Backward projection three-dimensional imaging method and system based on CZT

Abstract

The invention relates to the technical field of backward projection imaging, and provides a CZT-based backward projection three-dimensional imaging method and system, which replace a traditional FFT transformation method based on CZT, and optimize a frequency domain processing process in a backward projection algorithm on the premise that a known test target distance is concentrated in a certain range. And calculating a propagation distance from each scattering point to an equivalent channel formed by the transmitting and receiving antennas, mapping the propagation distance into a CZT frequency point index position, and rounding the CZT frequency point index position, thereby positioning the position of the signal in the frequency domain data. For phase errors caused by frequency point rounding, compensation factors are further constructed, accurate phase correction is carried out on CZT frequency domain signals, and the imaging quality reflected by each pixel point in a three-dimensional imaging image is improved. On the basis of a traditional backward projection imaging method, linear frequency modulation Z transformation is introduced to improve the imaging resolution, compensation is carried out according to a phase error caused by ID rounding, and the imaging resolution is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of back-projection imaging, in particular to a back-projection three-dimensional imaging method and system based on CZT. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] Terahertz waves are located between the infrared and microwave bands of the electromagnetic spectrum, with characteristics such as short wavelength, strong penetration, and non-ionizing radiation. They can penetrate non-metallic materials such as wood, clothing, masonry, paper, and plastic, and are harmless to biological tissues, so they are widely used in imaging, non-destructive testing, and medical diagnosis. Combining terahertz technology with synthetic aperture radar (SAR) can achieve high-resolution imaging. Further introducing multiple-input multiple-output (MIMO) technology, through the combination of M transmit waveforms and N receive channels, MxN equivalent SAR channels can be obtained, significantly improving the system's observation freedom and imaging capability, making it a hot research direction in current terahertz imaging.

[0004] Existing terahertz MIMO array imaging systems usually use the back-projection (BP) algorithm for time-domain imaging. This method first divides the target area into a three-dimensional grid. For a grid point in the grid, the fast Fourier transform is used in the distance direction to generate N-point data. Then the slant range and time delay between the transmitting antenna and each grid point are calculated. According to the slant range, the ID number of the grid point in the N-point data is found, and then the phase factor is compensated. All azimuth points are iterated for coherent accumulation. According to the penetration ability of terahertz signals and the characteristics of the system test target, the distance between the test target scattering points and the antenna is generally concentrated in a certain range, that is, the ID number is generally distributed in a limited concentrated area, and will not be evenly distributed between 0 and N-1. That is, due to the penetration characteristics of terahertz signals, the distance from the target scattering point to the antenna is concentrated in a specific range, and using FFT transformation will result in a large amount of redundant data in the N-point data, causing waste of computing resources and affecting imaging efficiency. SUMMARY

[0005] To solve the above problems, the present application proposes a back-projection three-dimensional imaging method and system based on CZT, which can be applied to terahertz MIMO array imaging systems. On the basis of the traditional back-projection imaging method, the chirp Z transform (CZT) is introduced to improve the imaging resolution, and the phase error caused by ID rounding is compensated to improve the imaging resolution.

[0006] To achieve the above object, the present application adopts the following technical solutions: One or more embodiments provide a CZT-based back-projection three-dimensional imaging method, comprising the following steps: Obtaining three-dimensional data calibrated by channel error; Dividing the target imaging area into a three-dimensional grid to obtain grid points distributed in three-dimensional space, and obtaining the coordinate position of each grid point; presetting the slant range between the target grid and the transmit-receive antenna; At each target position j, for each equivalent channel i, extracting the echo signal, performing CZT transformation on the echo signal in the frequency range corresponding to the slant range, and obtaining the CZT transformed frequency domain signal; Calculating the CZT frequency point index position corresponding to the propagation distance of the current grid point and the i-th equivalent channel and rounding it off as the signal position of the current grid point echo, and extracting the CZT transformed frequency domain signal at the corresponding signal position point; Constructing a compensation factor based on the CZT frequency point index positions before and after rounding off, and performing phase compensation on the extracted CZT transformed frequency domain signal to obtain the compensated data of the current grid point; Iterating through all target positions and equivalent channels, coherently superimposing the compensated data of each grid point to form three-dimensional imaging image data.

