A method and system for generating a hologram for a high robust flat-top beam

Abstract

The application discloses a hologram method and system for generating a high-robust flat-top light spot, and the method comprises the following steps: firstly, completing simulation parameter configuration and input light field initialization, and specifying an optimization region with the original focal plane as the center; selecting a plane as an additional optimization target along the optical axis at equal intervals; performing Fourier transform on the input light field to obtain the original focal plane light field; synchronously calculating the additional optimization plane light field; applying the same target constraint to all optimization planes; propagating and optimizing the light field from the original focal point to other constraint planes; calculating the light field propagated from all constraint planes to the original focal point; performing inverse Fourier transform to obtain the input light field after the calculation is completed; calculating the average value of the input light field and retaining the phase; replacing the amplitude with an initial Gaussian distribution to obtain a new round of input light field; repeating the foregoing steps until a threshold value of iteration times or a convergence condition is reached; and outputting a final DOE phase distribution value. The method avoids the problem of the decline of the uniformity of the light field in the defocus region caused by the optimization of a single plane.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser processing and computational optics, and more particularly, to a hologram method and system for generating a high-robustness flat-top spot. BACKGROUND

[0002] In the fields of laser processing, optical imaging, material processing, etc., flat-top spots have become an important optical target form due to their uniform light intensity distribution, which can effectively improve processing accuracy, imaging quality, and processing efficiency. Traditional methods for generating flat-top spots rely on hologram technology, which uses diffractive optical elements to regulate the incident light field to form the desired spot distribution on a specific plane.

[0003] The flat-top light formed by the Gaussian light after correction by the ordinary spot shaping device only shows good uniformity and complete structure at the lens focal point, but presents a focal point-like distribution with higher light intensity in the two regions before and after the lens focal point, which is not conducive to the correct positioning of the use area in actual production. In existing technologies, most methods only optimize a single focal plane, and the light field distribution is calculated by Fourier transform and other means to design the corresponding diffractive optical element phase. Although this single-plane optimization method can achieve good flat-top effects on the target plane, it lacks control over the light field uniformity in the defocus region. When there is a slight defocus deviation in actual application, the spot uniformity will decrease significantly, and the robustness is insufficient, making it difficult to meet the needs of high-precision scenarios.

[0004] Traditional hologram algorithms also have limitations, as they can only form flat-top light with good uniformity at the lens focal point, while in the regions before and after the focal point, the natural focusing effect of the lens dominates, causing the light intensity distribution to converge towards the center, presenting a focal point-like shape. This characteristic not only makes it difficult to position the area, but also makes the spot shaping device have low alignment tolerance in actual use, increasing the difficulty of using the device. At the same time, the traditional algorithm has a simple weight distribution during the iterative optimization process, usually using equal weights or empirical weights, and cannot dynamically adjust the optimization effort according to the light field distribution quality of different planes. This results in insufficient optimization of regions with poor light field uniformity, slow overall convergence, and insufficient stability of the generated spot in the spatial range, limiting its application in a wider range of fields. SUMMARY

[0005] The present application aims to solve the problem of flat-top spots generated by traditional methods, which only have good uniformity at the lens focal point and present a focal point-like distribution before and after the focal point, making it difficult to position, and have low alignment tolerance and high difficulty of use. It also aims to improve the limitations of traditional algorithms, such as simple weight distribution, slow convergence, and insufficient spatial stability. The present application provides a hologram method that can improve the alignment tolerance of spot shaping devices, reduce the difficulty of use, and generate flat-top spots with high robustness within a certain spatial range.

[0006] In view of the above defects or improvement needs of the prior art, as a first aspect of the present application, the present application provides a hologram method for generating a high-robust flat-top light spot, comprising:

[0007] S1. Complete the simulation parameter configuration and initialize the input light field; specify a specified length of the optimization region centered on the original focal plane when inputting the parameters, and select a plane as an additional optimization target along the optical axis direction centered on the original focal point;

[0008] S2. Fourier transform the input light field to obtain ; when the original focal plane light field distribution calculation is completed, the calculation of the light field distribution on the additional optimization plane is also completed; the same target constraint condition is applied to all optimization planes including the original focal point plane and the newly added plane, and the constraint only acts on the replaced amplitude during the reverse propagation and each constraint plane is independent; the light field distribution of all forward-propagated focal points is calculated and optimized by propagating from the original focal point to other constraint planes;

[0009] S3. Calculate the light field distribution of all constraint planes propagating to the original focal point; after all the reverse propagation calculations are completed, calculate the inverse Fourier transform of all the reverse-propagated light field distributions to obtain the input light field , calculate the average value of the input light field and retain the phase value;

[0010] S4. Replace the amplitude distribution with the initial Gaussian distribution to obtain a new round of input light field , complete S2 and S3 again until the preset iteration threshold is reached or the convergence condition is met, and output the final optimized DOE phase distribution value.

