Super-lens-based optical microscope objective lens structure and preparation method thereof
By adopting an ultralens structure and a bilayer subwavelength grating design in an optical microscope objective, the structural complexity and processing problems of the microscope objective under high magnification and high numerical aperture are solved, and compact and efficient large numerical aperture imaging is achieved.
Patent Information
- Application Number
- CN202510173908.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-18
- Publication Date
- 2025-07-18
AI Technical Summary
When the existing optical microscope objectives pursue high magnification and high numerical aperture, they have complex structure, large volume, difficult processing and low efficiency.
Using an optical microscope objective structure based on the ultralens, a phase-modulated subwavelength grating is designed using a double-layer high-refractive index dielectric material to achieve high numerical aperture and large imaging field of view by optimizing the antenna material and geometric size.
It realizes compact and efficient large-numerical aperture imaging, overcomes the large size and complex processing problems of traditional lenses, and improves the resolution and magnification of the microscope.
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Figure CN120335136A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of optical microscopes, and in particular to an optical microscope objective lens structure based on a metalens and a preparation method thereof. Background Art
[0002] An optical microscope is an optical instrument that uses the optical principle to magnify and image tiny objects that cannot be distinguished by the human eye, so as to provide people with information on fine structures. The structure diagram is as shown in Figure 1 Figure []. After the light rays of the object pass through the objective lens, a real image is formed, realizing the first magnification; then after passing through the eyepiece, a virtual image is formed, realizing the second magnification.
[0003] In an optical microscope, compared with the eyepiece, the optical parameters of the objective lens are more important. Its main technical parameter, the numerical aperture (abbreviated as NA), is an important indicator for judging performance, and is proportional to the resolution and magnification. The larger the NA value, the higher the optical resolution and the larger the magnification. The expression of the numerical aperture is:
[0004] NA = nsin(μ / 2)
[0005] Where n is the refractive index of the medium between the front lens of the objective lens and the object to be inspected, and μ is the aperture angle.
[0006] The aperture angle, also known as the "mirror angle", is the angle formed by the object point on the optical axis of the objective lens and the effective diameter of the front lens of the objective lens. The larger the aperture angle, the greater the light flux entering the objective lens. The expression of the aperture angle is:
[0007] μ = 2arctan(D / 2f)
[0008] Where D is the entrance pupil diameter of the front lens of the objective lens, and f is the focal length. As shown in Figure 2 Figure [].
[0009] When the requirements for magnification and numerical aperture are not high, the objective lens structure can adopt a single spherical mirror as shown in Figure 3 Figure []. Aberrations such as spherical aberration, coma, and axial chromatic aberration of this structure are easy to eliminate and can be eliminated by a simple double cemented lens, as shown in Figure 4 Figure [].
[0010] When the requirements for magnification and numerical aperture are relatively high, it is not easy to eliminate spherical aberration and the like of the above structure, and a more complex objective lens structure needs to be adopted, such as an Amici objective lens, as shown in Figure 5 Figure []. The left hemispherical lens in the figure has no spherical aberration, and its focal length is equivalent to the aperture.
[0011] It can be seen that in order to obtain an objective lens with high magnification and high numerical aperture, the structural design of the objective lens becomes increasingly complex. In addition, in order to increase the numerical aperture, the refractive index of the medium between the front lens of the objective lens and the object to be inspected can be increased. This has given rise to water-immersion objective lenses and oil-immersion objective lenses. For example, bromonaphthalene with a refractive index n = 1.66 has a corresponding numerical aperture NA = 1.4. This value is already the limit of the current technology.
[0012] Moreover, currently, large numerical aperture lenses also have problems such as large volume and weight, difficult processing, and low efficiency. Summary of the Invention
[0013] The technical problem to be solved by the present invention is how to further improve the optical performance of the microscope objective lens and realize a super lens with compactness, high efficiency, and large aperture. In view of this, the present invention provides an optical microscope objective lens structure based on a super lens.
[0014] The technical solution adopted by the present invention is that the optical microscope objective lens structure based on a super lens includes:
[0015] A lens barrel and a front lens and a flat mirror located at both ends of the lens barrel, and the front lens and the flat mirror make the lens barrel a closed structure;
[0016] Wherein, the front lens is a super lens, and a sub-wavelength unit structure is arranged on the side of the super lens close to the inside of the lens barrel;
[0017] The sub-wavelength unit structure includes: a substrate and sub-wavelength grating arrays arranged on the upper and lower surfaces of the substrate in an array form; the central positions of the sub-wavelength grating arrays on the upper and lower surfaces of the substrate correspond; the sub-wavelength grating arrays are two-dimensional arrays, and the directions parallel to the rows and columns of the sub-wavelength grating arrays are used as the x-axis and y-axis respectively; the cross-sectional shapes of each sub-wavelength grating along the xy plane are all centrosymmetric.
