CN117031471A - Handheld synthetic aperture radar imaging method and system for near-field three-dimensional - Google Patents
Handheld synthetic aperture radar imaging method and system for near-field three-dimensional Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/904—SAR modes
- G01S13/9056—Scan SAR mode
Abstract
The invention provides a handheld synthetic aperture radar imaging method and system for near-field three-dimensional. The method comprises the following steps: positioning the moving handheld synthetic aperture millimeter wave radar by using a positioning camera, and realizing oversampling of the target object and the reference object by improving the frame rate of the handheld synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object; the frame data of the target object are uniformly spaced in a resampling mode, so that the speed compensation of the frame data of the target object is realized, and a primary calibration result is obtained; based on the spatial asymmetry and the local similarity of the phase error, carrying out phase error estimation on frame data of a reference object, and carrying out phase compensation on a primary calibration result according to a phase error estimation result to obtain a secondary calibration result of the frame data; and performing three-dimensional near-field imaging on the secondary calibration result by using a range migration imaging algorithm to obtain an imaging result of the target object.
Description
Technical Field
The invention belongs to the field of signal processing, and particularly relates to a near-field three-dimensional handheld synthetic aperture radar imaging method and system, electronic equipment and a storage medium.
Background
Millimeter wave imaging has wide application in many fields, such as security imaging, autopilot, and medical detection. Millimeter wave imaging has an irreplaceable application scenario compared to traditional optical imaging thanks to the unique advantages of millimeter wave signals.
Current millimeter wave imaging systems are mainly based on large-scale antenna arrays to obtain high angular resolution. But large-scale antenna arrays are difficult to manufacture, have high hardware complexity, and are expensive. In order to reduce the system cost, the existing work adopts the imaging principle of a synthetic aperture radar, and the antenna transmits signals at different positions by moving the antenna according to a specified motion mode, so that a virtual aperture is synthesized. By means of the principle of synthetic aperture imaging, a resolution far higher than that of the original physical antenna can be obtained. However, to ensure that the received signals can be coherently superimposed, the position of the motion of the device needs to be precisely located. And for 77GHZ millimeter wave, to ensure that the image quality is not obviously affected, the positioning error can not exceed 0.5 millimeter. The positioning accuracy of the existing mobile positioning technology cannot meet the requirement. Therefore, in the prior art, the huge mechanical motion control device is adopted to precisely control the motion of the equipment, so that the mobility and the application scene of the imaging system are limited.
Disclosure of Invention
In view of the above, the present invention provides a handheld synthetic aperture radar imaging method for near-field three-dimensional, in order to solve at least one of the above problems.
According to a first aspect of the present invention there is provided a hand-held synthetic aperture radar imaging method for near-field three-dimensional, comprising:
positioning the moving handheld synthetic aperture millimeter wave radar by using a positioning camera to obtain a positioning result, and realizing oversampling of the target object and the reference object by improving the frame rate of the handheld synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object;
according to the positioning result, the frame data of the target object are uniformly spaced in a resampling mode, so that the speed compensation of the frame data of the target object is realized, and the primary calibration result of the frame data of the target object is obtained;
based on the spatial asymmetry and the local similarity of the phase error, carrying out phase error estimation on frame data of a reference object to obtain a phase error estimation result, and carrying out phase compensation on a primary calibration result of frame data of a target object according to the phase error estimation result to obtain a secondary calibration result of frame data of the target object;
and performing three-dimensional near-field imaging on the secondary calibration result by using a range migration imaging algorithm to obtain an imaging result of the target object.
According to the embodiment of the invention, the spatial asymmetry represents that the same motion error generates different phase errors in different directions of the three-dimensional space in the motion process of the target object in the three-dimensional space;
the spatial asymmetry based on the phase error can simplify the phase error estimation problem in the three-dimensional space to the phase error estimation problem in the distance dimension.
According to an embodiment of the present invention, the local similarity of the phase errors indicates that the phase errors generated by two objects having different position information are within a preset range in a three-dimensional space;
wherein the phase difference of one object in the three-dimensional space can be approximated by estimating the phase difference of another object in the three-dimensional space based on the local similarity of the phase errors.
