JP4369915B2 - Electromagnetic imaging system - Google Patents

Description

  The present invention relates to an imaging technique for seeing through a medium using electromagnetic waves, and more particularly to an electromagnetic imaging technique applicable to nondestructive inspection inside a concrete structure such as a building or a tunnel.

  In general, concrete widely used in the world's buildings often suffers from decay and defects as the manufacturing process and years progress. Such decay and defects significantly degrade the strength of the concrete and put the building in a dangerous state. For example, if cracks or delamination occur inside a concrete structure, the strength of the structure may decrease, and there is a risk of eventually collapsing. Examples include the collapse of buildings due to earthquakes and the fall of tunnel lining concrete blocks.

  In order to prevent such an accident, it is necessary to detect cracks and peeling in the concrete at an early stage. A simple method is to visually inspect the deterioration of the concrete from the outside, but in reality the surface of the concrete is often covered with a medium that does not transmit visible light, such as wallpaper cloth or paint. In such a case, deterioration cannot be found visually.

  In contrast, conventional X-ray CT, ultrasonic imaging, thermal distribution imaging, and microwave imaging may be applied to nondestructive inspection techniques inside concrete structures such as buildings and tunnels.

  X-ray CT utilizes the high X-ray transmission ability, and an X-ray generator and an X-ray detector are arranged opposite to each other, and the inside of the target is detected from the X-ray data detected through the target. It is a technology to visualize.

  Ultrasonic imaging is a technique in which ultrasonic waves are incident in a pulsed manner from the surface of concrete, and an elastic wave propagating in the concrete is detected to detect decay and defects (for example, see Patent Document 1). Also in this case, basically, the ultrasonic generator and the detection device are arranged to face each other with the inspection object interposed therebetween.

  Thermal distribution imaging is a technology that detects infrared radiation radiated from the surface of a building and visualizes the temperature distribution on the surface, and utilizes the fact that the heat conduction characteristics differ between healthy sites and decayed / defect sites. .

Microwave imaging is a technology that employs a radar system to transmit microwaves inside concrete and receive microwaves reflected from the interface of materials with different electrical characteristics, and is a metal tube buried inside concrete. (For example, refer nonpatent literature 1).
International Publication No. WO00 / 52418 Pamphlet Harayuki Ohara "Development of 3D imaging radar for concrete slab inspection", Proceedings of the 7th Underground Electromagnetic Measurement Workshop, 2003

  However, in X-ray CT and ultrasonic imaging, it is necessary to place a detection device behind the concrete surface, such as a target tunnel or the outer wall of a high-rise building. There is a problem that it takes a long time.

  On the other hand, in heat distribution imaging and microwave imaging, since it is the structure which detects the electromagnetic waves from a target, the application range with respect to a target can be expanded with a simple system configuration.

  However, in thermal distribution imaging, when the target surface is covered with a medium, only the temperature distribution on the surface of the medium can be visualized, and thermal diffusion may spread quickly, which may cause a problem of spatial resolution.

  On the other hand, in order to diagnose defects such as concrete cracks and delamination at an early stage, accuracy of millimeters is required at the minimum, but since this size is smaller than the wavelength of microwaves, in microwave imaging, fine cracks are required. In order to know the exact shape of the image, spatial resolution becomes a problem.

  In view of the above problems, the present invention has an object to perform a non-destructive inspection in real time at a high spatial resolution while expanding the application range for a target, such as cracks and peeling, occurring in the surface layer of a concrete structure. And

