A signal-triggered switchable beam splitter atmospheric lidar receiving system

Abstract

This invention relates to the field of lidar detection and discloses a signal-triggered switchable beam splitter atmospheric lidar receiving system. It solves the problems of existing atmospheric lidar receiving beam splitter systems, which struggle to provide fine spectral information using broadband detection and suffer from complex structures and high resource consumption when using multiple narrowband parallel methods. This invention first performs a broadband search using a coarse detection channel A. When the detected signal meets the triggering conditions, the control module controls the beam splitting switching mechanism to activate the fine detection channel B for narrowband fine detection. This simultaneously considers the initial target acquisition probability and fine spectral resolution, ensuring efficient detection of weak signals while obtaining high-resolution spectral information when needed. The fine detection channel B is only activated after the target signal is confirmed, avoiding long-term parallel operation of multiple narrowband channels. This forms a closed-loop operation of coarse detection – trigger determination – channel switching – fine detection – reset and search, improving automated response efficiency and the reliability of continuous monitoring.

Description

Technical Field

[0001] This invention relates to the field of lidar detection, and in particular to a signal-triggered switchable beam splitter atmospheric lidar receiving system. Background Technology

[0002] Atmospheric lidar detects aerosols, pollutants, clouds, and atmospheric components by emitting laser pulses into the target atmosphere and receiving characteristic light signals such as backscattered light and fluorescence radiation. In scenarios involving fluorescence signal recognition or multi-band spectral analysis, the spectroscopic and acquisition scheme at the receiver directly affects the system's target detection capability, anti-interference performance, and spectral resolution accuracy.

[0003] Existing atmospheric lidar receiving and beam splitting systems are mainly:

[0004] I. Broadband filter receiving system: By configuring a filter with a wide passband in the receiving optical path, it can capture signals in a wider wavelength range, which is beneficial to improve the initial detection probability of weak signals or wavelength-drift signals. However, due to the wide passband, a large amount of background radiation, stray light and interference signals from adjacent wavelengths enter the detector at the same time, resulting in a decrease in the purity of the received signal. It is impossible to obtain the fine spectral structure of the target signal, making it difficult to meet the needs of subsequent high-resolution identification and fine analysis.

[0005] II. Multi-channel parallel beam splitting systems employ multiple narrowband filters and multiple detectors to simultaneously distribute echo signals to multiple channels to achieve multi-band synchronous detection, which can obtain relatively rich spectral information. However, multiple narrowband channels operate in parallel for a long time, and even during periods when the target signal has not yet appeared or when fine detection is not required, they still continuously occupy a large amount of detection, acquisition, and processing resources, resulting in waste of system resources and a decrease in operating efficiency. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of existing atmospheric lidar receiving and splitting systems, which are difficult to provide fine spectral information when using broadband detection and have complex structures and high resource consumption when using multiple narrowband parallel methods. The invention provides a signal-triggered switchable splitting atmospheric lidar receiving system.

[0007] To achieve the above-mentioned objectives, the embodiments of the present invention provide the following technical solutions:

[0008] A signal-triggered switchable beam splitter atmospheric lidar receiving system includes a laser transmission and reception module, a beam splitting and acquisition module, a control module, and a data processing module.

[0009] The laser transceiver module is used to emit lasers into the target space and receive characteristic light signals generated in the target space.

[0010] The beam splitting and acquisition module uses a beam splitting switching mechanism to switch the characteristic light signal, so that the characteristic light signal goes to the coarse detection channel A to obtain the digital sampling point sequence, and the characteristic light signal goes to the fine detection channel B to obtain each group of digital sampling point sequences;

[0011] The control module is used to receive the detection signal of the coarse detection channel A. If the detection signal meets the triggering condition, it controls the optical switching mechanism to select the receiving optical path of the fine detection channel B. If the reception is complete, it controls the optical switching mechanism to select the receiving optical path of the coarse detection channel A.

[0012] The data processing module processes the digital sampling sequence of the coarse detection channel A and returns the detection signal of the coarse detection channel A to the control module. It processes each group of digital sampling sequences of the fine detection channel B to obtain the relative intensity of each narrowband channel and the signal difference between different narrowband channels, and outputs the completed signal to the control module.

[0013] Compared with existing technologies, the advantages of this invention are as follows: This invention, through a beam-splitting mechanism, a coarse detection channel A, a fine detection channel B, and a control module, first performs a broadband search using the coarse detection channel A. When the detection signal meets the trigger condition, the control module controls the beam-splitting mechanism to activate the fine detection channel B for narrowband fine detection. This simultaneously considers the initial target acquisition probability and fine spectral resolution, ensuring both efficient detection of weak signals and obtaining high-resolution spectral information when needed. Furthermore, by sharing a receiving optical path and using a time-division switching mode, this invention activates the fine detection channel B only after confirming the target signal, avoiding long-term parallel operation of multiple narrowband channels, simplifying the system structure, reducing the number of components, and lowering assembly and adjustment difficulty and cost. Finally, through the interaction of detection and completion signals between the data processing module and the control module, this invention forms a closed-loop operation of coarse detection-trigger determination-channel switching-fine detection-reset and search, improving automated response efficiency and the reliability of continuous monitoring.

