JP2004275359A - Measuring endoscope apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring endoscope apparatus which confirms the accuracy in measurement stably irrespectively of an illuminated state by the endoscope. <P>SOLUTION: A measurement accuracy confirmation plate 40 is constituted of a plate body 43 of the plate and an index plate 44 attached to and fixed on the plate body 43. The index plate 44 is equipped with an examination index 45 constituted of penetrating holes 45a, 45b, 45c. The examination plate 45 has penetrating holes set at respective intervals of prescribed values. The surface of the index plate 44 has a lusterless finish to reduce regular reflection caused by the illuminating light from the endoscope. The plate body 43 has an anti-reflection opening 43a. The inner surface of the anti-reflection opening 43a has a dull finish in black to absorb the light. The penetrating holes 45a, 45b, 45c constituting the examination index 45 are observed as black circles under the illuminating light of the endoscope because of the illuminating light which passes the penetrating holes 45a, 45b, 45c on the index plate 44 and is guided to the anti-reflection opening 43a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a measurement endoscope apparatus that performs stereo measurement.
[0002]
[Prior art]
Endoscope devices are widely used in the medical and industrial fields. 2. Description of the Related Art As an endoscope apparatus used in the industrial field, there is an endoscope apparatus in which an elongated endoscope insertion portion is inserted into a jet engine, a pipe of a power plant, or the like so as to observe a test site and perform various treatments.
In recent years, in endoscopic observation, it has been desired to measure the size and position of the test site in addition to observing the test site. Various devices for measuring objects have been proposed.
[0003]
For example, Japanese Patent Application Laid-Open No. 2001-275934 proposes a measurement endoscope apparatus that automatically selects and executes a measurement method that differs depending on the type of optical adapter according to the type of optical adapter.
[0004]
This measurement endoscope apparatus includes a connection portion provided at an endoscope end portion, a plurality of types of optical adapters for forming an image of a subject detachable from the connection portion on an image sensor, and one of the optical adapters. The image signal of the image pickup device is connected and measured by image processing, and a menu display process for performing a selection operation and a selection by the menu display process are performed based on display data previously associated with the plurality of optical adapters. And a measurement processing means for performing a measurement process based on the result.
[0005]
For this reason, when an optical adapter is selected on the menu, a measurement method corresponding to the optical adapter is automatically selected, and when performing measurement, simply press a measurement execution switch provided in the endoscope operation unit. Then, a measurement process corresponding to the selected measurement method is executed.
[0006]
In the embodiment of the above publication, calibration processing is performed for each of a plurality of optical adapters, and the processing results are stored as environmental data in an external storage medium such as a compact flash (registered trademark) and used on the menu. A configuration is disclosed in which environmental data corresponding to the optical adapter is selected by selecting the corresponding optical adapter.
[0007]
In this measurement endoscope device, when a plurality of optical adapters are owned and exchanged for measurement, the results of the calibration process performed for each optical adapter are stored as environmental data. By switching this environmental data when the adapter is replaced, measurement can be performed easily.
[0008]
At the time of the calibration process, since the shape and position of the mask at the time of production are compared, it is necessary to accurately acquire the mask shape of the stereo measurement optical adapter. In Application 2001-34228, an optimal white image is obtained by observing a center index provided at the center of the bottom of a white concave portion having a white hemispherical inner surface with an endoscope to obtain a white image and obtain a mask shape. There has been proposed a measurement endoscope apparatus having a calibration jig capable of clearly projecting the outline of a mask. The calibration jig is provided with an index for confirming the measurement accuracy. By measuring this index, it is possible to confirm whether or not the calibration has been correctly performed.
Patent Document 1: JP-A-2001-275934 (pages 3 to 7, FIG. 1 to FIG. 15)
[Problems to be solved by the invention]
However, with the index provided on the calibration jig of the measurement endoscope apparatus of the above-mentioned Japanese Patent Application No. 2001-342284, when trying to confirm the measurement accuracy, depending on the relative positional relationship between the index and the endoscope, The illumination light from the endoscope shines brightly on the surface of the index, making it impossible to check the index, which may cause a problem that measurement cannot be performed.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a measurement endoscope apparatus capable of stably confirming measurement accuracy regardless of an illumination state of an endoscope.
