CN116520318A - Millimeter wave imaging real-time calibration method, device, computer equipment and storage medium - Google Patents
Millimeter wave imaging real-time calibration method, device, computer equipment and storage medium Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
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- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
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Abstract
The application relates to a millimeter wave imaging calibration method, a millimeter wave imaging calibration device, computer equipment and a storage medium, wherein the millimeter wave imaging calibration device comprises an antenna array and a calibration object parallel to the antenna array, and an imaging channel is formed between the antenna array and the calibration object; the imaging object is arranged in the imaging channel; the method is applied to a millimeter wave imaging calibration device and comprises the steps of receiving and transmitting step frequency signals through an antenna array, and acquiring echo data of an imaging object and a calibration object to obtain first echo data; screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering; and when the calibration parameters meet preset conditions, compensating and calibrating the first echo data according to the calibration parameters. The method and the device can acquire the calibration parameters in real time, are used for compensating and calibrating the first echo data, and solve the problem that the consistency of the receiving and transmitting channels cannot be calibrated in real time, so that the imaging quality is poor.
Description
Technical Field
The present disclosure relates to the field of millimeter wave imaging technologies, and in particular, to a millimeter wave imaging calibration method, device, computer device, and storage medium.
Background
In the security inspection field, human body security inspection imaging equipment based on millimeter wave can accurately image human bodies, and meanwhile, dangerous goods and categories carried by the human bodies can be accurately identified by combining an advanced artificial intelligent identification algorithm. For millimeter wave security inspection imaging equipment, the antenna array comprises a large number of receiving and transmitting channels, and the imbalance of the amplitude and the phase of the receiving and transmitting channels limits the image quality of security inspection imaging, so that the accuracy of dangerous goods detection is affected, and therefore, the consistency of the receiving and transmitting channels is required to be calibrated.
At present, the phase compensation value of each transceiver channel with reference to the reference channel can be obtained through mutual calibration among the transceiver antennas so as to calibrate the consistency of the transceiver channels for imaging, but when the inconsistency of the transceiver channels frequently occurs, real-time calibration cannot be performed, thereby causing the problem of poor imaging quality.
Aiming at the problem that the consistency of a receiving and transmitting channel cannot be calibrated in real time in the related technology, so that the imaging quality is poor, no effective solution is proposed at present.
Disclosure of Invention
In this embodiment, a millimeter wave imaging calibration method, device, computer equipment and storage medium are provided to solve the problem that in the related art, consistency of a transceiver channel cannot be calibrated in real time, resulting in poor imaging quality.
In a first aspect, in this embodiment, there is provided a millimeter wave imaging calibration method applied to a millimeter wave imaging calibration apparatus, the millimeter wave imaging calibration apparatus including an antenna array and a calibration object parallel to the antenna array, an imaging channel being formed between the antenna array and the calibration object; an imaging object is arranged in the imaging channel; the method comprises the following steps:
receiving and transmitting a step frequency signal through the antenna array, and acquiring echo data of the imaging object and the calibration object to obtain first echo data;
screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering;
and when the calibration parameters meet preset conditions, performing compensation calibration on the first echo data according to the calibration parameters.
In some embodiments, the step frequency signal is received and transmitted by the antenna array, and echo data of the imaging object and the calibration object are acquired, so as to obtain first echo data, including:
Collecting echo data reflected by the imaging object and the calibration object through a receiving and transmitting channel of the antenna array to serve as the first echo signal; the first echo data are echo data of the imaging object and the calibration object of each receiving and transmitting channel at each frequency point.
In some embodiments, the filtering the second echo data from the first echo data according to the reference position of the calibration object relative to the antenna array, and obtaining the calibration parameter through matched filtering includes:
acquiring a distance range between the calibration object and the antenna array according to a reference position of the calibration object relative to the antenna array;
screening the second echo data reflected by the calibration object from the first echo data based on the distance range;
and establishing a matched filtering model according to the reflection area of the calibration object and the reference position, carrying out matched filtering on the second echo data, and solving to obtain the calibration parameters.
In some embodiments, the method further comprises:
calibrating the second echo data based on the calibration parameters, and obtaining a calibration object image through an imaging algorithm;
Calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets a preset condition or not by combining a preset threshold;
when the confidence coefficient is smaller than the preset threshold value, judging that the calibration parameter does not meet the preset condition;
and when the confidence coefficient is larger than or equal to the preset threshold value, judging that the calibration parameter meets the preset condition.
In some embodiments, the method further comprises:
and when the calibration parameters do not meet the preset conditions, the reference position of the calibration object relative to the antenna array is adjusted, second echo data are screened from the first echo data again, and the calibration parameters are obtained through matched filtering.
In some embodiments, the method further comprises:
according to the reference position of the imaging object relative to the antenna array, third echo data are obtained through screening and processing from the calibrated first echo data;
and reconstructing and imaging the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
In a second aspect, in this embodiment, there is provided a millimeter wave imaging calibration apparatus, characterized by comprising: the antenna array, the calibration object parallel to the antenna array and the calibration module; forming an imaging channel between the antenna array and the calibration object; an imaging object is arranged in the imaging channel;
The antenna array is used for receiving and transmitting step frequency signals, and acquiring echo data of the imaging object and the calibration object to obtain first echo data;
the imaging object and the calibration object are used for reflecting the step frequency signals emitted by the antenna array;
the calibration module is used for screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering;
and when the calibration parameters meet preset conditions, performing compensation calibration on the first echo data according to the calibration parameters.
In some of these embodiments, the calibration object includes a reflective region and a hollow region, and the hollow region has an area that is greater than the size of the imaging subject;
the reflecting area is made of diffuse reflecting material; or, a metallic material.
