Defect inspection device and defect inspection method

Abstract

To provide a defect inspection device and a defect inspection method capable of inspecting a defect in a cylinder where a transparent part and an opaque part exist even a line sensor is one sequence.SOLUTION: A defect inspection device is a device for inspecting a defect in a cylinder 100 where a transparent part and an opaque part exist in a peripheral wall part, and comprises: a first ring-shaped illuminating part 21 and a second ring-shaped illuminating part 22 penetrating the cylinder 100 in an axial direction of the cylinder 100 for radiating light toward a whole circumferential direction of the peripheral wall part in a prescribed portion of the cylinder 100 in an axial direction; a line sensor 23 for receiving transmitted light which is emitted from the first ring-shaped illuminating part 21 and transmitted the prescribed portion and at least reflected light which is emitted from the second ring-shaped illuminating part 22 and reflected on the prescribed portion, for imaging the prescribed portion; and a defect detection part for detecting a defect on the cylinder 100 on the basis of image data acquired from the line sensor 23.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] Patent Document 1 discloses a defect inspection device that inspects the outer wall surface of an opaque cylindrical body for defects. The defect inspection device of Patent Document 1 has a ring-shaped illumination unit that illuminates the outer wall surface of the cylindrical body, a line sensor (line CCD camera) that is arranged concentrically with the central axis of the cylindrical body and captures reflected light from the outer wall surface of the cylindrical body, and an image processing unit for detecting defects based on image data obtained from the line sensor. In this defect inspection device, the cylindrical body, which is the subject of the inspection, is continuously moved in its axial direction, and the reflected light is captured by the line sensor, so that the defect inspection of the outer wall surface of the cylindrical body can be performed continuously in the axial direction of the cylindrical body. Defects are detected by the light and dark (contrast) in the obtained image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-258169 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the defect inspection device of Patent Document 1 cannot inspect defects in a cylindrical body having a mixture of transparent and opaque parts in the peripheral wall (mixed cylindrical body). To explain this point, when the defect inspection device of Patent Document 1 is used to inspect the above-mentioned mixed cylindrical body, the light irradiated from the ring-shaped illumination unit to the cylindrical body is reflected by the opaque parts, but is mostly transmitted through the transparent parts. Therefore, in an image obtained by a line sensor that captures the reflected light, the opaque parts of the cylindrical body are bright and the transparent parts are dark. In other words, the obtained image shows the light and dark (contrast) due to the opaque and transparent parts of the cylindrical body. Therefore, it is difficult to detect defects from the obtained image.

[0005] In addition, in the defect inspection device of Patent Document 1, for example, in addition to a line sensor that captures light reflected from an opaque part of the cylindrical body, another line sensor that captures light transmitted through a transparent part of the cylindrical body may be prepared, and defects may be detected based on images obtained by these two types of line sensors (two series). However, having two series of line sensors is not preferable because it increases the cost of the defect inspection device.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a defect inspection device and a defect inspection method that are capable of inspecting defects in a cylindrical body containing a mixture of transparent and opaque parts, even with a single series of line sensors. [Means for solving the problem]

[0007] The defect inspection device of the present invention is a defect inspection device that inspects for defects in a cylindrical body having a transparent portion and an opaque portion in a peripheral wall portion, and includes a first ring-shaped illumination unit and a second ring-shaped illumination unit that pass the cylindrical body in the axial direction of the cylindrical body and irradiate light toward the entire circumferential direction of the peripheral wall portion at a predetermined portion of the cylindrical body in the axial direction, a line sensor that images the predetermined portion by receiving transmitted light emitted from the first ring-shaped illumination unit and transmitted through the transparent portion located at the predetermined portion, and reflected light emitted from at least the second ring-shaped illumination unit and reflected at the predetermined portion, and a defect detection unit that detects defects in the cylindrical body based on image data obtained from the line sensor.

[0008] In addition, the defect inspection method of the present invention is a defect inspection method for inspecting defects in a cylindrical body having a transparent portion and an opaque portion in a peripheral wall portion, in which the cylindrical body is passed through a first ring-shaped illumination unit and a second ring-shaped illumination unit in an axial direction of the cylindrical body, and light is irradiated from the first ring-shaped illumination unit and the second ring-shaped illumination unit toward the entire circumferential direction of the peripheral wall portion at a predetermined portion of the cylindrical body in the axial direction, and a line sensor receives transmitted light emitted from the first ring-shaped illumination unit and transmitted through the transparent portion located at the predetermined portion, and reflected light emitted from at least the second ring-shaped illumination unit and reflected at the predetermined portion to image the predetermined portion, and defects in the cylindrical body are detected based on image data obtained from the line sensor. Effect of the Invention

