JP2008203168A - Visual inspection method for belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visual inspection method and a visual inspection device for a belt, capable of inspecting a micro irregular shape existing on a surface of the belt. <P>SOLUTION: This visual inspection device 1 includes a driving roll 2 and a driven roll 3 laid with the belt 100 to direct an inspection face 101A of the belt toward an outside, a laser irradiation device 4 for irradiating the inspection face 101A from a diagonal direction thereto with a laser beam, a digital camera 5 for photographing a light intensity pattern generated by the irradiation of the inspection face 101A with the laser beam to acquire an image data, an image processing part 14 for image-processing the image data, and a determination part 15 for determining the quality of a surface state of the belt 100, based on the image-processed data. The visual inspection device 1 can detect the irregular shape on the surface of the belt even in the micro irregular shape, and can inspect easily and precisely the surface of the belt. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an appearance inspection method and an appearance inspection apparatus for inspecting the surface of a belt.

  Conventionally, as an inspection device for detecting defects on the surface of the belt, a laser beam is irradiated on the surface of the belt that is suspended on two rolls and runs under a constant tension, and the reflected light is applied to a PSD (semiconductor position detection element). There is a method of detecting a defective portion on the surface by receiving light with the provided light receiving portion (see, for example, Patent Document 1). The light energy received by the light receiving unit including the PSD is converted into a photocurrent. Based on this current displacement, a defect on the surface of the belt can be detected.

Japanese Patent Publication No. 8-23531

  However, according to the inspection method of Patent Document 1, if the unevenness on the surface of the belt is very small, it is difficult to distinguish between the current displacement and the electronic noise. For this reason, it has been difficult to detect minute irregularities on the belt surface.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a belt appearance inspection method and an appearance inspection apparatus capable of inspecting minute uneven shapes present on the surface of the belt.

Means for Solving the Problems and Effects of the Invention

  The method of inspecting the appearance of a belt according to claim 1 is a belt suspension step of suspending the belt on a plurality of rolls so that the inspection surface is outside, and laser light is applied to the inspection surface from an oblique direction with respect to the inspection surface. An irradiation step of irradiating, an image data acquisition step of capturing a light and dark pattern generated by irradiating the concavo-convex shape of the inspection surface with the laser light, and acquiring the image data; and a belt based on the image data And a determination step of determining whether the surface state is good or bad.

  When laser light is irradiated onto the concave and convex shape of the belt inspection surface from a direction inclined with respect to the inspection surface, the laser light is blocked by the convex portion to generate a shadow, and the shadow becomes dark according to the depth of the unevenness. That is, a light and dark pattern is formed on the surface of the belt according to the uneven shape of the surface of the belt. Since the quality of the surface of the belt is judged based on the image data composed of the light and dark patterns, it can be detected even if the uneven surface of the belt is minute, and the belt surface can be inspected easily and accurately. can do.

  The belt appearance inspection method according to claim 2 is characterized in that, in the belt suspension step according to claim 1, the plurality of rolls are rotated to cause the belt to travel.

  By running the belt, the entire circumference of the belt can be inspected without changing the light emission position of the irradiation means and the position of the photographing means. Therefore, the entire circumference can be inspected more easily than when the belt is not run.

  According to a third aspect of the belt visual inspection method of the present invention, in the irradiation step according to the first or second aspect, the laser light is irradiated from a direction that forms an angle of 0.3 to 3.0 degrees with respect to the inspection surface. It is characterized by.

  When the laser beam is irradiated at the irradiation angle, a light / dark pattern corresponding to a concavo-convex shape having a concavo-convex height difference of 1 to 30 μm and a concavo-convex pitch of 1 to 10 mm can appear on the inspection surface. Therefore, such uneven shape on the surface of the belt can be detected by irradiating at the irradiation angle.

