JP2012173194A - Surface inspection device, surface inspection method, and film manufacturing devise - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that it is not possible to accurately detect minute irregular defects occurring on a surface of an inspection object in which the surface of the inspection object is a side surface of a cylinder and has mirror reflectivity, and at least one of curvature of the surface of the inspection object rotating relative to a central cylindrical axis and positions of the surface of the inspection object changes temporally.SOLUTION: A surface inspection device includes light radiation means for radiating light of a bright/dark pattern to the inspection object, imaging means for imaging the bright/dark pattern reflected by the inspection object, and data processing means for inspecting the surface of the inspection object based on an imaged image having the bright/dark pattern imaged by the imaging means. The data processing means compares bright/dark pattern regions in respective images in two images successively imaged by the imaging means. Consequently, minute irregular defects are detected accurately.

Description

  The present invention relates to a surface inspection apparatus, a surface inspection method, and a film manufacturing method.

  In general, when inspecting uneven defects present on the surface of an object to be inspected, a method of detecting unevenness defects on the surface by irradiating the object with light and referring to the state of reflected light is often used. Yes. Specifically, the methods described in Patent Documents 1 and 2 are known.

The method described in Patent Document 1 will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing the apparatus configuration of the inspection apparatus described in Patent Document 1. In FIG. 1, 1 is a light irradiation means, 2 is a to-be-inspected object, 3 is an imaging means, 4 is a data processing means, 5 is an external output means. FIG. 2 is an image illustrating an image processing method used in the inspection apparatus described in Patent Document 1.
Patent Literature 1 irradiates a light to be inspected with light having brightness of a light and dark pattern, images reflected light on the surface of the object to be inspected, and obtains a light and dark pattern previously created from information on spatial frequencies in the obtained captured image. By comparing with the master, the distortion of the light and dark pattern is extracted, and the uneven defect that caused the distortion is detected.

  The method described in Patent Document 2 will be described with reference to FIG. FIG. 3 is a diagram illustrating an image processing method used in the inspection apparatus described in Patent Document 2.

  Patent document 2 extracts only a component having a high frequency region and a level of a predetermined value or more as a defect candidate region from among the spatial frequency components in the image data obtained by illuminating a light / dark pattern, and the defect candidate The area of each region is calculated. In order to prevent detection of extremely thin irregularities called yuzu skin as defects for the area calculated above, only the defect candidate area with the area satisfying the predetermined condition is expanded or processed after being processed in the order of expansion and contraction. Whether or not the defect candidate area is a defect is determined based on the area of the candidate area. This method is premised on that when inspecting the entire surface to be inspected, the object to be inspected or the illumination means and the imaging means are sequentially moved so that the field of view of the camera scans the entire surface to be inspected.

JP 2007-71562 A Japanese Patent No. 3159063

  Patent Document 1 is a method of cutting a spatial frequency component corresponding to a light and dark pattern. However, according to the knowledge of the present inventors, this method is based on the premise that the area of pattern distortion in the image is large like wrinkles generated in the circumferential direction. Very little of this area occurs. Therefore, if the spatial frequency component is cut, distortion due to fine unevenness does not remain and it is difficult to detect.

  According to the knowledge of the inventors of Patent Document 2, since the vicinity of the boundary of the light / dark pattern is integrated using the expansion / contraction means, the fine protrusion defect generated at the boundary cannot be detected. Therefore, in order to inspect the entire surface to be inspected, it is necessary to sequentially move the object to be inspected or the illuminating unit and the imaging unit. In an environment where the illuminating unit and the imaging unit cannot move, it is possible to inspect the vicinity of the boundary of the light / dark pattern. Can not.

  In view of the above, the object of the present invention is to solve the above-mentioned problems of the prior art, and to accurately detect fine irregularities on the surface of the object to be inspected having specular reflection without moving the object to be inspected or the illumination means and the imaging means. An object of the present invention is to provide a surface inspection apparatus and a surface inspection method that can be well detected.

  In order to achieve the above object, the surface defect detection apparatus of the present invention has the following configuration.

