Surface inspection apparatus and surface inspection method

Abstract

In the present invention, a magnetization unit magnetizes an object to be inspected. A magnetic powder adhesion unit causes magnetic powder to adhere to the magnetized object through the application of a magnetic powder liquid. An illumination unit illuminates, with ultraviolet light, a space which includes the object. An image capture unit: generates a first captured image by capturing an image of the surface of the object to which the magnetic powder has adhered through a first optical filter for transmitting a first wavelength, which is the wavelength of the ultraviolet light, in the space illuminated with the ultraviolet light; and generates a second captured image by capturing an image through a second optical filter for transmitting a second wavelength, which is the wavelength of excitation light from the magnetic powder having undergone excitation by the ultraviolet light. An inspection unit inspects a visible first surface property of the surface of the object on the basis of the first captured image and inspects, on the basis of the second captured image, a second surface property that can be visually identified by magnetic particle inspection on the surface of the object.

Description

Technical Field

[0001] The present disclosure relates to a surface inspection apparatus and a surface inspection method, and more particularly to a surface inspection apparatus and a surface inspection method for inspecting the surface properties of an object using an image.

Background Art

[0002] In magnetic particle inspection, the object to be inspected is magnetized, and a magnetic particle liquid is applied to the magnetized object. The magnetized object leaks magnetic flux from open or unopened flaws, and the applied magnetic particles are adsorbed to the flaws, emit excitation light when irradiated with ultraviolet light, and the light-emitting part appears as a flaw pattern. An inspector visually observes the flaw pattern in a dark room to inspect the surface properties of the object. The flaws that can be confirmed by magnetic particle inspection have a wide variety of shapes and patterns, and may also closely resemble pseudo-patterns caused by magnetic particle liquid accumulation or the like. The inspector needs to distinguish between the flaw pattern and the pseudo-pattern and determine whether it is harmful or harmless. However, this determination is very difficult and largely depends on the skill of the inspector. In addition, magnetic particle inspection is a long-term operation in a dark room, which also makes the inspection work difficult. Furthermore, when the shape of the object is complex, the inspection work becomes difficult. Therefore, in magnetic particle inspection by an inspector, there are cases where the object flows out with the surface flaw overlooked, resulting in a serious claim. Therefore, automation of magnetic particle inspection work is required.

[0003] In addition to the flaws targeted by magnetic particle inspection, there are also defects such as handling scratches, base material surface remnants, and surface roughness that occur on the object surface and to which magnetic particles do not adsorb in magnetic particle inspection. These defects have a wide opening width or a shape equivalent to the product surface, and there is a situation where magnetic particle inspection cannot be applied because the leakage magnetic flux is weak or does not occur. For these defects, it is common to irradiate normal illumination such as visible light illumination and monitor visually or with a camera.

[0004] Traditionally, magnetic particle testing and inspection of defects other than those targeted by magnetic particle testing (hereinafter referred to as "normal inspection") had to be performed separately, regardless of whether the inspection was conducted visually by an inspector or automatically by a camera.

[0005] Various proposals have been made regarding magnetic particle testing. For example, Japanese Patent Publication No. 2000-258398 proposes a method for performing magnetic particle testing and penetrant testing in parallel or simultaneously by equipping the equipment with ultraviolet and white illumination and capturing images suitable for each type of testing. In the method described in Japanese Patent Publication No. 2000-258398, during magnetic particle testing, the test specimen irradiated with ultraviolet light is imaged by a video camera through an ultraviolet cut filter to improve the contrast of the resulting image.

[0006] Furthermore, Japanese Patent Publication No. 2007-17376 proposes a method for performing magnetic particle testing and conventional inspection in parallel or simultaneously by equipping the facility with ultraviolet and white illumination and capturing images suitable for each inspection. In the method described in Japanese Patent Publication No. 2007-17376, images for each inspection are captured at different timings. In addition, the method described in Japanese Patent Publication No. 2007-17376 uses a long-pass filter that transmits fluorescent and visible light. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, both the methods described in Japanese Patent Publication No. 2000-258398 and Japanese Patent Publication No. 2007-17376 require the deployment of two types of illumination and the process of switching between the two types of illumination to perform imaging. In other words, both the methods described in Japanese Patent Publication No. 2000-258398 and Japanese Patent Publication No. 2007-17376 involve processes in different environments where the type of illumination is switched. Furthermore, when a long-pass filter is used, as in the method described in Japanese Patent Publication No. 2007-17376, the components used for magnetic particle inspection and normal inspection contained in each illumination will be mixed, resulting in a decrease in the contrast of the resulting image.