  The method of inspecting the appearance of a belt according to claim 4 includes an image processing step of converting image data obtained from the image data acquisition step into a grayscale pattern according to any one of claims 1 to 3, wherein the determination step includes: The quality of the surface state of the belt is determined based on the converted gray scale pattern.

  When image data composed of a light and dark pattern is converted into a gray scale pattern, the tone information of the image data is lost and only luminance information is extracted. Therefore, the uneven shape on the surface of the belt can be inspected based on the gray scale pattern.

  The belt appearance inspection method according to claim 5 derives, from the converted grayscale pattern according to claim 4, a plurality of representative values of grayscale values with respect to a plurality of pixel columns extending in a width direction of the belt, and the determination. In the process, a difference between the average value of the plurality of derived representative values and each representative value is calculated, and a value obtained by dividing the sum of the absolute values of the differences by the number of pixels in the belt longitudinal direction of the gray scale pattern is calculated. The variation evaluation index of the scale value is used, and the quality of the surface state of the belt is determined by comparing the variation evaluation index with a predetermined determination value.

  When laser light is irradiated on the surface of a belt having a concavo-convex shape in which the distribution of concavo-convexity does not change significantly in the belt width direction, the light / dark distribution of the light / dark pattern caused by this concavo-convex shape does not change significantly in the belt width direction. Therefore, for each pixel column extending in the belt width direction, a representative value of the gray scale value is derived, and by using the plurality of representative values, the uneven shape of the belt surface can be inspected. Further, the gray scale value is a value corresponding to the unevenness of the surface, and the variation evaluation index of the gray scale value represents the average of the deviation between the average value of the plurality of representative values and each representative value. Therefore, it is possible to determine the quality of the irregular shape on the surface of the belt based on the grayscale value variation evaluation index.

  A belt appearance inspection method according to a sixth aspect of the present invention is the belt visual inspection method according to the fifth aspect, wherein the representative value is an average value of gray scale values of pixel rows in the belt width direction.

  By using the average value of the gray scale values of the pixel rows in the belt width direction as a representative value, the unevenness distribution in the belt width direction does not change greatly, and a concave portion different from the distribution is formed on a part of the belt surface. Or when the convex part is formed, the influence of the gray scale value corresponding to the different concave part or convex part can be reduced, and the uneven | corrugated shape of a belt surface can be test | inspected. In addition, the influence of the gray scale value corresponding to a portion that is particularly brightly formed by reflection of laser light or a portion to which minute dust is attached can be reduced, and the uneven shape of the belt surface can be inspected.

  A belt appearance inspection method according to a seventh aspect of the present invention is the belt visual inspection method according to the fifth aspect, wherein the representative value is a grayscale value of each pixel in an arbitrary pixel row in the belt longitudinal direction extracted from the grayscale pattern. And

  By extracting an arbitrary pixel row in the belt longitudinal direction from the gray scale pattern and using the gray scale value of each pixel in the pixel row as a representative value, the uneven shape in which the uneven distribution does not change greatly in the belt width direction is obtained. The surface of the belt it has can be inspected.

  The method for inspecting the appearance of a belt according to claim 8 is characterized in that in any one of claims 1 to 7, the belt is a V-ribbed belt, and the inspection surface is a front end surface or a side surface of a rib portion of the V-ribbed belt. A method for inspecting the appearance of the belt as described in the above.

  In general, in the manufacturing process of a V-ribbed belt, the surface of the belt is polished to form a rib portion by bringing a rotated annular V-shaped grinding wheel into contact with the surface of the belt that has traveled. By this polishing, a minute concavo-convex shape (polishing stripes) extending in the belt width direction and having concavo-convex alternately formed in the belt longitudinal direction is likely to occur on the front end surface and the side surface of the rib portion. By the inspection method of the present invention, it is possible to easily and accurately inspect the front end surface or the side surface of the rib portion of the V-ribbed belt having the polishing stripes.