In some embodiments, the apparatus further comprises: the device comprises a judging module and an imaging module;
the judging module is used for calibrating the second echo data based on the calibration parameters and obtaining calibration object imaging through an imaging algorithm;
calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets a preset condition or not by combining a preset threshold;
When the confidence coefficient is smaller than the preset threshold value, judging that the calibration parameter does not meet the preset condition; when the confidence coefficient is larger than or equal to the preset threshold value, judging that the calibration parameter meets the preset condition;
the imaging module is used for screening and processing the calibrated first echo data to obtain third echo data according to the reference position of the imaging object relative to the antenna array;
and reconstructing and imaging the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
In a third aspect, in this embodiment, there is provided a computer device including a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor implements the millimeter wave imaging calibration method according to the first aspect.
In a fourth aspect, in the present embodiment, there is provided a storage medium having stored thereon a computer program which, when executed by a processor, implements the millimeter wave imaging calibration method of the first aspect described above.
Compared with the related art, the millimeter wave imaging calibration method, the device, the computer equipment and the storage medium provided in the embodiment are applied to the millimeter wave imaging calibration device, wherein the millimeter wave imaging calibration device comprises an antenna array and a calibration object parallel to the antenna array, and an imaging channel is formed between the antenna array and the calibration object; an imaging object is arranged in the imaging channel; the method comprises the following steps: receiving and transmitting a step frequency signal through the antenna array, and acquiring echo data of the imaging object and the calibration object to obtain first echo data; screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering; when the calibration parameters meet preset conditions, the first echo data are compensated and calibrated according to the calibration parameters, the calibration parameters can be acquired in real time during imaging, and the calibration parameters are used for calibrating the first echo data so as to compensate inconsistent phases of the receiving and transmitting channels, reduce the influence of phase fluctuation of the receiving and transmitting channels on imaging, and solve the problems that the consistency of the receiving and transmitting channels cannot be calibrated in real time, and the imaging quality is poor.
The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below to provide a more thorough understanding of the other features, objects, and advantages of the application.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:
FIG. 1 is a schematic diagram of the structure of a millimeter wave imaging calibration apparatus in one embodiment;
FIG. 2 is a schematic diagram of the spacing of frequency points in one embodiment;
FIG. 3 is a flow chart of a millimeter wave imaging calibration method in one embodiment;
fig. 4 is a schematic structural view of a millimeter wave imaging calibration apparatus in a preferred embodiment;
fig. 5 is a flow chart of a millimeter wave imaging calibration method in a preferred embodiment.
In the figure: 10. an antenna array; 11. a transmitting antenna; 12. a receiving antenna; 20. a calibrator; 21. a reflective region; 22. a hollow region; 30. imaging the object.
Detailed Description
For a clearer understanding of the objects, technical solutions and advantages of the present application, the present application is described and illustrated below with reference to the accompanying drawings and examples.
Unless defined otherwise, technical or scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms "a," "an," "the," "these," and the like in this application are not intended to be limiting in number, but rather are singular or plural. The terms "comprising," "including," "having," and any variations thereof, as used in the present application, are intended to cover a non-exclusive inclusion; for example, a process, method, and system, article, or apparatus that comprises a list of steps or modules (units) is not limited to the list of steps or modules (units), but may include other steps or modules (units) not listed or inherent to such process, method, article, or apparatus. The terms "connected," "coupled," and the like in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Reference to "a plurality" in this application means two or more. "and/or" describes an association relationship of an association object, meaning that there may be three relationships, e.g., "a and/or B" may mean: a exists alone, A and B exist together, and B exists alone. Typically, the character "/" indicates that the associated object is an "or" relationship. The terms "first," "second," "third," and the like, as referred to in this application, merely distinguish similar objects and do not represent a particular ordering of objects.
In the security inspection field, human body security inspection imaging equipment based on millimeter wave can accurately image human bodies, and meanwhile, dangerous goods and categories carried by the human bodies can be accurately identified by combining an advanced artificial intelligent identification algorithm.
For millimeter wave security inspection imaging equipment, the millimeter wave security inspection imaging equipment comprises a linear array flat scanning mode, a linear array circular scanning mode, an area array scanning mode and other working modes, each working mode corresponds to different imaging equipment structures, wherein a large antenna array comprises a large number of receiving and transmitting channels, the imbalance of the amplitude and the phase of the receiving and transmitting channels limits the image quality of security inspection imaging, and further the accuracy of dangerous article detection is affected, so that the consistency of the receiving and transmitting channels is required to be calibrated.
At present, the phase compensation value of each transceiver channel with reference to a reference channel can be obtained through mutual calibration among transceiver antennas, after the consistency of the transceiver channels is calibrated, the mode of combining a time domain or a wave number domain is used for imaging, for example, in the calibration system and method of an active millimeter wave real-time three-dimensional imaging security check system, the echo signal acquisition of a calibration body arranged on a floor is completed through configuring the port surfaces of millimeter wave antenna arrays on the left channel wall and the right channel wall of the security check channel, the calibration parameters are obtained to compensate and calibrate the phase inconsistency of the transceiver channels, and the calibration parameters are used in the imaging of the follow-up security check, but when the inconsistency of the transceiver channels frequently occurs, the calibration parameters before the use in the security check imaging are not necessarily used for realizing high-quality imaging, so that the real-time calibration cannot be performed, and the imaging quality is poor.
In order to solve the above problems, the following embodiments provide a millimeter wave imaging calibration method, apparatus, computer device, and storage medium capable of forming an imaging channel in an antenna array and a calibration object parallel to the antenna array by the antenna array and the calibration object, and setting the imaging object in the imaging channel to acquire echo data of the calibration object and the imaging object, calculate calibration parameters in real time, and use for imaging calibration of the imaging object.
In this embodiment, there is provided a millimeter wave imaging calibration apparatus, fig. 1 is a schematic structural view of the apparatus of this embodiment, as shown in fig. 1, the apparatus including: an antenna array 10, a calibration object 20 parallel to the antenna array, and a calibration module (not shown in the figure); forming an imaging channel between the antenna array and the calibration object; an imaging subject 30 is disposed in the imaging tunnel.
