Laser radar device for synchronously detecting reflected light and fluorescence signals of vegetation

Abstract

The invention discloses a laser radar device structure for synchronously detecting reflected light and fluorescence signals of vegetation. The laser radar device structure is characterized in that a laser emission unit emits monochromatic short-wave high-energy laser pulses which are irradiated to the vegetation through a coated total reflective mirror; the echo receiving unit and the spectrum light splitting unit are used for acquiring and carrying out light splitting processing on a short-wave reflected light signal reflected by a vegetation target and a wide-spectrum fluorescence signal generated by vegetation excitation; the spectral data acquisition unit performs signal conversion and recording on the received reflected light signal and the fluorescence signal; the sequential control unit is connected with the laser emission unit and the spectral data acquisition unit through a data transmission line; and the upper computer controls the laser emission unit, the spectral data acquisition unit and the time sequence control unit through connecting wires. According to the invention, vegetation reflected light and fluorescence bispectrum signal integrated imaging detection is realized while accurate spatial three-dimensional information of vegetation is acquired by a laser radar technology, and vegetation remote sensing monitoring and practical application are better served.

Description

Technical Field

[0001] The invention belongs to the technical field of laser radar remote sensing detection, and relates to a laser radar device for synchronously detecting vegetation reflected light and fluorescence signals. Background Art

[0002] As an active remote sensing detection technology, LiDAR can obtain accurate spatial three-dimensional information of vegetation targets, which is of great benefit to vegetation phenotypic detection, three-dimensional reconstruction, identification and classification. However, traditional LiDAR technology only emits single-wavelength lasers, and conducts vegetation remote sensing detection research by obtaining three-dimensional spatial information of vegetation and single-wavelength echo intensity. However, in various application scenarios such as vegetation growth state detection, biochemical component inversion, nutritional stress monitoring, and pest control, the ability of vegetation remote sensing monitoring based on three-dimensional spatial information and single-wavelength echo intensity is limited. To this end, domestic and foreign researchers have developed a variety of vegetation remote sensing detection technologies and methods based on LiDAR technology, such as active and passive fusion technology, multi- / hyperspectral LiDAR technology, and fluorescent LiDAR technology, to obtain more and wider range of spectral information to improve the monitoring ability of vegetation, but most of these technical means obtain spectral information of a single spectral dimension, and cannot achieve vegetation remote sensing monitoring of more dimensional spatial spectrum information.

[0003] As important spectral features in vegetation remote sensing detection, the spectral characteristics and changes of reflected light spectrum and fluorescence spectrum are closely related to vegetation growth status, physiological and biochemical components, nutritional stress, etc. At present, researchers at home and abroad use various types of sensors to obtain vegetation reflected light spectrum or fluorescence spectrum, analyze spectral characteristics and changes, and then carry out vegetation remote sensing monitoring, which has become the mainstream. However, single-dimensional spectral information can only reflect the spectral characteristics of vegetation in a certain spectral dimension, and cannot fully display the physiological and biochemical information of vegetation. Therefore, compared with single-dimensional spectral information, combining vegetation reflected light spectrum and fluorescence spectrum to carry out vegetation remote sensing monitoring can achieve the effect of 1+1>2, and organically combining the advantages of the two spectral characteristics can play an important role in vegetation physiological and biochemical state detection, pest and disease control, and nutritional stress monitoring.

[0004] However, the existing laser radar technology has not yet truly achieved the synchronous detection and acquisition of vegetation reflected light spectrum and fluorescence spectrum information, that is, the integrated synchronous detection of vegetation reflected light spectrum and fluorescence spectrum can be completed through a single device. Through the laser radar device for synchronously detecting vegetation reflected light and fluorescence signals of the present invention, the integrated synchronous detection of vegetation reflected light spectrum and fluorescence spectrum can be achieved, and considering that the intensity of the stimulated fluorescence signal is weak, the single photon counting technology is used to improve the fluorescence signal detection sensitivity, thereby realizing the integrated remote sensing monitoring of vegetation target spatial information, reflected light spectrum information, and fluorescence spectrum information, which has great research potential and commercial value in the fields of smart agriculture, forest management, biomass estimation, etc. Summary of the invention

