Design method of long-wave infrared minimalist optical system based on metasurface

Abstract

This invention provides a simplified design method for a long-wave infrared optical system based on metasurfaces. The method includes: determining the wavefront phase error based on the actual propagation paths and ideal equal-path reference paths of each ray in the wavefront equiphase surface of a refractive lens; determining the target phase distribution of the metalens based on the wavefront phase error; acquiring the phase modulation characteristics, transmission characteristics, and dispersion response of each metalens unit structure in the long-wave infrared band, and establishing a metalens unit structure response database; based on the target phase distribution of the metalens, traversing the metalens unit structure response database, using transmittance thresholds, phase error thresholds, and aspect ratio thresholds as constraints, screening target unit structures in the long-wave infrared band, and generating the target metalens structure. The optical system designed by this invention can operate with a large relative aperture without sacrificing imaging quality, thus meeting the requirements for high light throughput, large aperture, and wide-spectrum imaging.

Description

Technical Field

[0001] This invention belongs to the field of infrared optical engineering technology, specifically relating to a design method for a long-wave infrared minimalist optical system based on metasurfaces. Background Technology

[0002] Infrared imaging technology achieves passive imaging by detecting the thermal radiation of a target and is widely used in night vision surveillance, remote sensing, and other fields. Due to the long wavelength of infrared light, traditional infrared optical systems rely on a limited number of materials such as germanium and silicon, as well as complex multi-lens combinations, generally resulting in large size, heavy weight, and high cost. Metalenses, as novel planar optical elements based on subwavelength artificial structures, offer advantages such as thinness and high integration, making them a key technological path for realizing compact optical systems.

[0003] In related technologies, discrete frequency point design, dispersion modulation, multi-layer cascading, and hybrid refracto-metasurfaces are employed to achieve chromatic aberration correction in metalenses. Discrete frequency point design optimizes the unit structure at several long-wave infrared bands to meet the focusing phase; dispersion modulation methods establish a continuous functional relationship between phase and wavelength, achieving broadband compensation by adjusting the phase velocity and group velocity delay of the unit cells; multi-layer cascading methods connect multiple functional metasurfaces in series to expand the dispersion modulation capability.

[0004] The aforementioned methods lack sufficient compensation capabilities, making it difficult to meet the comprehensive performance requirements of high light throughput, large aperture, and wide spectral imaging. Especially under large aperture conditions, the phase and dispersion coupling effects between refraction and metalens are enhanced, making it difficult for existing methods to achieve effective matching, resulting in problems such as wavefront error accumulation, significant edge distortion, and excessive residual chromatic aberration. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a design method for a simplified long-wavelength infrared optical system based on metasurfaces. The technical problem to be solved by this invention is achieved through the following technical solution: In a first aspect, the present invention provides a design method for a long-wavelength infrared minimalist optical system based on a metasurface, the long-wavelength infrared minimalist optical system comprising a refractive lens, a metasurface lens, and a detector, wherein the metasurface lens is disposed between the refractive lens and the detector; the method includes: Based on system parameters, the surface parameters of the refractive lens are determined through even-order aspherical expressions; the system parameters include the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens; Using a ray tracing method, the wavefront isophase surface of the refractive lens is determined based on the surface parameters of the refractive lens. Based on the actual propagation paths of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, the wavefront phase error is determined. Based on the wavefront phase error, the target phase distribution of the metalens is determined. The unit structures of the metalenses under different geometric parameters are parametrically scanned using an isolated waveguide model. The phase modulation characteristics, transmission characteristics, and dispersion response of each unit structure of the metalenses in the long-wave infrared band are obtained. Based on the phase modulation characteristics, transmission characteristics, and dispersion response of each unit structure of the metalenses in the long-wave infrared band, a unit structure response database of the metalenses is established. Based on the target phase distribution of the metalens, the unit structure response database of the metalens is traversed, and the transmittance threshold, phase error threshold and aspect ratio threshold are used as constraints to screen the target unit structure in the long-wave infrared band. The target unit structure is spatially arranged according to the target phase distribution to generate the target meta-lens structure.

[0006] In one embodiment of the present invention, determining the surface profile parameters of the refractive lens based on system parameters using an even-order aspherical expression includes: The even-order aspherical expression is constructed based on the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens. The surface parameters of the refractive lens are obtained by solving the even-order aspherical expression using a damped least squares algorithm optimization method.

