CN115616593B - Laser radar, calibration method and method for improving laser radar measurement precision - Google Patents
Laser radar, calibration method and method for improving laser radar measurement precision Download PDFInfo
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- CN115616593B CN115616593B CN202211462938.6A CN202211462938A CN115616593B CN 115616593 B CN115616593 B CN 115616593B CN 202211462938 A CN202211462938 A CN 202211462938A CN 115616593 B CN115616593 B CN 115616593B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/497—Means for monitoring or calibrating
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
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Abstract
The invention relates to the technical field of laser radars, in particular to a laser radar, a calibration method and a method for improving the measurement precision of the laser radar, wherein the laser radar comprises a transmitting module, an optical module, a receiving module, a circuit module, a controller and a plurality of temperature regulating modules, the temperature regulating modules are arranged on the transmitting module, the optical module, the receiving module and the circuit module, and the controller acquires and controls the temperature of each module through all the temperature regulating modules; the temperature of each module is adjusted to change the distance difference value, when the distance difference value is reduced to be within a preset range, a target temperature data set is obtained, the temperature difference value data set is determined through the target temperature data set and the initial temperature data set, and the temperature difference value data set is used as a calibration data set of the laser radar, so that the laser radar is calibrated through the calibration data set, the measurement error of the laser radar is reduced, and the measurement accuracy of the laser radar is improved.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a laser radar, a calibration method and a method for improving the measurement accuracy of the laser radar.
Background
The laser radar is core detection equipment for reconstructing the space environment, and is widely applied to the fields of geographic information mapping, industrial automation, automatic driving and the like. With the development of application scenes such as "smart city", "live-action three-dimensional china", millimeter-level high-repetition frequency laser radar is becoming a necessary detection device. From the detection principle distinction, lidar is mainly divided into two technical directions of phase type and pulse type. The phase type distance measurement precision is more accurate, but the test distance and the repetition frequency have certain indexes; the pulse type test distance and the repetition frequency are more excellent, but the distance measurement precision has the technical index defect, the common precision is above the centimeter level, and the millimeter level application scene requirement cannot be met. Therefore, the pulse laser radar in the prior art has the problem of insufficient ranging precision, and the requirement of the pulse laser radar on the measuring precision in practical application is difficult to meet.
In view of this, overcoming the drawbacks of the prior art is a problem to be solved in the art.
Disclosure of Invention
The invention aims to solve the technical problems of providing a laser radar, a calibration method and a method for improving the measurement precision of the laser radar, and solves the problems that the pulse laser radar in the prior art has insufficient ranging precision and is difficult to meet the measurement precision requirement of the pulse laser radar in practical application.
In a first aspect, the present invention provides a lidar comprising a transmitting module 101, an optical module 102, a receiving module 103, a circuit module 104, a controller 105 and a plurality of temperature adjustment modules 106, wherein:
the temperature adjusting modules 106 are respectively arranged on the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104, and the temperature adjusting modules 106 are used for adjusting the temperature of the corresponding modules;
the controller 105 is respectively connected with each temperature adjustment module 106, and the controller 105 is configured to adjust the temperature values of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 according to a calibration data set stored in the laser radar, so as to improve the measurement accuracy of the laser radar.
Further, the calibration data set includes a plurality of temperature difference data sets, each of the temperature difference data sets corresponding to one of the initial temperature data sets; the controller 105 is configured to adjust the temperature values of the transmitting module 101, the optical module 102, the receiving module 103, and/or the circuit module 104 according to a calibration data set stored in the lidar specifically includes:
When the laser radar is started to work, the controller 105 is configured to obtain a current working temperature of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104;
the controller 105 is further configured to compare the current operating temperature with an initial temperature dataset in the calibration dataset, and find an initial temperature dataset that matches the current operating temperature to determine a corresponding temperature difference dataset;
the controller 105 is configured to obtain a target operating temperature of each module according to the temperature difference data set and the current operating temperature, so as to control each temperature adjustment module 106 to adjust the temperature of each module to the target operating temperature.
Further, the transmitting module 101 is configured to transmit an optical signal, and the optical module 102 is configured to split the optical signal into a main signal and a reference signal;
the controller 105 is configured to obtain a first time of flight of the main signal back to the receiving module 103 via a target object;
the controller 105 is configured to obtain a second time of flight for the reference signal to reach the receiving module 103 via the optical module 102;
the controller 105 is configured to determine an actual time of flight of the light signal based on the first time of flight and the second time of flight.