According to an embodiment of the present invention, the local similarity of the above-described phase errors is expressed by the following formula:
，
，
，
wherein,information representing the position of a first object in three-dimensional space, < >>Information representing the position of a second object in three dimensions, < >>Representing ideal motion position information of hand-held synthetic aperture millimeter wave radar in three-dimensional space, < >>And representing the actual motion position information of the hand-held synthetic aperture millimeter wave radar in the three-dimensional space.
According to an embodiment of the present invention, the performing phase error estimation on frame data of a reference object based on the spatial asymmetry and the local similarity of the phase error to obtain a phase error estimation result includes:
acquiring an original phase history of a reference object with a handheld motion error from frame data of the reference object;
fitting the original phase history of the reference object into a quadratic curve by using a least square method to obtain an estimation result of the ideal phase history of the reference object;
and performing difference operation on the original phase history of the reference object and the estimation result of the ideal phase history of the reference object to obtain a phase error estimation result.
According to an embodiment of the present invention, the estimation result of the ideal phase history of the reference object is expressed by the following formula:
，
wherein,indicating the%>Estimation of the ideal phase history of the frame data sampled by the individual hand-held synthetic aperture millimeter wave radar, < >>Representing the coefficients;
wherein the phase error estimation result is represented by the following formula:
，
wherein,indicate->The individual hand-held synthetic aperture millimeter wave radars sample the original phase of frame data of a reference object.
According to an embodiment of the present invention, the above-described hand-held synthetic aperture millimeter wave radar includes a multi-chip cascaded millimeter wave radar;
wherein the positioning camera comprises a camera with a motion tracking function and a spatial positioning function;
the hand-held synthetic aperture millimeter wave radar in motion represents that the hand-held synthetic aperture millimeter wave radar moves along the X axis of the three-dimensional space coordinate system.
According to a second aspect of the present invention there is provided a hand-held synthetic aperture radar imaging system for near-field three-dimensional, comprising:
the data acquisition module is used for positioning the moving handheld synthetic aperture millimeter wave radar by utilizing the positioning camera to obtain a positioning result, and oversampling of the target object and the reference object is realized by improving the frame rate of the handheld synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object;
the speed compensation module is used for resampling the frame data of the target object to have uniform intervals according to the positioning result so as to realize speed compensation of the frame data of the target object, and obtaining a primary calibration result of the frame data of the target object;
the phase compensation module is used for carrying out phase error estimation on frame data of a reference object based on the spatial asymmetry and the local similarity of the phase error to obtain a phase error estimation result, and carrying out phase compensation on a primary calibration result of the frame data of a target object according to the phase error result to obtain a secondary calibration result of the frame data of the target object;
and the imaging module is used for performing three-dimensional near-field imaging on the secondary calibration result of the frame data of the target object by utilizing a range migration imaging algorithm to obtain an imaging result of the target object.
According to a third aspect of the present invention, there is provided an electronic device comprising:
one or more processors;
storage means for storing one or more programs,
wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to perform a hand-held synthetic aperture radar imaging method for near-field three-dimensional.
According to a fourth aspect of the present invention there is provided a computer readable storage medium having stored thereon executable instructions which when executed by a processor cause the processor to perform a hand held synthetic aperture radar imaging method for near field three dimensions.
According to the handheld synthetic aperture radar imaging method for near-field three-dimension, provided by the invention, the technical problem that fast imaging based on Fourier transform cannot be performed due to non-uniform linear motion of handheld radar equipment is solved by performing speed compensation and phase compensation on radar echo signals of a target object; the imaging method of the handheld synthetic aperture radar for near-field three dimensions can solve the imaging problem of the handheld radar device, can solve the technical problems of blurring and deformation of imaging images of the handheld radar device in the prior art, improves the reconstruction quality of a target object, greatly expands the application scene of the handheld synthetic aperture radar, improves the convenience of the handheld synthetic aperture radar and reduces the imaging cost of the handheld synthetic aperture radar.