[0007] In one embodiment of the present invention, the wavefront isophase surface of the refractive lens includes at least one output wavefront of the refractive lens; determining the wavefront phase error based on the actual propagation paths of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, and determining the target phase distribution of the metalens based on the wavefront phase error, includes: The actual optical path of the light rays after propagation through the refracting lens at the reference coordinates is determined based on the actual propagation paths of each light ray in the equiphase surface of the wavefront of the refracting lens. Based on the actual optical path of light after propagation through the refractive lens at the reference coordinates, the ideal equal optical path corresponding to the long-wave infrared band in the ideal equal optical path reference path, and the long-wave infrared band, the phase of the output wavefront of the refractive lens at the reference coordinates is determined. The wavefront phase error is determined based on the phase of the output wavefront of the refracting lens at the reference coordinates and the phase of the ideal wavefront corresponding to the long-wave infrared band. The wavefront phase error is used as the target phase distribution of the metalens.

[0008] In one embodiment of the present invention, obtaining the phase modulation characteristics of each metalens unit structure in the long-wave infrared band includes: The phase modulation characteristics of the unit structure of the metalens in the long-wave infrared band are determined based on the long-wave infrared band, the equivalent refractive index corresponding to the long-wave infrared band, and the physical thickness of the metalens.

[0009] In one embodiment of the present invention, the method further includes: Using the ray tracing method, based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens, the point spread function and modulation transfer function of the long-wave infrared minimalist optical system are determined, and the imaging response results of the long-wave infrared band and under multiple field-of-view conditions are determined according to the point spread function and the modulation transfer function.

[0010] In one embodiment of the present invention, determining the point spread function of the long-wave infrared minimalist optical system using the ray tracing method, based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens, includes: The phase modulation amount of the refractive lens is determined based on the wavefront isophase surface of the refractive lens using the ray tracing method described above. The optical field after passing through the refractive lens is determined based on the phase modulation amount of the refractive lens; The light field after passing through the refracting lens is propagated to the metalens using the angular spectrum diffraction propagation method, and the target phase distribution of the metalens is applied. The light field after applying the target phase distribution of the metalens is propagated to the detector to obtain the complex amplitude corresponding to the detector. The point spread function is determined based on the complex amplitude corresponding to the detector.

[0011] In one embodiment of the present invention, determining the modulation transfer function of the long-wave infrared minimalist optical system using the ray tracing method, based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens, includes: The modulation transfer function is obtained by performing a Fourier transform on the point spread function.

[0012] Secondly, the present invention provides a design apparatus for a long-wave infrared minimalist optical system based on a metasurface, wherein the long-wave infrared minimalist optical system includes a refractive lens, a meta lens, and a detector, the meta lens being disposed between the refractive lens and the detector; the apparatus includes: The first determining module is used to determine the surface parameters of the refractive lens based on system parameters and through an even-order aspherical expression; the system parameters include the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens; The second determining module is used to determine the wavefront isophase surface of the refractive lens based on the surface parameters of the refractive lens by using a ray tracing method, determine the wavefront phase error based on the actual propagation path of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, and determine the target phase distribution of the metalens based on the wavefront phase error. A module is established to parametrically scan the unit structure of the metalens under different geometric parameters using an isolated waveguide model, obtain the phase modulation characteristics, transmission characteristics and dispersion response of the unit structure of each metalens in the long-wave infrared band, and establish a unit structure response database of the metalens based on the phase modulation characteristics, transmission characteristics and dispersion response of the unit structure of each metalens in the long-wave infrared band. The filtering module is used to traverse the unit structure response database of the metalens based on the target phase distribution of the metalens, and use transmittance threshold, phase error threshold and aspect ratio threshold as constraints to filter the target unit structure in the long-wave infrared band. The generation module is used to spatially arrange the target unit structure according to the target phase distribution to generate the target meta-lens structure.

[0013] Thirdly, the present invention provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; The processor, when executing a program stored in memory, implements any of the methods provided in the first aspect.

[0014] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements any of the methods provided in the first aspect.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a simplified long-wavelength infrared optical system design method based on metasurfaces. Based on system parameters, the surface parameters of the refractive lens are determined using an even-order aspherical expression. Using ray tracing, the wavefront isophase surface of the refractive lens is determined based on its surface parameters. The wavefront phase error is determined based on the actual propagation paths of each ray on the wavefront isophase surface and the ideal isopathic reference path in the ideal wavefront. The target phase distribution of the metalens is then determined based on the wavefront phase error. Finally, the unit structure of the metalens under different geometric parameters is parametrically scanned using an isolated waveguide model to obtain the phase distribution of each metalens. This invention analyzes the phase modulation, transmission, and dispersion responses of metalens units in the long-wave infrared band. Based on these characteristics, a metalens unit structure response database is established. Using the target phase distribution of the metalens, the database is traversed, and transmittance, phase error, and aspect ratio thresholds are used as constraints to select target unit structures within the long-wave infrared band. These target unit structures are then spatially arranged according to the target phase distribution to generate the target metalens structure. This invention optimizes wavefront phase error as the target, globally optimizing the structural parameters of the metalens to achieve high-precision compensation for residual aberrations across the entire image field. Furthermore, it selects target unit structures with smaller phase errors and higher transmittance within the long-wave infrared band, achieving wavefront dispersion compensation at the structural level. This allows for effective correction of chromatic aberration across a wide band, enabling the system to operate with a larger relative aperture without sacrificing imaging quality, thus meeting the requirements for high light throughput, large aperture, and wide-spectrum imaging.

