WO2021081998A1

WO2021081998A1 - Calibration method and calibration apparatus for laser radar system, medium, and ranging device

Info

Publication number: WO2021081998A1
Application number: PCT/CN2019/115119
Authority: WO
Inventors: 王超
Original assignee: 深圳市速腾聚创科技有限公司
Priority date: 2019-11-01
Filing date: 2019-11-01
Publication date: 2021-05-06
Also published as: CN112585495A; CN112585495B

Abstract

A calibration method for a laser radar system, comprising the following method steps: a laser radar system (230) uses a calibration box (210) to sequentially execute N instances of ranging, the emergent laser of each instance of ranging is delayed for a different length of time and ranging values of N different distances are obtained, and N calibration matrices are obtained according to the difference between a ranging value and a corresponding actual value (S120), N≥1 and N being an integer; and a calibration matrix of a measured value is acquired, and the measured value is calibrated and compensated (S140).

Description

Lidar system calibration method, calibration device, medium and ranging equipment

Technical field

The invention relates to the technical field of laser radar ranging, in particular to a calibration method and a calibration device, storage medium and ranging equipment of a laser radar system.

Background technique

The lidar system is a system that emits laser beams to detect the position and speed of the target. It is widely used in the field of laser detection, for example, in ranging systems, tracking and measurement of low-flying targets, weapon guidance, atmospheric monitoring, Fields such as surveying and mapping, early warning and traffic management.

During the distance measurement process of the lidar system, due to system differences and environmental influences, the measured value is deviated from the actual value, resulting in inaccurate detection results. The traditional calibration method uses the movement of the slide rail to change the distance between the target and the lidar system to perform calibration compensation. However, this method of calibration requires a large space and a cumbersome process, and the calibration error is large at a long distance.

Summary of the invention

According to various embodiments of the present application, a calibration method and a calibration device, a storage medium, and a ranging device of a lidar system are provided.

A method for calibrating a lidar system, the method steps are as follows:

The lidar system uses the calibration box to perform N ranges in sequence, and the outgoing laser of each range is delayed for a different time, and the range values at N different distances are obtained, and obtained according to the difference between the range value and the corresponding actual value N calibration matrices; where N≥1 and N is an integer;

The calibration matrix of the measurement value is obtained, and the measurement value is calibrated and compensated.

A calibration device of a lidar system includes:

The processing module is used to control the lidar system to use the calibration box to perform N range finding times in sequence. The emitted laser of each range finding is delayed by a different time to obtain N range finding values at different distances, and according to the range finding value and the corresponding N calibration matrices are obtained by the difference of the actual values of, where N≥1 and N is an integer;

The calibration module is used to obtain the calibration matrix of the measured value, and perform calibration compensation on the measured value.

A storage medium on which a computer program is stored, and when the computer program is executed by a processor, the steps of the aforementioned method are realized.

A distance measuring device includes a memory and a processor; the processor stores a computer program that can run on the processor, and the processor implements the steps of the aforementioned method when the processor executes the computer program.

The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, purposes and advantages of this application will become apparent from the description, drawings and claims.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, without creative work, the drawings of other embodiments can also be obtained based on these drawings.

Fig. 1 is a flowchart of a method for calibrating a lidar system in an embodiment.

Fig. 2 is a schematic structural diagram of a calibration box in an embodiment.

Fig. 3 is a specific flow chart of a method for calibrating a lidar system in an embodiment.

Fig. 4 is a schematic diagram of the working principle of the calibration of the lidar system in an embodiment.

Fig. 5 is a flowchart of specific steps of step S342 in an embodiment.

Fig. 6 is a partial function diagram of the data fitting process in an embodiment.

Fig. 7 is a flowchart of specific steps of step S344 in an embodiment.

Fig. 8 is a flowchart of a method for calibrating a lidar system in another embodiment.

Fig. 9 is a structural block diagram of a calibration device of a lidar system in an embodiment.

Detailed ways

In order to make the purpose, technical solutions, and advantages of this application clearer, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the application, and not used to limit the application.

In the description of this application, it should be understood that the terms "center", "lateral", "upper", "lower", "left", "right", "vertical", "horizontal", "top", " The orientation or positional relationship indicated by “bottom”, “inner” and “outer” is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description, and does not indicate or imply the device or The element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. In addition, it should be noted that when an element is referred to as being "formed on another element", it may be directly connected to another element or a centering element may exist at the same time. When an element is considered to be "connected" to another element, it can be directly connected to the other element or an intermediate element can be present at the same time. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

According to the scanning method, lidar is divided into mechanical lidar, micro-electro-mechanical system (MEMS, Micro-Electro-Mechanical System) lidar, Flash lidar and phased array lidar. Among them, the working principle of Flash lidar is to illuminate the entire field of view area to be detected by the outgoing laser at one time, and then receive all the echo lasers in the field of view at the same time, and complete it by directly or indirectly calculating the flight time of photons. Distance measurement. The advantage of Flash Lidar is that the transmitter has no mechanical movement and can quickly record the entire detection scene. While obtaining the distance information of the target, it can also obtain the gray-scale imaging information, avoiding the movement of the target or the lidar system itself during the scanning process. The interference caused by simple structure, low load, long life of the optical machine, convenient for miniaturization and modularization, low time cost of manual adjustment, and high cost performance. Flash lidar, as a lidar technology that can output target imaging information at the same time, has huge application potential in many aspects of social production and life in the future, such as topographic surveying and mapping, urban modeling, highway detection and other civilian fields, weapon guidance, Military aspects such as battlefield reconnaissance and underwater detection.