[0011] Further, the simulation parameters in S1 include the size of the simulation field, the size of the DOE, the accuracy of the DOE, the size of the input light, the simulation accuracy, the wavelength, the size of the focal spot, and the focal spot spacing.

[0012] Further, the calculation method of the light field distribution on the additional optimization plane in S2 is:

[0013] The light field complex amplitude distribution of the original focal plane is known , wherein is the coordinate of the plane;

[0014] The distance between the additional optimization plane and the original focal plane along the optical axis direction is set as , and the target plane coordinate is ;

[0015] According to the diffraction integral formula of the Rayleigh-Sommerfeld approximation, the light field complex amplitude distribution of the target plane is calculated The calculation formula is as follows:

[0016]

[0017] in, The wavelength of light; Wave number; The distance from the source point to the observation point; for The angle with the optical axis; The unit is the imaginary unit; the light field distribution of the additional optimization plane is calculated by solving the above integral using numerical integration.

[0018] Furthermore, the target constraint conditions in S2 are specifically as follows:

[0019] Let the first The actual optical field amplitude distribution of the optimized plane is as follows: The optimized plane includes the original focal plane and the newly added plane; the ideal flat-top light amplitude distribution is as follows: , is a constant, representing the uniform amplitude value of the flat-top light; for the ... Each optimization plane is subject to independent constraints.

[0020]

[0021] In the iterative optimization process, after backpropagation calculates the input light field, for each constraint surface, the replacement amplitude is adjusted according to the above formula to gradually approach the actual light field amplitude. Each facet executes the constraint independently.

[0022] Furthermore, the specific process of calculating and optimizing the light field distribution of all forward-propagating focal points in S2 is as follows:

[0023] For the input light field Perform a Fourier transform to obtain the light field distribution at the original focal plane. ;

[0024] Based on Kirchhoff diffraction theory, the original focal plane light field The optical field propagates along the optical axis to each additional constraint surface, yielding the actual complex amplitude distribution of the optical field at each constraint surface. The propagation formula is:

[0025]

[0026] in, , Wave number;

[0027] Set the ideal flat-top light amplitude as a constant By minimizing the difference function to make the actual amplitude approach the ideal distribution; calculate the uniformity of each plane and calculate the correction weight matrix according to the difference between the actual light field and the target light field .

[0028] Further, the calculation formula of the uniformity

[0029]

[0030] wherein, is the uniformity index of the light field on the i-th plane; is the modulus distribution of the complex amplitude of the light field on the i-th plane; is the maximum intensity value of the light field amplitude; is the minimum intensity value of the light field amplitude. Further, the specific method for calculating the correction weight matrix according to the difference between the actual light field and the target light field is:

[0031]

[0032]

[0033] wherein, is the mean value of the target light field amplitude; is the actual light field amplitude, is the adjustment coefficient.

[0034] Further, the convergence condition in S4 is that the average uniformity is not less than 0.99, and the calculation formula of the average uniformity is as follows:

[0035]

[0036] wherein, is the average uniformity of all planes; is the total number of planes; is the light field uniformity of the i-th plane. As a second aspect of the present application, the present application provides a hologram system for generating a high-robustness flat-top light spot, comprising:

[0037] a parameter configuration and optimization target selection unit for completing simulation parameter configuration and input light field initialization; when inputting parameters, an optimization region with a specified length centered on the original focal plane is specified, and an equal-interval selection of

[0038] planes is performed as additional optimization targets, with the original focal point as the center along the optical axis direction; a forward propagation and optimization unit for performing forward propagation and optimization on the input light field

[0039] ​​​​ The Fourier transform is performed to obtain ; when the original focal plane light field distribution calculation is completed, the calculation of the light field distribution on the additional optimization plane is also completed; the same target constraint condition is applied to all optimization planes including the original focal plane and the additional plane, the constraint only acts on the replaced amplitude during the reverse propagation, and each constraint plane is independent; the light field distribution of the original focal point is propagated to other constraint planes, and the light field distribution of all forward-propagated focal points is calculated and optimized;

