CN103576134B - A kind of Full-waveform laser radar system based on coaxial two-channel data acquisition - Google Patents

Abstract

The invention discloses a full-waveform laser radar system based on coaxial dual-channel data acquisition, which breaks through the limitation that conventional laser radars can only measure limited distance and intensity data, and at the same time solves the problem of non-coaxial laser radar detection blind spots; The full waveform laser radar system based on coaxial dual-channel data acquisition of the present invention includes a pulse laser, a laser emitting and receiving unit, a data acquisition unit, a control unit and a software unit; the control unit controls the pulse laser to emit laser pulses, and the laser pulses pass through the laser After the transmitting and receiving unit is divided into: the outgoing beam, the acquisition card control signal generating beam and the transmitting waveform recording beam, the outgoing beam is scattered by the target and is collected by the transmitting and receiving unit and entered into the data acquisition unit, which is collected as a received signal; the software unit is used for Provide human-computer interaction interface. The invention can store the complete waveforms of the emitted laser pulses and received laser pulses, and effectively enhances the detection ability of the full waveform laser radar.

Description

A full-waveform lidar system based on coaxial dual-channel data acquisition

technical field

The invention relates to the field of laser radar measurement, in particular to a full-waveform laser radar system based on coaxial dual-channel data acquisition.

Background technique

Lidar is an active remote sensing technology with the help of laser. It mainly measures the time for laser pulses to travel between the target and the LiDAR platform, and obtains the distance between the LiDAR platform and the target according to the relationship between the distance and the speed of light and time. The action of the scanning device, the laser radar can complete the scanning of the target surface, and combine the position and attitude data of the laser radar platform to obtain the digital surface model and digital elevation model of the target. Due to the fact that the pulse laser used in practice has a certain divergence angle, the emitted laser pulse beam propagates forward in the form of an approximate cone. When the laser pulse beam interacts with the target, it is no longer a point, but a A circular spot, which is called a laser spot, and due to the complexity and diversity of targets in the measurement environment, a laser spot may contain multiple scattering targets or a target has multiple scattering surfaces, resulting in laser The complexity of the pulse echo signal waveform, such as multiple pulses in one echo or pulse stretching. However, the conventional lidar only obtains the distance value of one or more targets in the laser spot by means of a certain threshold method (rising edge, peak value or center of gravity, etc.) (up to 6 at the present stage), and because different targets have different echoes Waveform, so only using a fixed threshold detection method will lead to different ranging accuracy for different targets. Although some foreign manufacturers can provide laser pulse echo acquisition modules, they are expensive. On the other hand, current laser radars use a nearly coaxial measurement method (the outgoing optical path is parallel to the echo optical path), which will cause loss of echo energy, close-range blind spots, and the complexity of adjusting the parallel optical path. Finally, due to the instability of the laser in the lidar, the laser pulse waveforms emitted in each measurement are different. If this difference is not considered in the subsequent data processing, the measurement accuracy will be reduced. Full waveform laser radar refers to the complete collection and storage of laser pulse signals within a certain time interval by means of high-speed data acquisition devices, so as to obtain the complete waveform of laser pulses. The collected waveform signals are called full waveform signals. According to laser The mechanism of the interaction between the pulse and the target shows that the full waveform signal contains rich information about the physical and geometric characteristics of the target.

Contents of the invention

The invention discloses a full-waveform laser radar system based on coaxial dual-channel data acquisition, the purpose of which is to improve the detection capability of conventional laser radars and reduce the detection blind area of laser radars, and simultaneously record the completeness of emitted laser pulses and received laser pulses. waveform.

The lidar system includes a pulse laser, a laser emitting and receiving unit, a data acquisition unit, a control unit and a software unit, the laser emitting and receiving unit is composed of a beam splitter and a coaxial module, and the data acquisition unit is composed of a laser emitting Detector, receiving laser detector, high-speed dual-channel data acquisition card and acquisition card control module, the control unit is composed of a main control computer and a laser control unit, the pulse laser receives the laser control signal from the laser control unit, and sends out Laser pulses with a certain frequency and pulse width, in order to realize the complete storage of the emitted laser pulse and received laser pulse waveform, and eliminate the emission delay of the pulsed laser, the laser pulse is divided into 3 beams by the beam splitter in the laser emitting and receiving unit , the first laser pulse is emitted to the target through the coaxial module in the laser emitting and receiving unit, and after the laser pulse is scattered by the target, it is focused by the coaxial module in the laser emitting and receiving unit to the receiving laser detection in the data acquisition unit The receiving laser detector converts the received optical signal into an electrical signal, which is collected by the high-speed dual-channel data acquisition card in the data acquisition unit. With the help of high-speed sampling frequency, the waveform of the received laser pulse can be completely collected, thus Realize the full waveform storage of the received laser pulse; the second laser pulse is incident on the emitting laser detector in the data acquisition unit, and the emitting laser detector converts the laser pulse into an electrical signal, which is acquired by the high-speed dual-channel data acquisition unit in the data acquisition unit Card acquisition, with the help of high-speed sampling frequency, the waveform of the emitted laser pulse can be completely collected, so as to realize the full waveform storage of the emitted laser pulse. Due to the instability of the pulsed laser, the emitted laser pulse has different waveforms. At the same time, the transmitted laser pulse waveform and the received laser pulse waveform are stored. In the later signal processing, the difference of the transmitted laser pulse waveform can be considered, so as to obtain more accurate measurement results, and can be based on the transmitted laser pulse waveform and the received laser pulse waveform. The difference of the object, inverting the physical and geometric characteristics of the target; the third laser pulse enters the acquisition card control module in the data acquisition unit to generate the acquisition card control signal, which is used to set the data reading reference position for The reference position when the main control computer reads the data in the high-speed dual-channel data acquisition card, by means of the data reading reference position can realize the complete reading of the emitted laser pulse waveform, and the consistency of the time coordinates of the transmitted waveform and the received waveform; the control The unit completes the control of the pulse laser and the high-speed dual-channel data acquisition card in the data acquisition unit, reads, displays, stores and calculates the data collected in the high-speed dual-channel data acquisition card, and provides a hardware platform for the software unit; The software unit provides a human-computer interaction interface, completes the configuration of the data acquisition unit and the control unit, and displays the collected data and data processing results; the patent of the present invention can realize the combination of the transmitting laser pulse optical path and the receiving laser pulse optical path in the laser radar optical path It is completely coaxial, and at the same time, it can realize the acquisition, display and storage of the full waveform of the emitted laser pulse and received laser pulse according to the set format.

