Scanning type hyperspectral imaging device and method based on linear gradient filter

Abstract

The invention discloses a scanning type hyperspectral imaging device and method based on a linear gradient filter. The device sequentially comprises an imaging objective lens, a gradient filter assembly, a telecentric imaging lens group and a camera along the incident direction of a light path, during working, the one-dimensional linear displacement table drives the gradient filter assembly to perform linear scanning motion in the direction perpendicular to the optical axis, so that light in an imaging view field penetrates through band-pass filtering areas with different central wavelengths on the gradient filter in a time-sharing manner. The filtered monochromatic or narrow-band light is projected to a photosensitive target surface of the camera through the telecentric imaging lens group, and multiple frames of spectral images with different wavebands are continuously acquired. Collected sequence images are processed and reconstructed to form a hyperspectral three-dimensional data cube containing spatial information and spectral information. The system has the advantages of high imaging speed, high luminous flux, compact system structure, low cost and the like, and is suitable for hyperspectral data acquisition scenes with higher real-time requirements.

Description

Technical Field

[0001] This invention belongs to the field of spectral imaging technology, and specifically relates to a scanning high-throughput fast hyperspectral imaging device based on a linear variable filter (LVF) and a corresponding hyperspectral data acquisition and reconstruction method. Background Technology

[0002] Hyperspectral imaging, as a detection method integrating image and spectral information, can acquire the two-dimensional spatial morphology and one-dimensional spectral characteristics of target objects in a continuous narrow band, thereby enabling in-depth analysis and accurate identification of the target material composition. With the development of sensor technology and optoelectronic materials, hyperspectral imaging has expanded from laboratory research to various practical applications such as agricultural remote sensing, industrial automation detection, food safety sorting, and biomedical diagnostics. However, achieving high light throughput, high acquisition speed, and low system cost while maintaining high spatial resolution remains a core requirement in the field of hyperspectral detection technology.

[0003] In agriculture and food safety, hyperspectral imaging technology can capture subtle spectral changes in crops, providing early warnings of pests and diseases before they are visible to the naked eye. By analyzing reflectance in specific wavelengths, the system can accurately assess chlorophyll content, water content, and nitrogen fertilizer levels in vegetation, providing data support for precision fertilization and irrigation. In food processing lines, this technology enables non-contact detection of the internal quality of agricultural products, such as sugar content grading of fruits, mold screening of grains, and component analysis of meat products, significantly improving the efficiency and accuracy of detection.

[0004] In the fields of industrial inspection and resource recycling, hyperspectral imaging, with its "image and spectrum integration" advantage, has become a core tool for identifying complex components. In lithium battery manufacturing, this technology can be used to detect the uniformity of electrode coatings and identify surface defects. In waste resource recycling, traditional machine vision struggles to distinguish between engineering plastics (such as PE, PP, and PET) that have similar colors but vastly different chemical compositions, while hyperspectral imaging can achieve highly pure automatic sorting based on its unique "spectral fingerprint." Furthermore, this technology also demonstrates irreplaceable application potential in textile composition identification and cultural relic restoration.

[0005] In the biomedical and pharmaceutical fields, hyperspectral imaging offers new avenues for non-invasive diagnostics. Because different tissues and lesion regions exhibit varying absorption and scattering characteristics to specific wavelengths of light, this technology can be used to assist in early screening for skin cancer, monitoring blood oxygen saturation during surgery, and precisely defining tumor margins. In pharmaceutical manufacturing, hyperspectral scanning of tablets or powders allows for real-time monitoring of the uniformity of active ingredient distribution and impurity content, ensuring drug quality meets standards. However, these fields place extremely high demands on the real-time performance and light throughput of imaging devices, and existing imaging equipment often struggles to achieve a balance between high performance and low cost.

[0006] Currently, mainstream hyperspectral imaging solutions on the market all have significant technical limitations in practical applications. Time-division imaging technology, represented by liquid crystal tunable filters (LCTFs), can quickly switch bands through electronic control, but its principle of polarization interference results in extremely low peak transmittance and light energy utilization of less than 20%. This requires the system to significantly extend the exposure time in low-light environments, greatly limiting the detection capability of dynamic targets. At the same time, the manufacturing process of such core components is complex and the purchase cost is expensive, making it difficult to widely adopt them on industrial production lines.

