Cylindrical surface imaging device

Abstract

To provide a cylindrical surface imaging device that can image the cylindrical surface of a cylindrical product under certain conditions.SOLUTION: A cylindrical surface imaging device (1) integrally includes irradiation means (2) that irradiates an imaging target area on a cylindrical surface (91) with light, a frame portion (4) that supports imaging means (3) at a position above the irradiation means and facing the imaging target area, and is arranged parallel to the axis of the cylindrical product in a state of use, and a pair of spacing holding portions (5) extending from both axial ends of the frame portion to a position in contact with the cylindrical surface to maintain a constant spacing (H1) between the imaging means and the cylindrical surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cylindrical surface imaging device for imaging the surface of a cylindrical product, i.e., the cylindrical surface. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 3-295450 (Patent Document 1) discloses a method for photographing a cylindrical object under inspection. This photographing method involves placing a flat reflector on the surface of the cylindrical object under inspection so as to surround the area under inspection, irradiating the area under inspection with light from a light source placed diagonally above along the axial direction of the object under inspection, and photographing the area under inspection with a camera placed opposite the light source in the axial direction of the object under inspection. The image of the object under inspection photographed by the camera is subjected to image analysis such as binarization processing by an image processing device to detect the presence of irregularities on the surface of the object under inspection, i.e., the presence of defective parts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 3-295450 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, a reflector is placed on the surface of the object to be inspected to increase the amount of light in the peripheral areas of the area to be inspected, thereby preventing a healthy surface from being displayed as a defective area due to insufficient brightness.

[0005] On the other hand, in order to quantitatively evaluate an object to be inspected using an image captured by a camera, it is necessary to capture an image of the inspection target area under constant conditions each time. To achieve this, it is necessary to keep the positional relationship between the light source, the image capturing means, and the object to be inspected constant each time. However, in the configuration of Patent Document 1, the positions of the light source and the camera are not fixed, so it is not possible to perform quantitative evaluation using the captured image.

[0006] The present invention has been made to solve the above-mentioned problems, and its object is to provide a cylindrical surface photographing device that can photograph the cylindrical surface of a cylindrical product under certain conditions. [Means for solving the problem]

[0007] A cylindrical surface photographing device according to one aspect of the present invention is a photographing device for photographing the cylindrical surface of a cylindrical product, and integrally comprises an illumination means for irradiating light onto the area to be photographed on the cylindrical surface, a frame portion that supports the photographing means at a position above the illumination means and facing the area to be photographed, and that is positioned parallel to the axis of the cylindrical product when in use, and a pair of spacing retaining portions that extend from both axial ends of the frame portion to positions abutting the cylindrical surface, for maintaining a constant distance between the photographing means and the cylindrical surface.

[0008] Preferably, the distal ends of the pair of spacing portions are formed by arc-shaped contact portions having a radius of curvature larger than the radius of curvature of the cylindrical surface.

[0009] Preferably, the imaging device further includes a cylindrical light-shielding member that surrounds the periphery of the space to be imaged by the imaging means and blocks external light. In this case, the pair of spacing retaining portions are preferably configured by a pair of axially opposing portions of the cylindrical light-shielding member that face each other along the axial direction.

[0010] It is also desirable that an elastic member having elasticity is provided on at least a part of the lower end of the cylindrical light-shielding member.

[0011] The illumination means preferably includes a pair of light sources fixed to the pair of spacer retaining portions, respectively.

