A complex amplitude imaging method and system based on an aperture multiplexing marlith superstructure surface

Abstract

The application relates to a complex-amplitude imaging method and system based on an aperture multiplexing Malus superstructure surface, and relates to a complex-amplitude imaging method and system. In order to solve the technical bottleneck problem of existing superstructure surfaces in amplitude regulation and aperture multiplexing, the application comprises the following steps: step 1, based on Malus theorem, a superstructure surface unit structure with polarization selection characteristics is designed and optimized by using simulation means, and a polarization multiplexing aperture modulation superstructure surface is constructed; step 2, a superstructure surface sample is prepared through a Wiener processing technology of electron beam lithography combined with reactive ion beam etching; step 3, a polarization regulation microscopic imaging optical system with the superstructure surface as the core is built; and step 4, differential phase contrast algorithm is used to process phase information, amplitude information of bright field imaging and quantitative phase information are fused, and finally complex-amplitude microscopic imaging is realized. The application belongs to the technical field of optical imaging and superstructure surface square regulation.

Description

Technical Field

[0001] This invention relates to a complex amplitude imaging method and system, belonging to the field of optical imaging and metasurface light field manipulation technology. Background Technology

[0002] In traditional optical imaging, the acquisition of complex amplitude information typically relies on interferometry or diffractive optical elements. These methods often require complex optical path systems and precise mechanical adjustment devices. Especially in microscopic imaging applications, existing bright-field imaging techniques can usually only acquire amplitude information of the sample, while the acquisition of phase information requires the introduction of additional phase contrast devices or interferometric optical paths, which not only increases system complexity but also reduces system stability and imaging throughput.

[0003] For target samples dominated by weak absorption, weak scattering, or phase modulation, their main optical information is usually manifested as phase changes rather than amplitude changes. Examples include biological tissue samples, cell samples, transparent section samples, and material microstructure samples. Traditional imaging methods struggle to effectively acquire complete complex amplitude information for such samples, while existing complex amplitude acquisition methods based on interference or phase contrast principles suffer from system complexity, weak disturbance resistance, and difficulty in achieving high-throughput imaging. Therefore, a novel optical imaging technology capable of achieving high-precision complex amplitude acquisition is urgently needed.

[0004] In recent years, metasurfaces have provided a novel technological approach for optical field manipulation due to their unique subwavelength structural characteristics. However, metasurfaces designed based on traditional Jones matrices are limited by unitarity conditions, making it difficult to achieve independent amplitude control across multiple channels, which severely restricts their application potential in complex amplitude imaging.

[0005] In aperture modulation technology, existing microscopic imaging systems mainly employ mechanical apertures or digital micromirror devices to achieve aperture adjustment. These methods suffer from inherent drawbacks such as slow response speed and large size. Although recent studies have attempted to utilize metasurfaces to achieve polarization-dependent aperture modulation, most of these schemes can only achieve simple binary switching functions and cannot meet the requirements of complex amplitude imaging for multi-channel, high-precision optical field control. Especially in fields such as biomedical detection and materials characterization, there is an urgent need for a novel optical imaging technology that can simultaneously achieve high-resolution amplitude imaging and quantitative phase measurement. This requires overcoming the technical bottlenecks of existing metasurfaces in amplitude control and aperture reuse. Summary of the Invention

[0006] To address the technical bottlenecks in amplitude control and aperture reuse of existing metasurfaces, this invention proposes a complex amplitude imaging method and system based on an aperture reused Malusian metasurface.

[0007] The technical solution adopted by the present invention to solve the above problems is as follows: The steps of the complex amplitude imaging method based on aperture-multiplexed Malus metasurfaces of the present invention include: Step 1: Based on Malus' theorem, design and optimize the metasurface unit structure with polarization selectivity using simulation methods to construct a polarization-multiplexed aperture modulation metasurface. Step 2: Prepare metasurface samples using a micro / nano fabrication process combining electron beam lithography and reactive ion beam etching; Step 3: Construct a polarization-controlled microscopic imaging optical system with metasurface as the core, and realize two working modes, bright-field amplitude imaging and quantitative phase imaging, by controlling the polarization state. Step 4: The phase information is processed using the differential phase contrast algorithm, and the amplitude information of bright field imaging is fused with the quantitative phase information to finally realize complex amplitude microscopy.

[0008] Furthermore, in step 1, Malus's theorem indirectly modulates the amplitude of light by introducing the polarization state of light; when the initial intensity is When linearly polarized light passes through a polarizer, the intensity of the transmitted light, neglecting absorption, can be expressed as: ,in It is the angle between the polarization direction of the incident linearly polarized light and the polarization direction of the linear polarizer; the Jones matrix of the anisotropic nanopillar structure is represented as: , The diagonal elements 1 and 0 represent the complex transmission coefficients when light propagates along the long and short axes of the nanopillar, respectively; in this case, the anisotropic nanopillar structure can be considered as an ideal polarizer. The in-plane orientation angle is... θ The nanopillar Jones matrix is ​​represented as: , in It is a rotation matrix; The intensity through the polarizer is I The Jones matrix of the output light after the polarized light passes through the anisotropic nanostructure and analyzer is expressed as: , in, and These represent the polarization directions of the polarizer and the analyzer, respectively. When the incident light intensity Given the polarization directions of the polarizer and analyzer, an anisotropic nanostructure, acting as an ideal polarizer, can be used for continuous intensity modulation; when the angle between the polarization directions of the polarizer and analyzer is π / 4 (i.e., ... When ), the output light intensity is expressed as: , When the nanostructure rotates between 0 and π, two directions exhibit zero transmittance, and the other two directions exhibit equal transmittance; the angular interval between the four directions is π / 4; this property can be used to design unit structures with transmittance of 0 and 1 under different polarization states, thereby realizing differential phase contrast imaging with asymmetric aperture illumination. When the polarization directions of the polarizer and the analyzer are perpendicular, the output light intensity is expressed as: , There exists a set of unit structures with rotation angles spaced at π / 4, where the four nanopillars have equal transmittance under cross-polarization conditions; this property can be used to design full-aperture metasurfaces for bright-field imaging.

