WO2024011772A1 - 一种光谱建立的方法及设备 - Google Patents

一种光谱建立的方法及设备 Download PDF

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WO2024011772A1
WO2024011772A1 PCT/CN2022/124582 CN2022124582W WO2024011772A1 WO 2024011772 A1 WO2024011772 A1 WO 2024011772A1 CN 2022124582 W CN2022124582 W CN 2022124582W WO 2024011772 A1 WO2024011772 A1 WO 2024011772A1
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nano
micro
spectrum
materials
nano filter
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PCT/CN2022/124582
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English (en)
French (fr)
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田蕾
聂杰文
杨海宁
初大平
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剑桥大学南京科技创新中心有限公司
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0205—Optical elements not provided otherwise, e.g. optical manifolds, diffusers, windows
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/133509—Filters, e.g. light shielding masks
    • G02F1/133514—Colour filters

Definitions

  • the present invention relates to the technical field of spectral measurement and imaging, and in particular to a filter-based spectrometer and a method for spectral reconstruction or establishment.
  • the spectra reflected by the substances under light are different, which can be used to reflect the properties of the substances themselves.
  • spectral technologies are divided into dispersive spectral imaging technologies that use prisms and gratings as light splitting elements, filter-type spectral imaging technologies, and interference-type spectral imaging technologies based on different light splitting methods.
  • the resolution of dispersive spectral imaging technology is greatly affected by the size of the spectroscopic element and has high insertion loss, high hardware cost, and complex operation.
  • Filter-type spectral imaging technology is divided into two types. One is achieved by designing a filter with a certain spectral transmittance, which requires a filter array to achieve higher spectral resolution. The other is achieved by cascading multiple filters.
  • Optical sheet tunable filter implementation has complex structure and low transmittance, which is not conducive to integration.
  • Interferometric spectrometers obtain spectral information based on Fourier transform and have high spectral resolution. However, they require a precise driving mechanism, which greatly increases the volume and weight of the system. At the same time, this type of system is sensitive to disturbances and has poor stability. These spectral measurement and reconstruction techniques hinder the high resolution capability and low cost of spectrometer detection in the broadband range.
  • the device may include a first electrode layer.
  • the device may also include a second electrode layer.
  • the device may further include a matrix layer between the first electrode layer and the second electrode layer.
  • the matrix layer may include a liquid crystal layer.
  • the matrix layer may also include at least one resonant element in contact with the liquid crystal layer.
  • the liquid crystal layer may be configured to switch at least from a first state to a second state in response to a voltage applied between the first electrode layer and the second electrode layer, thereby changing the optical properties of the matrix layer to control electromagnetic waves received by the matrix layer.
  • Figure 1 shows a schematic diagram of a typical spectral reconstruction and imaging system, including reconstruction or imaging targets, spectroscopic elements (tunable filters, dispersion elements or interferometers, etc.), Imaging lens and detector array.
  • the process is as follows. After the reconstruction or imaging target passes through the spectroscopic element, it is then imaged on the detector array through the imaging lens. The properties of light passing through the optical element in different bands are different. The image data of each band can be obtained through scanning. Finally, the algorithm is combined to achieve spectral reconstruction. .
  • spectral reconstruction and imaging technologies are mainly divided into dispersion type, filter type and interference type.
  • Spectrometers based on the principle of spatial dispersion use gratings or prisms as light splitting elements, as shown in Figure 2. After the reconstruction or imaging target is collimated by the collimation system, the grating has different diffraction angles for light of different wavelengths or the prism has different degrees of refraction for light of different wavelengths, causing the light beam to be dispersed, and the light of different wavelengths is mapped to a specific spatial position. It is focused onto the detector by the focusing lens.
  • spectrometers There are two types of spectrometers based on the filtering principle. One is to introduce a freely tunable filter device into the imaging optical path. A narrow-band image is obtained for each transient state, and a complete spectral data cube is obtained after multiple transient states.
  • common tunable filtering methods include acousto-optic tunable filters, liquid crystal tunable filters or Fabry-Perot filters, etc., which dynamically control the filter through changes in external signals (electrical, optical or other properties), thereby outputting Different spectral information; one is to introduce a spatial anisotropic filter and obtain different spectral information by designing a filter array with a determined spectral transmittance.
  • Figure 3 is a spectrum imaging structure based on a tunable filter in the prior art.
  • Figure 3 shows a spectrum imaging structure based on a tunable filter.
  • Figure 4 shows the spectral imaging structure based on spatial anisotropic filters.
  • the reconstruction or imaging target scans different positions of the filter array. Since different filters have different transmission properties of light in the same wavelength band, different spectral information is obtained.
  • Figure 4 The existing technology is based on the spectral imaging structure of a spatially anisotropic filter.
  • the spectrometer based on the interference principle uses Fourier transform to form stable interference fringes through coherent beams with optical path differences, and utilizes the existence of interference fringe light wave energy and polychromatic light spectrum. The Fourier transform relationship is used to obtain spectral information.
  • Figure 5 shows the principle of an interference spectrum imager.
  • a Michelson interferometer is used as a spectroscopic device.
  • the reconstruction or imaging target is divided into two beams through a beam splitter, a reflected beam and a transmitted beam.
  • the reflected beam is reflected by a static mirror and a beam splitter.
  • the transmitted beam reaches the focusing lens, and the transmitted beam is reflected by the moving mirror and the beam splitter to the focusing lens.
  • the two beams are imaged as interference fringes on the detector.
  • the spectral intensity of the polychromatic light is solved through the inverse Fourier transform.
  • the spectrometer of the existing technology is also called a spectrometer, and is also called a direct-reading spectrometer.
  • Spectral imaging technology based on the dispersion principle is relatively mature. However, the image formed by the target object passes through the dispersion element and is then converged into strips of spectral images by the image mirror. The imaging time is long, and the spectral resolution is greatly affected by the size of the spectroscopic element.
  • the grating system uses the diffraction principle of light to split the light.
  • the actual energy utilization rate is low, there is overlap between multiple orders of diffraction, the production process is demanding, and there is a lot of stray light.
  • the prism material uses different refractive indexes for different wavelengths to split the light, but refraction
  • the non-linear relationship between rate change and wavelength results in nonlinear spectral resolution, uneven dispersion, spectral line bending and color distortion.
  • the filter-based tunable filter spectrum imaging technology has continuous tuning, simple and compact structure, and fast response speed.
  • the tunable filter is composed of multiple devices cascaded, resulting in serious transmittance loss and low light energy utilization.
  • the bandwidth is extremely narrow, and high resolution capability and large free spectral range are contradictory, which is not conducive to applications where information is contained within the broadband.
  • Spectral imaging technology based on spatially anisotropic filters requires multiple spectral filters, has a limited number of channels and low spectral resolution, which limits practical applications.
  • Interference-based spectral imaging technology has higher resolution, but its optical components are precise, the system volume and weight are bulkier than other spectroscopic components, it is sensitive to disturbances, has poor stability, and has complex data processing.
  • the purpose of the present invention is to solve the problems and defects existing in the above-mentioned prior art, and propose a spectrum reconstruction or imaging system and method based on micro-nano filter devices (structures), aiming to control the filtering characteristics of the filter and thereby control the light wave Transmittance data and reconstruct or image the spectrum, improving the speed and resolution of spectral reconstruction or imaging, and making it easy to integrate.
  • the technical solution of the present invention is an equipment for establishing a spectrum, which includes a light source, a micro-nano filter device, and a voltage control device.
  • the micro-nano filter device includes a base and a cover plate. There is a conductive film layer between the base and the cover plate. Electronically controlled phase change material; the cover plate and the base are made of transparent materials. The surface of the transparent material is flat and covered with a conductive film layer including an ITO layer, which serves as an electrode for the applied external voltage;
  • a periodic array of nanostructured units is prepared on the conductive film layer.
  • the nanostructured units are made of one of metal materials, metal oxide materials or semiconductor materials.
  • the distribution of the nanostructured units is determined according to the properties of the spectrum required to be established.
  • the nanostructured units are Including nano-block distribution, grating distribution or nano-hole distribution structure with length, width and height; nano-block, grating or nano-hole unit having sub-wavelength size, periodic array of nano-structural units of micro-nano filter devices and electronically controlled phase change
  • the materials work together to control the transmission spectrum; a voltage control device is provided to apply voltage to the electronically controlled phase change material.
  • Nanoblocks, gratings, or nanohole units are all subwavelength in size, with dimensions of hundreds of nanometers.
  • the nanoblocks are metal, metal oxide or metal oxide or semiconductor material preparation blocks, or one or more of metal, metal oxide or semiconductor material blocks, and the nanoblock size is a sub-wavelength scale.
  • Nanostructures include hole arrays, gratings, nano-pillar arrays, etc.
  • Micro-nano filter structures realize control of the transmission spectrum, especially nanostructures, hole arrays or nanostructure array units with sub-wavelength size structures.
  • Nanostructured metal or metal oxide or semiconductor material blocks.
  • the length, width and elliptical size of the nanoblocks are 100nm-1000nm.
  • Several nanoblocks form a cycle, and the array is composed of a multi-period range.
