Cylindrical surface inspection device

Abstract

To provide a surface inspection device for cylindrical bodies that can inspect for various defects on the surface of cylindrical bodies with high precision using a simple device configuration. [Solution] The cylindrical surface inspection apparatus of the present invention comprises: one light irradiation means for irradiating light toward the surface of a cylindrical body that is rotating relative to it; one imaging means positioned to receive specularly reflected light, which is a portion of the irradiated light from the light irradiation means specularly reflected by the surface of the cylindrical body, and scattered light, which is another portion of the irradiated light scattered by the surface of the cylindrical body, and having a first imaging area for imaging the specularly reflected light and a second imaging area for imaging the scattered light; a light attenuation means positioned in the optical path from the light irradiation means to the first imaging area for reducing the intensity of the specularly reflected light incident on the first imaging area; and an image processing means for performing a process to detect defects from the image captured in the first imaging area and the image captured in the second imaging area, respectively.

Description

Technical Field

[0001] The present invention relates to an apparatus for inspecting the surface of a cylindrical body.

Background Art

[0002] Inspections are carried out in which defects present on the surface of a cylindrical body, such as a roll formed by winding fibers, films or the like around a cylindrical core, or a cylindrical case, are captured by a camera, and the defects are detected through image processing. In this inspection, since the defects present on the surface are diverse, it is necessary to capture images with an optical system suitable for each defect. For example, a reflective scattering optical system is suitable for adhered foreign matter, and a specular reflection optical system is suitable for dents. In order to inspect all of these types of defects, to respectively implement the reflective scattering optical system and the specular reflection optical system, an apparatus configuration is required, such as using a plurality of cameras and illuminations, or using a single camera and switching between a plurality of illuminations for imaging. These configurations have had problems such as high cost resulting from complicated apparatus structure and large installation space.

[0003] To address this problem, the surface inspection apparatus described in Patent Document 1 irradiates a cylindrical body with light from a single illumination, and images the surface of the cylindrical body with an area sensor camera via the reflected light from the surface. Since the area sensor camera can capture a wide image in the circumferential direction of the cylindrical body, it has optical systems with different light projection and receiving angles along the circumferential direction. That is, in the circumferential direction of the area sensor camera, one imaging region can be configured as a reflective scattering optical system, and another imaging region can be configured as a specular reflection optical system. Therefore, it is not necessary to prepare a plurality of cameras, the apparatus configuration can be simplified, and costs can be reduced.

Prior Art Literature

Patent Literature

[0004]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, as in Patent Document 1, when a single light source is used to realize both a reflective / scattering optical system and a specular reflection optical system, if, for example, the defect to be detected by the reflective / scattering optical system is a minute foreign object, it becomes necessary to increase the output of the light source to increase the intensity of the scattered light at the defect. However, increasing the output of the light source also increases the light intensity in the imaging region of the specular reflection optical system, causing the signal to saturate in the captured image and making inspection impossible. Patent Document 1 also describes a method using multiple lights, but this would prevent the simplification of the device configuration and the reduction of costs.

[0006] Therefore, the present invention provides a surface inspection device for cylindrical bodies that can inspect for various defects on the surface of cylindrical bodies with high precision using a simple device configuration. [Means for solving the problem]

[0007] [1] The cylindrical surface inspection device of the present invention solves the above problems. A light irradiation means that irradiates light toward the surface of a relatively rotating cylindrical body, An imaging means is positioned to receive specularly reflected light, which is a portion of the light emitted from the above-mentioned light irradiation means specularly reflected off the surface of the cylindrical body, and scattered light, which is another portion of the light emitted from the above-mentioned light irradiation means scattered off the surface of the cylindrical body, and has a first imaging area for imaging the specularly reflected light and a second imaging area for imaging the scattered light. A light-reducing means is positioned in the optical path from the light irradiation means to the first imaging region, and reduces the intensity of the specularly reflected light incident on the first imaging region. The system includes image processing means that performs a process for detecting defects in the image captured in the first imaging area and the image captured in the second imaging area.

