JPWO2017169242A1 - Defect inspection apparatus and defect inspection method - Google Patents

Abstract

Provided is a defect inspection device that optically emphasizes uneven defects on an inspection object and makes it easy to determine the presence or absence of defects by image processing. The conveyance part 10 which conveys an inspection target object, the 1st light source 21 which irradiates 1st inspection light to the inspection surface of an inspection target object from one side of an inspection target object, and inspection of an inspection target object from the other side of an inspection target object A second light source 22 that irradiates the surface with the second inspection light, a detection unit 30 that detects the luminance of the inspection surface in at least the width direction of the inspection object, and a processing unit 40 that analyzes the luminance data acquired from the detection unit 30. And a determination unit 50 that determines the presence or absence of defects on the inspection surface of the inspection object, and the first inspection light and the second inspection light are parallel lights in which the diffusion or convergence of light falls within a certain range, When the position of one end in the width direction of the inspection object is 0 and the position of the other end is 1, the first light source 21 emits at least a range of 0 to 0.5, and the second The light source 22 is configured to illuminate a range of at least 1 to 0.5. That.

Description

  The present invention relates to a defect inspection apparatus and a defect inspection method for inspecting a defect on an inspection surface of an inspection object.

  In general, the defect inspection performed in the manufacturing process of synthetic leather and fabric is an apparatus called an inspection table, and a visual inspection by an operator and an appearance inspection by a camera are performed. Defects often seen in synthetic leather and fabrics are dirt, stains, unevenness, gloss, wrinkles, poor adhesion layer, etc., especially in the case of wide fabrics, there is a risk that defects will be missed by visual inspection by the operator. . In addition, in the appearance inspection with a camera, an image that can clearly recognize defects such as wrinkles, unevenness, and adhesive layer failure may not be obtained depending on the color of the synthetic leather, the state of the inspection surface, the characteristics of the irradiation light, etc. . Therefore, the conventional defect inspection has a problem that it is not possible to detect all defects such as synthetic leather.

  Therefore, in the inspection of synthetic leather and fabric, development of a defect inspection apparatus capable of accurately determining uneven defects that are difficult to detect has been performed. The irregular defect can be caused not only by a defective adhesive layer in the adhesive layer coating process, which is one of the manufacturing processes of synthetic leather, but also by contamination of dust and insects. Furthermore, when a foreign substance adheres to the blade part of the coating machine, a part where the adhesive layer thickness becomes thinner than the surroundings is generated, and after the backing cloth is adhered, the part appears as an uneven defect. These uneven defects exist not only in the width direction of synthetic leather and the like, but also in the longitudinal direction. Therefore, in the conventional inspection method that irradiates inspection light along the conveying direction of synthetic leather, etc., and detects the reflected light with a sensor, especially for the concave and convex defects in the longitudinal direction, the defect generation direction and the inspection light irradiation direction Since it is the same, it is not possible to emphasize the unevenness with shading. Therefore, there is a demand for a technique that can optically enhance the unevenness and detect the minute defect without missing it.

  For example, according to Patent Document 1, in order to detect defects such as stitch skipping, thread dropout, and thread fishing, a blue wavelength light, a green wavelength light, and a red wavelength light are irradiated at different angles, and color line scanning is performed. A textile inspection apparatus for photographing is disclosed. Also, according to Patent Document 2, a paste inspection method is disclosed in which illumination light is irradiated from an oblique direction that is almost horizontal from both sides with respect to the surface to be inspected for the purpose of inspecting the state of the paste applied to the lead frame. Yes.

JP 2003-138468 A JP-A-7-86320

  However, in the textile inspection apparatus of Patent Document 1, since light of a plurality of different wavelength ranges is irradiated from different positions at different angles, the brightness value decreases as the distance from the illumination apparatus increases, and the inspection width is 1500 mm or more. It is difficult to inspect the entire surface of leather. Moreover, in the paste inspection method of Patent Document 2, illumination light is irradiated from an oblique direction that is almost horizontal from both sides to the surface to be inspected. When this technique is used for inspection of synthetic leather, light from both sides is irradiated. Irradiation erases the unevenness of the surface to be inspected, and it may be difficult to confirm the unevenness.

  The present invention has been made in view of the above problems, and provides a defect inspection apparatus and a defect inspection method that optically emphasizes uneven defects of an inspection object and makes it easy to determine the presence or absence of defects by image processing. The purpose is to provide.

The characteristic configuration of the defect inspection apparatus according to the present invention for solving the above problems is as follows.
A defect inspection apparatus for inspecting at least a longitudinal defect on an inspection surface of an inspection object,
A transport unit for transporting the inspection object;
A first light source that is orthogonal to the conveyance direction of the inspection object and is disposed along the conveyance surface, and irradiates the inspection surface of the inspection object from the one side of the inspection object with a first inspection light;
Arranged at a position symmetrical to the first light source in a top view with respect to the center in the width direction of the inspection object, the second inspection light is irradiated to the inspection surface of the inspection object from the other side of the inspection object A second light source;
A detection unit for detecting the luminance of the inspection surface in at least the width direction of the inspection object;
A processing unit for analyzing luminance data acquired from the detection unit;
Based on the analysis processing result by the processing unit, a determination unit that determines the presence or absence of defects on the inspection surface of the inspection object;
With
The first inspection light and the second inspection light are parallel light in which light diffusion or convergence is within a certain range,
When the position of one end in the width direction of the inspection object is 0 and the position of the other end is 1, the first light source emits at least a range of 0 to 0.5, The second light source is configured to irradiate at least a range of 1 to 0.5.

