Frequency modulated continuous wave lidar system and lidar-based target detection method

Abstract

This application provides a frequency-modulated continuous wave lidar system and a lidar-based target detection method. The system includes a transmitting unit, a receiving unit, a temperature sensor, and a controller unit. The transmitting unit includes a laser for transmitting a detection light signal to a detection area. The receiving unit receives reflected light signals from a target within the detection area, beats the reflected light signals with a local oscillator signal to obtain a beat frequency signal, and sends the beat frequency signal to the controller unit. The temperature sensor monitors the real-time temperature of the transmitting unit. The controller unit acquires sensor data from the temperature sensor, obtains the real-time temperature of the transmitting unit based on the sensor data, performs temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit, and analyzes the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of specified parameters of the target.

Description

Technical Field

[0001] This application relates to the field of radar technology, and more specifically, to a frequency modulated continuous wave lidar system and a lidar-based target detection method. Background Technology

[0002] In related technologies, frequency-modulated continuous wave lidar can be used for ranging. The ranging principle is as follows: a tunable laser emits a linearly modulated laser beam, which is reflected by the target and the reflected light beats with the local oscillator light on the photodetector of the receiving system. This converts the distance, speed and other information of the target into frequency, and the information of the target is obtained by solving the frequency information.

[0003] The ranging accuracy of frequency-modulated continuous wave (FM-CW) lidar depends on the modulation bandwidth of the laser, which is the difference between the maximum and minimum modulation frequencies of the laser. When an FM-CW lidar is operating, the receiving system calculates the distance based on the preset modulation bandwidth when it receives the beat frequency signal. However, because the modulation bandwidth can be affected by environmental factors, it can lead to issues with low radar detection accuracy. Summary of the Invention

[0004] This application provides a frequency modulated continuous wave lidar system and a lidar-based target detection method to at least solve the technical problem of low radar detection accuracy in related technologies.

[0005] According to one aspect of the embodiments of this application, a frequency-modulated continuous wave lidar system is provided, comprising: a transmitting unit, a receiving unit, a temperature sensor, and a controller unit, wherein the transmitting unit includes a laser for transmitting a detection light signal to a detection area; the receiving unit is configured to receive a reflected light signal reflected back from a target within the detection area by the detection light signal; beat the reflected light signal with a local oscillator signal to obtain a beat frequency signal; and send the beat frequency signal to the controller unit; the temperature sensor is configured to monitor the real-time temperature of the transmitting unit; the controller unit is configured to acquire sensor data from the temperature sensor, acquire the real-time temperature of the transmitting unit based on the sensor data; perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit; and analyze the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of specified parameters of the target.

[0006] According to another aspect of the embodiments of this application, a target detection method based on lidar is also provided. The lidar includes: a transmitting unit, a receiving unit, and a temperature sensor. The method includes: transmitting a detection light signal to a detection area through a laser of the transmitting unit; receiving a reflected light signal reflected back from a target within the detection area by the detection light signal, and performing a beat frequency comparison between the reflected light signal and a local oscillator signal to obtain a beat frequency signal; acquiring the real-time temperature of the transmitting unit through the temperature sensor, and performing temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit; and parsing the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of specified parameters of the target.

[0007] This application employs a bandwidth adjustment method based on the temperature of the transmitting unit. A laser in the transmitting unit emits a detection light signal into the detection area. The reflected light signal from the target within the detection area is received, and the reflected light signal is beat-frequencyd with the local oscillator signal to obtain a beat-frequency signal. The real-time temperature of the transmitting unit is acquired using a temperature sensor, and the modulation bandwidth of the laser is temperature-compensated based on this temperature. The beat-frequency signal is then analyzed according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target. Because the temperature of the transmitting unit is monitored and the modulation bandwidth is compensated based on this temperature, radar ranging accuracy can be guaranteed. Therefore, this solves the technical problem of low radar detection accuracy in related technologies, achieving the technical effect of improving ranging accuracy and precision. Attached Figure Description

[0008] Figure 1 This is a structural block diagram of an optional frequency-modulated continuous wave lidar system according to an embodiment of this application;

[0009] Figure 2 This is a structural block diagram of an optional transmitting unit according to an embodiment of this application;

[0010] Figure 3 This is a structural block diagram of an optional controller unit according to an embodiment of this application;

[0011] Figure 4 This is a structural block diagram of another optional frequency-modulated continuous wave lidar system according to an embodiment of this application;

[0012] Figure 5 This is a schematic flowchart of an optional target detection method based on lidar according to an embodiment of this application;

