CN115290188A

CN115290188A - Design method of miniature spectral imager

Info

Publication number: CN115290188A
Application number: CN202211014306.3A
Authority: CN
Inventors: 冯蕾; 周锦松; 黄旻; 何晓英; 魏立冬; 李雅灿; 景娟娟
Original assignee: Aerospace Information Research Institute of CAS
Current assignee: Aerospace Information Research Institute of CAS
Priority date: 2022-08-23
Filing date: 2022-08-23
Publication date: 2022-11-04

Abstract

The invention discloses a design method of a miniature spectral imager, which comprises the steps of determining the number of spectral channels and the spectral range of a single channel, determining a focusing phase function of an aberration correcting lens according to parameters such as a spectral band range and a system focal length, optimizing the mapping relation among phases, transmittances and structural parameters under different structures by combining a particle swarm optimization algorithm, and determining the full-mode structure and the period parameters of the aberration correcting lens; a filter array based on a distributed Bragg reflector is established, the central frequency, the spectral bandwidth, the long wave frequency and the short wave frequency of a single channel are determined according to requirements, two media with different high and low refractive indexes are determined according to the bandwidth parameters of the single channel, the film parameters of a filter cavity are determined according to the bandwidth parameters of the single channel, the filter structure parameters which meet certain requirements and have the highest unimodal transmittance are obtained by optimizing the number of the films and the thicknesses of the different media, and the design of narrow-band filtering is achieved. The imaging of space dimension and spectral dimension can be obtained simultaneously by taking a picture without any moving component, the time resolution is effectively improved, and the integration and miniaturization design of the system is realized.

Description

Design method of miniature spectral imager

Technical Field

The invention relates to a spectral imaging technology, in particular to a design method of a miniature spectral imager.

Background

The spectral imaging technology is different from the traditional single broadband imaging technology, is a new generation photoelectric detection technology integrating optics, spectroscopy, precision machinery, electronic technology and computer technology, combines the spectral technology and the imaging technology, obtains information not only including two-dimensional spatial information, but also including spectral radiation information distributed along with wavelength, and forms a Data cube (Data cube) including spatial dimension and spectral dimension. The data cube is used for analyzing the spatial characteristics and identifying the internal components of the target, and meanwhile, the timing, positioning, qualitative and quantitative analysis of the observed target is realized, and the unification of the spatial image and the spectral data is realized. Spectral imaging techniques can be divided into two categories: scanning spectral imagers and snapshot spectral imagers. The scanning spectral imager acquires a plurality of successive one-dimensional (1D) or two-dimensional measurement data and constructs a 3D spectral data cube. The scanning mode includes space dimension scanning, such as a sweep mode and a push sweep mode; a spectral dimension scan, such as a tunable filter system or a fourier transform spectrometer. Such systems are slow to acquire a complete data cube, especially in systems with mechanical scanning elements where long scan periods can cause image motion or other data redundancy. In contrast, snapshot-type spectral imagers acquire three-dimensional data cubes by imaging in both spatial and spectral dimensions during an integration period, taking a single photograph, and these systems do not require moving components or relative movement of the system and the object. Snapshot-type spectral imagers may use dispersive elements, spectral filters, or interferometers to acquire spectral information. The parallel multi-beam array spectral imager is a simple compact snapshot structure, a beam of parallel light is incident to different array channels, and each channel has different spectral filters. Compared with the chromatography and compression coding technology, the parallel spectrometer can obtain real-time information of space dimension and spectrum dimension without a large amount of calculation. Unlike a spectrometer using a dispersive element, the spectral channels using a filter system need not be continuous and can be developed flexibly according to the spectral characteristics of a particular application.

Super-surfacing is a technology that has emerged in recent years, being lighter and more compact than traditional optical components, and being processable using standard nano-fabrication techniques, making it an attractive option for size, weight or cost-limited applications. By modulating the phase, polarization and amplitude of light waves, the super-surface optical element can flexibly realize the functions of traditional optical elements such as gratings, wave plates, lenses and the like. While some optical systems can be miniaturized by super-surfaces, they are not alternatives to refractive elements. In the imaging field, an important limiting factor in designing a super-surface is the mutual constraints of aberration and bandwidth.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a design method of a miniature spectral imager, which aims to solve the technical problems in the prior art.