[0014] Furthermore, a signal-triggered switchable beam splitter atmospheric lidar receiving system, wherein the laser transceiver module includes a laser, a transmitting optical assembly, a receiving telescope, and a front-end coupling optical assembly:

[0015] The laser is used to output a detection laser with predetermined core parameters; the core parameters include wavelength, pulse energy, pulse width, and repetition frequency.

[0016] The transmitting optical component is used to expand, collimate, or shape the probe laser before emitting it into the target space;

[0017] The receiving telescope is used to collect characteristic light signals returned from the target space;

[0018] The front-end coupling optical component is used to output the characteristic optical signal to the beam splitting and acquisition module.

[0019] Furthermore, a signal-triggered switchable beam splitter atmospheric lidar receiving system, wherein the beam splitting and acquisition module includes a beam splitting switching mechanism, a coarse detection channel A, and a fine detection channel B:

[0020] The beam splitting switching mechanism is used to selectively conduct the receiving optical path between the coarse detection channel A and the fine detection channel B;

[0021] The coarse detection channel A is used to perform broadband detection on the characteristic optical signal to obtain a digital sampling point sequence;

[0022] The fine detection channel B is used to perform multi-band fine optical detection on the target signal after the coarse detection channel A has a target signal, and obtain multiple sets of digital sampling point sequences.

[0023] In the above scheme, the beam splitting switching mechanism realizes time-division multiplexing of the receiving optical path, avoiding interference caused by the simultaneous operation of multiple channels; the coarse detection channel A completes broadband detection and acquires the digital sampling point sequence, which can quickly capture the target signal, provide reliable detection basis for the control module, and improve the probability of weak signal detection; the fine detection channel B starts multi-band fine beam splitting after confirming the existence of the target, and acquires multiple sets of digital sampling point sequences; the beam splitting and acquisition module can activate fine detection as needed to reduce resource consumption, and can also obtain the spectral intensity distribution of each narrowband band, supporting subsequent fine spectral analysis.

[0024] Furthermore, a signal-triggered switchable beam splitter atmospheric lidar receiving system includes a beam splitting switching mechanism comprising a drive mechanism, a transmission mechanism, a movable beam splitter, a position detection unit, and a limiting unit.

[0025] The drive mechanism provides the driving force for switching the receiving optical path;

[0026] The transmission mechanism converts the driving force into a transmission force, driving the movable beam splitter to move to a first position or a second position; the first position is the working position where the receiving optical path is connected to the coarse detection channel A; the second position is the working position where the receiving optical path is connected to the fine detection channel B.

[0027] The position detection unit detects whether the movable beam splitter has moved to the working position;

[0028] The limiting unit restricts the maximum movement of the movable beam splitter.

[0029] In the above scheme, the drive mechanism provides the switching driving force, which is converted into linear or oscillating motion by the transmission mechanism, driving the movable beam splitter to move precisely to the first or second position, reliably realizing the switching of the receiving optical path between the coarse detection channel A and the fine detection channel B; the position detection unit detects in real time whether the movable beam splitter has accurately reached the working position, ensuring that subsequent detection can only be carried out after switching to the correct position, avoiding optical path misalignment or signal loss due to position deviation; the limit unit limits the maximum movement of the movable beam splitter to prevent mechanical collision or damage to optical components caused by overtravel; the beam splitting switching mechanism realizes the automation, precision and safety of optical path switching, ensuring that the system can quickly and stably switch between the two modes of broadband search and narrowband fine detection, improving response speed and long-term operational reliability.

[0030] Furthermore, a signal-triggered switchable beam splitter atmospheric lidar receiving system, wherein the coarse detection channel A includes a first coupling optics, a broadband filter, a focusing optics, a first photodetector, and a first acquisition circuit.

[0031] The first coupling optics is used to collimate, beam-contract, or focus the characteristic optical signal and output it to a broadband filter;

[0032] The broadband filter filters out background light that deviates from the target wavelength range and outputs the target signal to the focusing optics.

[0033] The focusing optics couples the target signal to the receiving surface of the first photodetector;

[0034] The first photodetector converts the target signal into a photocurrent signal and outputs it to the first acquisition circuit;

[0035] The first acquisition circuit sequentially performs transimpedance amplification, filtering, and analog-to-digital conversion on the photocurrent signal to obtain a digital sampling point sequence, which is then output to the data processing module.