Further, the emitting module 101 includes a semiconductor laser 201, the optical module 102 includes an emitting lens 202 and a partially reflecting mirror 203, and the receiving module 103 includes a first receiving lens 204, a second receiving lens 206, a first photodetector 205 and a second photodetector 207;
the semiconductor laser 201 is used for emitting optical signals;
the emission lens 202 is configured to collimate the optical signal and send the collimated optical signal to the partial reflector 203;
the partial reflector 203 is configured to divide the optical signal into a main signal and a reference signal, where the main signal is reflected by the partial reflector 203 to a target object, and the reference signal is transmitted to the first receiving lens 204 after passing through the partial reflector 203;
the first receiving lens 204 is configured to receive the reference signal and send the reference signal to the first photodetector 205 to obtain the second time of flight;
the second receiving lens 206 is configured to receive the main signal reflected by the target object and send the main signal to the second photodetector 207, so as to obtain the first time of flight.
Further, the emitting module 101 includes a fiber laser 301, the optical module 102 includes a fiber beam splitter 302, an emitting lens 202, and a total reflection mirror 303, and the receiving module 103 includes a second receiving lens 206, a first photodetector 205, and a second photodetector 207, wherein:
the fiber laser 301 is configured to emit an optical signal;
the optical fiber splitter 302 is configured to split an optical signal into a main signal and a reference signal, and send the main signal to the emission lens 202, and send the reference signal to the first photodetector 205, so as to obtain the second time of flight;
the emission lens 202 is configured to collimate the main signal and send the collimated main signal to the total reflection mirror 303;
the total reflection mirror 303 is used for reflecting the collimated main signal to the target object;
the second receiving lens 206 is configured to receive the main signal reflected by the target object and send the main signal to the second photodetector 207, so as to obtain the first time of flight.
In a second aspect, the present invention provides a method for improving the measurement accuracy of a lidar, where the method is applied to the lidar according to the first aspect, a calibration data set is stored in the lidar, the transmitting module 101 is used for transmitting an optical signal, and the optical module 102 is used for separating the optical signal into a main signal and a reference signal, and the method includes:
Adjusting temperature values of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 according to the calibration data set to improve measurement accuracy of the laser radar;
acquiring a first time of flight of the main signal back to the receiving module 103 via a target object, and acquiring a second time of flight of the reference signal to the receiving module 103 via the optical module 102;
determining an actual time of flight of the optical signal from the first time of flight and the second time of flight;
and calculating the distance between the laser radar and the target object according to the actual flight time.
In a third aspect, the present invention provides a method of calibrating a lidar according to the first aspect, the method comprising:
acquiring a measured distance between the laser radar and a target object through the laser radar, acquiring an actual distance between the laser radar and the target object, and determining a distance difference value between the actual distance and the measured distance;
adjusting the temperature adjustment module 106 to change the temperature of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 to reduce the distance difference;
When the distance difference value is reduced to be within a preset range, determining target temperature data sets corresponding to all the adjusted modules, and determining a temperature difference value data set according to the target temperature data sets and the initial temperature data sets;
obtaining a plurality of temperature difference data sets according to the initial temperature data sets, and adding the temperature difference data sets to a calibration data set of the laser radar so as to calibrate the laser radar through the calibration data set, wherein the calibration data set comprises a plurality of temperature difference data sets, and each temperature difference data set corresponds to one initial temperature data set.
Further, the obtaining the actual distance between the laser radar and the target object includes:
the installation position of the target object relative to the laser radar is relatively fixed, and the actual distance between the target object and the laser radar is a known value;
or the installation position of the target object relative to the laser radar is not fixed, and the actual distance between the laser radar and the target object is obtained through measurement of a precise distance measuring device.
Further, the method for acquiring the initial temperature data set includes:
And dividing a plurality of initial temperature data sets within the working environment temperature range of the laser radar according to the preset temperature value interval.
During each calibration, the controller 105 adjusts the initial temperature values of the transmitting module 101, the optical module 102, the receiving module 103, and the circuit module 104, respectively, to be the same as the initial temperature value in one of the initial temperature data sets, through the temperature adjustment module 106.
Further, when the distance difference is reduced to be within a preset range, determining a target temperature data set corresponding to all the adjusted modules, and determining a temperature difference data set according to the target temperature data set and the initial temperature data set includes:
when the temperature is regulated, the laser radar is used for acquiring the measurement distance in real time so as to update the distance difference value;
when the distance difference value is reduced to be within a preset range, the controller 105 respectively acquires target temperature values of the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104 through the temperature adjustment module 106 as a target temperature data set;
and respectively calculating the difference value of the initial temperature value and the corresponding target temperature value of the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104 to obtain the temperature difference value data set.