The laser emitting and receiving unit can realize the complete coaxiality of the optical path of the emitting laser pulse and receiving laser pulse, and realize the splitting of the laser pulse emitted by the pulse laser, so that the laser pulse signals of different components are used to generate the control signal of the acquisition card , emit the laser pulse waveform acquisition signal, and emit the laser pulse signal, the laser emitting and receiving unit is composed of two beam splitters and a coaxial module, the first beam splitter has a reflection-transmittance ratio of 9:1, thus the The laser pulse emitted by the pulse laser is divided into two laser pulses with a light intensity ratio of 9:1. The reflected beam accounts for a large proportion mainly because the reflected beam will pass through the coaxial module as the outgoing laser pulse and illuminate the target. The energy of the outgoing laser pulse The larger the measurement distance, the higher the signal-to-noise ratio of the laser pulse signal scattered by the target, so as to realize the long-distance and precise measurement of the target; the transmitted beam is split again by the second beam splitter, and the second beam splitter The reflection-transmittance ratio of the mirror is 1:9, of which the transmitted beam accounts for a large proportion mainly because the transmitted beam is received by the transmitting laser detector as the acquisition signal of the transmitted laser pulse waveform, and the higher signal energy ensures the collected transmitted laser pulse waveform It has a high signal-to-noise ratio, thereby ensuring the accurate storage of the emitted laser pulse waveform; the reflected beam enters the acquisition card control module in the data acquisition unit to generate the acquisition card control signal; the coaxial module consists of a plane mirror, The reflector base, the base bracket, the sleeve and the focusing lens are composed. The plane reflector is coated with a dielectric film to improve the reflectivity, mainly to reduce the energy loss of the reflected beam. The thickness of the plane reflector is 1-2mm, and the width is 2mm , the length is 4mm, and the smaller thickness is mainly to ensure that the reflector is fixed on the bracket and is still in the center of the coaxial module. The smaller area of the reflector is to reduce the shielding of the laser pulse signal scattered by the target by the reflector, thereby Reduce the loss of echo energy; the mirror base is half of a cube with a side length of 2mm cut along the diagonal, and the plane mirror is fixed on the slope of the mirror base by gluing; the base bracket It is composed of a ring-shaped base and a common point three-wire bracket. The width of the three-wire bracket is 2mm. On the one hand, it ensures that the mirror base can be fixed on the common point of the three-wire bracket and can bear the weight of the mirror base. shielding of the wave signal; the mirror base is fixed on the common point of the base bracket by gluing, the ring-shaped base of the base bracket is fixed on the front part of the sleeve through a nut, and the focusing lens is fixed on the base bracket through a nut The inside of the sleeve; since the plane mirror is located at the center of the base bracket, the optical axis of the focusing lens coincides with the central axis of the ring base of the base bracket, so the plane mirror is located on the optical axis of the focusing lens; reflected by the first beam splitter The laser pulse is incident on the plane reflector of the coaxial module at an angle of 45°, so that the beam propagation direction is changed by 90° to exit in the horizontal direction. Since the plane reflector is located on the optical axis of the focusing lens, the emitted laser pulse is emitted The emitted light path coincides with the optical axis of the focusing lens, and the emitted laser pulse returns along the optical axis after being scattered by the target. In this way, the optical path of the emitted laser pulse is coaxial with the optical path of the received laser pulse, and the focusing lens can focus the scattered laser pulse echo onto the receiving laser detector, thereby increasing the detected light energy of the received laser pulse.

