Hyperspectral scanning imaging system and method with dual tunable filter structure

Abstract

The application discloses a hyperspectral scanning imaging system and method based on a double adjustable filter structure, and the system further comprises a scanning mechanism for driving at least two of the first adjustable filter structure, the second adjustable filter structure and the target to perform relative scanning movement. The center transmission wavelength of the two adjustable filter structures continuously or discretely changes along the spatial position, and the spectral bandwidth and the free spectral range thereof satisfy a specific matching relationship. The total spectral transmission function of the system is equal to the product of the transmission functions of the two adjustable filter structures, so that the simultaneous acquisition of high spectral resolution and wide non-aliasing working spectral range is realized. The application overcomes the technical contradiction that the traditional single-stage filter structure is difficult to simultaneously consider high spectral resolution and wide spectral range, and has wide application value in the fields of spectral detection, machine vision and remote sensing.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging and spectral analysis technology, specifically relating to a hyperspectral imaging system and method, and more particularly to a hyperspectral imaging device that utilizes a bilinear graded filter to achieve high spectral resolution and a wide non-aliasing spectral range. Background Technology

[0002] Hyperspectral imaging technology, by acquiring a spatial-spectral three-dimensional data cube of a target scene, has been widely applied in various fields. Traditional hyperspectral systems, such as pushbroom instruments based on gratings or prisms, can acquire high-resolution spectra, but they are usually complex in structure, bulky, and have fixed inter-spectral resolution. Filter-type spectral imagers have attracted attention due to their relatively simple and compact structure. Among them, the technology based on linearly graded filters (LVFs) is one of the effective ways to achieve instrument miniaturization. An LVF is an optical element whose central transmission wavelength varies linearly with spatial position.

[0003] Traditional LVF spectral imaging schemes typically place the LVF in the converging optical path in front of the detector target. However, this traditional approach of placing a single LVF directly in front of the detector has limitations. As a thin-film interferometer (typically Fabry-Perot type) filter, the LVF inherently limits its spectral resolution and free spectral range (FSR, the wavelength interval between transmission peaks of adjacent interference orders). Achieving a narrow spectral bandwidth (high resolution) often requires using high-reflectivity films or increasing the interference order (increasing cavity thickness), but this usually leads to a decrease in FSR. Within a wide spectral operating range, a smaller FSR causes overlap of transmission peaks from different interference orders, resulting in spectral aliasing, making it difficult for the instrument to simultaneously achieve high spectral resolution and a wide unambiguous operating spectral band. Existing high-resolution broadband spectrometers, such as systems based on precision gratings or Fourier transform interferometers, are typically complex and bulky. Therefore, there is a lack of a compact and effective solution that can simultaneously achieve high spectral resolution and a wide, aliasing-free spectral range, especially in miniaturized LVF-based spectral imaging systems. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hyperspectral scanning imaging system based on a dual tunable filter structure.

[0005] To solve the above technical problems, some embodiments of the present invention provide a hyperspectral scanning imaging system based on a dual-tunable filter structure, which includes an objective lens group, a first tunable filter structure, an imaging transfer subsystem, a second tunable filter structure, and a planar array detector arranged in sequence along the optical path direction; the second tunable filter structure is disposed closely adjacent to the photosensitive surface of the planar array detector or fixedly connected to the planar array detector; further includes a scanning mechanism for driving at least two of the first tunable filter structure, the second tunable filter structure, and the target to perform relative scanning motion according to a preset mathematical relationship, so that the total spectral transmission characteristic of the system is jointly determined by the spectral transmission characteristics of the first tunable filter structure and the second tunable filter structure, to achieve hyperspectral imaging with high spectral resolution; wherein, both the first tunable filter structure and the second tunable filter structure are filter films with a central transmission wavelength varying continuously or discretely along the spatial position, and the filter film is realized based on at least one of multi-layer dielectric films, volume Bragg gratings, Fabry-Perot cavities, or metamaterial surface structures; the imaging transfer subsystem is configured to make the equivalent spectral gradient m1' of the first tunable filter structure (3) at the second tunable filter structure (6) satisfy a preset matching relationship with the spectral gradient m2 of the second tunable filter structure (6); the spectral bandwidth BW1 and the free spectral range FSR1 of the first tunable filter structure, and the spectral bandwidth BW2 and the free spectral range FSR2 of the second tunable filter structure, satisfy one of the following relationships: BW1 > BW2 and FSR1 > FSR2, or BW1 < BW2 and FSR1 < FSR2; the total spectral transmission function of the system is equal to the product of the spectral transmission function of the first tunable filter structure and the spectral transmission function of the second tunable filter structure, so as to simultaneously obtain high spectral resolution and a wide non-aliasing working spectral band.