In the embodiment of the present invention, a plurality of temperature adjustment modules 106 are disposed on the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104, and the controller 105 obtains and controls the temperatures of the respective modules through all the temperature adjustment modules 106; the temperature of each module is regulated through a pre-stored calibration data set, so that the working temperature of each module is close to the target working temperature, the influence of the temperature on the laser radar is eliminated as much as possible, the measuring error of the laser radar is reduced, and the measuring precision of the laser radar is improved.
Further, in the embodiment of the present invention, by dividing an optical signal into a main signal and a reference signal, acquiring a first flight time of the main signal returning to the receiving module 103 via a target object, and acquiring a second flight time of the reference signal reaching the receiving module 103 via the optical module 102, determining an actual flight time of the optical signal according to the first flight time and the second flight time, and calculating a distance between the lidar and the target object according to the actual flight time; the method can effectively reduce the measurement error of the light signal flight time caused by the circuit noise of the laser radar, improve the accuracy of flight time measurement and further improve the measurement accuracy.
Drawings
In order to more clearly illustrate the technical solution of the embodiments of the present invention, the drawings that are required to be used in the embodiments of the present invention will be briefly described below. It is evident that the drawings described below are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1 is a schematic structural diagram of a lidar according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an optical path of a semiconductor laser used in a lidar according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an optical path of a fiber laser for a lidar according to an embodiment of the present invention;
FIG. 4 is a schematic flow chart of a method for improving the measurement accuracy of a laser radar according to an embodiment of the present invention;
fig. 5 is a flow chart of a calibration method of a lidar according to an embodiment of the present invention.
Wherein, the reference numerals are as follows:
a transmitting module 101; an optical module 102; a receiving module 103; a circuit module 104; a controller 105; a temperature adjustment module 106; a semiconductor laser 201; an emission lens 202; a partial mirror 203; a first receiving lens 204; a first photodetector 205; a second receiving lens 206; a second photodetector 207; a fiber laser 301; a fiber optic splitter 302; a total reflection mirror 303; optical fiber pins 304.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In the description of the present invention, the terms "inner", "outer", "longitudinal", "transverse", "upper", "lower", "top", "bottom", etc. refer to an orientation or positional relationship based on that shown in the drawings, merely for convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Example 1:
the embodiment 1 of the present invention provides a lidar, as shown in fig. 1, which includes a transmitting module 101, an optical module 102, a receiving module 103, a circuit module 104, a controller 105 and a plurality of temperature adjusting modules 106, wherein the plurality of temperature adjusting modules 106 are respectively disposed on the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104, and the temperature adjusting modules 106 are used for adjusting the temperatures of the corresponding modules. Optionally, the temperature adjusting module comprises a semiconductor refrigerator and a thermistor, the working temperature of the corresponding module is obtained through the thermistor, and the working temperature of the corresponding module is adjusted through the semiconductor refrigerator.
In actual use, the controller 105 is respectively connected to each of the temperature adjustment modules 106, wherein the laser radar has a calibration data set stored therein. The controller 105 is configured to adjust temperature values (which may be understood as an operating temperature) of the transmitting module 101, the optical module 102, the receiving module 103, and/or the circuit module 104 according to a calibration data set stored in the lidar, so as to improve measurement accuracy of the lidar.
Specifically, the controller 105 may obtain or adjust the temperature of the corresponding module according to the temperature adjustment module 106 provided on each module. The optical module 102 communicates with the receiving module 103 and the transmitting module 101, and the circuit module 104 communicates with the transmitting module 101 and the receiving module 103, respectively, so as to implement conversion of optical signals during transmitting and receiving.
The temperature can influence circuit noise in the laser radar, emission intensity of an optical signal, sensitivity of the first photoelectric detector and the second photoelectric detector and the like, and further influence the range accuracy of the laser radar.
In the embodiment of the present invention, the temperature adjustment module 106 is disposed on the transmitting module 101, the optical module 102, the receiving module 103, and the circuit module 104, the calibration data set is stored on the lidar, and the controller 105 adjusts the temperature of each module according to the calibration data set, so as to achieve the purpose of calibrating the lidar and improving the measurement accuracy of the lidar.