  According to the defect inspection apparatus of the present configuration, the first light source and the second light source are arranged at symmetrical positions in the top view with respect to the center in the width direction of the inspection object. Here, the first light source and the second light source irradiate the inspection surface of the inspection object with the first inspection light and the second inspection light, respectively, and the first inspection light and the second inspection light are light diffusions. Alternatively, it is parallel light that converges within a certain range. For this reason, when the inspection object is irradiated with the first inspection light and the second inspection light, the first inspection light and the second inspection light wrap around the unevenness existing on the inspection surface and light scattering due to the unevenness There are few, and the shading of the unevenness can be clearly revealed. As a result, the detection unit can reliably detect the defect of the inspection object as a luminance change, and can prevent diffracted light and scattered light from being detected as noise. Further, when the position of one end in the width direction of the inspection object is 0 and the position of the other end is 1, the first light source emits at least a range of 0 to 0.5, Since the two light sources are configured to irradiate at least a range of 1 to 0.5, the inspection object is irradiated so that the entire width direction has a certain luminance or more. Therefore, it is possible to prevent the inspection light from reaching the center of the inspection object in the width direction with certainty, sufficiently highlighting the unevenness (contrast) of the unevenness of the inspection surface and overlooking the defect. The inspection objects irradiated with the respective inspection lights by the first light source and the second light source are conveyed by the conveyance unit, and the luminance of the inspection surface at least in the width direction of the inspection object is continuously increased to a predetermined number of lines by the detection unit. And brightness data is obtained. The luminance data is analyzed by the processing unit, and the determination unit determines whether there is a defect on the inspection surface of the inspection object based on the analysis processing result. In this way, it becomes possible to detect at least longitudinal defects in the inspection object that have been overlooked by conventional defect inspection apparatuses, such as irregularities, wrinkles, and adhesive layer defects.

In the defect inspection apparatus according to the present invention,
In the first inspection light and the second inspection light, a spread angle formed by the optical axis of the parallel light and the outermost traveling direction of the parallel light is θ _1, and the optical axis of the parallel light is the inspection object. When the incident angle incident on the inspection surface is θ ₂ , the following conditions are satisfied:
θ ₁ + θ ₂ ≦ 20 °
It is preferable to satisfy.

According to the defect inspection apparatus of this configuration, the first inspection light and the second inspection light, which are parallel lights, are angled from both sides in the width direction of the inspection object at an angle within the range of θ ₁ + θ ₂ ≦ 20 °. By irradiating so as to face each other, it is possible to prevent occurrence of a portion where the luminance is lowered in the width direction of the inspection object. As a result, it is possible to sufficiently enhance the unevenness (contrast) of the unevenness of the inspection surface.

In the defect inspection apparatus according to the present invention,
The spread angle θ ₁ preferably satisfies tan θ ₁ ≦ 7/100.

According to the defect inspection apparatus of the present configuration, the first light source and the second light source so that the angle of the first inspection light with respect to the inspection object and the angle of the second inspection light with respect to the inspection object satisfy tan θ ₁ ≦ 7/100. By arranging the two light sources and irradiating the respective inspection lights, it is possible to prevent occurrence of a portion where the luminance is lowered in the width direction of the inspection object. As a result, it is possible to sufficiently enhance the unevenness (contrast) of the unevenness of the inspection surface.

In the defect inspection apparatus according to the present invention,
The first inspection light and the second inspection light are preferably selected so that the wavelengths are different from each other.

  According to the defect inspection apparatus of this configuration, when the first inspection light and the second inspection light are selected so that the wavelengths are different from each other, the first inspection light and the second inspection light irradiated on the inspection object are mutually Even if the contrast is lowered with the naked eye, the contrast can be improved by removing one inspection light. Then, by extracting a channel (component) corresponding to the wavelength of the inspection light, it is possible to obtain an image photographed only with the inspection light. In particular, this is effective for preventing a decrease in contrast near the center in the width direction of the inspection object.

In the defect inspection apparatus according to the present invention,
It is preferable that the first light source and the second light source alternately irradiate the inspection surface of the inspection object.

  According to the defect inspection apparatus of this configuration, when the first inspection light and the second inspection light are alternately irradiated from both sides of the inspection object, the first inspection light and the second inspection light irradiated on the inspection object are mutually Since they do not overlap, it is possible to prevent the shadow of the unevenness generated when one inspection light irradiates the unevenness from being thinned or disappeared by the other inspection light illuminating. In particular, this is effective for preventing a decrease in contrast near the center in the width direction of the inspection object.

The characteristic configuration of the defect inspection method according to the present invention for solving the above problems is as follows:
A defect inspection method for inspecting at least a longitudinal defect on an inspection surface of an inspection object,
A transporting process for transporting the inspection object;
A first irradiation step of irradiating the inspection surface of the inspection object from the one side of the inspection object from a position perpendicular to the conveyance direction of the inspection object and along the conveyance surface;
Second inspection light is applied to the inspection surface of the inspection object from the other side of the inspection object from a position symmetrical to the emission position of the first inspection light in top view with respect to the center in the width direction of the inspection object. A second irradiation step of irradiating;
A detection step of detecting the brightness of the inspection surface in at least the width direction of the inspection object;
A processing step of analyzing the luminance data acquired in the detection step;
A determination step of determining the presence or absence of defects on the inspection surface of the inspection object based on the analysis processing result by the processing step;
Including
The first inspection light and the second inspection light are parallel light in which light diffusion or convergence is within a certain range,
When the position of one end in the width direction of the inspection object is 0 and the position of the other end is 1, the first irradiation step irradiates a range of at least 0 to 0.5, Said 2nd irradiation process exists in performing so that the range of at least 1-0.5 may be irradiated.

