Surface defect inspection apparatus and surface defect inspection method

Abstract

To provide a surface defect inspection method and a surface defect inspection apparatus capable of ensuring magnification even when a roll diameter is changed.SOLUTION: The surface defect inspection apparatus includes means for irradiating the cylindrical surface of a cylindrical sample with illumination light, a flat plate for projecting light reflected from the surface of the sample, means for observing the reflected light projected onto the surface of the flat plate, and means for rotating the sample. The surface defect inspection apparatus irradiates the surface of the sample with portion of the illumination light from a tangential direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surface defect inspection apparatus and a surface defect inspection method. [Background technology]

[0002] As a method for automatically detecting minute irregularities on a surface, a method for inspecting irregularities on the surface of a test object based on the magic mirror principle is known. Patent Document 1 discloses a method in which convergent light is irradiated onto the surface of a traveling flat steel sheet, and the light reflected by the steel sheet surface is projected onto a screen, thereby making the irregularities visible as a light-dark pattern on the screen. This document describes that, when the angle of incidence on the steel sheet is θ and the wavelength of light from the light source is λ, the irregularities can be made visible by making cosθ / λ equal to or less than a predetermined value. Patent Document 1 also describes that the steel sheet is wound around a roll, and the part wound around the roll is measured, thereby avoiding the influence of the pass line fluctuation of the traveling steel sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-139447 A Summary of the Invention [Problem to be solved by the invention]

[0004] Although Patent Document 1 does not mention the magnification of the optical image projected onto the screen, as the roll diameter increases, the magnification of the reflected light decreases with the change in roll curvature. In addition, since the illumination incident angle changes with the cylinder diameter, it is necessary to change the illumination incident angle in order to obtain the same magnification.

[0005] In view of the above, an object of the present invention is to provide a surface defect inspection device and a surface defect inspection method that can ensure the enlargement ratio even if the roll diameter is changed. [Means for solving the problem]

[0006] In the present invention, the surface defect inspection device is defined as "a means for irradiating illumination light onto the cylindrical surface of a cylindrical sample, a flat plate onto which the light reflected from the surface of the sample is projected, a means for observing the reflected light projected onto the surface of the flat plate, and a means for rotating the sample, wherein a portion of the illumination light is irradiated onto the surface of the sample from a tangential direction."

[0007] In the present invention, the method is defined as "a surface defect inspection method using a surface defect inspection device, characterized in that, when starting inspection for surface defects, the observation position (θ) on the cylindrical surface is obtained from the desired illumination incident angle, the illumination optical axis height is adjusted, the link installation angle is adjusted to determine the magnification of the cylindrical surface, and the rod rotation speed is determined." Effect of the Invention

[0008] According to the present invention, it is possible to obtain a surface defect inspection method and a surface defect inspection device that can ensure the magnification even if the rod diameter is changed.

[0009] More specifically, according to the embodiment of the present invention, cylindrical parts of different diameters can be observed at the same magnification (resolution), and therefore defect inspection can be performed with the same detection sensitivity. Also, according to the embodiment of the present invention, when defects of the same size exist in cylindrical parts of different diameters, they can be detected as defects of the same dimensions in the detected optical image. Furthermore, according to the embodiment of the present invention, when assuming a case where the cylindrical surface roughness is large (other than a glossy surface), the illumination incidence angle is an important parameter, and therefore the above can be achieved by controlling the illumination incidence angle on the cylindrical surface to a constant value. [Brief description of the drawings]

[0010] [Figure 1] 1 is a plan view showing an example of the basic configuration of a surface defect inspection device on which the present invention is based; [Diagram 2] FIG. 2 is a side view of the surface defect inspection device shown in FIG. [Diagram 3]FIG. 4 is an enlarged view for explaining an optical image in a state where the surface of a sample to be inspected is irradiated with irradiation light. [Figure 4] FIG. 1 is a diagram showing an example of a three-dimensional configuration of a surface defect inspection device according to a first embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram showing an example of an optical system arrangement in the surface defect inspection apparatus according to the first embodiment of the present invention. [Figure 6] FIG. 4 is an enlarged view for explaining an optical image in a state where the surface of a sample is irradiated with irradiation light in the case of the first embodiment of the present invention. [Figure 7] FIG. 11 is a diagram showing an example of a three-dimensional configuration of a surface defect inspection device according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a diagram showing an example of an optical system arrangement in a surface defect inspection apparatus according to a second embodiment of the present invention. [Figure 9] FIG. 11 is an enlarged view for explaining an optical image in a state where the surface of a sample is irradiated with irradiation light in the case of Example 2 of the present invention. [Figure 10] FIG. 11 is a diagram showing an example of the configuration of a surface defect inspection system according to a third embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing an example of a process flow of a surface defect inspection method implemented by a surface defect inspection system using a computer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] Before that, an example of the basic configuration and concept of a surface defect inspection device, which is the premise of the present invention, will be described with reference to FIGS.

