Spectral interference surface topography measurement method and device based on metasurface

Abstract

The invention relates to the technical field of surface topography measurement, and discloses a spectral interference surface topography measurement method and device based on a metasurface. The device comprises a spectrograph, a white light source, an optical fiber, a focusing metasurface and a dispersion metasurface, the focusing metasurface and the dispersion metasurface are arranged in parallel and aligned, a spherical thin lens and a micro-nano structure are arranged on the two sides of the focusing metasurface respectively, and a reflecting metal film is arranged between the two sides; a semi-transparent and semi-reflective film and a micro-nano structure are arranged on the two sides of the dispersion metasurface respectively; the focusing metasurface is used for converging parallel incident light, one part of light serves as reference light and is reflected and focused on the reflective coating by the semi-transparent and semi-reflective film, and the other part of light serves as measuring light and penetrates through the semi-transparent and semi-reflective film; the dispersion metasurface is used for carrying out axial dispersion on light penetrating through the semi-transparent and semi-reflective film, monochromatic light focused on the to-be-measured surface returns along a light path and interferes with reference light, and a confocal signal or an interference signal is generated to calculate morphology information of the to-be-measured surface. By adopting the device, high-precision surface topography measurement can be realized in a narrow space.

Description

Technical Field

[0001] This application relates to the fields of micro-nano optics and high-precision surface morphology measurement technology, and more specifically, to a method and apparatus for measuring surface morphology based on metasurface spectral interferometry. Background Technology

[0002] Surface topography measurement plays a crucial role in high-end manufacturing and strategic fields such as aerospace, precision instruments, and nuclear fusion. Existing surface topography measurement methods primarily rely on contact-based surface profilometers, but these methods are inefficient and prone to damaging sample surfaces, making them unsuitable for high-volume, non-destructive testing. While non-contact white light interferometers offer higher efficiency and do not damage sample surfaces, they suffer from drawbacks such as bulky equipment and difficulty in performing measurements in confined spaces.

[0003] Currently, measurement methods combining spectral confocal interferometry and white light interferometry are gaining popularity. This method balances the large range of spectral confocal interferometry with the high axial resolution of interferometry, enabling high-precision measurement of complex surface morphologies. Although its size is slightly smaller than that of a white light interferometer, the complex optical path system structure due to factors such as traditional optical lens materials and aberration optimization still makes it difficult to achieve high-precision measurement of surface morphologies in confined spaces such as integral bladed disks, micro-holes, and gaps. Summary of the Invention

[0004] To address the problem of low accuracy in surface morphology measurement within confined spaces, this invention provides a method and apparatus for measuring surface morphology using spectral interferometry based on metasurfaces. This method enables non-contact, high-precision spectral interferometry surface morphology measurement within confined spaces.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a metasurface-based spectral interferometry surface morphology measurement device is provided, comprising: The system comprises a spectrometer, a white light source, optical fibers, and a metasurface mirror assembly. The metasurface mirror assembly includes a collimating lens, a focusing metasurface and a dispersive metasurface placed in parallel alignment, with a predetermined distance between the dispersive metasurface and the focusing metasurface, equal to half the working focal length of the focusing metasurface. The first side of the focusing metasurface is a spherical thin lens, and its second side is a micro / nano structure. Its reflective coating is coated with a reflective metal film and is located between the first and second sides of the focusing metasurface. The first side of the dispersive metasurface is coated with a semi-transparent and semi-reflective film, and its second side is a micro / nano structure. White light source is used to provide divergent light; optical fiber is used to transmit light; collimating lens is used to collimate the divergent light emitted from the optical fiber outlet into parallel incident light, and its position is determined by the numerical aperture and diameter of the optical fiber outlet. A focusing metasurface is used to converge parallel incident light. Part of the light is used as reference light and is reflected and focused onto the reflective coating by a semi-transparent and semi-reflective film. The other part of the light is used as measurement light and passes through the semi-transparent and semi-reflective film. Dispersive metasurfaces are used to axially disperse light that has passed through a semi-transparent and semi-reflective film. The monochromatic light focused on the surface under test returns along the optical path to the metasurface mirror group and interferes with the reference light, generating a confocal signal or an interference signal. A spectrometer is used to receive confocal or interference signals, which are then used to calculate the morphological information of the surface under test.

