Inspection device

Abstract

To inspect a state of an inner surface of an inspected object having a cylindrical shape with satisfactory precision by applying terahertz waves to the inner surface of the inspected object along a circumferential direction from a center axis of the inspected object.SOLUTION: An inspection device is used to inspect an inner peripheral surface of an inspected object having a cylindrical shape. The device includes: an inspection section for applying terahertz waves to the inner peripheral surface and detecting the reflection waves of the terahertz waves; and a distance measurement section for measuring a distance between the inspection section and the inner peripheral surface. The inspection section and the distance measurement section are rotated along a circumferential direction of the inspected object. A relative axial position of the inspection section relative to the inspected object is adjusted. The position of the inspection section on a plane crossing an axial direction of the inspected object can be adjusted. The control of the position adjustment mechanism is performed such that a rotation center of a rotation section is positioned on a center axis of the inspected object on the basis of a measurement result of the distance measurement section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an inspection apparatus. [Background technology]

[0002] Patent Document 1 discloses a reflection-type terahertz wave measuring device (inspection device) configured to be capable of irradiating the surface of a structure with terahertz waves, which are a type of electromagnetic wave, and to detect terahertz waves reflected by the structure. Such a terahertz wave measuring device includes a terahertz wave transmitter as a terahertz wave transmitting means, and a terahertz wave detector as a terahertz wave detecting means. In such a terahertz wave measuring device, a terahertz wave generating element including a resonant tunneling diode (RTD) or a photoconductive antenna (PCA) is used for the terahertz wave transmitter, and a terahertz wave detecting element consisting of an RTD is used for the terahertz wave transmitter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-26991 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned inspection device using terahertz waves can be used to inspect objects such as cylindrical tubular members. In this case, the inspection device is placed on the central axis in the internal space of the object, and the device repeatedly performs an inspection operation of irradiating the inner surface of the object with terahertz waves in the circumferential direction while detecting reflected waves while moving in the axial direction, thereby inspecting the inner surface of the object over a wide range. In this inspection, the signal strength of the reflected waves from the inner surface is approximately constant in areas where the inner surface is healthy, whereas the signal strength of the reflected waves decreases in areas where there is an abnormality (corrosion, water, etc.) on the inner surface. Therefore, the condition of the inner surface can be imaged by plotting the distribution of signal strength.

[0005] Here, terahertz waves are electromagnetic waves with high directionality and excellent linearity due to their high frequency. Therefore, if the irradiation position of the terahertz waves deviates from the central axis, when the terahertz waves are irradiated on the inner surface along the circumferential direction, a substantially constant signal strength cannot be obtained even if the inner surface is in a healthy state, and it becomes impossible to accurately recognize abnormalities (corrosion, water, etc.) based on the signal strength.

[0006] At least one embodiment of the present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide an inspection device that can inspect the condition of the inner surface of an object to be inspected with high accuracy by irradiating terahertz waves from the central axis of the object to be inspected having a cylindrical shape along the circumferential direction of the inner surface of the object to be inspected. [Means for solving the problem]

[0007] In order to solve the above problems, an inspection device according to at least one embodiment of the present disclosure includes: An inspection apparatus for inspecting an inner peripheral surface of an inspection object having a cylindrical shape, comprising: an inspection unit for irradiating the inner circumferential surface with terahertz waves and detecting reflected waves of the terahertz waves; a distance measuring unit for measuring a distance between the inspection unit and the inner circumferential surface; a rotating unit for rotating the inspection unit and the distance measurement unit in a circumferential direction of the inspection object; a position adjustment mechanism for adjusting a position of the inspection unit in a plane intersecting an axial direction of the inspection object; an axial position adjustment unit for adjusting a relative axial position of the inspection unit with respect to the inspection object; Equipped with Based on the measurement result of the distance measurement unit, the position adjustment mechanism is controlled so that the rotation center of the rotation unit is positioned on the central axis of the object to be inspected. Effect of the Invention

[0008] According to at least one embodiment of the present disclosure, an inspection device can be provided that can inspect the condition of the inner surface of an object to be inspected with high accuracy by irradiating terahertz waves from the central axis of the object to be inspected having a cylindrical shape along the circumferential direction of the inner surface of the object to be inspected. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic external view of an inspection device according to an embodiment; [Diagram 2] FIG. 2 is a block diagram of a control device shown in FIG. [Diagram 3] 1 is a flowchart illustrating an inspection method according to an embodiment. [Figure 4] 4 is an example of the inspection result obtained in step S107 of FIG. [Diagram 5] 13 is a flowchart illustrating an inspection method according to another embodiment. [Figure 6] 6 is an example of correction data prepared in step S200 of FIG. 5. [Figure 7] 13 is a flowchart illustrating an inspection method according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an inspection device according to an embodiment will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as the embodiment or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0011] The configuration of an inspection device 1 according to at least one embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic external view of the inspection device 1 according to one embodiment.