[0036] In the above scheme, the first coupling optics collimates, reduces, or focuses the characteristic optical signal to improve light energy utilization efficiency; the broadband filter filters out background light deviating from the target band, effectively suppressing environmental interference; the focusing optics converges the target signal to the receiving surface of the first photodetector, enhancing the coupling effect; the first photodetector converts the optical signal into photocurrent, and the first acquisition circuit sequentially performs transimpedance amplification, filtering, and analog-to-digital conversion to finally obtain a high-quality digital sampling point sequence; the coarse detection channel A realizes high signal-to-noise ratio signal acquisition under broadband conditions, providing a reliable data foundation for subsequent target existence determination, while significantly reducing out-of-band noise and improving the detection capability of weak signals.

[0037] Furthermore, a signal-triggered switchable beam splitter atmospheric lidar receiving system, wherein the fine detection channel B includes a second coupling optics, multiple narrowband filters, a photoelectric conversion component, and a second acquisition circuit.

[0038] The second coupling optics is used to collimate, beam-shrink, or focus the characteristic optical signal and output it to a narrowband filter;

[0039] The narrowband filter decomposes the characteristic optical signal into multiple narrowband signals and outputs them to the photoelectric conversion component.

[0040] The photoelectric conversion component converts multiple narrowband signals into multiple photocurrent signals and outputs them to the second acquisition circuit.

[0041] The second acquisition circuit sequentially amplifies, filters, and converts each photocurrent signal across impedance, obtains multiple sets of digital sampling point sequences, and outputs them to the data processing module.

[0042] In the above scheme, the second coupling optics collimates, beam-shrinks, or focuses the characteristic optical signal to improve the light energy transmission efficiency; multiple narrowband filters decompose the signal into narrowband bands with different center wavelengths to achieve fine spectral separation; the photoelectric conversion component synchronously converts each narrowband optical signal into multiple photocurrents to avoid crosstalk; the second acquisition circuit sequentially amplifies, filters, and converts each current through transimpedance amplification, filtering, and analog-to-digital conversion to obtain multiple sets of digital sampling point sequences; the fine detection channel B is activated only after the existence of the target is confirmed, and can obtain the spectral intensity distribution of multiple narrowband bands in parallel or time-division, which reduces system resource consumption and provides a high-resolution data foundation for subsequent fine spectral analysis.

[0043] Furthermore, in a signal-triggered switchable beam splitter atmospheric lidar receiving system, the photoelectric conversion component is selected from one of the following: a photodetector array, multiple independent detectors, or a single photodetector with a switchable sampling structure.

[0044] In the above schemes, the photoelectric conversion component can be selected from photodetector arrays, multiple independent detectors, or a single detector combined with a switching sampling structure. Multiple independent detectors can acquire all narrowband bands in parallel, achieving the fastest speed in obtaining complete spectral data; a single photodetector combined with a switching sampling structure requires only a single detector, resulting in the lowest hardware cost and making it suitable for slowly changing signals or cost-sensitive scenarios; photodetector arrays have high integration and small size, facilitating system miniaturization. The photoelectric conversion component can be flexibly selected according to actual needs, balancing detection speed, cost, and size.

[0045] Furthermore, in a signal-triggered switchable beam splitter atmospheric lidar receiving system, the determination of whether the triggering condition is met specifically includes:

[0046] like or If the characteristic optical signal is determined to contain a target signal, the optical switching mechanism is controlled to select and activate the receiving optical path of the fine detection channel B.

[0047] in, For the effective signal amplitude, For signal-to-noise ratio, For amplitude threshold, This is the signal-to-noise ratio threshold.

[0048] In the above scheme, when the effective signal amplitude exceeds the amplitude threshold or the signal-to-noise ratio exceeds the signal-to-noise ratio threshold, the presence of a target signal is determined, and the optical switching mechanism is automatically controlled to activate the fine detection channel B. The scheme employs dual-parameter OR logic of amplitude and signal-to-noise ratio, which ensures a fast response when there is a strong signal and reliable triggering when there is a weak signal but the signal-to-noise ratio meets the standard, avoiding missed detections or false detections that may occur under a single threshold condition. By presetting calibrable thresholds, the scheme can flexibly adapt to different atmospheric environments and detection scenarios, achieving accurate and timely switching from coarse detection to fine detection, thus improving the reliability of triggering and environmental adaptability.

[0049] Furthermore, a signal-triggered switchable beam splitter atmospheric lidar receiving system includes a data processing module comprising a coarse detection data processing module and a fine detection data processing module.