In order to improve the measurement accuracy of the lidar by adjusting the temperature of each module, the calibration data set includes a plurality of temperature difference data sets, each corresponding to an initial temperature data set; the controller 105 adjusts the temperature values of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 according to the calibration data set stored in the laser radar specifically includes:
when the laser radar is started to work, the controller 105 is configured to obtain a current working temperature of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104;
the controller 105 is further configured to compare the current operating temperature with an initial temperature dataset in the calibration dataset, and find an initial temperature dataset that matches the current operating temperature to determine a corresponding temperature difference dataset; the controller 105 is configured to obtain a target operating temperature of each module according to the temperature difference data set and the current operating temperature, so as to control each temperature adjustment module 106 to adjust the temperature of each module to the target operating temperature.
In the actual use, after the laser radar is started, the current working temperature of the laser radar is firstly obtained, then the temperature difference data set corresponding to the current working temperature is determined according to the current working temperature, and then the temperature calibration is carried out according to the temperature difference data set.
The temperature value of each module influences the accuracy of the distance measurement of the laser radar, namely the absolute accuracy and the repeated accuracy of the distance measurement, wherein the absolute accuracy refers to the difference value after the distance value measured by the laser radar is compared with the true value; the repetition accuracy is the relative difference value after a number of measurements by the lidar. Under the actual condition, the laser radar is difficult to work at the optimal temperature, and the laser radar can be allowed to deviate from the optimal temperature on the premise of meeting the index, so that the temperature can be adjusted according to the temperature difference data set, the overall temperature adjusting time of the laser radar can be saved, and the working efficiency is improved.
In order to further improve the measurement accuracy of the laser radar, the measurement error of the flight time of the optical signal can be reduced, and the specific implementation scheme is as follows: the transmitting module 101 is configured to transmit an optical signal, and the optical module 102 is configured to split the optical signal into a main signal and a reference signal; the controller 105 is configured to obtain a first time of flight of the main signal back to the receiving module 103 via a target object; the controller 105 is configured to obtain a second time of flight for the reference signal to reach the receiving module 103 via the optical module 102; the controller 105 is configured to determine an actual time of flight of the light signal based on the first time of flight and the second time of flight.
In the use process of the laser radar, a time measurement error is caused by circuit noise in the laser radar. In order to reduce the time measurement error caused by circuit noise, the optical signal may be subjected to a spectral process, the optical signal is divided into a main signal and a reference optical signal, and the starting time point of the optical signal transmitted by the transmitting module 101 is replaced by the time point of the reference optical signal received by the receiving module 103, i.e. the actual time of flight of the optical signal is determined by the first time of flight and the second time of flight. Thus, the measuring error of the light signal flight time caused by circuit noise of the laser radar can be effectively reduced.
A preferred embodiment is to select a semiconductor laser 201 as the light source, as shown in fig. 2, where the emitting module 101 comprises a semiconductor laser 201, the optical module 102 comprises an emitting lens 202 and a partially reflecting mirror 203, and the receiving module 103 comprises a first receiving lens 204, a second receiving lens 206, a first photodetector 205 and a second photodetector 207.
In practical use, the semiconductor laser 201 is configured to emit an optical signal, and the emission lens 202 is configured to collimate the optical signal and send the collimated optical signal to the partially reflecting mirror 203;
The partial reflector 203 is configured to split the optical signal into a main signal and a reference signal, where the main signal is reflected by the partial reflector 203 to the target object, and the reference signal is transmitted to the first receiving lens 204 after passing through the partial reflector 203.
The first receiving lens 204 is configured to receive the reference signal and send the reference signal to the first photodetector 205 to obtain the second time of flight.
The second receiving lens 206 is configured to receive the main signal reflected by the target object and send the main signal to the second photodetector 207, so as to obtain the first time of flight.
Another preferred embodiment is to select a fiber laser 301 as the light source, as shown in fig. 3, where the emitting module 101 includes a fiber laser 301, the optical module 102 includes a fiber beam splitter 302, an emitting lens 202, and a total reflection mirror 303, and the receiving module 103 includes a second receiving lens 206, a first photodetector 205, and a second photodetector 207.
In practical use, the fiber laser 301 is configured to emit an optical signal, and the fiber-optic splitter 302 is configured to split the optical signal into a main signal and a reference signal, and send the main signal to the emission lens 202, and send the reference signal to the first photodetector 205, so as to obtain the second time of flight.
The emission lens 202 is configured to collimate the main signal and send the collimated main signal to the total reflection mirror 303, the total reflection mirror 303 is configured to reflect the collimated main signal to the target object, and the second receiving lens 206 is configured to receive the main signal reflected by the target object and send the main signal to the second photodetector 207, so as to obtain the first flight time.
In this embodiment, the main signal is emitted from the optical fiber splitter 302 and then emitted onto the total reflection mirror 303 through the optical fiber pin 304.