[0040] The reverse calculation input field unit is configured to calculate the light field distribution of all constraint planes propagated to the original focal point; after all the reverse propagation calculations are completed, the inverse Fourier transform of all the reverse-propagated light field distributions is calculated to obtain the input light field , the average value of the input light field is calculated and the phase value is retained;

[0041] The iterative output phase value unit is configured to replace the amplitude distribution with the initial Gaussian distribution to obtain a new round of input light field , and the forward propagation and optimization unit and the reverse calculation input field unit are processed again until a preset iteration number threshold is reached or a convergence condition is met, and the final optimized DOE phase distribution value is output.

[0042] As a third aspect of the present application, the present application provides a computer readable storage medium having a computer program stored thereon, the computer program being executed by a processor to perform any step of the hologram generation method for generating a high-robustness flat-top light spot.

[0043] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0044] 1. The hologram generation method for generating a high-robustness flat-top light spot of the present application realizes the basic layout of multi-plane collaborative regulation by specifying the optimization region centered on the original focal plane in the simulation parameter configuration stage and selecting additional optimization planes along the optical axis at equal intervals. This technical feature breaks the limitation of single focal plane optimization, extends the light field regulation range from a single point to a spatial region, allows the subsequent optimization to simultaneously consider the light field characteristics of the original focal plane and multiple additional planes, provides structural support for generating a light spot with stable flat-top characteristics in a spatial range, and avoids the problem of decreased light field uniformity in the defocus region caused by optimizing only a single plane.

[0045] 2. The hologram method for generating a high-robust flat-top light spot of the present application, by inverse Fourier transform of the light field distribution after back propagation to obtain the input light field and retain its phase information, while replacing the amplitude distribution with an initial Gaussian distribution to update the input light field. This technical feature realizes the effective transmission of the light field phase information and the specification reset of the amplitude distribution, which not only retains the adjustment results of the phase by the previous optimization, but also maintains the basic form stability of the input light field by fixing the amplitude distribution, so that the iterative process can gradually approach the target in an orderly update, ensuring the continuity and effectiveness of the optimization process. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 Flow chart of the hologram method for generating a high-robust flat-top light spot of the present application;

[0047] Figure 2 Optical path schematic diagram of the present application;

[0048] Figure 3 System unit diagram of the present application. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0050] Embodiment 1

[0051] Please refer to Figure 1 , the present embodiment 1 provides a hologram method for generating a high-robust flat-top light spot, comprising:

[0052] S1. Complete simulation parameter configuration and input light field initialization; when inputting parameters, specify an optimization area of a specified length centered on the original focal plane, and select an equal interval plane along the optical axis direction as an additional optimization target, with the original focal point as the center;

[0053] S2. Fourier transform is performed on the input light field to obtain ; when the original focal plane light field distribution is calculated, the light field distribution on the additional optimization plane is also calculated; the same target constraint condition is applied to all optimization planes including the original focal point plane and the newly added plane, the constraint only acts on the replaced amplitude during back propagation and each constraint surface is independent; the light field distribution of all forward propagated focal points is calculated and optimized by propagating from the original focal point to other constraint surfaces;

[0054] S3. Calculate the light field distribution of all the constraint surfaces towards the principal focus; when all the back propagation calculations are completed, calculate the inverse Fourier transform of all the back propagated light field distribution to obtain the input light field , calculate the average value of the input light field and retain the phase value;

[0055] S4. Replace the amplitude distribution with the initial Gaussian distribution to obtain a new round of input light field , complete S2 and S3 again until the preset iteration threshold is reached or the convergence condition is met, and output the final optimized DOE phase distribution value.

[0056] This embodiment 1 further expands the above steps.

[0057] (1) Parameter configuration and optimization target selection

[0058] Please refer to Figure 2 , Figure 2 provides a light path schematic diagram of this embodiment 1. Under the method support of this embodiment 1, the laser light source can form a flat-top light spot in the area near the principal focus of the lens through the DOE and the lens, and the light spot beyond the area still presents a focal point distribution.

[0059] The basic preparation stage of this embodiment 1 mainly covers two aspects of simulation parameter configuration and input light field initialization.