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the implementation process of a simplified long-wave infrared optical system design method based on metasurfaces provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a long-wave infrared minimalist optical system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the wavefront equiphase surface of a metalens provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a unit structure of a metalens provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the scanning simulation calculation distribution of a unit structure of a metalens provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a system simulation focusing effect provided by an embodiment of the present invention; Figure 7This is a schematic diagram of the modulation transfer function simulation results of a long-wave infrared minimalist optical system provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the structure of a simplified long-wave infrared optical system design device based on a metasurface provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the hardware entity of an electronic device to which embodiments of the present invention are applied. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0019] Please see Figure 1 , Figure 1 This is a schematic diagram illustrating the implementation process of a simplified long-wavelength infrared optical system design method based on metasurfaces provided in an embodiment of the present invention. Figure 1 As shown, the design method for a long-wavelength infrared minimalist optical system based on metasurfaces provided in this embodiment of the invention may include the following steps: Step S101: Based on the system parameters, determine the surface parameters of the refractive lens using the even-order aspherical expression.

[0020] The system parameters include the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens.

[0021] like Figure 2 As shown, the long-wave infrared minimalist optical system provided in this embodiment of the invention includes a refractive lens 201, a metalens 202, and a detector 203. The metalens 202 is disposed between the refractive lens 201 and the detector 203. The refractive lens 201 has a focusing imaging function and can allocate more than 90% of the optical power. The metalens 202 is disposed in the region near the exit pupil behind the refractive lens 201, facing the image plane, and can perform phase compensation for residual higher-order aberrations generated during the previous imaging process, improving the overall imaging quality of the long-wave infrared minimalist optical system to the diffraction-limited level.

[0022] In one possible implementation, the aperture stop can be placed on the exit surface of the germanium window at the front end of the detector 203, so that the aperture stop is conjugate with the cold stop plane and directly serves as the exit pupil of the system, thereby blocking the retroreflected beams from the inner wall of the Dewar and subsequent optical surfaces from returning to the focal plane and eliminating the influence of cold reflection noise.

[0023] In one possible implementation, the same infrared material can be used as the optical medium for the entire long-wave infrared minimalist optical system.

[0024] In one possible implementation, as shown in the following formula (1), an even-order aspherical expression can be constructed based on the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens; the even-order aspherical expression is solved by the damped least squares algorithm optimization method to obtain the surface parameters of the refractive lens.

[0025] (1); in, The surface height of the refractive lens, Let be the curvature of the refractive lens. Let be the conic constant of the refractive lens. is the higher-order aspherical coefficient of the refractive lens.

[0026] Step S102: Using the ray tracing method, determine the wavefront isophase surface of the refractive lens based on the surface parameters of the refractive lens. Based on the actual propagation path of each ray in the wavefront isophase surface of the refractive lens and the ideal isophase reference path in the ideal wavefront, determine the wavefront phase error. Based on the wavefront phase error, determine the target phase distribution of the metalens.

[0027] In one possible implementation, the wavefront isophase surface of the refractive lens includes the output wavefront of at least one refractive lens; the actual optical path of the light rays after propagation through the refractive lens at the reference coordinate can be determined by the following formula (2) based on the actual propagation path of each ray in the wavefront isophase surface of the refractive lens; the phase of the output wavefront of the refractive lens at the reference coordinate is determined by the actual optical path of the light rays after propagation through the refractive lens at the reference coordinate, the ideal isophase path corresponding to the long-wave infrared band in the ideal isophase reference path, and the long-wave infrared band; the wavefront phase error is determined by the following formula (3) based on the phase of the output wavefront of the refractive lens at the reference coordinate and the phase of the ideal wavefront corresponding to the long-wave infrared band; the wavefront phase error is used as the target phase distribution of the metalens.

[0028] (2); in, Let be the phase of the output wavefront of the refracting lens at the reference coordinates (x, y). Let be the actual optical path length of the light ray at the reference coordinates (x, y) after propagation through the refracting lens. For an ideal equal optical path reference path, the ideal equal optical path corresponds to the long-wave infrared band. For the long-wave infrared band, the design band value can be selected between 7.7μm and 9.5μm.

