阅读说明：本技术 一种三维目标成像方法及装置 (Three-dimensional target imaging method and device ) 是由 陈硕 常超 庾韬颖 王睿星 黄崟东 张鹏程 于 2019-09-19 设计创作，主要内容包括：本发明实施例公开了一种三维目标成像方法及装置,方法包括：对三维回波信号矩阵进行傅里叶变换,得到空间域回波向量；对参考信号矩阵进行傅里叶变换,得到空间域参考信号矩阵；提取二维成像平面各分区的有脉冲响应的回波向量,并构造与有脉冲响应的回波向量对应的参考信号矩阵；对二维成像平面各分区进行成像后,进行三维目标成像。本发明采用傅里叶变换方法得到空间域回波向量。进一步提取空间域回波向量中的有脉冲响应的空间域回波向量,剔除噪声,提高了信噪比。此外,二维成像平面区域的划分,使得二维成像平面各区域并行独立成像,减小了参考信号矩阵规模,提高了计算能力和计算精度。(The embodiment of the invention discloses a three-dimensional target imaging method and a device, wherein the method comprises the following steps: performing Fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector; performing Fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix; extracting echo vectors with impulse response of each partition of the two-dimensional imaging plane, and constructing a reference signal matrix corresponding to the echo vectors with the impulse response; and imaging each subarea of the two-dimensional imaging plane, and then carrying out three-dimensional target imaging. The invention adopts a Fourier transform method to obtain the echo vector of the spatial domain. And further extracting the space domain echo vector with the impulse response in the space domain echo vector, eliminating noise and improving the signal-to-noise ratio. In addition, due to the division of the two-dimensional imaging plane areas, all the areas of the two-dimensional imaging plane are independently imaged in parallel, the scale of a reference signal matrix is reduced, and the calculation capacity and the calculation precision are improved.)

1. A method of imaging a three-dimensional object, comprising:

performing Fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector;

performing Fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix;

extracting echo vectors with impulse response of each partition of the two-dimensional imaging plane based on the echo vectors in the spatial domain, and constructing a reference signal matrix corresponding to the echo vectors with impulse response based on the reference signal matrix in the spatial domain;

and imaging each subarea of the two-dimensional imaging plane according to the echo vector with the impulse response and the reference signal matrix corresponding to the echo vector with the impulse response, and imaging the three-dimensional target according to the imaging of each subarea of the two-dimensional imaging plane.

2. The method of claim 1, wherein before performing the fourier transform on the three-dimensional echo signal matrix to obtain the spatial-domain echo vector, the method further comprises:

determining an echo signal according to the radiation field signal and the three-dimensional target;

performing frequency mixing processing on the echo signal and a local oscillator signal inside the terahertz aperture coding transceiving antenna to obtain a baseband echo signal;

sampling the baseband echo signal to obtain a sampled baseband echo signal;

and constructing a three-dimensional echo signal matrix according to the sampled baseband echo signals.

3. The three-dimensional target imaging method according to claim 1, wherein the fourier transform is performed on the three-dimensional echo signal matrix to obtain a spatial domain echo vector, and specifically comprises:

performing Fourier transform on the third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile;

fourier transformation is respectively carried out on the second dimension and the first dimension of the three-dimensional echo signal matrix to obtain an azimuth imaging result and a pitching imaging result;

and obtaining a spatial domain echo vector according to the one-dimensional range image, the azimuth imaging result and the elevation imaging result.

4. The three-dimensional target imaging method according to claim 1, wherein the constructing a reference signal matrix corresponding to an echo vector having an impulse response based on the spatial domain reference signal matrix specifically comprises:

and extracting the row vector of the spatial domain reference signal matrix according to the extracted row coordinate position of the echo vector with the impulse response of each partition of the two-dimensional imaging plane in the total echo vector to obtain a reference signal matrix corresponding to the echo vector with the impulse response.

5. The three-dimensional target imaging method according to claim 1, wherein the imaging of each partition of the two-dimensional imaging plane specifically comprises:

one of the two-dimensional planes of the named three-dimensional object is partitioned into xa, where xa ∈ { x1, x2, x3, x4},

using the model:

Sr″_xa＝S″_xaβ_xa+w″_xa

parallel independent imaging is carried out on each subarea of the two-dimensional imaging plane; wherein, the two-dimensional imaging plane is divided into xa, xa epsilon { x1, x2, x3, x4}, Sr ″)_xa、S″_xa、β_xaAnd w ″)_xaRespectively corresponding echo vectors, reference signal matrixes, target scattering coefficient vectors and noise vectors of the two-dimensional imaging plane subareas xa; n is a radical of_xaEcho vector length, K, for two-dimensional imaging plane partition xa_xaThe number of split grid cells for two-dimensional imaging plane partition xa.