[0010]
[Means for Solving the Problems]
The measurement endoscope apparatus according to the present invention includes an endoscope having an imaging device constituting a stereo measurement optical system at a distal end portion of an elongated insertion portion, and an imaging signal transmitted from the imaging device of the endoscope. An image processing unit that generates a video signal, a display device that receives an image signal generated by the image processing unit and displays an endoscope image, and measures based on an imaging signal transmitted from the imaging device. An arithmetic processing unit for performing processing, and a measurement accuracy check tool having an inspection index configured by arranging a plurality of holes at predetermined intervals for checking the measurement accuracy of the stereo measurement optical system are provided.
[0011]
Then, a predetermined surface treatment is applied to the periphery of the hole and the inner surface side of the hole which constitute the inspection index of the measurement accuracy checking tool.
[0012]
According to these configurations, a plurality of holes constituting the inspection index of the measurement accuracy confirmation tool are confirmed as black circles.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 8 relate to an embodiment of the present invention, FIG. 1 is a diagram illustrating a measurement endoscope device, FIG. 2 is a block diagram illustrating a configuration of an electric circuit of the measurement endoscope device, and FIG. FIG. 4 is a cross-sectional view illustrating the configuration of the calibration jig, FIG. 4 is a side view illustrating the configuration of the calibration jig, FIG. 5 is a diagram illustrating the configuration of the measurement accuracy confirmation plate, and FIG. FIG. 7 is a diagram illustrating the configuration and operation of the confirmation plate, FIG. 7 is a diagram illustrating another configuration of the measurement accuracy confirmation plate, and FIG. 8 is a diagram illustrating another configuration of the measurement accuracy confirmation plate.
[0014]
As shown in FIG. 1, the measurement endoscope apparatus 1 has a stereo measurement optical adapter 2 and an image pickup device and an illumination optical system (not shown) built in a distal end portion 11 to which the stereo measurement optical adapter 2 is detachably connected. Of the stereo measurement optical adapter 2 in which the endoscope 10 having the elongated elongated endoscope insertion portion 12 and the distal end portion 11 of the endoscope insertion portion 12 to which the stereo measurement optical adapter 2 is attached are arranged. A calibration jig 3 for capturing a mask shape, a control unit 4 in which the endoscope 10 is housed, and operations necessary to execute various operation controls of the entire system of the measurement endoscope apparatus 1 are described. A remote controller 5 that can perform the operation, a liquid crystal monitor (hereinafter, referred to as an LCD) 6 that is a display device that displays an endoscope image, operation control contents (for example, a processing menu), and the like. It mainly comprises a face-mount display (hereinafter, referred to as FMD) 7 capable of stereoscopically viewing an endoscope image or its endoscope image as a stereo image, and an FMD adapter 7a for supplying image data to the FMD 7. Have been.
[0015]
In the present embodiment, an optical adapter for comparison measurement 8 is detachably connected to the distal end of the endoscope insertion section 12. Reference numeral 9 denotes an external video input terminal for inputting video to a video signal processing circuit without passing through a CCU described later.
[0016]
The measurement endoscope apparatus 1 will be described in detail with reference to FIG.
As shown in the figure, the base end of the endoscope insertion section 12 is connected to an endoscope unit 24. The endoscope unit 24 is housed in the control unit 4 shown in FIG.
In the endoscope unit 24, a light source device for obtaining illumination light necessary for photographing, an electric bending device for electrically driving a bending portion (not shown) of the endoscope insertion portion 12, and the like are built. ing.
[0017]
An imaging device (not shown) is built in the distal end portion 11 of the endoscope insertion portion 12, and an imaging signal output from the imaging device is a camera control unit (hereinafter referred to as CCU) as an image processing unit. Yes) 25. The CCU 25 converts the input image signal into a video signal such as an NTSC signal and supplies the video signal to a main processing circuit group in the control unit 4.
[0018]
A main circuit group mounted in the control unit 4 includes a CPU 26 serving as a control unit for executing and operating various functions based on a main program and an arithmetic processing unit for performing measurement processing, a ROM 27, a RAM 28, and a PC card interface (hereinafter referred to as a PC card interface). , PC card I / F) 29a, USB interface (hereinafter, described as USB I / F) 29b, RS-232C interface (hereinafter, described as RS-232C I / F) 29c, audio signal processing circuit 19, and video signal And a processing circuit 30.