Drawings
FIG. 1 is a flow chart of a method for three-dimensional hand-held synthetic aperture radar imaging in accordance with an embodiment of the present invention;
FIG. 2 (a) is a schematic diagram of a motion error and a phase error in an X-axis direction in a three-dimensional space coordinate system according to an embodiment of the present invention;
FIG. 2 (b) is a schematic diagram of a Z-axis direction motion error and a phase error in a three-dimensional space coordinate system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of phase error relationships of different target objects in three-dimensional space according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of the distribution of propagation distance differences of different target objects in an X-Z axis plane in three-dimensional space according to an embodiment of the present invention;
fig. 5 is a flowchart of a phase error estimation result according to an embodiment of the present invention;
FIG. 6 is a flow chart of phase error estimation and compensation according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a data acquisition scenario and hardware device according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a hand-held synthetic aperture radar imaging system for near-field three-dimensional according to an embodiment of the invention;
FIG. 9 is a comparative schematic diagram of non-phase compensation, phase compensation followed by true values in performing image reconstruction according to an embodiment of the present invention;
FIG. 10 (a) is a schematic diagram of peak signal-to-noise ratio of an image after phase compensation according to an embodiment of the present invention;
FIG. 10 (b) is a schematic diagram of structural similarity after phase compensation according to an embodiment of the present invention;
FIG. 11 is a schematic illustration of imaging effects with an angular reaction reference object in different positions, according to an embodiment of the present invention;
FIG. 12 is a schematic view of imaging effects under non-line-of-sight conditions according to an embodiment of the present invention;
FIG. 13 is a schematic illustration of a multi-scan imaging effect according to an embodiment of the invention;
fig. 14 is a block diagram of an electronic device suitable for implementing a hand-held synthetic aperture radar imaging method for near-field three-dimensions in accordance with an embodiment of the invention.
Detailed Description
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Millimeter wave imaging is widely applied to the fields of security inspection imaging, automatic driving, medical detection and the like. Millimeter wave signals have many advantages, for example, millimeter wave signals are not affected by light, so that their operation is not affected by the surrounding illumination environment; secondly, millimeter wave signals are transparent to certain materials so that they can be imaged at non-line-of-sight conditions; finally, compared with X-ray, the millimeter wave signal has smaller radiation to human body and safer use.
However, the existing millimeter wave imaging system is mainly based on a large-scale antenna array, and has the disadvantages of complex hardware structure, high manufacturing difficulty and high manufacturing cost; the technical disadvantages limit the application scenarios of the millimeter wave imaging system and reduce the convenience of the millimeter wave imaging system. From this, it is known that current millimeter wave imaging cannot be popularized and popularized on a large scale. Therefore, research on how to improve the resolution ratio of the millimeter wave imaging system, reduce the hardware cost of the system, improve the flexibility and portability of the system, and have important significance for promoting the application of the millimeter wave imaging to the ground actual scene.
In order to solve various technical problems in the prior art, the invention completes the synthetic aperture imaging by realizing the scanning of the handheld device, thereby improving the resolution of the device, ensuring the low cost and portability of the system, and avoiding the use of an expensive antenna array and a heavy mechanical scanning device.
It should be specifically noted that, in the technical scheme disclosed by the invention, the related millimeter wave imaging data is obtained by authorization of the related party, and the related millimeter wave imaging data is processed, applied and stored under the permission of the related party, so that the related process accords with the rules of laws and regulations, necessary and reliable confidentiality measures are adopted, and the requirements of popular regulations are met.
FIG. 1 is a flow chart of a method for three-dimensional hand-held synthetic aperture radar imaging in accordance with an embodiment of the present invention.
As shown in fig. 1, the above-mentioned hand-held synthetic aperture radar imaging method for near-field three-dimension includes: operations S110 to S140.
In operation S110, the moving hand-held synthetic aperture millimeter wave radar is positioned by using the positioning camera to obtain a positioning result, and the oversampling of the target object and the reference object is achieved by increasing the frame rate of the hand-held synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object.
Alternatively, the hand-held synthetic aperture millimeter wave radar moves along the X-axis of the three-dimensional spatial coordinate system. The positioning camera tracks and positions the motion process of the hand-held synthetic aperture millimeter wave radar.