6. The three-dimensional target imaging method according to claim 1, wherein the three-dimensional target imaging according to the imaging of each partition of the two-dimensional imaging plane specifically comprises:

and (3) according to the imaging of each partition of the two-dimensional imaging plane, performing three-dimensional target imaging by adopting a compressed sensing algorithm.

7. A three-dimensional object imaging apparatus, comprising: the device comprises a vector obtaining module, a matrix obtaining module, an extraction and construction module and an imaging and synthesis module;

the vector obtaining module is used for carrying out Fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector;

the matrix obtaining module is used for carrying out Fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix;

the extraction and construction module is used for extracting echo vectors with impulse response of each partition of the two-dimensional imaging plane based on the spatial domain echo vectors and constructing a reference signal matrix corresponding to the echo vectors with impulse response based on the spatial domain reference signal matrix;

and the imaging and synthesizing module is used for imaging each subarea of the two-dimensional imaging plane according to the echo vector with the impulse response and the reference signal matrix corresponding to the echo vector with the impulse response, and imaging the three-dimensional target according to the imaging of each subarea of the two-dimensional imaging plane.

8. The three-dimensional object imaging apparatus according to claim 7, wherein the vector obtaining module is specifically configured to:

performing Fourier transform on the third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile;

fourier transformation is respectively carried out on the second dimension and the first dimension of the three-dimensional echo signal matrix to obtain an azimuth imaging result and a pitching imaging result;

and obtaining a spatial domain echo vector according to the one-dimensional range image, the azimuth imaging result and the elevation imaging result.

9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor, when executing the program, implements the method of imaging a three-dimensional object as claimed in any one of claims 1 to 6.

10. A non-transitory computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method of imaging a three-dimensional object according to any one of claims 1 to 6.

Technical Field

The invention relates to the technical field of radar three-dimensional imaging, in particular to a three-dimensional target imaging method and device.

Background

With the development of society, radar high-resolution imaging plays an increasingly important role in ensuring national strategic safety and promoting national economic development.

The terahertz aperture coding imaging is used for reference from the idea of microwave correlation imaging, and the radar array in the microwave correlation imaging is replaced by real-time modulation of terahertz wave beams by the array coding aperture, so that more complex and diversified space wave modulation is realized. Compared with the traditional radar, the terahertz wave has higher frequency and shorter wavelength, so that the terahertz radar can provide larger absolute bandwidth, an aperture coding technology is combined under the condition of the same aperture antenna, the irradiation mode and the faster mode switching speed are more easily generated, the more diverse the irradiation mode, the higher the degree of freedom is, the richer the target information carried in the echo is, and the potential of utilizing the echo to perform target high-resolution imaging is higher.

However, there are two main problems with terahertz aperture coding three-dimensional imaging. On one hand, the calculation difficulty of terahertz aperture coding imaging depends on the scale size of a reference signal matrix. Compared with two-dimensional imaging, the scale of the three-dimensional imaging reference signal matrix is expanded in multiples, and higher requirements are put forward on computing power and computing precision. On the other hand, the real imaging environment has large noise, so that the conventional method is difficult to realize three-dimensional high-resolution imaging under the condition of low signal-to-noise ratio.

Disclosure of Invention

Because the existing method has the problems, the embodiment of the invention provides a three-dimensional target imaging method and a three-dimensional target imaging device.

In a first aspect, an embodiment of the present invention provides a three-dimensional target imaging method, including:

performing Fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector;

performing Fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix;

extracting echo vectors with impulse response of each partition of the two-dimensional imaging plane based on the echo vectors in the spatial domain, and constructing a reference signal matrix corresponding to the echo vectors with impulse response based on the reference signal matrix in the spatial domain;

and imaging each subarea of the two-dimensional imaging plane according to the echo vector with the impulse response and the reference signal matrix corresponding to the echo vector with the impulse response, and imaging the three-dimensional target according to the imaging of each subarea of the two-dimensional imaging plane.

