Chlorophyll fluorescence imaging system, imaging method and application

Abstract

The invention relates to the field of remote sensing detection imaging systems, in particular to a chlorophyll fluorescence imaging system, an imaging method and application. The imaging system comprises a housing, an imaging lens, a moving assembly and a processor. The imaging lens is installed on the moving assembly and extends out of the machine shell. The moving assembly is used for driving the imaging lens to move; a slit sheet, a first lens group, a grating, a second lens group and an area array detector are sequentially arranged in the shell from the imaging lens to the back; an illumination intensity acquisition module is arranged on one side of the slit sheet; the slit sheet and the first lens group are arranged in parallel with the imaging lens; the first lens group and the second lens group are not parallel to the grating and are not parallel to each other; the processor is arranged in the shell and is electrically connected with the moving assembly and the area array detector; an electronic interface for outputting data is installed on the outer wall of the machine shell and electrically connected with the processor. According to the invention, fluorescence imaging with high spectral resolution, high spatial resolution and high signal-to-noise ratio can be realized.

Description

Technical Field

[0001] The present invention relates to the field of remote sensing detection imaging systems, and in particular to a chlorophyll fluorescence imaging system, an imaging method and applications. Background Art

[0002] Hyperspectral imaging technology is an imaging data technology based on a large number of narrow bands. It combines imaging technology with spectral technology to detect the two-dimensional geometric space and one-dimensional spectral information of the target and obtain continuous, narrow-band image data with high spectral resolution. It can achieve rapid identification and quantitative analysis of objects by obtaining spectral information of objects in different bands. Hyperspectral imaging technology has the advantages of ultra-multiple bands (hundreds of bands), high spectral resolution (several nm), narrow bands (≤10 -2 λ), a wide spectral range (200-2500nm), and integrated image and spectrum. Its advantages lie in the rich information captured in the images, high recognition accuracy, and multiple data description models. Because the reflectance spectrum of an object has a "fingerprint" effect, it can be combined with hyperspectral imaging technology to distinguish different material information based on the principle that different objects have different spectra, while the same object has the same spectrum. Currently, hyperspectral imaging technology is widely used in agriculture, environmental monitoring, geological exploration, remote sensing, and medicine.

[0003] Sun / Solar-induced Chlorophyll Fluorescence (SIF) is a spectral signal (650-800 nm) emitted by the photosynthetic center of plants under sunlight. It has two peaks, one in the red (around 690 nm) and the other in the near-infrared (around 740 nm), and can directly reflect the dynamic changes in a plant's actual photosynthesis. SIF remote sensing is a rapidly developing vegetation remote sensing technology that can address the shortcomings of current vegetation remote sensing observations and provide new insights and technologies for terrestrial ecosystem carbon cycling and vegetation monitoring. Vegetation remote sensing technologies, represented by vegetation indices based on "greenness" observations (such as the Normalized Difference Vegetation Index (NDVI)), have greatly advanced our understanding of the Earth's biosphere at a macroscale over the past 30 years. However, these technologies can only detect a plant's "potential photosynthesis" through "greenness." Chlorophyll fluorescence imaging offers unique technical advantages in detecting vegetation photosynthetic physiology and is a direct method for detecting "actual photosynthesis." At the same time, it is also a major breakthrough based on the current non-imaging system SIF system. From traditional spectral research to the current research and application model based on the integration of "image and spectrum", it can be said that vegetation chlorophyll fluorescence imaging is the most groundbreaking research frontier in the field of vegetation remote sensing in the past 10 years.

[0004] A hyperspectral imager (also known as a spectral camera, hyperspectral camera, or hyperspectrometer) is a nondestructive testing and analysis instrument that seamlessly combines an imaging spectrometer with an area array detector, enabling simultaneous and rapid acquisition of spectral and imaging information. The imaging spectrometer forms an image of a line on the target at a time and splits the light so that each spectral component corresponds to a pixel on the line array. Therefore, each image from the imaging spectrometer consists of linear array pixels along one dimension (the spatial axis) and the spectral distribution (the intensity of light within the spectral elements) along another dimension (the spectral axis). Generally, the main components of an imaging spectrometer are a collimator, a spectrometer, and a focusing lens.