[0007] One or more embodiments provide a CZT-based back-projection three-dimensional imaging system, comprising: An acquisition module configured to acquire three-dimensional data calibrated by channel error; A target modeling module configured to divide the target imaging area into a three-dimensional grid to obtain grid points distributed in three-dimensional space, and obtain the coordinate position of each grid point; and preset the slant range between the target grid and the transmit-receive antenna; A CZT transformation module configured to, at each target position j, for each equivalent channel i, extract the echo signal, perform CZT transformation on the echo signal in the frequency range corresponding to the slant range, and obtain the CZT transformed frequency domain signal; An index module configured to calculate the CZT frequency point index position corresponding to the propagation distance of the current grid point and the i-th equivalent channel and round it off as the signal position of the grid point echo, and extract the CZT transformed frequency domain signal at the corresponding signal position point; A compensation module configured to construct a compensation factor based on the CZT frequency point index positions before and after rounding off, and perform phase compensation on the extracted CZT transformed frequency domain signal to obtain the compensated data of the current grid point; A superposition module configured to iterate through all target positions and equivalent channels, coherently superimpose the compensated data of each grid point to form three-dimensional imaging image data. An electronic device comprising a memory and a processor and computer instructions stored on the memory and running on the processor, when the computer instructions are run by the processor, complete the steps in the above-mentioned CZT-based back-projection three-dimensional imaging method.

[0008] A computer-readable storage medium for storing computer instructions, when the computer instructions are executed by a processor, complete the steps in the above-mentioned CZT-based back-projection three-dimensional imaging method.

[0009] Compared with the prior art, the beneficial effects of the present application are: By introducing the CZT transform, the present application significantly reduces the generation of redundant information in the frequency domain data by utilizing the characteristics of the imaging target distance range set, reduces the computational resource consumption and storage overhead compared with the FFT processing method, and improves the system operation efficiency. At the same time, for the phase error caused by the rounding processing of the CZT frequency index, the present embodiment designs a phase compensation strategy, effectively suppresses the sidelobes in the imaging result, improves the imaging contrast and accuracy, and is particularly suitable for high-resolution image construction of the terahertz MIMO imaging system. In addition, the method enhances the position sensitivity of the system to scattering points, is suitable for accurate reconstruction of complex targets, and effectively improves the spatial resolution and structure restoration ability of the imaging.

[0010] The advantages of the present application and the advantages of additional aspects will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0011] The drawings accompanying the specification of the present application form a part thereof and serve to provide further understanding of the present application, the illustrative embodiments of the present application and their description serve to explain the present application, and do not constitute limitations thereof.

[0012] Fig. 1 is a structural schematic diagram of a terahertz MIMO array imaging system of embodiment 1 of the present application; Fig. 2 is a flowchart of a CZT-based back-projection three-dimensional imaging method of embodiment 1 of the present application. DETAILED DESCRIPTION

[0013] The present application will be further described below in conjunction with the drawings and embodiments.

[0014] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0015] It is to be noted that the terms used herein are merely for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. It is to be noted that the various embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The embodiments will be described in detail below with reference to the accompanying drawings.

