Multi-channel data synchronous acquisition system and method for hyperspectral lidar

Abstract

The application relates to the technical field of surveying and mapping remote sensing, in particular to a multi-channel data synchronous acquisition system and method for a hyperspectral lidar, which comprises the following units: an optoelectronic conversion unit, which is used for converting optical signals of echo signals of the hyperspectral lidar into electrical signals; a clock synchronization unit, which is used for sending a global trigger signal and a unified clock signal; a plurality of waveform acquisition units, which are used for synchronously acquiring echo signals of the hyperspectral lidar based on the global trigger signal and the unified clock signal, wherein each waveform acquisition unit comprises a plurality of waveform acquisition channels; a plurality of disk storage units, which are used for storing the echo signals of the hyperspectral lidar; and an upper computer control unit, which is used for controlling corresponding target actions of the above units after detecting laser pulse signals emitted by the hyperspectral lidar. Thus, the problem that the hyperspectral lidar lacks an effective multi-channel synchronous acquisition mechanism and further influences the quality of subsequent data is solved.

Description

Technical Field

[0001] The present application relates to the field of surveying, mapping and remote sensing technology, and in particular to a multi-channel data synchronous acquisition system and method for hyperspectral lidar. Background Art

[0002] Hyperspectral LiDAR is a new type of LiDAR technology that combines the advantages of traditional single-wavelength LiDAR and hyperspectral imaging, enabling the integrated acquisition of spatial geometric and spectral information of ground objects. Hyperspectral LiDAR's components primarily include a supercontinuum laser, a scanning mirror, an optical receiving unit, a photoelectric conversion unit, a signal acquisition unit, and a host computer control unit. Its workflow involves the laser emitting a supercontinuum laser pulse, which is reflected by the scanning mirror onto the ground object. The backscattered echo from the interaction between the emitted laser and the ground object then returns to the optical receiving unit via the scanning mirror. The optical receiving unit uses grating spectroscopy to split the continuum echo into dozens of spectral signals. These dozens of spectral signals are then converted by the photoelectric conversion unit into analog voltage signals containing ground object geometric distance and spectral intensity information. These analog voltage signals are then collected by the acquisition unit, while the host computer control unit coordinates and manages the coordinated and orderly operation of all components of the system.

[0003] In existing hyperspectral lidar systems, due to the lack of an effective multi-channel synchronization mechanism, data collection in multiple bands often has time deviations. In other words, existing technologies cannot achieve synchronous collection of data from multiple channels, which makes it difficult to match data from different bands, affecting the quality of the final data and the application effect. Summary of the Invention

[0004] The present application provides a multi-channel data synchronous acquisition system and method for hyperspectral lidar to solve the problem that hyperspectral lidar lacks an effective multi-channel synchronous acquisition mechanism, which in turn affects the subsequent data quality.

[0005] The first aspect of the present application provides a multi-channel data synchronization acquisition system for a hyperspectral laser radar, including: a photoelectric conversion unit for converting the optical signal of the echo of the hyperspectral laser radar into an electrical signal; a clock synchronization unit for issuing a global trigger signal and a unified clock signal; multiple waveform acquisition units for controlling the multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar based on the global trigger signal and the unified clock signal, wherein each waveform acquisition unit includes multiple waveform acquisition channels; multiple disk storage units for storing the echo signal of the hyperspectral laser radar; and a host computer control unit for controlling the photoelectric conversion unit, the clock synchronization unit, the multiple waveform acquisition units and the multiple disk storage units to perform corresponding target actions after detecting the laser pulse signal emitted by the hyperspectral laser radar.

[0006] Optionally, the upper computer control unit is also used to: determine a reference waveform acquisition unit from multiple waveform acquisition units; perform signal threshold detection on the echo signal acquired by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information; distribute the cross-threshold waveform segment reference information to each waveform acquisition unit, and each waveform acquisition unit determines the target cross-threshold waveform segment from the acquired echo signal according to the cross-threshold waveform segment reference information; and store the target cross-threshold waveform segment in multiple disk storage units.

[0007] Optionally, the waveform acquisition unit includes: a core circuit, a signal conditioning circuit, a multi-channel digital-to-analog conversion circuit, a clock management circuit, a cache unit and an interface circuit, wherein the core circuit is used to read and process the echo signal of the hyperspectral laser radar in the multi-channel digital-to-analog conversion circuit, and cache the echo signal of the hyperspectral laser radar in the multi-channel digital-to-analog conversion circuit; the signal conditioning circuit is used to convert the single-ended signal output by the photoelectric conversion unit into a differential signal, and input the signal amplitude into the multi-channel analog-to-digital conversion circuit after adjusting the signal amplitude; the multi-channel digital-to-analog conversion circuit is used to sample and digital-to-analog convert the echo signal of the hyperspectral laser radar; the clock management circuit is used to receive the unified clock signal issued by the clock synchronization unit to achieve multi-channel synchronization; the cache unit is used to temporarily cache the echo signal of the hyperspectral laser radar before and after processing by the core circuit; the interface circuit is used to receive the unified clock signal and global trigger signal issued by the clock synchronization unit, and transmit the echo signal of the hyperspectral laser radar processed by the core circuit to multiple disk storage units.