[0005] like Figure 1 The figure shows a schematic diagram of the system structure of a common imaging spectrometer based on the Offner structure. Its spectroscopic structure generally adopts an off-axis three-reflection structure based on the Rowland circle, that is, it consists of a first concave reflector, an ellipsoidal convex grating, and a second concave reflector, wherein: the first ellipsoidal concave reflector, the second ellipsoidal concave reflector and the ellipsoidal convex grating are confocal and have the same focus and optical axis. The first ellipsoidal concave reflector and the second ellipsoidal concave reflector are respectively located on both sides of the main plane perpendicular to the major axis direction, the ellipsoidal convex grating is distributed on both sides of the main plane perpendicular to the major axis direction, the short semi-axis length of the second ellipsoid is half of the projection distance from the incident slit in the optical axis direction to the first ellipsoidal concave reflector, and the incident slit and the detection unit are respectively placed near the two focal points. While this optical system boasts advantages such as compact structure, minimal inherent aberration, high light energy utilization, and high resolution, its imaging principle is as follows: light emitted from the object plane, after being reflected by the first concave spherical reflector, is split by the convex spherical grating to produce monochromatic diffracted light. This monochromatic diffracted light is then reflected by the second concave spherical reflector and focused onto the image plane. Therefore, except for light rays emitted at different angles on the meridional plane, which have the same optical path difference as the principal ray passing through the principal axis, light rays incident at different angles on other planes have different optical path differences with the principal ray. Therefore, the Rowland circle off-axis three-reflection spectroscopic structure can only ensure that light rays emitted from the meridional plane have the same optical path difference as the principal ray passing through the principal axis, thus eliminating meridional aberrations without simultaneously addressing the effects of other aberrations. Consequently, image quality remains poor.

[0006] like Figure 2 Figure 2 shows another common imaging spectrometer system architecture based on a prism-grating-prism (PGP) combination, in which a prism-grating-prism structure serves as the beam splitting structure. In this system, the grating can be a volume holographic phase grating, which can achieve high diffraction efficiency. The collimation and imaging mirrors use a symmetrical structure, effectively eliminating vertical axis aberrations. However, the grating plus prism mode still suffers from the problem of ghost images. The specific reasons are as follows:

[0007] like Figure 3 and Figure 4As shown, a system including a prism is analyzed as an example. The system's light splitting structure includes a first imaging lens group B, a grating C, a wedge prism D, and a second imaging lens group E. First, the first imaging lens group B collimates the image from the incident slit A (the incident slit dimensions are: length 16mm, width 30μm) to form collimated parallel light. This light is then dispersed by the grating C to form monochromatic light of different color wavelengths. The monochromatic light continues to enter the wedge-shaped prism D, which can deflect the light beam normally incident on the vertical surface of the prism by 2° to 10°. The wedge-shaped prism D can be used for beam steering applications. The grating dispersion width is closely related to the deflection angle of the wedge-shaped prism. The monochromatic light output from the wedge-shaped prism is then collimated by the second imaging lens group E to form parallel light. This parallel light is then mapped onto the target surface of the area array detector, where the target surface dimensions of the area array detector are: X-axis: 13.3mm (6.5μm*2048), Y-axis 13.3mm (6.5μm*2048). That is, the width of the monochromatic light output through the grating and prism is within 13.3 mm, and is actually around 10 mm. The number of grating lines, the beam deflection angle, etc. all have an impact on this dispersion width.

[0008] Gratings, whether they are transmissive or reflective, can separate light of different wavelengths through a repetitive structure within the grating. This structure affects the amplitude and / or phase of the incident light, causing interference in the outgoing light. For example, a common transmission grating, such as Figure 5 As shown in Figure 1, a series of repetitive narrow grooves with a spacing of α are engraved on a transparent substrate. This repetitive structure can be regarded as many closely arranged slits and creates an area where light can be scattered. i Solving for the illumination incident on the grating as a function of wavelength and slit position, we obtain a general expression for θ i = 0° for all diffraction gratings:

[0009] αsin(θ m )=mλ (1)

[0010] This equation is called the grating equation. It states that a grating with a spacing of α will scatter light at discrete angles (θ m ) deflection, where m is the main maximum order, and the diffraction angle θ m is the angle of emission measured perpendicular to the surface of the diffraction grating. It is easy to see from equation (1) that for a given order m, light of different wavelengths will exit the grating at different angles. For a white light source, this is equivalent to a continuous spectrum that is angle-dependent. Using the geometric transformation relationship and equation (1), the expression for the transmission grating can be obtained:

[0011] α[sin(θ m )-sin(θ i)]=mλ (2)

[0012] However, when the beam splitting structure is designed with a wedge-shaped prism, ghost images will be generated in specific areas due to the scattering effect between diffraction orders. This is because although the grating has high first-order diffraction efficiency in a wide bandwidth range and the scattering between different diffraction order peaks is extremely low and there is almost no ghosting, some stray light effects will still be generated, such as Figure 6 In the image shown, the horizontal bright track is an abnormally protruding peak in the spectrum (such as Figure 7 ), which seriously affects the imaging quality and spectral accuracy.

[0013] Therefore, when the above-mentioned common hyperspectral imaging system is applied to the field of SIF remote sensing detection, it still cannot fully meet the usage requirements. Therefore, it is urgent to develop a hyperspectral imaging system suitable for SIF remote sensing detection. Summary of the Invention

[0014] In response to the above problems, the present invention provides a chlorophyll fluorescence imaging system, an imaging method, and an application solution combined with a drone.