[0016] Embodiment 1 This embodiment is based on a terahertz MIMO array, introduces a CZT transformation in the BP method, and corrects the phase error caused by the decimal residual to form an improved BP method for three-dimensional imaging. The improved BP method is described as follows. In the technical solutions disclosed in one or more embodiments, as shown in Figs. 1-2 a CZT-based back-projection three-dimensional imaging method includes the following steps: Step 1, obtaining three-dimensional data Data[n][i][j] after channel error calibration; Step 2, performing three-dimensional grid division on the target imaging area to obtain grid points distributed in three-dimensional space, obtaining the coordinate position of each grid point; and presetting the range of the slant range between the target grid and the transceiving antenna; Step 3, at each target position j, for each equivalent channel i, extracting the echo signal Data[n][i][j], performing a CZT (Chirp Z Transform) transformation on the echo signal in the frequency range corresponding to the slant range to obtain a CZT transformed frequency domain signal; Step 4, calculating the integer of the index position (ID) of the CZT frequency point corresponding to the propagation distance of the current grid point (x, y, z) and the i-th equivalent channel, as the signal position of the grid point echo , and extracting the CZT transformed frequency domain signal at the signal position ; Step 5, constructing a compensation factor based on the index positions of the CZT frequency points before and after the integer operation, performing phase compensation on the extracted CZT transformed frequency domain signal to obtain the compensated data of the current grid point; Step 6, traversing all target positions j and equivalent channels i, coherently superimposing the compensated data of each grid point to form three-dimensional imaging image data; The embodiment is based on a CZT (Chirp Z-Transform) instead of a traditional FFT transform method, and optimizes a frequency domain processing process in a back-projection algorithm on the premise that a test target distance is concentrated in a certain range. First, a three-dimensional imaging target region is divided into grids, and the spatial coordinates of each grid point are accurately obtained. By performing a CZT transform on echo signals in a set slant distance corresponding frequency range under each equivalent channel i, effective information in a distance range of interest can be concentrated and processed, and a CZT frequency domain signal is generated. Subsequently, the propagation distance of each grid point to the equivalent channel formed by the transmitting and receiving antennas is calculated, and is mapped to a CZT frequency point index position and is rounded, so as to locate the position of the signal in the frequency domain data. In view of the phase error caused by rounding of the frequency point, a compensation factor is further constructed to accurately correct the phase of the CZT frequency domain signal, and the imaging quality reflected by each pixel point is improved. Finally, the compensation signals obtained by traversing all target positions and channels are coherently added, and a three-dimensional image is reconstructed.

[0017] By introducing the CZT transform, the embodiment significantly reduces the generation of redundant information in the frequency domain data by using the characteristic that the imaging target distance range is concentrated, reduces the calculation resource consumption and storage overhead compared with the FFT processing method, and improves the system operation efficiency. Meanwhile, in view of the phase error caused by rounding of the CZT frequency index, the embodiment designs a phase compensation strategy, effectively suppresses the sidelobe in the imaging result, improves the imaging contrast and accuracy, and is particularly suitable for high-resolution image construction of a terahertz MIMO imaging system. In addition, the method enhances the position sensitivity of the system to scattering points, is suitable for accurate reconstruction of complex targets, and effectively improves the spatial resolution and structure restoration capability of the imaging.

[0018] In step 1, three-dimensional data Data[n][i][j] after channel error calibration is obtained; Wherein, n represents the number of sampling points, n=0, 1, …N-1; i represents an equivalent channel, i=0, 1, 2, …L*G-1; j represents a target position of a moving target, j=0, 1, 2..J-1, which corresponds to the position of the target object after moving in the y-axis in the embodiment; Specifically, the embodiment is based on a terahertz MIMO array imaging system, and the spatial scanning and data acquisition of a target region are completed by combining target movement and an antenna array; As shown in Fig. 2 The terahertz MIMO array imaging system includes L transmitting antennas, G receiving antennas, and a measured target driven by a motion device to move at a constant speed in a straight line. A three-dimensional coordinate system is arranged on the plane of the antennas, and the direction is as shown in Fig. 2 ​The MIMO antenna array of the L transmitting antennas and the G receiving antennas is arranged in the X axis, and a time division multiplexing transmitting mode is adopted, that is, the transmitting antennas transmit in turn, and the G antennas simultaneously receive.

[0019] The measured target moves in the Y axis direction, and J times of position change can be regarded as J times of spatial sampling in the y direction. The transmitting and receiving antennas form L*G equivalent channels, which can be regarded as L*G times of spatial sampling in the x axis direction, which is equivalent to spatial sampling in the two-dimensional space of the x axis and the y axis. The signal source generates a linear frequency modulation (LFM) signal through a terahertz frequency doubling module to form a terahertz signal, and then transmits the terahertz wave to the target through the transmitting antenna to form a scattered signal. After the scattered signal is received by the receiving antenna, the receiver performs AD sampling on the signal. When the measured target moves along the y axis once, N points of data are collected by each equivalent channel, and finally a three-dimensional digital signal Data[n][i][j] is obtained; In step 1, the process of obtaining the three-dimensional data after channel error calibration includes the following steps: Step 11, the echo signal received by the receiving antenna and the reference signal are mixed to obtain a continuous signal by using a dechirp processing method ; When the target moves to the jth position, the terahertz signal is transmitted by the ith equivalent channel, and then the electromagnetic wave is scattered after passing through the ideal point target, and the receiving antenna receives the echo signal. The continuous signal output by mixing the echo signal and the reference signal by using a dechirp processing method is: (1); Wherein, is the frequency modulation slope; is too small and can be ignored; t represents time, is the two-way time delay, represents the starting frequency; Step 12, according to the distance from the transmitting antenna in the equivalent channel to the target and the distance from the target to the receiving antenna , the propagation time delay of the echo signal is calculated: ; Wherein, is the two-way time delay, is the distance from the transmitting antenna to the scattering point on the target object, is the distance from the receiving antenna to the scattering point on the target object, and C is the electromagnetic wave propagation speed.