[0012] The cylindrical product is typically a cast iron pipe manufactured by a centrifugal die casting method. [Effects of the Invention]

[0013] According to the present invention, the cylindrical surface of a cylindrical product can be photographed under certain conditions, and as a result, the image photographed by the photographing means can be used for quantitative evaluation of each cylindrical product. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are diagrams showing a schematic configuration of a cylindrical surface imaging device according to an embodiment of the present invention, in which (A) and (B) are a side view and a cross-sectional view showing the relationship between the cylindrical surface imaging device and a cylindrical product when not in use. [Figure 2] 1A and 1B are diagrams showing a schematic configuration of a cylindrical surface imaging device according to an embodiment of the present invention, in which (A) and (B) are a side view and a cross-sectional view showing the relationship between the cylindrical surface imaging device and a cylindrical product in use. [Figure 3] 1A and 1B are a perspective view and a side view showing a specific example of the configuration of a cylindrical surface imaging device according to an embodiment of the present invention. [Figure 4] 3A and 3B are diagrams illustrating the function of a contact portion of the cylindrical surface imaging device according to the embodiment of the present invention. [Figure 5] FIG. 10 is a diagram schematically illustrating a cylindrical surface imaging device according to a modified example of an embodiment of the present invention. [Figure 6] FIG. 6(A) is a perspective view showing a cast iron pipe manufactured by the mold centrifugal casting method, and FIG. 6(B) is a diagram showing an image obtained by photographing a part of the casting surface (cylindrical surface) of the cast iron pipe using a normal photographing means. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals and description thereof will not be repeated.

[0016] <Overview of the configuration> The schematic configuration of a cylindrical surface imaging device 1 according to this embodiment will be described with reference to Figures 1 and 2. The cylindrical surface imaging device 1 is a device for imaging the cylindrical surface of a cylindrical product 90 such as a cast iron pipe. Figure 1 shows the cylindrical surface imaging device 1 in an unused state, and Figure 2 shows the cylindrical surface imaging device 1 in an used state. Note that Figure 1(B) is a cross-sectional view taken along line IB-IB in Figure 1(A), and Figure 2(B) is a cross-sectional view taken along line IIB-IIB in Figure 2(A).

[0017] The cylindrical surface imaging device 1 images the cylindrical surface 91 of the cylindrical product 90 from above, acquiring an image of a partial region (image target region) of the cylindrical surface 91. Arrow A1 in Figures 1 and 2 indicates a direction parallel to the axis O of the cylindrical product 90, and this direction is also referred to as the "left-right direction." Arrow A2 indicates a direction perpendicular to the left-right direction, and this direction is also referred to as the "depth direction." The "depth direction" coincides with the radial direction of the cylindrical product 90. Arrow A3 indicates a direction away from the cylindrical product 90, and this direction is referred to as the "upward direction." The opposite direction is referred to as the "downward direction." The left-right direction, depth direction, and up-down direction of the cylindrical surface imaging device 1 can be referred to as the x-direction, y-direction, and z-direction, respectively.

[0018] The cylindrical surface imaging device 1 according to this embodiment images the cylindrical surface 91 of a cylindrical product 90 placed horizontally on a conveying means (such as a belt conveyor) in a factory from vertically above. Therefore, in this embodiment, the up-down direction represents the vertical direction, and the left-right direction and the depth direction correspond to the horizontal direction. Note that the cylindrical surface imaging device 1 may be configured to image the cylindrical surface 91 from the side (for example, directly beside it), and "above" is not limited to vertically above.

[0019] The cylindrical surface photographing device 1 integrally comprises a camera 3 as a photographing means, a light source 2 as an illuminating means for irradiating a photographing target area of ​​the cylindrical surface 91 (the area surrounded by a dashed line in FIG. 1) with light, a frame section 4 for supporting the camera 3, and a pair of spacing units 5. In this embodiment, such an integrated unit is called a photographing unit PU. Note that the light source 2 is not shown in FIGS. 1(B) and 2(B).

[0020] The cylindrical surface imaging device 1 includes, for example, an elevator means 8 connected to the frame unit 4, and the imaging unit PU is provided so as to be slidable up and down between an upper retracted position (corresponding to a non-use state) shown in Fig. 1 and a working position (corresponding to a use state) shown in Fig. 2 by the elevator means 8. The elevator means 8 may be realized, for example, by a mechanical control means (not shown), or may be realized by the operator himself. In other words, the imaging unit PU can be automatically or manually slid up and down between the upper retracted position and the working position.