[0009] Furthermore, in step 3, quantitative phase imaging adopts the differential phase contrast imaging principle. By polarization-controlled Malus metasurface to generate asymmetric illumination, the phase information of the sample is converted into intensity information. The differential phase contrast information of the sample is processed by deconvolution algorithm to achieve low-noise and high-precision quantitative phase reconstruction results.

[0010] The complex amplitude imaging system based on an aperture-multiplexed Malus metasurface described in this invention includes an optical fiber coupled LED. A collimating lens is located to the right of the optical fiber coupled LED. To the right of the collimating lens are a first focusing lens and a second focusing lens, arranged sequentially. A filter pinhole is located between the first focusing lens and the second focusing lens. A polarizer is located to the right of the second focusing lens. To the right of the polarizer are a converging lens and a microscope objective, arranged sequentially. A sample stage is located between the converging lens and the microscope objective. A plane mirror is located to the right of the microscope objective. A tube mirror is located below the plane mirror. Below the tube mirror are a first Fourier lens, a metasurface, an analyzer, and a second Fourier lens, arranged sequentially. A CMOS camera is located below the second Fourier lens.

[0011] Furthermore, the fiber-coupled LED, collimating lens, focusing lens one, filter pinhole, focusing lens two, polarizer, converging lens, sample stage, and microscope objective are all located in the same horizontal direction. The endoscope, Fourier lens 1, metasurface, analyzer, Fourier lens 2, and CMOS camera are located in the same vertical direction, and the central axes of the endoscope, Fourier lens 1, metasurface, analyzer, and Fourier lens 2 coincide in the vertical direction.

[0012] Furthermore, the imaging system is a transmission-type complex vibration imaging system, and its imaging process is as follows: Step a: The fiber-coupled LEDs arranged along the beam propagation direction emit incoherent light with strong monochromaticity. After passing through the collimating lens and the Kohler illumination system, parallel light with uniform illumination effect is formed. The collimated light is polarized by the polarizer to generate linearly polarized light with a specific polarization direction, and then focused on the sample mounted on the sample stage by the converging lens. Step b: Image the sample using a microscope objective and a tube lens. The back focal plane of the tube lens coincides with the front focal plane of Fourier lens 1, and the back focal plane of Fourier lens 1 coincides with the front focal plane of Fourier lens 2. Fourier lens 1 and Fourier lens 2 have the same focal length and aperture, forming a 4f system. A metasurface capable of producing different aperture modulations is placed on the back focal plane of Fourier lens 1, which is also the front focal plane of Fourier lens 2. The analyzer is placed behind the metasurface. The aperture-modulated image of the sample is collected by a CMOS camera. Step c: By changing the polarization states of the polarizer and analyzer, full-aperture modulation or different half-aperture modulations are generated; the amplitude information of the sample is obtained through full-aperture modulation, and the phase information of the sample is obtained by deconvolution of the results of different half-aperture modulations. The two are combined to obtain the complex amplitude information of the sample.

[0013] The complex amplitude imaging system based on an aperture-multiplexed Malus metasurface described in this invention includes an optical fiber coupled LED. A collimating lens is located to the right of the optical fiber coupled LED. To the right of the collimating lens are a first focusing lens and a second focusing lens, arranged sequentially. A filter pinhole is located between the first focusing lens and the second focusing lens. To the right of the second focusing lens is a polarizer. To the right of the polarizer is a converging lens. To the right of the converging lens is a semi-reflective lens. Above the semi-reflective lens is a microscope objective. Above the microscope objective is a sample stage. Below the semi-reflective lens is a tube mirror. Below the tube mirror are, in sequence, a first Fourier lens, the metasurface, an analyzer, and a second Fourier lens. Below the second Fourier lens is a CMOS camera.

[0014] Furthermore, the fiber-coupled LED, collimating lens, focusing lens one, filter pinhole, focusing lens two, polarizer, and converging lens are located in the same horizontal direction; The semi-reflective mirror, microscope objective, sample stage, tube mirror, Fourier lens 1, metasurface, analyzer, Fourier lens 2, and CMOS camera are located in the same vertical direction, and the central axes of the microscope objective, sample stage, tube mirror, Fourier lens 1, metasurface, analyzer, and Fourier lens 2 coincide in the vertical direction.

[0015] Furthermore, the imaging system is a reflective complex vibration imaging system, and its imaging process is as follows: Step a: The fiber-coupled LEDs arranged along the beam propagation direction emit incoherent light with strong monochromaticity. After passing through the collimating lens and the Kohler illumination system, parallel light with uniform illumination effect is formed. The collimated light is converted into linearly polarized light with a specific polarization direction by the polarizer and then converged on the back focal plane of the microscope objective by the converging lens. The microscope objective has a numerical aperture that matches the detail size of the sample to be resolved on the sample stage, which can uniformly project the beam processed by the half-reflective half-lens onto the sample to be inspected. Step b: The microscope objective collects the reflected light from the sample under test, which is then focused by the tube lens after passing through a semi-reflective lens. The back focal plane of the tube lens coincides with the front focal plane of Fourier lens one, and the back focal plane of Fourier lens one coincides with the front focal plane of Fourier lens two. Fourier lens one and Fourier lens two have the same focal length and aperture, forming a 4f system. A metasurface capable of generating different aperture modulations is placed on the back focal plane of Fourier lens one, which is also the front focal plane of Fourier lens two. The analyzer is placed after the metasurface, and the image of the sample after aperture modulation is collected by the CMOS camera. Step c: By changing the polarization states of the polarizer and analyzer, full-aperture modulation or different half-aperture modulations are generated; the amplitude information of the sample is obtained through full-aperture modulation, and the phase information of the sample is obtained by deconvolution of the results of different half-aperture modulations. The two are combined to obtain the complex amplitude information of the sample.