  The belt appearance inspection apparatus according to claim 9 is a plurality of rolls on which the belt is suspended so that the inspection surface is on the outside, and irradiation means for irradiating the inspection surface with laser light from an oblique direction with respect to the inspection surface. And image data acquisition means for capturing a light and dark pattern generated by irradiating the concavo-convex shape of the inspection surface with the laser light, and acquiring the image data, and the quality of the surface state of the belt based on the image data And a judging means for judging whether or not.

  With this appearance inspection device, it is possible to detect even a minute uneven shape on the belt surface, and it is possible to easily and accurately inspect the surface of the belt.

Next, an embodiment of the present invention will be described.
As shown in FIG. 1, an appearance inspection apparatus 1 according to the present embodiment inspects the surface of a belt 100, and includes a drive roll 2, a driven roll 3, a laser irradiation apparatus (irradiation means) 4, a digital camera 5, A control device 6 is provided.

  As shown in FIG. 2, the belt 100 is a V-ribbed belt having a plurality of V-shaped rib portions 101 extending in the longitudinal direction of the belt on the contact surface side with the pulley. The belt 100 is composed mainly of rubber, for example.

  In general, in the manufacturing process of a V-ribbed belt, a vulcanized cylindrical rubber sleeve is suspended between a driving roll and a driven roll and travels under a predetermined tension, and at the same time, a rotating polishing wheel having an annular V-shaped grindstone is used. Contact the rubber sleeve while running. Thereby, a plurality of V-shaped groove portions (rib portions) are formed on the surface of the rubber sleeve. Then, the rubber sleeve is cut into a predetermined width to finish each V-ribbed belt. For this reason, the tip surface 101A and the side surface 101B of the rib portion 101 of the V-ribbed belt extend in the width direction of the belt by polishing and have a minute uneven shape (polishing stripes) in which unevenness is alternately formed in the belt longitudinal direction. ) Is easily formed. When the belt having the polishing fringes is used for a pulley, abnormal noise may occur due to the convex portion periodically contacting the surface of the pulley. The appearance inspection apparatus 1 according to this embodiment inspects the uneven shape of the tip surface (hereinafter referred to as an inspection surface) 101A of the rib portion 101.

  As shown in FIG. 1, the belt 100 is suspended from the driving roll 2 and the driven roll 3 so that the inspection surface 101 </ b> A is outside. The drive roll 2 and the driven roll 3 are arranged so that their rotation axes are parallel and at the same height. The drive roll 2 is connected to a motor 7, and the motor 7 is connected to a control device 6. When the drive roll is rotationally driven by the motor 7 in the direction of the arrow in FIG. 1 (clockwise direction), the belt 100 travels by the rotation.

  The laser irradiation device 4 is arranged so as to irradiate the inspection surface 101A with laser light in a direction at an angle θ1 with respect to the inspection surface 101A and perpendicular to the width direction of the belt 100. The irradiation angle θ1 is set to an appropriate value according to the uneven shape of the surface. The irradiation angle θ1 will be described in detail later. As an example of the laser irradiation apparatus 4, a semiconductor laser having a wavelength of 400 to 800 nm can be exemplified.

  As shown in FIG. 3, when the laser beam is irradiated from a direction that forms an angle θ1 smaller than the angle of the concavo-convex shape of the inspection surface 101A, the laser beam is blocked by the convex portion, and the laser light source of the convex portion Shadows appear on the opposite side. The intensity of the brightness of the shadow corresponds to the height difference of the unevenness. That is, a light and dark pattern is formed according to the uneven shape of the inspection surface 101A. In addition, when the inspection surface 101A of the belt 100 has polishing stripes, and the uneven shape extends in the belt width direction and is alternately formed in the longitudinal direction of the belt, the brightness of the light / dark pattern can also be changed. It extends in the width direction and appears alternately in the longitudinal direction of the belt.

