Metasurface edge detection imaging method and system based on first-order two-dimensional differential operation

Abstract

The present invention provides a metasurface edge detection imaging method and system for first-order two-dimensional differential operation, wherein the method comprises: step 1: designing and processing a metasurface with first-order two-dimensional differential operation function characteristics; step 2: imaging the image to be tested based on the metasurface and the edge detection image model to obtain an edge detection image; step 3: obtaining an edge detection result based on the edge detection image. The present invention is based on the traditional first-order two-dimensional differential operation function imaging method, and uses a metasurface to generate a first-order two-dimensional differential operation function modulation, which not only avoids the influence of the zero-order diffraction spot, improves energy utilization and imaging efficiency, but also improves the integration and lightweight of the system. Combining the characteristics of the first-order two-dimensional differential operation function with the advantages of the metasurface, while being able to perform high-precision edge detection, reduces the complexity of the system, makes the system easier to integrate, and meets the current use requirements of edge detection systems.

Description

Technical Field

[0001] The present invention belongs to the field of microscopic imaging technology, and more specifically, relates to a metasurface edge detection imaging method and system involving first-order two-dimensional differential operations. Background Art

[0002] The first-order two-dimensional differential operation function describes the gradient of the input image data. Since the image can be represented as a collection of points of different intensities, edge detection is to extract the edge information of the image. The first-order two-dimensional differential operation function is used to obtain the gradient information of each part of the image. Among them, the part with the largest gradient change is the edge of the image. The existing edge detection function is mainly designed for the amplitude transmittance and phase transmittance of the pupil function. By introducing the corresponding amplitude and phase modulation at the exit pupil plane of the system, the differential function of the system can be adjusted. The control of the light field is usually achieved by traditional light field control elements, including amplitude / phase masks, spatial light modulators, deformable mirrors, and digital micromirror devices, etc. Among them, the most commonly used is the spatial light modulator. The quantization level distribution of its phase structure and the structural characteristics of the control unit determine the existence of the zero-order diffraction spot. The zero-order diffraction spot often occupies a large part of the energy and is often aliased with the modulated effective image, making the displayed image dim and blurred, seriously reducing the imaging quality. At the same time, the spatial light modulator can usually only control the amplitude or phase separately, and cannot control them at the same time. In addition, the spatial light modulator is large in size, making it impossible to integrate it into the edge detection imaging optical system.

[0003] In order to solve the problems of poor imaging quality, difficulty in integration and high cost of spatial light modulators, the idea of ​​metasurfaces was introduced. Metasurfaces are artificial components composed of nanostructures that can arbitrarily control the phase, intensity and polarization response of the incident field with sub-wavelength resolution. Using metasurface structures instead of traditional optical components for imaging improves the problems of zero-order diffraction and difficulty in integration of traditional three-dimensional imaging optical systems based on spatial light modulators, greatly reduces the size of components, and improves imaging quality. In addition, when metasurfaces that are compatible with semiconductor processing technology are mass-produced, the cost is much lower than that of spatial light modulators composed of controllers, liquid crystal panels and communication modules, resulting in a significant reduction in the cost of the entire system and increasing its practicality. Summary of the invention

[0004] The purpose of the present invention is to provide a metasurface edge detection imaging method and system based on first-order two-dimensional differential operation, aiming to solve the technical problems in the prior art that three-dimensional imaging optical systems based on spatial light modulators have zero-order higher-order diffraction and are difficult to integrate.

[0005] To achieve the above object, the technical solution adopted by the present invention is: to provide a first-order two-dimensional differential operation metasurface edge detection imaging method, comprising:

[0006] Step 1: Design and process a metasurface with first-order two-dimensional differential operation function characteristics;

[0007] Step 2: Imaging the image to be tested based on the metasurface and edge detection image model to obtain an edge detection image;

[0008] Step 3: Obtain edge detection results based on the edge detection image.