[0021] The frame unit 4 is a member that supports the camera 3 at a position facing the cylindrical surface 91 (the area to be photographed). The camera 3 is attached to the frame unit 4 so that it faces directly downward and is located above the light source 2. The space 30 from the lens of the camera 3 to the area to be photographed on the cylindrical surface 91 is referred to as the "space to be photographed 30."

[0022] The frame part 4 is arranged parallel to the axis O when viewed from the side of the cylindrical product 90, and is arranged horizontally in this embodiment. More specifically, when viewed in the direction of the axis O of the cylindrical product 90, the frame part 4 is arranged so as to be perpendicular to an imaginary line connecting the axis center (axis O) of the cylindrical product 90 and the lens center of the camera 3. The point where the cylindrical surface 91 intersects with this imaginary line is the circumferential center position 91t of the area to be photographed, and in this embodiment, this is the uppermost end of the cylindrical surface 91.

[0023] The frame 4 is formed in a rectangular shape with the long sides extending in the left-right direction and the short sides extending in the depth direction. The frame 4 may be formed by assembling a plurality of plates or rods into a frame shape, or may be formed from a single flat plate as shown in Fig. 3(A).

[0024] The pair of spacing retaining portions 5 extend downward from both ends of the frame portion 4 in the axial direction O (left-right direction). The pair of spacing retaining portions 5 are disposed on the left and right sides of the imaging target space 30, respectively, and are equal in length. As shown in FIGS. 2(A) and 2(B), the pair of spacing retaining portions 5 abut at their lower ends against the cylindrical surface 91 in the usage state, and function as legs of the imaging unit PU. In this way, the tip end portion (the portion including the lower end surface) of each spacing retaining portion 5 forms an "abutment portion 51" that abuts against the cylindrical surface 91 in the usage state. This allows the distance H1 between the camera 3 and the cylindrical surface 91 (specifically, the shortest distance between the lens of the camera 3 and the imaging target area) to be maintained constant in the usage state.

[0025] 1(B) and 2(B), the spacing members 5 extend in the up-down direction (vertical direction in this embodiment) so as to overlap an imaginary line connecting the axis (axis O) of the cylindrical surface 91 and the lens center of the camera 3 when viewed in the direction of axis O. Each spacing member 5 may be formed of a rod-like member that is long in the up-down direction, or may be formed of, for example, a substantially rectangular plate-like member with its long sides extending in the up-down direction and its short sides extending in the depth direction. In either case, it is desirable that the pair of spacing members 5 have the same shape.

[0026] The light sources 2 are typically fixed to the inside (on the side of the space to be photographed) of each of the pair of spacing members 5. In other words, the illumination means provided in the photographing unit PU includes a pair of light sources 2, which are attached so as to illuminate the photographing area on the cylindrical surface 91 from both sides in the direction of the axis O of the cylindrical product 90. It is desirable that each light source 2 is arranged in a position overlapping with an imaginary line connecting the axis center (axis O) of the cylindrical surface 91 and the lens center of the camera 3 when viewed in the direction of the axis O.

[0027] The heights from the contact portions 51 to the installation positions of the light sources 2 are all equal. As a result, the distance H2 between each light source 2 and the cylindrical surface 91 (specifically, the height H2 from the area to be photographed to the light source 2) is maintained constant during use, eliminating the need to adjust the height of the light source 2. As a result, by using the photographing unit PU, it is possible to photograph the cylindrical surface 91 of the cylindrical product 90 under conditions that optimize the positional relationship of the light source 2 and camera 3 with respect to the area to be photographed.

[0028] The photographing unit PU preferably further includes a cylindrical light-shielding member 6 (shown by imaginary lines in FIGS. 1 and 2) that surrounds the periphery of the space 30 to be photographed by the camera 3 and blocks external light. This allows the photographing area of ​​the cylindrical surface 91 to be photographed under constant conditions (the same conditions) without being affected by the surrounding lighting environment, etc.