[0019]
The RS-232C I / F 29c is connected to the CCU 25, the endoscope unit 24, and the remote controller 5, respectively. That is, the remote controller 5 is for controlling the CCU 25 and the endoscope unit 24 and instructing the operation.
[0020]
On the other hand, the RS-232C I / F 29c is for performing communication necessary for controlling the operation of the CCU 25 and the endoscope unit 24 based on the operation of the remote controller 5.
[0021]
The USB I / F 29b is an interface for electrically connecting the control unit 4 and the personal computer 21. When the control unit 4 and the personal computer 21 are connected via the USB I / F 29b, various instructions such as an instruction to display an endoscopic image in the control unit 4 and an image processing at the time of measurement are also performed on the personal computer 21 side. Control can be performed, and control information and data necessary for various processes can be input and output between the control unit 4 and the personal computer 21.
[0022]
The PC card I / F 29a is configured such that an external storage medium such as a PCMCIA memory card 22 and a compact flash (registered trademark) memory card 23 is detachably connected. That is, when an external storage medium is mounted, the control unit 4 reproduces data such as control processing information and image information stored in the external storage medium under the control of the CPU 26, and transmits the data via the PC card I / F 29a. Data such as control processing information and image information can be supplied to a memory card via the PC card I / F 29a and recorded in the control unit 4.
[0023]
The video signal processing circuit 30 controls the video signal from the CCU 25 and the operation menu generated under the control of the CPU 26 so as to display a synthesized image obtained by synthesizing the endoscopic image supplied from the CCU 25 and the operation menu by graphics. The display signal is synthesized with a display signal based on the display signal, and further subjected to processing necessary for display on the screen of the LCD 6 and supplied to the LCD 6. Thus, a composite image of the endoscope image and the operation menu is displayed on the LCD 6. Note that the video signal processing circuit 30 can also perform processing for simply displaying an image such as an endoscope image or an operation menu alone.
[0024]
Further, the control unit 4 is provided with an external video input terminal 9 for inputting a video to the video signal processing circuit 30 without passing through the CCU 25. When a video signal is input to the external video input terminal 9, the video signal processing circuit 30 outputs the composite image in preference to the endoscopic image from the CCU 25.
[0025]
The audio signal processing circuit 19 is generated by collecting sound by the microphone 20 and recorded on a storage medium such as a memory card, or an audio signal obtained by reproducing a storage medium such as a memory card, or generated by the CPU 26. The supplied audio signal is supplied. The audio signal processing circuit 19 performs processing (amplification processing or the like) necessary for reproducing the supplied audio signal, and outputs the processed audio signal to the speaker 19a. Thus, the audio signal is reproduced by the speaker 19a.
[0026]
The CPU 26 executes a program stored in the ROM 27, controls various circuit units so as to perform processing according to the purpose, and controls the operation of the entire system.
[0027]
The remote controller 5 includes a joystick (not shown), a lever switch, a freeze switch, a store switch, a measurement execution switch, and the like, which are provided at least on the upper surface.
[0028]
The configuration and operation of the calibration jig 3 will be described with reference to FIGS.
As shown in FIGS. 3 and 4, the calibration jig 3 includes a substantially cylindrical jig body 31 and a substantially tubular endoscope guide member 32. The jig body 31 and the endoscope guide member 32 are integrally fixed by screwing.
[0029]
The jig body 31 includes a white concave portion 33 having a circular opening shape, a hemispherical bottom side, and a white inner surface, and a direct-viewing endoscope formed to be inclined by a predetermined amount with respect to the center axis of the jig body 31. And a side-viewing inspection hole 35 through which a side-viewing endoscope formed perpendicular to the center axis of the jig main body 31 is inserted and arranged. A plate mounting surface 36a on which a measurement accuracy confirmation plate (refer to FIG. 4, hereinafter, referred to as a plate) 40 serving as a measurement accuracy confirmation tool provided with inspection reference holes at 0.1 inch intervals and 2 mm intervals is provided. For example, a plate arrangement hole 36 perpendicular to the central axis of the jig body 31 is provided. The direct-viewing inspection hole 34 is provided with an endoscope butting portion 34a for keeping a constant distance to the plate 40 attached to the plate attachment surface 36a.
