JP7796565B2 - Cylindrical surface imaging device - Google Patents

Description

The present invention relates to a cylindrical surface imaging device that images the surface of a cylindrical product, i.e., the cylindrical surface.

JP 3-295450 A (Patent Document 1) discloses a method for photographing a cylindrical object under inspection. This method involves placing a flat reflector on the surface of the cylindrical object under inspection, surrounding the area under inspection; illuminating the area under inspection with light from a light source positioned diagonally above and along the axial direction of the object; and photographing the area under inspection with a camera positioned 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.

Japanese Patent Application Publication No. 3-295450

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

On the other hand, in order to quantitatively evaluate an object being inspected using images captured by a camera, it is necessary to photograph the area being inspected under consistent conditions each time. To do this, it is necessary to maintain a consistent positional relationship between the light source, imaging means, and object being inspected each time. However, with the configuration described in Patent Document 1, the positions of the light source and camera are not fixed, making it impossible to perform quantitative evaluation using the captured images.

The present invention was made to solve the above-mentioned problems, and its purpose is to provide a cylindrical surface imaging device that can capture images of the cylindrical surface of cylindrical products under certain conditions.

A cylindrical surface imaging device according to one aspect of the present invention is an imaging device for imaging the cylindrical surface of a cylindrical product, and integrally comprises: an illumination means for irradiating light onto an area to be imaged on the cylindrical surface; a frame portion that supports the imaging means at a position above the illumination means and facing the area to be imaged, and that is positioned parallel to the axis of the cylindrical product when in use; and a pair of spacing retainers that extend from both axial ends of the frame portion to positions where they abut the cylindrical surface, maintaining a constant distance between the imaging means and the cylindrical surface.

Preferably, the tip ends of the pair of spacing retainers are configured as arc-shaped abutment portions having a radius of curvature greater than the radius of curvature of the cylindrical surface.

Preferably, the device further includes a cylindrical light-shielding member that surrounds the space to be photographed by the photographing means and blocks external light. In this case, the pair of spacing portions is preferably formed by a pair of axially facing portions of the cylindrical light-shielding member that face each other along the axial direction.

It is also desirable that at least a portion of the lower end of the cylindrical light-blocking member be provided with an elastic member.

It is desirable that the illumination means include a pair of light sources fixed to each of the pair of spacing portions.

The above cylindrical products are typically cast iron pipes manufactured using the mold centrifugal casting method.

This invention makes it possible to photograph the cylindrical surface of a cylindrical product under certain conditions. As a result, the images captured by the photographing means can be used for quantitative evaluation of each cylindrical product.

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. 1A and 1B are side and cross-sectional views showing the relationship between the cylindrical surface imaging device and a cylindrical product in use; 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. 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. FIG. 10 is a diagram schematically illustrating a cylindrical surface imaging device according to a modified example of an embodiment of the present invention. FIG. 6A is a perspective view showing a cast iron pipe manufactured by a mold centrifugal casting method, and FIG. 6B 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.

Embodiments of the present invention will be described in detail with reference to the drawings. Note that identical or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

<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).

The cylindrical surface imaging device 1 images the cylindrical surface 91 of the cylindrical product 90 from above, acquiring an image of a partial area (the imaging target area) of the cylindrical surface 91. Arrow A1 in Figures 1 and 2 represents the direction parallel to the axis O of the cylindrical product 90, and is also referred to as the "left-right direction." Arrow A2 represents the direction perpendicular to the left-right direction, and is also referred to as the "depth direction." The "depth direction" coincides with the radial direction of the cylindrical product 90. Arrow A3 represents the direction away from the cylindrical product 90, and 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.

The cylindrical surface imaging device 1 according to this embodiment images the cylindrical surface 91 of a cylindrical product 90 placed horizontally on a transport 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 depth direction correspond to the horizontal direction. Note that the cylindrical surface imaging device 1 may also be configured to image the cylindrical surface 91 from the side (for example, directly beside it), and "above" is not limited to vertically above.

