Three-dimensional imaging methods and devices, software products, and storage media

Abstract

This application discloses a three-dimensional imaging method, apparatus, program product, and storage medium. The method includes: dividing sub-apertures with equivalent phase centers at the same location in a multi-input multi-output (MIMO) array into the same sub-aperture group, resulting in multiple sub-aperture groups. The sub-apertures are obtained by pre-dividing the receiving and transmitting antennas in the MIMO array, and the equivalent phase center is the center of the line connecting the centers of all antennas in the sub-aperture. Based on the echo data acquired by the multiple sub-aperture groups during the transmit-receive cycle, spectral compression is performed on the multiple sub-aperture groups to determine multiple target sub-images corresponding to the multiple sub-aperture groups. The multiple target sub-images are coherently superimposed to obtain a target three-dimensional image. This application solves the problem of low imaging efficiency in related technologies and achieves high-efficiency imaging.

Description

Technical Field

[0001] This application relates to the field of radar imaging technology, and more specifically, to a three-dimensional imaging method and apparatus, program product, and storage medium. Background Technology

[0002] Active millimeter-wave and microwave imaging technologies typically employ single-base arrays or sparse multiple-input multiple-output (MIMO) array structures, using digital beamforming (DBF) or back-projection (BP) algorithms to image the target area.

[0003] However, the aforementioned traditional techniques still have significant limitations: on the one hand, after the BP algorithm performs sub-aperture processing in the polar coordinate system, an additional interpolation step is required to transform the image from polar coordinates to Cartesian coordinates. This process not only introduces interpolation errors but also increases computational overhead. On the other hand, after each sub-aperture is imaged independently, it still needs to be upsampled at high resolution. Moreover, due to the uneven spectral distribution in the polar coordinate system, the upsampling process is prone to spectral aliasing, leading to a decrease in image quality. In addition, after the sub-apertures are divided, sub-apertures with the same equivalent phase center are not merged, resulting in a large number of redundant sub-image generation and independent upsampling operations, which significantly limits the feasibility and real-time performance of the algorithm on parallel hardware platforms.

[0004] In summary, the relevant technologies suffer from low imaging efficiency. Summary of the Invention

[0005] This application provides a three-dimensional imaging method and apparatus, program product, and storage medium to at least solve the technical problem of low imaging efficiency in related technologies.

[0006] According to one aspect of the embodiments of this application, a three-dimensional imaging method is provided, comprising: dividing sub-apertures with equivalent phase centers at the same position in a multiple-input multiple-output (MIMO) array into the same sub-aperture group to obtain multiple sub-aperture groups, wherein the sub-apertures are obtained by pre-dividing the receiving antennas and transmitting antennas in the MIMO array, and the equivalent phase center is the center of the line connecting the centers of each antenna in the sub-aperture; performing spectral compression on the multiple sub-aperture groups based on echo data acquired by the multiple sub-aperture groups during the transmit-receive cycle to determine multiple target sub-images corresponding to the multiple sub-aperture groups; and coherently superimposing the multiple target sub-images to obtain a target three-dimensional image.

[0007] In an exemplary embodiment, the above-mentioned method of determining multiple target sub-images corresponding to the multiple sub-aperture groups by performing spectral compression on the multiple sub-aperture groups based on the echo data acquired during the transmit-receive cycle includes: traversing each sub-aperture in the target sub-aperture group, generating an initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture; performing spectral compression on the initial sub-image to obtain a first sub-image; performing upsampling on the first sub-image to obtain a second sub-image, wherein the resolution of the second sub-image is greater than the resolution of the first sub-image; and performing spectral decompression on the second sub-image to obtain the target sub-image.

[0008] In an exemplary embodiment, the process of traversing each sub-aperture in the target sub-aperture group and generating an initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture includes: traversing each sub-aperture in the target sub-aperture group; performing a range-direction fast Fourier transform on the echo data associated with the transceiver antenna pair corresponding to each sub-aperture to obtain a range signal corresponding to each sub-aperture, wherein the transceiver antenna pair includes the receiving antenna and the transmitting antenna; performing linear interpolation on the range signal corresponding to each sub-aperture to obtain a range domain signal for each pixel in the imaging grid; performing phase compensation on the range domain signal for each pixel in the imaging grid and coherently accumulating it to the imaging grid to generate the initial sub-image.

[0009] In one exemplary embodiment, the process of traversing each sub-aperture in the target sub-aperture group and performing a range-oriented Fast Fourier Transform on the echo data associated with the transceiver antenna pair corresponding to each sub-aperture to obtain a range signal corresponding to each sub-aperture includes: traversing each sub-aperture in the target sub-aperture group to obtain the original frequency domain echo data associated with each transceiver antenna pair in the MIMO array; performing zero-padding on the original frequency domain echo data to obtain the echo data, wherein the echo data and the original frequency domain echo data have the same frequency interval, and the number of sampling points of the echo data is greater than the number of sampling points of the original frequency domain echo data; and performing a Fast Fourier Transform on the echo data to obtain a range signal corresponding to each sub-aperture.

