JP2022169238A - Internal inspection device and internal inspection method - Google Patents

Abstract

To provide an internal inspection device and an internal inspection method that can inspect the internal structure and defect shape of an object to be inspected with high resolution.SOLUTION: An internal inspection device includes: a millimeter wave transmission/reception antenna 2 that emits millimeter waves to an object to be inspected 1 and receives reflected waves from the object; a millimeter wave transmission/reception circuit 3 connected to the millimeter wave transmission/reception antenna; and an electric stage 4 that is moving means for moving the object to be inspected 1. A personal computer 5 includes synthetic aperture processing means for performing synthetic aperture processing using a plurality of millimeter wave signals received for a plurality of relatively different positions between the object to be inspected 1 and the millimeter wave transmission/reception antenna 2, and positional data indicating the plurality of relatively different positions. The internal inspection device receives the millimeter wave signals reflected from the object to be inspected 1 at preset moving intervals, obtains the internal structure or internal defect shape of the object to be inspected 1 by the synthetic aperture processing means, and displays it on a display unit 6.SELECTED DRAWING: Figure 1

Description

The present invention relates to an internal inspection apparatus and an internal inspection method for non-destructively determining the internal structure or internal defect shape of an object to be inspected using millimeter waves.

2. Description of the Related Art Conventionally, as methods and apparatuses for non-destructively detecting defects inside an object, for example, methods and apparatuses described in Patent Documents 1 to 3 are known. The inspection device described in Patent Document 1 irradiates an electromagnetic wave such as a microwave to a concrete structure to be measured, and detects the intensity and phase of the reflected wave from there, thereby detecting the inside of the structure. Defects such as cracks and delamination that have occurred are detected, and detection results are output as image data by scanning an object to be measured with electromagnetic wave irradiation/detection means.

The device described in Patent Document 2 is mainly a device for non-destructively measuring internal defects such as small parts, etc., and is configured using a transmitting and receiving antenna for the purpose of detecting easily and with high accuracy. An object to be measured is placed in a microwave resonance system, and a change in the amplitude of a transmitted or reflected microwave wave due to a defect is detected. In the device described in Patent Document 3, when detecting layered defects inside an object, noise signal components are removed by utilizing the fact that the polarization directions of incident microwaves and reflected waves from defects inside the object to be inspected are different. By doing so, high detection accuracy is obtained.

Japanese Patent Application Laid-Open No. 2002-350365 JP-A-2004-156987 JP 2014-219238 A

Equipment that can non-destructively inspect the inside of objects is necessary for detecting defective parts and analyzing failures in the manufacturing process of various products, and inspection equipment that can detect the internal structure and shape of defects with high resolution. There is an increasing demand for Conventionally, as described in the above patent document, it has been possible to detect the presence or absence of defects inside an object using microwaves, but an inspection apparatus that can detect the shape of defects and detailed internal structures has been obtained. Not done.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve such problems, and it is an object of the present invention to provide an internal inspection apparatus and an internal inspection method capable of inspecting the internal structure and defect shape of an object to be inspected with high resolution. and

In a first aspect, an internal inspection apparatus of the present invention includes a millimeter wave transmitting/receiving antenna for radiating millimeter waves toward an object to be inspected and receiving the millimeter waves reflected from the object to be inspected; By providing at least one means of a connected millimeter wave transmitting/receiving circuit, means for moving at least one of the millimeter wave transmitting/receiving antenna or the object to be inspected, or means having a plurality of the millimeter wave transmitting/receiving antennas, means for radiating the millimeter wave at a plurality of relatively different positions between the object under test and the millimeter wave transmitting/receiving antenna and receiving the reflected millimeter wave signal; the received plurality of millimeter wave signals; synthetic aperture processing means for performing synthetic aperture processing using position data indicating the plurality of relatively different positions; A millimeter wave signal reflected from an object is received, and the internal structure or internal defect shape of the object to be inspected is obtained by the synthetic aperture processing means and displayed on the display means.

In the present invention, as described above, synthetic aperture processing is performed using a plurality of millimeter wave signals received by millimeter wave transmitting/receiving antennas at different positions relative to the object to be inspected. Find the structure and shape of the defect. This enables detection with much higher resolution than when the shape is obtained simply from the distribution of the intensity and phase of the reflected millimeter wave. In order to perform synthetic aperture processing, it is necessary that the millimeter-wave radiation angle of the millimeter-wave transmitting/receiving antenna to be used is wide to some extent. For example, a probe antenna, a patch antenna, a horn antenna, or the like can be used.