[0012] The inspection device 1 is a device for inspecting an inspection object TG. The inspection object TG is a pipe member having a substantially cylindrical shape and containing a metal material such as an iron pipe. The inspection object TG has an internal space 2 extending in an axial direction X. The inner peripheral surface of the internal space 2 has a substantially constant curvature in a YZ plane perpendicular to the axial direction X. The inner peripheral surface is also lined with a resin material RM. When this resin material RM deteriorates, water may penetrate the resin material RM, causing corrosion on the inner wall of the iron pipe. The inspection device 1 is intended to detect such corrosion on the inner peripheral surface of the inspection object TG and the presence of water that causes corrosion as abnormalities.

[0013] The inspection device 1 has a main body 6 that houses an optical system 4 as an inspection unit for performing inspection. The optical system 4 includes a light source 8, a nonlinear optical crystal 10, a half mirror 12, a mirror 14, a condenser lens 16, and a detector 18.

[0014] The light source 8 is configured to output a pulsed excitation light LB. The pulsed excitation light LB is output with a pulse time width of, for example, 1 microsecond or less, preferably 1 nanosecond or less. In this embodiment, the light source 8 outputs a pulsed excitation light LB with a time width of 10 picoseconds to 10 nanoseconds. The light source 8 is configured with a beam light source such as a chip laser. 1, the light source 8 may be arranged outside the main body 6. In this case, the light source 8 may be configured to transmit pulsed excitation light from the light source 8 located outside the main body 6 to the inside of the main body 6 by an optical fiber or the like.

[0015] The nonlinear optical crystal 10 is configured to generate terahertz waves TH by optical wavelength conversion of pulsed excitation light LB. The nonlinear optical crystal 10 is, for example, a periodically poled lithium niobate (LiNbO3) crystal, and the periodically poled lithium niobate crystal generates terahertz waves TH by backward terahertz wave TH oscillation. The terahertz waves TH have a frequency of 10 12 It is an electromagnetic wave in the range of 0.1 to 100 THz (1 trillion Hertz).

[0016] The terahertz waves TH generated by the nonlinear optical crystal 10 pass through the half mirror 12, are deflected by the mirror 14, and are irradiated onto the inner circumferential surface of the inspection object TG via the condenser lens 16. The reflected waves RW from the inspection object TG are collected by the condenser lens 16, are deflected by the mirror 14, pass through the half mirror 12, and are detected by the detector 18. In this manner, in the optical system 4, when inspecting the inspection object TG, the terahertz waves TH are collected by the condenser lens 16 and are irradiated onto the inspection object TG. Therefore, the terahertz waves TH are collected on the inspection object TG, and the reflected waves RW can be detected with high resolution by the detector 16.

[0017] In this manner, in the optical system 4, the pulsed excitation light LB having a time width of 10 picoseconds to 10 nanoseconds is transmitted through the nonlinear optical crystal 10 to generate the terahertz wave TH that has been optically wavelength converted, and is therefore more powerful (higher output) than the terahertz wave irradiated from a semiconductor element such as an RTD or PCA. Therefore, the optical components (light source 8, nonlinear optical crystal 10, etc.) that constitute the optical system 4 can be disposed at a position separated from the inspection object TG. Even if the resin material RM provided on the inner peripheral surface of the inspection object TG is a poorly permeable material, the terahertz wave TH passes through the resin material RM and is reflected by the inspection object TG. Therefore, even if the inspection object TG is covered with the resin material RM that contains a poorly permeable material, the inspection object TG can be inspected.

[0018] Furthermore, in imaging of difficult-to-penetrate materials, the light source 8 needs to be highly output in order to ensure a high signal-to-noise ratio, but continuous wave oscillation such as with a gyrotron consumes a lot of power and may burn the object. On the other hand, the light source 8 consumes low power while ensuring high peak power because the terahertz wave TH is pulsed. This makes it possible to achieve non-destructive imaging with high transmission performance without burning the inspection object TG.

[0019] The main body 6 housing the optical system 4 having such a configuration includes a housing 20 and an arm mechanism 22 attached to the housing 20 so as to be rotatable.

[0020] The housing 20 houses the light source 8, the nonlinear optical crystal 10, the half mirror 12, and the detection unit 18 of the optical system 4. The light source 8 and the nonlinear optical crystal 10 are disposed so that the terahertz wave TH outputted from the nonlinear optical crystal 10 passes through a rotation center C1 of the arm mechanism 22.

