  • the second light source is turned on for the time T4, the current I4;
  • FIG. 6 it is a time sequence diagram of multi-light source coordinated stroboscopic staircase lighting imaging in the defect detection method according to the embodiment of the present application.
  • the first camera, the second camera, the first light source, the second light source, the third light source, the fourth light source, and the Nth light source are used, wherein the first light source and the second light source are the main light sources, and the other light sources are auxiliary light sources.
  • the D1C1 photo for reflection brightfield imaging of defect 1 because the pulse width T1 of the light source can be adjusted, and the current values I11, I12, I13, I14, ...
  • I1N corresponding to each light source can be set independently; the same Reason, in the D2C2 photo of the transmission dark field imaging of defect 2, because the pulse width T2 of the light source can be adjusted, and the current values I21, I22, I23, I24, ... I2N corresponding to each light source can be set separately. ; Similarly, in the D1C2 photo of the transmission brightfield imaging of defect three, because the pulse width T3 of the light source can be adjusted, and the current values I31, I32, I33, I34, ...
  • I3N corresponding to each light source can be individually In the same way, in the D2C1 photo of the reflection dark field imaging of defect four, because the pulse width T4 of the light source can be adjusted, and the current values I41, I42, I43, I44, ... I4N corresponding to each light source are all It can be set separately; and so on, in the same way, you can take the photo of the reflected bright field of defect five, the photo of the transmitted dark field of defect six, the photo of the transmitted bright field of defect seven, and the photo of the reflected dark field of defect eight.
  • the main feature of shooting is that the turn-on pulse width of the light source is different, and the turn-on current value of each light source can be set separately.

Abstract

一种用于产品的外观缺陷检测的频闪阶梯照明缺陷检测系统，系统包括图像提取单元(101)、明暗调节单元(102)、数据处理单元(103)和频闪控制单元(104)。图像提取单元(101)与频闪控制单元(104)相连，用于在各种透射/反射视觉明场/暗场中获取稳定清晰的图像；明暗调节单元(102)与频闪控制单元(104)相连，用于设置多种透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换。缺陷检测系统在采用多相机条件下，同时改变光源的开启脉宽宽度和工作电流值，以及采用多光源协同工作，达到对各种缺陷多方位的成像目的。

Description

频闪阶梯照明缺陷检测系统
相关申请的交叉引用
本申请要求2021年02月25日提交的中国专利申请第202110207353.9号的优先权，该申请的全部内容通过引用并入本文用于所有目的。
技术领域
本申请涉及机器视觉缺陷检测技术领域，特别涉及一种多相机和频闪阶梯照明的机器视觉外观缺陷检测系统及实现方法。
背景技术
机器视觉系统是通过图像摄取装置(分CMOS和CCD传感器两种)将被摄取的目标转换成图像信号，传送给专用的图像处理系统，图像系统对这些信号进行各种运算来抽取目标的特征。其基本组成通常包括像机、镜头、光源、图像采集卡、图像处理器、图像处理软件和算法。
