Laser radar and laser radar ranging method

Abstract

The application discloses a laser radar and a laser radar ranging method, and comprises a field programmable gate array, a laser emitting unit and a laser receiving unit, and a return signal processing unit is arranged between the laser receiving unit and the field programmable gate array; the laser receiving unit is used for receiving two return signals of the same laser pulse signal; the two return signals have an overlapping area and different peak positions; the return signal processing unit is used for obtaining a capacitance current signal according to the two return signals, and converting the capacitance current signal to obtain two rectangular pulses; the field programmable gate array is used for determining a timing start signal and a timing end signal of the laser pulse signal based on the two rectangular pulses, and obtaining a target distance between a target object and the laser radar according to the timing start signal and the timing end signal. The application can accurately distinguish the vertexes and corresponding rising edges of different return signals, and can eliminate the influence of a large blind area generated by stray light on ranging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, in particular to a laser radar and a laser radar ranging method. BACKGROUND

[0002] The laser radar is a device for detecting distance and target position by using the time of flight (TOF) of laser, and its principle is to emit continuous laser pulses to a target object, and then receive the echo signal returned from the object by a receiving assembly, and calculate the distance information of the target object according to the time difference between the emission and reception of the light pulse.

[0003] In the prior art, the principle of laser ranging is to first integrate the received echo signal into a rectangular wave, and then measure the rising edge of the emission pulse (the starting signal of timing) to the rising edge of the reception pulse (the ending signal of timing). A part of the outgoing laser is directly shot to the receiving assembly after being reflected by internal optical devices and structural members, and this part of laser is called stray light (pulse width is about 5-10 ns, and the distance is 0.75-1.5 meters). If the target object is located outside the coverage distance of the stray light pulse width, the echo signal reflected by the target object and the echo signal generated by the received stray light will not overlap, and the laser radar can accurately range the target object.

[0004] However, if the target object is located within the coverage distance of the stray light pulse width, the echo signal generated by the received stray light and the echo signal reflected by the target object will overlap, and the rising edges of the two will be mixed together, so that the starting signal and the ending signal of timing of the target object cannot be distinguished from each other, thereby resulting in a large blind area. SUMMARY

[0005] The technical problem solved by the present application is to provide a laser radar and a laser radar ranging method, which can solve the problem of large blind area of the laser radar affecting ranging.

[0006] To solve the above technical problems, the first technical solution adopted by the present application is to provide a laser radar, comprising a field programmable gate array, and a laser emitting unit and a laser receiving unit connected with the field programmable gate array respectively, and a return signal processing unit is arranged between the laser receiving unit and the field programmable gate array; the laser receiving unit is used for receiving two return signals of the same laser pulse signal emitted by the laser emitting unit; wherein, the two return signals have an overlapping area and different peak positions; the return signal processing unit is used for obtaining a capacitance current signal according to the two return signals, and converting the capacitance current signal to obtain two rectangular pulses; the field programmable gate array is used for determining a timing start signal and a timing end signal of the laser pulse signal based on the two rectangular pulses, and obtaining a target distance between the target object and the laser radar according to the timing start signal and the timing end signal.

[0007] Wherein, the return signal processing unit comprises a capacitance charging and discharging unit, a current sampling unit and a zero-crossing comparator connected in sequence; the capacitance charging and discharging unit is connected with the laser receiving unit, and the return signal processed by the laser receiving unit is used to charge and discharge the capacitance charging and discharging unit; the current sampling unit is used for collecting a capacitance current signal generated by the capacitance charging and discharging unit in the charging and discharging process, and converting the capacitance current signal into an analog voltage signal; wherein, the peak value of the return signal corresponds to the zero-crossing point of the capacitance current signal; the zero-crossing comparator is used for converting the analog voltage signal into a rectangular pulse; wherein, the zero-crossing point of the capacitance current signal corresponds to the rising edge of the rectangular pulse.

[0008] Wherein, the field programmable gate array comprises a signal separation unit and a time-to-digital converter connected with each other; the signal separation unit is used for determining the first received return signal and the corresponding rectangular pulse as the first return signal and the first rectangular pulse; and determining the second received return signal and the corresponding rectangular pulse as the second return signal and the second rectangular pulse; the time-to-digital converter is used for taking the rising edge signal of the first rectangular pulse as the timing start signal, and taking the rising edge signal of the second rectangular pulse as the timing end signal.

[0009] Wherein, the laser radar further comprises a high-speed digital-to-analog converter connected with the field programmable gate array; the high-speed digital-to-analog converter is used for transmitting the rising edge signal of the second rectangular pulse transmitted by the timing end signal separation unit, and transmitting the signal intensity information obtained based on the rising edge signal of the second rectangular pulse to the field programmable gate array.

[0010] Wherein, the laser radar further comprises a galvanometer / rotary mirror unit connected with the field programmable gate array; the galvanometer / rotary mirror unit is used for determining the angle position information of the target object.

[0011] To solve the above technical problems, the second technical solution adopted by the present application is to provide a laser radar ranging method, which is realized by a laser radar. The laser radar comprises a field programmable gate array, and a laser emitting unit and a laser receiving unit connected with the field programmable gate array respectively. A return signal processing unit is arranged between the laser receiving unit and the field programmable gate array. The laser radar ranging method comprises: receiving, by the laser receiving unit, two return signals of the same laser pulse signal emitted by the laser emitting unit and reflected; wherein the two return signals have an overlapping region and different peak positions; obtaining, by the return signal processing unit, a capacitance current signal according to the two return signals, and converting the capacitance current signal to obtain two rectangular pulses; determining, by the field programmable gate array, a timing start signal and a timing end signal of the laser pulse signal based on the two rectangular pulses, and obtaining a target distance between a target object and the laser radar according to the timing start signal and the timing end signal.