In the embodiment of the present invention, the plurality of temperature adjustment modules 106 are disposed on the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104, so that the controller 105 obtains and controls the temperatures of the respective modules through all the temperature adjustment modules 106, thereby facilitating the calibration of the laser radar through the calibration data set, further reducing the measurement error of the laser radar, and improving the measurement accuracy of the laser radar.
Further, in the embodiment of the present invention, by dividing the optical signal into the main signal and the reference signal, obtaining the first flight time of the main signal returned to the receiving module 103 via the target object, and obtaining the second flight time of the reference signal reaching the receiving module 103 via the optical module 102, determining the actual flight time of the optical signal according to the first flight time and the second flight time, and calculating the distance between the laser radar and the target object according to the actual flight time, the measurement error of the flight time of the optical signal due to the circuit noise of the laser radar can be effectively reduced.
Example 2:
embodiment 2 provides a method for improving measurement accuracy of a laser radar, where the method is applied to the laser radar according to embodiment 1, a calibration data set is stored in the laser radar, the transmitting module 101 is configured to transmit an optical signal, and the optical module 102 is configured to split the optical signal into a main signal and a reference signal, where the main signal is emitted to a target object, and the method includes:
the measurement accuracy of the laser radar is improved by adjusting the temperature of each module, specifically, the temperature values of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 are adjusted according to the calibration data set, so as to improve the measurement accuracy of the laser radar.
Specifically, when the lidar is turned on, the controller 105 is configured to obtain a current operating temperature of the transmitting module 101, the optical module 102, the receiving module 103, and/or the circuit module 104; the controller 105 is further configured to compare the current operating temperature with an initial temperature dataset in the calibration dataset, and find an initial temperature dataset that matches the initial operating temperature to determine a corresponding temperature difference dataset; the controller 105 is configured to obtain a target operating temperature of each module according to the temperature difference data set and the current operating temperature, so as to control each temperature adjustment module 106 to adjust the temperature of each module to the target operating temperature.
The temperature of each module mainly influences the absolute precision and the repeated precision of the laser radar distance measurement, wherein the absolute precision refers to the difference value after the distance value measured by the laser radar is compared with the true value; the repetition accuracy is a relative difference value after laser radar is measured for a plurality of times; both indexes are key indexes of the laser radar.
Dividing the optical signal into a main signal and a reference signal, and respectively obtaining a first flight time of the main signal and a second flight time of the reference signal to determine an actual flight time of the optical signal, thereby improving the measurement accuracy of the laser radar, as shown in fig. 4, specifically comprising the following steps:
step 401: acquiring a first time of flight of the main signal back to the receiving module 103 via a target object, and acquiring a second time of flight of the reference signal to the receiving module 103 via the optical module 102;
step 402: determining an actual time of flight of the optical signal from the first time of flight and the second time of flight;
step 403: and calculating the distance between the laser radar and the target object according to the actual flight time.
Wherein the actual time of flight of the optical signal refers to the time of flight of the optical signal emitted from the optical module 102 to the target object and reflected by the target object to the receiving module 103, in this embodiment, the actual time of flight satisfies the following formula:
t1=(t+t3)-(t0+t3)=t-t0
Wherein t1 is the actual flight time of the optical signal, t+t3 is the first flight time measured by the laser radar, t0+t3 is the second flight time measured by the laser radar, and t3 is the time measurement error of the laser radar.
Because the reference signal is transmitted from the optical module 102 to the receiving module 103 at a small distance, the time from the optical module 102 to the receiving module 103 is also extremely short; the distance from the optical module 102 to the target object is far greater than the distance from the optical module 102 to the receiving module 103, so that the time that the main signal is transmitted from the optical module 102 to the target object and reflected to the receiving module 103 by the target object is far greater than the time that the reference signal is transmitted from the receiving module 103 to the optical module 102, that is, the first flight time is far greater than the second flight time, and the time measurement errors of the laser radar are carried in the first flight time and the second flight time, and the time measurement errors can be counteracted after the first flight time and the second flight time are subtracted, so that the time measurement errors caused by circuit noise can be reduced by taking the difference value between the second flight time and the first flight time as the actual flight time, thereby improving the measurement accuracy of the laser radar.
In the embodiment of the invention, on one hand, the laser radar is calibrated through the calibration data set, so that each module of the laser radar can work at a proper temperature, the measurement error of the laser radar is reduced, and the measurement accuracy of the laser radar is improved. On the other hand, by dividing the optical signal into the main signal and the reference signal, a first flight time of the main signal returning to the receiving module 103 via the target object is acquired, and a second flight time of the reference signal reaching the receiving module 103 via the optical module 102 is acquired, an actual flight time of the optical signal is determined according to the first flight time and the second flight time, and a distance between the laser radar and the target object is calculated according to the actual flight time, so that a measurement error of the flight time of the optical signal due to circuit noise of the laser radar is effectively reduced.