[0016] The beneficial effects of this invention are as follows: This invention, based on an aperture-multiplexed Malusian metasurface, constructs a complex amplitude imaging method and system, possessing multiple technical advantages. This method overcomes the unitarity limitation of traditional Jones matrices, achieving amplitude modulation of five independent channels through the Malusian metasurface, thus enhancing the information dimension and degree of freedom in metasurface amplitude modulation. This system utilizes polarization state switching to achieve dynamic aperture modulation without mechanically moving parts, integrating full-aperture bright-field imaging and asymmetric illumination quantitative phase imaging dual modes on a single compact platform, achieving high-precision complex amplitude imaging. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method described in this invention; Figure 2 This is a schematic diagram of a transmission complex amplitude imaging method and system based on aperture-multiplexed Malus metasurfaces; Figure 3 This is a schematic diagram of a reflective complex amplitude imaging method and system based on aperture-multiplexed Malus metasurfaces; Figure 4 This is a schematic diagram of the unit structure of the metasurface in this invention; Figure 5 The transmittance and reflectance of the metasurface unit structure in the present invention in the visible light band; Figure 6 This is a schematic diagram showing the overall imaging results of the metasurface under an optical microscope and the local imaging results under an electron microscope in this invention. Figure 7 The amplitude and phase images are obtained by performing complex amplitude imaging on transparent mouse colon tissue sections using the present invention; Figure 2In the diagram, 1-fiber coupled LED, 2-collimating lens, 3-focusing lens one, 4-filter pinhole, 5-focusing lens two, 6-polarizer, 7-converging lens, 8-sample stage, 9-microscope objective, 10-plane mirror, 11-tube mirror, 12-Fourier lens one, 13-metasurface, 14-analyzer, 15-Fourier lens two, 16-CMOS camera; Figure 3 In the diagram, 1-fiber coupled LED, 2-collimating lens, 3-focusing lens one, 4-filter pinhole, 5-focusing lens two, 6-polarizer, 7-converging lens, 8-semi-reflective lens, 9-microscope objective, 10-sample stage, 11-tube lens, 12-Fourier lens one, 13-meta-surface, 14-analyzer, 15-Fourier lens two, 16-CMOS camera. Detailed Implementation

[0018] Specific implementation method one: as follows Figure 1 As shown, the steps of the complex amplitude imaging method based on an aperture-multiplexed Malus metasurface described in this embodiment include: Step 1: Based on Malus' theorem, design and optimize the metasurface unit structure with polarization selectivity using simulation methods to construct a polarization-multiplexed aperture modulation metasurface. Malus's theorem indirectly modulates the amplitude of light by introducing the polarization state of light. When the initial intensity is... When linearly polarized light passes through a polarizer, the intensity of the transmitted light, neglecting absorption, can be expressed as: ,in It is the angle between the polarization direction of the incident linearly polarized light and the polarization direction of the linear polarizer. The Jones matrix of an anisotropic nanopillar structure can be represented as: , The diagonal elements 1 and 0 represent the complex transmission coefficients as light propagates along the long and short axes of the nanopillar, respectively. In this case, the anisotropic nanopillar structure can be considered an ideal polarizer. The in-plane orientation angle is... θ The nanopillar Jones matrix is ​​represented as: , in It is a rotation matrix.

[0019] The intensity through the polarizer is I After the polarized light passes through the anisotropic nanostructure and analyzer, the Jones matrix of the output light can be expressed as: , in and These represent the polarization directions of the polarizer and the analyzer, respectively.

[0020] When the incident light intensity Given the polarization directions of the polarizer and analyzer, an anisotropic nanostructure, acting as an ideal polarizer, can be used for continuous intensity modulation. When the angle between the polarization directions of the polarizer and analyzer is π / 4 (i.e., ... When ), the output light intensity can be expressed as: .

[0021] When the nanostructure rotates between 0 and π, two directions exhibit zero transmittance, while the other two directions exhibit equal transmittance. Notably, the angular interval between these four directions is π / 4. This property can be used to design unit structures with transmittance of 0 and 1 under different polarization states, thereby enabling differential phase-contrast imaging with asymmetric aperture illumination.

[0022] When the polarization directions of the polarizer and the analyzer are perpendicular, the output light intensity can be expressed as: .

[0023] There exists a set of unit structures with rotation angles spaced at π / 4, where the four nanopillars exhibit equal transmittance under cross-polarization conditions. This property can be used to design full-aperture metasurfaces for bright-field imaging; Step 2: Prepare metasurface samples using a micro / nano fabrication process combining electron beam lithography and reactive ion beam etching; Step 3: Construct a polarization-controlled microscopic imaging optical system with metasurface as the core, and realize two working modes, bright-field amplitude imaging and quantitative phase imaging, by controlling the polarization state. Quantitative phase imaging employs the differential phase contrast imaging principle. By polarization-controlled Malus metasurface generating asymmetric illumination, the phase information of the sample is converted into intensity information. The differential phase contrast information of the sample is then processed by a deconvolution algorithm to achieve low-noise and high-precision quantitative phase reconstruction results. Step 4: The phase information is processed using the differential phase contrast algorithm, and the amplitude information of bright field imaging is fused with the quantitative phase information to finally realize complex amplitude microscopy.

[0024] In this embodiment, the basic unit structure of the transmissive Malusian metasurface consists of a substrate and nanopillars. The substrate and nanopillar materials are polarization-insensitive, high-transmittance, and compatible with semiconductor processing technologies. The substrate materials include, but are not limited to, sapphire (Al2O3) and fused silica (SiO2), and the nanopillar materials include, but are not limited to, amorphous silicon (α-Si), single-crystal silicon (c-Si), and silicon nitride (SiN). xGallium nitride (GaN) was used. Electromagnetic simulation software was used to scan the length and width of the nanopillars to obtain the corresponding S-parameter curves, which were then used to select a suitable unit structure for a transmissive nanopolarizer. The nanopillar structure is an asymmetric unit structure with anisotropy; specifically, the transmittance along the long axis is close to zero, while the transmittance along the short axis is close to 100%.

[0025] In some embodiments, the entire circular aperture is divided into four identical regions. The unit structures of the metasurface have identical geometric dimensions. By assigning different rotation angles to the unit structures in each quarter aperture, the transmittance of these regions under different polarization states can be represented by binary values ​​(0 and 1) by utilizing the properties of nanopolarizers. By controlling the polarization state of light, the metasurface can achieve independent control of the light field and efficiently switch between the full aperture and the four half apertures.

