WO2022057390A1

WO2022057390A1 - Light emitting module, optical signal detection module, optical system, and lidar system

Info

Publication number: WO2022057390A1
Application number: PCT/CN2021/104439
Authority: WO
Inventors: 胡小波; 刘孙光; 刘尚贤
Original assignee: 深圳市镭神智能系统有限公司
Priority date: 2020-09-16
Filing date: 2021-07-05
Publication date: 2022-03-24
Also published as: CN112034436A

Abstract

A light emitting module, an optical signal detection module, an optical system, and a lidar system. The light emitting module comprises: a high-frequency modulation signal output unit (10), configured to output at least two preset high-frequency modulation signals having different frequency; and a laser emitting unit (20), connected to the high-frequency modulation signal output unit (10) and configured to emit at least two laser beams having different frequency which are respectively modulated by the at least two high-frequency modulation signals having different frequency, wherein the laser emitting unit (20) comprises a laser, the laser comprises a seed source (201) and an optical fiber amplifier (203), and the optical fiber amplifier (203) is used for amplifying an optical signal emitted by the seed source (201).

Description

Optical emission module, optical signal detection module, optical system and lidar system

This application claims the priority of the Chinese patent application filed on September 16, 2020 with the application number 202010973713.1 and the application name is "optical emission module, optical signal detection module, optical system and lidar system", all of which are The contents are incorporated herein by reference.

technical field

The embodiments of the present application relate to the technical field of laser ranging, for example, to an optical emission module, an optical signal detection module, an optical system, and a lidar system.

Background technique

The lidar system is a radar system that emits a laser beam (detecting light signal) to detect the position, speed and other characteristic quantities of the target. The lidar system can detect the relevant information of the target object, such as the orientation, distance, height, speed, attitude, and even the shape of the target object, so as to detect, track and identify the target object. LiDAR system is an indispensable core sensor in the fields of auto-driving, robot positioning and navigation, space environment mapping and security. In practical applications, according to different principles, lidar systems can be divided into: triangulation lidar systems, pulse-based lidar systems based on time-of-flight, and phase-based lidar systems. Among them, the phase method lidar system is to load a sinusoidal modulation signal of a certain frequency on the laser, and use the distance information contained in the phase difference between the transmitted signal (detection light signal) and the received signal (echo signal). The measurement of the distance of the measured target object.

However, the existing phase method lidar scheme mainly uses dual transmission to achieve signal comparison. The stability of the transmitter is lower than that of the receiver, and the stability of the entire system will be affected by the dual transmission.

SUMMARY OF THE INVENTION

The present application provides an optical emission module, an optical signal detection module, an optical system and a laser radar system, which can achieve high detection accuracy for a target object and distance measurement with a large detection range with high stability.

In a first aspect, an embodiment of the present application proposes a light emission module including:

a high-frequency modulation signal output unit, configured to output preset high-frequency modulation signals of at least two different frequencies;

a laser emitting unit, connected to the high-frequency modulation signal output unit, and configured to emit at least two laser beams of different frequencies modulated by the at least two high-frequency modulation signals of different frequencies respectively;

Wherein, the laser emitting unit includes a laser, and the laser includes a seed source and a fiber amplifier, and the fiber amplifier is used for amplifying the optical signal emitted by the seed source.

In a second aspect, an optical signal detection module includes:

The echo signal receiving unit is configured to receive a first high-frequency echo signal and a second high-frequency echo signal, where the first high-frequency echo signal is a laser beam after the first laser beam is reflected by the target object, the The second high-frequency echo signal is the laser beam after the second laser beam is reflected by the target object;

The reference signal receiving unit is configured to receive a first reference signal and a second reference signal, wherein the first reference signal is a reference signal modulated by a first high frequency modulation signal, and the second reference signal is a reference signal modulated by a second high frequency modulation signal. The reference signal modulated by the frequency modulated signal;

The first laser beam is a laser beam modulated by the first high-frequency modulation signal, and the second laser beam is a laser beam modulated by the second high-frequency modulation signal; the first high-frequency modulation signal the frequency of the modulation signal is greater than the frequency of the second high frequency modulation signal;

a signal processing unit, which is electrically connected to the echo signal receiving unit and the reference signal receiving unit at the same time; the signal processing unit is configured to: according to the first reference signal and the first high frequency echo signal A first reference distance value of the target object is obtained by a phase difference; a second reference distance value of the target object is obtained according to the first phase difference and the second phase difference, and a second reference distance value of the target object is obtained according to the first reference distance value and the The second reference distance value determines the measured distance value of the target object; wherein, the second phase difference is the phase difference between the second reference signal and the second high frequency echo signal.

