Laser radar calibration method

Abstract

The invention provides a laser radar calibration method, and relates to the field of laser radar calibration, and the method comprises the steps: enabling a to-be-calibrated laser radar to be disposed on a light-transmitting plate of each container, and obtaining the detection distance between the light-transmitting plate and a reflector, each laser radar is calibrated according to detection distance data of the laser radars and real data between the light-transmitting plate and the reflecting plate. In the laser radar calibration method provided by the invention, aiming at a specific liquid environment in radar practical application, distance measurement data of the radars in the specific liquid environment are acquired, and the distance measurement data of the radars in the specific liquid environment are acquired; and single-machine calibration and correction are carried out on each radar, so that the distance measurement accuracy of each radar in a specific liquid environment is ensured.

Description

Technical Field

[0001] The present application relates to the field of laser radar technology, and in particular, to a laser radar calibration method. Background Art

[0002] LiDAR (Light Detection and Ranging) is a radar system that emits laser beams to detect the position, distance and other characteristic quantities of a target. Its working principle is to emit a detection signal (laser beam) to the target, and then compare the received signal reflected from the target (target echo) with the transmitted signal. After appropriate processing and calculation, the relevant distance, direction and other information of the target can be obtained.

[0003] Usually, LiDAR is mainly used for target detection in air environments. With the development of science and technology, the application of LiDAR has become increasingly diversified, and some underwater applications have also emerged. Among them, the calibration of LiDAR underwater is particularly important. At present, the calibration of LiDAR is mainly carried out in the air, with the help of specific reflectivity plates for calibration. When used underwater, the speed of light propagating in water is different from the coefficient of light propagating in air, so a coefficient conversion is performed to perform ranging activities.

[0004] The existing conversion method is only based on theoretical data. In actual applications, the distance measurement of LiDAR will also be affected by many factors such as the turbidity of the liquid and the consistency of the distance measurement of different radars. Therefore, simple theoretical calculations alone cannot completely solve the problem of the accuracy of LiDAR distance measurement in liquid environments (the degree of closeness between the detected value and the true value). Summary of the invention

[0005] The purpose of this application is to provide a calibration device and method for a laser radar used in a liquid environment. The laser radar can be calibrated according to the liquid state and turbidity of the radar in actual application, so as to ensure the ranging accuracy of the laser radar when used in a liquid environment, so as to solve the calibration problem of the laser radar when used in a liquid medium environment.

[0006] In order to achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows: On the one hand, a laser radar calibration method includes: a laser radar to be calibrated, no less than two containers for storing liquid, each container has a different length, each container includes a light-transmitting plate and a reflecting plate, the light-transmitting plate and the reflecting plate are respectively arranged at one end of the container to form a liquid storage space; the light-transmitting plate is used to transmit the detection light emitted by the laser radar, and the transmitting plate is used to reflect the detection light emitted by the laser radar to form an echo signal; the laser radar to be calibrated is respectively set on the light-transmitting plate of each container to obtain the detection distance between the light-transmitting plate and the reflecting plate, and each laser radar is calibrated according to the detection distance data of the laser radar and the real data between the light-transmitting plate and the reflecting plate.

[0007] Optionally, each laser radar is calibrated by a piecewise linear interpolation calibration method according to the detection distance data of the laser radar and the real data between the light-transmitting plate and the reflective plate.

[0008] Optionally, a first container and a second container are included, and the positions of the laser radar are moved respectively to obtain a detection distance N1 between the light-transmitting plate and the reflective plate of the first container and a detection distance N2 between the light-transmitting plate and the reflective plate of the second container; the linear correction parameters K1 and B1 between the real distance R1 between the light-transmitting plate and the reflective plate of the first container and the real distance R2 between the light-transmitting plate and the reflective plate of the second container are: K1=((N2*H-R2) - (N1*H-R1)) / (R2-R1); B1 = (N1*H-R1)- K1*R1; Where H is the coefficient ratio of the speed of light in liquid to the speed of light in air.

[0009] Optionally, according to K1 and B1, a correction value of the distance interval from R1 to R2 is obtained: Error = K1*R+B1, where Error is the compensation value and R is the actual distance.

[0010] Optionally, the laser radar is fixed in a fixture, and the laser radar is connected to the host computer through a Uart interface.

[0011] Optionally, the clamp is controlled to move by a host computer to move the laser radar to detection positions of different light-transmitting plates of the container.

[0012] Optionally, a calibration correction table of the laser radar is calculated using the detection distance data of the laser radar, the calculated correction table is written into the laser radar, and the laser radar is calibrated and corrected on a single machine by piecewise linear interpolation calibration.

