Microscopic imaging method and device based on dispersive double helix point spread function metalens

Abstract

A method and device for microscopic imaging based on a dispersive double-helix point spread function metalens, which relates to a method and device for microscopic imaging. The present invention is to solve the problems of poor imaging quality, inconvenience of integration and high cost of a spatial light modulator. The present invention relates to a method and device for microscopic imaging based on a dispersive double-helix point spread function metalens. The microscopic imaging system based on a dispersive double-helix point spread function comprises a white light source, a filter, a collimating lens, a polarizer, a quarter-wave plate, a converging lens, a sample stage, a metalens, a microscope objective, a right-handed circular polarizer, a tube lens and a CMOS camera; the white light source, the filter, the collimating lens, the polarizer, the quarter-wave plate and the converging lens are arranged on one side of the sample stage from left to right, and the metalens, the microscope objective, the right-handed circular polarizer, the tube lens and the CMOS camera are arranged on the right side of the sample stage from left to right. The present invention belongs to the field of optical microscopic imaging and optical manipulation technology.

Description

Technical Field

[0001] The invention relates to a microscopic imaging method and a device, belonging to the technical field of optical microscopic imaging and optical manipulation. Background Art

[0002] The point spread function describes the response of the imaging system to a point source or point object. The three-dimensional point spread function encodes the depth information in the different morphological features of the detected image, and the known point spread function information is used to restore the axial information corresponding to each lateral position on the two-dimensional image plane. The existing three-dimensional point spread function modulation method is mainly to design 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 point spread 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 quantitative 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. In addition, the spatial light modulator is large in size, making it impossible to integrate the three-dimensional imaging optical system.

[0003] In order to solve the problems of poor imaging quality, poor integration and high cost of spatial light modulators, the idea of ​​metasurfaces is introduced. The subwavelength structure of metasurfaces can interact with the incident electromagnetic field, thereby introducing a mutation of optical parameters on the surface and realizing extraordinary properties that natural materials do not have. By utilizing the highly integrated characteristics of metasurfaces, the lens phase is integrated into the modulation of the double helix point spread function, which improves the problems of zero-order diffraction and difficulty in integration of traditional three-dimensional imaging optical systems based on spatial light modulators, greatly reducing the size of components. At the same time, by utilizing the characteristics of metasurfaces that can arbitrarily control the light field, double helix light spots of different wavelengths are gathered at different axial positions to achieve multi-period connection, and the axial detection depth is extended while the accuracy remains unchanged. In addition, 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, resulting in a significant reduction in the cost of the entire system and increasing its practicality. Summary of the invention

[0004] In order to solve the problems of poor imaging quality, difficulty in integration and high cost of spatial light modulators, the present invention further proposes a microscopic imaging method and device based on a dispersive double-helix point spread function metalens.

[0005] The technical solution adopted by the present invention to solve the above problems is: the steps of the microscopic imaging method based on the dispersed double helix point spread function metalens of the present invention include:

[0006] S100, design and process the dispersive double helix point spread function meta-lens by FDTD simulation;

[0007] S200: Build an optical system with a meta-lens as the core to modulate the dispersion double helix point spread function, image the molecules to be tested through the meta-lens, and obtain double helix images at different incident wavelengths.

[0008] S300, determining the lateral position of the molecule to be detected by the midpoint of the double helix light spot in the double helix image, and determining the axial position of the molecule to be detected by the angle between the centers of the two light spots.

[0009] Furthermore, the meta-lens forms a complete meta-lens by periodically arranging the basic unit structures according to the double helix point spread function phase and the lens phase distribution through a geometric phase arrangement method.

[0010] The dispersive double-helix point spread function metalens microscopic imaging system of the present invention comprises a white light source, a filter, a collimating lens, a polarizer, a quarter-wave plate, a converging lens, a sample stage, a metalens, a microscope objective, a right-handed circular polarizer, a tube lens and a CMOS camera;

[0011] The white light source, filter, collimating lens, polarizer, quarter-wave plate and converging lens are arranged on one side of the sample stage from left to right, and the meta-lens, microscope objective, right-handed circular polarizer, tube lens and CMOS camera are arranged on the right side of the sample stage from left to right.