The antenna array 10 is configured to receive and transmit a step frequency signal, and acquire echo data of the imaging object 30 and the calibration object 20 to obtain first echo data; wherein the imaging subject 30 and the calibration object 20 are used to reflect the step frequency signal emitted by the antenna array 10.
The antenna array 10 includes a plurality of transmitting antennas and receiving antennas, any of which constitutes a transceiving channel. In this embodiment, fig. 2 is a schematic diagram of the interval between each frequency point in the embodiment, as shown in fig. 2, the horizontal axis of the coordinate system represents the period T of the frequency point, the vertical axis of the coordinate system represents the frequency of the frequency point, the intervals between each frequency point may be equal, or may be arranged according to a certain rule, the number of frequency points is not limited to 32 and 64, and may specifically be selected according to the maximum non-ambiguity detectable distance and the distance resolution. The receiving antenna adopts a superheterodyne structure for mixing, the frequency of the intermediate frequency signal depends on factors such as an ADC (Analog-to-digital converter) sampling rate and a filter characteristic of a radio frequency chip, and the ADC sampling rate specifically needs to meet the requirement of sampling the intermediate frequency signal in the whole period.
Further, the antenna array 10 is a sparse antenna array, and the array antenna distribution thereof is not limited to a square array, a circular array, and the like. An example layout of a transmitting antenna and a receiving antenna is that the transmitting antenna and the receiving antenna are all arranged linearly, and two columns of transmitting antennas and two columns of receiving antennas are disposed opposite to each other, respectively.
The calibration object 20 is arranged parallel to the antenna array 10 as a calibration reference for reflecting the step frequency signal emitted by the antenna array 10. The shape of the calibration object 20 may be configured corresponding to the shape of the antenna array 10 and the arrangement of the transmitting antennas and the receiving antennas in the antenna array, so as to better obtain echo data in the antenna array 10. Preferably, the depth of the calibration object 20 from the antenna array 10 may be set to 2m in practical application.
In the field of security inspection, the imaging subject 30 may specifically be a person or object to be detected for reflecting the step frequency signal emitted by the antenna array 10. In addition, the imaging object 30 is disposed in an imaging channel formed between the antenna array 10 and the calibration object 20, the imaging object 30 and the calibration object 20 have different depths (distances) relative to the antenna array 10, and the antenna array 10 acquires echo data of the calibration object 20 and the imaging object 30, so as to distinguish the echo data of the calibration object 20 and the imaging object 30 according to the different depths when obtaining the first echo data. Preferably, the depth of the imaging subject 30 from the antenna array 10 may be set to 0.5m in practical applications. The first echo data acquired by the antenna array 10 may be in a multi-dimensional ADC data format.
The calibration module is connected with the antenna array 10, and is configured to screen out second echo data from the first echo data according to a reference position of the calibration object 20 relative to the antenna array 10, and obtain calibration parameters through matched filtering; and when the calibration parameters meet preset conditions, compensating and calibrating the first echo data according to the calibration parameters.
Specifically, the size of the calibration object 20 may be obtained by a high-precision measuring instrument such as a vernier caliper or the like. The antenna coordinate system of the XYZ axis is established with the plane of the antenna array 10, and the above reference position is the set of the coordinate systems of the antenna projected by the calibration object 20, and can be obtained by combining the alignment of the laser and the size of the calibration object 20.
According to the reference position of the calibration object 20 relative to the antenna array 10, the maximum distance and the minimum distance between the reflection point on the calibration object 20 and the antenna array 10 can be calculated to obtain the distance range between the calibration object 20 and the antenna array 10.
Because the imaging object 30 and the calibration object 20 have different distances relative to the antenna array 10, echo data reflected by the calibration object 20 is obtained by screening from the first echo data based on the distance range, is used as second echo data, and is subjected to matched filtering, so that calibration parameters are obtained. Wherein the calibration parameter is a compensation value for the phase of the transmit-receive channel.
Further, by judging the threshold of the calibration parameter, specifically, the preset condition can be established by calculating the confidence coefficient of the calibration parameter and combining with the preset threshold, and when the calibration parameter meets the preset condition, the first echo data is calibrated in real time by the obtained calibration parameter so as to compensate the inconsistent phase of the receiving and transmitting channel and reduce the influence on the imaging quality.
According to the device provided by the embodiment, the imaging channel is formed between the antenna array and the calibration object through the antenna array and the calibration object parallel to the antenna array, the imaging object is arranged in the imaging channel, echo data of the imaging object and the calibration object are collected through the antenna array, echo data reflected by the calibration object are obtained through screening according to the reference position of the calibration object relative to the antenna array, calibration parameters are further calculated and used in imaging calibration, the calibration parameters can be obtained in real time and used for compensating phase inconsistency of the receiving and transmitting channels, the influence of phase fluctuation of the receiving and transmitting channels on imaging is reduced, and the problem that consistency of the receiving and transmitting channels cannot be calibrated in real time, and poor imaging quality is caused is solved.
In some embodiments, the calibration object includes a reflective region and a hollow region, and the hollow region has an area greater than a size of the imaging object. Wherein the reflective region is a diffuse reflective material; or, a metallic material.
Specifically, the reflection area of the calibration object is used for reflecting the step frequency signal emitted by the antenna array, and may be specifically a diffuse reflection material or other metal materials capable of realizing reflection, which is specifically determined according to the actual reflection effect.
Furthermore, a hollow area is formed in the middle of the calibration object, and the area of the hollow area is larger than the size of the imaging object, so that interference of echo reflected between the calibration object and the imaging object for multiple times can be reduced through the hollow structure of the calibration object in the embodiment, and echo data reflected by the calibration object and the imaging object can be better distinguished only through reflection areas at the edges of the calibration object.
In some embodiments, the apparatus further comprises: the device comprises a judging module and an imaging module.
The judging module is used for calibrating the second echo data based on the calibration parameters and obtaining the imaging of the calibration object through an imaging algorithm; calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets the preset condition by combining with the preset threshold; when the confidence coefficient is smaller than a preset threshold value, judging that the calibration parameter does not meet a preset condition; and when the confidence coefficient is larger than or equal to a preset threshold value, judging that the calibration parameter meets a preset condition.
