JP2016003885A - Hole inner surface inspection apparatus, hole inner surface image processing method, and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hole inner surface inspection apparatus configured to precisely inspect a state of a hole inner surface regardless of a hole shape, a hole inner surface image processing method for converting an image formed by capturing a hole inner surface to an accurate two-dimensional development image regardless of the hole shape, and an apparatus.SOLUTION: A hole inner surface inspection apparatus acquires a first image formed by capturing an inside surface of a hole by means of imaging means, extracts a cross-sectional shape of the hole from the first image, sets a first shape formed by approximating the cross-sectional shape by a polygon, on the first image, sets a second shape formed by reducing or enlarging the first shape based on an optical axis of an optical system of the imaging means, on the first image, defines a plurality of trapezoidal areas in an area between the first shape and the second shape with a line segment connecting vertices of the first shape and the second shape, and performs projective transformation on the first images in the trapezoidal areas to be synthesized, to acquire a two-dimensional development image of the inside surface of the hole.

Description

  The present invention relates to a hole inner surface inspection apparatus for inspecting an inner surface of a hole, and an image processing method and apparatus for processing an image obtained by photographing the hole inner surface.

  A method and an apparatus for observing the inner surface of a hole are disclosed in Patent Document 1 and Patent Document 2. Patent Document 1 describes a method of capturing an image of the inner surface of a hole using a cone mirror and acquiring a developed image of the inner surface of the hole by performing polar coordinate conversion on the captured image. In Patent Document 2, the inner circle and the outer circle of the hole are extracted from the photographed image, and polar coordinates are converted while sequentially moving the center coordinates in consideration of the deviation of the center of these circles. A method for reducing distortion caused by camera misalignment is described.

JP 2003-31024 A JP 2013-084156 A

  However, in the conventional method of acquiring an image of the inner surface of a hole by expanding into an orthogonal coordinate system by polar coordinate conversion, when the hole to be observed is a non-circular shape, distortion occurs in the image conversion process, and an accurate image of the inner surface of the hole is obtained. Could not get. For this reason, when a defect etc. are formed in the inner surface of a hole, the exact identification was difficult.

  An object of the present invention is to provide a hole inner surface inspection apparatus capable of accurately inspecting the state of the inner surface of a hole regardless of the shape of the hole, and to convert a captured image of the inner surface of the hole into an accurate developed image regardless of the shape of the hole. A hole inner surface image processing method and apparatus are provided.

  According to one aspect of the present invention, an imaging unit that captures a first image including an inner surface of a hole to be observed, and a two-dimensional developed image of the inner surface from the first image acquired by the imaging unit. An image processing means for acquiring, wherein a cross-sectional shape of the hole is extracted from the first image acquired by the photographing means, and a first shape approximating the cross-sectional shape by a polygon is formed on the first image. A second shape obtained by reducing or enlarging the first shape with reference to the optical axis of the optical system of the photographing unit is set on the first image, and the first shape and the second shape are set. A plurality of trapezoidal regions are defined in a region between the first shape and the second shape by a line segment connecting each vertex with the shape, and the first in the plurality of trapezoidal regions 1 images are combined after projective transformation, and in the first depth region of the hole Bore inner surface inspection apparatus having the configuration image processing unit to obtain a first inner surface image is a development image of the serial inner surface is provided.

  According to another aspect of the present invention, there is provided a hole inner surface image processing apparatus that acquires a two-dimensional developed image of the inner surface from an image obtained by photographing the inner surface of a hole to be observed, the inner surface of the hole A first image obtained by photographing a side surface by a photographing unit is acquired, a cross-sectional shape of the hole is extracted from the first image, and a first shape that approximates the cross-sectional shape by a polygon is formed on the first image. And a second shape obtained by reducing or enlarging the first shape on the basis of the optical axis of the optical system of the photographing means is set on the first image, and the first shape and the second shape are set. A plurality of trapezoidal regions are defined in a region between the first shape and the second shape by a line segment connecting each vertex with the shape of the plurality of trapezoidal regions. Each of the first images is combined after projective transformation, and the inner side in the first depth region of the hole 2-dimensional development image in which the first bore inner surface image is configured to acquire the inner surface image processing apparatus is provided.