The data acquisition unit can realize dual-channel simultaneous acquisition of emitted laser pulses and received laser pulses, and simultaneously realizes complete acquisition and storage of emitted laser pulses and received laser pulse waveforms, thereby realizing full waveform storage of laser pulses. The data acquisition The unit includes: emitting laser detector, receiving laser detector, high-speed dual-channel data acquisition card and acquisition card control module; the emitting laser detector and receiving laser detector realize the photoelectric conversion of emitting laser pulse and receiving laser pulse respectively, and respectively The two acquisition channels of the high-speed dual-channel data acquisition card are connected; the high-speed dual-channel data acquisition card completes the conversion of analog signals to digital signals, and stores the collected signals in its own onboard memory; the control module of the acquisition card consists of photodiodes and The signal conditioning circuit is composed of a photodiode that receives the laser pulse signal from the laser emitting and receiving unit, and converts the laser pulse signal into an electric pulse. Control of the acquisition card; when the acquisition is completed, the main control computer in the control unit reads the data in the dual-channel data acquisition card, thereby realizing the storage and calculation of the transmitted laser pulse and the received laser pulse waveform; dual-detector dual-channel acquisition It can ensure the simultaneous acquisition of the transmitted pulse and the received pulse, and ensure that the transmitted signal and the received signal have the same time coordinates. Compared with the single-detector single-channel acquisition, it can eliminate the measurement blind area and realize close-range measurement. At the same time, it can avoid the difference between the transmitted signal and the received signal. Mutual interference; since the transmitted waveform acquisition signal and the control signal of the acquisition card come from different modules, there is a time delay between the acquisition card control signal and the transmitted laser pulse signal. When the transmitted pulse signal reaches the acquisition card, the acquisition card has not been triggered to collect. In order to ensure the complete storage of the emitted laser pulse waveform, the high-speed dual-channel data acquisition card works in real-time acquisition mode, and stores the collected data in the onboard memory. When the high-speed dual-channel data acquisition card receives the When collecting the control signal of the card, the reading data reference position will be set at the current sampling point. When the sampling meets the sampling configuration requirements, the main control computer will take the reading data reference position as the reference, and read the reading data before and after the reading data reference position. Taking a certain length of data, reading a certain length of data before storing the mark is to eliminate the lag of the control signal of the acquisition card relative to the emitted laser pulse, and reading a certain length of data after storing the mark is to ensure the integrity of the data, thus Realize the complete reading of the transmitted laser pulse waveform, and finally complete the complete storage of the transmitted laser pulse waveform and the received laser pulse waveform.

The software unit includes: a high-speed dual-channel data acquisition card configuration part, a laser control unit configuration part and a waveform display part. The high-speed dual-channel data acquisition card configuration part includes file settings, acquisition channel voltage settings, acquisition channel time settings, acquisition channel input settings, and acquisition card trigger settings. The file setting includes the setting of the file storage path and the display of the number of stored files. The acquisition channel voltage setting includes the reference voltage setting of the acquisition channel 0 and the acquisition channel 1 and the setting of the bias voltage of the acquisition channel. Sampling channel time setting includes sampling frequency setting, record length setting and reference position setting. The input setting of the acquisition channel includes the setting of the maximum input frequency of acquisition channel 0 and acquisition channel 1 (through low-pass filtering before sampling) and the input signal coupling mode. Acquisition card trigger setting includes trigger source setting, trigger level setting, trigger channel coupling mode setting and trigger edge selection. The laser control unit configuration section includes laser control signal frequency, amplitude and duty cycle settings. The waveform display window is used for real-time display of transmitting and receiving waveforms.

The data storage format is that the configuration parameters are stored separately from the data blocks, and the data blocks are divided into data sub-blocks; the first 1-17 bytes store the configuration parameters, and the data blocks are stored after the 17th byte; the specific storage format is as follows : The first 1-4 bytes store the starting time of the system, and the starting time of the system includes the year, month and day; the fifth byte is the connection mode of the sampling channel, and 0 represents the connection between the emitting laser detector and the high-speed dual-channel data acquisition card The first channel is connected, and the receiving laser detector is connected to the second channel of the high-speed dual-channel data acquisition card. 1 means that the transmitting laser detector is connected to the second channel of the high-speed dual-channel data The first channel of the channel data acquisition card is connected; the 6th-9th bytes store the number of sampling points set by the first channel of the high-speed dual-channel data acquisition card, and adopt the storage method of high-order first and low-order; the 10th-13th bytes are stored The number of sampling points set by the second channel of the high-speed dual-channel data acquisition card adopts the storage method of high-order first and low-order; the 14th-15th bytes store the sampling frequency set by the high-speed dual-channel data acquisition card, and the sampling frequency is expressed in megahertz The unit is stored in the high-order first low-order form; the 16th byte stores the reference voltage set by the first channel of the high-speed dual-channel data acquisition card, and the reference voltage is in millivolts; the 17th byte stores the high-speed The reference voltage set by the second channel of the dual-channel data acquisition card, the reference voltage is in millivolts, and the data sub-blocks of each measurement are stored after the 17th byte, and each data sub-block corresponds to the pulse laser emission. A laser pulse and the received scattered laser pulse, the data sub-block includes the laser pulse emission time, the full waveform data of the transmitted laser pulse and the full waveform data of the received laser pulse.