[0009] The design steps of the metasurface in step 1 include:

[0010] Optimizing the basic unit structure parameters in the metasurface, wherein the basic unit structure is a single-crystal silicon multi-degree-of-freedom nanocolumn on a sapphire substrate;

[0011] The electromagnetic simulation software GST is used to simulate the basic unit structure parameters in the optimized metasurface to obtain the designed metasurface.

[0012] Optionally, the step of simulating the basic unit structure parameters in the optimized metasurface includes:

[0013] The frequency domain calculation module of electromagnetic simulation software CST is used to perform parameter scanning on the basic unit structure of the metasurface and obtain the parameter curve.

[0014] Analyzing the transmittance of circularly polarized light based on the parameter curve to obtain a basic unit structure with the highest transmittance of circularly polarized light;

[0015] Based on the complex oscillation expression of the first-order two-dimensional differential operation, the phase distribution of the first-order two-dimensional differential operation function is obtained;

[0016] Based on the phase distribution of the first-order two-dimensional differential operation function, the basic unit structures with the highest circularly polarized light transmittance are periodically arranged to obtain the designed metasurface;

[0017] The expression of the phase distribution of the first-order two-dimensional differential operation function is:

[0018]

[0019] In formula (1), F{} is the Fourier transform operation, E(-x) is the complex amplitude distribution of the metasurface, and E 像 (x) is the complex amplitude distribution of the image plane light field, E 物 (x) is the complex amplitude distribution of the light field on the object plane, j is an imaginary unit, and x is the horizontal axis coordinate of the light field centered on the optical axis.

[0020] Optionally, the processing steps of the metasurface in step 1 include:

[0021] A single-crystal silicon epitaxial wafer grown on double-sided polished sapphire with a thickness of 360 nm was selected as the processing material, and an electron beam photoresist PMMAA4 was spin-coated on the single-crystal silicon epitaxial wafer at a speed of 3000 rpm;

[0022] Using electron beam lithography technology, at an acceleration voltage of 30 kV, a beam current of 360 pA, and a 100 × 100 μm 2 Under a writing field condition of , a superlens mask is prepared on a photoresist coated on a single crystal silicon epitaxial wafer;

[0023] The image to be tested was immersed in a 25% tetramethylammonium hydroxide solution at 25°C for 2 minutes, then rinsed in deionized water for 20 seconds, immersed in an isopropanol solution for 10 seconds, and dried with nitrogen gas;

[0024] Using inductively coupled plasma to perform reactive ion etching, the superlens mask pattern is transferred to the silicon film of the single crystal silicon epitaxial wafer, and the single crystal silicon epitaxial wafer is etched based on the reactive ion etching technology;

[0025] The etched single crystal silicon epitaxial wafer is immersed in 10% hydrofluoric acid for 15 seconds, and the hydrofluoric acid after immersion is cleaned with ionized water, and then dried with nitrogen to obtain a processed meta-structure surface.

[0026] Optionally, the step of etching the single crystal silicon epitaxial wafer includes:

[0027] Using carbon tetrafluoride at 100W ICP power and 100W bias power, with a gas flow rate of 45sccm for 5s, the surface oxide layer of the single crystal silicon epitaxial wafer was removed by dry etching;

[0028] The single crystal silicon epitaxial wafer after removing the surface oxide layer was etched at a speed of 83 nm / min using hydrogen bromide gas with a gas flow rate of 100 sccm, an ICP power of 400 W, and a bias power of 100 W.

