CN113848547B - Digital holographic fast imaging method - Google Patents
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Abstract
The invention relates to the technical field of optical imaging, microwave imaging, radar detection, wireless communication, sonar, ultrasonic imaging, target detection and imaging identification based on media such as sound, light, electricity and the like, in particular to a digital holographic rapid imaging method and application thereof in the fields. The method is based on the lens imaging principle, combines the electromagnetic field theory, and obtains the image field distribution corresponding to the target by the amplitude and phase weighting of unit signals and the efficient parallel algorithm according to the target signals received by the antenna array. The invention has the advantages of small operation amount, low hardware cost, high imaging speed, suitability for remote imaging and the like, and can be widely applied to the fields of optical imaging, microwave imaging, radar detection, sonar imaging, ultrasonic imaging, target detection, imaging identification and wireless communication taking sound, light, electricity and the like as media.
Description
Technical Field
The invention relates to the technical fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, target detection based on media such as sound, light, electricity and the like, imaging identification and wireless communication, in particular to a digital holographic rapid imaging method and application thereof in the fields.
Background
The digital holographic imaging technology evolved from the laser holographic imaging technology has high imaging resolution, is one of the first-choice technologies of millimeter wave active imaging at present, and related products are popularized and applied in different fields at home and abroad.
However, the conventional digital holographic imaging technology still has many defects and shortcomings, mainly including:
1) large computation, high cost and low speed
In the existing digital holographic imaging technology, two operations of Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) are required to be performed in sequence during imaging, the operation amount is extremely large, the configuration requirements on hardware environment and computing resources are high, the hardware price and the operation cost are high, and in addition, the two operations of FFT and IFFT are required to be performed in sequence, so the imaging speed is low.
2) Cannot image remotely
In the existing digital holographic imaging technology, when the target distance is long, the phase compensation can be ignored, which is equivalent to performing "FFT-IFFT" operation, and imaging distortion and even imaging failure can be caused.
In addition, the prior art "microwave array fast imaging method" (CN 112612024 a), but this method is not suitable for short-distance digital holographic imaging application, and when the imaging distance is close, this method cannot obtain satisfactory imaging effect because of poor imaging effect and low resolution.
Disclosure of Invention
In order to overcome the defects and shortcomings of the traditional digital holographic imaging technology, the invention provides a set of solutions.
As shown in fig. 1, a coordinate system of an imaging system is established, wherein: p is the target, Q is the image of the target, the antenna array is located on the plane where z is 0, and X denotes the transmit and receive antenna elements. And sequentially opening the receiving and transmitting antenna units, recording the scattering signals of the target, obtaining the holographic data of the target when the whole antenna array is scanned, and carrying out imaging processing on the holographic data to obtain the image of the target.
The propagation phase shift introduced when a signal propagates through a single pass of R1, R2 is:
among the components useful for imaging focusing are:
wherein phi is 1 Is the propagation phase shift, phi, of the scattering source P to the array elements 2 For the propagation phase shift of the array element to the image point Q,
is the wave number, U is the object distance, V is the image distance; (ζ, ξ) are target coordinates, (x, y) are array element coordinates, and (δ, σ) are image point coordinates.
By equating the antenna array as a lens with focal length F, the effective phase shift of the lens elements is:
wherein phi is L F is the focal length for the lens phase shift of the array element.
In the holographic imaging system, a signal is transmitted from an antenna unit, reflected to a target and received by the antenna unit, the signal undergoes two-pass transmission with a path R1, and the corresponding phase delay is 2 phi 1 . In the imaging process, the lens unit phase shift and the R2 propagation phase shift are processed in two passes: the receiving and transmitting antenna units sequentially transmit detection signals, and the signals reflected by the target P are subjected to secondary scattering in the form of spherical waves after reaching the receiving and transmitting antenna units and then pass through different transmission paths R 1 、R 2 And the field strength at the image plane after the two-way phase shift is as follows:
wherein the content of the first and second substances,
in order to be the image field distribution,
is the target reflected signal. Substitution of phi 1 、φ 2 、φ L The expression of (A) is obtained after the arrangement:
wherein the content of the first and second substances,
when the imaging conditions are satisfied:
at this time there is Ψ 1 0, order
Finishing to obtain:
for an ideal rectangular lens front:
substituting the formula to carry out definite integration to obtain:
where Sinc represents the Sinc function. It can be seen that there is a good mapping between the image field distribution and the object.