  • the "channel" in the device of the present invention is formed in time, that is, the device forms an optical transmission channel under different refractive indexes of liquid crystals. This periodic distribution exists within the beam range.
  • Micro-nano filter devices or structures are composed of periodic nanostructures using one or more of metal materials, metal oxide materials or semiconductor materials, metal blocks, metal materials, metal oxide materials or semiconductor materials whose size is smaller than the wavelength, including gold (Au), silver (Ag), aluminum (Al), titanium dioxide (TiO2), silicon nitride (SiN), gallium nitride (GaN), silicon (Si), germanium (Ge), etc., SiO2, TiO2, all sizes It is a sub-wavelength size and exhibits low absorption in the infrared and visible spectrum range; the electronically controlled phase change materials are liquid crystal, graphene, lithium niobate, germanium antimony telluride, and vanadium dioxide, all of which have light transmittance and can be controlled by power. Refractive index; the higher the transmittance, the better, and the larger the range of phase change change refractive index, the better.
  • the periodic nanostructures distributed on the film plane of the micro-nano filter device control the spectral information of multiple channels.
  • the nanostructures are staggered by blocks of metal materials, metal oxides, or semiconductor materials, and the blocks of metal materials, metal oxides, or semiconductor materials are long. is 200 ⁇ 50nm, and the width is 100 ⁇ 30nm (the dimensions of other shapes of nanoblocks are also within this range, such as the diameter of a circle, the maximum length of a cross-shaped straight line, the maximum diameter of an egg shape, etc.).
  • the thickness of the metal or metal oxide or semiconductor material block of the micro-nano filter structure is 250 ⁇ 100nm.
  • the metal material or metal oxide or semiconductor material block can be prepared by coating, masking, photolithography or other etching methods, but is not limited thereto.
  • the periodic array of nanostructure units of the micro-nano filter device is distributed on either side of the conductive film layer on both sides of the substrate and the covering plate or on the surface of the conductive film on both sides; that is, the nanostructure can be on either side or both sides of the ITO distributed on the surface.
  • the liquid crystal layer is directly in contact with the periodic nanostructure, and the ITO conductive layers on both sides are connected to a power supply with adjustable amplitude.
  • the refractive index changes, and the resonance of the micro-nano filter device or structure changes. , thereby changing the filtering characteristics of the device.
  • the micro-nano filter device or structure can be a stack of multiple periodic nanostructure materials, such as high refractive index and low refractive index nanostructure blocks staggered, and different materials with large differences in light transmission properties for the same wavelength band can be selected.
  • Micro-nano filter devices or structures can change the distribution, hole structure, length-width-height ratio, etc. according to the required properties, including but not limited to hole arrays, gratings, nano-pillars, and nano-block arrays; in the infrared band, gold, silver, aluminum, Titanium nitride, germanium, silicon dioxide, etc. are used in the visible light band.
  • the materials and morphology of micro-nano filter devices and structures need to be selected according to the wavelength band.
  • the method of establishing a spectrum using the equipment described above is to control the refractive index of the liquid crystal by controlling the voltage of the substrate 1 and the cover plate 4, or to change the properties of the filter device according to the change in the distribution of the micro-nano filter structure, thereby obtaining different wavelength bands.
  • the spectral information is solved using the pseudo-inverse method based on the transmission information; by controlling the intensity of the applied electric field, the actual refractive index of the liquid crystal material is changed, and the resonant frequency of the light source spectrum is changed, realizing the programmability of the spectrum.
  • Filtering; the sizes of micro-nano filtering structures used in different bands are different.
  • the composition and morphology of micro-nano filter devices can also be changed, but the main change is the size of the nanostructure.
  • Nanostructures will block light, but their period is smaller than the wavelength. This is not understood by traditional geometric optics theory. As long as the blocking ratio is not particularly large, the transmittance is still high. In addition, many dielectric materials have poor absorption at certain wavelengths. Very low; the purpose of adjusting the voltage is to change the actual refractive index of electronically controlled phase change materials such as liquid crystal, so the voltage and the refractive index of the liquid crystal are actually the same variable.
  • Nanostructure arrays and tunable materials are used to adjust the properties of materials under different control conditions (reflecting changes in the refractive index of materials), change the transmittance information of light passing through the device of the invention, and then reconstruct the spectrum.
  • the length of the metal material, metal oxide or semiconductor material block of the nanostructure array is 200 ⁇ 50nm and the width is 100 ⁇ 30nm.
  • the metal material or metal oxide or semiconductor material block is prepared by coating, masking, photolithography, etc.
  • the thickness of the metal or metal oxide or semiconductor material block in the nanostructure of the micro-nano filter device is 250 ⁇ 100nm.
  • the obtained spectrum and distribution can be further referred to the description in CN108885365B/US10514573:
  • the nanostructure array has a periodic structure with comparable subwavelength size, which can be understood as a resonant element.
  • the resonant frequency is consistent with the structural configuration and the refractive index of the structural material.
  • CN108885365B clarifies that the liquid crystal material is controlled by an electric field.
  • the liquid crystal material also needs to be controlled by an electric field.
  • Liquid crystal materials also need to be controlled by electric fields.
  • Various adjustable electronically controlled phase change materials, including liquid crystals can be used to adjust various properties of the materials under different control conditions, change the transmittance information of light passing through the device, and then reconstruct the spectrum.
  • the nanostructure array is a resonant element.
  • the resonant frequency is related to the structural configuration and the refractive index of the structural material.
  • the resonant frequency determines the light transmission spectrum.
  • the "channel" in the device of the present invention is formed by the change of the refractive index over time, and the device forms a channel under different refractive indexes of the liquid crystal.
  • the nanostructure array has this periodic distribution within the beam range.
  • the described method of establishing a spectrum controls the refractive index of the liquid crystal by controlling the voltage of the substrate 1 and the cover plate 4, and then changes the properties of the filter device according to the distribution of the film layer of the micro-nano filter structure, thereby obtaining filtered results in different bands.
  • the transmittance curve of the device is calculated, and the spectral information is solved using the pseudo-inverse method based on the transmission information.
  • the periodic nanostructures distributed on the film plane of the micro-nano filter device control the spectral information of multiple channels.
  • the nanostructures are staggered by blocks of metal materials, metal oxides, or semiconductor materials, and the blocks of metal materials, metal oxides, or semiconductor materials are long. is 200 ⁇ 50nm, and the width is 100 ⁇ 30nm.
  • the thickness of the metal or metal oxide or semiconductor material block of the micro-nano filter structure is 250 ⁇ 100nm.
  • Multi-channel here means that the periodic nanostructure controls the transmission characteristics of a spectrum.
  • Multi-channel also means that this spectrum is not a single frequency, but can also be a continuous spectrum.
  • a region can be understood as a channel, and generally 16 or 32 channels are needed to achieve a better restoration effect. Theoretically, the more channels the better, but this conflicts with the requirement of spatial resolution. It is good to achieve a balance between the number of channels and spatial resolution.
  • the existing channels in "space” are converted into channels in "time”. Because the refractive index of phase-change materials such as liquid crystal changes continuously under external force, under different refractive indexes, this device becomes a specific channel, and theoretically "countless" channels can be realized. In actual use, 16 or 32 channels are needed for better restoration.
  • Periodic nanostructure distribution and relationship with channels The periodic nanoblock structure distribution is periodically repeated.
  • the spatial period is generally smaller than or similar to the wavelength of the spectrum to be measured (500nm-1500nm).
  • the material block or hole or grating Coverage rates of 20%-90% are possible.
  • the nanoblocks can be uniformly distributed in at least one or more of rectangular, circular, and cross shapes, and then repeated periodically.
  • the 12 spectra are rectangular nanoblocks that repeat periodically.
  • the method of the present invention is not limited to these 12 types. In theory, spectra of any shape can be reconstructed.
  • the existing "space” channels are converted into “time” channels. Because the refractive index of phase-change materials such as liquid crystal changes continuously under external force, under different refractive indexes, this device becomes a specific channel, and theoretically "countless" channels can be realized. In actual use, 16 or 32 channels are needed for better restoration.
  • micro-nano filter devices or structures can be distributed on both sides of the ITO surface separately or simultaneously (such as a periodic nanoparticle lattice composed of media), and are not limited to one side of the substrate.
  • the nanostructure of the micro-nano filter device or structure can be a stack of multiple materials, such as high refractive index and low refractive index materials staggered distribution, and different materials with large differences in light transmission properties for the same wavelength band can be selected.
  • High refractive index and low refractive index materials refer to high refractive index and low refractive index materials prepared into different nanoblocks, or a nanoblock can be composed of a multi-layer structure, and each layer has a different refractive index.
  • Periodic nanostructures generally need to have a width that exceeds the beam width of the light source.
  • the nanostructure of micro-nano filter devices or structures can change the distribution, hole structure, length-width-height ratio, etc. according to the required properties, including but not limited to hole arrays, gratings, nanopillar arrays, etc.
  • the light wave matrix is affected by the thickness of the nanostructure of the micro-nano filter device or structure, and the anti-noise performance is poor when it is thin.
  • Micro-nano filter devices or structures composed of multiple structures and nanostructures of multiple materials are beneficial to improving anti-noise performance.