[0029] (3); in, Let represent the target phase distribution of the metalens at reference coordinates (x, y). For an ideal wavefront, the phase corresponds to the long-wave infrared band. Let be the phase of the output wavefront of the refracting lens at the reference coordinates (x, y).

[0030] Step S103: Parametrically scan the unit structure of metalenses under different geometric parameters using an isolated waveguide model to obtain the phase modulation characteristics, transmission characteristics, and dispersion response of each metalens unit structure in the long-wave infrared band. Based on the phase modulation characteristics, transmission characteristics, and dispersion response of each metalens unit structure in the long-wave infrared band, establish a metalens unit structure response database.

[0031] For example, the numerical simulation of the unit structure can be achieved by parametrically scanning the geometric dimensions of the unit structure using a fine-mesh finite-difference time-domain (FDTD) unit model. The lattice period of the metalens unit structure is selected as 'a', arranged in a tetragonal lattice. The light source is located on one side of the interface, incident from the bottom surface, passing sequentially through the dielectric substrate, the dielectric unit structure enclosed by an air layer, and then exiting. After traveling through a certain space, the phase in space gradually becomes uniformly distributed due to Huygens' principle. The phase of a point in the exit space is output using a point monitor, and the phase introduced by the light propagating in space, calculated based on the optical path length at different wavelengths, is subtracted to obtain the additional phase introduced by the unit structure. The phase values ​​of the actual unit structure under different lattice constants, radii, and micro / nano unit heights are extracted to construct a unit structure database.

[0032] In one possible implementation, the phase of the unit structure of the metalens in the long-wave infrared band can be determined by the following formula (4) based on the long-wave infrared band, the equivalent refractive index corresponding to the long-wave infrared band, and the physical thickness of the metalens, so as to characterize the phase modulation characteristics of the unit structure of the metalens in the long-wave infrared band by the phase of the unit structure of the metalens in the long-wave infrared band.

[0033] (4); in, This represents the phase of the unit structure of the metalens in the long-wave infrared band. It is in the long-wave infrared band. This represents the equivalent refractive index corresponding to the long-wave infrared band. The physical thickness of the metalens.

[0034] Step S104: Based on the target phase distribution of the metalens, traverse the unit structure response database of the metalens, and use the transmittance threshold, phase error threshold and aspect ratio threshold as constraints to screen the target unit structure in the long-wave infrared band.

[0035] For example, based on the target phase distribution of the metalens, the unit structure response database of the metalens can be traversed, and target unit structures with modulated similar phase differences and high transmittance can be selected by using transmittance ≥ 50%, phase error ≤ π / 10, and aspect ratio ≤ 6 as constraints. The transmittance threshold, phase error threshold, and aspect ratio threshold can be set according to actual needs.

[0036] Step S105: Arrange the target unit structure in space according to the target phase distribution to generate the target meta-lens structure.

[0037] The present invention provides a simplified design method for long-wave infrared optical systems based on metasurfaces, which determines the surface parameters of the refractive lens based on system parameters and even-order aspherical expressions. Using ray tracing, the wavefront isophase surface of the refractive lens is determined based on its surface parameters. The wavefront phase error is determined based on the actual propagation paths of each ray on the isophase surface and the ideal isopathic reference path in the ideal wavefront. The target phase distribution of the metalens is then determined based on this wavefront phase error. The unit structures of the metalens under different geometric parameters are parametrically scanned using an isolated waveguide model to obtain the phase modulation characteristics, transmission characteristics, and dispersion response of each unit structure in the long-wave infrared band. A unit structure response database for the metalens is established based on these characteristics. Based on the target phase distribution of the metalens, the unit structure response database is traversed, and target unit structures in the long-wave infrared band are selected using transmittance thresholds, phase error thresholds, and aspect ratio thresholds as constraints. The target unit structures are then spatially arranged according to the target phase distribution to generate the target metalens structure. This invention optimizes wavefront phase error by globally optimizing the structural parameters of the metalens, achieving high-precision compensation for residual aberrations across the entire image field. Furthermore, it selects target unit structures with smaller phase errors and higher transmittance in the long-wave infrared band to achieve wavefront dispersion compensation at the structural dimension. This allows for effective correction of chromatic aberration across a wide band, enabling the system to operate with a large relative aperture without sacrificing imaging quality. Thus, it meets the requirements for high light transmittance, large aperture, and wide-spectrum imaging.

[0038] In one possible implementation, the point spread function (PSF) and modulation transfer function (MTF) of a long-wave infrared minimalist optical system can be determined by ray tracing based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens. The imaging response results under long-wave infrared band and multi-field conditions can then be determined based on the PSF and MTF.