[0020] In this embodiment, the scattering point is the actual physical point on the target object for signal transmission, and the grid point is the grid point obtained by dividing the target object in actual data processing, which is a name in the computer layer, and the two points can be corresponding points. Step 13, based on the set sampling interval , the continuous signal is sampled at equal intervals to obtain discrete time domain data; Set the sampling time interval Sample the continuous signal to obtain an N-point digital signal: (2); Step 14, based on the frequency modulation slope and the sampling time interval, construct the standardized parameter T, and optimize the signal model to construct the discrete time domain data signal into a standard form containing a distance-to-frequency item linearly related to the distance; Let , then the standard form of the discrete time domain data signal is: (3); In the formula of the standard form of the discrete time domain data signal, the first phase factor is a constant term, and the second term is a distance-to-frequency item linearly related to the distance, which is the basis for phase compensation and accumulation during image reconstruction.

[0021] The bandwidth of the transmitted LMF signal is , then: ; This formula establishes the relationship between the frequency modulation slope, the sampling interval, the number of sampling points, and the system resolution, which helps to design the CZT parameters and map the ID index according to the distance accuracy in the subsequent process.

[0022] Step 2, divide the target imaging area into a three-dimensional grid to obtain grid points distributed in three-dimensional space, and obtain the coordinate position of each grid point; preset the range of the slant range between the target grid and the transceiver antenna; In this embodiment, the distance between the test target and the transceiver antenna is in the range of , ; and ; represents the minimum slant range, represents the maximum slant range; Step 3, traverse in the azimuth direction, i.e., the y direction, calculate the slant range and time delay between the transceiver antenna and each target grid point at the current position j; taking the acquisition signal of the target at the jth position on the y axis and the i th equivalent channel on the x axis as an example, the echo data at this time is: ; perform M-point CZT transformation on the echo data to obtain , k = 0, …, M-1; Perform CZT transformation on the echo signal. Specifically, perform M-point CZT transformation on N-point data , and the analytical expression is: (4) wherein, is the slant range minimum corresponding digital angular frequency; is the slant range maximum corresponding digital angular frequency; , represents the sampling rate in the distance dimension; M is the corresponding point number of the CZT transform.

[0023] According to the standard form formula (3) of the discrete time domain data signal, the output signal of the CZT transform is represented as: (5) wherein, .

[0024] Step 4, calculate the slant range and propagation time delay between each grid point (x, y, z) and the current transmit-receive channel antenna, and according to the sampling parameters of the CZT transform, the propagation time delay is corresponded to the position of the ID index number in the CZT transform frequency domain ; wherein, ID represents the index number in the CZT frequency domain data, that is, the position of the distance (or time delay) corresponding to a certain grid point in the CZT result array.

[0025] Calculate the distance and time delay between the transmit-receive antenna of the i-th equivalent channel of the current azimuth and each grid point, and calculate the position of each grid point corresponding to the ID index number in the CZT transform frequency domain according to formulas (6) and (7) ; When , the maximum value is obtained, and the main lobe center corresponds to the strongest response of the target position, based on the distance between the transmit-receive antenna of the equivalent channel and each grid point, the index position of the grid point in the CZT transform frequency domain is calculated, and the calculation formula is: (6); wherein, is the frequency point index (ID) used to extract the amplitude corresponding to the grid point in the imaging process.

[0026] Due to the calculation resolution, the calculated according to formula (6) is generally not an integer, in the traditional BP method, the integer value is obtained by rounding , that is: (7); wherein, round() represents rounding.

[0027] The compensation factor constructed in step 5 is: (8); in, Indicates decimal residual error ; In equation (5) This phase error, if not compensated for, will lead to an increase in the sidelobe level of the final image.