[0050] The coarse detection data processing module processes the digital sampling sequence to obtain the detection signal of coarse detection channel A, and outputs it to the control module; the detection signal includes the effective signal amplitude and the signal-to-noise ratio;

[0051] The fine detection data processing module performs background subtraction and sliding window filtering on each group of digital sampling sequences to obtain the filtered signal. It then uses the filtered signal and the target sampling area to obtain the feature intensity of each narrowband channel. The feature intensity of each narrowband channel is normalized to obtain the relative intensity of each narrowband channel. By comparing the feature intensity of different narrowband channels, the signal difference between different narrowband channels is obtained. Finally, the completion signal of the fine detection data processing is output to the control module.

[0052] In the above scheme, the coarse detection data processing module extracts the effective signal amplitude and signal-to-noise ratio from the digital sampling sequence, providing the control module with accurate trigger judgment basis and ensuring that fine detection can be started in time when the target is present. The fine detection data processing module performs background subtraction, sliding window filtering, feature intensity extraction, normalization processing and inter-channel difference comparison on each group of digital sampling sequences in sequence, and finally feeds back the signal completed by fine detection to the control module. It forms a closed-loop management from raw data to detection signal and then to fine spectral features, which reduces the burden of host computer or manual intervention and improves the level of automation of data processing and real-time response capability.

[0053] Furthermore, in a signal-triggered switchable beam splitter atmospheric lidar receiving system, the fine detection data processing module specifically comprises:

[0054] The last M digital sampling points in the j-th group of digital sampling sequence are used as the background sampling area of ​​the j-th group to obtain the background mean of the j-th group.

[0055] The background subtraction is performed on the digital sampling point sequence of the j-th group based on the background mean of the j-th group to obtain the net signal of the j-th group;

[0056] The j-th net signal is filtered through a sliding window to obtain the j-th filtered signal;

[0057] The feature intensity of the j-th narrowband channel is extracted by using the preset target sampling area and the j-th group of filtered signals.

[0058] The characteristic intensity of the j-th narrowband channel is normalized to obtain the relative intensity of the j-th narrowband channel;

[0059] The signal difference between any two narrowband channels can be obtained by comparing the characteristic intensities of any two narrowband channels.

[0060] In the above scheme, the fine detection data processing module performs background subtraction and sliding window filtering on the digital sampling sequences of each narrowband channel, effectively suppressing dark current, ambient light, and random noise, and improving the signal-to-noise ratio. By extracting the characteristic intensity of each channel and performing normalization processing, common-mode interference such as laser energy fluctuation and distance attenuation is eliminated, and the relative intensity reflecting the intrinsic spectral characteristics of the material is obtained. By comparing the intensity difference between any two channels, the relative strength of different bands is highlighted for material identification, spectral comparison, or concentration inversion. At the same time, the completed signal is fed back to the control module to realize channel reset and closed-loop control. Attached Figure Description

[0061] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is a structural diagram of a switchable beam splitter atmospheric lidar receiving system.

[0063] Figure 2 This is a structural diagram of the laser transceiver module.

[0064] Figure 3 This is a structural diagram of the spectral splitting and acquisition module. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0066] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance, or suggesting any such actual relationship or order between these entities or operations. Additionally, the terms "connected," "linked," etc., can refer to a direct connection between elements or an indirect connection via other elements.

[0067] like Figure 1 As shown, a signal-triggered switchable beam splitting atmospheric lidar receiving system includes a laser transmitting and receiving module, a beam splitting and acquisition module, a control module, and a data processing module.

[0068] The laser transceiver module is used to emit laser light into the target space and receive characteristic light signals generated in the target space.

[0069] like Figure 2 As shown, the laser transceiver module includes a laser, a transmitting optical component, a receiving telescope, and a front-end coupling optical component.

[0070] The laser is used to output a detection laser with predetermined core parameters, which is then output to the emitting optical components; the core parameters include wavelength, pulse energy, pulse width, and repetition frequency;

[0071] The transmitting optical component is used to expand, collimate, or shape the detection laser before transmitting it to the target space; the target space specifically refers to the atmospheric region detected by the switchable beam splitter atmospheric lidar receiving system;

[0072] The receiving telescope is used to collect characteristic light signals returning from the target space and output them to the front-end coupling optical components; the characteristic light signals include backscattered light signals, fluorescence radiation light signals or other characteristic light signals; the other characteristic light signals include Raman scattering light signals, Doppler frequency shift light signals, resonance scattering light signals, etc.

[0073] The front-end coupling optical component is used to output the characteristic optical signal to the beam splitting and acquisition module.

[0074] The beam splitting and acquisition module uses a beam splitting switching mechanism to switch the characteristic light signal, so that the characteristic light signal goes to the coarse detection channel A to obtain the digital sampling point sequence, and the characteristic light signal goes to the fine detection channel B to obtain each group of digital sampling point sequences.