The type of detector at the receiving end of Flash Lidar is related to its working principle. The basic principle of continuous wave Flash lidar is that the emitted laser light is a light signal modulated by a carrier of a specific frequency, and the distance between the light source and the target is calculated by calculating the phase difference between the echo laser and the emitted laser light. The pulsed Flash lidar can be subdivided into two types, one of which is called the iTOF type, that is, pulse integral ranging. The light source periodically emits wide pulse lasers and collects echo lasers in different integration time windows. The flight time of the photons can be obtained through the proportional relationship to calculate the distance information. The second type is called the DTOF type, which is the same as the traditional mechanical lidar. The light source is a pulsed light source with high peak power. It emits periodic narrow pulse lasers and measures the flight of photons by detecting echo lasers. Time to calculate distance information. Among them, the pulsed Flash lidar detector can use two-dimensional silicon photomultiplier (SIPM, Silicon photomuitiplier) or avalanche photodiode (APD, Avalanche Photon Diode) arrays, and continuous wave Flash lidars mostly use charge-coupled elements ( CCD, Charge-coupled Device) or Complementary Metal Oxide Semiconductor (CMOS, Complementary Metal Oxide Semiconductor).

Regardless of the working principle of the lidar system, calibration and compensation are necessary links to determine its ranging accuracy. For the Flash lidar system, the physical quantities that need to be calibrated and compensated include static errors (circuit wiring, signal loading path length differences, optical system distortion, etc.), temperature errors, distance response unevenness errors, and detector pixel differences Error etc. The following takes the Flash lidar as an example to introduce the calibration method of the lidar system in detail. The calibration method of the lidar system can calibrate and compensate the measured value obtained during the distance measurement of the Flash lidar system, so that the final measured value of the target distance is closer to the actual value. However, it should be noted that the calibration method of the lidar system provided in this application is not limited to the calibration of the Flash lidar, and can also be calibrated for other types of lidars, such as phased array lidars.

Fig. 1 is a calibration method of a lidar system in an embodiment. As shown in Figure 1, the calibration method of the lidar system includes the following steps:

In step S120, the lidar system uses the calibration box to perform N range finding times in sequence, and the emitted laser of each range finding is delayed by a different time to obtain N range finding values at different distances, and according to the difference between the range finding value and the corresponding actual value Get N calibration matrices.

Specifically, the lidar system emits the outgoing laser, and receives the echoed laser that is reflected by the target object, and calculates the distance measurement value based on the time difference between the time of emitting the outgoing laser and the time of receiving the echoed laser. The lidar system can be a Flash lidar system or other lidar systems, such as phased array lidar systems, multi-line lidar systems, MEMS lidar systems, etc. After the outgoing laser is projected into the calibration box and projected to the target, the target will reflect the echo laser. The laser radar system receives the echo laser, and calculates the distance measurement value between the laser radar system and the target. A calibration of the lidar system. During the calibration process, both the outgoing laser and echo laser propagate in the calibration box. The calibration box is used to establish the calibration environment. Therefore, the above-mentioned lidar system ranging is carried out in the calibration environment, which reduces the influence of environmental factors. For example, The calibration box can shield the ambient light and so on. In this embodiment, the lidar system uses the calibration box to perform N ranges in sequence, and the emitted laser of each range is delayed by a different time, and N (N≥1 and N is an integer) different range values are obtained; due to the laser The radar system calculates the distance of the target object by the flight time of the emitted laser, so the flight time of the emitted laser can be directly converted into the distance; the emitted laser of each range measurement is delayed by a different time, which is equivalent to flying a different distance and then shooting direction after the emitted laser is emitted Calibrate the box to get the distance measurement values corresponding to N different actual values; the actual value of each distance measurement is the sum of the distance corresponding to the delay time and the length of the calibration box; so there is no need to really change the actual spatial distance between the lidar system and the target , You can simulate the different distances between the lidar system and the target. As the delay time increases, the actual value of the simulation also increases. The delay time can be realized by the delay line, and the different delay time can make the outgoing laser pass through the delay line of different length. Due to the error, the distance measurement value obtained from each distance measurement has a certain difference with its corresponding actual value, which is not completely equal; therefore, N calibration matrices can be obtained according to the difference between the N distance measurement values and the corresponding actual values.

Step S140: Obtain a calibration matrix of the measured value, and perform calibration compensation on the measured value.

What needs to be distinguished is that the measured value refers to the range measurement distance of the target obtained during the range measurement process of the lidar system in actual application, and the range measurement value refers to the calibration matrix obtained by the lidar system during N times of range measurement. The ranging distance of the target obtained during the calibration process; the calibration process needs to be carried out in the calibration box.