  According to the defect inspection method of this configuration, the inspection surface of the inspection object is irradiated with the first inspection light and the second inspection light from positions that are symmetrical with each other in top view with respect to the center in the width direction of the inspection object. . The first inspection light and the second inspection light are parallel light in which the diffusion or convergence of light falls within a certain range. For this reason, when the inspection object is irradiated with the first inspection light and the second inspection light, the first inspection light and the second inspection light wrap around the unevenness existing on the inspection surface and light scattering due to the unevenness There are few, and the shading of the unevenness can be clearly revealed. As a result, in the detection step, it is possible to reliably detect the defect of the inspection object as a luminance change and prevent detection of diffracted light or scattered light as noise. Further, when the position of the end on one side in the width direction of the inspection object is 0 and the position of the end on the other side is 1, the first irradiation step irradiates a range of at least 0 to 0.5, Since the second irradiation process is performed so as to irradiate at least a range of 1 to 0.5, the inspection object is irradiated so that the entire width direction has a certain luminance or more. Accordingly, it is possible to prevent the inspection light from reliably reaching the vicinity of the center in the width direction of the inspection object, sufficiently highlighting the unevenness (contrast) of the unevenness of the inspection surface, and preventing the defect near the center from being overlooked. The inspection objects irradiated with the respective inspection lights in the first irradiation process and the second irradiation process are conveyed in the conveyance process, and the luminance of the inspection surface in at least the width direction of the inspection object is increased to a predetermined number of lines by the detection process. It is detected continuously and luminance data is obtained. The luminance data is analyzed by a processing step, and the presence or absence of a defect on the inspection surface of the inspection object is determined by a determination step based on the analysis processing result. In this way, it is possible to inspect at least longitudinal defects in the inspection object that have been overlooked in the conventional defect inspection apparatuses such as irregularities, wrinkles, and adhesive layer defects.

It is a schematic block diagram of the defect inspection apparatus of this invention. It is explanatory drawing of the irradiation angle of test | inspection light. It is the picked-up image of the test target object which changed the irradiation angle of test light. It is an imaging image of the inspection target object by the defect inspection apparatus of 1st embodiment. It is a processing-process figure of the image image | photographed by irradiating the test | inspection object with the inspection light from which a wavelength mutually differs. It is a picked-up image of the inspection object by the defect inspection apparatus of a second embodiment. It is a flowchart of the defect inspection method of the present invention.

  Hereinafter, embodiments relating to a defect inspection apparatus and a defect inspection method of the present invention will be described with reference to the drawings. However, the present invention is not intended to be limited to the configurations described in the embodiments and drawings described below.

[Overall configuration of defect inspection system]
FIG. 1 is a schematic configuration diagram of a defect inspection apparatus 100 according to the present invention. The defect inspection apparatus 100 is an apparatus that inspects defects in at least the longitudinal direction (Y direction) of the inspection surface A3 of the inspection object A. In the present embodiment, a strip-shaped synthetic leather having a texture on the inspection surface A3 is assumed as the inspection object A. The defect inspection apparatus 100 is disposed along the conveyance surface that is orthogonal to the conveyance direction of the inspection object A and the conveyance unit 10 that conveys the inspection object A, and one side (end A1 side) of the inspection object A. The first light source 21 that irradiates the inspection surface A3 of the inspection object A with the first inspection light L1 and the first light source 21 in top view with respect to the center in the width direction (X direction) of the inspection object A. A second light source 22 that is disposed at a position and irradiates the inspection surface A3 of the inspection object A from the other side (end A2 side) of the inspection object A in the width direction of the inspection object A. Based on the detection unit 30 that detects the luminance of the inspection surface A3, the processing unit 40 that analyzes the luminance data acquired from the detection unit 30, and the analysis processing result by the processing unit 40, the inspection surface A3 of the inspection target A And a determination unit 50 that determines the presence or absence of a defect. Each of the above-described units is controlled in an integrated manner by a control unit 60 configured by, for example, a computer.

  The transport unit 10 includes a driver 12 that drives a transport roller 11 that transports the inspection object A, and an encoder 13 that detects the rotation of the transport roller 11. When the transport roller 11 rotates, a pulse signal corresponding to the rotation angle is generated, and the pulse signal is transmitted to the encoder 13. Based on the pulse signal received by the encoder 13, the control unit 60 controls the driver 12 of the transport unit 10 so that the transport roller 11 transports the inspection object A to a predetermined position. Further, based on the pulse signal transmitted from the transport roller 11, the control unit 60 informs the encoder 13 of the position of the inspection object A for the line sensor 33 to be described later to take an image for each line at a predetermined cycle. Set.

  The defect inspection of the inspection object A is performed in the longitudinal direction (Y direction). Here, the longitudinal direction is a direction parallel to the conveyance direction of the inspection object A. The defect of the inspection object A is likely to occur in the same direction as the conveyance direction (that is, the longitudinal direction), and mainly occurs as an uneven defect. The irregular defect can be caused not only by a defective adhesive layer in the adhesive layer coating process, which is one of the manufacturing processes of synthetic leather, but also by contamination of dust and insects.

