JP2013167529A - Wave imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a subject image to be imaged by a single reception element unit without use of a two-dimensional sensor or a line sensor for receiving a thermal noise in a wave imaging device imaging a subject by receiving the thermal noise of a microwave band radiated from the subject such as a human body.SOLUTION: By rotating two reflecting plates 14 and 18 arranged on both sides of a lens 16 in a vertical scanning direction of a subject 2 and in a horizontal scanning direction thereof respectively, a millimeter wave constituting an image of a subject 2 to be imaged by the lens 16 is input to a millimeter wave sensor 20 for each pixel. By taking a signal level of the millimeter wave of each pixel sequentially, image data is generated. Further, the reflecting plate 14 is oscillated within a range of a predetermined angle to thereby perform a vertical scanning, and the reflecting plate 18 is continuously rotated to perform a horizontal scanning such that the reflecting plate 18 is rotated a 180-degree for each predetermined angle of the vertical scanning.

Description

  The present invention relates to a radio wave imaging apparatus that captures an image of a subject by receiving thermal noise in a microwave band radiated from the subject.

  Conventionally, a subject is imaged by receiving thermal noise in a microwave band (0.3 GHz to 3 THz) radiated from a subject such as a human body (preferably, thermal noise in a millimeter wave band (30 GHz to 0.3 THz)). In addition, it has been proposed to detect weapons, smuggled goods, and the like hidden in the subject from the captured image (see, for example, Patent Documents 1 and 2).

  Also, in this type of radio wave imaging apparatus, the thermal noise radiated from the subject is collected via the radio wave lens to form a subject image at a predetermined imaging position, and the signal of each part of the subject image The level is received by a receiving element such as a millimeter wave sensor.

  Since the receiving element needs to be able to detect the reception level of radio waves with extremely high frequencies such as millimeter waves with high accuracy, the receiving element receives the received signal in addition to the receiving unit (antenna etc.). It is necessary to provide a low noise amplifier to amplify, and the gains of the receiving unit and the low noise amplifier need to be constant.

  For this reason, in this type of radio wave imaging apparatus, a receiving element for receiving thermal noise is extremely expensive. Therefore, a two-dimensional sensor in which a receiving element is arranged two-dimensionally cannot be used for imaging a subject. A line sensor in which receiving elements are arranged in one direction is used as an imaging element.

  That is, conventionally, by providing a reflecting plate that reflects thermal noise in the microwave band at the imaging position of the subject image by the radio wave lens, by rotating the reflecting plate around the central axis within a predetermined angular range, While scanning the subject in one direction, thermal noise for one line at each scanning position is sequentially input to the line sensor.

JP 2008-241352 A JP 2010-281737 A

  By the way, when a subject is imaged using a line sensor as in the prior art, the cost of the radio wave imaging device can be reduced compared to the case where a two-dimensional sensor is used. Since the receiving elements are arranged in one direction, there is a problem that a subject image cannot be satisfactorily picked up if there are variations in characteristics of the receiving elements.

  In order to reduce such variations in characteristics, it is sufficient to review the manufacturing process and inspection / adjustment process of the receiving element and use only the receiving element that provides the desired characteristics. There is a problem that the cost of the sensor is increased and the radio wave imaging device cannot be mass-produced.

  The present invention has been made in view of these problems, and a receiving element that receives thermal noise in a radio wave imaging device that images a subject by receiving thermal noise in a microwave band radiated from the subject such as a human body. An object of the present invention is to make it possible to capture a subject image with a single receiving element without using a two-dimensional sensor or line sensor that uses a large number of sensors.

The radio wave imaging device according to claim 1, which has been made to achieve such an object,
A radio wave lens that forms a subject image by transmitting the thermal noise of the microwave band emitted from the subject; and
A first reflector that reflects the thermal noise of the microwave band emitted from the subject toward the radio lens;
By rotating the first reflecting plate around a first rotation axis that penetrates the first reflecting plate in the direction of the plate surface, the center position of the subject image formed by the radio wave lens is first scanned by the subject. First scanning means for changing the direction,
A second reflector that is disposed at a position where an object image is formed by the radio wave lens and reflects thermal noise of a microwave band transmitted through the radio wave lens in a direction different from that of the radio wave lens;
Receiving means arranged in the direction of reflection of the thermal noise by the second reflector and receiving thermal noise reflected from the second reflector;
The center position of the subject image reflected from the second reflecting plate toward the receiving means by rotating the second reflecting plate around a second rotation axis that penetrates the second reflecting plate in the plate surface direction. A second scanning unit that changes a second scanning direction perpendicular to the first scanning direction in the subject;
Image data generating means for generating image data of the subject from a reception level of thermal noise by the receiving means;
One of the first scanning means and the second scanning means includes a first reflector or a second reflector arranged around the first rotational axis or the second rotational axis. The other scanning means continuously rotates the first reflecting plate or the second reflecting plate around the first rotating shaft or the second rotating shaft. It was configured as described above.

