JP2008275496A - Defect detection method and device of foam roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a surface defect of a cylindrical foam roller with high accuracy. <P>SOLUTION: The foam roller 1 includes a urethane foam layer on a core bar as a shaft, and a part of a foam cell of a surface layer part is opened on its surface. In order to detect abnormality in an opening shape and dimension of the foam cell, light is irradiated from a light projecting means 23 to the foam roller 1. Reflected light is imaged by an imaging means 21 and image processing is applied to an obtained image. An LED or the like which generates light of an ultraviolet region (a short wavelength region) is used as a light source of the light projection means 23. Thereby, defect of the foam roller 1 is defected efficiently with high accuracy. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a foam roller defect detection method and apparatus for detecting surface defects by irradiating light to a foam roller having foam cell openings on the roller surface.

  As a method for discriminating the surface defect of the foam roller, conventionally, there have been a manual method and a method using an inspection apparatus. In the manual method, as the accuracy of the product increases, it is necessary to find minute defects as compared with the conventional method, which makes it a laborious task that must be concentrated for a long time, increasing the mental burden and fatigue. Will also double. In addition, the visual inspection is a subjective inspection judgment by the inspector, and depends on the inspector's judgment. There is a possibility that the standard changes with the transition.

  As an alternative to the inspector, an appearance inspection method using an electronic imaging device using a CCD camera has also been clarified (see Patent Document 1). This is to make the surface state easy to see by changing the light source wavelength by applying blue cellophane to a fluorescent lamp made of monochromatic light on the foam surface.

However, when observing the urethane foam layer with light whose wavelength has been changed by applying blue cellophane, there are variations in fluorescence wavelength due to differences in observation conditions, light emission unevenness of the light source, and the like. Therefore, there is a problem that it is difficult to see the opening of the foam cell when there is a difference in the amount of unevenness on the roller surface or a difference in the size of the foam cell depending on the manufacturing conditions of the foam roller.
JP-A-2005-274140

  The present invention provides a defect detection method for a foam roller that enables high-precision appearance inspection even when there are differences in surface irregularities due to differences in foam roller production conditions, differences in the size of foam cells, etc. And an object of the present invention.

  The defect detection method for a foam roller of the present invention includes a step of generating light in a short wavelength region from a light source of a light projecting unit, and irradiating the surface of the foam roller with light in the short wavelength region, and an image by reflected light thereof. And a step of detecting a surface defect of the foam roller by performing digital processing of an image obtained by imaging the reflected light.

  Even when there is a difference in surface irregularities due to differences in the manufacturing conditions of the foam roller, or differences in the size of the foam cells, the use of a light source that generates light in the short wavelength region enables high Accurate appearance inspection can be performed.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  As shown to (a) of FIG. 1, the foam roller 1 has the rod-shaped metal core 2 and the foaming urethane layer 3 provided in the outer peripheral part of the metal core 2 by integral molding. (B) of FIG. 1 expands the surface 4 of the urethane foam layer 3, and shows the urethane skin layer 4a and the opening 5 of the foam cell.

  FIG. 2 shows a defect detection device, which includes an inspection stage 11, a cored bar rotating mechanism 12, a cored bar gripping mechanism 13, a gripping mechanism 14, a connector box 15, a gripping / drive control device 16, and processing / processing as image processing means. It has a storage device 17 and a display device 18. Furthermore, the imaging means 21, the camera lens 22, and the light projection means 23 are provided.

  The surface defect of the foam roller 1 is detected by irradiating the foam roller 1 which is an object to be inspected with light from the light projecting means 23 and performing image processing of an image obtained by imaging the reflected light. In this apparatus, a light source such as an ultraviolet light source that emits light in a short wavelength region is used as the light source of the light projecting means 23.

  In the present embodiment, a CCD camera is used as the photographing means, and the photographing range is arranged so that the entire surface of the foam roller 1 can be set within the inspection target range.

  The CCD camera used as the imaging means uses a one-dimensional imaging CCD camera in which the pixel arrangement of the camera is a one-dimensional plane. This camera is configured to have, for example, about 5150 pixels to form one image, and the pixel has a digital gradation, and a camera that can divide the light quantity in 256 levels is selected. However, it is not limited to this camera specification as long as it is an imaging means capable of detecting a surface defect of a foam roller having foam cells opened on the surface.

  At the time of inspection, by rotating the foam roller, the imaging unit sequentially photographs the inspection target range on the surface of the foam roller, and images the entire inspection target range. Foam roller by performing image processing of the captured image, calculating position information inside the image in the image where the defect is found, and synchronizing the capture start position with the trigger in the rotating device and combining them The position information of the defective part is obtained.

  At the same time, the size of the surface defect at the defective portion, the number of surface defects in one inspection, and the like are stored and displayed.

