Low-altitude weak target detection method and device based on synthetic wavelength

Abstract

The invention provides a low-altitude weak target detection method and device based on synthetic wavelength, which can be applied to the field of target detection. The method comprises the following steps: imaging echo data of a to-be-detected area without any to-be-detected target to obtain a first image; imaging the echo data of the to-be-detected area with the to-be-detected target to obtain a second image; performing interference operation on the first image and the second image to obtain a phase interferogram frequency spectrum; cutting the phase interferogram frequency spectrum to obtain a first wavelength phase interferogram and a second wavelength phase interferogram; generating a differential synthesis wavelength interferogram and an additive synthesis wavelength interferogram according to the first wavelength phase interferogram and the second wavelength phase interferogram; and unwrapping the additive synthetic wavelength interferogram by using the differential synthetic wavelength interferogram, and detecting the target to be detected based on the unwrapped additive synthetic wavelength interferogram. In this way, the target and clutter in the low-altitude environment are effectively recognized, and the detection precision is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of target detection, specifically applied to the low-altitude target detection scene, and more particularly to a low-altitude weak target detection method, device, equipment, medium and program product based on a synthetic wavelength. BACKGROUND

[0002] Low-altitude economy refers to a comprehensive economic form taking low-altitude airspace (usually below 1000 meters, and extending to 3000 meters in some scenarios) as a carrier, taking unmanned aerial vehicles, electric vertical take-off and landing aircraft, general aircraft and the like as tools, and covering manufacturing, operation, services and derivative business forms. The core application scenarios of low-altitude economy include logistics and distribution, emergency rescue, agricultural plant protection, urban governance, low-altitude tourism and the like. Low-altitude economic activities are highly dependent on flight safety, and illegal use of "low, slow and small" targets (low-altitude, slow-speed, small aircraft such as consumer-level unmanned aerial vehicles) poses a serious threat to public safety and airspace management, so it is particularly important to detect "low, slow and small" targets.

[0003] Currently, the detection means for low-altitude weak targets (i.e., "low, slow and small" targets) can be mainly divided into optical detection, radio detection and radar imaging. The optical detection technology mainly uses visible light, infrared and other optical sensors to capture target images, and realizes target recognition through image processing algorithms. For example, infrared thermal imaging technology can detect targets by the difference in thermal radiation between the target and the background, and is suitable for night or low-light environments, but is greatly affected by weather (such as rainy and snowy weather), and target features are easily disturbed by environmental noise. Radio detection technology realizes positioning by analyzing the radio signals (such as unmanned aerial vehicle remote control signals) emitted by the target, and is suitable for scenarios without active return signals, but needs to rely on active communication of the target, and is easily disturbed by the electromagnetic environment. Radar-based detection technology has become the most widely used detection technology at present due to its small weather influence and independence from active communication of the target, but the current radar-based detection technology has the following problems: (1) easily disturbed by low-altitude clutter: in a low-altitude environment, radar signals are easily disturbed by ground, building, vegetation and other reflected clutter, resulting in target echoes being submerged, for example, the ground clutter intensity can be tens of times higher than the target echo, and traditional radars are difficult to distinguish. (2) difficult to detect slow targets: the Doppler shift of the echo of slow or hovering targets is close to zero, which is difficult to distinguish from stationary clutter, and traditional moving target display technology will filter out such signals, resulting in missed detection. (3) difficult to detect small targets: the radar scattering cross section of low, slow and small targets is usually less than 2 m², the echo energy of small targets is weak, and small targets can use non-metallic materials, which will further reduce the signal strength, making it more difficult to detect weak small targets. SUMMARY

[0004] In view of the above problems, the application provides a low-altitude weak target detection method based on a synthetic wavelength, a device, equipment, medium and program product, which can improve the detection accuracy, especially the detection accuracy of low-altitude, slow and small targets, and reduce noise.

[0005] According to a first aspect of the application, a low-altitude weak target detection method based on a synthetic wavelength is provided, comprising: imaging echo data of a to-be-detected region without any to-be-detected target to obtain a first image; imaging echo data of a to-be-detected region with a to-be-detected target to obtain a second image; performing an interference operation on the first image and the second image to obtain a phase interference spectrum; clipping the phase interference spectrum to obtain a first wavelength phase interference and a second wavelength phase interference; generating a differential synthetic wavelength interference and an additive synthetic wavelength interference according to the first wavelength phase interference and the second wavelength phase interference; unwrapping the additive synthetic wavelength interference using the differential synthetic wavelength interference, and detecting the to-be-detected target based on the unwrapped additive synthetic wavelength interference.

[0006] According to an embodiment of the application, before performing the interference operation on the first image and the second image, the method comprises: registering the first image and the second image, comprising: calculating a cross-correlation function using image features of the first image and the second image, determining an offset of the first image and the second image according to the cross-correlation function; adjusting the second image according to the offset, calculating an offset of the adjusted second image and the first image; repeating the second image adjustment and the offset calculation until the obtained offset is less than a preset threshold.

[0007] According to an embodiment of the application, the clipping of the phase interference spectrum to obtain the first wavelength phase interference and the second wavelength phase interference comprises: clipping a high-frequency part of the phase interference spectrum, and performing linear phase compensation and inverse fast Fourier transform on the clipped spectrum to obtain the first wavelength phase interference; clipping a low-frequency part of the phase interference spectrum, and performing linear phase compensation and inverse fast Fourier transform on the clipped spectrum to obtain the second wavelength phase interference.

[0008] According to an embodiment of the application, the generation of the differential synthetic wavelength interference and the additive synthetic wavelength interference according to the first wavelength phase interference and the second wavelength phase interference comprises: adding the first wavelength phase interference and the second wavelength phase interference to obtain the additive synthetic wavelength interference; subtracting the first wavelength phase interference from the second wavelength phase interference to obtain the differential synthetic wavelength interference.