[0015] To achieve the above objectives, the present invention provides a chlorophyll fluorescence imaging system, specifically:

[0016] A chlorophyll fluorescence imaging system comprises a housing, an imaging lens, a moving assembly and a processor; a mounting hole is provided on a side wall of the housing; the imaging lens is mounted on the moving assembly and extends out of the housing through the mounting hole, and the width of the mounting hole is greater than that of the imaging lens; the moving assembly is located in the housing and is used to drive the imaging lens to move laterally along the mounting hole; a slit sheet, a first lens group, a grating, a second lens group and a planar array detector are sequentially provided in the housing from the imaging lens to the rear; a light intensity sampling device for collecting light intensity of a light source is provided on one side of the slit of the slit sheet. The invention relates to a light emitting diode (LED) optical system comprising a slit plate, a first lens group, a first lens group, a second lens group, a first lens group, a second lens group, and a first lens group. The slit plate and the first lens group are both arranged in parallel with the imaging lens. The grating and the first lens group are arranged non-parallel. The second lens group and the grating are arranged non-parallel, and the second lens group and the first lens group are arranged non-parallel. The optical path formed by the imaging lens, the slit plate, the light intensity acquisition module, the first lens group, the grating, the second lens group and the area array detector is enclosed in a housing. The processor is arranged in the housing and is electrically connected to the moving component and the area array detector. An electronic interface for outputting data is installed on the outer wall of the housing, and the electronic interface is electrically connected to the processor.

[0017] The light intensity collection module is an optical fiber.

[0018] Preferably, the moving assembly includes a motor, a screw and a connecting block, the motor is installed in the housing and the output shaft is fixedly connected to one end of the screw, the mounting part of the imaging lens is fixedly connected to the screw nut on the screw through the connecting block, and the motor is controlled by a processor.

[0019] As an improvement, a telescopic dustproof baffle is provided on the side wall of the mounting hole.

[0020] As an improvement, an auxiliary camera is further included. The auxiliary camera is installed on one side of the imaging lens and is used to monitor the field of view of the imaging lens. The auxiliary camera is electrically connected to the processor.

[0021] As an improvement, a heat dissipation structure is provided on the casing.

[0022] As an improvement, the invention further comprises a fan arranged inside the casing.

[0023] To achieve the above objectives, the present invention further provides an imaging method of a chlorophyll fluorescence imaging system, which specifically includes:

[0024] The imaging method of the chlorophyll fluorescence imaging system specifically includes:

[0025] The processor controls the movement of the mobile component;

[0026] Driven by the mobile assembly, the imaging lens moves according to the prescribed stroke to perform push-scan acquisition of the target to be measured;

[0027] The target to be measured is focused by the imaging lens and formed into an image on the slit. The image is then collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector. The light intensity acquisition module simultaneously collects the light intensity of the light source and forms an image on the slit, is collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector.

[0028] The processor receives and stores the output information of the area array detector, and outputs the output information to the outside of the imaging system through an electronic interface.

[0029] As an improvement, when the imaging system further includes an auxiliary camera, the imaging method is:

[0030] The auxiliary camera monitors the field of view of the imaging lens and feeds the field of view information back to the processor;

[0031] The processor controls the movement of the mobile assembly;

[0032] The imaging lens moves according to the prescribed stroke driven by the mobile component to perform push-scan acquisition of the target to be measured;

[0033] The target to be measured is focused by the imaging lens and formed into an image on the slit. The image is then collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector. The light intensity acquisition module simultaneously collects the light intensity of the light source and forms an image on the slit, is collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector.

[0034] The processor receives and stores the output information of the area array detector and the output information of the auxiliary camera, and outputs the output information to the outside of the imaging system through an electronic interface.

[0035] To achieve the above objectives, the present invention also provides a chlorophyll fluorescence imaging system carried by a drone, comprising the aforementioned chlorophyll fluorescence imaging system, and the chlorophyll fluorescence imaging system is fixed on the drone.

[0036] The present invention has the following beneficial effects:

[0037] 1. The chlorophyll fluorescence imaging system based on the transmission imaging principle of the present invention adopts a prism-free imaging mode. In this mode, the monochromatic light output by the grating has a large dispersion angle, forming a structural anomaly and eliminating the existence of ghost images;

[0038] 2. The chlorophyll fluorescence imaging system based on the transmission imaging principle of the present invention can detect signals in the 650nm-800nm spectral range and simultaneously obtain images with high spectral resolution, high spatial resolution, and high signal-to-noise ratio;

[0039] 2. The chlorophyll fluorescence imaging system based on the transmission imaging principle described in the present invention adopts a lens scanning imaging method and is a fluorescence hyperspectral imaging system that integrates acquisition, control, real-time data calibration, and processing;

[0040] 3. The chlorophyll fluorescence imaging system based on the transmission imaging principle of the present invention can achieve synchronization of uplink and downlink information through a unique light intensity collection and acquisition method, which not only ensures the independence of the split light path but also achieves high consistency of the system;