[0018] In one embodiment, the length and width of each grating in the sub-wavelength grating array are both 1 / 8 to 1 / 2 of the working wavelength, the heights of each sub-wavelength grating are equal and all within the sub-wavelength range, and the center distances between adjacent sub-wavelength gratings are equal and do not exceed half of the working wavelength.
[0019] Another aspect of the present invention also provides a method for preparing the optical microscope objective lens structure based on a super lens as described above, including:
[0020] Step S1, preparing a first-layer sub-wavelength grating array structure, where the first layer refers to the sub-wavelength grating array structure closer to the incident light;
[0021] Step S101: According to the working wavelength λ, use the finite-difference time-domain (FDTD) method or the rigorous coupled-wave analysis (RCWA) method to calculate the modulation of the phase and transmittance of the incident light by a single sub-wavelength grating under different heights, center distances, lengths, and widths. Keep the center distance between adjacent sub-wavelength gratings and the height of each sub-wavelength grating unchanged, and save the phase, transmittance, and the length and width ranges of all sub-wavelength gratings in the simulation results into a database.
[0022] Step S102: Use N-order linear phase equal division to divide the 0 - 360-degree phase evenly. Traverse the data in the database within the set error range of ±360 / N to find the sub-wavelength grating sizes that meet the above phase basis requirements.
[0023] Step S103: According to the requirements of the working wavelength λ, focal length f, and diameter D, use the first algorithm to determine the target phase of the incident light of the sub-wavelength grating at any coordinate within the diameter range of the imaging diffractive optical device. :
[0024] Convert the updated into the values of the N-order phase basis within the error range of ±360 / N.
[0025] Step S104: Assume that the working wavelength λ, focal length f1, and diameter D of the first-layer sub-wavelength grating array structure meet the requirements, and use the second algorithm to determine the target phase of the incident light of the sub-wavelength grating at any coordinate within the diameter range of the first-layer sub-wavelength grating array.
[0026] Step S105: Use the minimum variance between the actual phase of the sub-wavelength grating and the phase in the corresponding phase basis to determine each optimal phase basis and the sub-wavelength grating size corresponding to the optimal phase basis, and construct a corresponding table of the phase basis and sub-wavelength grating size for the first layer.
[0027] Step S2: Fabricate the second-layer sub-wavelength grating array structure, where the second layer refers to the sub-wavelength grating array structure farther away from the incident light.
[0028] Step S201: According to the working wavelength λ, use the finite-difference time-domain (FDTD) method or the rigorous coupled-wave analysis (RCWA) method to calculate the modulation of the phase and transmittance of the incident light by a single sub-wavelength grating under different heights, center distances, lengths, and widths. Keep the center distance between adjacent sub-wavelength gratings and the height of each sub-wavelength grating unchanged, and save the phase, transmittance, and the length and width ranges of all sub-wavelength gratings in the simulation results into a database.
[0029] Step S202: Use N-order linear phase equal division to divide the 0 - 360-degree phase evenly. Traverse the data in the database within the set error range of ±360 / N to find the sub-wavelength grating sizes that meet the above phase basis requirements.
[0030] Step S203: Use the third algorithm to determine the incident light target phase of the sub-wavelength grating at any coordinate within the diameter range of the second metasurface diffractive optical device
[0031] Convert the updated to the values of the N-order phase basis according to the error range of ±360 / N;
[0032] Step S204: Use the minimum variance between the actual phase of the sub-wavelength grating and the phases in the corresponding phase basis to determine each optimal phase basis and the sub-wavelength grating size corresponding to the optimal phase basis, and construct the corresponding table of the phase basis and sub-wavelength grating size for the second layer accordingly;
[0033] Step S3: Based on the corresponding table of the phase basis and sub-wavelength grating size for the two-layer structure, construct the sub-wavelength unit structure, and assemble the lens barrel and the front lens and the flat mirror located at both ends of the lens barrel.
[0034] In one embodiment, the first algorithm includes:
[0035]
[0036] where, -D / 2 ≤ x ≤ D / 2, -D / 2 ≤ y ≤ D / 2.
[0037] In one embodiment, the second algorithm includes:
[0038]
[0039] where, f1 > f.
[0040] In one embodiment, the third algorithm includes:
[0041] φ2 = φ - φ1.