[0013] Figure 6 This is a flowchart illustrating another optional target detection method based on lidar according to an embodiment of this application. Detailed Implementation

[0014] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0015] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0016] According to one aspect of the embodiments of this application, a frequency-modulated continuous wave lidar system is provided. Optionally, Figure 1 This is a schematic diagram of an optional frequency-modulated continuous wave lidar system according to an embodiment of this application, as shown below. Figure 1 As shown, the frequency-modulated continuous wave lidar system may include a transmitting unit 101, a receiving unit 102, a temperature sensor 103, and a controller unit 104. The transmitting unit 101 includes a laser; wherein,

[0017] The transmitting unit 101 is used to transmit a detection light signal to the detection area via a laser;

[0018] The receiving unit 102 is used to receive the reflected light signal reflected back by the target under test in the detection area from the detection light signal; beat the reflected light signal and the local oscillator light signal to obtain the beat frequency signal; and send the beat frequency signal to the controller unit 104.

[0019] Temperature sensor 103 is used to monitor the real-time temperature of transmitting unit 101;

[0020] The controller unit 104 is used to acquire sensor data from the temperature sensor 103, acquire the real-time temperature of the transmitting unit 101 based on the sensor data, perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit, and analyze the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target under test.

[0021] Here, the transmitting unit can emit linearly modulated laser light and send the parameters of the emitted laser light to the controller unit. The receiving unit can receive the laser light emitted by the transmitting unit and reflected by the target, and send the received laser light data to the controller unit. The controller unit, combining the parameters from the transmitting unit and the data from the receiving unit, can determine the distance, velocity, and other information of the target. The parameters of the emitted laser light may include, but are not limited to, at least one of the following: laser power, laser wavelength, frequency modulation slope, frequency of the emitted signal, and laser emitter temperature. The data of the received laser light may include, but is not limited to, at least one of the following: frequency of the echo signal, phase of the echo signal, Doppler frequency difference, etc. The controller unit calculates the distance, velocity, and other information of the target by analyzing the frequency of the emitted signal and the frequency of the echo signal (first performing frequency mixing, then performing frequency analysis on the mixed signal).

[0022] The frequency-modulated continuous wave (FM-CW) lidar system in this embodiment can be applied to the field of radar technology, specifically to scenarios where FM-CW radar is used for ranging or speed measurement. FM-CW radar offers advantages such as high measurement accuracy, long measurement range, and high range resolution, making it a commonly used technology in vehicle-mounted lidar. Its core feature lies in transmitting a continuous wave whose frequency is modulated by a specific signal. By comparing the difference between the frequency of the echo signal (i.e., the reflected light signal) and the frequency of the transmitted signal (i.e., the local oscillator signal of the probe light signal) at any given time, the target's distance information is obtained; the distance is proportional to the frequency difference. Simultaneously, the radial velocity of the target can also be measured. The method for obtaining the difference between the echo signal frequency and the transmitted signal frequency is called beat frequency. While the laser emits the probe light signal, a beam can be retained locally as the local oscillator light (the frequency of the local oscillator light signal is the same as the emitted probe light signal). Beat frequency is the process of conjugate mixing and elimination of the local oscillator light signal and the reflected light signal to obtain a low-frequency beat frequency signal. Beat frequency signal is a low-frequency amplitude signal generated by the frequency difference caused by the time delay between transmission and reception (i.e., the time delay between the signal being transmitted to the object under test, then reflected, and finally received) after the received and transmitted signals are combined. By measuring the frequency of the beat frequency signal, the distance from the target to the radar can be accurately calculated. At the same time, the beat frequency signal also carries the target's speed information, and the target's speed can be obtained through further processing.

[0023] Ranging accuracy is a crucial performance indicator for frequency-modulated continuous wave (FM-CVW) radar, and this accuracy depends on the laser modulation bandwidth. Modulation bandwidth refers to the range of frequency variation of the radar's transmitted signal; specifically, it's the difference between the maximum and minimum modulation frequencies of the laser. A wider modulation bandwidth allows the radar to measure a greater range of distances, and the broadband signal carries more information, enabling the radar to more accurately identify target distances when receiving echoes, thus improving range resolution.

[0024] In related technologies, when a frequency-modulated continuous wave radar is operating and the receiving system receives a beat frequency signal for distance calculation, the distance and velocity values ​​can be calculated according to a preset modulation bandwidth. However, when changes in ambient temperature cause the laser modulation bandwidth to deviate from the preset value, the calculated distance and velocity are not the true values. That is, temperature changes can lead to measurement errors in distance and velocity. The effects of temperature changes are mainly twofold: firstly, temperature changes cause changes in the modulation circuit and DC drive circuit, which in turn change the laser modulation bandwidth; secondly, temperature changes cause changes in the laser modulation bandwidth, which in turn causes the laser modulation bandwidth to deviate from the preset value.