[0028] Phase compensation is performed on the data at each grid point. In this embodiment, two phase compensation terms are constructed: a compensation factor and a constant term. ; Phase compensation is performed on the extracted CZT transform frequency domain signal based on the compensation factor. The data after compensation at the corresponding grid points are as follows: ; in, In the frequency domain of CZT transform signal The signal at the point; At the current target position j, for each equivalent channel i, the echo signal is processed by steps 3 to 5 to extract the CZT transform frequency domain signal corresponding to the grid point; i = i + 1, and then jump to step 3 to process the next echo signal; in this way, the echo signals of all effective channels i at a position j are traversed. At the current target position j, after traversing all the echo signals corresponding to all valid channels i, j = j + 1 is set, and the signal at the next position j is obtained for the next round of traversal. This process is repeated until all echo signals have been processed. All grid points undergo the above process to complete data extraction and obtain the corresponding data for each grid point. ; In step 6, iterate through i=0,1,2,…L*G-1;j=0,1,2..J-1, and the data corresponding to each grid point... Perform coherent accumulation separately: After accumulation, three-dimensional imaging image data is obtained.

[0029] Example 2 Based on Embodiment 1, this embodiment provides a CZT-based rear projection 3D imaging system, including: The acquisition module is configured to acquire 3D data calibrated for channel errors; The target modeling module is configured to divide the target imaging area into a three-dimensional mesh, obtain mesh points distributed in three-dimensional space, and acquire the coordinate position of each mesh point; and preset the slant distance range between the target mesh and the transceiver antenna. The CZT transformation module is configured to extract, at each target position j, echo signals for each equivalent channel i, perform a CZT transformation on the echo signals in a frequency range corresponding to a slant range, and obtain a CZT transformed frequency domain signal; The index module is configured to calculate and round an index position of a CZT frequency point corresponding to a propagation distance of a current grid point and the i th equivalent channel as a signal position of a grid point echo, and extract a CZT transformed frequency domain signal at the corresponding signal position point; The compensation module is configured to construct a compensation factor based on the index positions of the CZT frequency points before and after rounding, and perform phase compensation on the extracted CZT transformed frequency domain signal to obtain compensated data of the current grid point; The superposition module is configured to iterate through all target positions and equivalent channels, and coherently superimpose the compensated data of each grid point to form three-dimensional imaging image data.

[0030] It should be noted that each module in the embodiment corresponds to each step in Embodiment 1 one by one, and the specific implementation process is the same, which will not be repeated here.

[0031] Embodiment 3 Based on Embodiment 1, an electronic device is provided, which includes a memory and a processor, and computer instructions stored in the memory and running on the processor, when the computer instructions are run by the processor, the steps in the CZT-based back-projection three-dimensional imaging method described in Embodiment 1 are completed.

[0032] Embodiment 4 Based on Embodiment 1, a computer readable storage medium is provided for storing computer instructions, when the computer instructions are executed by a processor, the steps in the CZT-based back-projection three-dimensional imaging method described in Embodiment 1 are completed.

[0033] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0034] The above describes the specific embodiments of the present application in conjunction with the accompanying drawings, but is not intended to limit the protection scope of the present application. Those skilled in the art should understand that various modifications or changes made on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A CZT-based back projection three-dimensional imaging method, characterized in that, Includes the following steps: Acquire 3D data after channel error calibration; The target imaging area is divided into three-dimensional grids to obtain grid points distributed in three-dimensional space, and the coordinate position of each grid point is obtained. Preset the slant distance range between the target grid and the transceiver antenna; At each target position j, for each equivalent channel i, the echo signal is extracted, and CZT transformation is performed on the echo signal within the frequency range corresponding to the slant range to obtain the CZT transformed frequency domain signal. Calculate the CZT frequency index position corresponding to the propagation distance of the current grid point and the i-th equivalent channel, round it down, and use it as the signal position of the grid point echo. Extract the CZT transform frequency domain signal at the corresponding signal position point. Based on the CZT frequency point index positions before and after rounding, a compensation factor is constructed, and phase compensation is performed on the extracted CZT transform frequency domain signal to obtain the compensated data of the current grid point. By traversing all target locations and equivalent channels, the compensated data of each grid point is coherently superimposed to form three-dimensional imaging image data.

