CN112326668B - Same-frequency LED illumination light source construction method for product surface two-dimensional defect detection - Google Patents
Same-frequency LED illumination light source construction method for product surface two-dimensional defect detection Download PDFInfo
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- G—PHYSICS
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- 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
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Abstract
The invention discloses a method for constructing an identical-frequency LED illumination light source for detecting two-dimensional defects on the surface of a product, which selects the identical-frequency LED illumination light source to illuminate according to the attribute characteristics of the two-dimensional defects on the surface of the product, is convenient for detecting the two-dimensional defects including different colors, stains and breakage, can instantly lighten LED lamp beads, can lighten single-point LED illumination light sources, can lighten the LED lamp beads at corresponding positions in a mapping control mode according to the working characteristics, can lighten the LED lamp beads instantly, can obviously improve the brightness, has short practical power consumption and small heating value due to short electrifying time, does not need an active heat dissipation part, has small integral volume, is convenient for the field installation of the surface detection of the product, and is synchronously and sequentially lightened with pixels of a CCD sensor, thereby prolonging the service life, having good illumination effect and high heat dissipation efficiency, greatly improving the accuracy of the detection and sampling of the two-dimensional defects on the surface of the product, and having good application prospect.
Description
Technical Field
The invention relates to the technical field of product surface detection, in particular to a method for constructing a same-frequency LED illumination light source for product surface two-dimensional defect detection.
Background
The CCD sensor is made of a semiconductor material with high sensitivity, can convert light into electric charge, and can be converted into digital signals through an analog-to-digital converter for processing by a computer. At present, CCD sensors are widely used for detecting surface flaws of industrial products. In particular to the detection of various defects on the surface of a product.
In the detection process of the defects (with high accuracy requirement) on the surface of the product, the sampling environment is very important, and reliable and high-accuracy data must be provided for the subsequent image processing process so as to obtain accurate defect detection results.
In the prior art, aiming at the detection of defects presented in a two-dimensional space, such as different colors, stains, damages and the like on the surface of a product, the sampling environment is very important, because a transmission light source (a CCD sensor and an illumination light source are arranged on two sides of the surface of the product) is required to detect the damages (holes) in the two-dimensional defects; a diffuse light source (a CCD sensor and an illumination light source are arranged on the same side of the product surface) is required to detect the surface heterochromatic stain in the two-dimensional defects. Because of the different mounting locations of the two types of illumination sources, and because of the limited mounting environments in an industrial environment, the requirements for the size of the illumination sources for two-dimensional defect detection are relatively high.
Currently, in the scanning and sampling process of the CCD sensor, the brightness and stability of the illumination light source directly influence the dynamic range and accuracy of the scanning and sampling of the CCD sensor, and the illumination light source has high brightness and good stability, so that more accurate sampling data can be obtained, the dynamic range is wider, and more sample types are adapted. At present, most of illumination light sources are LED illumination light sources, and illumination brightness is improved and is limited by the heat dissipation capacity of the LED illumination light sources to a great extent. For product surface inspection equipment in operation, the installation space of the illumination source is limited, and in practice it is often difficult to apply an excessively large and heavy LED illumination source. Moreover, the shaking generated during the operation of the device can affect the illumination stability, thereby affecting the dynamic range and the accuracy of the scanning sampling of the CCD sensor.
Therefore, how to construct a same-frequency LED illumination light source construction method for detecting two-dimensional defects on the surface of a product according to the working characteristics of scanning and sampling of a CCD sensor and the characteristics of defects on the surface of the product can reduce the volume of the product, ensure good working of the product, and improve the accuracy of scanning and sampling of the CCD sensor, so that the method is a problem to be solved currently.