Specifically, the second echo data obtained by screening is multiplied by the calibration parameters correspondingly, and then a K-space and other rapid imaging algorithms are adopted to image the calibrated calibration object, so that the imaging of the calibration object is obtained.
And comparing the imaging size of the calibration object with the real measurement size of the calibration object, and obtaining the comprehensive error by accumulating squares of all differences. In the accumulation process, different weights can be set for the squares of each difference value, and the weight values are obtained specifically according to experimental analysis.
After the integrated error is obtained, a Bayesian network can be used for calculating the confidence coefficient, or the integrated error can be judged in a layering way. For example, when the integrated error is greater than a certain threshold (set according to the actual result), the confidence is 0; when the integrated error is less than the threshold, a linear equation is used to calculate the confidence level. And establishing preset conditions by combining the preset threshold value obtained through theoretical simulation and the confidence coefficient.
The imaging module is used for screening and processing the calibrated first echo data to obtain third echo data according to the reference position of the imaging object relative to the antenna array; and reconstructing an image of the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
Specifically, the calibration parameters and the first echo data are multiplied in a pairwise corresponding manner, and the first echo data after compensation and calibration are obtained.
And performing inverse Fourier transform on the compensated first echo data to obtain a distance-power spectrum, selecting echo data with a distance less than or equal to D (the minimum distance between the calibration object and the antenna array) and greater than or equal to L (the depth of the imaging object relative to the antenna array) according to the reference position of the imaging object relative to the antenna array, performing Fourier transform, and optimizing a window function, such as a Hamming window, for example, on the third echo data to obtain third echo data reflected by the imaging object in order to make radar echoes uniform and reduce the influence of mirror radiation. The third echo data is reconstructed based on a BP (back propagation) algorithm.
Through the judging module and the imaging module provided in the embodiment, the confidence coefficient of the calibration parameter can be calculated through imaging the calibration object and the size of the calibration object, and the confidence coefficient of the calibration parameter is judged, so that the non-conforming calibration parameter is corrected on line, the accuracy of the calibration parameter is improved, further echo data reflected by the imaging object is obtained through screening from the calibrated first echo data, and the imaging algorithm is combined to obtain imaging with higher quality.
The above-described respective modules may be functional modules or program modules, and may be implemented by software or hardware. For modules implemented in hardware, the various modules described above may be located in the same processor; or the above modules may be located in different processors in any combination.
In this embodiment, a millimeter wave imaging calibration method is provided, which is applied to the millimeter wave imaging calibration device in the above embodiment, and fig. 3 is a flowchart of the method in this embodiment, as shown in fig. 3, and the method includes the following steps:
step S310, step frequency signals are received and transmitted through an antenna array, and echo data of an imaging object and a calibration object are acquired to obtain first echo data.
Specifically, in the millimeter wave imaging device, the antenna array includes a plurality of transmitting antennas and receiving antennas, and any transmitting antenna and receiving antenna form a receiving and transmitting channel. The transmitting antenna radiates the step frequency signal outwards, the imaging object and the calibration object are used for reflecting the step frequency signal transmitted by the antenna array, receiving the step frequency signal through the receiving antenna, and acquiring first echo data in a multi-dimensional ADC data format, wherein the first echo data comprises echo data reflected by the imaging object and the calibration object.
Step S320, screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering.
Specifically, the size of the calibration object can be obtained by a high-precision measuring instrument, such as a vernier caliper. The antenna coordinate system of the XYZ axis is established by the plane of the antenna array, and the reference position is the set of the calibration object projected to the antenna coordinate system, and can be obtained by combining the alignment of the laser and the size of the calibration object.
According to the reference position of the calibration object relative to the antenna array, the maximum distance and the minimum distance between all reflection points on the calibration object and the antenna array can be calculated, so that the distance range between the calibration object and the antenna array can be obtained.
Because the imaging object and the calibration object have different distances relative to the antenna array respectively, echo data reflected by the calibration object is obtained by screening from the first echo data based on the distance range and is used as second echo data, matched filtering is carried out, and calibration parameters are obtained by solving. Wherein the calibration parameter is a compensation value for the phase of the transmit-receive channel.
Step S330, when the calibration parameters meet the preset conditions, the first echo data is compensated and calibrated according to the calibration parameters.
Specifically, by judging the threshold of the calibration parameter, the preset condition can be established by calculating the confidence coefficient of the calibration parameter and combining with the preset threshold, and when the calibration parameter meets the preset condition, the first echo data is calibrated in real time through the obtained calibration parameter so as to compensate the inconsistent phase of the receiving and transmitting channel and reduce the influence on the imaging quality.
The imaging channel is formed between the antenna array and the calibration object parallel to the antenna array, the imaging object is arranged in the imaging channel, echo data of the imaging object and the calibration object are collected through the antenna array, echo data reflected by the calibration object are obtained through screening according to the reference position of the calibration object relative to the antenna array, and the calibration parameters are further calculated and used in imaging calibration.
In some embodiments, the process of obtaining the first echo data in the step S310 may be specifically implemented by the following steps:
collecting echo data reflected by an imaging object and a calibration object through a receiving and transmitting channel of an antenna array to serve as a first echo signal; the first echo data are echo data of an imaging object and a calibration object of each receiving and transmitting channel at each frequency point.
Specifically, the antenna array includes a plurality of transmitting antennas and receiving antennas, and any transmitting antenna and receiving antenna form a receiving and transmitting channel. For the acquired first echo data, specifically, echo data of the imaging object and the calibration object, which are received by each receiving and transmitting channel of the antenna array at each frequency point.
In one example, the Data format of the first echo Data may be set to Data [ TxNum ] [ RxNum ] [ FreNum ], where TxNum is the number of transmit antennas, rxNum is the number of receive antennas, freNum is the number of frequency points, and the set of echo Data corresponding to each transmit/receive channel (assuming that the transmit antenna ID is TxIdx and the receive antenna ID is RxIdx) is { Data [ TxIdx ] [ RxIdx ] [0], data [ TxIdx ] [ RxIdx ] [1], … …, data [ TxIdx ] [ RxIdx ] [ FreNum-1] }.