[0008] The second aspect of the present application provides a multi-channel data synchronization acquisition method for a hyperspectral laser radar, which is acquired using a multi-channel data synchronization acquisition system for a hyperspectral laser radar as in the above embodiment, and includes the following steps: detecting the laser pulse signal emitted by the hyperspectral laser radar; after detecting the laser pulse signal, controlling the clock synchronization unit to send a global trigger signal and a unified clock signal; based on the global trigger signal and the unified clock signal, controlling multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar, wherein each waveform acquisition unit includes multiple waveform acquisition channels; and storing the echo signal of the hyperspectral laser radar in multiple disk storage units.

[0009] Optionally, based on a global trigger signal and a unified clock signal, multiple waveform acquisition units are controlled to synchronously acquire the echo signal of the hyperspectral lidar, including: using a photoelectric conversion unit to convert the optical signal of the echo of the hyperspectral lidar into an electrical signal; controlling multiple waveform acquisition channels of the multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral lidar.

[0010] Optionally, before storing the echo signal of the hyperspectral lidar in multiple disk storage units, it also includes: determining a reference waveform acquisition unit from multiple waveform acquisition units; performing signal threshold detection on the echo signal acquired by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information; distributing the cross-threshold waveform segment reference information to each waveform acquisition unit, and each waveform acquisition unit determines the target cross-threshold waveform segment from the acquired echo signal according to the cross-threshold waveform segment reference information; and storing the target cross-threshold waveform segment in multiple disk storage units.

[0011] Optionally, an over-threshold detection is performed on the echo signal collected by the reference waveform acquisition unit to obtain over-threshold waveform segment reference information, including: obtaining the echo signals cached in multiple waveform acquisition channels of the reference waveform acquisition unit; performing a noise threshold evaluation on the cached echo signals; determining a target value of the signal threshold based on the result of the noise threshold evaluation; and performing a signal threshold detection on the echo signal collected by the reference waveform acquisition unit based on the target value to obtain over-threshold waveform segment reference information.

[0012] Optionally, the noise threshold evaluation is calculated as:

[0013] threshold noise =m noise +λ·σ noise ;

[0014] Among them, threshold noise is the noise threshold, m noise is the mean value of the amplitude of multiple sampling points at the beginning and end of the echo signal band, σ noise is the standard deviation of multiple sampling points at the beginning or end of the echo signal waveform, and λ is the noise threshold coefficient.

[0015] Optionally, the threshold-crossing waveform segment reference information algorithm is:

[0016] P latency =∪(T cuts (i,j));

[0017] Among them, T cuts are the cross-threshold waveform segments on each reference waveform acquisition channel, i is the channel number, j is the cross-threshold waveform segment number on each reference waveform acquisition channel, and ∪ represents the union of the time position information of the cross-threshold waveform segments.

[0018] The third aspect of the present application provides a host computer, including: a memory, a processor, and a computer program stored in the memory and runnable on the processor. The processor executes the program to perform the multi-channel data synchronization acquisition method for hyperspectral lidar as described in the above embodiment.

[0019] The fourth aspect of the present application provides a computer-readable storage medium having a computer program or instruction stored thereon, and the computer program or instruction is executed by a processor to perform a multi-channel data synchronous acquisition method for hyperspectral lidar.

[0020] Therefore, this application has at least the following beneficial effects:

[0021] After detecting the laser pulse signal emitted by the hyperspectral lidar, the embodiment of the present application can send a global trigger signal and a unified clock signal through the clock synchronization unit. Multiple waveform acquisition channels in multiple waveform acquisition units can synchronously acquire the hyperspectral lidar's echo signal, thereby achieving high-precision synchronous acquisition of data from multiple band channels, thereby improving the subsequent data quality. This solves the technical problem that hyperspectral lidar lacks an effective multi-channel synchronous acquisition mechanism, which in turn affects the subsequent data quality.

[0022] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0024] Figure 1 Schematic diagram of a multi-channel data synchronization acquisition system for hyperspectral lidar provided according to an embodiment of the present application;

[0025] Figure 2 A schematic diagram of a synchronous acquisition system provided according to a specific embodiment of the present application;

[0026] Figure 3 A schematic diagram of the structure of a clock synchronization unit provided according to an embodiment of the present application;

[0027] Figure 4 A schematic structural diagram of a waveform acquisition unit provided according to an embodiment of the present application;

[0028] Figure 5 This is a flowchart of a method for synchronously acquiring multi-channel data for a hyperspectral lidar according to an embodiment of the present application;

[0029] Figure 6 Schematic diagram of the structure of the host computer provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0031] The following describes the multi-channel data synchronization acquisition system and method for hyperspectral laser radar in accordance with an embodiment of the present application with reference to the accompanying drawings. In view of the existing hyperspectral laser radar system mentioned in the background technology center, due to the lack of an effective multi-channel synchronization mechanism, there is often a time deviation in the data acquisition of multiple bands. In other words, the existing technology cannot achieve the synchronous acquisition of multiple channel data, which leads to difficulties in matching data between different bands, affecting the quality of the final data and the application effect. The present application provides a multi-channel data synchronization acquisition system for hyperspectral laser radar. In this system, after detecting the laser pulse signal emitted by the hyperspectral laser radar, a global trigger signal and a unified clock signal can be sent through the clock synchronization unit, and multiple waveform acquisition channels in the multiple waveform acquisition units synchronously acquire the echo signal of the hyperspectral laser radar. In this way, the problem of the lack of an effective multi-channel synchronization acquisition mechanism for the hyperspectral laser radar, which in turn affects the subsequent data quality, is solved.