[0009] According to the present invention, even with a single line sensor, it is possible to inspect a cylindrical object having a mixture of transparent and opaque portions for defects. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram showing a defect inspection device according to an embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view of a cylindrical body to be inspected, taken perpendicular to the axial direction of the cylindrical body; [Diagram 3]1 is a front view showing the arrangement of a first ring-shaped illumination unit, a second ring-shaped illumination unit, and a line sensor as viewed from the axial direction of a cylindrical body in a defect inspection device according to an embodiment of the present invention. FIG. [Figure 4] 1 is a side view showing an arrangement of a first ring-shaped illumination unit, a second ring-shaped illumination unit, and a line sensor as viewed from the side in a defect inspection device according to an embodiment of the present invention. FIG. [Diagram 5] 4 is a diagram showing the positional relationship between an exit surface of a first ring-shaped illumination unit and a line sensor in the defect inspection device of FIGS. 1 and 3. FIG. [Figure 6] 6 is a diagram illustrating the light amount distribution on the emission surface of the first ring-shaped illumination unit in FIG. 5. FIG. [Figure 7] 5 is a line sensor waveform obtained by imaging a portion of a transparent part of a cylindrical body having a transparent defect by a line sensor disposed at a reference position in the configuration shown in FIG. 4. [Figure 8] 5 is a line sensor waveform obtained by imaging a portion of a transparent part of a cylindrical body having a transparent defect using a line sensor disposed at a predetermined position moved from a reference position in the configuration shown in FIG. 4. [Figure 9] 5 is a line sensor waveform obtained by imaging a defect-free portion of the transparent portion of the cylindrical body using a line sensor disposed at a predetermined position in the configuration shown in FIG. [Figure 10] FIG. 13 is a schematic diagram to explain why transparent defects cannot be detected when the optical axis of the line sensor is aligned with the "100% position" of the first ring-shaped illumination unit, and shows a state in which the optical axis of the line sensor is not refracted. [Figure 11] FIG. 13 is a schematic diagram to explain why transparent defects cannot be detected when the optical axis of the line sensor is aligned with the "100% position" of the first ring-shaped illumination unit, and shows the state in which the optical axis of the line sensor is bent. [Figure 12] FIG. 13 is a schematic diagram to explain why a transparent defect can be detected when the optical axis of the line sensor is aligned with the “50% position” of the first ring-shaped illumination unit, and shows a state in which the optical axis of the line sensor is not bent. [Figure 13]FIG. 13 is a schematic diagram to explain why a transparent defect can be detected when the optical axis of the line sensor is aligned with the “50% position” of the first ring-shaped illumination unit, and shows the state in which the optical axis of the line sensor is bent. [Figure 14] 5 is a line sensor waveform obtained by imaging a portion of an opaque part of a cylindrical body having a colored defect using a line sensor disposed at a predetermined position in the configuration shown in FIG. 4. [Figure 15] 5 is a line sensor waveform obtained by imaging a portion of a transparent part of a cylindrical body having a colored defect by a line sensor disposed at a predetermined position in the configuration shown in FIG. 4. [Figure 16] 11 is a side view showing the arrangement of a first ring-shaped illumination unit and a line sensor as viewed from the side in the defect inspection device of the comparative example. FIG. [Figure 17] 17 is a line sensor waveform obtained by imaging a portion of a transparent part of a cylindrical body having a transparent defect by a line sensor in the configuration shown in FIG. 16. [Figure 18] 13 is a side view showing the arrangement of a first ring-shaped illumination unit, a second ring-shaped illumination unit, and a line sensor, as viewed from the side, in a defect inspection device according to another embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A defect inspection device according to an embodiment of the present invention will now be described with reference to the drawings. As shown in FIG. 1, the defect inspection device 1 has an imaging unit 11 and a defect detection unit 12, and inspects a cylindrical body 100 (inspection object) for defects.

[0012] The cylindrical body 100 is a cylindrical object that is continuous in its axial direction. The cylindrical body 100 may be a rigid body that does not deform, or may be flexible. Specific examples of the cylindrical body 100 include products such as tubes and hoses.

[0013] As shown in FIG. 2, the cylindrical body 100 has a peripheral wall 110 having transparent portions 111 that transmit light and opaque portions 112 that do not transmit light. The transparent portions 111 and the opaque portions 112 are arranged in the peripheral direction of the peripheral wall 110. The number of the transparent portions 111 and the opaque portions 112 in the peripheral direction of the peripheral wall 110, the dimensions of the transparent portions 111 and the opaque portions 112 in the peripheral direction, and the like may be arbitrary. However, in order to detect defects in the transparent portions 111, the number of the transparent portions 111 and the opaque portions 112 is the same. In addition, as illustrated in FIG. 2, it is necessary to arrange the multiple transparent portions 111 so that two transparent portions 111 face each other in the radial direction of the cylindrical body 100.

[0014] The transparent portion 111 may have transparent defects such as surface irregularities or fish eyes, and colored defects such as foreign matter or dirt. Transparent defects are often defects that cannot be detected by a regular transmission optical system. The opaque portion 112 may have colored defects such as foreign matter or dirt.

[0015] In the defect inspection device 1 shown in Fig. 1, a cylindrical body 100 that is continuous in the axial direction is transported in the axial direction. In Fig. 1, the transport direction (also called the running direction) of the cylindrical body 100 is indicated by an arrow D1.

[0016] As shown in FIGS. 3 and 4, the imaging section 11 of the defect inspection apparatus 1 includes a first ring-shaped illumination section 21, a second ring-shaped illumination section 22, and a line sensor . The first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 pass the cylindrical body 100 inside them in the axial direction of the cylindrical body 100, and irradiate light toward the entire circumferential direction of the peripheral wall portion 110 (see Figure 2) at a specific portion 120 of the cylindrical body 100 in the axial direction of the cylindrical body 100.

[0017] The irradiation lights 31, 32, 33 emitted from the first and second ring-shaped illumination units 21, 22 proceed in the axial direction of the cylindrical body 100 as they proceed radially inward of the first and second ring-shaped illumination units 21, 22, respectively. That is, the irradiation lights 31, 32, 33 emitted from the first and second ring-shaped illumination units 21, 22 proceed in a direction inclined with respect to the radially inward of the first and second ring-shaped illumination units 21, 22, respectively. In Fig. 4, the inclination angle of the traveling direction of the irradiation lights 31, 32 emitted from the first ring-shaped illumination unit 21 and the inclination angle of the traveling direction of the irradiation light 33 emitted from the second ring-shaped illumination unit 22 are different, but may be the same, for example. The first and second ring-shaped illumination units 21 and 22 may use, for example, LED illumination, optical fiber illumination, or the like.

[0018] The amount of light of the irradiation light 31, 32 emitted from the first ring-shaped illumination unit 21 (output of the first ring-shaped illumination unit 21) and the amount of light of the irradiation light 33 emitted from the second ring-shaped illumination unit 22 (output of the second ring-shaped illumination unit 22) can be adjusted independently.

[0019] In this embodiment, the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 are located on opposite sides of a predetermined portion 120 of the cylindrical body 100 in the axial direction of the cylindrical body 100. Therefore, the light emitted from the first ring-shaped illumination unit 21 and the light emitted from the second ring-shaped illumination unit 22 are inclined in opposite directions to each other in the axial direction of the cylindrical body 100.

[0020] 3 and 4, the diameter dimension of the second ring-shaped illumination unit 22 is smaller than the diameter dimension of the first ring-shaped illumination unit 21. This makes it possible to prevent the optical axis 23A of the line sensor 23 from interfering with the second ring-shaped illumination unit 22. The diameter dimensions of the first and second ring-shaped illumination units 21 and 22 may be of any size.