Through the calibration matrix corresponding to the measured value, the measured value is calibrated and compensated, the error in the measured value is corrected, and the measured value is closer to the corresponding actual value, thereby improving the ranging accuracy of the lidar system.

The calibration method of the lidar system mentioned above delays the emitted lasers of multiple ranging for different times to simulate the actual value of the different distances between the lidar system and the target, so that the measurement corresponding to the actual values of N different distances can be obtained. Distance value, and then obtain N calibration matrices; and according to the calibration matrix to calibrate the measured values in practical applications; thereby improving the accuracy of the measured values obtained by the lidar system in practical applications. In the process of obtaining the calibration matrix, there is no need to change the actual value of the distance between the lidar system and the target, so there is no need for a huge slide rail and a larger calibration space, the required resource consumption is less, and the operation process is simpler; and Since the actual value of the distance between the lidar system and the target includes the distance corresponding to the delay time and the length of the calibration box, the outgoing laser does not actually fly through the space of the same distance, and the environment has little interference and loss of the outgoing laser and echo laser, so Even when the detection distance of the lidar system is long, it can still accurately measure the distance by simulating the actual value of the distance, so as to obtain an accurate calibration matrix and improve the accuracy of the measurement value calibration.

In one of the embodiments, the lidar system is set at one end of the calibration box, and the target is set at the other end of the calibration box. The outgoing laser emitted by the lidar system is delayed by a delay line for a period of time and then enters from one end of the calibration box, and shoots toward The target on the other end of the calibration box is reflected by the target and returns to the echo laser, which is received by the lidar system.

The outer surface of the calibration box is set to black to shield the ambient light, and there is a light-absorbing material inside to reduce the interference of the echo laser caused by multiple reflections of the outgoing laser on the inner surface of the calibration box. In this way, the calibration box is used to establish the calibration environment, so that the interference of environmental factors is avoided during the calibration process of the lidar system. The shape, structure, and size of the calibration box can be set according to actual needs.

Exemplarily, referring to FIG. 2, the calibration box 210 includes a first surface 212 and a second surface 214 opposite thereto. The target 220 is disposed on the first surface 212 and the lidar system 230 is disposed on the second surface 214. That is, the lidar system 230 is disposed on one end of the calibration box 210, and the target 220 is disposed on the other end of the calibration box 210. A through hole is opened on the second surface 214, and the target 220 is arranged opposite to the through hole. The laser beam emitted by the laser radar system enters the calibration box 210 through the through hole of the calibration box 210 and is directed to the target 220 inside the calibration box 210. . The size of the through hole can be designed according to the aperture size of the optical lens at the transmitting end of the lidar system 230.

In one of the embodiments, the number of the target 220 is at least one; when the number of the target 220 is greater than one, the reflectivity of each target 220 is different; the target 220 in the calibration box 210 can be exchanged for different Reflectivity objects are calibrated. For example, a white paper with known reflectivity is attached to the first surface 212 as the target 220, and N calibration matrices of the target 220 are obtained after N times of distance measurement; the measurement of the target 220 with different reflectivity is required When the value is calibrated and compensated, it is only necessary to replace it with another reflectance target 220, which is easy to operate.

Specifically, the lidar system 230 includes a transmitting device 232 and a receiving device 234. The connection between the calibration box 210 and the lidar system 230 is provided with a suitable combination structure, so that the outgoing laser emitted by the transmitter 232 can enter the calibration box 210 to reach the target 220, and the echo laser returned after being reflected by the target 220 can be received The device 234 receives. Specifically, as shown in FIG. 2, the second side 214 of the calibration box 210 has a through hole, the launching device 232 is aligned with the through hole, and the outgoing laser emitted by the launching device 232 enters the calibration box 210 through the through hole; the calibration box 210 A light path pipe 216 is arranged inside, and a receiving device 234 is arranged at the end of the light path pipe 216. The echo laser passes through the light path pipe 216 during propagation and is finally received by the receiving device 234. Wherein, the echo laser can be received by the receiving device 234 after being reflected multiple times in the light path pipe 216, or it can be reflected from the target 220 and directly pass through the light path pipe 216 and be received by the receiving device 234. Optionally, the light path pipe 216 is a black plastic pipe, and its length can be 1/2, 2/3, 3/4, etc. of the length of the calibration box 210, and it can be set as required.

Among them, the transmitting device 232 and the receiving device 234 may be arranged side by side up and down, side by side, or the transmitting device 232 arranged around the receiving device 234. The opening position of the through hole on the second surface 214 needs to match the emitting device 232 to ensure that enough photons in the emitted laser light emitted by the emitting device 232 reach the end of the calibration box 210 without being blocked, that is, the target in the calibration box 210 220 places. It should be noted that if the outgoing laser emitted by the transmitter 232 is aligned with a specific angle direction, the design of the calibration box 210 does not need to extend the size according to the specific angle direction, because the calibration compensation of the measured value has nothing to do with the field of view angle of the lidar system 230 Therefore, it is also possible to separately design a set of emission devices 232 for calibration according to the number of light sources of the emission devices 232; for example, all the light sources of the emission devices 232 are installed on the same plane.