[0006] In some embodiments, the imaging transfer subsystem is a relay lens group, and the optical magnification of the relay lens group is N; the preset matching relationship is: m1' = m1 / N = m2, where m1 is the spectral gradient of the first tunable filter structure.

[0007] In some embodiments, the configuration of the relay lens group satisfies the following conditions: the center transmission wavelength of the first tunable filter structure at position x1, after being imaged by the relay lens group, is equal to the center transmission wavelength of the second tunable filter structure at that position; the equivalent spectral gradient satisfies the relationship: m1' = m1 / N = m2, where: m1 is the spectral gradient of the first tunable filter structure, defined as the rate of change of its center transmission wavelength along the spatial position; m2 is the spectral gradient of the second tunable filter structure, and N is the lateral magnification of the relay lens group; through the above configuration, the transmission wavelength at any position on the first tunable filter structure, after being imaged by the relay lens group, is consistent with the transmission wavelength of the second tunable filter structure at the corresponding position, thereby achieving wavelength alignment of the two-stage filter structures.

[0008] In some embodiments, the optical magnification N of the relay lens group is adjustable to adapt to filter combinations with different spectral gradients.

[0009] In some embodiments, the imaging transfer subsystem is an optical window without optical power or a direct air gap; the preset matching relationship is: m1' = m1 = m2, that is, the spectral gradient of the first tunable filter structure is directly equal to or proportional to the spectral gradient of the second tunable filter structure.

[0010] In some embodiments, the linear gradient direction of the first adjustable filter structure and the linear gradient direction of the second adjustable filter structure are set to be parallel or perpendicular to each other; the scanning mechanism is configured such that the direction of the relative scanning motion is parallel to the gradient direction of the first adjustable filter structure.

[0011] In some embodiments, the first adjustable filter structure is disposed on the intermediate image plane or its conjugate plane formed by the objective lens group.

[0012] In some embodiments, one of the first tunable filter structure and the second tunable filter structure is used for high-resolution spectral dispersion, and the other is used for spectral order selection, and the two functions can be configured interchangeably.

[0013] In some embodiments, the second tunable filter structure is fixed to the photosensitive surface of the array detector by optical bonding or bonding processes, and the distance between the two is less than or equal to 100 μm.

[0014] In some embodiments, the scanning mechanism is configured to one of the following scanning modes: push-broom imaging mode: keeping the first tunable filter structure relatively stationary, driving the target and the area array detector integrating the second tunable filter structure to perform relative scanning motion; or driving the first tunable filter structure and the target to perform relative scanning motion, while the second tunable filter structure and the area array detector remain stationary; staring imaging mode: keeping the target and the area array detector relatively stationary, driving the first tunable filter structure and the second tunable filter structure to perform relative scanning motion.

[0015] In some embodiments, the operating band of the system is applicable to any one or any combination of the visible light band (400~760nm), the near-infrared band (760~2500nm), the short-wave infrared band (1000~3000nm), the mid-wave infrared band (3~5μm), or the long-wave infrared band (8~14μm).

[0016] In some embodiments, the present invention provides a hyperspectral scanning imaging method based on a dual tunable filter structure, which uses the hyperspectral scanning imaging system based on a dual tunable filter structure described above. The method includes the following steps: S1 System calibration: Performing spectral calibration on the hyperspectral scanning imaging system. For each pixel at a spatial location on the area array detector, establishing a mapping relationship λ = f(x, y, s) between the position coordinates of the relative scanning motion and the system transmission center wavelength. S2 Synchronous Scan Acquisition: Control the scanning mechanism to make at least two of the first adjustable filter structure, the second adjustable filter structure, and the target perform relative scanning motion according to a preset mathematical relationship; During the scanning process, control the area array detector to continuously acquire two-dimensional image frame sequences at a frame rate synchronized with the scanning motion, and record the quasi-monochrome two-dimensional spatial information after filtering by the first adjustable filter structure and the second adjustable filter structure at the scanning position; S3 Data Storage: Store the acquired image frame sequences and corresponding scanning position information; S4 Spectral Extraction: Process the stored image frame sequences, and for any spatial pixel (x0, y0) in the imaging area, extract the intensity value sequence I1 to I2 recorded at different image frames and different scanning positions. n S5 Spectral Correlation: Using the mapping relationship established in step S1, the intensity value sequence I1 to I... n With the corresponding center wavelength sequence λ1 to λ n Correlated, construct the spectral curve I(λ) of the spatial pixel; S6 Data reconstruction: repeat steps S4 and S5 for all spatial pixels in the imaging area, and finally reconstruct the three-dimensional hyperspectral data cube I(x, y, λ) of the target.