[0029] <Specific configuration example> Fig. 3(A) is a perspective view showing a specific example of the configuration of the cylindrical surface imaging device 1. The cylindrical surface imaging device 1 has a case 10 that is roughly rectangular parallelepiped and has an open bottom end, and a camera 3 and a pair of light sources 2 are attached to this case 10. The case 10 is made of a material that has light-blocking properties and a certain degree of rigidity (for example, resin, wood, cardboard, etc.). The case 10 forms the outer shell of the imaging unit PU.

[0030] The frame 4 and cylindrical light-shielding member 6 described above are realized by the case 10. Specifically, the top panel 10a of the case 10 forms the frame 4, and the four side surfaces 10b to 10e of the case 10 form the cylindrical light-shielding member 6. The camera 3 is provided in the center of the top panel 10a of the case 10. The top panel 10a forms an upper light-shielding member that covers the upper opening of the cylindrical light-shielding member 6.

[0031] Four side surfaces 10b to 10e of the case 10 surround the periphery of the space 30 to be photographed by the camera 3. Of the four side surfaces 10b to 10e, a pair of side surface portions 10b, 10c facing each other along the axis O (hereinafter referred to as "axial facing portions") block external light from entering from both sides in the axis O (left-right direction), and a pair of side surface portions 10d, 10e facing each other along the radial direction (hereinafter referred to as "radial facing portions") block external light from entering from both sides in the radial direction (depth direction).

[0032] In the photographing unit PU shown in Fig. 3(A), the axial facing portions 10b, 10c of the cylindrical light blocking member 6 function as a pair of spacing retaining portions 5. In other words, the pair of spacing retaining portions 5 are configured by the pair of axial facing portions 10b, 10c of the cylindrical light blocking member 6. Therefore, in this embodiment, the spacing retaining portions 5 are formed by flat plate-like portions. The two light sources 2 are attached to the inner surfaces of the pair of axial facing portions 10b, 10c, facing each other.

[0033] Each light source 2 may be realized by a single LED lighting fixture having a length in the depth direction as shown in the figure, or may include a plurality of LED bulbs arranged along the depth direction as a form not shown. The light sources 2 may also be attached to the inner surfaces of the pair of radially facing portions 10d, 10e so as to face each other.

[0034] FIG. 3(B) is a schematic side view of the cylindrical surface imaging device 1 as viewed from one side in the direction of the axis O. The lower ends of the axial facing portions 10b, 10c are cut out in an arc shape along the depth direction. That is, when viewed in the direction of the axis O, the abutting portion (tip) 51 of the spacing portion 5 is formed in an arc shape. The radius of curvature R2 of the arc of the abutting portion 51 is (slightly) larger than the radius of curvature R1 of the cylindrical surface 91. As a result, when the lifting means 8 lowers the imaging unit PU from the upper retracted position to the working position, the upper end portion of the cylindrical product 90 fits into the arc-shaped abutting portion 51, so that the imaging unit PU (case portion 10) can be stably placed on the cylindrical product 90 when in use.

[0035] The ratio "R2 / R1" of the radius of curvature of the contact portion 51 to the cylindrical surface 91 is greater than 1.0 and less than or equal to 2.0, and preferably less than or equal to 1.7. More preferably, it is greater than 1.0 and less than or equal to 1.1. This reduces the gaps between the cylindrical surface 91 and both ends of the contact portion 51 in the lateral direction (depth direction of the photographing unit PU) and the gaps between the lower ends of the radial facing portions 10d, 10e and the cylindrical surface 91, thereby reducing the intrusion of external light into the photographing target space 30 through these gaps.

[0036] By photographing the cylindrical surface 91 with the camera 3 mounted on the above-mentioned photographing unit PU, a good image can be obtained even when the cylindrical product 90 is a cast iron pipe manufactured by the centrifugal die casting method. This will be explained with reference to Figure 6. Figure 6(A) is a perspective view showing a cast iron pipe 100, and Figure 6(B) is an image obtained by photographing a portion of the cast surface (cylindrical surface) of the cast iron pipe 100 with ordinary photographing means. Arrow A4 in Figures 6(A) and (B) indicates the circumferential direction of the cast iron pipe 100.