[0032] Specifically, Figure 1 Schematic diagram of a multi-channel data synchronization acquisition system for hyperspectral lidar provided in an embodiment of the present application.

[0033] like Figure 1 As shown, the multi-channel data synchronization acquisition system 10 for hyperspectral lidar includes: a photoelectric conversion unit 11, a clock synchronization unit 12, multiple waveform acquisition units 13, multiple disk storage units 14 and a host computer control unit 15.

[0034] Among them, the photoelectric conversion unit 11 is used to convert the optical signal of the echo of the hyperspectral laser radar into an electrical signal; the clock synchronization unit 12 is used to generate a global trigger signal and a unified clock signal after detecting the laser pulse signal emitted by the hyperspectral laser radar; multiple waveform acquisition units 13 are used to control multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar based on the global trigger signal and the unified clock signal, wherein each waveform acquisition unit includes multiple waveform acquisition channels; multiple disk storage units 14 are used to store the echo signal of the hyperspectral laser radar; the host computer control unit 15 is used to control the photoelectric conversion unit, the clock synchronization unit, the multiple waveform acquisition units and the multiple disk storage units to perform corresponding target actions.

[0035] It can be understood that the host computer control unit 15 in the multi-channel data synchronous acquisition system 10 for hyperspectral laser radar (hereinafter referred to as the acquisition system 10) of the embodiment of the present application respectively controls the photoelectric conversion unit 11, the clock synchronization unit 12, multiple waveform acquisition units 13 and multiple disk storage units to perform corresponding target actions, that is, to perform corresponding operations, specifically: the photoelectric conversion unit 10 converts the optical signal of the echo of the hyperspectral laser radar into an electrical signal, and the clock synchronization unit 12 generates a global trigger signal and a unified clock signal after detecting the laser pulse signal emitted by the hyperspectral laser radar. Further, after receiving the global trigger signal and the unified clock signal, the multiple acquisition units 13 control the multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar, and each waveform acquisition unit 13 includes multiple waveform acquisition channels, and the multiple disk storage units store the echo signal of the hyperspectral laser radar, thereby realizing high-precision synchronous acquisition of the echo signal of the hyperspectral laser radar through multiple waveform acquisition channels.

[0036] In an embodiment of the present application, the host computer control unit 15 is also used to: determine a reference waveform acquisition unit from multiple waveform acquisition units; perform signal threshold detection on the echo signal acquired by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information; distribute the cross-threshold waveform segment reference information to each waveform acquisition unit, and each waveform acquisition unit determines the target cross-threshold waveform segment from the acquired echo signal based on the cross-threshold waveform segment reference information; and store the target cross-threshold waveform segment in multiple disk storage units.

[0037] The cross-threshold waveform segment information includes the timing offset of the cross-threshold waveform segment relative to the trigger sampling moment and the length of the cross-threshold waveform segment.

[0038] It can be understood that the upper computer control unit 15 of the embodiment of the present application is also used to determine the reference waveform participating unit from multiple waveform acquisition units, perform signal threshold detection on the echo signal collected by the reference waveform acquisition unit, obtain cross-threshold waveform segment reference information, and distribute the cross-threshold waveform segment reference information to each waveform acquisition unit. Each waveform acquisition unit determines the qualified cross-threshold waveform segment from the collected echo signal according to the cross-threshold waveform segment reference information, that is, the target cross-threshold waveform segment, and stores the target cross-threshold waveform segment in multiple disk storage units.

[0039] Among them, the embodiment of the present application selects a reference waveform acquisition unit to perform threshold-crossing judgment on the collected signal, and then synchronously transmits the threshold-crossing information to the remaining waveform acquisition units, thereby achieving the purpose of removing redundancy of noise components and compressing data volume for the signals collected by all acquisition channels of the hyperspectral lidar.

[0040] In the embodiment of the present application, the waveform acquisition unit 13 includes: a core circuit, a signal conditioning circuit, a multi-channel digital-to-analog conversion circuit, a clock management circuit, a cache unit and an interface circuit.