[0026] In this design, the Malusian metasurface is placed on the Fourier plane of a 4f system composed of two Fourier lenses. A phase gradient image is generated at the back focal plane of the second Fourier lens after manipulation. Quantitative phase information is obtained by single-step deconvolution of the intensity distributions detected under different illumination apertures. Under weak phase approximation conditions, the complex amplitude distribution of the sample can be expressed as: , in and Let represent the absorption coefficient and phase, respectively. The light carrying sample information undergoes a Fourier transform through a Fourier lens. The aperture modulation function generated by the metasurface on the Fourier plane can be expressed as: After the inverse Fourier transform of the second Fourier lens, a phase gradient image is formed on the back focal plane, i.e., the image plane, of the second Fourier lens. Like a plane coordinate system Representation. Phase transfer function under single asymmetric aperture illumination conditions. It can be represented as: , in The intensity distribution of an asymmetric, incoherent light source.

[0027] Under complementary aperture illumination, the phase transfer function of differential phase-contrast imaging is expressed as: , in For asymmetric illumination, the phase transfer function is... This represents the differential distribution of illumination intensity at the half-aperture in this direction. Based on this, the Tikhonov regularization criterion is applied, and the quantitative phase distribution of the sample is obtained by deconvolving the phase contrast image spectrum with the phase transfer function: , in Represents the conjugate of the phase transfer function on different axes. Regularization parameter. It is used to suppress reconstruction artifacts caused by excessive amplification of minute values ​​of the phase transfer function during deconvolution.

[0028] Specific implementation method two: such as Figure 2 As shown, the complex amplitude imaging system based on an aperture-multiplexed Malus metasurface described in this embodiment includes an optical fiber coupled LED1. A collimating lens 2 is provided on the right side of the optical fiber coupled LED1. A focusing lens 3 and a focusing lens 5 are sequentially provided on the right side of the collimating lens 2. A filter pinhole 4 is provided between the focusing lens 3 and the focusing lens 5. A polarizer 6 is provided on the right side of the focusing lens 5. A converging lens 7 and a microscope objective 9 are sequentially provided on the right side of the polarizer 6. A sample stage 8 is provided between the converging lens 7 and the microscope objective 9. A plane mirror 10 is provided on the right side of the microscope objective 9. A tube mirror 11 is provided below the plane mirror 10. A Fourier lens 12, a metasurface 13, an analyzer 14, and a Fourier lens 15 are sequentially provided below the tube mirror 11. A CMOS camera 16 is provided below the Fourier lens 15.

[0029] Among them, fiber-coupled LED1, collimating lens2, focusing lens one3, filtering pinhole4, focusing lens two5, polarizer6, converging lens7, sample stage8, and microscope objective9 are located in the same horizontal direction. The tube lens 11, Fourier lens 12, metasurface 13, analyzer 14, Fourier lens 2 15 and CMOS camera 16 are located in the same vertical direction, and the central axes of the tube lens 11, Fourier lens 12, metasurface 13, analyzer 14 and Fourier lens 2 15 in the vertical direction coincide.

[0030] The imaging system described in this embodiment is a transmission complex vibration imaging system, and its imaging process is as follows: Step a: The fiber-coupled LED1, arranged along the beam propagation direction, emits incoherent light with strong monochromaticity. After passing through the collimating lens 2 and the Kohler illumination system, it forms parallel light with uniform illumination effect. The collimated light passes through the polarizer 6 to generate linearly polarized light with a specific polarization direction, and is focused on the sample mounted on the sample stage 8 by the converging lens 7. Step b: The sample is imaged using the microscope objective 9 and the tube lens 11. The back focal plane of the tube lens 11 coincides with the front focal plane of Fourier lens 12, and the back focal plane of Fourier lens 12 coincides with the front focal plane of Fourier lens 15. Fourier lens 12 and Fourier lens 15 have the same focal length and aperture, forming a 4f system. A metasurface capable of generating different aperture modulations is placed on the back focal plane of Fourier lens 12, which is also the front focal plane of Fourier lens 15. The analyzer 14 is placed behind the metasurface 13. The aperture-modulated image of the sample is collected by the CMOS camera 16. Step c: By changing the polarization state of polarizer 6 and analyzer 14, full aperture modulation or different half aperture modulations are generated; the amplitude information of the sample is obtained through full aperture modulation, and the phase information of the sample is obtained by deconvolution of the results of different half aperture modulations. The two are combined to obtain the complex amplitude information of the sample.

[0031] Specific implementation method three: such as Figure 3 As shown, the complex amplitude imaging system based on an aperture-multiplexed Malus metasurface described in this embodiment includes an optical fiber coupled LED1. A collimating lens 2 is provided on the right side of the optical fiber coupled LED1. A focusing lens 3 and a focusing lens 5 are sequentially provided on the right side of the collimating lens 2. A filter pinhole 4 is provided between the focusing lens 3 and the focusing lens 5. A polarizer 6 is provided on the right side of the focusing lens 5. A converging lens 7 is provided on the right side of the polarizer 6. A semi-reflective lens 8 is provided on the right side of the converging lens 7. A microscope objective 9 is provided above the semi-reflective lens 8. A sample stage 10 is provided above the microscope objective 9. A tube lens 11 is provided below the semi-reflective lens 8. A Fourier lens 12, a metasurface 13, an analyzer 14, and a Fourier lens 15 are sequentially provided below the tube lens 11. A CMOS camera 16 is provided below the Fourier lens 15.

[0032] Among them, fiber-coupled LED1, collimating lens2, focusing lens one 3, filter pinhole 4, focusing lens two 5, polarizer 6, and converging lens 7 are located in the same horizontal direction. The semi-reflective mirror 8, microscope objective 9, sample stage 10, tube lens 11, Fourier lens 12, metasurface 13, analyzer 14, Fourier lens 2 15, and CMOS camera 16 are located in the same vertical direction, and the central axes of the microscope objective 9, sample stage 10, tube lens 11, Fourier lens 12, metasurface 13, analyzer 14, and Fourier lens 2 15 in the vertical direction coincide.