In a third aspect, an optical system includes: the above-mentioned optical signal detection module, and an optical emission module connected to the optical signal detection module;

The light emission module includes a high-frequency modulation signal output unit and a laser emission unit, the high-frequency modulation signal output unit is configured to output preset high-frequency modulation signals of at least two different frequencies; the laser emission unit is configured to emit At least two laser beams of different frequencies modulated by at least two high-frequency modulation signals of different frequencies respectively;

A part of the at least two laser beams of different frequencies is emitted and reflected by the target object and received by the echo signal receiving unit; the other part of the two laser beams of different frequencies is directly received by the reference signal as a reference signal unit receives;

In a fourth aspect, a lidar system includes the above-mentioned optical system

The optical transmission module provided by the embodiment of the present application adopts a laser including a seed source and a fiber amplifier, so that the transmission power is greatly improved; the optical signal detection module provided adopts a dual receiving scheme of an echo signal receiving unit and a reference signal receiving unit, Because the stability of the receiver is greater than that of the transmitter, the stability of the optical system and lidar system using the optical signal detection module is greatly improved. In addition, the emitted laser light is modulated by at least two high-frequency modulation signals, so that both measurement accuracy and range measurement can be taken into account.

The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features and advantages of the present application will be apparent from the description, drawings, and claims.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for 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, the drawings of other embodiments can also be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a light emission module provided by an embodiment of the present application;

2 is a schematic diagram of the working principle of a frequency synthesizer provided by an embodiment of the present application;

3 is a schematic structural diagram of a laser emitting unit provided by an embodiment of the present application;

FIG. 4 is a schematic structural diagram of an optical signal detection module provided by an embodiment of the present application;

5 is a schematic diagram of the principle of a difference frequency phase detection technology provided by an embodiment of the present application;

6 is a schematic flowchart of a digital phase detection technology provided by an embodiment of the present application;

7 is a schematic structural diagram of a laser emitting unit and a signal receiving unit provided by an embodiment of the present application;

8 is a structural block diagram of an optical system provided by an embodiment of the present application;

FIG. 9 is a schematic diagram of a hardware principle of a lidar provided by an embodiment of the present application;

FIG. 10 is a schematic work flow diagram of a lidar system provided by an embodiment of the present application;

FIG. 11 is a schematic flowchart of an algorithm of a lidar system provided by an embodiment of the present application.

detailed description

The present application will be described below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, the drawings only show some but not all the structures related to the present application.

The optical emission module and the optical signal detection module provided by the embodiments of the present application can be applied to a lidar system, and the optical emission module and the optical signal detection module will be described below in combination with application scenarios.

FIG. 1 is a schematic structural diagram of a light emitting module according to an embodiment. Referring to FIG. 1 , the light emitting module includes: a high-frequency modulation signal output unit 10 and a laser emitting unit 20 .

In one embodiment, the high-frequency modulation signal output unit 10 is configured to output at least two preset high-frequency modulation signals of different frequencies; the laser emission unit 20 is connected to the high-frequency modulation signal output unit 10 and is configured to transmit the signals respectively. At least two laser beams of different frequencies modulated by high-frequency modulation signals of at least two different frequencies.

In one embodiment, each high-frequency modulation signal is a main oscillator high-frequency modulation signal; the high-frequency modulation signal output unit 10 is further configured to output at least two local oscillator high-frequency modulation signals of different frequencies, wherein at least two of the local oscillator high-frequency modulation signals are The vibration high-frequency modulation signal corresponds to at least two main vibration high-frequency modulation signals one-to-one, and each local oscillator high-frequency modulation signal differs from the corresponding main vibration high-frequency modulation signal by a preset frequency.