Optionally, before performing fourier transform on the three-dimensional echo signal matrix to obtain the spatial domain echo vector, the three-dimensional target imaging method further includes:

determining an echo signal according to the radiation field signal and the three-dimensional target;

performing frequency mixing processing on the echo signal and a local oscillator signal inside the terahertz aperture coding transceiving antenna to obtain a baseband echo signal;

sampling the baseband echo signal to obtain a sampled baseband echo signal;

and constructing a three-dimensional echo signal matrix according to the sampled baseband echo signals.

Optionally, the performing fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector specifically includes:

performing Fourier transform on the third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile;

fourier transformation is respectively carried out on the second dimension and the first dimension of the three-dimensional echo signal matrix to obtain an azimuth imaging result and a pitching imaging result;

and obtaining a spatial domain echo vector according to the one-dimensional range image, the azimuth imaging result and the elevation imaging result.

Optionally, the constructing a reference signal matrix corresponding to an echo vector with an impulse response based on the spatial domain reference signal matrix specifically includes:

and extracting the row vector of the spatial domain reference signal matrix according to the extracted row coordinate position of the echo vector with the impulse response of each partition of the two-dimensional imaging plane in the total echo vector to obtain a reference signal matrix corresponding to the echo vector with the impulse response.

Optionally, the imaging the partitions of the two-dimensional imaging plane specifically includes:

one of the two-dimensional planes of the named three-dimensional object is partitioned into xa, where xa ∈ { x1, x2, x3, x4},

using the model:

Sr″_xa＝S″_xaβ_xa+w″_xa

parallel independent imaging is carried out on each subarea of the two-dimensional imaging plane; wherein, the two-dimensional imaging plane is divided into xa, xa epsilon { x1, x2, x3, x4}, Sr ″)_xa、S″_xa、β_xaAnd w ″)_xaRespectively corresponding echo vectors, reference signal matrixes, target scattering coefficient vectors and noise vectors of the two-dimensional imaging plane subareas xa; n is a radical of_xaEcho vector length, K, for two-dimensional imaging plane partition xa_xaThe number of split grid cells for two-dimensional imaging plane partition xa.

Optionally, the imaging of the three-dimensional target according to the imaging of each partition of the two-dimensional imaging plane specifically includes:

and (3) according to the imaging of each partition of the two-dimensional imaging plane, performing three-dimensional target imaging by adopting a compressed sensing algorithm.

In a second aspect, an embodiment of the present invention further provides a three-dimensional target imaging apparatus, including: the device comprises a vector obtaining module, a matrix obtaining module, an extraction and construction module and an imaging and synthesis module;

the vector obtaining module is used for carrying out Fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector;

the matrix obtaining module is used for carrying out Fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix;

the extraction and construction module is used for extracting echo vectors with impulse response of each partition of the two-dimensional imaging plane based on the spatial domain echo vectors and constructing a reference signal matrix corresponding to the echo vectors with impulse response based on the spatial domain reference signal matrix;

and the imaging and synthesizing module is used for imaging each subarea of the two-dimensional imaging plane according to the echo vector with the impulse response and the reference signal matrix corresponding to the echo vector with the impulse response, and imaging the three-dimensional target according to the imaging of each subarea of the two-dimensional imaging plane.

Optionally, the vector obtaining module is specifically configured to:

performing Fourier transform on the third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile;

fourier transformation is respectively carried out on the second dimension and the first dimension of the three-dimensional echo signal matrix to obtain an azimuth imaging result and a pitching imaging result;

and obtaining a spatial domain echo vector according to the one-dimensional range image, the azimuth imaging result and the elevation imaging result.

In a third aspect, an embodiment of the present invention further provides an electronic device, including:

at least one processor; and

at least one memory communicatively coupled to the processor, wherein:

the memory stores program instructions executable by the processor, which when called by the processor are capable of performing the above-described methods.

In a fourth aspect, an embodiment of the present invention further provides a non-transitory computer-readable storage medium storing a computer program, which causes the computer to execute the above method.

