A method for optimizing antenna parameters in microwave optical aperture transformation imaging system

Abstract

The present invention relates to the field of microwave optics, and discloses an antenna parameter optimization design method for a microwave optical aperture transformation imaging system. The present invention optimizes the Gaussian beam waist radius, the aperture of the optical antenna, and the relative position between array elements for the microwave optical aperture transformation imaging system, and can improve the imaging quality by effectively reducing the side lobes and extrapolating them under the condition of fixed incident microwave wavefront and microwave antenna size, that is, when the system resolution remains unchanged. The present invention can guide the design of a microwave optical aperture transformation imaging system.

Description

Technical Field

[0001] The present application relates to the field of microwave optics, and in particular to an antenna parameter optimization design method for a microwave optical aperture transformation imaging system. Background Art

[0002] Millimeter wave imaging technology is a technology that uses the millimeter wave frequency band for imaging. It has high penetration ability and can image targets in low-visibility atmospheric conditions. Common millimeter wave imaging technologies include synthetic aperture radar (SAR) imaging, inverse synthetic aperture radar (ISAR) imaging, and integrated aperture radiometer imaging. Microwave optical imaging technology has significant advantages over traditional millimeter wave imaging technology. Microwave optical imaging technology based on the fusion of microwave array aperture and three-dimensional information processing can achieve real-time forward-looking two-dimensional imaging, and has the characteristics of high sensitivity, low cost, low computing resource overhead and low power consumption. Microwave optical aperture transformation imaging systems based on the fusion of microwave array aperture and three-dimensional information processing, such as Figure 1 As shown. The system uses an array microwave antenna to perform spatial sampling of the microwave wavefront, which is converted to the optical domain through an electro-optical conversion array. Except for the carrier frequency up-conversion to the optical domain, the phase, amplitude and other information of the microwave wavefront remain unchanged, and the microwave antenna is replicated through the optical array antenna. This process is called aperture transformation. After the signal light of each channel is emitted through the optical array antenna, it is imaged on the focal plane through an optical lens in the optical domain.

[0003] In the above-mentioned microwave optical aperture transformation imaging system, the array antenna includes a microwave antenna and an optical antenna, and the spatial topological structures of the two are geometrically replicated according to the scaling factor, that is, the array apertures and array element spacings of the two satisfy a certain scaling relationship. After the array element layout of the optical antenna and the parameter design of the array aperture are completed according to specific requirements, the relevant parameters of the microwave antenna can be obtained according to the scaling factor, and the geometric scaling reconstruction of the light wavefront to the microwave wavefront can be realized. The design of the array antenna is very important, and its design parameters include the topological structures of the optical antenna and the microwave antenna, the waist radius of the optical array antenna output light beam and other parameters. These parameters determine the core parameters such as the microwave field of view of the imaging system. At present, in the microwave optical aperture transformation imaging system, the design method of antenna parameters is still imperfect. The present invention proposes an antenna parameter design method for a microwave optical aperture transformation imaging system. Through this method, targeted optimization design can be performed for different antenna apertures and array element number requirements, and corresponding antenna design parameters can be provided, thereby obtaining an excellent system point spread function, including requirements such as sharp main lobe, low side lobes and clean field of view around the main lobe, so as to achieve high-quality imaging within the required field of view. Summary of the invention

[0004] The purpose of the present application is to provide a method for designing structural parameters of a microwave optical aperture transformation imaging system that can improve imaging quality.

[0005] To this end, the present application proposes an antenna parameter optimization design method for a microwave optical aperture transformation imaging system, which includes the following steps: simulation modeling of the microwave optical aperture transformation imaging system; constructing a mathematical model for the target optimization problem of the optical antenna imaging quality in the microwave optical aperture transformation imaging system model; optimizing the mathematical model with an optimization algorithm; the optimization algorithm includes:

[0006] A one-dimensional array is constructed as a first individual using the aperture d of the optical antenna of the first value, the beam waist radius ω0 of the Gaussian beam, and the array element position arrangement of the regular circular array, and other arrays, i.e., other individuals, are constructed using a second value and a third value different from the first value, and the multiple individuals constitute an initial population;