[0030]
At the center of the bottom surface of the white concave portion 33, a center index 37 serving as a standard of the exposure amount is provided. The center index 37 is a hemispherical concave portion having a predetermined diameter. By forming the center index 37 to have a predetermined diameter, an image is taken in a state where the center of the field of view of the endoscope 10 faces the center index 37. When the exposure amount is gradually increased while the center index 37 is being melted into the white concave portion 33, it becomes invisible. At that time, the mask shape becomes clearest. In other words, an image having an appropriate brightness for obtaining the mask shape is obtained based on the time when the center index 37 has melted into the white concave portion 33.
[0031]
On the other hand, a direct-viewing endoscope 10 to which the stereo measurement optical adapter 2 is attached is inserted through the endoscope guide member 32, and the center of the visual field of the direct-viewing endoscope 10 is set to the center index 37. A side-viewing endoscope having a side-viewing calibration guide 41 and a side-viewing stereo measurement optical adapter (not shown) mounted thereon is inserted into the side-viewing endoscope. And a side-view calibration guide 42 for arranging the center of the visual field at the center of the center index. The direct-view calibration guide 41 is provided with a direct-view guide abutting portion 41b for positioning in the depth direction when the endoscope 10 of the direct-view specification is inserted.
[0032]
As shown in FIGS. 5 and 6, the plate 40 disposed on the plate mounting surface 36 a includes a plate body 43 and a thin plate-like index that is attached and fixed to the plate body 43 and has a thickness of, for example, 0.04 mm. And a plate 44.
[0033]
The index plate 44 is provided with an inspection index 45 composed of, for example, three circular through holes 45a, 45b, and 45c having a diameter of 0.2 mm. In the inspection index 45, the distance L1 between the first through hole 45a and the second through hole 45b is set to 0.1 inch, and the distance L2 between the second through hole 45b and the third through hole 45c is set to 2 mm. ing. The surface of the index plate 44 has a matte finish as a surface treatment for reducing the regular reflection of illumination light from the endoscope.
[0034]
On the other hand, an antireflection hole 43a is formed at a predetermined position of the plate body 43. The antireflection hole 43a is set to a size that does not block the through holes 45a, 45b, and 45c that constitute the inspection index 45. Therefore, when the indicator plate 44 is irradiated with the illumination light, a part of the illumination light passes through the through holes 45a, 45b, 45c and is guided to the antireflection hole 43a. At this time, in order to prevent the inner surface of the anti-reflection hole 43a from being reflected by the illumination light guided to the anti-reflection hole 43a, the inner surface of the anti-reflection hole 43a has a black surface as a surface treatment for absorbing light. Has a matte finish.
[0035]
Therefore, as shown by the broken line in the figure, the illumination light guided through the through holes 45a, 45b, 45c of the indicator plate 44 into the anti-reflection hole 43a is an inner surface having a black matte finish. Absorbed.
[0036]
That is, an endoscope (not shown) is arranged in the inspection hole 34 for direct vision or the inspection hole 35 for side vision, and illumination light is emitted toward the plate 40 from the illumination optical system of the endoscope. Most of the illuminating light is reflected by the matte-finished surface of the index plate 44, and only a part of the illuminating light passes through the through holes 45a, 45b, 45c and is guided into the anti-reflection hole 43a. This illuminating light is absorbed by the black matte finish. As a result, the through holes 45a, 45b, 45c constituting the inspection index 45 are observed as black circles under the illumination light of the endoscope.
[0037]
As described above, the measurement accuracy confirmation plate, which is a measurement accuracy confirmation tool attached to the plate mounting surface, has a matte finish on the surface side, and has a thin plate-like index plate having a plurality of through-holes to constitute an inspection index. By using a plate body with an anti-reflection hole with a black matte finish on the inner surface that prevents the through hole of the indicator plate from being blocked, the penetration indicator that constitutes the inspection indicator based on the illumination light of the endoscope The holes can always be clearly observed as black circles.