  That is, the surface to be inspected is a cylindrical side surface and has specular reflectivity, and the curvature corresponding to the surface to be inspected and / or the position of the surface to be inspected changes with time, which rotates with respect to the central axis of the cylinder. A light irradiating means for irradiating a body with a light / dark pattern light, an imaging means for capturing the light / dark pattern reflected from the object to be inspected by the irradiated means, and a captured image including the light / dark pattern imaged by the imaging means. In the surface inspection apparatus comprising data processing means for inspecting the surface of the object to be inspected on the basis of the data processing means, the data processing means uses the image pickup means to obtain a plurality of captured images whose positions are different from each other in the circumferential direction of the object to be inspected. A surface inspection apparatus comprising defect detection means for detecting a surface defect of the object to be inspected by comparing reflected images of light and dark patterns in the plurality of captured images. It is subjected.

  Further, according to a preferred aspect of the present invention, it is characterized in that it has a control means for controlling the imaging cycle of the imaging means so as to change according to a change in at least one of the diameter and rotation speed of the object to be inspected. A surface inspection apparatus is provided.

  According to a preferred aspect of the present invention, there is provided a surface inspection apparatus characterized in that a boundary of a light / dark pattern possessed by the light irradiation means continuously changes with respect to a rotation axis direction of the object to be inspected. .

  Further, according to a preferred embodiment of the present invention, the surface to be inspected is a cylindrical side surface having specular reflectivity, the curvature corresponding to the surface to be inspected rotating with respect to the central axis of the cylinder, and the position of the surface to be inspected. A light irradiating step of irradiating an object to be inspected, at least one of which changes with time, a light / dark pattern light, an imaging step of imaging the light / dark pattern reflected from the object to be inspected, and the light / dark pattern imaged by the imaging means A data processing step for inspecting the surface of the object to be inspected based on a captured image including the image processing method, wherein the data processing step includes the object to be inspected among the captured images captured in the imaging step. A defect detection step of detecting a surface defect of the inspection object by comparing light and dark patterns of a plurality of captured images having different positions with respect to the circumferential direction of Surface inspection method according to symptoms is provided.

  Moreover, according to the preferable form of this invention, the surface inspection method in which the imaging period of the said imaging step changes according to the change of the diameter and / or rotation speed of the said to-be-inspected object is provided.

  Also, according to a preferred embodiment of the present invention, the light irradiation step comprises light having a stripe pattern that can image defects appearing at different locations in the circumferential direction when imaged at different times at a portion that is not a boundary. A surface inspection method for irradiating is provided.

  Moreover, according to the preferable form of this invention, the manufacturing method of the film characterized by inspecting the unevenness | corrugation of the surface of a to-be-inspected object is provided using said surface inspection method.

  In the present invention, the “surface to be inspected” refers to the surface of an object to be inspected that reflects light from the light emitting portion when the imaging means images the light emitting portion of the light irradiation means.

  In the present invention, “specular reflection” means that when an object is irradiated with light, the light is reflected to such an extent that a defect in the reflected image can be recognized even if the light is not completely reflected.

  In the present invention, the “curvature corresponding to the surface to be inspected” refers to the reciprocal of the arc radius of the cylinder that is the object to be inspected.

  According to the present invention, as will be described below, a surface inspection apparatus and a surface inspection method for accurately detecting minute irregularities on the surface of an object to be inspected including a portion having a cylindrical side surface and having specular reflectivity are realized. it can.

