CN110031865B - Vegetation detection binary channels fluorescence laser radar system - Google Patents
Vegetation detection binary channels fluorescence laser radar system Download PDFInfo
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- CN110031865B CN110031865B CN201910397408.XA CN201910397408A CN110031865B CN 110031865 B CN110031865 B CN 110031865B CN 201910397408 A CN201910397408 A CN 201910397408A CN 110031865 B CN110031865 B CN 110031865B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
- G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
- G01N21/64—Fluorescence; Phosphorescence
- G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
- G01N21/643—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes" non-biological material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention provides a vegetation detection double-channel fluorescent laser radar system, which comprises a laser emission unit, a ranging unit, a scanning unit, a receiving detection unit and a time sequence control unit, wherein the laser emission unit emits ultraviolet laser and is used as excitation light of vegetation fluorescence and ranging laser of the ranging unit; the laser emission unit generates ultraviolet laser and emits the ultraviolet laser through the scanning unit, the receiving and detecting unit separates and outputs the ultraviolet laser echo to the ranging unit, and the receiving and detecting unit processes the fluorescent signal by itself; the receiving and detecting unit adopts an optical telescope to realize optical condensation, adopts a dichroic lens to separate ultraviolet laser echoes and transmit fluorescent signals, and respectively enters two photoelectric detectors corresponding to vegetation fluorescent characteristic wave bands through an optical beam splitting module after being coupled by a coupling optical fiber. The invention supports the synchronous acquisition of the laser point cloud space information and the fluorescence dual-channel information of the vegetation target, and completes the integrated monitoring of the vegetation space structure and the physiological state.
Description
Technical Field
The invention belongs to the technical field of mapping remote sensing, and particularly relates to a vegetation detection double-channel fluorescent laser radar system.
Background
The laser radar technology has outstanding advantages in the field of earth observation, in particular to the rapid detection of a three-dimensional space structure of vegetation. The point cloud data formed by the laser radar echo signals can provide vegetation space distribution information, but is limited by single wavelength, and the spectral characteristics of vegetation are difficult to acquire.
The active laser-induced fluorescence technology is applied to vegetation to generate fluorescence characteristic peaks, and the generation of fluorescence is derived from radiation energy level transition performed in photosynthesis sites inside the vegetation. Photosynthesis of vegetation is an important physiological activity of vegetation and is closely related to its physiological state. Therefore, the fluorescence can be used as an early probe for photosynthesis and health conditions of vegetation to indicate physiological states of vegetation growth, biochemical parameter stress, diseases and insect pests and the like, can be used for early forecasting when the vegetation is subjected to internal or external stress factors, quantitatively, rapidly and nondestructively monitor the physiological and growth states of the vegetation, and has important significance for vegetation ecological research and precise agricultural application.
However, current detection imaging of plant fluorescence signals cannot be realized to explain the distribution of the fluorescence signals in the form of point clouds, that is, the advantages of laser radar space detection and the advantages of fluorescence spectrum cannot be combined. According to the invention, the dual-channel fluorescent laser radar system aims at vegetation detection targets, adopts an ultraviolet laser light source, and simultaneously induces plant fluorescence to perform biochemical state monitoring by reflecting echoes to perform space ranging, so that a dual detection mechanism of reflecting ranging and laser-induced fluorescence is realized. The system adopts single-band ultraviolet laser as excitation light of ranging light and vegetation fluorescence, and two channel receiving plants receive fluorescence characteristic peak signals in 685nm and 740nm wave bands on the basis of single-band ranging, so that synchronous observation of vegetation target point cloud and fluorescence double-channel characteristics is realized, and further integrated monitoring of a space structure and a physiological state of a vegetation target is realized.