[0037] Since minute irregularities (irregularities due to peening) are formed on the inner peripheral surface of the cylindrical mold used in the mold centrifugal casting method, a cast surface (cylindrical surface) 101 of a cast iron pipe 100 manufactured by the mold centrifugal casting method has a number of annular irregularity patterns 102 appearing in a striped pattern, as shown in Figure 6(B). Therefore, when the cylindrical surface 101 of the cast iron pipe 100 is illuminated from only one side in the direction of the axis O, shadows are cast on the concaves of the irregularity pattern 102. This makes it difficult to accurately grasp the condition of the cast surface from an image captured by a photographing means.

[0038] In contrast, in this embodiment, the intrusion of external light is suppressed, and the cylindrical surface 91 is photographed from directly above by the camera 3 while a pair of light sources 2 at the same height illuminate the target area of ​​the cylindrical surface 91 from both sides (diagonally downward) along the axis O. This prevents shadows from being cast on the recesses of the uneven pattern 102, as described above. This allows for a clear image of the uneven shape of the cylindrical surface 91 to be obtained. Therefore, as schematically shown in FIG. 3(B), for example, by processing the image photographed by the camera 3 in an image processing device PC, it becomes possible to quantitatively evaluate the quality of the cylindrical surface 91 of the cylindrical product 90. As a result, the image of the cylindrical surface 91 photographed by the camera 3 can be suitably used as an image for machine learning.

[0039] Here, the central angle θ of the arc of the abutment portion 51 is less than 180 degrees, preferably less than 120 degrees. Furthermore, it is desirable that the photographing unit PU be able to move horizontally along the depth direction while being raised or lowered by the lifting means 8. In this case, as shown in FIG. 4 , even if the center position of the case portion 10 (the position of the camera 3) is relatively shifted to one side in the depth direction (the left side in the drawing) during the process of lowering the photographing unit PU from the upper retracted position to the working position by the lifting means 8, the end portion on the opposite side (the right side in the drawing) of the abutment portion 51 first contacts the cylindrical surface 91a and continues to descend along the cylindrical surface 91a, thereby suppressing or preventing positional shifting during use. In other words, the abutment portion 51 functions as a guide member, allowing the light source 2 and the camera 3 to be appropriately positioned (centered) relative to the photographing target area on the cylindrical surface 91.

[0040] Therefore, for example, when photographing cylindrical products 90 that are continuously transported in a factory, etc., even if the position of the cylindrical products 90 is slightly shifted, images of the cylindrical surface 91 photographed under the same conditions (constant conditions) can be obtained each time.

[0041] The radius of curvature R2 (FIG. 3(B)) of the contact portion 51 may be determined so as to be compatible with a plurality of cylindrical products 90 of different diameters. In this case, by determining the radius of curvature R2 to be (slightly) larger than the radius of curvature R1b of the cylindrical surface 91b of a cylindrical product 90 with a relatively large diameter, as shown in FIG. 4, the center of the contact portion 51 can be reliably contacted with the cylindrical surface 91a (radius of curvature R1a) of a cylindrical product 90 with a relatively small diameter.

[0042] However, when the case 10 is to be adapted to accommodate a plurality of cylindrical products 90 with different diameters, as shown in FIG. 5, a resilient member 7 may be attached to the lower end (lower end surface) of the radially facing portions 10d, 10e of the case 10. The resilient member 7 is formed, for example, from a foam such as urethane or sponge, and has light-blocking properties. It is desirable that the resilient member 7 extend in the left-right direction across the entire width of the lower edge of the radially facing portions 10d, 10e. In this case, the intrusion of external light into the case 10 can be more sufficiently suppressed during use, thereby improving the photographing conditions.

[0043] The elastic member 7 may also be provided at the lower end (lower end surface) of the pair of axial facing portions 10b, 10c (not shown). That is, all or part of the abutting portion 51 may be realized by the elastic member 7. In this case, even when the cylindrical surface 91a of a cylindrical product 90 with a relatively small diameter is to be photographed, the contact area of ​​the abutting portion 51 becomes large, thereby further improving the photographing conditions.