[0041] Among them, the core circuit is used to read and process the echo signal of the hyperspectral laser radar in the multi-channel digital-to-analog conversion circuit, and cache the echo signal of the hyperspectral laser radar in the multi-channel digital-to-analog conversion circuit; the signal conditioning circuit is used to convert the single-ended signal output by the photoelectric conversion unit into a differential signal, and input the signal amplitude into the multi-channel analog-to-digital conversion circuit after adjusting the signal; the multi-channel digital-to-analog conversion circuit is used to sample and digital-to-analog convert the echo signal of the hyperspectral laser radar; the clock management circuit is used to receive the unified clock signal issued by the clock synchronization unit to achieve multi-channel synchronization; the cache unit is used to temporarily cache the echo signal of the hyperspectral laser radar before and after processing by the core circuit; the interface circuit is used to receive the unified clock signal and global trigger signal issued by the clock synchronization unit, and transmit the echo signal of the hyperspectral laser radar processed by the core circuit to multiple disk storage units.

[0042] It can be understood that the waveform acquisition unit 13 of the embodiment of the present application includes: a core circuit, a signal conditioning circuit, a multi-channel digital-to-analog conversion circuit, a clock management circuit, a cache unit and an interface circuit. The core circuit can be an FPGA (Field-Programmable Gate Array) core circuit, the multi-channel digital-to-analog conversion circuit can be a multi-channel ADC (Analog-to-Digital Converter) circuit, the cache unit can be a DDR4 (Double Data Rate 4 Synchronous Dynamic Random-Access Memory, double data rate fourth generation synchronous dynamic random access memory) unit, and the interface circuit can be a PXIe (PCI Express-based PXI, an instrument bus standard) interface circuit, wherein,

[0043] The core circuit reads, processes, and caches the echo signal of the hyperspectral lidar in the digital-to-analog conversion circuit;

[0044] The signal conditioning circuit converts the single-ended signal output by the photoelectric conversion unit into a differential signal, and then adjusts the signal amplitude before inputting it into the digital-to-analog conversion circuit;

[0045] Multi-channel digital-to-analog conversion circuits perform high-speed sampling and digital-to-analog conversion of signal waveforms;

[0046] The clock management circuit receives the unified clock signal sent by the synchronization unit to achieve multi-channel synchronization;

[0047] The cache unit temporarily caches the echo signals before and after the core circuit processing;

[0048] The interface circuit receives the global trigger signal and the unified clock signal sent by the clock synchronization unit and transmits the target threshold-crossing waveform segment processed by the core circuit to the disk storage unit.

[0049] The following is an explanation of the multi-channel data synchronization acquisition system for hyperspectral lidar of the present application through a specific embodiment. The acquisition system comprises a chassis with a PXIe backplane, a clock synchronization unit for receiving laser emission pulse trigger signals and generating a global system clock signal to realize multi-channel synchronous sampling, a waveform acquisition unit for digitally acquiring and processing the full waveform of the echo analog voltage signal, a host computer control unit for human-computer interaction and communication control of other units, and a disk storage unit for storing the multi-channel raw waveform data of the hyperspectral lidar.

[0050] Among them, the clock synchronization unit is placed in the system timing slot of the PXIe chassis. On the one hand, it is responsible for receiving the trigger level signal of the external laser emission unit, and on the other hand, it serves as the source of the unified clock signal and waveform sampling trigger signal of the entire acquisition system; the waveform acquisition unit performs full waveform digital synchronous acquisition and online processing of the echo signals of dozens of bands of the hyperspectral lidar under the control of the control unit and the clock synchronization unit; the disk storage unit is responsible for storing the waveforms and additional information data packaged according to the defined data frame format; each unit works closely together to realize the synchronous acquisition of dozens of channel data signals of the hyperspectral lidar.

[0051] like Figure 2 As shown in the figure, based on the PXIe modular instrument bus platform, the entire acquisition system consists of one clock synchronization unit, 14 waveform acquisition units, one host control unit, and two disk storage units, deployed in a standard 3U PXIe chassis with 18 PXIe slots. Each waveform acquisition unit contains four waveform acquisition channels, for a total of 56 waveform acquisition channels.

[0052] like Figure 3 As shown in the figure, the clock synchronization unit consists of functional modules such as FPGA core circuit, external input signal processing circuit, clock management circuit, PXIe interface circuit, etc. This unit distributes global clock signals and trigger signals to each waveform acquisition unit through the dedicated high-performance star bus of the PXIe backplane to realize the synchronous acquisition of multi-channel data of hyperspectral lidar.

[0053] like Figure 4As shown in the figure, the waveform acquisition unit consists of functional modules such as FPGA core circuit, signal conditioning circuit, ADC circuit, clock management circuit, DDR4 cache unit and PXIe interface circuit. The FPGA circuit is responsible for ADC data readout, ADC data processing, data caching and uploading, peripheral management and other functions. The signal conditioning circuit is responsible for converting the single-ended signal output by the detector into a differential signal and then adjusting the signal amplitude before inputting it into the ADC circuit module. The ADC circuit is responsible for high-speed sampling and digital-to-analog conversion of the signal waveform. The clock management circuit is responsible for receiving the external clock to achieve multi-channel synchronization. The DDR4 storage unit is responsible for temporarily caching the waveform signals before and after FPGA processing; the PXIe interface circuit is responsible for receiving the global clock signal and trigger signal fanned out by the clock synchronization unit and transmitting the waveform data processed by the FPGA to the computer disk storage unit.