The above-mentioned limitation on the calibration box 210 and the lidar system 230 is only one of the reference examples. This application does not impose any special restrictions on the internal structure of the calibration box 210 and the lidar system 230, but it is necessary to ensure the lidar system 230 There are enough photons in the outgoing laser light to reach the target 220 on the first surface 212 without being blocked, and the lidar system 230 can receive enough photons of the echo laser reflected by the target 220.

Fig. 3 is a specific flow chart of a method for calibrating a lidar system in an embodiment. As shown in Figure 3, in step S120, the lidar system uses the calibration box to perform N range finding times in sequence, and the outgoing laser of each range finding is delayed by a different time to obtain N range finding values at different distances, and according to the range finding value and The difference of the corresponding actual values obtains N calibration matrices, including: step S320, the lidar system executes N range finding in sequence, the outgoing laser of the i-th range finding passes through (i-1) delay lines and then shoots to the calibration box, Obtain the distance measurement value at the distance of (i-1)*L+K, and obtain the calibration matrix according to the difference between the distance measurement value and (i-1)*L+K. Among them, i=1, 2,...,N, L is the distance corresponding to the delay line, and K is the length of the calibration box.

When calculating the calibration matrix, the calibration matrix is obtained according to the difference between the ranging value and (i-1)*L+K. Exemplarily, the lidar system 230 performs multiple calibrations on the actual value of the same distance to obtain multiple ranging values corresponding to the actual value of the same distance; respectively calculate the difference between these ranging value and the actual value, and The average value of these differences is calculated as the calibration matrix; this improves the accuracy of the obtained calibration matrix.

The smaller the distance L corresponding to the delay line, the smaller the difference between the actual values of the N times of ranging within the range of the lidar system 230 (that is, the smaller the actual value step of the N times of ranging), and the resulting calibration The more matrices, the more accurate the calibration of the measurement value of the lidar system 230.

In one of the embodiments, the length distance K of the calibration box may be equal to the distance L corresponding to the delay line. The outgoing laser from the i-th distance measurement passes through the (i-1) delay line and then hits the calibration box to obtain the distance measurement value at the distance i*L, and obtain the calibration matrix according to the difference between the distance measurement value and i*L. Simplify the calculation process of obtaining the calibration matrix, reduce the amount of calculation, and improve the calibration efficiency.

It should be noted that, as shown in FIG. 2, the transmitting device 232 and the receiving device 234 are not located at the same position, and the optical paths of the outgoing laser and the echo laser are not on the same axis, and there is a certain angle between the optical paths. The sum of the distance between the light-emitting surface of the transmitting device 232 and the target 220 and the distance of the echo laser from the target 220 to the light-receiving surface of the receiving device 234 is the actual distance traveled by photons in the calibration box 210. In order to simplify the calculation process of the above calibration matrix, half of the actual distance traveled by the photon in the calibration box 210 is equal to the distance L corresponding to the delay line. At this time, the length of the calibration box is not equal to the distance L corresponding to the delay line. However, the difference between K and L is often very small. In order to simplify the calibration device, it is usually set as the length of the calibration box and the distance K is equal to the distance L corresponding to the delay line.

Specifically, referring to FIG. 4, the lidar system 230 includes a transmitting device 232, a receiving device 234, a delay line 235, and a clock device 236; the clock device 236 sends a clock signal to the delay line 235 and the receiving device 234; the delay line 235 is based on the i-th After the delay time required for the second ranging is delayed, the clock signal is sent to the transmitter 232; the transmitter 232 receives the clock signal sent by the delay line, and emits the laser. After the outgoing laser enters the calibration box, it is reflected by the target 220 and then returns to the echo laser. The echo laser is received by the receiving device 234, and the receiving device 234 calculates the time difference between transmission and reception according to the clock signal sent by the clock device 236, thereby calculating the ranging value. The delay line 235 includes N delay quantities τ, the delay quantity τ=L/c, where c is the speed of light; after the clock signal is sent to the delay line 235, the i-th ranging requires a delay time (i-1)*τ , The clock signal is delayed and then output outward; the delay line includes N delay blocks 237 and gates 238, each delay block 237 is delayed by a delay amount τ, delay time τ,..., N*τ The clock signals are all sent to the gate 238, and the gate 238 selects and outputs the corresponding delay time (i-1)*τ according to the delay time required for the current ranging. For example, for the fifth ranging, the delay line delay time is 4τ, and the corresponding actual ranging value is 4L+K. After obtaining the fifth ranging value, compare it with the actual value. If the length distance K of the calibration box is equal to the distance L corresponding to the delay line, the actual value of the fifth distance measurement is 5L. The transmitter 232 includes a transmitter driver 2322 and a transmitter 2324. After the transmitter driver 2322 receives the clock signal, it sends a driving signal to the transmitter 2324, which drives the transmitter 2324 to emit laser light. In this embodiment, there is no need to increase the distance between the lidar system 230 and the target 220 during the calibration process, only the delay time needs to be increased.