The purpose of the invention is realized by the following technical scheme:

the design method of the miniature spectral imager comprises the following steps:

A. determining the number of spectral channels and the spectral range of a single channel according to requirements, determining a focusing phase function of the aberration correcting lens according to parameters such as a spectral range, a system focal length and the like, optimizing mapping relations among phases, transmittances and structural parameters under different structures by combining a particle swarm optimization algorithm, establishing a relation between parameters of a unit structure and the phase function, and further determining a full-mode structure and a period parameter of the aberration correcting lens;

B. the method comprises the steps of establishing a filter array based on a distributed Bragg reflector, firstly determining the central frequency, the spectral bandwidth, the long wave frequency and the short wave frequency of a single channel according to requirements, determining two media with different high and low refractive indexes, determining the film parameters of a filter cavity according to the bandwidth parameters of the single channel, obtaining the filter structure parameters with the highest unimodal transmittance and meeting certain requirements by optimizing the number of the films and the thicknesses of the different media, and realizing the design of narrow-band filtering.

Compared with the prior art, the design method of the micro spectral imager provided by the invention is based on the multi-beam interference principle and the diffraction theory, and forms a double-peak array by combining the two super-surface arrays, wherein each pair of super-surfaces realizes the function equivalent to a narrow-band lens. The same scene is divided into a plurality of channels, and only the wavelength in the passband of the related filter array can be imaged to the corresponding position of the image plane, so a plurality of image channels with narrow spectrum are formed on the image plane, and finally a multicolor image composed of different wavelengths is obtained. The design method breaks through the design method of the traditional spectral imaging system, does not need any moving component, can simultaneously obtain the imaging of space dimension and spectral dimension by taking a picture at one time, effectively improves the time resolution, and realizes the integrated and miniaturized design of the system.

Drawings

FIG. 1 is a schematic diagram of a micro spectral imager system provided in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a cell structure according to an embodiment of the present invention;

FIG. 3 is a structural diagram of a 3um wavelength whole system according to an embodiment of the present invention;

FIG. 4 is a block diagram of a spatial division filter unit according to an embodiment of the present invention;

fig. 5 is a graph of the full width at half maximum of the focused spot for different channels according to the embodiment of the present invention.

Detailed Description

The technical scheme in the embodiment of the invention is clearly and completely described below by combining the attached drawings in the embodiment of the invention; it is to be understood that the described embodiments are merely exemplary of the invention, and are not intended to limit the invention to the particular forms disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

The terms that may be used herein are first described as follows:

the term "and/or" means that either or both can be achieved, for example, X and/or Y means that both cases include "X" or "Y" as well as three cases including "X and Y".

The terms "comprising," "including," "containing," "having," or other similar terms of meaning should be construed as non-exclusive inclusions. For example: including a feature (e.g., material, component, ingredient, carrier, formulation, material, dimension, part, component, mechanism, device, process, procedure, method, reaction condition, processing condition, parameter, algorithm, signal, data, product, or article of manufacture), is to be construed as including not only the particular feature explicitly listed but also other features not explicitly listed as such which are known in the art.

The term "consisting of … …" is meant to exclude any technical feature elements not explicitly listed. If used in a claim, the term shall render the claim closed except for the usual impurities associated therewith which do not include the technical features other than those explicitly listed. If the term occurs in only one clause of the claims, it is defined only to the elements explicitly recited in that clause, and elements recited in other clauses are not excluded from the overall claims.

Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "secured," etc., are to be construed broadly, as for example: can be fixedly connected, can also be detachably connected or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms herein can be understood by those of ordinary skill in the art as appropriate.

Recitation of ranges of values herein are intended to include both the end values and all integers and fractions subsumed within the range.

The terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in an orientation or positional relationship that is indicated based on the orientation or positional relationship shown in the drawings for ease of description and simplicity of description only, and are not intended to imply or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting herein.

Details which are not described in detail in the embodiments of the invention belong to the prior art which is known to the person skilled in the art. The examples of the present invention, in which specific conditions are not specified, were carried out according to the conventional conditions in the art or conditions suggested by the manufacturer. The reagents or instruments used in the examples of the present invention are not specified by manufacturers, and are all conventional products available by commercial purchase.

A. determining the number of spectral channels and the spectral range of a single channel according to requirements, determining a focusing phase function of the aberration correction lens according to parameters such as a spectral band range and a system focal length, optimizing mapping relations among phases, transmittances and structural parameters under different structures by combining a particle swarm optimization algorithm, establishing a relation between the parameters of a unit structure and the phase function, and further determining a full-mode structure and a period parameter of the aberration correction lens;

B. establishing a filter array based on a distributed Bragg reflector, firstly determining the central frequency, the spectral bandwidth, the long wave frequency and the short wave frequency of a single channel according to requirements, determining two media with different high and low refractive indexes, determining the film layer parameters of a filter cavity according to the bandwidth parameters of the single channel, and obtaining the filter structure parameters with the highest single-peak transmittance meeting certain requirements by optimizing the number of the film layers and the thicknesses of different media, thereby realizing the design of narrow-band filtering.