[0039] In one possible implementation, referring to the following formula (5), the phase modulation amount of the refracting lens can be determined by ray tracing based on the wavefront isophase surface of the refracting lens.

[0040] (5); in, This refers to the phase modulation amount of the refracting lens, that is, the amount of phase modulation introduced into the light beam after passing through the refracting lens. For wave number, For refractive lens materials in the long-wave infrared band The refractive index below, The position in front of the refracting lens. The position transmitted through the refracting lens.

[0041] Refer to the following formula (6) to determine the light field after passing through the refracting lens based on the phase modulation amount of the refracting lens.

[0042] (6); in, This refers to the light field after passing through the refracting lens, that is, the outgoing complex amplitude light field after phase modulation by the refracting lens. The initial complex amplitude light field incident on the refracting lens; Referring to the following formula (7), the light field after passing through the refracting lens can be propagated to the superlens using the angular spectrum diffraction propagation method, and the target phase distribution of the superlens can be applied. The light field after applying the target phase distribution of the superlens can be propagated to the detector to obtain the complex amplitude corresponding to the detector.

[0043] (7); in, This is the complex amplitude corresponding to the detector, that is, the complex amplitude light field after propagation to the metalens and phase modulation by the metalens; and These are the Fourier transform function and the inverse Fourier transform function, respectively. Let be the free-space transfer function in the angular spectrum diffraction propagation method. This function is calculated as follows: , and These are the transverse spatial frequencies, The propagation distance from the exit surface of the refracting lens to the plane of the metalens is given by the following formula: This represents the target phase distribution of the metalens.

[0044] Refer to the following formula (8) to determine the point spread function based on the complex amplitude corresponding to the detector.

[0045] (8); in, Let be the point spread function. and These are the Fourier transform function and the inverse Fourier transform function, respectively. The complex amplitude corresponding to the detector. The free-space transfer function in the angular spectrum diffraction propagation method. and These are the transverse spatial frequencies, This represents the propagation distance from the metalens to the final imaging surface.

[0046] In one possible implementation, referring to the following formula (9), the point spread function can be Fourier transformed to obtain the modulation transfer function.

[0047] (9); in, For modulation transfer function, and These are the transverse spatial frequencies, It is the Fourier transform function. is the point spread function.

[0048] In one possible implementation, a Fourier transform can be performed on the point spread function to obtain the modulation transfer function, and the one-dimensional modulation transfer function curves of the central horizontal and vertical axes can be extracted. The corresponding Nyquist cutoff frequency is set to half the reciprocal of the detector pixel size, and the imaging performance of the optical system is measured by calculating the modulation transfer function value at this cutoff frequency.

[0049] In the above implementation, the imaging process of the metalens is numerically modeled using the angular spectrum diffraction propagation method. The light field propagating to the metalens is superimposed with the target phase distribution of the metalens, and the propagation behavior of the light field in free space is simulated using the angular spectrum diffraction propagation method to obtain the light field distribution on the final imaging surface. This method allows for characterizing the wavefront modulation effect of large-aperture systems within the spatial frequency range without requiring global electromagnetic modeling of the entire metalens.

[0050] In one possible implementation, a simplified long-wave infrared optical system is designed according to the above method. The system parameters of this simplified long-wave infrared optical system are as follows: focal length of 88mm, F-number of 2, long-wave infrared band of 7.7-9.5μm, matched with L615 cooled infrared camera module, and its effective pixel count is 640. 512px, pixel size is 15μm, and the geometric dimensions of the imaging surface are... The effective half-field angle of this long-wave infrared minimalist optical system can be determined by the following formula (10): (10); in, For the effective half-field of view of a long-wave infrared minimalist optical system, The half-height of the detector's diagonal. The focal length is for a long-wave infrared minimalist optical system.

[0051] Based on the system parameters of the long-wave infrared minimalist optical system, the effective entrance pupil diameter of the long-wave infrared minimalist optical system can be determined by the following formula (11): (11); in, The effective entrance pupil diameter of a long-wave infrared minimalist optical system. The focal length of a long-wave infrared minimalist optical system. This is the F-number of the optical system.

[0052] The parameters of the refractive lens can be obtained through optimization using a damped least squares algorithm.

[0053] The parameters of the long-wave infrared minimalist optical system of the present invention are shown in Table 1.

[0054] Table 1

[0055] The parameters of the refractive lens of the present invention are shown in Table 2.