[0054] The host computer control unit provides a human-computer interaction interface to control the operation of the entire acquisition system; the disk storage unit stores the data stream collected and transmitted from each waveform acquisition unit in real time.

[0055] According to the multi-channel data synchronization acquisition system for hyperspectral lidar proposed in the embodiment of the present application, after detecting the laser pulse signal emitted by the hyperspectral lidar, a global trigger signal and a unified clock signal can be sent through the clock synchronization unit, and multiple waveform acquisition channels in multiple waveform acquisition units can synchronously acquire the echo signal of the hyperspectral lidar, thereby realizing high-precision synchronous acquisition of multiple band channel data, thereby improving the subsequent data quality.

[0056] Next, a multi-channel data synchronization acquisition method for a hyperspectral lidar proposed in accordance with an embodiment of the present application will be described with reference to the accompanying drawings.

[0057] Figure 5 This is a flowchart of a multi-channel data synchronous acquisition method for a hyperspectral lidar according to an embodiment of the present application.

[0058] like Figure 5 As shown, the multi-channel data synchronous acquisition method for hyperspectral lidar includes the following steps:

[0059] In step S101 , a laser pulse signal emitted by a hyperspectral laser radar is detected.

[0060] It is understandable that the embodiment of the present application can detect the laser pulse signal emitted by the hyperspectral lidar so as to subsequently execute the acquisition process of the embodiment of the present application.

[0061] In step S102, after the laser pulse signal is detected, the time synchronization unit is controlled to send out a global trigger signal and a unified clock signal.

[0062] It can be understood that, in the embodiment of the present application, after detecting the laser pulse signal, the clock synchronization unit generates a global trigger signal and a unified clock signal.

[0063] In step S103 , multiple waveform acquisition units are controlled to synchronously acquire echo signals of the hyperspectral lidar based on a global trigger signal and a unified clock signal, wherein each waveform acquisition unit includes multiple waveform acquisition channels.

[0064] It can be understood that the embodiment of the present application can control multiple waveform acquisition units to synchronously acquire echo signals of hyperspectral lidar based on a global trigger signal and a unified clock signal, specifically controlling multiple waveform acquisition channels of multiple waveform acquisition units to synchronously acquire signals.

[0065] In an embodiment of the present application, multiple waveform acquisition units are controlled to synchronously acquire the echo signal of the hyperspectral laser radar based on a global trigger signal and a unified clock signal, including: using a photoelectric conversion unit to convert the optical signal of the echo of the hyperspectral laser radar into an electrical signal; controlling multiple waveform acquisition channels of the multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar.

[0066] It can be understood that the embodiment of the present application can use the photoelectric conversion unit to convert the optical signal of the echo of the hyperspectral laser radar into telecommunication, and control multiple waveform acquisition channels of multiple waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar.

[0067] In step S104 , the echo signals of the hyperspectral laser radar are stored in a plurality of disk storage units.

[0068] It is understandable that the embodiment of the present application can store the collected echo signals of the hyperspectral lidar in multiple disk storage units.

[0069] In an embodiment of the present application, before storing the echo signal of the hyperspectral laser radar in multiple disk storage units, it also includes: determining a reference waveform acquisition unit from multiple waveform acquisition units; performing cross-threshold detection on the echo signal acquired by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information; distributing the cross-threshold waveform segment reference information to each waveform acquisition unit, and each waveform acquisition unit determines the target cross-threshold waveform segment from the acquired echo signal according to the cross-threshold waveform segment reference information; and storing the target cross-threshold waveform segment in multiple disk storage units.

[0070] Among them, the reference waveform acquisition unit is preferably a waveform acquisition unit corresponding to a band with greater signal intensity and higher signal-to-noise ratio.

[0071] It can be understood that the embodiment of the present application can determine a reference waveform acquisition unit from multiple waveform acquisition units, and perform signal threshold detection on the echo signal acquired by the reference waveform unit to obtain cross-threshold waveform segment reference information, and distribute the cross-threshold waveform segment reference information to each waveform acquisition unit. Each waveform acquisition unit determines the target cross-threshold waveform segment from the acquired echo signal according to the cross-threshold waveform segment reference information, and stores the target cross-threshold waveform segment in multiple disk storage units. The specific method for performing signal threshold detection is as follows.

[0072] In an embodiment of the present application, a signal threshold detection is performed on the echo signal collected by the reference waveform acquisition unit to obtain reference information of the cross-threshold waveform segment, including: obtaining the echo signals cached in multiple waveform acquisition channels of the reference waveform acquisition unit; performing a noise threshold evaluation on the cached echo signals; determining a target value for crossing the threshold based on the result of the noise threshold evaluation; and performing a cross-threshold detection on the echo signal collected by the reference waveform acquisition unit based on the target value to obtain reference information of the cross-threshold waveform segment.

[0073] The calculation formula for noise threshold evaluation is:

[0074] threshold noise =m noise +λ·σ noise ;

[0075] Among them, threshold noise is the noise threshold, m noise is the mean value of the amplitude of multiple sampling points at the beginning and end of the echo signal band, σ noise is the standard deviation of multiple sampling points at the beginning or end of the echo signal waveform, and λ is the noise threshold coefficient.