[0038]
Instead of forming antireflection holes 43a of such a size that the through holes 45a, 45b, 45c are not closed in the plate body 43 constituting the plate 40, as shown in FIG. , 45b, 45c, a plurality of antireflection holes 43b, 43c having a predetermined size may be formed. In the present embodiment, the surface of the plate mounting surface 36a on which the plate body 43 is disposed is subjected to a black matte finish as a surface treatment, and the antireflection holes 43b and 43c are formed as through holes.
As a result, the through holes 45a, 45b, 45c are observed in black, and the same operation and effect as in the above-described embodiment can be obtained.
[0039]
Further, instead of arranging the index plate 44 having the inspection index 45 on the plate body 43 to form the plate 40, as shown in FIG. 8, the plate body 43 has a predetermined diameter and a predetermined depth on the inner surface. The inspection holes 45d, 43e, and 43f, which have been subjected to a black matte finish as a surface treatment, may be arranged at predetermined intervals to form the inspection indices 45. In the present embodiment, a matte finish for preventing total reflection is applied as a surface treatment for the surface of the plate body 43.
This makes it possible to simplify the configuration of the measurement accuracy confirmation plate, and to observe the indicator holes 43d, 43e, and 43f of the plate main body 43 in black, and obtain the same operation and effect as in the above-described embodiment. Can be
[0040]
Here, stereo measurement by the measurement endoscope apparatus 1 will be briefly described.
In the stereo measurement by the measurement endoscope device 1, a first process of reading optical information from the storage medium in which optical data of the stereo measurement optical adapter 2 is recorded, and imaging of the distal end portion 11 of the endoscope 10 A second process for reading positional information between the element and the objective lens system of the stereo measurement optical adapter 2, an image pickup device of a main endoscope obtained at the time of the positional relationship information and production, and the stereo measurement optical system. A third process of obtaining a position error of the imaging device of the measurement endoscope apparatus from information on a positional relationship between the objective lens systems of the adapter 2, and a fourth process of correcting the optical data from the position error. A fifth process of performing coordinate conversion on an image to be measured based on the corrected optical data, and a sixth process of obtaining three-dimensional coordinates of an arbitrary point by matching two images based on the coordinate-converted image. It is performed by performing at least the.
[0041]
The CPU 26 controls, for example, to execute the first to fourth processes once for the stereo measurement optical adapter 2 and record the result as measurement environment data on a storage medium. The first to fourth processes are collectively called a calibration process. At this time, information on the date and time when the calibration process was executed is also recorded as a part of the measurement environment data. Thereafter, when performing stereo measurement, the CPU 26 controls the CPU 26 to load the measurement environment data on the RAM and execute the fifth and sixth processes.
[0042]
In addition, when performing the second process of reading the positional relationship information between the imaging element of the distal end portion 11 and the objective lens system of the stereo measurement optical adapter 2, the mask provided on the stereo measurement optical adapter 2 This is done by capturing the shape and comparing the shape and position of the mask during production. In this case, the capture of the mask shape is performed by capturing a white image, that is, by displaying an image of the white concave portion 33 of the calibration jig 3. At this time, the brightness of the white image is determined based on how the above-described center index 37 has blended into the white concave portion 33 as a guide.
[0043]
Then, the end of the endoscope after calibration is inserted into the inspection holes 34 and 35, and stereo measurement is performed. At this time, since the hole constituting the inspection index 45 is confirmed as a black circle, the interval between the black circles is measured, and the measurement result is compared with a nominal value, with an accuracy within ± 10%. Confirm that the measurement has been made and record the result.
As a result, the accuracy can be checked using the calibration jig without using a new measurement accuracy jig.
Then, after replacing the optical adapter, the hole interval of the inspection index 45 is always measured and compared with the recorded value. Thus, it is possible to confirm whether or not there is a mistake in mounting the optical adapter. In addition, even after the endoscope inspection, the hole interval of the inspection index 45 is always measured and compared with the recorded value. This makes it possible to confirm whether or not the optical adapter has become loose during the inspection.
[0044]
It should be noted that the present invention is not limited to only the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.
[0045]
[Appendix]
According to the above-described embodiment of the present invention as described in detail above, the following configuration can be obtained.