In the present invention, millimeter wave signals at relatively different positions between the object to be inspected and the millimeter wave transmitting/receiving antennas are required. As a means for radiating millimeter waves and receiving reflected waves, means for moving at least one of the millimeter wave transmitting/receiving antenna and the object to be inspected, or means for providing a plurality of millimeter wave transmitting/receiving antennas. or both means may be provided. That is, either one or both of the object to be inspected and the millimeter wave transmitting/receiving antenna may be moved, or a plurality of millimeter wave transmitting/receiving antennas may be arranged so that the millimeter wave is irradiated to the entire required inspection area. Just do it. The millimeter wave used in the present invention refers to electromagnetic waves with a frequency of 20 to 300 GHz.

In the synthetic aperture processing, for example, the reflection position can be grasped in the range direction using the FM-CW radar method or the like. In this case, a millimeter-wave reflection plate is installed in advance at a reference position where the object to be inspected is placed, and a millimeter-wave reflection signal is obtained. Reflection positions within the object to be inspected can be grasped, and high resolution can be achieved. In addition, as an example of synthetic aperture processing in the azimuth direction, range migration correction is performed, the complex conjugate of the transfer function at each range position is analytically generated from the measurement conditions, and it is measured as a two-dimensional or one-dimensional reference signal. Synthetic aperture processing data can be obtained by performing data and correlation processing.

In a second aspect, the present invention provides, in the internal inspection apparatus of the first aspect, a millimeter wave signal obtained between the set positions based on the data of the millimeter wave signal obtained for each of the preset positions. and interpolating means for estimating and interpolating data obtained from each of the set positions, and determining the shape of the internal structure or the internal defect based on the data obtained for each of the set positions and the interpolated data. .

In the invention of this aspect, using data obtained by measuring millimeter wave signals at a plurality of preset relatively different positions, interpolation estimated to be obtained by measurement between the above set positions The data is obtained by calculation, and the interpolated data is added to the data actually obtained by the millimeter wave signal to obtain the internal structure of the object to be inspected or the shape of the internal defect. This makes it possible to grasp the internal structure and defect shape with higher resolution. In addition, by performing interpolation processing by calculation without actually performing measurement at the interpolation position, it is possible to significantly reduce the time required for measurement and processing of measurement results.

In a third aspect, the present invention provides the internal inspection apparatus according to the first or second aspect, wherein the object to be inspected has a substantially rectangular parallelepiped shape, and the millimeter wave is applied to one surface of the object to be inspected. means for moving at least one of the object to be inspected and the millimeter wave transmitting/receiving antenna in a plane parallel to the surface, or the plurality of millimeter wave transmitting/receiving antennas, and the plurality of millimeter wave transmitting/receiving antennas. and means for arranging the wave transmitting/receiving antenna in a plane parallel to the surface, so that different portions of the object to be inspected are positioned sequentially in the millimeter wave radiation direction of the millimeter wave transmitting/receiving antenna. It is characterized in that it is set to

In the invention of this aspect, the object to be measured has a substantially rectangular parallelepiped shape, and one surface of the object is irradiated with millimeter waves substantially perpendicularly. Furthermore, when a moving means is provided, at least one of the object to be inspected and the transmitting/receiving antenna is moved within a plane parallel to its irradiation surface. At this time, for example, when the width direction of the surface to be irradiated with millimeter waves is the X axis and the length direction is the Y axis, the Y coordinate is moved after all the measurements in the X direction are completed for a certain Y coordinate. may Alternatively, the X-direction movement speed may be increased relative to the Y-direction movement speed, and the X and Y directions may be moved simultaneously to measure the entire irradiation surface. In this case, the measurement operation and the processing of the measurement results are continuously performed, and the time required for inspection can be shortened. Also, by arranging a plurality of millimeter-wave transmitting/receiving antennas in a plane parallel to the irradiated surface, it is possible to reduce the above-mentioned necessary movement amount. Furthermore, even if a moving means is not provided, if the object to be inspected is small, there are cases where the data required for synthetic aperture processing can be obtained simply by arranging a plurality of millimeter wave transmitting/receiving antennas.

In a fourth aspect of the present invention, in the internal inspection apparatus according to the first or second aspect, the object to be inspected has a substantially plate-like shape, and the millimeter wave is applied to one of the objects to be inspected. means for obliquely irradiating a surface and moving at least one of the object to be inspected and the millimeter wave transmitting/receiving antenna in a plane parallel to the surface in a direction substantially perpendicular to the radiation direction of the millimeter wave; or at least one of means comprising the plurality of millimeter wave transmitting/receiving antennas and arranging the plurality of millimeter wave transmitting/receiving antennas in a plane parallel to the surface and in a direction substantially perpendicular to the radiation direction of the millimeter wave. It is characterized by setting such that different parts of the object to be inspected are sequentially positioned in the radiation direction of the millimeter wave by having means.