[0025] To at least partially solve the above-mentioned technical problems, this embodiment provides a frequency-modulated continuous wave lidar system. By measuring the ambient temperature and adjusting it in real time, the frequency-modulated continuous wave lidar is temperature compensated, which can eliminate the influence of temperature changes and thus ensure the accuracy of radar ranging.

[0026] Here, the impact of temperature changes is mainly reflected in the laser. Temperature compensation involves adjusting the preset modulation bandwidth according to the temperature change of the transmitting unit. This temperature compensation can be performed by the controller unit 104. The controller unit 104 can acquire sensor data from the temperature sensor, obtain the real-time temperature of the transmitting unit based on the sensor data, and perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit. Then, it analyzes the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain the parameter information of the specified parameters of the target under test. The specified parameters of the target under test may include, but are not limited to, at least one of the following: the distance between the target under test and the frequency-modulated continuous wave lidar, and the velocity of the target under test relative to the frequency-modulated continuous wave lidar.

[0027] To perform temperature compensation, the impact of temperature changes on modulation bandwidth can be pre-determined. For example, the changes in modulation bandwidth under various temperature conditions can be statistically analyzed, and corresponding temperature-modulation bandwidth function curves can be plotted. The formula relating temperature change to modulation bandwidth change can then be calculated, and the calculated bandwidth can be directly substituted into this formula during temperature compensation. Alternatively, the changes in modulation bandwidth under various temperature conditions can be statistically analyzed, and the statistical data recorded as a temperature-modulation bandwidth table. During temperature compensation, the temperature can be substituted into this table to directly find the corresponding modulation bandwidth and obtain the temperature-compensated modulation bandwidth. Furthermore, temperature compensation can be performed in other ways, which are not limited in this embodiment.

[0028] The embodiments provided in this application acquire sensor data from a temperature sensor, obtain the real-time temperature of the transmitting unit based on the sensor data, perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit, and analyze the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target under test. This solves the problem of low radar detection accuracy in related technologies and improves ranging accuracy and precision.

[0029] In one exemplary embodiment, for temperature compensation, the correspondence between the temperature of the transmitting unit and the modulation bandwidth of the laser can be configured by establishing a preset correspondence table. Here, the preset correspondence table can be pre-stored in the controller unit, and it can be used to indicate the correspondence between the temperature of the transmitting unit and the modulation bandwidth of the laser.

[0030] Correspondingly, the controller unit is also used to look up the modulation bandwidth corresponding to the real-time temperature of the transmitting unit in the preset correspondence table, and obtain the temperature-compensated modulation bandwidth.

[0031] When the controller unit obtains the beat frequency signal from the receiving unit, it can obtain the real-time temperature of the transmitting unit and look up the corresponding modulation bandwidth in the preset correspondence table according to the real-time temperature of the transmitting unit to obtain the temperature-compensated modulation bandwidth. Then, it analyzes the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain information such as the distance and speed of the target under test.

[0032] By pre-storing a table showing the relationship between the temperature of the transmitting unit and the modulation bandwidth of the laser, this embodiment improves the convenience and timeliness of temperature compensation for the modulation bandwidth, avoiding unreasonable temperature compensation due to excessive delay.

[0033] In an exemplary embodiment, the temperature change of the transmitting unit affects both the modulation circuit and the DC drive circuit, thus altering the laser modulation bandwidth. To confirm the correspondence between the transmitting unit temperature and the modulation bandwidth, a temperature-current table and a current-bandwidth table can be established. These tables together constitute a preset correspondence table, specifically, the temperature-current table and the current-bandwidth table. The temperature-current table represents the correspondence between the temperature of the laser's modulation circuit and its output current, while the current-bandwidth table represents the correspondence between the laser's injection current and its modulation bandwidth at different temperatures or within different temperature ranges. Here, the modulation circuit can output current to the laser; that is, the output current of the modulation circuit is the laser's injection current.

[0034] It should be noted that the independent variable of the temperature-ammeter is temperature, and the dependent variable is current. The form is that one temperature corresponds to one current. The current mentioned above refers to the current output by the modulation circuit to the laser, that is, the output current of the modulation circuit, which is also the injection current of the laser. The current-bandwidth table, on the other hand, is a table in which the independent variable is current and the dependent variable is modulation bandwidth within a certain temperature or a certain temperature range. The form is that one current corresponds to one modulation bandwidth, and there can be multiple current-bandwidth tables. There is a corresponding current-bandwidth table for each temperature or temperature range.