目前，机器视觉系统已经深入应用于工业检测系统中，用于识别产品的信息、测量产品的尺寸、检测产品的缺陷等多种环节中。其中，由于用户对3C类消费电子产品的外观要求非常高，因此在产品的生产中，进行产品的外观缺陷检测显得尤为重要。
这些缺陷包括划伤、崩边、凹凸点、丝印区的芽、缺、锯齿边、透光、夹脏、毛丝/纤维、漏印、印错、IR孔及主孔瑕疵等，检测精度要求达到微米级别，人的肉眼很难达到这种高精度以及24小时高强度的工作要求。
在工业生产中，现有的产品外观缺陷检测的图像获取技术方式可分为三类。
一种是采用高精度的面阵摄像机和光源，通过合适的拍摄角度和光强，获取产品的反射或透射、明场或暗场的图片，然后对目标的信息进行处理。这种方案可以获取大部分产品特征并且得到广泛的应用，缺点是工业流水线中往往是运动的，需要在图像中消除运动的影响，而且受到现有面阵相机的分辨率限制，往往不能达到3C消费产品中微米级别缺陷的识别，或者此时对图像处理算法的要求极高，目前很难达到要求。
二是采用3D视觉技术。3D视觉技术包括双目视觉、结构光、TOF(飞行时间)、三角测距、激光雷达等，这些技术目前广泛应用于三维立体物理的识别、测量、定位中，但在缺陷检测中应用少，并且也很难达到3C类产品的微米级高精度的要求。
三是采用线阵相机和光源，获取目标物体的反射明场、反射暗场、透射明场、透射暗场的图像后提供给计算机系统进行处理。这种方案的优点是线阵相机分辨率高，可以达到微米级缺陷的识别，而且线阵相机和光源组合的方案，结合运动系统的编码器后特别适合工业流水线中的应用，因此目前的高精度缺陷检测系统一般都是采用这种方案。
但是，现有技术中，被检测物体经过线阵相机的检测系统获取的四种场景的图片(反射明场、反射暗场、透射明场、透射暗场)反映的缺陷往往有限，因为线阵相机拍照的速率是固定的，拍摄角度对应的光源的驱动电流是固定的，因此拍摄不同的缺陷往往需要改变对应的光源的开启的脉宽，而光源的开启脉宽最大为线阵相机的曝光时间，再宽的脉宽对线阵相机已无作用，因此这样极大的限制了拍照的数量，也限制了缺陷检测的种类。而且，因为单个光源对应的驱动电路的电流固定，在变化光照角度拍摄不同明场或暗场的照片时，往往此光源是不会在每种缺陷中都同时使用的，这样光源的使用率很低，同时拍摄的种类缺陷少。 这时，只能增加光源和相机的数量，以拍摄出所需的照片或者更多缺陷的种类，这样增加了系统的成本和复杂度。
发明内容
鉴于现有技术存在的不足，本申请公开了一种频闪阶梯照明缺陷检测系统。本申请缺陷检测系统在采用多相机条件下，通过对光源的频闪阶梯控制，即同时改变光源的开启脉宽宽度和工作电流值，以及采用多光源协同工作，达到对各种缺陷多方位的成像目的。并且，更进一步的，本申请采用双相机的优选实施例方案可以在一个流水线工位工作中，拍摄更多的物体明暗场的照片，提高光源的利用率，增加了可检测的缺陷的种类和数量，实现了现有技术中4-8个相机才能实现的图像采集效果。
为解决上述技术问题，本申请提供了一种频闪阶梯照明缺陷检测系统，所述系统用于产品的外观缺陷检测，包括：图像提取单元(101)、明暗调节单元(102)、数据处理单元(103)和频闪控制单元(104)。
所述图像提取单元(101)，与所述频闪控制单元(104)相连，用于在各种透射/反射视觉明场/暗场中获取稳定清晰的图像；
所述明暗调节单元(102)，与所述频闪控制单元(104)相连，用于设置多种透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换；
所述数据处理单元(103)，与所述频闪控制单元(104)相连，用于产生脉冲编码信号，检测被测产品后产生使能信号，将所述使能信号传送给所述频闪控制单元(104)；
所述频闪控制单元(104)，分别与所述图像提取单元(101)、明暗调节单元(102)和数据处理单元(103)相连，用于实时记录数据处理单元(103)传送的信号，对信号进行倍频和/或分频；使用倍频和/或分频后的信号控制所述图像提取单元(101)获取图像；使用倍频和/或分频后的信号控制所述明暗调节单元(102)设置透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换。
优选地，所述图像提取单元(101)进一步包括多个相机；所述明暗调节单元(102)进一步包括多个光源。
优选地，所述数据处理单元(103)，进一步包括编码器和PLC控制器；所述频闪控制单元(104)，进一步包括：频闪控制电路、驱动电路、输入接口电路和输出接口电路。
优选地，所述图像提取单元(101)进一步包括两部相机；所述相机为线阵相机；所述明暗调节单元(102)进一步包括多个光源。
优选地，所述相机为线阵相机；所述编码器根据机械转动系统的转速产生相应的脉冲编码信号；所述PLC控制器为可编程控制器，其检测到被测物体后产生使能信号提供给所述频闪控制单元(104)。
优选地，所述驱动电路，输出恒流信号，用于驱动所述明暗调节单元(102)；能够实现在PWM控制下设置输出电流的脉宽和周期；能够实现脉宽在每个周期中设置成任意不同数值；能够实现在每个PWM调制的脉宽输出电流设置成任意不同数值。
优选地，所述多个相机和所述多个光源中，第一相机位于第一光源的反射明场中，第二相机位于第一光源的透射明场中；同时，第一相机位于第二光源反射暗场中，第二相机位于第二光源的透射暗场中。
优选地，所述频闪控制单元(104)，进一步用于实时记录所述编码器的信号，获取上升沿和周期；
所述频闪控制单元(104)，进一步用于根据运行速度、拍照数量或缺陷种类、 相机参数，对所述编码器的信号进行倍频和/或分频；
所述频闪控制单元(104)，进一步用于判断所述PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机以及对应的光源的驱动电路，进行频闪阶梯打光和拍照。
为解决上述技术问题，本申请又提供了一种频闪阶梯照明缺陷检测方法，包括以下步骤：
步骤1，选择相机光源：根据系统要检测的缺陷种类和/或拍摄照片数量，选择与其适应的第一相机、第二相机和第一光源、第二光源；
