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

Abstract

The present invention provides a metasurface edge detection imaging method and system for second-order two-dimensional differential operation, wherein the method includes: simulating the unit structure and phase distribution of the metasurface based on the finite element method and the second-order two-dimensional differential operation function; preparing the metasurface based on the simulation results to obtain a metasurface with the characteristics of the second-order two-dimensional differential operation function; constructing a number of edge detection units based on the metasurface, selecting the corresponding edge detection unit based on the characteristics of the image to be measured to perform edge detection, obtain the contour information of the image to be measured, and complete edge detection. The technical solution of the present invention improves the problem that the traditional three-dimensional imaging optical system based on the spatial light modulator has zero-order higher-order diffraction and is difficult to integrate, greatly reduces the size of the component, and improves the imaging quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical microscopic imaging, and in particular relates to a metasurface edge detection imaging method and system based on second-order two-dimensional differential operations. Background Art

[0002] The second-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 second-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. Summary of the invention

[0003] The purpose of the present invention is to provide a metasurface edge detection imaging method and system with second-order two-dimensional differential operation, which solves the technical problems in the prior art that the spatial light modulator cannot simultaneously control the amplitude and phase, is large in size, and is difficult to integrate.

[0004] To achieve the above object, the present invention provides a second-order two-dimensional differential operation metasurface edge detection imaging method, comprising:

[0005] Step 1, simulating the unit structure and phase distribution of the metasurface based on the finite element method and the second-order two-dimensional differential operation function;

[0006] Step 1 specifically includes:

[0007] Step 101: using simulation software to obtain length data and width data of a metasurface with maximum circular polarization transmittance under a set size of the metasurface, and using the length data and width data as a unit structure of a transmission phase;

[0008] Step 102: Calculate the phase distribution of the transmission phase based on the second-order two-dimensional differential operation complex amplitude expression,

[0009] Step 103: generating a simulation result of a metasurface having second-order two-dimensional differential operation function characteristics based on the unit structure and phase distribution;

[0010] The expression of the second-order two-dimensional differential operation function is:

[0011]

[0012] 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, x is the horizontal axis coordinate of the light field centered on the optical axis, and y is the vertical axis coordinate of the light field centered on the optical axis.

[0013] Step 2: preparing a metasurface based on the simulation results to obtain a metasurface having second-order two-dimensional differential operation function characteristics;

[0014] Step 3: Construct several edge detection units based on the metasurface.

[0015] Step 4: Select a corresponding edge detection unit to perform edge detection based on the characteristics of the image to be tested, obtain contour information of the image to be tested, and complete edge detection.

[0016] Optionally, the preparation process of the metasurface in step 2 specifically includes:

[0017] Obtain a substrate, and perform photolithography on the substrate through a coating machine. During the photolithography process, spin-coat photoresist on the substrate, fix the photoresist by hot plate baking, and expose and develop it through an electron beam exposure lithography machine. After the exposure and development are completed, the surface oxide layer is removed by dry etching and the substrate is etched with hydrogen bromide gas. After the etching is completed, the photoresist layer is removed and washed with deionized water to complete the preparation of the meta-structure surface.

[0018] Optionally, the edge detection unit in step 3 includes a transmission edge detection unit and a reflection edge detection unit.

[0019] Optionally, the transmission-type edge detection unit includes: an illumination module, the illumination module is used to emit laser, and an image to be measured and an imaging module are sequentially arranged on the optical path of the laser;

[0020] The lighting module includes a laser and a collimating lens arranged in sequence;

[0021] The imaging module comprises a microscope objective lens, a metasurface and a camera; the collimating lens, the image to be measured, the microscope objective lens, the metasurface and the camera are sequentially arranged on the optical path of the laser emitted by the laser.

[0022] Optionally, the edge detection processing process of the transmission edge detection unit includes:

[0023] The laser is emitted by a laser, and the laser passes through a collimating lens to form parallel light, and the parallel light is emitted through the image to be measured, and the microscope objective collects the transmitted light through the image to be measured and modulates the collected transmitted light by a second-order two-dimensional differential operation function through the metasurface, and the light modulated by the metasurface is collected by a camera to obtain first modulated image data;

[0024] The first modulated image data is resolved to obtain light field intensity data of the first modulated image data, and contour information of the image to be tested is determined based on the light field intensity data to complete edge detection.

