JP2018036203A - Hole internal inspection device and hole internal inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hole internal inspection device inspecting presence of detection objects consisting of debris inside of the hole and pin hole appearing on the internal perimeter surface of the hole accurately.SOLUTION: A hole internal inspection device 100 comprises: a captured image acquisition unit 30 acquiring images captured inside of a hole 91; a coordinate calculation unit 31 calculating a coordinate of a first position set in the opening side of the hole 91 and a coordinate of a second position set in the deeper side than the first position of the hole 91 on the basis of the captured image; a spread image generation unit 32 generating a first spread image that the captured image is spread around the first position along the hoop direction of the hole 91 on the basis of the coordinate of the first position, and a second spread image that the image is spread around the second position along the hoop direction of the hole 91 on the basis of the coordinate of the second position; and a determination unit 37 determining presence of detection objects consisting of at least one of debris inside of the hole 91 and pin hole appearing on the internal perimeter surface of the hole 91 on the basis of the first spread image and the second spread image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hole internal inspection device and a hole internal inspection method for inspecting the presence or absence of a detection object composed of at least one of a foreign substance existing inside a hole and a cast hole appearing on an inner peripheral surface of the hole.

  When forming a hole in a metal body by cutting, chips generated during the cutting process remain as foreign matter in the hole, or a cast hole formed when forming the metal body appears on the surface of the hole. Sometimes. Since these are defects due to the quality of the metal body, inspection techniques have been studied (for example, Patent Documents 1 and 2).

  The internal surface inspection apparatus described in Patent Document 1 develops a captured image of the internal surface of a hole imaged by a camera, and inspects the presence or absence of the defect based on the brightness of the developed image obtained by the development. Moreover, even in the screw hole inspection apparatus described in Patent Document 2, a developed image of the inner peripheral surface of the screw hole is acquired, and the feature points of the screw thread included in the acquired developed image are acquired in advance. Comparing with the feature point of the master, the quality determination regarding the screw shape of the screw hole is performed.

JP 2011-89826 A JP 2009-14347 A

  In the technique described in Patent Document 1, when the hole is a screw hole, the wavy noise component of the screw thread, which is image information unnecessary for defect detection, is removed, but the defect information deteriorates at this time. It is necessary to set a high luminance threshold value for use in the inspection for the presence or absence of defects because the wavy noise component cannot be removed. For this reason, there is a possibility that chips having a small luminance difference with respect to the luminance of the screw thread cannot be detected, and other inspection processes and measures are required to reliably detect chips.

  Moreover, in the technique described in Patent Document 2, it is possible to make a pass / fail judgment related to the screw shape of the screw hole as described above. For example, chips having the same size as the pitch of the screw thread remain. May not be detected properly.

  Therefore, there is a need for a hole interior inspection apparatus and a hole interior inspection method that can accurately inspect the presence or absence of a foreign object existing inside a hole or a detection target consisting of a cast hole appearing on the inner peripheral surface of the hole.

  The characteristic configuration of the hole interior inspection apparatus according to the present invention includes a captured image acquisition unit that acquires a captured image obtained by capturing the inside of the hole from a position that is a predetermined distance away from the opening of the hole and outside the hole, and the captured image A coordinate calculation unit that calculates the coordinates of the first position set on the opening side of the hole and the coordinates of the second position set on the deeper side of the hole than the first position; Based on the coordinates of the first position, the first developed image obtained by developing the captured image along the circumferential direction of the hole around the first position, and the second position based on the coordinates of the second position. A developed image generating unit that generates a second developed image obtained by developing the captured image along the circumferential direction around the center, and the inside of the hole based on the first developed image and the second developed image. At least one of the foreign matter present and the cast hole appearing on the inner peripheral surface of the hole In that it includes a, a determination unit for determining whether the detection target made of a certain.

  With such a feature configuration, a developed image composed of a first developed image and a second developed image generated by converting the captured image, which is a polar coordinate system image acquired by the captured image acquisition unit, into an orthogonal coordinate system image is generated. By offsetting in the direction corresponding to the circumferential direction of the hole and subtracting the images before and after the offset, it is possible to extract only the portion where the luminance change is large. Thereby, it is possible to make the chips and the casting hole conspicuous, so that it is possible to easily determine the presence or absence of the detection target.