According to the technical scheme, the spatial domain echo vector is obtained through a Fourier transform method. And further extracting the space domain echo vector with the impulse response in the space domain echo vectors, and rejecting the space domain echo vector without the impulse response, namely rejecting noise, so that the signal-to-noise ratio is improved. In addition, due to the division of the two-dimensional imaging plane areas, all the areas of the two-dimensional imaging plane are independently imaged in parallel, the scale of a reference signal matrix is reduced, and the calculation capacity and the calculation precision are improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic diagram of imaging of a terahertz aperture coding three-dimensional target based on fourier transform according to an embodiment of the present invention;

fig. 2 is a schematic flowchart of a three-dimensional target imaging method according to an embodiment of the present invention;

fig. 3 is a schematic diagram of spatial domain echo vector extraction and reference signal matrix construction based on fourier transform according to an embodiment of the present invention;

FIGS. 4(a) - (i) are schematic diagrams illustrating comparison of imaging results at different signal-to-noise ratios, respectively, according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a three-dimensional target imaging apparatus according to an embodiment of the present invention;

fig. 6 is a logic block diagram of an electronic device according to an embodiment of the present invention.

Detailed Description

The following further describes embodiments of the present invention with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

At present, the idea of microwave correlation imaging is used for reference in aperture coding imaging, terahertz wave beams are coded and modulated in real time through array coding apertures, so that a time-space two-dimensional randomly distributed radiation field is formed, and finally high-resolution, forward-looking and staring imaging is realized by utilizing a detection echo and radiation field reference signal matrix through a matrix equation solving mode, so that the defect that synthetic aperture high-resolution imaging depends on target motion is overcome. However, the aperture coding three-dimensional imaging has two problems of high computational complexity and low signal-to-noise ratio: (1) the three-dimensional imaging grid resolution unit has large scale, the combined reconstruction calculation burden is heavy, and the conventional calculation power is difficult to solve; (2) the actual imaging signal is weak, the noise is prominent, and the reconstruction precision of the three-dimensional target is low under the low signal-to-noise ratio. Therefore, the invention provides a three-dimensional imaging method, as shown in fig. 1, a schematic diagram of terahertz aperture coding three-dimensional imaging based on fourier transform is shown, in the diagram, capital letters a-F respectively calculate a control system, a multi-transmission multi-reception array aperture coding transceiver antenna, a transceiver array element, a transmitting signal, an echo signal and a three-dimensional imaging region, an x axis is an axis passing through a central bisector of a coding aperture in a horizontal direction, a y axis is an axis passing through a central bisector of a coding aperture in a vertical direction, a coordinate center o is at a central position of the coding aperture, and a z axis is an axis passing through centers of the terahertz transmitter antenna and the array aperture coding antenna. For the sake of image, the three-dimensional imaging region is represented as 1 and 2 two imaging planes, each imaging plane is divided into four plane partitions, and the three-dimensional imaging in practical application is not limited to two imaging planes and four plane partitions. In the terahertz aperture coding imaging system, a terahertz time-domain echo signal is processed to obtain a one-dimensional range profile, a range domain echo with target scattering is extracted, the core of the terahertz aperture coding imaging system is that a Fourier transform method is adopted to project the echo onto a two-dimensional imaging plane slice of a corresponding range unit, then a space domain echo corresponding to each partition is extracted according to the scattering condition of a plane target, finally algorithms such as compressed sensing and the like are adopted to reconstruct the target, and finally each plane partition is combined to obtain a three-dimensional high-resolution imaging result. The invention can realize high frame frequency and high resolution imaging of the three-dimensional target under the condition of low signal to noise ratio, and can be applied to the near-distance imaging fields of security inspection, anti-terrorism, target detection and identification and the like.

In the embodiment of the invention, different from a traditional aperture coding imaging system, each array element of the array aperture coding antenna of the FT-TCAI is a receiving and transmitting body, and not only signals are transmitted, but also echoes are received. The array elements of different gray levels represent random amplitude or phase modulation of the echo signal at the receiving end. And the computing control system controls each transmitting-receiving array element to sequentially and independently irradiate the three-dimensional target, so that each transmitting-receiving array element can be regarded as a single-station radar antenna. In order to realize high-resolution imaging, the traditional aperture coding imaging system tries to form space-time independent random radiation fields in an imaging area, but the randomness of the radiation fields can reduce the radar range. The aperture coding imaging system based on Fourier transform only modulates the echo randomly during receiving detection, and the radar action distance is not influenced.

It should be noted that, in the embodiment of the present invention, the terahertz aperture coding imaging based on fourier transform is uniformly abbreviated as FT-TCAI; uniformly abbreviating the terahertz aperture coding three-dimensional imaging based on the distance domain slice as RD-TCAI; the terahertz aperture coding three-dimensional imaging based on the time domain echo is uniformly abbreviated as TD-TCAI.