[0033] The imaging system described in this embodiment is a reflection-based complex vibration imaging system, and its imaging process is as follows: Step a: The fiber-coupled LED1, arranged along the beam propagation direction, emits incoherent light with strong monochromaticity. After passing through the collimating lens 1 and the Kohler illumination system, it forms parallel light with uniform illumination effect. The collimated light passes through the polarizer 6 to generate linearly polarized light with a specific polarization direction, and is converged by the converging lens 7 onto the back focal plane of the microscope objective 9. The microscope objective 9 has a numerical aperture that matches the detail size of the sample to be resolved on the sample stage 10, and can uniformly project the beam processed by the semi-reflective mirror 8 onto the sample to be inspected. Step b: The microscope objective 9 collects the reflected light from the sample under test, which is then focused by the tube lens 11 after passing through the semi-reflective lens 8. The back focal plane of the tube lens 11 coincides with the front focal plane of Fourier lens 12, and the back focal plane of Fourier lens 12 coincides with the front focal plane of Fourier lens 2 15. Fourier lens 12 and Fourier lens 2 15 have the same focal length and aperture, forming a 4f system. The metasurface 13, which can generate different aperture modulation, is placed on the back focal plane of Fourier lens 12, which is also the front focal plane of Fourier lens 2 15. The analyzer 14 is placed after the metasurface 13. The image of the sample after aperture modulation is collected by the CMOS camera 16. Step c: By changing the polarization state of polarizer 6 and analyzer 14, full aperture modulation or different half aperture modulations are generated; the amplitude information of the sample is obtained through full aperture modulation, and the phase information of the sample is obtained by deconvolution of the results of different half aperture modulations. The two are combined to obtain the complex amplitude information of the sample.

[0034] Example The steps of the complex amplitude imaging method based on aperture-multiplexed Malus metasurfaces described in this embodiment include: S100. Based on Malus' theorem, a metasurface unit structure with polarization selectivity was designed and optimized using simulation methods, and a polarization-multiplexed aperture modulation metasurface was constructed. S200: Through a micro-nano fabrication process combining electron beam lithography and reactive ion beam etching, metasurface samples are prepared. S300: Construct a polarization-controlled microscopic imaging optical system with metasurface as the core, and realize two working modes, bright-field amplitude imaging and quantitative phase imaging, by controlling the polarization state. The S400 uses a differential phase contrast algorithm to process phase information, fusing the amplitude information of bright-field imaging with quantitative phase information to ultimately achieve complex amplitude microscopy.

[0035] This embodiment utilizes the amplitude modulation characteristics of metasurfaces to generate polarization-dependent multi-aperture modulation, overcoming the unitarity limitation of the Jones matrix. Within the same system, dynamic aperture modulation without mechanically moving parts is achieved through polarization state switching. This integrates full-aperture bright-field imaging and asymmetric illumination quantitative phase imaging into a single compact platform, enabling high-precision complex amplitude imaging.

[0036] Specifically, step S100 includes: S101. Analyze the properties of Malusian metasurfaces. Malus's theorem indirectly modulates the amplitude of light by introducing the polarization state of light. Selecting a unit structure with transmissive nanopolarizer characteristics, and through different combinations of input and output polarization states, when the nanostructure rotates between 0 and π, two directions exhibit zero transmittance, while the other two directions exhibit equal transmittance. Similarly, for this set of unit structures, while satisfying the above conditions, there exists a set of input and output polarization states that make the transmittance of the four nanopillars the same.

[0037] S102. Optimize the material, shape, and geometric parameters of the metasurface. Use electromagnetic simulation software to scan the length and width of the nanopillars to obtain the corresponding S-parameter curves, thereby selecting a suitable unit structure as a transmissive nanopolarizer. The nanopillar structure is an asymmetric unit structure with anisotropy, specifically exhibiting near-zero transmittance along the long axis and near-100% transmittance along the short axis.

[0038] More specifically: To verify the effectiveness of the device described above, the basic unit structure of the Marius metasurface was configured as amorphous silicon (α-Si) nanopillars on a fused silica (SiO2) substrate, wherein the nanopillars are periodically... P = 350 nm, height H = 320 nm, basic unit structure as follows Figure 4 As shown, the length and width of the nanopillars were scanned using electromagnetic simulation software to obtain the corresponding S-parameter curves. This was used to select a suitable unit structure for a transmission-type nanopolarizer. The optimized nanopillar length was then obtained. L = 270 nm, width W = 60 nm. At an operating wavelength of 632 nm, this asymmetric unit structure exhibits significant anisotropy, specifically, the transmittance along the long axis is close to zero, while the transmittance along the short axis is close to 100%, such as... Figure 5 As shown.

[0039] When the polarization states of the polarizer and analyzer are (-π / 8, π / 8), (π / 8, 3π / 8), (3π / 8, 5π / 8), (5π / 8, 7π / 8), and (0, π / 2), respectively, the transmittance of the nanopillar can be modulated in five channels. Dividing the entire circular aperture into four identical regions, the rotation angles of the metasurface region R1 ~ R4 unit structures... θ The transmittance values ​​are 3π / 8, π / 8, 7π / 8, and 5π / 8. Utilizing the characteristics of nanopolarizers, the transmittance of these regions under different polarization states can be represented by binary values ​​(0 and 1). By controlling the polarization state of light, the metasurface can achieve independent modulation of the optical field, efficiently switching between the full aperture and the four half-apertures.

[0040] Specifically, step S200 includes: Metasurfaces are fabricated using a combination of electron beam lithography and reactive ion beam etching. In a cleanroom environment, an electron beam lithography system directly writes nanoscale patterns onto a substrate coated with electron beam resist. This system uses a high-energy focused electron beam to achieve high-precision feature size patterning, ensuring the accurate formation of the metasurface unit structure. Subsequently, reactive ion beam etching is used for pattern transfer. By optimizing key parameters such as etching gas ratios, RF power, and chamber pressure, anisotropic etching is achieved, transferring the resist pattern onto the substrate material with high fidelity. The entire process is completed in a Class 100 cleanroom environment, effectively avoiding the impact of micro-dust contamination on device performance.