The cylindrical surface imaging device 1 integrally comprises a camera 3 as an imaging means, a light source 2 as an illumination means for irradiating the imaging target area of the cylindrical surface 91 (the area surrounded by the dashed line in Figure 1) with light, a frame unit 4 for supporting the camera 3, and a pair of spacing units 5. In this embodiment, this integrated unit is referred to as the imaging unit PU. Note that the light source 2 is not shown in Figures 1(B) and 2(B).

The cylindrical surface imaging device 1 includes, for example, an elevator 8 connected to the frame 4, and the imaging unit PU is arranged to be slidable vertically by the elevator 8 between the upper retracted position (corresponding to the non-use state) shown in FIG. 1 and the working position (corresponding to the use state) shown in FIG. 2. The elevator 8 may be realized, for example, by a mechanical control means (not shown), or by the operator's own hand. In other words, the imaging unit PU can be automatically or manually slid vertically between the upper retracted position and the working position, and thus can be repositioned.

The frame 4 is a member that supports the camera 3 in a position facing the cylindrical surface 91 (the area to be photographed). The camera 3 is attached to the frame 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 "photography target space 30."

When viewed from the side of the cylindrical product 90, the frame portion 4 is arranged parallel to the axis O, and in this embodiment, it is arranged horizontally. More specifically, when viewed in the direction of the axis O of the cylindrical product 90, the frame portion 4 is arranged so that it is perpendicular to an imaginary line connecting the axis (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, which in this embodiment is the uppermost end of the cylindrical surface 91.

The frame portion 4 is formed, for example, in a rectangular shape with the long sides extending left to right and the short sides extending in the depth direction. The frame portion 4 may be formed, for example, by assembling multiple plates or rods into a frame shape, or may be formed from a single flat plate as shown in Figure 3(A).

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 arranged on both the left and right sides of the imaging target space 30, and are equal in length. As shown in Figures 2(A) and 2(B), the pair of spacing retaining portions 5 abut at their lower ends against the cylindrical surface 91 when in use, functioning as legs of the imaging unit PU. In this way, the tip (portion including the lower end surface) of each spacing retaining portion 5 forms an "abutment portion 51" that abuts against the cylindrical surface 91 when in use. This maintains a constant 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) when in use.

As shown in Figures 1(B) and 2(B), the spacing retaining portions 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 retaining portion 5 may be formed from a rod-shaped member that is long in the up-down direction, or may be formed from, for example, a substantially rectangular plate-shaped 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 retaining portions 5 have the same shape.

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 positioned, when viewed in the direction of the axis O, so as to overlap with an imaginary line connecting the axis center (axis O) of the cylindrical surface 91 and the lens center of the camera 3.

The height from the abutment portion 51 to the installation position of the light source 2 is the same for all light sources 2. As a result, the distance H2 between each light source 2 and the cylindrical surface 91 (specifically, the height from the target area 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, the cylindrical surface 91 of the cylindrical product 90 can be photographed under conditions that optimize the positional relationship of the light source 2 and camera 3 relative to the target area.

It is desirable that the photographing unit PU further include a cylindrical light-shielding member 6 (shown by phantom lines in Figures 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 on the cylindrical surface 91 to be photographed under constant conditions (the same conditions) without being affected by the surrounding lighting environment, etc.

<Specific configuration example>
3A 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 the 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.

The frame 4 and cylindrical light-blocking 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-blocking member 6. The camera 3 is located in the center of the top panel 10a of the case 10. The top panel 10a forms an upper light-blocking member that covers the upper opening of the cylindrical light-blocking member 6.

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

In the photographing unit PU shown in Figure 3 (A), the axially facing portions 10b, 10c of the cylindrical light-blocking member 6 function as a pair of spacing retainers 5. In other words, the pair of spacing retainers 5 is composed of the pair of axially facing portions 10b, 10c of the cylindrical light-blocking member 6. Therefore, in this embodiment, the spacing retainers 5 are formed from flat plate-like portions. The two light sources 2 are attached facing each other to the inner surfaces of the pair of axially facing portions 10b, 10c.

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

Figure 3 (B) shows 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 axially opposing 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, allowing the imaging unit PU (case portion 10) to be stably placed on the cylindrical product 90 when in use.

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), as well as the gaps between the lower ends of the radial facing portions 10d and 10e and the cylindrical surface 91, thereby reducing the intrusion of external light into the photographing target space 30 through these gaps.

