Modulation structure for infrared hyperspectral imaging, detector, and infrared spectrometer

Abstract

A modulation structure (20) for infrared hyperspectral imaging, a detector, and an infrared spectrometer. The modulation structure (20) comprises: a detector window packaging layer (10); an infrared antireflection film (40), wherein the infrared antireflection film (40) is arranged on the surface of the side of the detector window packaging layer (10) facing a pixel array (30), and the refractive index of the material of the infrared antireflection film (40) is smaller than that of the material of the detector window packaging layer (10); and a plurality of microstructure modulation units (21), wherein the plurality of microstructure modulation units (21) are arranged, according to a preset arrangement rule, on the surface of the side of the infrared antireflection film (40) facing away from the detector window packaging layer (10), so that a partial area on the surface of the side of the infrared antireflection film (40) facing away from the detector window packaging layer (10) is vacant to form at least one vacancy modulation unit (22). By means of the infrared antireflection film (40) and the vacancy design, the luminous fluxes of the microstructure modulation units (21) are increased, so that a high signal-to-noise ratio can be achieved.

Description

Modulation structure, detector and infrared spectrometer for infrared hyperspectral imaging Technical Field

[0001] The present application relates to the field of infrared hyperspectral imaging technology, and in particular to a modulation structure, a detector and an infrared spectrometer for infrared hyperspectral imaging. Background Art

[0002] In hyperspectral imaging related technologies, micro-nano modulation structures made of high-refractive index materials (such as micro-nano circular hole structures etched on silicon plates, etc.) can be used to modulate the spectral dimension of the incident light, and computational optics methods can be combined to obtain spectral images in a snapshot manner.

[0003] Summary of the Invention

[0004] The main purpose of this application is to provide a modulation structure, a detector and an infrared spectrometer for infrared hyperspectral imaging, aiming to solve the technical problem of low signal-to-noise ratio after hyperspectral imaging caused by the spectral modulation structure.

[0005] To achieve the above-mentioned objectives, the present application proposes a modulation structure for infrared hyperspectral imaging, comprising: a detector window packaging layer; an infrared anti-reflection film, the infrared anti-reflection film is arranged on the side surface of the detector window packaging layer facing the pixel, and the refractive index of the material of the infrared anti-reflection film is smaller than the refractive index of the material of the detector window packaging layer; and a plurality of microstructure modulation units, the plurality of microstructure modulation units are arranged on the side surface of the infrared anti-reflection film facing away from the detector window packaging layer according to a preset arrangement rule, so that a partial area of ​​the surface of the infrared anti-reflection film facing away from the detector window packaging layer is left vacant to form at least one empty modulation unit.

[0006] In a possible embodiment of the present application, the preset arrangement rules include at least one of the following: the microstructure modulation unit is adjacent to the at least one empty modulation unit; in the first direction or the second direction of the pixel array, there are at most two empty modulation units between two adjacent microstructure modulation units, and the first direction is perpendicular to the second direction; among all the microstructure modulation units adjacent to each empty modulation unit, the structures of any two microstructure modulation units are different from each other.

[0007] In a possible embodiment of the present application, in the first direction, the microstructure modulation units and the empty modulation units are alternately arranged, and in the second direction, the microstructure modulation units and the empty modulation units are alternately arranged.

[0008] In a possible embodiment of the present application, the infrared antireflection film includes at least two transparent film layers stacked in sequence, and the refractive index of the at least two transparent film layers gradually decreases in a direction away from the detector window packaging layer.

[0009] In a possible embodiment of the present application, the material of the transparent film layer includes ZnS zinc sulfide, ZnSe zinc selenide, BaF2 barium fluoride, CaF2 calcium fluoride, YbF3 ytterbium fluoride, Ge germanium or Si silicon.

[0010] In a possible embodiment of the present application, each of the microstructure modulation units includes a plurality of micro-nanostructure sub-units arranged in a rectangular array, and the plurality of micro-nanostructure sub-units are spaced apart from each other.

[0011] In a possible embodiment of the present application, the multiple micro-nanostructure sub-units are constructed as a columnar structure protruding from the sub-area, and the material of the columnar structure is an infrared high-refractive index material; or an infrared high-refractive index medium layer is provided on the surface of the infrared anti-reflection film on the side facing away from the detector window packaging layer, and the multiple micro-nanostructure sub-units are constructed as a hole structure that penetrates the infrared high-refractive index medium layer along the thickness direction of the detector window packaging layer.

[0012] In a possible embodiment of the present application, the cross-sectional shape of the micro-nanostructure subunit is configured as a rotationally symmetrical figure with a rotation angle of 90°.

[0013] In a possible embodiment of the present application, the side length of a pixel in the pixel array is less than or equal to 17 μm, the number of micro-nanostructure sub-units in the third direction of the rectangular array is less than or equal to 10, and the number of micro-nanostructure sub-units in the fourth direction of the rectangular array is less than or equal to 10; wherein the third direction is perpendicular to the fourth direction.