An electromagnetic wave imaging system according to a first aspect of the present invention includes an electromagnetic wave generating means that generates an electromagnetic wave in a millimeter wave band, a transmission antenna that radiates an electromagnetic wave to a target, a receiving antenna that receives an electromagnetic wave reflected by the target, and a receiving antenna. A detector for converting the reflected intensity of the received electromagnetic wave into an electrical signal, a housing capable of scanning at least the transmitting antenna and the receiving antenna along the target, and a distance detecting means for detecting a distance scanned by the housing. Image data is generated based on the mobile electromagnetic radiation irradiation / detection device provided, the lock-in amplifier to which the output from the detector is input, the output signal of the lock-in amplifier and the distance information detected by the distance detection means And an image data generating means for transmitting to the target of the electromagnetic wave emitted from the antenna main axis. The receiving antenna is arranged so as to be inclined with respect to the vertical axis perpendicular to the target surface at the launch point, and the receiving antenna receives the electromagnetic wave reflected from the transmitting antenna beyond the vertical axis and facing the transmitting antenna. The angle formed between the main axis and the vertical axis of the transmitting antenna is different from the angle formed between the main axis and the vertical axis of the receiving antenna, and a plurality of receiving antennas are arranged . A plurality of switches connected to each other, each having a switch for sequentially switching and outputting an output signal from each detector, and the lock-in amplifier has a single channel input for phase-sensitive detection of the input signal. Where the output from the switch is input in a single channel.

  The target in the present invention refers to concrete used for structures such as buildings and tunnels, and the electromagnetic wave in the millimeter wave band refers to an electromagnetic wave having a frequency of 30 GHz to 300 GHz. The medium refers to a mediator that can transmit millimeter wave electromagnetic waves between the antenna and the target. Millimeter-wave electromagnetic waves are transmitted through not only air and other media that allow visible light to pass through, but also through media that do not pass through visible light, such as clothing worn by humans and wood used as residential building materials. For concrete, when the frequency is 100 GHz, it passes through the surface of the concrete to a depth of about 10 mm.

In the present invention, the electromagnetic wave in the millimeter wave band radiated from the transmitting antenna is reflected by the target, and the intensity of the reflected wave detected by the receiving antenna and the detector is digitized by the lock-in amplifier so that the target The defect portion is detected from the difference in reflection intensity between the reflected wave reflected from the surface and the reflected wave scattered and reflected by the millimeter-order defect portion inside the target surface layer. Further, by scanning along the target with the casing, two-dimensional image data of the target surface is formed over a wide range based on the intensity of the reflected wave and the distance information detected by the distance detecting means. Furthermore, the angle between the main axis of the transmitting antenna and the vertical axis perpendicular to the target is made different from the angle between the main axis of the receiving antenna and the vertical axis, so that the electromagnetic wave component reflected on the surface of the target is received by the receiving antenna. And the SN ratio of the electromagnetic wave component scattered and reflected by the defect portion of the target surface layer, which is a desired signal, is improved, and the detection accuracy of the defect portion is improved.

  In the present invention, the output signal from each of a plurality of detectors arranged in sequence is sequentially switched by a switch so that a plurality of parallel signals from each detector can be output at a single high speed. The target two-dimensional image data is generated in real time by scanning in one direction. In addition, a lock-in amplifier that is input with a single channel can construct a system that is easy to design and inexpensive.

  The casing of the mobile electromagnetic wave irradiation / detection device in the electromagnetic wave imaging system has a wheel provided so as to be in contact with the surface of the target, and at least the transmitting antenna and the receiving antenna are moved along the surface of the target by the wheel. It can be scanned.

  In the present invention, the wheels provided in contact with the surface of the target in the housing facilitate moving scanning along the surface of the target and improve the operability of the moving electromagnetic wave irradiation / detection device.

  According to the present invention, it is possible to perform non-destructive inspection in real time with high spatial resolution while expanding the application range for a target, such as cracks and peeling, occurring in the surface layer of a concrete structure such as a building or a tunnel. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present invention, the target refers to concrete used for structures such as buildings and tunnels, and the electromagnetic wave in the millimeter wave band (hereinafter referred to as millimeter wave) refers to an electromagnetic wave having a frequency of 30 GHz to 300 GHz. In addition, the medium refers to an intermediary that can transmit millimeter waves between the antenna and the target. Millimeter waves transmit not only air and other media that allow visible light to pass through, but also materials that do not transmit visible light, such as clothing worn by humans and wood used as housing construction materials. For example, when the frequency is 100 GHz, it passes through the concrete surface layer to a depth of about 10 mm.