[0041] More specifically, to verify the effectiveness of the device described above, a Malusian metasurface with an amorphous silicon nanopillar unit structure on a fused silica substrate was fabricated using electron beam lithography combined with reactive ion beam etching. The specific steps were as follows: a 320 nm thick amorphous silicon layer was grown on the fused silica substrate using physical vapor deposition as the functional layer. Subsequently, a spin-coating process was used to sequentially coat photoresist layers: hydrogen silsesquioxane (HSQ, Dow Corning XR-1541-006) photoresist was spin-coated at 5000 rpm to form a 150 nm thick photosensitive layer; then, AR-PC 5090 conductive adhesive was spin-coated at 2000 rpm to construct an 80 nm thick antistatic layer. Patterning was achieved using electron beam lithography (Raith-Eline Plus), with exposure parameters set to an accelerating voltage of 30 keV and a current of 450 pA. After exposure, the sample underwent a three-step cleaning process to remove residual photoresist mask. First, the conductive layer was removed by rinsing with deionized water. Then, it was developed for 3 minutes using a 25% tetramethylammonium hydroxide solution. Finally, the reaction was terminated with deionized water. After development, the sample was cleaned with isopropanol and dried with nitrogen to complete the pretreatment. Amorphous silicon etching was performed using an inductively coupled plasma reactive ion etching system (Oxford Instruments Plasmalab system 100). This system had an inductively coupled plasma power of 300 W, an RF power of 100 W, and a Cl2 gas flow rate of 22 sccm. The chamber pressure was maintained at 5 mTorr, and the cooling temperature was set to 10 °C. The imaging results of the processed metasurface under optical and electron microscopes are shown below. Figure 6 As shown, the metasurface is divided into four regions of equal size, and the rotation angle of the metasurface region R1 ~ R4 unit structure is shown. θ are 3π / 8, π / 8, 7π / 8 and 5π / 8.

[0042] This invention provides a transmission complex amplitude imaging system based on an aperture-multiplexing Malus metasurface, such as... Figure 2 As shown, the system includes an optical fiber coupled LED1, a collimating lens2, a focusing lens 13, a filter pinhole 4, a focusing lens 25, a polarizer 6, a converging lens 7, a sample stage 8, a microscope objective 9, a plane mirror 10, a tube mirror 11, a Fourier lens 12, a metasurface 13, an analyzer 14, a Fourier lens 2 15, and a CMOS camera 16 arranged along the beam propagation direction, corresponding to step S300.

[0043] Specifically, step S300 includes: S301. Fiber-coupled LED1, arranged along the beam propagation direction, emits incoherent light with strong monochromaticity. This light passes through collimating lens 2 and the Kohler illumination system to form parallel light with uniform illumination. The collimated light is then polarized by polarizer 6 to produce linearly polarized light with a specific polarization direction, and focused by converging lens 7 onto the sample mounted on sample stage 8.

[0044] S302. The sample is imaged using the microscope objective 9 and the tube lens 11. The back focal plane of the tube lens 11 coincides with the front focal plane of Fourier lens 12, and the back focal plane of Fourier lens 12 coincides with the front focal plane of Fourier lens 15. Fourier lens 12 and Fourier lens 15 have the same focal length and aperture, forming a 4f system. A metasurface 13 capable of producing different aperture modulations is placed on the back focal plane of Fourier lens 12, which is also the front focal plane of Fourier lens 15. The analyzer 14 is placed behind the metasurface. The aperture-modulated image of the sample is collected by the CMOS camera 16.

[0045] S303. By changing the polarization states of polarizer 6 and analyzer 14, full-aperture modulation or different half-aperture modulations are generated. The amplitude information of the sample is obtained through full-aperture modulation, and the phase information of the sample is obtained by deconvolving the results of different half-aperture modulations. The two are combined to obtain the complex amplitude information of the sample.

[0046] The fiber-coupled LED 1, collimating lens 2, focusing lens 1 3, filter pinhole 4, focusing lens 2 5, polarizer 6, converging lens 7, sample stage 8, and microscope objective 9, arranged along the beam propagation direction, are located in the same horizontal direction. The tube mirror 11, Fourier lens 12, metasurface 13, analyzer 14, Fourier lens 2 15, and CMOS camera 16 are located in the same vertical direction, and the central axes of the tube mirror 11, Fourier lens 12, metasurface 13, and Fourier lens 2 15 coincide in the vertical direction.

[0047] Fourier lens 12 and Fourier lens 2 15 together constitute a 4f system, and metasurface 13 is placed on the Fourier plane of this 4f system.

[0048] The wavelength of the fiber-coupled LED1 arranged along the beam propagation direction can be any wavelength in the visible light band of 400 nm to 700 nm. The light emitted from the fiber passes through the collimating lens 2 to produce a parallel beam with good collimation.

[0049] The focusing lens 1 3, the filter pinhole 4, and the focusing lens 2 5 arranged along the direction of beam propagation together form the Kohler illumination system, which avoids the influence of the light source on the imaging and creates a uniform illumination effect with consistent brightness on the object plane.

[0050] This invention provides a reflective complex amplitude imaging system based on an aperture-multiplexing Malus metasurface, such as... Figure 3 As shown, it includes an optical fiber coupled LED 1, a collimating lens 2, a focusing lens 1 3, a filter pinhole 4, a focusing lens 2 5, a polarizer 6, a converging lens 7, a semi-reflective lens 8, a microscope objective 9, a sample stage 10, a tube lens 11, a Fourier lens 12, a metasurface 13, an analyzer 14, a Fourier lens 2 15, and a CMOS camera 16 arranged along the beam propagation direction, corresponding to step S300.

[0051] Specifically, step S300 includes: S301. Fiber-coupled LEDs 1, arranged along the beam propagation direction, emit incoherent light with strong monochromaticity. This light passes through collimating lens 2 and the Kohler illumination system to form parallel light with uniform illumination. The collimated light is then polarized by polarizer 6 to produce linearly polarized light with a specific polarization direction. This light is then converged by converging lens 7 onto the back focal plane of microscope objective 9. Microscope objective 9 has a numerical aperture that matches the detail size of the sample to be resolved on the sample stage 10, enabling it to uniformly project the beam processed by the semi-reflective mirror 8 onto the sample under inspection.

[0052] S302, the microscope objective 9 collects the reflected light from the sample under test, which is then focused by the tube lens after passing through the semi-reflective mirror 8. The rear focal plane of the tube lens 11 coincides with the front focal plane of Fourier lens 12, and the rear focal plane of Fourier lens 12 coincides with the front focal plane of Fourier lens 15. Fourier lenses 12 and 15 have the same focal length and aperture, forming a 4f system. A metasurface 13 capable of producing different aperture modulations is placed on the rear focal plane of Fourier lens 12, which is also the front focal plane of Fourier lens 15. The analyzer 14 is placed behind the metasurface 13. The aperture-modulated image of the sample is collected by the CMOS camera 16.