[0035] Correspondingly, the controller unit is also used to look up a temperature-current table based on the real-time temperature of the transmitting unit to obtain a target injection current that matches the real-time temperature of the transmitting unit; and to look up a current-bandwidth table based on the real-time temperature of the transmitting unit and the target injection current, and to determine the modulation bandwidth that matches the real-time temperature of the transmitting unit and the target injection current as the temperature-compensated modulation bandwidth.

[0036] When the controller unit obtains the beat frequency signal from the receiver unit, it can obtain the real-time temperature of the transmitter unit and find the matching target injection current in the temperature-current table based on the temperature. Then, it finds the corresponding current-bandwidth table based on the real-time temperature of the transmitter unit and finds the matching modulation bandwidth in the corresponding current-bandwidth table based on the target injection current to obtain the temperature-compensated modulation bandwidth.

[0037] In this embodiment, by configuring a temperature-current meter and a current-bandwidth meter, and sequentially looking up the two relational tables based on the real-time temperature of the transmitting unit to determine the modulation bandwidth after temperature compensation, the measurement accuracy of the frequency-modulated continuous wave lidar can be improved.

[0038] In an exemplary embodiment, the transmitting unit further includes: a modulation signal circuit, a beam splitter, and a DC drive circuit, wherein the laser is used to emit a laser beam; the modulation signal circuit is used to generate a modulation signal and use the generated modulation signal to modulate the laser beam; the beam splitter is used to split the modulated laser beam into a probe light signal and a local oscillator light signal, and to emit the probe light signal to the detection area; and the DC drive circuit is used to drive the laser to emit light and drive the modulation signal circuit to perform signal modulation.

[0039] In order to emit modulated laser light, the emitting unit includes a laser, a modulation signal circuit, a beam splitter, and a DC drive circuit, in addition to a temperature sensor. The structure of the emitting unit is as follows: Figure 2 As shown, it includes: a temperature sensor for monitoring the real-time temperature of the transmitting unit, which is then acquired by the controller unit; a laser for emitting a laser beam; a modulation signal circuit for generating a modulation signal and using the generated modulation signal to modulate the laser beam emitted by the laser; a beam splitter for splitting the modulated laser beam into a probe light signal and a local oscillator light signal, and emitting the probe light signal to the detection area; and a DC drive circuit for providing energy to the transmitting unit to drive the laser to emit light and to drive the modulation signal circuit to modulate the signal.

[0040] Here, the modulation signal circuit modulates the laser beam signal linearly. The laser's optical frequency is controlled by a linear modulation signal, causing the laser's output frequency to change linearly with time. The beam splitter divides the modulated laser beam into a probe light signal and a local oscillator light signal with the same frequency. The probe light signal can be emitted towards the detection area and reflected as a reflected light signal on the surface of the target. This reflected light signal is received by the receiving unit and beats with the local oscillator light signal to obtain a beat frequency signal.

[0041] During the laser emission process of the transmitting unit, a DC drive current first powers the laser and modulation signal circuit. The laser then emits a laser beam, which passes through the modulation signal circuit. The modulation signal current uses a generated modulation signal to modulate the emitted laser beam. A beam splitter then separates the modulated laser beam into a probe signal and a local oscillator signal. The local oscillator signal is retained for beat frequency control, while the probe signal is emitted towards the detection area. Simultaneously, a temperature sensor continuously monitors the real-time temperature of the transmitting unit. At this point, the transmitting unit has completed the emission of the modulated laser beam.

[0042] In this embodiment, by setting up a laser, a modulation signal circuit, a beam splitter, and a DC drive circuit in the transmitting unit, a modulated laser beam can be emitted for ranging by frequency modulated continuous wave radar.

[0043] In one exemplary embodiment, the controller unit includes: a temperature acquisition module for acquiring sensor data from a temperature sensor; parsing the real-time temperature of the transmitting unit from the sensor data; a data processing module for acquiring the beat frequency signal of the receiving unit; performing temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit parsed by the temperature acquisition module; and parsing the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of specified parameters of the target under test.

[0044] Here, a temperature sensor can be installed on the circuit board of the transmitting unit to measure the temperature of the circuit board and use that temperature as the temperature of various components on the circuit board. That is, the real-time temperature of the transmitting unit circuit board is regarded as the real-time temperature of the transmitting unit.