[0014] In one possible embodiment of the present application, the height of the micro-nanostructure subunit is greater than 5 μm.

[0015] In a second aspect, the present application also provides a detector comprising: an image sensor, the image sensor comprising a pixel array; and a modulation structure for infrared hyperspectral imaging as in the first aspect, wherein the microstructure modulation unit and the pixel array of the modulation structure are arranged relative to each other.

[0016] In a third aspect, the present application further provides an infrared spectrometer, comprising: a detector as provided in the second aspect; and an image signal processor, the image signal processor being connected to the detector.

[0017] The technical solution of the present application is to add an infrared anti-reflection film to the detector window packaging layer, and arrange multiple microstructure modulation units on the infrared anti-reflection film according to a preset arrangement rule, so that part of the surface of the infrared anti-reflection film is left vacant to form at least one empty modulation unit. The microstructure modulation unit and the empty modulation unit together form the spectral modulation structure of the detector. In this way, the embodiment of the present application, on the one hand, uses the anti-reflection capability provided by the infrared anti-reflection film, and on the other hand, uses the unstructured empty modulation unit to reduce the used area of ​​the micro-nano structure in the detector window, thereby improving the transmittance reduction caused by microstructure reflection, thereby jointly improving the signal-to-noise ratio after hyperspectral imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without any creative work.

[0019] FIG1 is a schematic structural diagram of an embodiment of a modulation structure for infrared hyperspectral imaging according to the present application;

[0020] FIG2 is a schematic diagram of the spectral modulation structure distribution of an embodiment of a modulation structure for infrared hyperspectral imaging according to the present application;

[0021] FIG3 is a schematic structural diagram of another embodiment of the modulation structure for infrared hyperspectral imaging of the present application, wherein the infrared antireflection film is a double-layer structure;

[0022] FIG4 is a schematic structural diagram of another embodiment of the modulation structure for infrared hyperspectral imaging of the present application, wherein the infrared antireflection film is a three-layer structure;

[0023] FIG5 is a schematic structural diagram of an embodiment of a modulation structure for infrared hyperspectral imaging according to the present application, wherein the micro-nanostructure subunit is a hole-shaped structure;

[0024] FIG6 is a schematic diagram of the antireflection effect of Example 1;

[0025] FIG7 is a comparison diagram of modulation curves of the five microstructure modulation units 21 and the four empty modulation units 22 of Example 1;

[0026] FIG8 is a comparison diagram of the average light transmittance of the spectrum modulation unit of Example 1 and the average light transmittance of the microstructure modulation unit (such as micro-nanohole) generally provided on the Si window;

[0027] FIG9 is a graph showing nine spectrum modulation curves generated by nine spectrum modulation units of Example 1;

[0028] FIG10 is a schematic diagram showing the arrangement of the microstructure modulation unit and the empty modulation unit of Example 2 of the present application.

[0029] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0032] In this application, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0034] Hyperspectral imaging can simultaneously obtain information about the spatial distribution of objects and high spectral resolution, and has wide applications in areas such as material identification, environmental monitoring, chemical engineering, and food safety. Traditional hyperspectral imaging solutions often use a single-point spectrometer coupled with a mechanical device for spatial scanning imaging, but such devices are often large in size and take a long time to acquire spectral images. In related technologies, micro-nano modulation structures made of high-refractive-index materials (such as micro-nano circular hole structures etched on silicon flat plates) can be used to modulate the spectral dimensions of the incident light, and computational optics methods can be combined to obtain spectral images in a snapshot manner.

[0035] In the long-wave infrared band, due to the small number of infrared detector pixels, the area occupied by the micro-nano modulation structure is limited. To improve the modulation effect, the spatial proportion of the micro-nano modulation structure can be increased. However, increasing the spatial proportion of the micro-nano modulation structure will result in high reflectivity and low light transmittance, which in turn leads to a low signal-to-noise ratio after imaging.

[0036] To obtain high-spectral-resolution images, the spectral modulation of micro-nano modulation structures must meet the following conditions: large modulation amplitude, numerous modulation peaks, and narrow peak widths. To meet these conditions, the micro-nano modulation structures must use materials with high refractive indices in the corresponding wavelength bands. However, due to the visible light loss and high reflectivity of silicon (Si), micro-nano modulation structures, such as micro-nano circular hole structures etched into silicon flat plates, have low modulation transmittance (often less than 50%), resulting in poor signal-to-noise ratios.

[0037] In particular, in the long-wave infrared band (8μm-14μm), the infrared detectors used are typically photothermal, which exhibits high noise. Combined with the weak signal from the object being measured, the signal-to-noise ratio is lower than that of visible light band technologies. Although materials such as germanium (Ge) and silicon (Si) exhibit virtually no light loss in the long-wave infrared band, the small number of infrared detector pixels and the limited area occupied by the micro-nano modulation structure necessitate increasing the spatial proportion of the micro-nano modulation structure to enhance the modulation effect. This results in high reflectivity and low light transmittance for micro-nano modulation structures made of materials such as Ge and Si, leading to a low signal-to-noise ratio after imaging.