[0007] Iteratively create optimization options based on the initial population; measure the set population once to obtain an updated point spread function; determine whether the preset number of iterations has been reached at this time; if the preset number of iterations has been reached, output the waist radius of the Gaussian beam optimized by the algorithm, the aperture of the optical antenna, the array element position arrangement, and the three-dimensional energy distribution diagram of the point spread function of the corresponding point source under the above parameters; otherwise, select individuals that meet the set convergence requirements from the obtained evaluation results as the parent individuals of the second-generation population; select individuals with higher levels in the quality evaluation from the second-generation parent individuals for crossover operations to generate offspring individuals, perform crossover and mutation operations on some of the offspring individuals, introduce random perturbations, and generate the second-generation population with the generated individuals; repeatedly execute the above judgment steps to optimize the maximum value of the peak-to-sidelobe ratio and the minimum value of the sidelobe extrapolation angle until the number of iterations is reached and the iterative optimization is stopped; and output the waist radius of the Gaussian beam optimized by the algorithm, the aperture of the optical antenna, the array element position arrangement, and the three-dimensional energy distribution diagram of the point spread function of the corresponding point source under the above parameters.

[0008] The method proposed in the embodiment of the present application improves the imaging quality by changing other parameters in the microwave optical aperture transformation imaging system under fixed microwave antenna aperture and wavelength. By deriving the formula of the point spread function model of the microwave optical aperture transformation imaging system, several factors that can optimize its quality and are actually selectable are clarified, namely, the waist radius of the Gaussian beam emitted by the fiber array, the aperture of the optical antenna, and the relative position relationship between the array elements, wherein the beam is coherently synthesized by each array element, and by adjusting the phase relationship between the array elements, the synthesis of fine beams in any direction is achieved. If the array elements are regularly arranged and the array element interval is greater than half a microwave wavelength, high side lobes will be formed under the common diffraction of a large number of redundant baselines, and even grating lobes will be formed under completely regular arrangement.

[0009] The method proposed in the embodiment of the present application optimizes the waist radius of the Gaussian beam, the aperture of the optical antenna, and the relative position between array elements for the microwave optical system. It can reduce the side lobes and extrapolate to improve the imaging quality under the condition of fixed incident microwave wavefront and microwave antenna size, that is, when the system resolution remains unchanged. This, on the one hand, provides inspiration for solving similar imaging quality optimization problems in the field of microwave photon radar, and on the other hand, obtains a structural parameter design scheme for microwave optical aperture transformation imaging systems with practical value, which can guide the design of microwave optical aperture transformation imaging systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of a microwave optical aperture transformation imaging system; Figure 1 In the figure, 3 is a laser light source, 4 is an optical phase control module, 5 is an optical antenna array, 6 is an optical beam splitter module, 7 is an optical filter, 8 is an optical lens, 9 is an infrared camera, 10 is a microwave signal source, and 11 is a microwave antenna array.

[0011] Figure 2 The present invention is a flow chart of a method for optimizing the design of structural parameters of a microwave optical aperture transformation imaging system according to an embodiment of the present application.

[0012] Figure 3 are the input parameters before optimization, including array element position structure, Gaussian beam waist radius and optical antenna aperture.

[0013] Figure 4 Three-dimensional energy distribution of the point spread function before parameter optimization.

[0014] Figure 5 The input and output parameters are optimized by the optimization design method of the present invention, including the array element position structure, the Gaussian beam waist radius and the optical antenna aperture.

[0015] Figure 6 It is a three-dimensional energy distribution diagram of the point spread function measured after the parameters are optimized by the optimization design method of the present invention.

[0016] Figure 7 Schematic diagram of the propagation of a Gaussian beam in free space.

[0017] Figure 8 A detailed flow chart of a structural parameter optimization design method for a microwave optical aperture transformation imaging system according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] The invention proposes an antenna parameter optimization design method for a microwave optical aperture transformation imaging system, which is used for optimizing the structural parameters of the microwave optical aperture transformation imaging system.

[0019] In the design of microwave optical aperture transform imaging system, point spread function is used to evaluate the imaging quality, which has the following indexes: sharp main lobe, low side lobe and clear field of view around the main lobe.