[0060] In the simulation parameter configuration, a series of key parameters supporting the simulation running need to be manually input. These parameters include the size of the simulation field, which determines the range of the simulation space; the size of the DOE, which relates to the physical size setting of the diffractive optical element; the DOE precision, which affects the accuracy of the element performance; the input light size, which is related to the spatial range of the incident light; the simulation precision, which is directly related to the accuracy of the entire simulation result; the wavelength, which is a basic attribute parameter of the incident light; the focal spot size, which determines the size of the target light spot; and the focal spot spacing, which involves the distance setting between multiple focal spots. In the process of inputting these parameters, it is also necessary to specify the optimization region of a specified length centered on the principal focal plane. This region is the main range of subsequent light field optimization. At the same time, a plurality of planes are selected as additional optimization targets along the optical axis direction with the principal focus as the center and according to equal spacing, thereby laying a foundation for multi-plane collaborative optimization.

[0061] ​Input light field initialization is another important step in this process. During this process, a random phase needs to be set for the input light field, providing initial conditions for subsequent iterative optimization. Simultaneously, the amplitude of the input light field is set to a Gaussian distribution with a specified radius, a common pattern for light field amplitude. The target focus is set as a square light spot of a specified size without phase constraints, clearly defining the target shape to be achieved through optimization.

[0062] By completing the simulation parameter configuration and input light field initialization, a database for the hologram algorithm was built. This data provides necessary and comprehensive data support for the subsequent optimization of the flat-top light, ensuring that the optimization process can be carried out in an orderly manner based on clear parameters and initial states.

[0063] (2) Forward propagation and optimization

[0064] The input light field is Fourier transformed to obtain the light field distribution of the original focal plane. Simultaneously, using the original focal plane as the diffraction source, and based on the diffraction integral relationship of the Rayleigh-Somerset approximation, combined with parameters such as light wavelength and propagation distance, the complex amplitude distribution of the light field on the additional optimization plane is calculated synchronously through numerical integration. This synchronous calculation ensures the correlation and consistency of the light field data of the original focal plane and the additional plane, providing coherent and reliable basic data for subsequent multi-plane collaborative optimization, and avoiding local deviations that may be caused by calculations on a single plane.

[0065] In a preferred embodiment, the method for further optimizing the calculation of the light field distribution on the plane is as follows:

[0066] The complex amplitude distribution of the light field at the original focal plane (which serves as the diffraction source plane) is known. ,in These are the coordinates of the plane;

[0067] The distance between the additional optimization plane and the original focal plane along the optical axis is set to... (Determined according to the principle of equal spacing), the target plane coordinates are: ;

[0068] Based on the diffraction integral formula of the Rayleigh-Somerfi approximation, the complex amplitude distribution of the optical field on the target plane is calculated. The calculation formula is as follows:

[0069]

[0070] in, The wavelength of light; Wave number; The distance from the source point to the observation point; for With optical axis ( The included angle of the axis; The unit is the imaginary unit; the light field distribution of the additional optimization plane is calculated by solving the above integral using numerical integration.

[0071] For all optimized planes, including the original focal plane and the newly added plane, it is uniformly required that the actual light field amplitude approaches the uniform amplitude distribution of the ideal flat-top light. The constraint is achieved by measuring the difference between the actual distribution and the ideal distribution. The constraint only acts on the amplitude replaced during back propagation and each constraint plane is independent.

[0072] In a preferred embodiment, the target constraint is specifically as follows:

[0073] Let the first The actual optical field amplitude distribution of the optimized plane is as follows: The optimized plane includes the original focal plane and the newly added plane; the ideal flat-top light amplitude distribution is as follows: , is a constant, representing the uniform amplitude value of the flat-top light; for the ... Each optimization plane is subject to independent constraints.

[0074]

[0075] In the iterative optimization process, after backpropagation calculates the input light field, for each constraint surface, the replacement amplitude is adjusted according to the above formula to gradually approach the actual light field amplitude. Each facet executes the constraint independently.

[0076] Finally, based on Kirchhoff diffraction theory, the original focal plane light field is propagated to each constraint surface and optimized. The uniformity is obtained by calculating the maximum and minimum intensity values ​​of the light field amplitude in the plane, and then the correction weight matrix is ​​calculated based on the difference between the actual light field and the target light field.