  Two light sources (first light source 21 and second light source 22) are used as light sources for irradiating the inspection object A with inspection light. The first light source 21 and the second light source 22 can use dimmable high-intensity LED illumination. There are a constant current type and a PWM type power source for the high-intensity LED illumination because of the difference in the dimming method. However, when the number of clocks of the line sensor 33 described later is large, it is preferable to use the constant current type. As for the 1st light source 21 and the 2nd light source 22, the irradiation state of each test | inspection light is adjusted by the adjustment part 20. FIG. The adjustment unit 20 adjusts the irradiation state of the first inspection light L2 emitted from the second light source 22 and the first light source adjustment unit 23 that adjusts the irradiation state of the first inspection light L1 emitted from the first light source 21. And a second light source adjustment unit 24. The irradiation state of each inspection light includes an irradiation range, an irradiation angle, an irradiation distance, an irradiation intensity, and the like. Moreover, when the 1st light source 21 and the 2nd light source 22 are variable illumination, the adjustment part 20 can also adjust the color tone (wavelength) of irradiated light. Adjustment of the irradiation state of each inspection light is performed when the adjustment unit 20 receives an instruction from the control unit 60. The first light source 21 is disposed perpendicular to the transport direction (that is, the Y direction) of the inspection object A and along the transport surface. That is, the first light source 21 is generally arranged in the X direction, but the first inspection light L1 emitted from the first light source 21 only has to hit the inspection surface A3 of the inspection object A. The second light source 22 is disposed at a position symmetrical to the first light source 21 in top view with the center in the width direction of the inspection object A as a reference. The top view is a scene that can be seen from the vertically upward direction with respect to the conveyance direction of the inspection object A. That is, the second light source 22 is arranged at a position symmetrical to the first light source 21 in a top view with the center line C in the width direction of the inspection object A shown in FIG. Here, when the position of one end A1 in the width direction (X direction) of the inspection object A is 0 and the position of the other end A2 is 1, the first light source 21 is at least 0 to 0. .5, preferably in the range of −0.1 to 0.6, and the second light source 22 is at least in the range of 1 to 0.5, preferably 1.1 to 0.4. The adjustment unit 20 adjusts the first light source 21 and the second light source 22 so as to irradiate the second inspection light L <b> 2 in the range of.

  For the inspection object A irradiated with the first inspection light L1 and the second inspection light L2, the line sensor 33 detects the luminance of the inspection surface A3. As the line sensor 33, for example, a color line scan camera provided with an imaging device (for example, an image sensor such as a CCD or CMOS), an output amplifier, a drive circuit for outputting signals in time series, an imaging lens, and the like is used. . The line sensor 33 is installed at a position vertically above at least a region of the inspection object A to which the first inspection light L1 and the second inspection light L2 are irradiated, and the inspection is irradiated with the respective inspection lights L1 and L2. A line image in the width direction (X direction) of the object A is acquired. Instead of the line sensor 33, an area sensor that can detect a certain range in the longitudinal direction (Y direction) can also be used.

  The detection unit 30 includes a shooting operation adjustment unit 31 that adjusts the shooting operation of the line sensor 33 and an image recognition unit 32 that recognizes an image shot by the line sensor 33. The shooting timing of the line sensor 33 is determined by the control unit 60. That is, based on the pulse signal of the encoder 13 of the transport unit 10, the line sensor 33 determines a predetermined region in the width direction (X direction) of the inspection object A irradiated with the first inspection light L1 and the second inspection light L2. The control unit 60 controls the shooting operation adjustment unit 31 of the detection unit 30 so as to capture every line at a cycle. The grayscale image (line image) for each line in the width direction of the inspection object A imaged by the line sensor 33 is recognized as luminance data of a digital signal by the image recognition unit 32 of the detection unit 30, and the data is transmitted via the control unit 60. It is stored in the storage unit 70. The imaging operation adjustment unit 31 of the detection unit 30 adjusts the imaging operation of the line sensor 33 until the line image reaches a predetermined number of lines, and acquires a plurality of digital luminance data.

  The processing unit 40 synthesizes the captured image based on the plurality of digital luminance data. The captured image synthesized by the processing unit 40 includes a plurality of channel images (R channel image, G channel image, B channel image) obtained according to the type of light source. Here, the image (digital brightness data) captured by the line sensor 33 may not be able to obtain uniform brightness due to uneven sensitivity of the image sensor or the illumination method. Therefore, the processing unit 40 can process the digital luminance data into a uniform luminance image suitable for defect detection by performing shading correction. Further, in the processing unit 40, further image processing is performed, and the accuracy of defect detection is increased. Image processing includes necessary processing for determining the presence or absence of defects, such as feature point extraction processing, smoothing processing, and edge detection.

  The determination unit 50 determines whether there is a defect in the inspection target A based on the processed image generated by the processing unit 40. As a defect determination method, for example, a spatial filter process is performed on a processed image, and a region having a defect in the processed image is extracted by binarization processing, and a threshold value is set as the area of the extracted region. And determining whether or not it is a defect, or preparing a non-defective inspection image (control image) as a control in advance, and comparing the control image with the processed image 40 generated by the processing unit 40 A method for determining whether or not a defect is present based on the difference between the two. In addition, the determination result by these methods can be displayed on a display or the like of the output unit 80 described later. In this case, since the defect determination result by the determination unit 50 is simultaneously displayed on the output unit 80 together with the processed image by the processing unit 40, the defect can be easily detected while visually confirming the presence or absence of the defect and the degree of the defect. It is possible to determine whether or not there is. As a result, the accuracy of defect detection of synthetic leather and the like and the reliability of inspection are improved.

  When the determination unit 50 determines that the inspection object A is defective, or when the operator recognizes the defect, the determination result is sent to the control unit 60. Thereafter, when the defect position of the inspection target part A is specified through the encoder 13 of the transport unit 10 and the control unit 60 transmits a stop signal to the transport unit 10, the driver 12 stops the transport roller 11. When the portion including the defect of the inspection object A stops at the predetermined position, the operator can check the defect of the inspection object A on the display of the output unit 80 and perform operations such as marking and determination of the defect level. When the determination of the defect by the operator is completed or when it is determined that there is no defect, the control unit 60 transmits a conveyance signal to the conveyance unit 10 and the conveyance of the inspection object A is started or continued. Note that the start or stop of the conveyance of the inspection object A may be manually performed by the operator operating the defect inspection apparatus 100.