The step A comprises the following steps:

comprehensive use requirements, selecting a spectral range: 3-5 um, spectral band number: 6, focal length: 2mm;

the system consists of a target, an aberration correcting imaging lens array, a spatial division filter and an area array detector;

each lens is subjected to aberration correction at a specific wavelength, and the filter effectively improves the image resolution and the contrast by inhibiting transmission far away from the designed wavelength;

when the target is positioned at a limited distance, the light source illuminates the target, the same object point emits spherical waves, and the target space dimension imaging is realized after the spherical waves pass through the aberration correction imaging lens;

each aberration correcting lens can form a multicolor image, and after passing through a filter, the image resolution and contrast are improved by inhibiting transmission far away from the designed wavelength, so that the spectral dimension imaging of a target is realized;

the image plane is reached only by the target image in the pass band of the associated filter, the image plane being composed of a plurality of image channels having a narrow spectral range, the spectral data cube being composed by stacking the channels;

dynamic image and spectrum video data acquisition is realized through continuous acquisition;

the step B comprises the following steps:

the aberration correcting imaging lens in the whole system adopts a super lens array, a filter is composed of a super surface filtering array, and the phase distribution of the lens is written as follows:

wherein phi is the phase required by the lens, r is a radial coordinate, f is a focal length, lambda is a designed working wavelength, and the phase formula is based on phase distribution under a target wavelength;

the phase distribution formula shows that the phase value is minimum at the center of the lens, and the phase regulation quantity is increased at the edge of the lens;

adopting transmission phase modulation, firstly setting target basic index parameters such as focal length, device size and the like; then, establishing a unit structure model, and scanning the relation between phases and structure parameters under different wavelengths to further construct a whole system structure under different wavelengths;

the unit structure is a cylindrical structure arranged on the substrate, the material is silicon, the cylindrical radius of the lens at different positions is calculated through a formula (1), target performance and analysis parameters are set, and the full system structure with the wavelength of 3 micrometers is finally determined by utilizing an optimization algorithm;

the space division filter is composed of an array structure, each filter is composed of a Bragg reflector DBR and a middle micro-structure array, and each pair of DBRs and the middle micro-structure array form a resonant cavity;

the design process firstly determines the center frequency of the DBR, determines two high-low refractive index dielectric materials used according to the center wavelength, the DBR is composed of amorphous silicon a-Si and silicon dioxide SiO2 layers in an alternating mode, the microstructure is composed of a nanopore array, nanopores are arranged on a hexagonal lattice, the DBR structure in each filter is the same, the whole filter structure is periodic, and the resonance wavelength is changed by adjusting the structure size of a unit, so that the peak output of different design wavelengths is realized.

Through electromagnetic simulation software and programming software, a total system model is established and scripts are compiled, the total system structure is scanned under different wavelengths respectively to obtain energy focusing maps of different channels, the brightness of different channels in the images is normalized to obtain focusing light spot maps of six channels, the horizontal axis represents the wavelength, the vertical axis is brightness normalization information of the focusing light spots, and a single channel is effectively focused at different positions, namely, the focusing and the dispersion at the same focal plane are effectively realized.

In summary, the design method of the micro spectral imager in the embodiment of the invention combines the super-surface technology with the parallel array multispectral technology, and provides a design method of a super-surface micro spectral imaging system, wherein the super-surface micro spectral imaging system is a spectral imaging structure formed by two array super-surfaces. The first layer super surface is composed of a plurality of arrays for correcting monochromatic aberration, and the degradation of imaging quality caused by chromatic aberration of a traditional system is effectively improved by correcting the monochromatic aberration of a specific wavelength. The second super surface layer is composed of band-pass filter arrays with different wave bands, and the image resolution and contrast are effectively improved by inhibiting the transmission of light far away from the designed wavelength. The design method can improve the imaging performance and the energy utilization rate of the system. Compared with the conventional common system, the system disclosed by the invention has the advantages that the volume is millimeter-scale, a single system does not need moving parts, target two-dimensional spatial information and spectral information can be simultaneously obtained by taking a picture once, a dynamic target acquisition function is realized, the time resolution of the system is effectively improved, and the system can be applied to platforms with high requirements on system compactness, such as the fields of medical microscopic spectroscopy, handheld miniaturized spectral systems, security monitoring and the like.