For an actual holographic imaging discrete array system, assuming that a target transmission signal received by a transceiving antenna unit is E, a reflected signal received by an array needs to be subjected to the following two-way phase shift processing during imaging:
wherein the content of the first and second substances,
for the field received by the array element, A mn The amplitude weighting coefficients of the array elements. The formula is developed and finished to obtain:
wherein the content of the first and second substances,
when the imaging conditions are satisfied:
at this time has psi 1 ＝0。
Let x m ＝x 0 +mΔ x ，y n ＝y 0 +nΔ y M and n are respectively the serial numbers of the array units in the x direction and the y direction, delta x 、Δ y Array unit spacing in x-direction and y-direction respectively, (x) 0 ,y 0 ) Is the array starting cell coordinate. The formula is simplified and arranged as follows:
wherein the content of the first and second substances,
the right coefficient of the above formula satisfies
The spatial fluctuation characteristic of an image field is reflected, and the influence on imaging is basically avoided and can be ignored. The summation operation can be rapidly solved by two-dimensional IFFT, and then an image field calculation formulaComprises the following steps:
where IFFT represents a two-dimensional inverse fast fourier transform. Omega corresponding to IFFT calculation result δ 、ω σ The value range is as follows: omega δ ∈[0,2π]、ω σ ∈[0,2π]After fftshift operation, the value of ω is calculated δ 、ω σ The value range is transformed into: omega δ ∈[-π,π]、ω σ ∈[-π,π]The image at this time is the image which is in accordance with the actual distribution, and has a good linear mapping relation with the source field.
In connection with the theory of array antennas, there is omega δ ＝2kΔ x sinθ δ 、ω σ ＝2kΔ y sinθ σ The condition that the directional diagram has no grating lobe is as follows:
and finally, correcting the scanning angular coordinate of the image point by adopting an array antenna theory:
on the basis of the knowledge, the invention provides a digital holographic rapid imaging method, which is based on a lens imaging principle, combines an electromagnetic field theory, and adopts an efficient parallel algorithm to obtain image field distribution corresponding to a target by weighting the amplitude and the phase of a unit signal according to a target signal received by an antenna array.
Further, in the method, the image field distribution corresponding to the target is obtained by weighting the amplitude and the phase of the unit signal and adopting an efficient parallel algorithm, and the specific algorithm is as follows:
wherein: j is an imaginary unit, e is an Euler constant,
in order to be the image field distribution,
for the target signal received by the array unit, A mn Is a weighting coefficient for the array element amplitude,
in order to focus the phase weighting coefficients,
for scanning the phase weighting coefficients, M is the number of array elements in the x-direction, and N is the number of array elements in the y-direction, (x) m ，y n ) Is the coordinate of the array unit, (delta, sigma) is the coordinate of the image point, V is the image distance, i.e. the distance from the image plane to the array plane, m, n are the serial numbers of the array unit in the x direction and the y direction respectively,
in wavenumber, λ is the wavelength, and the symbol Σ represents the summation operation.
Specifically, the digital holographic rapid imaging method comprises the following steps:
the method comprises the following steps: carrying out amplitude weighting on the array unit signals to reduce side lobe levels;
step two: carrying out scanning phase weighting on the array unit signals to adjust the central visual angle direction of the imaging system;
step three: carrying out focusing phase weighting on the array unit signals to realize imaging focusing;
step four: performing rapid imaging processing on signals of the array unit by adopting an efficient parallel algorithm;
step five: and resolving the image field coordinates, and performing coordinate inversion on the image field to obtain the position of the real target.
Further, the amplitude weighting method in step one of the method of the present invention includes, but is not limited to, uniform distribution, cosine weighting, hamming window, Taylor distribution, chebyshev distribution, and hybrid weighting method.
Further, in step two of the method of the present invention, the scanning phase is weighted to adjust the central view direction of the imaging system, and the phase calculation formula of the scanning phase weighting is as follows:
wherein:
the phase difference between the adjacent cells of the array in the x direction and the y direction respectively has the following calculation formula:
wherein: delta x 、Δ y The array unit pitch theta in the x direction and the y direction ζ 、θ ξ The x and y scanning angle coordinates when the central visual angle direction points to the source coordinates (zeta, xi) are respectively calculated as follows:
wherein: u is the object distance, i.e., the distance from the plane of the target to the plane of the array.