[0017] In some embodiments, step S6 further includes performing at least one of the following post-processing steps on the three-dimensional hyperspectral data cube: spectral correction to eliminate the effects of dark current and non-uniform response; and wavelength registration to spatially align images of different wavelength channels.

[0018] This invention provides a hyperspectral scanning imaging system based on a dual-tunable filter structure. The core technical solution involves employing two stages of tunable filter structures arranged sequentially along the optical path. The first stage tunable filter structure has a wide free spectral range, used for broad-band coarse selection and filtering out higher-order interference light. The second stage tunable filter structure has a narrow full width at half maximum (FWHM), used for high-resolution fine filtering. The spectral center wavelength gradient directions of the two stages are set to be non-parallel. The positions of the two stages are synchronously adjusted by a scanning drive device to achieve continuous tunability of the spectral center wavelength.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. Through the cascaded configuration of dual tunable filter structures, the first tunable filter structure utilizes its wide free spectral range to perform order selection, effectively filtering out higher-order interference light that may be generated by the second tunable filter structure, thus avoiding spectral aliasing; the second tunable filter structure utilizes its narrow-band high-resolution characteristics to achieve fine spectral selection. This complementary configuration simultaneously satisfies high spectral resolution (narrow full width at half maximum) and a wide non-aliasing working spectral band (covering the entire visible-near-infrared range), overcoming the technical contradiction between spectral resolution and free spectral range in traditional single-stage LVF systems.

[0021] 2. Compared with traditional solutions such as external mechanical rotating filter and grating beam splitting, this invention directly integrates the two-stage adjustable filter structure into a compact double-layer structure, and achieves synchronous wavelength adjustment through a single scanning drive device, which significantly reduces the system size and weight, improves the system reliability and response speed, and is easy to apply on platforms such as UAVs and satellites where there are strict requirements for size and weight.

[0022] 3. Some embodiments of the present invention utilize tunable filter structures, which have the advantages of relatively mature manufacturing processes and low costs. This solution can also be applied to mid- and long-wave infrared light, avoiding the use of low-temperature optical systems and greatly reducing system complexity and cost. Attached Figure Description

[0023] Figure 1 A schematic diagram of a hyperspectral scanning imaging system based on a dual-tunable filter structure, which is an embodiment of the present invention.

[0024] Figure 2A schematic diagram of a hyperspectral scanning imaging system based on a dual-tunable filter structure, which is another embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of a first tunable filter structure, a second tunable filter structure, and their spectral transmittance product according to an embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram illustrating the matching relationship between the rate of change of the first tunable filter structure and the second tunable filter structure according to an embodiment of the present invention.

[0027] Figure 5 This is a flowchart of a hyperspectral scanning imaging method based on a dual tunable filter structure according to an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0029] The core technical idea of ​​the hyperspectral scanning imaging system based on a dual-tunable filter structure in this invention lies in overcoming the inherent contradiction between spectral resolution and free spectral range in traditional single-stage filters by cascading two tunable filter structures. In traditional single-stage LVF systems, pursuing high spectral resolution usually leads to a narrower FSR, and spectral aliasing is easily generated over a wide spectral operating range. This invention employs a dual-filter structure, where the total spectral transmittance function T(λ) of the system is equal to the product of the transmittance functions T1(λ) and T2(λ) of the two filter structures.