[0042] In one embodiment, N is 6 to 10.
[0043] Adopting the above technical solutions, the present invention has at least the following advantages:
[0044] An optical microscope objective lens structure based on a metalens provided by the present invention designs a phase-modulated subwavelength grating using a bilayer dielectric material with a high refractive index. By selecting a suitable antenna material and reasonably designing the geometric size of the antenna, arbitrary phase modulation within a range from ultraviolet to microwave bands can be achieved for the same unit structure, and a high transmittance or reflectance can be maintained. By designing and optimizing the size and arrangement of each antenna in the bilayer, imaging elements with a high numerical aperture and a large imaging field of view can be realized. The present invention realizes high-numerical-aperture imaging with a bilayer metasurface, which is expected to overcome problems such as large mass and volume and complex processing of traditional large-numerical-aperture lenses, making it possible to have a high-efficiency and integrated large-numerical-aperture module. BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Figure 1 FIG. 6 is a schematic diagram of an optical microscope in the prior art;
[0046] Figure 2 FIG. 10 is a schematic diagram of the entrance pupil diameter and focal length of an objective lens in the prior art;
[0047] Figure 3 FIG. 14 is a schematic diagram of an objective lens based on a single spherical mirror in the prior art;
[0048] Figure 4 FIG. 18 is a schematic diagram of an objective lens based on a doublet lens in the prior art;
[0049] Figure 5 FIG. 22 is a schematic diagram of an objective lens based on an Amici structure in the prior art;
[0050] Figure 6 FIG. 26 is a schematic diagram of an optical microscope objective lens structure based on a metalens according to an embodiment of the present invention;
[0051] Figure 7 FIG. 30 is a schematic diagram of the surface structure of a metalens according to an embodiment of the present invention.
[0052] REFERENCE SIGNS
[0053] 10 - barrel, 20 - metalens, 30 - flat mirror, 201 - subwavelength structure. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0054] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.
[0055] It should be understood that the terms "comprising", "including", "having", "containing" and / or "including" when used in this specification denote the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof. In addition, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than an individual element in the list. In addition, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the term "exemplary" is intended to refer to an example or illustration.
[0056] As used herein, the terms "substantially", "about" and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by a person of ordinary skill in the art.
[0057] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0058] In a first embodiment of the present invention, an optical microscope objective lens structure based on a metalens is as Figure 6 shown and includes:
[0059] A front lens and a flat mirror 30 located at both ends of the lens barrel 10, and the front lens and the flat mirror 30 make the lens barrel 10 a closed structure;
[0060] In this embodiment, the front lens is a metalens 20, and a sub-wavelength structure 201 is provided on one side of the metalens 20 close to the inside of the lens barrel 10.
[0061] As Figure 7 shown, the metalens 20 provided in this embodiment is a planar light-transmitting material, and a sub-wavelength structure 201 is provided on one side.
[0062] Specifically, the sub-wavelength structure 201 specifically includes: consisting of a substrate and sub-wavelength gratings arranged in an array form on the upper and lower surfaces of the substrate; the central positions of the sub-wavelength grating arrays on the upper and lower surfaces correspond; the sub-wavelength grating array is a two-dimensional array, with the directions parallel to the rows and columns of the sub-wavelength grating array being the x-axis and y-axis respectively; the cross-sectional shapes of each sub-wavelength grating along the xy plane all have central symmetry, the length and width of each sub-wavelength grating are respectively 1 / 8 to 1 / 2 of the working wavelength, the heights of each sub-wavelength grating are equal and all within the sub-wavelength range, and the center distances between adjacent two sub-wavelength gratings are equal and do not exceed half of the working wavelength.
[0063] In the second embodiment of the present invention, this embodiment is a preparation method for preparing the structure described in the first embodiment.
[0064] S1. The distribution of each sub-wavelength grating in the first-layer two-dimensional array is determined according to the following steps. The first layer is the layer close to the incident light:
[0065] 1) According to the working wavelength λ, using the finite-difference time-domain or rigorous coupled-wave analysis method, calculate the modulation of the phase and transmittance of the incident light when a single sub-wavelength grating is at different heights, center distances, lengths, and widths; keep the center distance between adjacent two sub-wavelength gratings and the height of each sub-wavelength grating unchanged, and store the phase, transmittance, and the length and width ranges of all sub-wavelength gratings in the simulation results in a database.
[0066] 2) Use the N-order linear phase equal division to evenly divide the 0-360 degree phase, where N is taken as 6-10 as the phase basis; traverse each data in the database within the set error range of ±360 / N to find the sub-wavelength grating sizes that meet the requirements of the above phase basis.