  According to still another aspect of the present invention, a step of obtaining a first image obtained by photographing an inner surface of a hole to be observed by a photographing unit, and extracting a cross-sectional shape of the hole from the first image And setting the first shape approximating the cross-sectional shape as a polygon on the first image, and reducing or enlarging the first shape with reference to the optical axis of the optical system of the photographing means The step of setting a second shape on the first image, and a line segment connecting the vertices of the first shape and the second shape, the first shape and the second shape, Defining a plurality of trapezoidal regions in a region between the first image and the first image in the plurality of trapezoidal regions, respectively, after projective transformation, and combining the first images to form a first depth region of the hole A step of acquiring a first inner surface image that is a developed image of the inner surface in FIG. Hole inner surface image processing method and a flop is provided.

  According to the present invention, an accurate two-dimensional developed image of the inner surface of a hole can be acquired from the hole inner surface image regardless of the cross-sectional shape of the hole. Thereby, the state of the inner surface of the hole can be inspected in detail and accurately.

FIG. 1 is a block diagram showing the configuration of the hole inner surface inspection apparatus according to the first embodiment of the present invention. FIG. 2 is a flowchart showing the hole inner surface image processing method according to the first embodiment of the present invention. FIG. 3 is a schematic view showing a hole inner surface inspection method according to the first embodiment of the present invention. FIG. 4 is a schematic diagram (part 1) illustrating the hole inner surface image processing method according to the first embodiment of the present invention. FIG. 5 is a schematic diagram (part 2) illustrating the hole inner surface image processing method according to the first embodiment of the present invention. FIG. 6 is a schematic diagram (part 3) illustrating the hole inner surface image processing method according to the first embodiment of the present invention. FIG. 7 is a schematic diagram (part 4) illustrating the hole inner surface image processing method according to the first embodiment of the present invention. FIG. 8 is a diagram illustrating a problem when a two-dimensional developed image is acquired by polar coordinate conversion. FIG. 9 is a schematic view showing a hole inner surface inspection method and apparatus according to a second embodiment of the present invention. FIG. 10 is a schematic diagram illustrating a hole inner surface image processing method according to a modified embodiment of the present invention.

[First Embodiment]
A hole inner surface inspection apparatus, a hole inner surface inspection method, and a hole inner surface image processing method according to a first embodiment will be described with reference to FIGS.

  FIG. 1 is a block diagram showing the configuration of the hole inner surface inspection apparatus according to the present embodiment. FIG. 2 is a flowchart showing the hole inner surface image processing method according to the present embodiment. FIG. 3 is a schematic view showing the hole inner surface inspection method according to the present embodiment. 4 to 7 are schematic views showing the hole inner surface image processing method according to the present embodiment. FIG. 8 is a diagram illustrating a problem when a two-dimensional developed image is acquired by polar coordinate conversion.

  First, the configuration of the hole inner surface inspection apparatus according to the present embodiment will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the hole inner surface inspection device 10 according to the present embodiment includes a camera 12, a moving mechanism 18, a displacement sensor 20, a control device 22, an image processing device 24, and an input / output device 28.

  The camera 12 is for taking an image of the inner side surface 34 of the hole 32 provided in the work 30 to be inspected. The camera 12 may be provided with an illumination system 14 such as a coaxial epi-illumination as necessary to brighten the inside of the hole 32 during photographing. The camera 12 preferably uses a lens system 16 (wide-angle lens) for widening the angle of view in order to obtain an angle of view necessary for taking an image of the inner surface of the hole.

  The moving mechanism 18 is for moving the camera 12 along the optical axis of the optical system. The moving mechanism 18 is for changing the relative positional relationship between the camera 12 and the workpiece 30, and the workpiece 30 may be moved instead of moving the camera 12. Alternatively, both the camera 12 and the work 30 may be moved.

  The displacement sensor 20 is for measuring a relative displacement amount of the camera 12 with respect to the workpiece 30. When the camera 12 is moved by the moving mechanism 18, the displacement amount of the camera 12 is detected by the displacement sensor 20. When the workpiece 30 is moved by the moving mechanism 18, the displacement amount of the workpiece 30 is detected by the displacement sensor 20. The displacement sensor 20 is not particularly limited as long as the displacement amount of the camera 12 or the work 30 can be measured.

  The control device 22 is for controlling the photographing of the work 30 by the camera 12, the movement of the camera by the moving mechanism 18, the detection of the relative displacement amount of the camera 12 with respect to the work 30 by the displacement sensor 20, and the like.