[0021] The line sensor 23 is disposed so that the longitudinal direction of its imaging range is perpendicular to the axial direction (traveling direction D1) of the cylindrical body 100. The line sensor 23 is also disposed so that a predetermined portion 120 of the cylindrical body 100 is included in its imaging range. The line sensor 23 receives the transmitted light of the irradiation light 31 emitted from the first ring-shaped illumination unit 21, which is transmitted through the transparent portion 111 (see FIG. 2) of the cylindrical body 100 located at the predetermined portion 120 of the cylindrical body 100. The line sensor 23 also receives the reflected light of the irradiation light 33 emitted from the second ring-shaped illumination unit 22, which is reflected at the predetermined portion 120 of the cylindrical body 100. The line sensor 23 also receives the reflected light of the irradiation light 32 emitted from the first ring-shaped illumination unit 21, which is reflected at the predetermined portion 120 of the cylindrical body 100. That is, the line sensor 23 receives the composite light 35 that is a combination of the transmitted light and the reflected light. The "reflected light" received by the line sensor 23 includes not only the reflected light reflected at the opaque portion 112 of the cylindrical body 100, but also the reflected light reflected at the transparent portion 111 of the cylindrical body 100.

[0022] In this embodiment, the line sensor 23 is disposed such that its optical axis 23A is inclined toward the second ring-shaped illumination unit 22 with respect to the radial direction of the cylindrical body 100. For this reason, the line sensor 23 does not receive the reflected light that is emitted from the second ring-shaped illumination unit 22 and specularly reflected at the predetermined portion 120 of the cylindrical body 100. The line sensor 23 receives both the transmitted light and the reflected light, thereby capturing an image of the predetermined portion 120 of the cylindrical body 100 .

[0023] The line sensor 23 used has, for example, 2048 to 8192 elements. A line sensor 23 having an appropriate number of elements and speed (e.g., data rate, scan rate, etc.) is used depending on the width, running speed, resolution, installation space, etc. of the cylindrical body 100. Furthermore, multiple line sensors 23 (six in the example of FIG. 3) are used so as to be able to image the entire circumferential direction of the cylindrical body 100. As shown in FIG. 3, the multiple line sensors 23 are arranged at intervals in the circumferential direction of the cylindrical body 100.

[0024] The line sensor 23 receives reflected light and transmitted light while the cylindrical body 100 is being transported in the traveling direction D1. The line sensor 23 outputs an electrical signal (defect data) corresponding to the light and dark shade of the cylindrical body 100 to the defect detection unit 12. In other words, the line sensor 23 outputs an electrical signal corresponding to the light intensity distribution on the surface of the cylindrical body 100 for each line (hereinafter, inspection line) in a direction perpendicular to the traveling direction D1 of the cylindrical body 100. Examples of the line sensor 23 include a CMOS (complementary metal oxide semiconductor) camera and a CCD (charge-coupled device) camera.

[0025] The defect detection unit 12 shown in FIG. 1 is composed of an image processing computer and an image board connected to the line sensor 23 of the imaging unit 11, and detects defects in the cylindrical body 100 based on image data obtained from the line sensor 23. The defect detection unit 12 is composed of, for example, a binarization unit, a run-length encoding unit, and a connectivity processing unit. The defect detection unit 12 binarizes the defect data input from the line sensor 23 of the imaging unit 11 based on a predetermined threshold, compresses the defect data, performs connectivity processing, and measures the feature amount of the defect (information representing the features of the shape of the defect, for example, the perimeter, area, width, length, aspect ratio, and area rate of the defect). An image processing device LSC-6000 manufactured by MEC Co., Ltd. can be used as this defect detection unit 12.

[0026] Next, the first ring-shaped illumination unit 21 will be further described with reference to FIGS. As shown in Fig. 5, the first ring-shaped illumination unit 21 has an emission surface 21a that emits light mainly toward the line sensor 23. In Fig. 5, the emission surface 21a is linearly inclined with respect to the traveling direction D1 of the cylindrical body 100, but this is not limited thereto. The exit surface 21a of the first ring-shaped illumination unit 21 has a distribution (light amount distribution) in which the amount of light changes in the running direction D1 of the cylindrical body 100. The light amount distribution on the exit surface 21a of the first ring-shaped illumination unit 21 is shown in FIG. 6. The vertical axis of FIG. 6 is the camera output (256 gradations) of the line sensor. The horizontal axis of FIG. 6 is the camera pixels of the line sensor, which correspond to the direction along the exit surface 21a inclined with respect to the running direction D1 of the cylindrical body 100. The line sensor camera for examining the light amount distribution on the exit surface 21a is positioned so that the longitudinal direction of its imaging range corresponds to the direction along the exit surface 21a inclined with respect to the running direction D1.

[0027] As shown in Fig. 6, the emission surface 21a of the first ring-shaped illumination unit 21 has a light amount distribution in which the amount of light decreases with increasing distance from the brightest part. The brightest part of the emission surface 21a is defined as the "100% position". The "100% position" is often the center position of the emission surface 21a as illustrated in Fig. 5, but the position varies depending on the type of illumination. Figs. 5 and 6 also show a "50% position" that is shifted from the "100% position" in a direction corresponding to the traveling direction D1 of the cylindrical body 100. The "50% position" indicates a position where the amount of light (brightness) is half that of the "100% position".

[0028] Furthermore, in the defect inspection device 1 of this embodiment, the amount of light received by the line sensor 23 from the first ring-shaped illumination unit 21 is changed by changing the relative positions of the first ring-shaped illumination unit 21 and the line sensor 23. Specifically, as shown in Fig. 5, the line sensor 23 is moved (shifted) along the running direction D1 of the cylindrical body 100 relative to the first ring-shaped illumination unit 21 within a range where the optical axis 23A of the line sensor 23 intersects with the emission surface 21a of the first ring-shaped illumination unit 21. As a result, the position of the optical axis 23A of the line sensor 23 moves on the emission surface 21a. Fig. 5 shows that the optical axis 23A of the line sensor 23 moves from the "100% position" to the "50% position" on the emission surface 21a by moving the line sensor 23 along the running direction D1 of the cylindrical body 100.