[0008] Therefore, the purpose of this disclosure is to provide a surface inspection apparatus and a surface inspection method that can integrate magnetic particle testing and conventional inspection under the same environment. [Means for solving the problem]

[0009] A first aspect of this disclosure is a surface inspection apparatus comprising: a magnetization unit for magnetizing an object to be inspected; a magnetic powder attachment unit for applying a magnetic powder liquid to the magnetized object to adhere magnetic powder; an illumination unit for illuminating a space containing the object with ultraviolet light; a first optical filter that transmits a first wavelength, which is the wavelength of the ultraviolet light; a second optical filter that transmits a second wavelength, which is the wavelength of the excitation light of the magnetic powder excited by the ultraviolet light; an imaging unit that, in the space illuminated by the ultraviolet light, images the surface of the object to which the magnetic powder has adhered via the first optical filter to generate a first image, and images the surface of the object to which the magnetic powder has adhered via the second optical filter to generate a second image; and an inspection unit that, based on the first image, inspects a first surface condition visible on the surface of the object; and based on the second image, inspects a second surface condition visible by magnetic particle testing on the surface of the object.

[0010] A second aspect of the present disclosure is a surface inspection apparatus according to the first aspect, wherein the apparatus has a rotation mechanism that rotates the object about a rotation axis perpendicular to the viewing axis of the imaging unit, and the imaging unit switches between a process of generating a first image by imaging the surface of the object to which the magnetic powder is attached via a first optical filter and a process of generating a second image by imaging the surface of the object to which the magnetic powder is attached via a second optical filter at predetermined intervals of the rotation of the object by the rotation mechanism.

[0011] A third aspect of the present disclosure is a surface inspection apparatus according to the first or second aspect, wherein the imaging unit comprises a first imaging unit for generating the first image and a second imaging unit for generating the second image, and includes an optical member for inducing reflected light from the surface of the object to which the magnetic powder is attached into the first imaging unit via the first optical filter in a space illuminated by ultraviolet light, and for inducing excitation light from the surface of the object to which the magnetic powder is attached into the second imaging unit via the second optical filter.

[0012] A fourth aspect of this disclosure is a surface inspection method comprising: a magnetization step of magnetizing an object to be inspected; a magnetic powder attachment step of applying a magnetic powder liquid to the magnetized object to adhere magnetic powder; an illumination step of illuminating a space containing the object with ultraviolet light; a first optical filter that transmits a first wavelength which is the wavelength of the ultraviolet light; a second optical filter that transmits a second wavelength which is the wavelength of the excitation light of the magnetic powder excited by the ultraviolet light; and an imaging unit, wherein the imaging step involves imaging the surface of the object to which the magnetic powder has adhered through the first optical filter in the space illuminated with ultraviolet light to generate a first image; imaging the surface of the object to which the magnetic powder has adhered through the second optical filter to generate a second image; and an inspection step of inspecting a first surface condition on the surface of the object that is visible based on the first image; and inspecting a second surface condition on the surface of the object that is visible by magnetic particle testing based on the second image.

[0013] A fifth aspect of the present disclosure is a surface inspection method according to the fourth aspect of the present disclosure, comprising a rotation step in which the object is rotated about a rotation axis perpendicular to the viewing axis of the imaging unit, and in the imaging step, at predetermined intervals of the rotation of the object by the rotation step, a process of generating a first image by imaging the surface of the object to which the magnetic powder is attached via the first optical filter and generating a second image by imaging the surface of the object to which the magnetic powder is attached via the second optical filter.

[0014] A sixth aspect of the present disclosure is a surface inspection method according to the fourth or fifth aspect, wherein the imaging unit comprises a first imaging unit for generating the first image and a second imaging unit for generating the second image, and in the imaging step, an optical member is used to generate the first image and the second image by inducing reflected light from the surface of the object to which the magnetic powder is attached into the first imaging unit via the first optical filter in a space illuminated with ultraviolet light, and by inducing excitation light from the surface of the object to which the magnetic powder is attached into the second imaging unit via the second optical filter. [Effects of the Invention]

[0015] According to this disclosure, a surface inspection apparatus and a surface inspection method are provided that can integrate magnetic particle testing and conventional inspection under the same environment. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows a schematic configuration of a surface inspection apparatus and an object according to an embodiment. [Figure 2] This figure shows an example of a filter device. [Figure 3] This figure shows an example of the transmission characteristics of the first optical filter and the second optical filter. [Figure 4] This is a diagram illustrating the arrangement of the imaging device. [Figure 5] This is a schematic plan view showing the relative positions of each component. [Figure 6] This is a functional block diagram of the processing unit. [Figure 7] This diagram illustrates the process of acquiring images during a normal examination. [Figure 8] This is a diagram illustrating the process of capturing images during magnetic particle inspection. [Figure 9] This figure shows an example of a typical examination image from a real sample. [Figure 10] This figure shows an example of a magnetic particle inspection image from an actual sample. [Figure 11]It is a block diagram showing the hardware configuration of a processing device. [Figure 12] It is a flowchart showing the flow of surface inspection processing. [Figure 13] It is a diagram showing a part of the schematic configuration of Modification 1. [Figure 14] It is a diagram showing a part of the schematic configuration of Modification 2. [Figure 15] It is a plan view of a part of the schematic configuration of Modification 3.

Mode for Carrying Out the Invention

[0017] Hereinafter, an example of an embodiment of the present disclosure will be described while referring to the drawings.