The control unit includes a laser control unit and a main control computer, and adopts a distributed control mode in which the main control computer and independent sub-controllers of each unit are combined. The sub-controllers control the subordinate units respectively, and the overall control only realizes the configuration and monitoring, which can reduce the workload of the total control unit, achieve more precise control and increase the stability of the system; because most of the microprocessors at this stage use a single-threaded execution method, such as the need to implement multiple tasks during the running process , the tasks will affect each other, and because this system requires high-speed data collection and storage, a small impact will cause data loss and confusion, which will cause system instability. Therefore, the use of distributed control methods can ensure that the entire system stable operation.

The laser control unit is composed of a microprocessor and an adapter, and the microprocessor can be a single-chip microcomputer, CPLD or FPGA; the microprocessor receives a configuration signal from the general controller, and outputs a certain frequency, amplitude and duty cycle square wave signal, the adapter amplifies the square wave signal according to the requirements of the laser for the control signal, so as to drive the laser to emit a certain frequency of laser light, and the adapter is also used for the isolation between the laser and the microprocessor to realize the control of the microprocessor protection of.

The beneficial effect of the present invention is that the full-waveform lidar system based on coaxial dual-channel data acquisition can simultaneously provide the transmitted laser pulse waveform and the received laser pulse waveform in a single measurement, and make the transmitted laser pulse optical path and the received laser pulse optical path completely the same axis, thereby eliminating the measurement blind zone of the full-waveform lidar and increasing the detection distance of the full-waveform lidar.

Description of drawings

Figure 1 is a schematic diagram of a full-waveform lidar system based on coaxial dual-channel data acquisition.

Figure 2 is a complete schematic diagram of a full-waveform lidar system based on coaxial dual-channel data acquisition.

Figure 3 is a mechanical schematic diagram of the coaxial module.

Figure 4 is a sequence diagram of data acquisition and storage.

Fig. 5 is a schematic diagram of a data storage format.

Figure 6 is the software interface of the full-waveform laser radar system based on coaxial dual-channel data acquisition.

Detailed ways

As shown in Figure 2, a pulsed laser 1 is a light source that provides laser pulses for the measurement of the system. The wavelength selection of pulsed laser 1 depends on the transmission window of the transmission medium in the measurement environment and the scattering characteristics of the measured target. For example, in urban surveying and mapping, the laser transmission medium is the atmosphere, and the measured target is tall buildings, grass and roads. The wavelength of laser 1 It can be selected as 1064nm; another example is in ocean measurement, the transmission medium of the laser is water, at this time the wavelength of laser 1 can be selected as 532nm. The pulse laser has the characteristics of high repetition frequency and high peak power, which can meet the requirements of fast and long-distance measurement, so the laser source is selected as pulse laser 1. The laser pulse width emitted by the pulsed laser 1 is generally selected to be 5-10 ns. On the one hand, a laser pulse that is too narrow leads to a short contact time between the laser pulse and the target, and the echo signal fails to contain rich target information, losing the advantages of full-waveform lidar; on the other hand, it leads to an increase in the cost of the laser and an increase in the bandwidth requirements of the laser detector , thereby increasing the cost of the system. Under the same frequency and the same measurement distance, an excessively wide laser pulse will increase the power demand of the laser, thereby increasing energy consumption. The pulsed laser 1 is a frequency-tunable laser, and the emission frequency of the laser can be flexibly adjusted according to the needs of the measurement task.

The pulse laser 1 receives the laser control signal 14 from the laser control unit, and emits a laser pulse with a certain frequency and pulse width. The laser pulse is divided into a beam 20 and a beam 21 by a beam splitter 2, and the beam splitter 2 has a reflective transmittance of 9:1 spectroscopic plain film. The beam 20 is a reflected beam, and the beam 21 is a transmitted beam. The reflected beam accounts for a large proportion mainly because the reflected beam will pass through the coaxial module as the outgoing beam and illuminate the target. The greater the energy of the outgoing beam, the farther the measurement distance will be, and the higher the signal-to-noise ratio of the laser pulse signal detected by the receiving laser detector will be. , so as to realize the long-distance and precise measurement of the target. The light beam 20 exits in the horizontal direction through the coaxial module and illuminates the target.