[0077] In a preferred embodiment, the specific process for calculating and optimizing the light field distribution of all forward-propagating focal points is as follows:

[0078] For the input light field Perform a Fourier transform to obtain the light field distribution at the original focal plane. ;

[0079] Based on Kirchhoff diffraction theory, the original focal plane light field The optical field propagates along the optical axis to each additional constraint surface, yielding the actual complex amplitude distribution of the optical field at each constraint surface. The propagation formula is:

[0080]

[0081] in, , Wave number;

[0082] Set the ideal flat-top light amplitude as a constant By minimizing the difference function This makes the actual amplitude approach the ideal distribution; the uniformity of each plane is calculated. The corrected weight matrix is ​​calculated based on the difference between the actual light field and the target light field. .

[0083] In a preferred embodiment, uniformity The calculation formula is:

[0084]

[0085] in, For the first The uniformity index of the light field on a plane; For the first Mode distribution of complex amplitude of light field on a plane; This represents the maximum intensity value of the light field amplitude. This represents the minimum intensity value of the light field amplitude.

[0086] In a preferred embodiment, the specific method for calculating the correction weight matrix based on the difference between the actual light field and the target light field is as follows:

[0087]

[0088] in, The mean amplitude of the target light field; This represents the actual light field amplitude. This is the adjustment coefficient.

[0089] This step guides the calculation of light field propagation through physical laws and strengthens the optimization of non-uniform regions by adjusting weights, thereby improving the overall optimization efficiency and pushing the light field closer to the ideal state more quickly.

[0090] (3) Reverse calculation of input field

[0091] Calculate the light field distribution of all constraint surfaces propagating to the original focal plane, and transfer the light field information of each constraint surface to the original focal plane through backpropagation to form the backpropagated light field data, which provides the basis for subsequent processing.

[0092] After all backpropagation calculations are completed, inverse Fourier transforms are performed on the light field distributions backpropagated to the original focal plane. The original focal plane has corresponding spatial coordinates, while the input light field plane has corresponding spatial frequency coordinates. The input light field is obtained through a two-dimensional inverse fast Fourier transform operation.

[0093] Afterwards, the average value of these input light field is calculated, and only the phase information is kept, ignoring the amplitude distribution - which will be replaced by the initial Gaussian amplitude later. The kept phase information will serve as the basis for the phase update of the input light field in the next iteration, ensuring the iterative process can continuously adjust based on the previous optimization results, and push the light field towards the target distribution.

[0094] In the preferred embodiment, the calculation method of the inverse Fourier transform of the back-propagated light field distribution is:

[0095] Obtain the light field distribution of each constraint plane back-propagated to the original focal plane

[0096] For each light field distribution Perform the inverse Fourier transform, the formula is:

[0097]

[0098] Where, is the spatial coordinate of the original focal plane, is the spatial frequency coordinate of the input light field plane, represents the two-dimensional inverse fast Fourier transform operation.

[0099] Keep the phase information of the input light field obtained after the inverse Fourier transform, ignore its amplitude distribution (which will be replaced by the initial Gaussian amplitude later), and provide the phase basis for the input light field update in the next iteration.

[0100] (4) Iterative output phase value

[0101] After completing the forward and backward propagation calculation of a round of light field, the initial set Gaussian distribution is used to replace the amplitude distribution, thereby obtaining a new round of input light field. Take this input light field as the starting point, perform the forward propagation and optimization and the backward calculation of the input field steps again, that is, re-perform the multi-plane distribution calculation of the light field, the application of the constraint condition, the propagation optimization and the weight adjustment, and the reverse propagation processing and other operations.

[0102] This iterative process will be repeated continuously, and each iteration is based on the optimization results of the previous round to adjust and gradually push the light field to the ideal flat-top distribution. There are two termination conditions for iteration, either reaching the preset iteration number threshold, or the average uniformity of all planes meets the convergence requirement - the average uniformity is not less than 0.99, where the average uniformity is calculated from the light field uniformity of each plane, reflecting the uniformity of the overall light field.

[0103] In the preferred embodiment, the calculation formula of the average uniformity is as follows:

[0104] ​

[0105] wherein, is the average uniformity of all planes; is the total number of planes; is the light field uniformity of the th plane.

[0106] When the iteration is terminated, the final optimized DOE phase distribution value is output. The phase distribution value is the core result of the entire optimization process and can be used to generate a flat-top light spot with high robustness, providing key optical element parameters for related applications.