[0038] To this end, an embodiment of the present application provides a modulation structure for infrared hyperspectral imaging, which adds an infrared anti-reflection film to the packaging layer of the detector window, and arranges a plurality of microstructure modulation units on the infrared anti-reflection film according to a preset arrangement rule, so that part of the surface area of ​​the infrared anti-reflection film is left vacant to form at least one empty modulation unit. The microstructure modulation unit and the empty modulation unit together form the spectral modulation structure of the detector. In this way, the embodiment of the present application, on the one hand, uses the anti-reflection capability provided by the infrared anti-reflection film, and on the other hand, uses the unstructured empty modulation unit to reduce the use area of ​​the micro-nano structure in the detector window, thereby improving the transmittance drop caused by microstructure reflection, thereby jointly improving the signal-to-noise ratio after hyperspectral imaging.

[0039] The inventive concept of the embodiments of the present application will be described in detail below with reference to some specific embodiments.

[0040] The embodiments of the present application provide a modulation structure for infrared hyperspectral imaging.

[0041] As shown in FIG1 , the spectral modulation structure 20 of the infrared hyperspectral imaging and the pixel array 30 on the image sensor are arranged relative to each other and are used to spectrally modulate the incident light. After receiving the modulated spectral signal, the pixel array 30 on the image sensor outputs a detection signal.

[0042] 1 and 2 , in this embodiment, the modulation structure for infrared hyperspectral imaging includes a detector window packaging layer 10 , an infrared anti-reflection film 40 , and a plurality of microstructure modulation units 21 .

[0043] Among them, the infrared anti-reflection film 40 is arranged on the side surface of the detector window packaging layer 10 facing the pixel array 30, and the refractive index of the material of the infrared anti-reflection film 40 is smaller than the refractive index of the material of the detector window packaging layer 10; a plurality of microstructure modulation units 21 are arranged on the side surface of the infrared anti-reflection film 40 facing away from the detector window packaging layer 10 according to a preset arrangement rule, so that a partial area of ​​the side surface of the infrared anti-reflection film 40 facing away from the detector window packaging layer 10 is left vacant to form at least one empty modulation unit 22.

[0044] Specifically, the detector comprises a sealing cover plate, the plate body of which has an infrared window region through which infrared light can pass, namely, the detector window encapsulation layer 10 in this embodiment. The detector window encapsulation layer 10 is disposed relative to the pixel array 30, so that infrared light passing through the infrared window region is received by the pixel array 30. The material of the detector window encapsulation layer 10 includes germanium (Ge) or silicon (Si).

[0045] An infrared anti-reflection film 40 is applied to the side of the detector window encapsulation layer 10 facing the pixel array 30. The side of the infrared anti-reflection film 40 facing away from the detector window encapsulation layer 10 is divided into at least four sub-regions arranged in a rectangular array. In the imaging field, a rectangular array is typically constructed as a square array with an equal number of rows and columns, so each sub-region is square. For example, the surface of the infrared anti-reflection film 40 is divided into nine sub-regions arranged in a 3×3 pattern, or sixteen sub-regions arranged in a 4×4 pattern.

[0046] In this embodiment, multiple spectral modulation structures 20 are disposed on the surface of the infrared anti-reflection film 40 facing away from the detector window encapsulation layer 10. The number of spectral modulation structures 20 is equal to the number of imaging pixels in the hyperspectral camera, and the spectral modulation structures 20 include different spectral modulation units. For example, the surface of the infrared anti-reflection film 40 is divided into nine spectral modulation units (including microstructure modulation units 21 and empty modulation units 22) arranged in a 3×3 pattern. Each spectral modulation unit corresponds one-to-one with a pixel, resulting in a one-to-one correspondence between the spectral modulation structures 20 and the pixel. For example, referring to Figure 1 , the dashed box represents a spectral modulation structure 20, which corresponds one-to-one with a pixel 30 below it. It is particularly important to note that in this embodiment, the spectral modulation structure 20 includes microstructure modulation units 21 and empty modulation units 22. Each microstructure modulation unit 21 protrudes from a subregion and internally supports a waveguide mode for spectral modulation. For some sub-regions, there is no structure distributed in the space at the same height as the microstructure modulation unit 21 , thereby forming an empty modulation unit 22 without a structure thereon.

[0047] It can be understood that since the pixel 30 of the detector is relatively small, for example, the pixel 30 size of 17 μm only corresponds to 1-2 infrared band wavelengths, the number of microstructure modulation units 21 is limited, so the edge scattering intensity of the microstructure modulation unit 21 is relatively large, so that under the scattering effect of the surrounding microstructure modulation units 21, the empty modulation unit 22 also has spectral modulation capability.