[0007] Another common pushbroom spectral imaging technique uses slits and dispersive elements (such as gratings or prisms) for beam splitting. Although it offers high spectral resolution, the physical slits significantly reduce the light flux entering the detector. Furthermore, factors such as grating diffraction efficiency and lens surface reflectivity further reduce the light flux. To obtain a sufficiently strong signal, the system often requires an extremely high-power light source or an expensive cooled camera, resulting in a bulky and costly imaging device. It also demands extremely precise alignment of the optical path, has poor shock resistance, and is difficult to adapt to complex industrial environments.

[0008] In recent years, linear variable filters (LVFs) have gradually become a research hotspot in the field of spectral imaging due to their high transmittance (nearly 90%) and excellent filtering characteristics. In existing technologies, LVFs are often directly integrated or bonded to the surface of the image sensor's photosensitive chip. While this design reduces size, it suffers from several insurmountable drawbacks: First, the physical gap between the photosensitive chip and the filter leads to severe spectral aliasing and crosstalk between pixels, reducing the purity of the spectral data; second, this tightly coupled design makes the imaging system inflexible, preventing users from changing objectives or adjusting the imaging magnification for different targets; furthermore, limited by chip size, the spectral adjustment range and sampling step size of such devices are fixed after leaving the factory, making it difficult to meet diverse scientific and industrial needs.

[0009] Therefore, there is an urgent need to develop a scanning high-throughput hyperspectral imaging system that is fast in imaging, has high spectral fidelity, flexible in structure, and low in cost. Summary of the Invention

[0010] To address the technical problems of existing hyperspectral imaging devices, such as the extremely low transmittance and high cost of liquid crystal tunable filters (LCTFs), the limited light throughput of traditional pushbroom systems, and the severe spectral aliasing and lack of flexibility of bonded LVFs, this invention provides a scanning high-throughput fast hyperspectral imaging device and method based on a linear graded filter. This invention aims to achieve high-precision, low-cost, and rapid spectral data acquisition while maintaining extremely high light throughput through an independent linear graded filter scanning assembly combined with a telecentric optical structure.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A scanning hyperspectral imaging device based on a linearly graded filter includes: An imaging objective, a graduated filter assembly, a telecentric imaging lens group, and a camera are arranged sequentially along the incident direction of the light path. The gradient filter assembly is mounted on a one-dimensional linear displacement stage, and the displacement stage drives the gradient filter assembly to perform linear scanning motion in a direction perpendicular to the system optical axis. The gradient filter assembly has a center wavelength transmittance characteristic that varies linearly along its surface spatial position, and is used to split the incident beam. The telecentric imaging lens group is used to project the split beam onto the photosensitive target surface of the camera to ensure that the main ray is incident parallel to the optical axis and to ensure the consistency of spectral characteristics at each position of the filter. The camera continuously acquires images at a high frame rate during the scanning process, and each frame image corresponds to a scanning position of the gradient filter assembly and the corresponding spectral band. The device may optionally include a bandwidth adjustment mechanism for adjusting the bandwidth of the transmitted spectrum; The one-dimensional linear displacement stage is equipped with a position feedback sensor to provide real-time feedback on the current position of the gradient filter assembly, thereby establishing a mapping relationship between the scanning position and the center wavelength.

[0012] The gradient filter assembly includes a linearly gradient long-pass filter and a linearly gradient short-pass filter stacked in parallel along the optical axis. The two filters change in the same direction and have a peak transmittance of not less than 90%. They form an adjustable bandwidth bandpass window by adjusting their relative positions. The bandwidth adjustment mechanism is used to adjust the relative positions of the two filters to achieve continuous fine-tuning of the bandwidth in the range of 5 nm to 50 nm.

[0013] The gradient filter assembly is a single linear gradient bandpass filter with a transmission center wavelength that changes linearly and continuously along one geometric axis of the filter. The wavelength gradient range is 400 nm to 1000 nm, the full width at half maximum (FWHM) is 10 nm to 20 nm, and the peak transmittance is not less than 80%.