[0020] The inventors derived the formula of the point spread function model of the microwave optical aperture transformation imaging system and determined several factors that can be optimized and are actually selectable, namely the waist radius ω0 of the Gaussian beam emitted by the fiber array, the aperture d of the optical antenna, and the relative position relationship between the optical antenna array elements.

[0021] The inventors discovered that the beam is synthesized by the coherent synthesis of each array element. By adjusting the phase relationship between the array elements, it is possible to synthesize a thin beam in any direction. If the array elements are arranged regularly and the array element interval is greater than half a microwave wavelength, high side lobes will be formed under the common diffraction of a large number of redundant baselines, and even grating lobes will be formed under a completely regular arrangement.

[0022] Therefore, the present invention proposes a method for optimizing the Gaussian beam waist radius ω0, the aperture of the optical antenna, and the relative position between array elements for microwave optical systems. Under the condition of fixed incident microwave wavefront and microwave antenna size, that is, when the system resolution λ / D remains unchanged, the side lobes can be reduced and extrapolated to improve the imaging quality. On the one hand, this method provides inspiration for solving similar imaging quality optimization problems in the field of microwave photon radar, and on the other hand, a practical structural parameter design scheme for microwave optical aperture transformation imaging systems is obtained, which can guide the design of microwave optical aperture transformation imaging systems.

[0023] like Figure 2 , Figure 8 As shown, an embodiment of the structural parameter design method of the microwave optical aperture transformation imaging system for improving imaging quality proposed in the present application may include the following steps:

[0024] Step S1: Simulate and model the microwave optical aperture transformation imaging system.

[0025] The principle of the simulation modeling is as follows: In the microwave optical aperture transformation imaging system, the microwave echo beam scattered or reflected by the observed target is sampled and received by the array microwave antenna array 11, which includes multiple microwave antennas with a spacing of D; the far-field microwave point source is located in the θ direction, and the angle between the incident wave surface at the receiving end of the microwave antenna and the microwave antenna array 11 surface is θ. The microwave signal is received by the microwave antenna 11, and there is a time difference in the two microwave antenna channels: The phase difference introduced in the two channels is: Among them, ω RFis the angular frequency of the microwave signal. The received microwave signal is up-converted to the optical domain by the optical phase modulation module 4 with the help of the laser emitted by the laser light source 3, and the microwave wave is transformed into the corresponding light wave beam with full aperture fidelity mapping. The microwave wavefront is reconstructed in the optical domain, and then transmitted through an optical channel of equal length, and finally emitted again at the optical antenna array 5. In the process of full aperture fidelity mapping transformation, the topological structure of the optical antenna array 5 and the microwave antenna array 11 must be matched. The optical antenna array 5 includes multiple optical antennas, and the spacing between the optical antennas is d. Assuming that the outgoing light beams of any two channels have equal phase planes, and the angle with the surface of the optical antenna array 5 is β, the phase difference of the upper sideband of the modulated optical signal is: Where: SB is the angular frequency of the sideband signal, and c is the speed of light, i.e. the frequency of light. Since the frequencies of the carrier signal and the upper and lower sideband signals in the modulated optical signal are different and the phase differences reflected in the two channels are different, three wavefronts will be generated when the optical signal reconstructs the wavefront in free space, and three sets of interference fringes will appear on the infrared imaging camera 9 when performing spatial optical domain information processing. In order to avoid the interference of the three sets of interference fringes on the detection target recognition, we use the optical domain spectrum selection technology to extract one of the sideband signals carrying the microwave amplitude and phase information in the modulated optical signal to realize the mapping transformation from microwave to optical domain.

[0026] For the upper sideband signal: SB =ω opt +ω RF ω opt is the angular frequency of the optical carrier. According to the interference theory of light, when the phase difference is an integer multiple of 2π, interference bright fringes will be generated in space, that is: Wherein k is an integer.

[0027] According to the interference theory of light, since the zero-order fringe (k=0) concentrates most of the energy in the interference fringe, its center is the geometric image point of the target, so we can get: but It is the scaling factor of the system, which directly determines the imaging quality of the system.

