Object perspective device and object perspective method

Abstract

An object perspective device (100) is provided with: a transmission unit (101) that transmits, to a target object (T), a transmission radio wave obtained by repeatedly performing a frequency scan in which the frequency is changed from a first frequency to a second frequency at a frequency scan time; a reception unit (102) for receiving, using the array antenna element, a received radio wave in which the transmission radio wave is reflected by the target object (T); a three-dimensional image generation unit (8) that generates a three-dimensional image on the basis of a reception signal of the array antenna element by each frequency scan; and an object detection unit (9) that detects an object on the basis of the plurality of three-dimensional images, the object perspective device changing at least one of the first frequency, the second frequency, the frequency scanning time, and the number of array antenna elements used in the detection of the object in a time division manner.

Description

Technical Field

[0001] The present invention relates to an object perspective device and an object perspective method for perspective seeing objects using radio waves. Background Art

[0002] In foreign matter detection during food inspections, security gates at airports, and the like, devices that see through objects are used to detect foreign matter and dangerous objects. Conventional object see-through devices generally use X-rays. Object see-through devices that use X-rays have the problem of X-ray radiation, and their use is limited. As a method without radiation problems, object see-through devices that use nuclear magnetic resonance have been put into practical use for medical purposes. However, object see-through devices that use nuclear magnetic resonance require a strong magnetic field, and the device is large. If magnetic bodies such as iron are present, a large force is required. Therefore, in object see-through devices that use nuclear magnetic resonance, a larger space is required to set up the device. In addition, the entry and exit of people and objects relative to the place where the device is set up must be managed, and there are large restrictions on the place where the device is set up, so its use is limited.

[0003] In contrast, if it is an object perspective device that uses radio waves, there is no radiation problem, and there are fewer restrictions on the location of the device. When using radio waves, the limit of resolution is limited by the wavelength of the radio waves used. Therefore, in the past, the resolution of the object perspective image using radio waves was low, and it was difficult to identify the object. However, with the advancement of equipment technology in recent years, radio waves above 100 GHz can be used, and it is expected that the resolution will be improved. For example, Patent Document 1 discloses a device that uses microwaves to inspect defects inside tires.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-77192 Summary of the invention

[0007] Problems to be solved by the invention

[0008] However, according to the above-mentioned prior art, there is a problem that the detection accuracy is reduced when the detection object moves.

[0009] The present disclosure has been made in view of the above-mentioned circumstances, and an object thereof is to obtain an object see-through device capable of suppressing a decrease in detection accuracy even when a detection object moves.

[0010] Means for solving problems

[0011] In order to solve the above-mentioned problems and achieve the purpose, the object perspective device disclosed in the present invention is characterized in that it comprises: a transmitting unit, which transmits a transmission wave to the target object, and the transmission wave is obtained by repeatedly performing a frequency scan in which the frequency changes from a first frequency to a second frequency at a frequency scanning time; a receiving unit, which uses an array antenna element to receive a reception wave obtained by the transmission wave being reflected by the target object; a three-dimensional image generating unit, which generates a three-dimensional image according to the reception signal of the array antenna element at each frequency scan; and an object detecting unit, which detects the object based on a plurality of three-dimensional images, and the object perspective device changes at least one of the first frequency, the second frequency, the frequency scanning time, and the number of array antenna elements used in the detection of the object in a time-division manner.

[0012] Effects of the Invention

[0013] The object see-through device of the present disclosure has an effect of being able to suppress a decrease in detection accuracy even when the detection target moves. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram showing the structure of the object perspective device according to the first embodiment.

[0015] Figure 2 This is a diagram showing a first example of the waveform of the transmitted radio wave.

[0016] Figure 3 This is a diagram showing a second example of the waveform of the transmitted radio wave.

[0017] Figure 4 Yes means Figure 1 Diagram of the structure of the transmitter shown.

[0018] Figure 5 Yes means Figure 1 Figure 2 shows the structure of a receiver.

[0019] Figure 6 Yes means Figure 1 The diagram shows the structure of the analog parallel-serial conversion section. DETAILED DESCRIPTION

[0020] Hereinafter, an object perspective device and an object perspective method according to an embodiment of the present disclosure will be described in detail based on the drawings.

[0021] Implementation method 1.

[0022] Figure 1 1 is a diagram showing the structure of an object perspective device 100 according to Embodiment 1. The object perspective device 100 has a function of perspective objects using radio waves. The object perspective device 100 is used, for example, to detect dangerous objects such as weapons at airports or to detect foreign objects mixed in products at production sites.