[0056] Table 2

[0057] The wavefront isophase surface of the metalens obtained by this invention is as follows: Figure 3 As shown, Figure 3In this paper, X and Y represent the two-dimensional spatial coordinates on the plane of the metalens. Based on vector light field analysis and parameter scanning strategy, using the two-dimensional phase surface distribution of the metalens obtained by this invention, the finite-difference time-domain (FDTD) algorithm is used to perform full vector simulation of the nanopillar unit structure at a grid accuracy of λ / 20, extracting its complex transmission coefficient and phase delay database (i.e., the unit structure response database of the metalens in the above method); then, using this database as a constraint, the radial periodic arrangement of the entire lens Wiener structure is achieved through an optimization algorithm. Figure 4 This is a schematic diagram of a unit structure of a meta-lens provided in an embodiment of the present invention, wherein D is the diameter of the unit structure, H is the height of the unit structure, and a is the period of the unit structure.

[0058] Set the substrate thickness to The height range of the unit structure is The radius of the hexagonal prism element is The lattice constant is a key dimension for adjustment as a design parameter. This is achieved under three long-wave infrared bands. By systematically scanning the structural parameters within the range and combining this with database optimization methods, the phase-transmittance response distribution of the metalens unit structure was obtained. Figure 5 This is a schematic diagram of the scanning simulation calculation distribution of the unit structure of the metalens. Figure 5 The phase-transmittance response distribution of the unit cell structure is shown for long-wave infrared bands of 7.7 μm, 8.6 μm, and 9.5 μm.

[0059] When the unit structure radius is higher than 0.8 μm, the resonance effect in the micro / nano structure results in a large low-transmittance region in the transmittance distribution map, limiting focusing efficiency. The establishment of a unit structure response database for metalenses includes extracting phase-dispersion parameters based on raw data and matching parameters between actual unit structures and the target. Furthermore, to address issues encountered in actual fabrication processes, the database needs optimization based on the characteristic dimensions of the metalenses. This ensures that the units in the database conform to actual fabrication results, the height of the metalens unit should be less than 8 μm, and the designed unit structure for achromatic metalenses satisfies dispersion compensation conditions in more than half of the metalens region, with other regions also well-fitting the dispersion compensation conditions. This maximizes the elimination of first-order dispersion of the metalens at the unit design level.

[0060] Structures with transmittance below 50% were excluded by calculating the average transmittance using a scatter plot of the phase-dispersion parameters of the unit structure. Considering both the transmittance and the 0-2π phase coverage condition of the unit structure, a unit structure height of 4.5μm is the optimal choice when the unit structure period is 5μm. The phase distribution plot shows a smoother phase change, which is closer to the phase modulation effect of a periodic array under ideal conditions, controlling the focusing efficiency attenuation caused by scattering and improving the overall efficiency of the metalens.

[0061] The field distribution at the detector focal plane position is calculated using the method described in this invention, as follows: Figure 6 As shown, Figure 6 The image shows the field distribution of the detector focal plane at long-wave infrared bands of 7.7 μm, 8.6 μm, and 9.5 μm, with incident angles of 0°, 5.6°, and 8°, respectively. It is evident that the system exhibits excellent diffraction-limited focusing characteristics under central field-of-view conditions. The PSF distributions for each band are similar, the energy concentration is high, and sidelobe suppression is significant, achieving effective chromatic aberration compensation and off-axis aberration correction. Figure 7 The solid and dashed lines represent the sagittal and meridional directions, respectively. Figure (a) shows the MTF values ​​in the meridional and sagittal directions for incident angles of 0°, 2.8°, and 4° at a long-wave infrared wavelength of 7.7 μm. Figure (b) shows the MTF values ​​in the meridional and sagittal directions for incident angles of 0°, 2.8°, and 4° at a long-wave infrared wavelength of 8.6 μm. Figure (c) shows the MTF values ​​in the meridional and sagittal directions for incident angles of 0°, 2.8°, and 4° at a long-wave infrared wavelength of 9.5 μm. It can be seen that the MTF decreases with increasing incident angle, consistent with the PSF trend. The MTF in the center field of view remains at 0.2 at the cutoff frequency. The MTF curves in different wavelength bands show good consistency within the field of view, indicating good chromatic aberration correction capability.