  Further, the hole interior inspection device generates a composite developed image by combining the first position side image in the first developed image and the second position side image in the second developed image. An offset image generation unit that generates an offset expanded image obtained by offsetting the combined expanded image by a predetermined offset amount in a direction corresponding to a circumferential direction of the hole, a luminance value for each pixel in the combined expanded image, and the offset expansion A luminance difference calculation unit that calculates a luminance value difference for each pixel based on a luminance value for each pixel in the image, and the determination unit is configured to detect the detection target based on the luminance value difference. It is preferable to determine the presence or absence.

  For example, if an axial misalignment occurs between the center of the hole and the center of the image, the expansion distortion at the top of the hole will be reduced if converted to the Cartesian coordinate system using the center coordinates of the region above the hole on the polar coordinate system image. The amount of distortion increases toward the lower part. On the other hand, if the center coordinate of the lower region of the hole is converted into an orthogonal coordinate system, the development distortion at the lower part of the hole is reduced, but the distortion amount is increased toward the upper part of the hole. Therefore, by configuring as described above, the composite developed image is composed of an image based on the center coordinates at the first position set at the upper part of the hole and an image based on the center coordinates at the second position set at the lower part of the hole. Therefore, a composite image with little distortion can be generated. Therefore, it is possible to improve the detection accuracy of the detection object.

  Further, the hole inside inspection device includes an inner diameter calculating unit that calculates a maximum inner diameter of a region formed by grouping pixels having a value larger than a preset value and a difference between the luminance values. It is preferable that the determination unit determines that the detection target exists when the maximum inner diameter is larger than the size of the detection target.

  With such a configuration, it is possible to make chips and cast holes conspicuous due to the difference in luminance value, and thus it is possible to easily determine the presence or absence of these.

  In addition, the characteristic configuration of the hole interior inspection method according to the present invention includes a captured image acquisition step of acquiring a captured image obtained by capturing the inside of the hole from a position away from the opening by a predetermined distance from the opening of the hole; A coordinate calculation step for calculating, based on the captured image, the coordinates of the first position set on the opening side of the hole and the coordinates of the second position set on the deeper side of the hole than the first position; Based on the coordinates of the first position, the first developed image in which the captured image is developed around the first position along the circumferential direction of the hole, and on the basis of the coordinates of the second position, Based on the developed image generation step of generating a second developed image obtained by developing the captured image along the circumferential direction around two positions, the first developed image and the second developed image, On the foreign matter present inside and the inner peripheral surface of the hole In that it includes a determining step of determining whether the detection target made of at least one of the casting cavity to be, a.

  Such a hole interior inspection method is not substantially different from the above-described hole interior inspection apparatus in terms of the substantial characteristic configuration, and the above-described effects can be obtained.

It is a schematic diagram which shows the structure of a hole inside inspection apparatus. It is an example of a captured image. It is the figure shown about calculation of the coordinate of a 1st position, and the coordinate of a 2nd position. It is the figure shown about the production | generation of a 1st expansion | deployment image and a 2nd expansion | deployment image. It is the figure shown about the production | generation of a synthetic | combination expansion | deployment image. It is the figure shown about the offset expansion | deployment image. It is the figure shown about the calculation of a brightness | luminance difference. It is the figure shown about the determination by the determination part. It is the figure shown about the determination using a luminance profile.

  The hole interior inspection device according to the present invention has a function of inspecting the presence or absence of an inspection object existing inside a hole, specifically, a foreign object existing inside the hole or a cast hole appearing on the inner peripheral surface of the hole. Composed. Hereinafter, the hole interior inspection apparatus 100 of this embodiment will be described.

  FIG. 1 is a diagram schematically showing the configuration of the hole interior inspection device 100 of the present embodiment. As shown in FIG. 1, the hole interior inspection apparatus 100 includes an inspection head 1, a robot 2, a robot controller 3, an illumination power supply 4, a control unit 5, a captured image acquisition unit 30, a coordinate calculation unit 31, and a developed image generation unit 32. , A composite image generation unit 33, an offset image generation unit 34, a luminance difference calculation unit 35, an inner diameter calculation unit 36, and a determination unit 37. Functions of the control unit 5, the captured image acquisition unit 30, the coordinate calculation unit 31, the developed image generation unit 32, the composite image generation unit 33, the offset image generation unit 34, the luminance difference calculation unit 35, the inner diameter calculation unit 36, and the determination unit 37 The unit is constructed with hardware and / or software using the CPU as a core member in order to perform processing related to the inspection of the presence or absence of the inspection object existing inside the hole.