[0005] (I) Purpose of the invention

[0006] The purpose of the present invention is to provide a laser radar device for synchronously detecting vegetation reflected light and fluorescence signals, to realize integrated remote sensing monitoring of vegetation target spatial information, reflected light spectral information, and fluorescence spectral information, and to comprehensively improve the laser radar vegetation remote sensing detection performance and application scope.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention provides a laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals, which includes: a laser emitting unit, an echo receiving unit, a spectral spectrometer unit, a spectral data acquisition unit, a timing control unit and a host computer; the laser emitting unit emits a monochromatic short-wave high-energy laser pulse which is irradiated to the vegetation through a coated total reflector; the echo receiving unit and the spectral spectrometer unit acquire and perform spectroscopic processing on the short-wave reflected light signal reflected by the vegetation target and the wide-spectrum fluorescence signal generated by the vegetation when stimulated; the spectral data acquisition unit performs signal conversion and records the received reflected light signal and the fluorescence signal; the timing control unit connects the laser emitting unit and the spectral data acquisition unit through a data transmission line; and the host computer controls the laser emitting unit, the spectral data acquisition unit and the timing control unit through the connecting line.

[0009] Among them, the laser emitting unit is connected to the timing control unit, and the laser pulse emission is controlled according to the periodic timing signal output generated by the timing control unit, and the frequency and pulse width parameters of the emitted laser are set by the host computer to meet the needs of different detection targets.

[0010] Among them, the laser emitting unit includes a laser module, a water cooler, a modulation module, and a total reflection mirror L1; the modulation module enables the laser module to emit a monochromatic short-wave laser with a set frequency and a set pulse energy, and then the laser beam is reflected to the surface of the vegetation through the coated total reflection mirror L1 arranged at a 45° angle; the thermal effect caused by the monochromatic short-wave laser emitted by the laser module is circulated and cooled by the water cooler to achieve stable output of laser energy.

[0011] Among them, the echo receiving unit includes an optical telescope, a focusing lens, and a collimator. The echo receiving unit uses the optical telescope and the focusing lens to optically focus the mixed spectrum composed of the single-band reflected light of the vegetation and the wide-spectrum fluorescence signal, and uses a collimator to collimate the received mixed spectrum signal, and then transmits it to the spectrum splitting unit through space light beam or optical fiber transmission; the optical telescope and the total reflection mirror L1 in the laser emitting unit are placed at 45°, and the laser emission light path is reflected by the 45° total reflection mirror placed at the front end of the optical telescope to ensure that the laser emission light path, the vegetation reflected light signal and the excitation fluorescence signal, and the central axis of the optical telescope are all on the same axis. After focusing the mixed spectrum signal at the receiving end of the optical telescope, a collimator is used to collimate the focused light beam so that the light beam enters the spectrum splitting unit in parallel.

[0012] Wherein, the spectral spectrometer unit includes a dichroic mirror L2, a dichroic mirror L3, a narrow-band filter L4, a narrow-band filter L6, a narrow-band filter L7, and three focusing lenses L5; the narrow-band filter L4 and a focusing lens L5 are arranged in sequence on the reflective side of the dichroic mirror L2, the dichroic mirror L3 is arranged on the transparent side of the dichroic mirror L2, the narrow-band filter L6 and a focusing lens L5 are arranged in sequence on the reflective side of the dichroic mirror L3, and the narrow-band filter L7 and a focusing lens L5 are arranged on the transparent side of the dichroic mirror L3; the spectral spectrometer unit is used to separate the mixed spectral signal obtained by the echo receiving unit, separate the single-wavelength reflected light signal and the dual-wavelength fluorescent band signal, and use the focusing lens to transmit the separated light signal to the photoelectric detector of the spectral data acquisition unit.

[0013] Among them, the central wavelengths of narrow-band filter L4, narrow-band filter L6, and narrow-band filter L7 correspond to the laser emission wavelength and two vegetation fluorescence characteristic bands of 685nm and 740nm respectively.

