Inversion imaging method for cloud-obscured targets based on unbounded cloud transfer function

Abstract

The present invention relates to the field of image processing technology, and in particular to a method for inverting and imaging a target obscured by cloud and fog based on a boundless cloud and fog transfer function, comprising the following steps: obtaining a reflected three-dimensional light field of a target obscured by cloud and fog; determining characteristics of the cloud and fog, and obtaining a boundless cloud and fog transfer function; using an equivalent propagation distance as a variable, frequency-domain filtering the reflected three-dimensional light field based on the boundless cloud and fog transfer function, then inverting the target light field imaging using a free-space light field inversion method, determining the corresponding relationship between the equivalent propagation distance and the inverted target light field imaging result; and determining a final imaging result through parametric scanning or optimization solution based on the corresponding relationship between the equivalent propagation distance and the inverted target light field imaging result. The present invention does not need to consider the actual boundaries of the cloud and fog, and can effectively image targets obscured by cloud and fog bodies of any shape.

Description

Technical Field

[0001] The present invention relates to the field of image processing technology, and in particular to a method, device, electronic device and storage medium for inversion imaging of a cloud-obscured target based on a boundless cloud-fog transfer function. Background Art

[0002] The light scattering effect of fog and clouds severely restricts the ability of optical detection and ranging systems to image through fog and clouds. This method, which divides the light field's propagation through space into distinct components, accurately simulates the light transmission process of each component, and ultimately inverts the target image, has gradually become the mainstream method for imaging through fog and clouds.

[0003] Currently, existing technologies for simulating light transmission through clouds and fog typically require strict definition of cloud boundaries and shape constraints, and require the calculation of excessive parameters. In practice, defining cloud boundaries is often difficult, and cloud shapes are often irregular. Without clear boundary conditions, existing technologies often struggle to accurately invert the target image. Summary of the Invention

[0004] Based on the problem that the existing technology is difficult to achieve inversion imaging of cloud-obscured targets in the absence of clear boundary conditions, the embodiments of the present invention provide a method, device, electronic device and storage medium for inversion imaging of cloud-obscured targets based on a boundaryless cloud transfer function.

[0005] In a first aspect, the present invention provides a cloud-masked target inversion imaging method based on an unbounded cloud-masked transfer function, comprising:

[0006] Acquire a reflected three-dimensional light field of a target obscured by fog and cloud; the reflected three-dimensional light field includes a time domain interval light signal corresponding to a two-dimensional space, and the time domain interval of the reflected three-dimensional light field includes the time range in which the pulsed light is collected after being reflected by the target and penetrating the fog and cloud;

[0007] Determine the characteristics of the cloud and fog, and obtain the unbounded cloud and fog transmission function; the characteristics of the cloud and fog include the reduced scattering coefficient of the cloud and fog, the speed of light in the cloud and fog, and the maximum thickness of the cloud and fog; the unbounded cloud and fog transmission function φ inf The expression of (t,r) is:

[0008]

[0009]

[0010] Where t represents the transmission time of the optical signal, r = (r x ,r y ,r z ) represents the light signal exit cloud point, r x 、r y and rz They represent the coordinates of the outgoing cloud point on the x, y, and z axes, respectively. z is the diffusion direction of light in the cloud. r0 = (0, 0, 0) represents the incident cloud point of the light signal. c represents the speed of light in the cloud. μ s ' represents the reduced scattering coefficient of cloud and fog, z effect Represents the equivalent propagation distance, when light propagates in a cloud of infinite size z effect The diffusion behavior of light and the propagation of light in a finite size cloud z The diffusion behavior is equivalent to z effect Not exceeding the maximum thickness d of clouds and fog;

[0011] The equivalent propagation distance z effect As a variable, the reflected three-dimensional light field is frequency-domain filtered based on the unbounded cloud transfer function, and then the target light field imaging is inverted by the free-space light field inversion method to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging results;

[0012] According to the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging result is determined by parametric scanning or optimization solution to determine the final imaging result.

[0013] Optionally, obtaining a reflected three-dimensional light field of a target obscured by clouds and fog includes:

[0014] Illuminate targets obscured by clouds and fog with monochromatic pulsed laser;

[0015] On the transmitting side, a single-photon detector is used to obtain the time-domain optical signal waveform of each two-dimensional spatial point by scanning. The time-domain optical signal waveform includes the peak caused by the target reflection, but does not include the peak caused by the cloud reflection.

[0016] According to the spatial position relationship of the two-dimensional space scanning points, the time domain optical signal waveforms corresponding to each scanning point are combined to obtain a reflected three-dimensional light field.

[0017] Optionally, performing frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function includes:

[0018] Based on the unbounded cloud transfer function, frequency domain filtering is performed on the reflected three-dimensional light field by blind deconvolution filtering, minimum mean square error filtering, geometric mean filtering or least squares filtering.