[0029] Incidentally, even if the first ring-shaped illumination unit 21 is moved along the traveling direction D1 of the cylindrical body 100 relative to the line sensor 23, the amount of light received by the line sensor 23 from the first ring-shaped illumination unit 21 changes.

[0030] Table 1 below explains an embodiment of the devices and cylindrical body 100 used in the above-mentioned defect inspection device 1.

[0031] [Table 1]

[0032] Fig. 7 shows a line sensor waveform obtained by imaging a cylindrical body 100 having a transparent portion 111 and an opaque portion 112 by the imaging unit 11 in Fig. 4. The vertical axis in Fig. 7 is the camera output (256 gradations) of the line sensor 23, and the horizontal axis is the camera pixels of the line sensor 23, which correspond to the direction perpendicular to the axial direction (traveling direction D1) of the cylindrical body 100. The line sensor waveform in Fig. 7 is imaged in a state where the optical axis 23A of the line sensor 23 is aligned with the "100% position" of the first ring-shaped illumination unit 21 (see Fig. 5). The position of the line sensor 23 where the optical axis 23A of the line sensor 23 is aligned with the "100% position" of the first ring-shaped illumination unit 21 is set as the reference position (reference position).

[0033] 7 is acquired in a state where the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 are simultaneously turned on. When acquiring the line sensor waveform, the optical axis 23A of the line sensor 23 is aligned with the "100% position" of the first ring-shaped illumination unit 21, and then the output of the first ring-shaped illumination unit 21 is adjusted so that the amount of light received by the line sensor 23 in the areas corresponding to the spaces 99 on both sides of the cylindrical body 100 is approximately 128 Lv. In addition, the output of the second ring-shaped illumination unit 22 is adjusted so that the amount of light received by the line sensor 23 in the area of ​​the opaque portion 112 of the cylindrical body 100 is approximately 128 Lv. 7, the camera output (amount of received light) is approximately equal in the transparent portion 111 and the opaque portion 112 of the cylindrical body 100 and in the space 99. This makes it easier to detect defects (mainly colored defects caused by dirt, foreign matter, etc.) in the cylindrical body 100.

[0034] 7 is a waveform obtained by imaging a predetermined portion 120 of the cylindrical body 100 in which a transparent defect 131 exists in the transparent portion 111 of the cylindrical body 100. However, in the line sensor waveform of FIG. 7, the peak Lv of the transparent defect 131 is close to the texture Lv of the transparent portion 111 (the difference is only a few Lv), so the transparent defect 131 cannot be detected by the defect detection unit 12.

[0035] Therefore, the position of the line sensor 23 was changed from the "100% position" of the first ring-shaped illumination unit 21 to the "0% position" in 10% increments to check whether transparent defects were detected. When acquiring the line sensor waveform at each position of the line sensor 23, after arranging the optical axis 23A of the line sensor 23 at each position, the output of the first ring-shaped illumination unit 21 is adjusted so that the amount of light received by the line sensor 23 in the area corresponding to the space 99 on both sides of the cylindrical body 100 is approximately 128Lv. In addition, the output of the second ring-shaped illumination unit 22 is adjusted so that the amount of light received by the line sensor 23 in the area of ​​the opaque part 112 of the cylindrical body 100 is approximately 128Lv. The results are shown in Table 2 below.

[0036] [Table 2]

[0037] "Camera position" in Table 2 is the position of optical axis 23A of line sensor 23 on exit surface 21a of first ring-shaped illumination unit 21, and the numerical value (%) indicated by "camera position" corresponds to "100% position", "50% position", etc. shown in FIG. 5. "Defect peak Lv" in Table 2 is the peak Lv of transparent defect 131, and "detection or not" indicates whether or not a transparent defect was detected by defect detection unit 12. In "detection or not", "◯" indicates that a transparent defect was detected, and "×" indicates that a transparent defect was not detected.

[0038] As shown in Table 2, when the optical axis 23A of the line sensor 23 is located at the "100% position" or "90% position" of the first ring-shaped illumination unit 21, the difference between the peak Lv of the transparent defect and the texture Lv of the transparent portion 111 is about several Lv. In other words, the contrast of the transparent defect is low. For this reason, the defect detection unit 12 was unable to detect the transparent defect.

[0039] Furthermore, when the optical axis 23A of the line sensor 23 is located at the "0% position", the transmitted light from the first ring-shaped illumination unit 21 does not reach the line sensor 23, so the texture Lv of the transparent portion 111 becomes very small. As a result, the difference between the peak Lv of the transparent defect and the texture Lv of the transparent portion 111 becomes about several Lv, and the contrast of the transparent defect is low, so that the defect detection unit 12 cannot detect the transparent defect. Furthermore, because the transmitted light from the first ring-shaped illumination unit 21 does not reach the line sensor 23, the amount of light received by the line sensor 23 in the areas corresponding to the spaces 99 on both sides of the cylindrical body 100 becomes very small, so that the defect detection unit 12 cannot detect the transparent defect.

[0040] On the other hand, when the optical axis 23A of the line sensor 23 is located between the "80% position" and the "10% position" of the first ring-shaped illumination unit 21, the difference between the peak Lv of the transparent defect and the texture Lv of the transparent part 111 is 17 Lv or more. In other words, the contrast of the transparent defect is high. This allows the defect detection unit 12 to detect the transparent defect.

[0041] For example, the line sensor waveform in Fig. 8 is a waveform captured under the same conditions as the line sensor waveform in Fig. 7, except that the optical axis 23A of the line sensor 23 is aligned with the "50% position" of the first ring-shaped illumination unit 21. That is, the line sensor waveform in Fig. 8 is a waveform captured by the line sensor 23 that has been moved from a reference position corresponding to the "100% position" and placed at a predetermined position corresponding to the "50% position". In the line sensor waveform in Fig. 8, the camera outputs (received light amounts) in the transparent portion 111 and the opaque portion 112 of the cylindrical body 100 and in the space 99 are approximately equal, and only the output of the transparent defect 131 is prominently displayed. This allows stable inspection and allows the transparent defect 131 to be detected.