[0041] 4. When the chlorophyll fluorescence imaging system based on the transmission imaging principle described in the present invention is implemented in combination with unmanned aerial vehicle technology, the application scheme of combined data calibration, splicing and real-time correction provides better efficiency for fluorescence imaging based on higher resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the system structure of an imaging spectrometer based on the Offner structure;

[0043] Figure 2This is a schematic diagram of the system structure of an imaging spectrometer based on a prism-grating-prism (PGP) combination element;

[0044] Figure 3 This is a schematic diagram of the imaging spectrometer system containing a prism;

[0045] Figure 4 This is a schematic diagram of the imaging spectrometer system containing a prism;

[0046] Figure 5 This is the working principle diagram of the grating;

[0047] Figure 6 This is an imaging effect diagram of an existing imaging spectrometer system containing a prism;

[0048] Figure 7 It is a spectrum data diagram of an existing imaging spectrometer system containing a prism;

[0049] Figure 8 It is a structural schematic diagram of the present invention;

[0050] Figure 9 It is a schematic diagram of the internal structure of the present invention;

[0051] Figure 10 It is a bottom view of the present invention;

[0052] Figure 11 It is a partial structural cross-sectional view of the present invention;

[0053] Figure 12 It is a partial structural schematic diagram of the present invention;

[0054] Figure 13 It is a partial structural schematic diagram of the present invention;

[0055] Reference numerals:

[0056] 1. Casing, 101. Upper housing, 102. Side panels, 103. Bottom panel, 104. Retractable dust shield, 105. Heat dissipation structure;

[0057] 2. Imaging lens;

[0058] 3. Slit sheet, 301. Slit;

[0059] 4. Light intensity acquisition module;

[0060] 5. Moving assembly, 501. Motor, 502. Screw, 503. Screw nut, 504. Connecting block;

[0061] 6. First lens group, 601. First convex lens, 602. Second convex lens, 603. First plano-convex lens, 604. Second plano-convex lens;

[0062] 7. Grating, 701. Grating fixing parts;

[0063] 8. Second lens group, 801. Third plano-convex lens, 802. Fourth plano-convex lens, 803. Third convex lens, 804. Fourth convex lens;

[0064] 9. Area array detector;

[0065] 10. Processor;

[0066] 11. Fan;

[0067] 12. Auxiliary camera;

[0068] 13. Electronic interface;

[0069] 14. Shell. DETAILED DESCRIPTION

[0070] Combine Figures 8 to 13 (in Figure 11-13 The present invention is described in detail in the following manner, but does not limit the claims of the present invention.

[0071] Example 1

[0072] like Figure 8-13 As shown, the chlorophyll fluorescence imaging system includes a housing, an imaging lens, a slit plate, a light intensity acquisition module, a moving component, a first lens group, a grating, a second lens group, an array detector and a processor;

[0073] in:

[0074] A mounting hole is opened on one side wall of the housing, the imaging lens is mounted on the moving assembly and the lens extends out of the housing through the mounting hole, and the width of the mounting hole is greater than the width of the imaging lens;

[0075] The moving assembly is located within the housing and is used to drive the imaging lens to move laterally along the mounting hole. The moving assembly includes a motor, a lead screw, and a connecting block. The motor is installed within the housing, and the output shaft is fixedly connected to one end of the lead screw. The mounting portion of the imaging lens is fixedly connected to the lead screw nut on the lead screw via the connecting block. The motor is controlled by a processor.

[0076] A slit sheet, a first lens group, a grating, a second lens group and an area array detector are sequentially arranged in the housing from the imaging lens to the rear;

[0077] A light intensity collection module for collecting light intensity of the light source is provided on one side of the slit of the slit sheet;

[0078] The slit plate and the first lens group are both arranged parallel to the imaging lens;

[0079] The grating is arranged non-parallel to the first lens group;

[0080] The second lens group is arranged non-parallel to the grating, and the second lens group is arranged non-parallel to the first lens group;

[0081] An optical path formed by the imaging lens, the slit plate, the light intensity acquisition module, the first lens group, the grating, the second lens group and the area array detector is enclosed in a housing;

[0082] The processor is arranged in the housing and is electrically connected to the mobile component and the area array detector;

[0083] An electronic interface for outputting data is installed on the outer wall of the casing, and the electronic interface is electrically connected to the processor.

[0084] Example 2

[0085] like Figure 8-13 As shown, considering that the hyperspectral spatial scanning imaging process of the imaging lens belongs to push-broom imaging, it is difficult for the slit to accurately judge the target to be measured, and thus it is impossible to accurately control the imaging lens to collect images of the target to be measured. An improvement is made on the basis of Example 1, and an auxiliary camera is installed on one side of the imaging lens for real-time monitoring of the field of view of the imaging lens. The auxiliary camera is electrically connected to the processor.