[0014] The telecentric imaging lens group is an object-oriented telecentric lens or a double telecentric lens, whose object plane position matches the center position of the graduated filter assembly to ensure that the incident principal ray is parallel to the optical axis, and the optical system error of the lens group is controlled within λ / 10.

[0015] The camera is a high frame rate area array detector (such as CMOS or CCD), which is electrically connected to a one-dimensional linear displacement stage through a synchronization control unit. During the scanning process, the camera triggers acquisition at a preset frame rate (≥60 fps) to achieve precise synchronization between image acquisition and filter position. The one-dimensional linear displacement stage includes a precision electric slide and a position feedback sensor (such as an optical encoder). The sensor is used to provide real-time feedback on the current position of the gradient filter assembly (position accuracy ≤ 50 μm) and to support wavelength positioning and data reconstruction.

[0016] The bandwidth adjustment mechanism achieves fine-tuning of the synthesized spectral bandwidth by adjusting the relative position or transmission characteristics of each filter inside the gradient filter assembly. The adjustment range is from 5 nm to 50 nm, and the adjustment step is ≤10 μm.

[0017] The spectral calibration process for hyperspectral data using the aforementioned device includes: (i) Remove the imaging objective lens and illuminate the device with a wide-field standard characteristic spectrum light source (such as a NIST certified light source); (ii) Extract the pixel width coordinate w of the feature spectral line from the image corresponding to the position x of each one-dimensional linear displacement stage, and combine it with the known standard wavelength λ0 to establish the wavelength function relationship λ(x,w) = a·x + b·w +c using the least squares method; (iii) The data reconstruction process includes: calculating the actual center wavelength corresponding to each pixel of each frame image according to the wavelength function λ(x,w); performing spatial alignment and stitching of the image sequence based on the calculation results; setting a fixed spectral coordinate grid, and reconstructing the spectral information of all pixels to the grid through an interpolation algorithm (such as cubic spline interpolation) to generate a hyperspectral three-dimensional data cube.

[0018] The process of establishing the wavelength function λ(x,w) also includes: performing multi-frame averaging on the calibration image sequence to reduce noise and improve fitting accuracy, with a fitting residual ≤2 nm.

[0019] The system luminous flux of the device is not less than 80%, the single frame exposure time is ≤10 ms, and the acquisition speed can reach 0.8 seconds to complete one 300-frame acquisition in the visible light band.

[0020] The device is suitable for applications such as tissue blood oxygenation imaging, short-wave infrared identification of medicinal materials, agricultural remote sensing, food safety testing, or industrial sorting.

[0021] A method for acquiring hyperspectral data using the aforementioned device includes the following steps: S1: The light from the target scene is introduced into the optical path through the imaging objective lens; S2: Control the one-dimensional linear displacement stage to drive the gradient filter assembly to perform linear scanning in the direction perpendicular to the optical axis (speed 5-50 mm / s). S3: During the scanning process, the camera synchronously acquires a series of two-dimensional narrowband images through the filter at a preset frame rate (≥60 fps). Each frame corresponds to the scanning position x and the center wavelength λ. S4: Record the scanning position x corresponding to each frame of the image, and determine the center wavelength corresponding to each frame of the image based on the linear dispersion characteristics of the gradient filter and the wavelength function λ(x,w). S5: Spatial alignment and spectral interpolation reconstruction are performed on the acquired image sequence to generate a hyperspectral three-dimensional data cube containing spatial and spectral information, with a spectral dimension step size ≤ 5 nm.

[0022] Compared with the prior art, the beneficial effects of the present invention are reflected in: High luminous flux and high transmittance: Using a linear gradient filter as the beam splitter, its peak transmittance can reach 80%-90%, which is far higher than LCTF technology. This greatly shortens the exposure time of a single frame image and improves the system's imaging capability in low-light environments.

[0023] High spectral accuracy and no aliasing: By placing the filter between the objective lens and the telecentric imaging lens group, and combining it with the telecentric optical path design, the beam is ensured to be perpendicularly incident, eliminating pixel crosstalk and spectral aliasing problems caused by traditional bonding designs. This expands the combination matching of filters of different sizes with cameras, and the spectral resolution can be further improved by using longer filters.

