Near space ozone differential absorption lidar detection platform and detection method

Abstract

This invention discloses a near-space ozone differential absorption lidar detection platform and method, belonging to the field of remote sensing technology. The platform includes: a laser emission unit employing independent dual high-power pulsed laser sources with non-parametric oscillation, namely, a 308nm XeCl excimer laser and a 355nm Nd:YAG third-harmonic laser; an optical receiving and detection unit, whose collimating lens has a single-blade mechanical chopper rotating at 6000rpm near its focal plane, which, controlled by a photoelectric encoder, physically blocks strong low-altitude echo signals from 0-15km within 0-100μs after laser emission; a beam splitter containing three dichroic mirrors to sequentially separate the 308nm, 355nm, and 386nm nitrogen Raman signals; and a data processing unit that inputs the nitrogen Raman signal into an atmospheric extinction coefficient correction model and combines it with an improved differential absorption algorithm to invert the ozone concentration profile. This invention fundamentally guarantees the detection energy requirements in the near-space region of 50km, achieves "surgical" precise removal of strong low-altitude signals, reduces the ozone detection error at an altitude of 30km to within 5%, and significantly improves temporal and spatial resolution.

Description

Technical Field

[0001] This invention belongs to the field of remote sensing technology, specifically relating to a near-space ozone differential absorption lidar detection platform and detection method. Background Technology

[0002] Near space, as a crucial region connecting aviation and aerospace, has significant implications for atmospheric chemical cycles, climate change, and the operational safety of aerospace vehicles due to its ozone distribution characteristics. As an important greenhouse gas and atmospheric chemical tracer, accurate detection of ozone's vertical distribution and spatiotemporal evolution is a key requirement for atmospheric science research, climate change assessment, and air pollution control.

[0003] Currently, the mainstream ozone detection methods internationally include satellite remote sensing, ozone sounding, ground-based air sampling and analysis, and lidar detection. While satellite remote sensing can achieve global-scale coverage, its spatial resolution is low, making it difficult to meet the needs of continuous observation; ozone sounding relies on radiosonde balloons, which are costly and have limited coverage.

[0004] In existing lidar detection technologies, differential absorption (DIAL) is the mainstream approach for high-altitude detection. Some solutions utilize all-solid-state optical parametric oscillator (OPO) technology to generate multi-wavelength lasers for detection. However, when extending the detection altitude to near space (2050 km), existing DIAL systems face three major physical and engineering bottlenecks:

[0005] First, there is the bottleneck of energy conversion during transmission. Multi-wavelength technologies such as all-solid-state OPO are limited by the energy conversion efficiency of nonlinear optical crystals, making it difficult to achieve ultra-high energy output of single pulses. When the detection altitude is extended to 50km, the extremely low photon budget results in a very low signal-to-noise ratio for weak echo signals at high altitudes, making it impossible to overcome the physical energy bottleneck of near-space detection.

[0006] Second, the dynamic range of the signal is extremely unbalanced. The intensity of the lidar echo signal decreases inversely with the square of the distance; the strong echo signal intensity at 0.15 km in the troposphere is millions of times stronger than that at 50 km. Most existing systems only use conventional chopper discs and lack precise mechanical and timing isolation designs for the optical focal plane. If the gain of the photomultiplier tube (PMT) is increased to detect weak signals at high altitudes, the strong echoes at low altitudes will cause the detector photocathode to be overexposed or even damaged momentarily, making the system unable to achieve continuous high-gain detection at both high and low altitudes.

[0007] Third, nonlinear interference from stratospheric aerosols. In the stratosphere above 30 km, the scattering characteristics of aerosols are exceptionally complex. Traditional DIAL algorithms typically assume that aerosol scattering at the two detection wavelengths is linear or easily derived, and the system hardware lacks an independent auxiliary channel for accurately measuring aerosol extinction characteristics, leading to a sharp increase in ozone concentration inversion errors under complex high-altitude environments.