[0045] Correspondingly, the controller unit is also used to calculate the frequency information of the beat frequency signal according to the modulation bandwidth after temperature compensation, and determine at least one of the following information based on the calculated frequency information: the distance value of the target under test, and the velocity value of the target under test.

[0046] To analyze the beat frequency signal and eliminate temperature interference to obtain the specified parameters of the target under test, the controller unit may include a temperature acquisition module and a data processing module. The structure of the controller unit is as follows: Figure 3 As shown, it includes: a temperature acquisition module, which can be used to acquire sensor data from a temperature sensor and parse the real-time temperature of the transmitting unit from the sensor data; and a data processing module, which can be used to acquire data from the receiving unit and perform distance and velocity calculations. Specifically, it includes acquiring the beat frequency signal of the receiving unit, then performing temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit parsed by the temperature acquisition module, and parsing the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target under test. The parameter information of the specified parameters of the target under test includes, but is not limited to, at least one of the following: the distance between the target under test and the frequency-modulated continuous wave lidar (distance value of the target under test), and the velocity of the target under test relative to the frequency-modulated continuous wave lidar (velocity value of the target under test).

[0047] In this embodiment, after the controller unit acquires the beat frequency signal of the receiver unit, the temperature acquisition module can acquire the temperature sensor data of the transmitter unit to obtain the real-time temperature of the transmitter unit. Then, the data calculation module looks up the temperature-current table to obtain the target injection current and looks up the current-bandwidth table to obtain the temperature-compensated modulation bandwidth. Finally, the temperature-compensated modulation bandwidth is updated to the data calculation module to calculate the current ranging distance or speed value.

[0048] In this embodiment, by setting a temperature acquisition module and a data processing module in the controller unit, temperature compensation can be performed on the modulation bandwidth and the specified parameters of the target under test can be obtained, thereby improving the detection accuracy.

[0049] The frequency-modulated continuous wave lidar system in the embodiments of this application will be explained and described below with reference to optional examples. For example... Figure 4 As shown, the frequency-modulated continuous wave lidar system in this optional example may include:

[0050] The transmitting unit includes a laser for transmitting a detection light signal to the detection area. In addition, the transmitting unit also includes a temperature sensor, a modulation signal circuit, a DC drive circuit, a beam splitter, and the laser.

[0051] The receiving unit is used to receive the reflected light signal from the target under test in the detection area; beat the reflected light signal with the local oscillator signal to obtain the beat frequency signal; and send the beat frequency signal to the controller unit.

[0052] Temperature sensor used to monitor the real-time temperature of the transmitting unit.

[0053] The controller unit is used to acquire sensor data from the temperature sensor, obtain the real-time temperature of the transmitting unit based on the sensor data, perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit, and analyze the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain the parameter information of the specified parameters of the target under test.

[0054] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to these: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0055] According to another aspect of the embodiments of this application, a target detection method based on lidar is provided. Optionally, in this embodiment, the above-mentioned target detection method based on lidar can be applied to any frequency modulated continuous wave lidar system in the foregoing embodiments, as has been described before, and will not be repeated here.

[0056] In this embodiment, the aforementioned lidar includes a transmitting unit, a receiving unit, and a temperature sensor, and may further include a controller unit. Optionally, the lidar-based target detection method in this embodiment can be executed by the controller unit or an external device (e.g., a vehicle-mounted unit). Taking execution by the controller unit as an example... Figure 5 This is a flowchart illustrating an optional target detection method based on lidar according to an embodiment of this application, as shown below. Figure 5 As shown, the process of the above method may include the following steps:

[0057] S502 emits a detection light signal into the detection area through the laser of the transmitting unit;

[0058] S504 receives the reflected light signal from the target under test reflected back through the detection area, and beats the reflected light signal with the local oscillator signal to obtain the beat frequency signal;

[0059] S506 obtains the real-time temperature of the transmitting unit through a temperature sensor and performs temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit.

[0060] S508 analyzes the beat frequency signal according to the modulation bandwidth after temperature compensation to obtain the parameter information of the specified parameters of the target under test.

[0061] The target detection method based on lidar in this embodiment can be applied to the field of radar technology, specifically to scenarios where frequency-modulated continuous wave radar is used for ranging or velocity measurement. The methods for transmitting the detection light signal, receiving the beat frequency signal, performing temperature compensation on the modulation bandwidth, and parsing the parameter information of the target to be measured are the same as or similar to those in the previous embodiments, and have already been described, so they will not be repeated here.