[0019] Optionally, the performing frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function includes:

[0020] Based on the unbounded cloud transfer function, frequency-domain filtering is performed on the reflected three-dimensional light field by minimum mean square error filtering;

[0021] The scattered field expression after frequency domain filtering is:

[0022]

[0023] in, is φ inf (t,r)*φ inf The frequency domain discretization expression of (t,r), * represents the three-dimensional convolution operation, for The conjugate matrix of , F represents the Fourier transform operation, F -1 represents the inverse Fourier transform operation, τ is the reflected three-dimensional light field is the discretized expression of , and α represents the noise term parameter related to the signal power spectrum and the noise power spectrum.

[0024] Optionally, the free-space light field inversion method includes:

[0025] Frequency beam migration method, light cone transformation method, back projection method or virtual wave phasor field method.

[0026] Optionally, the free-space light field inversion method is a frequency beam migration method;

[0027] The inverting target light field imaging by the free space light field inversion method includes:

[0028] Perform a translation coordinate system transformation, set the z-axis plane where the light signal exits the cloud point to the known z=0 plane, and transform the scattered field I(r, t) after frequency domain filtering to Ψ(x, y, z=0, t);

[0029] Perform Fourier transform on the scattered field Ψ(x, y, z=0, t) after coordinate transformation to obtain the corresponding frequency domain expression Φ(k x ,k y ,f); f represents the time frequency, k x 、k y and k z Represents the spatial frequencies corresponding to the x, y, and z directions respectively. Since z = 0, the transformed frequency domain expression does not include k z ;

[0030] Using dispersion relations and Get the value containing k x 、k y and k z Frequency domain expression of the scattered field:

[0031]

[0032] For k x 、k y and k z Frequency domain expression of the scattered field Φ(k x ,k y ,k z ) performs inverse Fourier transform to obtain the target scattering field Ψ(x, y, z, t=0).

[0033] In a second aspect, an embodiment of the present invention further provides a cloud-masked target inversion imaging device based on an unbounded cloud-masked transfer function, comprising:

[0034] A light field acquisition module is used to acquire a reflected three-dimensional light field of a target obscured by fog and cloud; the reflected three-dimensional light field includes a time domain interval light signal corresponding to a two-dimensional space, and the time domain interval of the reflected three-dimensional light field includes the time range in which the pulsed light is captured after being reflected by the target and penetrating the fog and cloud;

[0035] The function determination module is used to determine the characteristics of the cloud and obtain the unbounded cloud transmission function; the characteristics of the cloud include the reduced scattering coefficient of the cloud, the speed of light in the cloud and the maximum thickness of the cloud; the unbounded cloud transmission function φ inf The expression of (t,r) is:

[0036]

[0037]

[0038] Where t represents the transmission time of the optical signal in the cloud, r = (r x ,r y ,r z ) represents the light signal exit cloud point, r x 、r y and r z They represent the coordinates of the outgoing cloud point on the x, y, and z axes, respectively. z is the diffusion direction of light in the cloud. r0 = (0, 0, 0) represents the incident cloud point of the light signal. c represents the speed of light in the cloud. μ s ' represents the reduced scattering coefficient of cloud and fog, z effect Represents the equivalent propagation distance, when light propagates in a cloud of infinite size z effect The diffusion behavior of light and the propagation of light in a finite size cloud z The diffusion behavior is equivalent to z effect Not exceeding the maximum thickness d of clouds and fog;

[0039] Relationship determination module, used to convert the equivalent propagation distance z effectAs a variable, the reflected three-dimensional light field is frequency-domain filtered based on the unbounded cloud transfer function, and then the target light field imaging is inverted by the free-space light field inversion method to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging results;

[0040] Imaging determination module, used to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging result is determined by parametric scanning or optimization solution to determine the final imaging result.

[0041] Optionally, the device further comprises:

[0042] The result display module is used to display the final imaging result in a graphical manner.

[0043] In a third aspect, an embodiment of the present invention further provides an electronic device comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the cloud-obscured target inversion imaging method based on the unbounded cloud transfer function described in any embodiment of this specification is implemented.

[0044] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed in a computer, the computer is caused to execute the cloud-obscured target inversion imaging method based on the unbounded cloud transfer function described in any embodiment of this specification.

[0045] The above-mentioned technical solution of the present invention has the following advantages: the embodiment of the present invention provides a method, device, electronic device and storage medium for inversion imaging of cloud-obscured targets based on a boundaryless cloud-fog transfer function. The present invention proposes a boundaryless cloud-fog transfer function. Providing this function can accurately simulate the diffusion behavior of the light field in clouds and fog without obtaining cloud boundary information. By utilizing the frequency domain filtering technology and free space light field inversion technology based on this function, the target light field can be effectively restored in the absence of cloud boundary information, and inversion imaging of cloud-obscured targets can be performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the steps of a method for inverting and imaging a cloud-obscured target based on an unbounded cloud transfer function provided by one embodiment of the present invention;

[0047] Figure 2(a) is a reflected 3D light field original image of a target obscured by clouds and fog;

[0048] Figure 2(b) is the scattered field image after frequency domain filtering of the reflected three-dimensional light field corresponding to Figure 2(a);