[0021] A multi-axis arm 24 is provided on the outer periphery of the housing 20. The arms of the multi-axis arm 24 are provided at equal intervals in the circumferential direction of the housing 20 and are configured to extend radially outward from the housing 20. These arms extend and contract to form a YZ direction position adjustment mechanism for adjusting the position of the inspection device 1 on the YZ plane (a plane perpendicular to the axial direction X). Each arm of the multi-axis arm 24 is in the shape of a pantograph, and a running wheel 26 is provided at each joint for supporting the housing 20 on the inner peripheral surface of the inspection object TG while allowing it to move along the axial direction X inside the inspection object TG. In this embodiment, the multi-axis arm 24 is shown as an example of the YZ direction position adjustment mechanism, but the configuration of the YZ direction position adjustment mechanism is not limited.

[0022] The arm mechanism 22 is a rotating part that can rotate the optical system 4, which is an inspection part, and the distance measurement part 28 along the circumferential direction. The arm mechanism 22 is attached to the housing 20 so as to be rotatable around a rotation center C1 along the axial direction X, and houses the mirror 14 and the condenser lens 16 of the optical system 4. The arm mechanism 22 includes one end side where the mirror 14 is provided and the other end side where the condenser lens 16 is provided, and the one end side is rotatably attached to the housing 20. In particular, the mirror 18 is disposed on the rotation center C1 of the arm mechanism 22, so that the mirror 18 is disposed at a position where it can receive the terahertz wave TH output from the nonlinear optical crystal 10 contained in the housing 20. The arm mechanism 22, which is attached so as to be rotatable at one end side, is rotated by an actuator such as a motor (not shown). From the other end side of the arm mechanism 22, the terahertz wave TH generated by the optical system 4 is irradiated onto the inner peripheral surface of the inspection object TG, and the reflected wave RW from the inner peripheral surface is captured.

[0023] The arm mechanism 22 is provided with a distance measuring unit 28 for measuring the distance between the arm mechanism 22 and the inner circumferential surface of the test object TG. The distance measuring unit 28 is, for example, a laser distance measuring device capable of measuring the distance using laser light LL. The distance measuring unit 28 can measure the distance between the arm mechanism 22 and the inner circumferential surface of the test object TG by irradiating the inner circumferential surface of the test object TG with laser light LL from approximately the same position as the terahertz wave TH and approximately parallel to the terahertz wave TH, and detecting the laser reflected light LR from the inner circumferential surface of the test object TG at approximately the same position as the reflected wave RW. Such a distance measuring unit 28 is fixed to the arm mechanism 22 and can rotate around the rotation center C1 together with the arm mechanism 22. The distance measured by the distance measuring unit 28 can be converted to the distance from the rotation center C1 to the inner circumferential surface of the test object TG by considering the length from the rotation center C1 to the irradiation position of the laser light LL or the detection position of the laser reflected light LR.

[0024] The inspection device 1 also includes a control device 30 for controlling the above-mentioned components. The control device 30 is a control unit for controlling the inspection device 1, and is composed of, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads the program into the RAM or the like and executes information processing and arithmetic processing to realize various functions. The program may be installed in a ROM or other storage medium in advance, may be provided in a state stored in a computer-readable storage medium, or may be distributed via a wired or wireless communication means. The computer-readable storage medium may be a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

[0025] 1, the control device 30 is configured as a separate entity from the main body 6 of the inspection device 1 and configured to be able to communicate with each other, but at least a part of it may be configured integrally with the main body 6. Also, the control device 30 is connected to the main body 6 by a wired or wireless communication means, so that various data can be transmitted and received.

[0026] Fig. 2 is a block diagram of the control device 30 of Fig. 1. The control device 30 includes an inspection control unit 32, an X-direction position adjustment unit 34, a YZ-direction position adjustment unit 36, a data storage unit 38, and an analysis unit 40.

[0027] The inspection control unit 32 is configured to control the inspection operation by the inspection device 1. The inspection operation includes irradiating the inner peripheral surface of the inspection object TG with the terahertz wave TH while rotating the arm mechanism 22 with respect to the housing 20, and detecting the reflected wave RW from the inner peripheral surface of the inspection object TG. In addition, the inspection operation may include a distance measurement operation by the distance measurement unit 28 as a part of such an inspection, as necessary. That is, when inspecting the inner peripheral surface of the inspection object TG while rotating the arm mechanism 22, distance measurement by the distance measurement unit 28 may be performed at the same time. In addition, in the inspection operation, only distance measurement by the distance measurement unit 28 may be performed (the inspection operation in this case is appropriately referred to as a "distance measurement operation"). Data (inspection data) acquired in these inspection operations are associated with each other together with the circumferential position on the inner peripheral surface, and are appropriately stored in a data storage unit 38 described later.