[0013] FIG. 1 is a plan view showing an example of the basic configuration of a surface defect inspection apparatus on which the present invention is based, and FIG. 2 is a side view of the surface defect inspection apparatus shown in FIG.

[0014] In these figures, the sample 100 to be inspected is, for example, a piston rod used in a shock absorber. The spring and the shock absorber are assembled into the body of an automobile as a suspension strut assembly. The piston rod is a cylindrical structural part that seals the highly airtight cylinder interior with a cylindrical sliding surface, and if there are irregularities on the surface of the piston rod of several um, it will cause oil leakage in the suspension system. Therefore, the roundness and cylindricity of the piston rod are controlled on the order of micrometers, and the arithmetic mean roughness (Ra) of the surface is 0.05 um or less. The piston rod is a cylindrical part made of low carbon steel such as S25C, and after undergoing quenching and forming processes, it is subjected to surface treatment to finish the surface flat before being put into the assembly process. The piston rod, which is the sample to be inspected (hereinafter simply referred to as the "sample") 100, is formed, for example, with a diameter of about 22 mm and a total length of about 250 mm. At both ends of the sample 100, connection parts 100a and 100b are formed for mechanical connection. The connection parts 100a and 100b at both ends are not subject to inspection.

[0015] The surface defect inspection device 1 includes a laser oscillator 104 that irradiates a sample 100 with laser light (irradiation light), a Powell lens 105, a cylindrical lens 106, rollers 101a and 101b, a line sensor camera 107, a TV camera lens 108, and a screen 102.

[0016] The sample 100 is mounted across the rollers 101a and 101b. The rollers 101a and 101b have the same diameter, and are arranged at the same height in the Y direction and spaced apart in the Z direction with their axes parallel to the X axis. The sample 100 is mounted on the rollers 101a and 101b so that its axis is located on the center line of the boundary between the rollers 101a and 101b. The roller 101a is connected to a motor 103. The roller 101b is free to rotate about its axis. By driving the motor 103 to rotate, the roller 101a rotates, and the sample 100 and roller 101b rotate. In other words, by controlling the rotation of the motor 103, the sample 100 can be controlled to rotate at any speed.

[0017] Although not shown, the rollers 101a and 101b are attached to a moving stage and are capable of moving integrally in the vertical direction (Y direction).

[0018] The laser oscillator (illumination light source) 104 outputs a parallel beam (sometimes called "illumination light") 10 having a wavelength of 670 nm and a diameter of 2 mm, for example. The output of the laser oscillator 104 is, for example, about 100 mW. The parallel beam 10 output from the laser oscillator 104 is expanded into a fan shape only in the XZ plane by the Powell lens 105. The Powell lens 105 is a cylindrical lens having a rounded ridgeline, and is also called a laser line generator. It is often used to expand the parallel beam 10 output from the laser oscillator 104 into a linear shape with a uniform intensity distribution. In this embodiment, the Powell lens 105 is illustrated as expanding the parallel beam 10 having a diameter of 2 mm from the laser oscillator 104 to a full angle of 30°. The laser oscillator 104 is a single mode laser, and the intensity distribution of the output beam is a Gaussian distribution, with a 1 / e 2 The diameter is called the beam diameter. In other words, the beam diameter is 1 / e from the peak intensity value. 2 (13.6%).