[0049] Figure 2(c) is the target scattered field image corresponding to the scattered field inversion target light field imaging in Figure 2(b);

[0050] Figure 3 This is a hardware architecture diagram of an electronic device provided by one embodiment of the present invention;

[0051] Figure 4 This is a structural diagram of a cloud-masked target inversion imaging device based on a boundless cloud transfer function provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0053] As mentioned above, when existing technologies simulate the process of light transmission in clouds and fog, it is usually necessary to strictly define the boundaries of the clouds and fog and constrain the shape of the clouds and fog, and it is necessary to calculate too many parameters. In actual applications, it is usually difficult to define the boundaries of clouds and fog, and the shapes of clouds and fog are also irregular. In the absence of clear boundary conditions, existing technologies often find it difficult to correctly invert the target image. In view of this, the present invention proposes a boundaryless cloud and fog transmission function, and utilizes frequency domain filtering technology and free space light field inversion technology based on this function. It can effectively restore the target light field (also called target scattering field) in the absence of cloud and fog boundary information, thereby realizing the inversion imaging of the target obscured by clouds and fog.

[0054] The specific implementation of the above concept is described below.

[0055] Please refer to Figure 1 The embodiment of the present invention provides a cloud-mass obscured target inversion imaging method based on an unbounded cloud-mass transfer function, the method comprising:

[0056] Step 100, obtaining a reflected three-dimensional light field of a target obscured by clouds and fog;

[0057] The reflected three-dimensional light field includes a time domain interval light signal corresponding to the two-dimensional space, and the time domain interval of the reflected three-dimensional light field includes the time range in which the pulse light is reflected by the target and penetrates the cloud and fog and is collected;

[0058] The three dimensions of the reflected three-dimensional light field are two-dimensional space and one-dimensional time. The two-dimensional space includes multiple points, each of which corresponds to a light signal waveform collected within a time domain interval. To ensure that the inversion imaging can fully reflect the target characteristics, the two-dimensional spatial area of ​​the reflected three-dimensional light field should cover the area where the target is located, and the time domain interval of the reflected three-dimensional light field preferably covers the time required for the pulse light to enter the target, be reflected by the target, penetrate the cloud and fog, and reach the plane where the light signal is collected.

[0059] Step 102, determining the characteristics of the cloud and fog, and obtaining the unbounded cloud and fog transfer function;

[0060] Among them, the characteristics of clouds and fog include the reduced scattering coefficient of clouds and fog, the speed of light in clouds and fog, and the maximum thickness of clouds and fog;

[0061] The unbounded cloud transmission function φ inf The expression of (t,r) is:

[0062]

[0063]

[0064] Where t represents the transmission time of the optical signal, r = (r x ,r y ,r z ) represents the light signal exit cloud point, r x 、r y and r z They represent the coordinates of the outgoing cloud point on the x, y, and z axes, respectively. z is the diffusion direction of light in the cloud. r0 = (0, 0, 0) represents the incident cloud point of the light signal. c represents the speed of light in the cloud. μ s ' represents the reduced scattering coefficient of the cloud, which can be determined based on the reflection characteristics of the cloud, z effect Represents the equivalent propagation distance, when light propagates in a cloud of infinite size z effect The diffusion behavior of light and the propagation of light in a finite size cloud z The diffusion behavior is equivalent to z effect Not exceeding the maximum thickness d of clouds and fog;

[0065] Step 104: convert the equivalent propagation distance z effect As the variable to be determined, the reflected three-dimensional light field is frequency-domain filtered based on the unbounded cloud transfer function, and then the target light field imaging is inverted by the free-space light field inversion method to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging results;

[0066] Based on the unbounded cloud transfer function, the reflected three-dimensional light field is subjected to frequency domain filtering using frequency domain filtering technology to obtain a filtered light field. Then, the free-space light field inversion technology is used to invert the target light field imaging result based on the frequency domain filtered light field to obtain a target scattered field image.

[0067] Step 106: According to the equivalent propagation distance z effect The corresponding relationship between the inverted target light field imaging result and the final imaging result is determined through parametric scanning or optimization solution;

[0068] Parametric sweep, that is, at the equivalent propagation distance z effect Sweep parameters within the feasible range to obtain multiple groups of different z effect The target light field imaging results corresponding to the numerical values ​​are then screened according to actual needs to determine the final imaging results;

[0069] Optimization solution, that is, iteratively optimize z with the imaging results meeting the preset requirements as the goal effect The numerical value is finally obtained to obtain the best target light field imaging result, and the z effect The optimal value of .

[0070] The above embodiment of the present invention provides a cloud-masked target inversion imaging method based on a boundless cloud-masked transmission function. The present invention proposes a boundless cloud-masked transmission function. The equivalent propagation distance z in this function is effect is a length parameter, and its value is generally smaller than the maximum thickness d of the cloud; by changing z effect The numerical value can obtain different imaging results. For different sizes of z effect By screening the corresponding imaging results and selecting the best image, the target light field imaging can be inverted without obtaining cloud boundary information, thus obtaining better imaging results.