Disclosure of Invention
The invention aims to provide a vegetation detection double-channel fluorescent laser radar system which realizes integrated monitoring of a vegetation target space three-dimensional structure and fluorescent characteristics.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a vegetation detection double-channel fluorescent laser radar system comprises a laser emission unit, a ranging unit, a scanning unit, a receiving detection unit and a time sequence control unit, wherein the time sequence control unit is respectively connected with the laser emission unit, the ranging unit, the scanning unit and the receiving detection unit, and the laser emission unit emits ultraviolet laser and is used as excitation light of vegetation fluorescence and ranging laser of the ranging unit;
the laser emission unit generates ultraviolet laser and emits the ultraviolet laser through the scanning unit, the receiving and detecting unit separates and outputs the ultraviolet laser echo to the ranging unit, and the receiving and detecting unit processes the fluorescent signal by itself;
the receiving and detecting unit comprises an optical telescope, a dichroic lens, a coupling optical fiber, an optical light splitting module and corresponding photoelectric detectors for providing double-channel detection, wherein the optical telescope is used for realizing optical light condensation, the dichroic lens is used for separating ultraviolet laser echoes and transmitting fluorescent signals, and the coupling optical fiber is used for coupling the ultraviolet laser echoes and transmitting fluorescent signals to the photoelectric detectors corresponding to two vegetation fluorescent characteristic wave bands through the optical light splitting module.
And the ultraviolet laser emission optical axis coincides with the central axis of the optical telescope in the receiving and detecting unit.
Furthermore, a turning mirror is provided in the scanning unit.
And the turning mirror adopts an aluminum film total reflection mirror.
And the dichroic mirror is placed at 135 degrees with the central axis of the optical telescope after being placed at the converging port of the optical telescope.
Furthermore, the two vegetation fluorescence characteristic bands are 685nm and 740nm.
And the distance measuring unit is triggered and received outside through the time sequence control unit, an optical telescope in the receiving and detecting unit receives and separates ultraviolet distance measuring echo and outputs the ultraviolet distance measuring echo to the distance measuring unit, the center of an incident scanning rotating mirror is reflected to a vegetation target when laser is emitted so as to realize scanning by rotating a turntable where the rotating mirror is positioned, and distance data of the distance measuring unit and scanning angle pulses of the scanning unit jointly form vegetation three-dimensional space structure data.
And the time sequence control unit outputs a digital pulse signal, completes distance detection, turning mirror scanning and photoelectric conversion action of the double-channel detector on a time sequence, and records vegetation target distance, turning mirror movement step length and integral intensity of the double-wavelength fluorescent signal.
The invention has the following differences and effects with the prior art: the dual-channel fluorescent laser radar system breaks through the limitation of single space detection capability of the traditional single-band laser radar, realizes detection of dual-wavelength fluorescent characteristics of vegetation on the basis of single-band laser ranging, adopts a reflection ranging and laser-induced fluorescence dual-detection mechanism, can support synchronous acquisition of laser point cloud space information and fluorescence dual-channel information of a vegetation target, realizes integrated monitoring of a vegetation target space structure and physiological state, and can be widely applied to the fields of digital mapping, vegetation remote sensing and the like.
Drawings
Fig. 1 is a schematic diagram of a system structure according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a coaxial design of a system optical path according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a ranging unit according to an embodiment of the invention.
Fig. 4 is a schematic diagram of a design of a spectroscopic probe optical path according to an embodiment of the present invention.
Detailed Description
The technical scheme of the invention is described in detail below with reference to the accompanying drawings and examples.