[0018] (Explanation of Magnetic Particle Inspection and Normal Inspection) In the present embodiment, a surface inspection apparatus that integrally performs magnetic particle inspection and normal inspection on the surface properties of an inspection object in the same environment will be described. In magnetic particle inspection, among the defects on the surface of the object, inspections are performed on fine defects (hereinafter referred to as "magnetic particle defects") such as defects under the skin that are difficult to visually recognize by the naked eye. In normal inspection, among the defects on the surface of the object, inspections are performed on defects other than magnetic particle defects (hereinafter referred to as "normal defects") such as defects of visible size, base material surface remaining, surface roughness, etc. Note that normal defects are an example of the first surface property of the present disclosure, and magnetic particle defects are an example of the second surface property of the present disclosure.

[0019] (Explanation of the Configuration of the Surface Inspection Apparatus 10) FIG. 1 is a diagram showing a schematic configuration of a surface inspection apparatus 10 according to an embodiment of the present disclosure and an object 60 that is an object of inspection of surface properties. The object 60 is a ferromagnetic object. In the present embodiment, for example, a case where a cylindrical object such as a wheel or a crank is used as the object 60 will be described.

[0020] As shown in Figure 1, the surface inspection apparatus 10 includes a magnetization apparatus 12, a magnetic powder deposition apparatus 14, a rotating mechanism 16, an illumination apparatus 18, a filter apparatus 20, an imaging apparatus 22, a marking apparatus 24, a maintenance apparatus 26, and a processing apparatus 28.

[0021] The magnetization device 12 is a device that magnetizes an object 60 which is a ferromagnetic material. Note that the magnetization device 12 is an example of a magnetization unit of this disclosure.

[0022] The magnetic powder adhesion device 14 is a device that applies magnetic powder liquid to an object 60 magnetized by the magnetization device 12 to adhere magnetic powder to it. Note that the magnetic powder adhesion device 14 is an example of a magnetic powder adhesion unit of this disclosure.

[0023] The rotation mechanism 16 is a mechanism for rotating the object 60 with respect to the viewing axis (i.e., the imaging direction) of the imaging device 22, which will be described later. In this embodiment, the rotation mechanism 16 rotates the cylindrical object 60 using its central axis, which is perpendicular to the viewing axis of the imaging device 22, as the axis of rotation.

[0024] The illumination device 18 illuminates the space including the object 60 with ultraviolet light. For example, the illumination device 18 may be a ring-shaped illumination device that emits ultraviolet light. The illumination device 18 is also positioned coaxially with the imaging device 22, which will be described later, so as to irradiate an area including the imaging range of the imaging device 22 with ultraviolet light. In addition to the illumination device 18 and the imaging device 22 being positioned coaxially, a diffusion film is provided on the surface of the illumination device 18, so that the ultraviolet light from the illumination device 18 is uniformly irradiated to the irradiation area. Note that the illumination device 18 is an example of an illumination unit in this disclosure.

[0025] The filter device 20 includes a first optical filter, a second optical filter, and a switching mechanism. Figure 2 shows an example of the filter device 20 that switches between the two filters using a sliding mechanism. The first optical filter 20A is a bandpass filter that transmits the first wavelength, which is the wavelength of ultraviolet light used for illumination by the lighting device 18. The center of the first wavelength is the central wavelength of the ultraviolet band. Specifically, the first optical filter 20A transmits light with wavelengths in the range of approximately 360 nm ± 15 nm. The second optical filter 20B is a bandpass filter that transmits the second wavelength, which is the wavelength of the excitation light of magnetic powder excited by ultraviolet light. The center of the second wavelength is the central wavelength of the magnetic powder emission band. Specifically, the second optical filter 20B transmits light with wavelengths in the range of approximately 585 nm ± 15 nm. Figure 3 shows an example of the transmission characteristics of the first optical filter 20A and the second optical filter 20B. The first optical filter 20A and the second optical filter 20B are arranged side by side on a sheet-like filter section 20D.

[0026] The switching mechanism 20C moves the filter section 20D, which has the first optical filter 20A and the second optical filter 20B, using a drive mechanism including a motor and actuator, so that the filter section 20D is slid so that either the first optical filter 20A or the second optical filter 20B is set at the position of the aperture corresponding to the lens surface of the imaging device 22, which will be described later. Although Figure 2 describes an example of a filter device 20 that switches between two filters by sliding, a filter device that switches between two filters by rotation may also be applied. In the case of a rotational filter device, the first optical filter 20A and the second optical filter 20B are provided at positions with different angles from the center of the circular filter section 20D, and by rotating the filter section 20D, the filter set at the position of the aperture is changed.