[0048] Compared with the densely arranged micro-nanostructure modulation units, the empty modulation unit 22 without structure in this embodiment reduces the use area of ​​the micro-nanostructure in the detector window, improves the transmittance reduction problem caused by the reflection of the micro-nanostructure, and improves the luminous flux of the spectral modulation unit of the micro-nanostructure, thereby improving the signal-to-noise ratio after hyperspectral imaging.

[0049] In addition, the refractive index of the material of the infrared anti-reflection film 40 is lower than the refractive index of the material of the detector window packaging layer 10, thereby forming a gradient distribution of high refractive index material-low refractive index material-air in the direction from the detector window packaging layer 10 to the pixel 30. It can be understood that when light enters from one medium into another medium, if the difference in the refractive indices of the two media decreases, the energy of the reflected light decreases and the energy of the transmitted light increases. Thus, in this embodiment, the transmittance of infrared light can be improved when it penetrates the region of the gradient refractive index distribution. Furthermore, this embodiment reduces the use area of ​​the micro-nano structure in the detector window by combining the air-retention control unit with the anti-reflection ability provided by the infrared anti-reflection film, thereby jointly improving the transmittance drop problem caused by the reflection of the micro-nano structure and jointly improving the signal-to-noise ratio after hyperspectral imaging.

[0050] In addition, in this embodiment, the transmittance of the infrared band is improved by the infrared anti-reflection film 40, and the passage of the spectral modulation structure 20 set on the surface of the infrared anti-reflection film 40 facing the pixel 30 in the infrared band is increased by setting the air-retention modulation unit 22. In this way, the spectral modulation structure 20 has a larger light transmittance and the scattering effect of the microstructure modulation unit 21 is stronger, thereby also improving the spectral modulation capability of the air-retention modulation unit 22, thereby not only improving the signal-to-noise ratio after hyperspectral imaging, but also improving the accuracy of spectral reconstruction.

[0051] In a possible embodiment of the present application, the preset arrangement rule includes at least one of the following:

[0052] (1) The microstructure modulation unit 21 is adjacent to at least one empty modulation unit 22;

[0053] (2) In the first direction or the second direction of the pixel array 30, there are at most two empty modulation units 22 between two adjacent microstructure modulation units 21, and the first direction is perpendicular to the second direction;

[0054] (3) Among all the microstructure modulation units 21 adjacent to each empty modulation unit 22, the structures of any two microstructure modulation units 21 are different from each other.

[0055] The pixel array 30 is arranged in a matrix. In this case, the first direction may be the row direction of the pixel array 30, and the second direction may be the column direction of the pixel array 30. Alternatively, the first direction may be the column direction of the pixel array 30, and the second direction may be the row direction of the pixel array 30. In this embodiment, the microstructure modulation units 21 are arranged according to the above-mentioned preset arrangement rules, so that the microstructure modulation units 21 and the space modulation units 22 form the mosaic arrangement required for spectral reconstruction.

[0056] In the formed mosaic arrangement, each microstructure modulation unit 21 is surrounded by at least one empty modulation unit 22. For example, in the first direction, the microstructure modulation unit 21 may have two empty modulation units 22 located on different sides, and in the second direction, the microstructure modulation unit 21 may also have two empty modulation units 22 located on different sides.

[0057] In the first direction or the second direction, since the spectral modulation capability of the air modulation unit 22 is provided by the microstructure modulation units 21 around it, there are at most two continuous air modulation units 22 to avoid too many continuous air modulation units 22 affecting the spectral modulation capability of the air modulation unit 22 due to the absence of edge scattering of the microstructure modulation unit 21.

[0058] In addition, among all the microstructure modulation units 21 adjacent to the empty modulation unit 22 where there is no structure, the structures of any two microstructure modulation units 21 are different from each other, so that the modulation curves of the multiple spectral modulation structures 20 are different from each other and have large differences, thereby ensuring that the spectrum reconstruction accuracy is high after the algorithm is used to reconstruct the spectrum.

[0059] In some embodiments, the microstructure modulation units 21 are arranged according to the above preset arrangement rules.

[0060] In some possible embodiments of the present application, in the first direction, the microstructure modulation units 21 and the empty modulation units 22 are alternately arranged, and in the second direction, the microstructure modulation units 21 and the empty modulation units 22 are alternately arranged.

[0061] Specifically, on any row of the rectangular array formed by at least 4 sub-regions, the microstructure modulation units 21 and the empty modulation units 22 are alternately arranged with each other, and on any column of the rectangular array formed by at least 4 sub-regions, the microstructure modulation units 21 and the empty modulation units 22 are alternately arranged with each other.

[0062] Please refer to Figure 2. For a 3×3 rectangular array, microstructure modulation units 21 are set in the upper left corner sub-region, upper right corner sub-region, center sub-region, lower left corner sub-region and lower right corner sub-region, and the remaining sub-regions are empty modulation units 22.

[0063] In this embodiment, the microstructure modulation units 21 and the air-retained modulation units 22 are arranged alternately with each other, so that the microstructure modulation units 21 with edge scattering capability are distributed more evenly around the air-retained modulation units 22, thereby enabling the air-retained modulation units 22 to have spectral modulation capability.