[0008] In summary, the existing technology has the following main drawbacks: limited transmission energy and insufficient detection altitude; lack of high-precision strong signal physical isolation structure, limiting the dynamic range of the detector; lack of independent atmospheric parameter depth correction mechanism, resulting in large high-altitude inversion errors (generally higher than 5%). Summary of the Invention

[0009] In view of this, the purpose of the present invention is to provide a near-space ozone differential absorption lidar detection platform and detection method.

[0010] A near-space ozone differential absorption lidar detection platform includes: The laser emitting unit is configured to emit a 308nm absorption wavelength laser and a 355nm reference wavelength laser. An optical receiving and detection unit, configured to receive atmospheric echo signals, includes a telescope, a collimating lens group, and a mechanical chopper disposed near the focal plane of the collimating lens group; The beam splitter is configured to separate 308nm signal light, 355nm signal light and 386nm nitrogen Raman signal light from the atmospheric echo signal; The photoelectric detection unit includes multiple photodetectors, each corresponding to a separated signal light; The data processing unit is configured to receive the signal output by the photoelectric detection unit, execute the improved differential absorption algorithm, and input the detection data from the 386nm nitrogen Raman signal light into the atmospheric extinction coefficient correction model to eliminate the interference of stratospheric aerosols on ozone concentration inversion, thereby obtaining the ozone concentration profile.

[0011] Preferably, the laser emitting unit includes: The first laser is a XeCl excimer laser, used to generate the 308nm absorption wavelength laser with a single pulse energy ≥500 mJ and a repetition frequency ≥50 Hz. The second laser is a third-harmonic output of the Nd:YAG laser, used to generate the 355nm reference wavelength laser, with an output power ≥20W and a repetition frequency ≥100 Hz.

[0012] Preferably, the mechanical chopper has a single-blade structure, a rotation speed of 6000 rpm, and is equipped with a photoelectric encoder; the mechanical chopper is configured to physically block the echo signal entering the optical receiving and detection unit within a 0-100μs time window after laser emission, so as to block the low-altitude strong echo signal in the 0-15km altitude range.

[0013] Preferably, the beam-splitting optical path includes: The first dichroic mirror is configured to reflect light with a wavelength of 308nm and transmit light with a wavelength greater than 320nm. The second dichroic mirror is configured to reflect light with a wavelength of 355nm and transmit light with a wavelength greater than 370nm. The third dichroic mirror is configured to reflect light with a wavelength of 386nm and transmit light with a wavelength greater than 400nm; And narrowband interference filters corresponding to wavelengths of 308nm, 355nm and 386nm respectively.

[0014] 5. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that the telescope is a Cassegrain reflecting telescope with an effective aperture ≥1000mm, the primary mirror is coated with an ultraviolet-enhanced aluminum film, and the primary mirror reflectivity ≥85%.

[0015] Preferably, the photodetector is a metal-encapsulated photomultiplier tube with an integrated thermoelectric cooling module, and its dark count rate is <20 cps and rise time is ≤0.78ns.

[0016] Furthermore, it also includes a data acquisition unit, which includes a Licel transient recorder with a sampling rate of 20MHz, and features both a 12-bit analog acquisition mode and a 250MHz photon counting mode.

[0017] Furthermore, the beam splitter is also equipped with a fourth dichroic mirror and a corresponding narrowband interference filter to separate the 407nm water vapor Raman signal light for water vapor concentration detection.

[0018] Preferably, the platform has an ozone detection error of less than 5% in the altitude range of 20km-50km, a time resolution of 30 minutes, and a spatial resolution of 1000 meters.