1 is a schematic configuration diagram showing a device configuration in an embodiment of Patent Document 1. FIG. 10 is an explanatory diagram of an image processing method of Patent Document 1. FIG. 10 is an explanatory diagram of an image processing method of Patent Document 2. FIG. It is a schematic block diagram which shows the apparatus structure in one Embodiment of this invention. It is a perspective view which shows the structural example of the light irradiation means 1 in one Embodiment of this invention. 6 is a flowchart of the image processing means 6. FIG. It is a block diagram when the to-be-inspected object 2 in one Embodiment of this invention does not have an uneven | corrugated defect. It is a schematic diagram of the captured image I3 in one Embodiment of this invention. It is a block diagram in case the to-be-inspected object 2 in one Embodiment of this invention has an uneven | corrugated defect. It is a schematic diagram of the captured image I4 in one Embodiment of this invention. It is explanatory drawing of the uneven | corrugated defect detection in one Embodiment of this invention. It is a block diagram of the to-be-inspected object 2 and the imaging means 3 in one Embodiment of this invention. It is explanatory drawing when the imaging cycle in one Embodiment of this invention synchronizes with the imaging position of roll rotation. It is explanatory drawing when the imaging period in one Embodiment of this invention is optimized. It is a schematic diagram of the captured image I1 when the boundary of the light and dark pattern in one Embodiment of this invention corresponds with the circumferential direction. It is a schematic diagram of the captured image I2 when the boundary of the light-dark pattern in one Embodiment of this invention corresponds with the circumferential direction. It is a light-dark pattern schematic diagram of the light irradiation means 1 in one Embodiment of this invention. It is a schematic diagram of the image imaged when the light and dark pattern in one Embodiment of this invention was changed with respect to the rotating shaft direction. It is explanatory drawing when the light-and-dark pattern in one Embodiment of this invention is changed with respect to the rotating shaft direction. It is a schematic diagram of the light-dark pattern using the curve of the light irradiation means 1 in one Embodiment of this invention. It is a schematic diagram of the light-and-dark pattern using the some straight line of the light irradiation means 1 in one Embodiment of this invention. 6 is a calculation graph of a winding length and an imaging cycle in Example 2.

  Hereinafter, the best embodiment of the present invention will be described with reference to the drawings, taking as an example the case of detecting fine unevenness defects generated on the surface of a transparent plastic film roll wound up in a cylindrical shape.

  The apparatus configuration of the embodiment will be described with reference to FIG. FIG. 4 is a schematic apparatus configuration diagram of the embodiment. Reference numeral 1 denotes a light irradiating means having a light emitting part A having a bright and dark pattern, and is configured to irradiate light on the surface of the inspection object 2. Reference numeral 2 denotes an object to be inspected, here a transparent plastic film roll. Reference numeral 3 denotes an imaging unit, which is installed so as to capture the reflected light of the light L1 emitted from the light irradiation unit 1 on the surface of the inspection object 2.

  The imaging unit 3 in the embodiment is capable of adjusting zoom and focus by receiving a control signal from the outside. The image pickup means 3 is connected to the data processing means 4 and can send an image picked up by the image pickup means 3 from the image pickup means 3 to the data processing means 4 and adjust the zoom and / or focus of the image pickup means 3. The control signal can be received from the data processing means 4. The data processing means 4 is connected to an external output means 5 such as a display, a printer, an alarm device, etc., and outputs information on the irregularities on the surface of the inspected object 2 detected based on the image received from the imaging means 3 to the external output. It can be transmitted to the means 5.

  Next, the light irradiation means 1 is demonstrated using FIG. FIG. 5 is a perspective view illustrating a configuration example of the light irradiation unit 1. The light irradiation means 1 has a structure having a light emitting portion A having a bright and dark pattern, and irradiates the object 2 with light L1 having a brightness of a striped bright and dark pattern. The light irradiating means 1 has, for example, a light source unit 6 having a light source that emits light from a plane having a rectangular outer shape as shown in FIG. 5 and a light / dark pattern light creating means 7 in which a light transmitting part and a light shielding part are arranged. Things can be used.

  Next, the imaging means 3 will be described with reference to FIG. The image pickup means 3 picks up the light irradiation means 1 through the surface of the inspection object 2 and transmits the picked up image to the data processing means 4. The shutter speed of the image pickup means 3 is desirably 1/5000 second or more. The camera can use interlace or non-interlace. Further, it is desirable that the imaging cycle of the imaging means 3 is 200 milliseconds or less. Further, the imaging means 3 can enter the imaging visual field from the light irradiation means 1 and reflected by the plastic film roll from the beginning to the end of winding of the plastic film roll as the object 2 to be inspected. Is. If the bright and dark pattern enters the imaging field, the arrangement of the light irradiation unit 1 and the imaging unit 3 may not be the same as the incident angle and the reflection angle with respect to the surface to be inspected. Moreover, the focus of the imaging means 3 must be suitable for the light emission site | part A which has a light-dark pattern. Further, the image pickup means 3 in the embodiment can adjust zoom and focus by an external control signal, and adjusts the zoom and / or focus when receiving a control signal from the data processing means 4. . The data processing unit 4 includes an image processing unit 6 and an imaging adjustment unit 7.