Fig. 2 shows a schematic flowchart of a three-dimensional target imaging method provided in this embodiment, including:

and S21, carrying out Fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector.

And the three-dimensional echo signal matrix is an echo signal obtained by processing the sampled baseband echo signal.

And the spatial domain echo vector is an echo signal of a spatial domain obtained after Fourier transform is carried out on the three-dimensional echo signal matrix. Specifically, when a three-dimensional target is imaged, after a three-dimensional echo signal matrix is obtained, in order to obtain a spatial domain echo vector, fourier transform is performed on a third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile, fourier transform is performed on a second dimension and a first dimension of the three-dimensional echo signal matrix respectively to obtain an azimuth imaging result and a pitch imaging result, that is, a spatial projection result is obtained. The space projection result is the space domain echo vector.

And S22, carrying out Fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix.

Wherein, a reference signal matrix can be determined according to the reference signals, and each dimension of the reference signal matrix represents one reference signal. And then projecting the reference signal matrix to a spatial domain, namely performing Fourier transform on the reference signal matrix to obtain the spatial domain reference signal matrix.

And S23, extracting echo vectors with impulse response of each partition of the two-dimensional imaging plane based on the spatial domain echo vectors, and constructing a reference signal matrix corresponding to the echo vectors with impulse response based on the spatial domain reference signal matrix.

And the spatial domain echo vector is a spatial projection result obtained after Fourier change is carried out on the three-dimensional echo signal matrix. The two-dimensional imaging plane is shown as F in fig. 1. In the embodiment of the invention, the echo vector with the impulse response of each partition of the two-dimensional imaging plane is extracted, and the echo vector without the impulse response is removed, namely, the noise is removed, so that the signal-to-noise ratio is improved. And then constructing a spatial domain reference signal matrix corresponding to the echo vector with the impulse response, reducing the scale of the reference signal matrix, and improving the calculation capacity and the calculation precision.

And S24, imaging each subarea of the two-dimensional imaging plane according to the echo vector with the impulse response and the reference signal matrix corresponding to the echo vector with the impulse response, and imaging the three-dimensional target according to the imaging of each subarea of the two-dimensional imaging plane.

In the embodiment of the present invention, specifically, under the condition that the spatial domain echo vector and the spatial domain reference signal matrix are known, each partition of the two-dimensional imaging plane can be imaged independently in parallel. Each two-dimensional imaging plane is divided into four regions as shown in fig. 1. It should be noted that the partitions divided by the two-dimensional imaging plane include, but are not limited to, four partitions. On the basis that each partition of the two-dimensional imaging plane is imaged, a three-dimensional target can be imaged by utilizing a compressed sensing algorithm such as an orthogonal matching tracking method, a sparse Bayesian learning method and the like.

According to the embodiment of the invention, the space domain echo vector is obtained by a Fourier transform method. And further extracting the space domain echo vector with the impulse response in the space domain echo vectors, and rejecting the space domain echo vector without the impulse response, namely rejecting noise, so that the signal-to-noise ratio is improved. In addition, due to the division of the two-dimensional imaging plane areas, all the areas of the two-dimensional imaging plane are independently imaged in parallel, the scale of a reference signal matrix is reduced, and the calculation capacity and the calculation precision are improved.

Further, on the basis of the foregoing method embodiment, before S21, the method further includes: determining an echo signal according to the radiation field signal and the three-dimensional target; performing frequency mixing processing on the echo signal and a local oscillator signal inside the terahertz aperture coding transceiving antenna to obtain a baseband echo signal; sampling the baseband echo signal to obtain a sampled baseband echo signal; and constructing a three-dimensional echo signal matrix according to the sampled baseband echo signals. Wherein the echo signal is a signal returned after the radiation field signal reaches the three-dimensional target. Specifically, a transmitting and receiving array element in the terahertz aperture coding transmitting and receiving antenna transmits a chirp signal, which is shown as follows:

s_t(t)＝exp[j2πf·t]

f＝f₀+0.5 gamma t is the signal frequency, f₀And γ is the signal center frequency and the tuning frequency, respectively.

