Object perspective device

Abstract

An object see-through scanning device (100) comprises: a transmission unit (101) that transmits, to a target object (T), transmission radio waves obtained by repeatedly performing frequency sweep which changes a frequency from a first frequency to a second frequency over a frequency sweep time; a reception unit (102) that uses array antenna elements to receive reception radio waves obtained as a result of the transmission radio waves being reflected by the target object (T); a three-dimensional image generation unit (8) that, for each frequency sweep, generates a three-dimensional image from a reception signal from the array antenna elements; and an object detection unit (9) that detects an object on the basis of a plurality of three-dimensional images. At least one of the first frequency, the second frequency, the frequency sweep time, and the number of array antenna elements used in the detection of the object is changed in a time-divided manner.

Description

[Technical field]

[0001] The present disclosure relates to an object see-through device and an object see-through method for seeing through an object using radio waves. [Background technology]

[0002] Devices that see through objects to detect foreign objects and dangerous objects are used in food inspections and security gates at airports. Conventional object viewing devices generally use X-rays. Object viewing devices using X-rays have the problem of X-ray exposure, and their use is limited. As a method that does not have the problem of exposure, object viewing devices using nuclear magnetic resonance have been put to practical use for medical use. However, object viewing devices using nuclear magnetic resonance require a strong magnetic field, are large, and are subjected to a large force when magnetic materials such as iron are present. For this reason, object viewing devices using nuclear magnetic resonance require a large space to install the device, and there are many restrictions on the location where the device is installed, such as the need to manage the entry and exit of people and objects to the location where the device is installed, so their use is limited.

[0003] In contrast, an object see-through device using radio waves does not have the problem of radiation exposure, and there are few restrictions on where the device can be installed. When using radio waves, the limit of resolution is limited by the wavelength of the radio waves used. For this reason, object see-through images using radio waves have traditionally had low resolution and made it difficult to identify objects, but recent advances in device technology have made it possible to use radio waves of 100 GHz or more, and improvements in resolution are expected. For example, Patent Document 1 discloses a device that uses microwaves to inspect defects inside tires. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-77192 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional technology has a problem in that the detection accuracy decreases when the detection target moves.

[0006] The present disclosure has been made in consideration of the above, and has an object to provide an object see-through device that can suppress a decrease in detection accuracy even when a detection target moves. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the object see-through device according to the present disclosure includes a transmitting unit that transmits to a target object a transmission radio wave that has been repeatedly frequency swept to change the frequency from a first frequency to a second frequency over a frequency sweep time, a receiving unit that receives, by using an array antenna element, a reception radio wave that is the transmission radio wave reflected by the target object, a three-dimensional image generating unit that generates a three-dimensional image from the reception signal of the array antenna element for each frequency sweep, and a three-dimensional image generating unit that generates a three-dimensional image based on a plurality of three-dimensional images. subject an object detection unit that detects an object, the object detection unit including a first frequency, a second frequency, a frequency sweep time, subject At least one of the number of array antenna elements used for object detection is changed in a time-division manner. The receiving unit has a plurality of array antenna elements, performs parallel-serial conversion on a plurality of analog signals for each array antenna element, converts the signals into digital signals using one analog-to-digital converter, and limits the number of array antenna elements used to detect a target object by changing the conversion pattern of the parallel-serial conversion. The present invention is characterized by the above. Effect of the Invention

[0008] The object see-through apparatus according to the present disclosure has an advantage in that it is possible to suppress a decrease in detection accuracy even when the detection target moves. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of an object see-through apparatus according to a first embodiment; [Diagram 2] FIG. 1 is a diagram showing a first example of a waveform of a transmission radio wave. [Diagram 3] FIG. 2 is a diagram showing a second example of a waveform of a transmitted radio wave. [Figure 4] FIG. 2 shows the configuration of the transmitter shown in FIG. 1. [Diagram 5] FIG. 2 shows the configuration of the receiver shown in FIG. 1. [Figure 6] FIG. 2 is a diagram showing a configuration of an analog-to-parallel serial conversion unit shown in FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An object see-through apparatus and an object see-through method according to embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.

[0011] Embodiment 1 1 is a diagram showing a configuration of an object see-through device 100 according to the first embodiment. The object see-through device 100 has a function of seeing through an object using radio waves. The object see-through device 100 is used, for example, to detect dangerous objects such as weapons at an airport, or to detect foreign objects mixed into products at a production site.

[0012] The object see-through 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-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 a transmitting unit 101. The receiving antenna 3, the receiver 4, the analog-parallel-serial conversion unit 5, and the analog-digital converter 7 are collectively referred to as a receiving unit 102.