  Next, the image processing means 6 will be described with reference to FIG. The image processing means 6 acquires two images that are continuous by the imaging means 3. The two images to be imaged at this time must be images having different positions in the roll circumferential direction at the time of imaging. If the positions in the roll circumferential direction are different at the time of imaging, the images need not always be two consecutive images. Moreover, if the amount of movement in the roll circumferential direction is more than the vertical width of the concave and convex defect, the concave and convex defect may appear in both of the two images. As for the imaging cycle when acquiring an image, in addition to the method of performing automatic control by a method described later, an imaging cycle that satisfies different conditions in the roll circumferential direction may be manually set. After obtaining two images, binarization processing is performed on each image. Difference processing is performed between the two binary images after the binarization processing, and an area satisfying the feature of the unevenness defect is detected as an unevenness defect in the image after the difference processing.

  Further, before performing the binarization process, a process such as noise removal may be used on the captured image.

  Next, the imaging adjustment unit 7 obtains zoom and focus adjustment amounts at the beginning and end of winding of the plastic film roll in a state where the light and dark pattern is focused through the roll surface, and the obtained value By interpolating the adjustment amount between the winding start and the winding end, the inspection can be performed within a predetermined imaging range and the pattern can be focused.

  Alternatively, an intermediate zoom focus amount may be obtained in advance and an interpolation method may be used.

  Hereinafter, a method for detecting fine irregularities on the surface of the inspection object 2 using this apparatus will be described. A convex defect occurs as a convex defect on the roll surface by winding the film on a foreign substance adhering to the film. In addition, since the film is thin, the convex shape remains even if it is rolled up, and several tens of layers remain depending on the thickness of the film. Therefore, it is only necessary that the convex defect can be imaged while the roll is rotating several tens of times. Utilizing this feature, a fine irregularity defect is detected by the following method. First, two images of the light and dark pattern reflected on the roll surface are obtained in succession. As will be described later, since the imaging interval between the two images taken during one rotation is short, they do not become the same position in the roll rotation direction. If the two images have no irregularities when imaged as shown in FIG. 7, the light / dark pattern does not change as shown in FIG. If there is a defect at the time of imaging as shown in FIG. 9, the light / dark pattern is distorted at the place where the defect exists as shown in FIG. Therefore, a fine unevenness defect is detected by comparing two light and dark patterns captured successively.

  First, the captured image will be described. First, for obtaining two captured images, it is desirable that the diameter of the object to be inspected hardly changes. The imaging interval needs to be set so that the roll rotation period does not become an integral multiple of the imaging period. In addition, as a method of acquiring two captured images, a method of acquiring in as short a time as possible with a non-interlaced camera, or after capturing one image with an interlaced camera, two images are divided into odd lines and even lines. There are methods. In general, an interlace camera captures one image at a period of 33 msec, but the odd and even lines are separated by 16 msec. When these two images have no defects on the roll surface as shown in FIG. 7, a bright and dark pattern is imaged as shown in FIG. However, when the roll surface is uneven as shown in FIG. 9, the reflection angle changes depending on the inclination of the uneven surface, so that an image having a change in the light and dark pattern at the uneven portion as shown in FIG. Since it is very unlikely that the unevenness defect exists in exactly the same position in the two images, when the difference between the two images is obtained, only the unevenness defect is emphasized as shown in FIG. By the above method, fine irregularities on the roll surface can be detected.

  Next, the timing for acquiring an image will be described with reference to FIGS. FIG. 12 is a configuration diagram of the device under test 2 and the imaging means 3. In this method, since the fine unevenness defect detection process is performed after imaging, when the roll is rotating at high speed, a non-inspected area x that is not captured occurs from the time lag until the next imaging. Although the non-inspection region x exists in the roll circumferential direction, as described above, the convex defect exists over several tens of layers, so it is only necessary to detect the defect while the roll is rotating several tens of times. However, as shown in FIG. 13, if the roll rotation period is an integral multiple of the imaging period, the same position on the roll surface is continuously imaged, so the entire roll circumference cannot be inspected. Since the diameter of the roll increases as it rolls, it does not continue to image the exact same position as described above, but it may take tens of laps to inspect the entire circumference. For this reason, there is a risk of overlooking while a defect occurs. Ideally, as shown in FIG. 14, it is preferable to adjust the imaging cycle so that the imaging ranges do not overlap. By doing so, the entire circumference of the roll can be imaged at the minimum number of rotations.