[0025] Optionally, the reflective edge detection unit includes: an illumination module, an image to be detected and an imaging module;

[0026] The imaging module and the image to be measured are located in the same vertical direction, the lighting module is used to emit laser, and the optical path of the laser emitted by the lighting module is perpendicular to the imaging module;

[0027] The lighting module includes a laser and a collimating lens arranged in sequence;

[0028] The imaging module includes a camera, a metasurface, a semi-reflective lens, and a microscope objective lens;

[0029] The camera, the metasurface, the half-reflecting half-mirror, the microscope objective lens and the image to be measured are arranged in sequence in the same vertical direction; the laser, the collimating lens and the half-reflecting half-mirror are arranged in sequence in the same horizontal direction.

[0030] Optionally, the edge detection processing process of the reflective edge detection unit includes:

[0031] The laser emits a laser, which is collimated by a collimating lens to form parallel light. The parallel light is reflected by a reflective surface of a semi-reflective and semi-transparent mirror and then passes through a microscope objective lens to reach an image to be measured to form reflected light. The microscope objective lens collects the reflected light that passes through the image to be measured and modulates the collected transmitted light by a second-order two-dimensional differential operation function through a metasurface. The light modulated by the metasurface is collected by a camera to obtain second modulated image data.

[0032] The second modulated image data is resolved to obtain light field intensity data of the second modulated image data, and contour information of the image to be tested is determined based on the light field intensity data to complete edge detection.

[0033] The second-order two-dimensional differential operation metasurface edge detection imaging system comprises:

[0034] Metasurface simulation module, used to simulate the unit structure and phase distribution of the metasurface;

[0035] A metasurface preparation module is used to prepare a metasurface with second-order two-dimensional differential operation function characteristics according to simulation results;

[0036] An edge detection unit module, used to construct a plurality of edge detection units according to the metasurface;

[0037] The edge detection imaging module is used to perform edge detection on the image to be tested by imaging the image to be tested according to the edge detection unit.

[0038] The technical effects of the present invention are:

[0039] 1. The present invention has the advantages of easy integration, no zero-order diffraction spot, and high imaging efficiency. A metasurface that generates a second-order two-dimensional differential operation function phase modulation is placed on the Fourier plane of a 2f system to replace a traditional spatial light modulator, and the image information of the sample is mapped to the Fourier plane. The edge contour information of the sample is extracted on the Fourier plane through a second-order two-dimensional differential operation form. The edge information of the sample to be measured on the imaging plane is obtained by solving the collected image contour information. The present invention is intended to solve the problems of poor imaging quality, difficulty in integration, and high cost of a spatial light modulator.

[0040] 2. The present invention introduces the concept of metasurface, which is an artificial element composed of nanostructures. It can arbitrarily control the phase, intensity and polarization response of the incident field with subwavelength resolution. The use of metasurface structures instead of traditional optical elements for imaging improves the problem 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 the imaging quality. When metasurfaces 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, which greatly reduces the cost of the entire system and increases its practicality; the application of metasurfaces is conducive to the integration and miniaturization of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments 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.

[0042] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0043] Figure 1A flow chart of a metasurface edge detection and imaging method using second-order two-dimensional differential operations provided by an embodiment of the present invention;

[0044] Figure 2 A schematic diagram of the transmission-type illumination light path structure provided by an embodiment of the present invention;

[0045] Figure 3 A schematic diagram of the reflective lighting optical path structure provided by an embodiment of the present invention;

[0046] Figure 4 A schematic diagram of the structure of a metasurface provided by an embodiment of the present invention; wherein: Figure 4 (a) is a schematic diagram of the structure of a metasurface unit in an embodiment of the present invention. Figure 4 (b) is a schematic diagram of the nanocolumn structure of the metasurface in an embodiment of the present invention;

[0047] Figure 5 The phase distribution and amplitude distribution of the metasurface provided by the embodiment of the present invention;

[0048] Figure 6 A micro-nano processing process of a metasurface provided by an embodiment of the present invention;

[0049] Figure 7 Electron microscope imaging results of a local part of the metasurface provided by an embodiment of the present invention;

[0050] Figure 8 A flow chart of a metasurface edge detection imaging system for second-order two-dimensional differential operations provided by an embodiment of the present invention;

[0051] In the figure, 1 is a fiber-coupled laser, 2 is a collimating lens, 3 is an image to be measured, 4 is a microscope objective lens, 5 is a metasurface, 6 is a CMOS camera, and 7 is a semi-reflective and semi-transparent mirror. Example

[0052] like Figure 1 - Figure 7 As shown, this embodiment provides an edge detection imaging method based on a metasurface, including: simulating the unit structure and phase distribution of the metasurface based on the finite element method and the second-order two-dimensional differential operation function; preparing the metasurface based on the simulation result to obtain a metasurface with second-order two-dimensional differential operation function characteristics; constructing a plurality of edge detection units based on the metasurface, selecting the corresponding edge detection unit based on the characteristics of the image to be measured to perform edge detection, obtaining the contour information of the image to be measured, and completing the edge detection.