  • Gold, silver, aluminum, titanium nitride, etc. are commonly used in the infrared band, and germanium, silicon dioxide, etc. are commonly used in the visible light band.
  • the materials and morphology of micro-nano filter devices and structures need to be selected according to the wavelength band.
  • the liquid crystal layer is directly in contact with the micro-nano filter device or structure, and the ITO grade conductive layers on both sides are connected to a power supply with adjustable amplitude.
  • the refractive index changes, and the micro-nano filter device or structure The resonance changes, thereby changing the filtering characteristics of the device.
  • the thickness of the liquid crystal layer determines the voltage required to change the liquid crystal state. High voltage may cause the electrodes to heat up.
  • the detector contains CCD or CMOS, which is used to measure the transmission spectrum of micro-nano filter devices or structures, and obtain multiple sets of light waves received by the detector under different driving voltages, that is, under different liquid crystal refractive indexes, to realize micro-nano filter devices or structures. Dynamically adjustable over time.
  • Spectral information is reconstructed from multiple sets of transmittance data of an array of micro-nano filter devices.
  • the method can be the least squares method, pseudo-inverse method, neural network method, etc.
  • the detailed steps for reconstructing spectral information using the least squares method are as follows:
  • S represents a matrix composed of spectral transmission curve sets of the nanoblock structure and electrically controlled phase change material components of the present invention under different voltage controls.
  • the transmittance curve is the result of both the structure of the nanoblock and the electronically controlled refractive index.
  • the present invention demonstrates the entire process of spectrum reconstruction.
  • the number of filters required to reconstruct the input signal can be much smaller than the number of channels (a channel is a spectrum with a transmission when the refractive index is at one value).
  • a channel is a spectrum with a transmission when the refractive index is at one value.
  • the transmission curvature characteristics of the filter are the spectral filtering characteristics of this structure, which has a crucial influence on the spectral reconstruction results.
  • the transmittance curve should cover both high-frequency and low-frequency information of the reconstructed signal.
  • the pre-protection point lies in constructing a filter with a certain adjustable material and changing the transmittance of different wavelength bands after the continuous light source passes through the device by controlling a certain condition, thus providing a solution for the miniaturization, speed and accuracy of the spectrum reconstruction system.
  • Figure 1 is a schematic diagram of a typical spectral reconstruction and imaging system.
  • Figure 2 is a schematic diagram of the optical dispersion spectral imaging method
  • Figure 3 is a schematic diagram of the structure of spectral imaging based on tunable filters in the prior art
  • Figure 4 is a schematic diagram of the spectral imaging structure based on spatial anisotropic filters in the prior art
  • Figure 5 is a schematic diagram of the principle of an interference spectrum imager in the prior art
  • Figure 6 is a spectrum filter structure based on nanostructures of the present invention.
  • Figure 7 shows the spectrum reconstruction system of the present invention
  • Figure 8 is a schematic diagram of the hole array structure of the present invention.
  • Figure 8 shows a layer of gold being laid on the substrate, circular holes are dug in the gold, and then liquid crystal is filled in. At this time, it is a hole array;
  • Figure 9 is a top view of the hole array structure of the present invention (a certain cross-sectional plane, that is, the structure of Figure 8);
  • Figure 10 is a schematic diagram of the grating structure of the present invention.
  • Figure 11 is a top view of the grating structure (a certain cross-sectional plane) of the present invention.
  • Figure 12 is a schematic diagram of the nanoblock structure of the present invention.
  • Figure 13 is a top view of the nanoblock structure (a certain cross-sectional plane) of the present invention.
  • Figure 14 is a simulated transmittance curve of the nanoblock micro-nano filtering structure of the present invention.
  • Figure 15 (a), (b), (c), and (d) are respectively the change curves of transmittance with the refractive index of liquid crystal at four different wavelengths (1300nm, 1400nm, 1500nm, 1600nm) of the present invention
  • Figure 16 is the original spectrum of the present invention.
  • Figure 17 is the transmission spectrum of the original spectrum of the present invention after passing through the nanoblock micro-nano filtering structure
  • Figure 18 is the light intensity information of the original spectrum of the present invention after passing through the nanoblock micro-nano filtering structure
  • Figure 19 is the reconstructed spectrum after passing through the nanoblock micro-nano filtering structure according to the present invention.
  • the micro-nano filter structure is a disc and cross nanostructure array
  • Figure 22 is a front (top) view of the micro-nano filter structure of Figure 21.
  • the following is a specific example to illustrate that a spectrum reconstruction system is constructed with the reconstruction or imaging target, micro-nano filter device or structure, voltage control module and detector as the main units, as shown in Figure 7, light source, micro-nano filter device and voltage control device;
  • the micro-nano filter device includes a substrate 4 with conductive electrodes and a cover plate 1, a film layer and an electronically controlled phase change material between the substrate 4 and the cover plate; the cover plate and the base layer are made of glass material or other transparent materials, and the surface of the transparent material is smooth And cover the conductive film 3-1 of ITO; serve as an electrode for applying external voltage; prepare periodic nanostructures 3 on the conductive film, and the nanostructure unit adopts one of metal materials, metal oxide materials or semiconductor materials, according to The properties of the spectrum that need to be established determine the distribution of nanostructures, which include nanoblock distribution or nanohole distribution structures with a ratio of length, width, and height.
  • the light source transmission is controlled by micro-nano filter devices to obtain the required spectrum.
  • the reconstructed target is continuous in the visible and infrared bands, and is injected into the micro-nano filter device or structure, changing the voltage at both ends of the liquid crystal layer to adjust the spatial arrangement of the liquid crystal molecules, that is, the spatial refractive index distribution characteristics of the liquid crystal material, resulting in the magnetic dipole of the nanostructure Resonance and electric dipole resonance change within the resonant element, thereby changing the amount of modulation of the beam amplitude and phase due to the switching of the liquid crystal layer. Since the resonance characteristics of the nanostructure are wavelength-dependent, the transmission spectrum response of the device will change in different states of liquid crystal 2. Spectral information can be reconstructed using the transmission spectra in different liquid crystal states.
  • the present invention can be used in ultraviolet light, but liquid crystal materials have poor stability under ultraviolet light irradiation and have relatively high energy absorption. Non-liquid crystal materials and materials with tuning functions for ultraviolet light can be used.
  • Figures 6 and 12 show spectral filters based on nanostructures.
  • the micro-nano filter structure is connected to an amplitude-adjustable power supply to adjust the refractive index of the liquid crystal layer, thereby changing the filtering characteristics of the device.
  • the transmission spectrum of the micro-nano filter structure is measured.
  • the detector contains CCD or CMOS, and the filter characteristics of the device are obtained under multiple sets of different driving voltages, that is, under different refractive indexes of liquid crystals.
  • cover plate 1 and base 4 is provided with a conductive film of ITO layer (all other commercial transparent conductive films can be used).
  • the cover plate and base layer are made of glass material or other transparent materials (quartz, PMMA, etc.), and the conductive film refers to ITO layer and other various conductive films that match the substrate (physical plating or CVD method);
  • Figure 12 shows the liquid crystal 2, the nanostructure of the micro-nano filter device, that is, nanoblocks or nanopores 3, and the conductive film 3-1.
  • the spectral information that constitutes multiple channels is composed of metal materials (or metal oxides or semiconductor materials) staggeredly distributed nanoblocks.
  • the length of the nanoblocks is 200nm, the width is 100nm, and the height is 250nm.
  • Figure 13 is a top view of the micro-nano filter structure.
  • the liquid crystal can be changed to lithium niobate, germanium telluride, germanium antimony tellurium, silver indium antimony tellurium, antimony telluride, and vanadium dioxide.
  • Figure 14 shows the simulated transmittance curve of this example of micro-nano filtering structure.
  • Figure 15(a), (b), (c), and (d) are the change curves of transmittance with the refractive index of liquid crystal at four different wavelengths (1300nm, 1400nm, 1500nm, and 1600nm) respectively; 1300nm and 1400nm in Figure 15 , the change curve of transmittance with the refractive index of liquid crystal at 1500nm and 1600nm. Beams in different wavelength bands have different transmittances when the refractive index of the liquid crystal is different.
  • S is a matrix consisting of groups of transmittance curves
  • P represents the spectrum of the incident beam
  • D is the measurement value of the detector corresponding to the filter.
  • the embodiment shows the entire process of spectrum reconstruction.
  • the number of filters required to reconstruct the input signal can be much smaller than the number of channels. It is superior to previous spectrometers in many aspects such as hardware cost, system operation complexity, and spectral resolution. It is expected to realize Intelligent and miniaturized spectrometers provide ideas.
  • the transmission curvature characteristics of the filter have a crucial impact on the spectral reconstruction results.
  • the transmittance curve should cover both high-frequency and low-frequency information of the reconstructed signal.
  • the present invention proposes a spectrum reconstruction system based on micro-nano filter devices or structures, which consists of a filter structure, a voltage control system and a light intensity detector. It abandons the traditional method of using dispersion components and multiple filters and uses only one
  • the filter structure uses the refractive index of liquid crystal to reconstruct the spectrum based on the different transmittances of light beams in different wavelength bands, which greatly simplifies the structure of the optical system and is small in size and light in weight.