  FIG. 1 is a diagram showing a schematic configuration of an electromagnetic wave imaging system according to the present embodiment. As shown in the figure, the electromagnetic wave imaging system 1 includes a mobile electromagnetic wave irradiation / detection device 2, a lock-in amplifier 3, and a control personal computer (hereinafter referred to as control PC 4).

  The mobile electromagnetic wave irradiation / detection device 2 irradiates the target with millimeter waves from the electromagnetic wave irradiation unit 5, and measures the response to the millimeter wave target with the electromagnetic wave detection unit 6. The measured detection signal is transmitted to the lock-in amplifier 3. On the other hand, the distance scanned by the wheeled casing 7 is detected by the distance sensor 8, and the detected distance information is transmitted to the control PC 4.

The lock-in amplifier 3 performs phase-sensitive detection on a detection signal input through a single channel, and outputs a millimeter wave reflection intensity. Single channel input type lock-in amplifiers are much easier to design and less expensive than realization of multi-channel input lock-in amplifiers.

  The control PC 4 generates target image data based on the intensity signal detected by the phase-sensitive detection by the lock-in amplifier 3 and the distance information detected by the distance sensor 8, and displays the image.

  Next, a specific configuration of the mobile electromagnetic wave irradiation / detection device will be described with reference to FIG. As shown in the figure, the mobile electromagnetic wave irradiation / detection device 2 includes an electromagnetic wave irradiation unit 5, an electromagnetic wave detection unit 6, and a distance sensor 8 in a housing 7 with wheels.

  The electromagnetic wave irradiation unit 5 includes an electromagnetic wave generator 9, a low frequency signal device 10, a modulator 11, and a transmission antenna 12.

  The electromagnetic wave generator 9 generates millimeter waves. Here, for example, a GNNN oscillator is used to generate a 94 to 120 GHz millimeter wave.

  The low-frequency signal device 10 outputs a frequency signal in a range in which the external lock-in amplifier 3 can detect the phase sensitivity. On the other hand, a frequency signal is output to the modulator 11. Here, for example, a synthesizer is used.

  The modulator 11 modulates the output signal of the electromagnetic wave generator 9 using the output signal of the low frequency signal device 10. Here, for example, a PIN switch is used.

  The transmitting antenna 12 radiates millimeter waves to the target concrete 16. Here, for example, a horn antenna is used to diffusely irradiate concrete with millimeter waves.

  The electromagnetic wave detection unit 6 includes a reception antenna 13, a detector 14, and a switch 15.

  The receiving antenna 13 receives the millimeter wave reflected by the concrete 16. Here, for example, a planar slot antenna is used.

  For example, 16 detectors 14 are arranged in a row, and convert the reflection intensity of millimeter waves received by the receiving antenna 13 into an electrical signal. Here, for example, the detector 14 uses a Schottky diode connected to the receiving antenna 13 to detect the reflection intensity of the millimeter wave.

  The switch 15 sequentially switches the output from each detector 14 and outputs it to the external lock-in amplifier 3. Here, an electronic circuit type PIN diode switch capable of switching speed of 400 microseconds or less is used as the switch 15. As a result, the parallel signals output from each of the 16 detectors 14 are output to the single-input lock-in amplifier 3 at high speed.

  The wheeled casing 7 scans the mobile electromagnetic wave irradiation / detection device 2 along the concrete 16. Here, a housing provided with wheels so as to be in contact with the surface of the concrete 16 is used to facilitate scanning of movement along the surface of the concrete 16. The size of the wheeled casing 7 is, for example, a handy type with a size of about several tens of centimeters, and the operator can operate with one hand.

  The distance sensor 8 detects the moving distance scanned by the wheeled casing 7 and transmits the distance information to the external control PC 4. Here, for example, the amount of movement of the wheel is detected by a rotary encoder provided on the rotation shaft of the wheel of the wheeled casing 7, distance information is calculated by a microcomputer inside the distance sensor 8, and transmitted to the control PC 4.