[0046]
(1) an endoscope having an imaging element that constitutes a stereo measurement optical system at the distal end of an elongated insertion portion;
An image processing unit that generates a video signal based on an imaging signal transmitted from the imaging device of the endoscope,
A display device that receives an image signal generated by the image processing unit and displays an endoscope image;
An arithmetic processing unit that performs a measurement process based on an imaging signal transmitted from the imaging device;
To confirm the measurement accuracy of the stereo measurement optical system, a measurement accuracy check tool having an inspection index configured by arranging a plurality of holes at predetermined intervals,
A measurement endoscope device comprising:
[0047]
(2) an endoscope having a built-in image sensor constituting an observation optical system at the distal end of the elongated insertion portion;
A plurality of optical adapters that are detachable from the distal end of the insertion section of the endoscope and include at least a stereo measurement optical adapter,
Based on an imaging signal transmitted from the imaging device of the endoscope, an image processing unit that generates a video signal,
A display device that receives an image signal generated by the image processing unit and displays an endoscope image;
An arithmetic processing unit that performs a measurement process based on an image signal transmitted from the image sensor,
Confirming the measurement accuracy of the stereo measurement optical system, a measurement accuracy check tool having an inspection index configured by arranging a plurality of holes at predetermined intervals,
A measurement endoscope device comprising:
[0048]
(3) The measurement endoscope apparatus according to Supplementary Note 1 or 2, in which a predetermined surface treatment is applied to a periphery of the hole and an inner surface side of the hole that constitute an inspection index of the measurement accuracy checking tool.
[0049]
(4) A thin plate-like indicator plate having a plurality of through-holes to form an inspection indicator, and a plate body having an anti-reflection hole for preventing the through-holes of the indicator plate from being closed. Consisting of
4. The measurement endoscope apparatus according to claim 3, wherein a matte finish is applied to a surface side of the indicator plate, and a black matting process is applied to an inner surface of the antireflection hole of the plate body.
[0050]
(5) The measurement endoscope apparatus according to supplementary note 4, wherein the anti-reflection hole formed in the plate main body is a single hole having a size that prevents blocking of a plurality of through holes.
[0051]
(6) The measurement endoscope apparatus according to attachment 4, wherein the anti-reflection holes formed in the plate body are a plurality of holes formed in sizes corresponding to the plurality of through holes, respectively.
[0052]
(7) The measurement accuracy checking tool according to Appendix 3, which is a plate main body having a matte finish on the periphery of the hole and having an inspection index formed of a plurality of holes having an inner surface subjected to a black matting process. Measurement endoscope device.
[0053]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a measurement endoscope apparatus capable of stably confirming measurement accuracy regardless of the illumination state of the endoscope.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a measurement endoscope device. FIG. 2 is a block diagram illustrating a configuration of an electric circuit of the measurement endoscope device. FIG. 3 is a cross-sectional view illustrating a configuration of a calibration jig. FIG. 4 is a side view illustrating the configuration of a calibration jig. FIG. 5 is a diagram illustrating the configuration of a measurement accuracy confirmation plate. FIG. 6 is a diagram illustrating the configuration and operation of a measurement accuracy confirmation plate. FIG. 8 illustrates another configuration of the measurement accuracy confirmation plate. FIG. 8 illustrates another configuration of the measurement accuracy confirmation plate.
3: Calibration jig 31: Jig body 40: Measurement accuracy confirmation plate

Claims (2)

An endoscope having an imaging element constituting an optical system for stereo measurement at the distal end of the elongated insertion portion,
An image processing unit that generates a video signal based on an imaging signal transmitted from the imaging device of the endoscope,
A display device that receives an image signal generated by the image processing unit and displays an endoscope image;
An arithmetic processing unit that performs a measurement process based on an imaging signal transmitted from the imaging device;
Confirming the measurement accuracy of the stereo measurement optical system, a measurement accuracy check tool having an inspection index configured by arranging a plurality of holes at predetermined intervals,
A measurement endoscope apparatus comprising: 2. The measurement endoscope apparatus according to claim 1, wherein a predetermined surface treatment is applied to a periphery of the hole and an inner surface side of the hole that constitute an inspection index of the measurement accuracy checking tool. 3.

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