[0062] Please see Figure 8 , Figure 8 This is a schematic diagram of a design device for a long-wavelength infrared simplified optical system based on a metasurface, provided by an embodiment of the present invention. The long-wavelength infrared simplified optical system provided by the present invention includes a refractive lens, a metasurface lens, and a detector, with the metasurface lens disposed between the refractive lens and the detector. The design device for the long-wavelength infrared simplified optical system based on a metasurface provided by the present invention includes a first determining module 801, a second determining module 802, a building module 803, a filtering module 804, and a generating module 805. Wherein, The first determining module 801 is used to determine the surface parameters of the refractive lens based on the system parameters and through the even-order aspherical expression; the system parameters include the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens; The second determining module 802 is used to determine the wavefront isophase surface of the refractive lens based on the surface parameters of the refractive lens by using a ray tracing method, determine the wavefront phase error based on the actual propagation path of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, and determine the target phase distribution of the metalens based on the wavefront phase error. Module 803 is established to parametrically scan the unit structure of metalenses under different geometric parameters using an isolated waveguide model, obtain the phase modulation characteristics, transmission characteristics and dispersion response of the unit structure of each metalens in the long-wave infrared band, and establish a unit structure response database of metalenses based on the phase modulation characteristics, transmission characteristics and dispersion response of the unit structure of each metalens in the long-wave infrared band. The screening module 804 is used to traverse the unit structure response database of the metalens based on the target phase distribution of the metalens, and use the transmittance threshold, phase error threshold and aspect ratio threshold as constraints to screen the target unit structure in the long-wave infrared band. The generation module 805 is used to spatially arrange the target unit structure according to the target phase distribution to generate the target meta-lens structure.

[0063] Please see Figure 9 , Figure 9 This is a schematic diagram of the hardware entity of an electronic device applicable to an embodiment of the present invention. The electronic device provided in this embodiment includes a processor 901, a communication interface 902, a memory 903, and a communication bus 904. The processor 901, communication interface 902, and memory 903 communicate with each other via the communication bus 904. The memory 903 stores computer programs. When the processor 901 executes the program stored in the memory 903, it implements the steps provided in the above-described method embodiment.

[0064] The communication bus 904 mentioned in the above electronic device can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus 904 can be divided into address bus, data bus, control bus, etc. For ease of illustration, it is represented by only one thick line in the figure, but this does not indicate that there is only one bus or one type of bus.

[0065] The communication interface 902 is used for communication between the above-mentioned electronic device and other devices.

[0066] The memory 903 may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory 903 may also be at least one storage device located remotely from the aforementioned processor.

[0067] The processor 901 mentioned above can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0068] The method provided in this invention can be applied to electronic devices. Specifically, the electronic device can be a desktop computer, a portable computer, a smart mobile terminal, a server, etc. No limitation is made herein; any electronic device that can implement this invention falls within the protection scope of this invention.

[0069] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps provided in the above-described method embodiments.

[0070] For embodiments of the apparatus / electronic device / storage medium, since they are basically similar to the method embodiments, the description is relatively simple. For specific details and beneficial effects, please refer to the description of the method embodiments. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0072] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, disclosure, and appended claims, will understand and implement other variations of the disclosed embodiments in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0073] Those skilled in the art will understand that embodiments of this application can be provided as methods, apparatus (devices), or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects, all of which are collectively referred to herein as "modules" or "systems." Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The computer program may be stored / distributed in a suitable medium, provided with or as part of other hardware, or may take other distribution forms, such as via the Internet or other wired or wireless telecommunications systems.

[0074] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0075] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0076] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the functions specified in one or more boxes. The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments, and it should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

Claims

1. A method for designing a simplified long-wavelength infrared optical system based on metasurfaces, characterized in that, The long-wave infrared minimalist optical system includes a refractive lens, a metalens, and a detector, wherein the metalens is disposed between the refractive lens and the detector; the method includes: Based on system parameters, the surface parameters of the refractive lens are determined through even-order aspherical expressions; the system parameters include the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens; Using a ray tracing method, the wavefront isophase surface of the refractive lens is determined based on the surface parameters of the refractive lens. Based on the actual propagation paths of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, the wavefront phase error is determined. Based on the wavefront phase error, the target phase distribution of the metalens is determined. The unit structures of the metalenses under different geometric parameters are parametrically scanned using an isolated waveguide model. The phase modulation characteristics, transmission characteristics, and dispersion response of each unit structure of the metalenses in the long-wave infrared band are obtained. Based on the phase modulation characteristics, transmission characteristics, and dispersion response of each unit structure of the metalenses in the long-wave infrared band, a unit structure response database of the metalenses is established. Based on the target phase distribution of the metalens, the unit structure response database of the metalens is traversed, and the transmittance threshold, phase error threshold and aspect ratio threshold are used as constraints to screen the target unit structure in the long-wave infrared band. The target unit structure is spatially arranged according to the target phase distribution to generate the target meta-lens structure.

2. The design method for a long-wavelength infrared minimalist optical system based on a metasurface according to claim 1, characterized in that, The determination of the surface profile parameters of the refractive lens based on system parameters and using an even-order aspherical expression includes: The even-order aspherical expression is constructed based on the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens. The surface parameters of the refractive lens are obtained by solving the even-order aspherical expression using a damped least squares algorithm optimization method.