[0012] The steps of the microscopic imaging method based on the dispersive double helix point spread function metalens of the present invention include:

[0013] Step 1: A white light source arranged along the propagation direction of the light beam emits incoherent light, which is passed through a filter to generate light beams of the required wavelengths, and then passes through a collimating lens to form parallel light. The collimated light passes through a polarizer and a quarter-wave plate, and left-handed circularly polarized light is generated by adjusting the quarter-wave plate. The light is then converged on the sample to be tested through a converging lens, and the sample is placed on a sample stage;

[0014] Step 2: The light passing through the sample passes through the meta-lens to achieve dispersion double-helix point spread function modulation. The modulated image is imaged again by a microscope system consisting of a microscope objective and a tube lens and is collected by a CMOS camera.

[0015] Step 3: Calculate the collected double-helix point spread function modulation image, determine the lateral position of the molecule to be measured by the midpoint of the double-helix spot in the double-helix image, and determine the axial position of the molecule to be measured by the angle between the centers of the two spots.

[0016] The dispersive double-helix point spread function metalens microscopic imaging system of the present invention comprises a white light source, a filter, a collimating lens, a polarizer, a quarter-wave plate, a converging lens, a half-reflecting half-mirror, a first microscope objective lens, a sample stage, a first tube lens, a metalens, a second microscope objective lens, a right-handed circular polarizer, a second tube lens and a CMOS camera;

[0017] The white light source, filter, collimating lens, polarizer, quarter wave plate and converging lens are arranged on one side of the half-reflecting half-mirror from left to right, the sample stage and the first microscope objective are arranged above the half-reflecting half-mirror from top to bottom, and the first tube lens, metalens, second microscope objective, right-handed circular polarizer, second tube lens and CMOS camera are arranged below the half-reflecting half-mirror from top to bottom.

[0018] The steps of the microscopic imaging method based on the dispersive double helix point spread function metalens of the present invention include:

[0019] Step 1: A white light source arranged along the propagation direction of the light beam emits incoherent light, and generates light beams of required wavelengths through a filter, and forms parallel light through a collimating lens. The collimated light passes through a polarizer and a quarter-wave plate, and left-handed circularly polarized light is generated by adjusting the quarter-wave plate. The light is converged on the rear focal plane of the first microscope objective lens through a converging lens. The first microscope objective lens has a numerical aperture that matches the size of the details to be resolved on the sample on the sample stage, and can evenly project the light beam processed by the half-reflecting and half-mirror lens onto the sample to be inspected;

[0020] Step 2: The first microscope objective collects the light reflected by the sample to be tested, and the light is focused by the first tube lens after passing through the half-reflecting half-mirror lens. The focused light is modulated by the dispersive double-helix point spread function through the meta-lens. The modulated image is imaged by the microscopic system composed of the second microscope objective and the second tube lens for secondary imaging, and is collected by the CMOS camera.

[0021] Step 3: Calculate the collected double-helix point spread function modulation image, determine the lateral position of the molecule to be measured by the midpoint of the double-helix spot in the double-helix image, and determine the axial position of the molecule to be measured by the angle between the centers of the two spots.

[0022] The beneficial effects of the present invention are as follows: the three-dimensional microscopic imaging method and system based on the dispersive double-helix point spread function meta-lens of the present invention has the advantages of easy integration, no zero-order diffraction spot, and wide imaging depth. Combined with the integrated characteristics of the metasurface, the phase of the lens with dispersion modulation is superimposed with the phase of the double-helix point spread function, which further improves the integration. The existence of dispersion changes the axial focus position of different incident wavelengths, and the multi-period connection is realized, which greatly improves the imaging range of the system. Furthermore, it can replace the setting of combining the spatial light modulator with the 4f system in the traditional point spread function, and overcomes the shortcomings of the spatial light modulator having zero-order diffraction spot that affects the imaging quality and is large in size and difficult to integrate. Through the application of the dispersive double-helix point spread function meta-lens, the three-dimensional information of the sample can be encoded in the rotation angle of the two main lobes of the double-helix spot. By solving the collected two-dimensional intensity information, the three-dimensional depth information can be obtained while obtaining the two-dimensional morphology distribution of the imaging plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a three-dimensional microscopic imaging method and system based on a dispersive double-helix point spread function metalens provided by the present invention;