The design method of the miniature imaging spectrometer combines the correction monochromatic aberration lens and the sub-wavelength filter array, utilizes the sub-wavelength structure to freely modulate the multi-dimensional information of electromagnetic waves, solves the problems of large volume, high cost and the like caused by the limitation of a light splitting element on the traditional spectral imaging system, and realizes the light, small and integrated design of the system. The monochromatic aberration is corrected at a specific wavelength position through different channels, so that the imaging quality of a single channel is far higher than that of a traditional achromatic lens, and the bottleneck problem that a wide-spectrum system constructed by a sub-wavelength structure is difficult to achromatize is effectively solved. The sub-wavelength band-pass filter array is correspondingly matched with a transmission window of the monochromatic aberration correction lens, transmission outside the designed wavelength is restrained, so that the image resolution is improved, the defect that the spectral resolution of a traditional system cannot be flexibly modulated is overcome, and the discontinuous flexible modulation of the spectral resolution and the spectrum section is realized.

The invention is based on the multi-beam interference principle and the diffraction theory, and forms a double-peak array by combining two super-surface arrays, wherein each pair of super-surfaces realizes the function equivalent to a narrow-band lens. The same scene is divided into a plurality of channels, and only the wavelength in the passband of the related filter array can be imaged to the corresponding position of the image plane, so a plurality of image channels with narrow spectrum are formed on the image plane, and finally a multicolor image composed of different wavelengths is obtained. The design method breaks through the design method of the traditional spectral imaging system, does not need any moving assembly, can simultaneously obtain the imaging of space dimension and spectral dimension by taking a picture once, effectively improves the time resolution, and realizes the integrated and miniaturized design of the system.

The technical scheme of the invention has the following beneficial effects:

compared with the technical scheme of the existing imaging spectrometer, the miniature imaging spectrometer provided by the invention has the following characteristics:

the traditional imaging spectrometer is limited by the size of a dispersion element, the size of the traditional imaging spectrometer is more than hundreds of millimeters, the system only needs two millimeter-level array components to realize the dispersion and focusing performance of the traditional system, and the contradiction between the high performance of the system and the miniaturization and integration is effectively solved.

The system effectively overcomes the contradiction between the chromatic aberration of the traditional super-surface micro-lens and the bandwidth of a spectral band by combining the filter array and the aberration correction lens array, can effectively realize wide-spectral-band imaging, and the wave band range of the system can be flexibly adjusted according to requirements. Through the hole array structure, the ultra-wide frequency doubling filtering in the spectral range can be realized.

The numerical aperture NA of the traditional super-surface micro-lens is limited by a wave band range, along with the widening of the wave band range, the numerical aperture is limited, the large relative aperture focusing imaging in a wide spectrum range is difficult to realize, the system decomposes a spectrum channel through a filter array, the numerical aperture of the system is effectively improved, and therefore the energy utilization rate of the system is improved.

In a traditional dispersion element such as a grating, the dispersion width of different wavelengths is determined by a diffraction angle, the diffraction angle is limited by a diffraction theory, the diffraction angle is limited to dozens of degrees, the dispersion width is greatly limited by the factors, and the system can set different dispersion widths aiming at different wave band ranges according to different requirements and flexibly regulate and control the spectral resolution.

Compared with a micro spectral imager, the system does not need any pushing or swinging moving part, and only needs to take a picture once to collect space dimension and spectral dimension data so as to obtain the spectral dimension and space dimension information of the target. The system has the key advantages that all spectral data are captured simultaneously, and the function can acquire dynamic spectral videos, so that high-time resolution detection is realized, the detection sensitivity is effectively improved, and a certain theoretical basis is provided for the application in the fields of security monitoring and the like.

The image obtained by the system has no spectral distortion and spatial distortion, and a data cube is reconstructed without performing a characterization matrix and subsequent processing, so that the problems caused by subsequent data processing are reduced.

The image plane and the incident plane of the system are coplanar, and the image planes of different channels are located in the same plane, so that the system is convenient to install, adjust, test and calibrate.

The spectral range of the system can be flexibly adjusted according to different detection requirements, and compared with the traditional spectral imager, the continuity of the spectral range and the continuity of the spatial spectrum are not required to be ensured.