The local oscillation signal is in the form of a linear frequency modulation signal and is used for carrying out frequency mixing processing on an echo signal to obtain a baseband echo signal; then, generating an echo signal after the radiation field signal is projected to a three-dimensional target; specifically, the transmit/receive array element in the P-th row and Q-th column is represented by (P, Q), where P is 1,2, …, and P, Q is 1,2, …, Q. The radiation field signals from the transmitting array element (p, q) to the k grid unit are:

s_rad(t,k,p,q)＝exp[j(2πf·(t-t_p,q,k))]

after the radiation field signal and the three-dimensional target act, the echo signal returning to the transmitting and receiving array element (p, q) is in the form of:

is the phase modulation term of the transmitting and receiving array element (p, q) at the time t. Because the coding array elements are transmitted and received integrally, the total signal time delay is 2t_p,q,k。

And (3) performing frequency mixing processing on the echo signal and the local oscillator signal to obtain a baseband echo signal:

and directly sampling the baseband echo signals to obtain the sampled baseband echo signals of all the transmitting and receiving array elements.

According to the embodiment of the invention, the echo signal and the local oscillator signal are subjected to frequency mixing processing to obtain a baseband echo signal, and then the baseband echo signal is sampled to obtain a sampled baseband echo signal for constructing a subsequent three-dimensional echo signal matrix. Specifically, sample t_nThe base band echo signal of the moment is obtained to obtain sr_base(p,q,t_n)：

By sr_base(t_nP, q) constructing a three-dimensional echo signal matrix

SR_3D＝[sr_base(p,q,t_n)],p＝1,2,…,P,q＝1,2,…,Q,n＝1,2,…,N

Three-dimensional matrix SR_3DThe first two dimensions of the array are respectively corresponding to the receiving and transmitting array elements in the azimuth direction and the pitching direction, and the third dimension of the array is corresponding to time sampling.

According to the embodiment of the invention, the frequency mixing processing is carried out on the echo signal and the local oscillator signal to obtain the baseband echo signal, so that the frequency of the echo signal is reduced, and the receiving end of the terahertz aperture coding transceiving antenna can receive the echo signal.

Further, on the basis of the above method embodiment, the performing fourier transform on the three-dimensional echo signal matrix to obtain a spatial domain echo vector specifically includes: performing Fourier transform on the third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile; fourier transformation is respectively carried out on the second dimension and the first dimension of the three-dimensional echo signal matrix to obtain an azimuth imaging result and a pitching imaging result; according to the one-dimensional range image and the azimuth directionAnd obtaining a spatial domain echo vector according to the imaging result and the pitching imaging result. In particular, a three-dimensional echo signal matrix SR_3DThe first two dimensions of the array are respectively corresponding to the receiving and transmitting array elements in the azimuth direction and the pitching direction, and the third dimension of the array is corresponding to time sampling. And carrying out Fourier transform on each dimension of the three-dimensional echo signal matrix to obtain a space projection result. The space projection result is the space domain echo vector. Specifically, the principle of three-dimensional imaging is realized by three-dimensional fourier transform, and the spatial projection of a three-dimensional region is:

β_3D＝ftx(fty(ftz(SR_3D)))

wherein ftx (-), fty (-), and ftz (-), represent Fourier transforms on the first, second, and three dimensions of the three-dimensional matrix, respectively. First to SR_3DThe third dimension of the time domain echo is subjected to Fourier transform to obtain a one-dimensional range image, namely the time domain echo can be projected to a range domain. Then to the matrix SR_3DThe second dimension and the first dimension are subjected to Fourier transform, so that an azimuth imaging result and a pitching imaging result can be obtained, namely a space projection result is obtained, and a main region containing target scattering information can be detected.

From the coarse imaging result beta_3DIs provided withIs beta_3DCoarse imaging result of the middle corresponding plane partition xa, then the space domain echo vectorThe form is as follows:

Sr″_xa＝[Sr″_xa(1),Sr″_xa(2),…,Sr″_xa(N_xa)]^T

wherein N is_xaIs a plane subarea xa, Sr_xa(1),Sr″_xa(2),…,Sr″_xa(N_xa) From beta_3DDirectly extracting.

According to the embodiment of the invention, the three dimensions of the three-dimensional echo signal matrix are respectively subjected to Fourier transform to obtain a space projection result, namely a space domain echo vector.