[0024] Accurate data reconstruction: With the help of precision displacement stage feedback and calibration algorithm, wavelength shift during the scanning process can be eliminated, and the generated reconstructed data has extremely high spatial and spectral fidelity.

[0025] Flexible structure and low cost: The device adopts a modular design, which eliminates the need for customized chip bonding processes. Different magnification objectives or cameras can be replaced as needed, and it avoids expensive photoacoustic or liquid crystal tuning components, which significantly reduces hardware costs. Attached Figure Description

[0026] Figure 1 : Schematic diagram of the optical path structure of the device of the present invention; In the figure, there are: 1. Imaging objective lens; 2. One-dimensional linear displacement stage; 3. Linearly graded long-pass filter; 4. Linearly graded short-pass filter; 5. Telecentric imaging lens group; 6. Camera; 7. Bandwidth adjustment mechanism.

[0027] Figure 2 : Wavelength-position relationship curve of linear gradient filter.

[0028] Figure 3 : Flowchart of spectral calibration and data reconstruction.

[0029] Figure 4 Visible-near-infrared tissue oxygenation imaging for hyperspectral imaging of the neck.

[0030] Figure 5 Visible-near-infrared tissue oxygenation imaging image.

[0031] Figure 6 : The main control software interface of the visible-near-infrared tissue oxygenation rapid imaging instrument (scanning imaging parameter control area).

[0032] Figure 7 Photographs of Panax notoginseng samples; Figure 8 Shortwave infrared reflectance spectrum image; Figure 9 Short-wave infrared reflectance spectrum curve.

[0033] Figure 10 Photo of the prototype of the hyperspectral analyzer for rapid identification of medicinal materials in operation. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0035] Example 1: Visible-Near Infrared Tissue Oxygenation Rapid Imaging Device This embodiment provides a device specifically designed for tissue hyperspectral image acquisition and blood oxygen saturation analysis. Its core design employs a linear gradient spectrometer covering the 400-1000nm wavelength band, enabling continuous and efficient spectral imaging in the visible to near-infrared range.

[0036] like Figure 1 As shown, this embodiment uses the following configuration: (1) An industrial lens with an imaging objective of 1:50 mm focal length, f / 2.8, magnification of 1:1, and working wavelength of 400-1000 nm; (2) Graded-pass filter assembly: This assembly consists of a linearly graded long-pass filter 3 and a linearly graded short-pass filter 4 stacked together with matched parameters. Both achieve linear tuning of the spectral edges within the 400-1000 nm range, with a linear gradient of 10.9 nm / mm. This assembly forms a movable bandpass window by adjusting the overlap position, and thanks to the high transmittance (>90%) and deep cutoff (>OD5) of a single filter, it effectively ensures high light throughput and signal-to-noise ratio of the system. The 50% transmittance position is shown below. Figure 2 As shown, the bandwidth adjustment mechanism 7 is a manual fine-tuning screw with an adjustment range of 5-50 nm; (3) One-dimensional linear displacement stage 2: driven by a linear motor, with a stroke of 100 mm and a position feedback accuracy of 50 μm; (4) Telecentric imaging lens group 5: object-side telecentric lens, the object plane matches the center plane of the filter (error ≤ 0.1mm); (5) Camera: 6:5 MP CMOS array detector, response band 400-1000nm, peak quantum efficiency ≥70%@550nm, frame rate ≥60 fps, minimum exposure 100 us; (6) Synchronization control unit: Based on the control software of DotNetFramework4.8, the displacement table and the camera are synchronously triggered.

[0037] like Figure 1 As shown, at the optical front end, the imaging objective 1 is a 50mm focal length industrial lens with aberration correction for the broad spectral range (visible-near infrared), ensuring clear imaging across the entire working wavelength band. The innovation of the beam-splitting module lies in its graded filter array. It is not a single filter, but rather a precisely parallel stack of a linearly graded long-pass filter 3 and a linearly graded short-pass filter 4. By fine-tuning their relative starting positions, the overlap area of ​​their transmission curves can be precisely controlled, thereby stably locking the full width at half maximum (FWHM) of the synthesized effective bandpass window at 10nm, forming a movable, extremely narrow spectral screening "window."