By photographing the cylindrical surface 91 with the camera 3 mounted on the above-mentioned photography unit PU, good images can be obtained even when the cylindrical product 90 is a cast iron pipe manufactured using the mold centrifugal casting method. This will be explained with reference to Figure 6. Figure 6(A) is a perspective view of 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 using conventional photography means. Arrow A4 in Figures 6(A) and (B) indicates the circumferential direction of the cast iron pipe 100.

The inner surface of the cylindrical mold used in mold centrifugal casting is formed with minute irregularities (irregularities caused by peening), so the casting surface (cylindrical surface) 101 of a cast iron pipe 100 manufactured using mold centrifugal casting has numerous annular irregular 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 recesses of the irregular pattern 102. This makes it difficult to accurately grasp the condition of the casting surface from images captured by a photographing means.

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 on the cylindrical surface 91 from both sides in the axial direction O (diagonally downward). This prevents shadows from being cast on the recesses of the uneven pattern 102, as described above. This makes it possible to obtain a good image that clearly shows the uneven shape of the cylindrical surface 91. Therefore, as schematically shown in Figure 3(B), by processing the image captured by the camera 3 in an image processing device PC, for example, it is 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.

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 (position of the camera 3) is relatively shifted to one side in the depth direction (left side of the page) 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 (right side of the page) 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 camera 3 to be properly positioned (centered) relative to the area to be photographed on the cylindrical surface 91.

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.

The radius of curvature R2 (Figure 3(B)) of the contact portion 51 may be determined so as to accommodate multiple 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 Figure 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.

However, when the case 10 is to be made compatible with multiple cylindrical products 90 of different diameters, as shown in FIG. 5, a resilient member 7 may be attached to the lower end (bottom 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 edges of the radially facing portions 10d, 10e. In this case, external light can be more effectively prevented from entering the case 10 when in use, improving photography conditions.

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

In this embodiment, an example in which the cylindrical light-shielding member 6 is prismatic has been described, but the present invention is not limited to this example. The cylindrical light-shielding member 6 may also be cylindrical, for example.

In addition, in this embodiment, the cylindrical light-blocking member 6 is realized by the rigid case portion 10. However, if the cylindrical light-blocking member 6 and the pair of spacing members 5 are configured separately as shown in FIG. 1, the cylindrical light-blocking member 6 does not have to be rigid. For example, the cylindrical light-blocking member 6 may be realized by a flexible piece of fabric suspended from the frame portion 4.

Furthermore, while the example described above is one in which the cylindrical product 90 is a cast iron pipe 100 manufactured using the mold centrifugal casting method, the cylindrical surface imaging device 1 can also be used effectively for cast iron pipes manufactured using other methods and other types of pipe products. Note that when targeting other types of pipe products, the number and installation positions of the light sources 2 that illuminate the cylindrical surface 91 are not limited to the example described above.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications that are equivalent in meaning to and within the scope of the claims.

1 Cylindrical surface imaging device, 2 Light source, 3 Camera, 4 Frame portion, 5 Spacing portion, 6 Cylindrical light-blocking member, 7 Elastic member, 8 Elevation means, 10 Case portion, 10b, 10c Axial facing portion, 10d, 10e Radial facing portion, 30 Space to be imaged, 51 Contact portion, 90 Cylindrical product, 91, 91a, 91b Cylindrical surface, 100 Cast iron pipe, 102 Textured pattern, O Axis, PU Photography unit.

Claims (7)

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 . The cylindrical surface imaging device of claim 1, wherein the tip ends of the pair of spacing retainers are configured as arc-shaped abutment portions having a radius of curvature larger than the radius of curvature of the cylindrical surface. 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. The cylindrical surface imaging device of claim 3, wherein an elastic member having elasticity is provided on at least a portion of the lower end of the cylindrical light-shielding member. A cylindrical surface imaging device according to any one of claims 1 to 4, wherein the illumination means includes a pair of light sources fixed to each of the pair of spacing retainers. 6. The cylindrical surface imaging device according to claim 1, wherein the cylindrical product is a cast iron pipe. An imaging device for imaging a cylindrical surface of a cylindrical product,
an illumination means for irradiating a region to be photographed on the surface of the cylinder 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.