[0053] S303. By changing the polarization states of polarizer 6 and analyzer 14, full-aperture modulation or different half-aperture modulations are generated. The amplitude information of the sample is obtained through full-aperture modulation, and the phase information of the sample is obtained by deconvolving the results of different half-aperture modulations. The two are combined to obtain the complex amplitude information of the sample.

[0054] The fiber-coupled LED 1, collimating lens 2, focusing lens 1 3, filter pinhole 4, focusing lens 2 5, polarizer 6, and converging lens 7, arranged along the beam propagation direction, are located in the same horizontal direction. The semi-reflective mirror 8, microscope objective 9, sample stage 10, tube mirror 11, Fourier lens 1 12, metasurface 13, analyzer 14, Fourier lens 2 15, and CMOS camera 16 are located in the same vertical direction, and the central axes of the microscope objective 9, tube mirror 11, Fourier lens 1 12, metasurface 13, and Fourier lens 2 15 coincide in the vertical direction.

[0055] Fourier lens 12 and Fourier lens 2 15 together constitute a 4f system, and the metasurface is placed on the Fourier plane of this 4f system.

[0056] The wavelength of the fiber-coupled LED1 arranged along the beam propagation direction can be any wavelength in the visible light band of 400 nm to 700 nm. The light emitted from the fiber passes through the collimating lens 2 to produce a parallel beam with good collimation.

[0057] The focusing lens 1 3, the filter pinhole 4, and the focusing lens 2 5 arranged along the direction of beam propagation together form the Kohler illumination system, which avoids the influence of the light source on the imaging and creates a uniform illumination effect with consistent brightness on the object plane.

[0058] Specifically, step S400 includes: The samples to be tested include, but are not limited to, cleared tissue sections, pathological sections, cell samples, material microstructure samples, and other weak phase targets.

[0059] In this embodiment, a transparent mouse colon tissue slice is used as the test sample, and the transparent mouse colon tissue slice is placed on a sample stage for imaging detection.

[0060] By acquiring sample intensity image information corresponding to different illumination channels under aperture reuse Marius metasurface control, and performing differential processing on multi-channel intensity images based on the differential phase contrast imaging principle, differential phase contrast image data related to sample phase gradient is obtained.

[0061] Furthermore, based on the differential phase-contrast imaging algorithm, frequency domain inversion and phase calculation are performed on the differential phase-contrast image data to obtain the phase distribution information of the sample. Then, combined with the corresponding intensity information, the complex amplitude distribution of the sample is reconstructed to obtain... Figure 7 The complex amplitude distribution of the reconstructed sample is shown.

[0062] The complex amplitude distribution includes both amplitude and phase information of the sample. For transparent mouse colon tissue sections, since their optical response is mainly characterized by phase modulation, the method of the present invention can effectively achieve high-precision reconstruction of their complex amplitude information, thereby characterizing their internal microstructure distribution features.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A complex amplitude imaging method based on an aperture-multiplexing Malusian metasurface, characterized in that, The specific steps include: Step 1: Based on Malus' theorem, design and optimize the metasurface unit structure with polarization selectivity using simulation methods to construct a polarization-multiplexed aperture modulation metasurface. Step 2: Prepare metasurface samples using a micro / nano fabrication process combining electron beam lithography and reactive ion beam etching; Step 3: Construct a polarization-controlled microscopic imaging optical system with metasurface as the core, and realize two working modes, bright-field amplitude imaging and quantitative phase imaging, by controlling the polarization state. Step 4: The phase information is processed using the differential phase contrast algorithm, and the amplitude information of bright field imaging is fused with the quantitative phase information to finally realize complex amplitude microscopy.

2. The complex amplitude imaging method based on an aperture-multiplexing Malus metasurface according to claim 1, characterized in that, In step 1, Malus's theorem indirectly modulates the amplitude of light by introducing the polarization state of light; when the initial intensity is When linearly polarized light passes through a polarizer, the intensity of the transmitted light, neglecting absorption, can be expressed as: ,in It is the angle between the polarization direction of the incident linearly polarized light and the polarization direction of the linear polarizer; the Jones matrix of the anisotropic nanopillar structure is represented as: ， The diagonal elements 1 and 0 represent the complex transmission coefficients when light propagates along the long and short axes of the nanopillar, respectively; in this case, the anisotropic nanopillar structure can be considered as an ideal polarizer. The in-plane orientation angle is... θ The nanopillar Jones matrix is ​​represented as: ， in It is a rotation matrix; The intensity through the polarizer is I The Jones matrix of the output light after the polarized light passes through the anisotropic nanostructure and analyzer is expressed as: ， in, and These represent the polarization directions of the polarizer and the analyzer, respectively. When the incident light intensity Given the polarization directions of the polarizer and analyzer, an anisotropic nanostructure, acting as an ideal polarizer, can be used for continuous intensity modulation; when the angle between the polarization directions of the polarizer and analyzer is π / 4 (i.e., ... When ), the output light intensity is expressed as: ， When the nanostructure rotates between 0 and π, two directions exhibit zero transmittance, and the other two directions exhibit equal transmittance; the angular interval between the four directions is π / 4; this property can be used to design unit structures with transmittance of 0 and 1 under different polarization states, thereby realizing differential phase contrast imaging with asymmetric aperture illumination. When the polarization directions of the polarizer and the analyzer are perpendicular, the output light intensity is expressed as: ， There exists a set of unit structures with rotation angles spaced at π / 4, where the four nanopillars have equal transmittance under cross-polarization conditions; this property can be used to design full-aperture metasurfaces for bright-field imaging.

3. The complex amplitude imaging method based on an aperture-multiplexing Malusian metasurface according to claim 1, characterized in that, In step 3, quantitative phase imaging adopts the differential phase contrast imaging principle. Asymmetric illumination is generated by polarization-controlled Malus metasurface, and the phase information of the sample is converted into intensity information. The differential phase contrast information of the sample is processed by deconvolution algorithm to achieve low-noise and high-precision quantitative phase reconstruction results.