[0014] Among them, the spectral data acquisition unit includes photomultiplier tube 1 PMT1, photomultiplier tube 2 PMT2, photomultiplier tube 3 PMT3 and ADC, TDC acquisition board, photomultiplier tube 1 PMT1, photomultiplier tube 2 PMT2, photomultiplier tube 3 PMT3 are respectively arranged on the light output side of the three focusing lenses L5; the spectral data acquisition unit detects the separated three light signals through a photodetector.

[0015] Among them, when the three light signals are transmitted to the three photomultiplier tubes through the focusing lens, the first PMT1 receives the reflected light spectrum signal, and obtains the vegetation target distance information and reflected light intensity information through the detector ADC conversion and the acquisition card full waveform recording method; the signals of the two fluorescence bands of 685nm and 740nm are obtained by the second PMT2 and the third PMT3, and the number of photons is recorded through the detector TDC conversion and photon counting method to obtain the intensity information of the two fluorescence bands of the vegetation target, and save it in the counter through the data transmission protocol.

[0016] Among them, the timing control unit includes a digital delay generator, which outputs a periodic digital pulse signal, synchronously controls the high-energy short-wave laser emission and the photoelectric detector spectrum detection, and sets multiple repeated observations to effectively accumulate the single-wavelength reflected light intensity and the dual-band 685nm and 740nm fluorescence intensity, thereby improving the detection signal-to-noise ratio of the vegetation target reflected light signal and the dual-band fluorescence signal, and completing the recording of the detection distance, reflected light echo signal intensity, and dual-band fluorescence signal intensity in a time series.

[0017] Among them, the host computer controls the digital delay generator through the connecting line, and the digital delay generator is connected to the laser emission module and the ADC and TDC acquisition boards respectively through the control connecting lines. The digital delay generator periodically outputs three TTL amplitude pulse signals to control the laser pulse output and the synchronous detection of the two acquisition boards respectively, thereby realizing the laser emission and the synchronous detection of the three-way spectral signal, and completing the integrated synchronous detection of the vegetation target spatial information, reflected light spectral information, and fluorescence spectral information.

[0018] (III) Beneficial effects

[0019] The laser radar device provided by the above technical solution for synchronously detecting vegetation reflected light and fluorescence signals can realize integrated remote sensing monitoring of vegetation target spatial information, reflected light spectral information, and fluorescence spectral information, better monitor the physiological and biochemical state of vegetation, and achieve better vegetation monitoring effects. The invention emits high-energy short-wave laser pulses to the surface of vegetation, and after the pulses interact with the surface and internal physiological and biochemical molecules of the vegetation, when the echo signal with the same wavelength is reflected, a wide-spectrum fluorescence signal is synchronously excited and generated. The wavelength of the emitted short-wave laser is consistent with the physiological and biochemical sensitive wavelength of the vegetation, so that both the reflected light spectrum and the fluorescence spectrum can serve the vegetation remote sensing monitoring well. Based on the dichroic mirror and the narrow-band filter in the step-by-step spectral splitting module, the reflected light and the fluorescence mixed spectrum obtained by the echo receiving unit are subjected to step-by-step spectral separation. Since the intensity of the fluorescence signal generated by the excitation is relatively weak, the spectral data acquisition unit adopts a linear full-waveform sampling method to acquire the reflected light signal, and the fluorescence signal generated by the excitation adopts a single-photon counting method to acquire the signal, thereby improving the acquisition quality of the two spectral information. The timing control unit outputs a periodic digital pulse signal, synchronously controls the emission of the high-energy short-wave laser and the spectral detection of the photoelectric detector, so that the reflected light signal and the fluorescence signal of the vegetation target are synchronously and efficiently detected and acquired, and the detection distance, the intensity of the reflected light echo signal, and the intensity of the dual-band fluorescence signal are recorded in the time series. To this end, based on the present invention, the laser radar technology can truly obtain accurate spatial three-dimensional information of vegetation while realizing integrated imaging detection of vegetation reflected light and fluorescence bispectral signals, so as to better serve vegetation remote sensing monitoring and practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a laser radar device for synchronously detecting vegetation reflected light and fluorescence signals provided by the present invention.

[0021] Figure 2 This is a schematic diagram of the spectral splitting and spectral data acquisition structure provided by the present invention.