In operation S120, according to the positioning result, the frame data of the target object is uniformly spaced by a resampling method, so as to implement speed compensation of the frame data of the target object, and obtain the initial calibration result of the frame data of the target object.
Imaging methods based on fourier transforms require radar motion to be uniform. In order to realize uniform motion under the condition of handholding, the invention utilizes a positioning camera to track the motion of the radar, and realizes oversampling by improving the frame rate of the radar, so as to resample the frame data acquired by the radar to uniform intervals by utilizing the positioning result of the camera.
The frame data of the target object may be made to have a uniform time interval by resampling.
In operation S130, based on the spatial asymmetry and the local similarity of the phase error, the phase error estimation is performed on the frame data of the reference object to obtain a phase error estimation result, and the primary calibration result of the frame data of the target object is phase-compensated according to the phase error estimation result to obtain a secondary calibration result of the frame data of the target object.
According to the embodiment of the invention, the spatial asymmetry represents that the same motion error generates different phase errors in different directions of the three-dimensional space in the motion process of the target object in the three-dimensional space; wherein the spatial asymmetry based on the phase error can simplify the phase error estimation problem in three-dimensional space to a phase error estimation problem in distance dimension.
According to an embodiment of the present invention, the local similarity of the phase errors indicates that the phase errors generated by two objects having different position information are within a preset range in a three-dimensional space; wherein the phase difference of one object in the three-dimensional space can be approximated by estimating the phase difference of another object in the three-dimensional space based on the local similarity of the phase errors.
In operation S140, a range migration imaging algorithm is used to perform three-dimensional near-field imaging on the secondary calibration result, so as to obtain an imaging result of the target object.
According to the handheld synthetic aperture radar imaging method for near-field three-dimension, provided by the invention, the technical problem that fast imaging based on Fourier transform cannot be performed due to non-uniform linear motion of handheld radar equipment is solved by performing speed compensation and phase compensation on radar echo signals of a target object; the imaging method of the handheld synthetic aperture radar for near-field three dimensions can solve the imaging problem of the handheld radar device, can solve the technical problems of blurring and deformation of imaging images of the handheld radar device in the prior art, improves the reconstruction quality of a target object, greatly expands the application scene of the handheld synthetic aperture radar, improves the convenience of the handheld synthetic aperture radar and reduces the imaging cost of the handheld synthetic aperture radar.
In order to illustrate the principle and effectiveness of the method provided by the present invention, the method provided by the present invention is described in further detail below with reference to the specific embodiments and fig. 2 to 4.
Fig. 2 is a schematic diagram of motion error and phase error in a specific axis direction in a three-dimensional space coordinate system according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of phase error relationships of different target objects in three-dimensional space according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of the distribution of propagation distance differences of different target objects in an X-Z axis plane in three-dimensional space according to an embodiment of the present invention.
The technical difficulty of the invention is mainly how to overcome the motion error during hand-held scanning. In order to apply the fast imaging method based on the fourier transform, the motion track of the antenna should be uniform linear motion. However, in the case of hand-held scanning, this requirement is not met. In addition, existing mobile positioning techniques are also unable to meet the requirements of using existing motion compensation algorithms. The motion error can cause phase error of the received signal, so that coherent superposition of the signal cannot be realized, finally, image blurring and deformation are caused, and a target object cannot be reconstructed correctly.
In order to solve the technical difficulty, the invention reveals two important characteristics by analyzing the generation reason of the phase error: spatial asymmetry and local similarity. Spatial asymmetry refers to the fact that the same motion error will have different effects (e.g., phase error) in different directions of motion. As shown in fig. 2 (a) and fig. 2 (b), wherein fig. 2 (a) is a schematic diagram of a motion error and a phase error in an X-axis direction in a three-dimensional space coordinate system according to an embodiment of the present invention, and fig. 2 (b) is a schematic diagram of a motion error and a phase error in a Z-axis direction in a three-dimensional space coordinate system according to an embodiment of the present invention; assuming that a point target is 1m away from a 77GHz radar, the phase error generated when the radar device deviates from the Z axis is significantly larger than that of the X axis (the space coordinate system is that the X axis is the radar motion direction, the Y axis is the vertical direction, and the Z axis is the distance dimension direction). The spatial asymmetry allows for phase error estimation and compensation with respect to only the Z-axis direction that is most sensitive to motion errors.