  The light source wavelength of the light projecting means is set to a short wavelength region by utilizing the property that it is difficult to transmit short wavelengths in the transmittance characteristics of urethane. For example, by irradiating the surface of the foam roller with ultraviolet light from an ultraviolet light source that generates light in the ultraviolet region and reflecting it, the opening of the foam cell on the surface of the foam roller is accurately observed, and the difference in opening shape and size Etc. are identified.

  From the viewpoint of tolerance as a product having a urethane surface having an opening of a foam cell, an imaging unit and a light projecting unit are arranged so as not to deviate from the depth of field in the captured image. Further, in order to capture a characteristic defect image on the surface of the foam roller, it was difficult to combine the lens magnification, the lens light amount diaphragm, the light amount of the light projecting means, the frequency of the light source, the irradiation range of the light source, and the like.

  That is, when light from one light projecting means forms an image on the imaging means, it is arranged so as to be reflected by the surface of the foam roller having the opening of the foam cell, or reflected light is incident on the imaging means. There was a conforming arrangement instead of just arranging. In addition, the installation position of the light projecting unit needs to sufficiently enter the image capturing unit in the captured image range.

  For the distance between the light projecting means and the foam roller surface and the arrangement angle between the light projecting means and the foam roller surface, optimum values are obtained experimentally.

  In addition, the position of the light projecting unit is preferably in the range of 20 [mm] or more and 200 [mm] or less from the foam roller surface from the viewpoint of allowing the reflected light to be uniformly input to the imaging unit. The angle formed by the optical axis of the imaging means for imaging the foam roller surface and the light projecting means is preferably set in the range of 60 [degrees] to 150 [degrees].

  The frequency of the light source of the light projecting means must be such that the light reflected from the surface of the foam roller is not completely absorbed and is sufficiently absorbed by a defect on the surface of the foam roller to cause a difference in light quantity. There is. Therefore, from the viewpoint of making the frequency easy to extract the surface defect of the foam roller, a light source in a short wavelength region of 200 [nm] or more and 450 [nm] or less is used.

  Regarding the imageable range of the imaging means, the imaging position of the imaging means needs to be set so that the flat part of the foam roller surface falls within the imageable range, and changes occur due to the tolerance of the inspection object However, it is necessary to enter the imaging range.

  In the present embodiment, a lens whose lens magnification is adjustable from 0.05 [times] to 4.0 [times] depending on the focal length by changing the focal length from the imaging means to the foam roller that is the object to be inspected. Was used. For example, in the examples described later, the lens magnification is set to 3.0 [times], but is not limited to this value as long as the surface of the foam roller can be photographed.

  The depth of field of the imaging unit needs to be set at a position where the flat portion of the foam roller surface photographed by the imaging unit falls within the depth of field of the imaging unit. At the same time, it is necessary to enter the depth of field even when a change occurs in the height direction due to distortion of the foam roller.

  In the present embodiment, a lens that can adjust the depth of field and that can adjust the depth of field from 0.3 [mm] to 1.0 [mm] is used. As a result, the foam roller surface can be imaged regardless of tolerances, and defects can be captured as image data. For example, in the examples described later, the depth of field is set to 0.3 [mm]. However, the value is not limited to this value as long as the object can be photographed.

  FIG. 1 and FIG. 2 show an embodiment. As shown in FIG. 1A, the foam roller 1 has a core metal 2 and a urethane foam layer 3.

  FIG. 1 (b) is a plan view showing a part of the surface 4 of the foamed urethane layer 3 in a two-dimensional development, a part of the urethane skin layer 4a and a part of the foamed cells in the surface layer part of the foamed urethane. Has an opening 5 formed by opening in the surface 4.

  FIG. 2 (a) shows the entire defect detection apparatus. The inspection stage 11, the cored bar rotating mechanism 12, the cored bar gripping mechanism 13, the gripping mechanism 14, the connector box 15, the gripping / drive control device 16, the processing / It has a storage device 17 and a display device 18. Furthermore, an imaging means (one-dimensional CCD camera) 21, a camera lens 22 and a light projecting means 23 are provided.

  As shown in FIG. 2B, the light from the light projecting unit 23 is reflected on the surface of the foam roller, forms an image through the camera lens 22, and is photographed by the imaging unit 21. The photographed image is transferred to the processing / storage device 17, and the number of the transferred image is stored in the processing / storage device 17.

  As shown in FIG. 2B, the installation position of the imaging means 21 needs to be within a range where the entire surface of the foam roller 1 can be imaged in the captured image.

  About the light projection means 23, it is necessary to arrange | position in the position which reflects a foam roller surface and the light quantity reaches the imaging means 21 enough.

  Regarding the positional relationship between the light projecting means 23, the imaging means 21, and the foam roller 1 as the inspection object, when manufacturing this apparatus, the positional relationship is instructed on the drawing, and the manufactured and processed bracket is used. ing.