[0029] Optionally, the edge detection image model in step 2 includes an illumination module and an edge detection imaging module;

[0030] The lighting module includes a transmissive lighting layer and a reflective lighting layer;

[0031] The transmissive illumination module comprises a fiber-coupled laser, a collimating lens, a half-reflecting half-mirror, a microscope objective, a metasurface and a CMOS camera arranged along a light beam propagation direction, wherein the fiber-coupled laser and the collimating lens arranged along the light beam propagation direction are located in the same horizontal direction, the half-reflecting half-mirror, the microscope objective, the metasurface and the CMOS camera are located in the same vertical direction, and the central axes of the microscope objective and the metasurface in the vertical direction coincide with each other;

[0032] The reflective lighting module includes a fiber-coupled laser, a collimating lens, a semi-reflecting and semi-transparent mirror, a microscope objective lens, a metasurface, and a CMOS camera arranged along the propagation direction of the light beam. The fiber-coupled laser and the collimating lens arranged along the propagation direction of the light beam are located in the same horizontal direction. The semi-reflecting and semi-transparent mirror, the microscope objective lens, the metasurface, and the CMOS camera are located in the same vertical direction, and the central axes of the microscope objective lens and the metasurface in the vertical direction coincide with each other.

[0033] The object plane, metasurface and image plane constitute a 2f system, and the metasurface is placed on the Fourier plane of the 2f system.

[0034] The edge detection imaging module includes a transmissive edge detection layer and a reflective edge detection layer.

[0035] Optionally, the step of acquiring the edge detection image in step 2 includes:

[0036] Based on the characteristics of the imaging sample, if the image to be tested is a transmissive image to be tested, a transmissive illumination layer and a transmissive edge detection layer are placed to obtain an edge detection image;

[0037] If the image to be measured is a reflective image to be measured, a reflective lighting layer and a reflective edge detection layer are placed to obtain an edge detection image.

[0038] Optionally, the step of obtaining edge detection of the transmission image to be tested includes:

[0039] The fiber-coupled laser arranged along the propagation direction of the light beam emits a monochromatic and coherent laser, which is then transformed into parallel light through a collimating lens. The parallel light then exits through a transmission-type image sample to be measured.

[0040] The transmission image to be tested is imaged by a microscope and a metasurface to obtain an image of the transmission image to be tested, the amplitude and phase of the emitted parallel light are controlled based on the transmission phase through the metasurface to obtain a first-order two-dimensional differential operation function modulated image of the transmission image to be tested, and the first-order two-dimensional differential operation function modulated image of the transmission image to be tested is collected using a CMOS camera;

[0041] The first-order two-dimensional differential operation function modulated image of the collected transmission image to be tested is solved to obtain the light field intensity of the transmission image to be tested, and the contour information of the transmission image to be tested is obtained based on the light field intensity of the transmission image to be tested to complete edge detection.

[0042] Optionally, the step of obtaining edge detection of the reflective image to be tested includes:

[0043] The fiber-coupled laser arranged along the propagation direction of the light beam emits a monochromatic and coherent laser, which is formed into parallel light through a collimating lens, and then the parallel light is emitted through the sample to be reflected and measured.

[0044] The parallel light is absorbed by the objective lens through the half-reflecting half-mirror lens, and the light beam absorbed by the half-reflecting half-mirror lens is evenly projected onto the reflective image to be measured through the numerical aperture that matches the detail size to be resolved in the microscope object;

[0045] The reflected light of the reflective image sample passes through a half-reflecting half-mirror and then is modulated in amplitude and phase by a metasurface to obtain a first-order two-dimensional differential operation function modulated image of the reflective image. A CMOS camera is used to collect the first-order two-dimensional differential operation function modulated image of the reflective image.

[0046] The first-order two-dimensional differential operation function modulated image of the collected reflective image to be tested is solved to obtain the light field intensity of the reflective image to be tested, and the contour information of the reflective image to be tested is obtained based on the light field intensity of the reflective image to be tested to complete edge detection.

[0047] A first-order two-dimensional differential operation metasurface edge detection imaging system, comprising:

[0048] The metasurface design and processing module is used to design and process metasurfaces with first-order two-dimensional differential operation function characteristics;

[0049] An edge detection image acquisition module is used to image the image to be tested according to the metasurface and the edge detection image model to obtain an edge detection image;

[0050] The edge detection result acquisition module is used to obtain the edge detection result.