Through utilizing millimeter wave imaging calibration device in this embodiment, set up the imaging object in the imaging passageway between antenna array and the demarcation thing to make demarcation thing and imaging object have different degree of depth for antenna array, can once gather the echo data that obtains demarcation thing and imaging object, respectively through the distance with antenna array, distinguish the echo data of demarcation thing and imaging object.
In some embodiments, in the step S320, second echo data is obtained by screening from the first echo data according to the reference position of the calibration object with respect to the antenna array, and calibration parameters are obtained by matched filtering, including the following steps:
step S321, according to the reference position of the calibration object relative to the antenna array, the distance range between the calibration object and the antenna array is obtained.
Specifically, the size of the calibration object is obtained by a high-precision measuring instrument, such as a vernier caliper, wherein parameters such as the height of the calibration object are included. In an antenna coordinate system established by a plane where the antenna array is located, all reflection points on the calibration object are projected to a set of the antenna coordinate system through laser alignment, so that a reference position of the calibration object relative to the antenna array is obtained.
In the above reference position, if the minimum distance between the calibration object and the antenna array is known to be D, the distance between the reflection point on the calibration object and the antenna is greater than or equal to D, and then the maximum distance DMax between the reflection point on the calibration object and the antenna array is obtained by using the pythagorean theorem according to the height of the calibration object and the minimum distance D, so as to obtain the distance range between the calibration object and the antenna array.
Step S322, screening the second echo data reflected by the calibration object from the first echo data based on the distance range.
Specifically, the first echo Data is converted into a distance-power spectrum through inverse fourier transformation, targets with distances outside a distance range [ D, DMax ] are filtered out on the distance-power spectrum based on the distance range, and then the targets are converted into a time domain through fourier transformation, so that second echo Data reflected by a calibration object is obtained, wherein the format of the second echo Data is also multidimensional ADC Data [ TxNum ] [ RxNum ] [ frenum ].
Step S323, a matched filtering model is established according to the reflection area and the reference position of the calibration object, matched filtering is carried out on the second echo data, and calibration parameters are obtained through solving.
Specifically, the position set of the reflecting area of the calibration object is set to be P, and the position set is combined with the reference position (x Ref ,y Ref ,z Ref ) Performing conversion, and establishing a matched filtering model in the following form:
where j indicates that the current expression is a complex expression, k represents wave number, k=2 pi/λ, λ represents wavelength,representing the spatial position of a certain transmitting antenna, +.>Representing the spatial position of a certain receiving antenna, +.>Representing a set P of marker positions.
Further, each receiving and transmitting channelAssuming that the target reflection points are formed, each reflection point on the calibration object is regarded as an equivalent antenna, and the second echo data is subjected to matched filtering in the time domain, wherein the matched filtering is specifically as follows:
W (T, R, F) is an additional amplitude-phase compensation value of the transmitting channel T and the receiving channel R under the frequency point F; s (T, R, F) is the ADC sampling value (i.e. the second echo data) of the receiving channel R at the frequency point F, and the transmitting channel T after the distance screening.
After the above additional amplitude-phase compensation value w (T, R, F) is obtained, since the influence of the phase error of the transmit-receive channel on the imaging is greater than the influence of the amplitude inconsistency of the transmit-receive channel on the imaging quality, the phase compensation value Φ (T, R, F) =abs (w (T, R, F))/w (T, R, F) is calculated, and the phase compensation value is used as the calibration parameter.
According to the embodiment, according to the fact that the calibration object and the imaging object respectively have different depths relative to the antenna array, the first echo data can be converted to a distance-power spectrum, the second echo data reflected by the calibration object can be obtained by combining the distance range of the calibration object and the antenna array through screening, and the phase compensation value for the receiving and transmitting channel can be obtained through matched filtering calculation and used as a calibration parameter.
After obtaining the calibration parameters, in order to improve the accuracy of the calibration parameters, in some embodiments, the confidence level of the calibration parameters may be determined by imaging the calibration object, and the non-conforming calibration parameters may be corrected online, which may be specifically implemented by the following steps:
Step S410, calibrating the second echo data based on the calibration parameters, and obtaining the imaging of the calibration object through an imaging algorithm.
Specifically, the second echo data obtained by screening is multiplied by the calibration parameters correspondingly, and then a K-space and other rapid imaging algorithms are adopted to image the calibrated calibration object, so that the imaging of the calibration object is obtained.
Step S420, calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets the preset condition by combining the preset threshold.
Specifically, the dimensions of the calibration object in the imaging of the calibration object, such as the peripheral length and width of the calibration object, are calculated, and for the case that the calibration object includes the reflective area and the hollow area in the above embodiment, the peripheral length and width of the calibration object, and the contrast of the reflective area and the hollow area in the calibration object are further calculated, wherein the contrast can be obtained by calculating the ratio of the power average value of the solid portion (reflective area) to the power average value of the hollow portion (hollow area), and then obtaining the logarithmic value thereof.
And comparing the imaging size of the calibration object with the real measurement size of the calibration object, and obtaining the comprehensive error by accumulating squares of all differences. In the accumulation process, different weights can be set for the squares of each difference value, and the weight values are obtained specifically according to experimental analysis.
After the integrated error is obtained, a Bayesian network can be used for calculating the confidence coefficient, or the integrated error can be judged in a layering way. For example, when the integrated error is greater than a certain threshold (set according to the actual result), the confidence is 0; when the integrated error is less than the threshold, a linear equation is used to calculate the confidence level. And establishing preset conditions by combining the preset threshold value obtained through theoretical simulation and the confidence coefficient.
Step S430, when the confidence coefficient is smaller than a preset threshold value, the calibration parameters do not meet the preset condition; when the confidence coefficient is greater than or equal to a preset threshold value, the calibration parameter meets a preset condition.