In one embodiment, the high-frequency modulation signal output unit 10 includes at least two groups of phase-locked loops, each group of phase-locked loops includes at least two phase-locked loops, and the at least two groups of phase-locked loops are respectively configured to output a main oscillator high-frequency modulation. signal and a local oscillator high frequency modulation signal corresponding to the main oscillator high frequency modulation signal.

In one embodiment, the absolute value of the difference between the frequencies of the different main oscillator high-frequency modulation signals is within a preset frequency range. For example, the preset frequency range is 0 to 100 MHz.

In one embodiment, the high-frequency modulation signal output unit 10 includes two groups of phase-locked loops, each group of phase-locked loops includes four phase-locked loops, wherein each phase-locked loop in a group of phase-locked loops It can output a main oscillator high-frequency modulation signal, and each phase-locked loop in the other group of phase-locked loops can output a local oscillator high-frequency modulation signal. Therefore, at least two groups of phase-locked loops can output at least four groups of high-frequency modulation signals with different frequencies. A phase-locked loop is a feedback control circuit, referred to as a phase-locked loop (PLL, Phase-Locked Loop).

In this embodiment, a group of high frequency modulation signals includes a main oscillator high frequency modulation signal and a local oscillator high frequency modulation signal corresponding to the main oscillator high frequency modulation signal.

It can be understood that, in other embodiments, a direct digital frequency synthesizer (DDS, Direct Digital Synthesizer) may also be used in the high-frequency modulation signal output unit 10 to replace the phase-locked loop.

Exemplarily, FIG. 2 is a schematic diagram of a working principle of a DDS provided by an embodiment. Referring to FIG. 2, the DDS includes a phase accumulator 111, a sine look-up table 112, a digital to analog converter (DAC) 113 and a low pass filter (LTP) 114. At the same time, the clock signal fc is respectively input To the phase accumulator 111 and the sine look-up table 112, the frequency control word K is input to the phase accumulator 111.

Among them, the phase accumulator 111 is the core of the DDS. The phase accumulator 111 is composed of an N-bit binary adder and an N-bit register sampled by the clock signal fc, and is used for linearly accumulating the frequency control word K (decimal). The phase accumulator 111 is used to realize the accumulation of phases and store the accumulation result. When the phase accumulator 111 accumulates the full amount, it will generate an overflow to complete one cycle of action. This cycle is a frequency cycle of the synthesized signal of the DDS system, and the overflow frequency of the phase accumulator 111 is the output signal frequency.

The sine look-up table 112 is a programmable read-only memory, which stores the sampled code value of a period sinusoidal signal whose phase is the address, and includes the digital amplitude information of a periodical sinusoid, and each address corresponds to 0～2π in the sinusoid. A phase point of the range (the phase from 0 to 2π is divided into M equal parts).

The role of the digital-to-analog converter 113 is to convert the digital signal into an analog signal. In one embodiment, the sequence of sinusoidal amplitudes is converted into a sinusoidal wave. In addition, the higher the resolution of the digital-to-analog converter 113, the better the continuity of the output sine wave; when the resolution of the digital-to-analog converter 113 is low, the output sine wave is a trapezoidal waveform, and the trapezoidal waveform passes through a low-pass After filtering by the filter 114 (the low-pass filter can also be a band-pass filter), it becomes an analog waveform fout whose quality (here mainly refers to the continuity of the waveform) meets the requirements. Here, the frequency of the output analog waveform fout can be changed by changing the clock signal fc, the number of bits N of the phase accumulator 111 or the number of bits M of the sine look-up table 112 .

In one embodiment, the laser emitting unit 20 may include a laser, and the wavelength of the laser beam emitted by the laser may be in the 1550 nm band or the 2000 nm band.