Local similarity refers to two objects in space that are located differently, and their phase errors may also be very close.
As shown in FIG. 3, it is assumed that there are coordinates of two different point target objects in the x-z plane、/>Ideal motion position information of hand-held synthetic aperture millimeter wave radar in three-dimensional space>Actual motion position information of hand-held synthetic aperture millimeter wave radar in three-dimensional space>The difference between the propagation distance errors of the two target objects is>Can be expressed as the following formula:
，
，
，
smaller represents closer phase error between the two targets. As shown in FIG. 4, when->Is 10mm in diameter and is preferably used for the treatment of the heart disease,，/>when (I)>Along with->Is a variation of (c). The dark black area in FIG. 4 represents the same +.>In this position, its phase error can be relatively close to +.>Is a phase error of (a) in the phase of the signal. The local similarity allows the phase error of one object to be approximated by estimating the phase error of another object.
Based on the two characteristics, the invention provides a speed compensation, phase error estimation and compensation method for near-field three-dimensional hand-held synthetic aperture imaging, so that high-resolution images are reconstructed from signals containing phase errors.
Fig. 5 is a flowchart of a phase error estimation result according to an embodiment of the present invention.
As shown in fig. 5, the phase error estimation is performed on the frame data of the reference object based on the spatial asymmetry and the local similarity of the phase error, and the phase error estimation result includes operations S510 to S530.
In operation S510, an original phase history of a reference object having a hand-held motion error is acquired from frame data of the reference object.
In operation S520, the original phase history of the reference object is fitted to a quadratic curve by using a least square method, and an estimation result of the ideal phase history of the reference object is obtained.
In operation S530, the original phase history of the reference object is subjected to a difference operation with the estimation result of the ideal phase history of the reference object, to obtain a phase error estimation result.
Fig. 6 is a schematic flow chart of phase error estimation and compensation according to an embodiment of the invention.
The process of phase error estimation and compensation described above is described in further detail below in conjunction with fig. 6.
As shown in fig. 6, the present invention approximates the phase error of an imaging target by estimating the phase error of a reference by setting an angular reaction as a reference in an imaging scene based on the spatial asymmetry and local similarity of the phase error. First, an original phase history of the reference object including a handheld motion error is obtained. When the equipment moves linearly at a uniform speed, the phase course of a single point target is supposed to be quadratic curve change, and the invention fits the original phase course of the reference object into quadratic curve through a least square method to obtain ideal phase change of the reference object, and then makes a difference with the actual phase change to obtain a phase error estimation result.
According to an embodiment of the present invention, the estimation result of the ideal phase history of the reference object is expressed by the following formula:
，
wherein,indicating the%>Estimation of the ideal phase history of the frame data sampled by the individual hand-held synthetic aperture millimeter wave radar, < >>Representing the coefficients;
wherein the phase error estimation result is represented by the following formula:
，
wherein,indicate->Hand-held synthetic aperture millimeter wave radar sampling reference objectThe original phase of the frame data of the volume.
According to an embodiment of the present invention, the above-described hand-held synthetic aperture millimeter wave radar includes a multi-chip cascaded millimeter wave radar; wherein the positioning camera comprises a camera with a motion tracking function and a spatial positioning function; the hand-held synthetic aperture millimeter wave radar in motion represents that the hand-held synthetic aperture millimeter wave radar moves along the X axis of the three-dimensional space coordinate system.
Fig. 7 is a schematic diagram of a data acquisition scenario and hardware device according to an embodiment of the present invention.