In the invention of this aspect, the millimeter wave is obliquely incident on the plate-shaped object to be inspected, for example, at an angle of 30 to 60 degrees with respect to the surface. Since the millimeter-wave transmitting/receiving antenna has a wide radiation angle, it is possible to detect a wide area in the width direction perpendicular to the moving direction, and depending on the object to be inspected, it is possible to inspect the object even if it moves in only one direction. In addition, by arranging multiple millimeter-wave transmitting/receiving antennas, it is possible to reduce the required amount of movement. may be obtained.

In a fifth aspect of the present invention, in the internal inspection apparatus of the first or second aspect, the means for rotating the object to be inspected or changing the angle of the millimeter wave transmitting/receiving antenna, or the plurality of a millimeter wave transmitting/receiving antenna; and means for arranging the plurality of millimeter wave transmitting/receiving antennas at different angles with respect to the object to be inspected. It is characterized by receiving a reflected wave by changing the incident angle and performing synthetic aperture processing in a spotlight mode. The invention of this aspect radiates millimeter waves toward a reference position for inspection in an object to be inspected, and performs synthetic aperture processing in a spotlight mode for receiving the reflected waves. This is to obtain the structure of the defect and the shape of the defect. By using this spotlight mode, the resolution in the azimuth direction can be improved. Further, in the spotlight mode synthetic aperture processing according to the present invention, the acquired reflected signal is expanded in the wavenumber space, and the reflected position can be obtained by two-dimensional inverse Fourier transform.

In a sixth aspect of the present invention, in the internal inspection apparatus of the fifth aspect, the object to be inspected is rotated by 360 degrees within a plane including the incident direction of the millimeter wave emitted from the millimeter wave transmitting/receiving antenna. Accordingly, the incident angle of the millimeter wave incident on the object to be inspected is rotated by 360 degrees and the reflected wave is received. In this way, the object to be inspected is rotated to expand the data in the wave number space to 360 degrees so that the millimeter waves can be emitted from 360 degrees to the object to be inspected and the reflected waves can be measured. By performing synthetic aperture processing, that is, two-dimensional inverse Fourier transform, high resolution can be achieved regardless of the measurement direction. In addition, in the internal inspection apparatus of the present invention, the arrangement of the object to be inspected and the millimeter wave transmitting/receiving antenna can be freely selected, and the millimeter wave can be irradiated by rotating it 360 degrees in the same plane. Analysis in synthetic aperture processing becomes easier than in the case of millimeter wave irradiation.

In a seventh aspect, the present invention provides the internal inspection apparatus according to the sixth aspect, wherein the deviation of focus in synthetic aperture processing caused by a reflected wave from a position away from the rotation center of the 360-degree rotation is is corrected by performing phase correction of the received millimeter wave signal within a predetermined area around the . When the incident angle of the millimeter wave incident on the object to be inspected is rotated by 360 degrees and the reflected wave is received, the synthetic aperture processing data is focused near the central axis of rotation and is not processed at a location away from the central axis. However, by correcting the phase of the received millimeter-wave signal, it is possible to focus at an arbitrary location and sharpen the processed image.

In an eighth aspect of the present invention, in the internal inspection apparatus according to the fifth to seventh aspects, the object to be inspected has a columnar, cylindrical or spherical shape, and the millimeter waves are applied to the object to be inspected. The object to be inspected is irradiated substantially perpendicularly to the central axis, the object to be inspected is rotated with respect to the central axis, and the object to be inspected or the transmitting/receiving antenna is moved in a direction parallel to the central axis. It is characterized in that different parts of the object are set so as to be sequentially positioned in the millimeter wave radiation direction of the transmitting/receiving antenna. When the object to be inspected is rotationally symmetrical with respect to the central axis, a method for inspecting the entire object to be inspected is to rotate the object to be inspected and move the transmitting/receiving antenna along the central axis direction. A method of irradiating millimeter waves perpendicular to the central axis is efficient. At this time, for example, the object to be inspected may be rotated about the central axis, and after completing the rotation of 360 degrees, the object to be inspected or the transmitting/receiving antenna may be moved in a direction parallel to the central axis. Alternatively, the object to be inspected or the transmitting/receiving antenna may be moved in a direction parallel to the central axis at the same time that the object to be inspected is rotated about the central axis, that is, moved in a spiral manner.

