Laser radar ranging method and ranging system

Abstract

The invention discloses a laser radar ranging method, which belongs to the technical field of laser ranging, and comprises the following steps: S1, a laser transmitting module transmits dTOF pulse signals for multiple times, and transmits a phase pulse signal once every k times of dTOF pulse signals; s2, weighted averaging is carried out on measured values of dTOF pulse signal measurement for a times before and after the ith emission phase pulse signal measurement; s3, respectively calculating the difference between the measured values of the i-th and (i + 1)-th transmitted phase pulse signals and the corresponding weighted averages as correction values; and S4, correcting the measured value of the dTOF pulse signal measurement between the ith correction value and the (i + 1) th correction value by using the ith correction value and the (i + 1) th correction value to obtain an output result. The dTOF measurement value is compensated by using the phase measurement value, that is, high-speed and low-precision dTOF measurement is compensated by using low-speed and high-precision phase measurement, so that the dTOF high-speed distance measurement precision can be improved, and the system error of a dTOF distance measurement system is reduced.

Description

Technical Field

[0001] The present invention relates to the field of laser ranging, and in particular to a laser radar ranging method and ranging system. Background Art

[0002] With the rapid development of science and technology, LiDAR plays a key role in many fields such as autonomous driving, intelligent robots, surveying and mapping, industrial inspection, etc. Its core function is to accurately measure the distance between the target object and itself, and provide basic data for subsequent tasks such as environmental perception, path planning, and object recognition.

[0003] LiDAR ranging methods include pulse ranging, phase ranging and triangulation ranging. Pulse ranging is the most widely used method. The system emits a narrow pulse laser beam to the target and calculates the distance by measuring the time between the emission and reception of the reflected pulse. The phase ranging method determines the distance by emitting a continuous laser beam modulated by intensity and measuring the phase difference between the transmitted and received signals. The phase method has advantages in ranging accuracy, but because it requires a large power to emit a continuous laser beam, the ranging range is relatively short. The triangulation ranging method calculates the distance through the angular relationship between the emitted light and the received light and the known structural parameters.

[0004] The pulse ranging method includes the direct time-of-flight (dToF) ranging method, which measures the time difference from the emission to the reception of the laser pulse and calculates the distance based on the principle of the constancy of the speed of light. The dTOF ranging principle is simple and direct, easy to understand and implement, the system architecture is relatively simple, and the hardware cost is controllable to a certain extent. In addition, this method has a fast response speed, can obtain target distance information in real time, has a high distance resolution, and can accurately distinguish the position changes of the target object when measuring at close range.

[0005] However, dToF has extremely high requirements for time measurement accuracy. Taking centimeter-level ranging accuracy as an example, the required time measurement resolution must reach the picosecond level. Current technology faces problems such as high cost, high power consumption, and device performance bottlenecks when achieving such high-precision time measurement. Moreover, dToF is seriously interfered by ambient light. Interference light generated by natural light or other light sources can easily be mistakenly received by the detector. In a strong light environment, the echo signal may be submerged, resulting in a significant increase in ranging errors or even inability to accurately measure distance. In addition, as the distance to the target increases, the intensity of the laser echo signal decays rapidly, the accuracy drops sharply during long-distance measurement, and the effective measurement range is limited.

[0006] Therefore, in practical applications, a single dTOF ranging method is difficult to meet the needs of complex and changing scenarios, and its high-speed ranging accuracy needs to be compensated to reduce the system error of dTOF measurement. Summary of the invention

[0007] In order to solve the problems of large system error and low ranging accuracy in the dTOF ranging method, the present invention aims to provide a laser radar ranging method and a ranging system.

[0008] To achieve the above object, the present invention first provides a laser radar ranging method, comprising the following steps:

[0009] S1: The laser emission module emits dTOF pulse signals multiple times, and emits a phase pulse signal after every k dTOF pulse signals;

[0010] S2, taking a weighted average of the measurement values ​​of the a dTOF pulse signal measurements before and after the i-th transmission phase pulse signal measurement;

[0011] S3, respectively calculating the difference between the measured value of the i-th and (i+1)-th transmitted phase pulse signals and their corresponding weighted averages as correction values;

[0012] S4, using the correction values ​​of the i-th and (i+1)-th times to correct the measurement values ​​of the dTOF pulse signal measurement in between to obtain an output result.

[0013] In one embodiment, in step S2, the measured value of the transmitted iTOF pulse signal for ranging is recorded as M i , where i is the number of times the iTOF pulse signal is transmitted, and the measured value of the k-th dTOF signal ranging between the i-th and (i+1)-th iTOF pulse signals is recorded as N ki , N ki+1 , N ki+2 …N ki+k-2 , N ki+k-1 ; The measured value of the k-th dTOF signal ranging between the (i-1)th and i-th iTOF pulse signals is recorded as N ki-1 , N ki-2 …N ki-k .