  The image processing device 24 performs image processing on the image of the inside surface of the hole based on the image taken by the camera 12, the measurement result of the relative movement amount of the camera 12 with respect to the work 30 by the displacement sensor 20, and the like. This is for obtaining a two-dimensional developed image of the inner side surface 34.

  The control device 22 and the image processing device 24 are typically configured by an arithmetic device 26 such as a computer. The computing device 26 may include an input / output device 28 such as an input device for an operator to input predetermined information for inspection and a display device for displaying an image processing result.

  Next, the in-hole surface inspection method and the in-hole image processing method according to the present embodiment will be described with reference to FIGS. Here, a case will be described as an example in which an inner surface 34 of a work 30 having a rectangular hole 32 whose cross-sectional shape is constant in the depth direction as shown in FIG. 3 is inspected.

  The in-hole inspection method and the in-hole image processing method according to the present embodiment are executed by the control device 22 and the image processing device 24 as follows, for example, according to the flowchart shown in FIG.

  First, as shown in FIG. 3, the camera 12 is positioned so that the entrance of the hole 32 of the workpiece 30 is positioned in the shooting area (frame) 36 of the camera 12, and a hole inner surface image is taken (step S11). . Here, the hole inner surface image is a photographed image of the work 30 including an image of the inner surface 34 of the hole 32. Here, in step S11, it is assumed that a hole inner surface image including the inner surfaces 34a, 34b, 34c, and 34d of the hole 32 as shown in FIG. In FIG. 4A, it is assumed that defects 38a and 38b have been photographed on the lower inner surface 34d and the right inner surface 34c of the hole 32, respectively.

  The camera 12 is installed so that the axial direction of the hole 32 provided in the workpiece 30 is parallel to the optical axis direction of the optical system of the camera 12. The axial direction of the hole 32 is a direction along a line (center axis) connecting the centers of the cross sections of the holes 32 in the depth direction. Although it is desirable that the optical axis of the optical system of the camera 12 coincides with the central axis of the hole 32, it does not necessarily need to coincide. In other words, according to the in-hole inspection method and the in-hole image processing method according to the present embodiment, even if an axial deviation occurs between the optical axis of the optical system of the camera 12 and the central axis of the hole 32, the distortion is caused. An unfolded image can be acquired. In FIG. 4A, the intersection of two alternate long and short dash lines represents the optical axis (center of the screen) of the optical system of the camera 12. The hole inner surface image shown in FIG. 4A is an example of photographing when the optical axis of the optical system of the camera 12 is displaced with respect to the center of the hole 32.

  Next, the cross-sectional shape 40 of the hole 32 is extracted from the hole inner surface image photographed in step S11 (step S12). In this specification, the cross-sectional shape of the hole 32 is the shape of the hole 32 that passes through a plane orthogonal to the axial direction of the hole 32. When the cross-sectional shape of the hole 32 is constant in the depth direction, the cross-sectional shape of the hole 32 is equal to the shape of the entrance portion of the hole 32 viewed from the camera 12. Therefore, in the method of the present embodiment, the shape of the entrance portion of the hole 32 is extracted from the captured hole inner surface image, and this is used as the cross-sectional shape 40 of the hole 32. Here, it is assumed that the shape indicated by the bold line in FIG. 4B is extracted as the cross-sectional shape 40 of the hole 32.

  The method for extracting the shape of the entrance portion from the hole inner surface image is not particularly limited. For example, when the aspect ratio of the hole 32 is known, the shape of the entrance portion can be specified by matching the rectangular shape of the aspect ratio with the image of the entrance portion of the hole 32 of the photographed hole inner surface image. it can. Alternatively, edge detection may be performed on the photographed hole inner surface image to specify the shape of the entrance portion.

  Next, the cross-sectional shape 40 of the hole 32 extracted in step S12 is approximated by a polygonal shape 42 (step S13). In the example of this embodiment, the cross-sectional shape 40 of the hole 32 is a quadrangle, and the polygonal shape 42 to be approximated is also a quadrangle. Here, it is assumed that the cross-sectional shape 40 of the hole 32 is approximated to a polygonal shape 42 having sides 42a, 42b, 42c, and 42d, as shown in FIG.

  Next, a similar figure 44 of the polygonal shape 42 is set on the hole inner surface image by reducing the polygonal shape 42 thus approximated with the optical center (screen center) of the camera 12 as a reference point (step S14). Here, it is assumed that the polygonal shape 42 is reduced and a similar figure 44 having sides 44a, 44b, 44c, and 44d is set as shown in FIG.