The invention provides a vegetation detection double-channel fluorescent laser radar system, wherein a laser emission unit adopts a pumping tunable laser to pump frequency multiplication ultraviolet laser, and is used as excitation light of vegetation fluorescence and ranging laser of a ranging unit. The system consists of a laser transmitting unit, a ranging unit, a scanning unit, a receiving detection unit and a time sequence control unit, is similar to the existing single-channel laser radar system, but the system is improved in each unit to realize pumping frequency doubling ultraviolet laser of a pumping tunable laser as ranging laser for distance measurement of the ranging unit, and meanwhile the ultraviolet laser acts on vegetation as excitation light to generate characteristic fluorescence based on a vegetation laser-induced fluorescence mechanism. The invention completes a vegetation detection double-channel fluorescent laser radar system for actively imaging vegetation fluorescent point cloud through system construction, optical design and time sequence control. The distance measuring unit is triggered and received outside through the time sequence control unit, an optical telescope in the receiving and detecting unit receives and separates ultraviolet distance measuring echo and outputs the ultraviolet distance measuring echo to the distance measuring unit, when laser is emitted, the center of an incident scanning rotating mirror reflects to a vegetation target to rotate a turntable where the rotating mirror is located to realize scanning, and distance data of the distance measuring unit and scanning angle pulses of the scanning unit jointly form vegetation three-dimensional space structure data.
Referring to fig. 1, the structural distribution of a vegetation detection dual-channel fluorescent laser radar system in the embodiment of the invention mainly comprises a laser transmitting unit 1, a scanning unit 2, a ranging unit 3, a receiving and detecting unit 4 and a time sequence control unit 5.
As shown in fig. 1, a laser emitting unit 1 generates ultraviolet laser and emits the ultraviolet laser through a scanning unit 2, a receiving and detecting unit 4 outputs the ultraviolet laser echo to a ranging unit 3 in a separated manner, and the receiving and detecting unit 4 processes a fluorescence signal by itself. The time sequence control unit 5 is connected with the laser transmitting unit 1, the scanning unit 2, the ranging unit 3 and the receiving detection unit 4 through communication connection wires at the same time, and scanning detection is performed through the multichannel time sequence pulse control system.
The laser emission unit 1 comprises a laser module, a frequency multiplication module, a light splitting module, an ultraviolet high-reflection lens, a first total reflection lens 6 and a second total reflection lens 7.
In an embodiment, the vegetation detection dual-channel fluorescent laser radar system emits ultraviolet laser light through pumping a pump tunable laser. The laser comprises a laser module, a frequency multiplication module and a light splitting module. The laser module pumps out 1064nm fundamental frequency laser with a certain repetition frequency, and the laser with 532nm and 355nm wavelengths is obtained through frequency multiplication of the frequency multiplication crystal of the frequency multiplication module and then is input into the light splitting module. The light splitting module separates 355nm laser light source, and then the redundant laser is further filtered by the ultraviolet high-reflection lens. The 355nm ultraviolet laser emitted by the laser emitting unit is used as fluorescence excitation light and ranging laser.
The scanning unit 2 comprises a rotary table, an electric cabinet and a rotary mirror 8. The electric cabinet is connected with the rotary table, and the rotary mirror 8 is arranged on the rotary table of the scanning unit and can rotate along with the rotary table. The turning mirror 8 is preferably an aluminum film total reflection mirror, and has the advantages of large receiving field, wide reflection wavelength range, small influence on reflectivity due to wavelength and incidence angle, high reflectivity and low price.
Referring to fig. 2, an ultraviolet laser emission optical axis of a vegetation detection dual-channel fluorescent laser radar system in an embodiment of the invention coincides with a central axis of an optical telescope in a receiving detection unit, so as to form a coaxial design. The coaxial optical design comprises in particular a first total reflection mirror 6, a second total reflection mirror 7, a turning mirror 8, an optical telescope 9 and a dichroic mirror 10. The first total reflection lens 6 is placed at an angle of 45 degrees with incident ultraviolet laser, the second total reflection lens 7 is placed at the center of a receiving field of view of the optical telescope of the receiving and detecting unit and at an angle of 45 degrees with the central axis of the telescope, the rotating lens 8 is placed at an angle of 45 degrees with the laser from the second total reflection lens 7 and can change the angle along with the rotation of the bottom turntable, the central axis of the optical telescope 9 coincides with the optical axis of the second total reflection lens 7 to the rotating lens 8 to form an optical coaxial, ultraviolet laser echo and vegetation fluorescence can be received at the same time, single-point synchronous acquisition of distance and fluorescence dual-wavelength are supported, and signal to noise ratio can be effectively improved. The dichroic mirror 10 is placed at 135 degrees to the central axis of the optical telescope 9 after being placed at the converging port of the optical telescope 9.