  The inspection head 1 includes a camera 6, a lens unit 7, and a spot illumination 8. The camera 6 images a hole (imaged target) 91 of the workpiece 90. The lens unit 7 bends light from the wide-angle lens 9 having an optical axis parallel to the axis of the hole 91 of the workpiece 90, the relay lens 10 configured by combining a plurality of high-precision lenses, and the spot illumination 8. It is composed of a half mirror 11 that irradiates the hole 91. The spot illumination 8 corresponds to a light source that emits light.

  The robot 2 moves the inspection head 1 at a predetermined distance from the opening of the hole 91. The robot 2 is controlled by a robot controller 3. The illumination power supply 4 supplies power to the spot illumination 8. The control unit 5 controls the robot controller 3 and the illumination power source 4.

  Light from the spot illumination 8 is bent by the half mirror 11, passes through the relay lens 10 and the wide-angle lens 9, and is evenly applied to the inner surface of the hole 91. The reflected light from the hole 91 passes through the wide-angle lens 9, the relay lens 10, and the half mirror 11 and enters the camera 6, and the camera 6 moves from a position away from the opening of the hole 91 to the outside of the hole 91 by a predetermined distance. The inside of the hole 91 is imaged. Therefore, the inspection head 1 is held in a state of being separated from the hole 91.

  The inspection head 1 is held as described above, and images the inner surfaces of the plurality of holes 91 while moving on the holes 91. That is, the robot controller 3 controls the robot 2 according to an instruction from the control unit 5 to move the inspection head 1, and images the inner surface of the hole 91 irradiated with the spot illumination 8 with the camera 6. After imaging, the robot controller 3 moves the inspection head 1 over the next hole 91, and when the robot controller 3 reaches the next hole 91, the camera 6 images the inner surface of the hole 91. This series of operations is performed until all the holes 91 to be inspected are completed.

  The captured image acquisition unit 30 acquires a captured image obtained by capturing the inside of the hole 91 from a position away from the opening of the hole 91 by a predetermined distance outside the hole 91. As described above, in this embodiment, the camera 6 images the inside of the hole 91 from a position that is a predetermined distance away from the opening of the hole 91 to the outside of the hole 91. A captured image captured by the camera 6 is transmitted to the captured image acquisition unit 30. FIG. 2 shows an example of a captured image acquired by the captured image acquisition unit 30. As shown in FIG. 2, the captured image is an image as if the inside of the hole 91 was looked into from above the hole 91. Further, as shown in FIG. 2, in the present embodiment, a screw hole having a thread formed on the inner peripheral surface as the hole 91 will be described as an example.

  The step of acquiring a captured image obtained by capturing the inside of the hole 91 from a position away from the opening of the hole 91 by a predetermined distance outside the hole 91 is referred to as a captured image acquisition step in the hole interior inspection method.

  Returning to FIG. 1, the coordinate calculation unit 31 sets the coordinates of the first position set on the opening side of the hole 91 and the second position set on the deeper side of the hole than the first position based on the captured image. Calculate the coordinates. The “first position set on the opening side of the hole 91” corresponds to the opening edge of the hole 91, for example. Of course, the first position may be a position that is a predetermined distance from the opening edge to the bottom side of the hole 91. The “second position set on the back side of the hole with respect to the first position” corresponds to a position on the bottom side of the hole 91 with respect to the first position. In the present embodiment, description will be made assuming that the first position is the opening edge of the hole 91 and the second position is the bottom. Of course, the second position can be a position spaced a predetermined distance from the bottom toward the opening edge. In addition, although the coordinate calculation part 31 detects an opening edge part and a bottom part from a captured image, these can be detected based on a luminance difference, for example. Such detection can be performed using known image recognition.

  The “coordinate of the first position” corresponds to the center coordinate of the region orthogonal to the axial center of the hole 91 at the first position when the hole 91 is viewed from above, and the “coordinate of the second position” The center coordinates of the region orthogonal to the axial center of the hole 91 at the second position when 91 is viewed from above are equivalent. In FIG. 3A, the opening area at the opening edge of the hole 91 is indicated by a broken line 21 and the center is indicated by a + mark 22. In FIG. 3B, the open area at the bottom of the hole 91 is indicated by a broken line 23 and the center is indicated by a + mark 24. The coordinate calculation unit 31 has center coordinates of the opening area at the opening edge of the hole 91 as shown by the broken line 21 (corresponding to the + mark 22) and the center of the opening area at the bottom of the hole 91 as shown by the broken line 23. Coordinates (corresponding to + mark 24) are calculated.