[0064] In one embodiment of the present application, the infrared anti-reflection film 40 includes at least two transparent film layers stacked in sequence, and the refractive index of the multiple transparent film layers gradually decreases in a direction away from the detector window packaging layer 10 .

[0065] In this embodiment, the infrared anti-reflection film 40 includes at least two layers stacked in sequence, and the refractive index of the transparent film layers gradually decreases in the direction away from the detector window packaging layer 10, thereby further reducing the refractive index difference between the two adjacent transparent film layers in the propagation path of the infrared band after entering the detector window, improving the transmittance between the adjacent transparent film layers, and then improving the overall transmittance of the refractive index gradient distribution area.

[0066] It is understood that the specific thickness of each transparent film layer depends on the wavelength of the infrared band and the refractive index of the infrared band in each transparent film layer. In this embodiment, the transparent film layer is made of ZnS zinc sulfide, ZnSe zinc selenide, BaF2 barium fluoride, CaF2 calcium fluoride, YbF3 ytterbium fluoride, Ge germanium, or Si silicon. The refractive indices of ZnS and ZnSe are between 2 and 3, while those of BaF2, CaF2, and YbF3 are between 1 and 2. The refractive index of Si is greater than 3, and the refractive index of Ge is greater than 4.

[0067] In one example, referring to FIG3 , the material of the detector window encapsulation layer 10 is silicon (Si). In this case, the infrared anti-reflection film 40 employs a dual-layer transparent film design, comprising a ZnS transparent film layer 41 disposed on the detector window encapsulation layer 10, and a BaF2 transparent film layer 42 disposed on the side of the ZnS transparent film layer 41 facing away from the detector window encapsulation layer 10. Therefore, the ZnS transparent film layer 41 has a thickness of h1, where 0.5 μm ≤ h1 ≤ 1.5 μm; the BaF2 transparent film layer 42 has a thickness of h2, where 1 μm ≤ h2 ≤ 2 μm.

[0068] In another example, as shown in FIG4 , the material of the detector window encapsulation layer 10 is germanium (Ge). In this case, the infrared antireflection coating 40 employs a three-layer antireflection coating design, including a Si transparent film layer 43 disposed on the detector window encapsulation layer 10, a ZnS transparent film layer 41 disposed on the side of the Si transparent film layer 43 facing away from the detector window encapsulation layer 10, and a BaF2 transparent film layer 42 disposed on the side of the ZnS transparent film layer 41 facing away from the Si transparent film layer 43. The Si transparent film layer 43 has a thickness of h3, where 0.1 μm ≤ h3 ≤ 1 μm; the ZnS transparent film layer 41 has a thickness of h1, where 0.5 μm ≤ h1 ≤ 1.5 μm; and the BaF2 transparent film layer 42 has a thickness of h2, where 0.8 μm ≤ h2 ≤ 2 μm.

[0069] In a possible embodiment of the present application, referring to FIG. 2 and FIG. 10 , the microstructure modulation unit 21 includes a plurality of micro-nanostructure sub-units 211 arranged in a rectangular array, and the plurality of micro-nanostructure sub-units 211 are spaced apart from each other.

[0070] At this time, among all the microstructure modulation units 21 adjacent to each empty modulation unit 22, if any two microstructure modulation units 21 have different structures, the structure of the microstructure modulation unit 21 includes at least one of the shape of the micro-nanostructure subunits 211, the arrangement period of the micro-nanostructure subunits 211, or the number of the micro-nanostructure subunits 211. If the structures of two microstructure modulation units 21 are different, then at least one of the shape of the micro-nanostructure subunits 211, the arrangement period of the micro-nanostructure subunits 211, or the number of the micro-nanostructure subunits 211 of the two microstructure modulation units 21 is different.

[0071] Specifically, for any microstructure modulation unit 21, changes in at least one of the following parameters of the microstructure modulation unit 21 will affect the spectrum modulation capability of the microstructure modulation unit 21:

[0072] 1) Shape of the micro-nanostructure subunit 211. The shape parameters of the micro-nanostructure subunit 211 include, but are not limited to, the height, cross-sectional shape, or cross-sectional dimensions of each micro-nanostructure subunit 211. The cross-sectional area of ​​the micro-nanostructure subunit 211 is the area obtained by cutting the micro-nanostructure subunit 211 along a plane parallel to the plane of the detector window encapsulation layer 10.

[0073] 2) Arrangement Period of the Micro-Nanostructure Subunits 211. It is understood that the plurality of micro-nanostructure subunits 211 may be arranged in a rectangular array. In this case, the arrangement period of the micro-nanostructure subunits 211 is the distance between the axes of adjacent micro-nanostructure subunits 211 in the row and column directions of the rectangular array.