[0010] In an exemplary embodiment, performing linear interpolation on the range signal corresponding to each sub-aperture to obtain the range domain signal of each pixel in the imaging grid includes: determining a first distance based on the coordinates of each pixel in the imaging grid and the coordinates of the receiving antenna, wherein each pixel and the receiving antenna are located in the same three-dimensional Cartesian coordinate system; determining a second distance based on the coordinates of each pixel in the imaging grid and the coordinates of the transmitting antenna, wherein each pixel and the transmitting antenna are located in the same three-dimensional Cartesian coordinate system; and performing linear interpolation on the range signal based on the first distance and the second distance to obtain the range domain signal.

[0011] In an exemplary embodiment, the upsampling of the first sub-image to obtain the second sub-image includes: performing a two-dimensional fast Fourier transform on each depth layer of the first sub-image to obtain a corresponding two-dimensional spectrum, wherein the size of the two-dimensional spectrum is the number of pixels in the horizontal direction of the first sub-image; dividing the two-dimensional spectrum into four quadrant sub-spectrums of the same size; filling the four quadrant sub-spectrums into the four corner regions of the target spectrum to obtain a filled target spectrum, wherein the size of the target spectrum is determined based on the size of the first sub-image and the upsampling factor, and the four corner regions include the upper left corner, the upper right corner, the lower left corner, and the lower right corner of the target spectrum; and performing a two-dimensional inverse fast Fourier transform on the filled target spectrum to obtain the second sub-image.

[0012] In an exemplary embodiment, the method further includes: determining a phase factor based on the distance from the equivalent phase center to each pixel and the center frequency of the transmitting antenna, wherein the phase factor is used to perform the spectrum compression and the spectrum decompression.

[0013] According to another aspect of the embodiments of this application, a three-dimensional imaging device is also provided, comprising: a first partitioning module, configured to partition sub-apertures with equivalent phase centers having the same position in a multiple-input multiple-output (MIMO) array into the same sub-aperture group to obtain multiple sub-aperture groups, wherein the sub-apertures are obtained by pre-dividing the receiving antennas and transmitting antennas in the MIMO array, and the equivalent phase center is the center of the line connecting the centers of each antenna in the sub-aperture; a first determining module, configured to perform spectral compression on the multiple sub-aperture groups based on the echo data acquired by the multiple sub-aperture groups during the transmit-receive cycle to determine multiple target sub-images corresponding to the multiple sub-aperture groups; and a first superposition module, configured to coherently superimpose the multiple target sub-images to obtain a target three-dimensional image.

[0014] According to another aspect of the embodiments of this application, a computer-readable storage medium is also provided, wherein a computer program is stored therein, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed by a processor.

[0015] According to another aspect of the embodiments of this application, a computer program product or computer program is provided, the computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, causing the computer device to perform the steps in any of the method embodiments described above.

[0016] According to another aspect of the embodiments of this application, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to perform the steps of any of the above method embodiments through the computer program.

[0017] This application combines sub-apertures with the same equivalent phase center into a sub-aperture group, significantly reducing the number of imaging sub-images that need to be processed independently and lowering the computational load. Simultaneously, by implementing spectral compression in a Cartesian coordinate system, it avoids the computational overhead and accuracy loss associated with traditional polar coordinate interpolation. Therefore, it can solve the problem of low imaging efficiency in related technologies and achieve highly efficient imaging. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating an application scenario of a three-dimensional imaging method according to an embodiment of this application;

[0019] Figure 2 This is a schematic flowchart of an optional three-dimensional imaging method according to an embodiment of this application;

[0020] Figure 3 This is a schematic diagram of an optional MIMO array according to an embodiment of this application. Figure 1 ;

[0021] Figure 4 This is a schematic diagram of an optional MIMO array according to an embodiment of this application. Figure 2 ;

[0022] Figure 5 This is a flowchart illustrating another optional three-dimensional imaging method according to an embodiment of this application;

[0023] Figure 6 This is a schematic diagram of another optional MIMO array according to an embodiment of this application. Figure 1 ;

[0024] Figure 7 This is a schematic diagram of another optional MIMO array according to an embodiment of this application. Figure 2 ;

[0025] Figure 8 This is a schematic diagram of an optional spectrum compression according to an embodiment of this application;

[0026] Figure 9 This is an optional upsampling schematic diagram according to an embodiment of this application;

[0027] Figure 10 This is a structural block diagram of an optional three-dimensional imaging device according to an embodiment of this application. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] According to one aspect of the embodiments of this application, a three-dimensional imaging method is provided. Optionally, in this embodiment, the above-described three-dimensional imaging method may be applied, but is not limited to, to applications such as... Figure 1 The hardware environment shown includes terminal device 102 and server 104. Server 104 can be connected to terminal device 102 via a network and can be used to provide services (e.g., application services, etc.) to terminal device 102 or clients installed on terminal device 102. A database can be set up on server 104 or independently of server 104 to provide data storage services for server 104.

[0031] The aforementioned network may include, but is not limited to, at least one of the following: wired network and wireless network. The aforementioned wired network may include, but is not limited to, at least one of the following: wide area network (WAN), metropolitan area network (MAN), and local area network (LAN). The aforementioned wireless network may include, but is not limited to, at least one of the following: Wireless Fidelity (WIFI) and Bluetooth. Terminal device 102 may be, but is not limited to, a personal computer (PC), mobile phone, tablet computer, etc. Server 104 may be, but is not limited to, a cloud server, server cluster, or other server types.