[0086] Example 3

[0087] like Figure 8-13 As shown, considering that the imaging systems of Example 1 and Example 2 have higher requirements on the ambient temperature, based on Example 1 or Example 2, the heat dissipation performance of the system is improved by the following means:

[0088] 1. A heat dissipation structure is provided on the casing. The heat dissipation structure can be in the form of heat dissipation holes, heat dissipation windows, etc. The shape of the heat dissipation holes can be various shapes such as round, strip or irregular. These shapes can be used alone or in combination as long as the required heat dissipation effect can be guaranteed.

[0089] 2. On the basis of the heat dissipation structure, a fan for cooling can be further provided inside the casing to dissipate heat from the imaging system through the fan. The heat generated by the casing imaging structure can be quickly discharged to the outside of the casing through the heat dissipation structure through the fan.

[0090] In summary, through the design of the heat dissipation structure and the fan, the electronic components, optical structures, etc. inside the casing will avoid the influence of high temperature when working or under the influence of the external ambient temperature, so that each unit is kept at the specified operating ambient temperature.

[0091] For the above three embodiments, the following preferred designs or improvements can be made:

[0092] 1. The housing can be constructed using an upper outer shell, a bottom panel, and at least two side panels. The bottom panel and side panels can be integrally formed. The shape of the upper outer shell, the shape of the side panels, and the number of them can be determined by the overall shape formed by assembling the "imaging lens, slit plate, light intensity acquisition module, moving assembly, first lens group, grating, second lens group, area array detector, and processor." The primary considerations are to maximize the space required for installation within the housing, reduce the overall volume of the housing, and ensure the imaging performance of the imaging system. The housing is preferably constructed of aluminum alloy, which not only reduces the overall weight of the system and facilitates in-depth application development on small airborne platforms, but also reduces costs and provides sufficient strength to ensure system stability and safety. Retractable dust shields can be installed on the side walls of the housing mounting holes to provide varying degrees of shielding, depending on the movement of the imaging lens, to prevent external dust and other contaminants from entering the housing.

[0093] 2. The imaging lens should preferably be a standard C-mount lens with a back focal length of 17.52mm. The standard C-mount lens is a standard component of the system. Lenses with different fields of view and focal lengths can be selected as needed to meet shooting requirements. The system's entrance slit is linear and 16mm long. If a standard C-mount is selected, the target surface size is between 18-20mm. If a structure similar to an F-mount is selected, the imaging effect is difficult to control and the weight will be greater than the standard C-mount. In addition, the standard C-mount is selected to be achromatic within its application band, while other F-mount-like lenses can only meet the visible band and have no achromatic ability in the near-infrared region. Considering that lens distortion is also an important factor affecting the imaging effect, because the system uses a lens scanning method, there are certain requirements for the relative size of the slit length and the lens target surface, and they should match each other.

[0094] 3. The total effective stroke length of the imaging lens driven by the moving component can be selected to be 1.2 cm. At this size, the moving component will not significantly increase the volume of the imaging system and the specifications of the imaging lens mounting hole on the casing, and can ensure that the imaging lens push-sweep range is greater than 1 cm. Considering that the system may be equipped with a drone for hovering push-sweep, in addition to the linear field of view width (determined by the slit length), there is another dimension, which is the field of view width of the scanning dimension. When the drive motor drives the lens to move, the longer the stroke, the larger the image area formed, which will also improve the overall acquisition efficiency of the system.

[0095] 4. The image of the target to be measured is focused by the imaging lens and formed on the slit. The size of the slit is preferably: 16 mm in length and 30 μm in width.

[0096] 5. The light intensity acquisition module is an optical fiber. The slit of the slit sheet has a space of about 4-5mm reserved for the installation and fixation of the optical fiber, and the core diameter of the optical fiber is fixed so that it is opposite to the slit. The optical fiber can be selected with a length of 1.5m and a core diameter of 100μm or 200μm. The core diameter of the optical fiber is selected to be 100μm or 200μm. The larger the diameter, the better the luminous flux effect; because when the system is designed, the information collected by the optical fiber is directly imaged on the incident slit, and the slit is used synchronously in the entire system to obtain the image of the target to be measured and the image of the light intensity. The sources of the target image are different, but after the slits converge, they will be recorded synchronously when entering the lens, grating, array detector, etc., which ensures the image of the target to be measured itself and the light required for its correction, realizing the ability to collect and record in the same frame.

[0097] 6. The grating can be a transmissive blazed grating, which can be installed in the housing through the grating fixing parts.

[0098] 7. The first lens group collimates the composite light information after passing through the slit to form parallel light; this parallel light will enter the grating, and the grating will disperse the light entering it to form monochromatic light at different angles.

[0099] 8. The second lens group collimates and focuses different monochromatic lights, and finally maps the spatial dimension (corresponding to the slit) and spectral dimension (grating dispersion) onto the target surface of the area array detector. On the detector target surface, although it appears that only the information of the target spatial dimension is recorded, in fact, the corresponding spectral information after grating dispersion is also hidden at different pixel points in this spatial dimension.