FIG. 3 is a schematic structural diagram of a laser emitting unit provided by an embodiment. Referring to FIG. 3 , the laser emitting unit 20 includes a seed source 201, a pump source 202 and at least one stage of a fiber amplifier 203. The seed source 201 is used to emit a laser beam of one wavelength or multiple wavelengths modulated by the high-frequency modulation signal, and the laser beam can be a continuous sine wave or cosine wave optical signal. The pump source 202 is used to provide energy to the fiber amplifier 203, and the fiber amplifier 203 is used to amplify the modulated laser beam output by the seed source, and output the amplified modulated laser beam.

In one embodiment, the wavelength of the laser beam emitted by the seed source 201 is in the 1550 nm band or the 2000 nm band, and the fiber amplifier 203 is an erbium-doped fiber amplifier or a thulium-doped fiber amplifier or an erbium-ytterbium co-doped fiber amplifier. The damage threshold of the human eye in the 1550nm band and the 2000nm band is high, so this band is also called the "eye-safe band", and the output power can be greatly improved by the amplification of the fiber amplifier 203 .

In one embodiment, the fiber amplifier 203 can be a one-stage amplifier, or can be a series of multi-stage amplifiers, which can be configured according to actual needs.

It should be noted that, FIG. 3 only exemplarily shows that the laser emitting unit 20 includes the first-stage fiber amplifier 203 . In other embodiments, it can also be a multi-stage fiber amplifier. In addition, a collimating lens may also be arranged between any two optical elements in the beam propagation path to reduce the divergence angle of the beam, or a collimating element may be directly arranged inside the seed source 201, which is not strictly limited here. In one embodiment, the collimating lens may use a spherical lens.

In one embodiment, exemplary, the high-frequency modulation signal output unit 10 outputs the preset four groups of high-frequency modulation signals with different frequencies. Modulation signal fg1'=1000MHz; main oscillator high frequency modulation signal fg2=1091.75MHz, local oscillator high frequency modulation signal fg2'=998MHz; main oscillator high frequency modulation signal fg3=1081.75MHz, local oscillator high frequency modulation signal fg3'=988MHz , the main oscillator high-frequency modulation signal fg4 = 1073.75MHz, the local oscillator high-frequency modulation signal fg3' = 980MHz, the main oscillator high-frequency modulation signal in each group of high-frequency modulation signals is loaded into the laser emitting unit 20 to make the laser emission The unit 20 emits a laser beam of a corresponding frequency.

It should be noted that the specific frequency values of the above-mentioned four groups of high-frequency modulation signals are only illustrative, not limiting; at the same time, the number of groups of high-frequency modulation signals output by the above-mentioned high-frequency modulation signal output unit 10 is also only an example It is illustrative, but not limiting, for example, the output may be two or more groups of high-frequency modulation signals. In other embodiments, the selection of the frequency value of the high-frequency modulation signal may be set according to the actual requirements of the lidar system for the light emitting module, which is not strictly limited here.

In the light emitting module provided by the embodiment of the present application, the high-frequency modulation signal output unit 10 outputs preset high-frequency modulation signals with at least two different frequencies, and loads them onto the laser emitting unit, so that the laser emitting unit emits at least two different frequencies. Frequency laser beam, using more than two laser beams with different frequencies to detect the same distance can not only ensure the measurement accuracy but also ensure the measurement range. At the same time, using the seed source + fiber amplifier as the light source can greatly improve the output power.

In the phase method lidar system in the related art, electrical components are used to modulate the frequency of the transmitted signal, the modulation speed of the transmitted signal is slow, and the electromagnetic interference is serious, resulting in a slow detection speed of the existing phase method lidar system.

Exemplarily, the probe light signal may include a high-frequency emission signal of 1093.75 MHz and a high-frequency emission signal of 1091.75 MHz; a low-frequency emission signal of 2 MHz can be obtained by performing a frequency difference between 1093.75 MHz and 1091.75 MHz. The high-frequency transmission signal can be used as a fine ruler to measure a more accurate distance, and the low-frequency transmission signal can be used as a coarse ruler to measure a longer distance.

It should be noted that the specific frequency values of the above-mentioned high-frequency emission signal and low-frequency emission signal are only illustrative, not limiting; at the same time, the selection of the frequency value of the above-mentioned detection light signal is only an illustrative description, not a limitation. limited. In other embodiments, the frequency values of the high-frequency transmission signal and the low-frequency transmission signal and the selection of the frequency value of the detection optical signal may be set according to the actual requirements of the laser radar system for the optical transmission unit.