[0051] The beneficial effects of the first-order two-dimensional differential operation metasurface edge detection imaging method and system provided by the present invention are:

[0052] 1. The metasurface edge detection imaging method and system based on first-order two-dimensional differential operation of the present invention has the advantages of easy integration, no zero-order diffraction spot, and high imaging efficiency.

[0053] 2. The present invention is based on the traditional first-order two-dimensional differential operation function imaging method, and uses a metasurface to generate a first-order two-dimensional differential operation function modulation, which not only avoids the influence of the zero-order diffraction spot, improves energy utilization and imaging efficiency, but also improves the integration and lightweight of the system. Combining the characteristics of the first-order two-dimensional differential operation function with the advantages of the metasurface, while being able to perform high-precision edge detection, it reduces the complexity of the system, making the system easier to integrate and meeting the current use requirements of edge detection systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] Figure 1 A flow chart of a metasurface edge detection and imaging method using first-order two-dimensional differential operations provided by an embodiment of the present invention;

[0056] Figure 2 A structural diagram of an edge detection image model provided by an embodiment of the present invention;

[0057] Figure 3 A structural diagram of an imaging module and an edge detection module in an edge detection image model provided by an embodiment of the present invention;

[0058] Figure 4 A unit structure diagram of a metasurface provided by an embodiment of the present invention;

[0059] Figure 5 Phase distribution and amplitude distribution diagram of the metasurface provided by an embodiment of the present invention;

[0060] Figure 6 A flow chart of the micro-nano processing of a metasurface provided by an embodiment of the present invention;

[0061] Figure 7 An electron microscope imaging result diagram of a local portion of a metasurface provided by an embodiment of the present invention;

[0062] Figure 8 A flow chart of a metasurface edge detection imaging system with first-order two-dimensional differential operation provided by an embodiment of the present invention.

[0063] In the figure, 1-fiber coupled laser, 2-collimating lens, 3-semi-reflective and semi-transparent mirror, 4-microscope objective, 5-image to be measured, 6-metasurface, 7-CMOS camera. Example

[0064] Exemplary embodiments of the present invention will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual implementation are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary from implementation to implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is only a routine task for those skilled in the art who benefit from the disclosure of the present invention.

[0065] like Figure 1 As shown, the edge detection imaging method of the first-order two-dimensional differential operation function metasurface provided by the present invention comprises the following steps:

[0066] S100, designing and processing a metasurface having first-order two-dimensional differential operation function characteristics by means of simulation;

[0067] S200, build an optical system with a metasurface as the core to perform first-order two-dimensional differential operation function modulation, image the molecules to be tested through the metasurface, and obtain edge detection images;

[0068] S300, developing edges in the edge detection image, determining the image contour, and achieving edge detection effect.

[0069] The present invention is based on the traditional first-order two-dimensional differential operation function imaging method, and uses a metasurface to generate a first-order two-dimensional differential operation function modulation, which not only avoids the influence of the zero-order diffraction spot, improves energy utilization and imaging efficiency, but also improves the integration and lightweight of the system. Combining the characteristics of the first-order two-dimensional differential operation function with the advantages of the metasurface, while being able to perform high-precision edge detection, it reduces the complexity of the system, making the system easier to integrate and meeting the current use requirements of edge detection systems.

[0070] Specifically, the step S100 includes:

[0071] S101. Optimize the material, shape, and geometric parameters of the metasurface, and use the frequency domain calculation module based on the finite element method in the electromagnetic simulation software CST to perform simulation operations. By changing the length and width of the nanocolumns, find the length and width with the maximum circular polarization transmittance within the size range suitable for processing, as the unit structure of the transmission phase.

[0072] S102. Obtain the phase distribution of the first-order two-dimensional differential operation function from the first-order two-dimensional differential operation complex amplitude expression.

[0073] S103. Generate a processing file of the edge detection metasurface according to the selected unit structure and the phase distribution of the transmission phase.

[0074] S104, using electron beam lithography combined with reactive ion beam etching to process the meta-structure surface.