[0100] 9. Area array detectors can use SCMOS detectors, CCD cameras, etc., which achieve photoelectric conversion through SCMOS detectors or CCD cameras, and realize visual and digital output through these photosensitive components. Relatively speaking, SCMOS detectors can achieve a better signal-to-noise ratio.

[0101] 10. When the present invention is applied, the angle between the grating and the first lens group, and the angle between the grating and the second lens group are closely related to parameters such as the focal length of the first lens group, the number of lines on the grating, the focal length of the second lens group, the spectral response range required by the application, and the size and corresponding position center of the area array detector target surface. The selection should be based on the specific application. Taking a specific application scheme of this application as an example, the following is a detailed explanation:

[0102] The required spectral response range is 650-800nm; the detector target surface is 13.3mm*13.3mm (2048*6.5um); the spectral resolution is 0.3nm, the optical numerical aperture is F2.0; the grating dispersion area is up to 13.3mm.

[0103] The focal lengths of the first and second lens groups are both 50mm. The first lens group consists of four lens groups. Based on the index requirements, the properties and spatial positions of the lenses can satisfy the 50mm fixed focal length imaging relationship. The lens composition of the second lens group is the same as that of the first lens group, with the only difference being that they are mirror-symmetrical with the first lens group with the grating as the center. Figure 11 As shown, from the imaging lens toward the grating direction, the first lens group includes a first convex lens, a second convex lens, a first plano-convex lens, and a second plano-convex lens in sequence, and the second lens group includes a third plano-convex lens, a fourth plano-convex lens, a third convex lens, and a fourth convex lens in sequence.

[0104] The grating adopts a transmission diffraction blazed grating with high-density lines (1200l / mm) and a blazed wavelength of 840nm, which realizes spectral splitting and forms monochromatic light output. Because it needs to decompose the parallel light output by the first lens group, the monochromatic light split by the grating needs to be collimated under the action of the second lens group so that the collimated light is mapped on different pixel points of the detector. At the same time, it is necessary to ensure the characteristic spectral response range (650nm-800nm area) and extremely high spectral resolution (spectral resolution 0.3nm) and meet the requirement of the maximum dispersion area of 2048*6.5um=13.3mm. Therefore, it is necessary to have a certain optical angle relationship with the first lens group. Figure 4 According to the expression of the transmission grating mentioned in the background technology, it can be concluded that the angle between the grating and the first lens group is preferably 34.5 degrees, and the angle between the grating and the second lens group is preferably 34.5 degrees.

[0105] When the system described in the present invention is actually used, the selection and parameters of the grating, the composition and parameters of the first lens group, the composition and parameters of the second lens group, the selection and parameters of the area array detector, etc. are not limited to the above-mentioned examples, but are specifically selected and configured according to the needs of the application to meet the spectral performance output requirements of the application.

[0106] 11. The electronic interface shall include at least a USB 3.0 interface and an HDMI interface. These two interfaces are currently the most widely used interfaces and can efficiently and comprehensively transmit the output information of the area array detector to external devices (such as computers), ensuring the reliability of the imaging system's data output performance.

[0107] 2. The auxiliary camera should preferably be a 5-megapixel RGB camera with an 80° field of view, and the communication method should be USB 3.0.

[0108] 13. The fan should preferably have a working voltage of DC5V and an inward blowing design.

[0109] 14. The heat dissipation structure can be made of aluminum-magnesium alloy, which is lighter in weight than traditional aluminum material and has good strength.

[0110] 15. The entire chlorophyll fluorescence imaging system can be mounted on a drone and used for flight. The system can be powered by the drone or other power supply methods.

[0111] The following takes Example 2 as an example to illustrate the overall working principle of the present invention:

[0112] The auxiliary camera monitors the field of view of the imaging lens and feeds the field of view information back to the processor;

[0113] The processor controls the movement of the mobile component in combination with the field of view information;

[0114] The imaging lens moves according to the prescribed stroke driven by the mobile component to perform push-scanning and image acquisition on the target to be measured;

[0115] The target to be measured is focused by the imaging lens and imaged on the slit. The image is then collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector. The light intensity acquisition module simultaneously collects the light intensity of the light source (the light source can be sunlight or its special auxiliary light source, depending on the application scenario), and then images the target on the slit, is collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector.

[0116] The processor receives and stores the output information of the area array detector and the output information of the auxiliary camera, and outputs the output information to the outside of the imaging system through an electronic interface.

[0117] Based on the above working principle, we can know that:

[0118] 1. When the target to be measured is static, the imaging spectrometer (i.e., the imaging optical structure composed of a slit, a first lens group, a grating, and a second lens group) and the area array detector integrated in the casing are an integrated structure and will not move in space. When imaging, the system relies on the mobile component to drive the imaging lens to achieve spatial movement, thereby realizing hyperspectral spatial scanning imaging.