[0012] The step of obtaining, by the return signal processing unit, a capacitance current signal according to the two return signals, and converting the capacitance current signal to obtain two rectangular pulses comprises: charging and discharging a capacitance charging and discharging unit of the return signal processing unit by using the return signal processed by the laser receiving unit; collecting, by a current collection unit of the return signal processing unit, a capacitance current signal generated by the capacitance charging and discharging unit in the charging and discharging process, and converting the capacitance current signal into an analog voltage signal; wherein the peak value of the return signal corresponds to the zero-crossing point of the capacitance current signal; converting, by a zero-crossing comparator of the return signal processing unit, the analog voltage signal into a rectangular pulse; wherein the zero-crossing point of the capacitance current signal corresponds to the rising edge of the rectangular pulse.

[0013] The step of determining, by the field programmable gate array, a timing start signal and a timing end signal of the laser pulse signal based on the two rectangular pulses, and obtaining a target distance between a target object and the laser radar according to the timing start signal and the timing end signal comprises: determining, by a signal separation unit of the field programmable gate array, the first received return signal and the corresponding rectangular pulse as a first return signal and a first rectangular pulse; and determining the second received return signal and the corresponding rectangular pulse as a second return signal and a second rectangular pulse; taking, by a time-to-digital converter of the field programmable gate array, the rising edge signal of the first rectangular pulse as the timing start signal, and taking the rising edge signal of the second rectangular pulse as the timing end signal; calculating, by the field programmable gate array, a time difference between the timing start signal and the timing end signal, and calculating the target distance based on the time difference.

[0014] After the step of taking the rising edge signal of the first rectangular pulse as the timing start signal and the rising edge signal of the second rectangular pulse as the timing end signal by the time-to-digital converter of the field programmable gate array, the method comprises: transmitting the rising edge signal of the second rectangular pulse to a high-speed digital-to-analog converter connected to the field programmable gate array, and sampling the rising edge signal of the second rectangular pulse by using the high-speed digital-to-analog converter to obtain the signal intensity information of the second echo signal.

[0015] After the step of calculating the time difference between the timing start signal and the timing end signal by using the field programmable gate array, and calculating the target distance based on the time difference, the method comprises: obtaining the angle position information of the target object by the galvanometer / rotating mirror unit of the laser radar; fusing the angle position information and the target distance by using the field programmable gate array to obtain spatial three-dimensional data; and fusing the spatial three-dimensional data and the signal intensity information to generate a laser point cloud map with reflection characteristic information.

[0016] The application has the following beneficial effects: Different from the prior art, the application provides a laser radar and a laser radar ranging method, two echo signals with an overlapping area are processed by an echo signal processing unit, different peaks of the two echo signals are converted into different zero points in a capacitance current signal, so that the vertexes of different echo signals are accurately distinguished, and the influence of a large blind area caused by stray light on ranging is eliminated, and the ranging range is expanded. Further, the capacitance current signal is converted into two rectangular pulses, and the two rising edges are determined as a timing start signal and a timing end signal by a field programmable gate array, so that the echo time can be accurately obtained, and the accuracy of close-range ranging is improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0018] Figure 1 is a structural schematic diagram of an embodiment of the laser radar of the application;

[0019] Figure 2 is an overlapping schematic diagram of echo signals received by the laser receiving unit of the application and a corresponding rectangular pulse schematic diagram;

[0020] Figure 3 is Figure 1 a conversion schematic diagram of the echo signal processing unit processing the echo signal in the application;

[0021] Figure 4is a flowchart of a first embodiment of a laser radar ranging method of the present application;

[0022] Figure 5 is a flowchart of a second embodiment of a laser radar ranging method of the present application;

[0023] Figure 6 is a work flow diagram of an application scenario of a laser radar ranging method of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0025] The terms used in the embodiments of the present application are merely for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless otherwise clearly indicated. "Plural" generally includes at least two, but does not exclude the case of including at least one.

[0026] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0027] It should be understood that the terms "include", "contain" or any other variant used herein are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or device. Without more limitations, the elements defined by the statement "include" do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0028] Please refer to Figure 1 , Figure 1is a structural schematic diagram of an embodiment of the laser radar of the present application. In the embodiment, the laser radar 100 comprises a Field Programmable Gate Array (FPGA) 10, and a laser emitting unit 20 and a laser receiving unit 30 connected with the Field Programmable Gate Array 10 respectively, and a return signal processing unit 40 is arranged between the laser receiving unit 30 and the Field Programmable Gate Array 10.

[0029] In the embodiment, the laser receiving unit 30 is configured to receive two return signals of the same laser pulse signal emitted by the laser emitting unit 20, wherein the two return signals have an overlapping region and different peak positions.

[0030] The first received return signal is generated by direct absorption of stray light, and the second received return signal is reflected by a close-range target object. It can be understood that the stray light is generated inside the laser radar 100 and thus is received first.