The core diameter d, the outer diameter D, the winding length L, the film thickness u, the film traveling speed v, the bright / dark pattern imaging range H _s in the circumferential direction of the imaging means 3, the imaging interval moving distance P ₁ , imaging Using the period P _{2 of} time and the number of times of imaging n, P ₂ is obtained from Expression (1), Expression (2), and Expression (3) by Expression (4). It acquires a test L, by determining a P ₂ from equation (4), overlapping the image regardless of the outer diameter D can little inspection.

  Next, the light / dark pattern will be described. When the boundary between the light and dark patterns is parallel to the circumferential direction and the uneven defect exists in the middle of the light and dark pattern as shown in FIG. 15, the size of the uneven defect can be obtained. However, as shown in FIG. 16, when there are uneven defects at the boundary between the light and dark patterns, the traces of the uneven defects in the captured image are interrupted at the light and dark pattern boundaries, and the size of the uneven defects is accurate regardless of how many times the roll rotates. Can not ask for. Therefore, it is a preferable form that the light and dark pattern is changing in the width direction of the roll. Therefore, by using a light / dark pattern that can image unevenness defects appearing in different places in the circumferential direction when imaged at different times as shown in FIG. 17 at a portion that is not a boundary between light and dark, a roll as shown in FIG. Since it is possible to capture an image in which the concave / convex defect does not contact the light / dark pattern boundary during the rotation, the size of the concave / convex defect may be obtained by obtaining the maximum area size among the plurality of captured images. A method for obtaining the maximum area of the irregularities and the detection duration will be described. It is assumed that only one piece is generated in the circumferential direction from the occurrence of the uneven defect until the defect disappears. First, when the uneven defect is detected, the detected position in the roll width direction is confirmed. If the confirmed position in the roll width direction is the same as the position in the roll width direction detected in the past, it is regarded as the same uneven defect, and the detection duration time is updated based on the determination of the maximum area and the initial detection time. When the irregularity defect disappears due to the winding of the roll and it can no longer be detected, the position and area in the roll width direction of the defect, the initial detection time and the detection duration time are recorded, and the information used in the confirmation and determination of the detection result is Reset. When the above method is carried out, the defect occurs over several tens of layers, so that the defect can be detected a plurality of times at the same position in the roll width direction. Since the defect having a larger size has a longer convex shape, the defect size can be determined based on the detection duration.

  The light / dark pattern may be determined according to the size of the defect and the slope. As shown in FIG. 19, by changing the boundary between the light and dark patterns with respect to the rotation axis direction, it is possible to image the uneven defect that does not contact the pattern boundary, and the area of the uneven defect can be calculated with high accuracy.

  Further, as shown in FIG. 20, the light / dark pattern may be a curve.

  As shown in FIG. 21, the light / dark pattern may be a combination of a plurality of straight lines.

[Example 1]
The device under test 2 in this embodiment is formed of a tube called a core and a transparent plastic film wound around the core. The traveling speed when the inspection object 2 was rolled up by rotation was 100 m / min. As a light irradiation means, a light source unit of 2000 mm × 500 mm × 100 mm equipped with a fluorescent lamp is used. Immediately after the irradiation surface of the light source unit 1, there are a 10 mm light transmitting portion and a 10 mm light shielding portion corresponding to a light / dark pattern creating means. A transparent acrylic plate printed with alternating light and dark stripe patterns was installed. As an imaging means, a CCD area sensor camera of 480 pixels × 640 pixels in an interlaced format was used, and it was installed so as to have a camera resolution of 0.5 mm. As a data processing means, an image of a light and dark pattern captured by an interlaced area sensor camera was separated into even line and odd line images having different camera scan timings. For each separated image, the bright and dark areas are clarified by binarization, and the unevenness defects of 1 mm or more generated on the surface of the plastic film roll are detected by comparing the light and dark areas of the even and odd lines. We were able to.
[Example 2]
Next, the effect of the image acquisition timing in the present embodiment will be shown. For the object 2 to be inspected, the plastic film roll outer diameter D was φ600 mm, and the film running speed when winding up by rotation was 120 m / min. As the imaging means, using the CCD area sensor camera trigger input expression that can arbitrarily change the period of the imaging time, the circumferential direction of the light-dark pattern imaging range H _s is 50mm imaging means 3, the period P ₂ of the imaging time Figure The value was calculated from the equation (4) as shown in FIG. As a result, the entire circumference of the roll could be inspected by rotation.
[Example 3]
Next, when the inclination of the light and dark stripe pattern is 90 °, it is defined that it coincides with the circumferential direction. When the inclination of the light and dark stripe pattern is set to 80 °, the image taken until the plastic film roll rotates 80 times The size of the irregular defect could be obtained.