[0009] According to an embodiment of the present application, unwrapping the additive synthetic wavelength interferogram based on the differential synthetic wavelength interferogram comprises: calculating a distance difference corresponding to the differential phase according to the differential synthetic wavelength corresponding to the differential synthetic wavelength interferogram and the differential phase contained in the differential synthetic wavelength interferogram; calculating a distance difference of an ideal differential phase corresponding to the differential phase according to the distance difference corresponding to the differential phase and the differential synthetic wavelength interferogram; and obtaining the unwrapped additive synthetic wavelength interferogram according to the distance difference of the ideal differential phase corresponding to the differential phase and the synthetic phase contained in the additive synthetic wavelength interferogram.

[0010] According to an embodiment of the present application, the distance difference of the ideal differential phase corresponding to the differential phase is calculated according to the distance difference corresponding to the differential phase and the differential synthetic wavelength interferogram, comprising: disentangling the differential phase contained in the differential synthetic wavelength interferogram to obtain an ideal differential phase corresponding to the differential phase; and calculating the distance difference of the ideal differential phase according to the ideal differential phase, an ideal differential synthetic wavelength corresponding to the ideal differential phase, and the distance difference of the differential phase corresponding to the ideal differential phase.

[0011] According to an embodiment of the present application, the unwrapped additive synthetic wavelength interferogram is obtained according to the distance difference of the ideal differential phase corresponding to the differential phase and the synthetic phase contained in the additive synthetic wavelength interferogram, comprising: unwrapping the corresponding synthetic phase in the additive synthetic wavelength interferogram according to the distance difference of the ideal differential phase corresponding to the differential phase to obtain an unwrapped synthetic phase; and generating the unwrapped additive synthetic wavelength interferogram according to the unwrapped synthetic phase.

[0012] According to an embodiment of the present application, the target to be detected is detected based on the unwrapped additive synthetic wavelength interferogram, comprising: extracting a feature of the unwrapped additive synthetic wavelength interferogram; wherein the feature comprises a phase statistical feature, an interference fringe feature, and a multi-scale feature, the multi-scale feature comprising a phase statistical feature and / or an interference fringe feature extracted at different resolutions; and detecting the target to be detected based on the feature by using a preset target detection algorithm.

[0013] The second aspect of the present application provides a low-altitude weak target detection device based on synthetic wavelength, comprising:

[0014] The radar imaging module is configured to image echo data of a detection area in which no target to be detected exists to obtain a first image, and image echo data of a detection area in which a target to be detected exists to obtain a second image.

[0015] The phase interferogram spectrum acquisition module is configured to perform an interference operation on the first image and the second image to obtain a phase interferogram spectrum.

[0016] a phase interference spectrum spectrum clipping module configured to clip a phase interference spectrum to obtain a first wavelength phase interference and a second wavelength phase interference;

[0017] a wavelength synthesis module configured to generate a differential synthetic wavelength interference and an additive synthetic wavelength interference according to the first wavelength phase interference and the second wavelength phase interference;

[0018] a target detection module configured to unwrap the additive synthetic wavelength interference using the differential synthetic wavelength interference, and detect a target to be detected based on the unwrapped additive synthetic wavelength interference.

[0019] A third aspect of the present application provides an electronic device, comprising: one or more processors; a memory for storing one or more computer programs, wherein the one or more processors execute the one or more computer programs to implement the steps of the method.

[0020] A fourth aspect of the present application further provides a computer-readable storage medium having stored thereon a computer program or instructions, wherein the computer program or instructions, when executed by a processor, implement the steps of the method.

[0021] A fifth aspect of the present application further provides a computer program product comprising a computer program or instructions, wherein the computer program or instructions, when executed by a processor, implement the steps of the method.

[0022] The one or more embodiments have the following beneficial effects: the phase interference method can effectively identify noise, thereby effectively identifying targets and clutter in a low-altitude environment, and can also accurately identify slow targets and small targets. Compared with the traditional amplitude interference method, the phase interference method can effectively avoid false alarms and missed alarms caused by improper detection threshold division, thereby improving detection accuracy and reducing the probability of false detection and missed detection. The wavelength synthesis method uses the differential synthetic wavelength interference to unwrap the additive synthetic wavelength interference, which can greatly reduce the error diffusion and other problems existing in the traditional unwrapping method, thereby greatly reducing the influence of noise on target detection. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application, taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 An application scenario diagram of a synthetic wavelength-based low-altitude weak target detection method, device, equipment, medium and program product according to an embodiment of the present application is schematically shown;

[0025] Figure 2 A flowchart of a synthetic wavelength-based low-altitude weak target detection method according to an embodiment of the present application is schematically shown.

[0026] Figure 3 A schematic diagram of an image registration method according to an embodiment of the present application is shown;

[0027] Figure 4 A schematic diagram of a flowchart for obtaining unwrapped additive synthetic wavelength interferograms according to an embodiment of the present application is shown;

[0028] Figure 5 A block diagram of a structure of a low-altitude weak target detection device based on synthetic wavelengths according to an embodiment of the present application is shown;

[0029] Figure 6 A block diagram of an electronic device suitable for implementing a low-altitude weak target detection method based on synthetic wavelengths according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary of the present application, and is not intended to limit the scope of the present application. In the following detailed description of the embodiments of the present application, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring aspects of the present application.

[0031] The terms used herein are merely used to describe specific embodiments, and are not intended to limit the present application. The terms "include" and "have" and the like used herein indicate the presence of the described features, steps, operations, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

[0032] All terms used herein, including technical and scientific terms, have the same meanings as those generally understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the present specification, and should not be interpreted in an idealized or excessively formal manner.

[0033] In the case of using expressions similar to "at least one of A, B, and C, etc.", it is generally to be interpreted as including one or more of the same. For example, "a system having at least one of A, B, and C" should be interpreted as including a system having A alone, a system having B alone, a system having C alone, a system having both A and B, a system having both A and C, a system having both B and C, and / or a system having A, B, and C together, etc.