  The digital camera 5 is installed vertically above the inspection surface 101A on which a light and dark pattern is formed. The digital camera 5 captures the light and dark pattern formed on the inspection surface 101A and acquires the image data. The visual field of the digital camera 5 is adjusted so that image data in a predetermined inspection range can be acquired. As an example of the inspection range, a range in which the length in the longitudinal direction of the belt is 50 to 100 mm is set.

  The control device 6 controls the entire inspection device 1. The control device 6 includes a roll control unit 10, a laser control unit 11, a camera control unit 12, a storage unit 13, an image processing unit 14, and a determination unit 15, which are a CPU, a ROM, a RAM, and the like. Consists of

  The roll controller 10 controls the motor 7 to control the rotation of the drive roll 2, that is, the traveling speed of the belt 100.

  The laser control unit 11 performs control to turn the laser irradiation device 4 on or off. The camera control unit 12 performs control so that the digital camera 5 performs shooting at a timing according to the traveling speed of the belt 100. Thus, the entire circumference of the belt can be inspected without moving the positions of the digital camera 5 and the laser irradiation means 4. Therefore, it is possible to easily perform the inspection as compared with the case where the belt 100 is not running.

  The storage unit 13 stores image data acquired by the digital camera 5. The image processing unit 14 performs image processing on the image data stored in the storage unit 13. The determination unit 15 determines the quality of the surface state of the belt 100 based on the data processed by the image processing unit 14.

  Next, an appearance inspection method using the appearance inspection apparatus 1 of the present embodiment will be described. First, the belt 100 is suspended on the drive roll 2 and the driven roll 3 so that the surface 101A is on the outer side (belt suspension process). Then, the drive roll 2 is rotationally driven by the motor 7 to run the belt 100. By controlling the rotation speed of the motor 7 to be constant by the roll controller 10, the tension of the belt 100 can be kept constant. Next, the laser irradiation device 4 irradiates the inspection surface 101A of the belt 100 with laser light (irradiation process). Then, a light and dark pattern corresponding to the uneven shape appears on the inspection surface 101A. Then, the light and dark pattern of the inspection surface 101A is photographed by the digital camera 5 and image data is acquired (image data acquisition step). Based on the image data, the quality of the state of the inspection surface 101A is determined (determination step).

  Hereinafter, a specific method from when the image data is acquired by the digital camera 5 to when the quality of the inspection surface 101A is determined will be described in detail. FIG. 4 is a flowchart showing an inspection procedure after image data is acquired by the digital camera 5. Operation procedures of the storage unit 13, the image processing unit 14, and the determination unit 15 will be described with reference to FIG.

  First, in step S <b> 1, image data acquired by the digital camera 5 is stored in the storage unit 13.

  Next, in step S2, the image data stored in the storage unit 13 is converted into a grayscale pattern of 256 gradations. As a result, the light / dark pattern of the image data is represented by shades of white and black, and each pixel is given a gray scale value of 0 to 255 according to the brightness level. FIG. 5A is a diagram schematically illustrating a gray scale pattern with three gradations. As described above, when the concavo-convex shape of the inspection surface 101A extends in the belt width direction and is alternately formed in the belt longitudinal direction, as shown in FIG. Thus, black and white stripes of gray scale pattern extend in the width direction of the belt, and these stripes are alternately formed in the belt longitudinal direction.

  In step S3, an arbitrary pixel row in the longitudinal direction of the belt is extracted from the gray scale pattern. The extracted gray scale value of one pixel column in the belt longitudinal direction becomes a plurality of representative values of gray scale values related to the plurality of pixel columns in the belt width direction. That is, the gray scale value of each pixel included in one pixel column in the belt longitudinal direction becomes a representative value of the gray scale value in each pixel column in the belt width direction. When the uneven shape of the inspection surface 101A does not change significantly in the width direction of the belt, as shown in FIG. 5A, the black and white stripes of the gray scale pattern do not change greatly in the width direction of the belt. Therefore, as shown in FIG. 5B, one arbitrary pixel column in the longitudinal direction of the belt represents substantially the same black and white shading as the pixel column in the longitudinal direction of the belt other than the extracted pixel column. Therefore, the inspection surface 101A having such a concavo-convex shape can be inspected by using data obtained by extracting an arbitrary pixel row of the gray scale pattern in the belt longitudinal direction. The image processing unit 14 performs steps S2 to S3.