[0076] It can be understood that the embodiments of the present application can obtain the echo signals cached in multiple waveform acquisition channels of the reference waveform acquisition unit, perform noise threshold evaluation on them, and determine the target value of the signal threshold based on the result of the noise threshold evaluation, and perform signal threshold detection on the echo signals collected by the reference waveform acquisition unit based on the target value, thereby obtaining cross-threshold waveform segment information.

[0077] In the embodiment of the present application, the threshold waveform segment reference information algorithm is:

[0078] P latency =∪(T cuts (I,J));

[0079] Among them, T cuts is each cross-threshold waveform segment on each reference waveform acquisition channel, I is the channel number, J is the cross-threshold waveform segment number on each reference waveform acquisition channel, and ∪ represents the union of the time position information of the cross-threshold waveform segments.

[0080] It should be noted that the aforementioned explanation of the embodiment of the multi-channel data synchronous acquisition system for hyperspectral lidar is also applicable to the multi-channel data synchronous acquisition method for hyperspectral lidar of this embodiment, and will not be repeated here.

[0081] The following is a specific example of a method for synchronously collecting multi-channel data for a hyperspectral laser radar according to an embodiment of the present application. In combination with the above-mentioned collection system, the method is as follows:

[0082] Step 1: Laser emission pulse trigger signal distribution and unified clock signal distribution.

[0083] For trigger signal distribution, the hyperspectral lidar laser emission unit simultaneously transmits laser pulses at a high repetition rate of 130kHz and transmits the trigger level signal via a cable to the acquisition system's clock synchronization unit. The clock synchronization unit's LEMO single-core connector receives the trigger level signal, which is then processed by the internal external trigger signal processing circuit for leading-edge timing. This generates a system-wide trigger signal, which is then fanned out to each waveform acquisition unit via the PXIe_DSTARB star line on the chassis backplane.

[0084] Unified clock signal distribution: The 100MHz crystal oscillator in the clock synchronization unit cooperates with the clock management module to generate a high-precision system clock signal. The system clock signal is transmitted to each waveform acquisition unit via the PXIe_DSTARA star line on the chassis backplane.

[0085] Step 2: Each waveform acquisition unit receives a global trigger signal and a unified clock signal, and samples multi-channel signals synchronously.

[0086] Each waveform acquisition unit receives a trigger signal fanned out from the clock synchronization unit via the chassis backplane PXIe_DSTARC star line. This global trigger signal serves as an instruction for each acquisition channel of each waveform acquisition unit to start acquiring waveforms.

[0087] The FPGA on each waveform acquisition unit sends a trigger signal to the ADC circuit module on the unit according to the received trigger signal to control the four waveform acquisition channels to achieve signal synchronous sampling;

[0088] The clock management module in each waveform acquisition unit receives the high-precision system clock signal from the PXIe_DSTARA star line on the chassis backplane, eliminates clock jitter, optimizes clock performance, and then sends it to each ADC circuit module, thereby ensuring that the clock signal of each waveform acquisition channel in each waveform acquisition unit is synchronized.

[0089] The star-shaped lines on the chassis backplane are strictly of equal length, ensuring that the clocks and triggers received by each waveform acquisition unit are synchronized, thereby ensuring the synchronization of the entire acquisition system.

[0090] Step 3: The reference waveform acquisition unit detects the cross-threshold waveform.

[0091] Step 3.1: The waveform acquisition unit corresponding to the band with greater signal intensity and higher signal-to-noise ratio is preferably selected as the reference waveform acquisition unit.

[0092] Step 3.2: Perform noise threshold evaluation on the digitized waveforms collected by the reference waveform acquisition unit from the 4-channel buffer. The noise threshold evaluation is based on the following formula:

[0093]

[0094] m noise =min(m beginning , m ending ); (4)

[0095]

[0096] threshold noise =m noise +λ·σ noise ; (5)

[0097] In the above formula, V i is the amplitude of the i-th sampling point in the waveform segment collected under each laser trigger; m beginning and m ending are the mean amplitudes of the 10 sampling points at the beginning and end of the band respectively; σ noise is the standard deviation of the ten sampling points at the beginning or end of the waveform, V noise_i The amplitude of the i-th sampling point at the beginning or end of the waveform segment is collected. The beginning or end depends on formula (3). noise is the noise threshold, used to remove the noise component, in formula (5) noise The noise threshold coefficient λ can be adjusted according to the actual noise situation, and is generally 3 or 4. The reason why the ten points at the beginning or end are not fixedly selected as the noise estimation area is that spike noise or the echo of the detected object may randomly appear at the beginning or end in the actual detection and acquisition waveform, so the noise estimation area is taken as the one with the smaller mean of the two.

[0098] Step 3-3: Set the threshold baseline according to the noise threshold evaluation result to perform threshold detection on the collected waveform and record the threshold waveform segment information. The threshold information includes the timing offset of the threshold waveform segment relative to the trigger sampling moment and the length of the threshold waveform segment.