[0075] like Figure 3 As shown, the beam splitting and acquisition module includes a beam splitting switching mechanism, a coarse detection channel A, and a fine detection channel B; the first output terminal of the beam splitting switching mechanism is connected to the input terminal of the coarse detection channel A, and the second output terminal of the beam splitting switching mechanism is connected to the input terminal of the fine detection channel B.

[0076] The beam splitting switching mechanism is used to selectively conduct the receiving optical path between the coarse detection channel A and the fine detection channel B.

[0077] The beam splitting switching mechanism includes a drive mechanism, a transmission mechanism, a movable beam splitter, a position detection unit, and a limit unit.

[0078] The driving mechanism provides the driving force for switching the receiving optical path; the transmission mechanism converts the driving force into a transmission force (linear motion or oscillation), driving the movable beam splitter to move to a first position or a second position; the first position is the working position where the receiving optical path is connected to the coarse detection channel A; the second position is the working position where the receiving optical path is connected to the fine detection channel B; the position detection unit detects whether the movable beam splitter has moved to the working position; the limiting unit restricts the movable beam splitter to the furthest position it can move.

[0079] The driving mechanism is selected from one of the following: servo motor, stepper motor, voice coil motor, piezoelectric driver, and electromagnetic flipping mechanism; the movable beam splitter is selected from one of the following: reflector, beam splitter, flipping mirror, prism, slider-type light guide element, or other optical element capable of changing the direction of the light path. The position detection unit is selected from one of the following: photoelectric switch, Hall sensor, or limit switch, and determines whether the receiving light path has been switched based on the position detection signal of the movable beam splitter.

[0080] In this embodiment, the movable beam splitter is a reflector assembly.

[0081] Specifically, in the initial working state of the switching beam splitter atmospheric lidar receiving system, the movable beam splitter is in the first position, allowing the characteristic light signal to enter the coarse detection channel A through the receiving optical path for broadband detection. The control module determines the detection signal of the coarse detection channel A. If the detection signal meets the trigger condition, it controls the servo motor to move the movable beam splitter to the second position, switching to the fine detection channel B for fine detection. After the detection is completed, the movable beam splitter is moved back to the first position to return to its original position.

[0082] The coarse detection channel A is used to perform broadband detection on the characteristic optical signal to obtain a digital sampling point sequence.

[0083] The coarse detection channel A includes a first coupling optics, a broadband filter, a focusing optics, a first photodetector, and a first acquisition circuit.

[0084] The passband width of the broadband filter is greater than the bandwidth of a single narrowband filter in the fine detection channel B.

[0085] In this embodiment, the passband width of the broadband filter in the coarse detection channel A is 120nm (target wavelength range).

[0086] The first coupling optics is used to collimate, beam-shrink, or focus the characteristic optical signal and output it to a broadband filter; the broadband filter filters out background light that deviates from the target wavelength range and outputs the target fluorescence signal (or other target signals that are first coarsely detected and then finely spectroscopically detected) to the focusing optics; the focusing optics couples the target fluorescence signal to the receiving surface of the first photodetector; the first photodetector converts the target fluorescence signal into a photocurrent signal and outputs it to the first acquisition circuit; the first acquisition circuit sequentially performs transimpedance amplification, filtering, and analog-to-digital conversion on the photocurrent signal to obtain a digital sampling point sequence, which is then output to the data processing module.

[0087] In this embodiment, the first photodetector is a photomultiplier tube (PMT).

[0088] The first acquisition circuit specifically amplifies the photocurrent signal across impedance and converts it into a voltage signal, as shown in the formula:

[0089] ;

[0090] in, The voltage signal at time t. The photocurrent signal at time t. t represents the feedback resistor of the transimpedance amplifier, and t is the time step index.

[0091] In the embodiments, .

[0092] The voltage signal is passed through a low-pass filter to suppress high-frequency noise, resulting in a filtered voltage signal, as shown in the formula:

[0093] ;

[0094] in, Let be the filtered voltage signal at time t. Let be the integral variable (all past moments). for Voltage signal at time, for The impulse response value of the low-pass filter at any given time.

[0095] The filtered voltage signal is converted from analog to digital to obtain digital sampling points. These digital sampling points are then integrated to obtain a digital sampling point sequence, as shown in the formula:

[0096] ;

[0097] in, For the nth digital sampling point, For discrete sampling point index, N is the total number of discrete sampling points. The sampling time of the nth sampling point Sampling time The filtered voltage signal For ADC analog-to-digital conversion operation, The sampling period.

[0098] In the embodiments, .