[0119] 2. The sunlight intensity information or the illumination intensity information of other light sources is collected by the illumination intensity acquisition module and enters the imaging spectrum module (i.e., the imaging optical structure composed of a slit, a first lens group, a grating, and a second lens group) and the area array detector as a light detection unit. When the area array detector collects each frame of target data, it also records the illumination intensity information of the corresponding light source, thereby realizing the acquisition of the target image and illumination at the same frame rate. That is, the detector can synchronously record the image information and illumination information of the target to be measured.

[0120] 3. The auxiliary camera, as a monitoring unit, is used to locate the area captured by the imaging system for easy observation and adjustment. It also provides a set of RGB images of the synchronized area to facilitate later data image processing. The auxiliary camera's field of view is designed to be much larger than that of the imaging lens in the imaging system. Software can be used to modify corresponding parameters to ensure that the captured area and the monitoring area are consistent. It also provides an image reference for later data image stitching, calibration, and correction, and can also serve as an auxiliary tool or diagram to provide a basis for data acquisition quality.

[0121] 4. The electronic interface serves as the external output interface of the imaging system. Its purpose is to connect the internal units (auxiliary cameras, array detectors, drive motors, etc.) with the external terminals. The data collected by the system is not transmitted to the ground terminal in real time. Instead, the real-time collected data is stored in the storage unit inside the processor for later processing. For data with a relatively simple processing and analysis process, the processor function can be expanded to directly output the data to the outside of the system after processing and analysis. If the amount of data is too large, the transmission function of the imaging system can be expanded, and a wireless transmission module can be added to transmit the real-time collected information back to the ground terminal wirelessly to achieve the purpose of real-time observation.

[0122] Based on the above working principle, the following describes the application scenarios of UAV-mounted hyperspectral imaging and details an implementation scheme of the imaging system of the present invention:

[0123] After the target image passes through the imaging lens, it is focused on the slit, which is the front-end window through which the target image enters the imaging spectrometer. Under the control of the software, the motor moves at a specific step distance (or speed), ultimately stitching together rows of data to form a complete two-dimensional array effect display. During this data acquisition process, the light intensity information collected by the light intensity acquisition module also moves synchronously with the relative displacement between the imaging spectrometer slit and the imaging lens. The light intensity information is also dispersed by the grating to form monochromatic light of different wavelengths, which is ultimately recorded on the array detector. This means that while scanning and imaging the ground target, the radiant brightness information of the ground target or the ambient light of the environment in which it is located is also recorded. The purpose of this ambient light is to perform radiant brightness correction on the brightness value of each pixel in the slit scanning area to restore the true brightness value of each pixel point, which can quantify the target attributes in quantitative units.

[0124] The push-scan imaging acquisition design of the imaging lens has an action time of about 10 seconds per push-scan imaging. The motor drives the imaging lens to move from the starting position until it completes a 1cm stroke. At this time, the entire drone-carrying system is in a hovering state in the air, and the gimbal matched with the camera will correct its posture in real time, so that the built-in push-scan imaging is in a relatively stable state, and a very high-precision hyperspectral image can be obtained.

[0125] After completing one cycle of data collection, the drone moves to the next hovering point and repeats the above steps. Generally, depending on the required flight altitude, the drone's onboard system can capture images from over 20 points. The data collected from each hovering point overlaps with adjacent points by approximately 25%. This overlap allows for data splicing from over 20 independent points to display a large image, paving the way for subsequent data processing and analysis.

[0126] The imaging system and imaging solution of the present invention have the following advantages:

[0127] 1. The chlorophyll fluorescence imaging system based on the transmission imaging principle of the present invention adopts a non-prism imaging mode. In this mode, the monochromatic light output by the grating has a large dispersion angle, forming a structural anomaly and eliminating the existence of ghost images;

[0128] 2. The chlorophyll fluorescence imaging system based on the transmission imaging principle described in the present invention can detect signals in the 650nm-800nm spectral range and simultaneously obtain fluorescence images with high spectral resolution, high spatial resolution, and high signal-to-noise ratio;

[0129] 3. The chlorophyll fluorescence imaging system based on the transmission imaging principle described in the present invention adopts a lens scanning imaging method and is a fluorescence hyperspectral imaging system that integrates acquisition, control, real-time data calibration, and processing;

[0130] 4. The chlorophyll fluorescence imaging system based on the transmission imaging principle described in the present invention can achieve synchronization of uplink and downlink information through a unique light intensity collection and acquisition method, which not only ensures the independence of the split light path but also achieves a high degree of system consistency;

[0131] 5. When the chlorophyll fluorescence imaging system based on the transmission imaging principle described in the present invention is implemented in combination with drone-mounted technology, the shooting field of view can be larger, and multiple areas can be photographed in one flight. The transmission imaging structure can have a high light transmission efficiency, thereby providing higher efficiency for fluorescence imaging.