[0027] The imaging device 22 is a camera capable of capturing the inspection surface of the object 60 as a monochrome or color image. The imaging device 22 may be a two-dimensional camera in which image sensors such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) are arranged in two dimensions. In this embodiment, as shown in Figure 4, the imaging device 22 is positioned such that its viewing axis is perpendicular to the rotation axis 62 of the object 60, which is rotated by the rotation mechanism 16 (not shown in Figure 4). That is, the imaging device 22 is positioned so that its viewing axis coincides with the normal direction of the inspection surface of the object 60, and it captures an image with the area including the inspection surface as the imaging range 64. Furthermore, the imaging device 22 is positioned coaxially with the illumination device 18 described above. By making the imaging device 22 and the illumination device 18 coaxial, the imaging sensitivity can be made close to its maximum.

[0028] Figure 5 shows a schematic plan view illustrating the positional relationship between the object 60, the illumination device 18, the filter device 20, and the imaging device 22. The illumination device 18 and the filter device 20 are positioned between the imaging device 22 and the object 60. As a result, the imaging device 22 captures an image of the surface of the object 60, to which magnetic powder is attached, through the first optical filter 20A in a space illuminated by ultraviolet light from the illumination device 18, and generates an image for normal inspection (hereinafter referred to as the "normal inspection image"). The imaging device 22 also captures an image of the surface of the object 60, to which magnetic powder is attached, through the second optical filter 20B in a space illuminated by ultraviolet light from the illumination device 18, and generates an image for magnetic particle testing (hereinafter referred to as the "magnetic particle inspection image"). The normal inspection image is an example of the first image captured in this disclosure, and the magnetic particle inspection image is an example of the second image captured in this disclosure.

[0029] Since magnetic particle testing and conventional inspection use different wavelengths for imaging, the imaging device 22 generates two types of images using the first optical filter 20A and the second optical filter 20B, which are bandpass filters, as described above.

[0030] In the conventional inspection in this embodiment, the first visible surface properties on the surface of the object 60 are inspected based on the shadows cast on the surface of the object 60 by illumination with ultraviolet light. However, because magnetic particles are attached to the object 60, the magnetic particles are excited and emit light when illuminated with ultraviolet light, and this light emission may interfere with the inspection of the first surface properties that is to be performed based on ultraviolet light. On the other hand, in the magnetic particle testing inspection in this embodiment, the second visible surface properties are inspected by magnetic particle testing based on the excitation light of the magnetic particles. However, the ultraviolet light that generates the excitation light may interfere with the inspection of the second surface properties that is to be performed based on the excitation light.

[0031] Therefore, in magnetic particle testing, a filter that transmits light in the frequency band with a central wavelength of 585 nm, or conversely, a filter that does not transmit light in the ultraviolet frequency band, is used as the second optical filter 20B to suppress the reception of light other than that emitted from the magnetic particle defects. This reduces base noise and makes it possible to clearly capture the light emitted from the magnetic particle defects, thereby improving the contrast of the magnetic particle inspection image.

[0032] Furthermore, in normal inspection, a filter that transmits frequencies in the band with a central wavelength of 360 nm, or conversely, a filter that does not transmit light in the frequency band of the excitation light of magnetic particles, is used as the first optical filter 20A to prevent interference with the inspection. This suppresses the reception of light from magnetic particle defects with strong magnetic particle emission intensity. As a result, normal defects and magnetic particle defects can be separated, and a normal inspection image suitable for inspecting normal defects can be generated. In addition, in the normal inspection image, by using the first optical filter 20A, only ultraviolet light is received, and a normal inspection image can be captured that shows shading due to ultraviolet illumination of the defective area, or a decrease in brightness due to diffuse reflection on the surface of the base material.

[0033] The marking device 24 is a device for marking the surface of the object 60. The marking device 24 may be, for example, a robotic arm with a drawing tool at its tip. In this case, the marking device 24 draws a specified symbol, character, mark, etc., at a specified location on the surface of the object 60, for example, at a location where a problematic first surface characteristic or second surface characteristic is detected. This makes it easy to identify locations on the surface of the object 60 that will become the product that are problematic in terms of quality.

[0034] The maintenance device 26 is a device for maintaining the surface of the object 60. The maintenance device 26 may be, for example, a robotic arm with a grinder at its tip. In this case, the maintenance device 26 performs polishing or other operations on a designated location on the surface of the object 60, for example, a location where a marking or the like has been drawn by the marking device 24. By doing so, the surface problems of the object 60 can be resolved by polishing the areas on the surface of the object 60 that are problematic in terms of quality and their surroundings.

[0035] The processing unit 28 is a functional unit that performs various controls related to the surface inspection device 10 and various calculations related to the inspection of the object 60, and is realized by a computer with a hardware configuration described later. Functionally, the processing unit 28 includes a control unit 30 and an inspection unit 32, as shown in Figure 6.

[0036] The control unit 30 controls the magnetization device 12, the magnetic powder deposition device 14, the rotation mechanism 16, the illumination device 18, the filter device 20, the imaging device 22, the marking device 24, and the maintenance device 26.