[0006] Furthermore, the material selection for the spherical thin lens in the focusing metasurface is determined by the working focal length of the focusing metasurface, the radius of curvature of the spherical thin lens obtained from preliminary calculations, the center wavelength of the incident light in the working band, and the refractive index of the spherical thin lens material corresponding to the center wavelength.

[0007] Furthermore, when focusing the working focal length of the metasurface... F Greater than When using a spherical thin lens, a material with a refractive index less than a set refractive index threshold and a dispersion less than a set dispersion threshold is selected; when focusing on the metasurface, the working focal length... F Not greater than When using a spherical thin lens, a material with a refractive index not less than a set refractive index threshold and a dispersion not less than a set dispersion threshold is selected. The formula for calculating the radius of curvature of the spherical thin lens, obtained from preliminary calculations, is as follows: ; Indicates the center wavelength of the incident light in its operating band. This represents the refractive index of the spherical thin lens material corresponding to the center wavelength. It represents the derivative of the refractive index of a spherical thin lens material with respect to wavelength.

[0008] Furthermore, the layout of the micro / nano structures in the focused metasurface is determined by the following equation: , in, Indicates the coordinates of the focused metasurface. Phase of micro / nano structures This indicates the working focal length of the focusing metasurface. Indicates the wavelength of the incident light. and The x and y coordinates represent the locations of the micro / nano structures, respectively.

[0009] Furthermore, focusing on metasurface coordinates The cross-sectional area of ​​the micro / nano structure is determined by the following formula: , in, Indicates the coordinates of the focused metasurface. The cross-sectional area of ​​the micro / nano structure This represents the cross-sectional area of ​​the periodic space in which the micro / nano structure resides. The refractive index of a material representing a micro / nano structure This represents the refractive index of the medium surrounding the metasurface. The height of the micro / nano structure.

[0010] Furthermore, the layout of the micro / nano structures in the dispersive metasurface is determined by the following equation: , in, Represents the coordinates of the dispersive metasurface Phase of micro / nano structures and Represents the wavelength sequence of the first wavelength. Each wavelength data and its corresponding focal length, N This represents the number of wavelength sequences.

[0011] Furthermore, dispersive metasurface coordinates The cross-sectional area of ​​the micro / nano structure is determined by the following formula: , in, Represents the coordinates of the dispersive metasurface The cross-sectional area of ​​the micro / nano structure This represents the cross-sectional area of ​​the periodic space in which the micro / nano structure resides. The refractive index of a material representing a micro / nano structure This represents the refractive index of the medium surrounding the metasurface. The height of the micro / nano structure.

[0012] According to a second aspect of the present invention, a method for measuring the spectral interferometric surface morphology based on a metasurface is also provided, applied to the aforementioned metasurface-based spectral interferometric surface morphology measuring device, the method comprising: Acquire the spectrometer signal data received by the spectrometer; Based on the spectrometer signal data, the morphology information of the surface to be tested is obtained.

[0013] Furthermore, based on the spectrometer signal data, the morphology information of the surface to be tested is obtained. This includes the spectrometer signal data, which includes confocal signals, wavelength sequence data, and light intensity sequence data, when the surface to be tested is within the dispersion range. Based on the wavelength sequence data, light intensity sequence data, and wavelength-focal length correspondence, the morphology information of the surface to be tested is obtained.

[0014] Furthermore, based on the spectrometer signal data, the morphology information of the surface to be measured is obtained, including when the surface to be measured is within the interferometric measurement range, the spectrometer signal data includes the interference signal, and the morphology information of the surface to be measured is obtained based on the interference signal.