  The output unit 80 can display a raw image of the inspection object A photographed by the line sensor 33, an image after image processing by the processing unit 40, a determination result by the determination unit 50, and the like. The output unit 80 can be configured by a display, a printer, or the like. The operator can confirm the presence or absence of a defect in the inspection object A based on the image displayed on the display of the output unit 80 or the like.

[Inspection light irradiation angle]
The defect inspection apparatus 100 according to the present invention uses two parallel lights in which the diffusion or convergence of light falls within a certain range as the inspection lights L1 and L2. That is, the parallel light does not need to be in a completely parallel state. For example, it is possible to use pseudo parallel light obtained by passing normal light having a certain scattering property through the rod lens and the slit. When a wide inspection object A is inspected with parallel light, the light irradiation angle greatly affects the inspection result. Therefore, the present inventors have examined appropriate irradiation angles for the first inspection light L1 emitted from the first light source 21 and the second inspection light L2 emitted from the second light source 22.

FIG. 2 is an explanatory diagram of the irradiation angle of the inspection light. In FIG. 2, the second inspection light L2 emitted from the second light source 22 is illustrated, but the second inspection light L1 is also the property and behavior of the first inspection light L1 emitted from the first light source 21. It can be the same as L2. As described above, when the position of the one end A1 in the width direction (X direction) of the inspection object A is 0 and the position of the other end A2 is 1, the first light source 21 is at least 0. The second light source 22 emits at least the range of 1 to 0.5. Here, as shown in FIG. 2 (a), the spread angle between the traveling direction Q of the outermost optical axis P and the second inspection light L2 of the second test light L2 is theta _1, FIG. 2 (b) as shown, when the incident angle of the optical axis P of the second inspection light L2 is incident on the inspection surface A3 of the inspection target a and theta _2, the following condition (1):
θ ₁ + θ ₂ ≦ 20 ° (1)
Preferably, the following condition (1 ′) is satisfied.
θ ₁ + θ ₂ ≦ 15 ° (1 ′)
It is more preferable to satisfy. When the sum of the theta ₁ and theta ₂ is more than 20 °, to become the second test light L2 is irradiated with a high angle with respect to the inspection surface A3 of the test object A, shadows of the unevenness of the inspection surface A3 May be difficult to occur, and defects may not be sufficiently emphasized.

In addition, the spread angle θ ₁ of the second inspection light L2 is as follows (2):
tan θ ₁ ≦ 7/100 (2)
Preferably, the following condition (2 ′) is satisfied:
tan θ ₁ ≦ 5/100 (2 ′)
It is more preferable to satisfy. When tan θ ₁ exceeds 7/100 (θ ₁ = about 4 °), the second inspection light L2 is scattered, so that the scattered light enters the portion where the unevenness of the inspection surface A3 originally occurs, and the unevenness of the unevenness Will be weakened.

  If the irradiation angle of the second inspection light L2 satisfies the condition (1) and the condition (2), it is possible to effectively prevent the occurrence of a portion with low luminance in the width direction (X direction) of the inspection object A. be able to. As a result, it is possible to sufficiently emphasize the unevenness (contrast) of the unevenness of the inspection surface A3 of the inspection object A, and it is possible to reliably determine the unevenness defect. As described above, the same can be said about the irradiation angle of the first inspection light L1.

FIG. 3 is a captured image of the inspection object A (synthetic leather) in which the irradiation angle of the inspection light is changed. With respect to the irradiation angle (θ ₁ + θ ₂ ), (a) is 0 °, (b) is 5 °, (c) is 10 °, (d) is 15 °, and (e) is 20 °. ing. 3A to 3E, it is confirmed that the unevenness of the inspection object A is emphasized as the irradiation angle (θ ₁ + θ ₂ ) decreases. That is, when the inspection lights L1 and L2 are irradiated as much as possible to the inspection surface A3 of the inspection object A, it becomes easy to detect a defect on the inspection surface A3. In the captured image of FIG. 3 (e) having the largest irradiation angle (θ ₁ + θ ₂ ), since the unevenness of the inspection surface A3 of the inspection object A can be confirmed, at least the irradiation angle (θ ₁ + θ ₂ ) is 20. It was suggested that if the temperature was set to be less than or equal to 0 °, luminance data sufficient for the inspection could be obtained, and the defect of the inspection object A could be determined.

[First embodiment]
FIG. 4 is a captured image of the inspection object A (synthetic leather) by the defect inspection apparatus 100 according to the first embodiment. In this embodiment, the synthetic leather is inspected as the inspection object A by the defect inspection apparatus 100 provided with the green LED illumination as the first light source 21 and the red LED illumination as the second light source 22. The specifications of the light source, line sensor, and synthetic leather used in this embodiment are as follows.