Specifically, when the confidence coefficient is greater than or equal to a preset threshold, the calibration parameter satisfies a preset condition, and the calibration parameter may be used to compensate the phase of the transceiver channel.
When the confidence coefficient is smaller than the preset threshold value, the calibration parameter does not meet the preset condition, and a reasonable upper limit of iteration times (obtained by allowing the calculation time through the system) is set in consideration of the calculation time. If the calculation confidence coefficient is smaller than the preset threshold value and the current calculation times are smaller than the upper limit of the iteration times, the on-line correction is continuously carried out on the calibration parameters which do not meet the preset conditions, so that the accuracy of the calibration parameters is improved.
Further, the calibration parameters which do not meet the preset conditions are corrected online through the following steps:
and when the calibration parameters do not meet preset conditions, the second echo data are obtained by screening from the first echo data again through adjusting the reference position of the calibration object relative to the antenna array, and the calibration parameters are obtained through matched filtering.
Specifically, the reference position is adjusted by adopting a genetic algorithm, a gradient descent algorithm or a rough and fine search method, etc., and in order to further reduce the calculation number of the algorithm, a search range with respect to the reference position may be defined in advance, for example, measurement uncertainty in combination with the laser measurement described above is obtained.
And after the reference position is adjusted, rescreening to obtain second echo data reflected by the calibration object, calculating to obtain a calibration parameter by the method in the embodiment, and judging the confidence coefficient of the calibration parameter.
In the embodiment, the confidence coefficient of the calibration parameter is calculated by imaging the calibration object and the size of the calibration object, and the confidence coefficient of the calibration parameter is judged, so that the non-conforming calibration parameter is corrected on line, the accuracy of the calibration parameter is improved, and better imaging is realized later.
In some embodiments, the method further comprises an imaging process of the imaging object, specifically by:
according to the reference position of the imaging object relative to the antenna array, screening and processing the calibrated first echo data to obtain third echo data; and reconstructing an image of the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
Specifically, the calibration parameters Φ (T, R, F) and the first echo data m (T, R, F) are multiplied by each other correspondingly, so as to obtain the first echo data m' (T, R, F) after compensation calibration. Where m (T, R, F) and m' (T, R, F) represent the ADC sample values of the transmit channel T and the receive channel R at the frequency point F.
And performing inverse Fourier transform on the compensated first echo data to obtain a distance-power spectrum, selecting echo data with a distance less than or equal to D (the minimum distance between the calibration object and the antenna array) and greater than or equal to L (the depth of the imaging object relative to the antenna array) according to the reference position of the imaging object relative to the antenna array, performing Fourier transform, and optimizing a window function, such as a Hamming window, for example, on the third echo data to obtain third echo data n (T, R, F) reflected by the imaging object in order to make radar echo uniform and reduce the influence of mirror radiation.
The reconstruction imaging of n (T, R, F) is carried out based on BP (back propagation) algorithm, and the specific steps are as follows:
where NK is the number of wavenumbers, NT is the number of transmit antennas, NR is the number of receive antennas,representing the spatial position of the corresponding transmitting antenna, +.>Representing the spatial position of the corresponding receiving antenna, +.>k represents wave number, λ represents wavelength, k=2 pi/λ.
The above is modified as follows:
the two-dimensional convolution may be implemented in the following two-dimensional fourier manner:
in this embodiment, echo data reflected by the imaging object can be obtained by screening from the calibrated first echo data, and higher-quality imaging can be obtained by combining an imaging algorithm.
The method embodiments provided in the above embodiments may be executed in a terminal, a computer or similar computing device. Such as on a terminal, which may include one or more processors and memory for storing data, where the processors may include, but are not limited to, a microprocessor MCU or a programmable logic device FPGA or the like. The terminal may further include a transmission device for a communication function and an input-output device. It will be appreciated by those skilled in the art that the foregoing description is merely illustrative and is not intended to limit the structure of the terminal. For example, the terminal may also include more or fewer components than are necessary, or have a different configuration.
The memory may be used to store a computer program, for example, a software program of application software and a module, such as a computer program corresponding to the millimeter wave imaging calibration method in the present embodiment, and the processor executes the computer program stored in the memory to perform various functional applications and data processing, that is, to realize the above-described method. The memory may include high speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid state memory. In some examples, the memory may further include memory remotely located with respect to the processor, the remote memory being connectable to the terminal through a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
The transmission device is used for receiving or transmitting data via a network. The network includes a wireless network provided by a communication provider of the terminal. In one example, the transmission device includes a network adapter (Network Interface Controller, simply referred to as NIC) that can connect to other network devices through the base station to communicate with the internet. In one example, the transmission device may be a Radio Frequency (RF) module, which is used to communicate with the internet wirelessly.
The present embodiment is described and illustrated below by way of preferred embodiments.
Fig. 4 is a schematic structural view of the millimeter wave imaging calibration apparatus of the present preferred embodiment, as shown in fig. 4, the millimeter wave imaging calibration apparatus includes: an antenna array 10, a calibration object 20 parallel to the antenna array, and a calibration module (not shown in fig. 4); forming an imaging channel between the antenna array and the calibration object; an imaging subject 30 is disposed in the imaging tunnel.
The antenna array 10 is configured to receive and transmit a step frequency signal, and acquire echo data of the imaging object 30 and the calibration object 20, so as to obtain first echo data.
The antenna array 10 includes a plurality of transmitting antennas 11 and receiving antennas 12, the transmitting antennas 11 and the receiving antennas 12 are linearly arranged, and two columns of transmitting antennas 11 and two columns of receiving antennas 12 are respectively arranged opposite to each other. The calibration object 20 is used as a calibration reference, is arranged parallel to the antenna array 10 and has a distance of 2m, and is used for reflecting the step frequency signal emitted by the antenna array 10.