[0074] 3) The number of micro-nanostructure subunits 211. The number of micro-nanostructure subunits 211 determines the overall arrangement of the array of micro-nanostructure subunits 211. For example, micro-nanostructure subunits 211 of the same shape may be arranged in a 2×2 pattern in one subregion, but in a 3×3 pattern in another subregion.

[0075] Of course, in order to make the spectral modulation capabilities of the microstructure modulation units 21 around each empty modulation unit 22 more different to facilitate subsequent spectral reconstruction, the shapes of the micro-nanostructure sub-units 211 of the microstructure modulation units 21 around each empty modulation unit 22, the arrangement period of the micro-nanostructure sub-units 211 and the number of the micro-nanostructure sub-units 211 are all different.

[0076] In one embodiment of the present application, the micro-nano structure subunit 211 is constructed as a columnar structure protruding from the infrared anti-reflection film 40 , and the material of the columnar structure is an infrared high refractive index material.

[0077] In one embodiment of the present application, for example, referring to Figure 5, an infrared high-refractive-index medium layer 212 is provided on the surface of the infrared anti-reflection film 40 facing away from the detector window packaging layer 10, and the micro-nanostructure subunit 211 is constructed as a porous structure 213 that penetrates the infrared high-refractive-index medium layer 212 along the thickness direction of the detector window packaging layer 10.

[0078] In one embodiment of the present application, the micro-nanostructure subunit 211 can be constructed as a micro-nano dielectric column formed of an infrared high refractive index material, which extends in a direction away from the detector window packaging layer 10 to protrude from the infrared anti-reflection film 40. Each micro-nano dielectric column supports a waveguide mode for spectral modulation.

[0079] In one embodiment of the present application, referring to FIG5 , an infrared high-refractive-index dielectric layer 212 formed of an infrared high-refractive-index material is disposed on the side of the subregion corresponding to the microstructure modulation unit 21, facing away from the detector window packaging layer 10. The infrared high-refractive-index dielectric layer 212 is provided with a pore structure 213 extending through the infrared high-refractive-index dielectric layer 212 along the thickness of the detector window packaging layer 10. It is worth noting that the infrared high-refractive-index material is Ge or Si.

[0080] The height of the micro-nanostructure subunit 211 is H, where H>5 μm, so that each micro-nanostructure subunit 211 can support multiple waveguide modes for spectral modulation.

[0081] In a possible embodiment of the present application, in order to ensure the high transmittance of the micro-nanostructure subunit 211, the spectral modulation of the micro-nanostructure subunit 211 should be polarization-independent. At this time, the cross-sectional shape of the micro-nanostructure subunit 211 is constructed as a rotationally symmetrical figure with a rotation angle of 90°, such as a square, a circle, etc.

[0082] In a possible embodiment of the present application, the side length of the pixel is n, the number of micro-nanostructure sub-units 211 in the third direction of the rectangular array of the microstructure modulation unit 21 is m1, and the number of micro-nanostructure sub-units 211 in the fourth direction of the rectangular array of the microstructure modulation unit 21 is m2, and m1 and m2 satisfy: m1≤10 and m2≤10; wherein the third direction is perpendicular to the fourth direction.

[0083] The third direction may be the row-extending direction of the rectangular array, and the fourth direction may be the column-extending direction of the rectangular array. Alternatively, the third direction may be the column-extending direction of the rectangular array, and the fourth direction may be the row-extending direction of the rectangular array. Furthermore, the third direction may be parallel to the first direction, in which case the fourth direction may be parallel to the second direction.

[0084] Specifically, since the size of a pixel is generally 17 μm or less, the side length of the sub-region can also be set to 17 μm. The pixel size of 17 μm is relatively small. For example, the side length of a single pixel corresponds to only 1-2 infrared wavelengths. At this time, the number of micro-nanostructure sub-units 211 that can be arranged in the sub-region is limited. In order to further improve the edge scattering of the micro-nanostructure sub-unit 211, thereby ensuring the spectral modulation capability of the air modulation unit 22, the number of micro-nanostructure sub-units 211 in the sub-region is less than 10×10.

[0085] In this embodiment, when the number of the micro-nanostructure subunits 211 in the sub-region is less than 10×10, the spectrum modulation capability of the empty modulation unit 22 can be comparable to that of the microstructure modulation unit 21.

[0086] It can be understood that m pixels in the pixel array constitute a macro pixel, and each macro pixel corresponds to m spectral modulation structures 20. The m spectral modulation structures 20 include n spectral channels in total, and the incident spectrum of the region is φ. At this time, the energy values ​​I1, I2, ... I received by the macro pixel are m Satisfy the underdetermined equation.

[0087] The underdetermined equation is:

[0088] Among them, M m is the high transmittance modulation curve of the mth spectral modulation structure 20. Of course, if the required number of spectral channels is large, that is, n ≥ m, the compressed sensing algorithm can be used to solve the above underdetermined equation to obtain the incident spectrum φ at the macro-pixel position. The entire infrared spectrum image can be obtained by solving the equation for each macro-pixel.