In order to more clearly show the technical solutions and effects provided by the present invention, the following detailed descriptions of the embodiments of the present invention are provided by specific embodiments.

Example 1

As shown in fig. 1 to 5:

the design method of the miniature imaging spectrometer is based on a multi-beam interference principle and a super-surface regulation mechanism, searches the focusing performance and spectral response characteristics of unit microstructures to different wavelengths, and realizes the design of the spectral imager with flexibly adjustable spectrum in a wide band range by combining a filter array and an aberration correcting single lens array.

The specific method comprises the following steps:

and determining the number of spectral channels and the spectral range of a single channel according to requirements. The focusing phase function of the aberration correcting lens is determined by parameters such as a spectrum range and a system focal length, the mapping relation among phases, transmittances and structure parameters under different structures is optimized by combining a particle swarm optimization algorithm, the relation between the parameters of a unit structure and the phase function is established, and then the full-mode structure and the period parameters of the aberration correcting lens are determined.

Establishing a filter array based on a distributed Bragg reflector, firstly determining the central frequency, the spectral bandwidth, the long wave frequency and the short wave frequency of a single channel according to requirements, determining two media with different high and low refractive indexes, determining the film layer parameters of a filter cavity according to the bandwidth parameters of the single channel, and obtaining the filter structure parameters with the highest single-peak transmittance meeting certain requirements by optimizing the number of the film layers and the thicknesses of different media, thereby realizing the design of narrow-band filtering.

Based on the design method, the embodiment of the invention designs a multi-spectral-band spectral imaging system in a mid-infrared range.

The specific implementation steps are as follows:

1. comprehensive use requirements, selecting a spectral range: 3-5 um, number of spectral bands: 6, focal length: 2mm;

the schematic diagram is shown in fig. 1, and the imaging optical system comprises three parts, namely an object, an aberration correcting imaging lens array, a spatial division filter and an area array detector. Each lens performs aberration correction at a specific wavelength, and the filter effectively improves image resolution and contrast by suppressing transmission away from the design wavelength. When the target is located at a limited distance, the light source illuminates the target, the same object point emits spherical waves, and the target space dimension imaging is realized after the spherical waves pass through the aberration correction imaging lens. Each aberration correcting lens can form a multicolor image, and after passing through a filter, the image resolution and contrast are improved by inhibiting transmission far away from the designed wavelength, and spectral dimensional imaging of a target is realized. But only the object image in the pass band of the associated filter is able to reach the image plane, which consists of a plurality of image channels with narrow spectral ranges. The spectral data cube is constructed by stacking the channels. By continuous acquisition, dynamic image and spectral video data acquisition can be achieved.

2. The aberration correcting imaging lens in the whole system adopts a super lens array, and the filter is composed of a super surface filter array. The phase profile of the lens can be written as:

where φ is the desired phase of the lens, r is the radial coordinate, f is the focal length, λ is the design operating wavelength, and the phase equation is based on the phase distribution at the target wavelength. The phase distribution formula can be used to obtain that the phase value is minimum at the center of the lens, and the phase regulation quantity is increased at the edge of the lens. Adopting transmission phase modulation, firstly setting target basic index parameters such as focal length, device size and the like; and then establishing a unit structure model, and scanning the relationship between the phase and the structure parameter under different wavelengths to further construct a whole system structure under different wavelengths. The unit structure is shown in fig. 2, red is a cylindrical structure, white is a substrate, the materials are all silicon, the cylindrical radius of the lens at different positions is calculated through a formula 1, target performance and analysis parameters are set, and the whole system structure with the wavelength of 3 micrometers is finally determined by utilizing an optimization algorithm and is shown in fig. 3.

The spatial division filter is composed of an array structure, as shown in fig. 4. Each filter is composed of a Bragg reflector (DBR)

And the middle microstructure array, wherein each pair of DBRs and the middle microstructure array form a resonant cavity. The design process firstly determines the center frequency of the DBR, and determines two high-low refractive index dielectric materials used according to the center wavelength. The DBR consists of alternating layers of amorphous silicon (a-Si) and silicon dioxide (SiO 2). The microstructure is composed of an array of nanopores arranged on a hexagonal lattice. The DBR structure in each filter is the same, the whole filter structure is periodic, and the resonance wavelength is changed by adjusting the structure size of the unit, so that the peak output of different design wavelengths is realized. In fig. 4, green and white represent the high and low refractive index layers of the DBR, the red circular hole structure, and the filled organic material around the hole, respectively.