Disclosure of Invention
The invention aims to solve the problems of insufficient lighting point of an illumination light source and poor heat dissipation in the scanning and sampling process of a CCD sensor aiming at the existing detection of the defects on the surface of a product. According to the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product, the same-frequency LED illumination light source is selected for illumination according to the attribute characteristics of the two-dimensional defects on the surface of the product, so that the two-dimensional defects comprise different colors, stains and broken projection imaging detection, the LED illumination light source can instantly illuminate LED lamp beads, overload can be achieved, brightness is remarkably improved, the LED illumination light source and pixels of a CCD sensor are synchronously and sequentially illuminated, the illumination requirement is met, meanwhile, energy consumption is greatly saved, the service life is prolonged, the illumination effect is good, the heat dissipation efficiency is high, the accuracy of detecting and sampling the two-dimensional defects on the surface of the product is greatly improved, more accurate sampling data are obtained, the dynamic range is wider, and the method is suitable for more sample types and has good application prospects.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product comprises the following steps,
step (A), acquiring a time sequence of sequential exposure of pixel points of a CCD sensor for detecting defects on the surface of a product along the working direction in the working state;
according to the number of the pixel points of the CCD sensor, an LED illumination light source which is matched with the CCD sensor and can be lighted at a single point is used, a corresponding mapping relation is established according to the pixel points of the CCD sensor and the LED lamp beads in the LED illumination light source according to the positions and the arrangement sequence, the LED lamp beads are divided into a plurality of subareas in the LED illumination light source, LED lamp bead units are formed, and the LED lamp beads in each LED lamp bead unit can be lighted or extinguished at the same time;
step (C), according to the working frequency of the pixel points of the CCD sensor in sequence exposure along the working direction, controlling the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source to be simultaneously turned on or turned off so as to enable the two lamp beads to synchronously work at the same frequency;
and (D) when the CCD sensor scans, sampling pixel points of the CCD sensor and lighting LED lamp beads in the LED lighting source keep working at the same frequency.
The method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product comprises the following steps of (A) obtaining the sequential exposure time sequence of pixel points of a CCD sensor for detecting the defects on the surface of the product along the working direction in the working state,
(A1) Connecting an electric signal testing instrument with a CCD sensor to establish a testing environment;
(A2) The CCD sensor is provided with a needed clock signal and power supply for working, so that the CCD sensor can work normally;
(A3) Sequentially carrying out instantaneous single-point illumination on each pixel point in a CCD sensor which normally scans, recording output signals of the pixel points of the CCD sensor through an electric signal testing instrument, and finishing recording of the output signals of each pixel point in the CCD sensor;
(A4) And obtaining the sequential exposure time sequence of the pixels of the CCD sensor along the working direction through the data statistics of the signal change period output by each pixel.
According to the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product, the step (B) is to use the LED illumination light sources which are matched with the CCD sensor pixel points and can be lighted at a single point according to the quantity of the CCD sensor pixel points, and establish a corresponding mapping relation according to the positions and the arrangement sequence of the LED lamp beads in the LED illumination light sources, and divide the LED lamp beads into a plurality of subareas in the LED illumination light sources to form an LED lamp bead unit, wherein the method comprises the following specific steps of: the CCD sensor pixel points are integral multiples of the number of LED lamp bead units in the LED illumination light source.
According to the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product, the step (C) is used for controlling the LED lamp bead units at corresponding positions in the LED illumination light source to be on or off according to the sequential exposure time sequence of the pixel points of the CCD sensor along the working direction so as to enable the LED lamp bead units to work synchronously at the same frequency, wherein the LED lamp bead units are internally provided with two LED lamp beads, and the specific implementation process is as follows:
(C1) When a current pixel point of the CCD sensor pixel point works, after the LED lamp bead T1 positioned at the front side in the LED lamp unit corresponding to the pixel point is lightened for a time, the LED lamp bead T2 positioned at the rear side in the LED lamp unit is lightened, and the LED lamp bead positioned at the front side in the LED lamp unit is extinguished;
(C2) The LED lamp beads positioned at the rear side in the LED lamp unit are turned off after being continuously turned on for T1 +T2;
(C3) And (3) sequentially exposing the CCD sensor pixel points along the working direction, repeating the steps (C1) - (C2), and completing the lighting or extinguishing of the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source, so that the CCD sensor pixel points and the LED lamp bead units at the corresponding positions in the LED illumination light source synchronously work at the same frequency.