Further, the method comprises the following steps: and carrying out focusing phase weighting on the array unit signals by using a focusing phase weighting method to realize imaging focusing, wherein:
the autofocus phase weighted focus phase calculation formula is:
the zoom or fixed focus phase weighted focus phase calculation formula is:
wherein F is the focal length, and F < U, F < V.
Further, the method of the invention comprises the following fourth step: performing rapid imaging processing on the signals after the amplitude and the phase of the array unit are weighted by adopting an efficient parallel algorithm; the efficient parallel algorithm includes, but is not limited to, two-dimensional or three-dimensional FFT, IFFT, non-uniform FFT, sparse FFT, and the calculation formula is:
wherein:
is like, symbol
Represents an efficient parallel algorithm function and is,
is a target scattered field received by the array unit, A is an array unit amplitude weighting coefficient, phi F For focusing the phase weighting coefficients, [ phi ] S Weighting coefficients for the scan phases;
omega corresponding to image field calculation result δ 、ω σ The value range is as follows: omega δ ∈[0,2π]、ω σ ∈[0,2π]After fftshift operation, the value of ω is calculated δ 、ω σ The value range is transformed into: omega δ ∈[-π,π]、ω σ ∈[-π,π]The image at this time is an image conforming to the actual distribution:
further, the method of the invention comprises the following step five: carrying out coordinate calculation on an image field obtained by the efficient parallel algorithm, and carrying out coordinate inversion on the image field to obtain the distribution condition of a real target; wherein:
for the IFFT-type efficient parallel algorithm, the calculation formula of the angular coordinate of the image field scanning is as follows:
for the FFT-like efficient parallel algorithm, the calculation formula of the image field scanning angle coordinate is as follows:
the rectangular coordinate calculation formula of the image is as follows:
δ＝Vtanθ δ ，
σ＝Vtanθ σ ；
the coordinate inversion calculation formula of the real target is as follows:
wherein, Delta x 、Δ y The array unit spacing in the x direction and the y direction respectively, U is the object distance, and zeta are source coordinates.
Furthermore, the method of the invention sets the unit spacing of the transmitting and receiving antenna
To avoid image aliasing.
Meanwhile, the invention also relates to the application of the method in the fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, sound, light and electric target detection, imaging identification and wireless communication.
In addition, the invention also provides a digital holographic fast imaging method, which is used for remote imaging and comprises the following steps: the image field is calculated by adopting the efficient parallel algorithm, and phi exists by selecting U ∞ F At 0, the simplified formula for the long range imaging is:
wherein, U is the object distance,
is like, symbol
Represents an efficient parallel algorithm function and is,
for the object fringe field received by the array unit, A is the array unitElement amplitude weighting coefficient, phi F For focusing the phase weighting coefficients, [ phi ] S And (3) obtaining the target distribution condition in a wide visual angle range through one-time operation, wherein j is an imaginary number unit, and e is an Euler constant.
In summary, the digital holographic fast imaging method of the invention has the following advantages:
1) small operation amount, low hardware cost and high imaging speed
Compared with the traditional holographic imaging algorithm, the phase compensation-IFFT algorithm framework is adopted, the FFT operation link with high requirement on hardware resources and low operation speed is removed, the operation amount is greatly reduced, and the operation speed is improved.
2) Can be used for long-distance imaging
In the invention, when the remote imaging is carried out, the phase compensation can be ignored, and the IFFT operation is equivalently carried out, so that the imaging of the remote target can be realized.
In addition, the method has good application prospect, can be widely applied to the technical field of target detection and wireless communication taking sound, light, electricity and the like as media, and when the detection media are electromagnetic waves, the technology is suitable for microwave imaging, radar detection, wireless communication, synthetic aperture radar and inverse synthetic aperture radar; when the detection medium is sound wave and ultrasonic wave, the technology is suitable for sonar, ultrasonic imaging and synthetic aperture sonar; when the detection medium is light, the technology is suitable for optical imaging and synthetic aperture optical imaging.