[0037] Specifically, at the start of the inspection, the control unit 30 operates the magnetization device 12 and the magnetic powder attachment device 14 to magnetize the object 60 and attach magnetic powder to its surface. The control unit 30 also operates the rotation mechanism 16 at the start of the inspection to rotate the object 60. Furthermore, the control unit 30 turns on the illumination device 18 at the start of the inspection to begin irradiating with ultraviolet light. The illumination device 18 remains on until the inspection is completed. In other words, the inspection environment can be kept constant from the start to the end of the inspection.

[0038] Furthermore, the control unit 30 controls the filter device 20 to set one of the first optical filter 20A and the second optical filter 20B in the switching mechanism 20C, so that either the first optical filter 20A or the second optical filter 20B is positioned directly in front of the lens surface of the imaging device 22. The control unit 30 also causes the switching mechanism 20C to switch the filter positioned in front of the lens surface to the other of the first optical filter 20A and the second optical filter 20B at predetermined rotational intervals of the object 60. The control unit 30 can synchronize the timing of various controls by obtaining the rotational period of the object 60 from a rotary encoder or the like provided in the rotation mechanism 16.

[0039] Furthermore, the control unit 30 instructs the imaging device 22 to generate a normal inspection image and a magnetic particle inspection image over the entire circumference of the object 60 by imaging the surface of the object 60 to be inspected in accordance with a predetermined rotation period of the object 60. The control unit 30 then acquires the normal inspection image and the magnetic particle inspection image generated by the imaging device 22.

[0040] Specifically, the unit pitch for the imaging device 22 is defined as the rotational pitch that changes the imaging range, including the surface of the object 60 being inspected. For example, if four images are required during one rotation of the object 60 to cover the entire surface of the object 60 being inspected, the unit pitch is 90°. For each unit pitch of rotation of the object 60, the control unit 30 sets the first optical filter 20A in the switching mechanism 20C, as shown in Figure 7, and causes the imaging device 22 to capture a normal inspection image. Then, for the same unit pitch, the control unit 30 switches the filter set in the switching mechanism 20C from the first optical filter 20A to the second optical filter 20B, as shown in Figure 8, and causes the imaging device 22 to capture a magnetic particle inspection image. In other words, the control unit 30 controls the imaging device 22 to perform two images for each unit pitch of rotation of the object 60.

[0041] Alternatively, the control unit 30 causes the imaging device 22 to capture multiple normal inspection images (four images in the case of a 90° unit pitch) with the first optical filter 20A set for each unit pitch during one rotation of the object 60, i.e., in the state shown in Figure 7. Then, the control unit 30 causes the switching mechanism 20C to switch the filter to be set from the first optical filter 20A to the second optical filter 20B. Furthermore, the control unit 30 causes the imaging device 22 to capture multiple magnetic particle inspection images (four images in the case of a 90° unit pitch) with the second optical filter 20B set for each unit pitch during one rotation of the object 60, i.e., in the state shown in Figure 8. In other words, the control unit 30 controls the switching mechanism 20C to switch between the first optical filter 20A and the second optical filter 20B each time the object 60 rotates once. Furthermore, the control unit 30 controls the imaging device 22 so that normal inspection images and magnetic particle inspection images for the entire circumference are acquired during two rotations of the object 60.

[0042] In this way, by switching between the first optical filter 20A and the second optical filter 20B, both normal inspection images and magnetic particle inspection images can be acquired in the same environment where ultraviolet light is irradiated by the illumination device 18. The control unit 30 concatenates the normal inspection images captured at unit pitch intervals while the object 60 rotates once or twice to acquire a normal inspection image covering the entire circumference of the object 60. Similarly, the control unit 30 concatenates the magnetic particle inspection images captured at unit pitch intervals while the object 60 rotates once or twice to acquire a magnetic particle inspection image covering the entire circumference of the object 60. An example of a normal inspection image in an actual sample is shown in Figure 9, and an example of a magnetic particle inspection image is shown in Figure 10.

[0043] Furthermore, the control unit 30 controls the marking device 24 to mark the position on the surface of the object 60 corresponding to the position indicated by the inspection result from the inspection unit 32, which will be described later. Specifically, the control unit 30 identifies the position of defects on the surface of the object 60 based on information such as the position of defects (normal defects and magnetic particle defects) extracted from the image, the pitch obtained from the rotary encoder of the rotating mechanism 16, and the size of the object 60. The control unit 30 then notifies the marking device 24 of the identified defect position, along with information distinguishing whether the defect was detected by magnetic particle testing or normal inspection, and controls the marking device 24 to apply a mark to the defect position. As information to distinguish defects, the color or type of marking indicating the defect position may be different, or characters or symbols indicating either magnetic particle testing or normal inspection may be drawn near the marking indicating the defect position.

[0044] Furthermore, the control unit 30 controls the maintenance device 26 to perform maintenance on the surface of the object 60 based on the marked position.

[0045] The inspection unit 32 performs a normal inspection, i.e., a normal inspection, on the surface of the object, based on the normal inspection image acquired by the control unit 30. The inspection unit 32 also performs a magnetic particle inspection, i.e., a magnetic particle flaw inspection, on the surface of the object 60, based on the magnetic particle inspection image acquired by the control unit 30, on the surface of the object, i.e., a magnetic particle flaw inspection, on the surface of the object 60, based on the magnetic particle inspection image acquired by the control unit 30.