In a ninth aspect, an internal inspection method of the present invention is an internal inspection method using the internal inspection apparatus according to any one of the first to eighth aspects, wherein A reflecting object that produces a reflected wave with respect to the millimeter wave is installed at a predetermined position in an area close to the millimeter wave, and the millimeter wave reflected by the reflecting object is received in advance, and the received signal is used to obtain the millimeter wave. It is characterized in that distortion of a received signal of a reflected wave from the object to be inspected caused by the wave transmitting/receiving antenna and the millimeter wave transmitting/receiving circuit is corrected.

Generally, in a millimeter wave transmitting/receiving system, a millimeter wave transmitting circuit generates a millimeter wave of a desired frequency, radiates it through a millimeter wave transmitting/receiving antenna, and receives the arriving millimeter wave. However, in this case, the millimeter wave transmission signal radiated through the millimeter wave transmission/reception antenna and the millimeter wave transmission/reception circuit and the millimeter wave reception signal received pass through the millimeter wave transmission/reception antenna and the millimeter wave transmission/reception circuit because they are not perfect. It will have some distortion component when In normal synthetic aperture processing, a reference signal is created from the frequency of the input millimeter wave signal and the analysis distance, and correlation processing and the like are performed on the received signal using the reference signal. However, in this case, if the millimeter wave signal actually radiated from the millimeter wave transmitting/receiving antenna and the received millimeter wave signal differ due to distortion, an error will occur in the shape obtained by the synthetic aperture processing. In the invention of this aspect, for example, a reflecting object whose reflection coefficient is known in advance is installed at a set position, the reflected wave of the millimeter wave is received as a received signal, and the received signal is used to perform processing and set. Corrections can be made to derive the correct reflection coefficient and correct position of the reflecting object. By using the received signal from the reflecting object to correct the received signal of the reflected wave from the object to be inspected and using it for synthetic aperture processing, the distortion of the entire transmission/reception system is compensated for, and data with little error is obtained. be able to. Similarly, in the spotlight mode, by referring to the signal of the reflecting object, the reflecting position within the object to be inspected can be grasped more accurately, and high resolution can be achieved.

As described above, according to the internal inspection apparatus and internal inspection method of the present invention, it is possible to inspect the internal structure and defect shape of an object to be inspected with high resolution.

1 is a block configuration diagram of an internal inspection apparatus according to a first embodiment of an internal inspection apparatus and an internal inspection method of the present invention; FIG. FIG. 4 is a diagram showing an example of a flowchart of an inspection procedure according to the first embodiment; FIG. 5 is a diagram showing an example of experimental results using the internal inspection device of Example 1; The block block diagram of the internal inspection apparatus which concerns on Example 2 of this invention. FIG. 10 is a diagram showing an example of experimental results using the internal inspection device of Example 2; FIG. 11 is a schematic configuration diagram showing the arrangement of a millimeter-wave transmitting/receiving antenna and an object to be inspected of the internal inspection apparatus according to the third embodiment; FIG. 11 is a schematic configuration diagram showing the arrangement of a millimeter-wave transmitting/receiving antenna and an object to be inspected of an internal inspection apparatus according to a fourth embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the internal inspection apparatus and internal inspection method of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions thereof are omitted.

FIG. 1 is a block configuration diagram of an internal inspection apparatus according to a first embodiment of the internal inspection apparatus and internal inspection method of the present invention. In FIG. 1, an internal inspection apparatus 10 of this embodiment includes a millimeter wave transmitting/receiving antenna 2 for radiating millimeter waves toward an object 1 to be inspected and receiving the millimeter waves reflected from the object 1 to be inspected, and a millimeter wave transmitting/receiving antenna. 2, and a motorized stage 4 as moving means for mounting the object 1 to be inspected and moving the object 1 to be inspected. Here, the object 1 to be inspected has a rectangular parallelepiped shape, and the millimeter waves radiated from the millimeter wave transmitting/receiving antenna 2 are radiated substantially perpendicularly to the surface 1a of the object 1 to be inspected. The motorized stage 4 moves the object 1 to be inspected 1 in a plane parallel to the surface 1a, that is, in the xy plane, so that different parts of the object 1 to be inspected are sequentially positioned in the millimeter wave radiation direction of the millimeter wave transmitting/receiving antenna 2. set to In this embodiment, a probe antenna is used as the millimeter wave transmitting/receiving antenna 2 .