[0019] As shown in FIG. 1, the cylindrical lens 106 (cylinder lens) has a curvature only in the XZ plane, acts as a convex lens in the horizontal direction, and does not act as a lens in the vertical direction. The parallel beam 10 emitted from the laser oscillator 104 is shaped into a parallel beam 10 with a width (length in the X direction) Wx and a thickness (length in the Y direction) t1 by the cylindrical lens 106. As an example, the cylindrical lens 106 with a focal length of 400 mm is used, and the distance between the Powell lens 105 and the cylindrical lens 106 is adjusted to approximately 400 mm, thereby forming the parallel beam 10 with a width W=200 mm and a thickness t1=2 mm. The parallel beam 10 shaped by the cylindrical lens 106 is irradiated in a stripe shape onto the outer peripheral surface of the sample 100. In FIG. 1, the irradiation area 110 of the irradiation light irradiated onto the outer peripheral surface of the sample 100 via the cylindrical lens 106 is shown by oblique hatching. The irradiated light is reflected by the outer peripheral surface of the sample 100 and projected onto the screen 102. The light reflected by the outer peripheral surface of the sample 100 is magnified by the curved surface of the outer peripheral surface of the sample 100 and projected onto the screen 102.

[0020] The screen 102 is disposed on the opposite side of the sample 100 from the laser oscillator 104 side, and is spaced apart from the sample 100. An optical image formed by the reflected light projected on the screen 102 in an enlarged form is read and observed by a line sensor camera 107 via a TV camera lens 108. The TV camera lens 108 and the line sensor camera 107 are disposed coaxially, and are disposed at an elevation angle β with respect to an optical surface on which the laser oscillator 104, the Powell lens 105, and the cylindrical lens 106 are linearly arranged. The material of the screen 102 can be plain paper that hardly transmits laser light and acts as a diffuser. In this case, the elevation angle β of the line sensor camera 107 is set to 30°.

[0021] FIG. 3 is an enlarged view for explaining an optical image in a state where the surface of a sample to be inspected is irradiated with irradiation light.

[0022] 3, the positional relationship between the field of view of the line sensor camera 107 on the screen 102 and the reflected light from the surface of the sample 100 will be described. Here, a YZ cross section of a three-dimensional coordinate system with the central axis O of rotation of the sample 100 as the origin is shown.

[0023] In this example, the illumination incident angle u1 to the specific position P on the sample 100 is set to 87°. Therefore, θ in FIG. 3 is 3°. As described above, the rollers 101a and 101b carrying the sample 100 can be moved up and down by a moving stage (not shown). Based on a predetermined inspection recipe, the moving stage moves the sample 100 up and down to accurately match the height of the optical axis 10' of the parallel beam 10 with the height of the apex A (one side edge) of the top of the sample 100. From this state, the sample 100 is raised in the Y direction so that the optical axis 10' of the parallel beam 10 matches the specific position P. If the movement amount of the sample 100, in other words, the height from the specific position P to the apex A is δ, then δ=R(1-cosθ) in FIG. 3. The diameter of the sample 100 is 22 mm, so the radius R=11 mm and θ=3°, and therefore δ=0.015 mm.

[0024] Here, the thickness t2 of the illumination light 10 that is directly irradiated onto the screen 102 without being irradiated onto the sample 100 is calculated as t1 / 2-δ. Since t1=2 mm, t2=0.985 mm. If the angle from the Y axis to the illumination incident point B where the light ray from the bottom surface of the parallel beam 10 with thickness t1 irradiates the outer peripheral surface of the sample 100 is v, then cos(v)=(R-(t1 / 2+δ)) / R. From this relational expression, the angle v is calculated as 24.8°.

[0025] If the distance L from the central axis O of the sample 100 to the screen 102 is 70 mm, the height h3 of the light ray reflected at the illumination incident point B when it reaches point S3 on the screen 102 can be calculated by substituting φ1 in equation (1) with v, resulting in h3 = 86.66 mm. In addition, since θ = 3°, when the light ray reflected at the specific position P reaches point S1 on the screen 102, h1 = 7.40 mm can be calculated from equation (1). [Number 1] h1=tan(φ1)·(L+R·sinθ)-R(1-cosθ)…(1) Here, φ1=180-2·u1, and u1=90-θ. Therefore, φ1=2θ. The thickness t2 of the irradiation light 10 that is directly irradiated onto the screen 102 is t1 / 2-R(1-cosθ).