[0032] The three-dimensional imaging method of this application embodiment can be executed by server 104, terminal device 102, or jointly by server 104 and terminal device 102. Alternatively, the three-dimensional imaging method of this application embodiment can be executed by a client installed on the terminal device 102.

[0033] Taking the execution of the three-dimensional imaging method in this embodiment by terminal device 102 as an example, wherein terminal device 102 is the first device, Figure 2 This is a schematic flowchart of an optional three-dimensional imaging method according to an embodiment of this application, such as... Figure 2 As shown, the process of this method may include the following steps:

[0034] Step S202: Divide the sub-apertures with the same equivalent phase center in the MIMO array into the same sub-aperture group to obtain multiple sub-aperture groups. The sub-apertures are obtained by dividing the receiving antennas and transmitting antennas in the MIMO array in advance. The equivalent phase center is the center of the line connecting the centers of each antenna in the sub-aperture.

[0035] Optionally, a MIMO array is a non-co-located, sparsely deployed radar antenna system consisting of multiple transmit antennas (Tx) and multiple receive antennas (Rx). Through time-division or frequency-division multiplexing, only one Tx transmits at a time, while all Rx receive, thus synthesizing a virtual channel number far exceeding the physical antenna number at the signal processing end. For example, composed of N transmit antennas and N receive antennas, through a time-division transmission mechanism (only one transmit antenna operates at any given time, and all receive antennas receive synchronously), N² virtual transmit and receive channels are synthesized in the digital domain, forming an equivalent aperture much larger than the physical array size, thereby achieving high-resolution imaging while reducing hardware costs.

[0036] Optionally, a sub-aperture is a local transceiver unit obtained by spatially dividing the transmit and receive antennas in the original MIMO array. Each sub-aperture contains a set of continuously or discretely distributed subsets of transmit and receive antennas, with a number of antennas much smaller than the total number of antennas, used to independently complete local imaging tasks. Figure 3 As shown, Figure 3 It is a MIMO antenna array arrangement, and the MIMO array is magnified as follows: Figure 4 As shown, the distance between the transmitting antenna and the receiving antenna is 3mm, and a "U"-shaped MIMO array has a total of 96 (Tx) × 96 (Rx) transmit and receive antenna pairs.

[0037] Optionally, for multiple sub-apertures with equivalent phase centers in the same location, their imaging angles and phase distributions are highly consistent, and they can be jointly processed in the same local imaging grid without repeated calculations.

[0038] Step S204: Based on the echo data acquired by the above-mentioned multiple sub-aperture groups during the transmission and reception cycle, the above-mentioned multiple sub-aperture groups are spectral compressed to determine the multiple target sub-images corresponding to the above-mentioned multiple sub-aperture groups.

[0039] Optionally, the transmit-receive cycle is the time unit required for the MIMO array to complete one full scan. Using a time-division multiplexing transmission mechanism (i.e., only one transmit antenna is active at any given time), a complete cycle includes: all transmit antennas sequentially transmitting a pulse signal; and during each transmission, all receive antennas synchronously acquiring the raw echo data. The raw echo data is a complex sequence of stepped-frequency signals, which can specifically take the following form:

[0040] ;

[0041] in, , , , The coordinates of the receiving antenna are ( , The coordinates of the transmitting antenna are (0), , The coordinates of the pixel are (0) and ... , , ), The center frequency of the transmitting antenna.

[0042] Step S206: Coherently superimpose the above multiple target sub-images to obtain a target 3D image.

[0043] Optionally, coherently superimposing the above multiple target sub-images to obtain a target 3D image includes: aligning the complex amplitude data of each target sub-image pixel by pixel to the corresponding position of the global 3D imaging grid according to its spatial coordinate position, wherein the complex amplitude data includes the amplitude and phase information of the target sub-image; during the alignment process, performing a coherent accumulation operation in the complex domain on the multiple target sub-image components contributed by different sub-aperture groups at the same spatial position; repeating the above superposition process for all depth layers, finally forming a complete complex scattering field in the global 3D Cartesian coordinate system; and extracting the amplitude of the complex scattering field to obtain the target 3D image.

[0044] The embodiments provided in this application merge sub-apertures with the same equivalent phase center into a sub-aperture group, significantly reducing the number of imaging sub-images that need to be processed independently and lowering the computational load. Simultaneously, by implementing spectral compression in a Cartesian coordinate system, the computational overhead and accuracy loss associated with traditional polar coordinate interpolation are avoided. Therefore, the problem of low imaging efficiency in related technologies can be solved, achieving efficient imaging.

[0045] In an exemplary embodiment, the above-mentioned method of determining multiple target sub-images corresponding to the multiple sub-aperture groups by performing spectral compression on the multiple sub-aperture groups based on the echo data acquired during the transmit-receive cycle includes: traversing each sub-aperture in the target sub-aperture group, generating an initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture; performing spectral compression on the initial sub-image to obtain a first sub-image; performing upsampling on the first sub-image to obtain a second sub-image, wherein the resolution of the second sub-image is greater than the resolution of the first sub-image; and performing spectral decompression on the second sub-image to obtain the target sub-image.

[0046] Optionally, the imaging grid corresponding to each sub-aperture is a three-dimensional voxel grid defined in a global rectangular coordinate system. Its spatial range is determined by the equivalent phase center of the sub-aperture and the observation angle. The grid size and resolution are uniformly set to coarse resolution to support efficient back projection calculation.