[0067] 3) According to the requirements of the working wavelength λ, focal length f, and diameter D of the imaging diffractive optical device, use the following formula to determine the target phase of the incident light of the sub-wavelength grating at any (x, y) coordinate within the diameter range of the imaging diffractive optical device
[0068]
[0069] where, -D / 2 ≤ x ≤ D / 2, -D / 2 ≤ y ≤ D / 2;
[0070] According to the error range of ±360 / N, update the Convert it to the value of the N-order phase basis;
[0071] 4) Assume that the first-layer metasurface realizes the requirements of the working wavelength λ, focal length f1, and diameter D of the imaging diffractive optical device, and use the following formula to determine the target phase of the incident light of the sub-wavelength grating at any (x, y) coordinate within the diameter range of the first-layer metasurface optical device :
[0072]
[0073] Among them, -D / 2 ≤ x ≤ D / 2, -D / 2 ≤ y ≤ D / 2, f1 > f.
[0074] 5) Determine each optimal phase basis and the sub-wavelength grating size corresponding to the optimal phase basis by using the minimum variance between the actual phase of the sub-wavelength grating and the phase in the corresponding phase basis, and construct a corresponding table of the sub-wavelength grating size corresponding to the phase basis.
[0075] S2. The distribution of each sub-wavelength grating in the second-layer two-dimensional array is determined according to the following steps. The second layer is the layer far from the incident light:
[0076] 1) According to the working wavelength λ, use the finite-difference time-domain or rigorous coupled-wave analysis method to calculate the modulation of the phase and transmittance of the incident light when a single sub-wavelength grating is under different heights, center distances, lengths, and widths; keep the center distance between adjacent sub-wavelength gratings and the height of each sub-wavelength grating unchanged, and store the phase, transmittance, and the length and width ranges of all sub-wavelength gratings in the simulation results in a database.
[0077] 2) Use N-order linear phase equal division to divide the 0-360 degree phase, and take N as 6-10 as the phase basis; traverse each data in the database within the set error range of ±360 / N to find the sub-wavelength grating size that meets the above phase basis requirements.
[0078] 3) Use the following formula to determine the target phase of the incident light of the sub-wavelength grating at any (x, y) coordinate within the diameter range of the second metasurface diffractive optical device
[0079] φ2 = φ - φ1.
[0080] According to the error range of ±360 / N, update the Convert it to the value of the N-order phase basis;
[0081] 4) Determine each optimal phase basis and the sub-wavelength grating size corresponding to the optimal phase basis by using the minimum variance between the actual phase of the sub-wavelength grating and the phase in the corresponding phase basis, and construct a corresponding table of the sub-wavelength grating size corresponding to the phase basis.
[0082] S3. Based on the corresponding table of the sub-wavelength grating size corresponding to the phase basis of the two-layer structure, construct the sub-wavelength unit structure, and assemble the lens barrel and the front lens and flat mirror located at both ends of the lens barrel.
[0083] In summary, the present invention designs a phase-modulated subwavelength grating using a double-layer high-refractive-index dielectric material. By selecting a suitable antenna material and reasonably designing the geometric dimensions of the antenna, arbitrary phase modulation within the range of 02 from ultraviolet to visible and up to the microwave band can be achieved for the same unit structure, while maintaining a high transmittance or reflectance. By designing and optimizing the size and arrangement of each antenna in the double layer, imaging elements with a high numerical aperture and a large imaging field of view can be realized. The present invention realizes high-numerical-aperture imaging with a double-layer metasurface, which is expected to overcome the problems of large mass and volume and complex processing of traditional large-numerical-aperture lenses, making it possible to have a high-efficiency and integrated large-numerical-aperture module.
[0084] Through the description of the specific embodiments, it should be possible to understand more deeply and specifically the technical means and effects adopted by the present invention to achieve the predetermined purpose. However, the accompanying drawings are only for reference and illustration purposes and are not used to limit the present invention.
Claims
1. An optical microscope objective lens structure based on a metalens, characterized in that Comprising: A lens barrel, a front lens and a plane mirror located at both ends of the lens barrel, wherein the front lens and the plane mirror make the lens barrel a closed structure; Wherein, the front lens is a meta-lens, and a sub-wavelength unit structure is arranged on one side of the meta-lens close to the inside of the lens barrel; The sub-wavelength unit structure includes: a substrate and a sub-wavelength grating array arranged on the upper and lower surfaces of the substrate in an array form; the central positions of the sub-wavelength grating arrays on the upper and lower surfaces of the substrate correspond; the sub-wavelength grating array is a two-dimensional array, and the directions parallel to the rows and columns of the sub-wavelength grating array are used as the x-axis and the y-axis respectively; the cross-sectional shape of each sub-wavelength grating along the xy plane has central symmetry.