  Next, the characteristics of the millimeter wave reflected by the concrete will be described with reference to FIG. The figure shows the reflection characteristics of millimeter waves on the concrete surface and cracks. The beam pattern of the reflected wave from the surface of the concrete 16 is schematically shown by a solid line, and the beam pattern of the reflected wave from the crack 17 is schematically shown by a broken line.

As shown in the figure, when the surface of the concrete 16 is flat and smooth, the millimeter wave incident at an angle theta ₁ with respect to axis perpendicular K against the concrete 16, the incident side with respect to the vertical axis K Reflects on the opposite side of the surface. At this time, due to the law of incidence angle and reflection angle, the intensity of the millimeter wave that is surface-reflected at an angle θ ₁ with respect to the vertical axis K is maximized.

  On the other hand, when the millimeter wave is incident through the concrete surface layer having a depth of about 10 mm, the millimeter wave that has penetrated into the concrete 16 is scattered and reflected in various angular directions by the uneven structure of the millimeter-order crack. To do.

  Thereby, the millimeter wave reflected by the concrete is received by the receiving antenna 13, and the crack can be detected from the difference in reflection characteristics between the millimeter wave reflected by the concrete and the millimeter wave scattered and reflected by the crack inside the concrete surface layer. .

  Next, the configuration and installation method of the transmission antenna and the reception antenna will be described with reference to FIGS.

  FIG. 4 is a diagram schematically showing the configuration of the transmission antenna and the reception antenna. In the electromagnetic wave irradiation unit 5 and the electromagnetic wave detection unit 6, millimeter waves are transmitted and received by a bistatic electromagnetic wave transmission / reception system using different antennas. As shown in FIGS. The transmitting antenna 12 in the irradiating unit 5 uses a horn antenna whose main axis is represented by B1, and the receiving antenna 13 in the electromagnetic wave detecting unit 6 uses a planar slot antenna whose main axis is represented by B2.

FIG. 5 shows an installation example of the electromagnetic wave irradiation unit and the electromagnetic wave detection unit on the concrete. As shown in the figure, when the vertical axis K is perpendicular to the surface of the concrete 16, the angle θ ₁ formed by the main axis B 1 and the vertical axis K of the transmitting antenna 12 and the main axis B 2 and the vertical axis K of the receiving antenna 13 are formed. Install so that the angle θ ₂ is different. In the drawing, the angle θ ₂ formed by the main axis B 2 and the vertical axis K of the receiving antenna 13 is larger than θ ₁ by an angle φ.

  By installing the transmitting antenna 12 and the receiving antenna 13 in this manner, the direction of the receiving antenna 13 and the traveling direction of the millimeter wave component reflected on the surface of the concrete 16 are different, so that the millimeter wave component reflected on the surface is applied to the receiving antenna 13. It is suppressed from entering, the SN ratio of the millimeter wave component scattered and reflected by the crack 17 inside the concrete 16 surface layer, which is a desired signal, is improved, and the detection accuracy of the crack 17 is improved.

With this configuration, the millimeter wave generated by the electromagnetic wave generator 9 of the mobile electromagnetic wave irradiation / detection device 2 is applied to the concrete 16 through the opening on the bottom surface of the wheeled housing 7 and reflected by the concrete 16. The reflected waves are received by the plurality of receiving antennas 13 and detected by the detectors 14 corresponding to the respective receiving antennas 13. The detected reflection intensity is converted into a voltage value by the rectifying action of the diode, and the intensity is digitized by the lock-in amplifier 3 and displayed on the screen of the control PC 4. At this time, the crack 17 can be detected from the difference in reflection intensity between the reflected wave reflected by the concrete 16 and the reflected wave scattered and reflected by the millimeter-order crack 17 inside the concrete surface layer.