[0019] A near-space ozone differential absorption lidar detection method includes the following steps: Step S1: The system starts up, power supply and control unit are turned on, and each unit completes self-test and initialization; Step S2: Parameter setting, setting laser emission parameters, data acquisition parameters and detection timing parameters through the power supply and control unit; Step S3: Laser emission. The laser emission unit simultaneously emits a 355nm reference wavelength laser and a 308nm absorption wavelength laser, which are then beam-expanded, collimated, and emitted vertically upwards into near space. Step S4: Signal reception and physical isolation. The optical receiving and detection unit captures the atmospheric echo signal. The mechanical chopper, located near the focal plane of the collimating lens, physically blocks the low-altitude strong echo signal corresponding to the altitude of 15km within the 0-100μm time interval after laser emission, so that the photomultiplier tube can receive the echo signal above 15km in a high-gain state. Step S5: Spectroscopy and photoelectric conversion. The received echo signal is separated into 308nm signal light, 355nm signal light and 386nm nitrogen Raman signal light through the spectroscopic optical path, and then converted into electrical signals by the corresponding photodetectors. Step S6: Data acquisition. The high-speed data acquisition device acquires the electrical signal and stores it as raw data synchronously with the laser emission trigger signal. Step S7: Data inversion. The data processing unit executes the improved differential absorption algorithm, inputs the detection data of the 386nm nitrogen Raman signal light into the atmospheric extinction coefficient correction model, eliminates stratospheric aerosol interference, and inverts to obtain the ozone concentration profile. Step S8: Data display and storage. The inversion results are displayed on the screen in real time and stored in the local database at the same time. Data export and remote transmission are supported. Step S9: The system shuts down, the laser emitting unit is turned off, the data acquisition and analysis unit completes the remaining data processing and storage, and the system enters standby mode.

[0020] The present invention has the following beneficial effects: 1. Breakthrough in all-solid-state nonlinear conversion energy bottleneck, achieving efficient detection at 50km altitude. This invention employs a combination of independent dual high-power pulsed laser sources with non-parametric oscillation, including a XeCl excimer laser emitting a 308nm absorption wavelength (single pulse energy ≥500 mJ) and an Nd:YAG third-harmonic laser emitting a 355nm reference wavelength (power ≥20W). This invention abandons existing solutions with low conversion efficiency, such as optical parametric oscillation (OPO), and creatively uses a heterogeneous high-energy emission base composed of a XeCl excimer laser and a Nd:YAG third-harmonic laser. Combined with a large-aperture telescope with an effective aperture ≥1000mm, this significantly increases the number of echo photons per pulse. This hardware architecture advantage fundamentally guarantees the detection energy requirements reaching near-space up to 50km, and improves the temporal resolution to 30 minutes and the spatial resolution to 1000m, providing strong instrumental support for capturing rapid spatiotemporal changes in near-space ozone concentration.

[0021] 2. Precise physical isolation of the focal plane enables secure high-gain detection of weak signals. This invention incorporates a mechanical chopper within the optical receiving and detection unit, specifically positioned near the focal plane of the collimating lens. This chopper (6000 rpm, single-blade) is controlled by a photoelectric encoder and configured to precisely physically block the laser emission within a specific timeframe of 0-100 μs (corresponding to an altitude of 0-15 km), completely blocking strong low-altitude echo signals. This allows the photomultiplier tube (PMT) to safely operate at its highest gain to detect weak high-altitude signals. Unlike the broad chopper anti-saturation design of typical systems, this invention strictly positions the 6000 rpm single-blade mechanical chopper near the focal plane of the collimating optical path, using a photoelectric encoder for microsecond-level phase feedback. This innovative micro-vision device structure achieves a "surgical" precise cutoff of strong low-altitude signals (0-15 km) at both physical and temporal levels. This allows the photoelectric detector to completely avoid the risk of overexposure to strong low-altitude light and maintain extremely high gain to effectively capture weak ozone echoes in the 20-50 km vicinity.