[0030] like Figure 3 As shown, the hyperspectral scanning imaging system based on a dual-tunable filter structure of the present invention utilizes one filter structure (a first linear graded filter in the embodiment) to achieve order selection over a wide free spectral range. It exhibits high transmittance only within a broad spectral band of target wavelengths λ1, λ2, and λ3, effectively suppressing sidelobes and higher-order interference light beyond the FSR. The other filter structure (a second linear graded filter in the embodiment) achieves high spectral resolution. It has a very narrow transmission peak, but its FSR is also narrow, resulting in multiple transmissions over a wide spectral range. When the two are connected in series, the total transmittance of the system is the product of the two functions mentioned above. Light only passes through the system when the wide passband of the first filter and the narrow transmission peak of the second filter are spectrally aligned. Ultimately, the system generates high-resolution narrow transmission peaks only at positions such as λ1, λ2, and λ3, while the aliasing orders of the second filter at other positions are completely filtered out by the first filter. Thus, the present invention achieves high spectral resolution while obtaining a broad, alias-free operating spectral band.

[0031]

Example 1

[0032] The structure of the hyperspectral scanning imaging system based on a dual tunable filter structure in this embodiment is as follows: Figure 1 As shown.

[0033] 1. System structure.

[0034] The system in this embodiment includes, sequentially along the X-axis of the optical path: a target 1, an objective lens group 2, a first linear graded filter 3, a relay lens group consisting of a first lens 4 and a second lens 5, a second linear graded filter 6, and an area array detector 7. It also includes a scanning mechanism configured to be coupled to the target 1, the first linear graded filter 3, and the second linear graded filter 6, to drive at least two of the three to perform relative scanning motion according to a preset mathematical relationship. The scanning mechanism is configured such that the direction of the relative scanning motion is parallel to the gradient direction of the first linear graded filter 3. In some embodiments, the first linear graded filter 3 is disposed on the intermediate image plane or its conjugate plane formed by the objective lens group 2.

[0035] Objective lens group 2 collects the light radiation from target 1 and images it onto the rear image plane; a first linear graded filter 3 is disposed on the intermediate image plane or its conjugate plane of objective lens group 2, with its central transmission wavelength varying linearly along the y-axis; a relay lens group, as an imaging transfer subsystem, relays the intermediate image plane containing the first linear graded filter 3 to the photosensitive surface of the area array detector 7 at a preset lateral magnification N; a second linear graded filter 6 is fixed to the photosensitive surface of the area array detector 7 by optical bonding or adhesive bonding, with a distance between the two of less than or equal to 100 μm. Alternatively, the two can be disposed separately with a distance between them of less than or equal to 100 μm.

[0036] In some embodiments, one of the first linear gradient filter 3 and the second linear gradient filter 6 is used for high-resolution spectral dispersion, and the other is used for spectral order selection; the two functions can be configured interchangeably.

[0037] 2. Mapping and scanning relationship.

[0038] In this embodiment, the physical spatial coordinate relationship for spectral matching on the two linear gradient filters 3 and 6 is as follows:

[0039]

[0040] in, The physical coordinates are on the first linear graded filter 3. The physical coordinates on the second linear gradient filter 6 The spectral gradient of the first linear graded filter 3, The spectral gradient of the second linear gradient filter 6, and This is the bias term. Specifically, after the first linear graded filter 3 passes through a relay lens group with a magnification of N, the equivalent spectral gradient of the second linear graded filter 6... .

[0041] In this example, the preset mathematical relationship is manifested as the synchronization between the continuous motion of target 1 (i.e., the overall movement of the hyperspectral camera) and the step scanning of the first linear graded filter 3. The system has two degrees of freedom. Assume target 1 moves at a velocity... Moving continuously along the y-axis, the single-frame exposure time of the area array detector 7 is... Between two adjacent image frames, the spatial displacement of target 1 is: To achieve continuous spectral sampling, the step size of the first linear graded filter 3... Must be related to the movement of objective 1 The following synchronization relationships must be satisfied:

[0042]

[0043] in, This represents the spectral sampling interval between adjacent frames. In the continuous motion mode of the first linear graded filter 3, the speed of the first linear graded filter 3... relative to target speed Must meet:

[0044]

[0045] 3. Parameter design example.

[0046] To illustrate this more clearly, a set of possible, non-restrictive design parameters is provided:

[0047] The operating wavelength is set to 400–600 nm; the first linear filter has a spectral bandwidth of 10 nm, a free spectral range of 200 nm, and a spectral gradient of 15 nm / mm; the second linear filter has a spectral bandwidth of 1 nm, a free spectral range of 20 nm, and a spectral gradient of 10 nm / mm; the detector exposure time is 10 ms; and the target movement speed is 20 mm / s.

[0048] Therefore, the magnification needs to be designed to be 1.5, and the speed of the first filter movement needs to be 13.33 mm / s.