[0042] The line sensor waveform in Fig. 9 is a waveform obtained by imaging a cylindrical body 100 without a transparent defect with the optical axis 23A of the line sensor 23 aligned with the "50% position" of the first ring-shaped illumination unit 21. In the line sensor waveform in Fig. 9, the camera output (amount of received light) in the transparent portion 111 and the opaque portion 112 of the cylindrical body 100 and in the space 99 are approximately equal, and no output value is observed that is equivalent to the transparent defect 131 that appeared in the line sensor waveform in Fig. 8. A comparison of the line sensor waveforms in Figs. 8 and 9 also makes it clear that transparent defects can be detected.

[0043] Hereinafter, with reference to Figures 10, 11, etc., the reason why transparent defects cannot be detected when the optical axis 23A of the line sensor 23 is aligned with the "100% position" or "90% position" of the first ring-shaped illumination unit 21 will be described. 10 and 11 show a state in which a transparent defect 131 having an uneven shape present in the transparent part 111 of the cylindrical body 100 passes between the line sensor 23 and the first ring-shaped illumination unit 21 when the optical axis 23A of the line sensor 23 is aligned with the "100% position" of the first ring-shaped illumination unit 21. In Figs. 10 and 11, reference numeral 23A1 denotes a sensor-side optical axis extending from the line sensor 23 to the transparent part 111. Reference numeral 23A2 denotes an illumination-side optical axis extending from the transparent part 111 to the first ring-shaped illumination unit 21.

[0044] 10, optical axis 23A of line sensor 23 passes through the center of transparent defect 131. Because the surface of the center of transparent defect 131 is perpendicular to optical axis 23A, optical axis 23A does not refract at the surface of transparent defect 131. In other words, illumination-side optical axis 23A2 of optical axis 23A extends without being inclined relative to sensor-side optical axis 23A1. For this reason, light from the "100% position" of first ring-shaped illumination unit 21 is incident on line sensor 23. 11, optical axis 23A of line sensor 23 passes through the peripheral portion of transparent defect 131. Because the surface of the peripheral portion of transparent defect 131 is inclined with respect to optical axis 23A, optical axis 23A is refracted at the surface of transparent defect 131. That is, illumination-side optical axis 23A2 of optical axis 23A extends at an angle with respect to sensor-side optical axis 23A1. For this reason, light is incident on line sensor 23 from a position slightly shifted from the "100% position" of first ring-shaped illumination unit 21.

[0045] 6, the light amount at a position slightly shifted from the "100% position" is almost the same as the light amount at the "100% position." Therefore, when the optical axis 23A of the line sensor 23 is aligned with the "100% position" of the first ring-shaped illumination unit 21, the transparent defect 131 cannot be emphasized in the line sensor waveform captured by the line sensor 23. As a result, the transparent defect 131 cannot be detected. Even if the optical axis 23A of the line sensor 23 is aligned with the "90% position" of the first ring-shaped illumination unit 21, the transparent defect 131 cannot be highlighted and therefore cannot be detected for the same reason as in the case of the "100% position."

[0046] Next, with reference to Figures 12, 13, etc., we will explain why transparent defects can be detected when the optical axis 23A of the line sensor 23 is aligned with a position between the "80% position" and the "10% position" of the first ring-shaped illumination unit 21. Figures 12 and 13 show the state when an unevenly shaped transparent defect 131 present in the transparent part 111 of the cylindrical body 100 passes between the line sensor 23 and the first ring-shaped illumination unit 21 when the optical axis 23A of the line sensor 23 is aligned with the "50% position" of the first ring-shaped illumination unit 21.

[0047] 12, optical axis 23A of line sensor 23 passes through the center of transparent defect 131. Because the surface of the center of transparent defect 131 is perpendicular to optical axis 23A, optical axis 23A does not refract at the surface of transparent defect 131. In other words, illumination-side optical axis 23A2 of optical axis 23A extends without being inclined relative to sensor-side optical axis 23A1. For this reason, light from the "50% position" of first ring-shaped illumination unit 21 is incident on line sensor 23. 13, on the other hand, optical axis 23A of line sensor 23 passes through the peripheral portion of transparent defect 131. Because the surface of the peripheral portion of transparent defect 131 is inclined with respect to optical axis 23A, optical axis 23A is refracted at the surface of transparent defect 131. In other words, illumination-side optical axis 23A2 of optical axis 23A extends at an angle with respect to sensor-side optical axis 23A1. For this reason, light is incident on line sensor 23 from a position slightly shifted from the "50% position" of first ring-shaped illumination unit 21.

[0048] 6, the light amount at a position slightly shifted from the "50% position" varies greatly with respect to the light amount at the "50% position." Therefore, when the optical axis 23A of the line sensor 23 is aligned with the "50% position" of the first ring-shaped illumination unit 21, the transparent defect 131 can be emphasized in the line sensor waveform captured by the line sensor 23. This makes it possible to detect the transparent defect 131. For the same reason, if the optical axis 23A of the line sensor 23 is aligned with a position between the "80% position" and the "10% position" of the first ring-shaped illumination unit 21, not limited to the "50% position," the transparent defect 131 can be emphasized, and therefore the transparent defect 131 can be detected.

[0049] Next, the presence or absence of detection of transparent defects was examined when the amount of light received by the line sensor 23 in the area of ​​the opaque portion 112 of the cylindrical body 100 was varied. Here, the optical axis 23A of the line sensor 23 was placed at the "50% position", and then the output of the first ring-shaped illumination unit 21 was adjusted so that the amount of light received by the line sensor 23 in the area corresponding to the space 99 on both sides of the cylindrical body 100 was approximately 128 Lv. Then, with the first ring-shaped illumination unit 21 turned on, the output of the second ring-shaped illumination unit 22 was adjusted to examine the presence or absence of detection of transparent defects when the amount of light received by the line sensor 23 in the area of ​​the opaque portion 112 of the cylindrical body 100 was varied from 35 Lv to 245 Lv. The results are shown in Table 3 below.