  • the filtering characteristics are flexible.
  • the nanostructure is independently controllable, and the nanostructure can be changed according to the requirements for transmittance, etc. to achieve different filtering characteristics.
  • Neural networks can be used for optimization during spectral reconstruction, further improving the resolution and accuracy of spectral detection and imaging.
  • the core is to change the properties of the filter device by controlling the refractive index of liquid crystal, etc., thereby obtaining the transmittance curves of the filter in different wavebands, and using the pseudo-inverse method to solve the spectral information based on the transmission information.
  • Various tunable materials can be used to adjust the various properties of the materials under different control conditions, change the transmittance information of the light passing through the device, and then reconstruct the spectrum.
  • the key point of the technology is to change the spectroscopic performance of the filter device by changing a certain parameter of the filter, continuously and finely adjust the light transmission curve, and calculate the spectral information using the pseudo-inverse method.
  • the pre-protection point lies in constructing a filter with a certain adjustable material and changing the transmittance of different wavelength bands after the continuous light source passes through the device by controlling a certain condition, thus providing a solution for the miniaturization, speed and accuracy of the spectrum reconstruction system.
  • Various tunable materials can be used to adjust the various properties of the materials under different control conditions, change the transmittance information of the light passing through the device, and then reconstruct the spectrum.
  • liquid crystal it can also be graphene, lithium niobate, germanium antimony telluride, and vanadium dioxide. The higher the transmittance, the better, and the larger the phase change (refractive index) change range, the better.
  • the system of the present invention can measure continuous spectrum: such as 400nm-1100nm or 1100nm-1700nm, and can also measure discontinuous spectrum with multiple narrow-band peaks. If you can measure it, you can construct a spectrum.
  • Figure 16 shows the original spectrum that needs to be reconstructed.
  • Figure 17 shows the transmission spectrum of the original spectrum after passing through the micro-nano filter structure shown in Figure 12.
  • Figure 18 shows the light intensity information after the original spectrum passes through the micro-nano filter structure shown in Figure 12. The incident beam is reconstructed using the least squares method based on the resulting transmission spectrum and intensity information.
  • Figure 19 is the pseudo-spectral reconstruction result diagram of this example.
  • Figure 20 shows 12 sets of original spectra and the spectra reconstructed after the above steps. Measure the transmitted light intensity of 16 or 32 types of liquid crystal devices (obtained channels) under different refractive indexes, and obtain the spectra of different channels. The detection spectral information can be restored.
  • the number of channels in the process of restoring spectral information can be much higher than 16 or 32.
  • the 12 spectral images in Figure 20 are only examples.
  • the nanostructure and 16 or 32 channels given in order to demonstrate can well reconstruct the transmitted light intensity of these 12 types of devices at different refractive indexes at different wavelengths, and obtain different channels.
  • the spectral characteristics of different spectra can be not limited to these 12 types of spectra. In theory, spectra of any shape can be reconstructed. In the process of reconstructing any of these 12 spectra, we need to set the liquid crystal in 16 or 32 different refractive index states, collect data respectively, that is, collect 16 or 32 channels, and reconstruct the spectrum.
  • the spectrum range is 1200nm–1700nm, and the reconstructed analysis accuracy is 1nm, then it can be said that the reconstructed spectrum covers 500 channels.
  • the accuracy of reconstructed spectra may vary.
  • the nanostructure unit in the micro-nano filter structure shown in Figure 12 is composed of metal material nanoblocks, metal oxide or semiconductor material blocks, or metal material nanoblocks and metal oxide or semiconductor material blocks staggered distribution, metal materials or metal oxide
  • the length of the material or semiconductor material block is 200nm and the width is 100nm; the thickness of the metal or metal oxide or semiconductor material block of the micro-nano filter structure can be 200 or 300nm.
  • Nanoblocks can be rectangular, round or square in shape.
  • the 32 sets of transmission spectra reflect the information of the micro-nano filter structure. After passing the 32 sets of transmission spectra, the original spectrum will obtain 32 sets of transmitted spectral information. The original spectrum can be decoded from the spectral information, which is the reconstructed spectrum.
  • Figure 20 shows 12 original spectra with different characteristics and the spectrum reconstructed from the transmission spectrum information using the least squares method after passing through the micro-nano filter structure.
  • Practical nanostructure arrays for micro-nano filter devices generally have more than three cycles ( Figure 13 shows a practical nanostructure with three cycles), and the practical cycles can range from dozens to more than 100;
  • the practical nanostructure distribution of the material block is fixed, and the micro-nano structure cannot be changed once it is processed.
  • the refractive index change generally ranges from 5% to 30%.
  • Figure 16 is the original spectrum that needs to be reconstructed
  • Figure 17 is the transmission spectrum of the original spectrum after passing through the nanoblock micro-nano filter structure
  • Figure 18 is the light intensity information of the original spectrum after passing through the nanoblock micro-nano filter structure
  • Figure 19 is the reconstructed spectrum after passing through the nanoblock micro-nano filtering structure
  • Figure 20 shows the results (ie reconstructed spectrum curves) from 12 kinds of original spectra to reconstructed spectra (ie 12 kinds of Figures 16 and 19).
  • These 12 types have different spectral properties, such as single peak, multi-peak and peak height, reflecting the reconstruction effect of micro-nano filtering structures on different spectra.
  • the arrow indicates the direction of the light source.
  • FIG. 19 is a pseudo spectrum reconstruction result diagram of the embodiment.
  • Figure 20 shows 12 sets of original spectra and the spectra reconstructed after the above steps.
  • the spectral information is reconstructed based on multiple sets of transmittance data.
  • the method can be the least squares method, pseudo-inverse method, neural network method, etc.
  • the detailed steps for reconstructing spectral information using the least squares method are as follows:
  • A is a matrix consisting of sets of transmittance curves, x represents the spectrum of the incident beam, and y is the measurement value of the detector corresponding to the filter.
  • a spectrum reconstruction system is constructed with a light source, micro-nano filter structure device, voltage control module and detector as the main units.
  • the light source is continuous in the infrared band and is injected into the micro-nano filter structure to adjust the micro-nano filter structure.
  • the voltage at both ends of the nanofilter structure liquid crystal layer then adjusts the refractive index of the liquid crystal to obtain the transmission spectral response of the incident light passing through different filter structures.
  • the incident light and spectral response are used to reconstruct the spectral information.
  • Figure 7 Spectral reconstruction system
  • Figure 8 shows the micro-nano filter structure
  • Figure 9 is a top view of the micro-nano filter structure; by changing the refractive index of the liquid crystal layer, the transmission spectrum of the micro-nano filter structure is measured, and 32 sets of transmission spectra are obtained, so ⁇ [a, b] ⁇ [1200, 1700]nm, sampling is performed at an interval of 1nm, and the data dimension is 501.
  • Figure 10 shows the simulated transmittance curve of this example.
  • A is a matrix consisting of sets of transmittance curves, x represents the spectrum of the incident beam, and y is the measurement value of the detector corresponding to the filter.
  • Figure 14 is a simulated transmittance curve, that is, a simulated spectrum reconstruction result of the present invention using the device of Figure 13 under continuous spectrum incident conditions and controlled by the size of the refractive index of the nanoblock micro-nano filtering structure.
  • the embodiment shows the entire process of spectrum reconstruction, which is superior to previous spectrometers in many aspects such as hardware cost, system operation complexity, and spectral resolution. It is expected to provide ideas for realizing intelligent and miniaturized spectrometers.
  • the transmission curvature characteristics of the micro-nano filter device have a crucial influence on the spectral reconstruction results.
  • the transmittance curve should cover both high-frequency and low-frequency information of the reconstructed signal.
  • the spectrum of the light source can be reconstructed through the micro-nano filter device and method in the present invention.
  • the spectrum of a light source can be continuous or discrete.
  • the number of filters required to reconstruct the light source can be much smaller than the number of channels, where the channel should be understood as the resolution of the reconstructed spectrum. Assuming that the spectrum of the light source covers 1200nm–1700nm, and the resolution of our reconstruction is 1nm, then we can say that the reconstructed spectrum has 501 channels. Theoretically, to achieve a resolution of 1 nm (i.e., 501 channels) completely accurately, the device in the present invention needs to have 501 states, that is, the electronically controlled phase change material must be set to 501 different refractive indexes, and then measured separately. The amount of light energy transmitted through the device.