Example 3:
embodiment 3 provides a calibration method for a laser radar according to embodiment 1, as shown in fig. 5, including the following steps:
step 501: acquiring a measured distance between the laser radar and a target object through the laser radar, acquiring an actual distance between the laser radar and the target object, and determining a distance difference value between the actual distance and the measured distance;
Step 502: adjusting the temperature adjustment module 106 to change the temperature of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 to reduce the distance difference;
step 503: when the distance difference value is reduced to be within a preset range, determining target temperature data sets corresponding to all the adjusted modules, and determining a temperature difference value data set according to the target temperature data sets and the initial temperature data sets;
step 504: and obtaining the temperature difference data set according to the initial temperature data set, and adding the temperature difference data set to a calibration data set of the laser radar so as to calibrate the laser radar through the calibration data set.
Wherein the calibration data set includes a plurality of temperature difference data sets, each corresponding to an initial temperature data set.
The foregoing steps 501 to 502 are required to be executed multiple times, and each calibration is performed to obtain one temperature difference data set, that is, one initial temperature data set corresponds to one temperature difference data set, and then the calibration data sets are formed after the correlation between the plurality of initial temperature data sets and the plurality of temperature difference data sets is established.
The distance difference is a difference between the measured distance and the actual distance, that is, a measurement error of the laser radar, and the distance difference is related to a state that temperatures corresponding to the plurality of temperature adjustment modules 106 deviate from an optimal temperature, and the distance difference can be reduced by adjusting the plurality of temperature adjustment modules 106, that is, simultaneously changing the temperatures of the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104.
In an ideal case, the distance difference should approach zero to achieve an optimal working state. In practical situations, it is necessary to consider the situation that the laser radar calibration fails in operation and the actual accuracy is not enough nor that the distance difference approaches zero. Therefore, a precision preset range of the laser radar is set, the temperature of each module is regulated by a plurality of temperature regulating modules 106, and when the distance difference is smaller than the preset range, the laser radar is considered to reach the expected working state, and the precision index of the laser radar can meet the use requirement.
In order to accurately acquire the distance difference value, the method for acquiring the actual distance between the laser radar and the target object includes: the installation position of the target object relative to the laser radar is relatively fixed, and the actual distance between the target object and the laser radar is a known value, namely, the actual distance is unchanged in each calibration process; or the installation position of the target object relative to the laser radar is not fixed, and the actual distance between the laser radar and the target object is obtained through measurement of a precise distance measuring device.
In order to determine a temperature difference data set, the method for acquiring the initial temperature data set comprises the following steps: and dividing a plurality of initial temperature data sets within the working environment temperature range of the laser radar according to the preset temperature value interval. During each calibration, the controller 105 adjusts the initial temperature values of the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104, respectively, by the temperature adjustment module 106 to be the same as the initial temperature values in the initial temperature data set.
Specifically, before the temperature adjustment module 106 is adjusted, the temperature of the transmitting module 101 is obtained and taken as a first initial temperature, the temperature of the optical module 102 is obtained and taken as a second initial temperature, the temperature of the receiving module 103 is obtained and taken as a third initial temperature, the temperature of the circuit module 104 is obtained and taken as a fourth initial temperature, and the initial temperature data set is obtained.
The method comprises the steps of dividing a laser radar working environment into a plurality of initial temperature data sets according to a certain temperature value interval, for example, the laser radar working environment is [ -10,60], the laser radar working environment is provided with a plurality of initial temperature data sets positioned at [ -10, -5,0, & gt.
Further, in order to determine the temperature difference data set, when the distance difference is reduced to be within a preset range, determining a target temperature data set corresponding to all the adjusted modules, and determining the temperature difference data set according to the target temperature data set and the initial temperature data set includes:
and when the temperature is regulated, acquiring the measurement distance in real time through the laser radar so as to update the distance difference value.
When the distance difference value is reduced to be within a preset range, the controller 105 acquires target temperature values of the transmitting module 101, the optical module 102, the receiving module 103, and the circuit module 104, respectively, as target temperature data sets through the temperature adjustment module 106.
And respectively calculating the difference value of the initial temperature value and the corresponding target temperature value of the transmitting module 101, the optical module 102, the receiving module 103 and the circuit module 104 to obtain the temperature difference value data set.