[0013] Compared with the prior art, this application has the following beneficial effects: The present application provides a laser radar calibration method, which includes: a laser radar to be calibrated, no less than two containers for storing liquid, each container has a different length, each container includes a light-transmitting plate and a reflecting plate, the light-transmitting plate and the reflecting plate are respectively arranged at one end of the container to form a liquid storage space; the light-transmitting plate is used to transmit the detection light emitted by the laser radar, and the transmitting plate is used to reflect the detection light emitted by the laser radar to form an echo signal; the laser radar to be calibrated is respectively arranged on the light-transmitting plate of each container, the detection distance between the light-transmitting plate and the reflecting plate is obtained, and each laser radar is calibrated according to the detection distance data of the laser radar and the real data between the light-transmitting plate and the reflecting plate. In the laser radar calibration method provided by the present application, for the specific liquid environment in the actual application of the radar, the ranging data of the radar in the specific liquid environment is collected, and each radar is calibrated and corrected individually, thereby ensuring the ranging accuracy of each radar in the specific liquid environment.

[0014] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 Schematic diagram of the laser radar calibration device provided in an embodiment of the present application.

[0017] Figure 2 It is a schematic diagram of the structure of the fixture in the calibration device according to the embodiment of the present application.

[0018] Figure 3 This is a flow chart of the calibration method according to an embodiment of the present application.

[0019] In the figure: 10 - fixture; 11 - laser radar; 12 - pressure plate; 20 - guide rail; 30 - light-transmitting baffle; 40 - reflective plate; 51 - first container; 52 - second container; 53 - third container. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0022] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0023] It should be noted that, in this document, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0024] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0025] As described in the background technology, the calibration process of the LiDAR is usually carried out in an air environment. For scenarios where the LiDAR needs to be used in other liquid environments, the calibration in the air environment cannot meet the actual usage requirements. The problem of the LiDAR's ranging accuracy cannot be completely solved only through theoretical calculations of medium changes, and independent calibration is required in this specific liquid environment.

[0026] In order to solve this problem, an embodiment of the present application provides a laser radar calibration device, which improves the ranging accuracy of the laser radar in a specific liquid environment through calibration in an actual liquid environment.

[0027] The following is an exemplary description of the laser radar calibration device provided in this application: As an implementation method, see the attached Figure 1The laser radar calibration device includes a fixture 10, a guide rail 20, a light-transmitting baffle 30, a reflective plate 40, a first container 51, a second container 52, and a third container 53. The above components are arranged on the same substrate. The substrate is, for example, an optical platform.

[0028] In order to stably fix the laser radar to be calibrated and reduce other influencing factors of the calibration process, the calibration device includes a fixture 10 for fixing the laser radar to be tested, and the fixture includes a space for stably placing the laser radar 11, and a pressure plate 12 for further fixing the position of the laser radar. The setting of the fixture allows the laser radar to maintain a fixed position so that it can maintain a relatively stable positional relationship with other components during the calibration process. An electrical connection component is provided in the fixture, which is used to electrically connect to the laser radar, power the laser radar, and communicate with the laser radar. The pressure plate 12 is connected to a pressure device, for example, the pressure device is a cylinder, and the cylinder provides power to the pressure plate to move to compress or release the pressure, thereby fixing or releasing the radar.

[0029] On this basis, the calibration device is provided with a guide rail, and the fixture 10 can be connected to a driving device, and the driving device drives the fixture to move in the same direction on the guide rail. In one embodiment, the driving device includes a motor and a transmission belt, and the motor drives the transmission belt to move, and then the transmission belt drives the fixture to move synchronously to different desired calibration positions.

[0030] In order to simulate the environment in which the laser radar works in liquid, the calibration device is provided with a container for storing liquid. The container is used to seal and store liquid. The number of the containers can be set according to the test points required for calibration. In this embodiment, three containers are taken as an example, including a first container 51, a second container 52 and a third container 53. The three containers have different lengths, corresponding to different calibration distances. The shape of the container is, for example, a columnar structure, and the liquid fully fills the container to ensure that the liquid is evenly distributed. A light-transmitting baffle is set at one end of the container, and a reflector is set at the other end to form a sealed space for storing liquid. Among them, the light-transmitting plate is used to transmit the detection light signal of the laser radar. The detection light signal propagates in the liquid of the container and irradiates the transmitting plate. The signal light (echo signal) reflected by the reflector is incident back to the laser radar. The receiving module of the laser radar receives the echo signal and calculates the detection distance. The reflectivity of the reflector can be set according to the needs of calibration. For example, the reflectivity of the reflector is 10%, 30%, 50%, 70%, 90%, etc. The transmittance of the light-transmitting plate can be set according to the need of calibration. For example, if the light-transmitting plate is made of glass, the transmittance of the light-transmitting plate can be 50%, 70%, 90%, 100%, etc.