The mechanical structure of the coaxial module is shown in Figure 3. Figure 3 (1) is a plane mirror 24, which mainly completes the 90° transformation of the laser beam propagation direction. The width of the mirror is 2mm and the length is 4mm. The size depends on the spot of the beam 20 Size, the thickness of the reflector is 1-2mm, the smaller thickness is mainly to ensure that the reflector is fixed on the bracket and still in the center of the coaxial module, and the smaller area of the reflector is to ensure the complete reflection of the laser spot. Reduce the shielding of the laser pulse echo signal scattered by the target by the plane reflector, thereby reducing the loss of echo energy. Fig. 3 (2) is reflector base 25, is used for fixing planar reflector 24, makes reflector 24 form 45 ° angle with horizontal direction, and reflector base 25 side length is half of the cube that side length is 2mm cut along the diagonal line, , the side length depends on the size of the plane reflector 24, and the aluminum material is mainly for reducing the weight of the reflector base, thereby increasing the bonding strength. The plane reflector 24 is fixed on the slope 26 of the reflector base 25 by gluing. Fig. 3 (3) is base support 27, and described base support is made up of ring-shaped base and common point three-line support, and the width of three-line support is 2mm, guarantees that reflector base can be fixed on the common point of three-line support on the one hand and can bear The weight of the reflector base, on the other hand, reduces the shielding of the laser pulse echo signal scattered by the target by the three-wire bracket. The mirror base 25 is fixed at the center position 28 of the base bracket 27 by gluing. The base bracket 27 is used to fix the reflector base 25 and is connected with the sleeve 30 shown in FIG. Figure 3 (6) shows the focusing lens group 34, which is used to focus the scattered laser pulse signal onto the photosensitive surface of the receiving laser detector. The focusing lens group 34 is fixed at the inner part 33 of the sleeve 30 through three threaded holes 32. Figure 3 (6) is a complete assembly diagram. Since the plane mirror is located at the center of the base bracket, the optical axis of the focusing lens is on the axis of the ring base of the base bracket, so the plane mirror is located on the optical axis of the focusing lens; since the plane mirror is located at the center of the base bracket, the optical axis of the focusing lens It coincides with the central axis of the ring-shaped base of the base bracket, so the plane reflector is located on the optical axis of the focusing lens; the laser pulse reflected by the first beam splitter is incident on the plane reflector of the coaxial module at an angle of 45° , so that the beam propagation direction is changed by 90° to exit in the horizontal direction. Since the plane reflector is located on the optical axis of the focusing lens, the outgoing optical path of the emitted laser pulse coincides with the optical axis of the focusing lens, and the emitted laser pulse is scattered along the optical axis after being scattered by the target. Return, so that the optical path of the emitted laser pulse is coaxial with the optical path of the received laser pulse, and at the same time, the focusing lens can focus the echo of the scattered laser pulse on the receiving laser detector, thereby increasing the detected light energy of the received laser pulse.

In FIG. 2 , the light beam 21 is split into a light beam 22 and a light beam 23 by a beam splitter 3 with a reflection and transmission ratio of 1:9. The beam 22 is a transmitted beam, and the beam 23 is a reflected beam. Among them, the transmitted beam accounts for a large proportion mainly because the transmitted beam is received by the transmitting laser detector as the acquisition signal of the transmitted laser pulse waveform, and the higher laser pulse energy ensures that the collected transmitted laser pulse waveform has a high signal-to-noise ratio. So as to ensure the precise storage of the emitted laser pulse waveform. The light beam 22 is incident on the emission laser detector 6 and converted into an emission waveform electrical signal 16 . The light beam 23 enters the photodiode 12, and the photodiode 12 converts the laser pulse signal into an electric pulse signal, and the electric pulse signal is filtered, shaped and amplified by the signal conditioning circuit 11 to become an acquisition card control signal capable of driving the high-speed dual-channel data acquisition card 7 15, thereby setting the data reading reference position of the high-speed dual-channel data acquisition card 7. Due to the time delay of the signal conditioning circuit 11 relative to the light beam 22, the control signal 15 of the acquisition card reaches the high-speed dual-channel data acquisition card 7 later than the electrical signal 16 of the transmission waveform, so the collected transmission waveform will be incomplete. In order to solve this problem, configure high-speed dual-channel data acquisition card 7 to work in the real-time acquisition mode. When the high-speed dual-channel data acquisition card 7 receives the acquisition card control signal 15, set the data reading reference position at the current sampling point, when After the sampling meets the sampling configuration requirements, the main control computer 8 takes the data reading reference position as a reference, and reads a certain number of sampling points before the data reading reference position, thereby eliminating the difference between the acquisition card control signal 15 and the transmitted waveform electrical signal 16 The time delay between, and then read the remaining points to complete the complete storage of the emitted laser pulse waveform.

Data acquisition and read sequence shown in Figure 4. The high-speed dual-channel data acquisition card works in real-time acquisition mode after power-on, and stores the collected data in the onboard memory. The laser control unit sends a laser control signal according to the set frequency and duty cycle. After receiving the laser control signal, the pulsed laser emits a laser pulse after a certain time delay. The laser pulse is split by the laser transmitting and receiving unit, and one of them enters the to the acquisition card control module in the data acquisition unit to generate the acquisition card control signal. Since the laser pulse needs to undergo photoelectric conversion, shaping, filtering and amplification, there is a delay in the acquisition card control signal relative to the laser pulse signal. When the acquisition card control When the signal reaches the high-speed dual-channel data acquisition card 7, the data reading reference position will be set at the current sampling point. When the high-speed dual-channel data acquisition card 7 satisfies the sampling configuration, the main control computer 8 will take the read data reference position as a benchmark , read a certain length of data before and after reading the reference position of the data, so as to complete the complete reading of the emitted laser pulse waveform, and read a certain length of data before storing the mark in order to eliminate the control signal of the acquisition card relative to the emitted laser pulse The hysteresis, reading a certain length of data after storing the mark is to ensure the integrity of the data and realize the complete storage of the emitted laser pulse waveform and the received laser pulse waveform.