[0023] The object perspective device 100 includes a transmitter 1, a transmitting antenna 2, a receiving antenna 3, a receiver 4, an analog parallel-serial conversion unit 5, an analog-to-digital converter 7, a three-dimensional image generation unit 8, an object detection unit 9, and an oscillator 10. The transmitter 1 and the transmitting antenna 2 are collectively referred to as the transmitting unit 101. The receiving antenna 3, the receiver 4, the analog parallel-serial conversion unit 5, and the analog-to-digital converter 7 are collectively referred to as the receiving unit 102.

[0024] The transmitter 1 generates a transmitted radio wave W1 to be sent to the target object T, and transmits the generated transmitted radio wave W1 using the transmitting antenna 2. Here, the waveform of the transmitted radio wave W1 will be described. The transmitter 1 generates a transmitted radio wave W1 having a waveform in which a frequency sweep is repeatedly performed, changing the frequency from a first frequency to a second frequency. Here, the time length taken for the frequency to change from the first frequency to the second frequency is referred to as the frequency sweep time. The transmitter 1 can change at least one of the first frequency, the second frequency, and the frequency sweep time, which are parameters of the frequency sweep, in a time-division manner.

[0025] Figure 2 is a diagram showing a first example of the waveform of the transmitted radio wave W1. In Figure 2 In the first example shown, the first frequency is 270 GHz and the second frequency is 290 GHz. The values of the first frequency and the second frequency are fixed, while the frequency sweep time is changed for each frequency sweep. In the first frequency sweep, the frequency sweep time is 10 μsec, in the second frequency sweep, the frequency sweep time is 20 μsec, in the third frequency sweep, the frequency sweep time is 40 μsec, in the fourth frequency sweep, the frequency sweep time is 80 μsec. Additionally, in the fifth frequency sweep, the frequency sweep time is 10 μsec, in the sixth frequency sweep, the frequency sweep time is 20 μsec, in the seventh frequency sweep, the frequency sweep time is 40 μsec, and in the eighth frequency sweep, the frequency sweep time is 80 μsec.

[0026] Figure 3 is a diagram showing a second example of the waveform of the transmitted radio wave W1. In Figure 3In the second example shown, the frequency sweep time is a constant value of 10 μsec. In contrast, the first frequency and the second frequency change with each frequency sweep. In the first frequency sweep, the first frequency is 278 GHz and the second frequency is 282 GHz. In the second frequency sweep, the first frequency is 276 GHz and the second frequency is 284 GHz. In the third frequency sweep, the first frequency is 274 GHz and the second frequency is 286 GHz. In the fourth frequency sweep, the first frequency is 272 GHz and the second frequency is 288 GHz. In the fifth frequency sweep, the first frequency is 270 GHz and the second frequency is 290 GHz. Additionally, in the sixth frequency sweep, the first frequency is 278 GHz and the second frequency is 282 GHz. In the seventh frequency sweep, the first frequency is 276 GHz and the second frequency is 284 GHz. In the eighth frequency sweep, the first frequency is 274 GHz and the second frequency is 286 GHz. In the ninth frequency sweep, the first frequency is 272 GHz and the second frequency is 288 GHz. In the tenth frequency sweep, the first frequency is 270 GHz and the second frequency is 290 GHz.

[0027] Figure 4 is a diagram showing Figure 1 the structure of the transmitter 1 shown. A constant envelope signal is input to the transmitter 1 from the oscillator 10. The transmitter 1 includes an N - multiplier 11 and a transmission amplifier 12. The transmitter 1 multiplies the constant envelope signal input from the oscillator 10 by N through the N - multiplier 11. Therefore, in the oscillator 10, a signal having a frequency that is one - Nth of the frequency of the transmission radio wave W1 is generated. The output of the N - multiplier 11 is amplified by the transmission amplifier 12, and the transmission radio wave W1 is transmitted from the transmission antenna 2.

[0028] Returns Figure 1 the description. The receiving antenna 3 receives the received radio wave W2, which is the radio wave transmitted by the transmitting unit 101 and reflected by the object T. The receiving antenna 3 is an array antenna element arranged in a two - dimensional array.

[0029] The receiver 4 is provided for each receiving antenna 3 and has the function of processing the analog signal of the radio wave received by the corresponding receiving antenna 3. The receiver 4 outputs the processed analog signal to the analog parallel - serial conversion unit 5.