[0031] As an implementation method, as shown in the attached Figure 2In the example shown, the three containers are all cylindrical structures. The length of the first container 51 is 100 mm and the cross-sectional diameter is 100 mm. The length of the second container 52 is 300 mm and the cross-sectional diameter is 100 mm. The length of the third container 53 is 550 mm and the cross-sectional diameter is 140 mm. The container length is selected according to the detection range of the laser radar, corresponding to different calibration distances. Among them, since the detection light emitted by the laser radar light source has a certain divergence angle, in order to avoid irradiating the side wall of the container at a long distance instead of irradiating the entire transmitting plate, the diameter of the container with a longer overall length is larger than the diameter of the container with other shorter lengths to ensure the accuracy of the calibration. The reflectivity of the three reflective plates is the same, all of which are 10% or 90%, and the transmittance of the light-transmitting plate is the same, all of which are glass with a transmittance of more than 90%. The reflective plate is arranged parallel to the light-transmitting plate and perpendicular to the central axis of the cylindrical container.

[0032] The liquid in the container is filled according to the usage scenario. For example, in the scenario of underwater detection, the liquid in the container is fresh water, clean water or sea water. It can also be filled with liquid with a certain turbidity according to the characteristics of water quality. As an implementation method, the liquid in the container is clean water.

[0033] Based on the calibration device of the above implementation, the present application embodiment also provides a calibration method. Figure 3 As shown in the flowchart, the laser radar 11 is fixed in the fixture 12, and the laser radar is connected to the host computer. In one implementation, the laser radar is connected to the host computer through a Uart interface. The calibration device is also connected to the host computer through the Uart interface.

[0034] The upper computer controls the movement of the fixture to move the laser radar to the first collection point facing the transparent plate of the first container. The laser radar works normally to detect the distance and collects the detection data of the laser radar at the first collection point. Similarly, the fixture is moved continuously to set the laser radar on the transparent plate of the second container and the transparent plate of the third container, and the distance detection data of the laser radar at the second collection point and the third collection point are collected. The calibration correction table of the laser radar is calculated through the collection data of the three groups of laser radars, and the calculated correction table is written into the laser radar. The output detection distance is calibrated through the internal algorithm of the laser radar. The laser radar is calibrated and corrected by the piecewise linear interpolation calibration method to ensure the ranging accuracy of each laser radar in a specific liquid environment.

[0035] Specifically, one implementation of the laser radar calibration method is as follows (this embodiment takes two-stage correction as an example, and the liquid is water): The laser radar is set in the fixture, and the pressure plate is pressed to fix the laser radar in the fixture. The upper computer controls the movement of the fixture to set the laser radar at a position directly opposite to the light-transmitting plate of the first container. The laser radar works to detect the distance. The light source of the laser radar sends out a detection light signal. The light-transmitting plate transmits the detection light signal of the laser radar. The detection light signal propagates in the liquid of the container and shines on the transmitting plate. The signal light (echo signal) reflected by the reflector is incident back to the laser radar. The receiving module of the laser radar receives the echo signal, and the laser radar calculates the detection distance N1 between the light-transmitting plate and the reflective plate of the first container. The actual distance between the light-transmitting plate and the reflective plate of the first container is R1.

[0036] The upper computer controls the movement of the fixture and sets the laser radar at a position directly opposite to the light-transmitting plate of the second container. The laser radar works to detect the distance. The light source of the laser radar sends out a detection light signal. The light-transmitting plate transmits the detection light signal of the laser radar. The detection light signal propagates in the liquid of the container and irradiates the transmitting plate. The signal light (echo signal) reflected by the reflecting plate is incident back to the laser radar. The receiving module of the laser radar receives the echo signal. The laser radar calculates the detection distance N2 between the light-transmitting plate and the reflective plate of the second container. The actual distance between the light-transmitting plate and the reflective plate of the second container is R2.

[0037] The upper computer controls the movement of the fixture and sets the laser radar at a position directly opposite to the light-transmitting plate of the third container. The laser radar works to detect the distance. The light source of the laser radar sends out a detection light signal. The light-transmitting plate transmits the detection light signal of the laser radar. The detection light signal propagates in the liquid of the container and irradiates the transmitting plate. The signal light (echo signal) reflected by the reflecting plate is incident back to the laser radar. The receiving module of the laser radar receives the echo signal. The laser radar calculates the detection distance N3 between the light-transmitting plate and the reflective plate of the third container. The actual distance between the light-transmitting plate and the reflective plate of the third container is R3.