[0047] Optionally, the initial sub-image is a coarse-resolution complex image generated on a shared imaging grid after back-projecting and coherently accumulating the echo data of all sub-apertures within the target sub-aperture group. It contains complete scattering information of the target, but has a wide spectral distribution and has not yet been optimized in the frequency domain.

[0048] Optionally, the phase factors for phase compensation in spectral compression and decompression are determined based on the equivalent phase center of the sub-aperture group. Spectral compression applies phase compensation to the initial sub-image in the frequency domain, compressing the target spectral energy from a dispersed state to a center frequency position referenced by the equivalent phase center, thereby eliminating aliasing for subsequent upsampling. Spectral decompression applies a phase factor with the opposite phase compensation to spectral compression to the second sub-image to recover its original echo phase, ensuring that the spectral distribution of this sub-image is consistent with the global imaging system and has a phase basis for coherent superposition with other sub-images.

[0049] Optionally, upsampling is used to perform center zero-padding and inverse Fourier transform in the two-dimensional frequency domain of the first sub-image, which improves the spatial resolution only in the xy plane while keeping the z-axis dimension unchanged, thereby obtaining a higher resolution second sub-image without introducing spatial interpolation blur.

[0050] Optionally, the target sub-aperture group is any one of multiple sub-aperture groups.

[0051] This embodiment achieves rapid 3D imaging in a Cartesian coordinate system without coordinate transformation, spectral aliasing, or other defects, while preserving complete phase information, by generating an initial sub-image, performing spectral compression, upsampling, and spectral decompression. Simultaneously, the spectral compression and decompression mechanisms avoid artifacts and geometric distortion problems caused by traditional polar coordinate interpolation, thus improving image quality.

[0052] In an exemplary embodiment, the process of traversing each sub-aperture in the target sub-aperture group and generating an initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture includes: traversing each sub-aperture in the target sub-aperture group; performing a range-direction fast Fourier transform on the echo data associated with the transceiver antenna pair corresponding to each sub-aperture to obtain a range signal corresponding to each sub-aperture, wherein the transceiver antenna pair includes the receiving antenna and the transmitting antenna; performing linear interpolation on the range signal corresponding to each sub-aperture to obtain a range domain signal for each pixel in the imaging grid; performing phase compensation on the range domain signal for each pixel in the imaging grid and coherently accumulating it to the imaging grid to generate the initial sub-image.

[0053] Optionally, the range signal is a complex signal obtained after a Fast Fourier Transform (FFT) in the range direction. It represents the scattering intensity and phase distribution of the target on the range axis and serves as intermediate data for performing linear interpolation and phase compensation operations. Specifically, it can take the following form:

[0054] Where R is the distance from the transmit / receive antenna pair to space, obtained through FFT. Where is the step frequency, and N is the number of frequency points of the transmitted signal. .

[0055] Optionally, linear interpolation is used to perform non-uniform sampling point interpolation calculations on the range axis, with reference to the distance between each pixel in the imaging grid and the receiving and transmitting antennas, to obtain the range domain response value corresponding to that pixel, thereby ensuring the geometric accuracy of the back projection.

[0056] Optionally, phase compensation is used to multiply the range domain signal of each pixel by a phase compensation factor to cancel the phase delay of the electromagnetic wave on the propagation path, enabling the echoes from the transmitting and receiving antenna pairs to coherently superimpose at the target location, thereby ensuring the accuracy of image focusing. The phase compensation factor can be... ,in , .

[0057] Optionally, coherent accumulation is used to sum the range domain signals of all transmit and receive antenna pairs at the same imaging grid pixel point in the complex domain, and generate an initial sub-image with high signal-to-noise ratio through phase alignment.

[0058] In one exemplary embodiment, the process of traversing each sub-aperture in the target sub-aperture group and performing a range-oriented Fast Fourier Transform on the echo data associated with the transceiver antenna pair corresponding to each sub-aperture to obtain a range signal corresponding to each sub-aperture includes: traversing each sub-aperture in the target sub-aperture group to obtain the original frequency domain echo data associated with each transceiver antenna pair in the MIMO array; performing zero-padding on the original frequency domain echo data to obtain the echo data, wherein the echo data and the original frequency domain echo data have the same frequency interval, and the number of sampling points of the echo data is greater than the number of sampling points of the original frequency domain echo data; and performing a Fast Fourier Transform on the echo data to obtain a range signal corresponding to each sub-aperture.

[0059] Optionally, the original echo data is a complex sequence, a stepped frequency signal, specifically in the following form:

[0060] ;

[0061] in, , , .

[0062] Optionally, zero-padding is used to add several zero-value samples to the end of the original frequency domain echo data to increase the number of sampling points after FFT, thereby increasing the distance domain sampling density, but without changing the original frequency interval.

[0063] This embodiment improves spectral resolution by padding the frequency dimension of the echo data with zeros before performing the distance-to-FFT.