Further, the internal inspection apparatus 10 receives a plurality of millimeter wave signals at a plurality of relatively different positions between the object 1 to be inspected and the millimeter wave transmitting/receiving antenna 2, and Synthetic aperture processing means for performing synthetic aperture processing using position data indicating . Specifically, as the object to be inspected 1 moves, millimeter wave signals reflected from the object to be inspected 1 are received at predetermined movement intervals, for example, every 0.5 to 5.0 mm, and each movement position is determined. Synthetic aperture processing is performed using a plurality of millimeter wave signals received in and position data indicating the position of the object 1 to be inspected with respect to the millimeter wave transmitting/receiving antenna 2 at each receiving position. The internal structure of the object to be inspected 1 or the shape of the defect therein is determined by this synthetic aperture processing means, and the internal structure and the shape of the defect are displayed on the display unit 6 of the personal computer 5 .

The motorized stage 4 is controlled by a controller 7 , and the controller 7 is controlled by control signals 11 from the personal computer 5 . Further, from the controller 7, a trigger signal 12 is sent to the personal computer 5 for receiving a received signal and for sending a transmission signal to the millimeter wave transmitting/receiving circuit 3 along with movement.

The inspection procedure of the internal inspection method by the internal inspection apparatus 10 of this embodiment will be described below. FIG. 2 is a diagram showing an example of a flow chart of an inspection procedure according to this embodiment. First, measurement conditions are set. As a specific example, when the FM-CW radar system is used to obtain the reflection position in the range direction, that is, in the z direction inside the object 1 to be inspected in FIG. Since a chirp signal obtained by periodically and linearly changing is used, the frequency, the width of change, the period, etc. in that case are set. Based on these set conditions, a millimeter wave transmission signal is generated and supplied to the millimeter wave transmitting/receiving antenna 2 . Note that, as an example of the frequency of the millimeter wave, it can be swept between 77 GHz and 81 GHz.

Next, when the object to be inspected 1 reaches the set moving position, as reception data processing, a reflected wave from the object to be inspected 1 is received by the millimeter wave transmitting/receiving antenna 2, and the frequency of the received millimeter wave is reduced to a low frequency. It converts it into a domain, converts the voltage value by an AD converter, etc., and outputs it as raw data of the received signal in the range direction. Next, correlation processing is performed in the range direction, that is, in the depth z direction of the object 1 to be inspected in FIG. Specifically, a reference signal is created based on the transmission signal, Fourier transform processing is performed on the reception signal and the reference signal, and correlation processing is performed by multiplying them in the frequency domain. Thereafter, inverse Fourier transform processing is performed on the data after the correlation processing to obtain range-compressed data.

However, in this embodiment, in the correlation processing in the range direction, the millimeter waves radiated to a predetermined position in the region where the object 1 to be inspected is arranged, for example, the position of the surface 1a of the object 1 to be inspected. A measuring system using a millimeter-wave transmitting/receiving antenna 2 and a millimeter-wave transmitting/receiving circuit 3 uses the received data to receive a reflected wave of a millimeter wave from a reflecting object that generates a reflected wave, such as a metal plate. Perform overall correction. Specifically, the above-described correlation processing is performed using the received signal of the reflected wave from the metal plate, and as a result, the reference signal is corrected so that the data correctly indicating the metal plate is output, and the correlation processing is performed. . By performing this correction, it is possible to compensate for the distortion of the entire transmission/reception system and obtain data with less error.

Next, in order to correct distortion caused by a change in distance in the range direction, range migration correction is performed on the range compression data, and correlation processing is performed in the azimuth direction, that is, the moving direction of the object 1 to be inspected in FIG. An azimuth reference signal is generated by analytically determining the complex conjugate of the transfer function at each range position based on the transmitted signal. Correlation processing is similar to correlation processing in the range direction, and synthetic aperture processing data is obtained by a procedure similar to general synthetic aperture processing from a plurality of received data in the movement direction. After performing synthetic aperture processing over the entire preset region while moving the object 1 to be inspected, the internal structure of the object 1 to be inspected is displayed on the display unit 6 using the obtained synthetic aperture processing data. .

However, in this embodiment, interpolated data estimated to be obtained by measurement during the movement interval is obtained by calculation using the data obtained from the reflected millimeter-wave reception signal for each set movement interval, The interpolated data is added to the data actually obtained from the millimeter wave signal to obtain the internal structure of the inspected object or the shape of the internal defect. Specifically, reference signals in the azimuth direction are created not only at positions where received signal data are obtained, but also at interpolated positions therebetween, and correlation processing is performed with the received signal data to obtain a synthetic aperture at the interpolated positions. Processing data is obtained, and the interpolation processing data is added to obtain the shape such as the internal structure of the object 1 to be inspected. For example, a reference signal for interpolation processing is created at intervals of 1/5 of the movement interval for obtaining the received signal, and correlation processing is performed with the obtained received signal. In this way, by performing interpolation processing by calculation without actually performing measurement at the interpolation position, it is possible to greatly reduce the time required for measurement and processing of the measurement results, and the resolution of the measured internal shape is also greatly increased. It has been confirmed that the

FIG. 3 is a diagram showing an example of experimental results using the internal inspection device 10 of the present embodiment, and is an image obtained by detecting the presence or absence of a smart phone packed in a package. FIG. 3(a) shows an image when the smartphone is built in, and FIG. 3(b) shows an image when the smartphone is missing. In FIG. 3(a), the reflected image of the smartphone inside the package was clearly confirmed.