[0038] The filter array is integrated onto a one-dimensional linear displacement stage 2. During data acquisition, the stage moves the stacked filter array laterally at a uniform speed, ensuring that the gradient direction aligns with the direction of motion. A telecentric imaging lens group 5 is specifically positioned in front of the camera's photosensitive area as a relay optical system. Its key function is to ensure that light reflected from the tissue and passing through the objective lens is incident on the graded filter at an approximately perpendicular angle. This design minimizes center wavelength drift caused by changes in the incident angle, guaranteeing the accuracy of the spectral data.

[0039] The acquisition action of the area-array CMOS camera 6 is triggered by a high-precision encoder on the displacement stage. During the uniform scanning process of the filter array, the camera rapidly captures a series of instantaneous narrowband images at an extremely high frame rate, with each image corresponding to a specific narrow wavelength of light. Due to the overall transmittance of the entire optical path, especially the customized filter array, which is over 85%, the system is able to capture extremely weak spectral fluctuation signals in skin reflection.

[0040] like Figure 3 The data acquisition and reconstruction process shown 1. Spectral Calibration: The imaging objective lens is removed, and the device is illuminated using a NIST-certified wide-field light source (such as a deuterium lamp). A sequence of 200 images is acquired, and the pixel width *w* of the characteristic spectral lines is extracted. Combined with the stage position *x*, a wavelength function λ(x,w) = a·x + b·w + c (fitting residual ≤ 2 nm) is established using the least squares method. Here, *a* represents the wavelength gradient rate (nm / mm) of the linearly graded filter, *b* corrects for spatial wavelength differences within the detector's field of view (nm / pixel), and *c* is the initial wavelength intercept of the system. In actual calculations, multiple sets of λ(x,w) data pairs are obtained by identifying characteristic peaks of multiple known standard wavelengths in the light source. Parameters *a*, *b*, and *c* are solved using multiple linear regression, thereby establishing a precise mapping model from the "mechanical-pixel" space to the "wavelength" space.

[0041] 2. Data Acquisition: Restore the imaging objective lens, control the stage to scan at a speed of 20mm / s, and the camera to simultaneously acquire 300 frames of narrowband images at 60 fps.

[0042] 3. Data Reconstruction: Calculate the actual wavelength corresponding to each pixel in each frame of the image based on λ(x,w), perform spatial alignment (column interpolation) on the image sequence, set the spectral grid (400-1000 nm, step size 2 nm), and reconstruct the hyperspectral three-dimensional data cube using cubic spline interpolation.

[0043] 4. Experimental results: Acquisition time 5 seconds, blood oxygen saturation spatial resolution 10 μm, spectral reconstruction error ≤2 nm.

[0044] Subsequent data processing is handled by the main control software (interface as shown in...). Figure 6 (As shown) for the acquired hyperspectral image data of the neck (such as Figure 4 Reconstruction and calculation are performed on the wavelengths shown (as illustrated), and the reflectance ratios of characteristic bands such as 660nm (the hemoglobin-sensitive band) and 940nm (the oxyhemoglobin-sensitive band) can be extracted. Based on a bio-optical model, this ratio is used for inversion calculations, ultimately achieving intuitive analysis and imaging of the spatial distribution of subcutaneous blood oxygen saturation (e.g., ...). Figure 5(As shown). Compared to the traditional liquid crystal tunable filter (LCTF) scheme, the mechanical scanning linear gradient filtering method used in this embodiment reduces the imaging time of a single hyperspectral data cube by more than 70%. This high-speed acquisition characteristic significantly reduces image registration errors and motion artifacts caused by unavoidable minor shaking of the subject, greatly improving the reliability and practicality of the measurement.

[0045] Example 2: Shortwave Infrared Medicinal Herb Identification Device This embodiment relates to a short-wave infrared hyperspectral imaging device for rapid identification of traditional Chinese medicinal materials. A photograph of the prototype in operation is shown below. Figure 10 As shown. The device operates in the short-wave infrared region of 1000-1700 nm, which is rich in characteristic absorption information of organic molecules (such as CH and OH bonds).