As shown in fig. 7, the hardware components of the present invention include a TI four chip cascaded millimeter wave radar development board and intel RealSense T265 tracking camera. The camera is used for positioning the motion of the radar in the x-axis, and resampling radar frames to uniform motion by utilizing the camera positioning result. At the time of data acquisition, the imaging system was held by the experimenter for approximately 20cm of motion. The reference is used for the subsequent phase error estimation.
Fig. 8 is a schematic diagram of a hand-held synthetic aperture radar imaging system for near-field three-dimensional use in accordance with an embodiment of the present invention.
As shown in fig. 8, the handheld synthetic aperture radar imaging system 800 for near-field three-dimensional applications described above includes a data acquisition module 810, a speed compensation module 820, a phase compensation module 830, and an imaging module 840.
The data acquisition module 810 is configured to position the moving handheld synthetic aperture millimeter wave radar with a positioning camera to obtain a positioning result, and to perform oversampling on the target object and the reference object by increasing a frame rate of the handheld synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object.
The speed compensation module 820 is configured to resample frame data of the target object to have a uniform interval according to the positioning result to implement speed compensation on the frame data of the target object, so as to obtain a primary calibration result of the frame data of the target object.
The phase compensation module 830 is configured to perform phase error estimation on frame data of a reference object based on spatial asymmetry and local similarity of phase errors to obtain a phase error estimation result, and perform phase compensation on a primary calibration result of frame data of a target object according to the phase error result to obtain a secondary calibration result of frame data of the target object.
And the imaging module 840 is used for performing three-dimensional near-field imaging on the secondary calibration result of the frame data of the target object by using a range migration imaging algorithm to obtain an imaging result of the target object.
The effectiveness of the handheld synthetic aperture radar imaging method for near-field three-dimension provided by the invention is further described in various aspects through specific experiments and fig. 9-13, wherein hardware equipment and a data acquisition scene adopted by the experiments are shown in fig. 7.
FIG. 9 is a comparative schematic diagram of the non-phase compensation, the phase compensation, and the true values during image reconstruction according to an embodiment of the present invention.
In terms of qualitative analysis, to verify the effectiveness of the present invention, 10 different metal letters were imaged 200 times from 4 different users. The radar is spaced 0.3 meters from the object being imaged and the reference is located at about 1.5 meters. The following is a comparison result of whether the phase error compensation method proposed by the present invention is used. It can be seen from fig. 9 that the method proposed by the present invention can effectively overcome the motion error in the hand-held synthetic aperture imaging and reconstruct a high quality image.
Fig. 10 (a) and 10 (b) are schematic diagrams of peak signal to noise ratio and structural similarity of an image after phase compensation according to an embodiment of the present invention, where fig. 10 (a) is a schematic diagram of peak signal to noise ratio of an image after phase compensation according to an embodiment of the present invention, and fig. 10 (b) is a schematic diagram of structural similarity after phase compensation according to an embodiment of the present invention.
In terms of quantitative analysis, by quantitatively analyzing the above-described collected imaging data, it is concluded that: after the phase error estimation and compensation method provided by the invention is used, the peak signal-to-noise ratio (PSNR) of the image is averagely improved by 4.54dB (shown in fig. 10 (a)), and the structural similarity is averagely improved by 31.19% (shown in fig. 10 (b)).
FIG. 11 is a schematic illustration of imaging effects with an angular reaction object in different positions, according to an embodiment of the present invention.
In order to verify that the method provided by the invention can effectively work under different reference object distances, an imaging object (a fruit knife) is placed at a position of 0.3m of a range radar, and angle counter references are respectively placed at a position of 1m and 2 m and a position of 3m, so that hand-held synthetic aperture imaging is carried out. As shown in fig. 11, after the phase compensation method provided by the invention is used, the quality of the reconstructed image is obviously improved, and the basic shape of an object can be obviously distinguished.
Fig. 12 is a schematic view of imaging effects under non-line-of-sight conditions according to an embodiment of the present invention.
In order to verify that the invention can effectively image under the non-line-of-sight condition, an imaging object (a pair of scissors) is placed at a position of 0.35 m from a radar, an angular counter reference is placed at a position of about 2 m, and cloth, paper and plastic objects are used for shielding respectively, and hand-held imaging is carried out. The results of fig. 12 verify that the present invention successfully reconstructs the shape of the object under non-line-of-sight conditions: the first behaviour does not use the phase compensation result and the second behaviour uses the phase compensation result.