The main control computer 8 stores the read data in binary form in units of bytes, and the storage format is shown in FIG. 6 . The data storage format is to store configuration parameters and data blocks separately, and the data blocks are divided into data sub-blocks. The 1st-17th bytes store the configuration parameters, and the data blocks are stored after the 17th byte; the specific storage format is as follows: the 1st-4th byte stores the working time of the system, and the working time includes year, month and day; The 5 bytes are the connection mode of the sampling channel, 0 means that the transmitting laser detector is connected to the first channel of the high-speed dual-channel data acquisition card, and the receiving laser detector is connected with the second channel of the high-speed dual-channel data acquisition card, and 1 means the transmission The laser detector is connected to the second channel of the high-speed dual-channel data acquisition card, and the receiving laser detector is connected to the first channel of the high-speed dual-channel data acquisition card; 6-9 bytes are stored in the first channel of the high-speed dual-channel data acquisition card The number of sampling points set is stored in the high order and the low order is in the back; the 10-13 bytes store the sampling points set in the second channel of the high-speed dual-channel data acquisition card, and the storage method is in the high order and the low order; The 14th-15th bytes store the sampling frequency set by the high-speed dual-channel data acquisition card. The reference voltage set by channel 1, the reference voltage is in millivolts; the 17th byte stores the reference voltage set by the second channel of the high-speed dual-channel data acquisition card, the reference voltage is in millivolts, the 17th byte After the byte, the data sub-blocks for each measurement are stored separately. Each data sub-block corresponds to a laser pulse emitted by the pulsed laser. The data sub-blocks include the emission time of the laser pulse, the full waveform data of the emitted laser pulse and the full waveform of the received laser pulse. data.

The software unit of the full-waveform laser radar system based on coaxial dual-channel data acquisition mainly completes the parameter configuration before the start of the full-waveform laser radar system based on coaxial dual-channel data acquisition, as well as the display of the transmitted laser pulse waveform and the received laser pulse waveform. The software unit interface is shown in Figure 6. The software unit interface is composed of a high-speed dual-channel data acquisition card configuration part, a laser control unit configuration part and a waveform display part. The high-speed dual-channel data acquisition card configuration part includes file settings, acquisition channel voltage settings, acquisition channel time settings, acquisition channel input settings, and acquisition card trigger settings. File settings include file storage path settings and the display of the number of stored files. The acquisition channel voltage setting includes the reference voltage setting of the acquisition channel 0 and the acquisition channel 1 and the setting of the bias voltage of the acquisition channel 0 and the acquisition channel 1. Sampling channel time setting includes sampling frequency setting, record length setting and reference position setting. The acquisition channel input setting includes the settings of the maximum input frequency and input signal coupling mode of acquisition channel 0 and acquisition channel 1. Acquisition card trigger setting includes trigger source setting, trigger level setting, trigger channel coupling mode setting and trigger edge selection. The laser control unit configuration section includes laser control signal frequency, amplitude and duty cycle settings. The waveform display window is used for real-time display of transmitting and receiving waveforms.

The above is only the basic scheme of the specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto, and any conceivable change or replacement within the technical scope disclosed by the present invention by anyone familiar with the technical field, All should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims. All changes that come within the equivalent meaning and range of the claims are intended to be included in the scope of the claims.

Claims (5)