[0050] [Table 3]

[0051] In Table 3, "texture level of opaque portion" indicates the amount of light received by line sensor 23 in the area of ​​opaque portion 112 of cylindrical body 100. When "texture level of opaque portion" is 35Lv, second ring-shaped illumination unit 22 is not lit, and only irradiation light 32 from first ring-shaped illumination unit 21 is reflected by opaque portion 112, and the reflected light is received by line sensor 23. In Table 3, "Defect peak level" is the peak level of a transparent defect, and "detection" indicates whether or not a transparent defect can be detected by defect detection unit 12. In "detection", "◯" indicates that a transparent defect could be detected, and "×" indicates that a transparent defect could not be detected. In "detection", "△" indicates that a transparent defect could be detected, but was more difficult to detect than "◯".

[0052] As shown in Table 3, when the "texture level of the opaque portion" was relatively low, such as 35Lv and 45Lv, the peak level of the transparent defect was higher than the texture level of the opaque portion, so that the transparent defect could not be detected by the defect detection unit 12. In addition, when the "texture level of the opaque part" is 65 Levels, although the peak level of the transparent defect is lower than the texture level of the opaque part, the difference between the two is small, at only a few Levels, so although the transparent defect can be detected, it is difficult to detect.

[0053] On the other hand, when the "texture level of the opaque part" is between 85 and 245 LV, the peak level of the transparent defect is lower than the texture level of the opaque part, and the difference between them is sufficiently large, at 20 LV or more. In other words, the contrast of the transparent defect is sufficiently high. This allows the defect detection unit 12 to detect the transparent defect.

[0054] From the above, it has been found that, when the line sensor light receiving amount Lv (space 99) of the first ring-shaped illumination unit 21 is set to 1, adjusting the output of the second ring-shaped illumination unit 22 so that the reflected light Lv at the opaque part 112 of the cylindrical body 100 is 0.35 or more, is effective in detecting transparent defects.

[0055] Next, the presence or absence of detection of transparent defects when the output of the first ring-shaped illumination unit 21 was varied was examined. Here, the optical axis 23A of the line sensor 23 was set to the "50% position", and then the output of the second ring-shaped illumination unit 22 was adjusted so that the amount of light received by the line sensor 23 in the area of ​​the opaque part 112 of the cylindrical body 100 was approximately 128 Lv. Then, with the second ring-shaped illumination unit 22 turned on, the output of the first ring-shaped illumination unit 21 was adjusted to examine the presence or absence of detection of transparent defects when the amount of light received by the line sensor 23 in the areas corresponding to the spaces 99 on both sides of the cylindrical body 100 varied from 0 Lv to 245 Lv. The results are shown in Table 4 below.

[0056] [Table 4]

[0057] "Space Lv" in Table 4 indicates the amount of light received by the line sensor 23 in the areas corresponding to the spaces 99 on both sides of the cylindrical body 100. When "space Lv" is 0Lv, the first ring-shaped illumination unit 21 is not lit. In Table 4, "Defect peak Lv" is the peak Lv of a transparent defect, and "Detection" indicates whether a transparent defect was detected by defect detection unit 12. In "Detection", "◯" indicates that a transparent defect was detected, and "×" indicates that a transparent defect was not detected.

[0058] As shown in Table 4, when the "space level" is low, such as 0Lv or 25Lv, the peak level of the transparent defect is higher than the space level. For this reason, the defect detection unit 12 was unable to detect the transparent defect. Furthermore, when the "space level" is 45 Lv, although the peak level of the transparent defect is lower than the space level, the difference between them is very small, about 1 Lv, so that the defect detection unit 12 was unable to detect the transparent defect.

[0059] On the other hand, when the "space level" is between 65 and 245 LV, the peak level of the transparent defect is lower than the space level, and the difference between them is sufficiently large, at 15 LV or more. In other words, the contrast of the transparent defect is sufficiently high. This allows the defect detection unit 12 to detect the transparent defect.

[0060] From the above, it was found that when the line sensor light receiving amount Lv (opaque portion 112) of the second ring-shaped illumination unit 22 is 1, adjusting the output of the first ring-shaped illumination unit 21 so that the space Lv is 0.66 or more is effective in detecting transparent defects.

[0061] The defect inspection device 1 of this embodiment can also detect colored defects in the opaque portion 112 and the transparent portion 111 of the cylindrical body 100. Fig. 14 is a line sensor waveform obtained by imaging a predetermined portion 120 where a colored defect 132 exists in an opaque portion 112 of a cylindrical body 100 by the line sensor 23 arranged at a predetermined position corresponding to the "50% position". The line sensor waveform in Fig. 14 is a waveform obtained when the output of the first ring-shaped illumination unit 21 is adjusted so that the amount of light received by the line sensor 23 in areas corresponding to the spaces 99 on both sides of the cylindrical body 100 is approximately 128Lv, and the output of the second ring-shaped illumination unit 22 is adjusted so that the amount of light received by the line sensor 23 in the area of ​​the opaque portion 112 of the cylindrical body 100 is approximately 128Lv, with the line sensor 23 arranged at a position corresponding to the "50% position". In the line sensor waveform in Fig. 14, the camera output (amount of light received) in the transparent portion 111 and the opaque portion 112 of the cylindrical body 100 and the space 99 are approximately equal, and only the output of the colored defect 132 in the opaque portion 112 is clearly shown. This allows stable inspection and detection of colored defects 132. That is, the defect inspection device 1 of this embodiment can detect not only transparent defects in the transparent portion 111 but also colored defects 132 in the opaque portion 112.

[0062] FIG. 15 shows a line sensor waveform obtained by imaging a predetermined portion 120 of the cylindrical body 100 where a colored defect 132 exists in the transparent portion 111 by the line sensor 23 arranged at a predetermined position corresponding to the "50% position". The line sensor waveform in FIG. 15 is a waveform obtained under the same conditions as the line sensor waveform in FIG. 14. In the line sensor waveform in FIG. 15, the camera output (amount of received light) in the transparent portion 111 and the opaque portion 112 of the cylindrical body 100 and in the space 99 are approximately equal, and only the output of the colored defect 132 in the transparent portion 111 is prominently displayed. This allows stable inspection and allows the colored defect 132 to be detected. That is, the defect inspection device 1 of this embodiment can detect not only the transparent defect in the transparent portion 111 but also the colored defect 132 in the transparent portion 111. It should be noted that the colored defect 132 in the transparent portion 111 can be detected even if, for example, the line sensor 23 is disposed at a predetermined position corresponding to the "100% position."