Furthermore, the output signals output in parallel from each of the detectors 14 arranged in a row are sequentially switched by the electronic circuit type changeover switch 15, so that a plurality of parallel signals from each detector are output at high speed. Thus, image data can be generated by scanning in one direction.

Thus, when the operator manually scans the wheeled casing 7 along the surface of the concrete, the movement distance information is transmitted to the control PC 4 by the distance sensor 8. On the other hand, the control PC 4 draws the intensity of the output signal from the switch 15 quantified by the lock-in amplifier 3 one after another in accordance with the moving distance, so that a two-dimensional image of the concrete 16 surface can be obtained over a wide range. It can be obtained in real time.

  Next, in order to demonstrate the effect of the present invention, an imaging experiment using an electromagnetic wave imaging system will be described with reference to FIGS.

  FIG. 6 is a plan view showing the outer wall of the concrete imaged by the electromagnetic wave imaging system. As shown in the drawing, a crack 17 having a width of 1 mm is generated on the surface layer of the concrete 16, and an opaque ABS resin plate 18 having a thickness of 5 mm is covered on the central portion of the concrete 16. Since the crack 17 is located under the ABS resin plate 18, it cannot be observed visually or with visible light from a CCD camera or the like.

  Here, the measurement conditions are: the medium is an ABS resin plate, the target is concrete, the center frequency of the electromagnetic wave generator is 100 GHz, the electromagnetic wave intensity is 40 mW, the interval between the planar slot antennas is every 5 mm, and 16 Schottky diodes are used as detectors. The sensitivity of the Schottky diode was set to 100 mV / mW.

  Under the conditions as described above, the mobile electromagnetic wave irradiation / detection device 2 was scanned along the surface of the ABS resin plate 18 to image the imaging region 19. As a result, a captured image as shown in FIG. 7 was obtained. The vertical axis indicates the direction in which the Schottky diodes are arranged, and the horizontal axis indicates the scanning direction. In the captured image, a white portion indicates that the reflection intensity is high, and a black portion indicates that the reflection intensity is low.

In the captured image, the reflection intensity of the millimeter wave reflected on the surface of the concrete 16 is large, and the reflection intensity of the millimeter wave scattered and reflected by the crack 17 generated on the concrete surface layer is a smaller value, and the difference between the two can be discriminated. .

  Thus, it can be seen that cracks in the concrete surface layer as the target can be clearly detected through the ABS resin as the medium.

  From the above, it has been shown that in an electromagnetic wave imaging system, the medium can be seen through with millimeter waves and applied to the detection of concealed dangerous objects and the nondestructive inspection of the target inside the medium.

  Also, since the wavelength of millimeter waves is much smaller than that of X-rays, for example, when the concrete surface is covered with a medium such as wallpaper cloth or paint, there is a risk of ionizing and damaging the medium. Absent.

  Therefore, according to the present embodiment, the millimeter wave radiated from the transmission antenna 12 is reflected by the target after passing through the medium, and the intensity of the reflected wave detected by the reception antenna 13 and the detector 14 is determined by lock-in. By digitizing with the amplifier 3, the crack 17 can be detected from the difference in reflection intensity between the reflected wave reflected from the concrete 16 and the reflected wave scattered by the millimeter-order crack 17 inside the concrete 16 surface layer. Furthermore, by scanning along the surface of the concrete 16 with the wheeled casing 7, it is possible to form two-dimensional image data of the surface of the concrete 16 over a wide range based on the distance information detected by the distance sensor 8. It becomes.

Further, the output signals output in parallel from each of the detectors 14 arranged in a row are sequentially switched by the electronic circuit type changeover switch 15, so that a plurality of parallel signals from each detector can be obtained. Output processing is performed at high speed, and image data can be generated by scanning in one direction. Thereby, the intensity of the output signal from the switch 15 quantified by the lock-in amplifier 3 is drawn one after another according to the moving distance, whereby a two-dimensional image of the concrete 16 surface can be obtained in real time.