[0071] Optionally, the reduced scattering coefficient μ of the cloud s ' can be determined as follows:

[0072] Get the cloud and fog reflected light field;

[0073] The expression of cloud and fog reflected light field is:

[0074]

[0075] in, is the mean scattering free path, is the diffusion coefficient, μ a is the absorption coefficient, usually μ a Much smaller than μ s ', generally can be ignored;

[0076] Taking the derivative of R(t,r) we can get:

[0077]

[0078] Let the time when R(t,r) reaches its extreme value be t max ;

[0079]

[0080] By taking the derivative of the obtained cloud reflected light field and determining the corresponding parameters, the reduced scattering coefficient μ of the cloud can be determined. s 'Specific value.

[0081] Optionally, the step of “obtaining a reflected three-dimensional light field of a target obscured by clouds and fog” in step 100 further includes:

[0082] Laser emission: From the emission side, a monochromatic pulse laser is used to illuminate the target obscured by clouds and fog;

[0083] Two-dimensional spatial scanning: On the transmitting side, a single-photon detector is used to scan and acquire the time-domain optical signal waveform of each two-dimensional spatial point. The time-domain optical signal waveform includes peaks caused by target reflection, but excludes peaks caused by fog reflection. In other embodiments, multiple detectors can also be used to acquire the time-domain optical signal waveform of the two-dimensional spatial point, which has the advantages of saving scanning time and fast processing speed.

[0084] Waveform combination: Based on the spatial position relationship of the two-dimensional scanning points, the time domain optical signal waveforms corresponding to each scanning point are combined to obtain a reflected three-dimensional light field.

[0085] The above embodiment provides a method of obtaining the time domain waveform at each spatial scanning point by irradiating with a monochromatic pulsed laser and performing a two-dimensional spatial scan, thereby obtaining the reflected three-dimensional light field of the target obscured by fog. In other embodiments, in order to verify the accuracy of the unbounded fog transfer function, it may be necessary to estimate z effect The optimal value of can also be obtained by simulating a monochromatic pulse electromagnetic wave to illuminate a cloud and fog to block the target and obtain the reflected three-dimensional light field.

[0086] Furthermore, the method of using a single photon detector to obtain the time domain optical signal waveform of each two-dimensional spatial point by scanning includes:

[0087] First, use a single-photon detector to scan and obtain the complete optical signal waveform corresponding to each two-dimensional spatial scanning point, and then filter out the peaks caused by cloud and fog reflections; or

[0088] First, determine the time when the peak caused by cloud and fog reflection reaches the single-photon detector, and then use the time threshold switch to block the single-photon detector from receiving the peak caused by cloud and fog reflection. That is, through time limit control, the single-photon detector only receives the peak caused by target reflection.

[0089] Considering that in the desired reflected three-dimensional light field, the optical signal waveform should include the peak caused by the target reflection, but not the peak caused by the cloud reflection. When a monochromatic pulsed laser is used to illuminate a target obscured by clouds and fog, the single-photon detector may first receive the peak caused by the cloud reflection and then receive the peak caused by the target reflection. Therefore, it is necessary to filter out the corresponding optical signal, that is, to eliminate it after receiving the optical signal, or to directly block the single-photon detector from receiving the corresponding optical signal, so as to obtain the peak caused by the target reflection, so as to perform subsequent filtering and inversion to obtain an accurate target light field image.

[0090] Optionally, in step 104, “performing frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function” includes:

[0091] Based on the unbounded cloud transfer function, frequency domain filtering is performed on the reflected three-dimensional light field by blind deconvolution filtering, minimum mean square error filtering, geometric mean filtering or least squares filtering.

[0092] After obtaining the boundless cloud-fog transfer function, frequency domain filtering is performed on the reflected three-dimensional light field based on this boundless cloud-fog transfer function. Different frequency domain filtering methods can be used depending on the selected overall light field transmission model. The overall light field transmission model is, that is, an overall transmission model that represents the transmission of light in various parts of space. For example, when the noise term introduced by the environment is not considered in the overall light field transmission model, blind deconvolution filtering can be selected for frequency domain filtering. The above embodiments provide some commonly used frequency domain filtering techniques. In other embodiments, other frequency domain filtering methods can also be used to perform frequency domain filtering on the reflected three-dimensional light field.

[0093] Furthermore, the step 104 of performing frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function includes:

[0094] Based on the unbounded cloud transfer function, frequency-domain filtering is performed on the reflected three-dimensional light field by minimum mean square error filtering;

[0095] The scattered field expression after frequency domain filtering is:

[0096]

[0097] Where t represents the transmission time of the optical signal, r = (r x ,r y ,r z) represents the light signal exit cloud point, is φ inf (t,r)*φ inf The frequency domain discretization expression of (t,r), * represents the three-dimensional convolution operation, for The conjugate matrix of , F represents the Fourier transform operation, F -1 represents the inverse Fourier transform operation, τ is the reflected three-dimensional light field is the discretized expression of , and α represents the noise term parameter related to the signal power spectrum and the noise power spectrum.