[0046] Specifically, the inspection unit 32 performs predetermined preprocessing, such as shading and smoothing, on both the normal inspection image and the magnetic particle inspection image. The inspection unit 32 then binarizes both the normal inspection image and the magnetic particle inspection image after preprocessing based on a predetermined threshold. The threshold may be determined experimentally in advance based on the type of object 60, etc. The inspection unit 32 then removes noise components from both the normal inspection image and the magnetic particle inspection image after binarization using predetermined processing. As a result, detection results are obtained in which the normal defect portion is extracted from the normal inspection image and the magnetic particle defect portion is extracted from the magnetic particle inspection image.

[0047] The processing unit 28 is comprised of a computer. Figure 11 is a block diagram showing the hardware configuration of the processing unit 28. As shown in Figure 11, the processing unit 28 includes a CPU (Central Processing Unit) 42, memory 44, storage device 46, input device 48, output device 50, storage medium reader 52, and communication I / F (Interface) 54. Each component is connected to the others via a bus 56 so as to be able to communicate with each other.

[0048] The storage device 46 stores a program for performing the surface inspection process described later. The CPU 42 is a central processing unit that executes various programs and controls each component. Specifically, the CPU 42 reads the program from the storage device 46 and executes the program using memory 44 as its workspace. The CPU 42 controls each component and performs various calculations according to the program stored in the storage device 46.

[0049] Memory 44 is composed of RAM (Random Access Memory) and temporarily stores programs and data as a working area. Storage device 46 is composed of ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), etc. and stores various programs and data, including the operating system.

[0050] The input device 48 is a device for performing various types of input, such as a keyboard or mouse. The output device 50 is a device for outputting various types of information, such as a display or printer. A touch panel display may be used as the output device 50 and function as the input device 48.

[0051] The storage medium reader 52 reads data stored on various storage media such as CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM, Blu-ray disc, and USB (Universal Serial Bus) memory, and writes data to the storage media. The communication I / F 54 is an interface for communication with other devices, and standards such as Ethernet (registered trademark), FDDI, or Wi-Fi (registered trademark) are used.

[0052] (Explanation of surface inspection method) Figure 12 is a flowchart showing the flow of the surface inspection process executed by the CPU 42 of the processing unit 28. The CPU 42 reads a program for executing the surface inspection process from the storage device 46, loads it into memory 44, and executes it. As a result, the CPU 42 functions as one of the functional components of the processing unit 28, and the surface inspection process shown in Figure 12 is executed. This executes the surface inspection method in the surface inspection device 10.

[0053] In step S10, the control unit 30 operates the magnetization device 12 and the magnetic powder attachment device 14 by controlling them. As a result, the magnetization device 12 performs a magnetization step in which it magnetizes the object 60, and the magnetic powder attachment device 14 performs a magnetic powder attachment step in which it applies magnetic powder liquid to the object 60 magnetized by the magnetization device 12 to attach the magnetic powder.

[0054] Next, in step S12, the control unit 30 turns on the lighting device 18 by controlling it. This causes the lighting device 18 to perform a lighting step in which it illuminates the space including the object 60 with ultraviolet light. The control unit 30 also operates the rotation mechanism 16 by controlling it. This causes the rotation mechanism 16 to perform a rotation step in which it rotates the cylindrical object 60 around its central axis as the axis of rotation.

[0055] Next, in step S14, the control unit 30 controls the filter device 20 to cause the switching mechanism 20C to set the first optical filter 20A directly in front of the lens surface of the imaging device 22. As a result, the switching mechanism 20C, driven by a motor and actuator, slides so that the first optical filter 20A is positioned in front of the lens surface of the imaging device 22, thereby setting the first optical filter 20A in front of the lens surface of the imaging device 22.

[0056] Next, in step S16, the control unit 30 controls the imaging device 22 to image the surface of the object 60 to be inspected in accordance with a predetermined rotation period of the object 60. As a result, the imaging device 22 performs a part of the imaging step that generates a normal inspection image by imaging the surface of the object 60 to which the magnetic powder is attached via the first optical filter 20A in a space illuminated with ultraviolet light by the illumination device 18.

[0057] Next, in step S18, the control unit 30 controls the filter device 20 to cause the switching mechanism 20C to set the second optical filter 20B directly in front of the lens surface of the imaging device 22. As a result, the switching mechanism 20C, driven by a motor and actuator, slides so that the second optical filter 20B is positioned at the opening corresponding to the lens surface of the imaging device 22, thereby setting the second optical filter 20B in front of the lens surface of the imaging device 22.

[0058] Next, in step S20, the control unit 30 controls the imaging device 22 to image the surface of the object 60 to be inspected in accordance with a predetermined rotation period of the object 60. This causes the imaging device 22 to image the surface of the object 60 to which the magnetic powder is attached via the second optical filter 20B in a space illuminated with ultraviolet light by the illumination device 18, thereby performing the other part of the imaging step to generate a magnetic powder inspection image.