[0024] Figure 2 It is a structural schematic diagram of a transmission-type three-dimensional microscopic imaging method and system based on a dispersive double-helix point spread function metalens provided by the present invention;

[0025] Figure 3 It is a structural schematic diagram of a reflective three-dimensional microscopic imaging method and system based on a dispersive double-helix point spread function metalens provided by the present invention;

[0026] Figure 4 It is a rectangular unit structure of the meta-lens in the present invention;

[0027] Figure 5 is the phase distribution and amplitude distribution of the meta-lens in the present invention;

[0028] Figure 6 is the simulation result of the meta-lens with different numerical apertures in the present invention;

[0029] Figure 7 The focusing effect of the meta-lens at different wavelengths in the present invention when D=400μm, f=800μm, and NA=0.2425;

[0030] Figure 8 It is a schematic diagram of the system axial measurement range at different wavelengths. DETAILED DESCRIPTION

[0031] Specific implementation method 1: Combination Figure 1This embodiment is described. The steps of the method for microscopic imaging of a metalens based on a dispersive double-helix point spread function in this embodiment include:

[0032] S100, design and process the dispersive double helix point spread function meta-lens by FDTD simulation;

[0033] S200: Build an optical system with a meta-lens as the core to modulate the dispersion double helix point spread function, image the molecules to be tested through the meta-lens, and obtain double helix images at different incident wavelengths.

[0034] S300, determining the lateral position of the molecule to be detected by the midpoint of the double helix light spot in the double helix image, and determining the axial position of the molecule to be detected by the angle between the centers of the two light spots.

[0035] In this embodiment, step S100 specifically includes:

[0036] S101, optimize the material, shape, geometric parameters, etc. of the metasurface, and use the frequency domain calculation module based on the finite element method in the electromagnetic simulation software CST to perform simulation operations. When the unit structure period and the height of the nanorods are constant, by changing the length and width of the nanorods, find the length and width with the maximum cross-polarization transmittance within the size range suitable for processing, as the unit structure of the geometric phase;

[0037] S102. Generate a dispersive double helix meta-lens phase distribution by superimposing the double helix point spread function phase by the lens phase. The dispersive double helix meta-lens phase distribution is obtained by superimposing Laguerre-Gaussian beams with different mode numbers. Optimization conditions are used to constrain the pupil plane, point spread function plane, and Laguerre-Gaussian mode plane, respectively, to obtain an optimized pure phase distribution double helix point spread function, which improves energy utilization. The rotation response of the improved double helix point spread function only appears in a specific area, which not only avoids sidelobe loss, but also ensures that the function has a rotation characteristic in the entire cross section but is approximately unchanged in a specific area. On this basis, a lens phase that can produce a dispersion effect is superimposed. By adjusting the numerical aperture of the lens, a dispersive double helix meta-lens phase with different working distances and positioning accuracy can be obtained.

[0038] S103, generating a processing file of a dispersive double-helix metalens according to the selected unit structure and the phase distribution of the geometric phase;

[0039] S104, processing the meta-lens by electron beam lithography combined with reactive ion beam etching;

[0040] The double helix point spread function is a special rotating beam whose focused spot is composed of two main lobes, and the angle between the centroids of the two main lobes changes with the axial position, which is manifested as the rotation of the main lobe. The rotation angle has an approximately linear relationship with the axial position, and can ensure that the main lobe size, main lobe spacing and clarity remain unchanged during the rotation process. Based on this characteristic, the rotating beam can be used to measure three-dimensional displacement. The double helix point spread function is formed by superimposing the Laguerre-Gaussian function whose modes are located on the same straight line. The slope of the straight line is related to the rotation speed of the main lobe; the mathematical model of the Laguerre-Gaussian function is:

[0041]

[0042] is the normalized radial coordinate, is the normalized radius of the light spot, w0 is the beam waist radius, To use the Rayleigh distance Normalized axial coordinate, λ is the wavelength of incident light, where:

[0043]

[0044] Φ m (φ)=exp(imφ)

[0045]

[0046] For the ancient phase, is the Laguerre polynomial, n and m are the Laguerre-Gaussian mode numbers, in the double helix point spread function, nm satisfies n=|m|,|m|+2,|m|+4,|m|+6,...., and the phase and intensity of the double helix point spread function can be obtained by selecting (1, 1), (3, 5), (5, 9), (7, 13), (9, 17) of the Laguerre-Gaussian modes (m, n) for equal weight superposition. The double-helix point spread function phase distribution generated by the above steps has a low light energy utilization rate. Three plane constraints are used to improve the modulation efficiency of the point spread function and eliminate the sidelobe effect as much as possible. They are: (1) pupil plane constraint, which removes the amplitude information and only retains the phase of the double-helix point spread function; (2) point spread function plane constraint, which introduces a weight function related to the main lobe energy distribution on different focal planes to make the main lobe energy distribution more concentrated; (3) Laguerre-Gaussian mode plane constraint, which decomposes the light field into a linear superposition of Laguerre-Gaussian modes of odd functions of different (m, n) modes, multiplied by the weight function, to ensure that the point spread function has a rotation characteristic and the rotation rate remains unchanged. The optimized double-helix point spread function phase distribution φ DHPSF like Figure 5 As shown in

[0047] The lens phase can be expressed as:

[0048]

[0049] Where λ is the wavelength of the incident light, x and y are the position coordinates in the plane, and f is the focal length of the lens;

[0050] The lens phase diagram is as follows Figure 5 As shown in b;

[0051] By utilizing the integrated characteristics of the metasurface, the double-helix point spread function phase distribution is superimposed with the phase distribution of the lens with dispersion modulation to obtain the phase distribution of the dispersive double-helix point spread function metalens with different numerical apertures, which can be expressed as:

[0052] φ=φ lens +φ DHPSF

[0053] The phase distribution of the superimposed dispersive double helix point spread function metalens is as follows: Figure 5 c; the amplitude type mask has a high absorption rate for light, which will cause most of the energy loss. Therefore, only the phase is selected as the basis for the construction of the metasurface, and the amplitude is fixed to 1, as shown in Figure 5 d; The size of the two main lobes of the generated point spread function, the distance between the main lobes and the degree of image blur remain basically unchanged, and the rotation rate remains unchanged, that is, the angle between the centers of the two main lobes of the double helix image is roughly linearly related to the change in defocus.

[0054] According to the phase distribution of the dispersed double helix point spread function meta-lens, the meta-lens is generated using the arrangement idea of ​​the geometric phase using the above-selected unit structure. The generated meta-lens is simulated using the FDTD algorithm to predict its dispersion focusing characteristics and the three-dimensional distribution of the point spread function. The simulation results are shown in Figure 6 ; The rotation rate of the two main lobes depends on the NA and the incident wavelength of the system, and has nothing to do with the size. Regardless of whether the numerical aperture is large or small, a continuously rotating light spot can be obtained near the focal plane, and the rotation period is π. The actual depth corresponding to the rotation period of meta-lenses with different numerical apertures is also different. As the numerical aperture increases, the rotation period also decreases accordingly. The simulation of light field propagation proves the feasibility of the double helix lens formed by the superposition of the double helix point spread function phase distribution and the lens phase distribution. In addition, by changing the numerical aperture of the superimposed lens phase, the depth range of the generated double helix light spot can be controlled. Based on this method, three-dimensional positioning with arbitrary depth and accuracy can be achieved in theory.

[0055] The dispersive double helix point spread function metalens has a dispersive characteristic. The axial focus changes under different incident wavelengths. The focusing imaging effect of the focus position under different wavelengths of the metalens D = 400μm, f = 800μm, NA = 0.2425 is as follows Figure 7 Greatly expand the system imaging range.