1. A full waveform laser radar system based on coaxial dual-channel data acquisition, characterized in that, the laser radar system comprises a pulsed laser, a laser emitting and receiving unit, a data acquisition unit, a control unit and a software unit, and the laser The transmitting and receiving unit is composed of a beam splitter and a coaxial module. The data acquisition unit is composed of a transmitting laser detector, a receiving laser detector, a high-speed dual-channel data acquisition card and an acquisition card control module. The control unit is composed of a main control unit Composed of a computer and a laser control unit, the pulsed laser receives the laser control signal from the laser control unit and sends out laser pulses with a certain frequency and pulse width. Transmission delay, the laser pulse is divided into 3 beams by the beam splitter in the laser transmitting and receiving unit, the first beam of laser pulse is emitted to the target through the coaxial module in the laser transmitting and receiving unit, and the laser pulse is scattered by the target , is focused by the coaxial module in the laser emitting and receiving unit to the receiving laser detector in the data acquisition unit, and the receiving laser detector converts the received optical signal into an electrical signal, thereby being captured by the high-speed dual-channel data Acquisition card acquisition, with the help of high-speed data sampling, the waveform of the received laser pulse can be completely collected, thereby realizing the full waveform storage of the received laser pulse; the second laser pulse is incident on the emitting laser detector in the data acquisition unit, and the emitted laser pulse The detector converts the laser pulse into an electrical signal, which is collected by the high-speed dual-channel data acquisition card in the data acquisition unit. With the help of high-speed data sampling, the waveform of the emitted laser pulse can be completely collected, thereby realizing the full waveform of the emitted laser pulse Storage, due to the instability of the pulsed laser, the emitted laser pulses have different waveforms, and the transmitted laser pulse waveform and the received laser pulse waveform are stored at the same time, so that in the later signal processing, the emitted laser pulse waveform width and The difference in amplitude can obtain more accurate measurement results, and can invert the physical and geometric characteristics of the target according to the difference between the transmitted laser pulse waveform and the received laser pulse waveform; the third laser pulse enters the data acquisition unit The control module of the acquisition card is used to generate the control signal of the acquisition card, which is used to set the reference position of data reading, and is used for the reference position when the main control computer reads the data in the high-speed dual-channel data acquisition card. The reference position can realize the complete reading of the transmitted laser pulse waveform, and the consistency of the time coordinates of the transmitted waveform and the received waveform; the control unit completes the control of the high-speed dual-channel data acquisition card in the pulse laser and the data acquisition unit, and the high-speed dual-channel The data collected in the channel data acquisition card is read, displayed, stored and calculated, and a hardware platform is provided for the software unit; the software unit provides a human-computer interaction interface to complete the configuration of the data acquisition unit and the control unit, and the collected Display of data and data processing results; it can realize the complete coaxiality of the transmitting laser pulse optical path and the receiving laser pulse optical path in the laser radar optical path, and can realize The full waveform of the emitted laser pulse and received laser pulse is collected, displayed and stored according to the set format. 2. A full-waveform lidar system based on coaxial dual-channel data acquisition according to claim 1, wherein the laser emitting and receiving unit can realize the complete coaxiality of the optical path of emitting laser pulses and receiving laser pulses , and realize the splitting of the laser pulses emitted by the pulse laser, so that the laser pulse signals of different components are used to generate the acquisition card control signal, emit the laser pulse waveform acquisition signal, and emit the laser pulse signal. The laser emitting and receiving unit Composed of two beam splitters and a coaxial module, the first beam splitter has a reflection-to-transmission ratio of 9:1, so that the laser pulse emitted by the pulsed laser is divided into two laser pulses with a light intensity ratio of 9:1 , the reflected beam accounts for a large proportion mainly because the reflected beam will pass through the coaxial module as the outgoing laser pulse and illuminate the target. The greater the energy of the outgoing laser pulse, the farther the measurement distance will be, and the higher the signal-to-noise ratio of the laser pulse signal scattered by the target. In order to achieve long-distance and accurate measurement of the target; the transmitted beam is split again by the second beam splitter, and the reflection-transmittance ratio of the second beam splitter is 1:9, of which the transmitted beam accounts for a large proportion mainly because of the transmission The light beam is received by the laser detector as the acquisition signal of the transmitted laser pulse waveform. The higher signal energy ensures that the collected transmitted laser pulse waveform has a higher signal-to-noise ratio, thereby ensuring accurate storage of the transmitted laser pulse waveform; the reflected beam enters The acquisition card control module in the data acquisition unit is used to generate the acquisition card control signal; the coaxial module is composed of a plane mirror, a mirror base, a base bracket, a sleeve and a focusing lens, and the plane mirror is coated with The dielectric film that improves the reflectivity is mainly to reduce the energy loss of the reflected beam. The thickness of the plane reflector is 1-2mm, the width is 2mm, and the length is 4mm. The smaller thickness is mainly to ensure that the reflector is fixed on the bracket. In the center of the coaxial module, the reflector with a smaller area is to reduce the shielding of the laser pulse signal scattered by the target, thereby reducing the loss of echo energy; the base of the reflector is a cube with a side length of 2 mm along the pair The half of the corner cut, the plane reflector is fixed on the slope of the reflector base by gluing; the base support is composed of a ring-shaped base and a three-line support with a common point, and the width of the three-line support is 2mm. On the one hand, it ensures The reflector base can be fixed on the common point of the three-wire support and can bear the weight of the reflector base, and on the other hand, the shielding of the echo signal by the three-line support is reduced; the reflector base is fixed on the common point of the base support by gluing Above, the ring-shaped base of the base bracket is fixed on the front of the sleeve by nuts, and the focusing lens is fixed on the inside of the sleeve by nuts; since the plane reflector is located in the center of the base bracket, the optical axis of the focusing lens is in line with the base The central axis of the ring-shaped base of the bracket coincides, so the plane reflector is located on the optical axis of the focusing lens; the laser pulse reflected by the first beam splitter is incident on the plane reflector of the coaxial module at an angle of 45°, thus Change the beam propagation direction by 90° to exit in the horizontal direction, because the plane reflector is located on the optical axis of the focusing lens , so that the outgoing optical path of the emitted laser pulse coincides with the optical axis of the focusing lens, and the emitted laser pulse returns along the optical axis after being scattered by the target, so that the optical path of the emitted laser pulse is coaxial with the optical path of the receiving laser pulse, and the focusing lens can transfer the scattered laser pulse The echoes are focused onto the receiving laser detector, thereby increasing the detected light energy of the receiving laser pulse. 