[0064] In an exemplary embodiment, performing linear interpolation on the range signal corresponding to each sub-aperture to obtain the range domain signal of each pixel in the imaging grid includes: determining a first distance based on the coordinates of each pixel in the imaging grid and the coordinates of the receiving antenna, wherein each pixel and the receiving antenna are located in the same three-dimensional Cartesian coordinate system; determining a second distance based on the coordinates of each pixel in the imaging grid and the coordinates of the transmitting antenna, wherein each pixel and the transmitting antenna are located in the same three-dimensional Cartesian coordinate system; and performing linear interpolation on the range signal based on the first distance and the second distance to obtain the range domain signal.

[0065] Optionally, the first distance is the three-dimensional straight-line distance from any pixel in the imaging grid to the specified receiving antenna, which can be determined by the following formula: .

[0066] Optionally, the second distance is the three-dimensional straight-line distance from any pixel in the imaging grid to the specified transmitting antenna, which can be determined by the following formula: .

[0067] Optionally, the range domain signal is the complex response value of each imaging grid pixel under the current transceiver antenna pair, obtained by linear interpolation. Specifically, the range domain signal can take the following form: .

[0068] In an exemplary embodiment, upsampling the first sub-image to obtain a second sub-image includes: performing a two-dimensional fast Fourier transform on each depth layer of the first sub-image to obtain a corresponding two-dimensional spectrum, wherein the size of the two-dimensional spectrum is the number of pixels in the horizontal direction of the first sub-image; dividing the two-dimensional spectrum into four quadrant sub-spectrums of the same size; filling the four quadrant sub-spectrums into the four corner regions of the target spectrum to obtain a filled target spectrum, wherein the size of the target spectrum is determined based on the size of the first sub-image and the upsampling factor, and the four corner regions include the upper left corner, the upper right corner, the lower left corner, and the lower right corner of the target spectrum; and performing a two-dimensional inverse fast Fourier transform on the filled target spectrum to obtain the second sub-image.

[0069] Optionally, the depth layer is a two-dimensional slice of the first sub-image along the Z-axis. Each depth layer contains the scattering response values ​​of all horizontal pixels at a fixed height. In this embodiment, each depth layer can perform upsampling operations independently, supporting large-scale parallel computing.

[0070] Optionally, the target spectrum is a high-resolution frequency domain matrix that has been upsampled and expanded, with a size equal to the original spectrum size multiplied by the upsampling factor.

[0071] Optionally, the two-dimensional fast Fourier transform is a spatial-frequency domain transform performed on the two-dimensional complex image of each depth layer, and the output is a two-dimensional spectrum of the corresponding size, which represents the energy distribution of the depth layer in the horizontal spatial frequency domain.

[0072] This embodiment achieves the goal of ensuring clear image edges after upsampling by filling the four corner regions of the target spectrum with the original quadrant sub-spectrum and setting the remaining regions to zero.

[0073] In an exemplary embodiment, the method further includes: determining a phase factor based on the distance from the equivalent phase center to each pixel and the center frequency of the transmitting antenna, wherein the phase factor is used to perform the spectrum compression and the spectrum decompression.

[0074] Optionally, the phase factor for phase factor spectrum compression phase compensation is determined based on the distance from the equivalent phase center to each pixel in the imaging grid and the center frequency of the transmitting antenna. ,in, It is the equivalent phase center of the above sub-aperture group. It is the center frequency of the aforementioned transmitting antenna; the phase factor of the aforementioned spectrum compression phase compensation = ,in, It is the equivalent phase center of the above sub-aperture group. It is the center frequency of the aforementioned transmitting antenna.

[0075] The three-dimensional imaging method in the embodiments of this application will be explained and described below with reference to optional examples.

[0076] Figure 5 This is a schematic flowchart of another optional three-dimensional imaging method according to an embodiment of this application. The method may include the following steps:

[0077] Step S502: Sub-aperture division needs to consider the balance between the computational costs of sub-aperture projection and upsampling from coarse-resolution image to fine-resolution image. For example, the number of transmit antennas and receive antennas is... The number of sub-apertures can then be determined based on the following formula: This can maximize operational efficiency. For example, there are 16 transmit and receive antenna pairs, with each sub-aperture consisting of 2×2 elements, for a total of 4 sub-apertures.

[0078] Step S504: The equivalent phase center of the sub-aperture is the center of the line connecting the centers of the transmitting and receiving antenna apertures, such as... Figure 6 As shown, a U-shaped MIMO array has 96 (Tx) × 96 (Rx) transmit / receive antenna pairs. If each 48 (Tx) × 48 (Rx) transmit / receive antenna pair is divided into a sub-aperture, then four sub-apertures can be created. The equivalent phase centers of these sub-apertures are the four points shown in the figure. The complete MIMO array in this case is as follows. Figure 7 As shown, the full aperture has 3072(Tx) × 3072(Rx) transmit / receive antenna pairs. Dividing these into sub-apertures of 48(Tx) × 48(Rx), there are 3072 × 3072 / 48 / 48 = 4096 sub-apertures before grouping. However, grouping them according to their equivalent phase centers results in only 420 sub-apertures. By merging the sub-apertures using this method, the number of sub-apertures becomes one-tenth of the original number. Subsequent sub-apertures within the same group are projected onto a single sub-map. This operation avoids increasing the computational load of the original sub-aperture projection and reduces the computational load of the subsequent upsampling algorithm by an order of magnitude. For example, if the equivalent centers of the four sub-apertures mentioned above are identical pairwise, two sub-aperture groups can be obtained.