The present invention is not limited to a method and apparatus for inspecting irregularities on a transparent plastic film roll having a curved surface, but also a method and apparatus for inspecting scratches on the surface of a steel sheet, or a roll of film-like material whose surface is coated with a high light reflectance material. Although it can be applied to the above unevenness inspection apparatus, the application range is not limited to these.

DESCRIPTION OF SYMBOLS 1 Light irradiation means 2 To-be-inspected object 3 Imaging means 4 Data processing means 5 External output means 6 Image processing means 7 Imaging adjustment means 8 Light source unit 9 Bright / dark pattern light creation means A Light emission site B Concavity and convexity C Roll surface I1 Concavity and convexity are light and dark Captured image when it is at the pattern boundary I2 Captured image when the uneven defect is inside the light-dark pattern I3 Captured image when the test object has no uneven defect I4 Captured image when the test object has no uneven defect I5 Captured image L1 Irradiation light P Bright / dark pattern d Roll core diameter of the inspection object 2 D Roll outer diameter of the inspection object 2 L Winding length of the inspection object 2 u Film thickness of the inspection object 2 v Film travel speed of the inspection object 2
Brightness / darkness pattern imaging range in the circumferential direction of the H _s imaging means 3
Moving distance of P ₁ imaging interval
P ₂ Imaging time period n Number of imaging times x Non-inspection area

Claims (7)

Inspected object in which at least one of a curvature corresponding to the inspected surface rotating with respect to the central axis of the cylinder and a position of the inspected surface changes with time, and the inspected surface is a cylindrical side surface A light irradiation means for irradiating light of a light / dark pattern, an image pickup means for picking up the light / dark pattern reflected from the object to be inspected, and the inspection object based on a captured image including the light / dark pattern picked up by the image pickup means And a data processing means for inspecting the surface of the imaging device, wherein the data processing means is a plurality of imagings whose positions differ from the circumferential direction of the object to be inspected among the captured images captured by the imaging means. A surface inspection apparatus comprising defect detection means for detecting a surface defect of the inspection object by comparing light and dark patterns of images. The surface inspection apparatus according to claim 1, further comprising a control unit that controls an imaging cycle of the imaging unit so as to change according to a change in at least one of a diameter and a rotation speed of the object to be inspected. 3. The surface inspection apparatus according to claim 1, wherein a boundary between light and dark patterns of the light irradiation unit is a pattern that continuously changes with respect to a rotation axis direction of the object to be inspected.   Inspected object in which at least one of a curvature corresponding to the inspected surface rotating with respect to the central axis of the cylinder and a position of the inspected surface changes with time, and the inspected surface is a cylindrical side surface A light irradiation step of irradiating light of a light / dark pattern, an imaging step of capturing the light / dark pattern reflected from the object to be inspected, and the inspected object based on a captured image including the light / dark pattern imaged by the imaging means And a data processing step for inspecting the surface of the test object, wherein the data processing step includes a plurality of different positions of the captured image captured in the imaging step with respect to a circumferential direction of the object to be inspected. And a defect detection step of detecting a surface defect of the object to be inspected by comparing the light and dark patterns of the captured images.   The surface inspection method according to claim 4, wherein an imaging cycle of the imaging step is changed according to a change in a diameter and / or a rotation speed of the inspection object.   5. The light irradiating step irradiates light having a stripe pattern that can image defects appearing at different locations in the circumferential direction when images are taken at different times at portions that are not boundaries. The surface inspection method in any one of -5.   A method for producing a film, wherein the surface irregularity of the surface of the object to be inspected is inspected using the surface inspection method according to claim 4.

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