  In step S <b> 4, a grayscale value variation evaluation index R is calculated from the grayscale value (a representative value of the grayscale value) of one pixel column extracted by the image processing unit 14. First, an average value AV of gray scale values of one extracted pixel row is calculated. When the number of pixels in one pixel column is P and the gray scale value of the nth pixel is Gn, the average value AV of the gray scale values is expressed by Equation 1.

(Formula 1)

  Next, a sum T of absolute values of differences between the gray scale value of each pixel and the average value AV is calculated. A value obtained by dividing the total T by the total number of pixels P is a grayscale value variation evaluation index R. The total T and the variation evaluation index R are expressed by Expression 2 and Expression 3. Specifically, FIGS. 6A and 6B show gray images when image data is acquired for two belts having different concavo-convex shapes, grayscale conversion is performed for each, and an arbitrary pixel row is extracted. It is an example which showed the scale value. In Table 1, No. 1 and No. 2 corresponds to FIG. 6A and FIG. 6B, respectively, and the number of pixels P, the average value AV, the sum T of the absolute values of the difference between the gray scale value of each pixel and the average value AV, and the variation An evaluation index R is shown.

(式３)

(Formula 2)

(Formula 3)

  Next, in step S5, the grayscale value variation evaluation index R is compared with a predetermined determination value set in advance to determine pass / fail. If the grayscale value variation evaluation index R is smaller than the determination value, it is determined as a non-defective product in step S6. On the other hand, if the grayscale value variation evaluation index R is larger than the determination value, it is determined as a defective product in step S7. The determination unit 15 performs steps 4 to 7 as described above. In setting the determination value, the noise between the variation evaluation index R and the uneven shape of the surface of the inspection surface 101A is verified by another measuring device, and no abnormal noise is generated when the belt is used. The judgment value is appropriately set to a value that ensures performance such as. In the case of the two specific examples shown in FIG. 6 and Table 1, the determination value is set to 8, and pass / fail is determined.

  Here, the laser beam irradiation angle θ1 will be described in detail. When the irradiation angle is too large, the laser beam is not blocked by the convex portion, so that no shadow is generated. On the other hand, if the irradiation angle is too small, the area of the shadow portion that is blocked by the convex portion is large, and the whole becomes dark uniformly. Therefore, the inspection accuracy is lowered. Therefore, by setting the irradiation angle to an appropriate range, the brightness of the shadow due to the uneven shape is clearly expressed, and the inspection accuracy can be improved. An appropriate irradiation angle is appropriately set depending on the height difference of the unevenness and the pitch of the unevenness.

  FIG. 7 is an enlarged view of a cross section along the longitudinal direction of the belt when it is assumed that the uneven shape of the inspection surface 101A of the belt 100 is a sinusoidal shape. Here, the maximum angle among the irradiation angles of the laser beam causing the shadow is defined as a limit angle θ2. If the uneven pitch is Amm and the uneven height is B μm, the sine curve can be expressed as y = B / 2 sin (2π / A) x as shown in FIG. At this time, the limit angle θ2 is an angle formed by the tangent line at the x = 0 of the sine curve and the x axis. As shown in FIG. 7, since the tangent at x = 0 is represented by y = (Bπ / A) x, the limit angle θ2 is represented by tan θ2 = Bπ / A. Therefore, when the uneven pitch A and the uneven height difference B are determined from this equation, the limit angle θ2 is calculated. That is, the limit angle θ2 is determined from the uneven shape.