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Abstract

一种光谱建立的方法及设备，设备包括光源、微纳滤波器件、电压控制装置，微纳滤波器件包括设有导电电极的基底（4）及覆盖板（1），基底（4）及覆盖板（1）之间膜层、电控相变材料（2）；覆盖板（1）和基底（4）层采用透明材料，透明材料表面平整且覆盖包括ITO层的导电膜（3-1），作为施加的外电压的电极；在导电膜（3-1）上制备周期阵列的纳米结构（3）单元，纳米结构（3）周期阵列单元采用金属材料、金属氧化物材料或半导体材料中的一种，根据所需要建立光谱的性质决定纳米结构（3）的分布，纳米结构（3）包括长、宽、高比例的纳米块分布或纳米孔洞分布结构。

Description

一种光谱建立的方法及设备 技术领域
本发明涉及光谱测量和成像的技术领域，尤其是涉及一种基于滤波器的光谱仪及光谱重建或建立的方法。
背景技术
不同物质由于其原子内部电子的运动情况不同，物质在光照下(包括从红外到紫外的光波)所体现出的光谱具有差异性，可以用来反映物质自身的性质。通过在一段连续光波范围内采集目标物体或物质的多个通道的光信息并用算法估算其光谱，在遥感、农作物监测、大气观察等领域具有重要应用。
现有光谱技术根据分光方式不同，分为以棱镜、光栅作为分光元件的色散型光谱成像技术，还有滤光片型光谱成像技术以及干涉型光谱成像技术。色散型光谱成像技术的分辨率受分光元件尺寸影响极大且插入损耗高，硬件成本高，操作复杂。滤光片型光谱成像技术分为两种，一种通过设计具有确定光谱透射率的滤光片实现，需要滤光片阵列才能实现较高的光谱分辨率，另一种通过级联多种滤光片可调谐滤波器实现，结构复杂，透射率低，不利于集成。
干涉型光谱仪基于傅里叶变换获取光谱信息，光谱分辨率较高，但其需要精密的驱动机构，系统的体积和重量大幅增加，同时该类系统对扰动敏感，稳定性差。这些光谱测量和重建技术都阻碍了光谱仪在宽带范围内探测的高分辨能力及低成本化。
CN108885365B/US10514573：提供了一种用于控制电磁波的设备。设备可包括第一电极层。设备还可包括第二电极层。设备可进一步包括位于第一电极层和第二电极层之间的矩阵层。矩阵层可包括液晶层。矩阵层还可包括至少一个与液晶层接触的谐振元件。液晶层可被配置为响应第一电极层与第二电极层之间施加的电压而至少从第一状态切换到第二状态，从而改变矩阵层的光学性质，以控制矩阵层收到的电磁波。
与本发明相关的现有技术方案可以参见图1，图1所示为典型的光谱重建和成像系统示意图，包括重建或成像目标、分光元件(可调谐滤波器、色散元件或干涉仪等)、成像透镜和探测器阵列。过程如下，重建或成像目标经过分光元件后，再经过成像透镜成像于探测器阵列上，不同波段的光经过光学元件的性质不同，通过扫描可以获得各个波段的图像数据，最后结合算法实现光谱重建。
图2的光学色散型光谱成像方式中，根据光谱分光方式的不同，光谱重建和成像技术主要分为色散型、滤光型和干涉型。基于空间色散原理的光谱仪采用光栅或棱镜作为分光元件，如图2所示。重建或成像目标经准直系统准直后，经过光栅对不同波长的光衍射角不同或棱镜对不同波长的光折射程度不同而使得光束发生色散，不同波长的光线被映射到特定的空间位置，由聚焦透镜聚焦到探测器上。
基于滤光型原理的光谱仪分为两种，一种是通过在成像光路中引入可自由调谐的滤光器件，每个瞬态得到一个窄带图像，在多个瞬态后获得完整的光谱数据立方体，常见的可调谐滤波方式有声光可调谐滤波器、液晶可调谐滤波器或法布里柏罗滤波器等，通过外界信号的变化(电、光或其他性质)动态控制滤波器，从而输出不同的光谱信息；一种是引入空间异性滤波器，通过设计具有确定光谱透射率的滤光片阵列得到不同的光谱信息。
图3为现有技术基于可调谐滤波器的光谱成像结构，如图3所示为基于可调谐滤波器的光谱成像结构。通过调节可调谐滤波器的透过波长以获得不同波长的光谱图像，控制器的条件不同，滤波器选择输出的窄带光也不同。
如图4所示为基于空间异性滤波器的光谱成像结构。重建或成像目标扫过滤光片阵列的不同位置，由于不同滤光片对同一波段光的透射性能不同，得到不同的光谱信息。
图4现有技术基于空间异性滤波器的光谱成像结构，基于干涉型原理的光谱仪利用傅里叶变换，通过具有光程差的相干光束形成稳定干涉条纹，利用干涉条纹光波能量与复色光光谱存在的傅里叶变换关系获取光谱信息。如图5所示为干涉型光谱成像仪原理，以迈克尔逊干涉仪作为分光器件，重建或成像目标经分束镜分成两束，反射光束和透射光束，反射光 束经静镜反射、分束镜透射到达聚焦透镜，透射光束经动镜反射、分束镜反射到聚焦透镜，两束光束成像在探测器上呈干涉条纹，通过傅里叶逆变换求解复色光的光谱强度。
现有技术的优缺点：现有技术的光谱仪又称分光仪，亦称直读光谱仪。以光电倍增管等光探测器测量谱线不同波长位置强度的装置。它由一个入射狭缝，一个色散系统，一个成像系统和一个或多个出射狭缝组成。基于色散型原理的光谱成像技术较为成熟，然而目标物体所成的像经过色散元件后再由像镜会聚成一条条的光谱像，摄像时间长，且光谱分辨率受分光元件尺寸影响极大，对光学系统数值孔径具有很强的依赖性。光栅系统利用光的衍射原理进行分光，实际能量利用率低，多级次的衍射之间存在重叠，制作工艺要求苛刻，杂散光多，棱镜材料利用对不同波长的折射率不同进行分光，但折射率变化与波长不呈线性关系导致光谱分辨率非线性，色散不均匀，产生谱线弯曲及色畸变。
基于滤光片型的可调谐滤波器光谱成像技术调谐连续、结构简单紧凑、响应速度快，但可调谐滤波器由多个器件级联而成，透过率损失严重，光能利用率低，带宽极窄，高分辨能力和大自由光谱范围相互矛盾，不利于信息包含在宽带内的应用。
基于空间异性滤波器的光谱成像技术需要多个光谱滤光片，通道数有限，光谱分辨率低，限制了实际应用。
基于干涉型的光谱成像技术分辨率较高，但光学元件精密，系统体积和重量相较于其他分光元件笨重，对扰动敏感，稳定性较差，数据处理复杂。
发明内容
本发明的目的在于，解决上述现有技术中存在的问题及缺陷，提出了一种基于微纳滤波器件(结构)的光谱重建或成像系统与方法，旨在控制滤波器的滤波特性进而控制光波透射率数据并对光谱进行重建或成像，提高光谱重建或成像的速度和分辨率，易于集成。
本发明技术方案是，一种光谱建立的设备，包括光源、微纳滤波器件、电压控制装置，所述微纳滤波器件包括设有基底及覆盖板，基底及覆盖板之间为导电膜层、电控相变材料；覆盖板和基底采用透明材料，透明材料表面平整且覆盖包括ITO层的导电膜层，作为施加的外电压的电极；
在导电膜层上制备周期性阵列的纳米结构单元，纳米结构单元采用金属材料、金属氧化物材料或半导体材料中的一种，根据所需要建立光谱的性质决定纳米结构单元的分布，纳米结构单元包括成具有长、宽、高的纳米块分布、光栅分布或纳米孔洞分布结构；纳米块、光栅或纳米孔洞单元具有亚波长尺寸，微纳滤波器件的周期阵列的纳米结构单元与电控相变材料共同作用实现对透射光谱调控；设有电压控制装置施加电压作用于电控相变材料。
纳米块、光栅、或纳米孔洞单元均为亚波长的尺寸，会有几百纳米的尺。
所述纳米块为金属、金属氧化物或金属氧化物或半导体材料制备块，或金属或金属氧化物或半导体材料块中的一种或多种，纳米块尺寸为亚波长的尺度。
微纳滤波结构纳米结构包括孔阵列、光栅、纳米柱阵列等，微纳滤波结构实现对透射光谱调控，尤其是纳米结构，孔阵列或纳米结构阵列单元具有亚波长尺寸的结构。纳米结构的金属或金属氧化物或半导体材料块纳米块长宽及椭圆尺寸100nm–1000nm，若干个纳米块构成一个周期，阵列为多周期范围构成。本发明器件中“通道”是在时间上构成的，即液晶不同折射率下器件构成一个光学透过通道。在光束范围内均有此周期性分布。
微纳滤波器件或结构由周期性纳米结构采用金属材料、金属氧化物材料或半导体材料中的一种或多种，金属块，金属材料、金属氧化物材料或半导体材料的尺寸小于波长，包括金(Au)、银(Ag)、铝(Al)、二氧化钛(TiO2)、氮化硅(SiN)、氮化镓(GaN)、硅(Si)、锗(Ge)等，SiO2，TiO2，尺寸均为亚波长尺寸，在红外和可见光谱范围内表现出低吸收；电控相变材料为液晶、石墨烯、铌酸锂、锗锑碲化、二氧化钒均具有透光率和能够加电控制折射率；透过率越高越好，相变改变折射率范围越大越好。