[0049]

Example 2

[0050] The structure of the hyperspectral scanning imaging system based on a dual tunable filter structure in this embodiment is as follows: Figure 1 As shown.

[0051] 1. System Structure

[0052] The hardware structure of this embodiment is the same as that of embodiment 1, the core difference being the configuration of the scanning method.

[0053] 2. Mapping and Scanning Relationship

[0054] In this example, the system is Wavelength selected at any time Effective relative displacement of two linear graded filters The only confirmed feature is that the relay lens assembly is fixedly positioned and has magnification. In some embodiments, the optical magnification N of the relay lens group is adjustable to adapt to filter combinations with different spectral gradients, by adjusting... This allows the effective slopes of the two LVFs to match, i.e., satisfy... The tuning relationship can be approximated as:

[0055]

[0056] in, This refers to the displacement of the first linear gradient filter 3. This refers to the motion displacement of the second linear graded filter 6. This is a constant offset term.

[0057] In this example, the preset mathematical relationship is manifested in the control of the relative velocity or relative displacement of the two linear graded filters 3 and 6. Assume the first linear graded filter 3 moves at a velocity... The second linear graded filter 6 moves at a speed Move. Based on magnification. The effective relative displacement velocity of the system is: In single frame exposure time Within, the effective relative displacement produced by the two linear graded filters is Therefore, the spectral sampling interval between two adjacent frames... Determined by the following formula:

[0058]

[0059] Other embodiments and variations

[0060] The present invention also includes several possible variations. In pushbroom imaging, in addition to the aforementioned method of driving the first linear graded filter 3 to move relative to the target 1, the first linear graded filter 3 can also be kept stationary while the target 1 and the area array detector 7 with the second linear graded filter 6 attached to it move relative to each other. Similarly, a pushbroom scanning method can also be used.

[0061] The tunable filter structure is not limited to a linear gradient filter (LVF). The first tunable filter structure 3 and the second tunable filter structure 6 can also be tunable filters based on multilayer dielectric films, volume Bragg gratings, Fabry-Perot cavities, or metamaterial surface structures.

[0062] In some other embodiments, such as Figure 2 As shown, the relay mirror group may not be placed, or in embodiments where the second linear graded filter 6 and sensor assembly 7 are separate, the relay mirror group may be placed after the second linear graded filter 6. In the embodiments described above where there is no relay mirror group or the relay mirror group is placed after the second linear graded filter 6, the slopes of the first linear graded filter 3 and the second linear graded filter 6 are the same. In this case, the target 1 can also be scanned using the pushbroom scanning or staring scanning described above to reconstruct the hyperspectral data cube of the target 1.

[0063] The first linear graded filter 3 can be disposed on the intermediate image plane or its conjugate plane formed by the objective lens group 2, or disposed between the relay lens group and the second linear graded filter 6.

[0064] The linear gradient direction of the first linear gradient filter 3 and the linear gradient direction of the second linear gradient filter 6 are set to be parallel or perpendicular to each other.

[0065] The first linear graded filter 3 and the second linear graded filter 6 have interchangeable spectral characteristics. That is, the first linear graded filter 6 has a narrow spectral bandwidth and a narrow interval between adjacent transmission peaks, while the second linear graded filter 7 has a wide spectral bandwidth and a wide interval between adjacent transmission peaks.

[0066] Furthermore, the operating band of the system is applicable to any one or any combination of the visible light band (400~760nm), near-infrared band (760~2500nm), short-wave infrared band (1000~3000nm), mid-wave infrared band (3~5μm), or long-wave infrared band (8~14μm).

[0067] All of the above-mentioned modified designs utilize the core idea of ​​dual-filter mode selection and fall within the protection scope of this invention.

[0068] Imaging methods

[0069] This invention also provides a hyperspectral scanning imaging method based on any of the above-described systems, using any of the hyperspectral scanning imaging systems based on a dual-tunable filter structure. For example... Figure 5 As shown, the method includes the following steps:

[0070] S1 System Calibration: Perform spectral calibration on the hyperspectral scanning imaging system. For each pixel point at a spatial position on the array detector 7, establish a mapping relationship λ = f(x, y, s) between the position coordinates of the relative scanning motion and the transmission center wavelength of the system, where (x, y) are the spatial coordinates of the pixel point, s are the scanning position coordinates, and λ is the corresponding center wavelength.