  According to the radio wave imaging apparatus of the present invention, the first reflector and the second reflector are provided with the radio wave lens interposed therebetween, and the thermal noise of the microwave band radiated from the subject is received through these parts. Lead to.

  The first reflecting plate is rotated around the first rotation axis penetrating the first reflecting plate in the plate surface direction by the first scanning means, and the subject image formed by the radio wave lens by this rotation. Of the subject changes in the first scanning direction of the subject.

  Further, the second reflecting plate is rotated around the second rotation axis penetrating the second reflecting plate in the plate surface direction by the second scanning unit, and by this rotation, the second reflecting plate is directed to the receiving unit. The center position of the reflected subject image changes in the second scanning direction perpendicular to the first scanning direction in the subject.

  Therefore, the receiving means scans the subject in the first scanning direction and the second scanning direction by rotating the first reflecting plate and the second reflecting plate by the first scanning means and the second scanning means. The thermal noise of each part of the subject is sequentially input.

  Therefore, the image data generation means generates image data corresponding to the two-dimensional image of the subject by taking in the reception level of the thermal noise by the reception means in accordance with the operations of the first scanning means and the second scanning means. Can do.

  In the present invention, one of the first scanning unit and the second scanning unit includes a first rotation plate or a second rotation plate that has a predetermined rotation angle around the first rotation axis or the second rotation axis. The other scanning unit is configured to continuously rotate the first reflecting plate or the second reflecting plate around the first rotating shaft or the second rotating shaft. .

  This is because, as in the present invention, when a two-dimensional image is captured by scanning the first reflector and the second reflector in directions orthogonal to each other, one reflector (for example, the first reflector) is predetermined. The other reflecting plate (for example, the second reflecting plate) needs to be rotated by one scanning while the scanning amount (angle) is rotated, and one scanning time of the other reflecting plate needs to be shortened. Because.

  That is, when the subject is scanned by rotating the reflecting plate, the reflecting plate is usually rotated around the rotation axis by a predetermined rotation angle as described in Patent Document 2. However, in order to take an image by rotating the two reflecting plates in this manner, it is necessary to rotate one of the reflecting plates at an extremely high speed, which is difficult to realize.

  In order to increase the scanning speed by the reflecting plate, it is conceivable to use a polygon mirror as described in Japanese Patent Application Laid-Open No. H11-228707. However, the polygon mirror has a difference in optical path length because the reflecting surface and the rotation axis do not coincide with each other, and image processing for correcting the difference in optical path length is necessary, or a clear captured image cannot be obtained. Problems arise.

  Therefore, in the present invention, by continuously rotating the reflecting plate that requires high-speed scanning, the subject can be scanned without switching the rotation direction as in the case of rotating the reflecting plate within a predetermined angle range, The time required for one scan of the reflection plate is shortened by making the front and back surfaces of the reflection plate available for the scanning.

  For this reason, according to the present invention, it is possible to prevent the imaging time of the subject from becoming long although the subject is scanned in the two-dimensional direction using the two reflectors. A subject image can be captured well.

It is a schematic structure figure showing the composition of the whole radio wave imaging device of an embodiment. It is a side view showing the internal structure of the imaging device main body shown in FIG. It is a perspective view explaining the arrangement | positioning state of the lens and a pair of reflecting plate which are provided in an imaging device main body. It is a flowchart showing the imaging process implemented in a control circuit.

Embodiments of the present invention will be described below with reference to the drawings.
The radio wave imaging apparatus of the present embodiment is used to check whether a passenger does not conceal a dangerous object at an airport or the like, and is configured as shown in FIG.