[0028] In one embodiment, the aperture D of the microwave antenna array 11 can be kept unchanged, and the aperture d of the optical antenna array 5 can be adjusted to change the scaling factor of the system, thereby adjusting the topological structure of the microwave optical aperture transformation imaging system and optimizing the imaging quality.

[0029] The light emitted from the end of each optical fiber of the optical antenna array 5 is a Gaussian beam. The propagation of the Gaussian beam in free space is as follows: Figure 7 As shown. The field amplitude distribution of the fundamental mode Gaussian beam in the cross section falls smoothly from the center to the outside according to the Gaussian function, and the amplitude falls to the central value The spot radius ω(z) defined by the point is: Where: ω0 is the waist radius of the Gaussian beam; z is the axial distance with the waist as the origin of the coordinate system; λ is the operating wavelength. hour, It is called the Rayleigh distance. Define the rate of change of the spot radius ω(z) of a Gaussian beam with the propagation distance Z is the divergence angle θ(z) of the light beam, and the far-field divergence angle of the Gaussian beam is obtained as:

[0030] In some embodiments, the waist radius ω0 of the Gaussian beam can be adjusted and optimized. The larger the waist radius ω0 of the Gaussian beam, the smaller the far-field divergence angle θ, the more concentrated the imaging energy, and the better the detection performance of the microwave optical aperture transformation imaging system. In addition, in some embodiments, a Gaussian beam with a specific far-field divergence angle is required to meet the requirements of the microwave field of view of the imaging system. In this case, it is necessary to set constraints to adjust and optimize the waist radius ω0 of the Gaussian beam.

[0031] The outgoing light at the end of the optical antenna array 5 is then split and filtered by the optical beam splitter module 6 and the optical filter 7, and then subjected to signal processing in the spatial light domain, that is, Fourier transform processing is completed through the optical lens 8, and finally the image of the observed target is obtained in real time through the infrared camera 9.

[0032] Based on the above imaging system principles and in comparison with other basic system assembly and index requirements, a microwave optical aperture transformation imaging system model is constructed in the simulation software.

[0033] The point spread function simulation model is used as a tool for evaluating the quality of the objective function. In one embodiment, the waist radius ω0 of the Gaussian beam emitted by the optical antenna array, the aperture d of the optical antenna, and the relative position relationship between the optical antenna array elements under a certain layout are determined under the initial parameter conditions, and a microwave optical imaging simulation is performed on the microwave signal source 10 in the form of a point source, so as to obtain the point spread function under the initial parameter conditions.

[0034] Step S2: constructing a mathematical model for the target optimization problem of the optical antenna imaging quality in the microwave optical aperture transformation imaging system model;

[0035]

[0036] The mathematical model takes the maximum value of the sidelobe extrapolation angle and the main-sidelobe ratio as the objective function of the mathematical model; takes the minimum position spacing of the array elements, the far-field divergence angle of the Gaussian beam, the field angle and the incident angle as the constraints of the mathematical model; and takes the position relationship between the array elements, the waist radius ω0 of the Gaussian beam and the optical antenna aperture d as the input and output of the mathematical model.

[0037] Step S2 is as follows Figure 8 Specifically shown include:

[0038] Step S21: determining a normalized objective function, including: Step S211: determining an objective function of the optimization algorithm according to the index requirements of the point spread function of the microwave optical aperture transform imaging system. In some embodiments, the objective function can be determined by the value of the peak sidelobe ratio (PSLL) or the sidelobe extrapolation angle value. The hardware parameters of the microwave optical aperture transform imaging system are optimized for a single objective, or both are optimized at the same time, i.e., multi-objective optimization. Step S212: Use any one of the above objective functions, or use a weighted method to combine the two objective functions into a normalized objective function. In this embodiment, a weighted method can be used to combine the peak sidelobe ratio (PSLL) value or the sidelobe extrapolation angle value. The two objective functions are combined into a normalized objective function to facilitate the optimization process of the algorithm. The basic idea of ​​the weighted method is to assign a weight to each objective function, and then multiply the values ​​of multiple objective functions by the corresponding weights and sum them to obtain the normalized objective function. For example, in this embodiment, the PSLL and sidelobe extrapolation angle values The weights can be u and v respectively, then the normalized objective function F(p) is defined as: where F sl represents the sidelobe energy, F cl Represents the main lobe energy.