  Based on such a captured image, the step of calculating the coordinates of the first position set on the opening side of the hole 91 and the coordinates of the second position set on the deeper side of the hole 91 than the first position is as follows. This is referred to as a coordinate calculation step in the hole interior inspection method.

  Returning to FIG. 1, the developed image generation unit 32 develops the captured image along the circumferential direction of the hole 91 around the first position based on the coordinates of the first position, and the second position. Based on the coordinates, a second developed image in which the captured image is developed along the circumferential direction around the second position is generated. “Developing the captured image along the circumferential direction of the hole 91 based on the coordinates of the first position based on the coordinates of the first position” means that the captured image in which the inner peripheral surface of the hole 91 is depicted is the first position. It means spreading in a strip as a reference. Specifically, this corresponds to performing viewpoint conversion by orthogonal coordinate conversion based on the coordinates of the first position in the captured image. Further, “develop the captured image along the circumferential direction of the hole 91 with the second position as the center based on the coordinates of the second position” means that the captured image in which the inner peripheral surface of the hole 91 is depicted is the second It means to spread in a band shape with reference to the position. Specifically, this is equivalent to performing viewpoint transformation by orthogonal coordinate transformation based on the coordinates of the second position in the captured image. Therefore, the developed image generation unit 32 performs the first developed image obtained by performing viewpoint conversion by orthogonal coordinate conversion based on the center coordinates (corresponding to + mark 22) of the opening edge in the captured image, and the center coordinates of the bottom in the captured image. Based on (corresponding to + mark 24), a second developed image that has undergone viewpoint transformation by orthogonal coordinate transformation is generated. 4A shows the first developed image, and FIG. 4B shows the second developed image.

  Based on the coordinates of the first position, the first developed image obtained by developing the captured image along the circumferential direction of the hole 91 with the first position as the center, and the second position based on the coordinates of the second position. The step of generating the second developed image obtained by developing the captured image along the circumferential direction as the center is referred to as a developed image generating step in the hole interior inspection method.

  Returning to FIG. 1, the composite image generation unit 33 generates a composite developed image obtained by combining the image on the first position side in the first developed image and the image on the second position side in the second developed image. The image on the first position side in the first developed image is an image closer to the first position in the first developed image. In the present embodiment, an image on the side close to the opening edge of the first developed image corresponds, and specifically, an upper half image of the first developed image corresponds. The image on the second position side in the second developed image is an image closer to the second position in the second developed image. In the present embodiment, the image on the side closer to the bottom of the second developed image corresponds, and specifically, the lower half of the second developed image corresponds. Therefore, the composite image generation unit 33 generates a composite expanded image by combining the upper half image of the first expanded image and the lower half image of the second expanded image. Such a composite developed image is shown in FIG. In the example of FIG. 5, the upper half image of the first expanded image is surrounded by a broken line, and the lower half image of the second expanded image is surrounded by an alternate long and short dash line.

  The step of generating a composite developed image obtained by combining the first position side image in the first developed image and the second position side image in the second developed image is referred to as a composite image generating step in the hole interior inspection method. Is done.

  Returning to FIG. 1, the offset image generation unit 34 generates an offset expanded image obtained by offsetting the combined expanded image by a predetermined offset amount in a direction corresponding to the circumferential direction of the hole 91. The direction corresponding to the circumferential direction of the hole 91 corresponds to the horizontal direction in the composite developed image. Therefore, the offset image generation unit 34 generates an offset expanded image obtained by offsetting the combined expanded image by a predetermined offset amount in the horizontal direction. Here, the offset amount is preferably set (for example, 2 mm) in accordance with the size of chips and castholes present inside the hole 91 to be inspected by the hole inside inspection device 100 (see FIG. 6). That is, it is possible to set according to the size of the chips that may be generated by the cutting process, the size of the cast hole that may be formed when the metal body is formed, or the hole 91 is formed. It is possible to set according to the size of the chip and the casting hole which are problematic at the time. FIG. 6 shows an example of an offset developed image generated by the offset image generation unit 34.