4. A complex amplitude imaging system based on an aperture-multiplexing Malusian metasurface, characterized in that, The system includes an optical fiber coupled LED (1), a collimating lens (2) on the right side of the optical fiber coupled LED (1), a focusing lens (3) and a focusing lens (5) on the right side of the collimating lens (2), a filter pinhole (4) between the focusing lens (3) and the focusing lens (5), a polarizer (6) on the right side of the focusing lens (5), a converging lens (7) and a microscope objective (9) on the right side of the polarizer (6), a sample stage (8) between the converging lens (7) and the microscope objective (9), a plane mirror (10) on the right side of the microscope objective (9), a tube mirror (11) below the plane mirror (10), a Fourier lens (12), a metasurface (13), an analyzer (14) and a Fourier lens (15) on the lower side of the tube mirror (11), and a CMOS camera (16) below the Fourier lens (15).

5. A complex amplitude imaging system based on an aperture-multiplexing Malusian metasurface according to claim 4, characterized in that, The fiber-coupled LED (1), collimating lens (2), focusing lens one (3), filter pinhole (4), focusing lens two (5), polarizer (6), converging lens (7), sample stage (8), and microscope objective (9) are located in the same horizontal direction. The tube lens (11), Fourier lens one (12), metasurface (13), analyzer (14), Fourier lens two (15) and CMOS camera (16) are located in the same vertical direction, and the central axis of the tube lens (11), Fourier lens one (12), metasurface (13), analyzer (14) and Fourier lens two (15) in the vertical direction coincides.

6. The complex amplitude imaging system based on an aperture-multiplexing Malusian metasurface according to claim 4, characterized in that, The imaging system is a transmission-type complex vibration imaging system, and its imaging process is as follows: Step a: The fiber-coupled LED (1) arranged along the beam propagation direction emits incoherent light with strong monochromaticity. After passing through the collimating lens (2) and the Kohler illumination system, it forms parallel light with uniform illumination effect. The collimated light passes through the polarizer (6) to generate linearly polarized light with a specific polarization direction, and is focused on the sample mounted on the sample stage (8) by the converging lens (7). Step b: Image the sample through a microscope objective (9) and a tube lens (11). The back focal plane of the tube lens (11) coincides with the front focal plane of Fourier lens 1 (12), and the back focal plane of Fourier lens 1 (12) coincides with the front focal plane of Fourier lens 2 (15). Fourier lens 1 (12) and Fourier lens 2 (15) have the same focal length and aperture, forming a 4f system. A metasurface capable of generating different aperture modulations is placed on the back focal plane of Fourier lens 1 (12), which is also the front focal plane of Fourier lens 2 (15). The analyzer (14) is placed behind the metasurface (13). The image of the sample after aperture modulation is collected by a CMOS camera (16). Step c: By changing the polarization state of the polarizer (6) and the analyzer (14), full aperture modulation or different half aperture modulations are generated; The amplitude information of the sample is obtained by full-aperture modulation, and the phase information of the sample is obtained by deconvolution of the results of modulation at different half-apertures. The two are combined to obtain the complex amplitude information of the sample.

7. A complex amplitude imaging system based on an aperture-multiplexing Malusian metasurface, characterized in that, The system includes an optical fiber coupled LED (1), a collimating lens (2) on the right side of the optical fiber coupled LED (1), a focusing lens (3) and a focusing lens (5) on the right side of the collimating lens (2), a filter pinhole (4) between the focusing lens (3) and the focusing lens (5), a polarizer (6) on the right side of the focusing lens (5), a converging lens (7) on the right side of the polarizer (6), a semi-reflective lens (8) on the right side of the converging lens (7), a microscope objective (9) above the semi-reflective lens (8), a sample stage (10) above the microscope objective (9), a tube mirror (11) below the semi-reflective lens (8), a Fourier lens (12), a metasurface (13), an analyzer (14) and a Fourier lens (15) on the lower side of the tube mirror (11), and a CMOS camera (16) below the Fourier lens (15).

8. A complex amplitude imaging system based on an aperture-multiplexing Malusian metasurface according to claim 7, characterized in that, The fiber-coupled LED (1), collimating lens (2), focusing lens one (3), filter pinhole (4), focusing lens two (5), polarizer (6), and converging lens (7) are located in the same horizontal direction; The semi-reflective mirror (8), microscope objective (9), sample stage (10), tube mirror (11), Fourier lens one (12), metasurface (13), analyzer (14), Fourier lens two (15) and CMOS camera (16) are located in the same vertical direction, and the central axis of the microscope objective (9), sample stage (10), tube mirror (11), Fourier lens one (12), metasurface (13), analyzer (14) and Fourier lens two (15) in the vertical direction coincides.

9. A complex amplitude imaging system based on an aperture-multiplexing Malusian metasurface according to claim 7, characterized in that, The imaging system is a reflection-based complex vibration imaging system, and its imaging process is as follows: Step a: The fiber-coupled LED (1) arranged along the beam propagation direction emits incoherent light with strong monochromaticity. After passing through the collimating lens (1) and the Kohler illumination system, it forms parallel light with uniform illumination effect. The collimated light passes through the polarizer (6) to generate linearly polarized light with a specific polarization direction, and is converged by the converging lens (7) onto the back focal plane of the microscope objective (9). The microscope objective (9) has a numerical aperture that matches the detail size of the sample to be resolved on the sample stage (10), and can uniformly project the beam processed by the semi-reflective mirror (8) onto the sample to be inspected. Step b: The microscope objective (9) collects the reflected light from the sample to be tested, which is then focused by the tube lens (11) after passing through the semi-reflective lens (8). The back focal plane of the tube lens (11) coincides with the front focal plane of Fourier lens one (12), and the back focal plane of Fourier lens one (12) coincides with the front focal plane of Fourier lens two (15). Fourier lens one (12) and Fourier lens two (15) have the same focal length and aperture, and the two form a 4f system. The metasurface (13) that can produce different aperture modulation is placed on the back focal plane of Fourier lens one (12), which is also the front focal plane of Fourier lens two (15). The analyzer (14) is placed after the metasurface (13), and the image of the sample after aperture modulation is collected by the CMOS camera (16). Step c: By changing the polarization state of the polarizer (6) and the analyzer (14), full aperture modulation or different half aperture modulations are generated; The amplitude information of the sample is obtained by full-aperture modulation, and the phase information of the sample is obtained by deconvolution of the results of modulation at different half-apertures. The two are combined to obtain the complex amplitude information of the sample.

Images