Further, referring to FIG. 3, step S140, obtaining a calibration matrix of the measurement value, and performing calibration compensation on the measurement value, includes:

In step S342, when the measured value M≤(N-1)*L+K, the calibration matrix corresponding to the measured value is used to calibrate and compensate the measured value.

When the measured value is within the range of the calibration process, the calibration matrix corresponding to the measured value can be directly obtained.

Specifically, referring to FIG. 5, step S342 includes:

In step S510, a calibration curve is generated by fitting the distance measurement values of the N times of distance measurement and the corresponding calibration matrix.

In one of the embodiments, referring to FIG. 6, the distance measurement values of N times of distance measurement and the corresponding calibration matrix in the calibration process are fitted to obtain a calibration curve. Use the calibration matrix as the Y axis and the measured value as the X axis to establish a coordinate system, and draw the N distance measurement values (corresponding to the X axis) during the calibration process and the corresponding calibration matrix in the coordinate system, which will be formed on the coordinate system Some discrete points. Fit these discrete points to get a smooth and coherent calibration curve. Specifically, the least squares method can be used for fitting. According to the calibration curve, the calibration matrix corresponding to any measured value within the range can be obtained.

Step S520: Obtain a calibration matrix corresponding to the measured value according to the calibration curve.

In step S530, the obtained calibration matrix is used to calibrate and compensate the measured value.

Through the calibration curve, input the measurement value within the range to get the corresponding calibration matrix. The obtained calibration matrix is used to calibrate and compensate the measured value. For example, the measurement value can be summed with the corresponding calibration matrix to obtain the calibrated measurement value.

In step S344, when the measured value M>(N-1)*L+K, the calibration matrix corresponding to the designated distance measurement value is used to calibrate and compensate the measured value.

When the measurement value exceeds the range of the calibration process, the calibration matrix corresponding to the specified distance measurement value corresponding to the measurement value can be called. Due to the complexity of the hardware design, the size of the calibration box, the cost of calibration and other factors, the distance L corresponding to the delay line and the number of calibrations N cannot be set to be very large. Therefore, in the actual application of the lidar system, the distance L The detection distance may be greater than the calibrated range.

Specifically, referring to FIG. 7, step S344 includes:

Step S710: Obtain a specified distance measurement value according to the measurement value.

The calculation formula of the specified ranging value corresponding to the measured value is:

X=M％[(N-1)*L+K]

Among them, X is the designated ranging value, and% is the remainder operation.

The specified distance measurement value X calculated by this formula is within the range of the calibration range, that is, X≤(N-1)*L+K.

Step S720: Obtain a calibration matrix corresponding to the specified distance measurement value.

Since the specified ranging value is within the range of the calibration process, the N calibration matrices obtained in the calibration process can be called, and there are many ways to obtain the calibration matrix. Exemplarily, the calibration matrix corresponding to the specified distance measurement value X can be obtained from the calibration curve.

In step S730, the obtained calibration matrix is used to calibrate and compensate the measured value.

Call the calibration matrix corresponding to the specified distance measurement value X, and use the obtained calibration matrix to calibrate and compensate the measured value.

By calling the calibration matrix corresponding to the specified ranging value to calibrate and compensate the measurement value exceeding the calibration range, the hardware setting of the calibration process can be simplified, the size of the calibration box and the number of ranging can be controlled, the calibration process is simplified, and the cost is controllable.

Further, the method of obtaining the calibration matrix corresponding to the specified distance measurement value may also be: when the specified distance measurement value is X=(j-1)*L+K, the calibration matrix corresponding to the distance measurement value is the specified distance measurement The calibration matrix corresponding to the value; when the specified ranging value X satisfies (j-1)*L+K＜X＜j*L+K, by fitting the calibration matrix at the distance of (j-1)*L+K and The calibration matrix at the distance of j*L+K to obtain the calibration matrix corresponding to the specified distance measurement value. Where j = 1, 2, ..., N.

Due to the N times of ranging in the calibration process, N discrete points are obtained in the coordinate system of the measurement value-calibration matrix; therefore, when the specified ranging value X is equal to the ranging value in the calibration process, the measurement is directly called The calibration matrix obtained during the distance calibration process is sufficient; when the specified distance measurement value X is between two adjacent distance measurement values in the calibration process, the corresponding calibration matrix can be obtained by fitting; optional Yes, the points in the coordinate system corresponding to the two adjacent distance measurement values can be fitted by linear difference.

In this embodiment, if the measured value is within or outside the calibration range, the calibration matrix can be accurately obtained to calibrate and compensate the measured value, which effectively improves the accuracy of the measured value of the lidar system; at the same time, the calibration compensation of the measured value is not Limited by the range of the calibration process, it can be effectively calibrated and compensated even when the measured value is large to ensure the accuracy of detection; in addition, the measurement value outside the calibration range can be calibrated corresponding to the specified range value in the calibration range The matrix is calibrated and compensated, so there is no need to increase the number of calibrations N indefinitely during the calibration process, the calibration process is simpler and the cost is lower.

In one of the embodiments, as shown in FIG. 8, FIG. 8 is a flowchart of a calibration method of a lidar system. In addition to the steps S120 and S140 described above, the calibration method of the lidar system may also include step S110, step S150 to step S160.