微纳滤波器件的膜层平面上分布的周期性纳米结构控制多个通道的光谱信息，纳米结构由金属材料或金属氧化物或半导体材料块交错分布，金属材料或金属氧化物或半导体材料块长为200±50nm，宽为100±30nm(纳米块的其它形状的尺寸亦在此范围内，如圆的直径，十字形的直线最大长度、卵形状的最大直径等)。微纳滤波结构的金属或金属氧化物或半导体 材料块厚度为250±100nm。
金属材料或金属氧化物或半导体材料块可以镀膜、掩膜、光刻或其它刻蚀方式制备，但不限于此。
微纳滤波器件的周期性阵列的纳米结构单元在基底与覆盖板的两侧导电膜层的任一侧导电膜或两侧导电膜表面上分布；即纳米结构可以在任一侧或两侧的ITO表面上分布。液晶层直接接触到周期性纳米结构，两侧ITO导电层连接幅值可调的电源，响应在基底与覆盖板之间施加的电压，折射率发生变化，微纳滤波器件或结构的谐振发生变化，进而改变器件的滤波特性。
微纳滤波器件或结构可以是多种周期性纳米结构材料的堆叠，如高折射率和低折射率的纳米结构块交错分布，可选取对于同一波段的光透射性能差异较大的不同材料。
微纳滤波器件或结构可以根据所需要的性质改变分布、孔洞结构、长宽高比例等，包括但不限于孔阵列、光栅、纳米柱、纳米块阵列；在红外波段用金、银、铝、氮化钛，在可见光波段用锗、二氧化硅等，微纳滤波器件与结构的材料和形貌需根据波段选择。
利用所述的设备建立光谱的方法，通过控制基底1及覆盖板4的电压，从而控制液晶的折射率，或再根据微纳滤波结构的分布的改变，改变滤波器件的性质，从而得到不同波段经过滤波器的透射率曲线，根据透射信息利用伪逆法等求解光谱信息；通过施加电场的控制强度从而改变液晶材料的实际折射率，改变对光源频谱的谐振频率，实现了对频谱的可编程滤波；不同波段使用的微纳滤波结构的尺寸大小不相同。微纳滤波器件的构成形貌也可改变，但主要是纳米结构尺寸大小的改变。
纳米结构会挡到光，但是其周期小于波长，并非用传统几何光学的理论去理解，只要遮挡比例不是特别大，透过率仍然很高；另外，很多电介质材料，在某些波长的吸收也很低；调节电压的目的是改变液晶等电控相变材料的实际折射率，所以电压和液晶折射率实际为同一变量。
利用纳米结构阵列与可调材料，调整不同控制条件下材料的性质(反应出材料折射率的改变)，改变光经过本发明器件的透射率信息，进而重建光谱。
纳米结构阵列的金属材料或金属氧化物或半导体材料块长为200±50nm，宽为100±30nm。金属材料或金属氧化物或半导体材料块以镀膜、掩膜、光刻等方式制备。微纳滤波器件的纳米结构中的金属或金属氧化物或半导体材料块厚度为250±100nm。
得到的光谱及分布可进一步参考CN108885365B/US10514573中的描述：纳米结构阵列具有亚波长尺寸相当的周期性结构，可以理解为一个谐振元件，谐振频率与结构构型和结构材料折射率有光。另外在CN108885365B明确了液晶材料受电场控制。本发明中液晶材料也需要受到电场调控。液晶材料也需要受到电场调控。可以利用包括液晶的各种可调电控相变材料，调整不同控制条件下材料的各种性质，改变光经过器件的透射率信息，进而重建光谱。纳米结构阵列为一个谐振元件，谐振频率与结构构型和结构材料折射率有关，谐振频率决定了光的透过光谱。本发明器件中“通道”是在时间上折射率的改变而构成的，液晶不同折射率下器件构成一个通道。纳米结构阵列在光束范围内均有此周期性分布。
所述的建立光谱的方法，通过控制基底1及覆盖板4的电压，从而控制液晶的折射率，再根据微纳滤波结构的膜层的分布，改变滤波器件的性质，从而得到不同波段经过滤波器的透射率曲线，根据透射信息利用伪逆法等求解光谱信息。
微纳滤波器件的膜层平面上分布的周期性纳米结构控制多个通道的光谱信息，纳米结构由金属材料或金属氧化物或半导体材料块交错分布，金属材料或金属氧化物或半导体材料块长为200±50nm，宽为100±30nm。微纳滤波结构的金属或金属氧化物或半导体材料块厚度为250±100nm。
这里“多通道”就是周期性纳米结构控制了一段光谱的透过特性。“多通道”也为了表达这个光谱不是单一频率的，也可以是一段连续的光谱。在现有的基于空间异性滤波器的光谱成像技术中，滤色片不同区域的滤波特性不同，然后通过采集不同区域的透射光强度，还原出待测光谱。一个区域可以理解成一个通道，一般需要16或者32个通道才能实现较好的还原的效果。理论上通道越多越好，但是这样与空间分辨率的要求产生冲突。通道数与空 间分辨率达到一个平衡就好。
在本发明中，把现有“空间”上的通道转换成“时间”上的通道。因为液晶等相变材料在外加作用力下的折射率变化是连续的，在不同的折射率下，这个器件成为一个特定的通道，理论上可以实现“无数”的通道。实际使用中，也是要16或者32个通道才能较好的还原。
周期性纳米结构分布及与通道关系：周期性纳米块结构分布上都是周期性重复的，空间上的周期一般小于或近似于待测光谱的波长(500nm–1500nm)，材料块或孔或光栅的覆盖率为20％-90％都可能。纳米块可以是矩形、圆形、十字形起码一种或二种以上均匀分布的，再进行周期性重复。为了演示本发明给出的这个结构可以很好的重建这12种特性不同的光谱，12种光谱是矩形纳米块周期性重复。但是本发明方法不限于这12种，理论上任意形貌的光谱都可以被重建出来。
在本发明中，把现有“空间”上的通道转换成“时间”上的通道。因为液晶等相变材料在外加作用力下的折射率变化是连续的，在不同的折射率下，这个器件成为一个特定的通道，理论上可以实现“无数”的通道。实际使用中，也是要16或者32个通道才能较好的还原。
图6基于纳米结构的光谱滤波器中，微纳滤波器件或结构可以分别或同时在两侧ITO表面上分布(如用介质构成的周期性纳米粒子晶格)，不局限于基底一侧。
微纳滤波器件或结构的纳米结构可以是多种材料的堆叠，如高折射率和低折射率的材料交错分布，可选取对于同一波段的光透射性能差异较大的不同材料。高折射率和低折射率的材料指可以是高折射率和低折射率的材料制备成不同的纳米块，也可以是一个纳米块由多层结构组成，每层的折射率不同。
周期纳米结构在宽度上一般需要超过光源的束宽。
微纳滤波器件或结构的纳米结构可以根据所需要的性质改变分布、孔洞结构、长宽高比例等，包括但不限于孔阵列、光栅、纳米柱阵列等，
光波矩阵受微纳滤波器件或结构的纳米结构厚度影响，较薄时抗噪性能较差。
多种结构、多种材料的纳米结构组合而成的微纳滤波器件或结构有利于提升抗噪性能。
在红外波段常用金、银、铝、氮化钛等，在可见光波段常用锗、二氧化硅等，微纳滤波器件与结构的材料和形貌需根据波段选择。
液晶层直接接触到微纳滤波器件或结构，两侧ITO等级导电层连接幅值可调的电源，响应在基底与覆盖板之间施加的电压，折射率发生变化，微纳滤波器件或结构的谐振发生变化，进而改变器件的滤波特性。液晶层的厚度决定了液晶状态改变所需的电压，高电压可能导致电极发热。
探测器包含CCD或CMOS，用于对微纳滤波器件或结构的透射光谱进行测量，得到多组不同驱动电压下，即不同液晶折射率下探测器接收到的光波，实现微纳滤波器件或结构随时间的动态可调。
基于微纳滤波器件的阵列的多组透过率数据重建光谱信息，方法可以是最小二乘法、伪逆法、神经网络法等。其中最小二乘法重建光谱信息详细步骤如下：
在理想的成像模型中，假设P(λ)为频谱功率分布函数，F(λ)为光谱透射率，则成像系统的检测功率D为D＝∫P(λ)F(λ)dλ
在重构过程中，将P（λ）、F（λ）数字化，其中m＝1，2，…M为重构输入信号的光谱分辨率， n＝1，2，…N为过滤器，则
Figure PCTCN2022124582-appb-000001
由此，在获得一组透射率曲线后，基于滤波的光谱仪的测量值可以表示为：D N×1＝S N×MP M×1S表示由透射率曲线组组成的矩阵，P表示输入光谱信息，D表示与滤波器相对应的探测器的测量值。
当N<<M的情况下，上述公式变为欠定线性代数问题，转化为：minimize||D-SP|| 2(0≤P≤1)
可利用CVX等算法求解。S表示不同电压控制下，本发明中纳米块结构和电控相变材料组成单元的频谱透射曲线组组成的矩阵。透射率曲线是由纳米块的结构与电控折射率两方面的结果。