[0026] The magnification M in the circumferential direction of the surface of the sample 100 at S1 is calculated using equation (2) to be M=13.03. [Number 2] M=L(tan(φ2)-tan(φ1)) / d ……(2) As mentioned above, φ1 = 2θ, φ2 = 2(θ + α). Also, α = 360 d / 2πR. Therefore, if the dimension of the arc portion PQ treated as an infinitesimal region, i.e., d, is constant, it can be seen that the magnification M increases with an increase in θ or L. In other words, under the condition that L is constant, when an optical image on the sample 100 (an optical image of the defect, if there is a defect) is projected onto the screen 102, the magnification differs depending on the height on the screen 102 (position in the Y direction).

[0027] The present invention will be described in detail below. In the following, a surface defect inspection device will be described in the first and second embodiments, and a surface defect inspection method will be described in the third embodiment. EXAMPLES

[0028] The first embodiment of the present invention is basically configured on the premise of the above-mentioned configurations in Figures 1 and 2. Figures 4 and 5 are diagrams showing an example of a three-dimensional configuration of a surface defect inspection device according to the first embodiment of the present invention and an example of an engineering system layout.

[0029] 4 and 5 is compared with the basic configuration examples of Figures 1 and 2 in that the light emitted by the laser 104 is collimated by the cylindrical lens 106, its direction is changed by the mirror 115, and the light is applied as irradiation light to the surface of the rotating cylindrical part 100. In this case, the screen 102 and the camera 107 are directly opposite each other, and this positional relationship is the basic arrangement.

[0030] 6 is an enlarged view for explaining an optical image in a state where the surface of the sample 100 in the case of Example 1 is irradiated with irradiation light. Here, the image is shown in XY coordinates based on the apex A of the rotating cylinder 100, and the coordinates of the apex A of the cylinder 100 are (X, Y)=(0, 0).

[0031] In contrast, P, indicated by the dotted line, is the incident position of the illumination light axis, B is the incident position of the lower end of the illumination light, t is the sheet thickness of the illumination light 10, R is the radius of the cylinder 100, u1 and u2 are the illumination incident angles at points P and B, φ1 and φ2 are the elevation angles of the reflected light at points P and B, L is the distance (A-S0) from the cylinder 100 to the screen 102, β1 and β2 are the incident angles of the reflected light at points S1 and S2 on the screen 102, and α is the installation angle of the screen 102.

[0032] As is clear from this figure, a part of the illumination light 10 is irradiated onto the sample surface from the tangential direction of a cylindrical sample 100 .

[0033] According to the first embodiment, the coordinates of each of points S1, S2, and S3 on the screen 102 can be obtained as follows. In this case, the parameters to be determined first are the sheet thickness t, the radius R of the sample 100, the distance L between the sample apex A and S0, the illumination incidence angle u1 at point P, and the installation angle α of the screen 102, and specific numerical examples thereof are t=1 mm, R=75 mm, L=30 mm, u1=87°, and α=45°.

[0034] Also, from the relationship in Figure 6, θ1=90-u1 θ2=acos(cosθ1ーt / (2·R)) u2=90-θ2 Φ1=180-2·u1 Φ2=180-2·u2 and Since Φ1+β1=α, β1=α-φ1 Since Φ2+β2=α, β2=α-φ2 It is as follows.

[0035] In this case, the line segment P-S1 can be expressed by equation (3), the line segment B-S2 can be expressed by equation (4), and the line segment S0-S2 can be expressed by equation (5). [Number 3] y=tanφ1 x+tanφ1 R sinθ1 (3) [Number 4] y=tanφ2 x+tanφ2 R sinθ2 (4) [Number 5] y=tanα x−L tanα (5) Furthermore, when (3)=(5), X1 of the coordinates (x1, y1) of S1 can be expressed by equation (6). [Number 6] x1=(R·sinθ1·tanφ1+L·tanα) / (tanα-tanφ1)=33.98mm···(6) Furthermore, substituting equation (6) into equation (5) gives y1 = 3.98 mm.

[0036] Next, when (4) = (5), X2, one of the coordinates (x2, y2) of S2, can be expressed by equation (7). [Number 7] x2=(R·sinθ2·tanφ2+L·tanα) / (tanα-tanφ2)=43.83mm···(7) Furthermore, substituting equation (7) into equation (5) gives y2 = 13.83 mm.