[0059] Next, in step S22, the inspection unit 32 performs predetermined preprocessing, binarization, and noise removal processing on the normal inspection image and the magnetic particle inspection image, respectively, to extract portions of normal defects from the normal inspection image and portions of magnetic particle defects from the magnetic particle inspection image.

[0060] Next, in step S24, the control unit 30 notifies the marking device 24 of the location of the defect, along with information distinguishing whether the defect was detected by magnetic particle testing or normal inspection (normal defect and magnetic particle defect), and controls the marking device 24 to mark the location of the defect. As a result, the marking device 24 marks the location of the defect at the specified position on the surface of the object 60 in a manner that allows for distinction between whether the defect was detected by magnetic particle testing or normal inspection.

[0061] Next, in step S26, the control unit 30 controls the maintenance device 26 to perform surface maintenance on the object 60 based on the marked position. As a result, the maintenance device 26 polishes the specified position on the surface of the object 60 using a grinder or the like. Then the surface inspection process is completed.

[0062] (Operation and effects of surface inspection equipment) As described above, the surface inspection device according to this embodiment magnetizes the object to be inspected, applies a magnetic powder solution to adhere the magnetic powder, and illuminates the space containing the object with ultraviolet light. The surface inspection device also has a first optical filter that transmits a first wavelength, which is the wavelength of ultraviolet light, and a second optical filter that transmits a second wavelength, which is the wavelength of the excitation light of the magnetic powder excited by the ultraviolet light. The surface inspection device generates a normal inspection image by imaging the surface of the object with the magnetic powder attached through the first optical filter in the space illuminated with ultraviolet light, and generates a magnetic powder inspection image by imaging the surface of the object with the magnetic powder attached through the second optical filter. Furthermore, the surface inspection device inspects for visible normal defects on the surface of the object based on the normal inspection image, and inspects for magnetic powder defects visible by magnetic powder testing on the surface of the object based on the magnetic powder inspection image. As a result, the surface inspection device can perform magnetic powder testing and normal inspection in an integrated manner under the same environment.

[0063] In other words, according to the surface inspection apparatus of this embodiment, due to the characteristics of magnetic particle testing, it becomes possible to perform two types of inspections, magnetic particle testing and conventional inspection, which are conventionally performed in separate processes, simultaneously in the same environment, which is advantageous in terms of cost and equipment space.

[0064] Furthermore, according to the surface inspection apparatus of this embodiment, since two types of surface inspection images, a normal inspection image and a magnetic particle inspection image, which are different wavelength images, are acquired in a single surface inspection process, it becomes possible to distinguish between normal defects and magnetic particle defects, and to identify the location of each defect.

[0065] Furthermore, a key advantage of the surface inspection apparatus according to this embodiment is that conventional inspection can be performed solely by irradiating with an ultraviolet light source for excitation in magnetic particle testing. The method of the above embodiment does not require multiple illumination devices and multiple imaging devices for magnetic particle testing and conventional inspection, thus enabling the acquisition of both magnetic particle inspection images and conventional inspection images with a single configuration, which is effective in simplifying the apparatus.

[0066] (Variation 1) Figure 13 shows a schematic configuration of Modification 1. In the above embodiment, the case where the illumination device 18 is ring-shaped was described, but in Modification 1, the configuration includes a linear illumination device 18A. In the example in Figure 13, two linear illumination devices 18A are shown arranged horizontally above and below the imaging device 22. Depending on the size and shape of the object 60, illumination may be provided from multiple directions. In addition, in the above embodiment and Modification 1, the configuration is such that light is projected perpendicularly to the inspection surface of the object 60, but this is not limited to the shape of the object, the form of the defect, etc. Furthermore, the shape of the illumination device 18 is not limited to ring-shaped or linear. Furthermore, the shape of the object 60 is not limited to cylindrical. Also, depending on the shape of the object 60, each image may be acquired without rotating the object 60, or each image may be acquired while translating the object 60.

[0067] (Modification 2) Figure 14 shows a schematic configuration of Modification 2. In the above embodiment, the case where the imaging device 22 is a two-dimensional camera was described, but in Modification 2, the imaging device 22 is configured to be a one-dimensional camera in which image sensors are arranged in one dimension. In the example in Figure 14, the illumination device is a linear illumination device 18A, similar to Modification 1. Also, Figure 14 shows an example in which the second optical filter 20B is set and a magnetic particle inspection image is captured. The magnetic particle image in the right figure of Figure 14 is an example in which images captured for each line are stitched together for the entire circumference of the object 60.