[0099] The fine detection channel B is used to perform multi-band fine spectrophotometric detection on the target fluorescence signal after the coarse detection channel A has a target fluorescence signal, and obtain multiple sets of digital sampling point sequences.

[0100] The fine detection channel B includes a second coupling optics, multiple narrowband filters, a photoelectric conversion component, and a second acquisition circuit.

[0101] The second coupling optics is used to collimate, beam-shrink, or focus the characteristic optical signal and output it to a narrowband filter; the narrowband filter decomposes the characteristic optical signal into multiple narrowband signals and outputs them to a photoelectric conversion component; the photoelectric conversion component converts the multiple narrowband signals into multiple photocurrent signals and outputs them to a second acquisition circuit; the second acquisition circuit sequentially performs transimpedance amplification, filtering, and analog-to-digital conversion on each photocurrent signal to obtain multiple sets of digital sampling point sequences and output them to the data processing module.

[0102] It should be noted that the specific processing procedure of the second acquisition circuit is the same as that of the first acquisition circuit. The difference is that the final result is a sequence of multiple digital sampling points (corresponding to each band).

[0103] In this embodiment, six narrowband filters are provided inside the fine detection channel B, each narrowband filter having a different center wavelength or a different band range.

[0104] The photoelectric conversion component can be selected from one of the following: a photodetector array, multiple independent detectors, or a single photodetector combined with a switching sampling structure;

[0105] Specifically, when selecting a photodetector array, each column of the photodetector array and each narrowband filter are configured accordingly, so that different narrowband signals are output to the second acquisition circuit. When selecting multiple independent detectors, each branch (which is achieved by beam splitter group, integrating beam splitter, and multi-path light guide structure) is equipped with a single narrowband filter and an independent detector. Each branch performs photoelectric conversion independently, so that different narrowband signals are output to the second acquisition circuit in parallel. When selecting a single photodetector in conjunction with a switching sampling structure, multiple narrowband filters are installed on the switching mechanism (filter wheel, filter stage), and different narrowband filters are driven to enter the optical path in sequence, so that different narrowband signals are output to a single photodetector in a time-division manner, and the single photodetector acquires signals band by band.

[0106] It is important to note that each photodetector in the photodetector array converts a fine band signal, achieving parallel conversion of electrical signals. Each of multiple independent detectors converts a fine band signal, achieving parallel conversion of electrical signals. A single photodetector, in conjunction with a switching sampling structure, converts electrical signals one fine band signal at a time, achieving serial switching of electrical signals.

[0107] The control module controls the coarse detection channel A, the beam splitting switching mechanism, and the fine detection channel B, respectively.

[0108] The control module is used to receive the detection signal of the coarse detection channel A. If the detection signal meets the triggering condition, it controls the optical switching mechanism to select the receiving optical path of the fine detection channel B. If the reception is complete, it controls the optical switching mechanism to select the receiving optical path of the coarse detection channel A.

[0109] The specific determination of whether the triggering condition is met is as follows:

[0110] like or If the characteristic optical signal is found to contain a target fluorescence signal, the optical switching mechanism is controlled to select and activate the receiving optical path of the fine detection channel B.

[0111] in, For amplitude threshold, This is the signal-to-noise ratio threshold.

[0112] The data processing module processes the digital sampling sequence of the coarse detection channel A and returns the detection signal of the coarse detection channel A to the control module. It processes each group of digital sampling sequences of the fine detection channel B to obtain the relative intensity of each narrowband channel and the signal difference between different narrowband channels, and outputs the completed signal to the control module.

[0113] The data processing module includes a coarse detection data processing module and a fine detection data processing module.

[0114] The coarse detection data processing module processes the digital sampling sequence to obtain the detection signal of coarse detection channel A, and outputs it to the control module; the detection signal includes the effective signal amplitude and signal-to-noise ratio.

[0115] The coarse detection data processing module specifically uses the last M digital sampling points in the digital sampling sequence as the background sampling area to obtain the background mean and background standard deviation, as follows:

[0116] ;

[0117] Where M is the number of digital sampling points in the background, and i is the index of the digital sampling point in the background sampling area. For the i-th digital sampling point, The background mean. The standard deviation is the background value.

[0118] In the embodiments, .

[0119] The peak signal is extracted through a preset target sampling area using the following formula:

[0120] ;

[0121] in, This is the peak signal. The target sampling area.

[0122] The effective signal amplitude is obtained by using the peak signal and the background mean, using the following formula:

[0123] ;

[0124] in, This represents the effective signal amplitude.

[0125] The signal-to-noise ratio (SNR) is obtained by using the effective signal amplitude and the background standard deviation, using the following formula:

[0126] ;

[0127] in, This refers to the signal-to-noise ratio.

[0128] It should be noted that the target sampling area refers to a continuous interval in the digital sampling point sequence where the target characteristic optical signal is expected to appear.