[0098] The above embodiment performs frequency domain filtering on the reflected three-dimensional light field through minimum mean square error filtering. Minimum mean square error filtering is applicable to scenarios where the noise term introduced by the environment is considered in the overall light field transmission model. Usually, when the specific signal power spectrum and noise power spectrum are unknown, α can be set to a certain fixed value to achieve filtering of the reflected three-dimensional light field.

[0099] Optionally, in step 104 of “inverting the target light field imaging by a free-space light field inversion method”, the free-space light field inversion method may include:

[0100] Frequency beam migration method, light cone transformation method, back projection method or virtual wave phasor field method.

[0101] The above embodiments illustrate some commonly used free-space light field inversion techniques. In other embodiments, other free-space light field inversion methods can be used to invert target light field imaging. The specific free-space light field inversion method used can be selected based on the target reflection type and the detection method (i.e., the method of collecting light signals).

[0102] Furthermore, the free-space light field inversion method is a frequency beam migration method.

[0103] The propagation of the electromagnetic field Ψ(x,y,z,t) in a homogeneous medium is governed by the wave equation:

[0104]

[0105] Among them, the Laplace operator v is the propagation velocity of electromagnetic waves in the medium (v = c). Signal measurement is generally performed on a known plane, which is set to z = 0. The scattered field after frequency domain filtering is Ψ(x, y, z = 0, t). The moment when the electromagnetic field is exactly reflected by the target is set to t = 0, then the target scattered field is Ψ(x, y, z, t = 0). Ψ(x, y, z = 0, t) and Ψ(x, y, z, t = 0) are the two boundary conditions of the wave equation. Ψ(x, y, z, t) is expressed using its spatial spectrum as:

[0106]

[0107] Substitute into the wave equation and we have the solution: Φ(k x ,k y ,k z ,t)=Φ(k x ,k y ,k z )e -2 π ift , using the dispersion relation The interpolation formula is obtained:

[0108]

[0109] For Φ(k x ,k y ,k z )The target scattering field Ψ(x, y, z, t=0) can be obtained through inverse Fourier transform.

[0110] Therefore, step 104 of “inverting target light field imaging by free-space light field inversion method” may include:

[0111] Perform a translation coordinate system transformation, let the z-axis plane where the light signal exits the cloud point be the known z=0 plane, and transform the scattered field I(r,t) after frequency domain filtering to Ψ(x,y,z=0,t); where x corresponds to r x , y corresponds to r y , the value does not change, z corresponds to r z , the value changes (the z-axis plane where the light signal emits the cloud point corresponds to z = 0), and t remains unchanged;

[0112] Perform Fourier transform on the scattered field Ψ(x, y, z=0, t) after coordinate transformation to obtain the corresponding frequency domain expression Φ(k x ,k y ,f); f represents the time frequency, k x 、k y and k z Represents the spatial frequencies corresponding to the x, y, and z directions respectively. Since z = 0, the transformed frequency domain expression does not include k z ;

[0113] Using dispersion relations and Get the value containing k x 、k y and k z Frequency domain expression of the scattered field:

[0114]

[0115] For k x 、k y and kz Frequency domain expression of the scattered field Φ(k x ,k y ,k z ) performs inverse Fourier transform to obtain the target scattering field Ψ(x, y, z, t=0).

[0116] See also Figure 2(a) to Figure 2(c) ,Figure 2(a) is a reflected three-dimensional light field original image of a target obscured by clouds and fog; Figure 2(b) is the scattered field image after frequency domain filtering of the reflected three-dimensional light field corresponding to Figure 2(a); Figure 2(c) is the target scattered field image of the target light field imaging corresponding to the scattered field inversion of Figure 2(b). For the convenience of display, Figure 2(a) to Figure 2(c) Take the maximum value of the corresponding three-dimensional image in the time domain direction (that is, take the peak value in the time domain) and display it as a two-dimensional image. Figure 2(a) to Figure 2(c) It can be seen that the method of the present invention can improve imaging quality or enhance imaging efficiency, and provide technical support for research on imaging of targets obscured by clouds or other strongly scattering media.

[0117] like Figure 3 、 Figure 4 As shown, the embodiment of the present invention provides a cloud-masked target inversion imaging device based on an unbounded cloud-masked transfer function. The device embodiment can be implemented by software, or by hardware or a combination of software and hardware. From the hardware level, Figure 3 As shown in FIG, a hardware architecture diagram of an electronic device where a cloud-masked target inversion imaging device based on a boundless cloud-masked transfer function is provided in an embodiment of the present invention includes Figure 3 In addition to the processor, memory, network interface, and non-volatile memory shown, the electronic device in the embodiment may also include other hardware, such as a forwarding chip responsible for processing messages, etc. Taking software implementation as an example, Figure 4 As shown, as a logical device, the CPU of the electronic device in which it is located reads the corresponding computer program in the non-volatile memory into the internal memory and runs it. This embodiment provides a cloud-mass obscured target inversion imaging device based on a boundless cloud-mass transfer function, including:

[0118] Light field acquisition module 401 is used to acquire a reflected three-dimensional light field of a target obscured by fog. The reflected three-dimensional light field includes a time domain interval light signal corresponding to a two-dimensional space. The time domain interval of the reflected three-dimensional light field includes the time range when the pulse light is reflected by the target and penetrates the fog and is collected.