According to the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product, f is the working frequency of a single pixel of the CCD sensor, the width of each pixel is i, the amplification factor of a scanning optical system is 1/X, the corresponding width of each pixel on an object image is i.X, the amplification factor of a light source lens is 1/Y, the width of a single LED lamp bead plus the distance between two LED lamp beads is S, the object image range S=s.Y of the single LED lamp bead to be illuminated is illuminated on the CCD sensor, the S/i.X pixels are illuminated, the time T1=S.f/i.X of each LED lamp bead to be illuminated is at least 1/f and is less than 2/f, and X, Y is the characteristic parameter of the lens.
According to the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product, the LED lamp beads in the LED lamp bead unit are turned on instantaneously and are overloaded.
The method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product comprises the following steps of: the LEDs are divided into odd-even fields, anodes of odd-numbered LEDs are controlled by an a power supply, the a power supply is a signal Pa array, anodes of even-numbered LEDs are controlled by a b power supply, and the b power supply is a signal Pb array.
The method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product comprises the following steps that when the CCD sensor scans, the sampling of the pixel points of the CCD sensor and the illumination of the LED lamp beads in the LED illumination light source keep the same-frequency operation,
(D1) Judging the type of the two-dimensional defects on the surface of the product to be detected, and executing the step (D2) if the two-dimensional defects on the surface of the product are detected as breakage; if the two-dimensional defects on the surface of the product are heterochromatic and stain detection, executing the step (D3);
(D2) The LED illumination light source and the CCD sensor are arranged on two sides of the surface of the product on opposite sides to form a transmission light source, and when the CCD sensor scans, sampling of pixel points of the CCD sensor and illumination of LED lamp beads in the LED illumination light source keep the same frequency;
(D3) The LED illumination light source and the CCD sensor are arranged on the same side of the surface of the product on opposite sides to form a diffuse light source, and when the CCD sensor scans, sampling of pixel points of the CCD sensor and illumination of LED lamp beads in the LED illumination light source keep the same frequency.
The beneficial effects of the invention are as follows: according to the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product, the same-frequency LED illumination light source is selected for illumination according to the attribute characteristics of the two-dimensional defects on the surface of the product, so that the two-dimensional defects comprise different colors and stains (one type), two types of defects such as breakage (the second type) are detected conveniently, the LED illumination light source can instantly lighten LED lamp beads, the LED illumination light source can be lighted at a single point, according to the working characteristics, the LED lamp beads at the corresponding positions are lighted in a mapping mode, the LED lamp beads are instantly lighted, the overload and the brightness are remarkably improved, and due to the fact that the power-on time is short, the actual power consumption is low, the heating quantity is small, an active radiating part is not needed, the whole size is small, the field installation of the surface detection of the product is convenient, the method is suitable for various industrial environments, the pixel synchronization with a CCD sensor is sequentially lighted, the lighting requirements are met, meanwhile, the energy consumption is greatly saved, the service life is prolonged, the lighting effect is good, the radiating efficiency is high, the accuracy of the two-dimensional defect detection sampling on the surface of the product is greatly improved, the sampling data is obtained, the more accurate sampling data is obtained, the dynamic range is wider, and the method is suitable for more sample types and good application prospect is achieved.
Drawings
FIG. 1 is a flow chart of the method of constructing a co-frequency LED illumination source for product surface two-dimensional defect detection of the present invention;
fig. 2 is a waveform diagram of control voltages of signals Pa and Pb used by the LED illumination source of the present invention.
Detailed Description
The invention will be further described with reference to the drawings.