[0031] Specifically, referring to Figure 2 , Figure 2 is a schematic diagram of overlapping return signals received by the laser receiving unit of the present application and a corresponding rectangular pulse diagram. Return signal A is the first received return signal, and return signal B is the second received return signal. The return signal A and the return signal B have an overlapping region and different peak positions. The return signal A is a return signal generated by stray light, and the return signal B is a return signal reflected by a close-range target object. Figure 2 It can be known that the rectangular pulses formed by the return signal A and the return signal B overlap, and the rising edges of the two are mixed together, and the rising edge of the return signal B cannot be distinguished by the rising edge, that is, the timing end signal of the return signal B cannot be distinguished by the rising edge. Moreover, since the stray light is generated inside the laser radar 100, the return signal A also overlaps with the emitted laser pulse signal, so that the timing start signal cannot be accurately obtained.

[0032] Based on this, the embodiment adds the return signal processing unit 40 between the laser receiving unit 30 and the Field Programmable Gate Array 10, so as to reprocess the return signal by using the return signal processing unit 40.

[0033] In the embodiment, the return signal processing unit 40 is configured to obtain a capacitance current signal according to the two return signals, and convert the capacitance current signal to obtain two rectangular pulses.

[0034] Specifically, the peak (waveform center) of the echo signal corresponds to a zero point in the capacitance current signal, and the peaks of different positions of the two echo signals correspond to different zero points, and when the rising edge of stray light and the near distance target in the target object overlap, different zero points in the capacitance circuit signal can distinguish different echo peaks. Further, the capacitance current signal is sampled to obtain an analog voltage signal, and the analog voltage signal is converted into a rectangular pulse, and the rising edge or falling edge of the rectangular pulse corresponds to a different zero point in the capacitance current signal. Among them, the two rising edges correspond to the peaks of the two echo signals respectively.

[0035] In some embodiments, the echo signal processing unit 40 includes a capacitance charging and discharging unit 41, a current sampling unit 42, and a zero-crossing comparator 43 connected in sequence.

[0036] The capacitance charging and discharging unit 41 is connected to the laser receiving unit 30, and the echo signal processed by the laser receiving unit 30 is used to charge and discharge the capacitance charging and discharging unit 41. The current sampling unit 42 is used to collect the capacitance current signal generated by the capacitance charging and discharging unit 41 during charging and discharging, and convert the capacitance current signal into an analog voltage signal. Among them, the peak of the echo signal corresponds to the zero-crossing point of the capacitance current signal. The zero-crossing comparator 43 is used to convert the analog voltage signal into a rectangular pulse. Among them, the zero-crossing point of the capacitance current signal corresponds to the rising edge of the rectangular pulse.

[0037] Specifically, please refer to Figure 3 , Figure 3 is Figure 1 the conversion schematic diagram of the echo signal processing unit in the echo signal processing unit processing the echo signal. First, the transimpedance amplifier (TIA) in the laser receiving unit 30 converts the echo signal A and the echo signal B into voltage, and then uses the above voltage to charge and discharge the capacitance charging and discharging unit 41. Secondly, the current sampling unit 42 collects the capacitance current signal generated by the capacitance charging and discharging unit 41 during charging and discharging, and converts the capacitance current signal into an analog voltage signal. Among them, the capacitance charges when the waveform of the echo signal A or the echo signal B rises, and the capacitance discharges when the waveform falls, and the waveform peaks (peaks) of the echo signal A and the echo signal B correspond to the zero points of the capacitance current signal. In the overlapping region of the echo signal A and the echo signal B, as the waveform of the echo signal A gradually falls and the waveform of the echo signal B gradually rises, the capacitance current signal changes from negative to positive, and there is also a zero-crossing point. Finally, the zero-crossing comparator 43 is used to convert the analog voltage signal into two rectangular pulses. Among them, the two zero-crossing points of the capacitance current signal correspond to the two rising edges of the rectangular pulse respectively, that is, the peaks of the echo signal A and the echo signal B correspond to the two rising edges of the rectangular pulse respectively.

[0038] It can be understood that, by converting the two overlapping echo signals into a capacitive current signal through the echo signal processing unit 40, and generating two discrete rectangular pulses based on the zero-crossing point of the capacitive current signal, the peak value of the echo signal corresponding to stray light and the peak value of the echo signal corresponding to a close-range target can be converted and processed into the rising edges of the two discrete rectangular pulses, avoiding the mixing of the rising edges, thereby distinguishing the vertex of the echo signal generated by stray light from the vertex of the echo signal generated by a close-range target.

[0039] It can be understood that, by distinguishing the two echo signals within the coverage distance of the stray light pulse width, the influence of the large blind area caused by stray light on ranging is eliminated, which is equivalent to reducing the detection blind area of the laser radar, thereby improving the ranging range of the laser radar and expanding the application scenarios of the laser radar. Further, the rising edge obtained in the above manner is not affected by the edge slope of the echo signal, and the measurement accuracy can also be effectively improved.

[0040] In this embodiment, the field programmable gate array 10 is used to determine the timing start signal (START signal) and the timing end signal (STOP signal) of the laser pulse signal based on the two rectangular pulses, and obtain the target distance between the target object and the laser radar 100 according to the timing start signal and the timing end signal.

[0041] The field programmable gate array 10 takes the rising edge of the first rectangular pulse (the peak value of the echo signal corresponding to stray light) as the timing start signal, takes the rising edge of the second rectangular pulse (the peak value of the echo signal reflected by the close-range target object) as the timing end signal, calculates the time difference between the two rising edges, and takes the time difference as the echo time, and then calculates the target distance based on the echo time.