[0037] Next, X3 of the coordinates (x3, y3) of S3 can be expressed by equation (8). [Number 8] y3=t / 2-R(1-cosθ1)=0.40mm...(8) Furthermore, by substituting equation (8) into equation (5), we can obtain x3 = 30.40 mm.

[0038] According to the above, points S1, S2, and S3 on the screen 102 can be determined, and the camera 107 facing directly thereto can then be positioned at point S1. EXAMPLES

[0039] Example 2 of the present invention is also basically configured on the premise of the above-mentioned configurations in Figures 1 and 2. Figures 7 and 8 are diagrams showing an example of a three-dimensional configuration of a surface defect inspection device according to Example 2 of the present invention and an example of an engineering system layout.

[0040] 7 and 8, compared with the basic configuration examples of Figures 1 and 2, the light emitted by laser 104 is collimated by cylindrical lens 106, its direction is changed by mirror 115, and the light is applied as illumination light to the surface of rotating cylindrical part 100. In this case, however, the observation magnification of screen 102 changes (cos γ) depending on the angle γ between the normal to screen 102 and the optical axis of camera 107, and when the optical axis of the camera is vertical, γ=α. This positional relationship is adopted in Example 2.

[0041] Fig. 9 is an enlarged view for explaining an optical image in a state where the surface of the sample is irradiated with irradiation light in the case of Example 2. Here, when the camera optical axis is perpendicular to the normal line of S1 on the screen, the arrangement is such that γ=α, and the other relationships are the same as in Fig. 6.

[0042] The surface defect inspection apparatus of the above-mentioned Examples 1 and 2 includes a means (laser 104, mirror 115) for irradiating illumination light 10 onto the cylindrical surface of a cylindrical sample 100, a flat plate 102 for projecting light reflected from the sample surface, a means (camera 107) for observing the reflected light projected onto the flat plate surface, and a means for rotating the sample 100, and is configured so that a portion of the illumination light 10 is irradiated onto the sample surface from the tangential direction of the cylindrical sample 100.

[0043] According to the first and second embodiments of the present invention, it is possible to obtain a surface defect inspection device that can ensure the enlargement ratio even if the roll diameter is changed.

[0044] More specifically, according to the embodiment of the present invention, cylindrical parts of different diameters can be observed at the same magnification (resolution), and therefore defect inspection can be performed with the same detection sensitivity. Also, according to the embodiment of the present invention, when defects of the same size exist in cylindrical parts of different diameters, they can be detected as defects of the same dimensions in the detected optical image. Furthermore, according to the embodiment of the present invention, when assuming a case where the cylindrical surface roughness is large (other than a glossy surface), the illumination incidence angle is an important parameter, and therefore the above can be achieved by controlling the illumination incidence angle on the cylindrical surface to a constant value.

[0045] Regarding the visibility of Examples 1 and 2, in these examples, a part of the illumination light is irradiated from the tangential direction of the cylindrical sample. Therefore, a part of the illumination light is not irradiated onto the sample, or a part of the illumination light is directly irradiated onto the screen. In this case, the screen installation angle (and / or screen installation position) is determined according to the diameter of the cylindrical sample and the illumination incident angle on the cylindrical sample surface.

[0046] Regarding the necessity of adopting this invention, in conventional optical inspection, dirt and color unevenness on the sample surface give false information and it is not possible to extract only the unevenness information, but the Magic Mirror method can extract and distinguish only the unevenness information of the surface. Also, in order to obtain a Magical Image for the surface of an inspection target with a large surface roughness (Ra>0.5um), it is necessary to control the illumination incident angle to a large value (≧85°), but in order to set the optimal illumination incident angle for the target (surface roughness) and maintain the same conditions (magnification ratio) for inspection, this invention is essential. EXAMPLES

[0047] In the third embodiment, a surface defect inspection method will be described in detail. The surface defect inspection method is realized by a surface defect inspection system configured using a computer. Fig. 10 is a diagram showing an example of the configuration of a surface defect inspection system according to an embodiment of the present invention.

[0048] 10 includes a surface defect inspection apparatus 1C. The surface defect inspection apparatus 1C includes an irradiation light source 171, rollers 101a and 101b, a roller unit 172, a screen 102, a light receiver 175, a screen rocking mechanism 176, a line sensor camera 107, and a TV camera lens 108.