As shown in fig. 1, the construction method of the co-frequency confocal LED illumination source for CCD sensor scanning of the present invention includes the steps of,
step (A) of acquiring the sequential exposure time sequence of pixel points of a CCD sensor for detecting the defects on the surface of a product in the working direction in the working state, comprising the following steps,
(A1) Connecting an electric signal testing instrument with a CCD sensor to establish a testing environment;
(A2) The CCD sensor is provided with a needed clock signal and power supply for working, so that the CCD sensor can work normally;
(A3) Sequentially carrying out instantaneous single-point illumination on each pixel point in a CCD sensor which normally scans, recording output signals of the pixel points of the CCD sensor through an electric signal testing instrument, and finishing recording of the output signals of each pixel point in the CCD sensor;
(A4) Acquiring a time sequence of sequential exposure of the pixel points of the CCD sensor along the working direction through data statistics of the signal change period of each pixel point output;
according to the number of the pixel points of the CCD sensor, the corresponding mapping relation is established according to the pixel points of the CCD sensor and the LED lamp beads in the LED lamp sources according to the positions and the arrangement sequence, the LED lamp beads are divided into a plurality of subareas in the LED lamp sources to form LED lamp bead units, and the LED lamp beads in each LED lamp bead unit can be simultaneously lighted or extinguished, specifically: the CCD sensor pixel point is an integral multiple of the number of LED lamp bead units in an LED illumination light source, the LED illumination light source is uniformly divided into M LED lamp bead units according to the position sequence, the LED lamp beads are lightened instantly, overload is carried out on the LED lamp beads, the brightness is improved, the rated voltage of the LED lamp beads can be selected to be 3V, the rated probability is 0.45w, the LED lamp beads can be overloaded to 11V and 4A by adopting instant lightening, the overload is 97 times, the brightness is obviously improved, the power-on time is short, the LED lamp beads cannot be damaged, the actual power consumption is low, the heating value is small, an active heat dissipation part is not needed, the whole size is small, the LED lamp beads are convenient to install on site, the LED lamp beads are lightened synchronously and sequentially, the LED lamp beads can meet the illumination requirement, meanwhile, the energy consumption is greatly saved, and the service life is prolonged;
step (C), according to the working frequency of the pixel points of the CCD sensor in sequence exposing along the working direction, the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source are controlled to be simultaneously lightened or extinguished, so that the two lamp beads and the CCD sensor work synchronously at the same frequency, and the specific implementation process is as follows:
(C1) When a current pixel point of the CCD sensor pixel point works, after the LED lamp bead T1 positioned at the front side in the LED lamp unit corresponding to the pixel point is lightened for a time, the LED lamp bead T2 positioned at the rear side in the LED lamp unit is lightened, and the LED lamp bead positioned at the front side in the LED lamp unit is extinguished;
(C2) The LED lamp beads at the rear side in the LED lamp unit are turned off after being continuously turned on for T1+ T2, f is set to be the working frequency of a single pixel of the CCD sensor, the width of each pixel is i, the amplification factor of a scanning optical system is 1/X, the corresponding width of each pixel on an object image is i.X, the amplification factor of a light source lens is 1/Y, the width of each single LED lamp bead plus the spacing between two LED lamp beads is S, the object image range S=s.Y required to be illuminated by each single LED lamp bead is S/i.X pixels when the single LED lamp bead is illuminated on the CCD sensor, the time T1 = S.f/i.X required to be illuminated by each LED lamp bead, the overlapping electric quantity time T2 of adjacent lamp beads is at least 1/f and less than 2/f, and X, Y is the characteristic parameter of the lens;
(C3) Sequentially exposing the CCD sensor pixel points along the working direction, repeating the steps (C1) - (C2), and completing the lighting or extinguishing of the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source, so that the CCD sensor pixel points and the LED lamp bead units at the corresponding positions in the LED illumination light source work synchronously with the same frequency;
step (D), during the scanning operation of the CCD sensor, sampling the pixel points of the CCD sensor and lighting the LED lamp beads in the LED lighting source keep the same-frequency confocal operation, comprising the following steps,
(D1) Judging the type of the two-dimensional defects on the surface of the product to be detected, and executing the step (D2) if the two-dimensional defects on the surface of the product are detected as through holes; if the two-dimensional defect on the surface of the product is heterochromatic detection, executing the step (D3);
(D2) The LED illumination light source and the CCD sensor are arranged on two sides of the surface of the product on opposite sides to form a transmission light source, and when the CCD sensor scans, sampling of pixel points of the CCD sensor and illumination of LED lamp beads in the LED illumination light source keep the same frequency;
(D3) The LED illumination light source and the CCD sensor are arranged on the same side of the surface of the product on opposite sides to form a diffuse light source, and when the CCD sensor scans, sampling of pixel points of the CCD sensor and illumination of LED lamp beads in the LED illumination light source keep the same frequency.