[0034] Embodiments of the present application provide a low-altitude weak target detection method based on synthetic wavelength. The method takes a first image as a base map, performs an interference operation on the first image and a second image to obtain a phase interference graph spectrum, wherein the first image is an image generated according to echo data of a to-be-detected region in which there is no to-be-detected target, the second image is an image generated according to echo data of a to-be-detected region in which there is a to-be-detected target, two single-wavelength corresponding phase interference graphs are obtained by clipping the phase interference graph spectrum, an additive synthetic wavelength interference graph is obtained by adding the two single-wavelength corresponding phase interference graphs, a differential synthetic wavelength interference graph is obtained by subtracting the two single-wavelength corresponding phase interference graphs, the differential synthetic wavelength interference graph is used to unwrap the additive synthetic wavelength interference graph to obtain an unwrapped additive synthetic wavelength interference graph, and the to-be-detected target is detected according to the unwrapped additive synthetic wavelength interference graph. In this way, the noise can be reduced, the probability that the target echo is submerged by clutter in the low-altitude environment can be reduced, the detection capability for slow and small targets can be improved, and thus the miss detection and false detection probabilities can be reduced, and the detection accuracy can be improved. When the target is detected, the phase interference method is used instead of the traditional amplitude interference method, which can effectively reduce the false alarm and missed alarm caused by improper detection threshold division, thereby significantly improving the robustness of dynamic noise and being more conducive to detecting weak targets.

[0035] Figure 1 An application scenario diagram of the low-altitude weak target detection method based on synthetic wavelength according to an embodiment of the present application is schematically shown.

[0036] As shown in Figure 1 The application scenario 100 according to the embodiment can include a first terminal device 101, a second terminal device 102, a third terminal device 103, a network 104, and a server 105. The network 104 is a medium for providing a communication link between the first terminal device 101, the second terminal device 102, the third terminal device 103, and the server 105. The network 104 can include various connection types, such as wired, wireless communication links, or optical fiber cables, and the like.

[0037] A user can use the first terminal device 101, the second terminal device 102, and the third terminal device 103 to interact with the server 105 through the network 104 to receive or send messages, and the like. Various communication client applications can be installed on the first terminal device 101, the second terminal device 102, and the third terminal device 103, such as shopping applications, web browser applications, search applications, instant messaging tools, email clients, social platform software, and the like (only as examples).

[0038] The first terminal device 101, the second terminal device 102, and the third terminal device 103 can be various electronic devices with display screens and supporting web browsing, including but not limited to smart phones, tablet computers, laptop computers, desktop computers, and the like.

[0039] Server 105 can be a server that provides various services, such as a backend management server that supports websites browsed by users using the first terminal device 101, the second terminal device 102, and the third terminal device 103 (this is just an example). The backend management server can analyze and process data such as received user requests, and feed back the processing results (such as web pages, information, or data obtained or generated according to user requests) to the terminal devices.

[0040] It should be noted that the low-altitude weak target detection method based on synthetic wavelength provided in this application embodiment can generally be executed by server 105. Correspondingly, the low-altitude weak target detection device based on synthetic wavelength provided in this application embodiment can generally be installed in server 105. The low-altitude weak target detection method based on synthetic wavelength provided in this application embodiment can also be executed by a server or server cluster that is different from server 105 and capable of communicating with the first terminal device 101, the second terminal device 102, the third terminal device 103, and / or server 105. Correspondingly, the low-altitude weak target detection device based on synthetic wavelength provided in this application embodiment can also be installed in a server or server cluster that is different from server 105 and capable of communicating with the first terminal device 101, the second terminal device 102, the third terminal device 103, and / or server 105.

[0041] It should be understood that Figure 1 The number of terminal devices, networks, and servers shown is merely illustrative. Depending on implementation needs, any number of terminal devices, networks, and servers can be included.

[0042] The following will be based on Figure 1 The described scene, through Figures 2-4 A detailed description is provided of a low-altitude weak target detection method based on synthetic wavelength according to embodiments of this application.

[0043] Figure 2 A flowchart illustrating a low-altitude weak target detection method based on synthetic wavelength according to an embodiment of this application is shown.

[0044] like Figure 2 As shown, the low-altitude weak target detection method 200 based on synthetic wavelength in this embodiment includes operations S210 to S250.

[0045] In operation S210, the echo data of the area to be detected where there is no target is imaged to obtain a first image; the echo data of the area to be detected where there is a target is imaged to obtain a second image.

[0046] In operation S220, an interference operation is performed on the first image and the second image to obtain the phase interferogram spectrum.

[0047] In operation S230, the phase interferogram spectrum is cropped to obtain a first wavelength phase interferogram and a second wavelength phase interferogram.

[0048] In operation S240, a differential synthetic wavelength interferogram and an additive synthetic wavelength interferogram are generated according to the first wavelength phase interferogram and the second wavelength phase interferogram.

[0049] In operation S250, the additive synthetic wavelength interferogram is unwrapped by using the differential synthetic wavelength interferogram, and the target to be detected is detected based on the unwrapped additive synthetic wavelength interferogram.

[0050] In some embodiments, in operation S210, a multiple-input multiple-output radar (MIMO radar) can be used to detect the target area without any target to be detected and the target area with the target to be detected respectively, to obtain corresponding multi-channel echo data, and to perform imaging based on the obtained multi-channel echo data to obtain a first image and a second image respectively.

[0051] In some embodiments, in operation S210, the target to be detected can be a small object such as a stone, a mineral, a micro unmanned aerial vehicle, or a large object such as steel or wood.

[0052] According to embodiments of the present application, the phase interference method can effectively distinguish noise, thereby effectively identifying targets and clutter in a low-altitude environment, and can also accurately identify slow targets and small targets. Compared with the traditional amplitude interference method, the phase interference method can effectively avoid false alarms and missed alarms caused by improper detection threshold division, thereby improving detection accuracy and reducing the probability of false detection and missed detection. By using the wavelength synthesis method and unwrapping the additive synthetic wavelength interferogram by using the differential synthetic wavelength interferogram, the error diffusion problem existing in the traditional unwrapping method can be greatly reduced, thereby greatly reducing the influence of noise on target detection.