Further, on the basis of the above method embodiment, fourier transform is performed on the reference signal matrix to obtain a spatial domain reference signal matrix. Specifically, it corresponds to the transmitting/receiving array element (p, q), kx_aA grid cell at t_nThe reference signals at the time are:

the kx (th)_aThe three-dimensional reference signal matrix corresponding to each grid unit is in the form of

S_3D(kx_a)＝[S(p,q,t_n,k_xa)],p＝1,2,…,P,q＝1,2,…,Q,n＝1,2,…,N

Matrix three-dimensional reference signalsProjection into the spatial domain:

β_3D(kx_a)＝ftx(fty(ftz(S_3D(kx_a))))

from beta_3D(kx_a) The spatial domain reference signal matrix S ″' can be extracted_xaThe kx (th)_aColumn vector S ″_xa(kx_a). Spatial domain reference signal matrix S' corresponding to planar subarea xa_xaThe form is as follows:

S″_xa(k_xa)＝[S″_xa(1,k_xa),S″_xa(2,k_xa),...,S″_xa(N_xa,k_xa)]^T

further, on the basis of the above method embodiment, the constructing a reference signal matrix corresponding to an echo vector having an impulse response based on the spatial domain reference signal matrix specifically includes: and extracting the row vector of the spatial domain reference signal matrix according to the extracted row coordinate position of the echo vector with the impulse response of each partition of the two-dimensional imaging plane in the total echo vector to obtain a reference signal matrix corresponding to the echo vector with the impulse response. Specifically, as shown in FIG. 3, Sr ″, is known_xAnd S ″)_xIndividual watchShowing the spatial domain echo vector and the spatial domain reference signal matrix after Fourier transformation. Each two-dimensional imaging plane in fig. 1 contains four regions, each region numbered x1, x2, x3, and x 4. From Sr_xFour groups of space domain echo vectors corresponding to each partition are extracted: sr_x1，Sr″_x2，Sr″_x3And Sr_x4As shown in fig. 3. Due to the scattering effect of the target, four groups of space domain echo vectors are gathered together in the form of impulse response. In the actual imaging process, more than four plane partitions need to be simply and conveniently divided according to the actual scattering condition and calculation. In addition, four sets of spatial domain echo vectors Sr ″' are labeled_x1，Sr″_x2，Sr″_x3And Sr_x4In the total echo vector Sr ″)_xThe row coordinate position in is r_x1，r_x2，r_x3And r_x4According to the above r_x1，r_x2，r_x3And r_x4And extracting the row vector of the spatial domain reference signal matrix to obtain a reference signal matrix corresponding to the echo vector with the impulse response.

According to the embodiment of the invention, the reference signal matrix corresponding to the echo vector with the impulse response in each partition of the two-dimensional imaging plane is constructed, so that the scale of the reference signal matrix is reduced, and the calculation capacity and the calculation precision are improved.

Further, on the basis of the above method embodiment, the imaging the partitions of the two-dimensional imaging plane specifically includes:

one of the two-dimensional planes of the named three-dimensional object is partitioned into xa, where xa ∈ { x1, x2, x3, x4},

using the model:

Sr″_xa＝S″_xaβ_xa+w″_xa

parallel independent imaging is carried out on each subarea of the two-dimensional imaging plane; wherein, the two-dimensional imaging plane is divided into xa, xa epsilon { x1, x2, x3, x4}, Sr ″)_xa、S″_xa、β_xaAnd w ″)_xaThe echo vector, the reference signal matrix, the target scattering coefficient vector and the noise vector which correspond to the two-dimensional imaging plane subarea xa are respectively. N is a radical of_xaEcho vector length, K, for two-dimensional imaging plane partition xa_xaThe number of split grid cells for two-dimensional imaging plane partition xa.

According to the embodiment of the invention, the imaging speed is improved by independently imaging each subarea of the two-dimensional imaging plane in parallel.

Further, on the basis of the above method embodiment, the imaging of the three-dimensional target according to the imaging of each partition of the two-dimensional imaging plane specifically includes:

according to the imaging of each subarea of the two-dimensional imaging plane, the beta is solved by utilizing a compressed sensing algorithm such as an orthogonal matching tracking method, a sparse Bayesian learning method and the like_xaNamely, the three-dimensional target imaging result is obtained.

The embodiment of the invention performs three-dimensional target imaging on the basis of the imaged subareas of the two-dimensional imaging plane, thereby improving the imaging speed of the synthetic three-dimensional target.