[0053] A metasurface with second-order differential function characteristics is designed and processed by FDTD simulation. An edge detection optical system with the metasurface as the core for second-order two-dimensional differential operations is built, and the image to be tested is imaged on the metasurface to obtain an edge detection image. The edge contour of the input image is determined by the development in the edge detection image to achieve the edge detection effect.

[0054] The metasurface with the characteristics of second-order two-dimensional differential operation function is designed and processed by simulation means; the material, shape, geometric parameters, etc. of the metasurface are optimized, and the frequency domain calculation module based on the finite element method in the electromagnetic simulation software CST is used for simulation calculation. When the unit structure period and the height of the nanocolumn are constant, by changing the length and width of the nanocolumn, the length and width with the maximum circular polarization transmittance are found within the size range suitable for processing as the unit structure of the transmission phase. The phase distribution of the second-order two-dimensional differential operation function is obtained from the complex amplitude expression of the second-order two-dimensional differential operation. According to the selected unit structure and the phase distribution of the transmission phase, the processing file of the edge detection metasurface is generated. The metasurface is processed by electron beam lithography combined with reactive ion beam etching.

[0055] The designed metasurface unit structure is as follows Figure 4 As shown in (a), a sapphire crystal (Al2O3) with good transmittance in the visible light band is used as a substrate, on which there are nanocolumns made of high refractive index material Si. The structure is as follows Figure 4 As shown in (b), the period P = 400nm and the nanorod height H = 360nm are selected, and the length and width of the nanorod are scanned to obtain the corresponding S parameter curve, which is used to analyze the cross-polarization transmittance of circularly polarized light. Finally, a structure with a higher 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.

[0056] The feasible preparation process of the meta-structured surface specifically includes: obtaining a substrate, performing photolithography on the substrate through a photolithography machine, during the photolithography process, spin-coating photoresist on the substrate, hot plate baking to fix the photoresist and performing exposure and development through an electron beam exposure lithography machine, after the exposure and development are completed, the surface oxide layer is removed by dry etching and the substrate is etched with hydrogen bromide gas, after the etching is completed, the photoresist layer is removed and washed with deionized water to complete the preparation of the meta-structured surface.

[0057] The second-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. Within a certain range, 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.

[0058]

[0059] 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, and x is the horizontal axis coordinate of the light field centered on the optical axis.

[0060] Combined with the selected unit structure and phase distribution, the FDTD algorithm is used to simulate and periodically arrange the complete metasurface. The metasurface is made using electron beam lithography (EBL) combined with reactive ion etching (RIE): a single-crystal silicon epitaxial wafer with a thickness of 360nm grown on double-sided polished sapphire is selected as the processing material. Then the electron beam photoresist PMMAA4 is spin-coated on the substrate at a speed of 3000 revolutions per minute (RPM). Using electron beam lithography technology, at an acceleration voltage of 30kV, a beam current of 360pA, and a 100×100μm 2 Under the writing field condition of , 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, with a gas flow rate of 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, the etching power to 400WICP power, and the bias power to 100W, and the silicon was etched 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.

[0061] An optical system with a metasurface as the core for second-order two-dimensional differential operation function modulation is built, and the molecules to be detected are imaged through the metasurface to obtain edge detection images; this embodiment uses the metasurface to generate second-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 second-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. This embodiment provides an edge detection imaging optical system, including an illumination module and an imaging module. According to the different characteristics of the sample, the optical path can be divided into a transmission illumination optical path and a reflection illumination optical path.

[0062] Transmitted illumination light path: Figure 2 As shown, it includes: an illumination module, the illumination module is used to emit laser, and the image to be measured and the imaging module are arranged in sequence on the optical path of the laser; the illumination module includes a laser and a collimating lens arranged in sequence; the imaging module includes a microscope objective lens, a metasurface and a camera; the collimating lens, the image to be measured, the microscope objective lens, the metasurface and the camera are arranged in sequence on the optical path of the laser emitted by the laser.

[0063] The transmission illumination optical path includes a fiber-coupled laser 1, a collimating lens 2, an image to be measured 3, a microscope objective 4, a metasurface 5 and a CMOS camera 6 arranged along the propagation direction of the light beam. The central axes of the fiber-coupled laser 1, the collimating lens 2, the image to be measured 3, the microscope objective 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; the microscope objective 4 and the metasurface 5 together constitute a 2f system, and the metasurface 5 is placed on the back focal plane of the microscope objective; 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.