In specific implementation, the laser emission unit pumps and emits ultraviolet laser, and the ultraviolet laser passes through the first total reflection lens 6 and the second total reflection lens 7 in turn at an incidence angle of 45 degrees in the optical structure of the system, and also enters the center of the turning mirror 8 at an incidence angle of 45 degrees. The turntable connected with the turning mirror 8 receives the digital signals transmitted by the time sequence control unit, completes the step scanning of the laser beam in two directions of space horizontal and vertical, returns step pulse signals and outputs the step pulse signals to the system.
Ultraviolet laser is received in a vegetation scene, and characteristic fluorescence is generated in a vegetation internal photoreaction center based on a laser-induced fluorescence mechanism. The optical signal received by the turning mirror 8 comprises an ultraviolet excitation light echo and a vegetation characteristic continuous spectrum fluorescent signal. The turning mirror 8 receives the optical signal into the field of view of the optical telescope 9 by large field reflection and focuses it on the mirror focal plane. At the receiving outlet of the optical telescope, based on the reflection and transmission characteristics of the dichroic mirror 10 in different wave bands, the ultraviolet laser echo signals are separated and output to the ranging unit, and the fluorescence continuous spectrum signals are transmitted to the coupling optical fiber.
The ultraviolet laser from the laser emitting unit acts on the vegetation surface to generate characteristic fluorescence, and the transmission of the ultraviolet laser echo and the fluorescence signal in space is not unidirectional. The back-scattering and fluorescence scattering properties of such echo signals are regular in spatial distribution. The echo signals in each direction will be received by the large field of view of the turning mirror 8 and reflected into the field of view of the optical telescope 9. The total reflection mirror 7 is positioned right at the center of the field of view of the optical telescope 9, but the small round field of view of the receiving field of view on the telescope side is not light-transmitting itself, so the front placement of the total reflection mirror 7 has no effect. Focusing is convenient for optical fiber coupling.
The receiving and detecting unit 4 comprises an optical telescope 9, a dichroic mirror 10, coupling fibers, an optical splitting module and photodetectors 19, 23. The optical spectroscopic module includes a first spectroscopic filter 16, a second spectroscopic filter 20, a first narrowband filter 17, a second narrowband filter 21, a first focusing lens 18, and a second focusing lens 22.
Referring to fig. 4, a receiving and detecting unit of a dual-channel fluorescent laser radar system for vegetation detection according to an embodiment of the present invention includes an optical telescope 9, a dichroic mirror 10, a coupling optical fiber, and an optical spectroscopic module and a corresponding photodetector for dual-channel detection in fig. 2. The optical spectroscopic module includes a first spectroscopic filter 16, a second spectroscopic filter 20, a first narrowband filter 17, a second narrowband filter 21, a first focusing lens 18, and a second focusing lens 22; the photodetectors comprise a first photodetector 19 and a second photodetector 23.