[0089] In order to enable those skilled in the art to better understand the scope of protection of the claims of this application, the following explains the technical solutions described in the claims of this application through specific implementation examples in specific application scenarios. It should be understood that the following examples are only used to explain this application and are not used to limit the scope of protection of the claims of this application.

[0090] Example 1: Referring to Figures 1 and 3 , the detector window encapsulation layer 10 is a Si window with a double-layer antireflection coating. The first transparent film layer, located near the Si window, is a ZnS transparent film layer 41 with a thickness of 0.88 μm. The second transparent film layer, located on the ZnS transparent film layer 41 and facing away from the Si window, is a BaF2 transparent film layer 42 with a thickness of 1.26 μm. The BaF2 transparent film layer contains 3×3 spectral modulation structures 20, each with a subregion size of 17 μm × 17 μm. Microstructure modulation units 21 are provided in five subregions: the upper left subregion, the upper right subregion, the center subregion, the lower left subregion, and the lower right subregion. The remaining four subregions contain empty modulation units 22.

[0091] The micro-nanostructure subunit 211 is a periodically arranged Ge cylinder, wherein the arrangement period of the Ge cylinder array in the five sub-regions is between 2.5 μm and 8 μm, the cylinder duty cycle is between 0.2 and 0.8, and the height is between 5 μm and 30 μm. Among them, the arrangement period of Ge cylinders in the upper left sub-region is 3μm, the cylinder duty cycle is 0.45, and the height is 20μm; the arrangement period of Ge cylinders in the upper right sub-region is 4μm, the cylinder duty cycle is 0.45, and the height is 20μm; the arrangement period of Ge cylinders in the center sub-region is 5.5μm, the cylinder duty cycle is 0.5, and the height is 20μm; the arrangement period of Ge cylinders in the lower left sub-region is 6.5μm, the cylinder duty cycle is 0.55, and the height is 20μm; the arrangement period of Ge cylinders in the lower right sub-region is 7.5μm, the cylinder duty cycle is 0.55, and the height is 20μm.

[0092] As shown in Figure 6, using a Si window without an AR coating as an example, the transmittance on one side of the Si window is approximately 70%, while the transmittance on both sides drops to less than 50%, a significant drop in transmittance. In this example, after adding the AR coating, the wavelength-averaged transmittance on one side of the Si window reaches over 98%, demonstrating a significant AR effect.

[0093] Figure 7 is a comparison diagram of the modulation curves of 5 microstructure modulation units 21 and 4 empty modulation units 22. Due to the edge scattering of the microstructure modulation unit 21, the modulation curve of the empty modulation unit 22 also has a stronger modulation intensity, a larger number of modulation peaks and a narrower peak width, which is similar to the modulation curve characteristics of the microstructure modulation unit 21.

[0094] Figure 8 is a comparison chart of the average light transmittance of the spectral modulation unit in this example and the average light transmittance of the microstructure modulation unit (such as micro-nanohole) generally set on the Si window. The light transmittance in this example is increased from an average of 48% to 82%, so the reconstructed spectral signal-to-noise ratio is expected to be improved by 71%.

[0095] Figure 9 shows the nine spectral modulation curves generated by the nine spectral modulation units of this example, and the spectral reconstruction results of a series of Gaussian spectra with different bandwidths in the range of 8μm-14μm. The solid line in the figure is the true spectrum, and the dotted line is the reconstructed spectrum. From left to right, the bandwidths of the series of Gaussian spectra in the figure are 400nm, 300nm and 200nm, respectively. Among them, the reconstruction effect of the Gaussian spectrum with a bandwidth as narrow as 300nm (about 2.7%λ) is still good. It can be seen that the high-light flux spectral modulation curve of this example can maintain a high reconstructed spectral resolution.

[0096] Example 2: Referring to Figures 4 and 10 , the detector window encapsulation layer 10 is a Ge window, which utilizes a three-layer antireflection coating. The first transparent film layer, located near the Ge window, is a Si transparent film layer 43, with a thickness between 0.1 μm and 1 μm. The second transparent film layer, located on the Si transparent film layer and facing away from the Ge window, is a ZnS transparent film layer 41, with a thickness between 0.5 μm and 1.5 μm. The third transparent film layer, located on the ZnS transparent film layer 41 and facing away from the Si transparent film layer 43, is a BaF2 transparent film layer 42, with a thickness between 0.8 μm and 2 μm.

[0097] The BaF2 transparent film layer 42 contains 4×4 spectrum modulation structures 30, each with a sub-region size of 12μm×12μm. From left to right, the spectrum modulation units in the first and fourth columns are microstructure modulation units 21, while the spectrum modulation units in the second and third columns are air-space modulation units 22.

[0098] The eight spectral modulation micro-nanostructure subunits 211 are periodically arranged Si square pillars, wherein the arrangement period of the Si square pillar array is between 3 μm and 10 μm, the duty cycle of the square pillars is between 0.2 and 0.8, and the height is between 5 and 30 μm.