[0062] The embodiments provided in this application involve transmitting a detection light signal to a detection area via a laser in a transmitting unit; receiving a reflected light signal from the target within the detection area; and performing a beat frequency comparison between the reflected light signal and the local oscillator signal to obtain a beat frequency signal. A temperature sensor is used to obtain the real-time temperature of the transmitting unit, and temperature compensation is applied to the modulation bandwidth of the laser based on this real-time temperature. The beat frequency signal is then analyzed according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target. This solves the problem in related technologies where the frequency modulation bandwidth may be affected by the objective environment, leading to low radar detection accuracy, and improves ranging accuracy and precision.

[0063] In one exemplary embodiment, for temperature compensation, a preset correspondence table is pre-stored. This table indicates the correspondence between the temperature of the transmitting unit and the modulation bandwidth of the laser. Correspondingly, temperature compensation of the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit includes: looking up the modulation bandwidth corresponding to the real-time temperature of the transmitting unit in the preset correspondence table to obtain the temperature-compensated modulation bandwidth.

[0064] The configuration method of the preset correspondence table and the method of finding the modulation bandwidth corresponding to the real-time temperature of the transmitting unit in the preset correspondence table are similar to those in the previous embodiments, and will not be repeated here.

[0065] By pre-storing a table showing the relationship between the temperature of the transmitting unit and the modulation bandwidth of the laser, this embodiment improves the convenience and timeliness of temperature compensation for the modulation bandwidth, avoiding unreasonable temperature compensation due to excessive delay.

[0066] In an exemplary embodiment, the preset correspondence table includes a temperature-current table and a current-bandwidth table. The temperature-current table is a correspondence table between the temperature of the modulation circuit of the laser and the output current of the modulation circuit. The current-bandwidth table is a correspondence table between the injection current of the laser and the modulation bandwidth of the laser at different temperatures or different temperature ranges. The output current of the modulation circuit is the injection current of the laser.

[0067] Correspondingly, the modulation bandwidth corresponding to the real-time temperature of the transmitting unit is searched in the preset correspondence table to obtain the temperature-compensated modulation bandwidth. This includes searching the temperature-current table based on the real-time temperature of the transmitting unit to obtain the target injection current that matches the real-time temperature of the transmitting unit; and searching the current-bandwidth table based on the real-time temperature of the transmitting unit and the target injection current to determine the modulation bandwidth that matches the real-time temperature of the transmitting unit and the target injection current as the temperature-compensated modulation bandwidth.

[0068] The temperature change of the transmitting unit affects the modulation circuit and DC drive circuit, thus changing the laser modulation bandwidth. Furthermore, it also affects the modulation bandwidth itself. To confirm the correspondence between the transmitting unit temperature and the modulation bandwidth, temperature-current and current-bandwidth tables can be established. The method for using these tables for temperature compensation is the same as or similar to that described in the previous embodiments and will not be repeated here.

[0069] In this embodiment, by configuring a temperature-current meter and a current-bandwidth meter, and sequentially looking up the two relational tables based on the real-time temperature of the transmitting unit to determine the modulation bandwidth after temperature compensation, the measurement accuracy of the frequency-modulated continuous wave lidar can be improved.

[0070] In an exemplary embodiment, the method further includes: testing the correspondence between the injection current and modulation bandwidth of the laser at different temperatures to obtain a first test result; fitting the correspondence between the injection current and modulation bandwidth of the laser at different temperatures based on the first test result to obtain a current-bandwidth table; calculating the theoretical correspondence between the temperature drift of the modulation circuit and the output current of the modulation circuit, wherein the output current of the modulation circuit is the injection current of the laser; testing the injection current of the laser at different temperatures to obtain a second test result; correcting the theoretical correspondence based on the second test result to obtain a corrected theoretical correspondence; and fitting the correspondence between the temperature of the transmitting unit and the injection current of the laser based on the corrected theoretical correspondence and the second test result to obtain a temperature-current table.

[0071] To obtain current-bandwidth tables and temperature-current tables, the correspondence between the laser's injection current and modulation bandwidth at different temperatures can be tested. Based on the test results, the correspondence between the laser's injection current and modulation bandwidth at different temperatures can be fitted to obtain several current-bandwidth tables for different temperatures. The theoretical correspondence between the temperature drift of the laser's modulation circuit and the output current of the modulation circuit can be calculated. The output current of the modulation circuit at different temperatures can be tested, and the theoretical correspondence can be corrected based on the test results to obtain a corrected theoretical correspondence. Then, based on the corrected theoretical correspondence and the test results, the correspondence between temperature and the output current of the modulation circuit can be fitted to obtain a temperature-current table. The fitting method for the correspondence between the laser's injection current and modulation bandwidth, and the fitting method for the correspondence between temperature and the output current of the modulation circuit, can be linear fitting.