步骤2，安装成像系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，对待测试的每种缺陷，分别调试第一相机、第二相机的角度和位置，需要增加成像数据时，添加补充第三相机，补充第四相机，直至补充第M相机，M为大于3的正整数；根据明场和暗场要求初步固定器件的位置；
步骤3，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
步骤4，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机参数设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
步骤5，调试光学参数：对待测试的每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，补光第四光源，直至补光第N光源，N为大于3的正整数；调试完成后固定各个部件的位置，使其之间不发生相对位移和角度转动；
步骤6，调试频闪控制单元：对待测试的每种缺陷，分别调试频闪和阶梯参数，修正相应的光源的脉宽和工作电流值，确保拍摄图像的灰度值落在设定能够接受的范围内；
步骤7，图像拆图：利用计算机系统对线阵相机拍摄的多行图像进行拆图；
步骤8，判断成像清晰度：判断图像缺陷成像清晰度是否到达设定阈值；清晰度未达到设定阈值则返回步骤5，清晰度达到设定阈值进行下一步；
步骤9，数据分析：利用计算机系统调试软件和算法缺陷进行数据分析完成检测。
为解决上述技术问题，本申请还提供了一种双相机频闪阶梯照明缺陷检测方法，所述方法中使用的相机数量仅为两部，包括以下步骤：
步骤1，选择相机光源：根据系统要检测的缺陷种类和/或拍摄照片数量，选择与其适应的第一相机、第二相机和第一光源、第二光源；
步骤2，安装成像系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，根据明场和暗场要求初步固定器件的位置；
步骤3，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
步骤4，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机参数设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
步骤5，调试光学参数：对待测试的每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，补光第四光源，直至补光第N光源，N为大于3的正整数；调试完成后固定各个部件的位置，使其之间不发生相对位移和角度转动；
步骤6，调试频闪控制单元：对待测试的每种缺陷，分别调试频闪和阶梯参数，修正相应的光源的脉宽和工作电流值，确保拍摄图像的灰度值落在设定能够接受的范围内；
步骤7，图像拆图：利用计算机系统对线阵相机拍摄的多行图像进行拆图；
步骤8，判断成像清晰度：判断图像缺陷成像清晰度是否到达设定阈值；清晰度未达到设定阈值则返回步骤5，清晰度达到设定阈值进行下一步；
步骤9，数据分析：利用计算机系统调试软件和算法缺陷进行数据分析完成检测。
优选地，所述频闪控制单元，用于实时记录所述编码器的信号，获取上升沿和周期；
优选地，所述频闪控制单元，用于根据运行速度、拍照数量或缺陷种类、相机参数，对所述编码器的信号进行倍频和/或分频；
优选地，所述频闪控制单元，用于判断所述PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机以及对应的光源的驱动电路，进行频闪阶梯打光和拍照。
本申请有益效果包括：
(1)采用线阵相机、编码器、PLC控制器的组合方案，能够保证检测消费类3C产品微米级缺陷，并且非常适合安装在生产的流水线中。
(2)采用多相机条件下，通过对光源的驱动电流的频闪和阶梯调节，可以充分利用每种光源的特点，实现多种打光效果，提高了对复杂的缺陷的拍摄能力。
(3)在一个流水线工位工作中，因为每个光源的不同周期中的脉宽和驱动电流值(对应亮度)可调，因此可以拍摄出更多明暗场的照片，增加了可检测的缺陷的种类和数量。
(4)采用专门的频闪控制单元实现对编码器、PLC控制器信号获取，以及对光源和相机的控制，可以实现系统的灵活调节和升级需求。
更进一步的技术效果，在本申请优选采用双相机的实施例方案中，可以在一个流水线工位工作中，拍摄更多的物体明暗场的照片，提高光源的利用率，增加了可检测的缺陷的种类和数量，实现了现有技术中4-8个相机才能实现的图像采集效果。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需使用的附图作简单的介绍，显而易见地，下面描述中的附图仅仅是一部分实施例或现有技术，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其它的类似或相关附图。
图1为本申请实施例所述频闪阶梯照明缺陷检测系统组成框图。
图2为本申请实施例所述频闪阶梯照明缺陷检测系统的结构示意图。
图3为本申请实施例所述添加第三光源至第N光源进行补光的频闪阶梯照明缺陷检测系统结构示意图。
图4为现有技术中进行频闪照明摄像的时序图。
图5为本申请实施例所述缺陷检测方法进行频闪阶梯照明摄像的时序图。
图6为本申请实施例所述缺陷检测方法中多光源协同频闪阶梯照明摄像的时序图。
图7为本申请实施例所述频闪控制单元工作方法的流程图。
图8为本申请实施例所述频闪阶梯照明缺陷检测方法的流程图。
具体实施方式
下面结合实施例详述本申请。为使本申请的目的、技术方案及优点更加清楚、明确，以下对本申请进一步详细说明，但本申请并不局限于这些实施例。
本申请多相机和频闪阶梯照明的外观缺陷检测系统，属于机器视觉领域，系统的组成包括第一相机，第二相机，光源，编码器，PLC控制器，频闪控制单元；所述的第一相机和第二相机为线阵相机；所述的光源至少包括第一光源和第二光源；所述的编码器根据机械转动系统的转速产生相应的脉冲编码信号；所说的PLC控制器为可编程控制器，由其检测到被测物体后产生使能信号提供给频闪控制单元；所述的频闪控制单元包括输入接口电路、输出接口电路、频闪控制电路，以及多个光源的驱动电路。本申请通过同时改变光源的开启脉宽宽度和工作电流值，采用多光源协同工作，达到对各种缺陷多方位打光成像目的，增加了可检测的缺陷的种类，提高了机器视觉外观缺陷检测系统的效率。