[0013] The transmitter 1 generates a transmission radio wave W1 to be transmitted toward the target object T, and transmits the generated transmission radio wave W1 using the transmission antenna 2. Here, the waveform of the transmission radio wave W1 will be described. The transmitter 1 generates the transmission radio wave W1 having a waveform obtained by repeatedly performing a frequency sweep that changes the frequency from a first frequency to a second frequency. Here, the length of time it takes to change the frequency from the first frequency to the second frequency is called 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.

[0014] FIG. 2 is a diagram showing a first example of the waveform of the transmission radio wave W1. In the first example shown in FIG. 2, the first frequency is 270 GHz, and the second frequency is 290 GHz. The values ​​of the first and second frequencies are fixed, whereas 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, and in the fourth frequency sweep, the frequency sweep time is 80 μsec. In addition, 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.

[0015] FIG. 3 is a diagram showing a second example of the waveform of the transmission radio wave W1. In the second example shown in FIG. 3, the frequency sweep time is a constant value of 10 μsec, whereas the first frequency and the second frequency are changed for 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. 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.

[0016] Fig. 4 is a diagram showing the configuration of the transmitter 1 shown in Fig. 1. A constant envelope signal is input to the transmitter 1 from the oscillator 10. The transmitter 1 has an N multiplier 11 and a transmission amplifier 12. The transmitter 1 multiplies the constant envelope signal input from the oscillator 10 by N using the N multiplier 11. Therefore, the oscillator 10 generates a signal having a frequency that is 1 / N times the frequency of the transmission radio wave W1. The output of the N multiplier 11 is amplified by the transmission amplifier 12, and the transmission radio wave W1 is emitted from the transmission antenna 2.

[0017] Returning to the explanation of Fig. 1, the receiving antenna 3 receives a receiving radio wave W2, which is a radio wave that is a transmission radio wave W1 transmitted by the transmitting unit 101 and reflected by a target object T. The receiving antenna 3 is an array antenna element arranged in a two-dimensional array.

[0018] The receiver 4 is provided for each receiving antenna 3, and has a function of processing an analog signal of the radio wave received by the corresponding receiving antenna 3. The receiver 4 outputs the processed analog signal to an analog parallel-serial conversion unit 5.

[0019] Fig. 5 is a diagram showing the configuration of the receiver 4 shown in Fig. 1. A constant envelope signal is input to the receiver 4 from the oscillator 10, and an analog signal of a radio wave received from the receiving antenna 3 is input to the receiver 4. The receiver 4 has a receiving amplifier 41, an N multiplier 42, a frequency mixer 44, an LPF (Low Pass Filter) 45, and a sample and hold 46, denoted as "S&H" in the figure.

[0020] The analog signal input from the receiving antenna 3 is amplified by the receiving amplifier 41 and then input to the frequency mixer 44. In addition, the constant envelope signal input from the oscillator 10 is multiplied by N by the N multiplier 42, and the N-multiplied signal is also input to the frequency mixer 44. The frequency mixer 44 mixes and down-converts the signals input from the receiving amplifier 41 and the N multiplier 42, and outputs the result to the LPF 45.

[0021] The LPF 45 is a filter with a variable cutoff bandwidth, which cuts off signals above a set frequency to remove unnecessary high frequencies and outputs the signal to the sample and hold 46. The sample and hold 46 samples and holds an analog signal. The sample and hold process is performed simultaneously in all receivers 4. The output of the sample and hold 46 is connected to the analog parallel-to-serial conversion unit 5.

[0022] Returning to the explanation of Fig. 1, the analog signals sampled and held in each of the multiple receivers 4 are converted into serial analog signals in an analog parallel-serial conversion unit 5. The serial analog signal is output to an analog-digital converter 7.

[0023] FIG. 6 is a diagram showing the configuration of the analog-parallel-serial conversion unit 5 shown in FIG. 1. 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 that the receiving unit 102 outputs to the three-dimensional image generating unit 8, in other words, the signal used for generating a three-dimensional image and detecting an object. For this reason, the array antenna element of the receiving antenna 3 connected to the analog switch 51 that is turned on can also be called the array antenna element used for detecting an object. Note that only one of the plurality of analog switches 51 is turned on at the same time, and the analog-parallel-serial conversion unit 5 can perform parallel-serial conversion by sequentially switching the analog switches 51 to be turned on. In addition, the analog-parallel-serial conversion unit 5 can change the array antenna element to be used by changing the switching pattern of the analog switches 51, that is, the conversion pattern of the parallel-serial conversion. The analog-parallel-serial conversion unit 5 can change the number of array antenna elements to be used for detecting an object for each frequency sweep by changing the conversion pattern of the parallel-serial conversion in a time-division manner at a timing synchronized with the frequency sweep of the transmission radio wave W1. It should be noted that the analog-parallel-serial conversion unit 5 does not necessarily have to turn on all of the analog switches 51. By changing the parallel-serial conversion pattern to limit the number of analog switches 51 that are turned on, the analog-parallel-serial conversion unit 5 can limit the number of array antenna elements that are used. For example, the larger the frequency sweep width, the fewer the number of array antenna elements that the analog-parallel-serial conversion unit 5 can use.