[0132] In summary, the imaging system provided by the present invention solves the technical bottleneck problem in multiple dimensions, from the design of optical principles to the formation of imaging structures and systematic output, and realizes the specific spectrum and image acquisition mode and method for specific targets. The imaging method based on the independent innovation of the lens push-scanning can ensure the accuracy of the output results with high quality. At the same time, combined with the technical means of real-time ambient light intensity acquisition, it can conduct quantitative analysis for the research object, expanding the traditional model of only conducting qualitative research and quantitative analysis at a later stage. It provides a more comprehensive daylight-induced chlorophyll fluorescence imaging solution based on hyperspectral imaging technology for vegetation remote sensing technology, and provides a more intuitive and efficient observation platform for application fields such as environmental monitoring, carbon emissions, crop pests and diseases, crop breeding, health status assessment, yield estimation, plant photosynthesis, etc.

[0133] It is understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced with equivalents to achieve the same technical effects; as long as the use requirements are met, they are all within the scope of protection of the present invention.

Claims

1. A chlorophyll fluorescence imaging system, characterized in that: Includes chassis, imaging lens, mobile components and processor; A mounting hole is provided on a side wall of the housing; The imaging lens is mounted on the mobile assembly and extends out of the housing through a mounting hole, wherein the width of the mounting hole is greater than the width of the imaging lens; The moving assembly is located in the housing and is used to drive the imaging lens to move laterally along the mounting hole; The housing is provided with a slit sheet, a first lens group, a grating, a second lens group and an area array detector in sequence from the imaging lens to the rear; A light intensity collection module for collecting light intensity from a light source is provided on one side of the slit of the slit sheet; The slit plate and the first lens group are both arranged parallel to the imaging lens; The grating is arranged non-parallel to the first lens group; The second lens group is arranged non-parallel to the grating, and the second lens group is arranged non-parallel to the first lens group; The optical path formed by the imaging lens, the slit plate, the light intensity acquisition module, the first lens group, the grating, the second lens group and the area array detector is enclosed in a housing; The processor is arranged in the housing and is electrically connected to the mobile component and the area array detector; An electronic interface for outputting data is installed on the outer wall of the casing, and the electronic interface is electrically connected to the processor.

2. The chlorophyll fluorescence imaging system according to claim 1, characterized in that: The light intensity collection module is an optical fiber.

3. The chlorophyll fluorescence imaging system according to claim 1, characterized in that: The moving assembly includes a motor, a screw and a connecting block. The motor is installed in the housing and the output shaft is fixedly connected to one end of the screw. The mounting portion of the imaging lens is fixedly connected to the screw nut on the screw through the connecting block. The motor is controlled by a processor.

4. The chlorophyll fluorescence imaging system according to claim 1, characterized in that: A telescopic dustproof baffle is provided on the side wall of the mounting hole.

5. The chlorophyll fluorescence imaging system according to claim 1, characterized in that: It also includes an auxiliary camera, which is installed on one side of the imaging lens and is used to monitor the field of view of the imaging lens. The auxiliary camera is electrically connected to the processor.

6. The chlorophyll fluorescence imaging system according to claim 1, characterized in that: The casing is provided with a heat dissipation structure.

7. The chlorophyll fluorescence imaging system according to claim 6, characterized in that: The invention also includes a fan arranged inside the casing.

8. The imaging method of the chlorophyll fluorescence imaging system according to claim 1, comprising: The processor controls the movement of the mobile component; Driven by the mobile assembly, the imaging lens moves according to the prescribed stroke to perform push-scan acquisition of the target to be measured; The target to be measured is focused by the imaging lens and imaged on the slit. Then, it is collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector. The light intensity acquisition module simultaneously collects the light intensity of the light source, and outputs the light intensity image to the area array detector after slit imaging, collimation by the first lens group, grating dispersion, and collimation by the second lens group; The processor receives and stores the output information of the area array detector, and outputs the output information of the area array detector to the outside of the imaging system through an electronic interface.

9. The imaging method of the chlorophyll fluorescence imaging system according to claim 5, comprising: The auxiliary camera monitors the field of view of the imaging lens in real time and feeds the field of view information back to the processor; The processor controls the movement of the mobile assembly; Driven by the mobile assembly, the imaging lens moves according to the prescribed stroke to perform push-scan acquisition of the target to be measured; The target to be measured is focused by the imaging lens and imaged on the slit. Then, it is collimated by the first lens group, dispersed by the grating, and collimated by the second lens group before being output to the area array detector. The light intensity acquisition module simultaneously collects the light intensity of the light source, and outputs the light intensity image to the area array detector after slit imaging, collimation by the first lens group, grating dispersion, and collimation by the second lens group; The processor receives and stores the output information of the area array detector and the output information of the auxiliary camera, and outputs the output information to the outside of the imaging system through an electronic interface.

10. A chlorophyll fluorescence imaging system carried by an unmanned aerial vehicle, characterized in that: The chlorophyll fluorescence imaging system comprises the chlorophyll fluorescence imaging system according to any one of claims 1 to 7, wherein the chlorophyll fluorescence imaging system is fixed on a drone.

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