Step S110, preheat the lidar system.

For example, you can turn on the lidar system for pre-calibration first, but the calibration data at this time is invalid, and will not be used in the subsequent steps, or you can just turn on the lidar system without calibration. Because the characteristics of the outgoing laser emitted by the launcher of the lidar system have a lot to do with its temperature; in the initial stage of the operation of the emitting device, the temperature will continue to rise as the working time increases. At this time, the characteristics of the outgoing laser are also constantly changing with the increase in temperature. ; After the launcher works for a period of time, the temperature reaches equilibrium, and the characteristics of the emitted laser are also stable. Therefore, preheating the lidar system can enable the transmitter to reach a stable state, thereby improving the accuracy of the calibration matrix obtained during the calibration process.

Step S150: Obtain a temperature compensation coefficient according to the temperature of the lidar system.

In step S160, the temperature compensation coefficient is calibrated to compensate the measured value.

Specifically, in the ranging process during the actual application of the lidar system, the operating temperature of the lidar system fluctuates due to the difference in the surrounding environment. Therefore, the influence of the temperature factor needs to be considered when calibrating and compensating the measured value. Through experience, the temperature compensation coefficient corresponding to the temperature of the lidar system can be obtained; the lidar system can obtain the corresponding temperature compensation coefficient by looking up the table. The temperature of the lidar system can be obtained by installing a temperature sensor in the lidar system. The temperature sensor can be arranged at one or more positions of the transmitting device, the receiving device, the control device, the gap in the lidar system housing, and so on. The output value can be obtained by multiplying the compensation measurement value after calibration and compensation by the calibration matrix by the temperature compensation coefficient. In this embodiment, the temperature compensation coefficient is introduced to further correct the measured value, which improves the calibration accuracy and improves the accuracy of the measured value of the lidar system.

In one of the embodiments, during the calibration process, the power of the emitted laser of the lidar system is controlled by the hardware system, so that the power of the emitted laser decreases as the delay time increases.

In the actual ranging scenario, there will be unavoidable loss due to the emitted laser flying in the environment. In this embodiment, the power of the emitted laser is gradually reduced as the flight distance increases, and the energy loss of the photons in the emitted laser and echo laser in the actual application scenario is simulated, so that the calibration process is closer to the actual ranging scenario, and the acquisition is improved. The accuracy of the calibration matrix improves the accuracy of the calibration of the measured value. Exemplarily, the power of the emitted laser and the delay time are in a negative quadratic relationship; since the actual value of the distance is related to the delay time during the calibration process, it increases with the increase of the delay time, and the power of the emitted laser increases with the flight distance. The reduction is in accordance with the law of energy loss in the actual ranging scenario, the accuracy of the obtained calibration matrix is improved, and the accuracy of the calibration of the measured value is improved.

The application also provides a calibration device for the lidar system. Fig. 9 is a structural block diagram of a calibration device of a lidar system in an embodiment. As shown in FIG. 9, the calibration device 900 of the lidar system includes a processing module 910 and a calibration module 920, which are used to implement the aforementioned calibration method of the lidar system.

The processing module 910 is used to control the lidar system to use the calibration box to perform N range measurements in sequence. The emitted laser of each range measurement is delayed by a different time to obtain the range measurement values at N different distances, and according to the range measurement value and the corresponding actual The difference in value results in N calibration matrices; where N≥1 and N is an integer.

The calibration module 920 is used to obtain a calibration matrix of the measured value, and perform calibration compensation on the measured value.

The calibration device 900 of the lidar system described above includes a processing module 910 and a calibration module 920. The processing module 910 controls the lidar system to use the calibration box to perform N range measurements, and delays the emitted lasers of multiple ranging for different times to simulate lidar The actual values of different distances between the system and the target object, so that the distance measurement values corresponding to the actual values of N different distances can be obtained, and then N calibration matrices are obtained according to the difference between the distance measurement value and the corresponding actual value; calibration module 920 According to the calibration matrix, the measurement value in the actual application is calibrated, thereby improving the accuracy of the measurement value obtained by the lidar system in the actual application. In the process of obtaining the calibration matrix, there is no need to change the actual value of the distance between the lidar system and the target, so there is no need for a huge slide rail and a larger calibration space, the required resource consumption is less, and the operation process is simpler; and Since the actual value of the distance between the lidar system and the target includes the distance corresponding to the delay time and the length of the calibration box, the outgoing laser does not actually fly through the space of the same distance, and the environment has less interference and loss of the outgoing laser and echo laser, so Even when the detection distance of the lidar system is long, it can still accurately measure the distance by simulating the actual value of the distance, so as to obtain an accurate calibration matrix and improve the accuracy of the measurement value calibration.

In one of the embodiments, the calibration box is used to establish a calibration environment, the lidar system is set at one end of the calibration box, and the target is set at the other end of the calibration box. The processing module 910 controls the lidar system to perform N ranges in sequence, and the outgoing laser from the i-th range passes through the (i-1) delay line and then shoots to the calibration box to obtain the distance at (i-1)*L+K The distance measurement value, and the calibration matrix is obtained according to the difference between the distance measurement value and (i-1)*L+K; where i=1, 2,...,N, L is the distance corresponding to the delay line, and K is the calibration box Length distance.