[0075] The metasurface unit structure designed in step S101 is as follows: Figure 4 As shown. Sapphire crystal (Al2O3) with transmittance in the visible light band is used as the substrate, on which there are nanocolumns made of high refractive index material Si. The structure is as follows Figure 4 As shown. The period P = 400nm, the nanorod height H = 360nm, and the length and width of the nanorods are scanned to obtain the corresponding S parameter curve, which is used to analyze the cross-polarization transmittance of circularly polarized light. Finally, the structure with the best cross-polarization transmittance under the condition of 632nm incident wave is found. At this time, the nanorod length L = 350nm and the width W = 350nm.

[0076] The first-order two-dimensional differential operation function is a special light beam, whose normalized amplitude is related to the horizontal and vertical coordinates of the light beam from the central axis. As the distance between the midpoint of the light field and the central axis increases, its normalized amplitude increases accordingly; the overall phase change is spiral, which is similar to the phase distribution of an ordinary lens.

[0077]

[0078] In formula (1), F{} is the Fourier transform operation, E{-x} is the complex amplitude distribution of the metasurface, and E 像 (x) is the complex amplitude distribution of the image plane light field, E 物 (x) is the complex amplitude distribution of the light field on the object surface, j is an imaginary unit, and x is the horizontal axis coordinate of the light field centered on the optical axis. The phase and intensity of the first-order two-dimensional differential operation function can be obtained from the complex amplitude distribution of the metasurface.

[0079] Combining the selected unit structure and phase distribution, the complete metasurface is formed by periodic arrangement through FDTD algorithm simulation.

[0080] The metasurface was fabricated using electron beam lithography (EBL) combined with reactive ion etching (RIE). A single-crystal silicon epitaxial wafer with a thickness of 360 nm grown on double-sided polished sapphire was selected as the processing material. Then, the electron beam photoresist PMMAA4 was spin-coated on the substrate at a speed of 3000 revolutions per minute (RPM). Using electron beam lithography technology, at an acceleration voltage of 30 kV, a beam current of 360 pA, and a 100×100 μm 2Under the writing field condition, the corresponding superlens mask was prepared on the photoresist. The sample was then exposed to 25% tetramethylammonium hydroxide (TMAH) solution at room temperature (25°C) for 2 minutes, rinsed with deionized water for 20 seconds, and soaked in isopropyl alcohol (IPA) solution for 10 seconds, and then blown dry with nitrogen. Subsequently, the pattern was transferred to the silicon film using inductively coupled plasma reactive ion etching. First, carbon tetrafluoride (CF4) was used at 100WICP power and 100W bias power, and the gas flow rate was 45sccm for 5s to remove the surface oxide layer by dry etching. Then, hydrogen bromide gas (HBr) was used to set the gas flow rate to 100sccm, 400WICP power, and 100W bias power to etch silicon at a rate of 83nm / min. During the etching process, the substrate workbench temperature was set to 20°C and the chamber pressure was set to 10mTorr. Finally, the sample was immersed in 10% hydrofluoric acid (HF) for 15 seconds to remove the residual photoresist mask, washed with deionized water, and finally dried with nitrogen to obtain the processed metasurface. The processing flow is as follows: Figure 6 The image of the processed metasurface under an electron microscope is shown in Figure 7 shown.

[0081] The present invention provides a first-order two-dimensional differential operation metasurface edge detection imaging method and system, such as Figure 2 As shown, it includes a fiber-coupled laser (1), a collimating lens (2), an image to be measured (3), an objective lens (4), a metasurface (5) and a CMOS camera (6) arranged along the propagation direction of the light beam, corresponding to step S200.

[0082] Specifically, the step S200 includes:

[0083] S201, a fiber-coupled laser (1) arranged along the propagation direction of a light beam emits a laser with monochromaticity and coherence, which passes through a collimating lens (2) to form parallel light, and the collimated light is emitted through an image to be measured (3).