[0072] Here, temperature drift refers to the change in equipment performance parameters caused by changes in ambient temperature. In this embodiment, the temperature drift of the modulation circuit is mainly the temperature drift of the components inside the modulation circuit, which will affect the output current of the modulation circuit.

[0073] In this embodiment, the correspondence between the injection current and modulation bandwidth of the laser at different temperatures can be tested first. Based on the test results, a table of correspondence between the injection current and modulation bandwidth is fitted, generating several current-bandwidth tables corresponding to each temperature or temperature range. Then, the temperature drift and output current of the laser modulation circuit are calculated, and the actual output current at different temperatures is measured for correction. Subsequently, a table of correspondence between temperature and output current is fitted based on the calculation and test results, generating a temperature-current table. The current-bandwidth table and the temperature-current table are downloaded to and stored in the controller unit, allowing the controller unit to store a preset correspondence table for temperature compensation.

[0074] In this embodiment, a current-bandwidth meter and a temperature-current meter are obtained through testing and calculation. These can be used to perform temperature compensation on the modulation bandwidth, thereby improving the measurement accuracy of frequency-modulated continuous wave lidar.

[0075] The target detection method of the lidar in this application embodiment will be explained below with reference to optional examples. In this optional example, the lidar is a frequency-modulated continuous wave lidar.

[0076] Figure 6 This is a flowchart illustrating the target detection method of the lidar in this optional example, such as... Figure 6 As shown, the target detection method of this lidar may include the following steps:

[0077] Step S602, obtaining the current-bandwidth correspondence table and the temperature-current correspondence table, including: testing the correspondence between laser injection current and modulation width at different temperatures, fitting the test results to obtain the correspondence table between injection current and modulation width; calculating the theoretical relationship between laser modulation current temperature drift and output current, measuring the laser modulation current as output current at different temperatures, correcting the theoretical value, fitting the test results to obtain the correspondence table between injection current and modulation width;

[0078] Step S604: Store the current-wideband correspondence table and the temperature-current correspondence table in the radar controller unit. Place a temperature sensor inside the radar to obtain the current device temperature in real time.

[0079] Step S606: Look up the temperature-current correspondence table to obtain the current actual injection current, and look up the current-bandwidth correspondence table to obtain the current actual modulation bandwidth.

[0080] Step S608: Update the current actual modulation bandwidth to the ranging solution module and calculate the current ranging distance or speed.

[0081] This optional example demonstrates how temperature compensation can be applied to the modulation bandwidth by measuring ambient temperature and adjusting it in real time to ensure radar ranging accuracy.

[0082] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0083] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM (Read-Only Memory) / RAM (Random Access Memory), magnetic disk, optical disk), and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods of the various embodiments of this application.

[0084] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented here, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0085] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A frequency-modulated continuous wave lidar system, characterized in that, include: The unit comprises a transmitting unit, a receiving unit, a temperature sensor, and a controller unit. The transmitting unit includes a laser for transmitting a detection light signal to the detection area via the laser; The receiving unit is configured to receive the reflected light signal from the target under test reflected back by the detection light signal within the detection area; beat the reflected light signal with the local oscillator light signal to obtain a beat frequency signal; and send the beat frequency signal to the controller unit. The temperature sensor is used to monitor the real-time temperature of the transmitting unit; The controller unit is configured to acquire sensor data from the temperature sensor, acquire the real-time temperature of the transmitting unit based on the sensor data, perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit, and analyze the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target under test.

2. The system according to claim 1, characterized in that, The controller unit stores a preset correspondence table, which is used to indicate the correspondence between the temperature of the transmitting unit and the modulation bandwidth of the laser. The controller unit is also used to look up the modulation bandwidth corresponding to the real-time temperature of the transmitting unit in the preset correspondence table, and obtain the temperature-compensated modulation bandwidth.

3. The system according to claim 2, characterized in that, The preset correspondence table includes a temperature-current table and a current-bandwidth table. The temperature-current table is a correspondence table between the temperature of the modulation circuit of the laser and the output current of the modulation circuit. The current-bandwidth table is a correspondence table between the injection current of the laser and the modulation bandwidth of the laser at different temperatures or different temperature ranges. The output current of the modulation circuit is the injection current of the laser. The controller unit is further configured to look up the temperature-current table based on the real-time temperature of the transmitting unit to obtain a target injection current that matches the real-time temperature of the transmitting unit; and to look up the current-bandwidth table based on the real-time temperature of the transmitting unit and the target injection current, and to determine the modulation bandwidth that matches the real-time temperature of the transmitting unit and the target injection current as the temperature-compensated modulation bandwidth.