双相机和频闪阶梯照明的外观缺陷检测系统，包括第一相机，第二相机，光源，编码器，PLC控制器，频闪控制单元；所述的第一相机和第二相机为线阵相机；所述的光源至少包括第一光源和第二光源；所述的编码器根据机械转动系统的转速产生相应的脉冲编码信号；所说的PLC控制器为可编程控制器，由其检测到被测物体后产生使能信号提供给频闪控制单元；所述的频闪控制单元包括输入接口电路、输出接口电路、频闪控制电路，以及多个光源的驱动电路。
光源中的各种光源为LED光源，可以为线光源、平面光源、环形光源、方形光源、条形光源、圆顶光源、平面无影光源、同轴光源、紫外光源、红外光源、点光源等中的一种或者几种的组合。
双相机和频闪阶梯控制的机器视觉外观缺陷检测系统，其中的光源除了包括第一光源、第二光源以外，还可以包括第三光源，或者第四光源，或者第三光源至第N光源，这里的N为大于“3”的任何自然数；第三光源至第N光源的位置原则上可以在XYZ三维坐标中的任何点，只要其不影响到第一相机、第二相机的摄像线路和第一光源、第二光源的光路；第三光源至第N光源的作用是配合第一光源和第N光源对被测对象进行补光打光，以使第一相机和第二相机中拍摄出产品外观中的各种不同的缺陷。
频闪控制单元，其中驱动电路特点为：输出为恒流信号，用于驱动所述的光源；支持频闪调节，即在PWM控制下的输出电流的脉宽和周期可设置，特别是脉宽在每个周期中可以不同；支持阶梯电流调节，即在每个PWM调制的脉宽中，输出电流值可以设置成不一样，输出电流值可在0A到最大输出电流之间任意设置。
双相机和频闪阶梯控制的机器视觉外观缺陷检测系统，系统中各组件的位置关系为：被测物体放置于机械转动系统中做匀速直线运动，以运动方向作为X轴，第一光源和第二光源打光的中心点为原点O，所要拍摄的物体的条形区域中心线为Y轴，原点向上为Z轴；则第一相机，第二相机，光源中的第一光源和第二光源的中心都在XOZ平面中，其中第一光源与X轴成夹角a，第二光源与X轴成夹角b；第一相机在第一光源的反射明场中，第二相机在第二光源的透射明场中，同时，第一相机在第二光源的反射暗场中，第二相机在第二光源的透射暗场中。
双相机和频闪阶梯控制的机器视觉外观缺陷检测系统，所述的频闪控制单元的工作方法为：一是先实时记录编码器信号，获取上升沿和周期；二是对根据运行速度、拍照数量(缺陷种类)、相机参数等，对编码器信号进行倍频和分频；三是判断PLC控制器使能是否有效，无效则返回步骤二，有效则进行后继的信号输出；四是用倍分频后的信号作为输出的行触发信号，控制第一相机和第二相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；五是同理，用行触发信号，控制第一相机和第二相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；六是同理，用行触发信号，控制第二相机和第二相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；七是同理，用行触发信号，控制第二相机和第二相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；八是同理，用行触发信号，控制第一相机和/或第二相机，以及对应的光源的驱动电路，进行频闪阶梯打光和拍照；直至所有打光完成；九是循环输出所有拍摄的行数，未完成则返回步骤3，完成了则一个产品的缺陷检测完成。
双相机和频闪阶梯控制的机器视觉外观缺陷检测系统，其检测方法的流程为：一是，选择相机和光源：根据系统要检测的缺陷种类或者拍摄照片的数量，选择合适的第一相机、第二相机和第一光源、第二光源，直至第N光源；二是，安装系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，根据明场和暗场要求初步固定器件的位置；三是，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；四是，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机的参数等，设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；五是调试光学参数：对每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，以至到补光第N光源，调试完成后固定器件位置；六是调试频闪控制单元：对每种缺陷，分别调试频闪和阶梯参数，即修正相应的光源的脉宽和工作电流值，使拍摄图像的灰度值在可接受的范围内；七是在计算机中，对线阵相机拍摄的多行图像进行拆图(如果拆图有问题，例如出现错图或叠图情况，返回第4步修改参数)；八是，判断缺陷成像清晰与否，不清晰则返回第五步，清晰 则往下运行；九是，在计算机中，调试软件和算法缺陷进行分析。
本申请实施例频闪阶梯照明缺陷检测系统，所述系统用于产品的外观缺陷检测，包括：图像提取单元(101)、明暗调节单元(102)、数据处理单元(103)和频闪控制单元(104)。
所述图像提取单元(101)，与所述频闪控制单元(104)相连，用于在各种透射/反射视觉明场/暗场中获取稳定清晰的图像；
所述明暗调节单元(102)，与所述频闪控制单元(104)相连，用于设置多种透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换；
所述数据处理单元(103)，与所述频闪控制单元(104)相连，用于产生脉冲编码信号，检测被测产品后产生使能信号，将所述使能信号传送给所述频闪控制单元(104)；
所述频闪控制单元(104)，分别与所述图像提取单元(101)、明暗调节单元(102)和数据处理单元(103)相连，用于实时记录数据处理单元(103)传送的信号，对信号进行倍频和/或分频；使用倍频和/或分频后的信号控制所述图像提取单元(101)获取图像；使用倍频和/或分频后的信号控制所述明暗调节单元(102)设置透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换。