[0042] In other embodiments, the falling edge of the first rectangular pulse can also be taken as the timing start signal, and the falling edge of the second rectangular pulse can also be taken as the timing end signal, which is not limited in the present application.

[0043] In some embodiments, the field programmable gate array 10 includes a signal separation unit 11 and a time-to-digital converter (TDC) 12 connected to each other. The signal separation unit 11 is used to determine the first received echo signal and the corresponding rectangular pulse as the first echo signal and the first rectangular pulse, and determine the second received echo signal and the corresponding rectangular pulse as the second echo signal and the second rectangular pulse. The signal separation unit 11 further transmits the separated first echo signal and the first rectangular pulse, the second echo signal and the second rectangular pulse to the time-to-digital converter 12. The time-to-digital converter 12 is used to take the rising edge signal of the first rectangular pulse as the timing start signal, and take the rising edge signal of the second rectangular pulse as the timing end signal.

[0044] In the prior art, due to the actual emission time of the laser pulse being affected by the wiring, device delay and the like, a large amount of calibration calculation is usually required to roughly estimate the position of the actual timing start signal. Referring to Figure 3 It can be seen that the peak value of the echo signal A is close to the starting point of the echo signal B. In the case where the actual timing start signal cannot be accurately obtained, directly taking the rising edge corresponding to the peak value of the echo signal A as the timing start signal can find the START signal close to the actual timing start signal as much as possible under the premise of avoiding a large amount of calculation work.

[0045] It can be understood that by distinguishing the two discrete rectangular pulses through the signal separation unit 11 and taking the peak value of the echo signal corresponding to the stray light as the timing start signal of the time-to-digital converter 12, the influence of circuit delay can be effectively reduced. Further, instead of simply taking the mixed rising edge of the overlapping rectangular pulses as the timing end signal, taking the peak value of the echo signal corresponding to the close-range target distinguished as the timing end signal of the time-to-digital converter 12 can more accurately calculate the real echo time, thereby improving the accuracy of close-range ranging.

[0046] In the embodiment, the laser radar 100 further includes a galvanometer / rotating mirror unit 60 connected to the field programmable gate array 10. The galvanometer / rotating mirror unit 60 is used to determine the angular position information of the target object. Specifically, the calculated target distance is combined with the angular position information to generate spatial three-dimensional data of the echo signal.

[0047] Based on the TOF principle, the distance and angle of the target can be measured, but only relying on the distance and angle for ranging will also lack some necessary details. For example, different targets have different materials and surfaces, and have different reflectivities to the same laser pulse signal. When the laser radar performs target detection, even if they are located at the same position, the detection intensities of the echo signals caused by targets with different reflectivities are inconsistent (difference in edge slope caused by different reflectivities), which will lead to errors in the echo distance determined based on the same position due to different intensities.

[0048] Without intensity information, the resolution of some specific targets will also be increased. For example, without intensity information, a car has only one outline. After the intensity information is added, because the reflectivities of the car lights, windows, license plates, wheels and other parts are different, the intensities of the echo signals are also different, which can better distinguish the details and be beneficial to judging and confirming the target.

[0049] In the prior art, the complete waveform of each echo signal is sampled by a high-speed ADC (Analog to Digital Converter), the waveform of the signal is restored for analysis and processing. However, the high-speed ADC is very expensive, and the sampling data volume of the above method is extremely large, and a large amount of system resources are required for data analysis and storage.

[0050] Based on this, the laser radar 100 provided by the embodiment further comprises a high-speed digital-to-analog converter 50 connected with the field programmable gate array 10. The high-speed digital-to-analog converter 50 is used for sampling the rising edge signal of the second rectangular pulse transmitted by the timing end signal separation unit 11, and transmitting the signal intensity information obtained based on the rising edge signal of the second rectangular pulse to the field programmable gate array 10.

[0051] Wherein, if the echo signal received by the laser receiving unit 30 is a discrete echo signal (echo signal reflected by a target outside the blind area), the rising edge signal of the extracted echo signal is directly transmitted to the high-speed digital-to-analog converter 50 to trigger ADC sampling. After completing a round of ADC sampling, the high-speed digital-to-analog converter 50 waits for the sampling trigger information of the next round to perform subsequent ADC sampling.

[0052] It can be understood that the embodiment triggers ADC sampling by using the rising edge signal of each echo signal, which can make the high-speed digital-to-analog converter 50 accurately collect the peak value of the echo signal and measure the echo intensity by using the peak value, thereby avoiding the error caused by the edge slope, and further improving the measurement accuracy. Further, since there is only one sampling point at the peak value of each waveform, the sampling rate requirement of the high-speed digital-to-analog converter 50 can be greatly reduced, thereby greatly reducing the calculation amount to release the processor resources, and then improving the measurement efficiency.

[0053] It can be understood that the field programmable gate array 10 is used to fuse the above generated spatial three-dimensional data and signal intensity information, which can generate a laser point cloud graph with reflection characteristic information, thereby improving the ranging accuracy of targets with different reflectivities.

[0054] Compared with the prior art, the embodiment can convert different peaks of the two echo signals into different zero points in the capacitance current signal, thereby accurately distinguishing the peaks of the different echo signals, eliminating the influence of the large blind area caused by stray light on the ranging, and expanding the ranging range. Furthermore, converting the capacitance current signal into two rectangular pulses can convert the zero points corresponding to the two peaks in the capacitance current signal into rising edges of different rectangular pulses. Furthermore, the two rising edges can be determined as a timing start signal and a timing end signal by the field programmable gate array, so that the echo time can be accurately obtained, thereby improving the accuracy of the close-range ranging. In addition, the peak value of each extracted echo signal is sampled by the high-speed digital-to-analog converter, which can also improve the ranging accuracy of different reflectivity targets.