[0053] In some embodiments, in operation S210, the echo data (belonging to the multi-channel echo data) of the target area without any target to be detected can be represented as , wherein represents the echo data received by the mthantenna unit, represents a fast time, the fast time representing a time at which the radar samples the echo within a single pulse signal, represents a time at which the radar obtains the echo return; and the echo data (belonging to the multi-channel echo data) of the target area with the target to be detected can be represented as . Each of the echo data in the first image is superimposed and SAR imaging is performed to obtain a first image , and each of the echo data in the second image is superimposed and SAR imaging is performed to obtain a second image each echo data and SAR imaging to obtain a second image Further, and The calculation formulas of and are as follows, respectively:

[0054]

[0055]

[0056] wherein, represents the wavelength of the echo, represents the position of a pixel unit with an azimuth position of and a range position of represents the azimuth position of the i-th antenna unit at time represents the range position of the i-th antenna unit at time

[0057] Figure 3 An image registration method according to an embodiment of the present application is schematically shown.

[0058] As shown in Figure 3 , before the interference operation on the first image and the second image, the method comprises:

[0059] The first image and the second image are registered, specifically comprising operations S310-S340.

[0060] In operation S310, a cross-correlation function is calculated by using image features of the first image and the second image.

[0061] In operation S320, the offset of the first image and the second image is determined according to the cross-correlation function.

[0062] In operation S330, the second image is adjusted according to the offset, and the offset of the adjusted second image and the first image is calculated.

[0063] In operation S340, the second image adjustment and the offset calculation are repeated until the obtained offset is less than a preset threshold.

[0064] ​​​​​For example, when the size of the target to be detected is small, the detection process is easily affected by noise, the coherence of the first image and the second image is poor, and the effect obtained by using phase interference for subsequent target detection can be unsatisfactory. Therefore, it is necessary to improve the coherence of the first image and the second image. Assuming that the target to be detected is a small stone, since the size of the small stone is very small and the small stone is not made of metal, the echo energy of the small stone is very weak and is easily submerged by the echoes reflected by objects such as vegetation and buildings. If the echo reflected by the small stone is submerged by the echoes reflected by the objects such as vegetation and buildings, the echo at the position of the small stone in the second image is actually the echo reflected by the objects such as vegetation and buildings at the position, and the echo at the position corresponding to the position of the small stone in the first image is the echo reflected by the objects such as vegetation and buildings at the position. Therefore, the reflection intensity of the echo at the position of the small stone in the second image is approximately equal to the reflection intensity of the echo at the corresponding position in the first image. In this way, the small stone cannot be accurately detected, and the correlation of the first image and the second image is also poor. To solve this problem, the first image and the second image need to be registered. For example, the reflection intensity and other image features of the first image and the second image are extracted, respectively. The cross-correlation function between the first image and the second image is calculated according to the image features. The shift between the first image and the second image can be estimated by the cross-correlation function. Then, the second image is adjusted according to the calculated shift. The cross-correlation function between the adjusted second image and the first image is recalculated to estimate the shift between the adjusted second image and the first image. The adjustment of the second image and the calculation of the shift are repeated until the calculated shift is less than a preset threshold. When the shift is less than the preset threshold, it can be considered that the coherence between the first image and the second image is maximum.

[0065] In some embodiments, the registered first image is represented as , and the second image is represented as .

[0066] In some embodiments, in operation S220, an interference operation is performed on the first image and the second image to obtain a phase interference image , which can be represented as:

[0067]

[0068] wherein is a conjugate operation of , and is a phase acquisition operation. A Fourier transform is performed on the obtained phase interference image to obtain a phase interference image spectrum.

[0069] According to the embodiments of the present application, the echo data is interfered to form an image by using the phase interference method, which can effectively avoid false alarm and missed alarm caused by improper threshold division. For example, assuming that the target to be detected is a very small object, the traditional amplitude interference method cannot clearly present the amplitude change of the small target to be detected. However, by using the phase interference technology, the phase change of the small target to be detected can be clearly found from the phase interference image, so that the small target to be detected can be accurately detected, and the robustness of the dynamic noise can be improved and the probability of misjudgment can be reduced.

[0070] In some embodiments, in operation S230, the phase interference spectrum is cropped to obtain the first wavelength phase interference image and the second wavelength phase interference image, including: cropping the high-frequency part of the phase interference spectrum, and performing linear phase compensation and inverse fast Fourier transform on the cropped spectrum to obtain the first wavelength phase interference image; cropping the low-frequency part of the phase interference spectrum, and performing linear phase compensation and inverse fast Fourier transform on the cropped spectrum to obtain the second wavelength phase interference image.

[0071] Further, the high-frequency part of the phase interference spectrum can be first set to zero. Assuming that the high-frequency part accounts for half of the entire phase interference spectrum width, the phase interference image after the high-frequency part is set to zero is shifted to the middle by one quarter of the phase interference spectrum width. If the high-frequency part accounts for one third of the entire phase interference spectrum width, the phase interference spectrum after the high-frequency part is set to zero needs to be shifted to the middle by one sixth of the phase interference spectrum width. In this way, the phase interference spectrum after the high-frequency part is set to zero is linearly compensated to be moved to the middle, and then the linearly compensated phase interference spectrum is subjected to inverse fast Fourier transform to obtain the first wavelength phase interference image. The first wavelength corresponding to the first wavelength phase interference image belongs to low frequency, and the first wavelength is greater than the echo wavelength . Then, the low-frequency part of the phase interference spectrum is set to zero. Assuming that the low-frequency part accounts for half of the entire phase interference spectrum width, the phase interference image after the low-frequency part is set to zero is shifted to the middle by one quarter of the phase interference spectrum width. If the low-frequency part accounts for one third of the entire phase interference spectrum width, the phase interference spectrum after the low-frequency part is set to zero needs to be shifted to the middle by one sixth of the phase interference spectrum width. In this way, the phase interference spectrum after the low-frequency part is set to zero is linearly compensated to be moved to the middle, and then the linearly compensated phase interference spectrum is subjected to inverse fast Fourier transform to obtain the second wavelength phase interference image. The second wavelength corresponding to the second wavelength phase interference image belongs to high frequency, and the second wavelength is less than the echo wavelength .