3. The design method for a long-wavelength infrared minimalist optical system based on a metasurface according to claim 1, characterized in that, The wavefront isophase surface of the refractive lens includes at least one output wavefront of the refractive lens; the determination of the wavefront phase error based on the actual propagation paths of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, and the determination of the target phase distribution of the metalens based on the wavefront phase error, includes: The actual optical path of the light rays after propagation through the refracting lens at the reference coordinates is determined based on the actual propagation paths of each light ray in the equiphase surface of the wavefront of the refracting lens. Based on the actual optical path of light after propagation through the refractive lens at the reference coordinates, the ideal equal optical path corresponding to the long-wave infrared band in the ideal equal optical path reference path, and the long-wave infrared band, the phase of the output wavefront of the refractive lens at the reference coordinates is determined. The wavefront phase error is determined based on the phase of the output wavefront of the refracting lens at the reference coordinates and the phase of the ideal wavefront corresponding to the long-wave infrared band. The wavefront phase error is used as the target phase distribution of the metalens.

4. The design method for a long-wavelength infrared minimalist optical system based on a metasurface according to claim 1, characterized in that, The step of obtaining the phase modulation characteristics of each metalens unit structure in the long-wave infrared band includes: The phase modulation characteristics of the unit structure of the metalens in the long-wave infrared band are determined based on the long-wave infrared band, the equivalent refractive index corresponding to the long-wave infrared band, and the physical thickness of the metalens.

5. The design method for a long-wavelength infrared minimalist optical system based on a metasurface according to claim 1, characterized in that, The method further includes: Using the ray tracing method, based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens, the point spread function and modulation transfer function of the long-wave infrared minimalist optical system are determined, and the imaging response results of the long-wave infrared band and under multiple field-of-view conditions are determined according to the point spread function and the modulation transfer function.

6. The design method for a long-wavelength infrared minimalist optical system based on a metasurface according to claim 5, characterized in that, The step of determining the point spread function of the long-wave infrared minimalist optical system using the ray tracing method, based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens, includes: The phase modulation amount of the refractive lens is determined based on the wavefront isophase surface of the refractive lens using the ray tracing method described above. The optical field after passing through the refractive lens is determined based on the phase modulation amount of the refractive lens; The light field after passing through the refracting lens is propagated to the metalens using the angular spectrum diffraction propagation method, and the target phase distribution of the metalens is applied. The light field after applying the target phase distribution of the metalens is propagated to the detector to obtain the complex amplitude corresponding to the detector. The point spread function is determined based on the complex amplitude corresponding to the detector.

7. The design method for a long-wavelength infrared minimalist optical system based on a metasurface according to claim 5, characterized in that, The step of determining the modulation transfer function of the long-wave infrared minimalist optical system using the ray tracing method, based on the wavefront isophase surface of the refractive lens and the target phase distribution of the metalens, includes: The modulation transfer function is obtained by performing a Fourier transform on the point spread function.

8. A simplified long-wavelength infrared optical system design device based on metasurfaces, characterized in that, The long-wave infrared minimalist optical system includes a refractive lens, a meta-lens, and a detector, wherein the meta-lens is disposed between the refractive lens and the detector; the device includes: The first determining module is used to determine the surface parameters of the refractive lens based on system parameters and through an even-order aspherical expression; the system parameters include the surface height of the refractive lens, the curvature of the refractive lens, the conic constant of the refractive lens, and the higher-order aspherical coefficients of the refractive lens; The second determining module is used to determine the wavefront isophase surface of the refractive lens based on the surface parameters of the refractive lens by using a ray tracing method, determine the wavefront phase error based on the actual propagation path of each ray in the wavefront isophase surface of the refractive lens and the ideal isopathic reference path in the ideal wavefront, and determine the target phase distribution of the metalens based on the wavefront phase error. A module is established to parametrically scan the unit structure of the metalens under different geometric parameters using an isolated waveguide model, obtain the phase modulation characteristics, transmission characteristics and dispersion response of the unit structure of each metalens in the long-wave infrared band, and establish a unit structure response database of the metalens based on the phase modulation characteristics, transmission characteristics and dispersion response of the unit structure of each metalens in the long-wave infrared band. The filtering module is used to traverse the unit structure response database of the metalens based on the target phase distribution of the metalens, and use transmittance threshold, phase error threshold and aspect ratio threshold as constraints to filter the target unit structure in the long-wave infrared band. The generation module is used to spatially arrange the target unit structure according to the target phase distribution to generate the target meta-lens structure.

9. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor, when executing a program stored in memory, implements the method described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method described in any one of claims 1-7.

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