[0119] Function determination module 402 is used to determine the characteristics of the cloud and obtain the unbounded cloud transmission function; the characteristics of the cloud include the reduced scattering coefficient of the cloud, the speed of light in the cloud, and the maximum thickness of the cloud; the unbounded cloud transmission function φ inf The expression of (t,r) is:

[0120]

[0121]

[0122] Where t represents the transmission time of the optical signal, r = (r x ,r y ,r z ) represents the light signal exit cloud point, r x 、r y and r z They represent the coordinates of the outgoing cloud point on the x, y, and z axes, respectively. z is the diffusion direction of light in the cloud. r0 = (0, 0, 0) represents the incident cloud point of the light signal. c represents the speed of light in the cloud. μ s ' represents the reduced scattering coefficient of cloud and fog, z effect Represents the equivalent propagation distance, when light propagates in a cloud of infinite size z effect The diffusion behavior of light and the propagation of light in a finite size cloud z The diffusion behavior is equivalent to z effect Not exceeding the maximum thickness d of clouds and fog;

[0123] Relationship determination module 403, used to convert the equivalent propagation distance z effect As a variable, the reflected three-dimensional light field is frequency-domain filtered based on the unbounded cloud transfer function, and then the target light field imaging is inverted by the free-space light field inversion method to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging results;

[0124] The imaging determination module 404 is configured to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging result is determined by parametric scanning or optimization solution to determine the final imaging result.

[0125] In an embodiment of the present invention, the light field acquisition module 401 may be used to execute step 100 in the above method embodiment, the function determination module 402 may be used to execute step 102 in the above method embodiment, the relationship determination module 403 may be used to execute step 104 in the above method embodiment, and the imaging determination module 404 may be used to execute step 106 in the above method embodiment.

[0126] Optionally, the light field acquisition module 401 is used to measure a time domain signal distributed in a two-dimensional space, that is, a reflected three-dimensional light field, or to read a reflected three-dimensional light field.

[0127] Light field acquisition module 401 may include a detector to measure the reflected 3D light field. Existing reflected 3D light field data may be stored on a CD, floppy disk, or computer hard drive. Light field acquisition module 401 may also include a data reader module to read the reflected 3D light field data and convert it into an executable format.

[0128] Optionally, the light field acquisition module 401 acquires the reflected three-dimensional light field of the cloud-covered target, including performing the following operations:

[0129] From the emission side, a monochromatic pulse laser is used to illuminate the target obscured by clouds and fog;

[0130] On the transmitting side, a single-photon detector is used to obtain the time-domain optical signal waveform of each two-dimensional spatial point through scanning. The time-domain optical signal waveform includes peaks caused by target reflection, but excludes peaks caused by cloud reflection. In other embodiments, multiple detectors can also be used to obtain the time-domain optical signal waveform of the two-dimensional spatial point, which has the advantages of saving scanning time and fast processing speed.

[0131] According to the spatial position relationship of the two-dimensional space scanning points, the time domain optical signal waveforms corresponding to each scanning point are combined to obtain a reflected three-dimensional light field.

[0132] Optionally, the relationship determination module 403 performs frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function, including performing the following operations:

[0133] Based on the unbounded cloud transfer function, frequency domain filtering is performed on the reflected three-dimensional light field by blind deconvolution filtering, minimum mean square error filtering, geometric mean filtering or least squares filtering.

[0134] Furthermore, the relationship determination module 403 performs frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function, including performing the following operations:

[0135] Based on the unbounded cloud transfer function, frequency-domain filtering is performed on the reflected three-dimensional light field by minimum mean square error filtering;

[0136] The scattered field expression after frequency domain filtering is:

[0137]

[0138] Where t represents the transmission time of the optical signal, r = (r x ,r y ,r z ) represents the light signal exit cloud point, is φ inf (t,r)*φ infThe frequency domain discretization expression of (t,r), * represents the three-dimensional convolution operation, for The conjugate matrix of , F represents the Fourier transform operation, F -1 represents the inverse Fourier transform operation, τ is the reflected three-dimensional light field is the discretized expression of , and α represents the noise term parameter related to the signal power spectrum and the noise power spectrum.

[0139] Optionally, the free-space light field inversion method may include:

[0140] Frequency beam migration method, light cone transformation method, back projection method or virtual wave phasor field method.