[0068] (Variation 3) Figure 15 shows a schematic plan view illustrating the positional relationship of some components of Modified Example 3. In the above embodiment, the case in which a normal inspection image and a magnetic particle inspection image are captured by switching filters was described. Modified Example 3 is configured to include two imaging devices 22A and 22B and a half mirror 21. Imaging device 22A is an example of the first imaging unit of this disclosure, imaging device 22B is an example of the second imaging unit of this disclosure, and the half mirror 21 is an example of an optical member of this disclosure. In the configuration of Modified Example 3, in a space illuminated with ultraviolet light, the reflected light and excitation light from the surface of the object 60 to which magnetic particles are attached are split into two by the half mirror 21, and one of the lights is incident on imaging device 22A via the first optical filter 20A. The other split light is incident on imaging device 22B via the second optical filter 20B. As a result, a normal inspection image is captured by imaging device 22A, and a magnetic particle inspection image is captured by imaging device 22B. According to the configuration of Modified Example 3, it is possible to simultaneously capture both a normal inspection image and a magnetic particle inspection image.

[0069] (Modification 4) In the above embodiment, a case was described in which a series of operations from magnetizing the object 60 to post-inspection maintenance are automated. However, in Modification 4, manual work may be included in any of the operations. For example, the surface of the object 60 may be manually maintained based on the markings made by the marking device 24. Alternatively, for example, the processing device 28 may output the inspection results, in which defects are extracted from each image, to a display device, and an inspector may check the display and mark the object 60.

[0070] The above is an example of this disclosure, but this disclosure is not limited to the above, and it is of course possible to implement it in various modified forms without departing from its intent.

[0071] The disclosure of Japanese Patent Application No. 2022-066522 is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Claims

1. A magnetization unit that magnetizes the object to be inspected, A magnetic powder attachment section for applying magnetic powder liquid to the magnetized object to adhere the magnetic powder, A lighting unit that illuminates the space containing the aforementioned object with ultraviolet light, A first optical filter that transmits a first wavelength, which is the wavelength of ultraviolet light, A second optical filter that transmits a second wavelength, which is the wavelength of the excitation light of the magnetic powder excited by the ultraviolet light, An imaging unit generates a first image by imaging the surface of the object to which the magnetic powder is attached through the first optical filter in a space illuminated by ultraviolet light, and generates a second image by imaging the surface of the object to which the magnetic powder is attached through the second optical filter, An inspection unit that inspects a first surface condition visible on the surface of the object based on the first image, and inspects a second surface condition visible by magnetic particle testing on the surface of the object based on the second image, A surface inspection device having the following features.

2. The object has a rotation mechanism that rotates it around a rotation axis perpendicular to the viewing axis of the imaging unit, The imaging unit switches between, at predetermined intervals of rotation of the object by the rotation mechanism, the process of generating a first image by imaging the surface of the object to which the magnetic powder is attached via the first optical filter, and the process of generating a second image by imaging the surface of the object to which the magnetic powder is attached via the second optical filter. The surface inspection apparatus according to claim 1.

3. The imaging unit includes a first imaging unit that generates the first image and a second imaging unit that generates the second image. In a space illuminated by ultraviolet light, the optical member includes a first optical filter for inducing reflected light from the surface of the object to which the magnetic powder is attached to the first imaging unit, and a second optical filter for inducing excitation light from the surface of the object to which the magnetic powder is attached to the second imaging unit, A surface inspection apparatus according to claim 1 or claim 2.

4. A magnetization step in which the object to be inspected is magnetized, A magnetic powder attachment step involves applying a magnetic powder liquid to the magnetized object to adhere the magnetic powder, A lighting step in which the space containing the aforementioned object is illuminated with ultraviolet light, An imaging step comprising: using a first optical filter that transmits a first wavelength which is the wavelength of ultraviolet light; a second optical filter that transmits a second wavelength which is the wavelength of the excitation light of the magnetic powder excited by the ultraviolet light; and an imaging unit, generating a first image by imaging the surface of the object to which the magnetic powder is attached in a space illuminated by the ultraviolet light through the first optical filter; and generating a second image by imaging the surface of the object to which the magnetic powder is attached through the second optical filter; An inspection step in which, based on the first image, a first surface condition visible on the surface of the object is inspected, and based on the second image, a second surface condition visible by magnetic particle testing is inspected on the surface of the object; A surface inspection method having the following characteristics.

5. The object has a rotation step that rotates it about an axis of rotation perpendicular to the viewing axis of the imaging unit, In the imaging step, at each predetermined period of rotation of the object by the rotation step, the process of generating a first image is switched between imaging the surface of the object to which the magnetic powder is attached via the first optical filter and generating a second image by imaging the surface of the object to which the magnetic powder is attached via the second optical filter. The surface inspection method according to claim 4.

6. The imaging unit includes a first imaging unit that generates the first image and a second imaging unit that generates the second image. In the imaging step, using an optical member, reflected light from the surface of the object to which the magnetic powder is attached is incident to the first imaging unit via the first optical filter in the space illuminated by ultraviolet light, and excitation light from the surface of the object to which the magnetic powder is attached is incident to the second imaging unit via the second optical filter to generate the first imaging image and the second imaging image. The surface inspection method according to claim 4 or claim 5.

Images