  Next, an annular region excluding the region of the similar figure 44 from the polygon shape 42 is divided by line segments respectively connecting the corresponding vertices of the polygon shape 42 and the similar figure 44 to obtain the number of sides of the polygon shape 42. A corresponding number of trapezoidal regions 46 are defined (step S15). Accordingly, a trapezoidal region 46a having sides 42a and 44a as bases, a trapezoidal region 46b having sides 42b and 44b as bases, a trapezoidal region 46c having sides 42c and 44c as bases, and sides 42d and 44d. A trapezoidal region 46d as a base is defined (FIG. 5B).

  Next, for each of the plurality of trapezoidal regions 46 set in this way, the hole inner surface image photographed in step S11 is projectively transformed. And the expansion | deployment image of the inner surface 34 of the hole 32 is acquired by combining the image which carried out the projective transformation (step S16). A developed image obtained by projective transformation of the trapezoidal regions 46a, 46b, 46c, and 46 in FIG. 5B is, for example, as shown in FIG. The inner surface images obtained by projective transformation of the trapezoidal regions 46a, 46b, 46c, and 46d correspond to the converted images 48a, 48b, 48c, and 48d, respectively.

  By acquiring the developed image from the hole inner surface image in this way, it is possible to acquire an accurate developed image while suppressing deformation of the shape accompanying image conversion. If the hole inner surface image acquired in step S11 is converted into an orthogonal coordinate system by polar coordinate conversion, for example, as shown in a hole inner surface image of FIG. 8A and a developed image of FIG. Therefore, the size of the defect cannot be correctly evaluated. For example, as indicated by the defect 38a, the shape of the defect 38a after image conversion is deformed, and the shape of the defect cannot be determined correctly. Further, as shown in the defect 38b, since the part closer to the polar coordinate origin is converted larger than the far part, the size of the defect cannot be evaluated correctly.

  Next, when acquiring images of the inner surface 34 having different depths of the hole 32, the camera 12 is moved along the optical axis of the optical system of the camera 12 (step S18). At this time, the displacement amount of the camera 12 relative to the workpiece 30 is measured by the displacement sensor 20.

  Next, after moving the camera 12 to a predetermined position, a hole inner surface image is taken (step S19). Here, it is assumed that a hole inner surface image as shown in FIG. By bringing the camera 12 closer to the hole 32, the inner side surface 34 of the deeper region of the hole 32 is positioned in the trapezoidal region 46 set in step S15.

  For example, as shown in FIG. 7, when the camera 12 takes the hole inner surface image in step S <b> 11 at the position drawn with a dotted line, the portion of the inner side surface 34 of the hole 32 that is located in the trapezoidal region 46. Is the region 50. From this state, when the camera 12 moves to the position drawn by the solid line and performs photographing in step S <b> 19, the inner side surface portion of the hole 32 located in the trapezoidal region 46 is a region 52 deeper than the region 50. Become.

  Next, the process returns to step S16, and the hole inner surface image photographed in step S19 is projectively transformed for each of the plurality of trapezoidal regions 46, and images of the inner side surfaces 34 corresponding to the plurality of trapezoidal regions 46 are obtained. . And the two-dimensional expansion | deployment image of the inner surface 34 of the hole 32 is acquired by combining the image of the some inner surface 34 obtained by projective transformation (step S16). A two-dimensional developed image of the inner side surface 34 obtained by projective transformation of the trapezoidal regions 46a, 46b, 46c, 46 in FIG. 6A is, for example, as shown in FIG. 6B. Images of the inner surface 34 obtained by projective transformation of the trapezoidal regions 46a, 46b, 46c, and 46d correspond to the converted images 54a, 54b, 54c, and 54d, respectively.

  In this manner, by developing Step S18, Step S19, and Step S16 a plurality of times as necessary, a developed image of the inner side surface 34 at different depths of the hole 32 can be acquired.

  Next, the plurality of developed images photographed in this way are combined by shifting by a depth corresponding to the displacement amount of the camera 12 measured by the displacement sensor 20 (step S20). Thereby, a two-dimensional developed image of the inner side surface 34 of the hole 32 over an arbitrary depth region can be acquired.

  By combining a plurality of developed images, the work 30 can be inspected in more detail and accurately. For example, when a defect (for example, defect 38b) over different depth regions exists, the entire defect can be accurately evaluated.