[0015] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: (1) The spectral interferometric surface morphology measurement device based on metasurfaces provided by the present invention includes a spectrometer, a white light source, an optical fiber, a collimating lens, a focusing metasurface and a dispersive metasurface placed in parallel alignment, wherein there is a set distance between the dispersive metasurface and the focusing metasurface, which is equal to half the working focal length of the focusing metasurface; the first side of the focusing metasurface is a spherical thin lens, and its second side is a micro-nano structure, wherein its reflective coating is coated with a reflective metal film, and the reflective coating is located between the first side and the second side of the focusing metasurface; the first side of the dispersive metasurface is coated with a semi-transparent and semi-reflective film, and its second side is a micro-nano structure; the white light source is used to provide divergent light, and the optical fiber is used to provide divergent light. To transmit the diverging light, a collimating lens is used to collimate the diverging light emitted from the fiber optic output port into parallel incident light. The parallel incident light is converged by a focusing metasurface. Part of the light serves as a reference light, which is reflected and focused onto the reflective coating by a semi-reflective film. The other part serves as the measurement light, which passes through the semi-reflective film and undergoes axial dispersion through a dispersive metasurface. The monochromatic light focused on the surface under test returns along the optical path to the measuring device and interferes with the reference light, and is received by a spectrometer at the back end. Based on the spectrometer signal data received by the spectrometer, the morphology information of the surface under test is obtained, thereby enabling non-contact, high-precision surface morphology measurement in a confined space. This measuring device uses a micro-nano structure to precisely control the phase, eliminating the need for aberration correction and optimization of the optical system. Compared with traditional lenses, it is smaller and lighter, making it suitable for measurement projects with high precision and stringent requirements regarding the size and weight of the measuring equipment.

[0016] (2) The surface morphology measurement method based on metasurface provided by the present invention realizes the dual measurement modes of spectral confocal and spectral interferometry in a set of optical path system, which takes into account the characteristics of high precision of large range of spectral confocal and high resolution of spectral interferometry, and can adapt to surface morphology measurement with longitudinal cross-scale characteristics. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1A schematic diagram of a spectral interferometric surface morphology measurement device based on a metasurface, provided for an embodiment of this application; Figure 2 A schematic diagram of the principle of a metasurface-based spectral interferometry surface morphology measurement device provided in this application embodiment; Figure 3 A schematic flowchart illustrating a method for measuring surface morphology based on spectral interferometry using metasurfaces, provided in an embodiment of this application; Figure 4 A schematic diagram of some micro / nano structures provided in the embodiments of this application; Figure 5 This is a schematic diagram illustrating the principle of calculating the cross-sectional area of ​​micro / nano structures provided in the embodiments of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0020] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0021] like Figure 1 As shown, a spectral interferometric surface morphology measurement device based on metasurfaces is provided. The measurement device includes a spectrometer, a white light source, an optical fiber, and a metasurface mirror group. The metasurface mirror group consists of a collimating lens, a focusing metasurface and a dispersive metasurface placed in parallel alignment. The collimating lens collimates the diverging light emitted from the optical fiber into parallel light, and its position is determined by the numerical aperture and aperture of the optical fiber's output port. There is a set distance between the dispersive metasurface and the focusing metasurface, which is equal to half the working focal length of the focusing metasurface.

[0022] Those skilled in the art will understand that Figure 1The structure shown is merely a block diagram of a portion of the structure relevant to this application and does not constitute a limitation on the metasurface-based spectral interferometric surface topography measurement device in this application. A specific metasurface-based spectral interferometric surface topography measurement device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0023] The first side of the focusing metasurface is a spherical thin lens, and the second side is a micro / nano structure. Its reflective coating is coated with a reflective metal film, and the reflective coating is located between the first and second sides of the focusing metasurface. The first side of the dispersive metasurface is coated with a semi-transparent and semi-reflective film, and the second side is a micro / nano structure. A white light source is used to provide divergent light. An optical fiber is used to transmit light. A collimating lens is used to collimate the divergent light emitted from the optical fiber outlet into parallel incident light. The focusing metasurface is used to converge the parallel incident light. Part of the light is used as reference light and is reflected and focused on the reflective coating by the semi-transparent and semi-reflective film. The other part of the light is used as measurement light and passes through the semi-transparent and semi-reflective film. The dispersive metasurface is used to axially disperse the light transmitted through the semi-transparent and semi-reflective film. The monochromatic light focused on the surface to be measured returns along the optical path to the metasurface mirror group and interferes with the reference light to generate a confocal signal or interference signal. A spectrometer is used to receive the confocal signal or interference signal, and the confocal signal or interference signal is used to calculate the morphology information of the surface to be measured. The surface to be tested can be the inner bore of an aero-engine main shaft, the surface of an integral bladed disk blade, the surface of a nuclear fusion target pellet, or other similar surfaces.