FIG. 4 is a block configuration diagram of an internal inspection apparatus according to Embodiment 2 of the present invention. 4, an internal inspection apparatus 20 of this embodiment includes a millimeter wave transmitting/receiving antenna 2 for radiating millimeter waves toward an object 21 to be inspected and receiving millimeter waves reflected from the object 21 to be inspected. Similarly, it has a millimeter wave transmitting/receiving circuit 3 connected to a millimeter wave transmitting/receiving antenna 2, and an electric stage 4 for mounting an object 21 to be inspected and moving the object 21 to be inspected. Here, the inspected object 21 has a rectangular plate-like shape, and the width in the x direction is smaller than the length in the y direction. The millimeter waves radiated from the millimeter wave transmitting/receiving antenna 2 are obliquely radiated with an inclination angle θ of 30 degrees to 60 degrees with respect to the surface 21a of the object 21 to be inspected. is irradiated. The electric stage 4 moves the object 21 to be inspected 21 in the y direction in a plane parallel to the surface 21 a , that is, in the xy plane, so that different parts of the object 21 to be inspected are aligned in the millimeter wave radiation direction of the millimeter wave transmitting/receiving antenna 2 . to be positioned sequentially.

Further, the internal inspection apparatus 20 includes a personal computer 5 and a display unit 6, and performs synthetic aperture processing similar to that of the first embodiment. As the object 21 to be inspected moves in the y direction, millimeter wave signals reflected from the object 1 to be inspected are received at predetermined movement intervals, for example, about 0.5 to 5.0 mm. Synthetic aperture processing is performed using a plurality of received millimeter wave signals and position data indicating the position of the inspected object 21 with respect to the millimeter wave transmitting/receiving antenna 2 at each receiving position. The internal structure of the object to be inspected 21 or the shape of the defect therein is determined by this synthetic aperture processing means, and the internal structure and the shape of the defect are displayed on the display unit 6 of the personal computer 5 .

The inspection procedure of the internal inspection apparatus 20 in this embodiment is the same as in the first embodiment. Using the received data, the millimeter wave transmitting/receiving antenna 2 and the millimeter wave transmitting/receiving circuit 3 correct the entire measurement system. Also, a reference signal in the azimuth direction is created at an interpolated position between positions where received signal data is obtained, and correlation processing is performed with the received signal data to obtain synthetic aperture processing data at that interpolated position. In addition, the internal structure of the inspected object 21 or the shape of internal defects is sought.

FIG. 5 is a diagram showing an example of experimental results using the internal inspection apparatus 20 of this embodiment, and is an image showing the inspection results of a sample simulating a conveyor belt in which reinforcing metal wires are embedded. A reflected image of the metal wire in the belt was confirmed, and it was confirmed that the metal wire was broken near x=60 mm and y=40 mm.

FIG. 6 is a schematic configuration diagram showing the arrangement of a millimeter wave transmitting/receiving antenna and an object to be inspected of an internal inspection apparatus according to a third embodiment of the present invention. As in the first and second embodiments, the internal inspection apparatus of this embodiment includes a millimeter wave transmitting/receiving antenna 2 for radiating millimeter waves toward an object 31 to be inspected and receiving millimeter waves reflected from the object 31 to be inspected. It has a millimeter wave transmitting/receiving circuit and the like connected to the wave transmitting/receiving antenna 2 . Also, although illustration is omitted, as in the first and second embodiments, a personal computer and a display unit are provided as synthetic aperture processing means. The object 31 to be inspected in this embodiment has a cylindrical shape, and the millimeter wave is irradiated substantially perpendicularly to the central axis 32 of the object 31 to be inspected. At the same time, by moving the millimeter wave transmitting/receiving antenna 2 in a direction parallel to the central axis 32, different portions of the object 31 to be inspected are set to be sequentially positioned in the millimeter wave radiation direction of the millimeter wave transmitting/receiving antenna 2. .