  Thus, according to the present embodiment, an accurate two-dimensional developed image of the inner surface of the hole can be acquired from the hole inner surface image regardless of the cross-sectional shape of the hole. Thereby, the state of the inner surface of the hole can be inspected in detail and accurately.

[Second Embodiment]
The hole inner surface inspection apparatus, hole inner surface inspection method, and hole inner surface image processing method according to the second embodiment will be described with reference to FIG. The same components as those in the hole inner surface inspection apparatus, the hole inner surface inspection method, and the hole inner surface image processing method according to the first embodiment shown in FIGS. 1 to 7 are denoted by the same reference numerals, and description thereof is omitted or simplified.

  FIG. 9 is a schematic view showing a hole inner surface inspection method and apparatus according to the present embodiment.

  First, the configuration of the hole inner surface inspection apparatus according to the present embodiment will be described with reference to FIG.

  The hole inner surface inspection apparatus according to the present embodiment is the same as the hole inner surface inspection apparatus 10 according to the first embodiment except that the configuration of the camera 12 is different.

  That is, the camera 12 of the hole inner surface inspection apparatus according to the present embodiment has a camera unit 56 and a laser light emitting unit 58 as shown in FIG. The laser light emitting unit 58 is disposed on the optical axis 60 of the optical system of the camera unit 56, and emits laser light radially in a direction parallel to a plane orthogonal to the optical axis 60.

  For example, when the laser light emitting portion 58 of the camera 12 is inserted into the rectangular hole 32 described in the first embodiment and laser light is irradiated, the inner surface of the hole 32 is, for example, as shown in FIG. A laser beam locus 62 is drawn. This locus 62 is equal to the cross-sectional shape of the hole 32. In this specification, the locus 62 drawn by the laser light may be referred to as reference light.

  Next, the hole inner surface inspection method and the hole inner surface image processing method according to the present embodiment will be described with reference to FIG.

  The hole inner surface inspection method and the hole inner surface image processing method according to the present embodiment are the same as the hole inner surface inspection method and the hole inner surface image processing method according to the first embodiment except that the method for extracting the cross-sectional shape of the hole 32 is different.

  In the method of the first embodiment, a hole inner surface image including the entrance portion of the hole 32 was taken, and the shape of the shape of the entrance portion of the hole 32 was extracted as the cross-sectional shape 40 of the hole 32. On the other hand, in the method of the present embodiment, the laser light emitted from the laser light emitting unit 58 is irradiated onto the inner side surface 34 of the hole 32, and the locus 62 drawn by this laser light is photographed by the camera 12, and the hole inner surface image is displayed. Is extracted as the cross-sectional shape 40 of the hole 32.

  By extracting the cross-sectional shape 40 of the hole 32 in this way, the hole inner surface image to be photographed does not necessarily need to include the shape of the entrance portion. In addition, when the shape of the hole 32 changes in the depth direction, this can be known based on the change in the shape and size of the locus 62, and a more accurate inspection of the hole 32 can be performed. . It is also possible to acquire a two-dimensional developed image of the inner surface in consideration of changes in the shape of the hole 32.

  Further, in the method of the present embodiment, since it is not necessary to take a hole inner surface image including the entrance portion of the hole 32, the inspection may be performed from the state where the camera 12 is inserted into the hole 32. In this case, photographing may be performed while gradually inserting the camera 12 into the hole 32, or photographing may be performed while gradually pulling out the camera 12 from the hole 32. Further, the setting of the similar figure 44 can be performed not only by reducing the cross-sectional shape 40 of the hole 32 as in the first embodiment but also by enlarging the cross-sectional shape 40.

  Thus, according to the present embodiment, an accurate two-dimensional developed image of the inner surface of the hole can be acquired from the hole inner surface image regardless of the cross-sectional shape of the hole. Even when the cross-sectional shape of the hole varies depending on the depth, an accurate two-dimensional developed image can be acquired. Thereby, the state of the inner surface of the hole can be inspected in detail and accurately.

[Modified Embodiment]
The present invention is not limited to the above embodiment, and various modifications are possible.