Further, on the basis of the above method embodiment, a specific process of the terahertz aperture coding three-dimensional imaging in the embodiment of the present invention is illustrated. The specific process is as follows:

the coded aperture antenna array adopting the multiple-transmission multiple-reception terahertz aperture coding imaging system shown in fig. 1 has the scale of 50 × 50 and the size of 0.5 × 0.5 m; the two-dimensional imaging plane is divided into 60 multiplied by 60 grids, each two-dimensional imaging plane comprises four evenly divided plane partitions, the number of the plane partition grid units is 30 multiplied by 30, and the size of a single grid unit is 2.5mm multiplied by 2.5 mm; the bandwidth of the terahertz signal is 20GHz, the carrier frequency is 340GHz, and the pulse width is 100 ns; imaging targets are placed on two-dimensional planes at distances of 1.5m and 3m, respectively. The method comprises the steps of respectively adopting a terahertz aperture coding three-dimensional imaging method (FT-TCAI) based on Fourier transform, a terahertz aperture coding three-dimensional imaging method (TD-TCAI) based on time domain echo and a terahertz aperture coding three-dimensional imaging method (RD-TCAI) based on distance domain slicing to carry out simulation imaging comparison under different signal-to-noise ratios, wherein the imaging result is shown in figure 4, and a sparse Bayesian learning method is adopted as a reconstruction algorithm. FIGS. 4(a-c) are the results of imaging with TD-TCAI at 30dB, 0dB, and-30 dB signal-to-noise ratios, respectively; FIG. 4(d-f) is the imaging results of RD-TCAI at different signal-to-noise ratios; FIG. 4(g-i) is the imaging results of FT-TCAI at different signal-to-noise ratios. When the SNR is 30dB, all three TCAI methods can reconstruct a three-dimensional object as in fig. 4(a), (d), and (g). When the SNR is 0dB, as shown in fig. 4(b), (e) and (h), although the three TCAI methods can reconstruct the target accurately, the reconstruction result of TD-TCAI has much grain noise. The main imaging contrast is shown in fig. 4(c), (f) and (i), when the SNR is-30 dB, TD-TCAI reconstruction fails, and FT-TCAI still maintains good imaging performance, and pseudo-scattering information exists in the imaging result of RD-TCAI. In addition, the sampling time and the number of grid units are the same, and the sizes of the reference signal matrixes of TD-TCAI, RD-TCAI and FT-TCAI are 7200 multiplied by 7200, 3600 multiplied by 3600 and 900 multiplied by 900 respectively, so that the computational complexity from TD-TCAI to RD-TCAI and then to FT-TCAI is gradually reduced.

Fig. 5 shows a schematic structural diagram of a three-dimensional target imaging device provided by the embodiment, and the device comprises: a vector obtaining module 50, a matrix obtaining module 51, an extraction and construction module 52 and an imaging and synthesis module 53;

the vector obtaining module 50 is configured to perform fourier transform on each dimension of the three-dimensional echo signal matrix to obtain a spatial domain echo vector;

the matrix obtaining module 51 is configured to perform fourier transform on the reference signal matrix to obtain a spatial domain reference signal matrix;

the extracting and constructing module 52 is configured to extract echo vectors with impulse responses of each partition of the two-dimensional imaging plane based on the spatial domain echo vectors, and construct a reference signal matrix corresponding to the echo vector with impulse responses based on the spatial domain reference signal matrix;

the imaging and synthesizing module 53 is configured to image each partition of the two-dimensional imaging plane according to the echo vector with the impulse response and the reference signal matrix corresponding to the echo vector with the impulse response, and perform three-dimensional target imaging according to the imaging of each partition of the two-dimensional imaging plane.

Optionally, the vector obtaining module is specifically configured to:

performing Fourier transform on the third dimension of the three-dimensional echo signal matrix to obtain a one-dimensional range profile;

fourier transformation is respectively carried out on the second dimension and the first dimension of the three-dimensional echo signal matrix to obtain an azimuth imaging result and a pitching imaging result;

and obtaining a spatial domain echo vector according to the one-dimensional range image, the azimuth imaging result and the elevation imaging result.

The three-dimensional target imaging device according to the embodiment of the present invention may be used to implement the above method embodiments, and the principle and technical effect are similar, which are not described herein again.

FIG. 6 is a logic block diagram of an electronic device according to an embodiment of the invention; the electronic device includes: a processor (processor)61, a memory (memory)62, and a bus 63;

wherein, the processor 61 and the memory 62 complete the communication with each other through the bus 63; the processor 61 is used for calling the program instructions in the memory 62 to execute the method provided by the above method embodiment.

An embodiment of the present invention also provides a non-transitory computer-readable storage medium storing a computer program, which causes the computer to execute the above method.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.

It should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.