[0022] 3. Combined with depth correction, significantly improve the accuracy of upper-air ozone inversion. In addition to the dichroic mirror that separates the 308nm and 355nm echo signals, the optical path of this invention also includes a third-order dichroic mirror (DM3) and a corresponding narrowband interference filter, specifically designed to separate and extract the 386nm nitrogen Raman echo signal. The system's data processing unit is configured to receive the signal acquired by this hardware channel and, in conjunction with an atmospheric extinction coefficient correction model, algorithmically eliminate the interference of stratospheric aerosols on ozone differential absorption inversion. Addressing the problem of large errors in existing high-altitude detection technologies, this system innovatively adds a dedicated 386nm nitrogen Raman hardware optical path. The measured atmospheric parameters obtained through this dedicated hardware channel are directly input into the matching extinction coefficient correction model, completely eliminating the idealized assumptions about aerosol scattering in the traditional DAL algorithm. This significantly improves the ozone detection accuracy at an altitude of 30km to an error of ≤5%, comprehensively outperforming the generally high error rate of over 10% found in existing technologies, and meeting the stringent research requirements of mid-to-upper atmospheric chemistry.

[0023] In summary, this invention, through the aforementioned dual-wavelength emission and detection architecture, focal plane precision mechanical chopper anti-saturation structure, and spectral separation and detection mechanism integrating nitrogen Raman channel and correction model, completely solves the problems of energy limitation, low-altitude signal saturation overexposure, and stratospheric aerosol nonlinear interference, achieving high-precision (error <5%) all-weather detection of ozone concentration in the 20-50km altitude range. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall system composition of the near-space ozone differential absorption lidar detection platform provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the beam-splitting optical path structure provided in an embodiment of the present invention, showing the optical paths of multiple dichroic mirrors and their corresponding channels; Figure 3 The timing control diagram provided for the embodiments of the present invention illustrates the timing relationship between laser emission, chopper operation, and signal acquisition; Figure 4 This is a flowchart of the data acquisition and control software provided in an embodiment of the present invention; Figure 5 This is a flowchart illustrating the operation of an ozone detection lidar provided in an embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] like Figure 1 As shown, this embodiment of the invention provides a near-space ozone differential absorption lidar detection platform, which employs the dual-wavelength differential absorption principle (DIAL) to achieve accurate detection of ozone density profiles. The system consists of four parts: a laser emitting unit, an optical receiving and detection unit, a data acquisition and analysis unit, and a power supply and control unit. These units work collaboratively through standardized interfaces.

[0027] I. Laser Emission Unit like Figure 1 As shown, the laser emitting unit provides a 355nm reference wavelength laser and a 308nm absorption wavelength laser. This embodiment abandons the low-energy Raman frequency-shifting source and uses two independent high-power pulsed lasers: Signal beam (onwavelength): Employs a XeCl excimer laser with an output wavelength of 308 nm, located at the center of the Hartley absorption band of ozone. Single pulse energy ≥ 500 mJ, repetition rate ≥ 50 Hz, and pulse width 1520 ns.

[0028] Reference light (Offwavelength): The third-harmonic output of an Nd:YAG laser with an output wavelength of 355nm (weak ozone absorption). Output power ≥20W, repetition rate ≥100 Hz, and divergence ≤1 mrad. This wavelength serves as the DIAL reference wavelength and also as the pump source for exciting N2 (386nm) and H2O (407nm) Raman scattering.

[0029] The two laser beams are each passed through a 5x beam expander collimator to compress the beam divergence angle from 35 mrad to below 0.5 mrad, thereby reducing background field noise.

[0030] II. Optical Receiving and Detection Unit like Figure 1 As shown, the optical receiving and detection unit is used to receive atmospheric echo signals and realize signal filtering, focusing and photoelectric conversion. It includes a large-aperture optical receiving unit telescope, a beam splitting optical path and detection unit, and a timing control and acquisition card.

[0031] 1) Large-aperture optical receiving unit telescope: Employs a Cassegrain reflecting telescope with an effective aperture ≥1000 mm. The primary mirror is coated with an ultraviolet-enhancing aluminum film, and its reflectivity is ≥85%. The telescope's focal plane is equipped with a variable aperture, allowing for a field of view adjustment range of 0.5-2.0 mrad. During daytime observation, the aperture can be reduced to 0.5 mrad to suppress background sky light.