3. a kind of full-waveform lidar system based on coaxial dual-channel data acquisition according to claim 1, is characterized in that, described data acquisition unit can realize the dual-channel acquisition of emitting laser pulse and receiving laser pulse simultaneously, Simultaneously realize the complete acquisition and storage of the transmitted laser pulse and received laser pulse waveform, thereby realizing the full waveform storage of the laser pulse. The data acquisition unit includes: a transmitting laser detector, a receiving laser detector, a high-speed dual-channel data acquisition card and an acquisition Card control module; the emitting laser detector and the receiving laser detector realize the photoelectric conversion of emitting laser pulses and receiving laser pulses respectively, and are respectively connected to the two acquisition channels of the high-speed dual-channel data acquisition card; the high-speed dual-channel data acquisition card completes the simulation The conversion of signal to digital signal, and the collected signal is stored in its own onboard memory; the control module of the acquisition card is composed of a photodiode and a signal conditioning circuit, the photodiode receives the laser pulse signal from the laser emitting and receiving unit, and the laser The pulse signal is converted into an electric pulse, and the electric pulse is shaped, filtered and amplified by the signal conditioning circuit to generate the control signal of the acquisition card, thereby completing the control of the acquisition card; when the acquisition is completed, the main control computer in the control unit reads the dual The data in the channel data acquisition card, so as to realize the storage and calculation of the transmitted laser pulse and received laser pulse waveform; the dual detector and dual channel acquisition can ensure the simultaneous acquisition of transmitted pulse and received pulse, and ensure that the transmitted signal and received signal have the same time Coordinates, compared with single-channel single-detector acquisition, can eliminate measurement blind spots, realize short-distance measurement, and avoid mutual interference between transmitted signals and received signals; since the transmitted waveform acquisition signal and the control signal of the acquisition card come from different modules, the acquisition There is a time delay between the card control signal and the emitted laser pulse signal. When the emitted pulse signal reaches the acquisition card, the acquisition card has not been triggered to collect. In order to ensure the complete storage of the emitted laser pulse waveform, the high-speed dual-channel data acquisition card works in real-time acquisition mode. , and store the collected data in the on-board memory. When the high-speed dual-channel data acquisition card receives the acquisition card control signal from the acquisition card control module, it will set the read data reference position at the current sampling point. When After the sampling meets the sampling configuration requirements, the main control computer takes the reference position of the read data as the reference, reads a certain length of data before and after the reference position of the read data, and reads a certain length of data before storing the mark to eliminate the acquisition card. The hysteresis of the control signal relative to the emitted laser pulse, reading a certain length of data after storing the mark is to ensure the integrity of the data, so as to realize the complete reading of the emitted laser pulse waveform, and finally complete the analysis of the emitted laser pulse waveform and received laser pulse Complete storage of waveforms. 4. A kind of full-waveform lidar system based on coaxial dual-channel data acquisition according to claim 1, is characterized in that, described software unit comprises: high-speed dual-channel data acquisition card configuration part, laser control unit configuration part and the waveform display part; the high-speed dual-channel data acquisition card configuration part includes file setting, acquisition channel voltage setting, acquisition channel time setting, acquisition channel input setting, acquisition card trigger setting; file setting includes file storage path setting and stored Display of the number of files; acquisition channel voltage setting includes acquisition channel 0 and acquisition channel 1 reference voltage setting and acquisition channel bias voltage setting; sampling channel time setting includes sampling frequency setting, record length setting and reference position setting Setting; acquisition channel input setting includes the setting of the maximum input frequency and input signal coupling mode of acquisition channel 0 and acquisition channel 1; acquisition card trigger setting includes trigger source setting, trigger level setting, trigger channel coupling mode setting and trigger edge setting Selection; the laser control unit configuration part includes laser control signal frequency, amplitude and duty cycle settings; the waveform display window is used for real-time display of the transmitted waveform and the received waveform. 5. A kind of full-waveform lidar system based on coaxial dual-channel data acquisition according to claim 1, characterized in that, said data storage format is to store configuration parameters and data blocks separately, and data blocks are divided into data Sub-block; the 1-17 bytes store configuration parameters, and the data blocks are stored after the 17th byte; the specific storage format, in which: the 1-4 bytes store the system start working time, and the system start working time includes year, month and Day; the fifth byte is the sampling channel connection mode, 0 means that the transmitting laser detector is connected to the first channel of the high-speed dual-channel data acquisition card, and the receiving laser detector is connected to the second channel of the high-speed dual-channel data acquisition card. 1 means that the transmitting laser detector is connected to the second channel of the high-speed dual-channel data acquisition card, and the receiving laser detector is connected to the first channel of the high-speed dual-channel data acquisition card; the 6th-9 bytes are stored in the high-speed dual-channel data acquisition card The number of sampling points set by the first channel adopts the storage method of high-order first and low-order; the 10-13 bytes store the number of sampling points set by the second channel of the high-speed dual-channel data acquisition card, and adopts the storage method of high-order first and low-order Storage method; the 14th-15th byte stores the sampling frequency set by the high-speed dual-channel data acquisition card, and the sampling frequency is in megahertz, and adopts the storage method of high-order first and low-order; the 16th byte stores high-speed dual-channel data The reference voltage set by the first channel of the acquisition card, the reference voltage is in millivolts; the 17th byte stores the reference voltage set by the second channel of the high-speed dual-channel data acquisition card, and the reference voltage is in millivolts , after the 17th byte, the data sub-blocks of each measurement are respectively stored. Each data sub-block corresponds to a laser pulse emitted by the pulsed laser and a scattered laser pulse received. Full waveform data and received laser pulse full waveform data.