[0055] Please refer to Figure 4 , Figure 4 is a flowchart of a first embodiment of a laser radar ranging method of the present application. In the embodiment, the laser radar ranging method is implemented by the laser radar described above, which includes a field programmable gate array, and a laser emitting unit and a laser receiving unit connected with the field programmable gate array, respectively. The laser receiving unit is provided with an echo signal processing unit between the field programmable gate array.

[0056] The laser radar ranging method includes:

[0057] S41: receiving, by the laser receiving unit, two echo signals of the same laser pulse signal emitted by the laser emitting unit and reflected.

[0058] In the embodiment, the two echo signals are respectively an echo signal generated by stray light and an echo signal reflected by a close-range target object (located in a blind area).

[0059] Since the stray light is generated inside the laser radar, it will be received first.

[0060] S42: obtaining, by the echo signal processing unit, a capacitance current signal according to the two echo signals, and converting the capacitance current signal to obtain two rectangular pulses.

[0061] Specifically, the peak (waveform center) of the echo signal corresponds to a zero point in the capacitance current signal, and the peaks of different positions of the two echo signals correspond to different zero points, and when the rising edge of the stray light and the near distance target in the target object overlap, different zero points in the capacitance circuit signal can distinguish different echo peaks. Further, the capacitance current signal is sampled to obtain an analog voltage signal, and the analog voltage signal is converted into a rectangular pulse, and the rising edge or falling edge of the rectangular pulse corresponds to the different zero points in the capacitance current signal. Among them, the two rising edges correspond to the different peaks of the two echo signals respectively.

[0062] S43: Determine the timing start signal and the timing end signal of the laser pulse signal based on the two rectangular pulses by using the field programmable gate array, and obtain the target distance between the target object and the laser radar according to the timing start signal and the timing end signal.

[0063] In this embodiment, the field programmable gate array takes the rising edge of the first rectangular pulse (the peak of the echo signal corresponding to the stray light) as the timing start signal, takes the rising edge of the second rectangular pulse (the peak of the echo signal reflected by the near distance target object) as the timing end signal, calculates the time difference between the two rising edges, and takes the time difference as the echo time, and then calculates the target distance based on the echo time.

[0064] It can be understood that in the case that the peak of the echo signal corresponding to the stray light is close to the waveform starting point of the echo signal reflected by the near distance target object, and the actual timing start signal cannot be accurately obtained, directly taking the rising edge corresponding to the peak of the echo signal corresponding to the stray light as the timing start signal can find the START signal close to the actual timing start signal as much as possible under the premise of avoiding a large amount of calculation work.

[0065] It can be understood that by taking the peak of the echo signal corresponding to the stray light as the timing start signal, the influence of circuit delay can be effectively reduced. Further, taking the distinguished peak of the echo signal corresponding to the near distance target as the timing end signal instead of simply taking the mixed rising edge of the overlapping rectangular pulse as the timing end signal can more accurately calculate the real echo time, thereby improving the accuracy of the near distance ranging.

[0066] Compared with the prior art, the embodiment can convert different peaks of the two echo signals into different zero points in the capacitance current signal, thereby accurately distinguishing the vertexes of the different echo signals, eliminating the influence of the large blind area caused by stray light on the ranging, and expanding the ranging range. Further converting the capacitance current signal into two rectangular pulses can convert the zero points corresponding to the two peaks in the capacitance current signal into rising edges of different rectangular pulses. Further determining the two rising edges as a timing start signal and a timing end signal by the field programmable gate array can more accurately obtain the echo time, thereby improving the accuracy of the close-range ranging.

[0067] Please refer to Figure 5 , Figure 5 is a flowchart of a second embodiment of the laser radar ranging method of the application. In the embodiment, the laser radar ranging method is implemented by the laser radar described above, which includes a field programmable gate array, and a laser emitting unit and a laser receiving unit connected with the field programmable gate array respectively, and a return signal processing unit arranged between the laser receiving unit and the field programmable gate array. The return signal processing unit includes a capacitance charging and discharging unit, a current sampling unit, and a zero-crossing comparator connected in sequence. The field programmable gate array includes a signal separation unit and a time-to-digital converter connected with each other, and the laser radar further includes a high-speed digital-to-analog converter and a galvanometer / rotating mirror unit connected with the field programmable gate array.

[0068] The laser radar ranging method includes:

[0069] S501: receiving two echo signals of the same laser pulse signal emitted by the laser emitting unit and reflected by the laser receiving unit; wherein the two echo signals have an overlapping region and different peak positions.

[0070] For details, please refer to the description in S41, which will not be repeated here.

[0071] S502: charging and discharging the capacitance charging and discharging unit of the return signal processing unit by using the echo signal processed by the laser receiving unit.

[0072] In the embodiment, the capacitance charging and discharging unit is connected with the laser receiving unit, and the echo signal processed by the laser receiving unit is used to charge and discharge the capacitance charging and discharging unit.

[0073] Specifically, the echo signal generated by the stray light and the echo signal reflected by the close-range target object are used to charge and discharge the capacitance charging and discharging unit.