[0099] Based on the position of the cross-threshold segment on the reference channel, the reference acquisition segment (i.e., the cross-threshold waveform segment) is obtained according to the following formula:

[0100] Tcuts (i, j) = U(t OT (i, j)-δ, t OT (i, j) + 2δ);

[0101] Among them, T cuts (i, j) is the reference acquisition segment, t OT (i, j) is the timing offset of the j-th threshold crossing segment of the reference channel with sequence number i, δ is the adaptive width parameter that can be set by the host computer, and its value range is between 1 times the actual pulse width and 3 times the actual pulse width. ∪ is the union calculation, which is performed by traversing all threshold crossing segments on all reference channels and taking the union.

[0102] Step 4: Transmit and distribute the reference acquisition segment information (and cross-threshold waveform segment reference information).

[0103] Step 4-1: The reference waveform acquisition unit transmits the reference acquisition segment information to the clock synchronization card via the PXIe_DSTARB star line;

[0104] Step 4-2: The clock synchronization card receives the reference acquisition segment information from the reference waveform acquisition unit via the PXIe_DSTARC star line, and then distributes it to each waveform digitization module via the PXI_STAR star line. The chassis backplane star line group from the slot where the clock synchronization card is located to the slots where the remaining waveform acquisition units are located is strictly equal in length to ensure that each waveform acquisition unit can synchronously receive the reference acquisition segment information.

[0105] Step 5: Each waveform acquisition unit selects, transmits and stores the acquired segments.

[0106] Step 5-1: Each waveform digitization module extracts a valid waveform segment from the collected waveform data according to the reference collected segment;

[0107] Step 5.2: The selected valid waveform segments are packaged according to the defined data frames and transmitted to the disk array unit through the chassis backplane PCIe bus for storage.

[0108] According to the multi-channel data synchronous acquisition method for hyperspectral lidar proposed in the embodiment of the present application, after detecting the laser pulse signal emitted by the hyperspectral lidar, the clock synchronization unit is controlled to send a global trigger signal and a unified clock signal, and based on the global trigger signal and the unified clock signal, multiple waveform acquisition channels in multiple waveform acquisition units are controlled to synchronously acquire the echo signal of the hyperspectral lidar, thereby realizing high-precision synchronous acquisition of multiple band channel data, thereby improving the subsequent data quality.

[0109] Figure 6 This is a schematic diagram of the structure of the host computer provided in the embodiment of the present application. The host computer may include:

[0110] A memory 601 , a processor 602 , and a computer program stored in the memory 601 and executable on the processor 602 .

[0111] When the processor 602 executes the program, the multi-channel data synchronous acquisition method for the hyperspectral laser radar provided in the above embodiment is implemented.

[0112] Furthermore, the host computer also includes:

[0113] The communication interface 603 is used for communication between the memory 601 and the processor 602 .

[0114] The memory 601 is used to store computer programs that can be run on the processor 602 .

[0115] The memory 601 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0116] If the memory 601, processor 602, and communication interface 603 are implemented independently, the communication interface 603, memory 601, and processor 602 can be connected to each other via a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 6 Only one thick line is used in the diagram, but this does not mean that there is only one bus or one type of bus.

[0117] Optionally, in a specific implementation, if the memory 601, the processor 602 and the communication interface 603 are integrated on a chip, the memory 601, the processor 602 and the communication interface 603 can communicate with each other through an internal interface.

[0118] The processor 602 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0119] The embodiment of the present application also provides a computer readable storage medium, which stores a computer program or instructions, and the computer program or instructions are executed by a processor to implement the multi-channel data synchronous acquisition method for hyperspectral lidar.

[0120] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0121] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "N" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0122] Any process or method descriptions in flow charts or described elsewhere herein can be understood as representing code modules, segments, or portions of code that include one or more executable instructions for implementing the specified logic functions (or steps) and / or can be implemented by hardware or a combination of hardware and software. The preferred embodiments of the present application thus include additional implementation in which the described functions are not performed by the described code modules but by hardware or a combination of hardware and software.

[0123] It should be understood that parts of the present application can be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. As in another embodiment, if implemented in hardware, any one or a combination of the following technologies known in the art can be used: discrete logic circuit with logic gate circuit for implementing logic functions on data signals, application specific integrated circuit with suitable combination logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA), etc.

[0124] Those skilled in the art will understand that all or part of the steps in the method of the above embodiment can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

Claims

1. A multi-channel data synchronous acquisition system for hyperspectral laser radar, characterized in that: include: A photoelectric conversion unit, used to convert the optical signal of the hyperspectral laser radar echo into an electrical signal; Clock synchronization unit, used to issue global trigger signals and unified clock signals; A plurality of waveform acquisition units, configured to synchronously acquire the echo signal of the hyperspectral laser radar based on the global trigger signal and the unified clock signal, wherein each waveform acquisition unit includes a plurality of waveform acquisition channels; A plurality of disk storage units, used for storing the echo signals of the hyperspectral laser radar; The host computer control unit is used to control the photoelectric conversion unit, the clock synchronization unit, the multiple waveform acquisition units and the multiple disk storage units to perform corresponding target actions after detecting the laser pulse signal emitted by the hyperspectral laser radar; the host computer control unit is also used to: determine a reference waveform acquisition unit from the multiple waveform acquisition units; perform signal threshold detection on the echo signal collected by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information; distribute the cross-threshold waveform segment reference information to each waveform acquisition unit, and each waveform acquisition unit determines the target cross-threshold waveform segment from the collected echo signal according to the cross-threshold waveform reference segment information; and store the target cross-threshold waveform segment in the multiple disk storage units.