[0022] Figure 3 This is a graph of the fluorescence signal intensity generated by the stimulation of healthy plant leaves. DETAILED DESCRIPTION

[0023] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0024] The laser radar device for synchronously detecting vegetation reflected light and fluorescence signals of the present invention comprises a laser emitting unit, an echo receiving unit, a spectral spectrometer unit, a spectral data acquisition unit and a timing control unit. It is similar to the traditional single-wavelength laser radar system, but the present invention further modifies each unit to realize the integrated remote sensing monitoring of vegetation target spatial information, reflected light spectrum and fluorescence spectrum. The laser emitting unit adopts a monochromatic short-wave high-energy pulse laser, which is used as the excitation light of the vegetation wide-spectrum fluorescence signal and the ranging light for distance detection. The distance measurement is mainly calculated based on the time difference of the pulse signal of the incident light during the air propagation process, and undergoes the process of mixed spectral spectrometry in the spectral spectrometer unit. The spectral spectrometer unit mainly relies on dichroic mirrors and narrow-band filters with different properties to separate the reflected light and fluorescence mixed spectral signals into reflected light signals and dual-wavelength fluorescence band signals in a step-by-step manner, and respectively uses full waveform technology and single photon counting technology to record the distance value, reflected light intensity value and fluorescence intensity value. The timing control unit achieves the optimal detection state of the reflected light signal intensity and the fluorescence signal intensity by synchronously controlling the high-energy short-wave laser emission and the photoelectric detector spectral detection, thereby improving the detection quality of the two spectral signals.

[0025] See also Figure 1 The structure of the laser radar device for synchronously detecting vegetation reflected light and fluorescence signals in this embodiment includes a laser emitting unit, an echo receiving unit, a spectral spectrometer unit, a spectral data acquisition unit, a timing control unit and a host computer; the laser emitting unit emits a monochromatic short-wave high-energy laser pulse and irradiates the vegetation through a coated total reflector; the echo receiving unit and the spectral spectrometer unit acquire and perform spectroscopic processing on the short-wave reflected light signal reflected by the vegetation target and the wide-spectrum fluorescence signal generated by the vegetation when stimulated; the spectral data acquisition unit performs signal conversion and records the received reflected light signal and the fluorescence signal; the timing control unit connects the laser emitting unit and the spectral data acquisition unit through a data transmission line; and the host computer controls the laser emitting unit, the spectral data acquisition unit and the timing control unit through the connecting line.

[0026] The laser emission unit is connected to the timing control unit, and controls the laser pulse emission according to the periodic timing signal output generated by the timing control unit, and sets the frequency, pulse width and other parameters of the emitted laser through the host computer to meet the needs of different detection targets.

[0027] The laser emitting unit includes a laser module, a water cooler, a modulation module, and a total reflection mirror L1; the modulation module enables the laser module to emit a monochromatic short-wave laser with a set frequency and a set pulse energy, and then the laser beam is reflected to the surface of the vegetation by the 45° coated total reflection mirror L1. The monochromatic short-wave high-energy pulse laser emitted by the laser emitting unit serves as both the excitation light of the vegetation target fluorescence signal and the ranging light for distance detection. The thermal effect caused by the high-energy laser pulse emitted by the laser module can be circulated and cooled by a water cooler to achieve stable output of laser energy.

[0028] When a monochromatic short-wave high-energy laser pulse is irradiated onto the surface of vegetation, the chlorophyll molecules inside the vegetation absorb the external light radiation energy, and the molecules are in an unstable state and will transition to a low energy level. In this process, a wide-spectrum fluorescence signal with a longer wavelength than the incident light will be generated. The intensity of the fluorescence signal is extremely linearly related to the laser incident energy, so the laser incident energy needs to be increased as much as possible.

[0029] Moreover, the wavelength of the monochromatic short-wave high-energy pulsed laser can be selected to be consistent with the sensitive wavelength of the physiological and biochemical state of the vegetation, such as 480nm, 532nm and other wavelength lasers, so that the obtained reflected light signal and the excited fluorescence signal can establish a good correlation with the physiological and biochemical information of the vegetation.