[0039] Step S22: using the field of view angle, the far-field divergence angle of the Gaussian light beam, the incident angle, etc. as constraints of the mathematical model.

[0040] This step specifically includes: Step S221: Determine the value range of the scaling factor S of the microwave optical aperture transformation imaging system by the range of the system microwave field of view (AFOV) in the microwave / optical mapping relationship and the lower limit of the optical antenna output optical far-field divergence angle β. The specific formula is: S = sin (1 / 2·AFOV) / sin β, and the aperture range d = S·D of the optical antenna is determined by the front-end microwave antenna aperture D and the scaling factor S in the microwave optical topology structure.

[0041] Step S222: Determine the value range of the far-field divergence angle of the Gaussian beam. That is, the light beam emitted from the optical fiber end face 5 is approximately transmitted as a Gaussian beam, with a small waist radius but a large divergence angle. The Gaussian beam with a large far-field divergence angle emitted from the optical fiber end face is collimated into a Gaussian beam with a far-field divergence angle that meets the field of view requirements of the system by using the plano-convex microlens 8 to transform the Gaussian beam. The specific formula is: ω0 = λ / (π·θ), where θ is the far-field divergence angle of the Gaussian beam.

[0042] Step S223: Determine the minimum position spacing between the optical antenna array elements 51. According to the Nyquist sampling theorem, in order to avoid aliasing of the signal received by the microwave antenna, thereby affecting the accurate analysis and processing of the signal, it is necessary to limit the minimum spacing of each microwave antenna, that is, each array element to λ / 2, where λ is the wavelength of the front-end received signal.

[0043] Step S23: According to the engineering index requirements such as detection distance, detection area, detection accuracy, etc., determine the position relationship between the optical antenna array elements 51, the waist radius ω0 of the Gaussian beam, and the aperture range d of the optical antenna as the input and output parameters of the mathematical model.

[0044] Step S3: Optimizing the mathematical model described in step S2 using an optimization algorithm. For example, in one embodiment, the optimization algorithm is a genetic algorithm, and the optimization performed by the genetic algorithm includes the following steps:

[0045] Step S31: In one embodiment, the positional relationship between the optical antenna array elements 51 as input parameters can be arranged in any manner, for example Figure 3 The figure shows the arrangement of the array elements of the regular circular array, including the aperture of the optical antenna as an input parameter, d = 6.8 × 10 -3 m and the waist radius of the Gaussian beam ω0=8.7562×10 -6 m, using the above values ​​as the aperture d of the optical antenna, the beam waist radius ω0 of the Gaussian beam, and the array element position arrangement of the regular circular array as the first value, jointly construct a one-dimensional array as the first individual, and using the second value, the third value, etc. different from the first value to construct other arrays, that is, other individuals, and the multiple individuals constitute the initial population;

[0046] Step S32: Iteratively create optimization options based on the initial population. For example, call the MATLAB function "optimoptions" to create and preset optimization options, including setting the population size, number of iterations, etc., and call the GPU parallel computing function "Useparallel" to significantly improve the computing speed.

[0047] Step S33: measure the set population once to obtain an updated point spread function. Figure 4 The three-dimensional energy distribution diagram of the point spread function obtained under the first value input parameter is shown, that is, the three-dimensional energy distribution diagram of the point spread function before the algorithm optimization; according to the objective function and the constraint condition requirements, the objective function is evaluated for each individual in the initial population in combination with the three-dimensional energy distribution diagram of the updated point spread function, and the quality of its structural scheme is evaluated. Specifically, it includes: Step S331: multiplying the area and power density of each pixel in the three-dimensional energy distribution diagram of the point spread function to obtain the energy of each pixel.

[0048] Step S332: summing up the energies of all pixels to obtain the total energy in the entire field of view.

[0049] Step S333: Calculate the number of pixels and energy occupied by the main lobe to obtain the main lobe energy F cl .

[0050] Step S334: Mask the pixel energy in the main lobe area and calculate the maximum value. The maximum value of the pixel energy in the remaining area is the side lobe maximum energy F sl , and then obtain the PSLL value corresponding to the individual and evaluate it.