[0024] The analog-digital converter 7 converts the serial analog signal output by 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, since the analog-parallel-serial conversion unit 5 has multiple analog signals received by multiple array antenna elements, the receiver 102 only needs to have one analog-digital converter 7. In addition, the analog-parallel-serial conversion unit 5 limits the number of array antenna elements used, so that the bandwidth of the analog-digital converter 7 can be reduced. When the object see-through device 100 sees a moving target object T, such as a walk-through security gate, for example, the receiver 102 needs to process a large amount of data at high speed, so that the analog-digital converter 7 needs to be very fast and expensive. Since the receiver 102 has the analog-parallel-serial conversion unit 5, the number of analog-digital converters 7 can be reduced, and the bandwidth of the analog-digital converter 7 can be reduced, so that the cost of the object see-through device 100 as a whole can be reduced.

[0025] For each frequency sweep, the three-dimensional image generator 8 generates a three-dimensional image from the digital signal output by the receiver 102. The three-dimensional image generator 8 outputs the generated three-dimensional image to the object detector 9.

[0026] 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 object detected by the object detection unit 9 is, for example, a preset type of object such as a foreign object or a murder weapon. The object detection unit 9 is configured with a neural network or the like, and can detect the preset object using a trained model that has been trained in advance for the object to be detected. When detecting an object using a neural network, the object detection unit 9 inputs a plurality of three-dimensional images into the trained model, and the trained model outputs a detection result indicating whether or not the target object T includes a preset type of object to be detected, such as a foreign object or a murder weapon. When a preset object is detected, the detection result may include, for example, the type of the detected object.

[0027] As described above, the object visualization device 100 according to the first embodiment includes a transmitting unit 101 that transmits to a target object T a transmission radio wave W1 that has been repeatedly swept at a frequency from a first frequency to a second frequency over a frequency sweep time, a receiving unit 102 that receives, using an array antenna element, a reception radio wave W2 that is the transmission radio wave W1 reflected by the target object T, a three-dimensional image generating unit 8 that generates a three-dimensional image from a reception signal of the array antenna element for each frequency sweep, and an object detecting unit 9 that detects an object based on a plurality of three-dimensional images, and at least one of the first frequency, the second frequency, the frequency sweep time, and the number of array antenna elements used for object detection is changed in a time-division manner.

[0028] The frequency sweep speed can be changed by changing at least one of the first frequency, the second frequency, and the frequency sweep time. The frequency sweep width can be changed by changing the first frequency or the second frequency. When the first frequency and the second frequency are the same, the shorter the frequency sweep time, the faster the frequency sweep speed. Also, when the frequency sweep time is the same, the larger the frequency sweep width, the faster the frequency sweep speed. When the frequency sweep speed is increased, even when the target object T moves, the deterioration of the image quality of the acquired three-dimensional image can be suppressed. However, when the frequency sweep width is increased to increase the frequency sweep speed, the output of the receiver 4 becomes wideband. In this case, the bandwidth of the analog-to-digital converter 7 can be reduced by reducing the number of array antenna elements used to detect the object, but the angular resolution is reduced when the number of array antenna elements used to detect the object is reduced. Also, when the frequency sweep speed is increased by shortening the frequency sweep time, the distance resolution is reduced. Therefore, by changing at least one of the first frequency, the second frequency, the frequency sweep time, and the number of array antenna elements used for object detection in a time-division manner, multiple three-dimensional images with different distance resolutions and angular resolutions can be obtained, and by combining these to detect an object, it is possible to suppress a decrease in detection accuracy even when the target object T moves.

[0029] In the first embodiment, the waveform shown in FIG. 2 and the waveform shown in FIG. 3 are shown as examples of the waveform of the transmission radio wave W1. Therefore, when the transmission radio wave W1 having the waveform shown in FIG. 2 is used, the transmission unit 101 changes the frequency sweep time in a time-division manner, and the reception unit 102 changes the number of array antenna elements used for object detection in a time-division manner. Also, when the transmission radio wave W1 having the waveform shown in FIG. 3 is used, 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 for object detection in a time-division manner. However, these are only examples, and the object see-through device 100 only needs to change at least one parameter among the first frequency, the second frequency, the frequency sweep time, and the array antenna elements used for object detection in a time-division manner. Also, in the first embodiment, the above parameters are changed every time for each frequency sweep, but the parameters do not need to be changed every time for each frequency sweep, and the parameters may be changed for each frequency sweep.