[0038] For example, if the liquid medium is water and the coefficient ratio of the light propagation speed in water to the light propagation speed in air is 0.75, the linear correction parameters K1 and B1 values ​​between the distance R1 and R2 can be calculated. The calculation formula is as follows: K1=((N2*0.75-R2) - (N1*0.75-R1)) / (R2-R1); B1 = (N1*0.75-R1)- K1*R1.

[0039] Similarly, through the data of distances R2, R3, N2 and N3, and the coefficient ratio of the speed of light in water to the speed of light in air, 0.75, the linear correction parameters K2 and B2 between the distances R2 and R3 can be calculated.

[0040] According to the K1 and B1 parameters, the correction value of the distance interval from R1 to R2 is: Error = K1*R+B1 (Error is the compensation value and R is the actual distance). Similarly, the correction value of the distance interval from R2 to R3 can be obtained.

[0041] The correction value obtained above is written into the laser radar to realize the distance calibration of the radar underwater.

[0042] According to the properties of specific liquids in the actual application of LiDAR, the ranging data of LiDAR in the specific liquid is collected, and each LiDAR is calibrated and corrected by piecewise linear interpolation calibration, so as to ensure the ranging accuracy of each LiDAR in the specific liquid medium.

[0043] The above is an embodiment of three containers using two-segment linear paper insertion calibration. Containers of different numbers and structures and different data calibration methods can be set according to specific circumstances.

[0044] In summary, the present application provides a laser radar calibration method, which includes: a laser radar to be calibrated, no less than two containers for storing liquid, each container has a different length, each container includes a light-transmitting plate and a reflecting plate, the light-transmitting plate and the reflecting plate are respectively arranged at one end of the container to form a liquid storage space; the light-transmitting plate is used to pass the detection light emitted by the laser radar, and the transmitting plate is used to reflect the detection light emitted by the laser radar to form an echo signal; the laser radar to be calibrated is respectively arranged on the light-transmitting plate of each container, and the detection distance between the light-transmitting plate and the reflecting plate is obtained, and each laser radar is calibrated according to the detection distance data of the laser radar and the real data between the light-transmitting plate and the reflecting plate. In the laser radar calibration method provided by the present application, for the specific liquid environment in the actual application of the radar, the ranging data of the radar in the specific liquid environment is collected, and each radar is calibrated and corrected individually, thereby ensuring the ranging accuracy of each radar in the specific liquid environment.

[0045] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0046] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A laser radar calibration method, characterized in that: The laser radar calibration method includes: a laser radar to be calibrated, no less than two containers for storing liquid, each container has a different length, each container includes a light-transmitting plate and a reflecting plate, the light-transmitting plate and the reflecting plate are respectively arranged at one end of the container to form a liquid storage space; the light-transmitting plate is used to transmit the detection light emitted by the laser radar, and the transmitting plate is used to reflect the detection light emitted by the laser radar to form an echo signal; the laser radar to be calibrated is respectively set on the light-transmitting plate of each container to obtain the detection distance between the light-transmitting plate and the reflecting plate, and each laser radar is calibrated according to the detection distance data of the laser radar and the real data between the light-transmitting plate and the reflecting plate.

2. The laser radar calibration method according to claim 1, characterized in that: Each LiDAR is calibrated using the piecewise linear interpolation calibration method based on the detection distance data of the LiDAR and the real data between the light-transmitting plate and the reflective plate.

3. The laser radar calibration method according to claim 1, characterized in that: Including a first container and a second container, the positions of the laser radar are moved respectively to obtain the detection distance N1 between the light-transmitting plate and the reflective plate of the first container and the detection distance N2 between the light-transmitting plate and the reflective plate of the second container; the linear correction parameters K1 and B1 between the real distance R1 between the light-transmitting plate and the reflective plate of the first container and the real distance R2 between the light-transmitting plate and the reflective plate of the second container are: K1=((N2*H-R2) - (N1*H-R1)) / (R2-R1); B1 = (N1*H-R1)- K1*R1; Where H is the coefficient ratio of the speed of light in liquid to the speed of light in air.

4. The laser radar calibration method according to claim 1, characterized in that: According to K1 and B1, the correction value of the distance interval from R1 to R2 is obtained: Error = K1*R+B1, where Error is the compensation value and R is the actual distance.

5. The laser radar calibration method according to claim 1, characterized in that: The method includes fixing the laser radar in a fixture, connecting the laser radar to a host computer, and connecting the laser radar to the host computer through a Uart interface.

6. The laser radar calibration method according to claim 1, characterized in that: The method includes controlling the movement of the fixture by a host computer and moving the laser radar to the detection positions of different light-transmitting plates of the container.

7. The laser radar calibration method according to claim 1, characterized in that: The laser radar calibration correction table is calculated through the laser radar detection distance data, and the calculated correction table is written into the laser radar. The laser radar is calibrated and corrected by piecewise linear interpolation calibration.

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