[0079] Step S506: Traverse multiple sub-apertures included in a sub-aperture group, wherein at any given time only one transmitting antenna is operational, while all receiving antennas synchronously acquire echo signals. The raw frequency domain echo data acquired by the MIMO array is... .

[0080] in, , , , .

[0081] Step S508: After determining the Cartesian coordinate grid of the sub-apertures in the current sub-aperture group, zero-padding is performed on the original frequency domain echo data in the frequency dimension before FFT to improve the accuracy of subsequent linear interpolation and improve spectral resolution. The range signal is obtained by performing a range FFT on the zero-padding original echo data. Where R is the distance from the transmit / receive antenna pair to space, obtained through FFT. Where is the step frequency, and N is the number of frequency points of the transmitted signal. For example, performing a distance FFT on the two sub-aperture groups above yields 4(Tx)×4(Rx)×16(R).

[0082] Step S510: Traverse each transmit / receive antenna pair included in the sub-aperture and each pixel in the imaging grid to determine the coordinates of the receiving antenna. , ,0), coordinates of the transmitting antenna ( , ,0) and the coordinates of the pixel ( , , ).

[0083] Step S512: Calculate the distance from the transceiver antenna to the pixel using the following formula:

[0084] , .

[0085] Step S514: Obtain the corresponding distance data through linear interpolation. Then, phase-compensated coherent accumulation is performed onto the imaging grid, and the compensated phase is... For example, one of the two sub-aperture groups mentioned above can be projected onto a 3D image 20(Y)×20(X)×10(Z) to generate an initial sub-image corresponding to the sub-aperture group.

[0086] Step S516: Determine whether all sub-apertures of the current sub-aperture group have been traversed. If yes, proceed to step S518; otherwise, proceed to step S506.

[0087] Step S518: The target spectrum in Cartesian coordinates is related not only to the sub-aperture length but also to the imaging range, such as... Figure 8 As shown, Figure 8 The left-middle section shows the projected two-dimensional spectrum. Spectral compression can bring the spectra of different targets to an equivalent phase center, avoiding spectral aliasing after subsequent upsampling. The phase factor compensated by spectral compression is: ,in It is the equivalent phase center of the sub-aperture of this group.

[0088] For example, according to the formula A three-dimensional phase compensation factor P(20(Y)×20(X)×10(Z)) is generated, and a dot product is performed to perform spectral compression on the initial sub-image.

[0089] Step S520: To refine the coarse-resolution image into a fine-resolution image using FFT, after the sub-aperture projection of the group is completed, a two-dimensional FFT needs to be performed on the sub-image at each depth, dividing the two-dimensional frequency domain image into four parts. For example, perform a two-dimensional FFT on the XY direction image, 2DFFT(20×20), and divide the result of the two-dimensional FFT into four parts, each 10×10.

[0090] Step S522: Then, center-paste zeros to the size of the fine-resolution image. For example, upsampling by a factor of 2 generates a 40(Y)×40(X) zero matrix, and the above four data sets are filled into the four corners.

[0091] Step S524: Perform a two-dimensional inverse fast Fourier transform (FFT) to obtain the two-dimensional upsampled result, as follows: Figure 9 As shown. For example, performing a 2DIFF will yield 40(Y)×40(X)×40(Z).

[0092] Step S526: To achieve coherent accumulation of the global spectrum, the spectrum of the upsampled, fine-resolution image needs to be decompressed and restored. The compensated phase factor is:

[0093] .

[0094] For example, according to the formula Generate a three-dimensional phase compensation factor P(40(Y)×40(X)×10(Z)) and perform a dot product.

[0095] Step S528: Since the image is in a Cartesian coordinate system, the sub-images after spectral reconstruction can be directly and coherently superimposed onto the overall image. By coherently superimposing all grouped sub-images onto the overall image, the imaging of the array is completed, resulting in a three-dimensional image.

[0096] Step S530: Determine whether all sub-apertures of all groups have been traversed. If yes, proceed to step S532; otherwise, proceed to step S504.

[0097] Step S532: Obtain a three-dimensional complex image.

[0098] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0099] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as read-only memory (ROM) / random access memory (RAM), magnetic disk, optical disk), and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0100] According to another aspect of the embodiments of this application, a three-dimensional imaging apparatus is also provided, which can be used to implement the three-dimensional imaging method provided in the above embodiments, and will not be repeated hereafter. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the apparatus described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0101] Figure 10 This is a structural block diagram of an optional three-dimensional imaging device according to an embodiment of this application, such as... Figure 10 As shown, the device includes:

[0102] The first partitioning module 1002 is used to partition sub-apertures with equivalent phase centers in the same position in the multiple input multiple output MIMO array into the same sub-aperture group to obtain multiple sub-aperture groups. The sub-apertures are obtained by pre-dividing the receiving antennas and transmitting antennas in the MIMO array, and the equivalent phase center is the center of the line connecting the centers of each antenna in the sub-aperture.

[0103] The first determining module 1004 is used to perform spectral compression on the multiple sub-aperture groups based on the echo data acquired by the multiple sub-aperture groups during the transmission and reception period, and to determine multiple target sub-images corresponding to the multiple sub-aperture groups.

[0104] The first overlay module 1006 is used to coherently overlay the above multiple target sub-images to obtain a target three-dimensional image.