Fig. 13 is a schematic diagram of a multi-scan imaging effect according to an embodiment of the present invention.
The method provided by the invention can be expanded to image a larger target by combining multiple scanning results. In the following figures, the object to be imaged is a five-pointed star with a length and width of 25cm, and the two angles are respectively located at 1.5 m and 1.8 m (to avoid shielding). Fig. 13 verifies that by combining multiple scan imaging results, the present invention can achieve image reconstruction for a larger imaging region.
Fig. 14 schematically shows a block diagram of an electronic device adapted to implement a hand-held synthetic aperture radar imaging method for near-field three-dimensional according to an embodiment of the invention.
As shown in fig. 14, an electronic device 1400 according to an embodiment of the present invention includes a processor 1401 that can perform various appropriate actions and processes according to a program stored in a Read Only Memory (ROM) 1402 or a program loaded from a storage section 1408 into a Random Access Memory (RAM) 1403. The processor 1401 may include, for example, a general purpose microprocessor (e.g., a CPU), an instruction set processor and/or an associated chipset and/or a special purpose microprocessor (e.g., an Application Specific Integrated Circuit (ASIC)), or the like. The processor 1401 may also include on-board memory for caching purposes. The processor 1401 may comprise a single processing unit or a plurality of processing units for performing different actions of the method flows according to embodiments of the invention.
In the RAM 1403, various programs and data necessary for the operation of the electronic device 1400 are stored. The processor 1401, ROM 1402, and RAM 1403 are connected to each other through a bus 1404. The processor 1401 performs various operations of the method flow according to the embodiment of the present invention by executing programs in the ROM 1402 and/or the RAM 1403. Note that the program may be stored in one or more memories other than the ROM 1402 and the RAM 1403. The processor 1401 may also perform various operations of the method flow according to embodiments of the present invention by executing programs stored in one or more memories.
According to an embodiment of the invention, the electronic device 1400 may also include an input/output (I/O) interface 1405, the input/output (I/O) interface 1405 also being connected to the bus 1404. Electronic device 1400 may also include one or more of the following components connected to I/O interface 1405: an input section 1406 including a keyboard, a mouse, and the like; an output portion 1407 including a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), and the like, a speaker, and the like; a storage section 1408 including a hard disk or the like; and a communication section 1409 including a network interface card such as a LAN card, a modem, and the like. The communication section 1409 performs communication processing via a network such as the internet. The drive 1410 is also connected to the I/O interface 1405 as needed. Removable media 1411, such as magnetic disks, optical disks, magneto-optical disks, semiconductor memory, and the like, is installed as needed on drive 1410 so that a computer program read therefrom is installed as needed into storage portion 1408.
The present invention also provides a computer-readable storage medium that may be embodied in the apparatus/device/system described in the above embodiments; or may exist alone without being assembled into the apparatus/device/system. The computer-readable storage medium carries one or more programs which, when executed, implement methods in accordance with embodiments of the present invention.
According to embodiments of the present invention, the computer-readable storage medium may be a non-volatile computer-readable storage medium, which may include, for example, but is not limited to: a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. For example, according to embodiments of the invention, the computer-readable storage medium may include ROM 1402 and/or RAM 1403 described above and/or one or more memories other than ROM 1402 and RAM 1403.
The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams or flowchart illustration, and combinations of blocks in the block diagrams or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present invention, and are not meant to limit the scope of the invention, but to limit the invention thereto.
Claims (10)
1. A hand-held synthetic aperture radar imaging method for near-field three-dimensional, comprising:
positioning a moving hand-held synthetic aperture millimeter wave radar by using a positioning camera to obtain a positioning result, and realizing oversampling of a target object and a reference object by improving the frame rate of the hand-held synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object;
according to the positioning result, the frame data of the target object are uniformly spaced in a resampling mode so as to realize the speed compensation of the frame data of the target object, and the initial calibration result of the frame data of the target object is obtained;
based on the spatial asymmetry and the local similarity of the phase error, carrying out phase error estimation on the frame data of the reference object to obtain a phase error estimation result, and carrying out phase compensation on a primary calibration result of the frame data of the target object according to the phase error estimation result to obtain a secondary calibration result of the frame data of the target object;
and performing three-dimensional near-field imaging on the secondary calibration result by using a range migration imaging algorithm to obtain an imaging result of the target object.