[0032] 2) Spectroscopic optical path and detection unit: The signal transmitted through the optical fiber enters the temperature-controlled, light-protected testing chamber and undergoes precision optical path processing: Collimation and Physical Chopper: The fiber-emerged light is collimated into parallel light by an ultraviolet fused silica lens group. A mechanical chopper is positioned near the focal plane of the collimating lens. The chopper wheel rotates at 6000 rpm (100 Hz) and employs a single-blade design. Through feedback control using a photoelectric encoder, the chopper phase is positioned within the 0-100 μs interval after laser emission, corresponding to an altitude of 0-15 km. This physical blocking of the strong echo signal at 0-15 km prevents overexposure of the PMT photocathode, allowing the detector to operate at its highest gain to detect weak signals at 50 km.

[0033] like Figure 2 As shown, the multi-stage spectral separation optical beam passes sequentially through three dichroic mirrors (DM) for spectral dispersion: First-stage beam splitting (308nm separation): DM1 reflects 308nm and transmits >320nm. The reflected light passes through interference filter IF1 (center wavelength 308.0 nm, bandwidth FWHM≤1.0 nm, optical density OD≥6) and then enters PMT1, forming channel 1 (308nm signal channel).

[0034] Second-stage beam splitting (355nm separation): DM2 reflects 355nm and transmits >370nm. The reflected light passes through IF2 (center wavelength 355.0 nm, FWHM ≤ 1.0 nm) and then enters PMT2, forming channel 2 (355nm reference / aerosol channel).

[0035] Third-stage beam splitting (Raman signal separation): DM3 reflects light at 386 nm and transmits light at >400 nm. The reflected light passes through IF3 (center wavelength 386.7 nm, FWHM ≤ 0.8 nm, OD ≥ 5) and then enters PMT3, forming channel 3 (386 nm nitrogen Raman channel, used to correct for aerosol interference). The transmitted light can pass through IF4 (center wavelength 407.5 nm) and enter PMT4, forming channel 4 (407 nm water vapor Raman channel, optional).

[0036] The detector assembly uses a small, metal-encapsulated photomultiplier tube with an extremely fast response time (rise time 0.78 ns). All PMTs integrate thermoelectric cooling modules, achieving a dark count rate of <20 cps.

[0037] 3) Timing control and data acquisition card It employs a Licel transient recorder with a sampling rate of 20 MHz (corresponding to a distance resolution of 7.5 m), and features both a 12-bit analog acquisition mode and a 250 MHz photon counting mode.

[0038] Timing control logic such as Figure 3 As shown: at time T0, the master controller triggers the XeCl and Nd:YAG lasers to emit; at time T0+100 μs, the chopper blades move away, the optical path is turned on, and signals above 15 km begin to be received. The acquisition card is pre-triggered at time T0 to record the entire waveform, and the effective segment is extracted by software later.

[0039] III. Data Acquisition and Analysis Unit The high-speed photonic data acquisition unit has a sampling rate of ≥2.5 GS / s and a bandwidth of ≥200 MHz.

[0040] like Figure 4 As shown in the flowchart of the data acquisition and control software, the data processing unit receives the signal output by the photoelectric detection unit, executes the improved differential absorption algorithm, and inputs the detection data from the 386nm nitrogen Raman signal light into the atmospheric extinction coefficient correction model to eliminate the interference of stratospheric aerosols on ozone concentration inversion, thereby obtaining the ozone concentration profile.

[0041] It integrates data storage and display modules with a storage capacity of ≥10 TB, supports real-time storage of raw data and inversion results, and is equipped with a 65-inch 2K resolution display screen with a latency of ≤1 second, enabling real-time visualization of data.