[0028] When the inspection data is obtained as analog data by the inspection operation, the inspection control unit 32 may include an A / D converter for converting the analog data into digital data that can be calculated.

[0029] The X-direction position adjustment unit 34 is configured to adjust the position (axial position) of the inspection device 1 along the axial direction X. The above-mentioned inspection operation is repeatedly performed while changing the X-direction position, so that the inner peripheral surface of the inspection target TG can be inspected over a wide range. The X-direction position adjustment unit 34 adjusts the position of the inspection device 1 along the axial direction X (hereinafter, appropriately referred to as "X-direction position adjustment operation") in conjunction with such an inspection operation.

[0030] In this embodiment, the X-direction position adjustment operation is performed by moving the inspection device 1 inserted into the internal space 2 of the inspection object TG while the inspection object TG is fixed, so that the X-direction position of the inspection device 1 changes. However, in other embodiments, the X-direction position adjustment operation may be performed by changing the X-direction position of the inspection object TG while the inspection device 1 is fixed. Also, the X-direction position adjustment operation may be performed by relatively changing the X-direction positions of both the inspection device 1 and the inspection object TG.

[0031] The YZ-direction position adjustment unit 36 ​​is configured to perform position adjustment (hereinafter, appropriately referred to as "YZ-direction position adjustment operation") of the inspection device 1 in the YZ plane (plane perpendicular to the axial direction X). The adjustment amount by the YZ-direction position adjustment unit 36 ​​is controlled based on the measurement result by the distance measurement unit 28. For example, in a state where the axial position of the inspection device 1 is fixed, the rotation center C1 is determined to be located on the central axis C2 of the inspection target TG based on the distance data obtained by the distance measurement unit 28 while rotating the arm mechanism 22. More specifically, the adjustment amount is determined by calculating the average value of the distance data in the circumferential direction and minimizing the deviation of each distance data from the average value. As a result, the position of the inspection device 1 in the YZ plane is suitably adjusted by the YZ-direction position adjustment operation so that the rotation center C1 of the inspection device 1 coincides with the central axis C2. As a result, by irradiating the terahertz waves TH and detecting the reflected waves RW on the central axis C2 of the object to be inspected TG, inspection using the terahertz waves TH, which are electromagnetic waves with high directionality and excellent linearity, can be performed with high accuracy.

[0032] The data storage unit 38 is configured to store various data necessary for control calculations in the control device 30. The data stored in the data storage unit 38 includes inspection data acquired in the inspection operation (including distance data acquired in the distance measurement operation).

[0033] The analysis unit 40 is configured to analyze the various data stored in the data storage unit 38 to obtain the test results.

[0034] Next, a description will be given of an inspection method performed by the inspection device 1 having the above configuration. Fig. 3 is a flow chart showing the inspection method according to one embodiment.

[0035] First, the control device 30 adjusts the axial position of the inspection device 1 by performing an X-direction position adjustment operation using the X-direction position adjustment unit 34 (step S100). For example, when inspection is performed at a plurality of axial positions in the inspection plan, the X-direction position is adjusted so that the inspection device 1 is at the first axial position.

[0036] Next, at the X-direction position adjusted in step S100, a distance measurement operation is performed (step S101). In the distance measurement operation, with the X-direction position fixed, distance measurement is performed while distance measurement unit 28 is rotated together with arm mechanism 22. Distance data measured by distance measurement unit 28 is appropriately stored in data storage unit 38 in a readable manner.

[0037] Next, the YZ direction position adjustment unit 36 ​​analyzes the distance data acquired in step S101 (step S102) and determines whether the rotation center C1 is displaced from the central axis C2 of the test object TG in the YZ plane (step S103). In step S102, the distance data acquired in step S101 is analyzed to, for example, calculate an average value of the distance data in the circumferential direction, and calculate the deviation of each distance data from the average value. Then, in step S103, it is determined whether the rotation center C1 is displaced from the central axis C2 of the test object TG based on whether the deviation is greater than a preset threshold value.

[0038] If it is determined that the rotation center C1 is deviated from the central axis C2 of the test object TG (step S103: YES), a YZ direction position adjustment operation is performed so that the rotation center C1 is positioned on the central axis C2 of the test object TG (step S104). The adjustment amount for the YZ direction position adjustment mechanism in step S104 is determined, for example, so that the deviation described above is equal to or smaller than a threshold value.

[0039] Incidentally, if the rotation center C1 is not displaced from the central axis C2 of the inspection target TG (step S103: NO), the YZ direction position adjustment operation in step S104 is not necessary.