[0014] In one embodiment, the measured values ​​of the a times of dTOF pulse signal measurement before and after the i-th emission iTOF pulse signal measurement are weighted averaged, and the average is calculated according to formula (1):

[0015]

[0016] Among them, W x is the weighting coefficient.

[0017] In one embodiment, 0≤a≤k / 2, 0≤W x ≤0.5 and meets And W 0 To W a-1 Decrease in sequence.

[0018] In one embodiment, the method of calculating the difference between the measured value of the i-th and (i+1)-th transmitted iTOF pulse signals and their corresponding weighted averages as the correction value in step S3 is respectively formula (2) and formula (3):

[0019]

[0020] Among them, E i is the difference between the measured value of the i-th emission iTOF pulse signal and its corresponding weighted average; E i+1 It is the difference between the measured value of the (i+1)th transmitted iTOF pulse signal and its corresponding weighted average.

[0021] In one embodiment, the calculation method of step S4 is shown in formula (4):

[0022]

[0023] Among them, 0≤x≤k-1.

[0024] In one embodiment, the phase pulse signal is an iTOF pulse signal.

[0025] Secondly, the present invention also provides a laser radar ranging system, which uses any of the ranging methods described above to measure distance, including a control module, a laser emitting module, a signal receiving module and a signal processing module.

[0026] In one embodiment, the laser emission module switches between emitting a dTOF pulse signal and emitting a phase pulse signal.

[0027] In one embodiment, the control module controls the laser emitting module to generate a dTOF pulse signal or a phase pulse signal, the signal receiving module receives the signal emitted by the laser emitting module, which is projected onto the object to be measured and reflected by the object to be measured, and the signal processing module processes the signal received by the signal receiving module to obtain a laser ranging result.

[0028] Beneficial effect: The present invention uses phase measurement values ​​to compensate for dToF measurement values, that is, uses low-speed and high-precision phase measurement to compensate for high-speed and low-precision dTOF measurement, which can improve the accuracy of dTOF high-speed ranging and reduce the system error of the dTOF ranging system.

[0029] In order to make the above features and advantages of the invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a module schematic diagram of the laser radar ranging system in the present invention.

[0031] Figure 2 It is a flow chart of the laser radar ranging method in the present invention.

[0032] Figure 3 It is a schematic diagram of marking the measured values ​​of iTOF pulse signal ranging and the measured values ​​of emitting dTOF signal ranging in the laser radar ranging method of the present invention.

[0033] Figure 4 It is a schematic diagram of the marking of the weighted average of step S2 in the laser radar ranging method of the present invention. DETAILED DESCRIPTION

[0034] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, the laser radar ranging system used in the present invention includes a control module 10, a laser emitting module 20, a signal receiving module 30 and a signal processing module 40. The laser emitting module 20 can be a semiconductor laser emitter, a solid laser emitter, or other types of laser emitters, which are only used as examples in the present invention and are not limited. The laser emitting module 20 can switch between dTOF mode and phase mode. The control module 10 can control the laser emitting module 20 to generate pulse signals suitable for dTOF mode and phase mode, respectively, and the pulse signals emitted by the laser emitting module 20 are mostly lasers with a certain wavelength in ranging applications. When the laser emitted by the laser emitting module 20 is projected onto the object to be measured and reflected by the object to be measured to the signal receiving module 30, the signal processing module 40 processes the signal received by the signal receiving module 30 to obtain a laser ranging result.

[0036] like Figure 2 As shown, the present invention provides a laser radar ranging method, which uses phase ranging to compensate for dTOF ranging, including the following steps:

[0037] S1, the laser emission module emits dTOF pulse signals multiple times, and emits a phase pulse signal every k times;

[0038] S2, taking a weighted average of the measurement values ​​of the a dTOF pulse signal measurements before and after the i-th transmission phase pulse signal measurement;

[0039] S3, respectively calculating the difference between the measured value of the i-th and (i+1)-th transmitted phase pulse signals and their corresponding weighted averages as correction values;

[0040] S4, using the i-th and (i+1)-th correction values ​​to correct the measurement values ​​of the dTOF pulse signal measured in between to obtain an output result.

[0041] The phase mode in the present invention is explained by taking the indirect time-of-flight (iToF) ranging method as an example, which is not intended to limit the phase mode.

[0042] Specifically, in one embodiment, iTOF ranging is used to compensate for dTOF ranging by the following method:

[0043] (1) The control module 10 controls the laser emission module 20 to emit a dTOF pulse signal, which has the characteristic of high speed. After emitting k dTOF pulse signals, the control module 10 controls the laser emission module 20 to switch to the phase mode and emit an iTOF pulse signal, which has the characteristic of low speed. The dTOF pulse signal and the iTOF pulse signal are cyclically emitted according to the above method.