[0099] In a second aspect, embodiments of the present application further provide a detector comprising: an image sensor and a modulation structure for infrared hyperspectral imaging, wherein the image sensor comprises a pixel array, and the microstructure modulation unit of the modulation structure is arranged relative to the pixel array.

[0100] The specific structure of the modulation structure for infrared hyperspectral imaging of this embodiment refers to the above embodiments. Since this detector adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0101] In a third aspect, an embodiment of the present application further provides an infrared spectrometer, comprising: a detector and an image signal processor, wherein the image signal processor is connected to the detector.

[0102] The image signal processor is used to receive the spectral image of the detector and output an image after processing.

[0103] The specific structure of the detector of this embodiment refers to the above embodiments. Since this infrared spectrometer adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0104] The above descriptions are merely some embodiments of the present application and are not intended to limit the scope of protection of the present application. All equivalent structural transformations made using the contents of the present application specification and drawings under the inventive concept of the present application, or direct / indirect applications in other related technical fields, are included in the scope of protection of the present application.

Claims

1. A modulation structure for infrared hyperspectral imaging, include: Detector window encapsulation layer; An infrared anti-reflection film, wherein the infrared anti-reflection film is arranged on a surface of the detector window packaging layer facing the pixel array, and the refractive index of the material of the infrared anti-reflection film is smaller than the refractive index of the material of the detector window packaging layer; as well as A plurality of microstructure modulation units are arranged on a surface of the infrared anti-reflection film on a side away from the detector window packaging layer according to a preset arrangement rule, so that a partial area of ​​the surface of the infrared anti-reflection film on a side away from the detector window packaging layer is left vacant to form at least one empty modulation unit.

2. The modulation structure for infrared hyperspectral imaging according to claim 1, in, The preset arrangement rule includes at least one of the following: The microstructure modulation unit is adjacent to the at least one air-retention modulation unit; In the first direction or the second direction of the pixel array, there are at most two empty modulation units between two adjacent microstructure modulation units, and the first direction is perpendicular to the second direction; or Among all the microstructure modulation units adjacent to each of the empty modulation units, the structures of any two microstructure modulation units are different from each other.

3. The modulation structure for infrared hyperspectral imaging according to claim 2, in, In the first direction, the microstructure modulation units and the empty modulation units are arranged alternately with each other, and in the second direction, the microstructure modulation units and the empty modulation units are arranged alternately with each other.

4. The modulation structure for infrared hyperspectral imaging according to claim 2, in, The infrared anti-reflection film comprises at least two transparent film layers stacked in sequence, and the refractive index of the at least two transparent film layers gradually decreases in a direction away from the detector window packaging layer.

5. The modulation structure for infrared hyperspectral imaging according to claim 4, in, The material of the transparent film layer includes ZnS zinc sulfide, ZnSe zinc selenide, BaF 2 Barium fluoride, CaF 2 Calcium fluoride, YbF 3 Ytterbium fluoride, Ge germanium or Si silicon.

6. The modulation structure for infrared hyperspectral imaging according to any one of claims 1 to 5, in, Each of the microstructure modulation units includes a plurality of micro-nanostructure sub-units arranged in a rectangular array, and the plurality of micro-nanostructure sub-units are spaced apart from each other.

7. The modulation structure for infrared hyperspectral imaging according to claim 6, in, The plurality of micro-nano structure sub-units are constructed as columnar structures protruding from the infrared anti-reflection film, and the columnar structures are made of infrared high refractive index material.

8. The modulation structure for infrared hyperspectral imaging according to claim 6, in, An infrared high refractive index medium layer is provided on the surface of the infrared anti-reflection film on the side away from the detector window packaging layer, and the multiple micro-nano structure sub-units are constructed as a hole structure that penetrates the infrared high refractive index medium layer along the thickness direction of the detector window packaging layer.

9. The modulation structure for infrared hyperspectral imaging according to claim 7 or 8, in, The cross-sectional shape of the micro-nano structure subunit is constructed as a rotationally symmetrical figure with a rotation angle of 90°.

10. The modulation structure for infrared hyperspectral imaging according to claim 6, in, The side length of the pixel in the pixel array is less than or equal to 17 μm, the number of the micro-nano structure sub-units in the third direction of the rectangular array is less than or equal to 10, and the number of the micro-nano structure sub-units in the fourth direction of the rectangular array is less than or equal to 10; wherein the third direction is perpendicular to the fourth direction.

11. The modulation structure for infrared hyperspectral imaging according to claim 6, in, The height of the micro-nano structure subunit is greater than 5 μm.

12. A detector, include: An image sensor, the image sensor comprising a pixel array; as well as According to the modulation structure for infrared hyperspectral imaging as described in any one of claims 1 to 11, the microstructure modulation unit of the modulation structure and the pixel array are arranged relative to each other.

13. An infrared spectrometer, include: The detector as claimed in claim 12; as well as An image signal processor is connected to the detector.

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