[0105] It should be noted that the first division module 1002 in this embodiment can be used to execute the above step S202, the first determination module 1004 in this embodiment can be used to execute the above step S204, and the first superposition module 1006 in this embodiment can be used to execute the above step S206.

[0106] In an exemplary embodiment, the first determining module 1004 includes: a first generating submodule, configured to traverse each sub-aperture in the target sub-aperture group and generate an initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture; a first compression submodule, configured to perform spectral compression on the initial sub-image to obtain a first sub-image; a first upsampling submodule, configured to perform upsampling on the first sub-image to obtain a second sub-image, wherein the resolution of the second sub-image is greater than the resolution of the first sub-image; and a first decompression submodule, configured to perform spectral decompression on the second sub-image to obtain the target sub-image.

[0107] In an exemplary embodiment, the first generation submodule includes: a first traversal unit, configured to traverse each sub-aperture in the target sub-aperture group, perform a range-direction fast Fourier transform on the echo data associated with the transceiver antenna pair corresponding to each sub-aperture, and obtain a range-direction signal corresponding to each sub-aperture, wherein the transceiver antenna pair includes the receiving antenna and the transmitting antenna; a first execution unit, configured to perform linear interpolation on the range-direction signal corresponding to each sub-aperture, and obtain a range-domain signal for each pixel in the imaging grid; and a first generation unit, configured to perform phase compensation on the range-domain signal of each pixel in the imaging grid, coherently accumulate it to the imaging grid, and generate the initial sub-image.

[0108] In an exemplary embodiment, the first traversal unit includes: a first traversal subunit, configured to traverse each sub-aperture in the target sub-aperture group and acquire the original frequency domain echo data associated with each of the transceiver antenna pairs in the MIMO array; a first execution subunit, configured to perform zero-padding on the original frequency domain echo data to obtain the echo data, wherein the echo data and the original frequency domain echo data have the same frequency interval, and the number of sampling points of the echo data is greater than the number of sampling points of the original frequency domain echo data; and a second execution subunit, configured to perform a fast Fourier transform on the echo data to obtain the range signal corresponding to each sub-aperture.

[0109] In an exemplary embodiment, the first execution unit includes: a first determining subunit, configured to determine a first distance based on the coordinates of each pixel in the imaging grid and the coordinates of the receiving antenna, wherein each pixel and the receiving antenna are located in the same three-dimensional Cartesian coordinate system; a second determining subunit, configured to determine a second distance based on the coordinates of each pixel in the imaging grid and the coordinates of the transmitting antenna, wherein each pixel and the transmitting antenna are located in the same three-dimensional Cartesian coordinate system; and a third execution subunit, configured to perform linear interpolation on the range signal based on the first distance and the second distance to obtain the range domain signal.

[0110] In an exemplary embodiment, the first upsampling submodule includes: a second execution unit, configured to perform a two-dimensional fast Fourier transform on each depth layer of the first sub-image to obtain a corresponding two-dimensional spectrum, wherein the size of the two-dimensional spectrum is the number of pixels in the horizontal direction of the first sub-image; a first partitioning unit, configured to divide the two-dimensional spectrum into four quadrant sub-spectrums of the same size; a first filling unit, configured to fill the four quadrant sub-spectrums into the four corner regions of the target spectrum to obtain a filled target spectrum, wherein the size of the target spectrum is determined based on the size of the first sub-image and the upsampling factor, and the four corner regions include the upper left corner, the upper right corner, the lower left corner, and the lower right corner of the target spectrum; and a third execution unit, configured to perform a two-dimensional inverse fast Fourier transform on the filled target spectrum to obtain the second sub-image.

[0111] In one exemplary embodiment, the apparatus further includes a second determining module, configured to determine a phase factor based on the distance from the equivalent phase center to each pixel and the center frequency of the transmitting antenna, wherein the phase factor is used to perform the spectrum compression and the spectrum decompression.

[0112] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0113] According to another aspect of the embodiments of this application, a computer-readable storage medium is provided, the computer-readable storage medium including a stored program, wherein the program executes the steps in any of the above method embodiments when it is run.

[0114] In one exemplary embodiment, the aforementioned computer-readable storage medium may include, but is not limited to, various media capable of storing computer programs, such as USB flash drives, ROMs, RAMs, portable hard drives, magnetic disks, or optical disks.

[0115] According to another aspect of the embodiments of this application, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor is configured to perform the steps of any of the method embodiments described above via the computer program. In an exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor, and the input / output device is connected to the processor.

[0116] Specific examples in this embodiment can be found in the examples described in the above embodiments and exemplary implementations, and will not be repeated here.

[0117] According to another aspect of the embodiments of this application, a computer program product is also provided, the computer program product including a computer program / instructions containing program code for performing the method shown in the flowchart.

[0118] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those described herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0119] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A three-dimensional imaging method, characterized in that, include: Sub-apertures with equivalent phase centers in the same position in a multiple input multiple output MIMO array are divided into the same sub-aperture group to obtain multiple sub-aperture groups. The sub-apertures are obtained by pre-dividing the receiving antennas and transmitting antennas in the MIMO array, and the equivalent phase center is the center of the line connecting the centers of each antenna in the sub-aperture. Based on the echo data acquired by the multiple sub-aperture groups during the transmit-receive cycle, spectral compression is performed on the multiple sub-aperture groups to determine multiple target sub-images corresponding to the multiple sub-aperture groups. The spectral compression is used to apply phase compensation to the initial sub-image, and the phase factor of the phase compensation is determined based on the equivalent phase center. The multiple target sub-images are coherently superimposed to obtain a target 3D image.