[0008] The cylindrical surface inspection device of the present invention is preferably in any of the following embodiments [2] to [4]. [2] The cylindrical surface inspection apparatus according to [1], wherein the light-reducing means is a light-reducing plate positioned in front of the irradiation surface of the light irradiation means. [3] A surface inspection device for a cylindrical body according to [1] or [2], comprising an adjustment mechanism for adjusting the position of the light-reducing means, and a control means for controlling the adjustment mechanism to move the light-reducing means according to the diameter of the cylindrical body. [4] The system includes a second light irradiation means arranged such that a portion of the irradiated light is shielded by the surface of the cylindrical body, and the transmitted light that is not shielded is received by the imaging means, The imaging means has a third imaging region that images the transmitted light irradiated from the second light irradiation means, The image processing means performs a process to detect defects from the image captured in the third imaging region. A surface inspection device for any of the cylindrical bodies described in [1] to [3] above. [Effects of the Invention]

[0009] According to the cylindrical surface inspection device of the present invention, various defects on the surface of a cylindrical body can be inspected with high accuracy using a simple device configuration. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram of a surface inspection apparatus according to Embodiment 1 of the present invention. [Figure 2] Figure 2 is a schematic diagram showing the inspection of a large-diameter cylindrical body in the embodiment of Figure 1. [Figure 3] Figure 3 is a schematic diagram of a surface inspection apparatus according to Embodiment 2 of the present invention. [Figure 4] Figure 4 is a schematic diagram of the image obtained in Example 1. [Figure 5] Figure 5 is a schematic diagram of the image obtained in Comparative Example 1. [Figure 6] Figure 6 is a schematic diagram of the image obtained in Comparative Example 2. [Figure 7] Figure 7 is a schematic diagram of the image captured in Example 2. [Modes for carrying out the invention]

[0011] The following describes embodiments for implementing the cylindrical surface inspection device of the present invention with reference to the drawings. However, the present invention is not limited to these embodiments.

[0012] [Embodiment 1] Refer to Figure 1. Figure 1 is a schematic diagram of a surface inspection apparatus according to Embodiment 1 of the present invention. The surface inspection apparatus 1a consists of a light irradiation means 2, an imaging means 3, a light reduction means 4, and an image processing means 5. Light is irradiated onto the cylindrical body 10 from the light irradiation means 2, the light reflected from the surface of the cylindrical body 10 is captured by the imaging means 3, and defects in the cylindrical body 10 are detected by the image processing means 5 based on the captured image. The light reduction means 4 will be described later.

[0013] The cylindrical body 10 may be made by winding fibers, film, paper, etc., around a cylindrical core, or it may be a cylindrical case, and it rotates relative to the light irradiation means 2 and the imaging means 3. In this embodiment 1, the cylindrical body 10 rotates while maintaining its positional relationship with the light irradiation means 2 and the imaging means 3. The light irradiation means 2 may be an LED, halogen, metal halide, fluorescent lamp, etc., and may irradiate in a strobe-like manner, and the wavelength band used may be arbitrary. The imaging means 3 is preferably a sensor in which light-receiving elements are arranged in two dimensions, for example, an area sensor camera is suitable. In this embodiment 1, an area sensor camera is used. The light-reducing means 4 is preferably a light-reducing plate that reduces the amount of light. As the light-reducing means 4, a polarizing filter that reduces only light vibrating in a specific direction, an interference filter that selectively reduces light of a specific wavelength, or a variable ND filter that can reduce light while adjusting the amount of light may be used. The image processing means 5 creates an image corresponding to the light intensity captured by the imaging means 3, and performs image processing such as smoothing, enhancement, and binarization on the image to detect defects based on size, shape, etc.

[0014] In FIG. 1, the light emitted from the light irradiation means 2 is reflected on the surface of the cylindrical body 10, and the optical system that is reflected and enters the imaging means 3 differs depending on the irradiation position on the cylindrical body 10. Specifically, the regular reflection light 2a forms a regular reflection optical system, and the scattered light 2b forms a reflection scattering optical system. Here, the imaging means 3 is an area sensor camera, and the light receiving elements that respectively image the regular reflection light 2a and the scattered light 2b are different. Therefore, in one captured image, a first imaging region imaged by the regular reflection optical system and a second imaging region imaged by the reflection scattering optical system are formed. In this case, when it is desired to increase the intensity of the scattered light 2b in order to improve the detection sensitivity of foreign matter adhering to the surface of the cylindrical body 10, it is necessary to increase the output of the light irradiation means 2. However, when the output of the light irradiation means 2 is increased, the intensity of the regular reflection light 2a becomes excessively high in the first imaging region which is the regular reflection optical system, so that the signal of the captured image is saturated and inspection by regular reflection cannot be performed. Therefore, a light reducing means 4 is provided in the middle of the optical path of the regular reflection optical system from the light irradiation means 2 to the cylindrical body 10, to prevent signal saturation in the first imaging region and adjust the light intensity to a level that enables inspection by regular reflection. By this means, appropriate light illuminance that enables inspection in each of the regular reflection optical system and the reflection scattering optical system is obtained, and various defects on the surface of the cylindrical body 10 can be inspected. Note that the light reducing means 4 may be provided in the middle of the optical path of the regular reflection optical system from the cylindrical body 10 to the imaging means 3.