  It is assumed that the inspection surface 101A of the belt 100 has an uneven shape in which, for example, the uneven pitch A is 1 to 10 mm and the uneven height difference B is 1 to 30 μm. The pitch of the unevenness is the distance from a certain convex part (concave part) to the next convex part (concave part) adjacent in the longitudinal direction of the belt, and the height difference of the uneven part is the top of the highest convex part. And the difference in height from the bottom of the lowest recess. As an example of the limit angle θ2 in this case, Table 2 shows the limit angles θ2 when A is 2.5 mm and 5 mm and B is 10 μm, 20 μm, and 30 μm. In Table 2, the limit angle θ2 is in the range of 0.36 ° to 2.16 °. Therefore, when inspecting the surface of the belt having the concavo-convex shape as described above, the irradiation angle θ1 is preferably set in a range of 0.3 to 3.0 °.

According to the appearance inspection method using the appearance inspection apparatus 1 described above, the following effects can be obtained.
The quality of the state of the inspection surface 101A is determined based on image data composed of a light and dark pattern corresponding to the uneven shape of the inspection surface 101A of the belt 100. Therefore, it is possible to inspect even if the uneven shape of the inspection surface 101A is minute, and it is possible to inspect simply and accurately.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, about the thing which has the structure similar to the said embodiment, the description is abbreviate | omitted suitably using the same code | symbol.

1] According to the belt appearance inspection method of the present invention, not only the front end surface 101A of the V-ribbed belt but also the side surface 101B (see FIG. 2) can be inspected. In this case, the laser irradiation device 4 is arranged so as to irradiate the side surface 101B with laser light in a direction at an angle θ1 with respect to the side surface 101B and from a direction perpendicular to the width direction of the side surface 101B. . Further, the irradiation angle θ1 is set to an appropriate value according to the uneven shape of the side surface 101B.

2] The belt that can be inspected by the appearance inspection method of the present invention is not limited to the V-ribbed belt, and the surface of a flat belt or a toothed belt can also be inspected.

3] The inspection range is not limited to a predetermined belt width, and the entire width of the belt may be inspected. For this purpose, for example, the positions of the laser irradiation device 4 and the digital camera 5 may be moved in the width direction of the belt. In this case, the laser control unit 11 and the camera control unit 12 control the positions of the laser irradiation device 4 and the digital camera 5. Further, the two rolls 2 and 3 on which the belt 100 is suspended may be moved by the same amount in the rotation axis direction (belt width direction).

4] In order to inspect the entire circumference of the belt, the positions of the laser irradiation device 4 and the digital camera 5 may be moved in the longitudinal direction of the belt without rotating the two rolls 2 and 3.

5] Further, only one point on the surface of the belt 100 may be inspected without rotating the two rolls 2 and 3.

6] The number of the plurality of rolls on which the belt 100 is suspended is not limited to two, and for example, the belt 100 may be suspended on three rolls.

7] The direction in which the laser beam is irradiated is not limited to the direction perpendicular to the width direction of the belt, and is appropriately set according to the uneven shape of the belt surface. For example, irradiation may be performed from a direction parallel to the width direction of the belt.

8] The representative value of the gray scale value relating to the pixel row extending in the belt width direction used for calculating the gray scale value variation evaluation index is limited to the gray scale value of each pixel in any one pixel row in the belt longitudinal direction. I can't. An average value of gray scale values of a plurality of pixels included in each pixel column extending in the belt width direction of the gray scale pattern may be calculated and used as a representative value. When the unevenness of the inspection surface is substantially the same in the width direction of the belt, as shown in FIG. 5A, the gray scale pattern is also substantially the same in the width direction of the belt. For this reason, the average value of the gray scale values of the pixel rows in the belt width direction is not significantly different from the gray scale value of each pixel of the pixel rows. Therefore, the surface of the belt having such a concavo-convex shape can be inspected by calculating the grayscale value variation evaluation index using the average value of the grayscale values of each pixel column in the belt width direction. Further, when the unevenness of the inspection surface is substantially the same in the width direction of the belt, and a concave or convex portion different from the unevenness is formed on a part of the inspection surface, the different concave or convex portion The influence of the corresponding gray scale value can be reduced, and the uneven shape of the belt surface can be inspected. Further, the influence of the gray scale value of the portion that is particularly brightened by the reflection of the laser beam on the inspection surface or the portion to which minute dust is attached can be reduced, and the uneven surface shape of the belt surface can be inspected.