优选地，所述图像提取单元(101)进一步包括多个相机；所述明暗调节单元(102)进一步包括多个光源。
优选地，所述数据处理单元(103)，进一步包括编码器和PLC控制器；所述频闪控制单元(104)，进一步包括：频闪控制电路、驱动电路、输入接口电路和输出接口电路。
优选地，所述图像提取单元(101)进一步包括两部相机；所述相机为线阵相机；所述明暗调节单元(102)进一步包括多个光源。
优选地，所述相机为线阵相机；所述编码器根据机械转动系统的转速产生相应的脉冲编码信号；所述PLC控制器为可编程控制器，其检测到被测物体后产生使能信号提供给所述频闪控制单元(104)。
优选地，所述驱动电路，输出恒流信号，用于驱动所述明暗调节单元(102)；能够实现在PWM控制下设置输出电流的脉宽和周期；能够实现脉宽在每个周期中设置成任意不同数值；能够实现在每个PWM调制的脉宽输出电流设置成任意不同数值。
优选地，所述多个相机和所述多个光源中，第一相机位于第一光源的反射明场中，第二相机位于第一光源的透射明场中；同时，第一相机位于第二光源反射暗场中，第二相机位于第二光源的透射暗场中。
优选地，所述频闪控制单元(104)，进一步用于实时记录所述编码器的信号，获取上升沿和周期；
所述频闪控制单元(104)，进一步用于根据运行速度、拍照数量或缺陷种类、相机参数，对所述编码器的信号进行倍频和/或分频；
所述频闪控制单元(104)，进一步用于判断所述PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机以及对应的光源的驱动电路，进行频闪阶梯打光和拍照。
本申请实施例频闪阶梯照明缺陷检测方法，包括以下步骤：
步骤1，选择相机光源：根据系统要检测的缺陷种类和/或拍摄照片数量，选择与其适应的第一相机、第二相机和第一光源、第二光源；
步骤2，安装成像系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，对待测试的每种缺陷，分别调试第一相机、第二相机的角度和位置，需要增加成像数据时，添加补充第三相机，补充第四相机，直至补充第M相机，M为大于3的正整数；根据明场和暗场要求初步固定器件的位置；
步骤3，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
步骤4，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机参数设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
步骤5，调试光学参数：对待测试的每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，补光第四光源，直至补光第N光源，N为大于3的正整数；调试完成后固定各个部件的位置，使其之间不发生相对位移和角度转动；
步骤6，调试频闪控制单元：对待测试的每种缺陷，分别调试频闪和阶梯参数，修正相应的光源的脉宽和工作电流值，确保拍摄图像的灰度值落在设定能够接受的范围内；
步骤7，图像拆图：利用计算机系统对线阵相机拍摄的多行图像进行拆图；
步骤8，判断成像清晰度：判断图像缺陷成像清晰度是否到达设定阈值；清晰度未达到设定阈值则返回步骤5，清晰度达到设定阈值进行下一步；
步骤9，数据分析：利用计算机系统调试软件和算法缺陷进行数据分析完成检测。
本申请实施例双相机频闪阶梯照明缺陷检测方法，所述方法中使用的相机数量仅为两部，包括以下步骤：
步骤1，选择相机光源：根据系统要检测的缺陷种类和/或拍摄照片数量，选择与其适应的第一相机、第二相机和第一光源、第二光源；
步骤2，安装成像系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，根据明场和暗场要求初步固定器件的位置；
步骤3，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
步骤4，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机参数设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
步骤5，调试光学参数：对待测试的每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，补光第四光源，直至补光第N光源， N为大于3的正整数；调试完成后固定各个部件的位置，使其之间不发生相对位移和角度转动；
步骤6，调试频闪控制单元：对待测试的每种缺陷，分别调试频闪和阶梯参数，修正相应的光源的脉宽和工作电流值，确保拍摄图像的灰度值落在设定能够接受的范围内；
步骤7，图像拆图：利用计算机系统对线阵相机拍摄的多行图像进行拆图；
步骤8，判断成像清晰度：判断图像缺陷成像清晰度是否到达设定阈值；清晰度未达到设定阈值则返回步骤5，清晰度达到设定阈值进行下一步；
步骤9，数据分析：利用计算机系统调试软件和算法缺陷进行数据分析完成检测。
优选地，所述频闪控制单元，用于实时记录所述编码器的信号，获取上升沿和周期；
优选地，所述频闪控制单元，用于根据运行速度、拍照数量或缺陷种类、相机参数，对所述编码器的信号进行倍频和/或分频；
优选地，所述频闪控制单元，用于判断所述PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
优选地，所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机以及对应的光源的驱动电路，进行频闪阶梯打光和拍照。
实施例1：
如图1所述，为本申请实施例所述频闪阶梯照明缺陷检测系统组成框图。其中，缺陷检测系统包括：图像提取单元(101)、明暗调节单元(102)、数据处理单元(103)和频闪控制单元(104)。所述图像提取单元(101)多个相机；所述明暗调节单元(102)进一步包括多个光源。所述数据处理单元(103)，进一步包括编码器和PLC控制器；所述频闪控制单元(104)，进一步包括：频闪控制电路、驱动电路、输入接口电路和输出接口电路。编码器根据机械转动系统的转速产生相应的脉冲编码信号；PLC控制器为可编程控制器，由其检测到被测物体后产生使能信号提供给频闪控制单元；频闪控制单元(104)包括输入接口电路、输出接口电路、频闪控制电路，以及多个光源的驱动电路。