[0074] S503: Collect the capacitive current signal generated by the capacitive charging and discharging unit in the charging and discharging process through the current collection unit of the echo signal processing unit, and convert the capacitive current signal into an analog voltage signal; wherein the peak value of the echo signal corresponds to the zero crossing point of the capacitive current signal.

[0075] Specifically, the stray light produces an echo signal or a close-range target object reflects an echo signal, and the capacitive charging is charged when the waveform rises, and the capacitive discharging is discharged when the waveform falls, and the peak value of the two echo signals corresponds to the zero point of the capacitive current signal. In the waveform overlap area, as the waveform of the stray light produced echo signal gradually falls and the waveform of the close-range target object gradually rises, the capacitive current signal changes from negative to positive, and there is also a zero crossing point.

[0076] S504: Convert the analog voltage signal into a rectangular pulse using the zero crossing comparator of the echo signal processing unit; wherein the zero crossing point of the capacitive current signal corresponds to the rising edge of the rectangular pulse.

[0077] Specifically, the two zero crossing points of the capacitive current signal correspond to the two rising edges of the rectangular pulse, that is, the peak values of the stray light produced echo signal and the close-range target object reflected echo signal correspond to the two rising edges of the rectangular pulse.

[0078] S505: Determine the first received echo signal and the corresponding rectangular pulse as the first echo signal and the first rectangular pulse using the signal separation unit of the field programmable gate array; and determine the second received echo signal and the corresponding rectangular pulse as the second echo signal and the second rectangular pulse.

[0079] Wherein, the first echo signal is the stray light produced echo signal, and the second echo signal is the close-range target object reflected echo signal. Correspondingly, the first rectangular pulse is the rectangular pulse converted from the stray light produced echo signal, and the second rectangular pulse is the rectangular pulse converted from the close-range target object reflected echo signal.

[0080] It can be understood that since the stray light is generated inside the laser radar, it will be received first.

[0081] S506: Take the rising edge signal of the first rectangular pulse as the timing start signal and the rising edge signal of the second rectangular pulse as the timing end signal through the time-to-digital converter of the field programmable gate array.

[0082] It can be understood that, in the case that the peak value of the echo signal corresponding to the stray light is close to the waveform starting point of the echo signal reflected by the near distance target object, and the actual timing starting signal cannot be accurately obtained, directly taking the rising edge corresponding to the peak value of the echo signal corresponding to the stray light as the timing starting signal can find the START signal close to the actual timing starting signal as much as possible under the premise of avoiding a large amount of calculation work.

[0083] It can be understood that, by distinguishing the two discrete rectangular pulses through the signal separation unit, and taking the peak value of the echo signal corresponding to the stray light as the starting signal of the time-to-digital converter, the influence of circuit delay can be effectively reduced. Further, instead of simply taking the mixed rising edge of the overlapping rectangular pulses as the timing ending signal, taking the peak value of the echo signal corresponding to the distinguished near distance target as the timing ending signal of the time-to-digital converter can more accurately calculate the real echo time, thereby improving the accuracy of the near distance ranging.

[0084] S507: The rising edge signal of the second rectangular pulse is transmitted to the high-speed digital-to-analog converter connected to the field programmable gate array, and the high-speed digital-to-analog converter is used to sample the rising edge signal of the second rectangular pulse to obtain the signal intensity information of the second echo signal.

[0085] In this embodiment, the rising edge signal of the second rectangular pulse transmitted by the high-speed digital-to-analog converter timing ending signal separation unit is used to trigger ADC sampling, and the signal intensity information obtained by sampling is transmitted to the field programmable gate array.

[0086] If the echo signal received by the laser receiving unit is a discrete echo signal (the echo signal reflected by the target outside the blind area), the rising edge signal of the extracted echo signal is directly transmitted to the high-speed digital-to-analog converter to trigger ADC sampling. After completing a round of ADC sampling, the high-speed digital-to-analog converter waits for the next round of sampling trigger information to perform subsequent ADC sampling.

[0087] It can be understood that, in this embodiment, the rising edge signal of each echo signal is used to trigger ADC sampling, so that the high-speed digital-to-analog converter can accurately collect the peak value of the echo signal and measure the echo intensity using the peak value, thereby avoiding errors caused by the edge slope and further improving the measurement accuracy. Further, since there is only one sampling point at the peak value of each waveform, the sampling rate requirement of the high-speed digital-to-analog converter can be greatly reduced, thereby greatly reducing the calculation amount, releasing the processor resources, and then improving the measurement efficiency.

[0088] S508: The time difference between the timing starting signal and the timing ending signal is calculated by using the field programmable gate array, and the target distance is calculated based on the time difference.

[0089] For details, please refer to the description in S43, which will not be repeated here.

[0090] S509: Obtain the angle position information of the target object through the galvanometer / rotary mirror unit of the laser radar.

[0091] S510: Fuse the angle position information with the target distance using a field programmable gate array to obtain spatial three-dimensional data.

[0092] S511: Fuse the spatial three-dimensional data with the signal strength information to generate a laser point cloud map with reflection characteristic information.

[0093] It can be understood that, since the intensity information can reflect the reflectivity of the object, the laser point cloud map fused with the intensity information has the reflection characteristic.