According to the method for constructing the same-frequency confocal LED illumination light source for scanning by the CCD sensor, according to the clock frequency of the measured CCD sensor pixel points which are sequentially exposed along the working direction, the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source are controlled to be on or off, so that the two lamp beads work synchronously at the same frequency, and one specific embodiment is as follows:
first, first LED lamp beads are lightened, after the first LED lamp beads are lightened for 10 mu s, second LED lamp beads are lightened, after the first LED lamp beads are lightened for 0.5 mu s, after the second LED lamp beads are lightened for 10.5 mu s, third LED lamp beads are lightened, after the second LED lamp beads are lightened for 0.5 mu s, and the like, except that the first LED lamp beads and the last LED lamp beads are lightened for 10.5 mu s, the lightening time of each lamp bead is 11 mu s, that is to say, after the former LED lamp bead is independently lightened for 10 mu s, the next LED lamp bead is lightened, the adjacent two lamp beads are lightened for 0.5 mu s, then the former LED lamp bead is extinguished, the next LED lamp bead is independently lightened for 10 mu s, when the single LED lamp bead is lightened, the middle is lightened, the edge is dark, in this way, the lighting conditions corresponding to the edge of the LED lamp beads are respectively corresponding to the middle, the two adjacent two LED lamp beads are lightened for 0 mu s, the brightness of the two adjacent LED beads is increased, the two edge-light-down condition is unified, and the edge-bright condition is provided, and the two edge-bright LED lamp beads are consistent and the edge brightness is increased;
the light emitted by the LED lamp beads passes through the lens to form parallel light beams, the larger the aperture of the lens is, the higher the brightness of the emitted light is, the aperture of the conventional industrial camera lens is generally not more than F/2.8, and in order to improve the brightness as much as possible, a large aperture photographic lens has to be selected. The number of the LED lamp beads matched by the lens is related to the picture corresponding to the lens, the maximum picture produced in mass is the picture in the GFX of Fuji, the picture size is 44 x 33mm rectangle, so the diameter of an imaging circle of the lens is 55mm of the diagonal line of the picture rectangle, the size of the lamp beads for selecting the LED is 0.33 x 0.81 x 0.15mm,0.33mm is the width of the LED lamp beads, the distance between the LED lamp beads is 0.15mm, so each lamp bead needs 0.48mm of width space, 55 is divided by 0.48 to be about equal to 114.6, and the maximum picture is used for guaranteeing the imaging circle, so the lamp beads are 116 in order to be convenient for the symmetrical design of a circuit to take even numbers. The number of the LED lamp beads can basically meet the requirements of all CCD sensors on the market. And the aperture in the used Fuji GFX lens is the largest lens with the middle optical distance of 85mm F/1.2, the focal length of the rear flange of the lens is 26.7mm, the distance between the lamp strips and the plane of the rear flange of the lens is 26.7mm, the distance L1 between the single LED lamp beads is 0.15mm, and the width L2 of the LED lamp beads is 0.33mm.