The optical telescope 9 focuses on the coupling entrance of the coupling optic fibre, and the dichroic mirror 10 sets up between the coupling entrance of optical telescope 9 and coupling optic fibre, and the ultraviolet echo output is exported to the range unit through dichroic mirror 10 reflection between optical telescope 9 and the coupling optic fibre, also prevents that the highlight from causing the harm to the detector. The coupling optical fiber is used for coupling and emitting continuous spectrum fluorescence signals, the continuous spectrum fluorescence signals are transmitted through the first light splitting filter 16 and enter the first narrow-band filter 17 to be filtered to obtain 685nm wavelength fluorescence, and the fluorescence enters the first photoelectric detector 19 through the first focusing lens 18; the light reflected by the first beam splitter 16 is incident on the second beam splitter 20, reflected by the second narrow band filter 21, filtered to obtain 740nm fluorescence, and enters the second photodetector 23 by the second focusing lens 22. The first photodetector 19 and the second photodetector 23 collect and output two-channel single-band signal photoelectric analog-to-digital conversion. The ranging unit 3 comprises an avalanche photodiode 12, a narrow-band filter 13, a high-speed collector 14 and a counter 15, wherein the avalanche photodiode 12, the high-speed collector 14 and the counter 15 are sequentially connected, and ultraviolet laser echoes are emitted into the avalanche photodiode 12 through the narrow-band filter 13. Avalanche photodiode 12 is abbreviated APD.
Referring to fig. 3, a ranging unit of a dual-channel fluorescent laser radar system for vegetation detection according to an embodiment of the present invention includes an avalanche photodiode 12, a narrowband filter 13, a high-speed collector 14, and a counter 15. The third digital delay generator 11 is connected with the avalanche photodiode 12 to trigger photoelectric detection, and meanwhile the avalanche photodiode 12 receives ultraviolet echoes which are separated and reflected by the dichroic mirror 10 in the detection receiving unit 4 and then filtered by the narrow-band filter 13. The avalanche photodiode 12 is connected to a high-speed collector 14 and a counter 15, and collects and records laser pulse waveforms.
The time sequence control unit 5 comprises a third-party digital delay generator 11 and BNC connecting lines, wherein the third-party digital delay generator 11 of the time sequence control unit outputs 4 paths of channel TTL amplitude pulse signals through the BNC connecting lines, and the third-party digital delay generator 11 is respectively connected to a laser module of the laser transmitting unit 1, an electric cabinet of the scanning unit 2, an avalanche photodiode 12 of the ranging unit 3 and photodetectors 19 and 23 in the receiving and detecting unit 4. The system can be connected to external interfaces of all parts, outputs digital pulse signals, completes system distance detection, turning mirror scanning and actions of a photoelectric conversion system of the double-channel detector on a time sequence, and records vegetation target distance, turning mirror movement step length and integral intensity of 685nm and 740nm double-wavelength fluorescent signals.
In an embodiment, the third digital delay generator 11 in the timing control unit transmits a pulse signal to trigger the avalanche photodiode 12 in the ranging unit to start detection. The ultraviolet laser is emitted to a vegetation target through a system optical structure and a scanning unit, and then a backward scattering signal enters a receiving and detecting unit and is reflected to a ranging unit through a dichroic mirror 10. The ultraviolet light echo enters the avalanche photodiode 12 through the narrowband filter 13. The high-speed collector 14 connected with the avalanche photodiode 12 collects photoelectric signals, and converts the time interval of the ultraviolet echo signals into distance information through the counter 15 to finish the distance measurement of a single point.
In specific implementation, the time sequence control unit 5 is connected with the laser transmitting unit 1, the scanning unit 2, the ranging unit 3 and the receiving and detecting unit 4, and transmits digital signals to fulfill the aim of controlling the system to operate in a certain time sequence. The time sequence control unit relies on the third-party digital delay generator 11 to construct multi-channel time sequence control, and the control system sequentially detects and records the distance of a single point in a vegetation scene and the fluorescence intensity of the double channels. The third party digital delay generator 11 of the time sequence control unit outputs 4 paths of channel TTL amplitude pulse signals to each unit through BNC connecting lines. When the system scans to a single point, a laser module in the laser transmitting unit receives channel 1 pulse signal pumping and frequency multiplication light splitting to transmit ultraviolet laser. The channels 2, 3 connect the distance measuring unit and the receiving detection unit, and after a short time delay is set, the avalanche photodiode 12 and the photodetectors 19, 23 detect the ultraviolet echo signal and the fluorescence two-channel signal, respectively. The channel 4 is connected with an electric cabinet in the scanning unit, and after a certain time delay, the electric cabinet is triggered to control the turntable to rotate by outputting a pulse, so that the system scans to the next point. And each unit controlled by the time sequence control unit executes the point-to-point distance value returned by the system action, the double-channel fluorescence intensity value and the step length value of the rotating mirror stepping motion to record and output the values to the system.