[0071] S2 Synchronous Scan Acquisition: Control the scanning mechanism to make at least two of the first adjustable filter structure 3, the second adjustable filter structure 6, and the target 1 perform relative scanning motion according to a preset mathematical relationship; during the scanning process, control the area array detector 7 to continuously acquire two-dimensional image frame sequences at a frame rate synchronized with the scanning motion, and record the quasi-monochrome two-dimensional spatial information after filtering by the first adjustable filter structure 3 and the second adjustable filter structure 6 at the scanning position in each frame;

[0072] S3 Data Storage: Stores the acquired image frame sequence and corresponding scan position information;

[0073] S4 Spectral Extraction: Process the stored image frame sequence, and for any spatial pixel (x0, y0) within the imaging area, extract the intensity value sequence I1 to In recorded under different image frames and different scanning positions;

[0074] S5 Spectral Correlation: Using the mapping relationship established in step S1, the intensity value sequence I1 to In is associated with the corresponding center wavelength sequence λ1 to λn to construct the spectral curve I(λ) of the spatial pixel.

[0075] S6 Data Reconstruction: Repeat steps S4 and S5 for all spatial pixels within the imaging area to finally reconstruct the three-dimensional hyperspectral data cube I (x, y, λ) of the target.

[0076] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0077] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A hyperspectral scanning imaging system based on a dual-tunable filter structure, characterized in that, include: The objective lens group (2), the first adjustable filter structure (3), the imaging transfer subsystem, the second adjustable filter structure (6), and the area array detector (7) are arranged sequentially along the optical path direction; the second adjustable filter structure (6) is set close to the photosensitive surface of the area array detector (7) or fixed to the area array detector (7); it also includes a scanning mechanism that drives at least two of the first adjustable filter structure (3), the second adjustable filter structure (6), and the target (1) to perform relative scanning motion according to a preset mathematical relationship, so that the total spectral transmission characteristics of the system are jointly determined by the spectral transmission characteristics of the first adjustable filter structure (3) and the second adjustable filter structure (6) to achieve high spectral resolution hyperspectral imaging; Wherein, the first tunable filter structure (3) and the second tunable filter structure (6) are both filters whose center transmission wavelength changes continuously or discretely along the spatial position, and the filters are realized based on at least one of the following: multilayer dielectric film, volume Bragg grating, Fabry-Perot cavity or metamaterial surface structure; The imaging transfer subsystem is configured such that the equivalent spectral gradient m1' of the first tunable filter structure (3) at the second tunable filter structure (6) satisfies a preset matching relationship with the spectral gradient m2 of the second tunable filter structure (6); The spectral bandwidth BW1 and free spectral range FSR1 of the first tunable filter structure (3) and the spectral bandwidth BW2 and free spectral range FSR2 of the second tunable filter structure (6) satisfy one of the following relationships: BW1> BW2 and FSR1>FSR2, or BW1< BW2 and FSR1<FSR2. The total spectral transmission function T(λ) of the system is equal to the product of the spectral transmission function T1(λ) of the first tunable filter structure (3) and the spectral transmission function T2(λ) of the second tunable filter structure (6), i.e., T(λ) = T1(λ) × T2(λ), thereby achieving simultaneous acquisition of high spectral resolution and wide non-aliasing working spectrum.

2. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 1, characterized in that, The imaging transmission subsystem is a relay lens group, and the optical magnification of the relay lens group is N; the preset matching relationship is: m1' = m1 / N = m2, where m1 is the spectral gradient of the first tunable filter structure (3).

3. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 2, characterized in that, The configuration of the relay mirror group meets the following conditions: The center transmission wavelength λ1(x1) of the first adjustable filter structure (3) at position x1, after being imaged by the relay mirror, is equal to the center transmission wavelength λ2(x2) of the second adjustable filter structure (6) at position x2 = N·x1. The equivalent spectral gradients satisfy the following relationship: m1' = m1 / N = m2, where: m1 is the spectral gradient of the first tunable filter structure (3), defined as the rate of change of its central transmission wavelength along the spatial position, i.e., m1 = dλ1 / dx1; m2 is the spectral gradient of the second tunable filter structure (6), i.e., m2 = dλ2 / dx2; N is the lateral magnification of the relay lens group; Through the above configuration, the transmission wavelength at any position on the first adjustable filter structure (3) is made consistent with the transmission wavelength at the corresponding position of the second adjustable filter structure (6) after being imaged by the relay mirror, thereby achieving wavelength alignment of the two-stage filter structure.

4. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 2, characterized in that, The optical magnification N of the relay lens group is adjustable, thereby adapting to filter combinations with different spectral gradients.

5. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 1, characterized in that, The imaging transmission subsystem is an optical window without optical focal length or a direct air gap; the preset matching relationship is: m1' = m1 = m2, that is, the spectral gradient of the first tunable filter structure (3) is directly equal to or in a preset proportional relationship with the spectral gradient of the second tunable filter structure (6).

6. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 1, characterized in that, The linear gradient direction of the first adjustable filter structure (3) and the linear gradient direction of the second adjustable filter structure (6) are set to be parallel or perpendicular to each other; the scanning mechanism is configured such that the direction of the relative scanning motion is parallel to the gradient direction of the first adjustable filter structure (3); The first adjustable filter structure (3) is disposed on the intermediate image plane or its conjugate plane formed by the objective lens group (2); In the first tunable filter structure (3) and the second tunable filter structure (6), one is used for high-resolution spectral dispersion and the other is used for spectral order selection. The functions of the two can be interchanged. The second tunable filter structure (6) is fixed to the photosensitive surface of the array detector (7) by optical bonding or bonding process, and the distance between the two is less than or equal to 100 μm.

7. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 1, characterized in that, The scanning mechanism is configured to one of the following scanning modes: Pushbroom imaging mode: The first adjustable filter structure (3) is kept relatively stationary, and the target (1) and the area array detector (7) integrated with the second adjustable filter structure (6) are driven to perform relative scanning motion; or the first adjustable filter structure (3) and the target (1) are driven to perform relative scanning motion, while the second adjustable filter structure (6) and the area array detector (7) remain stationary; Staring imaging mode: The target (1) and the area array detector (7) are kept relatively stationary, and the first adjustable filter structure (3) and the second adjustable filter structure (6) are driven to perform relative scanning motion.

8. The hyperspectral scanning imaging system based on a dual tunable filter structure according to claim 1, characterized in that, The operating band of the system is applicable to any one or any combination of the following: visible light band (400~760nm), near-infrared band (760~2500nm), short-wave infrared band (1000~3000nm), mid-wave infrared band (3~5μm), or long-wave infrared band (8~14μm).

9. A hyperspectral scanning imaging method based on a dual-tunable filter structure, using the hyperspectral scanning imaging system based on a dual-tunable filter structure as described in any one of claims 1 to 12, characterized in that, Includes the following steps: S1 System Calibration: Perform spectral calibration on the hyperspectral scanning imaging system. For each pixel point at a spatial position on the array detector (7), establish a mapping relationship λ = f(x, y, s) between the position coordinates of the relative scanning motion and the transmission center wavelength of the system, where (x, y) are the spatial coordinates of the pixel point, s are the scanning position coordinates, and λ is the corresponding center wavelength. S2 Synchronous Scan Acquisition: Control the scanning mechanism to make at least two of the first adjustable filter structure (3), the second adjustable filter structure (6) and the target (1) perform relative scanning motion according to a preset mathematical relationship; during the scanning process, control the area array detector (7) to continuously acquire two-dimensional image frame sequences at a frame rate synchronized with the scanning motion, and record the quasi-monochrome two-dimensional spatial information after filtering by the first adjustable filter structure (3) and the second adjustable filter structure (6) at the scanning position in each frame; S3 Data Storage: Stores the acquired image frame sequence and corresponding scan position information; S4 Spectral Extraction: Process the stored image frame sequence. For any spatial pixel (x0, y0) within the imaging region, extract the intensity value sequence I1 to I2 recorded at different image frames and scanning positions. n ; S5 Spectral Correlation: Using the mapping relationship established in step S1, the intensity value sequence I1 to I... n With the corresponding center wavelength sequence λ1 to λ n Correlate them and construct the spectral curve I(λ) of the spatial pixel; S6 Data Reconstruction: Repeat steps S4 and S5 for all spatial pixels within the imaging area to finally reconstruct the three-dimensional hyperspectral data cube I (x, y, λ) of the target.

10. The hyperspectral scanning imaging method based on a dual tunable filter structure according to claim 9, characterized in that: Step S6 further includes performing at least one of the following post-processing steps on the three-dimensional hyperspectral data cube: spectral correction to eliminate the effects of dark current and non-uniform response; and wavelength registration to spatially align images of different wavelength channels.

Images