[0015] Reference is made to FIG. 2. FIG. 2 is a schematic diagram showing a state in which a cylindrical body 10' having a larger diameter than the cylindrical body 10 is inspected in Embodiment 1 of FIG. 1. When the diameter of the cylindrical body 10 changes, the position at which the imaging means 3 captures an image via the regular reflection optical system changes. As shown in FIG. 2, for the cylindrical body 10' having a larger diameter than the cylindrical body 10, the regular reflection optical system incident on the imaging means 3 follows the optical path denoted by reference numeral 2c instead of the optical path denoted by reference numeral 2a. The position of the regular reflection light 2c in the light irradiation means 2 is different from that of the regular reflection light 2a in the cylindrical body 10 of FIG. 1, so it is necessary to adjust the position of the dimming means 4. For example, there is a method comprising: removing the dimming means 4, increasing the output of the light irradiation means 2 in this state, identifying a saturated imaging region in a captured image captured by the imaging means 3, determining that the imaging region corresponds to the regular reflection optical system, and then placing the dimming means 4 or adjusting the position thereof so that the signal value in the imaging region is reduced. In addition, when the cylindrical body 10 gradually increases in diameter over time as it is wound, it is preferable to enable automatic adjustment of the position of the dimming means 4 following the movement of the optical path of the regular reflection optical system. Note that the adjustment mechanism and control means for adjusting the position of the dimming means 4 are not illustrated in FIG. 1 and FIG. 2.

[0016] Reference is made again to FIG. 1. When rotation blurring occurs due to, for example, eccentricity of the cylindrical body 10, the positions of the first imaging region and the second imaging region change within the captured image. To address this problem, there is a method such that the dimming means 4 is designed to have a certain width in the circumferential range of the cylindrical body 10 to be dimmed, and the image processing means 5 is provided with a function of automatically setting the first imaging region and the second imaging region according to signal values in the captured image.

[0017] [Embodiment 2] Refer to Figure 3. Figure 3 is a schematic diagram of a surface inspection apparatus of Embodiment 2 of the present invention. Surface inspection apparatus 1b is configured by adding a second light irradiation means 20 to the surface inspection apparatus 1a of Figure 1. The second light irradiation means 20 is installed to form a transmission optical system that causes light shielding on the surface of the cylindrical body 10, and the imaging means 3 images the transmitted light 2d that is not shielded. In this surface inspection apparatus 1b, the imaging means 3 simultaneously images light that has passed through three optical systems: a specular reflection optical system using specular reflection light 2a, a reflection-scattering optical system using scattered light 2b, and a transmission optical system using transmitted light 2d, making it possible to inspect various defects using each optical system. [Examples]

[0018] Next, examples and comparative examples of the present invention will be described. However, the present invention is not limited to the following examples.

[0019] [Example 1] Surface inspection of the cylindrical body 10 was performed in Embodiment 1 shown in Figure 1. The cylindrical body 10 is a bobbin in which a fiber bundle is wound around a cylindrical resin core, and is placed on a rotating stage that rotates once every 10 seconds. The light irradiation means 2 uses LED bar illumination, and the longitudinal direction of the bar illumination is approximately aligned with the longitudinal direction of the bobbin. The imaging means 3 uses an area sensor camera, and the imaging resolution is set to 50 μm. The cylindrical body 10 rotates while maintaining its relative positional relationship with the light irradiation means 2 and the imaging means 3. A light-reducing plate is used as the light-reducing means 4, and the longitudinal direction of the light-reducing plate is approximately aligned with the longitudinal direction of the bobbin. The defects to be detected are dents and attached foreign matter, with dents being detected by specular reflection optical system and attached foreign matter by reflection scattering optical system.