[0040] Next, the inspection control unit 102 performs an inspection operation (step S105). In step S105, the arm mechanism 22 is rotated at the axial position adjusted in step S100 (the same axial position as when the distance measurement operation was performed in step S101), thereby performing an inspection (irradiation of the terahertz wave TH and detection of the reflected wave RW) along the circumferential direction of the inner circumferential surface of the inspection target TG. The inspection data obtained by the inspection is appropriately stored in the data storage unit 38 in a readable manner.

[0041] Next, the control device 30 judges whether the inspection contents in the inspection plan are completed (step S106). For example, when inspections are performed at a plurality of axial positions, whether the inspection contents are completed is judged based on whether the axial position moved to in step S100 is the last inspection position. If there is a next inspection position (step S106: NO), it is determined that the inspection is not completed, and the process returns to step S100, whereby the same process is repeatedly performed at the axial position that is the next inspection position.

[0042] When all the inspection contents in the inspection plan are completed (step S106: YES), the analysis unit 40 analyzes the data stored in the data storage unit 38 to obtain the inspection results (step S107).

[0043] Here, Fig. 4 is an example of the inspection result obtained in step S107 in Fig. 3. In Fig. 4, the vertical axis indicates the axial position (X-direction position), and the horizontal axis indicates the phase angle (0 to 360 degrees) corresponding to the circumferential position, and the surface condition of the inner circumferential surface of the inspection object TG is visualized as a distribution of the signal intensity of the reflected wave RW. As shown in Fig. 4, when the surface condition of the inner circumferential surface is sound, the signal intensity of the reflected wave RW is approximately constant, but the locations of abnormalities such as water or corrosion can be visually distinguished by the localized decrease in signal intensity.

[0044] Particularly in this embodiment, in the YZ direction position adjustment operation, the YZ direction position adjustment mechanism is adjusted so that the rotation center C1 becomes the central axis C2 of the inspection target TG based on the distance data, and then the inspection operation is performed. Therefore, when terahertz waves TH with high directivity and excellent linearity are used, if the surface condition of the inner circumferential surface is sound, the signal intensity of the reflected waves RW becomes approximately constant, so that an abnormal area can be displayed in a distinguishable manner, and good inspection accuracy can be obtained.

[0045] Next, an inspection method according to another embodiment will be described with reference to Fig. 5. Fig. 5 is a flow chart showing the inspection method according to the other embodiment.

[0046] In this embodiment, as a preliminary step, correction data for correcting the inspection data is first prepared (step S200). The correction data is prepared as correlation data indicating the relationship between the propagation distance and the signal intensity of the reflected wave RW detected by the detection unit 18.

[0047] Here, Fig. 6 is an example of the correction data prepared in step S200 of Fig. 5. In this example, the correction data is prepared as data showing the relationship between the propagation distance and the signal strength of the reflected wave RW, and shows that the signal strength tends to decrease as the propagation distance increases. Such correction data is prepared by an experimental, theoretical or simulation method under the same conditions as those of the inspection device 1 or similar conditions.

[0048] Next, the X-direction position adjustment unit 34 performs an X-direction position adjustment operation to adjust the axial position of the inspection device 1 in the same manner as in step S100 described above (step S201). For example, when inspection is performed at a plurality of axial positions in the inspection plan, the X-direction position is adjusted so that the inspection device 1 is at the first axial position.

[0049] Next, at the X-direction position adjusted in step S201, a distance measurement operation is performed similarly to step S101 described above (step S202). In the distance measurement operation, with the X-direction position fixed, distance measurement is performed while distance measurement unit 28 is rotated together with arm mechanism 22. Distance data measured by distance measurement unit 28 is appropriately stored in data storage unit 38 in a readable manner.

[0050] Next, the YZ direction position adjustment unit 36 ​​analyzes the distance data acquired in step S202 (step S203) in the same manner as in steps S102 and S103 described above, and determines whether the rotation center C1 is displaced from the central axis C2 of the test object TG in the YZ plane (step S204). In step S203, the distance data acquired in step S202 is analyzed to, for example, calculate an average value of the distance data in the circumferential direction, and calculate the deviation of each distance data from the average value. Then, in step S204, it is determined whether the rotation center C1 is displaced from the central axis C2 of the test object TG based on whether the deviation is greater than a preset threshold value.

[0051] If it is determined that the rotation center C1 is deviated from the central axis C2 of the test object TG (step S204: YES), a YZ direction position adjustment operation is performed so that the rotation center C1 is positioned on the central axis C2 of the test object TG (step S205). The adjustment amount for the YZ direction position adjustment mechanism in step S205 is determined, for example, so that the deviation described above is equal to or smaller than a threshold value.