A motorized rotation stage 33 is provided to mount and rotate the object 31 to be inspected. Also, the millimeter-wave transmitting/receiving antenna 2 is fixed to a moving table 34 and moves on an electric moving stage 35 in the z-direction. The motorized rotation stage 33 and the motorized movement stage 35 are connected to a controller, which is controlled by a personal computer.

Further, the internal inspection apparatus of the present embodiment performs spotlight mode synthetic aperture processing. receiving millimeter wave signals reflected from the object to be inspected 31 at predetermined movement intervals as the surface 31a of the object to be inspected 31 moves due to rotation; Synthetic aperture processing is performed using position data indicating the position of the object 31 to be inspected with respect to the millimeter wave transmitting/receiving antenna 2 at each receiving position. The internal structure of the object to be inspected 31 or the shape of the defect therein is determined by this synthetic aperture processing means, and the internal structure and the shape of the defect are displayed on the display unit of the personal computer. The basic inspection procedure of the internal inspection apparatus in this embodiment is the same as in Embodiments 1 and 2, but since the millimeter wave is reflected from the inside of the cylindrical surface, the distance and reflection position should be corrected in consideration of this. Is going.

As in the first and second embodiments, a metal plate is placed at the position of the surface 31a of the object 31 to be inspected, and a millimeter wave reflected by the metal plate is received in advance. Then, the entire measurement system is corrected by a millimeter wave transmission/reception circuit, synthetic aperture processing data is obtained, and the internal structure or internal defect shape of the object 31 to be inspected is obtained.

FIG. 7 is a schematic configuration diagram showing the arrangement of a millimeter wave transmitting/receiving antenna and an object to be inspected of an internal inspection apparatus according to a fourth embodiment of the present invention. As in the first and second embodiments, the internal inspection apparatus of this embodiment includes a millimeter wave transmitting/receiving antenna 2 for radiating millimeter waves toward an object 41 to be inspected and receiving millimeter waves reflected from the object 41 to be inspected. It has a millimeter wave transmitting/receiving circuit and the like connected to the wave transmitting/receiving antenna 2 . Also, although illustration is omitted, as in the first and second embodiments, a personal computer and a display unit are provided as synthetic aperture processing means. In this embodiment, the millimeter wave is irradiated toward an object 41 to be inspected, and the object 41 to be inspected is placed on a sample stage 42 and configured to rotate about the central axis 32 of an electric rotating stage 33. there is The electric rotating stage 33 is connected to a controller, which is controlled by a personal computer.

The internal inspection apparatus of this embodiment performs a spotlight mode synthetic aperture process, and in particular, a synthetic aperture called a circular SAR system that irradiates millimeter waves from 360-degree directions around an object 41 to be inspected and receives reflected waves. Processing is performed, and the internal defect shape and internal structure can be detected with high resolution. In addition, in the general circular SAR system, millimeter waves are emitted obliquely from above by an antenna mounted on an aircraft. Analysis becomes easier than the SAR method.

Also in this embodiment, a metal plate is placed on the surface of the object 41 to be inspected, and a millimeter wave reflected by the metal plate is received in advance. The entire measurement system is corrected by the circuit, synthetic aperture processing data is obtained, and the internal structure or internal defect shape of the object 41 to be inspected can be obtained.

Except when the millimeter wave is irradiated perpendicularly to the surface of the object to be inspected, when there is a defect or structure to be inspected in a shallow area from the surface of the object to be inspected, or when the permittivity of the object to be inspected is small, etc. , it is necessary to consider the refraction of millimeter waves on the surface of the object to be inspected for analysis and processing.

As described above, the present invention provides an internal inspection apparatus and an internal inspection method capable of inspecting the internal structure and defect shape of an object to be inspected with high resolution.

Needless to say, the present invention is not limited to the above embodiments, and design changes are possible according to the purpose and application. For example, electromagnetic waves outside the frequency band of 20 GHz to 300 GHz may be used, and the millimeter-wave transmitting/receiving antenna may be configured using an antenna other than the probe antenna, such as a patch antenna or horn antenna. As for the arrangement of the millimeter wave transmitting/receiving antenna and the object to be inspected, an optimum configuration may be selected according to the purpose, the shape of the object to be inspected, and the like. The material and position of the reflecting object used for correction, the interpolation interval for interpolation processing, and the like can also be arbitrarily selected according to the purpose.