[0046] The system's hardware configuration is specifically designed for short-wave infrared characteristics. Imaging objective 1 employs a dedicated SWIR lens that transmits short-wave infrared materials, while camera 6 uses a detector based on indium gallium arsenide (InGaAs) to ensure high sensitivity and responsivity in this band. The spectroscopic element uses a linearly graded filter (LVF), specifically a linearly graded bandpass filter in this embodiment. Its center wavelength changes linearly along the length of the filter, continuously grading from 1000 nm at one end of the stage to 1700 nm at the other, with a gradation rate of 12.7 nm / mm. The full width at half maximum (FWHM) of the spectral window is approximately 15 nm.

[0047] The drive mechanism employs a one-dimensional linear displacement stage 2 driven by a high-precision linear motor to meet the stringent requirements of repeatability and consistency in band positioning for short-wave infrared spectroscopy analysis. In the optical path design, the telecentric imaging lens group 5 plays a crucial role: on the one hand, its special lens coating provides anti-reflection protection for the short-wave infrared band, effectively suppressing stray light; on the other hand, its telecentric structure ensures that the principal ray passes perpendicularly through the linearly graded filter, fundamentally solving the problem of significant center wavelength drift caused by large-angle incident light in the infrared band, thus guaranteeing the authenticity and comparability of the spectral data.

[0048] In the case of Figure 7 When identifying the medicinal materials such as Panax notoginseng and Polygonatum sibiricum, the system workflow is as follows: The displacement stage moves the linear gradient filter at a constant speed, the camera is triggered synchronously, and a series of continuous narrow-band images of the medicinal material surface are quickly acquired, ultimately constructing a complete hyperspectral data cube containing both spatial two-dimensional and spectral dimensions. This data not only records the morphological characteristics of the medicinal material surface (short-wave infrared reflectance spectra under single bands, such as...), but also... Figure 8 As shown in the figure, it also contains information about the chemical composition of its near-surface material.

[0049] By analyzing the spectral curves and absorption peak shapes of the data cube at characteristic wavelengths such as 1450 nm (characteristic absorption of water and hydroxyl groups) and 1650 nm (carbon-hydrogen bond frequency absorption), the absorption peaks were analyzed. Figure 9 As shown, the system can effectively distinguish the authenticity and type of medicinal materials, and even identify the same medicinal material from different origins. This embodiment combines a clever telecentric optical path design with a cost-effective one-dimensional scanning mechanism, which significantly reduces equipment cost and size while ensuring professional-grade spectral performance. This allows the device to be easily deployed at rapid testing stations in places such as medicinal material wholesale markets and pharmaceutical factory quality inspection workshops, providing a powerful technical tool for quality control in the circulation of Chinese medicinal materials.

[0050] The performance comparison table of this invention with LCTF and push-broom systems is shown below:

[0051] The embodiments described above can be further combined or replaced, and these embodiments are merely descriptions of preferred embodiments of the present invention, not limitations on the concept and scope of the present invention. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the inventive concept are all within the protection scope of the present invention. The protection scope of the present invention is given by the appended claims and any equivalents.

Claims

1. A scanning hyperspectral imaging device based on a linearly graded filter, characterized in that, include: An imaging objective, a graduated filter assembly, a telecentric imaging lens group, and a camera are arranged sequentially along the incident direction of the light path. The gradient filter assembly is mounted on a one-dimensional linear displacement stage, and the displacement stage drives the gradient filter assembly to perform linear scanning motion in a direction perpendicular to the system optical axis. The gradient filter assembly has a center wavelength transmittance characteristic that varies linearly along its surface spatial position, and is used to split the incident beam. The telecentric imaging lens group is used to project the split beam onto the photosensitive target surface of the camera to ensure that the main ray is incident parallel to the optical axis and to ensure the consistency of spectral characteristics at each position of the filter. The camera continuously acquires images at a high frame rate during the scanning process, and each frame image corresponds to a scanning position of the gradient filter assembly and the corresponding spectral band. The one-dimensional linear displacement stage is equipped with a position feedback sensor to provide real-time feedback on the current position of the gradient filter assembly, thereby establishing a mapping relationship between the scanning position and the center wavelength.