[0030] Figure 5 is a diagram showing Figure 1Diagram of the structure of the receiver 4 shown. A constant envelope signal is input from the oscillator 10 to the receiver 4, and an analog signal of the radio wave received from the receiving antenna 3 is input. The receiver 4 includes a receiving amplifier 41, an N - multiplier 42, a mixer 44, an LPF (Low Pass Filter) 45, and a sample - and - hold circuit 46 marked as "S&H" in the figure.

[0031] The analog signal input from the receiving antenna 3 is amplified by the receiving amplifier 41 and then input to the mixer 44. In addition, the constant envelope signal input from the oscillator 10 is multiplied by N by the N - multiplier 42, and the signal after N - multiplication is also input to the mixer 44. The mixer 44 mixes, down - converts the signals input from the receiving amplifier 41 and the N - multiplier 42 respectively, and outputs to the LPF 45.

[0032] The LPF 45 is a filter with a variable cut - off bandwidth. It cuts off signals above the set cut - off frequency to remove unnecessary high frequencies and outputs to the sample - and - hold circuit 46. The sample - and - hold circuit 46 samples and holds the analog signal. The sampling and holding process is performed simultaneously in all receivers 4. The output of the sample - and - hold circuit 46 is connected to the analog parallel - to - serial conversion section 5.

[0033] Return Figure 1 description. The analog signals sampled and held in the multiple receivers 4 are converted into serial analog signals in the analog parallel - to - serial conversion section 5. The serial analog signal is output to the analog - to - digital converter 7.

[0034] Figure 6 It represents Figure 1A diagram showing the structure of the analog parallel-serial conversion unit 5. The analog parallel-serial conversion unit 5 is composed of a plurality of analog switches 51. By turning on the analog switches 51, the analog parallel-serial conversion unit 5 can select the signal output from the receiving unit 102 to the three-dimensional image generation unit 8. In other words, it can select the signal used for the generation of the three-dimensional image and the detection of the object. Therefore, the array antenna elements of the receiving antenna 3 connected to the analog switch 51 that is turned on can also be referred to as the array antenna elements used in the detection of the object. In addition, only one of the plurality of analog switches 51 is turned on simultaneously. By sequentially switching the turned-on analog switches 51, the analog parallel-serial conversion unit 5 can perform parallel-serial conversion. In addition, by changing the switching mode of the analog switches 51, that is, the conversion mode of the parallel-serial conversion, the analog parallel-serial conversion unit 5 can change the array antenna elements used. By changing the conversion mode of the parallel-serial conversion at a time division manner at a timing synchronized with the frequency scan of the transmitted radio wave W1, the analog parallel-serial conversion unit 5 can change the number of array antenna elements used in the detection of the object for each frequency scan. In addition, it is not necessary for the analog parallel-serial conversion unit 5 to turn on all the analog switches 51. By changing the conversion mode of the parallel-serial conversion and restricting the number of analog switches 51 to be turned on, the analog parallel-serial conversion unit 5 can restrict the number of array antenna elements used. For example, the larger the frequency scan range, the more the analog parallel-serial conversion unit 5 can reduce the number of array antenna elements used.

[0035] The analog-to-digital converter 7 converts the serial analog signal output from the analog parallel-serial conversion unit 5 into a digital signal and outputs the converted digital signal to the three-dimensional image generation unit 8. In this way, by having the analog parallel-serial conversion unit 5, the plurality of analog signals received by the plurality of array antenna elements are converted into a serial analog signal through parallel-serial conversion. Therefore, only one analog-to-digital converter 7 is required for the receiving unit 102. In addition, by restricting the number of array antenna elements used, the analog parallel-serial conversion unit 5 can reduce the bandwidth of the analog-to-digital converter 7. In the case where the object perspective device 100 perspectives a moving object T such as passing through a security checkpoint, the receiving unit 102 needs to process a large amount of data at high speed. Therefore, the analog-to-digital converter 7 needs to be very fast and the price becomes high. By having the analog parallel-serial conversion unit 5 in the receiving unit 102, the number of analog-to-digital converters 7 can be reduced and the bandwidth of the analog-to-digital converter 7 can be reduced. Therefore, the overall cost of the object perspective device 100 can be reduced.

[0036] The three-dimensional image generation unit 8 generates a three-dimensional image according to the digital signal output from the receiving unit 102 for each frequency scan. The three-dimensional image generation unit 8 outputs the generated three-dimensional image to the object detection unit 9.