[0129] The fine detection data processing module performs background subtraction and sliding window filtering on each group of digital sampling sequences to obtain the filtered signal. It then uses the filtered signal and the target sampling area to obtain the feature intensity of each narrowband channel. The feature intensity of each narrowband channel is normalized to obtain the relative intensity of each narrowband channel. By comparing the feature intensity of different narrowband channels, the signal difference between different narrowband channels is obtained. Finally, the completion signal of the fine detection data processing is output to the control module.

[0130] The fine detection data processing module specifically uses the last M digital sampling points in the j-th group of digital sampling sequences as the background sampling area of ​​the j-th group to obtain the background mean of the j-th group, as shown in the formula:

[0131] ;

[0132] in, Let J be the background mean of the j-th group, where j is the narrowband channel index, j=1,2,3...J, and J is the total number of narrowband channels (6 in the example). This is the i-th digital sampling point in the j-th group.

[0133] Background subtraction is performed on the j-th digital sampling point sequence based on the background mean of the j-th group to obtain the net signal of the j-th group. The formula is as follows:

[0134] ;

[0135] in, For the nth net signal in the j-th group, This is the nth digital sampling point in the j-th group.

[0136] Let the length of the sliding window be L. The formula for filtering the j-th group of net signals through the sliding window to obtain the j-th filtered signal is:

[0137] ;

[0138] in, Let j be the filtered signal of the j-th group. For the summation variable, This is the k-th net signal in the j-th group.

[0139] It should be noted that for sampling points that are not complete at the beginning or end of the window, the following methods should be used: fill in the boundary points, copy the boundary values, or shorten the length of the edge window.

[0140] The feature intensity of the j-th narrowband channel is extracted using a preset target sampling area and the filtered signal of the j-th group, as shown in the formula:

[0141] ;

[0142] in, Let be the characteristic intensity of the j-th narrowband channel.

[0143] The characteristic intensity of the j-th narrowband channel is normalized to obtain the relative intensity of the j-th narrowband channel, as shown in the formula:

[0144] ;

[0145] in, Let be the relative intensity of the j-th narrowband channel. For the summation variable, For the first The characteristic intensity of a narrowband channel.

[0146] The signal difference between any two narrowband channels is obtained by comparing their characteristic intensities, using the following formula:

[0147] ;

[0148] in, The signal difference between the j-th narrowband channel and the p-th narrowband channel is... Let p be the characteristic intensity of the p-th narrowband channel. It should be a small positive number (to prevent the denominator from being zero).

[0149] It should be noted that the broadband intensity of the coarse detection channel A can be used as a reference to calibrate the j-th group of net signals in the fine detection channel B, in order to eliminate the influence of factors such as laser energy fluctuations. Alternatively, a discrete feature spectrum can be constructed using the center wavelength of each narrowband filter in the fine detection channel B and the relative intensity of the corresponding narrowband channel, which can be used for subsequent spectral comparison and target analysis.

[0150] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A signal triggered switchable split-path atmospheric laser radar receiving system, characterized in that Includes a laser transceiver module, a beam splitting and acquisition module, a control module, and a data processing module: The laser transceiver module is used to emit lasers into the target space and receive characteristic light signals generated in the target space. The beam splitting and acquisition module uses a beam splitting switching mechanism to switch the characteristic light signal, so that the characteristic light signal goes to the coarse detection channel A to obtain the digital sampling point sequence, and the characteristic light signal goes to the fine detection channel B to obtain each group of digital sampling point sequences; The control module is used to receive the detection signal of the coarse detection channel A. If the detection signal meets the triggering condition, it controls the optical switching mechanism to select the receiving optical path of the fine detection channel B. If the reception is complete, it controls the optical switching mechanism to select the receiving optical path of the coarse detection channel A. The data processing module processes the digital sampling sequence of the coarse detection channel A and returns the detection signal of the coarse detection channel A to the control module. It processes each group of digital sampling sequences of the fine detection channel B to obtain the relative intensity of each narrowband channel and the signal difference between different narrowband channels, and outputs the completed signal to the control module.

2. The signal triggered switchable split-path atmospheric laser radar receiving system according to claim 1, characterized in that The laser transceiver module includes a laser, a transmitting optical assembly, a receiving telescope, and a front-end coupling optical assembly. The laser is used to output a detection laser with predetermined core parameters; the core parameters include wavelength, pulse energy, pulse width, and repetition frequency. The transmitting optical component is used to expand, collimate, or shape the probe laser before emitting it into the target space; The receiving telescope is used to collect characteristic light signals returned from the target space; The front-end coupling optical component is used to output the characteristic optical signal to the beam splitting and acquisition module.