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In order to more clearly illustrate the technical solutions of the prior art and the embodiments of the present invention, the drawings needed to be used in the description of the prior art and the embodiments of the present invention will be briefly described below, it is obvious that the following drawings are only some embodiments described in the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a coordinate system of a digital holographic imaging system according to the present invention.
FIG. 2 is an algorithm block diagram of the digital holographic imaging method of the present invention.
Fig. 3 is a comparison of the results of conventional holographic imaging and holographic imaging of the present invention in close range (U ═ 1m), where: (a) for conventional holographic imaging and (b) for holographic imaging according to the invention.
Fig. 4 shows the comparison between the conventional holographic imaging and the holographic imaging remote imaging (U1000 m), in which: (a) for conventional holographic imaging and (b) for holographic imaging according to the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail and completely with reference to the following embodiments and accompanying drawings. It is to be understood that the embodiments described are merely illustrative of some, but not all, of the present invention and that the invention may be embodied or carried out in various other specific forms, and that various modifications and changes in the details of the specification may be made without departing from the spirit of the invention.
Also, it should be understood that the scope of the invention is not limited to the particular embodiments described below; it is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.
Example 1: a digital holographic fast imaging method (refer to the attached figures 1-2) is based on the lens imaging principle, combines the electromagnetic field theory, and obtains the image field distribution corresponding to the target by the amplitude and phase weighting of unit signals and the high-efficiency parallel algorithm according to the target signals received by an antenna array, and the specific algorithm is as follows:
wherein: j is an imaginary unit, e is an Euler constant,
in order to be the image field distribution,
for the target signal received by the array unit, A mn Is a weighting coefficient for the array element amplitude,
in order to focus the phase weighting coefficients,
for scanning the phase weighting coefficients, M is the number of array elements in the x-direction, and N is the number of array elements in the y-direction, (x) m ，y n ) Is the coordinate of the array unit, (delta, sigma) is the coordinate of the image point, V is the image distance, i.e. the distance from the image plane to the array plane, m, n are the serial numbers of the array unit in the x direction and the y direction respectively,
in wavenumber, λ is the wavelength, and the symbol Σ represents the summation operation.
Specifically, the method comprises the following steps:
the method comprises the following steps: carrying out amplitude weighting on the array unit signals to reduce side lobe levels;
the amplitude weighting method comprises a uniform distribution method, a cosine weighting method, a Hamming window method, a Taylor distribution method, a Chebyshev distribution method and a mixed weighting method.
Step two: carrying out scanning phase weighting on the array unit signals to adjust the central visual angle direction of the imaging system;
wherein, the scanning phase weighting adjusts the central view angle direction of the imaging system, and the phase calculation formula of the scanning phase weighting is as follows:
wherein: m and n are serial numbers of the array units in the x direction and the y direction respectively,
are respectively xAnd the calculation formulas of the phase difference between the adjacent units of the array in the y direction are respectively as follows:
wherein: delta x 、Δ y The array unit spacing in the x-direction and the y-direction respectively, the symbol sin represents a sine function, theta ζ 、θ ξ The x and y scanning angle coordinates when the central visual angle direction points to the source coordinates (zeta, xi) are respectively calculated as follows:
wherein: u is the object distance, i.e. the distance from the plane of the target to the array plane, the symbol tan -1 Representing the arctan function.
Step three: carrying out focusing phase weighting on the array unit signals to realize imaging focusing;
the method specifically comprises the following steps: and carrying out focusing phase weighting on the array unit signals by using a focusing phase weighting method to realize imaging focusing, wherein:
the autofocus phase weighted focus phase calculation formula is:
the zoom or fixed focus phase weighted focus phase calculation formula is:
wherein F is the focal length, and F < U, F < V.