所述的光源中的各种光源为LED光源，可以为线光源、平面光源、环形光源、方形光源、条形光源、圆顶光源、平面无影光源、同轴光源、紫外光源、红外光源、点光源等中的一种或者几种的组合。
所述的频闪控制单元，其中驱动电路特点为：输出为恒流信号，用于驱动所述的光源；支持频闪调节，即在PWM控制下的输出电流的脉宽和周期可设置，特 别是脉宽在每个周期中可以不同；支持阶梯电流调节，即在每个PWM调制的脉宽中，输出电流值可以设置成不一样，输出电流值可在0A到最大输出电流之间任意设置。
如图2所示，为本申请实施例所述频闪阶梯照明缺陷检测系统的结构示意图。其中，各个组件分别为：第一相机201、第二相机202、第一光源203、第二光源204、被测物体205、编码器206、PLC控制器207、频闪控制单元104。
系统中各组件的位置关系为：被测物体放置于机械转动系统中做匀速直线运动，以运动方向作为X轴，第一光源和第二光源打光的中心点为原点O，所要拍摄的物体的条形区域中心线为Y轴，原点向上为Z轴；则所述的第一相机，所述的第二相机，所述的光源中的第一光源和第二光源的中心都在XOZ平面中，其中第一光源与X轴成夹角a，第二光源与X轴成夹角b；第一相机在第一光源的反射明场中，第二相机在第一光源的透射明场中，同时，第一相机在第二光源的反射暗场中，第二相机在第二光源的透射暗场中。
如图7所示，为本申请实施例所述频闪控制单元工作方法的流程图。其中，所述的频闪控制单元(104)的工作方法为：
701.先实时记录编码器信号，获取上升沿和周期；
702.对根据运行速度、拍照数量(缺陷种类)、相机参数等，对编码器信号进行倍频和分频；
703判断PLC控制器使能是否有效，无效则返回步骤702，有效则进行后继的信号输出；
704.用倍分频后的信号作为输出的行触发信号，控制第一相机和第一相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
705.同理，用行触发信号，控制第一相机和第一相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
706.同理，用行触发信号，控制第二相机和第二相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
707.同理，用行触发信号，控制第二相机和第二相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
708同理，用行触发信号，控制第一相机和/或第二相机，以及对应的光源的驱动电路，进行频闪阶梯打光和拍照；直至所有打光完成；
709.循环输出所有拍摄的行数，未完成则返回步骤703，完成了则一个产品的缺陷检测完成。
如图8所示，为本申请实施例所述频闪阶梯照明缺陷检测方法的流程图。所述双相机和频闪阶梯控制的机器视觉外观缺陷检测系统，其检测方法的流程为：
801.选择相机和光源：根据系统要检测的缺陷种类或者拍摄照片的数量，选择合适的第一相机、第二相机和第一光源、第二光源，直至第N光源；
802.安装系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，根据明场和暗场要求初步固定器件的位置；
803.设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
804.设置频闪控制单元：根据编码器周期，拍摄照片数量，相机的参数等，设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
805.调试光学参数：对每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，以至到补光第N光源，调试完成后固定器件位置；
806.调试频闪控制单元：对每种缺陷，分别调试频闪和阶梯参数，即修正相应 的光源的脉宽和工作电流值，使拍摄图像的灰度值在可接受的范围内；
807.在计算机中，对线阵相机拍摄的多行图像进行拆图(如果拆图有问题，例如出现错图或叠图情况，返回第4步修改参数)；
808.判断缺陷成像清晰与否，不清晰则返回第五步，清晰则往下运行；
809在计算机中，调试软件和算法缺陷进行分析。
实施例2：
如图3所示，为本申请实施例所述添加光源三至光源N进行补光的频闪阶梯照明缺陷检测系统结构示意图。其中，各个组件分别为：第一相机201、第二相机202、第一光源203、第二光源204、被测物体205、编码器206、PLC控制器207、频闪控制单元104、第三光源209、第四光源210、第N光源211。
第一相机和第二相机为线阵相机；光源至少包括第一光源和第二光源；编码器根据机械转动系统的转速产生相应的脉冲编码信号；PLC控制器为可编程控制器，由其检测到被测物体后产生使能信号提供给频闪控制单元；频闪控制单元(104)包括输入接口电路、输出接口电路、频闪控制电路，以及多个光源的驱动电路。
本实施例频闪阶梯控制的机器视觉外观缺陷检测系统，其中的光源除了包括第一光源、第二光源以外，还可以包括第三光源，或者第三光源和第四光源，或者第三光源至第N光源，这里的N为大于“3”的任何自然数；第三光源至第N光源的位置原则上可以在XYZ三维坐标中的任何点，只要其不影响到第一相机、第二相机的摄像线路和第一光源、第二光源的光路；第三光源至第N光源的作用是配合第一光源和第二光源对被测对象进行打光，以使第一相机和第二相机中拍摄出产品外观中的各种不同的缺陷。
第三光源和第四光源为从侧面打光，目的是为第一光源和第二光源打光时进行侧面补光；第N光源放置在被检测物体的底部，给被检测的物体底部进行打光，添加第三光源、第四光源以至第N光源的作用是为了使被检测的产品的负责表面缺陷更容易呈现；第三光源、第四光源和第N光源在工作时根据需要可以打光也可以不打光。同理在系统中添加其它光源的方法也类似。
频闪控制单元(104)的工作方法和频闪阶梯控制的机器视觉外观缺陷检测系统的检测方法同前一实施例。
实施例3：