[0030] The echo receiving unit includes an optical telescope, a focusing lens, and a collimator. The echo receiving unit uses the optical telescope and the focusing lens to optically focus the mixed spectrum composed of the single-band reflected light of the vegetation and the wide-spectrum fluorescence signal, and uses a collimator to collimate the received mixed spectrum signal, which can be transmitted to the spectrum splitting unit through space beam or optical fiber transmission. The type, size, focal length and other parameters of the optical telescope and the collimator can be adjusted according to the actual detection situation.

[0031] The optical telescope and the total reflection mirror L1 in the laser emitting unit are placed at a 45° angle. The laser emission light path is reflected by the 45° total reflection mirror placed at the front end of the optical telescope to ensure that the laser emission light path, the vegetation reflection light signal and the excitation fluorescence signal, and the central axis of the optical telescope are all on the same axis. After the mixed spectral signal is focused at the receiving end of the optical telescope, a collimator is used to collimate the focused light beam so that the light beam enters the spectral splitting unit in parallel.

[0032] The spectral splitting unit includes a dichroic mirror L2, a dichroic mirror L3, a narrow-band filter L4, a narrow-band filter L6, a narrow-band filter L7, and three focusing lenses L5; the narrow-band filter L4 and a focusing lens L5 are arranged in sequence on the reflective side of the dichroic mirror L2, the dichroic mirror L3 is arranged on the transparent side of the dichroic mirror L2, the narrow-band filter L6 and a focusing lens L5 are arranged in sequence on the reflective side of the dichroic mirror L3, and the narrow-band filter L7 and a focusing lens L5 are arranged on the transparent side of the dichroic mirror L3.

[0033] The spectral splitting unit is used to separate the mixed spectral signal obtained by the echo receiving unit, and use dichroic mirrors, narrow-band filters, etc. to gradually separate the single-wavelength reflected light signal and the dual-wavelength fluorescent band signal in steps, and use a focusing lens to transmit the separated light signal to the photoelectric detector of the spectral data acquisition unit.

[0034] The central wavelengths of the three narrow-band filters correspond to the laser emission wavelength and two vegetation fluorescence characteristic bands of 685nm and 740nm respectively. The half-width of the three filters can be adjusted as the detection application changes.

[0035] When the spectral splitting unit is working, the reflected light signal is first separated from the stimulated wide-spectrum fluorescence signal by the dichroic mirror L2 (low reflection and high transmittance, cut-off wavelength 600nm), and the narrow-band filter L4 (center wavelength corresponds to the wavelength of the incident light) is used for filtering, which can effectively avoid the influence of factors such as external light; the wide-spectrum fluorescence signal passing through the dichroic mirror L2 is further separated by the dichroic mirror L3 (low reflection and high transmittance, cut-off wavelength 710nm), and the two fluorescence characteristic bands are filtered by two narrow-band filters L6 and L7 (center wavelengths are 685nm and 740nm respectively), ensuring the accuracy of the spectral data acquisition of the two fluorescence characteristic bands. After the three signal light beams are filtered by the narrow-band filters, in order to improve the spectral signal acquisition capability, a focusing lens is added to each, so that the three light signals can be better transmitted to the receiving end of the photodetector.

[0036] The spectral data acquisition unit includes a photomultiplier tube 1 (PMT1), a photomultiplier tube 2 (PMT2), a photomultiplier tube 3 (PMT3), an ADC, a TDC acquisition board, and a signal transmission line. The photomultiplier tube 1 (PMT1), the photomultiplier tube 2 (PMT2), and the photomultiplier tube 3 (PMT3) are respectively arranged on the light-emitting side of the three focusing lenses L5. The spectral data acquisition unit mainly detects the separated three light signals through a photodetector.

[0037] In the embodiment, when the three light beams are transmitted to the three photomultiplier tubes through the focusing lens, the first PMT1 receives the reflected light spectrum signal, and obtains the vegetation target distance information and reflected light intensity information through the detector ADC conversion and the acquisition card full waveform recording method, wherein the detector end and the acquisition card end are connected by a signal transmission line. The two fluorescence band signals (685nm and 740nm) are obtained by the second PMT2 and the third PMT3, mainly through the detector TDC conversion and photon counting method to record the number of photons, and obtain the two fluorescence band intensity information of the vegetation target, and save it in the counter through the data transmission protocol. Similarly, the two detector ends and the acquisition card end are connected by a signal transmission line.