Step four: performing rapid imaging processing on signals of the array unit by adopting an efficient parallel algorithm;
the method specifically comprises the following steps: performing rapid imaging processing on the signals after the amplitude and the phase of the array unit are weighted by adopting an efficient parallel algorithm; the efficient parallel algorithm comprises two-dimensional or three-dimensional FFT, IFFT, non-uniform FFT and sparse FFT, and the calculation formula is as follows:
wherein:
is like, symbol
Represents an efficient parallel algorithm function and is,
for a target fringe field received by an array element, A is the array element amplitude weighting coefficient, φ F For focusing the phase weighting coefficients, [ phi ] S Weighting coefficients for the scan phases;
omega corresponding to image field calculation result δ 、ω σ The value range is as follows: omega δ ∈[0,2π]、ω σ ∈[0,2π]After fftshift operation, the value of ω is calculated δ 、ω σ The value range is transformed into: omega δ ∈[-π,π]、ω σ ∈[-π,π]The image at this time is an image conforming to the actual distribution:
step five: resolving an image field coordinate, and performing coordinate inversion on the image field to obtain the position of a real target;
the method specifically comprises the following steps: carrying out coordinate calculation on an image field obtained by the efficient parallel algorithm, and carrying out coordinate inversion on the image field to obtain the distribution condition of a real target; wherein:
for the efficient parallel algorithm of the IFFT class, the calculation formula of the angular coordinate of the image field scanning is as follows:
for the FFT-like efficient parallel algorithm, the calculation formula of the image field scanning angle coordinate is as follows:
the rectangular coordinate calculation formula of the image is as follows:
δ＝Vtanθ δ ，
σ＝Vtanθ σ ；
the coordinate inversion calculation formula of the real target is as follows:
wherein, Delta x 、Δ y The array unit spacing in the x direction and the y direction respectively, U is the object distance, and zeta are source coordinates.
In addition, the method can be used for producing a composite materialIn the method of the present invention, the unit spacing of the transmitting and receiving antennas is set
To avoid image aliasing.
Example 2: the digital holographic fast imaging (embodiment 1 method) of the invention is compared with the short-distance imaging result of the traditional holographic imaging (U is 1m), and the method comprises the following steps:
the working frequency is 30GHz, the antenna unit spacing is half wavelength, the array scale is 32 x 32, one target is located in the normal direction of the array, the other target deviates from the normal direction by 20 degrees, the distance between the target and the plane where the antenna array is located is 1m, and the imaging result is contrasted with that shown in figure 3.
Example 3: the digital holographic fast imaging (embodiment 1 method) of the invention is compared with the remote imaging result of the traditional holographic imaging (U is 1000m), and the method comprises the following steps:
the working frequency is 30GHz, the spacing between the antenna units is half wavelength, the array scale is 32 x 32, one target is located in the normal direction of the array, the other target deviates from the normal direction by 20 degrees, the distance between the target and the plane where the antenna array is located is 1000m, and the imaging result is contrasted with the imaging result shown in figure 4.
Example 4: a digital holographic fast imaging method for remote imaging, comprising: the image field is calculated by adopting the efficient parallel algorithm described in the embodiment 1, and phi exists by selecting U ∞ F At 0, the simplified formula for the long range imaging is:
wherein, U is the object distance,
is like, symbol
Represents an efficient parallel algorithm function and is,
is a target scattered field received by the array unit, A is an array unit amplitude weighting coefficient, phi F To focus the phase weighting coefficients, phi S And (3) obtaining the target distribution condition in a wide view angle range through one operation, wherein j is a scanning phase weighting coefficient, j is an imaginary number unit, and e is an Euler constant.
The embodiments of the present invention are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The above description is only an example of the present invention, and is not intended to limit the present invention. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, replacement, or the like that comes within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (10)
1. A digital holographic rapid imaging method is characterized in that the method is based on a lens imaging principle, combines an electromagnetic field theory, and obtains image field distribution corresponding to a target by adopting an efficient parallel algorithm through amplitude and phase weighting of unit signals according to target signals received by an antenna array, wherein the specific algorithm is as follows:
wherein: j is an imaginary unit, e is an Euler constant,
in order to be the image field distribution,
for the target signal received by the array element, A mn Is a weighting coefficient for the array element amplitude,
in order to focus the phase weighting coefficients,
for scanning the phase weighting coefficients, M is the number of array elements in the x-direction, and N is the number of array elements in the y-direction, (x) m ，y n ) Is the coordinate of the array unit, (delta, sigma) is the coordinate of the image point, V is the image distance, i.e. the distance from the image plane to the array plane, m, n are the serial numbers of the array unit in the x direction and the y direction respectively,
in wavenumber, λ is the wavelength, and the symbol Σ represents the summation operation.