In one of the embodiments, when the measured value M≤(N-1)*L+K, the calibration module 920 uses the calibration matrix corresponding to the measured value to calibrate and compensate the measured value; when the measured value M>(N-1) *When L+K, the calibration module uses the calibration matrix corresponding to the specified distance measurement value to calibrate and compensate the measured value.

In one of the embodiments, when the measured value M≤(N-1)*L+K, the calibration module 920 is configured to generate a calibration curve according to the distance measurement values of N times of distance measurement and the corresponding calibration matrix; Curve, obtain the calibration matrix corresponding to the measured value; use the obtained calibration matrix to calibrate and compensate the measured value.

In one of the embodiments, when the measured value M>(N-1)*L+K, the calibration module 920 is configured to obtain the specified ranging value according to the measured value; obtain the calibration matrix corresponding to the specified ranging value; use the obtained The calibration matrix calibrates and compensates the measured value.

In one of the embodiments, the end of the calibration box provided with the target is provided with a through hole, the inside of the calibration box is provided with a light path pipe connected to the lidar system, and the inner surface of the calibration box is provided with a light-absorbing material.

In one of the embodiments, the calculation formula of the specified ranging value corresponding to the measured value is:

X=M％[(N-1)*L+K]

Among them, X is the designated ranging value.

In one of the embodiments, when the specified ranging value is X=(j-1)*L+K, the calibration matrix corresponding to the ranging value is the calibration matrix corresponding to the specified ranging value; when the specified ranging value X When (j-1)*L+K＜X＜j*L+K is satisfied, the calibration matrix at the distance (j-1)*L+K and the calibration matrix at the distance j*L+K are fitted by linear interpolation , Get the calibration matrix corresponding to the specified distance measurement value; where j=1, 2,...,N.

In one of the embodiments, the distance L corresponding to the delay line is equal to the length distance K of the calibration box.

In one of the embodiments, the number of the target is at least one; when the number of the target is more than one, the reflectivity of the target is different.

In one of the embodiments, the processing device 910 is also used to control the power of the laser light emitted by the laser radar system through a hardware system, so that the power of the laser light decreases as the delay time increases.

In one of the embodiments, the power of the emitted laser light and the delay time have a negative power-of-two relationship.

In one of the embodiments, the calibration module 920 sums the measurement value with the corresponding calibration matrix to obtain the calibrated measurement value.

In one of the embodiments, the calibration module 920 is further configured to obtain the temperature compensation coefficient according to the temperature of the lidar system; calibrate the temperature compensation coefficient to compensate the measured value.

In one of the embodiments, the processing module 910 is also used to preheat the lidar system.

It should be noted that each module in the calibration device 900 of the lidar system described above can be implemented in whole or in part by software, hardware, and a combination thereof. Each module may be embedded in the processor of the server in the form of hardware or independent of the server, or stored in the memory of the server in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

The application also provides a distance measuring device. The distance measuring device includes a memory and a processor, and a computer program that can run on the processor is stored. The processor implements the steps of the method in any of the above embodiments when the computer program is executed.

The application also provides a storage medium on which a computer program is stored. When the computer program is executed by the processor, the steps of any of the above methods are realized.

A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage. In the medium, when the computer program is executed, it may include the procedures of the above-mentioned method embodiments. Wherein, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and/or volatile memory. Non-volatile memory may include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not a limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous chain Channel (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

It can be understood that the dimensions of all the drawings in this case do not represent actual proportions, and are merely schematic diagrams.

The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, All should be considered as the scope of this specification.

The above-mentioned embodiments only express several implementation manners of the present application, and their description is relatively specific and detailed, but they should not be understood as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of this application, several modifications and improvements can be made, and these all fall within the protection scope of this application. Therefore, the scope of protection of the patent of this application shall be subject to the appended claims.

Claims

A calibration method of lidar system, the method steps are as follows:

The lidar system uses the calibration box to perform N ranges in sequence, and the emitted laser of each range is delayed by a different time to obtain the range values at N different distances, and obtain the range values according to the difference between the range value and the corresponding actual value N calibration matrices; where N≥1 and N is an integer;

The calibration matrix of the measurement value is obtained, and the measurement value is calibrated and compensated.
The calibration method according to claim 1, wherein the lidar system is set at one end of the calibration box, the target is set at the other end of the calibration box, and the lidar system uses the calibration box to execute N In the second ranging, the emitted laser of each ranging is delayed for a different time, and N ranging values at different distances are obtained, and N calibration matrices are obtained according to the difference between the ranging value and the corresponding actual value, including:

The lidar system executes N ranges in sequence, and the outgoing laser from the i-th range passes through (i-1) delay lines and then shoots toward the calibration box to obtain the range at (i-1)*L+K distance Value, and obtain the calibration matrix according to the difference between the ranging value and (i-1)*L+K; where i=1, 2,...,N, L is the distance corresponding to the delay line, K Is the length of the calibration box.
The calibration method according to claim 2, characterized in that said obtaining the calibration matrix of the measurement value, calibrating and compensating the measurement value, comprises:

When the measured value M≤(N-1)*L+K, use the calibration matrix corresponding to the measured value to calibrate and compensate the measured value;

When the measured value M>(N-1)*L+K, the calibration matrix corresponding to the specified distance measurement value is used to calibrate and compensate the measured value.
The calibration method according to claim 3, wherein when the measured value M≤(N-1)*L+K, the calibration matrix corresponding to the measured value is used to calibrate the measured value Compensation, including:

Fitting and generating a calibration curve according to the distance measurement values of the N times of distance measurement and the corresponding calibration matrix;

Obtaining the calibration matrix corresponding to the measured value according to the calibration curve;

The obtained calibration matrix is used to calibrate and compensate the measured value.
The calibration method according to claim 3, wherein when the measurement value M>(N-1)*L+K, the calibration matrix corresponding to the specified distance measurement value is used to calibrate the measurement value Compensation, including:

Acquiring the specified distance measurement value according to the measurement value;

Acquiring the calibration matrix corresponding to the specified ranging value;

The obtained calibration matrix is used to calibrate and compensate the measured value.
The calibration method according to claim 5, wherein the obtaining the designated distance measurement value according to the measurement value is specifically:

The calculation formula of the designated ranging value corresponding to the measured value is:

X=M％[(N-1)*L+K]

Wherein, X is the specified ranging value.
The calibration method according to claim 5, wherein the obtaining the calibration matrix corresponding to the designated ranging value comprises:

When the specified ranging value is X=(j-1)*L+K, the calibration matrix corresponding to the ranging value is the calibration matrix corresponding to the specified ranging value;

When the specified ranging value X satisfies (j-1)*L+K<X<j*L+K, the calibration matrix at the distance (j-1)*L+K and j* The calibration matrix at the distance of L+K, obtaining the calibration matrix corresponding to the specified distance measurement value;

Where j = 1, 2, ..., N.
The calibration method according to claim 2, wherein the distance L corresponding to the delay line is equal to the length distance K of the calibration box.
The calibration method according to claim 2, wherein the number of the target is at least one; when the number of the target is more than one, the reflectivity of the target is different.
The calibration method according to claim 2, further comprising:

The power of the laser light emitted by the laser radar system is controlled by a hardware system, so that the power of the laser light decreases as the delay time increases.
The calibration method according to claim 10, wherein the power of the emitted laser light and the delay time have a negative power-of-two relationship.
The calibration method according to claim 2, characterized in that said obtaining the calibration matrix of the measurement value, performing calibration compensation on the measurement value, further comprises:

The measurement value is summed with the corresponding calibration matrix to obtain the calibrated measurement value.
The calibration method according to claim 1, further comprising:

Obtain the temperature compensation coefficient according to the temperature of the lidar system;

The temperature compensation coefficient is calibrated to compensate the measured value.
The calibration method according to claim 1, wherein the lidar system uses the calibration box to perform N ranges in sequence, and the outgoing laser of each range is delayed for a different time to obtain N range values at different distances , And before obtaining the calibration matrix according to the difference between the ranging value and the corresponding actual value, it also includes:

Warm up the lidar system.
A calibration device of a lidar system includes:

The processing module is used to control the lidar system to use the calibration box to perform N range finding times in sequence. The emitted laser of each range finding is delayed by a different time to obtain N range finding values at different distances, and according to the range finding value and the corresponding N calibration matrices are obtained by the difference of the actual values of, where N≥1 and N is an integer;

The calibration module is used to obtain the calibration matrix of the measured value, and perform calibration compensation on the measured value.
The calibration device according to claim 15, wherein the calibration box is used to establish a calibration environment, the lidar system is set at one end of the calibration box, and the target is set at the other end of the calibration box;

The processing module controls the lidar system to perform N range finding in sequence, and the outgoing laser of the i-th range finding passes through the (i-1) delay line and then shoots toward the calibration box to obtain (i-1)*L+K The distance measurement value at the distance, and the calibration matrix is obtained according to the difference between the distance measurement value and (i-1)*L+K; where i=1, 2,...,N, L is the delay line Corresponding distance, K is the length of the calibration box.
The calibration device according to claim 16, wherein when the measurement value M≤(N-1)*L+K, the calibration module uses the calibration matrix corresponding to the measurement value to compare the measurement value Perform calibration compensation; when the measurement value M>(N-1)*L+K, the calibration module uses a calibration matrix corresponding to the specified distance measurement value to perform calibration compensation on the measurement value.
The calibration device according to claim 16, wherein the end of the calibration box provided with the target is provided with a through hole, and the inside of the calibration box is provided with a light path pipe connected to the lidar system, The inner surface of the calibration box is provided with a light-absorbing material.
A storage medium on which a computer program is stored, and when the computer program is executed by a processor, the steps of the calibration method according to any one of claims 1 to 14 are realized.
A distance measuring device, comprising a memory and a processor; the processor stores a computer program that can run on the processor, and when the processor executes the computer program, it implements any one of claims 1-14 The steps of the calibration method.