[0024] The metasurface-based spectral interferometric surface morphology measurement device provided in this embodiment uses micro-nano structures to precisely control the phase, eliminating the need for aberration correction and optimization of the optical system. Compared with traditional lenses, it is smaller and lighter, and can adapt to measurement projects with high precision and strict requirements on the size and weight of the measurement equipment. It provides a solution for the measurement of key dimensions of the inner hole of the main shaft of aero-engines, and the high-precision detection of the surface morphology of integral bladed disk blades and nuclear fusion targets.

[0025] In one embodiment, such as Figure 2 As shown, the spectral interferometric surface topography measurement device based on metasurfaces utilizes micro / nano structures on a focusing metasurface and a dispersive metasurface to achieve focusing and axial dispersion of parallel incident light, respectively. In this device, one side (i.e., the first side) of the focusing metasurface is a spherical thin lens, and the other side (i.e., the second side) is a micro / nano structure. The central region between the two sides (i.e., the reflective coating) is coated with a reflective metal film. One side (i.e., the first side) of the dispersive metasurface is coated with a semi-transparent and semi-reflective film, and the other side (i.e., the second side) is a micro / nano structure.

[0026] When parallel light is incident, the light rays converge at the focusing metasurface. Part of the light serves as the reference light, which is reflected and focused at the reflective coating by the semi-reflective film. The other part of the light serves as the measurement light, which passes through the semi-reflective film and undergoes axial dispersion through the dispersive metasurface. The monochromatic light focused on the surface under test returns to the system along the optical path and interferes with the reference light. It is then received by the spectrometer at the back end. The morphology information of the surface under test is obtained by calculating the spectrometer signal data.

[0027] The measuring device has two working modes: (1) Spectral confocal mode: when the surface to be measured is within the dispersion range (also known as the dispersion range), the spectrometer receives the confocal signal, obtains wavelength sequence data and light intensity sequence data, and calculates the measurement result through the wavelength-focal length relationship. At this time, the spectral interferometric surface morphology measurement method based on metasurface has the characteristics of large range and high precision of spectral confocal sensing technology; (2) Spectral interferometric mode: when the surface to be measured is within the interferometric measurement range, the spectrometer receives the interferometric signal, and obtains the measurement result by calculating the interferometric signal. At this time, the spectral interferometric surface morphology measurement method based on metasurface has the characteristics of high resolution of interferometric measurement.

[0028] In one embodiment, such as Figure 3 As shown, a method for measuring the surface morphology of a metasurface based on spectral interferometry is provided and applied to the aforementioned measuring device. This method can be executed by a terminal or by a server communicating with the terminal via a network. The terminal can be, but is not limited to, various personal computers, laptops, smartphones, tablets, etc. The server can be a standalone server or a server cluster consisting of multiple servers. Taking the application of this measurement method to a terminal as an example, the following steps are included: Step 301: Obtain the spectrometer signal data received by the spectrometer.

[0029] The spectrometer signal data may include confocal signals or interference signals.

[0030] Step 302: Obtain the morphology information of the surface to be tested based on the spectrometer signal data.

[0031] For example, when the surface to be measured is within the dispersion range, the spectrometer signal data includes confocal signals, wavelength sequence data, and light intensity sequence data. The terminal obtains the morphology information of the surface to be measured based on the wavelength sequence data, light intensity sequence data, and wavelength-focal length correspondence. When the surface to be measured is within the interferometric measurement range, the spectrometer signal data includes interference signals. The terminal obtains the morphology information of the surface to be measured based on the interference signals.

[0032] The above-mentioned metasurface-based spectral interferometry surface morphology measurement method can realize dual measurement modes of spectral confocal and spectral interferometry in a single optical path system. It takes into account the characteristics of high precision with large range of spectral confocal and high resolution of spectral interferometry, and can adapt to surface morphology measurement with longitudinal cross-scale characteristics.