有益效果：本发明展现了光谱重建的全过程，重建输入信号所需的滤波器数量可以远小于通道数量(通道是折射率在一个值时均有一透射的光谱)，在硬件成本、系统操作复杂性及光谱分辨率等多个方面优于以前的光谱仪，有望为实现智能化小型化光谱仪提供思路。在该发明中，滤波器的透射曲率特性就是这个结构的光谱滤波特性，对光谱重建结果具有至关重要的影响。透射率曲线应涵盖重建信号的高频和低频信息。通过改变滤波器的某一参数改变滤波器的分光性能，连续、精细地调整光的透射曲线，利用伪逆法等计算出光谱信息。预保护点在于通过某一种可调材料构制滤波器，通过控制某一条件改变连续光源经过器件后不同波段的透射率，从而为光谱重建系统小型化、高速化和精确化提供解决方案。
附图说明
图1为典型的光谱重建和成像系统示意图，
图2为光学色散型光谱成像方式示意图；
图3为现有技术基于可调谐滤波器的光谱成像结构示意图；
图4为现有技术基于空间异性滤波器的光谱成像结构示意图；
图5为现有技术干涉型光谱成像仪原理示意图；
图6为本发明基于纳米结构的光谱滤波器结构；
图7为本发明光谱重建系统；
图8为本发明孔阵列结构示意图；其中图8为在衬底上铺一层金，在金上挖圆孔，然后填补液晶，此时为孔阵列；
图9为本发明孔阵列结构(某一截平面，即图8结构)的俯视图；
图10为本发明光栅结构示意图；
图11为本发明光栅结构(某一截平面)的俯视图；
图12为本发明纳米块结构示意图；
图13为本发明纳米块结构(某一截平面)的俯视图；
图14为本发明纳米块微纳滤波结构的仿真透过率曲线；
图15中(a)、(b)、(c)、(d)分别为本发明四个不同波长(1300nm、1400nm、1500nm、1600nm)下透过率随液晶折射率的变化曲线；
图16为本发明原始光谱；
图17为本发明原始光谱经过纳米块微纳滤波结构之后的透射光谱；
图18为本发明原始光谱经过纳米块微纳滤波结构之后的光强信息；
图19为本发明经过纳米块微纳滤波结构之后的重建光谱；
图20中共有12个重建光谱，经本发明实施例多个原始光谱经过纳米块微纳滤波结构之后的重建12种光谱。
图21微纳滤波结构为圆盘与十字纳米结构阵列；
图22是图21微纳滤波结构的正面(俯视)图。
具体实施方式
以下以具体实例说明，以重建或成像目标、微纳滤波器件或结构、电压控制模块和探测器为主要单元构建光谱重建系统，如图7所示，光源、微纳滤波器件和电压控制装置；微纳滤波器件包括设有导电电极的基底4及覆盖板1，基底4及覆盖板之间膜层、电控相变材料；覆盖板和基底层采用玻璃材料或其它透明材料，透明材料表面平整且覆盖ITO的导电膜3-1；作为施加的外电压的电极；在导电膜上制备周期性的纳米结构3，纳米结构单元采用金属材料、金属氧化物材料或半导体材料中的一种，根据所需要建立光谱的性质决定纳米结构的分布，纳米结构包括长、宽、高比例的纳米块分布或纳米孔洞分布结构。光源透射经微纳滤波器件控制得到需要的光谱。电压控制装置施加电压于电控相变材料。
重建目标在可见光和红外波段连续，射入微纳滤波器件或结构，改变液晶层两端的电压进而调整液晶分子的空间排布，即液晶材料的空间折射率分布特性，导致纳米结构的磁偶极谐振和电偶极谐振在谐振元件内发生变化，进而改变了由于所述液晶层切换而产生对光束振幅和相位的调制量。由于纳米结构的谐振特性具有波长相关性，因此液晶2在不同状态下，该器件的透射光谱响应会发生改变。利用不同液晶状态下的透射光谱可重建光谱信息。本发明可以用于紫外，但液晶材料在紫外光照射下稳定性差，能量吸收也比较高，非液晶材料及对紫外有调谐功能的材料可以应用。
图6、图12等为基于纳米结构的光谱滤波器，微纳滤波结构连接幅值可调的电源，调整液晶层的折射率，进而改变器件的滤波特性。对微纳滤波结构的透射光谱进行测量，探测器包含CCD或CMOS，得到多组不同驱动电压下，即不同液晶折射率下，器件的滤波特性。
覆盖板1，基底4的表面设有ITO层的导电膜(其它商用透明导电膜均能使用)，覆盖板和基底层采用玻璃材料或其它透明材料(石英、PMMA等均可)，导电膜指ITO层等与基底匹配(物理镀或CVD方式)的各种导电膜；图12示出了液晶2、微纳滤波器件的纳米结构即纳米块或纳米孔3，导电膜3-1，用来构成多个通道的光谱信息，由金属材料(或金属氧化物或半导体材料)交错分布纳米块，纳米块长为200nm，宽为100nm，高为250nm。所述结构为具体例。图13为其微纳滤波结构俯视图结构。
液晶改为铌酸锂、碲化锗,锗锑碲,银铟锑碲,碲化锑、二氧化钒是可以的。
通过改变液晶层的折射率，测量微纳滤波结构的透射光谱，得到32组透射光谱，令λ∈[a，b]∈[1200，1700]nm，间隔1nm进行采样，数据维数为501维。
图14示出了该例微纳滤波结构的仿真透过率曲线。
图15(a)、(b)、(c)、(d)分别为四个不同波长(1300nm、1400nm、1500nm、1600nm)下透过率随液晶折射率的变化曲线；图15中1300nm、1400nm、1500nm、1600nm时透过率随液晶折射率的变化曲线。不同波段的光束在液晶折射率不同时透过率不同。
在获得32组透射率曲线后，基于滤波的光谱仪的测量值可以表示为D 32×1＝S 32×501P 501×1
S是由透射率曲线组组成的矩阵，P表示入射光束的光谱，D是与滤波器相对应的探测器的测量值。
实施例展现了光谱重建的全过程，重建输入信号所需的滤波器数量可以远小于通道数量，在硬件成本、系统操作复杂性及光谱分辨率等多个方面优于以前的光谱仪，有望为实现智能化小型化光谱仪提供思路。在该发明中，滤波器的透射曲率特性对光谱重建结果具有至关重要的影响。透射率曲线应涵盖重建信号的高频和低频信息。
有益效果，与现有技术相比本发明的优点是：
其一，本发明提出了基于微纳滤波器件或结构的光谱重建系统，由滤波结构、电压控制系统和光强探测器组成，摒弃了传统利用色散元件和多个滤波片的方法，仅采用一块滤波结构，利用液晶折射率对不同波段光束的透过率不同进行光谱重建，极大简化了光学系统的结构，体积小重量轻。
其二，宽的光谱范围和高的光能利用率。
其三，滤波特性灵活。纳米结构自主可控，可根据对透过率等的需求更改纳米结构，实现不同的滤波特性。
其四，在重建过程中，数据的数量级减少，提高了光谱采集速度，光谱重建时可使用 神经网络进行优化，进一步提高光谱探测和成像的分辨力和精确度。
在本发明技术方案中，核心是在于通过控制液晶等的折射率改变滤波器件的性质，从而得到不同波段经过滤波器的透射率曲线，根据透射信息利用伪逆法等求解光谱信息。可以利用各种可调材料，调整不同控制条件下材料的各种性质，改变光经过器件的透射率信息，进而重建光谱。
技术关键点在于通过改变滤波器的某一参数改变滤波器件的分光性能，连续、精细地调整光的透射曲线，利用伪逆法等计算出光谱信息。预保护点在于通过某一种可调材料构制滤波器，通过控制某一条件改变连续光源经过器件后不同波段的透射率，从而为光谱重建系统小型化、高速化和精确化提供解决方案。
可以利用各种可调材料，调整不同控制条件下材料的各种性质，改变光经过器件的透射率信息，进而重建光谱。除了液晶外还可以是石墨烯、铌酸锂、锗锑碲化、二氧化钒。透过率越高越好，相变(折射率)改变范围越大越好。
本发明这个系统可以测量连续光谱：如400nm-1100nm或者1100nm-1700nm，也可以测有多个窄带峰的非连续光谱。能测量就能构建光谱。
图16为需要重建的原始光谱，图17为原始光谱经过图12所示微纳滤波结构之后的透射光谱，图18为原始光谱经过图12所示微纳滤波结构之后的光强信息。基于所得到的透射光谱和光强信息使用最小二乘法重建入射光束。图19为该例的仿光谱重建结果图。图20为12组原始光谱和经过上述步骤重建后的光谱。测量液晶16或者32种在不同折射率下器件(得到的通道)后的透射光强度，得到不同通道的光谱，可以还原出探测光谱信息，还原光谱信息过程时的通道数目可以远高于16或者32。图20中的12种光谱图像仅为举例，为了演示给出的这个纳米结构及16或者32通道可以很好的重建这12种在不同折射率下器件的不同波长下透射光强度，得到不同通道的光谱特性不同的光谱。但是方法不限于这12种光谱，理论上任意形貌的光谱都可以被重建出来。在重构这12种光谱中任意一种的过程中，我们需要把液晶设置在16或者32个不同的折射率的状态下，分别采集数据，即采集16或者32个通道，重构出该种光谱。
被重构出的光谱中，例如光谱范围在1200nm–1700nm，重构解析精度在1nm，那又可以说重构出的光谱涵盖了500个通道。不同的纳米结构，重建光谱的准确性可能有差异。