In the field of security inspection, the imaging subject 30 may specifically be a person or object to be detected for reflecting the step frequency signal emitted by the antenna array 10. Also, the imaging object 30 is disposed in an imaging path formed between the antenna array 10 and the calibration object 20, the imaging object 30 and the calibration object 20 have different depths (distances) with respect to the antenna array 10, respectively, and the depth of the imaging object 30 from the antenna array 10 may be set to 0.5m.
The calibration object 20 includes a reflective region 21 and a hollow region 22, and the hollow region 22 has an area larger than the size of the imaging subject 30. Wherein the reflective area 21 is a diffuse reflective material; or, a metallic material.
The calibration module is connected with the antenna array 10, and is configured to screen out second echo data from the first echo data according to a reference position of the calibration object 20 relative to the antenna array 10, and obtain calibration parameters through matched filtering; and when the calibration parameters meet preset conditions, compensating and calibrating the first echo data according to the calibration parameters.
Specifically, the size of the calibration object 20 may be obtained by a high-precision measuring instrument such as a vernier caliper or the like. The antenna coordinate system of the XYZ axis is established with the plane of the antenna array 10, and the above reference position is the set of the coordinate systems of the antenna projected by the calibration object 20, and can be obtained by combining the alignment of the laser and the size of the calibration object 20.
According to the reference position of the calibration object 20 relative to the antenna array 10, the maximum distance and the minimum distance between the reflection point on the calibration object 20 and the antenna array 10 can be calculated to obtain the distance range between the calibration object 20 and the antenna array 10.
Because the imaging object 30 and the calibration object 20 have different distances relative to the antenna array 10, echo data reflected by the calibration object 20 is obtained by screening from the first echo data based on the distance range, is used as second echo data, and is subjected to matched filtering, so that calibration parameters are obtained. Wherein the calibration parameter is a compensation value for the phase of the transmit-receive channel.
Further, by judging the threshold of the calibration parameter, specifically, the preset condition can be established by calculating the confidence coefficient of the calibration parameter and combining with the preset threshold, and when the calibration parameter meets the preset condition, the first echo data is calibrated in real time by the obtained calibration parameter so as to compensate the inconsistent phase of the receiving and transmitting channel and reduce the influence on the imaging quality.
Further, the apparatus further includes: the judgment module and the imaging module (both not shown in fig. 4). The judging module is used for calibrating the second echo data based on the calibration parameters and obtaining the imaging of the calibration object through an imaging algorithm; calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets the preset condition by combining with the preset threshold; when the confidence coefficient is smaller than a preset threshold value, judging that the calibration parameter does not meet a preset condition; and when the confidence coefficient is larger than or equal to a preset threshold value, judging that the calibration parameter meets a preset condition.
The imaging module is used for screening and processing the calibrated first echo data to obtain third echo data according to the reference position of the imaging object relative to the antenna array; and reconstructing an image of the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
The device provided in the preferred embodiment can collect echo data of an imaging object and a calibration object through the antenna array, screen and obtain echo data reflected by the calibration object according to the reference position of the calibration object relative to the antenna array, further calculate calibration parameters and use the calibration parameters in imaging calibration, acquire the calibration parameters in real time and compensate for inconsistent phases of the receiving and transmitting channels, reduce the influence of phase fluctuation of the receiving and transmitting channels on imaging, and solve the problem that the consistency of the receiving and transmitting channels cannot be calibrated in real time, resulting in poor imaging quality.
Through the hollow structure of the calibration object in the embodiment, interference of echo reflected between the calibration object and the imaging object for multiple times can be reduced, and echo data reflected by the calibration object and the imaging object can be better distinguished only through reflection areas at the edges of the calibration object.
Fig. 5 is a flowchart of a millimeter wave imaging calibration method of the present preferred embodiment, and as shown in fig. 5, the method is applied to the above preferred millimeter wave imaging calibration device, and specifically includes the following steps:
step S510, collecting echo data reflected by the imaging object and the calibration object through a receiving and transmitting channel of the antenna array as a first echo signal.
Step S520, according to the distance and the size of the calibration object relative to the antenna array, the distance range between the calibration object and the antenna array is obtained, and the second echo data reflected by the calibration object is obtained by screening from the first echo data based on the distance range.
Step S530, obtaining calibration parameters by carrying out matched filtering on the second echo data; and calibrating the second echo data based on the calibration parameters, and obtaining the imaging of the calibration object through an imaging algorithm.
Step S540, calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets the preset condition by combining with the preset threshold.
Step S550, when the calibration parameters do not meet the preset conditions, the second echo data is obtained by re-screening the first echo data by adjusting the reference position of the calibration object relative to the antenna array, and the calibration parameters are obtained by matched filtering.
Step S560, when the calibration parameters meet the preset conditions, compensating and calibrating the first echo data according to the calibration parameters, and screening and processing to obtain third echo data reflected by the imaging object according to the reference position of the imaging object relative to the antenna array; and reconstructing an image of the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
It should be noted that the steps illustrated in the above-described flow or flow diagrams of the figures may be performed in a computer system, such as a set of computer-executable instructions, and that, although a logical order is illustrated in the flow diagrams, in some cases, the steps illustrated or described may be performed in an order other than that illustrated herein. For example, step S550 and step S560 are performed accordingly according to whether the calibration parameters satisfy the preset conditions, respectively, without distinguishing the sequence.
According to the method provided by the preferred embodiment, the echo data of the imaging object and the calibration object can be acquired through the antenna array, the echo data reflected by the calibration object is obtained through screening according to the reference position of the calibration object relative to the antenna array, and the calibration parameters are further calculated and used in imaging calibration.
Further, by imaging the calibration object, calculating the confidence coefficient of the calibration parameter with the size of the calibration object, and judging the confidence coefficient of the calibration parameter, the non-conforming calibration parameter is corrected on line, so that the accuracy of the calibration parameter is improved, and better imaging is realized subsequently.
There is also provided in this embodiment a computer device comprising a memory in which a computer program is stored and a processor arranged to run the computer program to perform the steps of any of the method embodiments described above.