  That is, the radio wave imaging apparatus according to the present embodiment includes an imaging apparatus main body 10 that captures an image of the subject 2 by receiving millimeter-wave band thermal noise emitted from the subject 2 with a passenger located in the examination target area as the subject 2. The shielding plate 4 is provided on the opposite side of the imaging apparatus main body 10 with the inspection target region interposed therebetween.

The shielding plate 4 is for blocking unnecessary thermal noise that enters from the rear of the subject 2 when viewed from the imaging device main body 10 and is made of a metal plate.
2 and 3, the imaging apparatus main body 10 takes in millimeter-wave band thermal noise radiated from the subject 2 into the interior via the radio wave transmission unit 12, and reflects the reflection plate 14, the lens 16, It is configured to be guided to the millimeter wave sensor 20 through the reflection plate 18.

  Here, the lens 16 is disposed in the imaging apparatus main body 10 so that the central axis is in the vertical direction, and the reflecting plate 14 and the reflecting plate 18 are disposed above and below the lens 16 with the lens 16 in between. Yes.

The reflection plate 14 is for reflecting the thermal noise in the millimeter wave band radiated from the subject and entering the imaging apparatus main body 10 via the radio wave transmission unit 12 toward the lens 16.
From left and right side edges of the reflection plate 14, a support shaft 22 that supports the reflection plate 14 is provided so as to be rotatable around a horizontal rotation axis along the plate surface of the reflection plate 14. .

The support shaft 22 is rotatably fixed to the inner wall of the case of the imaging apparatus main body 10.
Further, the upper end portion of the back surface of the reflecting plate 14 (the surface opposite to the radio wave transmitting portion 12) is connected to a disk 26 provided on the rotating shaft 25 of the motor 24 via a link 28.

This is because the reflecting plate 14 is rotated around the rotation axis formed by the support shaft 22 within a predetermined angle range by the rotation of the motor 24 (and thus the disk 26).
The case of the imaging apparatus main body 10 is formed in a rectangular box shape with a metal material that can shield radio waves except for the radio wave transmission part 12, and the millimeter wave incident on the inside is formed on the inner wall surface of the case. Is provided with a radio wave absorber so that it is not reflected and diffused by the inner wall surface of the case.

Next, the lens 16 transmits the thermal noise of the millimeter wave body that has entered through the reflecting plate 14, thereby forming an image of the subject 2 at the position where the lower reflecting plate 18 is disposed.
The reflecting plate 18 is for reflecting the thermal noise transmitted through the lens 16 in the vertical direction at the imaging position of the subject image by the lens 16 toward the millimeter wave sensor 20 in the horizontal direction.

  In order to support the reflecting plate 18 from the upper and lower edges of the reflecting plate 18 so as to be rotatable about a central axis inclined approximately 45 degrees with respect to the vertical and horizontal directions along the plate surface of the reflecting plate 18. The support shaft 32 is projected.

  Of the support shafts 32, the support shaft 32 on the upper end edge side of the reflector 18 is rotatably supported by a support member 35 fixed to the imaging apparatus body 10, and the support shaft 32 on the lower end edge side of the reflector 18. Are coupled to the rotating shaft of a motor 34 fixed to the imaging apparatus main body 10.

As a result, the reflector 18 rotates around the rotation axis formed by the support shaft 32 by the rotation of the motor 34.
Note that both surfaces of the reflecting plate 18 are mirror-finished so that radio waves can be reflected, and only one side of the reflecting plate 14 facing the radio wave transmitting portion 12 is mirror-finished so that radio waves can be reflected. .

  An encoder 30 for detecting the rotational position of the reflecting plates 14 and 18 is provided on the supporting shaft 22 for rotatably supporting the reflecting plate 14 and the supporting shaft 32 for rotatably supporting the reflecting plate 18, respectively. , 36 are provided.

Next, the millimeter wave sensor 20 includes one antenna element that can receive millimeter-wave band thermal noise and a low-noise amplifier that amplifies a millimeter-wave band reception signal from the antenna element.
The received signal from the millimeter wave sensor 20 is input to the processing circuit 38 and detected and A / D converted in the processing circuit 38 to be converted into digital data representing the signal level of the received signal.