About the position and arrangement | positioning angle (theta) ₁ , (theta) ₂ of the imaging means 21 and the light projection means 23, between each bracket part which fixes these, and the bracket part which fixes the imaging means 21 and the light projection means 23 to the test | inspection stage 11 A commercially available fine movement stage is interposed. As a result, it is possible to finely move the θ angle and the three-dimensional axis.

The arrangement angle θ ₂ of the light projecting means 23 can be set to 0 [degrees] to 90 [degrees] by driving the bracket that fixes the light projecting means 23 and the fine movement stage. However, from the viewpoint that the light projecting unit 23 needs to be disposed at a position where the light amount reaches the imaging unit 21 by reflecting the surface of the foam roller, the range of 15 degrees or more and 60 degrees or less. Is desirable.

  Further, the angle formed by the optical axes of the imaging means 21 and the light projecting means 23 is 60 [degrees] or more from the viewpoint that the urethane skin layer 4a and the opening 5 on the surface of the foam roller can be easily discriminated. , 150 [degrees] or less is preferable.

  Further, the position of the imageable range may be a range in which the flat portion of the foam roller surface is reflected in the image to be captured, but in this embodiment, the depth of field of the camera lens 22 is the flat portion of the foam roller surface. Is set to a width that can be sufficiently covered.

  The light source wavelength of the light projecting means 23 is a light source having a wavelength of 200 [nm] or more and 450 [nm] or less, which is a short wavelength region, from the viewpoint of making the frequency at which surface defects of the foam roller 1 can be easily extracted. used.

  The light source output was 250 [w] output. When the cored bar rotating mechanism 12 is rotated at a high speed for the purpose of shortening the inspection tact, the shutter speed of the imaging means 21 is shortened in order to capture the image of the foam roller surface without blurring. At this time, 600 [w] or less is preferable in order to obtain a light quantity that facilitates extraction of surface defects of the foam roller 1. Or when using light sources, such as LED, for the cost reduction of a light source, in order to make the foam roller surface the light quantity which can be observed even when the shutter speed of the imaging means 21 is lengthened, it is 5 [w] or more. Set to light source output.

  Next, the operation will be described.

  The light projecting means 23 is supplied with power by a power supply device and a control unit (not shown).

  Upon receiving power supply, the light projecting means 23 emits a uniform amount of light. The width of the light source was about 260 [mm] in the longitudinal direction and about 10 [mm] in the lateral direction because it was necessary to irradiate the surface of the foam roller 1 uniformly.

  When there is a large hole that is recognized as a surface defect of the foam roller 1 or a defect that becomes a urethane portion without opening, this reflected light passes through the camera lens 22 and is photographed by the imaging means 21. Then, the image data is taken into the processing / storage device 17 as image data.

  The picked-up image is transferred from the image pickup means 21 to the processing / storage device 17 as an electrical signal, and stored as image data in the storage device of the processing / storage device 17.

  Thereafter, the image data is transferred to an integrated circuit for image processing.

  Since the image data photographed by the photographing device 21 uses a one-dimensional camera, the core metal rotating mechanism 12 is used to form an image while rotating the inspection object.

  As an operation of the drive unit, when an operation start signal is transmitted from the processing / storage device 17, the cored bar gripping mechanism 13 grips the cored bar 2 of the foam roller 1 placed on the cored bar rotating mechanism 12. Thereafter, the cored bar rotating mechanism 12 starts rotating at the number of rotations set by the processing / storage device 17. At the same time as the rotation is stabilized, a capture start trigger is transmitted from the processing / storage device 17 to the one-dimensional CCD camera which is the image pickup means 21. Based on the trigger, image capture is started and an image is formed simultaneously. After photographing for a time sufficient to form an image of the surface of the foam roller in the entire circumferential portion, the cored bar rotating mechanism 12 stops, and then the cored bar gripping mechanism 13 releases the gripped cored bar 2.

  The formed image is composed of about 15 million pixels, but is not limited to this camera specification as long as the surface defect of the foam roller 1 can be detected.

  The captured image is first subjected to image filter processing to remove noise and the like. This is a process of making a pixel equal to the surrounding pixel light amount when one pixel suddenly has a light amount that is significantly different from neighboring pixels, and has the effect of removing the sudden noise of the pixel. Have.

  The image data transferred to the processing / storage device 17 is binarized in which each pixel is regarded as “1” for pixels below a certain set value in 255 stages, and at the same time regarded as “0” for pixels above a certain set value. Processing is performed to digitize the pixels in the image. Thereafter, when the distance between the pixels regarded as “1” is equal to or smaller than the set distance, the pixels are connected. These digital processes are performed for each pixel, and are combined into one lump to form one island. At this time, when the interior defined as an island is hollow, a process of filling the interior to “1” is performed. This island is defined as one image processing opening.