[0072] In some embodiments, during operation S240, generating a differential composite wavelength interferogram and an additive composite wavelength interferogram based on the first wavelength phase interferogram and the second wavelength phase interferogram includes: adding the first wavelength phase interferogram and the second wavelength phase interferogram to obtain an additive composite wavelength interferogram; and subtracting the first wavelength phase interferogram and the second wavelength phase interferogram to obtain a differential composite wavelength interferogram.

[0073] Furthermore, pixel units in the additive composite wavelength interferogram The corresponding composite phase is represented as Pixel unit in differential synthesis wavelength interferogram The corresponding differential phase is represented as ,

[0074] and The calculation methods are as follows:

[0075]

[0076]

[0077] in, For pixel units in the second wavelength phase interferogram The corresponding entanglement phase, For the pixel unit in the first wavelength phase interferogram The corresponding entanglement phase, The noise is low, and the corresponding additive synthesis wavelength is , , The noise is relatively high, and its corresponding differential synthesis wavelength is , ,in, Indicates the first wavelength. This indicates the second wavelength.

[0078] Figure 4 The illustration shows a schematic diagram of the process for obtaining the additive composite wavelength interferogram after unpacking according to an embodiment of this application.

[0079] like Figure 4 As shown, the differential synthesized wavelength interferogram is used to wrap the additive synthesized wavelength interferogram, including operations S410 to S430.

[0080] In operation S410, the distance difference corresponding to the differential phase is calculated based on the differential synthesis wavelength corresponding to the differential synthesis wavelength interferogram and the differential phase contained in the differential synthesis wavelength interferogram.

[0081] At operation S420, the distance difference corresponding to the ideal differential phase is calculated according to the distance difference corresponding to the differential phase and the differential combined wavelength interferogram.

[0082] At operation S430, the unwrapped additive combined wavelength interferogram is obtained according to the distance difference corresponding to the ideal differential phase and the combined phase contained in the additive combined wavelength interferogram.

[0083] In some embodiments, at operation S410, the distance difference corresponding to the differential phase is calculated by the following formula :

[0084]

[0085] Although contains more noise, resulting in contains higher noise, but can reflect the phase fluctuation caused by the small target, so it can be used to calculate the distance difference corresponding to the ideal differential phase (i.e. the ideal differential phase) under ideal conditions, wherein represents the pixel unit corresponding differential phase, which belongs to the low-winding differential phase.

[0086] In some embodiments, at operation S420, the distance difference corresponding to the ideal differential phase is calculated according to the distance difference corresponding to the differential phase and the differential combined wavelength interferogram, including: unwrapping the differential phase contained in the differential combined wavelength interferogram to obtain the ideal differential phase corresponding to the differential phase; and calculating the distance difference of the ideal differential phase according to the ideal differential phase, the ideal differential combined wavelength corresponding to the ideal differential phase, and the distance difference corresponding to the differential phase of the ideal differential phase.

[0087] Further, the distance difference corresponding to the ideal differential phase of the pixel unit under ideal conditions is defined as , the ideal differential phase corresponding to the distance difference is , the corresponding ideal differential combined wavelength is , and the corresponding distance difference parameter is First, each differential phase contained in the differential combined wavelength interferogram is unwrapped, i.e. the differential phase is unwrapped to obtain the ideal differential phase corresponding to the pixel unit Since the ideal condition means that the differential combined wavelength interferogram and the additive combined wavelength interferogram both belong to the unwrapped condition, theoretically , therefore, the distance difference corresponding to the ideal differential phase can be calculated according to , and . corresponding distance difference , specifically, first calculate the pixel unit corresponding to the distance difference parameter in the ideal case , that is, then according to , and , calculate , that is, , wherein represents the nearest integer operation.

[0088] In some embodiments, in operation S430, according to the distance difference of the corresponding ideal differential phase of the differential phase and the synthetic phase contained in the additive synthetic wavelength interferogram, the unwrapped additive synthetic wavelength interferogram is obtained, including: according to the distance difference of the corresponding ideal differential phase of the differential phase, the corresponding synthetic phase in the additive synthetic wavelength interferogram is unwrapped to obtain the unwrapped synthetic phase; according to the unwrapped synthetic phase, the unwrapped additive synthetic wavelength interferogram is generated.

[0089] Further, with respect to , Although the noise is reduced while reflecting the distribution of the target to be detected, but is still limited to the single wavelength level, therefore, it is necessary to unwrap according to , first, according to , and , calculate the distance difference parameter corresponding to the additive synthetic wavelength , that is, , then according to and , calculate the unwrapped synthetic phase , that is, , according to the corresponding to each pixel unit , generate the unwrapped additive synthetic wavelength interferogram, since the noise contained is very low, so the detection accuracy of the obtained unwrapped additive synthetic wavelength interferogram is very high.

[0090] According to the embodiments of the present application, the present application adopts the unwrapping method of the synthetic wavelength to unwrap the additive synthetic wavelength interferogram, solves the problems of high error probability of residual point dense area, the need for manual intervention and path interruption and error diffusion in noise or low coherence area existing in the existing unwrapping method, thereby greatly reducing the noise and improving the detection accuracy.

[0091] In some embodiments, in operation S250, based on the unwrapped additive synthetic wavelength interferogram, the target to be detected is detected, including: extracting features of the unwrapped additive synthetic wavelength interferogram; wherein the features include phase statistical features, interference fringe features, and multi-scale features, the multi-scale features including phase statistical features and / or interference fringe features extracted at different resolutions; based on the features, a preset target detection algorithm is used to detect the target to be detected.