[0037] The object detection unit 9 detects an object based on a plurality of three-dimensional images output from the three-dimensional image generation unit 8. The objects detected by the object detection unit 9 are, for example, objects of a preset type such as foreign objects and weapons. The object detection unit 9 can be constituted by a neural network or the like, and uses a learned model that has been learned in advance for the objects to be detected to detect the set objects. When the object detection unit 9 detects an object using a neural network, it inputs a plurality of three-dimensional images into the learned model, and the learned model outputs a detection result indicating whether a detection target object of a preset type, such as a foreign object or a weapon, is included in the target object T. When the set object is detected, the detection result may also include, for example, the type of the detected object.

[0038] As described above, the object perspective device 100 of Embodiment 1 includes: a transmission unit 101 that transmits a transmission radio wave W1 to the target object T, the transmission radio wave W1 being obtained by repeatedly performing a frequency scan in which the frequency changes from a first frequency to a second frequency over a frequency scan time; a reception unit 102 that uses an array antenna element to receive a reception radio wave W2 obtained by reflecting the transmission radio wave W1 by the target object T; a three-dimensional image generation unit 8 that generates a three-dimensional image based on the reception signal of the array antenna element for each frequency scan; and an object detection unit 9 that detects an object based on a plurality of three-dimensional images. The object perspective device 100 changes at least one of the first frequency, the second frequency, the frequency scan time, and the number of array antenna elements used in the detection of the object in a time-division manner.

[0039] By changing at least one of the first frequency, the second frequency, and the frequency scan time, the frequency scan speed can be changed. By changing the first frequency or the second frequency, the frequency scan amplitude can be changed. When the first frequency and the second frequency are the same, the shorter the frequency scan time, the faster the frequency scan speed. Additionally, when the frequency scan time is the same, the larger the frequency scan amplitude, the faster the frequency scan speed. If the frequency scan speed is increased, even when the target object T is moving, it is possible to suppress a degradation in the quality of the acquired three-dimensional image. However, when increasing the frequency scan amplitude to increase the frequency scan speed, the output of the receiver 4 becomes broadband. In this case, by reducing the number of array antenna elements used in object detection, the bandwidth of the analog-to-digital converter 7 can be reduced. However, if the number of array antenna elements used in object detection is reduced, the angular resolution decreases. Additionally, when increasing the frequency scan speed by shortening the frequency scan time, the range resolution decreases. Therefore, by changing at least one of the first frequency, the second frequency, the frequency scan time, and the number of array antenna elements used in object detection in a time-division manner, a plurality of three-dimensional images with different range resolutions and angular resolutions can be obtained. By combining them for object detection, even when the target object T is moving, it is possible to suppress a degradation in detection accuracy.

[0040] In Embodiment 1, as an example of the waveform of the transmitted radio wave W1, the waveforms shown in Figure 2 and Figure 3 are shown. Therefore, in the case of the transmitted radio wave W1 using the waveform shown in Figure 2 , the transmission unit 101 changes the frequency scan time in a time-division manner, and the reception unit 102 changes the number of array antenna elements used in object detection in a time-division manner. Additionally, in the case of the transmitted radio wave W1 using the waveform shown in Figure 3 , the transmission unit 101 changes the first frequency and the second frequency in a time-division manner, and the reception unit 102 changes the number of array antenna elements used in object detection in a time-division manner. However, these are just examples, and the object perspective device 100 only needs to change at least one of the parameters of the first frequency, the second frequency, the frequency scan time, and the array antenna elements used in object detection in a time-division manner. Additionally, in Embodiment 1, in each frequency scan, the above parameters are changed each time. However, even if the parameters are not changed each time in each frequency scan, as long as the parameters are changed in units of frequency scans, the parameters can also be changed every multiple frequency scans.

[0041] In addition, in the object perspective device 100, the receiving unit 102 has a plurality of array antenna elements. For the plurality of analog signals corresponding to each array antenna element, parallel-to-serial conversion is performed and converted into digital signals by one analog-to-digital converter 7. Thereby, the number of analog-to-digital converters 7 can be reduced, and the cost of the object perspective device 100 can be lowered.

[0042] In addition, by changing the conversion mode of the parallel-to-serial conversion, the object perspective device 100 can limit the number of array antenna elements used in the detection of an object. Thereby, the angular resolution of the object detection can be changed.

[0043] In addition, by changing the conversion mode of the parallel-to-serial conversion in a time-division manner at a timing synchronized with the frequency scan, the object perspective device 100 can change the number of array antenna elements used. Thereby, the angular resolution of the object detection can be changed for each three-dimensional image.