[0052] Incidentally, if the rotation center C1 is not displaced from the central axis C2 of the inspection target TG (step S204: NO), the YZ direction position adjustment operation in step S205 is not necessary.

[0053] Next, similarly to step S105 described above, the inspection control unit 102 performs an inspection operation (step S206). In step S206, the arm mechanism 22 is rotated at the axial position adjusted in step S101 (the same axial position as when the distance measurement operation was performed in step S202), thereby performing an inspection (irradiation of the terahertz wave TH and detection of the reflected wave RW) along the circumferential direction of the inner circumferential surface of the inspection target TG. The inspection data obtained by this inspection is appropriately stored in the data storage unit 38 in a readable manner.

[0054] Next, the control device 30 judges whether the inspection contents in the inspection plan are completed (step S207) in the same manner as in step S106 described above. For example, when inspection is performed for a plurality of axial positions, whether the inspection contents are completed is judged based on whether the axial position moved in step S201 is the last inspection position. If there is a next inspection position (step S207: NO), the inspection is deemed not to be completed, and the X-direction position adjustment operation is performed again (step S208), and the process is returned to step S206, so that the same inspection operation is repeatedly performed at the axial position that is the next inspection position. That is, in this embodiment, the YZ-direction position adjustment operation is performed only at the first axial position, and is not performed at other axial positions thereafter. Therefore, the YZ-direction position adjustment operation is performed a small number of times (only once), and the time required for the entire inspection can be significantly reduced.

[0055] When the inspection operation is completed at each axial position in this manner (step S207: YES), the analysis unit 40 analyzes the data stored in the data storage unit 38 to obtain the inspection result (step S209). The data analysis in step S209 includes a correction process of the inspection data using the correction data prepared in step S200. In this correction process, the distance from the rotation center C1 to the inner peripheral surface of the inspection object TG is specified based on the distance data at the same time as the inspection data, and the signal intensity that should be obtained when the distance is the propagation distance is obtained based on the correction data (see FIG. 6) prepared in step S200. In the correction process, the signal intensity of the reflected wave RW obtained as the actual measurement value is corrected based on the signal intensity thus obtained, so that the deterioration of the inspection accuracy can be effectively suppressed even if the rotation center C1 is deviated from the central axis C2 of the inspection object TG.

[0056] Next, still another embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an inspection method according to another embodiment. In the above-mentioned embodiments, the inspection is performed while moving in one direction along the axial direction of the inspection target TG, but in the following embodiment, the inspection is performed while moving in at least two directions (i.e., an outward direction and a return direction) along the axial direction of the inspection target TG.

[0057] First, in the forward direction, the control device 30 adjusts the axial position of the inspection device 1 by performing an X-direction position adjustment operation (step S300), and performs a distance measurement operation (step S301). That is, in the forward direction, the inspection operation (irradiation of the terahertz wave TH and detection of the reflected wave RW) is not performed, and only the distance to the inner peripheral surface of the inspection target TG is measured along the circumferential direction (the distance measurement may be performed along the circumferential direction while the axial position is fixed as in each of the above-mentioned embodiments, or may be performed along a spiral by combining with the adjustment of the axial position). Steps S300 and S301 are repeatedly performed until the axial position reaches the forward end position in the inspection plan (step S302). As a result, in the forward direction, distance data is obtained over the range in the inspection plan. These distance data are associated with the axial position and appropriately stored in the data storage unit 38.

[0058] Next, using the distance data obtained in the forward direction, correction data is created (step S303). This correction data includes distance data (distance to the inner peripheral surface of the inspection target TG) for each axial position, and is used to correct the inspection data obtained in the backward direction. The correction data created in step S303 may be stored in the data storage unit 38 as appropriate.

[0059] Next, in the return direction, the control device 30 adjusts the axial position of the inspection device by performing an X-direction position adjustment operation (step S304), and performs an inspection operation (step S305). Steps S304 and S305 are repeatedly performed until the axial position reaches the return end position (step S306). As a result, in the return direction, inspection data is obtained over a range in the inspection plan. These inspection data are associated with the axial position and appropriately stored in the data storage unit 38.

[0060] In steps S300 to S302 in the forward direction, the X-direction position adjustment operation and the distance measurement operation may be performed simultaneously, so that, for example, distance measurement may be performed spirally on the inner peripheral surface of the inspection object TG. In this case, in steps S304 to S306 in the backward direction, the X-direction position adjustment operation and the inspection operation may be performed simultaneously, so that, for example, inspection may be performed spirally on the inner peripheral surface of the inspection object TG.