<Light source>
・ Lighting device: High brightness LED lighting (red, green, blue)
・ Illumination shape: Linear ・ Light emitting surface illuminance: 600,000 lux ・ Cooling method: Natural heat dissipation ・ Light: Pseudo parallel light, adjustable light concentration ・ Power source: Constant current method <Line sensor>
Number of pixels: 2048 pixels, 4096 pixels Pixel size: 14 μm (2048 pixels), 10 μm (4096 pixels)
Maximum line rate: 31.8 kHz (2048 pixels), 17.5 kHz (4096 pixels)
・ Data format: 8 bits, 12 bits ・ Dynamic range: 58 dB
・ Sensor structure: 3 lines ・ Interface: Camera link (MDRx2)
・ Exposure time: change according to each color <synthetic leather>
・ Color: Black, Brown, Beige, White ・ Thickness: 0.9-1.2mm

  FIG. 4A is an explanatory diagram of the irradiation state of the first inspection light L1 and the second inspection light L2 in the present embodiment. The solid line is the first inspection light L1 emitted from the first light source 21, and the broken line is the second inspection light L2 emitted from the second light source 22. The first light source 21 and the second light source 22 are arranged so as to face each other at symmetrical positions on the top view across the center line C of the inspection object A shown in FIG. The two inspection lights L2 are simultaneously irradiated so that the respective irradiation regions are at least adjacent to each other in the vicinity of the center of the inspection object A in the width direction, and preferably partially overlap each other. 4A shows a state in which two irradiation areas are adjacent to each other in the vicinity of the center of the inspection object A in the width direction. FIG. 4B shows a captured image obtained by the defect inspection apparatus 100 of the present invention (Example 1) and a captured image in which the first light source 21 and the second light source 22 are both white illumination for comparison (comparison). Example 1) is shown. Since the first inspection light L1 and the second inspection light L2 irradiated on the inspection object A overlap each other, the contrast of the captured image is reduced with the naked eye, but the captured image obtained by the defect inspection apparatus 100 of the present invention ( In Example 1), since the wavelengths of the first inspection light L1 and the second inspection light L2 are different from each other, the contrast can be improved by removing one of the lights. As a result, the concavo-convex defect is emphasized, and luminance data necessary for detecting the defect is obtained. On the other hand, in the captured image (Comparative Example 1) shown for comparison, the first light source 21 and the second light source 22 are both white illumination and have the same wavelength. Therefore, the luminance data necessary for this is not obtained. From these results, when the first inspection light L1 and the second inspection light L2 are selected so that their wavelengths are different from each other, the first inspection light L1 and the second inspection light L2 irradiated on the inspection object A are mutually It has been suggested that even if the contrast of the captured image is reduced with the naked eye, the contrast can be improved by removing one light. In particular, this is effective for preventing a decrease in contrast near the center of the inspection object A in the width direction. The first inspection light L1 and the second inspection light L2 are preferably selected so that the peak wavelengths are separated. In this embodiment, green light (peak wavelength: 555 nm) is used as the first inspection light L1, and red light (peak wavelength: 660 nm) is used as the second inspection light L2, but blue light (peak wavelength: 470 nm) and red light are used. If it is a combination with light (peak wavelength: 660 nm), the difference in peak wavelength becomes larger, and thus clearer luminance data can be obtained. On the other hand, when white light having the same wavelength is used as the first inspection light L1 and the second inspection light L2, the first inspection light L1 and the second inspection light L2 irradiated on the inspection object A overlap each other, The contrast of the captured image in the vicinity of the center in the width direction is lowered, and the uneven defect cannot be emphasized.

  FIG. 5 is a process chart of an image taken by irradiating inspection object A (synthetic leather) with inspection light having different wavelengths. In FIG. 5, blue LED illumination is used as the first light source 21, and red LED illumination is used as the second light source 22. (A) is the raw image data imaged by the line sensor 33. (B) is a B channel image generated based on the first inspection light (blue light) L1 emitted from the first light source 21. The left side (A1 side) close to the first light source 21 is bright and the right side (A2 side) far from the first light source 21 is dark. (C) is an R channel image generated based on the second inspection light (red light) L2 emitted from the second light source 22. The right side (A2 side) near the second light source 22 is bright and the left side (A1 side) far from the second light source 22 is dark. (D) is a corrected image obtained by shading correction of the B channel image of (b). The shading correction is to perform correction so that an image including luminance unevenness due to the characteristics of the optical system and the imaging system becomes uniform brightness. In the B channel image of (b), there is luminance unevenness on both sides of the image, but in the corrected image of (d) subjected to shading correction, uniform luminance is obtained, and the subsequent spatial filter processing Can improve the accuracy. Although a corrected image obtained by shading correction of the R channel image in (c) is not shown, an image similar to the shading corrected image in (d) is obtained. (E) is a processed image obtained by further performing spatial filtering on the shading correction image of (d). By performing the spatial filter processing, it is possible to reduce image noise and enhance edges. When unnecessary information in the image is removed, the unevenness of the object to be inspected can be clearly revealed. (F) is obtained by binarizing the spatial filter processed image of (e). For example, when the spatial filter processed image is an 8-bit (256 gradation) image, by setting a threshold value between 20 and 230 gradations, only irregularities can be extracted from the spatial filter processed image. From this binarized image, the presence / absence of the concave / convex defect of the inspection object A becomes clear.

[Second Embodiment]
FIG. 6 is an image of an inspection object A (synthetic leather) taken by the defect inspection apparatus 100 according to the second embodiment. In the present embodiment, synthetic leather is inspected by the defect inspection apparatus 100 having white LED illumination as the first light source 21 and the second light source 22. The specifications of the light source, line sensor, and synthetic leather used in this embodiment are the same as those in the first embodiment.