  The step of generating an offset developed image obtained by offsetting the composite developed image by a predetermined offset amount in a direction corresponding to the circumferential direction of the hole 91 is referred to as an offset image generating step in the hole interior inspection method.

  Returning to FIG. 1, the luminance difference calculation unit 35 calculates a difference in luminance value for each pixel based on the luminance value for each pixel in the combined developed image and the luminance value for each pixel in the offset developed image. The luminance difference calculation unit 35 superimposes the composite developed image and the offset developed image offset from the composite developed image, and calculates the luminance value of each pixel of the composite developed image and the luminance value of each pixel of the offset developed image. Calculate the difference. FIG. 7 shows an image difference corresponding to a difference in luminance value for each pixel calculated by the luminance difference calculation unit 35. In this way, by superimposing the composite developed image and the offset developed image offset with respect to the composite developed image, portions where the luminance values of the composite developed image and the offset developed image are large do not overlap with each other. A difference becomes large and the part with a large luminance value can be made conspicuous. Further, since the thread formed in the hole 91 is a convex portion along the offset direction in the composite developed image and the offset developed image, a luminance difference does not occur due to the image difference. For this reason, it is possible to make a shape that is not parallel to the offset direction stand out by the image difference.

  Based on the luminance value for each pixel in the composite developed image and the luminance value for each pixel in the offset developed image, the step of calculating the difference in luminance value for each pixel is the luminance difference calculating step in the hole interior inspection method. Called.

  Returning to FIG. 1, the inner diameter calculation unit 36 groups pixels having a luminance value difference larger than a preset value, and calculates the maximum inner diameter of a region formed by grouping. The inner diameter calculation unit 36 groups the portions with large luminance values that are made conspicuous by the luminance difference calculation unit 35 described above, as shown in FIG. In addition, in FIG. 8, in order to correct the known perspective correction (the opening side is larger than the bottom side), that is, the sizes of the opening side and the bottom side are unified. Correction to perform). The inner diameter calculation unit 36 calculates the maximum inner diameter of each region formed as a group. This calculation can be performed, for example, by forming a shape or an ellipse so that a region formed by grouping is inscribed, and setting the length in the longitudinal direction of the shape or the length of the major axis of the ellipse as the maximum inner diameter. is there.

  The process of grouping pixels having such a luminance value difference larger than a preset value and calculating the maximum inner diameter of the grouped region is referred to as an inner diameter calculating step in the hole interior inspection method. Is done.

  Returning to FIG. 1, the determination unit 37 is based on the first developed image and the second developed image, and the detection target is composed of at least one of the foreign matter existing inside the hole 91 and the cast hole appearing on the inner peripheral surface of the hole. The presence or absence of is determined. In the present embodiment, the luminance value and offset development of each pixel of the synthesized developed image generated by synthesizing the upper half image of the first developed image and the lower half image of the second developed image by the synthesized image generation unit 33. The presence / absence of the detection target is determined based on the difference from the luminance value of each pixel of the image.

  Here, in the present embodiment, pixels having a luminance value difference larger than a preset value are grouped by the inner diameter calculating unit 36, and the maximum inner diameter of the region formed by grouping is calculated. The determination unit 37 determines that the detection target exists when the maximum inner diameter of the grouped region is larger than the size of the detection target. Such determination by the determination unit 37 performs binarization processing on the image difference as shown in FIG. 8, generates a luminance profile along one of the vertical direction and the horizontal direction, and uses a predetermined threshold in the luminance profile. If the region having a larger value is larger than the size of the detection target, the detection target may be present. The size of the detection object is the size (standard size) of the detection object to be detected.

  FIG. 9 shows determination processing using a luminance profile. In FIG. 9, the brightness | luminance profile produced | generated along the A line of FIG. 8 is shown. The luminance profile is a diagram showing a luminance value for each position. In FIG. 9, the horizontal axis represents the luminance value, and the vertical axis represents the position on the A line. In this luminance profile, a portion B having a luminance value larger than a predetermined threshold corresponds to a grouped region C existing on the A line in FIG. 8, and the size of this portion B is the size of the detection object. If greater than, the determination unit 37 determines that the object is a foreign object. In the data indicating the image difference in FIG. 8, the determination unit 37 acquires and determines a luminance profile over the entire surface while changing the position of the A line in the horizontal direction in FIG. 8, for example. In addition, although the detection of the foreign object has been described as an example of the detection target object this time, it can be similarly detected in the cast hole.