2. The CZT-based back projection three-dimensional imaging method as described in claim 1, characterized in that: The process of acquiring 3D data after channel error calibration includes the following steps: The echo signal received by the receiving antenna is mixed with the reference signal using a frequency-modulation removal process to obtain a continuous signal. ; Based on the distance from the transmitting antenna to the target in the equivalent channel and the distance from the target to the receiving antenna Calculate the propagation delay of the echo signal; For continuous signals Perform equal-interval sampling to obtain discrete-time domain data; Based on the frequency modulation slope and sampling time interval, a standardized parameter T is constructed, and the signal model is optimized to construct the discrete-time domain data signal into a standard form containing a range-direction frequency modulation term that is linearly related to the distance.

3. The CZT-based back projection three-dimensional imaging method as described in claim 1, characterized in that: The formula for calculating the standardized parameter T is: ； in, It's the frequency modulation slope. Where C is the sampling time interval and C is the electromagnetic wave propagation speed.

4. The CZT-based back projection three-dimensional imaging method as described in claim 1, characterized in that: Perform CZT transformation on the echo signal; specifically, for N-point data... The analytical expression for the CZT transform at point M is: ； in, It is the minimum slope distance. The corresponding digital angular frequency; It is the maximum slant distance. The corresponding digital angular frequency; , represents the sampling rate in the distance dimension; M is the number of points corresponding to CZT; j represents the target position of the target object, and M is the number of points corresponding to the CZT transform.

5. The CZT-based back projection three-dimensional imaging method as described in claim 1, characterized in that: The index position of the echo data of each grid point in the CZT transform frequency domain is calculated based on the distance between the transmitting and receiving antennas of the equivalent channel and each grid point. The calculation formula is as follows: ； in, This indicates the maximum slope distance. This represents the minimum slope distance; It is the distance from the transmitting antenna to the scattering point on the target object. It is the distance from the receiving antenna to the scattering point on the target object.

6. The CZT-based back projection three-dimensional imaging method as described in claim 1, characterized in that: The constructed compensation factor is: ； in, Indicates decimal residual error ; The index position of the echo data of the calculated grid points in the CZT transform frequency domain. The index position is the integer part of the position; j represents the target position of the target object; T is the standardization parameter, N is the number of data points for signal discretization, and M is the number of points corresponding to the CZT transform. This indicates the maximum slope distance. This represents the minimum slope distance.

7. The CZT-based back projection three-dimensional imaging method as described in claim 6, characterized in that: Phase compensation is performed on the extracted CZT transform frequency domain signal based on the compensation factor. The data after compensation at the corresponding grid points are as follows: ； in, In the frequency domain of CZT transform signal The signal at the point; Indicates the starting frequency; It is the distance from the transmitting antenna to the scattering point on the target object. is the distance from the receiving antenna to the scattering point on the target object; C is the electromagnetic wave propagation speed.

8. A CZT-based back projection three-dimensional imaging system, characterized in that, include: The acquisition module is configured to acquire 3D data calibrated for channel errors; The target modeling module is configured to divide the target imaging area into a three-dimensional mesh, obtain the mesh points distributed in three-dimensional space, and obtain the coordinate position of each mesh point; Preset the slant distance range between the target grid and the transceiver antenna; The CZT transformation module is configured to extract the echo signal for each equivalent channel i at each target position j, and perform CZT transformation on the echo signal within the frequency range corresponding to the slant range to obtain the CZT transformed frequency domain signal. The index module is configured to calculate the CZT frequency index position corresponding to the propagation distance of the current grid point and the i-th equivalent channel, round it down, and use it as the signal position of the grid point echo, and extract the CZT transform frequency domain signal at the corresponding signal position point. The compensation module is configured to construct a compensation factor based on the CZT frequency point index position before and after rounding, perform phase compensation on the extracted CZT transform frequency domain signal, and obtain the compensated data of the current grid point. The overlay module is configured to traverse all target locations and equivalent channels, and coherently overlay the compensated data of each grid point to form three-dimensional imaging image data.

9. An electronic device, characterized in that, It includes a memory and a processor, as well as computer instructions stored in the memory and running on the processor, which, when executed by the processor, perform the steps in the CZT-based back projection three-dimensional imaging method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, Used to store computer instructions, which, when executed by a processor, complete the steps in the CZT-based back projection three-dimensional imaging method according to any one of claims 1-7.

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