  FIG. 6A is an explanatory diagram of an irradiation method of the first inspection light L1 and the second inspection light L2 in the present embodiment. The solid line is the first inspection light L1 emitted from the first light source 21, and the broken line is the second inspection light L2 emitted from the second light source 22. The first light source 21 and the second light source 22 are arranged so as to face each other at symmetrical positions on the top view across the center line C of the inspection object A shown in FIG. The two inspection lights L2 are irradiated alternately. The imaging timing of the line sensor 33 is synchronized with the timing of alternately irradiating the first inspection light L1 and the second inspection light L2, and the imaging is executed for each line in the direction in which the synthetic leather is conveyed. For this reason, the resolution in the conveyance direction of the image obtained in the second embodiment is ½ of the resolution in the conveyance direction of the image obtained in the first embodiment. In the second embodiment, an image only when the first inspection light L1 is irradiated and an image only when the second inspection light L2 is irradiated are obtained. FIG. 6B is a combined image of the region (line) irradiated with the first light source 21, and FIG. 6C is a combined image of the region (line) irradiated with the second light source 22. In this embodiment, since the first inspection light L1 and the second inspection light L2 irradiated on the synthetic leather do not overlap each other, the first inspection light L1 and the second inspection behind the unevenness present on the inspection surface A3. The wraparound of the light L2 and the scattering of light due to the unevenness do not occur, and the shadow of the unevenness can be clearly revealed. In particular, it is effective for preventing a decrease in contrast near the center in the width direction of the synthetic leather. As with the first embodiment, shading correction, spatial filter processing, and binarization processing can also be performed on the captured images in FIGS. 6B and 6C to further highlight the uneven defect.

[Defect inspection method]
Hereinafter, the defect inspection method of the present invention will be described. The synthetic leather to be inspected by the defect inspection apparatus of the present invention is usually shipped in a state of being wound in a roll shape. Therefore, when performing the defect inspection of the synthetic leather, it is necessary to pull the synthetic leather from the roll once. When the roll-shaped synthetic leather is set in the inspection device, the synthetic leather is drawn out from the roll in the conveyance direction while rotating, and the roll is formed again while being wound around another conveyance roller. At this time, the presence or absence of a defect is determined by the following processes with respect to the synthetic leather in the middle of conveyance. The defect inspection method is performed using the defect inspection apparatus 100 shown in FIG.

  FIG. 7 is a flowchart of the defect inspection method of the present invention. The defect inspection method is mainly performed through a transport process, an irradiation process (first inspection light irradiation process, second inspection light irradiation process), a detection process, a processing process, and a determination process. In the flowchart of FIG. 7, each step is indicated by a symbol “S”.

<Conveying process: S1>
First, inspection object A is conveyed as a conveyance process. After the inspection object A is installed in the defect inspection apparatus 100, when the transport roller 11 is rotated so as to wind up the inspection object A, a pulse signal corresponding to the rotation angle is generated, and the pulse signal is sent to the encoder 13. Sent. Based on the pulse signal received by the encoder 13, the transport roller 11 transports the inspection object A to a predetermined position (S1). Further, based on the pulse signal transmitted from the transport roller 11, the position of the inspection object A for the line sensor 33 to take an image for each line at a predetermined cycle is set in the encoder 13. The speed at which the inspection object A is wound (conveyance speed) is adjusted by the control unit 60 controlling the driver 12 based on the pulse signal of the encoder 13.

<Irradiation process: S2 to S3>
Next, as an irradiation process, the first inspection light L1 and the second inspection light L2 from the first light source 21 and the second light source 22 arranged at symmetrical positions in a top view across the center line C of the inspection object A. Is irradiated onto the inspection surface A3 of the inspection object A (S2, S3). For example, the first inspection light irradiation step of irradiating the first inspection light L1 of red (peak wavelength 660 nm) from the first light source 21 and the second inspection light L2 of green (peak wavelength 555 nm) from the second light source 22 are irradiated. A second inspection light irradiation step is performed. At this time, parallel light in which the diffusion or convergence of light falls within a certain range is used for each of the inspection lights L1 and L2. The irradiation range of each inspection light L1, L2 is the first inspection when the position of one end in the width direction (X direction) of the inspection object A is 0 and the position of the other end is 1. The light L1 is in the range of at least 0-0.5, preferably in the range of -0.1-0.6, and the second inspection light L2 is in the range of at least 1-0.5, preferably 1.1-0. 4 range.

<Detection process: S4 to S5>
Next, as a detection step, the luminance of the inspection surface A3 in the width direction (X direction) of the inspection object A is detected. In the detection step, the line sensor 33 detects a region in the width direction (X direction) of the inspection object A irradiated with the first inspection light L1 and the second inspection light L2 based on the pulse signal of the encoder 13 of the transport unit 10. The control unit 60 controls the shooting operation adjustment unit 31 of the detection unit 30 so as to take an image for each line at a predetermined cycle. The grayscale image (line image) for each line in the width direction of the inspection object A imaged by the line sensor 33 is recognized as luminance data of a digital signal by the image recognition unit 32 of the detection unit 30, and the data is transmitted via the control unit 60. It is stored in the storage unit 70. The control unit 60 counts the number of line images stored in the data storage unit 70, and determines whether or not a predetermined number of lines has been reached (S5). If the line image has not reached the predetermined number of lines (S5: NO), the process returns to the transport step (S1), and the inspection surface A3 is continuously irradiated with the inspection lights L1 and L2 while the inspection object A is being transported. The When the line image reaches the predetermined number of lines (S5: YES), the process proceeds to the next processing step.

<Processing steps: S6 to S9>
Next, as a processing step, a plurality of digital luminance data acquired in the detection step is analyzed. In performing the analysis process, first, the processing unit 40 synthesizes a captured image based on the plurality of digital luminance data (S6). This captured image includes a plurality of channel images (R channel image, G channel image, B channel image) obtained according to the type of light source. Here, when inspecting a wide inspection object A such as synthetic leather, the image (digital luminance data) captured by the line sensor 33 cannot obtain uniform luminance due to uneven sensitivity of the image sensor or the illumination method. Sometimes. Therefore, in the processing step, various image processes are performed on the composite image in order to remove this sensitivity unevenness and noise unrelated to the inspection object A. First, the shading correction (S7) is performed on the raw image to remove the sensitivity unevenness and the brightness unevenness and process the image into a uniform brightness image. Next, a spatial filter process (S8) is performed on the processed image to reduce image noise or enhance an edge. Further, binarization processing (S9) is performed on the image after the spatial filter processing, thereby extracting a region having a possibility of a defect.