[0061] Next, the correction data created in step S303 is used to correct the acquired inspection data by repeatedly performing steps S304 to S306 (step S307). In this embodiment, the YZ position adjustment operation is not performed in steps S304 to S306 in which the inspection data is acquired in the backward direction, but the influence of the deviation of the rotation center C1 from the central axis C2 of the inspection target TG can be reduced by performing the correction process using the correction data created based on the distance data acquired in the forward direction. As a result, it is possible to suitably improve the inspection accuracy while shortening the time required for the inspection, compared to the above-mentioned embodiment in which the YZ position adjustment operation is performed every time an inspection operation is performed.

[0062] In addition, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments may be combined as appropriate.

[0063] The contents described in each of the above embodiments can be understood, for example, as follows.

[0064] (1) An inspection apparatus according to one aspect of the present invention comprises: An inspection apparatus for inspecting an inner peripheral surface of an inspection object having a cylindrical shape, comprising: an inspection unit for irradiating the inner circumferential surface with terahertz waves and detecting reflected waves of the terahertz waves; a distance measuring unit for measuring a distance between the inspection unit and the inner circumferential surface; a rotating unit for rotating the inspection unit and the distance measurement unit in a circumferential direction of the inspection object; a position adjustment mechanism for adjusting a position of the inspection unit in a plane intersecting an axial direction of the inspection object; an axial position adjustment unit for adjusting a relative axial position of the inspection unit with respect to the inspection object; Equipped with Based on the measurement result of the distance measurement unit, the position adjustment mechanism is controlled so that the rotation center of the rotation unit is positioned on the central axis of the object to be inspected.

[0065] According to the above aspect (1), the inspection unit rotates in the circumferential direction while irradiating the inner peripheral surface of the inspection object with terahertz waves and detecting the reflected waves from the inner peripheral surface, thereby performing the inspection. The inspection device adjusts its position on a plane intersecting the axial direction based on the distance measurement result measured by the distance measurement unit that rotates together with the inspection unit, so that the rotation center is the central axis of the inspection object. This allows for accurate inspection using terahertz waves, which are electromagnetic waves with high directionality and excellent linearity.

[0066] (2) In another embodiment, in the above embodiment (1), The adjustment amount of the position adjustment mechanism is determined based on the distance measured when the distance measurement unit is rotated in the circumferential direction by the rotating unit with the axial position being fixed.

[0067] According to the above aspect (2), the rotation centers of the inspection unit and the distance measuring unit are suitably adjusted to the central axis of the object to be inspected, thereby effectively improving the accuracy of inspection using terahertz waves.

[0068] (3) In another embodiment, in the above embodiment (2), The adjustment amount is determined so that the deviation of the distance is minimized from the average value of the distance measured when the distance measurement unit is rotated circumferentially by the rotating unit while the axial position is fixed.

[0069] According to the above aspect (3), the adjustment amount of the position adjustment mechanism is calculated so that the deviation of the distances measured while rotating the distance measurement unit in the circumferential direction is minimized with the axial position of the moving body fixed. By controlling the position adjustment mechanism based on the adjustment amount calculated in this manner, the inspection unit can be appropriately positioned on the central axis.

[0070] (4) In another embodiment, in any one of the above (1) to (3), The position adjustment mechanism is controlled each time the axial position changes and before the inner circumferential surface is inspected by the inspection unit.

[0071] According to the above aspect (4), each time the axial position of the inspection part is changed, the position adjustment mechanism adjusts the rotation axis so that it is positioned on the central axis. By carrying out the inspection after such a position adjustment, good inspection accuracy can be obtained.

[0072] (5) In another embodiment, in any one of the above (1) to (3), After the position adjustment mechanism is controlled, inspection is performed by the inspection unit at a plurality of axial positions.

[0073] According to the above aspect (5), after the rotation axis is adjusted to be located on the central axis by the position adjustment mechanism, inspections are performed at a plurality of axial positions, which makes it possible to efficiently perform inspections at many axial positions while reducing the number of position adjustments.

[0074] (6) In another embodiment, in the above embodiment (5), The relationship between the signal strength of the reflected wave detected by the inspection unit and the distance measured by the distance measurement unit is prepared in advance as correction data, and the correction data is used to correct the signal strength of the reflected wave detected by the inspection unit based on the distance measured by the distance measurement unit.

[0075] According to the above aspect (6), the relationship between the signal strength of the reflected wave detected by the inspection unit and the distance measured by the distance measurement unit is prepared in advance as correction data. By referring to this correction data, the signal strength of the reflected wave detected corresponding to the distance measured by the distance measurement unit is corrected, thereby making it possible to improve the inspection accuracy while reducing the number of position adjustments by the position adjustment mechanism.