  The digital data generated by the processing circuit 38 is input to a control circuit 40 composed of a microcomputer mainly composed of a CPU, ROM, RAM and the like. The control circuit 40 is connected to drive circuits 42 and 44 for driving the motors 24 and 34, respectively.

  Then, the control circuit 40 rotates the motors 24 and 34 via the drive circuits 42 and 44, so that the generation position of the thermal noise incident on the millimeter wave sensor 20 is set in the vertical direction and the horizontal direction. Change to the scanned position.

  Further, the control circuit 40 takes in the digital data representing the received signal level from the processing circuit 38 in accordance with the change in the scanning position, thereby generating the millimeter wave image data of the subject 2, and the generated millimeter wave image data is By outputting to the external display device 46, the millimeter wave image of the subject 2 is displayed on the display device 46.

Hereinafter, the imaging process executed by the control circuit 40 will be described with reference to the flowchart shown in FIG.
This imaging process is a process repeatedly executed in the control circuit 40 when the operation mode of the control circuit 40 is set to the imaging mode of the image.

  As shown in FIG. 4, when the imaging process is started, first, in S110 (S represents a step), the motors 24 and 34 are driven via the drive circuits 42 and 44, whereby the reflectors 14 and 18 are driven. Are initialized at predetermined origin positions detected by the encoders 30 and 36, respectively.

  Next, in S120, the detection voltage or A / D in the processing circuit 38 is set so that the output of the millimeter wave sensor 20 (specifically, the digital data input from the processing circuit 38 becomes a predetermined value (for example, a value corresponding to 0V)). A calibration process for correcting the reference voltage and the like of the conversion circuit is executed.

  In subsequent S130, by driving the motor 24, the rotation position of the reflection plate 14 is set to the vertical scanning start position, and the reflection plate 18 is continuously rotated at a constant speed by the motor 34. An imaging process for capturing digital data from the processing circuit 38 is started.

  When the imaging process is started in this manner, first, in S140, the input data from the processing circuit 38 is sampled a predetermined number of times per horizontal scanning in which the reflector 18 rotates 180 degrees. Thus, the millimeter wave reception signal is read for one scanning of the reflection plate 18.

  In subsequent S150, it is determined whether or not the sampling process of the millimeter wave reception signal in S140 has been executed for the entire vertical scanning range by the reflector 14, and thus whether the reception signal reading for the entire scanning range has been completed. Judge whether or not.

  If it is determined in S150 that reading of the received signals for the entire scanning range has not been completed, the process proceeds to S160, and the reflector 24 is rotated by a predetermined angle by driving the motor 24. The vertical scanning position by the reflecting plate 14 is changed to the next scanning position, and the process proceeds to S140.

  On the other hand, when it is determined in S150 that reading of the received signals for the entire scanning range is completed, the process proceeds to S170, and the subject is based on the received level (digital data) of the received signals for the entire scanned range. Two screens of image data (two-dimensional image data) are generated.

  In S170, the generated image data for one screen is output to the external display device 46 to display the captured image of the subject 2 on the display device 46, and the image data is stored in an external storage device (hard disk). Etc .; not shown) and the imaging process is terminated once.

  As a result, the user of the radio wave imaging apparatus of the present embodiment can detect that there is a person who will be the subject 2 in the inspection target area by looking at the captured image displayed on the display device 46, or from the display image. It is possible to detect a weapon that is hidden by the person who is the subject 2.

  As described above, according to the radio wave imaging apparatus of the present embodiment, the two reflectors 14 and 18 are rotated in the vertical scanning direction and the horizontal scanning direction of the subject 2 to form an image with the lens 16. The millimeter wave constituting the image of the subject 2 is input to the millimeter wave sensor 20 for each pixel, and image data is generated by sequentially taking in the millimeter wave signal level of each pixel from the millimeter wave sensor 20.

  For this reason, the object 2 can be obtained by using a single millimeter wave sensor without using a two-dimensional image sensor in which millimeter wave sensors are two-dimensionally arranged or a line sensor in which millimeter wave sensors are arranged in a row. Imaged image data can be obtained, and the apparatus configuration can be simplified.

In addition, since the radio wave imaging apparatus can be configured with only one millimeter wave sensor, clear image data can be generated without being affected by variations in the millimeter wave sensor.
In particular, in this embodiment, the reflector 14 is swung within a predetermined angle range to perform vertical scanning, and the reflector 18 is rotated 180 degrees for each predetermined angle of the vertical scanning. Horizontal scanning is performed by continuously rotating 18.