[0084] S202, the microscope objective lens (4) collects the light transmitted by the image sample to be measured, and the metasurface (5) is placed on the back focal plane of the objective lens (4), and the two form a 2f system. The light received by the objective lens (4) passes through the metasurface (5) for amplitude and phase modulation, and the image after amplitude and phase modulation is collected by the CMOS camera (6). The image of the image sample to be measured is modulated by a first-order two-dimensional differential operation function, and the contour information of the image sample to be measured is obtained on the CMOS camera to obtain edge data.

[0085] The central axes of the fiber-coupled laser (1), the collimating lens (2), the image to be measured (3), the objective lens (4), the metasurface (5) and the CMOS camera (6) arranged along the propagation direction of the light beam coincide with each other in the vertical direction.

[0086] The objective lens (4) and the metasurface (5) together form a 2f system, and the metasurface (5) is placed on the rear focal plane of the objective lens.

[0087] The wavelength of the fiber-coupled laser (1) arranged along the propagation direction of the light beam can be any wavelength in the visible light band (400nm-650nm), and the light emitted from the optical fiber passes through the collimating lens (2) to generate a collimated parallel light beam.

[0088] like Figure 3 As shown, the imaging module and the edge detection module in the edge detection image model include a fiber-coupled laser (1), a collimating lens (2), a semi-reflective mirror (3), a microscope objective (4), an image to be measured (5), a metasurface (6) and a CMOS camera (7) arranged along the propagation direction of the light beam, corresponding to the step S200.

[0089] Specifically, the step S200 includes:

[0090] S201. A fiber-coupled laser (1) arranged along a light beam propagation direction emits a monochromatic and coherent laser, which is converted into parallel light through a collimating lens (2).

[0091] S202, parallel light is absorbed by the objective lens (4) through the half-reflecting half-mirror (3), and the microscope objective lens has a numerical aperture that matches the size of the details to be resolved in the image to be measured, and can evenly project the light beam processed by the half-reflecting half-mirror onto the image to be measured (5). The light reflected by the sample of the image to be measured (5) passes through the half-reflecting half-mirror (3) and then passes through the metasurface (6), where amplitude and phase are regulated to achieve first-order two-dimensional differential operation function modulation. The rear focal plane of the microscope objective lens coincides with the metasurface, and the two form a 2f system. The image after phase modulation is collected by the CMOS camera (7).

[0092] The fiber-coupled laser (1) and the collimating lens (2) arranged along the propagation direction of the light beam are located in the same horizontal direction. The semi-reflective and semi-transparent mirror (3), the microscope objective lens (4), the image to be measured (5), the metasurface (6) and the CMOS camera (7) are located in the same vertical direction, and the central axes of the microscope objective lens (4) and the metasurface (6) in the vertical direction coincide with each other.

[0093] The microscope objective lens (4) and the metasurface (6) together form a 2f system, and the metasurface (6) is placed on the Fourier plane of the 2f system.

[0094] The wavelength of the fiber-coupled laser (1) arranged along the propagation direction of the light beam can be any wavelength in the visible light band (400nm-650nm), and the light emitted from the optical fiber passes through the collimating lens (2) to generate a collimated parallel light beam.

[0095] like Figure 8 As shown, the first-order two-dimensional differential operation metasurface edge detection imaging system comprises:

[0096] The metasurface design and processing module is used to design and process metasurfaces with first-order two-dimensional differential operation function characteristics;

[0097] An edge detection image acquisition module is used to image the image to be tested according to the metasurface and the edge detection image model to obtain an edge detection image;

[0098] The edge detection result acquisition module is used to obtain the edge detection result.