[0030] In addition, in the object see-through apparatus 100, the receiving unit 102 has a plurality of array antenna elements, and performs parallel-serial conversion on a plurality of analog signals for each array antenna element, and converts them into digital signals by one analog-digital converter 7. This makes it possible to reduce the number of analog-digital converters 7, and thus makes it possible to reduce the cost of the object see-through apparatus 100.

[0031] In addition, the object see-through imaging apparatus 100 can limit the number of array antenna elements used for object detection by changing the parallel-serial conversion pattern, which makes it possible to change the angular resolution of object detection.

[0032] In addition, the object see-through imaging device 100 can change the number of array antenna elements to be used by changing the parallel-serial conversion pattern in a time-division manner at a timing synchronized with the frequency sweep. This makes it possible to change the angular resolution of object detection for each 3D image.

[0033] Furthermore, the object detection unit 9 can detect an object by using a neural network.

[0034] Furthermore, the object visualization device 100 can reduce the number of array antenna elements used for object detection as the difference between the first frequency and the second frequency increases. This allows the bandwidth of the analog-to-digital converter 7 to be reduced by reducing the number of array antenna elements used for object detection, even when the frequency sweep width is large and the output of the receiver 4 is broadband.

[0035] Each unit of the object perspective viewing apparatus 100 can be realized by using a processing circuit. The processing circuit may be realized by dedicated hardware, or may be a control circuit using a CPU (Central Processing Unit).

[0036] When the processing circuit is implemented by dedicated hardware, the processing circuit may be 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.

[0037] When the above processing circuit is realized 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 called 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 (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk), etc.

[0038] When the processing circuit is realized by a control circuit, the processing circuit is realized by the processor reading and executing a program corresponding to the processing of each component stored in the memory. The memory is also used as a temporary memory for each processing executed by the processor.

[0039] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0040] 1 transmitter, 2 transmitting antenna, 3 receiving antenna, 4 receiver, 5 analog parallel serial conversion section, 7 analog digital converter, 8 three-dimensional image generation section, 9 object detection section, 10 oscillator, 11, 42 N multiplier, 12 transmitting amplifier, 41 receiving amplifier, 44 frequency mixer, 45 LPF, 46 sample and hold, 51 analog switch, 100 object viewing device, 101 transmitting section, 102 receiving section, T target object, W1 transmitted radio wave, W2 received radio wave.

Claims

1. a transmission unit that transmits to a target object a transmission radio wave that has been repeatedly subjected to a frequency sweep in which the frequency is changed from a first frequency to a second frequency over a frequency sweep time; a receiving unit that receives, by using an array antenna element, a received radio wave that is the transmitted radio wave reflected by the target object; a three-dimensional image generating unit that generates a three-dimensional image from the received signals of the array antenna elements for each frequency sweep; an object detection unit that detects the target object based on a plurality of the three-dimensional images; Equipped with changing at least one of the first frequency, the second frequency, the frequency sweep time, and the number of the array antenna elements used for detecting the target object in a time division manner; The receiving unit is A method for converting a plurality of analog signals from each of the array antenna elements into digital signals by a single analog-to-digital converter, comprising: The number of the array antenna elements used for detecting the target object is limited by changing a conversion pattern of the parallel-to-serial conversion. An object visualization device comprising:

2. A transmitting unit that transmits to a target object a transmission radio wave that has been repeatedly subjected to a frequency sweep in which the frequency is changed over a frequency sweep time from a first frequency to a second frequency; a receiving unit that receives, by using an array antenna element, a received radio wave that is the transmitted radio wave reflected by the target object; a three-dimensional image generating unit that generates a three-dimensional image from the received signals of the array antenna elements for each frequency sweep; an object detection unit that detects the target object based on a plurality of the three-dimensional images; Equipped with changing at least one of the first frequency, the second frequency, the frequency sweep time, and the number of the array antenna elements used for detecting the target object in a time division manner; The receiving unit is A method for converting a plurality of analog signals from each of the array antenna elements into digital signals by a single analog-to-digital converter, comprising: The number of the array antenna elements used for detecting the target object is changed for each frequency sweep by changing the conversion pattern of the parallel-serial conversion in a time division manner at a timing synchronized with the frequency sweep. An object visualization device comprising:

3. The object detection unit detects the target object using a neural network.

3. An object viewing apparatus according to claim 1 or 2.

4. The greater the difference between the first frequency and the second frequency, the smaller the number of the array antenna elements used to detect the target object.

3. An object viewing apparatus according to claim 1 or 2.

Images