  For example, in the above-described embodiment, an example in which the inner surface 34 of the hole 32 having a quadrangular cross-sectional shape is inspected, but the cross-sectional shape of the hole 32 is not necessarily a polygonal shape such as a quadrangle, The shape may have a curved portion such as an ellipse. For example, it is assumed that a cross-sectional shape 40 of the hole 32 having a curved portion as shown in FIG. 10A is extracted from the shape of the entrance portion of the hole 32 and the locus of the reference light. In such a case, as shown in FIG. 10B, the sectional shape 40 is approximated to a polygonal shape 42 by dividing the curved portion of the sectional shape 40 into ranges that can be linearly approximated. Then, based on the polygonal shape 42, a similar figure 44 and a trapezoidal area 46 may be set.

  The above embodiments are merely examples of some aspects to which the present invention can be applied, and do not prevent appropriate modifications and variations from being made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Hole inner surface inspection apparatus 12 ... Camera 18 ... Moving mechanism 20 ... Displacement sensor 22 ... Control apparatus 24 ... Image processing apparatus 30 ... Work piece 32 ... Hole 34- ..Inner side surface 36 ... shooting area 40 ... cross-sectional shape 42 ... polygonal shape 44 ... similar figure 46 ... trapezoidal regions 48, 54 ... converted image

Claims (6)

Photographing means for photographing the first image including the inner surface of the hole to be observed;
Image processing means for obtaining a two-dimensional developed image of the inner surface from the first image obtained by the photographing means,
Extracting the cross-sectional shape of the hole from the first image acquired by the photographing means, and setting a first shape approximating the cross-sectional shape by a polygon on the first image;
A second shape obtained by reducing or enlarging the first shape on the basis of the optical axis of the optical system of the photographing means is set on the first image;
A plurality of trapezoidal regions are defined in a region between the first shape and the second shape by a line segment connecting the vertices of the first shape and the second shape,
The first images in the plurality of trapezoidal regions are each subjected to projective transformation and then combined to obtain a first inner surface image that is a developed image of the inner surface in the first depth region of the hole. And an image processing means configured as described above. A photographing means moving means for moving the position of the photographing means relative to the observation object;
The image processing means includes
After moving the photographing means along the depth direction of the hole, to obtain a second image obtained by photographing the inner surface of the hole by the photographing means,
The second images in the plurality of trapezoidal regions are combined after projective transformation to obtain a second inner surface image that is a developed image of the inner surface in the second depth region of the hole. ,
A third inner surface image that is a developed image of the inner surface in the first depth region and the second depth region by combining the first inner surface image and the second inner surface image. The hole inner surface inspection device according to claim 1, further configured to acquire the following. The image processing means is configured to extract the shape of the entrance of the hole as the cross-sectional shape of the hole when the first image includes an image of the entrance of the hole. 2. The hole inner surface inspection apparatus according to 2. The image processing means, when the first image includes a trajectory of reference light in a direction perpendicular to the optical axis of the optical system of the imaging means irradiated on the inner surface of the hole, The hole inner surface inspection device according to claim 1, wherein the trajectory of the reference light is extracted as the cross-sectional shape of the hole. A hole inner surface image processing device for acquiring a two-dimensional developed image of the inner surface from an image obtained by photographing the inner surface of a hole to be observed,
Obtaining a first image obtained by photographing the inner surface of the hole by a photographing means;
Extracting the cross-sectional shape of the hole from the first image, and setting a first shape that approximates the cross-sectional shape by a polygon on the first image;
A second shape obtained by reducing or enlarging the first shape on the basis of the optical axis of the optical system of the photographing means is set on the first image;
A plurality of trapezoidal regions are defined in a region between the first shape and the second shape by a line segment connecting the vertices of the first shape and the second shape,
The first images in the plurality of trapezoidal regions are each subjected to projective transformation and then combined to obtain a first inner surface image that is a two-dimensional developed image of the inner surface in the first depth region of the hole. A hole inner surface image processing apparatus configured to be. Obtaining a first image obtained by photographing an inner surface of a hole to be observed by photographing means;
Extracting a cross-sectional shape of the hole from the first image, and setting a first shape approximating the cross-sectional shape by a polygon on the first image;
Setting on the first image a second shape obtained by reducing or enlarging the first shape with respect to the optical axis of the optical system of the photographing means;
Defining a plurality of trapezoidal regions in a region between the first shape and the second shape by a line segment connecting the vertices of the first shape and the second shape; ,
The first images in the plurality of trapezoidal regions are each subjected to projective transformation and then combined to obtain a first inner surface image that is a developed image of the inner surface in the first depth region of the hole. And a hole inner surface image processing method.