2. The method according to claim 1, characterized in that, The step of performing spectral compression on the multiple sub-aperture groups based on the echo data acquired during the transmit-receive cycle, and determining multiple target sub-images corresponding to the multiple sub-aperture groups, includes: Traverse each sub-aperture in the target sub-aperture group, and generate the initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture; Spectral compression is performed on the initial sub-image to obtain the first sub-image; Upsampling is performed on the first sub-image to obtain a second sub-image, wherein the resolution of the second sub-image is greater than the resolution of the first sub-image; The second sub-image is subjected to spectral decompression to obtain the target sub-image.

3. The method according to claim 2, characterized in that, The process of traversing each sub-aperture in the target sub-aperture group, and generating an initial sub-image corresponding to the target sub-aperture group based on the echo data associated with each sub-aperture and the imaging grid corresponding to each sub-aperture, includes: Traverse each sub-aperture in the target sub-aperture group, perform a range-direction fast Fourier transform on the echo data associated with the transceiver antenna pair corresponding to each sub-aperture, and obtain the range-direction signal corresponding to each sub-aperture, wherein the transceiver antenna pair includes the receiving antenna and the transmitting antenna; Perform linear interpolation on the range signal corresponding to each sub-aperture to obtain the range domain signal of each pixel in the imaging grid; Phase compensation is performed on the range domain signal of each pixel in the imaging grid, and the signals are coherently accumulated into the imaging grid to generate the initial sub-image.

4. The method according to claim 3, characterized in that, The process of traversing each sub-aperture in the target sub-aperture group involves performing a range-oriented Fast Fourier Transform on the echo data associated with the transmit / receive antenna pairs corresponding to each sub-aperture to obtain the range signal corresponding to each sub-aperture, including: Traverse each sub-aperture in the target sub-aperture group to obtain the raw frequency domain echo data associated with each transmit / receive antenna pair in the MIMO array; Zero-padding is performed on the original frequency domain echo data to obtain the echo data, wherein the echo data and the original frequency domain echo data have the same frequency interval, and the number of sampling points of the echo data is greater than the number of sampling points of the original frequency domain echo data; Perform a Fast Fourier Transform on the echo data to obtain the range signal corresponding to each sub-aperture.

5. The method according to claim 3, characterized in that, The step of performing linear interpolation on the range signal corresponding to each sub-aperture to obtain the range domain signal of each pixel in the imaging grid includes: A first distance is determined based on the coordinates of each pixel in the imaging grid and the coordinates of the receiving antenna, wherein each pixel and the receiving antenna are located in the same three-dimensional Cartesian coordinate system; A second distance is determined based on the coordinates of each pixel in the imaging grid and the coordinates of the transmitting antenna, wherein each pixel and the transmitting antenna are located in the same three-dimensional Cartesian coordinate system; Linear interpolation is performed on the distance-direction signal based on the first distance and the second distance to obtain the distance-domain signal.

6. The method according to claim 2, characterized in that, The step of upsampling the first sub-image to obtain the second sub-image includes: Perform a two-dimensional fast Fourier transform on each depth layer of the first sub-image to obtain the corresponding two-dimensional spectrum, wherein the size of the two-dimensional spectrum is the number of pixels in the horizontal direction of the first sub-image; The two-dimensional spectrum is divided into four quadrant sub-spectrums of the same size; The four quadrant sub-spectrums are respectively filled into the four corner regions of the target spectrum to obtain the filled target spectrum. The size of the target spectrum is determined based on the size of the first sub-image and the upsampling factor. The four corner regions include the upper left corner, the upper right corner, the lower left corner, and the lower right corner of the target spectrum. Perform a two-dimensional inverse fast Fourier transform on the filled target spectrum to obtain the second sub-image.

7. The method according to claim 2, characterized in that, The method further includes: The phase factor is determined based on the distance from the equivalent phase center to each pixel and the center frequency of the transmitting antenna, wherein the phase factor is used to perform the spectrum compression and the spectrum decompression.

8. A three-dimensional imaging device, characterized in that, include: The first partitioning module is used to partition sub-apertures with equivalent phase centers in the same position in the multiple input multiple output MIMO array into the same sub-aperture group to obtain multiple sub-aperture groups. The sub-apertures are obtained by pre-dividing the receiving antennas and transmitting antennas in the MIMO array, and the equivalent phase center is the center of the line connecting the centers of each antenna in the sub-aperture. The first determining module is used to perform spectral compression on the multiple sub-aperture groups based on the echo data acquired by the multiple sub-aperture groups during the transmit-receive cycle, and to determine multiple target sub-images corresponding to the multiple sub-aperture groups. The spectral compression is used to apply phase compensation to the initial sub-image, and the phase factor of the phase compensation is determined based on the equivalent phase center. The first overlay module is used to coherently overlay the multiple target sub-images to obtain a target three-dimensional image.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of the method according to any one of claims 1 to 7.

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