The LED lamp beads in the LED illumination light source can be singly lightened or extinguished, and specifically comprises the following steps: the LEDs are divided into odd-even fields, anodes of the odd-numbered LEDs are controlled by a power supply, the a power supply is a signal Pa array, anodes of the even-numbered LEDs are controlled by a power supply B, the B power supply is a signal Pb array, namely, the LEDs are divided into odd-even fields, anodes of the odd-numbered LEDs are all connected to an MOS tube A in parallel, anodes of the even-numbered LEDs are all connected to an MOS tube B in parallel, the signal Pa controls the MOS tube A, the signal Pb controls the MOS tube B, when the control voltage of the MOS tube is high, the MOS tube is conducted, and the anode of the LEDs obtains external power supply; meanwhile, the cathode of each lamp bead is grounded through one MOS tube (0, 1, 2, 3, 4, etc.), when the voltage controlled by the MOS tube is high, the MOS tube is conducted, the cathode is grounded and is in low level, the lamp beads are lighted, wherein the waveforms of the control voltages of the signal Pa and the signal Pb are shown in figure 2, namely, the lighting time of each LED lamp bead positioned in the middle part is T2+T1+T2, the MOS tube of each cathode is given high level of T2+T2+T1+T2+T2 in turn, that is, the cathode is turned on earlier than the anode by T2, and turned off later by T2, so as to avoid unstable brightness caused by simultaneous turn-on of the anode and the cathode, and the backward MOS tube is turned on after the former MOS tube is turned on by 2×t2+t1.
In summary, the method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product according to the attribute characteristics of the two-dimensional defects on the surface of the product selects the same-frequency LED illumination light source to illuminate, so that the two-dimensional defects comprise different colors and stains (one type) and the defects of breakage (the second type) are detected, the LED illumination light source can instantly illuminate the LED lamp beads, the LED illumination light source can be lighted at a single point, the LED lamp beads at the corresponding position are lighted in a mapping manner according to the working characteristics, the overload and the brightness are remarkably improved, and the method is low in practical power consumption, small in heating value, does not need an active heat dissipation part, has a small overall size, is convenient for the field installation of the surface detection of the product, is suitable for various industrial environments, and is synchronously lighted with pixels of a CCD sensor in sequence, and has the advantages of greatly saving energy consumption, prolonging the service life, good illumination effect, high efficiency, greatly improving the accuracy of the two-dimensional defect detection sampling of the surface of the product, acquiring more accurate sampling data, wider dynamic range and adapting to more types of samples, and good application prospect.
The foregoing has outlined and described the basic principles, features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. The method for constructing the same-frequency LED illumination light source for detecting the two-dimensional defects on the surface of the product is characterized by comprising the following steps of: comprises the steps of,
step (A), acquiring a time sequence of sequential exposure of pixel points of a CCD sensor for detecting defects on the surface of a product along the working direction in the working state;
according to the number of the pixel points of the CCD sensor, an LED illumination light source which is matched with the CCD sensor and can be lighted at a single point is used, a corresponding mapping relation is established according to the pixel points of the CCD sensor and the LED lamp beads in the LED illumination light source according to the positions and the arrangement sequence, the LED lamp beads are divided into a plurality of subareas in the LED illumination light source, LED lamp bead units are formed, and the LED lamp beads in each LED lamp bead unit can be lighted or extinguished at the same time;
step (C), according to the working frequency of the pixel points of the CCD sensor in sequence exposure along the working direction, controlling the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source to be simultaneously turned on or turned off so as to enable the two lamp beads to synchronously work at the same frequency;
step (D), when the CCD sensor scans, sampling pixel points of the CCD sensor and lighting of LED lamp beads in the LED lighting source keep the same frequency,
wherein, the step (A) is to obtain the sequential exposure time sequence of the pixel points of the CCD sensor for detecting the defects on the surface of the product along the working direction in the working state, comprising the following steps,
(A1) Connecting an electric signal testing instrument with a CCD sensor to establish a testing environment;
(A2) The CCD sensor is provided with a needed clock signal and power supply for working, so that the CCD sensor can work normally;
(A3) Sequentially carrying out instantaneous single-point illumination on each pixel point in a CCD sensor which normally scans, recording output signals of the pixel points of the CCD sensor through an electric signal testing instrument, and finishing recording of the output signals of each pixel point in the CCD sensor;