[0092] For example, the phase statistical features (such as mean, variance, gradient, etc. of the phase), the interference fringe features (such as fringe spacing, direction, curvature, etc.), and the multi-scale features (such as features of the target at different resolutions obtained by using scale analysis methods such as wavelet transform, pyramid transform, etc.) of the unwrapped additive synthetic wavelength interferogram can be used to detect the target to be detected by using a detection threshold-based method, for example, when the change value of the interference fringe is greater than a preset detection threshold, it is considered that the target to be detected exists in the target to be detected region, the matching filter method can also be used to detect the target to be detected, for example, according to the extracted features, a corresponding matching filter is designed and a convolution operation is performed with the phase interferogram, if the output of the matching filter exceeds a preset threshold value, it is considered that the target to be detected is detected, and a machine learning algorithm can also be used to detect the target to be detected, through training of a machine learning model by using sample data of a plurality of target to be detected regions, the machine learning model can learn deep features in the phase interferogram and the relationship therebetween, so as to effectively identify the target, the machine learning algorithm can include an artificial neural network, a convolutional neural network, a support vector machine, etc.

[0093] Based on the above synthetic wavelength-based low-altitude weak target detection method, the application also provides a synthetic wavelength-based low-altitude weak target detection device. The following will be combined with the description of the synthetic wavelength-based low-altitude weak target detection method to describe the synthetic wavelength-based low-altitude weak target detection device. Figure 5 The device will be described in detail.

[0094] Figure 5 The structure block diagram of the synthetic wavelength-based low-altitude weak target detection device according to the embodiment of the application is schematically shown.

[0095] As shown in Figure 5 The synthetic wavelength-based low-altitude weak target detection device 500 of the embodiment includes a radar imaging module 510, a phase interferogram spectrum acquisition module 520, a phase interferogram spectrum clipping module 530, a wavelength synthesis module 540, and a target detection module 550.

[0096] The radar imaging module 510 is configured to image echo data of a to-be-detected region without any to-be-detected target to obtain a first image, and image echo data of the to-be-detected region with a to-be-detected target to obtain a second image. In an embodiment, the radar imaging module 510 can be configured to perform the operation S210 described above, and details are not repeated here.

[0097] The phase interferogram spectrum acquisition module 520 is configured to perform an interference operation on the first image and the second image to obtain a phase interferogram spectrum. In an embodiment, the phase interferogram spectrum acquisition module 520 can be configured to perform the operation S220 described above, and details are not repeated here.

[0098] The phase interferogram spectrum clipping module 530 is configured to clip the phase interferogram spectrum to obtain a first wavelength phase interferogram and a second wavelength phase interferogram. In an embodiment, the phase interferogram spectrum clipping module 530 can be configured to perform the operation S230 described above, and details are not repeated here.

[0099] The wavelength synthesis module 540 is configured to generate a differential synthetic wavelength interferogram and an additive synthetic wavelength interferogram according to the first wavelength phase interferogram and the second wavelength phase interferogram. In an embodiment, the wavelength synthesis module 540 can be configured to perform the operation S240 described above, and details are not repeated here.

[0100] The target detection module 550 is configured to unwrap the additive synthetic wavelength interferogram based on the differential synthetic wavelength interferogram, and detect the to-be-detected target based on the unwrapped additive synthetic wavelength interferogram. In an embodiment, the target detection module 550 can be configured to perform the operation S250 described above, and details are not repeated here.

[0101] In some embodiments, the apparatus 500 further includes an image registration module configured to register the first image and the second image before performing the interference operation on the first image and the second image. Specifically, the image registration module is configured to calculate a cross-correlation function based on image features of the first image and the second image, determine an offset of the first image and the second image based on the cross-correlation function, adjust the second image based on the offset, calculate an offset of the adjusted second image and the first image, and repeat the adjustment of the second image and the calculation of the offset until the obtained offset is less than a preset threshold.

[0102] In some embodiments, the phase interferogram spectrum clipping module 530 is specifically configured to clip a high-frequency part of the phase interferogram spectrum, perform linear phase compensation and inverse fast Fourier transform on the clipped spectrum to obtain the first wavelength phase interferogram, and clip a low-frequency part of the phase interferogram spectrum, perform linear phase compensation and inverse fast Fourier transform on the clipped spectrum to obtain the second wavelength phase interferogram.

[0103] In some embodiments, the wavelength synthesis module 540 is specifically configured to: add the first wavelength phase interferogram and the second wavelength phase interferogram to obtain an additive synthetic wavelength interferogram; and subtract the first wavelength phase interferogram and the second wavelength phase interferogram to obtain a differential synthetic wavelength interferogram.

[0104] In some embodiments, the target detection module 550 is specifically configured to: calculate a distance difference corresponding to a differential phase according to a differential synthetic wavelength corresponding to the differential synthetic wavelength interferogram and the differential phase included in the differential synthetic wavelength interferogram; calculate a distance difference of an ideal differential phase corresponding to the differential phase according to the distance difference corresponding to the differential phase and the differential synthetic wavelength interferogram; and obtain an unwrapped additive synthetic wavelength interferogram according to the distance difference of the ideal differential phase corresponding to the differential phase and the synthetic phase included in the additive synthetic wavelength interferogram.

[0105] In some embodiments, the target detection module 550 is specifically configured to: unwrap a differential phase included in the differential synthetic wavelength interferogram to obtain an ideal differential phase corresponding to the differential phase; and calculate a distance difference of the ideal differential phase according to the ideal differential phase, an ideal differential synthetic wavelength corresponding to the ideal differential phase, and a distance difference of a differential phase corresponding to the ideal differential phase.

[0106] In some embodiments, the target detection module 550 is specifically configured to: unwrap a corresponding synthetic phase in the additive synthetic wavelength interferogram according to a distance difference of an ideal differential phase corresponding to a differential phase to obtain an unwrapped synthetic phase; and generate an unwrapped additive synthetic wavelength interferogram according to the unwrapped synthetic phase.

[0107] In some embodiments, the target detection module 550 is specifically configured to: extract a feature of the unwrapped additive synthetic wavelength interferogram; wherein the feature includes a phase statistical feature, an interference fringe feature, and a multi-scale feature, the multi-scale feature including a phase statistical feature and / or an interference fringe feature extracted at different resolutions; and detect the target to be detected based on the feature using a preset target detection algorithm.