[0107] Embodiment 2

[0108] Please refer to Figure 3 , the embodiment 2 provides a hologram system for generating a high-robustness flat-top light spot, comprising:

[0109] A parameter configuration and optimization target selection unit is configured to complete simulation parameter configuration and input light field initialization; when inputting parameters, a specified length of an optimization region centered on the original focal plane is specified, and planes are selected as additional optimization targets at equal intervals along the optical axis direction centered on the original focal point;

[0110] A forward propagation and optimization unit is configured to perform Fourier transform on the input light field to obtain ; when the original focal plane light field distribution is calculated, the light field distribution on the additional optimization planes is also calculated; the same target constraint condition is applied to all optimization planes including the original focal point plane and the additional planes, the constraint only acts on the replaced amplitude during back propagation, and each constraint plane is independent; the light field distribution of all forward-propagated focal points is calculated and optimized by propagating from the original focal point to other constraint planes;

[0111] A reverse calculation input field unit is configured to calculate the light field distribution of all constraint planes propagating to the original focal point; after all back propagation calculations are completed, the inverse Fourier transform of all back-propagated light field distributions is calculated to obtain the input light field , the average value of the input light field is calculated and the phase value is retained;

[0112] An iteration output phase value unit is configured to replace the amplitude distribution with the initial Gaussian distribution to obtain a new round of input light field , and the forward propagation and optimization unit and the reverse calculation input field unit are processed again until the preset iteration number threshold is reached or the convergence condition is met, and the final optimized DOE phase distribution value is output.

[0113] Embodiment 3

[0114] The embodiment 3 also provides a computer readable storage medium, and the computer readable storage medium stores a computer program. The computer program is executed by a processor to implement any step of a hologram method for generating a high robust flat-top light spot.

[0115] The computer readable storage medium can include a U disk, a mobile hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and various media capable of storing program codes.

[0116] For the computer readable storage medium provided in the present application, refer to the above method embodiments, and the present application will not be repeated here.

[0117] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for generating a hologram for a high robust flat-top light spot, characterized in that, Comprise: S1. Complete the simulation parameter configuration and input light field initialization; specify a specified length optimization area centered on the original focal plane when inputting parameters, and select an equal interval plane as an additional optimization target along the optical axis direction centered on the original focal point ; S2. Fourier transforming the input light field to obtain ; When the original focal plane light field distribution calculation is completed, the calculation of the light field distribution on the additional optimization plane is also completed; the same target constraint condition is applied to all optimization planes including the original focal plane and the newly added plane, the constraint only acts on the replaced amplitude during the reverse propagation and each constraint plane is independent; the light field distribution of all forward propagated focal points is calculated and optimized by the original focal point to other constraint planes; S3. Calculate the light field distribution of all the constraint surfaces towards the original focal point; when all the reverse propagation calculations are completed, calculate the inverse Fourier transform of all the reverse propagated light field distribution to obtain the input light field , calculate the average value of the input light field and retain the phase value; S4. Replace the amplitude distribution with the initial Gaussian distribution to obtain a new round of input light field Again complete S2 and S3, until the preset iteration threshold is reached or the convergence condition is met, output the final optimized DOE phase distribution value; The target constraint condition in S2 is specifically: The actual light field amplitude distribution of the first optimization plane is ; the optimization plane includes the principal point plane and a newly added plane; the ideal flat-top light amplitude distribution is ; and the constant a represents the uniform amplitude value of the flat-top light. , The actual light field amplitude distribution of the first optimization plane is ; the optimization plane includes the principal point plane and a newly added plane; the ideal flat-top light amplitude distribution is In the iterative optimization process, after the input light field is calculated by back propagation, the replaced amplitude is adjusted according to the above formula for each constraint surface, and the actual light field amplitude is gradually approached , and each surface independently performs the constraint; The specific process of calculating and optimizing the light field distribution of all forward propagated focal points in S2 is: Fourier transforming the input light field to obtain a epiplanar light field distribution ; Based on the Kirchhoff diffraction theory, the original focal plane light field is propagated to each additional constraint surface along the optical axis to obtain the actual light field complex amplitude distribution of each constraint surface The propagation formula is: wherein , is the wave number; Setting ideal flat-top light amplitude as constant , by minimizing difference function , making actual amplitude approach ideal distribution; calculating each plane uniformity , and calculating correction weight matrix according to difference value of actual light field and target light field .