[0063] In the defect inspection device 1 of this embodiment, the line sensor 23 receives only the reflected light reflected by the cylindrical body 100 out of the irradiation light from the second ring-shaped illumination unit 22. In addition, the line sensor 23 receives both the transmitted light of the irradiation light from the first ring-shaped illumination unit 21 that has passed through the cylindrical body 100 and the reflected light reflected by the cylindrical body 100. For this reason, when adjusting the amount of light received by the line sensor 23, it is necessary to first adjust the amount of irradiation light 31, 32 from the first ring-shaped illumination unit 21, and then adjust the amount of irradiation light 33 from the second ring-shaped illumination unit 22. Specifically, first, the first ring-shaped illumination unit 21 is dimmed so that the amount of light received by the line sensor 23 in an area corresponding to the space 99 where there is no cylindrical body 100 is 128 Lv. Then, after dimming the first ring-shaped illumination unit 21, the second ring-shaped illumination unit 22 is turned on while the first ring-shaped illumination unit 21 is turned on, and the second ring-shaped illumination unit 22 is dimmed so that the amount of light received by the line sensor 23 in the cylindrical body 100 (transparent portion 111, opaque portion 112) is 128 Lv.

[0064] As described above, in the defect inspection device 1 of this embodiment, the transmitted light received by the line sensor 23 is light emitted from the first ring-shaped illumination unit 21 and transmitted through the transparent portion 111 of the cylindrical body 100. Moreover, the reflected light received by the line sensor 23 is mainly light emitted from the second ring-shaped illumination unit 22 and reflected by the opaque portion 112 and the transparent portion 111 of the cylindrical body 100. For this reason, by independently adjusting the amount of light emitted from the first ring-shaped illumination unit 21 and the amount of light emitted from the second ring-shaped illumination unit 22, the amount of transmitted light and the amount of reflected light received by the line sensor 23 can be independently adjusted.

[0065] This makes it possible to align the output value of line sensor 23 at transparent portion 111 (amount of light reaching line sensor 23 from transparent portion 111) and the output value of line sensor 23 at opaque portion 112 (amount of light reaching line sensor 23 from opaque portion 112) at predetermined portion 120 of cylindrical body 100 imaged by line sensor 23. As a result, the contrast of defects (particularly colored defects) is made prominent at predetermined portion 120 of cylindrical body 100 imaged by line sensor 23, making it possible to detect the defects. From the above, even if the line sensor 23 is a single series, it is possible to inspect the cylindrical body 100 in which the transparent portion 111 and the opaque portion 112 are mixed for defects.

[0066] Furthermore, in the defect inspection device 1 of this embodiment, the amount of light received by the line sensor 23 from the first ring-shaped illumination unit 21 changes by changing the relative positions of the first ring-shaped illumination unit 21 and the line sensor 23. This makes it possible to highlight the contrast of transparent defects (such as unevenness or fisheyes) in the transparent part 111 and detect the transparent defects.

[0067] Moreover, in the defect inspection device 1 of this embodiment, the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 are located on opposite sides of each other with respect to the predetermined portion 120 of the cylindrical body 100 in the axial direction of the cylindrical body 100. Even without considering the sizes (dimensions) of the first and second ring-shaped illumination units 21 and 22, the light (irradiation light) from each of the first and second ring-shaped illumination units 21 and 22 toward the predetermined portion 120 of the cylindrical body 100 can be easily prevented from being blocked by each other's ring-shaped illumination units 22 and 21. That is, the irradiation light 31 and 32 from the first ring-shaped illumination unit 21 toward the predetermined portion 120 of the cylindrical body 100 can be easily prevented from being blocked by the second ring-shaped illumination unit 22. Also, the irradiation light 33 from the second ring-shaped illumination unit 22 toward the predetermined portion 120 of the cylindrical body 100 can be easily prevented from being blocked by the first ring-shaped illumination unit 21.

[0068] If the imaging unit 11 of the defect inspection device 1 includes only the first ring-shaped illumination unit 21 and the line sensor 23, and does not include the second ring-shaped illumination unit 22, it is not possible to inspect the cylindrical body 100, which includes a mixture of transparent parts 111 and opaque parts 112, for defects. This point will be described below with reference to Figs. 16 and 17.

[0069] As shown in Figure 16, when the imaging unit 11 has only the first ring-shaped illumination unit 21 and the line sensor 23, the line sensor 23 receives a combined light 35 that is a combination of the transmitted light of the illumination light 31 of the first ring-shaped illumination unit 21 that passes through the tubular body 100 and the reflected light of the illumination light 32 of the first ring-shaped illumination unit 21 that is reflected at the tubular body 100.

[0070] Table 5 below explains examples of devices and cylindrical body 100 used in the defect inspection device including image pickup unit 11 of FIG.

[0071] [Table 5]

[0072] Fig. 17 shows a line sensor waveform obtained by imaging the cylindrical body 100 with the imaging unit 11 of Fig. 16. The line sensor waveform of Fig. 17 was acquired in a state where the output of the first ring-shaped illumination unit 21 was adjusted so that the amount of light received by the line sensor 23 in the areas corresponding to the spaces 99 on both sides of the cylindrical body 100 was around 128 Lv. In the line sensor waveform of FIG. 17, the amount of light received by the line sensor 23 in the area of ​​the transparent portion 111 of the cylindrical body 100 includes the amount of light transmitted through the transparent portion 111 of the cylindrical body 100 and the amount of light reflected at the transparent portion 111. On the other hand, the amount of light received by the line sensor 23 in the area of ​​the opaque portion 112 of the cylindrical body 100 includes only the amount of light reflected at the opaque portion 112. For this reason, the amount of light received by the line sensor 23 in the area of ​​the transparent portion 111 of the cylindrical body 100 becomes larger than the amount of light received by the line sensor 23 in the area of ​​the opaque portion 112 of the cylindrical body 100. In addition, these two amounts of light received cannot be made equal. For this reason, even if there is a defect in the cylindrical body 100, this defect cannot be detected by the defect detection unit 12. In other words, it is not possible to inspect the defect of the cylindrical body 100 in which the transparent portion 111 and the opaque portion 112 are mixed.