如图4所示，图4为现有技术中进行频闪照明摄像的时序图。其中，行频信号周期为T时，采用第一光源、第二光源、第一相机、第二相机进行四种被测产品缺陷检测拍照。可以看出，在反射明场的拍照的照片D1C1中，第一光源开启时间为T1，电流值为I1(电流值的大小对应LED光源光的强度)；在透射暗场的拍照的照片D2C2中，第二光源开启时间T2，电流I2；在透射明场的拍照的照片D1C2中，第一光源开启时间T3，电流I1；在反射暗场的拍照照片D2C1中，第二光源开启时间T4，电流I2；从以上拍照可以看出，常规频闪照明中只能改变脉宽T1、T2、T3、T4，而第一光源对应工作电流I1，第二光源对应工作电流I2是固定的。
如图5所示，为本申请实施例所述缺陷检测方法进行频闪阶梯照明摄像的时序图。其中，行频信号周期为T时，采用第一光源、第二光源、第一相机、第二相机进行四种被测产品缺陷检测拍照。可以看出，在反射明场的拍照的照片D1C1中，第一光源开启时间为T1，电流值为I1(电流值的大小对应LED光源光的强度)；在透射暗场的拍照的照片D2C2中，第二光源开启时间T2，电流I2；在透射明场的拍照的照片D1C2中，第一光源开启时间T3，电流I3；在反射暗场的拍照照片D2C1中，第二光源开启时间T4，电流I4；从以上拍照可以看出，本系统的频闪 阶梯照明中，不但能改变脉宽T1、T2、T3、T4，而且第一光源对应工作电流I1、I3，第二光源对应工作电流I2、I4，即在每个周期T中，在不同的脉宽下电流值是可以阶梯变化的，这样极大提高了对缺陷拍摄的能力。
实施例4：
如图6所示，为本申请实施例所述缺陷检测方法中多光源协同频闪阶梯照明摄像的时序图。其中，采用了第一相机、第二相机，第一光源、第二光源、第三光源、第四光源直至第N光源，其中第一光源和第二光源为主光源，其它光源为辅助光源。在进行缺陷一的反射明场成像的D1C1照片中，因为光源的脉宽T1可调节，并且每个光源对应的电流值I11、I12、I13、I14、……I1N都是可以单独设置的；同理，在进行缺陷二的透射暗场成像的D2C2照片中，因为光源的脉宽T2可调节，并且每个光源对应的电流值I21、I22、I23、I24、……I2N都是可以单独设置的；同理，在进行缺陷三的透射明场成像的D1C2照片中，因为光源的脉宽T3可调节，并且每个光源对应的电流值I31、I32、I33、I34、……I3N都是可以单独设置的；同理，在进行缺陷四的反射暗场成像的D2C1照片中，因为光源的脉宽T4可调节，并且每个光源对应的电流值I41、I42、I43、I44、……I4N都是可以单独设置的；以此类推，同理可以拍摄缺陷五的反射明场的照片、缺陷六的透射暗场的照片、缺陷七的透射明场的照片、缺陷八的反射暗场的照片，这些拍摄的主要特点是，光源的开启脉宽不一样，同时每个光源的开启电流值可以单独设置。
这样达到了所有光源协同工作的要求，极大提高了对缺陷照明检测的能力；采用相同的硬件条件下，可以拍摄出更多缺陷的照片，提高了整个检测系统的效率。
以上所述，仅是本申请的几个实施例，并非对本申请做任何形式的限制，虽然本申请以较佳实施例揭示如上，然而并非用以限制本申请，任何熟悉本专业的技术人员，在不脱离本申请技术方案的范围内，利用上述揭示的技术内容做出些许的变动或修饰均等同于等效实施案例，均属于本申请技术方案保护范围内。

Claims (12)

  1. 一种频闪阶梯照明缺陷检测系统，所述系统用于产品的外观缺陷检测，包括：图像提取单元(101)、明暗调节单元(102)、数据处理单元(103)和频闪控制单元(104)，其中，
    所述图像提取单元(101)，与所述频闪控制单元(104)相连，用于在各种透射/反射视觉明场/暗场中获取稳定清晰的图像；
    所述明暗调节单元(102)，与所述频闪控制单元(104)相连，用于设置多种透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换；
    所述数据处理单元(103)，与所述频闪控制单元(104)相连，用于产生脉冲编码信号，检测被测产品后产生使能信号，将所述使能信号传送给所述频闪控制单元(104)；
    所述频闪控制单元(104)，分别与所述图像提取单元(101)、明暗调节单元(102)和数据处理单元(103)相连，用于实时记录数据处理单元(103)传送的信号，对信号进行倍频和/或分频；使用倍频和/或分频后的信号控制所述图像提取单元(101)获取图像；使用倍频和/或分频后的信号控制所述明暗调节单元(102)设置透射/反射视觉明场/暗场，并在各种透射/反射视觉明场/暗场中转换；
    所述图像提取单元(101)进一步包括多个相机；所述明暗调节单元(102)进一步包括多个光源；
    所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元(104)，进一步用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照。
  2. 据权利要求1所述频闪阶梯照明缺陷检测系统，其中，
    所述数据处理单元(103)，进一步包括编码器和PLC控制器；所述频闪控制单元(104)，进一步包括：频闪控制电路、驱动电路、输入接口电路和输出接口电路；
    所述编码器根据机械转动系统的转速产生相应的脉冲编码信号；所述PLC控制器为可编程控制器，其检测到被测物体后产生使能信号提供给所述频闪控制单元(104)；
    所述驱动电路，能够实现在PWM控制下设置输出电流的脉宽和周期；能够实现脉宽在每个周期中设置成不同数值；能够实现在每个PWM调制的脉宽输出电流设置成不同数值；
    每个光源的不同周期中的脉宽和驱动电流值可调。
  3. 根据权利要求1所述频闪阶梯照明缺陷检测系统，其中，所述图像提取单元(101)进一步包括两部相机；所述相机为线阵相机。
  4. 根据权利要求1所述频闪阶梯照明缺陷检测系统，其中，所述驱动电路，输出恒流信号，用于驱动所述明暗调节单元(102)。
  5. 根据权利要求1所述频闪阶梯照明缺陷检测系统，其中，所述多个相机和所述多个光源中，第一相机位于第一光源的反射明场中，第二相机位于第一光源的透射明场中；同时，第一相机位于第二光源反射暗场中，第二相机位于第二光源的透射暗场中。