[0056] The axial measurement range of the system at different wavelengths is as follows: Figure 8 The application of different bands achieves multi-period connection, which has the function of splicing axial depth.

[0057] Specific implementation method 2: Combination Figure 1 To illustrate this embodiment, the metalens based on the dispersed double-helix point spread function metalens microscopic imaging method described in this embodiment forms a complete metalens by periodically arranging the basic unit structure according to the double-helix point spread function phase and lens phase distribution through a geometric phase arrangement method.

[0058] Specific implementation method three: Combination Figure 1 This embodiment is described. The dispersion double helix point spread function based metalens microscopic imaging system described in this embodiment includes a white light source 1, a filter 2, a collimating lens 3, a polarizer 4, a quarter wave plate 5, a converging lens 6, a sample stage 7, a metalens 8, a microscope objective 9, a right-handed circular polarizer 10, a tube lens 11 and a CMOS camera 12.

[0059] The white light source 1, filter 2, collimating lens 3, polarizer 4, quarter-wave plate 5 and converging lens 6 are arranged on one side of the sample stage 7 from left to right, and the meta-lens 8, microscope objective 9, right-handed circular polarizer 10, tube lens 11 and CMOS camera 12 are arranged on the right side of the sample stage 7 from left to right.

[0060] Specific implementation method four: Combination Figure 1 This embodiment is described. The steps of the method for microscopic imaging based on a dispersive double-helix point spread function metalens described in this embodiment include:

[0061] Step 1: a white light source 1 arranged along the propagation direction of the light beam emits incoherent light, passes through a filter 2 to generate light beams of required wavelengths, passes through a collimating lens 3 to form parallel light, and the collimated light passes through a polarizer 4 and a quarter-wave plate 5, and a left-handed circularly polarized light incident light is generated by adjusting the quarter-wave plate 5, and converged on the sample to be tested through a converging lens 6, and the sample is mounted on a sample stage 7;

[0062] Step 2: The light passing through the sample passes through the meta-lens 8 to realize the dispersion double-helix point spread function modulation. The modulated image is imaged by the microscope system composed of the microscope objective lens 9 and the tube lens 11 for secondary imaging and is collected by the CMOS camera 12.

[0063] Step 3: Calculate the collected double-helix point spread function modulation image, determine the lateral position of the molecule to be measured by the midpoint of the double-helix spot in the double-helix image, and determine the axial position of the molecule to be measured by the angle between the centers of the two spots.

[0064] The white light source 1, filter 2, collimating lens 3, polarizer 4, quarter-wave plate 5, converging lens 6, sample stage 7, meta-lens 8, microscope objective 9, right-handed circular polarizer 10, tube lens 11 and CMOS camera 12 arranged along the propagation direction of the light beam described in this embodiment are located in the same vertical direction, and the central axes of the meta-lens 8, microscope objective 9 and tube lens 11 in the vertical direction coincide.

[0065] The wavelength of the white light source 1 arranged along the propagation direction of the light beam can be any wavelength in the visible light band of 400nm-650nm. The light of the required wavelength is emitted through the filter 2, and the emitted light passes through the collimating lens 3 to generate a parallel light beam with good collimation.

[0066] The incident parallel light passes through the polarizer 4 and the quarter-wave plate 5 to generate left-handed circularly polarized light, and the right-handed circular polarizer 10 after the metalens 8 is adapted to the geometric phase to eliminate the output light with the same circular polarization state as the input light, so as to minimize the crosstalk of the incident light.

[0067] White light passes through filter 2 to generate light of various wavelengths, which are focused at different depths, produce dispersion, and extend the imaging depth of the system.

[0068] The overall system is a secondary imaging system, using a meta-lens for primary imaging. The object distance, image distance, and focal length f of the meta-lens at each wavelength are λ Satisfies Gauss's formula

[0069] The microscope objective lens 9 is used for secondary imaging. The microscope objective lens 9 can be a commercial objective lens and used in conjunction with the tube lens 11 .