The preferred product types proposed in each section are: the laser comprises a laser module, a frequency multiplication module and a light splitting module, and the optimal model is as follows: surelite I-20. The avalanche photodiode 11 is preferably of the product type: thorlabs APD410A2/M. The high-speed collector 13 is preferably of the type: teledyne SP Devices ADQ412 and 412. The counter 14 is preferably of the type: national Instruments PXIe-6612. The photodetectors 18, 20 are preferably of the type: licel SP32-200-2758. The preferred model of the rotary table: zolix Rauk100, rauk200. Electric cabinet preferred model: zolix MC600-2B. The third party digital delay generator 11 is preferably of the type: stanford Research Systems DG645 and 645. The rotating mirror 8 is preferably of the type: zolix TFAEFL-300S06-P.
By adopting the scheme, the invention can realize integrated monitoring of the vegetation space structure and physiological state information, and can form vegetation fluorescent imaging taking point cloud as a form and basis. The vegetation detection double-channel fluorescent laser radar system forms vegetation point cloud fluorescent data with three-dimensional space characteristics and double-wavelength fluorescent spectrum characteristics as a whole, can finish point cloud fluorescent spectrum imaging of a vegetation target, and realizes space characterization of the physiological state of the vegetation target.
The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical method of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the spirit of the present invention.
Claims (7)
1. The utility model provides a vegetation detection binary channels fluorescence laser radar system, includes laser emission unit, range unit, scanning unit, receives detection unit and time sequence control unit, and time sequence control unit connects laser emission unit, range unit, scanning unit and receives detection unit, its characterized in that respectively: the laser emission unit emits ultraviolet laser, and simultaneously serves as excitation light of vegetation fluorescence and ranging laser of the ranging unit, so that the reflection echo of the ultraviolet laser light source is used for space ranging, and the vegetation fluorescence is induced to be monitored in a biochemical state, and a reflection ranging and laser-induced fluorescence dual-detection mechanism is provided; on the basis of single-band ranging, two channels are added to receive fluorescence characteristic peak signals of plants in different bands, so that synchronous observation of vegetation target point cloud and fluorescence double-channel characteristics is realized, and further integrated monitoring of the spatial structure and physiological state of vegetation targets is realized;
the laser emission unit generates ultraviolet laser and emits the ultraviolet laser through the scanning unit, the receiving and detecting unit separates and outputs the ultraviolet laser echo to the ranging unit, and the receiving and detecting unit processes the fluorescent signal by itself;
the receiving and detecting unit comprises an optical telescope, a dichroic mirror, a coupling optical fiber, an optical light splitting module and a photoelectric detector for providing double-channel detection correspondingly, ultraviolet laser is received in a vegetation scene, characteristic fluorescence is generated in a vegetation internal photoreaction center based on a laser-induced fluorescence mechanism, the received optical signal comprises an ultraviolet excitation light echo and a vegetation characteristic continuous spectrum fluorescence signal, optical focusing is realized by the optical telescope, the ultraviolet laser echo is separated by the dichroic mirror and output to the ranging unit and the fluorescence signal is transmitted, and the transmitted fluorescence signal is coupled by the coupling optical fiber and then respectively enters the photoelectric detectors corresponding to two vegetation fluorescence characteristic wave bands through the optical light splitting module;
the ranging unit comprises an avalanche photodiode, a narrow-band filter, a high-speed collector and a counter, wherein the avalanche photodiode, the high-speed collector and the counter are sequentially connected, and ultraviolet laser echoes are emitted into the avalanche photodiode through the narrow-band filter;