[0108] According to embodiments of the present application, the device 500 can effectively avoid false alarms and missed alarms caused by improper threshold division, unwrap the additive synthetic wavelength interferogram using the differential synthetic wavelength interferogram, greatly reduce noise, and improve detection accuracy and accuracy.

[0109] According to embodiments of the present application, any of the radar imaging module 510, the phase interferogram spectrum acquisition module 520, the phase interferogram spectrum cropping module 530, the wavelength synthesis module 540 and the target detection module 550 can be combined in one module, or any of them can be split into multiple modules. Alternatively, at least part of the function of one or more of these modules can be combined with at least part of the function of other modules, and implemented in one module. According to embodiments of the present application, at least one of the radar imaging module 510, the phase interferogram spectrum acquisition module 520, the phase interferogram spectrum cropping module 530, the wavelength synthesis module 540 and the target detection module 550 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on chip, a system on board, a system on package, an application specific integrated circuit (ASIC), or any other reasonable way of integrating or packaging a circuit, etc. hardware or firmware, or in any one of the software, hardware and firmware implementation or in a suitable combination of any of them. Alternatively, at least one of the radar imaging module 510, the phase interferogram spectrum acquisition module 520, the phase interferogram spectrum cropping module 530, the wavelength synthesis module 540 and the target detection module 550 can be at least partially implemented as a computer program module which, when executed, can perform the corresponding function.

[0110] Figure 6 A block diagram of an electronic device suitable for implementing the method for detecting low-altitude weak targets based on synthesized wavelengths according to embodiments of the present application is schematically shown.

[0111] As shown in Figure 6 The electronic device 600 according to embodiments of the present application includes a processor 601 which can perform various appropriate actions and processes according to programs stored in a read-only memory (ROM) 602 or loaded from a storage portion 608 into a random access memory (RAM) 603. The processor 601 can include, for example, a general-purpose microprocessor (e.g., a CPU), an instruction set processor and / or a related chipset, and / or a special-purpose microprocessor (e.g., an application specific integrated circuit (ASIC)), etc. The processor 601 can also include an on-board memory for cache use. The processor 601 can include a single processing unit or multiple processing units for performing different actions of the method processes according to embodiments of the present application.

[0112] In the RAM 603, various programs and data required for the operation of the electronic device 600 are stored. The processor 601, the ROM 602, and the RAM 603 are connected to each other via the bus 604. The processor 601 performs various operations of the method flow according to the embodiments of the present application by executing the programs in the ROM 602 and / or the RAM 603. It should be noted that the programs can also be stored in one or more memories other than the ROM 602 and the RAM 603. The processor 601 can also perform various operations of the method flow according to the embodiments of the present application by executing the programs stored in the one or more memories.

[0113] According to the embodiments of the present application, the electronic device 600 can further include an input / output (I / O) interface 605, which is also connected to the bus 604. The electronic device 600 can further include one or more of the following components connected to the input / output (I / O) interface 605: an input part 606 including a keyboard, a mouse, and the like; an output part 607 including a cathode ray tube (CRT), a liquid crystal display (LCD), and the like, and a speaker, and the like; a storage part 608 including a hard disk, and the like; and a communication part 609 including a network interface card such as a LAN card, a modem, and the like. The communication part 609 performs communication processing via a network such as the Internet. A drive 610 is also connected to the input / output (I / O) interface 605 as necessary. A removable medium 611 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, and the like is mounted on the drive 610 as necessary, so that a computer program read therefrom is installed in the storage part 608 as necessary.

[0114] The present application also provides a computer readable storage medium, which can be included in the device / apparatus / system described in the above embodiments; or can exist separately without being assembled into the device / apparatus / system. The above computer readable storage medium carries one or more programs, when the one or more programs are executed, the method according to the embodiments of the present application is implemented.

[0115] According to an embodiment of the present application, the computer readable storage medium can be a non-transitory computer readable storage medium, for example, can include 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 this application, a computer readable storage medium can 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 an embodiment of the present application, a computer readable storage medium can include one or more of the above-described ROM 602 and / or RAM 603 and / or one or more memory other than the ROM 602 and the RAM 603.

[0116] Embodiments of the present application also include a computer program product, which includes a computer program containing program codes for executing the methods shown in the flowcharts. When the computer program product is run in a computer system, the program codes are used to make the computer system implement the low-altitude weak target detection method based on synthetic wavelengths provided by the embodiments of the present application.

[0117] The above-described functions defined in the system / device of the embodiments of the present application are performed when the computer program is executed by the processor 601. According to an embodiment of the present application, the above-described system, device, module, unit, etc. can be implemented by computer program modules.

[0118] In one embodiment, the computer program can rely on tangible storage media such as optical storage media, magnetic storage media, etc. In another embodiment, the computer program can also be transmitted, distributed, and downloaded in the form of signals on a network medium, and be downloaded and installed through the communication part 609, and / or installed from the detachable medium 611. The program codes contained in the computer program can be transmitted by any suitable network medium, including but not limited to: wireless, wired, etc., or any suitable combination of the foregoing.

[0119] In such an embodiment, the computer program can be downloaded and installed from the network through the communication part 609, and / or installed from the detachable medium 611. When the computer program is executed by the processor 601, the above-described functions defined in the system of the embodiments of the present application are performed. According to an embodiment of the present application, the above-described system, device, apparatus, module, unit, etc. can be implemented by computer program modules.

[0120] According to embodiments of the present application, program code for implementing the computer programs provided by embodiments of the present application can be written in any combination of one or more programming languages, and can be implemented in a high-level procedural and / or object-oriented programming language, and / or in assembly / machine language. Programming languages include, but are not limited to, Java, C++, python, "C", or the like. Program code can execute entirely on a user's computing device, partly on the user's device, as a stand-alone software package, partly on a remote computing device, or entirely on the remote computing device or server. In the latter scenario, the remote computing device can be connected to the user's computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computing device, such as through the Internet using an Internet Service Provider.