[0099] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A first-order two-dimensional differential operation metasurface edge detection imaging method, characterized in that: The steps of the first-order two-dimensional differential operation metasurface edge detection imaging method include: Step 1: Design and process a metasurface with first-order two-dimensional differential operation function characteristics; The design steps of metasurface include: Optimizing the basic unit structure parameters in the metasurface, wherein the basic unit structure is a single-crystal silicon multi-degree-of-freedom nanocolumn on a sapphire substrate; The electromagnetic simulation software GST is used to simulate the basic unit structure parameters in the optimized metasurface to obtain the designed metasurface. The processing steps of metasurface include: A single-crystal silicon epitaxial wafer grown on double-sided polished sapphire with a thickness of 360 nm was selected as the processing material, and an electron beam photoresist PMMAA4 was spin-coated on the single-crystal silicon epitaxial wafer at a speed of 3000 rpm; Using electron beam lithography technology, at an acceleration voltage of 30 kV, a beam current of 360 pA, and a 100 × 100 μm 2 Under a writing field condition of , a superlens mask is prepared on a photoresist coated on a single crystal silicon epitaxial wafer; The image to be tested was immersed in a 25% tetramethylammonium hydroxide solution at 25°C for 2 minutes, then rinsed in deionized water for 20 seconds, immersed in an isopropanol solution for 10 seconds, and dried with nitrogen gas; Using inductively coupled plasma to perform reactive ion etching, the superlens mask pattern is transferred to the silicon film of the single crystal silicon epitaxial wafer, and the single crystal silicon epitaxial wafer is etched based on the reactive ion etching technology; The etched single crystal silicon epitaxial wafer is immersed in 10% hydrofluoric acid for 15 seconds, and the hydrofluoric acid after immersion is cleaned with ionized water, and then dried with nitrogen to obtain a processed meta-structure surface; Step 2: imaging the image to be tested based on the metasurface and the edge detection image model to obtain an edge detection image; Step 3: Obtain edge detection results based on the edge detection image.

2. The first-order two-dimensional differential operation metasurface edge detection imaging method according to claim 1, characterized in that: The steps of simulating the basic unit structure parameters in the optimized metasurface include: The frequency domain calculation module of electromagnetic simulation software CST is used to perform parameter scanning on the basic unit structure of the metasurface and obtain the parameter curve. Analyzing the transmittance of circularly polarized light based on the parameter curve to obtain a basic unit structure with the highest transmittance of circularly polarized light; Based on the complex oscillation expression of the first-order two-dimensional differential operation, the phase distribution of the first-order two-dimensional differential operation function is obtained; Based on the phase distribution of the first-order two-dimensional differential operation function, the basic unit structures with the highest circularly polarized light transmittance are periodically arranged to obtain the designed metasurface; The expression of the phase distribution of the first-order two-dimensional differential operation function is: In formula (1), is the Fourier transform operation, E(-x) is the complex amplitude distribution of the metasurface, and E 像 (x) is the complex amplitude distribution of the image plane light field, E 物 (x) is the complex amplitude distribution of the light field on the object plane, j is an imaginary unit, and x is the horizontal axis coordinate of the light field centered on the optical axis.

3. The first-order two-dimensional differential operation metasurface edge detection imaging method according to claim 1, characterized in that: The steps of etching the single crystal silicon epitaxial wafer include: Using carbon tetrafluoride at 100 WICP power and 100 W bias power, the gas flow rate is 45 sccm for 5 s to remove the surface oxide layer of the single crystal silicon epitaxial wafer by dry etching; The single crystal silicon epitaxial wafer after removing the surface oxide layer was etched at a speed of 83 nm / min using hydrogen bromide gas with a gas flow rate of 100 sccm, a power of 400 WICP, and a bias power of 100 W.