9] The method of performing image processing on the image data acquired by the digital camera 5 is not limited to gray scale conversion, and image processing may be performed by other image processing techniques.

It is a figure which shows the external appearance inspection apparatus of the belt which concerns on embodiment of this invention. It is the figure which looked at the cross section of the V ribbed belt in perspective. It is an enlarged view of a section of a belt irradiated with laser light. It is a flowchart which shows the procedure of the test | inspection after acquiring image data. (A) is the figure which showed the gray scale pattern typically, (b) is the figure which showed typically the gray scale pattern extracted about one pixel column. (A) is a graph which shows the gray scale value regarding the belt of inferior goods, (b) is a graph which shows the gray scale value about the belt of good goods. It is an enlarged view of a section along the longitudinal direction of the belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Appearance inspection apparatus 2 Drive roll 3 Follower roll 4 Laser irradiation apparatus 5 Camera (image data acquisition means)
6 Control Device 14 Image Processing Unit 15 Judgment Unit 100 Belt 101 Rib 101A Front End Surface (Inspection Surface)
101B side

Claims (9)

A belt suspension process of suspending the belt on a plurality of rolls so that the inspection surface is on the outside;
An irradiation step of irradiating the inspection surface with laser light from an oblique direction with respect to the inspection surface;
An image data acquisition step of capturing a light and dark pattern generated by irradiating the uneven shape of the inspection surface with the laser light, and acquiring the image data;
And a determination step of determining whether the state of the surface of the belt is good or not based on the image data.   The belt appearance inspection method according to claim 1, wherein in the belt suspension step, the plurality of rolls are rotated to run the belt.   3. The belt appearance inspection method according to claim 1, wherein, in the irradiation step, the laser beam is irradiated from a direction that forms an angle of 0.3 to 3.0 ° with respect to the inspection surface. . An image processing step of converting the image data obtained from the image data acquisition step into a grayscale pattern;
The belt appearance inspection method according to any one of claims 1 to 3, wherein in the determination step, the quality of the surface state of the belt is determined based on the converted gray scale pattern. In the image processing step, a plurality of representative values of gray scale values are derived from the converted gray scale pattern for a plurality of pixel columns extending in the belt width direction,
In the determination step, a difference between the average value of the derived representative values and each representative value is calculated, and a sum of absolute values of the differences is divided by the number of pixels in the belt longitudinal direction of the gray scale pattern. 5. The belt appearance inspection according to claim 4, wherein the quality evaluation of the belt surface is determined by comparing the variation evaluation index with a predetermined determination value. Method.   6. The belt appearance inspection method according to claim 5, wherein the representative value is an average value of gray scale values of pixel rows extending in the belt width direction.   6. The belt appearance inspection method according to claim 5, wherein the representative value is a gray scale value of each pixel in an arbitrary pixel row in the belt longitudinal direction extracted from the gray scale pattern.   The belt appearance inspection method according to claim 1, wherein the belt is a V-ribbed belt, and the inspection surface is a front end surface or a side surface of a rib portion of the V-ribbed belt. A plurality of rolls on which the belt is suspended so that the inspection surface is on the outside;
Irradiation means for irradiating the inspection surface with laser light from an oblique direction with respect to the inspection surface;
Image data acquisition means for capturing a light and dark pattern generated by irradiating the uneven shape of the inspection surface with the laser light, and acquiring the image data;
A belt appearance inspection apparatus, comprising: a determination unit that determines whether the state of the surface of the belt is good based on the image data.

Images