Optionally, the computer device may further include a transmission device and an input/output device, where the transmission device is connected to the processor, and the input/output device is connected to the processor.
It should be noted that, specific examples in this embodiment may refer to examples described in the foregoing embodiments and alternative implementations, and are not described in detail in this embodiment.
In addition, in combination with the millimeter wave imaging calibration method provided in the above embodiment, a storage medium may be provided in the present embodiment. The storage medium has a computer program stored thereon; the computer program, when executed by a processor, implements any one of the millimeter wave imaging calibration methods of the above embodiments.
It should be noted that, user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, presented data, etc.) referred to in the present application are information and data authorized by the user or sufficiently authorized by each party.
It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to be limiting. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present application, are within the scope of the present application in light of the embodiments provided herein.
It is evident that the drawings are only examples or embodiments of the present application, from which the present application can also be adapted to other similar situations by a person skilled in the art without the inventive effort. In addition, it should be appreciated that while the development effort might be complex and lengthy, it would nevertheless be a routine undertaking of design, fabrication, or manufacture for those of ordinary skill having the benefit of this disclosure, and thus should not be construed as an admission of insufficient detail.
The term "embodiment" in this application means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive. It will be clear or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.
The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the patent. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application shall be subject to the appended claims.
Claims (11)
1. A millimeter wave imaging calibration method, which is characterized by being applied to a millimeter wave imaging calibration device, wherein the millimeter wave imaging calibration device comprises an antenna array and a calibration object parallel to the antenna array, and an imaging channel is formed between the antenna array and the calibration object; an imaging object is arranged in the imaging channel; the method comprises the following steps:
Receiving and transmitting a step frequency signal through the antenna array, and acquiring echo data of the imaging object and the calibration object to obtain first echo data;
screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering;
and when the calibration parameters meet preset conditions, performing compensation calibration on the first echo data according to the calibration parameters.
2. The millimeter wave imaging calibration method according to claim 1, wherein the step frequency signal is received and transmitted by the antenna array, echo data of the imaging object and the calibration object are acquired, and first echo data is obtained, including:
collecting echo data reflected by the imaging object and the calibration object through a receiving and transmitting channel of the antenna array to serve as the first echo signal; the first echo data are echo data of the imaging object and the calibration object of each receiving and transmitting channel at each frequency point.
3. The millimeter wave imaging calibration method according to claim 1, wherein the step of obtaining second echo data from the first echo data by filtering according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters by matched filtering includes:
Acquiring a distance range between the calibration object and the antenna array according to a reference position of the calibration object relative to the antenna array;
screening the second echo data reflected by the calibration object from the first echo data based on the distance range;
and establishing a matched filtering model according to the reflection area of the calibration object and the reference position, carrying out matched filtering on the second echo data, and solving to obtain the calibration parameters.
4. The millimeter wave imaging calibration method of claim 1, further comprising:
calibrating the second echo data based on the calibration parameters, and obtaining a calibration object image through an imaging algorithm;
calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets a preset condition or not by combining a preset threshold;
when the confidence coefficient is smaller than the preset threshold value, the calibration parameter does not meet the preset condition;
and when the confidence coefficient is larger than or equal to the preset threshold value, the calibration parameter meets the preset condition.
5. The millimeter wave imaging calibration method of claim 4, further comprising:
And when the calibration parameters do not meet the preset conditions, the reference position of the calibration object relative to the antenna array is adjusted, second echo data are screened from the first echo data again, and the calibration parameters are obtained through matched filtering.
6. The millimeter wave imaging calibration method of claim 1, further comprising:
according to the reference position of the imaging object relative to the antenna array, third echo data are obtained through screening and processing from the calibrated first echo data;
and reconstructing and imaging the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
7. A millimeter wave imaging calibration apparatus, comprising: the antenna array, the calibration object parallel to the antenna array and the calibration module; forming an imaging channel between the antenna array and the calibration object; an imaging object is arranged in the imaging channel;
the antenna array is used for receiving and transmitting step frequency signals, and acquiring echo data of the imaging object and the calibration object to obtain first echo data;
the imaging object and the calibration object are used for reflecting the step frequency signals emitted by the antenna array;
The calibration module is used for screening the first echo data to obtain second echo data according to the reference position of the calibration object relative to the antenna array, and obtaining calibration parameters through matched filtering;
and when the calibration parameters meet preset conditions, performing compensation calibration on the first echo data according to the calibration parameters.
8. The millimeter wave imaging calibration device of claim 7, wherein the calibration object comprises a reflective region and a hollow region, and wherein the hollow region has an area that is greater than a size of the imaging subject;
the reflecting area is made of diffuse reflecting material; or, a metallic material.
9. The millimeter wave imaging calibration device of claim 7, further comprising: the device comprises a judging module and an imaging module;
the judging module is used for calibrating the second echo data based on the calibration parameters and obtaining calibration object imaging through an imaging algorithm;
calculating the confidence coefficient of the calibration parameter based on the error between the imaging size of the calibration object and the size of the calibration object, and judging whether the calibration parameter meets a preset condition or not by combining a preset threshold;
when the confidence coefficient is smaller than the preset threshold value, judging that the calibration parameter does not meet the preset condition; when the confidence coefficient is larger than or equal to the preset threshold value, judging that the calibration parameter meets the preset condition;
The imaging module is used for screening and processing the calibrated first echo data to obtain third echo data according to the reference position of the imaging object relative to the antenna array;
and reconstructing and imaging the third echo data based on a back propagation algorithm to obtain an image of the imaging object.
10. A computer device comprising a memory and a processor, wherein the memory has stored therein a computer program, the processor being arranged to run the computer program to perform the millimetre wave imaging calibration method of any of claims 1 to 6.
11. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the millimetre wave imaging calibration method of any one of claims 1 to 6.
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| CN117388834B (en) * | 2023-12-12 | 2024-03-15 | 深圳英美达医疗技术有限公司 | Echo calibration method, calibration structure, device, equipment and storage medium |
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