Further, the transmitting antenna 12 and the receiving antenna 13 are installed so that the angle θ ₁ formed by the main axis B 1 and the vertical axis K of the transmitting antenna 12 is different from the angle θ ₂ formed by the main axis B 2 and the vertical axis K of the receiving antenna 13. Therefore, the millimeter wave component reflected on the surface by the target is prevented from entering the receiving antenna, the SN ratio of the millimeter wave component scattered and reflected by the crack 17 on the surface layer of the concrete 16 as the desired signal is improved, and the detection accuracy of the crack 17 is improved. Will improve.

  Therefore, according to the present embodiment, it is possible to perform non-destructive inspection in real time with high spatial resolution while expanding the application range for the target with respect to the deterioration state such as cracks and peeling occurring in the surface layer of the concrete structure. .

  In addition, in the electromagnetic wave imaging system 1, the lock-in amplifier 3 uses a single-channel input type lock-in amplifier that detects a phase-sensitive signal input through a single channel, thereby making the design easy and inexpensive. Can be built.

  Further, in the mobile electromagnetic wave irradiation / detection device 2, by using the wheeled casing 7 provided with wheels so as to be in contact with the surface of the target, moving scanning along the surface of the target is facilitated, and operability is improved. improves.

[Other forms]
In this embodiment, the antenna in the mobile electromagnetic wave irradiation / detection device transmits and receives electromagnetic waves by a bistatic electromagnetic wave transmission / reception method using different transmission antennas and reception antennas. The angle formed between the vertical axis and the vertical axis is different from the angle formed between the main axis of the receiving antenna and the vertical axis perpendicular to the target. However, the present invention is not limited to this. For example, electromagnetic waves may be transmitted and received by a monostatic electromagnetic wave transmission / reception system using transmission / reception antennas having the same main axes of the transmission antenna and the reception antenna.

  In such a case, the main axis of the transmitting / receiving antenna having the same main axis is not parallel to the vertical axis perpendicular to the target, so that the electromagnetic wave component reflected on the surface from the target is prevented from entering the receiving antenna. The SN ratio of the electromagnetic wave component scattered and reflected by the defect portion inside the target surface layer, which is a desired signal, is improved, and the detection accuracy of the defect portion is improved.

  In the present embodiment, 16 detectors 14 are arranged in a line, and a parallel signal output from each of the detectors 14 is output to the lock-in amplifier 3 by an electronic circuit type PIN diode switch. However, the present invention is not limited to this. For example, 100 detectors 14 may be arranged in parallel and output to the lock-in amplifier 3 by a PIN diode switch.

  In this configuration, in addition to the effects of the present embodiment, the PIN diode switch can be switched at a speed of 400 microseconds or less, so that the outputs of all the detectors 14 can be measured in a time of about 40 milliseconds. And the resolution of the image data is improved.

  In the present embodiment, the mobile electromagnetic wave irradiation / detection device is scanned along the surface of the target by the wheeled casing. However, the present invention is not limited to this. As long as at least the transmission antenna and the reception antenna are scanned, the same effects as those of the present embodiment can be obtained.

  In the present embodiment, the size of the housing with wheels of the mobile electromagnetic wave irradiation / detection device is a handy type with a size of about several tens of centimeters, so that the operator can operate with one hand. However, this is not a limitation.

  For example, by enlarging the size of the chassis with wheels and incorporating a lock-in amplifier or control PC inside the chassis, the operator can use the mobile electromagnetic wave irradiation / detection device, and in an environment where the inspection area is wide The system configuration may be such that the operator performs an inspection while driving the riding type mobile electromagnetic wave irradiation / detection device on the target. In this case, convenience is improved in addition to the same effects as the present embodiment.

  In the present embodiment, the distance sensor that detects the distance information scanned by the wheeled casing is provided on the rotating shaft of the wheel of the wheeled casing so as to detect the movement amount of the wheel by the rotary encoder. However, the present invention is not limited to this. For example, a light emitter and a light receiver are provided on the bottom surface of the housing, and a dedicated pad that easily reflects light is disposed on the target, and light from the light emitter is placed on the pad. The amount of movement may be optically detected from the intensity of the reflected light reflected and received by the light receiver. Thereby, in addition to the effect equivalent to this embodiment, the measurement accuracy of the distance information by the distance sensor is improved. Further, when the S / N ratio of the desired target signal is good, the lock-in amplifier is not necessary.