Specifically, after the temperature adjustment module 106 is adjusted, the temperature of the transmitting module 101 is obtained and taken as a first target temperature, the temperature of the optical module 102 is obtained and taken as a second target temperature, the temperature of the receiving module 103 is obtained and taken as a third target temperature, the temperature of the circuit module 104 is obtained and taken as a fourth target temperature, and the target temperature data set is obtained.
And taking the difference value of the first target temperature and the first initial temperature as first temperature difference value data, taking the difference value of the second target temperature and the second initial temperature as second temperature difference value data, taking the difference value of the third target temperature and the third initial temperature as third temperature difference value data, and taking the difference value of the fourth target temperature and the fourth initial temperature as fourth temperature difference value data to obtain the temperature difference value data set.
The temperature difference data set is then used as a calibration data set for the lidar to facilitate calibration of the lidar with the calibration data set. The reason why the target temperature data set is not used as the calibration data set, but the temperature difference data set is used as the calibration data set is that the target temperature set is not an absolute value in the actual use process of the laser radar, but is a temperature range which enables the measurement error of the laser radar to be smaller than a preset range, so that the temperature difference data set is adopted, the whole temperature adjusting time of the laser radar can be saved, and the working efficiency is improved.
In this embodiment, by adjusting the temperature adjustment module 106, the temperature of the transmitting module 101, the optical module 102, the receiving module 103 and/or the circuit module 104 is changed, so as to reduce the distance difference, and when the distance difference is reduced to be within a preset range, a target temperature dataset corresponding to all the adjusted modules is determined, a temperature difference dataset is determined according to the target temperature dataset and the initial temperature dataset, and the temperature difference dataset is used as a calibration dataset of the laser radar. In the use process of the laser radar, when the laser radar equipment is started, the temperature of each module of the laser radar is adjusted by using the calibration data set, so that the consistency and stability of the working state of the laser radar are ensured, and the measurement accuracy of the laser radar is also ensured.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (8)
1. A lidar comprising a transmitting module (101), an optical module (102), a receiving module (103), a circuit module (104), a controller (105) and a plurality of temperature adjustment modules (106), wherein:
the temperature adjusting modules (106) are respectively arranged on the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104), and the temperature adjusting modules (106) are used for adjusting the temperature of the corresponding modules;
the controller (105) is respectively connected with each temperature adjusting module (106), and the controller (105) is used for adjusting the temperature values of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) according to a calibration data set stored in the laser radar so as to improve the measurement accuracy of the laser radar;
The calibration data set comprises a plurality of temperature difference data sets, and each temperature difference data set corresponds to one initial temperature data set; dividing a plurality of initial temperature data sets within the working environment temperature range of the laser radar according to preset temperature value intervals; the temperature difference data set is obtained by the following steps: acquiring a measured distance between the laser radar and a target object through the laser radar, acquiring an actual distance between the laser radar and the target object, and determining a distance difference value between the actual distance and the measured distance;
-adjusting the temperature adjustment module (106), changing the temperature of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) to reduce the distance difference; when the distance difference value is reduced to be within a preset range, determining target temperature data sets corresponding to all the adjusted modules, and determining a temperature difference value data set according to the target temperature data sets and the initial temperature data sets;
the controller (105) is configured to adjust temperature values of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) according to a calibration data set stored in the lidar, and specifically includes:
When the laser radar is started to work, the controller (105) is used for acquiring the current working temperatures of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104);
the controller (105) is further configured to compare the current operating temperature with an initial temperature dataset in the calibration dataset, find an initial temperature dataset that matches the current operating temperature, and determine a corresponding temperature difference dataset; the controller (105) is used for acquiring the target working temperature of each module according to the temperature difference data set and the current working temperature so as to control each temperature adjusting module (106) to adjust the temperature of each module to the target working temperature.
2. The lidar according to claim 1, wherein the transmitting module (101) is configured to transmit an optical signal, and the optical module (102) is configured to split the optical signal into a main signal and a reference signal;
-the controller (105) is configured to obtain a first time of flight of the main signal back to the receiving module (103) via a target object;
-the controller (105) is configured to obtain a second time of flight of the reference signal to the receiving module (103) via the optical module (102);
The controller (105) is configured to determine an actual time of flight of the light signal from the first time of flight and the second time of flight.