[0141] Furthermore, the relationship determination module 403 inverts the target light field imaging by the free space light field inversion method, including performing the following operations:

[0142] Perform a translation coordinate system transformation, set the z-axis plane where the light signal exits the cloud point to the known z=0 plane, and transform the scattered field I(r, t) after frequency domain filtering to Ψ(x, y, z=0, t);

[0143] Perform Fourier transform on the scattered field Ψ(x, y, z=0, t) after coordinate transformation to obtain the corresponding frequency domain expression Φ(k x ,k y ,f); f represents the time frequency, k x 、k y and k z Represents the spatial frequencies corresponding to the x, y, and z directions respectively. Since z = 0, the transformed frequency domain expression does not include k z ;

[0144] Using dispersion relations and Get the value containing k x 、k y and k z Frequency domain expression of the scattered field:

[0145]

[0146] For k x 、k y and k z Frequency domain expression of the scattered field Φ(k x ,k y ,k z ) performs inverse Fourier transform to obtain the target scattering field Ψ(x, y, z, t=0).

[0147] Optionally, the imaging determination module 404 is further configured to output a final imaging result. For example, the imaging result may be output to a data window and an image window, and the result may be stored in a designated storage medium.

[0148] Optionally, the device may further include: a result display module 405 for displaying the final imaging result in a graphical manner. The result display module 405 may use a screen with text and graphic display capabilities to directly display the calculated imaging result.

[0149] It should be understood that the structure illustrated in the embodiments of the present invention does not constitute a specific limitation on the inversion imaging device for cloud-obscured targets based on a boundless cloud transfer function. In other embodiments of the present invention, the inversion imaging device for cloud-obscured targets based on a boundless cloud transfer function may include more or fewer components than illustrated, or may combine or separate certain components, or employ different component arrangements. The illustrated components may be implemented in hardware, software, or a combination of both.

[0150] The information interaction, execution process, etc. between the modules in the above-mentioned device are based on the same concept as the embodiment of the method of the present invention. For specific contents, please refer to the description in the embodiment of the method of the present invention and will not be repeated here.

[0151] An embodiment of the present invention also provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, a cloud-obscured target inversion imaging method based on a boundless cloud transfer function in any embodiment of the present invention is implemented.

[0152] An embodiment of the present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the processor executes a cloud-obscured target inversion imaging method based on an unbounded cloud transfer function in any embodiment of the present invention.

[0153] Specifically, a system or device equipped with a storage medium can be provided, on which software program codes that implement the functions of any of the above-mentioned embodiments are stored, and a computer (or CPU or MPU) of the system or device can be enabled to read and execute the program codes stored in the storage medium.

[0154] In this case, the program code itself read from the storage medium can realize the function of any one of the above-mentioned embodiments, and thus the program code and the storage medium storing the program code constitute part of the present invention.

[0155] Examples of storage media for providing program code include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, the program code can be downloaded from a server computer via a communication network.

[0156] In addition, it should be clear that the functions of any of the above embodiments can be achieved not only by executing the program code read by the computer, but also by enabling the operating system operating on the computer to complete part or all of the actual operations based on the instructions of the program code.

[0157] In addition, it can be understood that the program code read from the storage medium is written into a memory provided in an expansion board inserted into the computer or into a memory provided in an expansion module connected to the computer, and then based on the instructions of the program code, a CPU installed on the expansion board or expansion module is enabled to perform part or all of the actual operations, thereby realizing the functions of any of the above embodiments.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A cloud-mass-obscured target inversion imaging method based on an unbounded cloud-mass transfer function, characterized in that: include: Acquire a reflected three-dimensional light field of a target obscured by fog and cloud; the reflected three-dimensional light field includes a time domain interval light signal corresponding to a two-dimensional space, and the time domain interval of the reflected three-dimensional light field includes the time range in which the pulsed light is collected after being reflected by the target and penetrating the fog and cloud; Determine the characteristics of the cloud and fog, and obtain the unbounded cloud and fog transmission function; the characteristics of the cloud and fog include the reduced scattering coefficient of the cloud and fog, the speed of light in the cloud and fog, and the maximum thickness of the cloud and fog; the unbounded cloud and fog transmission function φ inf The expression of (t,r) is: Where t represents the transmission time of the optical signal, r = (r x ,r y ,r z ) represents the light signal exit cloud point, r x 、r y and r z They represent the coordinates of the outgoing cloud point on the x, y, and z axes, respectively. z is the diffusion direction of light in the cloud. r0 = (0, 0, 0) represents the incident cloud point of the light signal. c represents the speed of light in the cloud. μ s ' represents the reduced scattering coefficient of cloud and fog, z effect Represents the equivalent propagation distance, when light propagates in a cloud of infinite size z effect The diffusion behavior of light and the propagation of light in a finite size cloud z The diffusion behavior is equivalent to z effect Not exceeding the maximum thickness d of clouds and fog; The equivalent propagation distance z effect As a variable, the reflected three-dimensional light field is frequency-domain filtered based on the unbounded cloud transfer function, and then the target light field imaging is inverted by the free-space light field inversion method to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging results; According to the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging result is determined by parametric scanning or optimization solution to determine the final imaging result.