  A step of determining the presence / absence of a detection target consisting of at least one of a foreign matter existing inside the hole 91 and a cast hole appearing on the inner peripheral surface of the hole 91 based on the first developed image and the second developed image. Is referred to as a determination step in the hole interior inspection method.

[Other Embodiments]
In the above embodiment, the composite image generation unit 33 has been described as generating a composite developed image obtained by combining the image on the first position side in the first developed image and the image on the second position side in the second developed image. It is also possible to configure so that the developed image generated by the developed image generating unit 32 is used without being provided with the composite image generating unit 33.

  In the above embodiment, the offset image generation unit 34 has been described as generating an offset development image obtained by offsetting the composite development image by a predetermined offset amount in a direction corresponding to the circumferential direction of the hole 91. Instead, the composite image generated by the composite image generation unit 33 can be used as it is.

  In the above embodiment, the inner diameter calculation unit 36 has been described as grouping pixels having a luminance value difference larger than a preset value, and calculating the maximum inner diameter of the grouped region. It is also possible to configure so that pixels having a luminance value difference larger than a preset value are determined without grouping.

  INDUSTRIAL APPLICABILITY The present invention can be used for a hole internal inspection device and a hole internal inspection method for inspecting the presence or absence of a detection object consisting of at least one of foreign matter existing inside a hole and a cast hole appearing on the inner peripheral surface of the hole. is there.

30: Captured image acquisition unit 31: Coordinate calculation unit 32: Development image generation unit 33: Composite image generation unit 34: Offset image generation unit 35: Brightness difference calculation unit 36: Inner diameter calculation unit 37: Determination unit 91: Hole 100: Hole Internal inspection device

Claims (4)

A captured image acquisition unit that acquires a captured image obtained by imaging the inside of the hole from a position away from the opening of the hole by a predetermined distance outside the hole;
A coordinate calculation unit that calculates the coordinates of the first position set on the opening side of the hole and the coordinates of the second position set on the deeper side of the hole than the first position based on the captured image. When,
Based on the coordinates of the first position, the first developed image obtained by developing the captured image along the circumferential direction of the hole around the first position, and the second based on the coordinates of the second position. A developed image generating unit that generates a second developed image obtained by developing the captured image along the circumferential direction with a position at the center;
A determination unit that determines the presence or absence of a detection target composed of at least one of a foreign matter present inside the hole and a cast hole appearing on an inner peripheral surface of the hole based on the first developed image and the second developed image. When,
A hole inside inspection device. A combined image generating unit that generates a combined expanded image obtained by combining the image on the first position side in the first expanded image and the image on the second position side in the second expanded image;
An offset image generating unit that generates an offset developed image in which the composite developed image is offset by a predetermined offset amount in a direction corresponding to a circumferential direction of the hole;
A luminance difference calculation unit that calculates a difference in luminance value for each pixel based on a luminance value for each pixel in the composite developed image and a luminance value for each pixel in the offset developed image;
The hole determination apparatus according to claim 1, wherein the determination unit determines the presence / absence of the detection target based on the difference in luminance value. Grouping pixels having a value greater than a preset value for the difference in luminance value, and comprising an inner diameter calculating unit for calculating the maximum inner diameter of the region formed by grouping,
The hole internal inspection apparatus according to claim 2, wherein the determination unit determines that the detection target exists when the maximum inner diameter is larger than a size of the detection target. A captured image acquisition step of acquiring a captured image obtained by capturing the inside of the hole from a position away from the opening of the hole by a predetermined distance outside the hole;
A coordinate calculation step for calculating the coordinates of the first position set on the opening side of the hole and the coordinates of the second position set on the deeper side of the hole than the first position based on the captured image. When,
Based on the coordinates of the first position, the first developed image obtained by developing the captured image along the circumferential direction of the hole around the first position, and the second based on the coordinates of the second position. A developed image generating step for generating a second developed image obtained by developing the captured image along the circumferential direction with a position at the center;
A determination step for determining the presence or absence of a detection target consisting of at least one of a foreign matter present inside the hole and a cast hole appearing on an inner peripheral surface of the hole based on the first developed image and the second developed image. When,
A hole inside inspection method comprising:

Images