[0044] In addition, the object detection unit 9 can detect an object through a neural network.

[0045] In addition, the greater the difference between the first frequency and the second frequency, the more the object perspective device 100 can reduce the number of array antenna elements used in the detection of an object. Thereby, even when the frequency scan amplitude is large and the output of the receiver 4 becomes a wide band, by reducing the number of array antenna elements used in the detection of an object, the bandwidth of the analog-to-digital converter 7 can be reduced.

[0046] In addition, each unit of the object perspective device 100 can be implemented using a processing circuit. The processing circuit can be implemented by dedicated hardware or can be a control circuit using a CPU (Central Processing Unit).

[0047] When the above-mentioned processing circuit is implemented by dedicated hardware, the processing circuit is a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0048] In the case where the above processing circuit is implemented by a control circuit using a CPU, the control circuit includes, for example, a processor and a memory. The processor is a CPU, and is also referred to as an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), etc. The memory is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), an EEPROM (registered trademark) (Electrically EPROM), a magnetic disk, a floppy disk, an optical disk, a high-density disk, a minidisk, a DVD (Digital Versatile Disk), etc.

[0049] In the case where the above processing circuit is implemented by a control circuit, it is achieved by the processor reading and executing a program corresponding to the processing of each component stored in the memory. In addition, the memory is also used as a temporary memory in each process executed by the processor.

[0050] The structure shown in the above embodiment represents an example, and it may be combined with other known technologies, or a part of the structure may be omitted or changed without departing from the gist.

[0051] Reference Numeral Explanation

[0052] 1: Transmitter; 2: Transmitting Antenna; 3: Receiving Antenna; 4: Receiver; 5: Analog Parallel-Serial Conversion Unit; 7: Analog-to-Digital Converter; 8: Three-Dimensional Image Generation Unit; 9: Object Detection Unit; 10: Oscillator; 11, 42: N-Frequency Multiplier; 12: Transmitting Amplifier; 41: Receiving Amplifier; 44: Mixer; 45: LPF; 46: Sample and Hold Circuit; 51: Analog Switch; 100: Object Perspective Device; 101: Transmitting Unit; 102: Receiving Unit; T: Object Object; W1: Transmitted Radio Wave; W2: Received Radio Wave.

Claims

1. An object perspective device, characterized in that, Comprising: A transmitting unit that transmits a transmitted radio wave to an object, the transmitted radio wave being obtained by repeatedly performing a frequency scan in which the frequency changes from a first frequency to a second frequency over a frequency scan time; A receiving unit that uses an array antenna element to receive a received radio wave obtained by reflecting the transmitted radio wave from the object; A three-dimensional image generation unit that generates a three-dimensional image based on the received signal of the array antenna element for each frequency scan; And An object detection unit that detects an object based on a plurality of the three-dimensional images, The object perspective device changes at least one of the first frequency, the second frequency, the frequency scan time, and the number of the array antenna elements used in the detection of the object in a time-division manner.

2. The object perspective device according to claim 1, characterized in that, The receiving unit has a plurality of the array antenna elements, and parallel-to-serial conversion is performed on a plurality of analog signals corresponding to each of the array antenna elements, and the analog signals are converted into digital signals by one analog-to-digital converter.

3. The object perspective device according to claim 2, characterized in that, By changing the conversion mode of the parallel-to-serial conversion, the number of the array antenna elements used in the detection of the object is restricted.

4. The object perspective device according to claim 2, characterized in that, By changing the conversion mode of the parallel-to-serial conversion in a time-division manner at a timing synchronized with the frequency scan, the number of the array antenna elements used in the detection of the object is changed for each frequency scan.

5. The object perspective device according to any one of claims 1 to 4, characterized in that, The object detection unit detects an object through a neural network.

6. The object perspective device according to claim 1, characterized in that, The greater the difference between the first frequency and the second frequency, the smaller the number of the array antenna elements used in the detection of the object.

7. An object perspective method, characterized in that, Including the following steps: Transmitting a transmitted radio wave obtained by repeatedly performing a frequency scan in which the frequency changes from a first frequency to a second frequency over a frequency scan time to an object; Using an array antenna element to receive a received radio wave obtained by reflecting the transmitted radio wave from the object; Generating a three-dimensional image based on the received signal of the array antenna element for each frequency scan; And Detecting an object based on a plurality of the three-dimensional images, Changing at least one of the first frequency, the second frequency, the frequency scan time, and the number of the array antenna elements used in the detection of the object in a time-division manner.

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