the laser emission unit is used for pumping and emitting ultraviolet laser, sequentially passes through the first total reflection lens and the second total reflection lens at an incidence angle of 45 degrees in the optical structure of the system, and also enters the center of the rotating lens at the incidence angle of 45 degrees; the turntable connected with the turning mirror receives the digital signals transmitted by the time sequence control unit, completes the step-by-step scanning of the laser beam in two directions of space horizontal and vertical, returns step pulse signals and outputs the step pulse signals to the system;
the fluorescence characteristic wave bands of the two vegetation are 685nm and 740nm; the optical beam splitting module comprises a first beam splitting filter, a second beam splitting filter, a first narrow-band filter, a second narrow-band filter, a first focusing lens and a second focusing lens; the photoelectric detector comprises a first photoelectric detector and a second photoelectric detector;
the optical telescope is focused at the coupling entrance of the coupling optical fiber, the dichroic mirror is arranged between the optical telescope and the coupling entrance of the coupling optical fiber, the ultraviolet echo is reflected between the optical telescope and the coupling optical fiber through the dichroic mirror and output to the ranging unit, and the damage of strong light to the detector is prevented; coupling and emitting continuous spectrum fluorescent signals through a coupling optical fiber, and passing through a first light splitting filter; transmitting and entering a first narrow-band filter to obtain 685nm wavelength fluorescence, and entering a first photoelectric detector through a first focusing lens; the reflected light rays passing through the first light splitting filter are incident into the second light splitting filter to be reflected and enter the second narrow-band filter to be filtered to obtain 740nm fluorescence, the fluorescence enters the second photoelectric detector through the second focusing lens, and the first photoelectric detector and the second photoelectric detector acquire and output two-channel single-band signal photoelectric analog-to-digital conversion.
2. The vegetation detection dual channel fluorescent lidar system of claim 1, wherein: the ultraviolet laser emission optical axis coincides with the optical telescope axis in the receiving detection unit.
3. The vegetation detection dual channel fluorescent lidar system of claim 2, wherein: the scanning unit is internally provided with a turning mirror, the backscattering and fluorescence scattering characteristics of echo signals are regular in space distribution, the echo signals in all directions are received by a large view field of the turning mirror and reflected into the view field of the optical telescope, and the total reflection mirror is just positioned at the center of the view field of the optical telescope and is coupled by optical fibers after focusing.
4. The vegetation detection dual channel fluorescent lidar system of claim 3, wherein: the turning mirror adopts an aluminum film total reflection mirror.
5. The vegetation detection dual channel fluorescent lidar system of claim 2, wherein: the dichroic lens is placed at 135 degrees with the central axis of the optical telescope after being placed at the converging port of the optical telescope.
6. The vegetation detection dual channel fluorescent lidar system of claim 3 or 4 or 5, wherein: the distance measuring unit is triggered and received outside through the time sequence control unit, an optical telescope in the receiving and detecting unit receives and separates ultraviolet distance measuring echo and outputs the ultraviolet distance measuring echo to the distance measuring unit, when laser is emitted, the center of an incident scanning rotating mirror reflects to a vegetation target to rotate a turntable where the rotating mirror is located to realize scanning, and distance data of the distance measuring unit and scanning angle pulses of the scanning unit jointly form vegetation three-dimensional space structure data.
7. The vegetation detection dual channel fluorescent lidar system of claim 6, wherein: the time sequence control unit outputs a digital pulse signal, completes distance detection, turning mirror scanning and photoelectric conversion action of the double-channel detector on a time sequence, and records vegetation target distance, turning mirror movement step length and integral intensity of the double-wavelength fluorescent signal.
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| CN110673159B (en) * | 2019-09-30 | 2023-04-07 | 中国海洋大学 | Active radar hyperspectral detection system and method of unmanned aerial vehicle for marine environment monitoring |
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