3. The lidar according to claim 2, wherein the transmitting module (101) comprises a semiconductor laser (201), the optical module (102) comprises a transmitting lens (202) and a partially reflecting mirror (203), the receiving module (103) comprises a first receiving lens (204), a second receiving lens (206), a first photodetector (205) and a second photodetector (207);
the semiconductor laser (201) is used for emitting optical signals;
-the emission lens (202) is configured to collimate the optical signal and to send the collimated optical signal to the partial mirror (203);
the partial reflector (203) is used for dividing the optical signal into a main signal and a reference signal, wherein the main signal is reflected to a target object by the partial reflector (203), and the reference signal is transmitted to the first receiving lens (204) after passing through the partial reflector (203);
-the first receiving lens (204) is configured to receive the reference signal and to send the reference signal to the first photodetector (205) for obtaining the second time of flight;
The second receiving lens (206) is configured to receive a main signal reflected by the target object and send the main signal to the second photodetector (207) to obtain the first time of flight.
4. The lidar according to claim 2, wherein the transmitting module (101) comprises a fiber laser (301), the optical module (102) comprises a fiber-optic beam splitter (302), a transmitting lens (202) and a total reflection mirror (303), the receiving module (103) comprises a second receiving lens (206), a first photodetector (205) and a second photodetector (207), wherein:
-the fiber laser (301) is for emitting an optical signal;
the optical fiber beam splitter (302) is configured to split an optical signal into a main signal and a reference signal, and send the main signal to the emission lens (202), and send the reference signal to the first photodetector (205) to obtain the second time of flight;
the emission lens (202) is used for collimating the main signal and sending the collimated main signal to the total reflection mirror (303);
the total reflection mirror (303) is used for reflecting the collimated main signal to the target object;
The second receiving lens (206) is configured to receive a main signal reflected by the target object and send the main signal to the second photodetector (207) to obtain the first time of flight.
5. A method for improving the measurement accuracy of a lidar, wherein the method is applied to the lidar according to any of claims 1 to 4, wherein a calibration data set is stored in the lidar, the transmitting module (101) is used for transmitting an optical signal, and the optical module (102) is used for dividing the optical signal into a main signal and a reference signal, and the method comprises:
adjusting temperature values of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) according to the calibration data set so as to improve the measurement accuracy of the laser radar;
-obtaining a first time of flight of the main signal back to the receiving module (103) via a target object, and a second time of flight of the reference signal to the receiving module (103) via the optical module (102);
determining an actual time of flight of the optical signal from the first time of flight and the second time of flight;
And calculating the distance between the laser radar and the target object according to the actual flight time.
6. A method for calibrating a lidar according to any of claims 1 to 4, the method comprising:
acquiring a measured distance between the laser radar and a target object through the laser radar, acquiring an actual distance between the laser radar and the target object, and determining a distance difference value between the actual distance and the measured distance;
-adjusting the temperature adjustment module (106), changing the temperature of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) to reduce the distance difference;
when the distance difference value is reduced to be within a preset range, determining target temperature data sets corresponding to all the adjusted modules, and determining a temperature difference value data set according to the target temperature data sets and the initial temperature data sets;
obtaining a temperature difference data set according to the initial temperature data set, and adding the temperature difference data set to a calibration data set of the laser radar so as to calibrate the laser radar through the calibration data set, wherein the calibration data set comprises a plurality of temperature difference data sets, and each temperature difference data set corresponds to one initial temperature data set;
The method for acquiring the initial temperature data set comprises the following steps:
dividing a plurality of initial temperature data sets within the working environment temperature range of the laser radar according to preset temperature value intervals;
during each calibration process, the controller (105) adjusts the initial temperature values of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) through the temperature adjusting module (106) respectively to be the same as the initial temperature value in one of the initial temperature data sets.
7. The method of calibrating according to claim 6, wherein the obtaining the actual distance of the lidar from the target object comprises:
the installation position of the target object relative to the laser radar is relatively fixed, and the actual distance between the target object and the laser radar is a known value;
or the installation position of the target object relative to the laser radar is not fixed, and the actual distance between the laser radar and the target object is obtained through measurement of a precise distance measuring device.
8. The method of calibrating according to claim 6, wherein determining a target temperature dataset corresponding to all modules after adjustment when the distance difference is reduced within a preset range, determining a temperature difference dataset from the target temperature dataset and an initial temperature dataset comprises:
When the temperature is regulated, the laser radar is used for acquiring the measurement distance in real time so as to update the distance difference value;
when the distance difference value is reduced to be within a preset range, the controller (105) respectively acquires target temperature values of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) through the temperature adjusting module (106) as a target temperature data set;
and respectively calculating the difference value of the initial temperature value and the corresponding target temperature value of the transmitting module (101), the optical module (102), the receiving module (103) and the circuit module (104) to obtain the temperature difference value data set.
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