3. The signal triggered switchable split-path atmospheric laser radar receiving system according to claim 1, characterized in that The spectral splitting and acquisition module includes a spectral switching mechanism, a coarse detection channel A, and a fine detection channel B. The beam splitting switching mechanism is used to selectively conduct the receiving optical path between the coarse detection channel A and the fine detection channel B; The coarse detection channel A is used to perform broadband detection on the characteristic optical signal to obtain a digital sampling point sequence; The fine detection channel B is used to perform multi-band fine optical detection on the target signal after the coarse detection channel A has a target signal, and obtain multiple sets of digital sampling point sequences.

4. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 3, characterized in that, The beam splitting switching mechanism includes a driving mechanism, a transmission mechanism, a movable beam splitter, a position detection unit, and a limiting unit. The drive mechanism provides the driving force for switching the receiving optical path; The transmission mechanism converts the driving force into a transmission force, driving the movable beam splitter to move to a first position or a second position; the first position is the working position where the receiving optical path is connected to the coarse detection channel A; the second position is the working position where the receiving optical path is connected to the fine detection channel B. The position detection unit detects whether the movable beam splitter has moved to the working position; The limiting unit restricts the maximum movement of the movable beam splitter.

5. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 3, characterized in that, The coarse detection channel A includes a first coupling optics, a broadband filter, a focusing optics, a first photodetector, and a first acquisition circuit. The first coupling optics is used to collimate, beam-contract, or focus the characteristic optical signal and output it to a broadband filter; The broadband filter filters out background light that deviates from the target wavelength range and outputs the target signal to the focusing optics. The focusing optics couples the target signal to the receiving surface of the first photodetector; The first photodetector converts the target signal into a photocurrent signal and outputs it to the first acquisition circuit; The first acquisition circuit sequentially performs transimpedance amplification, filtering, and analog-to-digital conversion on the photocurrent signal to obtain a digital sampling point sequence, which is then output to the data processing module.

6. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 3, characterized in that, The fine detection channel B includes a second coupling optics, multiple narrowband filters, a photoelectric conversion component, and a second acquisition circuit. The second coupling optics is used to collimate, beam-shrink, or focus the characteristic optical signal and output it to a narrowband filter; The narrowband filter decomposes the characteristic optical signal into multiple narrowband signals and outputs them to the photoelectric conversion component. The photoelectric conversion component converts multiple narrowband signals into multiple photocurrent signals and outputs them to the second acquisition circuit. The second acquisition circuit sequentially amplifies, filters, and converts each photocurrent signal across impedance, obtains multiple sets of digital sampling point sequences, and outputs them to the data processing module.

7. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 6, characterized in that, The photoelectric conversion component can be selected from one of the following: photodetector array, multiple independent detectors, or a single photodetector with a switching sampling structure.

8. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 1, characterized in that, The determination of whether the triggering condition is met is specifically as follows: like or If the characteristic optical signal is determined to contain a target signal, the optical switching mechanism is controlled to select and activate the receiving optical path of the fine detection channel B. in, For the effective signal amplitude, For signal-to-noise ratio, For amplitude threshold, This is the signal-to-noise ratio threshold.

9. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 1, characterized in that, The data processing module includes a coarse detection data processing module and a fine detection data processing module. The coarse detection data processing module processes the digital sampling sequence to obtain the detection signal of coarse detection channel A, and outputs it to the control module; the detection signal includes the effective signal amplitude and the signal-to-noise ratio; The fine detection data processing module performs background subtraction and sliding window filtering on each group of digital sampling sequences to obtain the filtered signal. It then uses the filtered signal and the target sampling area to obtain the feature intensity of each narrowband channel. The feature intensity of each narrowband channel is normalized to obtain the relative intensity of each narrowband channel. By comparing the feature intensity of different narrowband channels, the signal difference between different narrowband channels is obtained. Finally, the completion signal of the fine detection data processing is output to the control module.

10. The signal-triggered switchable beam splitter atmospheric lidar receiving system according to claim 9, characterized in that, The detailed detection data processing module is specifically as follows: The last M digital sampling points in the j-th group of digital sampling sequence are used as the background sampling area of ​​the j-th group to obtain the background mean of the j-th group. The background subtraction is performed on the digital sampling point sequence of the j-th group based on the background mean of the j-th group to obtain the net signal of the j-th group; The j-th net signal is filtered through a sliding window to obtain the j-th filtered signal; The feature intensity of the j-th narrowband channel is extracted by using the preset target sampling area and the j-th group of filtered signals. The characteristic intensity of the j-th narrowband channel is normalized to obtain the relative intensity of the j-th narrowband channel; The signal difference between any two narrowband channels can be obtained by comparing the characteristic intensities of any two narrowband channels.

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