2. The cloud-obscured target inversion imaging method according to claim 1, characterized in that: The step of obtaining the reflected three-dimensional light field of the target obscured by clouds and fog includes: Illuminate targets obscured by clouds and fog with monochromatic pulsed laser; On the transmitting side, a single-photon detector is used to obtain the time-domain optical signal waveform of each two-dimensional spatial point by scanning. The time-domain optical signal waveform includes the peak caused by the target reflection, but does not include the peak caused by the cloud reflection. According to the spatial position relationship of the two-dimensional space scanning points, the time domain optical signal waveforms corresponding to each scanning point are combined to obtain a reflected three-dimensional light field.

3. The cloud-obscured target inversion imaging method according to claim 1, characterized in that: The performing frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function includes: Based on the unbounded cloud transfer function, frequency domain filtering is performed on the reflected three-dimensional light field by blind deconvolution filtering, minimum mean square error filtering, geometric mean filtering or least squares filtering.

4. The cloud-obscured target inversion imaging method according to claim 3, characterized in that: The performing frequency domain filtering on the reflected three-dimensional light field based on the unbounded cloud transfer function includes: Based on the unbounded cloud transfer function, performing frequency domain filtering on the reflected three-dimensional light field by minimum mean square error filtering; The scattered field expression after frequency domain filtering is: in, is φ inf (t,r)*φ inf The frequency domain discretization expression of (t,r), * represents the three-dimensional convolution operation, for The conjugate matrix of , F represents the Fourier transform operation, F -1 represents the inverse Fourier transform operation, τ is the reflected three-dimensional light field is the discretized expression of , and α represents the noise term parameter related to the signal power spectrum and the noise power spectrum.

5. The cloud-obscured target inversion imaging method according to claim 1, characterized in that: The free-space light field inversion method comprises: Frequency beam migration method, light cone transformation method, back projection method or virtual wave phasor field method.

6. The cloud-obscured target inversion imaging method according to claim 5, characterized in that: The free space light field inversion method is a frequency beam migration method; The inverting target light field imaging by the free space light field inversion method includes: Perform a translation coordinate system transformation, set the z-axis plane where the light signal exits the cloud point to the known z=0 plane, and transform the scattered field I(r, t) after frequency domain filtering to Ψ(x, y, z=0, t); Perform Fourier transform on the scattered field Ψ(x, y, z=0, t) after coordinate transformation to obtain the corresponding frequency domain expression Φ(k x ,k y ,f); f represents the time frequency, k x 、k y and k z Represents the spatial frequencies corresponding to the x, y, and z directions respectively. Since z = 0, the transformed frequency domain expression does not include k z ; Using dispersion relations and Get the value containing k x 、k y and k z Frequency domain expression of the scattered field: For k x 、k y and k z Frequency domain expression of the scattered field Φ(k x ,k y ,k z ) performs inverse Fourier transform to obtain the target scattering field Ψ(x, y, z, t=0).

7. A cloud-mass obscured target inversion imaging device based on a boundless cloud-mass transfer function, characterized in that: include: A light field acquisition module is used to acquire a reflected three-dimensional light field of a target obscured by fog and cloud; the reflected three-dimensional light field includes a time domain interval light signal corresponding to a two-dimensional space, and the time domain interval of the reflected three-dimensional light field includes the time range in which the pulsed light is captured after being reflected by the target and penetrating the fog and cloud; The function determination module is used to determine the characteristics of the cloud and obtain the unbounded cloud transmission function; the characteristics of the cloud include the reduced scattering coefficient of the cloud, the speed of light in the cloud and the maximum thickness of the cloud; the unbounded cloud transmission function φ inf The expression of (t,r) is: Where t represents the transmission time of the optical signal in the cloud, r = (r x ,r y ,r z ) represents the light signal exit cloud point, r x 、r y and r z They represent the coordinates of the outgoing cloud point on the x, y, and z axes, respectively. z is the diffusion direction of light in the cloud. r0 = (0, 0, 0) represents the incident cloud point of the light signal. c represents the speed of light in the cloud. μ s ' represents the reduced scattering coefficient of cloud and fog, z effect Represents the equivalent propagation distance, when light propagates in a cloud of infinite size z effect The diffusion behavior of light and the propagation of light in a finite size cloud z The diffusion behavior is equivalent to z effect Not exceeding the maximum thickness d of clouds and fog; Relationship determination module, used to convert the equivalent propagation distance z effect As a variable, the reflected three-dimensional light field is frequency-domain filtered based on the unbounded cloud transfer function, and then the target light field imaging is inverted by the free-space light field inversion method to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging results; Imaging determination module, used to determine the equivalent propagation distance z effect The corresponding relationship between the inversion target light field imaging result is determined by parametric scanning or optimization solution to determine the final imaging result.

8. The cloud-obscured target inversion imaging device according to claim 7, characterized in that: The device also includes: The result display module is used to display the final imaging result in a graphical manner.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the cloud-obscured target inversion imaging method according to any one of claims 1 to 6 is implemented.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed in a computer, the computer is caused to execute the cloud-obscured target inversion imaging method according to any one of claims 1 to 6.

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