  In addition, the mobile electromagnetic wave irradiation / detection device may be provided with a cleaner function that can remove dust, dust, moisture, and the like on the concrete surface as a target before measurement. As a result, in addition to the same effects as in the present embodiment, dust that affects reflected waves from fine defect portions such as cracks, moisture that affects the attenuation of reflected waves, and the like can be removed, which is a desired signal. The SN ratio of the reflected wave can be improved.

It is a figure which shows the schematic structure of the electromagnetic wave imaging system which concerns on this Embodiment. It is the schematic which shows the structure of the mobile electromagnetic wave irradiation and detection apparatus in the electromagnetic wave imaging system of FIG. It is the figure which showed the reflective characteristic of the millimeter wave in a concrete surface and a crack. FIG. 3 is a diagram illustrating a schematic configuration of a transmission antenna and a reception antenna in the mobile electromagnetic wave irradiation / detection device of FIG. 2. The example of installation with respect to the idiom REIT of the electromagnetic wave irradiation part and the electromagnetic wave detection part in the mobile electromagnetic wave irradiation / detection apparatus of FIG. 2 is shown. It is a top view which shows the outer wall of the concrete imaged with the electromagnetic wave imaging system. It is an imaging result by the electromagnetic wave imaging system of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electromagnetic wave imaging system 2 ... Mobile electromagnetic wave irradiation and detection apparatus 3 ... Lock-in amplifier 4 ... Control PC
DESCRIPTION OF SYMBOLS 5 ... Electromagnetic irradiation part 6 ... Electromagnetic wave detection part 7 ... Case 8 with a wheel ... Distance sensor 9 ... Electromagnetic wave generator 10 ... Low frequency signal device 11 ... Modulator 12 ... Transmission antenna 13 ... Reception antenna 14 ... Detector 15 ... Switch 16 ... Concrete 17 ... Crack 18 ... ABS resin cover 19 ... Imaging area

Claims (2)

An electromagnetic wave generating means for generating an electromagnetic wave in the millimeter wave band, a transmitting antenna for radiating the electromagnetic wave to the target, a receiving antenna for receiving the electromagnetic wave reflected by the target, and the reflection intensity of the electromagnetic wave received by the receiving antenna are electrically Mobile electromagnetic wave irradiation comprising: a detector for converting into a signal; a housing capable of scanning at least the transmitting antenna and the receiving antenna along the target; and distance detecting means for detecting a distance scanned by the housing. A detection device;
A lock-in amplifier to which the output from the detector is input;
Image data generation means for generating image data based on the output signal of the lock-in amplifier and the distance information detected by the distance detection means,
The transmitting antenna is arranged such that a main axis of the antenna is inclined with respect to a vertical axis perpendicular to a target surface at an incident point of an electromagnetic wave emitted to the target,
The receiving antenna is disposed so as to receive an electromagnetic wave reflected from the transmitting antenna across the vertical axis and facing the transmitting antenna.
The angle formed between the main axis of the transmitting antenna and the vertical axis is different from the angle formed between the main axis of the receiving antenna and the vertical axis.
A plurality of the receiving antennas are arranged,
The detector is connected to each of the plurality of receiving antennas and arranged in a plurality, and further includes a switch that sequentially switches and outputs an output signal from each detector,
The electromagnetic wave imaging system, wherein the lock-in amplifier is a single channel input type that detects a phase-sensitive detection of an input signal, and an output from the switch is input as a single channel.   The housing includes a wheel provided so as to be in contact with the surface of the target, and at least the transmitting antenna and the receiving antenna can be scanned along the surface of the target by the wheel. The electromagnetic wave imaging system according to claim 1.