[0064] The edge detection imaging method of the transmission illumination light path includes: performing a second-order two-dimensional differential operation function modulation on the image of the image sample to be measured, obtaining the contour information of the image sample to be measured on the CMOS camera, and acquiring the edge data. The fiber-coupled laser 1 arranged along the propagation direction of the light beam emits a laser with monochromaticity and coherence, which passes through the collimating lens 2 to form parallel light, and the collimated light is emitted through the image to be measured 3. The microscope objective 4 collects the light transmitted through the image sample to be measured, and the metasurface 5 is placed on the back focal plane of the microscope objective 4. The two form a 2f system. The light received by the microscope objective 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 collected second-order two-dimensional differential operation function modulated image is solved, and the contour information of the image to be measured is determined by the light field intensity displayed in the image, and the edge detection is completed.

[0065] Reflective lighting light path: Figure 3 As shown, it includes: an illumination module, an image to be measured and an imaging module; the imaging module and the image to be measured are located in the same vertical direction, the illumination module is used to emit laser, and the laser light path emitted by the illumination module is perpendicular to the imaging module; the illumination module includes a laser and a collimating lens arranged in sequence; the imaging module includes a camera, a metasurface, a semi-reflective semi-mirror and a microscope objective lens; the camera, the metasurface, the semi-reflective semi-mirror, the microscope objective lens and the image to be measured are arranged in sequence in the same vertical direction; the laser, the collimating lens and the semi-reflective semi-mirror are arranged in sequence in the same horizontal direction.

[0066] The reflective illumination optical path includes a fiber-coupled laser 1, a collimating lens 2, a semi-reflecting semi-mirror 7, a microscope objective 4, an image to be measured 3, a metasurface 5 and a CMOS camera 6 arranged along the propagation direction of the light beam. 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-reflecting semi-mirror 7, the microscope objective 4, the image to be measured 3, the metasurface 5 and the CMOS camera 6 are located in the same vertical direction, and the central axes of the microscope objective 4 and the metasurface 5 in the vertical direction coincide with each other; the microscope objective 4 and the metasurface 5 together constitute a 2f system, and the metasurface 5 is placed on the Fourier plane of the 2f system; 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.

[0067] The edge detection imaging method of the reflective illumination optical path includes: a fiber-coupled laser 1 arranged along the propagation direction of the light beam emits a laser with strong monochromaticity and coherence, and forms parallel light through a collimating lens 2. The parallel light is absorbed by a microscope 4 through a semi-reflective and semi-mirror lens 7. The microscope has a numerical aperture that matches the detail size to be resolved of the image to be measured, and can evenly project the light beam processed by the semi-reflective and semi-mirror lens onto the image to be measured 3. The light reflected by the image to be measured 3 passes through the semi-reflective and semi-mirror lens 7 and then passes through a metasurface 5 for amplitude and phase regulation to achieve second-order two-dimensional differential operation function modulation. The rear focal plane of the microscope coincides with the metasurface, and the two form a 2f system. The image after phase modulation is collected by a CMOS camera 6. The collected second-order two-dimensional differential operation function modulated image is solved, and the contour information of the image to be measured is determined by the light field intensity displayed in the image to complete edge detection. Based on the edge development in the edge detection image, the image contour is determined to achieve the edge detection effect.

[0068] like Figure 8 As shown, the second-order two-dimensional differential operation metasurface edge detection imaging system comprises:

[0069] Metasurface simulation module, used to simulate the unit structure and phase distribution of the metasurface;

[0070] A metasurface preparation module is used to prepare a metasurface with second-order two-dimensional differential operation function characteristics according to simulation results;

[0071] An edge detection unit module, used to construct a plurality of edge detection units according to the metasurface;

[0072] The edge detection imaging module is used to perform edge detection on the image to be tested by imaging the image to be tested according to the edge detection unit.

[0073] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A second-order two-dimensional differential operation metasurface edge detection imaging method, characterized in that: The steps of the second-order two-dimensional differential operation metasurface edge detection imaging method include: Step 1, simulating the unit structure and phase distribution of the metasurface based on the finite element method and the second-order two-dimensional differential operation function; Step 1 specifically includes: step 101, using simulation software to obtain length data and width data of a metasurface with maximum circular polarization transmittance under a set size of the metasurface, and using the length data and width data as a unit structure of a transmission phase; Step 102, calculating the phase distribution of the transmission phase based on the second-order two-dimensional differential operation complex amplitude expression; Step 103: generating a simulation result of a metasurface having second-order two-dimensional differential operation function characteristics based on the unit structure and phase distribution; Among them, the expression of the second-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, x is the horizontal axis coordinate of the light field centered on the optical axis, and y is the vertical axis coordinate of the light field centered on the optical axis; Step 2: preparing a metasurface based on the simulation results to obtain a metasurface having second-order two-dimensional differential operation function characteristics; Step 3: constructing a plurality of edge detection units based on the metasurface; Step 4: Select a corresponding edge detection unit to perform edge detection based on the characteristics of the image to be tested, obtain contour information of the image to be tested, and complete edge detection.