[0049] The irradiation light source 171 includes a laser oscillator 104 (see FIG. 1) and a lens unit that shapes the light beam emitted from the laser oscillator 104. Although the detailed optical path is omitted in the description of the irradiation light source 171 in FIG. 10, the irradiation light source 171 includes the laser 104, the cylinder lens 106, and the mirror 115 shown in FIG. 4, and is configured so that the light emitted by the laser 104 is collimated by the cylinder lens 106, and the direction of the light is changed by the mirror 115 to provide the light as the irradiation light 10 to the surface of the rotating cylindrical part 100.

[0050] Thus, a portion of the illumination light 10 positioned at a predetermined height is irradiated in a band shape onto an arc portion AB including the apex A and the specific position P of the sample 100, as shown in Fig. 6. The illumination light 10 irradiated onto the arc portion AB of the sample 100 is reflected by the arc portion AB of the sample 100 and irradiated onto the screen 102. Another portion of the illumination light 10, i.e., a light beam of thickness t2 above the apex A of the sample 100, is directly irradiated onto the screen 102, and a portion of it passes through an opening in the screen 102 and is detected by the photodetector 175.

[0051] A cylindrical sample 100 to be inspected is placed on a roller unit 172 by a loader (not shown). The roller unit 172 has a built-in sensor (not shown) that reads an identification number engraved on the surface of the sample 100. A computer 179 downloads an inspection recipe 181 for the sample 100 from a host server 182. The inspection recipe 181 includes the manufacturing history and diameter of the sample 100, and the inspection conditions for inspecting the surface defects.

[0052] Based on the contents of the inspection recipe 181, the computer 179 adjusts the height of the height adjustment stage 174 so that the irradiation light 10 emitted from the irradiation light source 171 has a desired angle of incidence with respect to the outer peripheral surface of the sample 100, thereby adjusting the height of the sample 100. At this time, the output of the photodetector 175, which changes depending on the height of the sample 100, is successively detected while adjusting the height of the height adjustment stage 174, thereby achieving precise setting of the height position.

[0053] The above procedure completes the relative alignment of the illumination light 10 and the sample 100. As a result, the illumination light 10 emitted from the illumination light source 171 is irradiated in a strip shape onto the arc portion AB (see FIG. 6) of the sample 100 from the tangential direction to the apex A of the sample 100. The light reflected by the arc portion AB of the sample 100 is projected onto a predetermined position on the screen 102.

[0054] The line sensor camera 107 and the TV camera lens 108 are mounted on a camera height adjustment stage 177. A computer 179 adjusts the height of the camera height adjustment stage 177 based on an inspection recipe 181 to adjust the observation height of the line sensor camera 107 on the screen 102.

[0055] After the positioning is completed as described above, the motor controller 173 is controlled based on the inspection recipe 181 to rotate the sample 100 once at a constant speed. While rotating the sample 100, the line sensor camera 107 is driven at a predetermined scan rate f to capture an optical image formed by the reflected light projected on the screen 102.

[0056] The image captured by the line sensor camera 107 is input to a computer 179. All of the above-mentioned operations of the apparatus are controlled by the computer 179 via an apparatus control unit 178. A defect detection algorithm is implemented in the computer 179, and the defect coordinates on the surface of the sample 100 are recorded in a storage device 180 by image processing, separately for the axial direction and the circumferential direction.

[0057] When the inspection of sample 100 is completed, an unloader (not shown) removes sample 100 from roller unit 172. The surface defect inspection system of the present invention realizes in-line 100-to-1 inspection of rods of different diameters. Therefore, if this surface defect inspection system is applied to each manufacturing process of the rods, which are samples, a process monitor that immediately detects defective parts in the manufacturing process can be realized. Furthermore, if the surface defect inspection system of the present invention is applied to the final appearance inspection process, 100-to-1 quality assurance of products can be realized.

[0058] In this embodiment, since the irradiation light source 171 is a laser light source, laser speckles occur on the screen 102. In order to eliminate these, a screen swinging mechanism 176 is provided.