  6. 根据权利要求2所述频闪阶梯照明缺陷检测系统，其中，
    所述频闪控制单元(104)，进一步用于实时记录所述编码器的信号，获取上升沿和周期；
    所述频闪控制单元(104)，进一步用于根据运行速度、拍照数量或缺陷种类、相机参数，对所述编码器的信号进行倍频和/或分频；
    所述频闪控制单元(104)，进一步用于判断所述PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出。
  7. 一种频闪阶梯照明缺陷检测方法，其中，包括以下步骤：
    步骤1，选择相机光源：根据系统要检测的缺陷种类和/或拍摄照片数量，选择与其适应的第一相机、第二相机和第一光源、第二光源；
    步骤2，安装成像系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，对待测试的每种缺陷，分别调试第一相机、第二相机的角度和位置，需要增加成像数据时，添加补充第三相机，补充第四相机，直至补充第M相机，M为大于3的正整数；根据明场和暗场要求初步固定器件的位置；
    步骤3，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
    步骤4，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机参数设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
    所述频闪控制单元，用于实时记录所述编码器的信号，获取上升沿和周期；
    所述频闪控制单元，用于根据运行速度、拍照数量或缺陷种类、相机参数，对所述编码器的信号进行倍频和/或分频；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
    步骤5，调试光学参数：对待测试的每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，补光第四光源，直至补光第N光源，N为大于3的正整数；调试完成后固定各个部件的位置，使其之间不发生相对位移和角度转动；
    步骤6，调试频闪控制单元：对待测试的每种缺陷，分别调试频闪和阶梯参数，修正相应的光源的脉宽和工作电流值，确保拍摄图像的灰度值落在设定能够接受的范围内；
    步骤7，图像拆图：利用计算机系统对线阵相机拍摄的多行图像进行拆图；
    步骤8，判断成像清晰度：判断图像缺陷成像清晰度是否到达设定阈值；清晰度未达到设定阈值则返回步骤5，清晰度达到设定阈值进行下一步；
    步骤9，数据分析：利用计算机系统调试软件和算法缺陷进行数据分析完成检 测。
  8. 根据权利要求7所述检测方法，其中，
    所述频闪控制单元，用于判断PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出。
  9. 根据权利要求7所述检测方法，其中，
    所述驱动电路，能够实现在PWM控制下设置输出电流的脉宽和周期；能够实现脉宽在每个周期中设置成不同数值；能够实现在每个PWM调制的脉宽输出电流设置成不同数值；
    每个光源的不同周期中的脉宽和驱动电流值可调。
  10. 一种双相机频闪阶梯照明缺陷检测方法，其中，所述方法中使用的相机数量仅为两部，包括以下步骤：
    步骤1，选择相机光源：根据系统要检测的缺陷种类和/或拍摄照片数量，选择与其适应的第一相机、第二相机和第一光源、第二光源；
    步骤2，安装成像系统：根据所要成像的缺陷，初步在结构上确定光源、第一相机、第二相机的角度和位置，根据明场和暗场要求初步固定器件的位置；
    步骤3，设置编码器参数：根据系统检测产品的速度，设置运动系统的速率，相应地获得编码器的周期；
    步骤4，设置频闪控制单元：根据编码器周期，拍摄照片数量，相机参数设置频闪控制单元的倍频和分频参数，初步设置频闪阶梯照明的参数；
    所述频闪控制单元，用于实时记录所述编码器的信号，获取上升沿和周期；
    所述频闪控制单元，用于根据运行速度、拍照数量或缺陷种类、相机参数，对所述编码器的信号进行倍频和/或分频；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射明场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的反射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射明场光源的驱动电路，进行频闪阶梯打光和拍照；
    所述频闪控制单元，用于根据倍频和/或分频的信号作为输出的行触发信号，控制各个相机对应的透射暗场光源的驱动电路，进行频闪阶梯打光和拍照；
    步骤5，调试光学参数：对待测试的每种缺陷，分别调试第一光源、第二光源的角度，需要补光时，添加补光第三光源，补光第四光源，直至补光第N光源，N为大于3的正整数；调试完成后固定各个部件的位置，使其之间不发生相对位移和角度转动；
    步骤6，调试频闪控制单元：对待测试的每种缺陷，分别调试频闪和阶梯参数，修正相应的光源的脉宽和工作电流值，确保拍摄图像的灰度值落在设定能够接受的范围内；
    步骤7，图像拆图：利用计算机系统对线阵相机拍摄的多行图像进行拆图；
    步骤8，判断成像清晰度：判断图像缺陷成像清晰度是否到达设定阈值；清晰度未达到设定阈值则返回步骤5，清晰度达到设定阈值进行下一步；
    步骤9，数据分析：利用计算机系统调试软件和算法缺陷进行数据分析完成检测。
  11. 根据权利要求10所述检测方法，其中，
    所述频闪控制单元，用于判断PLC控制器使能是否有效，无效返回前一步，有效则进行后继的信号输出。
  12. 根据权利要求10所述检测方法，其中，
    所述驱动电路，能够实现在PWM控制下设置输出电流的脉宽和周期；能够实现脉宽在每个周期中设置成不同数值；能够实现在每个PWM调制的脉宽输出电流设置成不同数值；
    每个光源的不同周期中的脉宽和驱动电流值可调。
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