4. The first-order two-dimensional differential operation metasurface edge detection imaging method according to claim 1, characterized in that: The edge detection image model in step 2 includes an illumination module and an edge detection imaging module; The lighting module comprises a transmissive lighting layer and a reflective lighting layer; The transmissive illumination module comprises a fiber-coupled laser, a collimating lens, a semi-reflecting and semi-transmissive mirror, a microscope objective lens, a metasurface and a CMOS camera arranged along a light beam propagation direction, wherein the fiber-coupled laser and the collimating lens arranged along the light beam propagation direction are located in the same horizontal direction, the semi-reflecting and semi-transmissive mirror, the microscope objective lens, the metasurface and the CMOS camera are located in the same vertical direction, and the central axes of the microscope objective lens and the metasurface in the vertical direction coincide with each other; The reflective illumination module comprises a fiber-coupled laser, a collimating lens, a half-reflecting mirror, a microscope objective lens, a metasurface and a CMOS camera arranged along a light beam propagation direction, wherein the fiber-coupled laser and the collimating lens arranged along the light beam propagation direction are located in the same horizontal direction, the half-reflecting mirror, the microscope objective lens, the metasurface and the CMOS camera are located in the same vertical direction, and the central axes of the microscope objective lens and the metasurface in the vertical direction coincide with each other; The edge detection imaging module includes a transmissive edge detection layer and a reflective edge detection layer.

5. The first-order two-dimensional differential operation metasurface edge detection imaging method according to claim 1, characterized in that: The steps of obtaining the edge detection image in step 2 include: Based on the characteristics of the imaging sample, if the image to be tested is a transmissive image to be tested, a transmissive illumination layer and a transmissive edge detection layer are placed to obtain an edge detection image; If the image to be measured is a reflective image to be measured, a reflective lighting layer and a reflective edge detection layer are placed to obtain an edge detection image.

6. The first-order two-dimensional differential operation metasurface edge detection imaging method according to claim 5, characterized in that: The steps of obtaining edge detection of a transmission image to be tested include: The fiber-coupled laser arranged along the propagation direction of the light beam emits a monochromatic and coherent laser, which is then transformed into parallel light through a collimating lens. The parallel light then exits through a transmission-type image sample to be measured. The transmission image to be tested is imaged by a microscope and a metasurface to obtain an image of the transmission image to be tested, the amplitude and phase of the emitted parallel light are controlled based on the transmission phase through the metasurface to obtain a first-order two-dimensional differential operation function modulated image of the transmission image to be tested, and the first-order two-dimensional differential operation function modulated image of the transmission image to be tested is collected using a CMOS camera; The first-order two-dimensional differential operation function modulated image of the collected transmission image to be tested is solved to obtain the light field intensity of the transmission image to be tested, and the contour information of the transmission image to be tested is obtained based on the light field intensity of the transmission image to be tested to complete edge detection.

7. The first-order two-dimensional differential operation metasurface edge detection imaging method according to claim 5, characterized in that: The steps of obtaining edge detection of a reflective image to be tested include: The fiber-coupled laser arranged along the propagation direction of the light beam emits a monochromatic and coherent laser, which is formed into parallel light through a collimating lens, and then the parallel light is emitted through the sample to be reflected and measured. The parallel light is absorbed by the objective lens through the half-reflecting half-mirror lens, and the light beam absorbed by the half-reflecting half-mirror lens is evenly projected onto the reflective image to be measured through the numerical aperture that matches the detail size to be resolved in the microscope object; The reflected light of the reflective image sample passes through a half-reflecting half-mirror and then is modulated in amplitude and phase by a metasurface to obtain a first-order two-dimensional differential operation function modulated image of the reflective image. A CMOS camera is used to collect the first-order two-dimensional differential operation function modulated image of the reflective image. The first-order two-dimensional differential operation function modulated image of the collected reflective image to be tested is solved to obtain the light field intensity of the reflective image to be tested, and the contour information of the reflective image to be tested is obtained based on the light field intensity of the reflective image to be tested to complete edge detection.

8. A first-order two-dimensional differential operation metasurface edge detection imaging system, applied to the first-order two-dimensional differential operation metasurface edge detection imaging method according to any one of claims 1 to 7, characterized in that: include: The metasurface design and processing module is used to design and process metasurfaces with first-order two-dimensional differential operation function characteristics; An edge detection image acquisition module is used to image the image to be tested according to the metasurface and the edge detection image model to obtain an edge detection image; The edge detection result acquisition module is used to obtain the edge detection result.

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