[0094] Please refer to Figure 6 , Figure 6is a work flow diagram of an application scenario of the laser radar ranging method of the present application. In the present embodiment, first, a laser emitting unit is used to emit laser to detect a target object, and a laser receiving unit is used to receive two echo signals of the same laser pulse signal emitted by the laser emitting unit. The two echo signals have an overlapping region and different peak positions. The two echo signals are an echo signal generated by stray light and an echo signal reflected by a close-range target object (located in a blind area). Then, the echo signal processed by the laser receiving unit is used to charge and discharge a capacitor charging and discharging unit of an echo signal processing unit, and a current collecting unit is used to collect a capacitor current signal generated by the capacitor charging and discharging unit during the charging and discharging process, and convert the capacitor current signal into an analog voltage signal; the peak value of the echo signal corresponds to the zero-crossing point of the capacitor current signal. Further, a zero-crossing comparator is used to convert the analog voltage signal into a rectangular pulse; the zero-crossing point of the capacitor current signal corresponds to the rising edge of the rectangular pulse. Then, a signal separation unit of a field programmable gate array (FPGA) is used to determine the first-received echo signal and the corresponding rectangular pulse as a first echo signal and a first rectangular pulse, and determine the second-received echo signal and the corresponding rectangular pulse as a second echo signal and a second rectangular pulse. The first echo signal is the echo signal generated by stray light, and the second echo signal is the echo signal reflected by the close-range target object. Correspondingly, the first rectangular pulse is the rectangular pulse converted from the echo signal generated by stray light, and the second rectangular pulse is the rectangular pulse converted from the echo signal reflected by the close-range target object. The first echo signal and the first rectangular pulse, the second echo signal and the second rectangular pulse are transmitted to a time-to-digital converter (TDC) of the FPGA, so that the rising edge signal of the first rectangular pulse is used as a timing start signal, and the rising edge signal of the second rectangular pulse is used as a timing end signal. At the same time, the second echo signal and the second rectangular pulse are transmitted to a high-speed digital-to-analog converter (DAC) connected to the FPGA, and the rising edge signal of the second rectangular pulse is sampled by the high-speed DAC to obtain signal intensity information of the second echo signal. After completing one round of ADC sampling, the high-speed DAC waits for the next round of sampling trigger information to perform subsequent ADC sampling. The FPGA is used to calculate the time difference between the timing start signal and the timing end signal, and calculate the target distance based on the time difference. Then, the FPGA is used to fuse the angle position information and the target distance to obtain spatial three-dimensional data. Finally, the FPGA is used to fuse the spatial three-dimensional data and the signal intensity information to generate a laser point cloud map with reflection characteristic information.

[0095] Different from the prior art, the embodiment can convert different peaks of the two echo signals into different zero points in the capacitance current signal, thereby accurately distinguishing the vertexes of the different echo signals, eliminating the influence of the large blind area caused by stray light on the ranging, and expanding the ranging range. Further converting the capacitance current signal into two rectangular pulses can convert the zero points corresponding to the two peaks in the capacitance current signal into rising edges of different rectangular pulses. Further determining the two rising edges as a timing start signal and a timing end signal by the field programmable gate array 10 can more accurately obtain the echo time, thereby improving the accuracy of the close-range ranging. In addition, ADC sampling of the peak value of each extracted echo signal by the high-speed digital-to-analog converter can also improve the ranging accuracy of different reflectivity targets.

[0096] The above only describes the embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation, or direct or indirect application in other related technical fields, which is based on the content of the specification and drawings of the present application, is also included in the patent protection scope of the present application.

[0097] If the technical solutions of the present application involve personal information, the product using the technical solutions of the present application has been explicitly informed of the personal information processing rules before processing the personal information, and has obtained the personal independent consent. If the technical solutions of the present application involve sensitive personal information, the product using the technical solutions of the present application has obtained the personal independent consent before processing the sensitive personal information, and at the same time meets the requirement of "explicit consent". For example, at the personal information collection device such as camera, a clear and prominent mark is set to inform that the personal information collection range has been entered and the personal information will be collected. If the individual voluntarily enters the collection range, it is considered to agree to collect the personal information. Or, on the device for processing personal information, the individual is informed of the personal information processing rules through obvious marks / information, and obtains the individual's authorization through pop-up information or asks the individual to upload his / her personal information. The personal information processing rules can include personal information processor, personal information processing purpose, processing method, and personal information type, etc.

Claims

1. A lidar comprising a field programmable gate array, and a laser emission unit and a laser reception unit connected to the field programmable gate array, respectively, characterized in that, The echo signal processing unit is arranged between the laser receiving unit and the field programmable gate array; The laser receiving unit is configured to receive two echo signals of the same laser pulse signal emitted by the laser emitting unit and reflected; the two echo signals have an overlapping region and different peak positions; The echo signal processing unit is configured to obtain a capacitive current signal from the two echo signals and convert the capacitive current signal to obtain two rectangular pulses; the two rectangular pulses are discrete; The field programmable gate array is configured to determine a timing start signal and a timing end signal of the laser pulse signal based on the two rectangular pulses and obtain a target distance between a target object and the laser radar according to the timing start signal and the timing end signal; The field programmable gate array determines the rectangular pulse corresponding to the first-received echo signal as a first rectangular pulse and the rectangular pulse corresponding to the second-received echo signal as a second rectangular pulse; and the field programmable gate array is configured to use a rising edge signal of the first rectangular pulse as the timing start signal and a rising edge signal of the second rectangular pulse as the timing end signal.