2. Method according to claim 1, characterized in that it comprises the following steps:
the method comprises the following steps: carrying out amplitude weighting on the array unit signals to reduce side lobe levels;
step two: carrying out scanning phase weighting on the array unit signals to adjust the central visual angle direction of the imaging system;
step three: carrying out focusing phase weighting on the array unit signals to realize imaging focusing;
step four: performing rapid imaging processing on signals of the array unit by adopting an efficient parallel algorithm;
step five: and resolving the image field coordinates, and performing coordinate inversion on the image field to obtain the position of the real target.
3. The method of claim 2, wherein the amplitude weighting method in step one comprises uniform distribution, cosine weighting, hamming window, Taylor distribution, chebyshev distribution and hybrid weighting method.
4. The method of claim 2, wherein in step two, the scan phase weighting adjusts the central view angle direction of the imaging system, and the phase calculation formula of the scan phase weighting is:
wherein:
the phase difference between the adjacent cells of the array in the x direction and the y direction respectively has the following calculation formula:
wherein: delta x 、Δ y The array unit spacing in the x-direction and the y-direction respectively, the symbol sin represents a sine function, theta ζ 、θ ξ The x and y scanning angle coordinates when the central visual angle direction points to the source coordinates (zeta, xi) are respectively calculated as follows:
wherein: u is the object distance, i.e. the distance from the plane of the target to the array plane, the symbol tan -1 Representing the arctan function.
5. The method of claim 4, wherein step three comprises: and carrying out focusing phase weighting on the array unit signals by using a focusing phase weighting method to realize imaging focusing, wherein:
the autofocus phase weighted focus phase calculation is given by:
the zoom or fixed focus phase weighted focus phase calculation formula is:
wherein F is the focal length, and F < U, F < V.
6. The method of claim 4, wherein step four comprises: performing rapid imaging processing on the signals after the amplitude and the phase of the array unit are weighted by adopting an efficient parallel algorithm; the efficient parallel algorithm comprises two-dimensional or three-dimensional FFT, IFFT, non-uniform FFT and sparse FFT, and the calculation formula is as follows:
wherein:
is like, symbol
Represents an efficient parallel algorithm function and is,
is a target scattered field received by the array unit, A is an array unit amplitude weighting coefficient, phi F For focusing the phase weighting coefficients, [ phi ] S Weighting coefficients for the scanning phases;
omega corresponding to image field calculation result δ 、ω σ Value rangeThe enclosure is as follows: omega δ ∈[0,2π]、ω σ ∈[0,2π]After fftshift operation, the value of ω is calculated δ 、ω σ The value range is transformed into: omega δ ∈[-π,π]、ω σ ∈[-π,π]The image at this time is an image conforming to the actual distribution:
7. the method of claim 4, wherein step five comprises: carrying out coordinate calculation on an image field obtained by the efficient parallel algorithm, and carrying out coordinate inversion on the image field to obtain the distribution condition of a real target; wherein:
for the IFFT-type efficient parallel algorithm, the calculation formula of the angular coordinate of the image field scanning is as follows:
for the FFT-like efficient parallel algorithm, the calculation formula of the image field scanning angle coordinate is as follows:
the rectangular coordinate calculation formula of the image is as follows:
δ＝Vtanθ δ ，
σ＝Vtanθ σ ；
the coordinate inversion calculation formula of the real target is as follows:
wherein, Delta x 、Δ y The array unit spacing in the x direction and the y direction respectively, U is the object distance, and zeta are source coordinates.
8. Method according to claim 4, characterized in that the element spacing of the transceiving antennas is set
To avoid imaging aliasing.
9. The method according to any one of claims 1 to 8, wherein the method is applied in the fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, and acoustic, optical, electrical target detection, image recognition, wireless communication.
10. A digital holographic fast imaging method, wherein the fast imaging method is used for long-distance imaging, comprising:
computing an image field using the efficient parallel algorithm of claim 6, with φ by choosing U ═ infinity F At 0, the simplified formula for the long range imaging is:
wherein, U is the object distance,
is like, symbol
Represents an efficient parallel algorithm function and is,
is a target scattered field received by the array unit, A is an array unit amplitude weighting coefficient, phi F For focusing the phase weighting coefficients, [ phi ] S And (3) obtaining the target distribution condition in a wide visual angle range through one-time operation, wherein j is an imaginary number unit, and e is an Euler constant.
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