[0038] The timing control unit includes a digital delay generator and a control connection line. The timing control unit outputs a periodic digital pulse signal, synchronously controls the emission of high-energy short-wave lasers and the spectrum detection of photoelectric detectors, and sets multiple repeated observations to effectively accumulate the single-wavelength reflected light intensity and the dual-band 685nm and 740nm fluorescence intensity, thereby improving the detection signal-to-noise ratio of the vegetation target reflected light signal and the dual-band fluorescence signal, and completing the recording of the detection distance, reflected light echo signal intensity, and dual-band fluorescence signal intensity in the time series.

[0039] In this embodiment, the host computer controls the digital delay generator through a connecting line, and the digital delay generator is connected to the laser emission module and the ADC and TDC acquisition boards respectively through control connecting lines. The third-party digital delay generator mainly controls the laser pulse output and the synchronous detection of the two acquisition boards respectively by periodically outputting three-way TTL amplitude pulse signals, thereby realizing the laser emission and the synchronous detection of three-way spectral signals, and finally completing the integrated synchronous detection of vegetation target spatial information, reflected light spectral information, and fluorescence spectral information.

[0040] The recommended models of each component are: Laser including laser module, water chiller, etc., the preferred model is CNILPS-532-A. The preferred model of photomultiplier tube PMT1 is Hamamatsu H10720-20; the preferred models of photomultiplier tube PMT2 and PMT3 are PicoQuant PMA 192; the preferred models of two high-speed acquisition cards are Teledyne SP Devices ADQ7 and PicoQuant HydraHarp 400; the preferred model of third-party digital delay generator is Stanford ResearchSystems DG645. The preferred model of counter is National Instruments PXIe6614.

[0041] It can be seen from the above technical scheme that the present invention breaks through the limitation of traditional single-wavelength laser radar that can only obtain spatial detection capabilities of vegetation targets. While obtaining vegetation spatial information, it realizes the synchronous acquisition of vegetation reflected light information and stimulated fluorescence information, and finally realizes the integrated remote sensing monitoring of vegetation target spatial information, reflected light spectrum, and fluorescence spectrum. It can effectively monitor the physiological and biochemical status information of vegetation, breaks through the limitations of traditional single-wavelength laser radar in the application of spectral information, increases the spectral dimension of vegetation remote sensing detection, and greatly expands the application scope of laser radar technology in vegetation target monitoring, biochemical content inversion, pest and disease control, etc., making detection and monitoring more accurate and efficient.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals, characterized in that: include: Laser emitting unit, echo receiving unit, spectral spectrometer unit, spectral data acquisition unit, timing control unit and host computer; the laser emitting unit emits monochromatic short-wave high-energy laser pulses which are irradiated to vegetation through a coated total reflector; the echo receiving unit and the spectral spectrometer unit acquire and perform spectroscopic processing on the short-wave reflected light signal reflected by the vegetation target and the wide-spectrum fluorescence signal generated by the vegetation when stimulated; the spectral data acquisition unit performs signal conversion and records the received reflected light signal and fluorescence signal; the timing control unit connects the laser emitting unit and the spectral data acquisition unit through a data transmission line; and the host computer controls the laser emitting unit, the spectral data acquisition unit and the timing control unit through the connecting line.

2. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 1, characterized in that: The laser emitting unit is connected to the timing control unit, and controls the laser pulse emission according to the periodic timing signal output generated by the timing control unit, and sets the frequency and pulse width parameters of the emitted laser through the host computer to meet the needs of different detection targets.

3. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 2, characterized in that: The laser emitting unit includes a laser module, a water cooler, a modulation module, and a total reflection mirror L1; the modulation module enables the laser module to emit a monochromatic short-wave laser with a set frequency and a set pulse energy, and then the laser beam is reflected to the surface of the vegetation by the coated total reflection mirror L1 arranged at a 45° angle; the thermal effect caused by the monochromatic short-wave laser emitted by the laser module is circulated and cooled by the water cooler to achieve stable output of laser energy.

4. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 3, characterized in that: The echo receiving unit includes an optical telescope, a focusing lens, and a collimator. The echo receiving unit uses the optical telescope and the focusing lens to optically focus the mixed spectrum composed of the single-band reflected light of the vegetation and the wide-spectrum fluorescence signal, and uses a collimator to collimate the received mixed spectrum signal, and then transmits it to the spectrum splitting unit through a space beam or optical fiber transmission method; the optical telescope and the total reflection mirror L1 in the laser emitting unit are placed at 45 degrees, and the laser emission light path is reflected by the 45-degree total reflection mirror placed at the front end of the optical telescope to ensure that the laser emission light path, the vegetation reflection light signal and the excitation fluorescence signal, and the central axis of the optical telescope are all on the same axis. After focusing the mixed spectrum signal at the receiving end of the optical telescope, a collimator is used to collimate the focused light beam so that the light beam enters the spectrum splitting unit in parallel.

5. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 4, characterized in that: The spectral spectrometer unit includes a dichroic mirror L2, a dichroic mirror L3, a narrow-band filter L4, a narrow-band filter L6, a narrow-band filter L7, and three focusing lenses L5; the narrow-band filter L4 and a focusing lens L5 are arranged in sequence on the reflective side of the dichroic mirror L2, the dichroic mirror L3 is arranged on the transparent side of the dichroic mirror L2, the narrow-band filter L6 and a focusing lens L5 are arranged in sequence on the reflective side of the dichroic mirror L3, and the narrow-band filter L7 and a focusing lens L5 are arranged on the transparent side of the dichroic mirror L3; the spectral spectrometer unit is used to separate the mixed spectral signal obtained by the echo receiving unit, separate the single-wavelength reflected light signal and the dual-wavelength fluorescent band signal, and use the focusing lens to transmit the separated light signal to the photoelectric detector of the spectral data acquisition unit.

6. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 5, characterized in that: The central wavelengths of narrow-band filter L4, narrow-band filter L6 and narrow-band filter L7 correspond to the laser emission wavelength and two vegetation fluorescence characteristic bands of 685nm and 740nm respectively.

7. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 6, characterized in that: The spectral data acquisition unit includes photomultiplier tube 1 PMT1, photomultiplier tube 2 PMT2, photomultiplier tube 3 PMT3 and ADC, TDC acquisition board. Photomultiplier tube 1 PMT1, photomultiplier tube 2 PMT2, photomultiplier tube 3 PMT3 are respectively arranged on the light output side of three focusing lenses L5; the spectral data acquisition unit detects the separated three light signals through a photodetector.

8. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 7, characterized in that: When the three light signals are transmitted to the three photomultiplier tubes through the focusing lens, the first PMT1 receives the reflected light spectrum signal, and obtains the vegetation target distance information and reflected light intensity information through the detector ADC conversion and the acquisition card full waveform recording method; the signals of the two fluorescence bands of 685nm and 740nm are obtained by the second PMT2 and the third PMT3, and the number of photons is recorded through the detector TDC conversion and photon counting method to obtain the intensity information of the two fluorescence bands of the vegetation target, and save it to the counter through the data transmission protocol.

9. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 8, characterized in that: The timing control unit includes a digital delay generator, which outputs a periodic digital pulse signal, synchronously controls the emission of high-energy short-wave lasers and the spectrum detection of photoelectric detectors, and sets multiple repeated observations to effectively accumulate the single-wavelength reflected light intensity and the dual-band 685nm and 740nm fluorescence intensities, thereby improving the detection signal-to-noise ratio of the vegetation target reflected light signal and the dual-band fluorescence signal, and completing the recording of the detection distance, the reflected light echo signal intensity, and the dual-band fluorescence signal intensity in a time series.

10. The laser radar device structure for synchronously detecting vegetation reflected light and fluorescence signals as claimed in claim 9, characterized in that: The host computer controls the digital delay generator through the connecting line, and the digital delay generator is connected to the laser emission module and the ADC and TDC acquisition boards respectively through the control connecting lines. The digital delay generator periodically outputs three TTL amplitude pulse signals to control the laser pulse output and the synchronous detection of the two acquisition boards respectively, thereby realizing the laser emission and the synchronous detection of the three-way spectral signal, and completing the integrated synchronous detection of the vegetation target spatial information, reflected light spectral information, and fluorescence spectral information.

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