2. The laser radar of claim 1, wherein The echo signal processing unit comprises a capacitive charging and discharging unit, a current sampling unit, and a zero-crossing comparator connected in sequence; The capacitive charging and discharging unit is connected to the laser receiving unit and is charged and discharged by the echo signal processed by the laser receiving unit; The current sampling unit is configured to collect a capacitive current signal generated by the capacitive charging and discharging unit during charging and discharging and convert the capacitive current signal into an analog voltage signal; the peak of the echo signal corresponds to a zero-crossing point of the capacitive current signal; The zero-crossing comparator is configured to convert the analog voltage signal into the rectangular pulse; the zero-crossing point of the capacitive current signal corresponds to a rising edge of the rectangular pulse.

3. The laser radar of claim 2, wherein The field programmable gate array comprises a signal separation unit and a time-to-digital converter connected to each other; The signal separation unit is configured to determine the first-received echo signal and the corresponding rectangular pulse as the first echo signal and the first rectangular pulse, and determine the second-received echo signal and the corresponding rectangular pulse as the second echo signal and the second rectangular pulse; The time-to-digital converter is configured to use a rising edge signal of the first rectangular pulse as the timing start signal and a rising edge signal of the second rectangular pulse as the timing end signal.

4. The laser radar of claim 3, wherein The laser radar further comprises a high-speed digital-to-analog converter connected to the field programmable gate array. The high-speed digital-to-analog converter is configured to receive the rising edge signal of the second rectangular pulse transmitted by the signal separation unit, and transmit signal intensity information obtained by sampling the rising edge signal of the second rectangular pulse to the field programmable gate array. 5.The lidar according to claim 4, wherein, The lidar further comprises a galvanometer / mirror unit connected to the field programmable gate array. The galvanometer / mirror unit is configured to determine the angular position information of the target object.

6. A laser radar ranging method characterized by comprising: The laser radar ranging method is implemented by a laser radar, which comprises a field programmable gate array, and a laser emitting unit and a laser receiving unit connected to the field programmable gate array, wherein a return signal processing unit is arranged between the laser receiving unit and the field programmable gate array; the laser radar ranging method comprises: The laser receiving unit receives two return signals of the same laser pulse signal emitted by the laser emitting unit; wherein the two return signals have an overlapping region and different peak positions; The return signal processing unit obtains a capacitive current signal from the two return signals, and converts the capacitive current signal to obtain two rectangular pulses; wherein the two rectangular pulses are discrete. The field programmable gate array determines a timing start signal and a timing end signal of the laser pulse signal based on the two rectangular pulses, and obtains the target distance between the target object and the laser radar according to the timing start signal and the timing end signal, including: the field programmable gate array determines the rectangular pulse corresponding to the first-received return signal as the first rectangular pulse; and determines the rectangular pulse corresponding to the second-received return signal as the second rectangular pulse; the field programmable gate array takes the rising edge signal of the first rectangular pulse as the timing start signal, and takes the rising edge signal of the second rectangular pulse as the timing end signal. 7.The laser radar ranging method according to claim 6, wherein, The step of obtaining a capacitive current signal from the two return signals by the return signal processing unit, and converting the capacitive current signal to obtain two rectangular pulses, comprises: The return signal processing unit charges and discharges the capacitor charging and discharging unit using the return signal processed by the laser receiving unit; The current acquisition unit of the return signal processing unit acquires the capacitive current signal generated by the capacitor charging and discharging unit during the charging and discharging process, and converts the capacitive current signal into an analog voltage signal; wherein the peak of the return signal corresponds to the zero-crossing point of the capacitive current signal; The zero-crossing comparator of the return signal processing unit converts the analog voltage signal into the rectangular pulse; wherein the zero-crossing point of the capacitive current signal corresponds to the rising edge of the rectangular pulse. 8.The laser radar ranging method according to claim 7, wherein, The step of determining a timing start signal and a timing end signal of the laser pulse signal based on two rectangular pulses by the FPGA, and obtaining a target distance between a target object and the laser radar according to the timing start signal and the timing end signal, comprises: determining the first received echo signal and the corresponding rectangular pulse as the first echo signal and the first rectangular pulse by a signal separation unit of the FPGA; and determining the second received echo signal and the corresponding rectangular pulse as the second echo signal and the second rectangular pulse; using a time-to-digital converter of the FPGA to determine the rising edge signal of the first rectangular pulse as the timing start signal, and the rising edge signal of the second rectangular pulse as the timing end signal; calculating the time difference between the timing start signal and the timing end signal by the FPGA, and calculating the target distance based on the time difference.

9. The laser radar ranging method of claim 8, wherein, after the step of using a time-to-digital converter of the FPGA to determine the rising edge signal of the first rectangular pulse as the timing start signal, and the rising edge signal of the second rectangular pulse as the timing end signal, comprises: transmitting the rising edge signal of the second rectangular pulse to a high-speed digital-to-analog converter connected to the FPGA, and sampling the rising edge signal of the second rectangular pulse by the high-speed digital-to-analog converter to obtain signal intensity information of the second echo signal.

10. The laser radar ranging method of claim 9, wherein, after the step of calculating the time difference between the timing start signal and the timing end signal by the FPGA, and calculating the target distance based on the time difference, comprises: obtaining angle position information of the target object by a galvanometer / rotary mirror unit of the laser radar; fusing the angle position information and the target distance by the FPGA to obtain spatial three-dimensional data; fusing the spatial three-dimensional data and the signal intensity information to generate a laser point cloud map with reflection characteristic information.

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