[0033] In one embodiment, the focusing metasurface consists of a spherical thin lens on one side and a micro / nano structure on the other side, wherein the material of the spherical thin lens is selected based on the working focal length of the focusing metasurface. F Greater than When using a spherical thin lens, a material with low refractive index and low dispersion should be selected; when focusing on a metasurface, the working focal length... F Less than or equal to When using spherical thin lenses, materials with high refractive index and high dispersion should be selected. Among these, The formula for calculating the radius of curvature of the spherical thin lens, obtained from preliminary calculations, is as follows: .

[0034] in, Indicates the center wavelength of the incident light in its operating band. This represents the refractive index of the spherical thin lens material corresponding to the center wavelength. It represents the derivative of the refractive index of a spherical thin lens material with respect to wavelength.

[0035] After determining the material of the spherical thin lens, the radius of curvature of the spherical thin lens... It can be calculated using the following formula: , in, This indicates the working focal length of the focusing metasurface. This represents the refractive index of a spherical thin lens material as a function of wavelength. This represents the derivative of the refractive index of a thin spherical lens material with respect to wavelength. For example, when... Focusing on metasurface radius The operating wavelength is 500nm to 700nm, and the spherical thin lens material is Chengdu Guangming H-FK95N. Calculations show... .

[0036] In this case, the phase relationship between the micro / nanostructures on the other side of the focused metasurface and their positional relationship, i.e., the layout of the micro / nanostructures, is determined by the following equation: , in, Indicates the coordinates of the focused metasurface. Phase of micro / nano structures Indicates the wavelength of the incident light. and The x and y coordinates represent the locations of the micro / nano structures, respectively.

[0037] Due to the characteristics of micro / nano structure fabrication methods, the height of micro / nano structures Generally unchanged, therefore coordinates Cross-sectional area of ​​micro / nano structures Determined by the following formula: , in, Represents the plane coordinates of the focused metasurface. The cross-sectional area of ​​the micro / nano structure This represents the cross-sectional area of ​​the periodic space in which the micro / nano structure resides. The refractive index of a material representing a metasurface micro / nanostructure is... This represents the refractive index of the medium surrounding the metasurface. The height of the micro / nano structure.

[0038] In one embodiment, such as Figure 4 As shown, the shapes of micro / nanostructures can be various centrally symmetric shapes, such as cylinders, hollow cylinders, squares, and crosses. The materials for the micro / nanostructures can be selected based on parameters such as the diameter, focal length, and operating wavelength of the designed focusing metasurface, including silicon nitride, silicon dioxide, and titanium dioxide. The height of the micro / nanostructure can be determined based on the material and the phase of the focusing metasurface. For example, if the diameter of the focusing metasurface is 0.5 mm and silicon nitride is used as the material, the height of the micro / nanostructure can be selected between 500 nm and 900 nm. Regardless of the material and size of the micro / nanostructure, as long as the phase distribution of the micro / nanostructure at each point on the focusing metasurface is satisfied... This allows parallel light of different wavelengths within the working band to be focused at the same focal point.

[0039] In one embodiment, such as Figure 5 As shown, when wavelength The periodic space is a square with a side length of 500 nm. The material of the micro / nano structure is silicon nitride. The height of the micro / nano structure is... When the shape is a hollow cylinder with an outer diameter of 400 nm and an inner diameter to be determined, the cross-sectional area of ​​the periodic space in which the micro / nano structure is located is... The refractive index of metasurface micro / nanostructures The metasurface is surrounded by air, and the refractive index of the surrounding medium is... If coordinates Phase Then the cross-sectional area of ​​the micro / nano structure can be calculated. 215199.94nm 2 That is, the inner diameter of the hollow cylinder is 302.5 nm, then the coordinates are... The shape design of the micro / nano structure has been completed.

[0040] In one embodiment, the dispersive metasurface consists of a semi-transparent and semi-reflective film on one side of the lens and micro / nano structures on the other side. The arrangement (i.e., layout) of the micro / nano structures is determined by the phase distribution, dispersion range, working focal length, working bandwidth, and center wavelength of the micro / nano structures. The arrangement is as follows: , in, Represents the coordinates of the dispersive metasurface Phase of micro / nano structures and Represents the wavelength sequence of the first wavelength. Each wavelength data and its corresponding focal length, N This represents the number of wavelength sequences. N The value depends on the dispersion range. L As for the formula, it can be determined by... Calculations are performed, generally Δ L =1μm.