<Determination step: S10>
Finally, as a determination step, the presence or absence of a defect on the inspection surface A3 of the inspection object A is determined based on the analysis processing result of the processing step. In the defect determination, for example, a threshold is set for the area of a region having a possibility of a defect to determine whether or not it is a defect (S10). In addition, as another defect determination, a non-defective inspection image (control image) having no defect is prepared in advance, the control image is compared with the processed image, and it is determined whether the defect is based on the difference between the two. Is possible. When it is determined that there is no defect in the inspection object A (S10: NO), the process returns to the transport process (S1), and each inspection light irradiation process (S2 to S3), detection process (S4 to S5), and processing. Steps (S6 to S9) are repeated. When it is determined that the inspection object A has a defect (S10: YES), the conveyance of the inspection object A is automatically or manually stopped, and the operator confirms the defect of the inspection object A on a display or the like and performs marking. Then, the inspection is completed by performing operations such as determining the defect level.

  The defect inspection apparatus and defect inspection method of the present invention are suitable for inspection of synthetic leather, but are also used for inspection of fabrics, wallpaper, heat insulating materials, sound absorbing materials, packaging films, plastic films, furniture top plates, etc. Is possible.

DESCRIPTION OF SYMBOLS 10 Conveyance part 21 1st light source 22 2nd light source 30 Detection part 40 Processing part 50 Judgment part 100 Defect inspection apparatus A Inspection object A3 Inspection surface L1 1st inspection light L2 2nd inspection light

Claims (13)

A defect inspection apparatus for inspecting at least a longitudinal defect on an inspection surface of an inspection object,
A transport unit for transporting the inspection object;
A first light source that is orthogonal to the conveyance direction of the inspection object and is disposed along the conveyance surface, and irradiates the inspection surface of the inspection object from the one side of the inspection object with a first inspection light;
Arranged at a position symmetrical to the first light source in a top view with respect to the center in the width direction of the inspection object, the second inspection light is irradiated to the inspection surface of the inspection object from the other side of the inspection object A second light source;
A detection unit for detecting the luminance of the inspection surface in at least the width direction of the inspection object;
A processing unit for analyzing luminance data acquired from the detection unit;
Based on the analysis processing result by the processing unit, a determination unit that determines the presence or absence of defects on the inspection surface of the inspection object;
With
The first inspection light and the second inspection light are parallel light in which light diffusion or convergence is within a certain range,
When the position of one end in the width direction of the inspection object is 0 and the position of the other end is 1, the first light source emits at least a range of 0 to 0.5, A defect inspection apparatus configured to irradiate at least a range of 1 to 0.5 with the second light source. In the first inspection light and the second inspection light, a spread angle formed by the optical axis of the parallel light and the outermost traveling direction of the parallel light is θ _1, and the optical axis of the parallel light is the inspection object. When the incident angle incident on the inspection surface is θ ₂ , the following conditions are satisfied:
θ ₁ + θ ₂ ≦ 20 °
The defect inspection apparatus according to claim 1, wherein: The defect inspection apparatus according to claim 2, wherein the spread angle θ ₁ satisfies tan θ ₁ ≦ 7/100.   The defect inspection apparatus according to claim 1, wherein the first inspection light and the second inspection light are selected so that wavelengths are different from each other.   The defect inspection apparatus according to claim 2, wherein the first inspection light and the second inspection light are selected so as to have different wavelengths.   The defect inspection apparatus according to claim 3, wherein the first inspection light and the second inspection light are selected so as to have different wavelengths.   The defect inspection apparatus according to claim 1, wherein the first light source and the second light source alternately irradiate the inspection surface of the inspection object.   The defect inspection apparatus according to claim 2, wherein the first light source and the second light source alternately irradiate the inspection surface of the inspection object.   The defect inspection apparatus according to claim 3, wherein the first light source and the second light source alternately irradiate the inspection surface of the inspection object.   The defect inspection apparatus according to claim 4, wherein the first light source and the second light source alternately irradiate the inspection surface of the inspection object.   The defect inspection apparatus according to claim 5, wherein the first light source and the second light source alternately irradiate the inspection surface of the inspection object.   The defect inspection apparatus according to claim 6, wherein the first light source and the second light source alternately irradiate the inspection surface of the inspection object. A defect inspection method for inspecting at least a longitudinal defect on an inspection surface of an inspection object,
A transporting process for transporting the inspection object;
A first irradiation step of irradiating the inspection surface of the inspection object from the one side of the inspection object from a position perpendicular to the conveyance direction of the inspection object and along the conveyance surface;
Second inspection light is applied to the inspection surface of the inspection object from the other side of the inspection object from a position symmetrical to the emission position of the first inspection light in top view with respect to the center in the width direction of the inspection object. A second irradiation step of irradiating;
A detection step of detecting the brightness of the inspection surface in at least the width direction of the inspection object;
A processing step of analyzing the luminance data acquired in the detection step;
A determination step of determining the presence or absence of defects on the inspection surface of the inspection object based on the analysis processing result by the processing step;
Including
The first inspection light and the second inspection light are parallel light in which light diffusion or convergence is within a certain range,
When the position of one end in the width direction of the inspection object is 0 and the position of the other end is 1, the first irradiation step irradiates a range of at least 0 to 0.5, The said 2nd irradiation process is a defect inspection method performed so that the range of at least 1-0.5 may be irradiated.

Images