Establishing a full-system model and compiling scripts through electromagnetic simulation software and programming software, and respectively aligning the full system

The structure is scanned under different wavelengths to obtain energy focusing images of different channels, and the brightness of different channels in the images is normalized to obtain focusing light spot images of six channels. The horizontal axis represents wavelengths 3,3.4,3.8,4.1,4.5,5um, and the vertical axis is the brightness normalization information of the focused spot. It can be seen from the figure that the single channel is effectively focused at different positions, i.e. the focusing and the dispersion at the same focal plane are effectively achieved.

The embodiments are given as illustrative examples only, and should not be construed as limiting the invention, any obvious local modifications thereof should be considered as alternatives. Such alternatives include the design of spectral imaging by combining a system aberration correcting lens with a spatial division filter, the use of the design in imaging systems in other wavelength ranges, the use of any other wavelength range change where the difference between the long and short wavelength frequencies in the wavelength range is the same or becomes narrower and wider, the change in the number of spectral bands, the design of the spatial division filter, the change in the form of the cell structure, the change in the number of DBR film layers and the high and low refractive index material, the change in the system focal length, the change in the electromagnetic wave modulation mode of the aberration correcting lens, the change in the design of the different channels of the spatial division filter, and the like, without departing from the essential scope of the present invention.

The technical key points of the invention are as follows:

a design method of a compact spectral imager is provided, the method combines a chromatic aberration correcting lens and a space division filter, adopts a DBR and microstructure regulation mechanism, and realizes the collection of space and spectrum information of a target through a cascade array structure. The system can realize flexible modulation of spectral resolution and flexible selection of band range in a wide band range. Meanwhile, the method has the advantages of dynamic target detection, does not need any moving part, can continuously acquire a multi-frame video function, and effectively improves the time resolution and the detection sensitivity;

a design method of a micro spectral imager is provided based on a multi-beam interference principle and a super-surface flexible regulation and control mechanism. A compact spectral imager is formed by a plurality of array structures through the combination of a color difference correcting lens and a space division filter. By utilizing the monochromatic aberration correcting lens, the contradiction that the strong dispersion of the traditional lens is limited by the numerical aperture and the spectral range is effectively overcome; and the peak tuning of different wavelengths is realized through the combination of the array hole structure and the DBR. The whole system does not need any moving part, and can realize the acquisition of space and spectral dimensional information of the moving target. The spectral resolution and the spectral range have flexible adjustability, and can be flexibly modulated according to different use requirements and application occasions;

based on the array structure form of the aberration correcting lens and the spatial division filter, the compact snapshot type spectral imager is formed by a plurality of channel arrays. The scene is divided into a plurality of quantitative narrow-band spectral channels, an array parallel optical processing method is adopted, crosstalk among image channels is reduced, and the method has the functions of static image acquisition and video acquisition while imaging without chromatic aberration.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Claims

1. A design method of a miniature spectral imager is characterized by comprising the following steps:

2. The design method of miniature spectral imager of claim 1, characterized by:

the step A comprises the following steps:

comprehensive use requirements, selecting a spectral range: 3-5 um, number of spectral bands: 6, focal length: 2mm;

each lens carries out aberration correction at a specific wavelength, and the filter effectively improves the image resolution and the contrast ratio by inhibiting transmission far away from the designed wavelength;

the step B comprises the following steps:

the space division filter consists of an array structure, each filter consists of a Bragg reflector DBR and a middle micro-structure array, and each pair of DBRs and the middle micro-structure array form a resonant cavity;

the design process comprises the steps of firstly determining the central frequency of the DBR, determining two high-refractive index and low-refractive index dielectric materials according to the central wavelength, wherein the DBR is composed of amorphous silicon a-Si layers and silicon dioxide SiO2 layers in an alternating mode, a microstructure is composed of a nanopore array, nanopores are arranged on hexagonal lattices, the DBR structures in all filters are the same, the whole filter structure is periodic, and the resonant wavelength is changed by adjusting the structural size of a unit, so that the peak output of different design wavelengths is realized.

3. The design method of the micro-spectral imager according to claim 2, characterized in that a total system model is established and scripts are compiled through electromagnetic simulation software and programming software, the total system structure is scanned under different wavelengths respectively to obtain energy focusing maps of different channels, the brightness of different channels in the image is normalized to obtain focusing light spot maps of six channels, the horizontal axis represents the wavelength, the vertical axis is brightness normalization information of the focusing light spots, and a single channel is effectively focused at different positions, namely, the focusing and the dispersion at the same focal plane are effectively realized.