2. The multi-channel data synchronous acquisition system for hyperspectral laser radar according to claim 1 is characterized in that: The waveform acquisition unit includes: a core circuit, a signal conditioning circuit, a multi-channel digital-to-analog conversion circuit, a clock management circuit, a cache unit and an interface circuit, wherein: The core circuit is used to read and process the echo signal of the hyperspectral laser radar in the multi-channel digital-to-analog conversion circuit, and cache the echo signal of the hyperspectral laser radar in the multi-channel digital-to-analog conversion circuit; The signal conditioning circuit is used to convert the single-ended signal output by the photoelectric conversion unit into a differential signal, and adjust the signal amplitude before inputting it into the multi-channel digital-to-analog conversion circuit; The multi-channel digital-to-analog conversion circuit is used to sample and perform digital-to-analog conversion on the echo signal of the hyperspectral laser radar; The clock management circuit is used to receive the unified clock signal sent by the clock synchronization unit to achieve multi-channel synchronization; The cache unit is used to temporarily cache the echo signals of the hyperspectral laser radar before and after processing by the core circuit; The interface circuit is used to receive the unified clock signal and global trigger signal sent by the clock synchronization unit, and transmit the echo signal of the hyperspectral laser radar processed by the core circuit to multiple disk storage units.

3. A multi-channel data synchronous acquisition method for hyperspectral laser radar, characterized in that: The method comprises the following steps: Detecting laser pulse signals emitted by hyperspectral lidar; After detecting the laser pulse signal, controlling the clock synchronization unit to send out a global trigger signal and a unified clock signal; Controlling a plurality of waveform acquisition units to synchronously acquire the echo signal of the hyperspectral laser radar based on the global trigger signal and the unified clock signal, wherein each waveform acquisition unit includes a plurality of waveform acquisition channels; The echo signal of the hyperspectral laser radar is stored in multiple disk storage units; before the echo signal of the hyperspectral laser radar is stored in the multiple disk storage units, it also includes: determining a reference waveform acquisition unit from the multiple waveform acquisition units; performing signal threshold detection on the echo signal acquired by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information; distributing the cross-threshold waveform segment reference information to each waveform acquisition unit, and each waveform acquisition unit determines a target cross-threshold waveform segment from the acquired echo signal according to the cross-threshold waveform segment reference information; and storing the target cross-threshold waveform segment in the multiple disk storage units.

4. The method for synchronously collecting multi-channel data for hyperspectral laser radar according to claim 3, characterized in that: Before controlling the multiple waveform acquisition units to synchronously acquire the echo signals of the hyperspectral laser radar based on the global trigger signal and the unified clock signal, the method includes: Converting the optical signal of the hyperspectral laser radar echo into an electrical signal using a photoelectric conversion unit; The multiple waveform acquisition channels of the multiple waveform acquisition units are controlled to synchronously acquire the echo signal of the hyperspectral laser radar.

5. The method for synchronously collecting multi-channel data for hyperspectral laser radar according to claim 3, characterized in that: The performing signal threshold detection on the echo signal acquired by the reference waveform acquisition unit to obtain cross-threshold waveform segment reference information includes: Acquiring echo signals buffered in multiple waveform acquisition channels of the reference waveform acquisition unit; performing a noise threshold evaluation on the buffered echo signal; determining a target value for the signal threshold based on a result of the noise threshold evaluation; Based on the target value, a signal threshold detection is performed on the echo signal collected by the reference waveform collection unit to obtain cross-threshold waveform segment reference information.

6. The method for synchronously collecting multi-channel data for hyperspectral laser radar according to claim 5, characterized in that: The calculation formula for the noise threshold evaluation is: ； in, is the noise threshold, is the mean value of the amplitudes of multiple sampling points at the beginning and end of the echo signal band, is the standard deviation of multiple sampling points at the beginning or end of the echo signal waveform, is the noise threshold coefficient.

7. The method for synchronously collecting multi-channel data for hyperspectral laser radar according to claim 5, characterized in that: The cross-threshold waveform segment reference information algorithm is: ； in, It is each cross-threshold waveform segment on each reference waveform acquisition channel, is the channel number, is the sequence number of the cross-threshold waveform segment on each reference waveform acquisition channel, Represents the union of the time position information of the threshold waveform segments.

8. A host computer, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the multi-channel data synchronous acquisition method for hyperspectral lidar as described in any one of claims 3 to 7.

9. A computer-readable storage medium having a computer program or instruction stored thereon, characterized in that: The computer program or instruction is executed by a processor to implement the multi-channel data synchronous acquisition method for hyperspectral lidar as described in any one of claims 3 to 7.

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