2. The objective lens structure of an optical microscope based on a metalens according to claim 1, wherein The length and width of each grating in the sub-wavelength grating array are both 1 / 8 to 1 / 2 of the working wavelength, the heights of each sub-wavelength grating are equal and all within the sub-wavelength range, and the center distances between adjacent two sub-wavelength gratings are equal and do not exceed half of the working wavelength.
3. A method for preparing a superlens-based optical microscope objective structure as described in any one of claims 1 or 2, characterized in that, Comprising: Step S1, preparing a first-layer sub-wavelength grating array structure, wherein the first layer refers to the sub-wavelength grating array structure closer to the incident light; Step S101, according to the working wavelength λ, using the finite-difference time-domain or rigorous coupled-wave analysis method, calculate the modulation of the phase and transmittance of the incident light when a single sub-wavelength grating is under different heights, center distances, lengths and widths; keep the center distance between adjacent two sub-wavelength gratings and the height of each sub-wavelength grating unchanged, and store the phase, transmittance, and the length and width ranges of all sub-wavelength gratings in the simulation results in a database; Step S102, use N-order linear phase equal division to divide 0-360 degrees of phase; traverse each data in the database within the set error range of ±360 / N to find the sub-wavelength grating sizes that meet the above phase basis requirements; Step S103: According to the requirements of the working wavelength λ, focal length f, and diameter D, use the first algorithm to determine the target incident light phase of the sub-wavelength grating at any coordinate within the diameter range of the imaging diffractive optical device. Convert the updated to the value of the Nth-order phase basis according to the error range of ±360 / N; Step S104, assuming that the working wavelength λ, focal length f1, and diameter D of the first-layer sub-wavelength grating array structure meet the requirements, use the second algorithm to determine the target phase of the incident light of the sub-wavelength grating at any coordinate within the diameter range of the first-layer sub-wavelength grating array Step S105, use the minimum variance between the actual phase of the sub-wavelength grating and the phase in the corresponding phase basis to determine each optimal phase basis and the sub-wavelength grating size corresponding to the optimal phase basis, and thus construct a phase-sub-wavelength grating size correspondence table for the first layer; Step S2, preparing a second-layer sub-wavelength grating array structure, wherein the second layer refers to the sub-wavelength grating array structure farther from the incident light; Step S201, according to the working wavelength λ, using the finite-difference time-domain or rigorous coupled-wave analysis method, calculate the modulation of the phase and transmittance of the incident light when a single sub-wavelength grating is under different heights, center distances, lengths and widths; keep the center distance between adjacent two sub-wavelength gratings and the height of each sub-wavelength grating unchanged, and store the phase, transmittance, and the length and width ranges of all sub-wavelength gratings in the simulation results in a database; Step S202, use N-order linear phase equal division to divide 0-360 degrees of phase; traverse each data in the database within the set error range of ±360 / N to find the sub-wavelength grating sizes that meet the above phase basis requirements; Step S203: Use the third algorithm to determine the target phase of the incident light of the sub-wavelength grating at any coordinate within the diameter of the second metasurface diffractive optical device Convert the updated to the value of the Nth-order phase basis according to the error range of ±360 / N; Step S204, use the minimum variance between the actual phase of the sub-wavelength grating and the phase in the corresponding phase basis to determine each optimal phase basis and the sub-wavelength grating size corresponding to the optimal phase basis, and thus construct a phase-sub-wavelength grating size correspondence table for the second layer; Step S3: Based on the phase sub-wavelength grating size correspondence table of the two-layer structure, construct the sub-wavelength unit structure, and assemble the lens barrel and the front lens and the flat mirror located at both ends of the lens barrel.
4. The preparation method of the optical microscope objective lens structure based on a metalens according to claim 3, characterized in that, The first algorithm includes: where, -D / 2 ≤ x ≤ D / 2, -D / 2 ≤ y ≤ D / 2.
5. The preparation method of the optical microscope objective lens structure based on a metalens according to claim 4, characterized in that The second algorithm includes: where, f1 > f.
6. The preparation method of the optical microscope objective lens structure based on a metalens according to claim 5, characterized in that, The third algorithm includes: φ2 = φ - φ1.
7. The preparation method of the optical microscope objective lens structure based on a metalens according to claim 3, wherein, N is 6 to 10.