2. The method of claim 1, wherein the spatial asymmetry indicates that the same motion error will produce different phase errors in different directions of the three-dimensional space during motion of the target object in the three-dimensional space.
3. The method according to claim 1, wherein the local similarity of the phase errors indicates that the phase errors generated by two objects having different position information are within a preset range in three-dimensional space;
wherein the spatial asymmetry based on the phase error can simplify the phase error estimation problem in three-dimensional space to a phase error estimation problem in distance dimension.
4. A method according to claim 3, wherein the local similarity of the phase errors is represented by the following formula:
，
，
，
wherein,information representing the position of a first object in said three-dimensional space,/or->Representing position information of a second object in the three-dimensional space, and (2)>Ideal motion position information representing the hand-held synthetic aperture millimeter wave radar in the three-dimensional space, +.>Representing a hand-held synthetic aperture millimeter wave in the three-dimensional spaceActual motion position information of the radar.
5. The method of claim 1, wherein performing phase error estimation on the frame data of the reference object based on the spatial asymmetry and the local similarity of the phase error, the obtaining a phase error estimation result comprises:
acquiring an original phase history of the reference object with a handheld motion error from frame data of the reference object;
fitting the original phase history of the reference object into a quadratic curve by using a least square method to obtain an estimation result of the ideal phase history of the reference object;
and performing difference operation on the original phase history of the reference object and the estimation result of the ideal phase history of the reference object to obtain the phase error estimation result.
6. The method of claim 5, wherein the estimation of the ideal phase history of the reference object is represented by the following formula:
，
wherein,indicating +.>Estimation of the ideal phase history of the frame data sampled by the individual hand-held synthetic aperture millimeter wave radar, < >>Representing the coefficients;
wherein the phase error estimation result is expressed by the following formula:
，
wherein,indicate->A hand-held synthetic aperture millimeter wave radar samples the raw phase of the frame data of the reference object.
7. The method of claim 1, wherein the hand-held synthetic aperture millimeter wave radar comprises a multi-chip cascaded millimeter wave radar;
wherein the positioning camera comprises a camera with a motion tracking function and a spatial positioning function;
the hand-held synthetic aperture millimeter wave radar in motion represents that the hand-held synthetic aperture millimeter wave radar moves along an X axis of a three-dimensional space coordinate system.
8. A hand-held synthetic aperture radar imaging system for near-field three-dimensional, comprising:
the data acquisition module is used for positioning the moving hand-held synthetic aperture millimeter wave radar by using a positioning camera to obtain a positioning result, and oversampling of a target object and a reference object is realized by improving the frame rate of the hand-held synthetic aperture millimeter wave radar to obtain frame data of the target object and frame data of the reference object;
the speed compensation module is used for resampling the frame data of the target object to have uniform intervals according to the positioning result so as to realize speed compensation of the frame data of the target object, and obtaining a primary calibration result of the frame data of the target object;
the phase compensation module is used for carrying out phase error estimation on the frame data of the reference object based on the spatial asymmetry and the local similarity of the phase error to obtain a phase error estimation result, and carrying out phase compensation on the primary calibration result of the frame data of the target object according to the phase error result to obtain a secondary calibration result of the frame data of the target object;
and the imaging module is used for performing three-dimensional near-field imaging on the secondary calibration result of the frame data of the target object by using a range migration imaging algorithm to obtain an imaging result of the target object.
9. An electronic device, comprising:
one or more processors;
storage means for storing one or more programs,
wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to perform the method of any of claims 1-7.
10. A computer readable storage medium having stored thereon executable instructions which, when executed by a processor, cause the processor to perform the method according to any of claims 1-7.
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