[0042] The data acquisition and analysis unit has a built-in self-calibration module that automatically calibrates system parameters periodically to ensure the long-term stability of detection accuracy.

[0043] IV. Power Supply and Control Unit The system employs a dual-power supply design, with a main power supply of 220V AC and a backup power supply (UPS) to ensure continuous system operation for ≥4 hours. It is equipped with a high-precision timing controller, providing unified allocation of chopper timing, optical switch timing, laser triggering timing, and signal acquisition timing, with a timing control accuracy of ≤1μs. The control unit has a built-in status monitoring module that monitors the operating status of each unit in real time, automatically alarming and activating protection mechanisms in case of abnormalities.

[0044] V. Work Process like Figure 5 As shown, the working process of the ozone detection lidar in this embodiment is as follows: Step S1: The system starts up, the power supply and control unit are turned on, and each unit completes self-test and initialization.

[0045] Step S2: Parameter setting, set the laser emission parameters, data acquisition parameters and detection timing parameters through the power supply and control unit.

[0046] Step S3: Laser emission. The laser emission unit simultaneously emits a 355nm reference wavelength laser and a 308nm absorption wavelength laser, which are then beam-expanded, collimated, and emitted vertically upwards into near space.

[0047] Step S4: Signal reception and physical isolation. The optical receiving and detection unit captures the atmospheric echo signal. The mechanical chopper, located near the focal plane of the collimating lens, physically blocks the low-altitude strong echo signal corresponding to the altitude of 15km within the 0-100μm time interval after laser emission, so that the photomultiplier tube can receive the echo signal above 15km in a high-gain state.

[0048] Step S5: Spectroscopy and photoelectric conversion. The received echo signal is separated into 308nm signal light, 355nm signal light and 386nm nitrogen Raman signal light by the spectroscopic optical path, and then converted into electrical signals by the corresponding photodetectors.

[0049] Step S6: Data acquisition. The high-speed data acquisition device acquires the electrical signal and stores it as raw data synchronously with the laser emission trigger signal.

[0050] Step S7: Data inversion. The data processing unit executes an improved differential absorption algorithm, inputs the detection data of the 386nm nitrogen Raman signal light into the atmospheric extinction coefficient correction model, eliminates stratospheric aerosol interference, and inverts to obtain the ozone concentration profile.

[0051] Step S8: Data display and storage. The inversion results are displayed on the screen in real time and stored in the local database. Data export and remote transmission are supported.

[0052] Step S9: The system shuts down, the laser emitting unit is turned off, the data acquisition and analysis unit completes the remaining data processing and storage, and the system enters standby mode.

[0053] The detection platform described in this embodiment can achieve high-precision, all-weather detection of ozone concentration within an altitude range of 20-50 km, with a detection error of <5%, improved temporal resolution to 30 minutes, and improved spatial resolution to 1000 m. The ozone detection accuracy error at an altitude of 30 km is ≤5%, which is significantly better than the error of over 10% commonly found in existing technologies.

[0054] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A near-space ozone differential absorption lidar detection platform, characterized in that, include: The laser emitting unit is configured to emit a 308nm absorption wavelength laser and a 355nm reference wavelength laser. An optical receiving and detection unit, configured to receive atmospheric echo signals, includes a telescope, a collimating lens group, and a mechanical chopper disposed near the focal plane of the collimating lens group; The beam splitter is configured to separate 308nm signal light, 355nm signal light and 386nm nitrogen Raman signal light from the atmospheric echo signal; The photoelectric detection unit includes multiple photodetectors, each corresponding to a separated signal light; The data processing unit is configured to receive the signal output by the photoelectric detection unit, execute the improved differential absorption algorithm, and input the detection data from the 386nm nitrogen Raman signal light into the atmospheric extinction coefficient correction model to eliminate the interference of stratospheric aerosols on ozone concentration inversion, thereby obtaining the ozone concentration profile.

2. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The laser emitting unit includes: The first laser is a XeCl excimer laser, used to generate the 308nm absorption wavelength laser with a single pulse energy ≥500 mJ and a repetition frequency ≥50 Hz. The second laser is a third-harmonic output of the Nd:YAG laser, used to generate the 355nm reference wavelength laser, with an output power ≥20W and a repetition frequency ≥100 Hz.

3. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The mechanical chopper has a single-blade structure, a rotation speed of 6000 rpm, and is equipped with a photoelectric encoder. The mechanical chopper is configured to physically block the echo signal entering the optical receiving and detection unit within a 0-100μs time window after laser emission, so as to block the low-altitude strong echo signal in the 0-15km altitude range.

4. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The beam-splitting optical path includes: The first dichroic mirror is configured to reflect light with a wavelength of 308nm and transmit light with a wavelength greater than 320nm. The second dichroic mirror is configured to reflect light with a wavelength of 355nm and transmit light with a wavelength greater than 370nm. The third dichroic mirror is configured to reflect light with a wavelength of 386nm and transmit light with a wavelength greater than 400nm; And narrowband interference filters corresponding to wavelengths of 308nm, 355nm and 386nm respectively.

5. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The telescope is a Cassegrain reflecting telescope with an effective aperture of ≥1000mm, a primary mirror coated with an ultraviolet-enhancing aluminum film, and a primary mirror reflectivity of ≥85%.

6. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The photodetector is a metal-encapsulated photomultiplier tube with an integrated thermoelectric cooling module. Its dark count rate is <20 cps and rise time is ≤0.78ns.

7. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, It also includes a data acquisition unit, which includes a Licel transient recorder with a sampling rate of 20MHz, and features both a 12-bit analog acquisition mode and a 250MHz photon counting mode.

8. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The beam splitter is also equipped with a fourth dichroic mirror and a corresponding narrowband interference filter to separate the 407nm water vapor Raman signal light for water vapor concentration detection.

9. The near-space ozone differential absorption lidar detection platform according to claim 1, characterized in that, The platform has an ozone detection error of less than 5% in the altitude range of 20km-50km, a time resolution of 30 minutes, and a spatial resolution of 1000 meters.

10. A near-space ozone differential absorption lidar detection method based on the platform described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step S1: The system starts up, power supply and control unit are turned on, and each unit completes self-test and initialization; Step S2: Parameter setting, setting laser emission parameters, data acquisition parameters and detection timing parameters through the power supply and control unit; Step S3: Laser emission. The laser emission unit simultaneously emits a 355nm reference wavelength laser and a 308nm absorption wavelength laser, which are then beam-expanded, collimated, and emitted vertically upwards into near space. Step S4: Signal reception and physical isolation. The optical receiving and detection unit captures the atmospheric echo signal. The mechanical chopper, located near the focal plane of the collimating lens, physically blocks the low-altitude strong echo signal corresponding to the altitude of 15km within the 0-100μm time interval after laser emission, so that the photomultiplier tube can receive the echo signal above 15km in a high-gain state. Step S5: Spectroscopy and photoelectric conversion. The received echo signal is separated into 308nm signal light, 355nm signal light and 386nm nitrogen Raman signal light through the spectroscopic optical path, and then converted into electrical signals by the corresponding photodetectors. Step S6: Data acquisition. The high-speed data acquisition device acquires the electrical signal and stores it as raw data synchronously with the laser emission trigger signal. Step S7: Data inversion. The data processing unit executes the improved differential absorption algorithm, inputs the detection data of the 386nm nitrogen Raman signal light into the atmospheric extinction coefficient correction model, eliminates stratospheric aerosol interference, and inverts to obtain the ozone concentration profile. Step S8: Data display and storage. The inversion results are displayed on the screen in real time and stored in the local database at the same time. Data export and remote transmission are supported. Step S9: The system shuts down, the laser emitting unit is turned off, the data acquisition and analysis unit completes the remaining data processing and storage, and the system enters standby mode.

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