[0073] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and can be modified as appropriate without departing from the spirit of the present invention.

[0074] In the defect inspection device 1 of the present invention, for example, as shown in FIG. 18, the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 may be located on the same side of the predetermined portion 120 of the cylindrical body 100 in the axial direction of the cylindrical body 100. In this case, the directions of the irradiation lights 31, 32, and 33 from the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 toward the predetermined portion 120 of the cylindrical body 100 are the same in the axial direction of the cylindrical body 100. In this case, one of the first and second ring-shaped illumination units 21 and 22 may be located at a position that does not block the illumination light of the other ring-shaped illumination unit toward the predetermined portion 120 of the cylindrical body 100. This makes it possible to prevent one of the first and second ring-shaped illumination units 21 and 22 from blocking the irradiation light from the other ring-shaped illumination unit toward the predetermined portion 120 of the cylindrical body 100.

[0075] 18, the diameter dimension of the second ring-shaped illumination unit 22 is smaller than the diameter dimension of the first ring-shaped illumination unit 21. In addition, the second ring-shaped illumination unit 22 is positioned farther from the predetermined site 120 of the cylindrical body 100 in the axial direction of the cylindrical body 100 than the first ring-shaped illumination unit 21. This makes it possible to prevent the first ring-shaped illumination unit 21 from blocking the irradiation light 33 directed from the second ring-shaped illumination unit 22 toward the predetermined site 120 of the cylindrical body 100.

[0076] When the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 are positioned on the same side with respect to the predetermined portion 120 of the cylindrical body 100, even if the angle of the optical axis 23A of the line sensor 23 is set arbitrarily, it is possible to prevent the transmitted light emitted from the first ring-shaped illumination unit 21 and transmitted through the cylindrical body 100 from being blocked by the second ring-shaped illumination unit 22. In other words, it is possible to freely set the orientation of the optical axis 23A of the line sensor 23 with respect to the cylindrical body 100.

[0077] The present invention is not limited to the defect inspection apparatus as described above, but may also be applicable to a defect inspection method corresponding to the defect inspection apparatus. The defect inspection method of the present invention is a method in which, with a cylindrical body 100 passed through a first ring-shaped illumination unit 21 and a second ring-shaped illumination unit 22 in the axial direction of the cylindrical body 100, light is irradiated from the first ring-shaped illumination unit 21 and the second ring-shaped illumination unit 22 toward the entire circumferential direction of the peripheral wall portion 110 at a predetermined portion 120 of the cylindrical body 100 in the axial direction, and a line sensor 23 receives transmitted light emitted from the first ring-shaped illumination unit 21 and transmitted through a transparent portion 111 located at the predetermined portion 120 of the cylindrical body 100, and reflected light emitted from at least the second ring-shaped illumination unit 22 and reflected at the predetermined portion 120 of the cylindrical body 100, to image the predetermined portion 120 of the cylindrical body 100, and defects in the cylindrical body 100 are detected based on the image data obtained from the line sensor 23. The defect inspection method of the present invention has the same effects as the above-mentioned defect inspection apparatus. [Explanation of symbols]

[0078] 1. Defect inspection equipment 11 Imaging unit 12 Defect detection section 21 First ring-shaped illumination unit 22 Second ring-shaped illumination unit 23 Line Sensor 100 Cylindrical body 110 Peripheral wall section 111 Transparent part 112 Opaque area 120 Predetermined part D1 Travel direction (axial direction)

Claims

1. A defect inspection device for inspecting a cylindrical body having a transparent portion and an opaque portion on a peripheral wall thereof, comprising: a first ring-shaped illumination unit and a second ring-shaped illumination unit that pass through the cylindrical body in an axial direction of the cylindrical body and irradiate light toward the entire circumferential direction of the peripheral wall portion at a predetermined portion of the cylindrical body in the axial direction; a line sensor that captures an image of the predetermined location by receiving transmitted light that is emitted from the first ring-shaped illumination unit and transmitted through the transparent portion located at the predetermined location, and at least reflected light that is emitted from the second ring-shaped illumination unit and reflected at the predetermined location; and a defect detection unit that detects defects in the cylindrical body based on image data obtained from the line sensor; A defect inspection device comprising:

2. 2. The defect inspection device according to claim 1, wherein an amount of light emitted from the first ring-shaped illumination unit and an amount of light emitted from the second ring-shaped illumination unit are independently adjustable.

3. 2. The defect inspection device according to claim 1, wherein the amount of light received by the line sensor from the first ring-shaped illumination unit is changed by changing a relative position between the first ring-shaped illumination unit and the line sensor.

4. The defect inspection device according to claim 1 , wherein the first ring-shaped illumination unit and the second ring-shaped illumination unit are located on opposite sides of the predetermined portion of the cylindrical body in the axial direction.

5. The defect inspection device according to claim 1 , wherein the first ring-shaped illumination unit and the second ring-shaped illumination unit are located on the same side of the predetermined portion of the cylindrical body in the axial direction.

6. 1. A defect inspection method for inspecting a cylindrical body having a transparent portion and an opaque portion on a peripheral wall thereof, comprising: a first ring-shaped illumination unit and a second ring-shaped illumination unit are arranged so that the cylindrical body is passed through the first ring-shaped illumination unit and the second ring-shaped illumination unit in an axial direction of the cylindrical body, and light is irradiated from the first ring-shaped illumination unit and the second ring-shaped illumination unit to a predetermined portion of the cylindrical body in the axial direction in a circumferential direction of the peripheral wall portion; a line sensor receives transmitted light emitted from the first ring-shaped illumination unit and transmitted through the transparent portion located at the predetermined location, and at least reflected light emitted from the second ring-shaped illumination unit and reflected at the predetermined location, to capture an image of the predetermined location; A defect inspection method for detecting defects in the cylindrical body based on image data obtained from the line sensor.

Images