[0041] At the height of micro-nano structures Under certain conditions, coordinates Cross-sectional area of ​​micro / nano structures Determined by the following formula: , in, Represents the plane coordinates of the dispersive metasurface The cross-sectional area of ​​the micro / nanostructure is calculated using the same method as that for focusing metasurfaces. The micro / nanostructures that make up dispersive metasurfaces and those that make up focusing metasurfaces differ only in phase; other parameters (including the refractive index of the material of the metasurface micro / nanostructure) are identical. The refractive index of the medium surrounding the metasurface The height of micro-nano structures The values ​​of ) are all the same.

[0042] In spectral confocal surfaces, axial dispersion is often sought to be linear, meaning the wavelength-focal length relationship is linear. In this case, the wavelength-focal length correspondence of the dispersive metasurface can be solved by fitting using the least squares method: .

[0043] in, Describing a dispersive metasurface with radius as The coordinates of each point on the circle, The wavelength sequence of the first wavelength is i Wavelength-focal length group This represents the residual function corresponding to the wavelength-focal length set. Indicates the center wavelength of the incident light in its operating band. mThis represents the number of radii divided on the dispersive metasurface when calculating the above formula, and is generally taken as 1000.

[0044] To approximate the model using the least squares method: .

[0045] make The residual can then be written as: .

[0046] To minimize the sum of squares of the residuals, it is equivalent to solving a system of linear equations. Its least squares solution is: .

[0047] in, , , therefore, .

[0048] When the incident light is broadband visible light ,in and Let be the minimum and maximum wavelengths of the incident light over a wide band, respectively. Then the corresponding dispersion range is: When the surface under test is within the dispersion range, the wavelength of maximum light intensity can be obtained using a spectrometer. And calculate the corresponding focal length based on the wavelength-focal length correspondence of the dispersive metasurface. This allows for the acquisition of measurement results, such as the airfoil profile of aircraft blades and the diameter of micro-holes inside the main shaft of aircraft engines. When the surface to be measured is within the range of interferometric measurement, it can be solved using methods such as the four-step phase shifting method and Fourier transform to obtain measurement results, such as the surface roughness of integral bladed disk blades and blade tenons, and the surface morphology of nuclear fusion target pellets.

[0049] The spectral interferometric surface morphology measurement device provided in this embodiment realizes dual measurement modes of spectral confocal and spectral interferometric in a single optical path system. It takes into account the characteristics of high precision with a large range of spectral confocal and high resolution of spectral interferometric, and can adapt to surface morphology measurement with longitudinal cross-scale characteristics.

[0050] The above description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metasurface-based spectral interferometric surface topography measurement apparatus, characterized in that, The device comprises a spectrometer, a white light source, an optical fiber, and a super surface mirror set, wherein the super surface mirror set comprises a collimating mirror, a focusing super surface and a dispersive super surface arranged in parallel, and a set distance exists between the focusing super surface and the dispersive super surface, and the set distance is equal to half of the working focal length of the focusing super surface; the first side of the focusing super surface is a spherical thin lens, the second side of the focusing super surface is a micro-nano structure, a reflective coating is coated with a reflective metal film, and the reflective coating is located between the first side and the second side of the focusing super surface; the first side of the dispersive super surface is coated with a semi-transparent and semi-reflective film, and the second side of the dispersive super surface is a micro-nano structure. The white light source is used to provide divergent light. The optical fiber is used to transmit light. The collimating mirror is used to collimate the divergent light emitted by the light outlet of the optical fiber into parallel incident light, and the position of the collimating mirror is determined by the numerical aperture and the aperture of the light outlet of the optical fiber. The focusing super surface is used to converge the parallel incident light, and a part of the light is focused on the reflective coating as reference light after being reflected by the semi-transparent and semi-reflective film, and another part of the light is transmitted through the semi-transparent and semi-reflective film as measurement light. The dispersive super surface is used to axially disperse the light transmitted through the semi-transparent and semi-reflective film, and the monochromatic light focused on the surface to be measured returns to the super surface mirror set along the light path and interferes with the reference light to generate a confocal signal or an interference signal.