4. The system according to claim 1, characterized in that, The transmitting unit further includes: a modulation signal circuit, a beam splitter, and a DC drive circuit, wherein... The laser is used to emit a laser beam; The modulation signal circuit is used to generate a modulation signal and to modulate the laser beam using the generated modulation signal. The beam splitter is used to split the modulated laser beam into the probe light signal and the local oscillator light signal, and to emit the probe light signal into the detection area; The DC drive circuit is used to drive the laser to emit light and to drive the modulation signal circuit to perform signal modulation.

5. The system according to claim 1, characterized in that, The controller unit includes: A temperature acquisition module is used to acquire sensor data from the temperature sensor and parse the real-time temperature of the transmitting unit from the sensor data. The data processing module is used to acquire the beat frequency signal of the receiving unit; perform temperature compensation on the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit parsed by the temperature acquisition module; and analyze the beat frequency signal according to the temperature-compensated modulation bandwidth to obtain parameter information of the specified parameters of the target under test.

6. The system according to any one of claims 1 to 5, characterized in that, The controller unit is further configured to calculate the frequency information of the beat frequency signal according to the modulation bandwidth after temperature compensation, and determine at least one of the following information based on the calculated frequency information: the distance value of the target to be measured, and the speed value of the target to be measured.

7. A target detection method based on lidar, characterized in that, The lidar includes a transmitting unit, a receiving unit, and a temperature sensor; the method includes: The laser of the transmitting unit emits a detection light signal toward the detection area; The detector light signal is received by reflecting the light signal back from the target under test within the detection area, and the reflected light signal is beat-frequencyed with the local oscillator light signal to obtain a beat-frequency signal. The real-time temperature of the transmitting unit is obtained through the temperature sensor, and the modulation bandwidth of the laser is compensated for based on the real-time temperature of the transmitting unit. The beat frequency signal is analyzed according to the temperature-compensated modulation bandwidth to obtain the parameter information of the specified parameters of the target under test.

8. The method according to claim 7, characterized in that, The temperature compensation of the modulation bandwidth of the laser based on the real-time temperature of the transmitting unit includes: The modulation bandwidth corresponding to the real-time temperature of the transmitting unit is found in the preset correspondence table to obtain the temperature-compensated modulation bandwidth. The preset correspondence table is used to indicate the correspondence between the temperature of the transmitting unit and the modulation bandwidth of the laser.

9. The method according to claim 8, characterized in that, The preset correspondence table includes a temperature-current table and a current-bandwidth table. The temperature-current table is a correspondence table between the temperature of the modulation circuit of the laser and the output current of the modulation circuit. The current-bandwidth table is a correspondence table between the injection current of the laser and the modulation bandwidth of the laser at different temperatures or different temperature ranges. The output current of the modulation circuit is the injection current of the laser. The step of searching the preset correspondence table for the modulation bandwidth corresponding to the real-time temperature of the transmitting unit to obtain the temperature-compensated modulation bandwidth includes: Based on the real-time temperature of the transmitting unit, the temperature-current meter is looked up to obtain the target injection current that matches the real-time temperature of the transmitting unit. Based on the real-time temperature of the transmitting unit and the target injection current, the current-bandwidth table is searched, and the modulation bandwidth that matches the real-time temperature of the transmitting unit and the target injection current is determined as the temperature-compensated modulation bandwidth.

10. The method according to claim 9, characterized in that, The method further includes: The relationship between the injection current and the modulation bandwidth of the laser at different temperatures was tested to obtain the first test result; Based on the first test results, the relationship between the injection current and the modulation bandwidth of the laser at different temperatures is fitted to obtain the current-bandwidth table; Calculate the theoretical correspondence between the temperature drift of the modulation circuit of the laser and the output current of the modulation circuit, wherein the output current of the modulation circuit is the injection current of the laser; The output current of the modulation circuit at different temperatures was tested to obtain a second test result; Based on the second test results, the theoretical correspondence is corrected to obtain the corrected theoretical correspondence; Based on the corrected theoretical correspondence and the second test result, the correspondence between temperature and the output current of the modulation circuit is fitted to obtain the temperature-current meter.

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