  Further, as another process, the pixel is not digitized as in binarization and is left with 255 gradations, and in this state, a portion where the amount of change in the amount of light between adjacent pixels in the image is large (can be set) is set. 1 ”is recognized. Thereafter, when the distance between the pixels regarded as “1” is equal to or smaller than the set distance, the pixels are connected. These processes are performed for each pixel, and are combined into one lump to form one island. At this time, when the interior defined as an island is hollow, a process of filling the interior to “1” is performed. This island is defined as an image processing opening as in the above processing. By performing the above processing, the image processing opening is recognized as the opening 5 on the surface of the foam roller 1. This processing is performed by the processing device of the processing / storage device 17.

  Next, a process of characterizing and recognizing the recognized image processing opening as the actual opening 5 is performed. For the recognized aperture, the number of pixels (area) of the pixels that are configured by filling the aperture, the distance between the farthest pixels in the aperture, the roundness of the ridge line connecting the aperture, and the aperture Calculate and digitize the aspect ratio of the connected ridgeline and the length of the ridgeline connecting the openings. From these conditions, by applying to a preset conditional expression, detection should be made based on the similarity rate between the part defined as the opening and the image processing opening determined by image processing, and the existence ratio of the opening. Recognize an aperture that is a defect.

  By performing these processes, it is possible to recognize and detect a defective opening.

  When performing these image processing processes, settings such as the magnification of the camera lens 22, the installation angle of the imaging device 21, and the position of the imageable range are registered in advance in the processing device. Based on the information, position information and size of the defect are calculated on the processing / storage device 17, recorded, and output to the display device 18.

  The processing / storage device 17 is linked with the gripping / drive control device 16, controls the gripping / drive control device 16 according to the set measurement resolution, and sequentially inspects the inspection object by changing the inspection position. Is possible.

(Comparative example)
For comparison, in the apparatus of FIG. 2, θ ₁ = 38 [degrees] and θ ₂ = 30 [degrees] are set in the imaging means 21 and the light projecting means 23, and the light projecting means 23 has a light source wavelength of 380 [ A visible light halogen light source of about nm to 600 nm was used. From the viewpoint of obtaining an output that makes it easy to extract defects on the surface of the foam roller, 150 [w] was used as the output of the light source, and the same defect inspection as in the example was performed.

  The sample is an appearance defect that has a foam cell opening on the surface of the product that can be visually confirmed, and a part of the opening is largely connected. The size of the defect is approximately the same as measured by a digital microscope. Twenty pieces of about 0.5 [mm] to 1.0 [mm] were selected. By defect inspection with a halogen light source, it was possible to detect a defect portion of 8 out of 20 samples.

  On the other hand, in the above-described embodiment, it was possible to detect a defective portion of 18 out of 20 samples by the inspection using the same sample and the same detection algorithm as in the comparative example.

  From this, it can be said that the defect detection method according to the present embodiment can be accurately inspected by the method according to the comparative example.

The foam roller is shown, (a) is a perspective view showing the whole, (b) is a plan view showing a part of the surface of the foam roller enlarged and two-dimensionally developed. BRIEF DESCRIPTION OF THE DRAWINGS The structure of the defect detection apparatus by one Example is shown, (a) is a model elevation which shows the whole apparatus, (b) is a perspective view which shows only the light projection means, imaging means, and foam roller of (a). It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foam roller 2 Core metal 3 Urethane foam layer 5 Opening 11 Inspection stage 12 Core metal rotation mechanism 16 Gripping / drive control device 17 Processing / storage device 18 Display device 21 Imaging means 22 Camera lens 23 Projection means

Claims (5)

Generating light in the short wavelength region from the light source of the light projecting means;
Irradiating the surface of the foam roller with light in the short wavelength region, and capturing an image of the reflected light with an imaging means;
And a step of detecting a surface defect of the foam roller by performing digital processing of an image obtained by imaging the reflected light, and a method for detecting a defect of the foam roller.   The defect detection method for a foam roller according to claim 1, wherein the short wavelength region is 200 [nm] or more and 450 [nm] or less.   The defect detection method for a foam roller according to claim 1 or 2, wherein an output of the light source is 5 [w] or more and 600 [w] or less.   4. The foam according to claim 1, wherein an angle formed by the optical axis of the light projecting unit and the optical axis of the imaging unit is 60 [degrees] or more and 150 [degrees] or less. Roller defect detection method.   A light projecting unit that irradiates light on the surface of the foam roller, an image capturing unit that captures an image of light reflected from the foam roller, and an image processing unit that performs digital processing of the image. In the foam roller defect detection apparatus for detecting surface defects of the foam roller by performing digital processing, the light projecting means has an ultraviolet light source that generates light in the ultraviolet region. Roller defect detection device.

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