2. A method for generating a hologram of a highly robust flat-top light spot according to claim 1, characterized in that, The simulation parameters in S1 include: the size of the simulation field, the size of the DOE, the accuracy of the DOE, the size of the input light, the simulation accuracy, the wavelength, the size of the focal spot and the focal spot spacing.

3. A method for generating a hologram of a highly robust flat-top light spot according to claim 1, characterized in that, The calculation method of the light field distribution on the additional optimization plane in S2 is: Known original focal plane light field complex amplitude distribution wherein are coordinates of the plane; The distance between the additional optimization plane and the original focal plane along the optical axis is set as , and the target plane coordinates are ; The complex amplitude distribution of the light field on the target plane is calculated according to the approximate diffraction integral formula of the Rayleigh-Sommerfeld The calculation formula is as follows: wherein, is the wavelength of the light; is the wave number; is the distance from the source point to the observation point; is the is the angle with the optical axis; is the imaginary unit; the light field distribution of the additional optimization plane is calculated by solving the above integral by means of numerical integration.

4. The method of claim 1, wherein, the uniformity The formula for the calculation is: wherein, is the uniformity index of the light field on the nth plane; is the modulus distribution of the complex amplitude of the light field on the nth plane; is the maximum intensity value of the light field amplitude; is the minimum intensity value of the light field amplitude.​​ 5. The method of claim 1, wherein, The specific method of calculating the correction weight matrix according to the difference between the actual light field and the target light field is: wherein, is the target light field amplitude mean; is the actual light field amplitude, is the adjustment coefficient.

6. The method of claim 1, wherein, The convergence condition in S4 is that the average uniformity is not less than 0.99, and the calculation formula of the average uniformity is as follows: wherein, is the average uniformity for all planes; is the total number of planes; is the light field uniformity for the th plane.

7. A hologram system for generating a highly robust flat-top light spot, characterized in that Comprise: The parameter configuration and optimization target selection unit is used to complete the simulation parameter configuration and input light field initialization. When inputting parameters, it specifies an optimization region of a specified length centered on the original focal plane, and selects optimization regions at equal intervals along the optical axis centered on the original focal point. A plane is used as an additional optimization objective; a forward propagation and optimization unit for performing a Fourier transform on the input light field ;​ When the original focal plane light field distribution calculation is completed, the calculation of the light field distribution on the additional optimization plane is also completed; the same target constraint condition is applied to all optimization planes including the original focal plane and the newly added plane, the constraint only acts on the replaced amplitude during the reverse propagation and each constraint plane is independent; the light field distribution of all forward propagated focal points is calculated and optimized by the original focal point to other constraint planes; a reverse calculation input field unit for calculating the light field distribution of all the constraint surfaces towards the principal point of propagation; and after all the reverse propagation calculations are completed, calculating the inverse Fourier transform of all the reverse propagated light field distributions to obtain the input light field , calculating the average value of the input light field and retaining the phase value; An iterative output phase value unit is configured to replace the amplitude distribution with the initial Gaussian distribution to obtain a new round of input light field The forward propagation and optimization unit and the backward calculation input field unit are repeatedly executed until a preset iteration threshold is reached or a convergence condition is met, and a final optimized DOE phase distribution value is output. The target constraint condition in the forward propagation and optimization unit is specifically: Let the first The actual optical field amplitude distribution of the optimized plane is as follows: The optimized plane includes the original focal plane and the newly added plane; the ideal flat-top light amplitude distribution is as follows: , is a constant, representing the uniform amplitude value of the flat-top light; for the ... Each optimization plane is subject to independent constraints. In the iterative optimization process, after the input light field is calculated by back propagation, the replaced amplitude is adjusted according to the above formula for each constraint surface, and the actual light field amplitude is gradually approached , and each surface independently performs the constraint; The specific process of calculating and optimizing the light field distribution of all forward propagated focal points in the forward propagation and optimization unit is: Fourier transforming the input light field to obtain a epiplanar light field distribution ; Based on the Kirchhoff diffraction theory, the original focal plane light field is propagated to each additional constraint surface along the optical axis to obtain the actual light field complex amplitude distribution of each constraint surface The propagation formula is: wherein , is the wave number; Setting ideal flat-top light amplitude as constant , by minimizing difference function , making actual amplitude approach ideal distribution; calculating each plane uniformity , and calculating correction weight matrix according to difference value of actual light field and target light field .

8. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to perform the hologram generation method for generating a high robustness flat top light spot according to any one of claims 1-6.

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