[0059] In the above description, a configuration has been described in which an optical image pattern due to light reflected on the outer peripheral surface of the screen 102 is observed. However, if a line sensor camera that directly observes the surface of the sample 100 is added, it is possible to improve the ability to distinguish whether the optical image obtained from the sample 100 is due to a defect or dust. In addition, in each of the embodiments described so far, the front surface of the screen 102 is observed by the line sensor camera 107, but the screen 102 may be made of a semi-transparent material and the rear surface of the screen 102 may be observed.

[0060] Fig. 11 shows an example of the process flow of a surface defect inspection method realized by a surface defect inspection system using a computer. Here, the procedure for inspecting a rod with a radius r is shown. However, the following are assumed to be predetermined or known before starting the inspection: the pixel size (c) of the line sensor on the screen 102, the driving frequency (line rate; f) of the line sensor, and the illumination is a parallel light beam.

[0061] 11, the observation position (θ) on the cylindrical surface is obtained from the desired illumination incident angle in the first process step S1, and the illumination optical axis height (YB) is adjusted in process step S2.

[0062] Next, in the present invention, in processing step S3, the link installation angle α is adjusted to determine the magnification M of the cylinder surface (observation position on the screen: height). At this time, it is preferable to further adjust α and the distance L between the cylinder and the screen.

[0063] In process step S4, the rod rotation speed N (rps) is determined as N≦c·f / (2πr·M). At this time, it is recommended to take into consideration the angle γ between the screen normal and the camera optical axis so as to observe the condition N≦c·f / (2πr·M·cosγ). In process step S5, inspection is started according to the conditions thus determined.

[0064] By satisfying the above conditions, cylindrical parts with different diameters can be observed at the same magnification (resolution), so defect inspection can be performed with the same detection sensitivity. Furthermore, if cylindrical parts with different diameters have defects of the same size, they can be detected as defects of the same dimensions in the detection optical image. In particular, when assuming that the cylindrical surface has a large roughness (other than a glossy surface), the illumination incidence angle is an important parameter, so the above can be achieved by controlling the illumination incidence angle on the cylindrical surface to a constant value. [Explanation of symbols]

[0065] 1: Surface defect inspection device 100: Sample 101a, 101b: Laura 102: Screen 104: Laser oscillator 105: Powell lens 106: Cylindrical lens 107: Line sensor camera 108: TV camera lens 115: Mirror

Claims

1. A surface defect inspection device comprising: a means for irradiating a cylindrical surface of a cylindrical sample with illumination light; a flat plate for projecting light reflected from the surface of the sample; a means for observing the reflected light projected onto the surface of the flat plate; and a means for rotating the sample, A surface defect inspection apparatus, characterized in that a part of the illumination light is irradiated onto the surface of the sample from a tangential direction.

2. 2. The surface defect inspection apparatus according to claim 1, A surface defect inspection device characterized in that the angle of incidence of illumination light incident on a cylindrical surface of a cylindrical sample is adjusted to a desired value by adjusting the relative position of the axis of illumination light and the cylindrical sample.

3. 3. The surface defect inspection apparatus according to claim 2, A surface defect inspection device characterized by determining the installation angle (installation position) of a flat plate onto which light reflected from the surface of a cylindrical sample is projected based on the radius of the cylindrical sample and the angle of incidence of illumination light incident on the surface.

4. 4. The surface defect inspection apparatus according to claim 3, A surface defect inspection device characterized in that the observation field position of a camera on a flat plate coincides with the position of the optical axis incident on the surface of a cylindrical sample at a desired angle of incidence.

5. A surface defect inspection method using the surface defect inspection apparatus according to claim 1, A surface defect inspection method characterized by the steps of: determining the observation position (θ) on the cylindrical surface from the desired illumination incidence angle when starting inspection for surface defects; adjusting the illumination optical axis height; adjusting the link installation angle to determine the magnification of the cylindrical surface; and determining the number of rod rotations.

6. A surface defect inspection method using the surface defect inspection apparatus according to claim 1, A surface defect inspection method characterized in that when determining the magnification of the cylindrical surface, the link installation angle and the distance L between the cylinder and the screen are further adjusted.

7. A surface defect inspection method using the surface defect inspection apparatus according to claim 1, A surface defect inspection method characterized in that, when determining the number of rod rotations N, the angle γ between the screen normal and the camera optical axis is determined to satisfy the condition N≦c·f / (2πr·M·cos γ) in relation to the pixel size C, scan rate f, and magnification.

Images