[0070] Specific implementation method five: Combination Figure 1 The present embodiment is described. The metalens microscopic imaging system based on the dispersive double helix point spread function described in the present embodiment comprises a white light source 1, a filter 2, a collimating lens 3, a polarizer 4, a quarter wave plate 5, a converging lens 6, a half-reflecting half-mirror 7, a first microscope objective 8, a sample stage 9, a first tube lens 10, a metalens 11, a second microscope objective 12, a right-handed circular polarizer 13, a second tube lens 14 and a CMOS camera 15.

[0071] The white light source 1, the filter 2, the collimating lens 3, the polarizer 4, the quarter-wave plate 5 and the converging lens 6 are arranged on one side of the half-reflecting half-mirror 7 from left to right, the sample stage 9 and the first microscope objective lens 8 are arranged above the half-reflecting half-mirror 7 from top to bottom, and the first tube lens 10, the metalens 11, the second microscope objective lens 12, the right-handed circular polarizer 13, the second tube lens 14 and the CMOS camera 15 are arranged below the half-reflecting half-mirror 7 from top to bottom.

[0072] Specific implementation method six: Combination Figure 1 This embodiment is described. The steps of the method for microscopic imaging based on a dispersive double-helix point spread function metalens described in this embodiment include:

[0073] Step 1, a white light source 1 arranged along the propagation direction of the light beam emits incoherent light, generates light beams of required wavelengths through a filter 2, forms parallel light through a collimating lens 3, and the collimated light passes through a polarizer 4 and a quarter-wave plate 5. Left-handed circularly polarized light is generated by adjusting the quarter-wave plate 5, and converged on the rear focal plane of a first microscope objective 8 through a converging lens 6. The first microscope objective 8 has a numerical aperture that matches the size of details to be resolved of the sample on a sample stage 9, and can evenly project the light beam processed by a half-reflecting half-mirror 7 onto the sample to be inspected;

[0074] Step 2, the first microscope objective lens 8 collects the light reflected by the sample to be tested, and after passing through the half-reflecting half-mirror lens 7, it is focused by the first tube lens 10. The focused light is modulated by the dispersion double-helix point spread function through the meta-lens 11. The modulated image is imaged by the microscopic system composed of the second microscope objective lens 12 and the second tube lens 14 for secondary imaging, and is collected by the CMOS camera 15.

[0075] Step 3: Calculate the collected double-helix point spread function modulation image, determine the lateral position of the molecule to be measured by the midpoint of the double-helix spot in the double-helix image, and determine the axial position of the molecule to be measured by the angle between the centers of the two spots.

[0076] In this embodiment, the wavelength of the white light source 1 arranged along the propagation direction of the light beam can be any wavelength in the visible light band (400nm-650nm), and the light of the required wavelength is emitted through the filter 2. The emitted light passes through the collimating lens 3 to produce a parallel light beam with good collimation.

[0077] The incident parallel light passes through the polarizer 4 and the quarter-wave plate 5 to generate left-handed circularly polarized light, which is adapted to the geometric phase meta-lens. The right-handed circular polarizer 13 after the meta-lens 11 is used to eliminate the output light with the same circular polarization state as the input light, so as to minimize the crosstalk of the incident light.

[0078] White light passes through filter 2 to generate light of various wavelengths, which are focused at different depths, produce dispersion, and extend the imaging depth of the system.

[0079] The overall system is a secondary imaging system, using a meta-lens for primary imaging. The object distance, image distance, and focal length f of the meta-lens at each wavelength are λ Satisfies Gauss's formula

[0080] The microscope objective lens 12 is used for secondary imaging. The microscope objective lens 12 can be a commercial objective lens and is used in conjunction with the tube lens 14.