2. The apparatus as claimed in claim 1, characterized in that, The device also includes a bandwidth adjustment mechanism for continuously fine-tuning the synthesized spectral bandwidth by adjusting the relative position or transmission characteristics of the filters inside the gradient filter assembly. The gradient filter assembly includes a linearly gradient long-pass filter and a linearly gradient short-pass filter stacked in parallel along the optical axis. The two filters change in the same direction and have a peak transmittance of not less than 90%. They form an adjustable bandwidth bandpass window by adjusting their relative positions. The bandwidth adjustment mechanism is used to adjust the relative positions of the two filters to achieve continuous fine-tuning of the bandwidth in the range of 5 nm to 50 nm.

3. The apparatus as described in claim 1, characterized in that, The gradient filter assembly is a single linear gradient bandpass filter with a transmission center wavelength that changes linearly and continuously along one geometric axis of the filter. The wavelength gradient range is 400 nm to 1000 nm, the full width at half maximum (FWHM) is 10 nm to 20 nm, and the peak transmittance is not less than 80%.

4. The apparatus as claimed in claim 1, characterized in that, The telecentric imaging lens group is an object-oriented telecentric lens or a double telecentric lens, whose object plane position matches the center position of the graduated filter assembly to ensure that the incident principal ray is parallel to the optical axis, and the optical system error of the lens group is controlled within λ / 10.

5. The apparatus as claimed in claim 1, characterized in that, The camera is a high frame rate area array detector, which is electrically connected to a one-dimensional linear displacement stage through a synchronization control unit. During the scanning process, the camera triggers acquisition at a preset frame rate to achieve precise synchronization between image acquisition and filter position. The one-dimensional linear displacement stage includes a precision electric slide and a position feedback sensor. The sensor is used to provide real-time feedback on the current position of the gradient filter assembly and to support wavelength positioning and data reconstruction.

6. The apparatus as claimed in claim 2, characterized in that, The bandwidth adjustment mechanism achieves fine-tuning of the synthesized spectral bandwidth by adjusting the relative position or transmission characteristics of each filter inside the gradient filter assembly. The adjustment range is from 5 nm to 50 nm, and the adjustment step is ≤10 μm.

7. The apparatus as claimed in claim 1, characterized in that, The spectral calibration process for hyperspectral data includes: (i) Remove the imaging objective lens and illuminate the device using a wide-field standard characteristic spectrum light source; (ii) Extract the pixel width coordinate w of the feature spectral line from the image corresponding to the position x of each one-dimensional linear displacement stage, and combine it with the known standard wavelength λ0 to establish the wavelength function relationship λ(x,w) = a·x + b·w + c using the least squares method; (iii) The data reconstruction process includes: calculating the actual center wavelength corresponding to each pixel of each frame image according to the wavelength function λ(x,w); performing spatial alignment and stitching of the image sequence based on the calculation results; setting a fixed spectral coordinate grid, and reconstructing the spectral information of all pixels to the grid through an interpolation algorithm to generate a hyperspectral three-dimensional data cube.

8. The apparatus as claimed in claim 7, characterized in that, The process of establishing the wavelength function λ(x,w) also includes: performing multi-frame averaging on the calibration image sequence to reduce noise and improve fitting accuracy, with a fitting residual ≤2 nm.

9. The apparatus as claimed in claim 1, characterized in that, The device is suitable for applications such as tissue blood oxygenation imaging, short-wave infrared identification of medicinal materials, agricultural remote sensing, food safety testing, or industrial sorting.

10. A method for acquiring hyperspectral data using the device as described in claim 7 or 8, characterized in that, Includes the following steps: S1: The light from the target scene is introduced into the optical path through the imaging objective lens; S2: Control the one-dimensional linear displacement stage to drive the gradient filter assembly to perform linear scanning in the direction perpendicular to the optical axis, at a speed of 5-50 mm / s; S3: During the scanning process, the camera synchronously acquires a series of two-dimensional narrowband images through the filter at a preset frame rate ≥60 fps. Each frame corresponds to the scanning position x and the center wavelength λ. S4: Record the scanning position x corresponding to each frame of the image, and determine the center wavelength corresponding to each frame of the image based on the linear dispersion characteristics of the gradient filter and the wavelength function λ(x,w). S5: Spatial alignment and spectral interpolation reconstruction are performed on the acquired image sequence to generate a hyperspectral three-dimensional data cube containing spatial and spectral information, with a spectral dimension step size ≤ 5 nm.

Images