[0020] First, with the dimming means 4 removed, the output of the light irradiation means 2 was increased, and the first imaging region, which is a specular reflection optical system, was examined in the image captured by the imaging means 3. In the 8-bit image, the signal value of the first imaging region was saturated at 255, and the dimming means 4 was installed there to reduce the signal value to approximately 180. At this time, the signal value of the second imaging region, which is a reflection-scattering optical system, was approximately 10.

[0021] When the bobbin was inspected in this state, the image shown in Figure 4 was obtained. The indentation 6 had an average signal value of 120 in the image taken in the first imaging region A1, and the attached foreign matter 7 had an average signal value of 50 in the image taken in the second imaging region A2, confirming that stable inspection was possible.

[0022] [Comparative Example 1] Except for removing the dimming means 4, the inspection was performed with the same apparatus configuration, the same cylindrical body 10, and the same conditions as in Example 1.

[0023] Upon inspecting the bobbin, the image shown in Figure 5 was obtained. The indentation 6 could not be inspected because the signal value in the first imaging region A1 was saturated, while the attached foreign object 7 was detected in the image acquired in the second imaging region A2 with an average signal value of 55.

[0024] [Comparative Example 2] Except for removing the dimming means 4, the same apparatus configuration and the same object to be inspected were used for the inspection as in Example 1. The output of the light irradiation means 2 was lowered compared to Example 1, and the average signal value in the image captured in the first imaging region, which is a specular reflection optical system, was adjusted to 180.

[0025] Upon inspecting the bobbin, the image shown in Figure 6 was obtained. The indentation 6 was detected with an average signal value of 110 in the image taken in the first imaging region A1, but the attached foreign matter 7 could not be inspected.

[0026] [Example 2] Surface inspection of the cylindrical body 10 was performed in Embodiment 2 shown in Figure 3. The inspection was performed with the same apparatus configuration, the same cylindrical body 10, and the same conditions as in Embodiment 1, except that a second light irradiation means 20 was added. The second light irradiation means 20 formed a transmission optical system with the imaging means 3 and was installed so that a portion of it was shielded from light on the surface of the cylindrical body 10. The defects targeted were dents, attached foreign matter, and fuzz. Fuzz was detected as a dark defect by the transmission optical system.

[0027] The output of the second light irradiation means 20 was adjusted to set the average signal value of the third imaging region in the image captured by the imaging means 3 to 120.

[0028] Upon inspecting the bobbin, the image shown in Figure 7 was obtained. In addition to the indentation 6 and attached foreign matter 7, the fluff 8 was confirmed to be stably inspected with an average signal value of 40 in the image captured in the third imaging region A3. [Explanation of Symbols]

[0029] 1a, 1b Surface inspection device 10, 10' cylindrical body 2 Light irradiation means 2a Specular reflection light 2b Scattered light 2c Specular reflection light 2d transmitted light 20 Second light irradiation means 3. Imaging means 4. Light-reducing means 5 Image processing means 6. Dent 7. Adhering foreign matter 8. Fluff A1 First imaging area A2 Second imaging area A3 Third imaging area

Claims

1. A light irradiation means that irradiates light toward the surface of a relatively rotating cylindrical body, An imaging means is positioned to receive specularly reflected light, which is a portion of the light emitted from the light irradiation means specularly reflected off the surface of the cylindrical body, and scattered light, which is another portion of the light scattered off the surface of the cylindrical body, and has a first imaging area for imaging the specularly reflected light and a second imaging area for imaging the scattered light. A light-reducing means is positioned in the optical path from the light irradiation means to the first imaging region, and reduces the intensity of the specularly reflected light incident on the first imaging region. Image processing means for performing a process to detect defects from the image captured in the first imaging area and the image captured in the second imaging area, A surface inspection device for cylindrical bodies, equipped with the following features.

2. The cylindrical surface inspection apparatus according to claim 1, wherein the light-reducing means is a light-reducing plate positioned in front of the irradiation surface of the light irradiation means.

3. A cylindrical surface inspection apparatus according to claim 1, comprising: an adjustment mechanism for adjusting the position of the dimming means; and a control means for controlling the adjustment mechanism to move the dimming means according to the diameter of the cylindrical body.

4. The system includes a second light irradiation means arranged such that a portion of the irradiated light is shielded by the surface of the cylindrical body, and the transmitted light that is not shielded is received by the imaging means. The imaging means has a third imaging region for imaging the transmitted light irradiated from the second light irradiation means, The image processing means performs a process to detect defects from the image captured in the third imaging region. A surface inspection apparatus for a cylindrical body according to claim 1.

Images