(A4) Acquiring a time sequence of sequential exposure of the pixel points of the CCD sensor along the working direction through data statistics of the signal change period of each pixel point output;
according to the number of the pixel points of the CCD sensor, the corresponding mapping relation is established according to the pixel points of the CCD sensor and the LED lamp beads in the LED lamp sources according to the position and the arrangement sequence, the LED lamp beads are divided into a plurality of subareas in the LED lamp sources, and an LED lamp bead unit is formed, wherein the LED lamp bead unit comprises: the pixel points of the CCD sensor are integral multiples of the number of LED lamp bead units in the LED illumination light source,
according to the sequential exposure time sequence of the pixel points of the CCD sensor along the working direction, the lighting or extinguishing of the LED lamp bead units at the corresponding positions in the LED illumination light source is controlled, so that the LED lamp bead units and the LED lamp bead units work synchronously at the same frequency, two LED lamp beads are arranged in the LED lamp bead units, and the specific implementation process is as follows:
(C1) When a current pixel point of the CCD sensor pixel point works, after the LED lamp bead T1 positioned at the front side in the LED lamp unit corresponding to the pixel point is lightened for a time, the LED lamp bead T2 positioned at the rear side in the LED lamp unit is lightened, and the LED lamp bead positioned at the front side in the LED lamp unit is extinguished;
(C2) The LED lamp beads positioned at the rear side in the LED lamp unit are turned off after being continuously turned on for T1 +T2;
(C3) And (3) sequentially exposing the CCD sensor pixel points along the working direction, repeating the steps (C1) - (C2), and completing the lighting or extinguishing of the LED lamp beads in the LED lamp bead units at the corresponding positions in the LED illumination light source, so that the CCD sensor pixel points and the LED lamp bead units at the corresponding positions in the LED illumination light source synchronously work at the same frequency.
2. The method for constructing a co-frequency LED illumination source for two-dimensional defect detection on a product surface as recited in claim 1, wherein: let f be CCD sensor single pixel operating frequency, the width of every pixel is i, scan the amplification factor of optical system is 1/X, and every pixel is i.X on the object image corresponding width, the amplification factor of light source camera lens is 1/Y, the width of single LED lamp pearl is S plus two LED lamp pearl intervals, and the object image scope S = s.Y that single LED lamp pearl needs to illuminate, illuminate to CCD sensor be S/i.X pixel, every LED lamp pearl need the time T1 = S.f/i.X that lights, adjacent lamp pearl overlap electric quantity time T2 is at least 1/f and is less than 2/f, X, Y is the characteristic parameter of camera lens.
3. The method for constructing a co-frequency LED illumination source for two-dimensional defect detection on a product surface as recited in claim 1, wherein: and the LED lamp beads in the LED lamp bead unit are lightened instantly and are overloaded.
4. The method for constructing a co-frequency LED illumination source for two-dimensional defect detection on a product surface as recited in claim 2, wherein: the LED lamp bead in the LED lamp bead unit is lightened or extinguished, and specifically comprises the following steps: the LEDs are divided into odd-even fields, anodes of odd-numbered LEDs are controlled by an a power supply, the a power supply is a signal Pa array, anodes of even-numbered LEDs are controlled by a b power supply, and the b power supply is a signal Pb array.
5. The method for constructing a co-frequency LED illumination source for two-dimensional defect detection on a product surface as recited in claim 2, wherein: step (D), when the CCD sensor scans, sampling the pixel points of the CCD sensor and lighting the LED lamp beads in the LED lighting source keep the same frequency to work, comprising the following steps,
(D1) Judging the type of the two-dimensional defects on the surface of the product to be detected, and executing the step (D2) if the two-dimensional defects on the surface of the product are detected as breakage; if the two-dimensional defects on the surface of the product are heterochromatic and stain detection, executing the step (D3);
(D2) The LED illumination light source and the CCD sensor are arranged on two sides of the surface of the product on opposite sides to form a transmission light source, and when the CCD sensor scans, sampling of pixel points of the CCD sensor and illumination of LED lamp beads in the LED illumination light source keep the same frequency;
(D3) The LED illumination light source and the CCD sensor are arranged on the same side of the surface of the product on opposite sides to form a diffuse light source, and when the CCD sensor scans, sampling of pixel points of the CCD sensor and illumination of LED lamp beads in the LED illumination light source keep the same frequency.
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