2. The measuring device of claim 1, wherein, The spectrometer is used to receive the confocal signal or the interference signal, and the confocal signal or the interference signal is used to calculate the topographic information of the surface to be measured.

3. The measuring device of claim 2, wherein, When focusing the working focal length of the metasurface F Greater than When using a spherical thin lens, a material with a refractive index less than a set refractive index threshold and a dispersion less than a set dispersion threshold is selected; when focusing on the metasurface, the working focal length... F Not greater than When using a spherical thin lens, a material with a refractive index not less than a set refractive index threshold and a dispersion not less than a set dispersion threshold is selected. The formula for calculating the radius of curvature of the spherical thin lens, obtained from preliminary calculations, is as follows: ; Indicates the center wavelength of the incident light in its operating band. This represents the refractive index of the spherical thin lens material corresponding to the center wavelength. It represents the derivative of the refractive index of a spherical thin lens material with respect to wavelength.

4. The measuring device of claim 1, wherein, The material of the spherical thin lens in the focusing super surface is selected according to the working focal length of the focusing super surface, the curvature radius of the spherical thin lens obtained by preliminary calculation, the central wavelength of the working wavelength range of the incident light, and the refractive index of the spherical thin lens material corresponding to the central wavelength. ， wherein, denotes the phase of the micro-nano structure at the coordinate of the focusing metasurface denotes the phase of the micro-nano structure at the coordinate of the focusing metasurface denotes the working focal length of the focusing metasurface, denotes the wavelength of the incident light, and denote the horizontal and vertical coordinate values of the position where the micro-nano structure is located, respectively.

5. The measuring device of claim 4, wherein, Focusing metasurface coordinates The cross-sectional area of the micro- and nano-structures is determined by the following equation: ， wherein, represents the focusing metasurface coordinate represents the cross-sectional area of the micro-nano structure at the point, represents the cross-sectional area of the periodic space where the micro-nano structure is located, represents the material refractive index of the micro-nano structure, represents the refractive index of the medium where the metasurface is located, is the height of the micro-nano structure.

6. The measuring device of claim 1, wherein, The layout of the micro-nano structure in the focusing super surface is determined by the following formula: ， wherein, denotes the dispersion metasurface coordinates phase of the micro-nano structure at the point, and denotes the wavelength data and its corresponding focal length of the nth wavelength in the wavelength sequence, N is the number of wavelength sequence.

7. The measuring device of claim 6, wherein, Dispersion metasurface coordinates The cross-sectional area of the micro- and nano-structures is determined by the following equation: ， wherein, represents the dispersion super surface coordinate represents the cross-sectional area of the micro-nano structure at represents the cross-sectional area of the periodic space where the micro-nano structure is located, represents the material refractive index of the micro-nano structure, represents the refractive index of the medium where the super surface is located, is the height of the micro-nano structure.

8. A method of spectral interferometric surface topography measurement based on a metasurface, characterized in that, The layout of the micro-nano structure in the dispersive super surface is determined by the following formula: The measurement method is applied to the super surface-based spectral interference surface topography measurement device according to any one of claims 1-7, and the measurement method comprises: obtaining the spectrometer signal data received by the spectrometer; 9. The measurement method of claim 8, wherein, obtaining the topographic information of the surface to be measured according to the spectrometer signal data. The method for obtaining the topographic information of the surface to be measured according to the spectrometer signal data comprises:

10. The measurement method of claim 8, wherein, when the surface to be measured is in the dispersion range, the spectrometer signal data comprises a confocal signal, wavelength sequence data and light intensity sequence data, and the topographic information of the surface to be measured is obtained according to the wavelength sequence data, the light intensity sequence data and the wavelength-focal length correspondence. The method for obtaining the topographic information of the surface to be measured according to the spectrometer signal data comprises: when the surface to be measured is in the interference measurement range, the spectrometer signal data comprises an interference signal, and the topographic information of the surface to be measured is obtained according to the interference signal.

Images