  For this reason, the scanning time per horizontal scanning can be shortened compared with the case where the reflecting plate 18 is rotated within a predetermined angle range to perform horizontal scanning, and the subject 2 can be imaged. It can be done faster.

  In this embodiment, the lens 16 corresponds to the radio wave lens of the present invention, the reflector 14 corresponds to the first reflector of the present invention, and the reflector 18 corresponds to the second reflector of the present invention. The millimeter wave sensor 20 corresponds to the receiving means of the present invention.

  In the present embodiment, the control circuit 40 realizes the functions of the first scanning unit, the second scanning unit, and the image data generation unit of the present invention. Specifically, among the imaging processes executed by the control circuit 40, the S130 and S160n processes, the motor 24, the encoder 30, and the drive circuit 42 correspond to the first scanning means of the present invention. The motor 34, the encoder 36, and the drive circuit 44 correspond to the second scanning unit of the present invention, and the processing of S150 and S170 corresponds to the image data generation unit of the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the above embodiment, the reflector 14 is rotated in a predetermined angle range to perform vertical scanning, and the reflector 18 is rotated 180 degrees and horizontally scanned at every predetermined scanning angle of the vertical scanning. As described above, it has been described that the subject 2 is imaged by continuously rotating the reflecting plate 18.

  However, on the contrary, the reflecting plate 18 is rotated within a predetermined angle range to perform horizontal scanning, and the reflecting plate 14 is rotated 180 degrees and vertically scanned at every predetermined scanning angle of the horizontal scanning. As described above, the subject 2 can be imaged even when the reflecting plate 14 is continuously rotated.

  In the above embodiment, the motor 24 connected to the reflecting plate 14 via the link 28 and the circular plate 26 is used to rotate the reflecting plate 14 at a predetermined angle, but the motor 24 is used instead. A solenoid capable of adjusting the protruding length of the rod may be used.

  In the above embodiment, it has been described that the subject 2 is imaged by receiving the thermal noise in the millimeter wave band radiated from the subject 2, but the thermal noise composed of microwaves other than the millimeter wave band is received. Even so, the subject 2 can be imaged.

  DESCRIPTION OF SYMBOLS 2 ... Subject, 4 ... Shielding board, 10 ... Imaging device main body, 12 ... Radio wave transmission part, 14 ... Reflecting plate, 16 ... Lens, 18 ... Reflecting plate, 20 ... Millimeter wave sensor, 22 ... Support shaft, 24 ... Motor, 25 ... Rotating shaft, 26 ... Disc, 28 ... Link, 30 ... Encoder, 32 ... Support shaft, 34 ... Motor, 35 ... Support member, 36 ... Encoder, 38 ... Processing circuit, 40 ... Control circuit, 42, 44 ... Drive circuit, 46... Display device.

Claims (1)

A radio wave lens that forms a subject image by transmitting the thermal noise of the microwave band emitted from the subject; and
A first reflector that reflects the thermal noise of the microwave band emitted from the subject toward the radio lens;
By rotating the first reflecting plate around a first rotation axis that penetrates the first reflecting plate in the direction of the plate surface, the center position of the subject image formed by the radio wave lens is first scanned by the subject. First scanning means for changing the direction,
A second reflector that is disposed at a position where an object image is formed by the radio wave lens and reflects thermal noise of a microwave band transmitted through the radio wave lens in a direction different from that of the radio wave lens;
Receiving means arranged in the direction of reflection of the thermal noise by the second reflector and receiving thermal noise reflected from the second reflector;
The center position of the subject image reflected from the second reflecting plate toward the receiving means by rotating the second reflecting plate around a second rotation axis that penetrates the second reflecting plate in the plate surface direction. A second scanning unit that changes a second scanning direction perpendicular to the first scanning direction in the subject;
Image data generating means for generating image data of the subject from a reception level of thermal noise by the receiving means;
One of the first scanning means and the second scanning means includes a first reflector or a second reflector arranged around the first rotational axis or the second rotational axis. The other scanning means continuously rotates the first reflecting plate or the second reflecting plate around the first rotating shaft or the second rotating shaft. A radio wave imaging device configured as described above.

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