[0076] (7) In another embodiment, in any one of the above (1) to (6), The signal strength of the reflected wave detected by the inspection unit is corrected using correction data that correlates the signal strength of the reflected wave detected by the inspection unit while moving along the axial direction with the distance measured by the distance measurement unit.

[0077] According to the above aspect (7), the relationship between the signal strength of the reflected wave detected by the inspection unit while moving along the axial direction and the distance measured by the distance measuring unit is prepared in advance as correction data. This correction data is used when performing the subsequent inspection to correct the signal strength of the reflected wave detected by the inspection unit, thereby effectively improving the inspection accuracy.

[0078] (8) In another embodiment, in any one of the above (1) to (7), The distance measurement unit is a laser measurement device capable of measuring the distance by using a laser beam.

[0079] According to the above aspect (8), by using a laser measurement device as the distance measurement unit, it is possible to suitably measure the distance between the inspection unit and the inner surface of the inspection object.

[0080] (9) In another embodiment, in any one of the above (1) to (8), The terahertz waves are generated by converting the optical wavelength of pulsed excitation light having a time width of 10 picoseconds to 10 nanoseconds using a nonlinear optical crystal.

[0081] According to the above aspect (9), the inspection unit converts the pulse excitation light having a time width of 10 picoseconds to 10 nanoseconds into an optical wavelength using a nonlinear optical crystal, thereby making it possible to irradiate a more powerful (high output) terahertz wave than an oscillator composed of semiconductor elements such as an RTD or PCA. By using such a powerful terahertz wave, it is possible to accurately inspect an object to be inspected that has a small SN ratio (signal-to-noise ratio) and is located under a poorly permeable material. [Explanation of symbols]

[0082] 1. Inspection equipment 2. Interior space 4 Optical system 8 light source 10 Nonlinear optical crystals 12 Half Mirror 14. Mirror 16 Condenser lens 18 Detector 20. Cabinet 22 Arm mechanism 24 Multi-axis arm 26 Running wheel 28 Distance measurement unit 30 Control device 32 Inspection control section 34 X direction position adjustment section 36 YZ direction position adjustment section 38 Data storage unit 40 Analysis Department TG Inspection object RM resin material LB Pulse Excitation Light TH Terahertz wave RW reflected wave LL Laser light LR Laser reflection C1 Rotation center C2 center axis

Claims

1. An inspection apparatus for inspecting an inner peripheral surface of an inspection object having a cylindrical shape, comprising: an inspection unit for irradiating the inner circumferential surface with terahertz waves and detecting reflected waves of the terahertz waves; a distance measuring unit for measuring a distance between the inspection unit and the inner circumferential surface; a rotating unit for rotating the inspection unit and the distance measurement unit in a circumferential direction of the inspection object; a position adjustment mechanism for adjusting a position of the inspection unit in a plane intersecting an axial direction of the inspection object; an axial position adjustment unit for adjusting a relative axial position of the inspection unit with respect to the inspection object; Equipped with an inspection apparatus in which the position adjustment mechanism is controlled based on a measurement result of the distance measurement unit so that the rotation center of the rotation unit is positioned on the central axis of the object to be inspected.

2. 2. The inspection device according to claim 1, wherein an adjustment amount of the position adjustment mechanism is determined based on the distance measured when the distance measurement unit is rotated circumferentially by the rotating unit while the axial position is fixed.

3. 3. The inspection device according to claim 2, wherein the adjustment amount is determined so as to minimize the deviation of the distance from an average value of the distances measured when the distance measuring unit is rotated circumferentially by the rotating unit while the axial position is fixed.

4. The inspection device according to claim 1 , wherein the position adjustment mechanism is controlled each time the axial position changes and before the inner circumferential surface is inspected by the inspection unit.

5. The inspection device according to claim 1 , wherein after the position adjustment mechanism is controlled, the inspection unit performs inspection at a plurality of axial positions.

6. The inspection device of claim 5, further comprising: a correction data set that is a relationship between the signal strength of the reflected wave detected by the inspection unit and the distance measured by the distance measurement unit; and a correction data set that is used to correct the signal strength of the reflected wave detected by the inspection unit based on the distance measured by the distance measurement unit.

7. The detection device according to claim 1 or 2, wherein the signal intensity of the reflected wave detected by the inspection unit is corrected using correction data that correlates the signal intensity of the reflected wave detected by the inspection unit while moving along the axial direction with the distance measured by the distance measuring unit.

8. The inspection device according to claim 1 , wherein the distance measuring unit is a laser measuring device capable of measuring the distance by using a laser beam.

9. 3. The inspection device according to claim 1, wherein the terahertz wave is generated by optical wavelength conversion of pulsed excitation light having a time width of 10 picoseconds to 10 nanoseconds using a nonlinear optical crystal.

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