Reference Signs List 1, 21, 31, 41 object to be inspected 1a, 21a, 31a surface 2 millimeter wave transmitting/receiving antenna 3 millimeter wave transmitting/receiving circuit 4 electric stage 5 personal computer 6 display unit 7 controller 10, 20 internal inspection device 11 control signal 12 trigger signal 32 Central axis 33 Electric rotary stage 34 Moving table 35 Electric moving stage 42 Sample table

Claims (9)

a millimeter wave transmitting/receiving antenna that radiates millimeter waves toward an object to be inspected and receives millimeter wave signals reflected from the object to be inspected;
a millimeter wave transmission/reception circuit connected to the millimeter wave transmission/reception antenna;
By providing at least one of means for moving at least one of the millimeter wave transmitting/receiving antenna and the object to be inspected, and means for providing a plurality of the millimeter wave transmitting/receiving antennas, the object to be inspected and the millimeter wave transmitting/receiving antenna means for radiating the millimeter wave and receiving the reflected millimeter wave signal at a plurality of relatively different locations between
synthetic aperture processing means for performing synthetic aperture processing using the plurality of received millimeter wave signals and position data indicating the plurality of relatively different positions;
display means;
has
receiving millimeter wave signals reflected from the object to be inspected at the plurality of preset relatively different positions, determining the internal structure of the object to be inspected or the shape of defects therein by the synthetic aperture processing means; An internal inspection device characterized by displaying on a display means. interpolation processing means for estimating and interpolating data by millimeter wave signals obtained between the set positions based on data by millimeter wave signals obtained for each of the preset positions;
2. The internal inspection apparatus according to claim 1, wherein the internal structure or the shape of the internal defect is obtained based on the data obtained for each of the set positions and the interpolated data. The object to be inspected has a substantially rectangular parallelepiped shape,
The millimeter wave is irradiated substantially perpendicularly to one surface of the object to be inspected,
means for moving at least one of the object to be inspected and the millimeter wave transmitting/receiving antenna in a plane parallel to the surface; and means for arranging in a plane, so that different parts of the object to be inspected are set so as to be sequentially positioned in the millimeter wave radiation direction of the millimeter wave transmitting/receiving antenna. The internal inspection device according to item 1 or 2. The object to be inspected has a substantially plate-like shape,
The millimeter wave is obliquely irradiated with respect to one surface of the object to be inspected,
means for moving at least one of the object to be inspected and the millimeter wave transmitting/receiving antenna in a plane parallel to the surface in a direction substantially perpendicular to the radiation direction of the millimeter wave, or the plurality of millimeter wave transmitting/receiving antennas and means for arranging the plurality of millimeter wave transmitting/receiving antennas in a plane parallel to the surface and in a direction substantially perpendicular to the radiation direction of the millimeter wave. 3. The internal inspection apparatus according to claim 1, wherein different parts of the object are positioned sequentially in the direction of radiation of the millimeter waves. means for rotating the object to be inspected or changing an angle of the millimeter wave transmitting/receiving antenna; and a means for arranging at an angle to receive the reflected waves by changing the incident angle of the millimeter waves incident on the object to be inspected, and perform synthetic aperture processing in a spotlight mode. 3. The internal inspection device according to claim 1 or 2. By rotating the object to be inspected by 360 degrees in a plane including the incident direction of the millimeter waves radiated from the millimeter wave transmitting/receiving antenna, the angle of incidence of the millimeter waves incident on the object to be inspected is rotated by 360 degrees. 6. The internal inspection apparatus according to claim 5, receiving reflected waves. Defocus in synthetic aperture processing caused by reflected waves from a position away from the rotation center of the 360-degree rotation is corrected by phase-correcting the received millimeter-wave signal within a predetermined region around the rotation center. 7. The internal inspection apparatus according to claim 6, wherein correction is performed. The object to be inspected has a cylindrical, cylindrical or spherical shape,
The millimeter wave is irradiated substantially perpendicularly to the central axis of the object to be inspected,
By rotating the object to be inspected about the central axis and moving the object to be inspected or the millimeter wave transmitting/receiving antenna in a direction parallel to the central axis, different parts of the object to be inspected are subjected to the millimeter wave transmission/reception. 8. The internal inspection apparatus according to any one of claims 5 to 7, wherein the internal inspection apparatus is set so as to sequentially position in the millimeter wave radiation direction of the antenna. An internal inspection method using the internal inspection apparatus according to any one of claims 1 to 8,
A reflective object that generates a reflected wave with respect to the millimeter wave is installed at a predetermined position in the area where the object to be inspected is arranged or in an area close to the area, and the millimeter wave is previously reflected by the reflective object. receive waves,
An internal inspection method, wherein the received signal is used to correct distortion of a received signal of a reflected wave from the object to be inspected caused by the millimeter wave transmitting/receiving antenna and the millimeter wave transmitting/receiving circuit.

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