[0044] In this embodiment, the cylindrical light shielding member 6 has been described as having a prismatic shape, but is not limited to this example. The cylindrical light shielding member 6 may have a cylindrical shape, for example.

[0045] In addition, in this embodiment, the cylindrical light-shielding member 6 is realized by the rigid case portion 10, but if the cylindrical light-shielding member 6 and the pair of spacing portions 5 are configured separately as shown in Fig. 1, the cylindrical light-shielding member 6 does not have to be rigid. For example, the cylindrical light-shielding member 6 may be realized by a flexible fabric suspended from the frame portion 4.

[0046] Although the example in which the cylindrical product 90 is a cast iron pipe 100 manufactured by the mold centrifugal casting method has been described, the cylindrical surface imaging device 1 can also be suitably used for cast iron pipes manufactured by other methods and other types of pipe products. When other types of pipe products are targeted, the number and installation positions of the light sources 2 that illuminate the cylindrical surface 91 are not limited to the example described above.

[0047] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0048] 1 cylindrical surface photographing device, 2 light source, 3 camera, 4 frame portion, 5 spacing holding portion, 6 cylindrical light blocking member, 7 elastic member, 8 lifting means, 10 case portion, 10b, 10c axial facing portion, 10d, 10e radial facing portion, 30 photographing target space, 51 abutment portion, 90 cylindrical product, 91, 91a, 91b cylindrical surface, 100 cast iron pipe, 102 uneven pattern, O axis line, PU photographing unit.

Claims

1. An imaging device for imaging a cylindrical surface of a cylindrical product, an illumination means for irradiating a target area on the cylindrical surface with light; a frame portion that supports the imaging means at a position above the irradiation means and facing the imaging target area, and that is disposed parallel to the axis of the cylindrical product in a state of use; a pair of interval retaining portions extending from both axial end portions of the frame portion to positions where the frame portion abuts against the cylindrical surface, for maintaining a constant interval between the imaging means and the cylindrical surface; A cylindrical surface imaging device in which the spacing retaining portion is positioned so as to overlap an imaginary line connecting the axial center of the cylindrical product and the lens center of the imaging means when viewed in the axial direction of the cylindrical product.

2. 2. The cylindrical surface imaging device according to claim 1, wherein the distal ends of the pair of spacing members are formed as arc-shaped contact portions having a radius of curvature larger than the radius of curvature of the cylindrical surface.

3. Further provided is a cylindrical light-shielding member that surrounds the periphery of the space to be photographed by the photographing means and blocks external light, 3. The cylindrical surface imaging device according to claim 1, wherein the pair of spacing portions are formed by a pair of axially facing portions of the cylindrical light blocking member that face each other along the axial direction.

4. 4. The cylindrical surface imaging device according to claim 3, wherein an elastic member having elasticity is provided on at least a part of the lower end of said cylindrical light blocking member.

5. 5. The cylindrical surface imaging device according to claim 1, wherein said illuminating means includes a pair of light sources fixed to said pair of spacing portions, respectively.

6. 6. The cylindrical surface imaging device according to claim 1, wherein the cylindrical product is a cast iron pipe.

7. An imaging device for imaging the cylindrical surface of a cylindrical product, comprising: an illumination means for irradiating a target area on the cylindrical surface with light; a frame portion that supports the imaging means at a position above the irradiation means and facing the imaging target area, and that is disposed parallel to the axis of the cylindrical product in a state of use; a pair of interval retaining portions extending from both axial end portions of the frame portion to positions where the frame portion abuts against the cylindrical surface, for maintaining a constant interval between the imaging means and the cylindrical surface; A cylindrical surface imaging device, wherein the tip portions of the pair of spacing maintaining portions are configured as arc-shaped abutment portions having a radius of curvature larger than the radius of curvature of the cylindrical surface.

Images