[0121] The computer program instructions can also be loaded onto a computer or other programmable information processing apparatus to cause a series of operations to be performed on the computer or other programmable information processing apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable information processing apparatus implement the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0122] Those skilled in the art will appreciate that features recited in the various embodiments of the present application can be combined and / or integrated in various combinations, even if such combinations have not been explicitly recited in the present application. In particular, the features recited in the various embodiments of the present application can be combined and / or integrated in various combinations, without departing from the spirit and teachings of the present application. All such combinations are within the scope of the present application.

Claims

1. A method for detecting low-altitude weak targets based on synthetic wavelengths, characterized in that, The method comprises: imaging echo data of a to-be-detected region without any to-be-detected target to obtain a first image; imaging echo data of a to-be-detected region with a to-be-detected target to obtain a second image; interfering the first image and the second image to obtain a phase interference spectrum; trimming the phase interference spectrum to obtain a first wavelength phase interference and a second wavelength phase interference; generating a differential synthetic wavelength interference and an additive synthetic wavelength interference according to the first wavelength phase interference and the second wavelength phase interference; unwrapping the additive synthetic wavelength interference by using the differential synthetic wavelength interference, and detecting the to-be-detected target based on the unwrapped additive synthetic wavelength interference.

2. The method of claim 1, wherein, Before the interfering the first image and the second image, the method comprises: registering the first image and the second image, comprising: calculating a cross-correlation function by using image features of the first image and the second image, determining an offset of the first image and the second image according to the cross-correlation function, adjusting the second image according to the offset, calculating an offset of the adjusted second image and the first image, and repeating the second image adjustment and the offset calculation until the obtained offset is less than a preset threshold.

3. The method of claim 1, wherein, The trimming the phase interference spectrum to obtain a first wavelength phase interference and a second wavelength phase interference comprises: trimming a high-frequency part of the phase interference spectrum, and performing linear phase compensation and inverse fast Fourier transform on the trimmed spectrum to obtain the first wavelength phase interference; trimming a low-frequency part of the phase interference spectrum, and performing linear phase compensation and inverse fast Fourier transform on the trimmed spectrum to obtain the second wavelength phase interference.

4. The method of claim 1, wherein, The generating a differential synthetic wavelength interference and an additive synthetic wavelength interference according to the first wavelength phase interference and the second wavelength phase interference comprises: adding the first wavelength phase interference and the second wavelength phase interference to obtain the additive synthetic wavelength interference; subtracting the first wavelength phase interference and the second wavelength phase interference to obtain the differential synthetic wavelength interference.

5. The method of claim 1, wherein, The unwrapping the additive synthetic wavelength interference by using the differential synthetic wavelength interference comprises: calculating a distance difference corresponding to a differential phase included in the differential synthetic wavelength interference according to a differential synthetic wavelength corresponding to the differential synthetic wavelength interference and the differential phase; calculating a distance difference of an ideal differential phase corresponding to the differential phase according to the distance difference corresponding to the differential phase and the differential synthetic wavelength interference; obtaining the unwrapped additive synthetic wavelength interference according to the distance difference of the ideal differential phase corresponding to the differential phase and a synthetic phase included in the additive synthetic wavelength interference.

6. The method of claim 5, wherein, The calculating a distance difference of an ideal differential phase corresponding to the differential phase according to the distance difference corresponding to the differential phase and the differential synthetic wavelength interference comprises: unwrap the corresponding synthetic phase in the additive synthetic wavelength interferogram according to the distance difference of the ideal differential phase corresponding to the differential phase to obtain an unwrapped synthetic phase; calculate the distance difference of the ideal differential phase according to the distance difference of the ideal differential phase corresponding to the differential phase and the synthetic phase contained in the additive synthetic wavelength interferogram.

7. The method of claim 5, wherein, The method comprises the following steps: unwrap the corresponding synthetic phase in the additive synthetic wavelength interferogram according to the distance difference of the ideal differential phase corresponding to the differential phase to obtain an unwrapped synthetic phase; generate an unwrapped additive synthetic wavelength interferogram according to the unwrapped synthetic phase.

8. The method of claim 1, wherein, The method comprises the following steps: extract features of the unwrapped additive synthetic wavelength interferogram; wherein the features include phase statistical features, interference fringe features and multi-scale features, and the multi-scale features include phase statistical features and / or interference fringe features extracted at different resolutions; detect the target to be detected by using a preset target detection algorithm based on the features.

9. A low-altitude weak target detection device based on a synthetic wavelength, characterized in that, The device comprises: a radar imaging module configured to image echo data of a detection area in which no target to be detected exists to obtain a first image, and image echo data of a detection area in which a target to be detected exists to obtain a second image; a phase interferogram spectrum acquisition module configured to perform an interference operation on the first image and the second image to obtain a phase interferogram spectrum; a phase interferogram spectrum clipping module configured to clip the phase interferogram spectrum to obtain a first wavelength phase interferogram and a second wavelength phase interferogram; a wavelength synthesis module configured to generate a differential synthetic wavelength interferogram and an additive synthetic wavelength interferogram according to the first wavelength phase interferogram and the second wavelength phase interferogram; a target detection module configured to unwrap the additive synthetic wavelength interferogram by using the differential synthetic wavelength interferogram, and detect the target to be detected based on the unwrapped additive synthetic wavelength interferogram.

10. An electronic device comprising: one or more processors; a memory for storing one or more computer programs, characterized in that the one or more processors execute the one or more computer programs to implement the steps of the method according to any one of claims 1-8.

11. A computer readable storage medium having stored thereon a computer program or instructions, characterized in that, The computer program or instructions are executed by the processor to implement the steps of the method according to any one of claims 1-8.

12. A computer program product comprising computer programs or instructions, characterized in that, The computer program or instructions are executed by the processor to implement the steps of the method according to any one of claims 1-8. The computer program or instructions are executed by the processor to implement the steps of the method according to any one of claims 1-8.

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