图12所示微纳滤波结构中纳米结构单元，由金属材料纳米块，也可以金属氧化物或半导体材料块，或金属材料纳米块与金属氧化物或半导体材料块交错分布，金属材料或金属氧化物或半导体材料块长为200nm，宽为100nm；微纳滤波结构的金属或金属氧化物或半导体材料块厚度为200、300nm均可。纳米块在形状上其它矩形、圆形或方形均可。
32组透射光谱反映了微纳滤波结构的信息，原始光谱经过32组透射光谱会得到32组透射后的光谱信息，由光谱信息可以反解出原始光谱，这时为重建后的光谱。图20表示了12种具有不同特征的原始光谱及经过微纳滤波结构后由透射光谱信息利用最小二乘法重建出的光谱。
微纳滤波器件的实用纳米结构阵列一般3个周期以上都可以(图13是三个周期的实用纳米结构)，可实用的周期可以在几十到100个以上均可；实施例：测量液晶16或者32种(通道)在不同折射率下器件的透射光强度，得到不同通道的光谱，可以还原出探测光谱信息，还原出的光谱信息中的通道数目可以远高于16或者32。
材料块的实用纳米结构分布是固定的，微纳结构一旦加工完就不能改变了。主要是相变材料的折射率变化。折射率改变的变化范围一般在5％-30％之间。
图16-图20中，图16为需要重建的原始光谱，图17为原始光谱经过纳米块微纳滤波结构之后的透射光谱，图18为原始光谱经过纳米块微纳滤波结构之后的光强信息，图19经过纳米块微纳滤波结构之后的重建光谱，因此图20表示了12种原始光谱到重建光谱(即12种图16和图19)的结果(即重建光谱曲线)。这12种是取了不同的光谱性质，单峰、多峰以及峰的高低，反映微纳滤波结构对于不同光谱的重建效果。箭头为光源方向。
基于所得到的透射光谱和光强信息使用最小二乘法重建入射光束。图19为实施例的仿光谱重建结果图。图20为12组原始光谱和经过上述步骤重建后的光谱。
基于多组透过率数据重建光谱信息，方法可以是最小二乘法、伪逆法、神经网络法等。最小二乘法重建光谱信息详细步骤如下：
令λ∈[a，b]，间隔进行采样，在获得一组透射率曲线后，基于滤波的光谱仪的测量值可以表示为Ax＝y
A是由透射率曲线组组成的矩阵，x表示入射光束的光谱，y是与滤波器相对应的探测器的测量值。
Figure PCTCN2022124582-appb-000002
使用最小二乘法重建入射光束：x＝(A TA) -1A Ty
以下以具体实例说明，以光源、微纳滤波结构器件、电压控制模块和探测器为主要单元构建光谱重建系统，如图7所示，光源在红外波段连续，射入微纳滤波结构，调整微纳滤波结构液晶层两端的电压进而调整液晶的折射率，得到入射光经过不同滤波结构的透射光谱响应，利用入射光及光谱响应重建光谱信息。
图7光谱重建系统，图8示出了微纳滤波结构，图9为微纳滤波结构的俯视图；通过改变液晶层的折射率，测量微纳滤波结构的透射光谱，得到32组透射光谱，令λ∈[a，b]∈[1200，1700]nm，间隔1nm进行采样，数据维数为501维。图10示出了该例的仿真透过率曲线。
在获得32组透射率曲线后，基于滤波的光谱仪的测量值可以表示为Ax＝y
A是由透射率曲线组组成的矩阵，x表示入射光束的光谱，y是与滤波器相对应的探测器的测量值。
Figure PCTCN2022124582-appb-000003
使用最小二乘法重建入射光束(光源)x＝(A TA) -1A Ty
图14为本发明以图13的器件在连续光谱入射条件下经纳米块微纳滤波结构折射率的大小控制下的仿真透过率曲线即仿真光谱重建结果。
实施例展现了光谱重建的全过程，在硬件成本、系统操作复杂性及光谱分辨率等多个方面优于以前的光谱仪，有望为实现智能化小型化光谱仪提供思路。在该发明中，微纳滤波器件的透射曲率特性对光谱重建结果具有至关重要的影响。透射率曲线应涵盖重建信号的高频和低频信息。
系统里面有个光源(即输入信号)，其光谱特性未知，通过本发明中的微纳滤波器件和方法可以重建出该光源的光谱。光源的光谱可以是连续的，也可以是离散的。
重建光源所需的滤波器数量可以远小于通道数量，此处的通道处应该理解为重建光谱的分辨率。假设光源的光谱覆盖1200nm–1700nm，我们重建的分辨率为1nm，那这样我们可以说重建出的光谱有501个通道。理论上，完全准确的实现1nm的分辨率(即501个通道)，本发明中的器件需要有501个状态，即电控相变材料要分别被设置在501种不同的折射率，再分别测量透射过器件的光能量。实际使用中，可以就测16或者32组数据(即测量过程中我们的微纳滤波器件设置16或32个通道)，然后利用一些算法，也能较好的以1nm分辨率重建光谱，实现501个通道。“通道”的概念有二，一个是重建出的光谱的通道数目，另一个是测量过程中本发明微纳滤波器件的一般设定的实际工作状态数目(每一个工作状态对应一个测试通道)。

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  1. 一种光谱建立的设备，其特征是，包括光源、微纳滤波器件、电压控制装置，所述微纳滤波器件包括设有基底及覆盖板，基底及覆盖板之间为导电膜层、电控相变材料；覆盖板和基底采用透明材料，透明材料表面平整且覆盖包括ITO层的导电膜层，作为施加的外电压的电极；
    在导电膜层上制备周期性阵列的纳米结构单元，纳米结构单元采用金属材料、金属氧化物材料或半导体材料中的一种，根据所需要建立光谱的性质决定纳米结构单元的分布，纳米结构单元包括成具有长、宽、高的纳米块分布、光栅分布或纳米孔洞分布结构；纳米块、光栅或纳米孔洞单元具有亚波长尺寸，微纳滤波器件的周期阵列的纳米结构单元与电控相变材料共同作用实现对透射光谱调控；设有电压控制装置施加电压作用于电控相变材料。
  2. 根据权利要求1所述的光谱建立的设备，其特征是，所述纳米块为金属、金属氧化物或半导体材料中的一种或多种，纳米块尺寸为亚波长的尺度。
  3. 根据权利要求2所述的光谱建立的设备，其特征是，金属、金属氧化物或半导体材料为金、银、铝、二氧化钛、氮化硅、氮化镓、硅、锗或二氧化硅，在红外和可见光谱范围内表现出低吸收；电控相变材料为液晶、石墨烯、铌酸锂、锗锑碲化或二氧化钒；纳米块的长宽均在100nm–1000nm范围。
  4. 根据权利要求1或2所述的光谱建立的设备，其特征是，微纳滤波器件的导电膜层平面上分布的周期阵列的纳米结构单元控制多个通道的光谱信息，纳米结构单元由金属、金属氧化物或半导体材料纳米块交错分布，纳米块长为200±50nm，宽为100±30nm；纳米块厚度为250±100nm。
  5. 根据权利要求1或2所述的光谱建立的设备，其特征是，微纳滤波器件的周期性阵列的纳米结构单元在基底与覆盖板的两侧导电膜层的任一侧导电膜或两侧导电膜表面上分布；电控相变材料直接接触到周期性阵列的纳米结构单元，电控相变材料两侧导电层连接幅值可调的外加电压，外加电压改变时微纳滤波器件对光的谐振发生变化，进而改变微纳滤波器件的滤波特性。
  6. 根据权利要求1或2所述的光谱建立的设备，其特征是，微纳滤波器件是多种周期性纳米结构材料的堆叠，包括高折射率和低折射率的纳米块交错分布，选取对于同一波段的光透射性能差异较大的不同材料制备纳米块。
  7. 根据权利要求1或2所述的光谱建立的设备，其特征是，微纳滤波器件根据所需要的性质改变分布、孔洞结构、长宽高比例：包括孔阵列、光栅、纳米柱、纳米块阵列；在红外波段用金、银、铝、氮化钛，在可见光波段用锗、二氧化硅，微纳滤波器件的纳米结构材料和 形貌需根据波段选择。
  8. 一种根据权利要求1-7任一所述的设备建立光谱的方法，其特征是，通过控制微纳滤波器件的基底及覆盖板的电压，从而控制液晶的折射率，再根据微纳滤波器件纳米结构的分布，改变微纳滤波器件的性质，从而得到不同波段经过滤波器的透射率曲线，根据透射信息利用伪逆法求解光谱信息；通过施加电场的控制强度从而改变液晶材料的实际折射率，改变对光源频谱的谐振频率，实现了对频谱的可编程滤波；调节电压的目的是改变电控相变材料的实际折射率。
  9. 根据权利要求8所述的建立光谱的方法，其特征是，利用可调电控相变材料，调整不同控制条件下相变材料的性质，改变光经过器件的透射率，进而重建光谱。
  10. 根据权利要求8所述的建立光谱的方法，其特征是，微纳滤波器件的周期性纳米结构为一个谐振元件，谐振频率与谐振元件结构构型和结构材料折射率有关，谐振频率决定了光的透过光谱。
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