[0044] (2) The measured value of the transmitted iTOF pulse signal is recorded as M i , where i is the number of times the iTOF pulse signal is transmitted. The measured value of the k-th transmission dTOF signal distance measurement between the i-th and (i+1)-th iTOF pulse signals is recorded as N ki , N ki+1 , N ki+2 …N ki+k-2 , N ki+k-1 ; The measured value of the k-th dTOF signal ranging between the (i-1)th and i-th iTOF pulse signals is recorded as N ki-1 , N ki-2 …N ki-k , the marking diagram is as follows Figure 3 shown.

[0045] (3) The measured values ​​of the a times of dTOF pulse signal measurement before and after the i-th emission iTOF pulse signal measurement are weighted averaged, and the weighting coefficient is based on the distance iTOF pulse signal M i The time distance is recorded as W 0 , W 1 , W 2 , …W a-1 , where 0≤a≤k / 2. The marking diagram is as follows Figure 4 The weighted average calculation obtains the average, as shown in formula (1):

[0046]

[0047] Among them, because the weighting coefficient W will be used twice, it needs to satisfy 0≤W x ≤0.5, and And W 0 To W a-1 Decrease in sequence.

[0048] (4) Calculate the difference between the measured value of the i-th and (i+1)-th transmitted iTOF pulse signals and their corresponding weighted average values ​​as the correction value, denoted as E i and E i+1 , as shown in formula (2) and formula (3):

[0049]

[0050] (5) Use the i-th and (i+1)-th correction values ​​to correct the measured value of the dTOF pulse signal measured in between to obtain the output result N' ki+x , as shown in formula (4):

[0051]

[0052] Among them, 0≤x≤k-1.

[0053] The present invention uses phase measurement values ​​to compensate for dToF measurement values, that is, uses low-speed and high-precision phase measurement to compensate for high-speed and low-precision dTOF measurement, which can improve the accuracy of dTOF high-speed ranging and reduce the system error of the dTOF ranging system.

[0054] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0055] It should also be noted that the term "module" used in this application is intended to represent a related entity, which can be hardware, software, a combination of hardware and software, or software in execution. The above is only a 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 changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A laser radar ranging method, characterized in that: The steps include: S1: The laser emission module emits dTOF pulse signals multiple times, and emits a phase pulse signal after every k dTOF pulse signals; S2, taking a weighted average of the measurement values ​​of the a dTOF pulse signal measurements before and after the i-th transmission phase pulse signal measurement; S3, respectively calculating the difference between the measured value of the i-th and (i+1)-th transmitted phase pulse signals and their corresponding weighted averages as correction values; S4, using the correction values ​​of the i-th and (i+1)-th times to correct the measurement values ​​of the dTOF pulse signal measurement in between to obtain an output result.

2. A laser radar ranging method according to claim 1, characterized in that: In step S2, the measured value of the transmitted iTOF pulse signal is recorded as M i , where i is the number of times the iTOF pulse signal is transmitted, and the measured value of the k-th dTOF signal ranging between the i-th and (i+1)-th iTOF pulse signals is recorded as N ki , N ki+1 , N ki+2 …N ki+k-2 , N ki+k-1 ; The measured value of the k-th dTOF signal ranging between the (i-1)th and i-th iTOF pulse signals is recorded as N ki-1 , N ki-2 …N ki-k .

3. A laser radar ranging method according to claim 2, characterized in that: The weighted average of the measured values ​​of the a times of dTOF pulse signal measurement before and after the i-th emission iTOF pulse signal measurement is calculated according to formula (1) to obtain the average value: Among them, W x is the weighting coefficient.

4. A laser radar ranging method according to claim 3, characterized in that: 0≤a≤k / 2,0≤W x ≤0.5 and meets 5. A laser radar ranging method according to claim 4, characterized in that: In step S3, the method of calculating the difference between the measured value of the i-th and (i+1)-th transmitted iTOF pulse signals and their corresponding weighted averages as the correction value is respectively formula (2) and formula (3): Among them, E i is the difference between the measured value of the i-th emission iTOF pulse signal and its corresponding weighted average; E i+1 It is the difference between the measured value of the (i+1)th transmitted iTOF pulse signal and its corresponding weighted average.

6. A laser radar ranging method according to claim 5, characterized in that: The calculation method of step S4 is shown in formula (4): Among them, 0≤x≤k-1.

7. A laser radar ranging method according to claim 1, characterized in that: The phase pulse signal is an iTOF pulse signal.

8. A laser radar ranging system, characterized in that: The method for measuring distance using the distance measuring method as claimed in any one of claims 1 to 7 comprises a control module, a laser emission module, a signal receiving module and a signal processing module.

9. A laser radar ranging system according to claim 8, characterized in that: The laser emission module switches between emitting a dTOF pulse signal and emitting a phase pulse signal.

10. A laser radar ranging system according to claim 9, characterized in that: The control module controls the laser emitting module to generate a dTOF pulse signal or a phase pulse signal, the signal receiving module receives the signal emitted by the laser emitting module, which is projected onto the object to be measured and reflected by the object to be measured, and the signal processing module processes the signal received by the signal receiving module to obtain a laser ranging result.

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