[0081] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for microscopic imaging based on a dispersive double-helix point spread function metalens, characterized in that: The steps of the dispersion double helix point spread function metalens microscopic imaging method include: S100, design and process the dispersive double helix point spread function meta-lens by FDTD simulation; Specifically include: S101, optimizing the material, shape or geometric parameters of the metasurface, using the frequency domain calculation module based on the finite element method in the electromagnetic simulation software CST to perform simulation operations, and by changing the length and width of the nanorods under the condition that the unit structure period and the height of the nanorods are constant, the length and width of the nanorods with the maximum cross-polarization transmittance are found within the size range suitable for processing, as the unit structure of the geometric phase; S102. Generate a dispersive double helix meta-lens phase distribution by superimposing the double helix point spread function phase by the lens phase. The dispersive double helix meta-lens phase distribution is obtained by superimposing Laguerre-Gaussian beams with different mode numbers. Optimization conditions are used to constrain the pupil plane, point spread function plane, and Laguerre-Gaussian mode plane, respectively, to obtain an optimized pure phase distribution double helix point spread function, which improves energy utilization. The rotation response of the improved double helix point spread function only appears in a specific area, which not only avoids sidelobe loss, but also ensures that the function has a rotation characteristic in the entire cross section but is approximately unchanged in a specific area. On this basis, a lens phase that can produce a dispersion effect is superimposed, and a dispersive double helix meta-lens phase with different working distances and positioning accuracy is obtained by adjusting the numerical aperture of the lens. S103, generating a processing file of a dispersive double-helix metalens according to the selected unit structure and the phase distribution of the geometric phase; S104, processing the meta-lens by electron beam lithography combined with reactive ion beam etching; Three plane constraints are used to improve the modulation efficiency of the point spread function and eliminate the sidelobe effect as much as possible, namely: (1) pupil plane constraint, which removes the amplitude information and only retains the phase of the double helix point spread function; (2) point spread function plane constraint, which introduces a weight function related to the main lobe energy distribution on different focal planes to make the main lobe energy distribution more concentrated; (3) Laguerre-Gaussian mode plane constraint, which decomposes the light field into a linear superposition of Laguerre-Gaussian modes of odd functions of different (m, n) modes, multiplied by the weight function, to ensure that the point spread function has a rotation characteristic and the rotation rate remains unchanged; The lens phase can be expressed as: Where λ is the wavelength of the incident light, x and y are the position coordinates in the plane, f is the focal length of the lens, and (m,n) represents the Laguerre-Gaussian mode; By utilizing the integrated characteristics of the metasurface, the double-helix point spread function phase distribution is superimposed with the phase distribution of the lens with dispersion modulation to obtain the phase distribution of the dispersive double-helix point spread function metalens with different numerical apertures, which can be expressed as: f=f lens +φ DHPSF The amplitude-type mask has a high absorption rate for light, which will cause most of the energy loss. Therefore, only the phase is selected as the basis for constructing the metasurface, and the amplitude is fixed to 1. The size of the two main lobes of the generated point spread function, the distance between the main lobes, and the image blur degree remain basically unchanged, and the rotation rate remains unchanged, that is, the angle between the centers of the two main lobes of the double helix image is roughly linearly related to the change in defocus. According to the phase distribution of the dispersive double helix point spread function meta-lens, the meta-lens is generated using the above-selected unit structure by utilizing the arrangement idea of ​​geometric phase; the generated meta-lens is simulated by using the FDTD algorithm to predict its dispersion focusing characteristics and the three-dimensional distribution of the point spread function; the rotation rate of the two main lobes depends on the NA and the incident wavelength of the system, and has nothing to do with the size. Whether it is a large numerical aperture or a small numerical aperture, a continuously rotating light spot can be obtained near the focal plane, and the rotation period is π; the actual depth corresponding to the rotation period of meta-lenses with different numerical apertures is also different. As the numerical aperture increases, the rotation period decreases accordingly. The simulation of light field propagation proves the feasibility of the double helix lens formed by the superposition of the double helix point spread function phase distribution and the lens phase distribution from another perspective; S200, build an optical system with a meta-lens as the core to modulate the dispersion double helix point spread function, image the molecules to be measured through the meta-lens, and obtain double helix images at different incident wavelengths; S300, determining the lateral position of the molecule to be detected by the midpoint of the double helix light spot in the double helix image, and determining the axial position of the molecule to be detected by the angle between the centers of the two light spots.