2. The second-order two-dimensional differential operation metasurface edge detection imaging method according to claim 1, characterized in that: The preparation process of the metasurface in step 2 includes: Obtain a substrate, and perform photolithography on the substrate through a coating machine. During the photolithography process, spin-coat photoresist on the substrate, fix the photoresist by hot plate baking, and expose and develop it through an electron beam exposure lithography machine. After the exposure and development are completed, the surface oxide layer is removed by dry etching and the substrate is etched with hydrogen bromide gas. After the etching is completed, the photoresist layer is removed and washed with deionized water to complete the preparation of the meta-structure surface.

3. The metasurface edge detection imaging method of second-order two-dimensional differential operation according to claim 1 is characterized in that: In step 3, the edge detection unit includes a transmission edge detection unit and a reflection edge detection unit.

4. The metasurface edge detection imaging method of second-order two-dimensional differential operation according to claim 3 is characterized in that: The transmission-type edge detection unit comprises: an illumination module, the illumination module is used to emit laser, and an image to be measured and an imaging module are sequentially arranged on the optical path of the laser; The lighting module includes a laser and a collimating lens arranged in sequence; The imaging module comprises a microscope objective lens, a metasurface and a camera; the collimating lens, the image to be measured, the microscope objective lens, the metasurface and the camera are sequentially arranged on the optical path of the laser emitted by the laser.

5. The metasurface edge detection imaging method of second-order two-dimensional differential operation according to claim 4 is characterized in that: The edge detection processing process of the transmission edge detection unit includes: The laser is emitted by a laser, and the laser passes through the collimating lens to form parallel light, and the parallel light is emitted through the image to be measured, and the microscope objective collects the transmitted light through the image to be measured and modulates the collected transmitted light by a second-order two-dimensional differential operation function through the metasurface, and the light modulated by the metasurface is collected by the camera to obtain first modulated image data; The first modulated image data is resolved to obtain light field intensity data of the first modulated image data, and contour information of the image to be tested is determined based on the light field intensity data to complete edge detection.

6. The metasurface edge detection imaging method of second-order two-dimensional differential operation according to claim 3 is characterized in that: The reflective edge detection unit comprises: an illumination module, an image to be detected and an imaging module; The imaging module and the image to be measured are located in the same vertical direction, the lighting module is used to emit laser, and the optical path of the laser emitted by the lighting module is perpendicular to the imaging module; The lighting module includes a laser and a collimating lens arranged in sequence; The imaging module includes a camera, a metasurface, a semi-reflective and semi-mirror lens, and a microscope objective lens; The camera, the metasurface, the half-reflecting half-mirror, the microscope objective lens and the image to be measured are arranged in sequence in the same vertical direction; the laser, the collimating lens and the half-reflecting half-mirror are arranged in sequence in the same horizontal direction.

7. The second-order two-dimensional differential operation metasurface edge detection imaging method according to claim 6, characterized in that: The edge detection processing process of the reflective edge detection unit includes: The laser emits a laser, and the laser passes through the collimating lens to form parallel light, and the parallel light is reflected by the reflecting surface of the semi-reflective and semi-transmissive mirror and passes through the microscope objective lens to reach the image to be measured to form reflected light, and the microscope objective lens collects the reflected light passing through the image to be measured and modulates the collected transmitted light by a second-order two-dimensional differential operation function through the metasurface, and collects the light modulated by the metasurface through the camera to obtain second modulated image data; The second modulated image data is resolved to obtain light field intensity data of the second modulated image data, and contour information of the image to be tested is determined based on the light field intensity data to complete edge detection.

8. A second-order two-dimensional differential operation metasurface edge detection imaging system, applied to the second-order two-dimensional differential operation metasurface edge detection imaging method according to any one of claims 1 to 7, characterized in that: include: Metasurface simulation module, used to simulate the unit structure and phase distribution of the metasurface; A metasurface preparation module is used to prepare a metasurface with second-order two-dimensional differential operation function characteristics according to simulation results; An edge detection unit module, used to construct a plurality of edge detection units according to the metasurface; The edge detection imaging module is used to perform edge detection on the image to be tested by imaging the image to be tested according to the edge detection unit.

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