[0051] Step S335: Mask the pixel energy in the main lobe area, find the pixel point closest to the center point of the field of view with an energy greater than -30 (-30 is the noise energy), calculate the distance (angle difference) between the pixel point and the center point, which is the sidelobe extrapolation angle corresponding to the individual, and evaluate it.

[0052] Step S34: Introducing iteration, including first determining whether a preset number of iterations has been reached at this time, if not, executing step S35, and optionally, if reaching the preset number of iterations, executing step S38;

[0053] Step S35: performing iteration, including selecting individuals that meet the set convergence requirements from the obtained evaluation results as parent individuals of the second generation population;

[0054] Step S36: Select individuals with higher levels in the quality evaluation from the second-generation parent individuals and perform crossover operations to generate offspring individuals, perform crossover mutation operations on some of the offspring individuals, introduce random disturbances, and use the generated individuals to construct the second-generation population; Step S37: Repeat steps S33, S34, S35 and S36, optimize the maximum value of PSLL and the minimum value of the sidelobe extrapolation angle, and stop the iterative optimization until the number of iterations is reached;

[0055] Step S38: Outputting the waist radius of the Gaussian beam, the aperture of the optical antenna, the array element position arrangement, and the three-dimensional energy distribution diagram of the point spread function of the corresponding point source under the above parameters.

[0056] Figure 5 This is a schematic diagram of the optimized array element position arrangement. Corresponding to the array element position arrangement, its beam waist radius, and the aperture of the optical antenna. Figure 6is a three-dimensional energy distribution diagram of the optimized point spread function. In this embodiment, the optical antenna with the initial circular array layout is designed to optimize the main lobe width, the intensity of the highest side lobe and the angle of the side lobe extrapolation of the system point spread function. After executing the above optimization program, the main lobe width of 0.2°, the highest side lobe intensity of 4dB and the side lobe extrapolation of 5° are reduced, and the corresponding optical antenna design parameters are obtained, and the design parameters of the microwave antenna can be obtained by geometric scaling using the scaling factor.

[0057] The above descriptions are only preferred specific embodiments of the present invention, which are all different implementation methods based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for optimizing antenna parameters of a microwave optical aperture transformation imaging system, characterized in that: include: Step S1: performing simulation modeling on the microwave optical aperture transformation imaging system to obtain a system model; Step S2: constructing a mathematical model for the target optimization problem of the optical antenna imaging quality in the system model; wherein the mathematical model takes the maximum value of the sidelobe extrapolation angle and the main-sidelobe ratio as the objective function of the mathematical model; takes the minimum position spacing of the optical antenna array elements, the far-field divergence angle of the Gaussian beam, the field angle and the incident angle as the constraints of the mathematical model; takes the position relationship between the optical antenna array elements, the waist radius of the Gaussian beam and the optical antenna aperture as the input and output of the mathematical model; Step S3: Optimizing the mathematical model to optimize the design method of the microwave optical aperture transformation imaging system, comprising step S31: constructing a one-dimensional array as a first individual by taking the position relationship between the optical antenna array elements, the aperture of the optical antenna, and the first value of the waist radius of the Gaussian beam, and constructing other arrays with other values ​​different from the first value to form other individuals, and the first individual and the other individuals constitute an initial population; Step S32: iteratively create and preset optimization options based on the initial population, including population size and number of iterations; Step S33: measuring the initial population once to obtain an updated point spread function, and evaluating the objective function of each individual in the initial population in combination with the three-dimensional energy distribution diagram of the updated point spread function according to the objective function and the constraint conditions, so as to evaluate the quality of the structural scheme; Step S34: introducing iteration, including first determining whether a preset number of iterations has been reached at this time, and if the preset number of iterations has not been reached, executing step S35; Step S35: performing iteration, including selecting individuals that meet the set convergence requirements from the obtained evaluation results as parent individuals of the second generation population; Step S36: Select individuals with higher levels in the quality evaluation from the parent individuals of the second generation population and perform a crossover operation to generate offspring individuals of the second generation population; perform a crossover mutation operation on some of the offspring individuals of the second generation population, and introduce individuals generated after random disturbance to construct the second generation population; Step S37: Repeat steps S33, S34, S35 and S36 to optimize the maximum value of the peak-to-sidelobe ratio and the minimum value of the sidelobe extrapolation angle until the iterative optimization is stopped when the number of iterations is reached.

2. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 1, characterized in that: In step S34, if the preset number of iterations is reached, step S38 is executed: outputting the optimized Gaussian beam waist radius, the aperture of the optical antenna, the array element position arrangement, and the three-dimensional energy distribution diagram of the point spread function of the corresponding point source under the above parameters.

3. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 1, characterized in that: The assessment includes: Step S331: multiplying the area and power density of each pixel in the three-dimensional energy distribution diagram of the point spread function to obtain the energy of each pixel; Step S332: summing up the energy of all pixels to obtain the total energy in the whole field of view; Step S333: Calculate the number of pixels and energy occupied by the main lobe to obtain the main lobe energy; Step S334: masking the pixel energy in the main lobe area, calculating the maximum value of the pixel energy in the maximum value remaining area as the sidelobe maximum energy, and then obtaining the value of the peak sidelobe ratio corresponding to the individual, and evaluating it; Step S335: Mask the pixel energy in the main lobe area, find the pixel point closest to the center point of the field of view whose energy is greater than the noise energy, calculate the distance between the pixel point and the center point as the sidelobe extrapolation angle corresponding to the individual, and evaluate it.

4. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 1, characterized in that: The point spread function simulation model is used as a tool to evaluate the quality of the objective function.

5. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 1, characterized in that: The aperture D of the microwave antenna array is kept unchanged, and the aperture d of the optical antenna array is adjusted to change the scaling factor of the system, thereby adjusting the topological structure of the microwave optical aperture transformation imaging system to optimize the imaging quality.

6. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 5, characterized in that: The step S2 of constructing a mathematical model for the target optimization problem of the optical antenna imaging quality in the microwave optical aperture transformation imaging system model comprises: Step S21: determining a normalized objective function; Step S211: determining the objective function of the optimization algorithm according to the index requirements of the point spread function of the microwave optical aperture transformation imaging system; Step S212: using any one of the objective functions or using a weighted method to combine the two objective functions into a normalized objective function; Step S22: using the field angle, the far-field divergence angle of the Gaussian light beam and the incident angle as constraint conditions of the mathematical model; The method comprises step S221: determining a value range of a scaling factor S of the microwave optical aperture transform imaging system according to a range of a system microwave field of view AFOV in a microwave / optical mapping relationship and a lower limit of an optical far-field divergence angle β of an optical antenna output; Step S222: determining a value range of the far-field divergence angle of the Gaussian beam; as well as Step S223: determining the minimum position spacing between the optical antenna array elements; Step S23: According to the engineering index requirements including detection distance, detection area, and detection accuracy, determine the positional relationship between the optical antenna array elements, the waist radius ω0 of the Gaussian beam, and the aperture range d of the optical antenna as the input and output parameters of the mathematical model.

7. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 6, characterized in that: The peak sidelobe ratio value or the sidelobe extrapolation angle value The single-objective optimization of the hardware parameters of the microwave optical aperture transformation imaging system is carried out.

8. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 6, characterized in that: A weighted method is used to convert the peak sidelobe ratio value or the sidelobe extrapolation angle value The two objective functions are combined into a normalized objective function.

9. The antenna parameter optimization design method of a microwave optical aperture transformation imaging system according to claim 6, characterized in that: In step S221, the specific formula used is S=Sin(1 / 2·AFOV) / Sinβ, where Where θ is the far-field divergence angle of the Gaussian beam, ω RF is the angular frequency of the microwave signal, ω SB is the angular frequency of the sideband signal; the aperture range of the optical antenna d=S·D is determined by the aperture D of the microwave antenna array and the scaling factor S in the microwave optical topology structure; In step S222, the Gaussian beam emitted from the end face of the optical fiber is collimated into a Gaussian beam whose far-field divergence angle meets the field of view requirement of the system by using the plano-convex microlens to transform the Gaussian beam. The specific formula used is: ω0=λ / (π·θ), where θ is the far-field divergence angle of the Gaussian beam.

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