2. The method for microscopic imaging based on a dispersive double-helix point spread function metalens according to claim 1, characterized in that: The meta-lens forms a complete meta-lens by periodically arranging basic unit structures according to the double-helix point spread function phase and lens phase distribution through a geometric phase arrangement method.

3. A microscopic imaging system based on the dispersed double helix point spread function metalens microscopic imaging method according to claim 1, characterized in that: Including white light source, filter, collimating lens, polarizer, quarter wave plate, converging lens, sample stage, meta-lens, microscope objective, right-hand circular polarizer, tube lens and CMOS camera; The white light source, filter, collimating lens, polarizer, quarter-wave plate and converging lens are arranged on one side of the sample stage from left to right, and the meta-lens, microscope objective, right-handed circular polarizer, tube lens and CMOS camera are arranged on the right side of the sample stage from left to right.

4. A microscopic imaging method using the microscopic imaging system according to claim 3, characterized in that: The steps of the dispersion double helix point spread function metalens microscopic imaging method include: Step 1: A white light source arranged along the propagation direction of the light beam emits incoherent light, which is passed through a filter to generate light beams of the required wavelengths, and then passes through a collimating lens to form parallel light. The collimated light passes through a polarizer and a quarter-wave plate, and left-handed circularly polarized light is generated by adjusting the quarter-wave plate. The light is then converged on the sample to be tested through a converging lens, and the sample is placed on a sample stage; Step 2: The light passing through the sample passes through the meta-lens to achieve dispersion double-helix point spread function modulation. The modulated image is imaged again by a microscope system consisting of a microscope objective and a tube lens and is collected by a CMOS camera. Step 3: Calculate the collected double-helix point spread function modulation image, determine the lateral position of the molecule to be measured by the midpoint of the double-helix spot in the double-helix image, and determine the axial position of the molecule to be measured by the angle between the centers of the two spots.

5. A microscopic imaging system based on the dispersed double helix point spread function metalens microscopic imaging method according to claim 1, characterized in that: It includes a white light source, a filter, a collimating lens, a polarizer, a quarter wave plate, a converging lens, a half-reflecting half-transmitting lens, a first microscope objective lens, a sample stage, a first tube lens, a meta-lens, a second microscope objective lens, a right-handed circular polarizer, a second tube lens and a CMOS camera; The white light source, filter, collimating lens, polarizer, quarter wave plate and converging lens are arranged on one side of the half-reflecting half-mirror from left to right, the sample stage and the first microscope objective are arranged above the half-reflecting half-mirror from top to bottom, and the first tube lens, metalens, second microscope objective, right-handed circular polarizer, second tube lens and CMOS camera are arranged below the half-reflecting half-mirror from top to bottom.

6. A microscopic imaging method of the microscopic imaging system according to claim 5, characterized in that: The steps of the dispersion double helix point spread function metalens microscopic imaging method include: Step 1: A white light source arranged along the propagation direction of the light beam emits incoherent light, and generates light beams of required wavelengths through a filter, and forms parallel light through a collimating lens. The collimated light passes through a polarizer and a quarter-wave plate, and left-handed circularly polarized light is generated by adjusting the quarter-wave plate. The light is converged on the rear focal plane of the first microscope objective lens through a converging lens. The first microscope objective lens has a numerical aperture that matches the size of the details to be resolved on the sample on the sample stage, and can evenly project the light beam processed by the half-reflecting and half-mirror lens onto the sample to be inspected; Step 2: The first microscope objective collects the light reflected by the sample to be tested, and the light is focused by the first tube lens after passing through the half-reflecting half-mirror lens. The focused light is modulated by the dispersive double-helix point spread function through the meta-lens. The modulated image is imaged by the microscope system composed of the second microscope objective and the second tube lens for secondary imaging, and is collected by the CMOS camera. Step 3: Calculate the collected double-helix point spread function modulation image, determine the lateral position of the molecule to be measured by the midpoint of the double-helix spot in the double-helix image, and determine the axial position of the molecule to be measured by the angle between the centers of the two spots.

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