In the solution provided by the embodiment of the present disclosure, the optical mixing technology is used to obtain the high-frequency transmission signal, and the difference frequency technology is used to obtain the low-frequency transmission signal, so as to avoid the problem that the detection optical signal is easily interfered by the electromagnetic signal when the light beam is modulated by the electrical element. . Therefore, the stability of the detected light signal is high.

Embodiments of the present application also provide an optical signal detection module for detecting echo signals. FIG. 4 is a schematic structural diagram of an optical signal detection module provided by an embodiment of the present application. Referring to FIG. 4 , the optical signal detection module includes: an echo signal receiving unit 42 , a reference signal receiving unit 44 and a signal processing unit 50 .

In an embodiment, the at least two high-frequency modulation signals of different frequencies include a first high-frequency modulation signal and a second high-frequency modulation signal, and the reference signal receiving unit 44 is configured to receive the first reference signal and the second reference signal; wherein , the first reference signal is the reference signal that is directly modulated by the first high-frequency modulation signal and passes through the internal optical path to the reference signal receiving unit 44, and the second reference signal is the second high-frequency modulation signal sent by the laser emitting unit and modulated by the internal optical path. The reference signal directly to the reference signal receiving unit 44; the echo signal receiving unit 42 is set to receive the first high-frequency echo signal and the second high-frequency echo signal, and the first high-frequency echo signal is the target object of the first laser beam The reflected laser beam, the second high-frequency echo signal is the laser beam after the second laser beam is reflected by the target object; the first laser beam is the laser beam modulated by the first high-frequency modulation signal, and the second laser beam is The laser beam modulated by the second high-frequency modulation signal; the frequency of the first high-frequency modulation signal is greater than the frequency of the second high-frequency modulation signal; the signal processing unit 50 is set to: according to the first reference signal and the first high-frequency echo The first phase difference between the signals obtains the first reference distance value of the target object; obtains the second reference distance value of the target object according to the first phase difference and the second phase difference, and obtains the second reference distance value of the target object according to the first reference distance value and the second phase difference. Two reference distance values determine the measured distance value of the target object; wherein, the second phase difference is the phase difference between the second reference signal and the second high-frequency echo signal.

Exemplarily, the first reference distance and the second reference distance can be fused to obtain the measured distance of the target object, for example, the sum of the integer part of the first reference distance and the decimal part of the second reference distance is taken as the Measure distance.

In an embodiment, the at least two reference signals with different frequencies are at least two reference laser beams with different frequencies or at least two reference electrical signals with different frequencies.

In one embodiment, when the at least two reference signals with different frequencies are at least two reference laser beams with different frequencies, the at least two reference signals can be transmitted through the laser transmitting unit and then directly reach the reference signal receiving unit through the inner optical path.

In one embodiment, the echo signal receiving unit 42 and the reference signal receiving unit 44 are both connected to the laser transmitting unit 20 in the optical transmitting module of the above-mentioned embodiment, and the first high-frequency modulation signal is output by the high-frequency modulation signal output unit 10. The high-frequency modulation signal with the highest frequency among the at least two high-frequency modulation signals of different frequencies, and the second high-frequency modulation signal is the high-frequency modulation signal with the highest frequency among the at least two high-frequency modulation signals of different frequencies output by the high-frequency modulation signal output unit 10. All high-frequency modulation signals other than the high-frequency modulation signal of the second high-frequency modulation signal, the number of the second high-frequency modulation signal can be one or more, and the first reference signal is the first high-frequency modulation signal transmitted by the laser emitting unit 20 after modulation by the first high-frequency modulation signal. The signal directly reaches the reference signal receiving unit 44 through the inner optical path, and the second reference signal is a signal transmitted by the laser emitting unit 20 and modulated by the second high-frequency modulation signal and directly reaches the reference signal receiving unit 44 through the inner optical path.

In one embodiment, when there are multiple second high-frequency modulation signals, the number of the second laser beam and the second reference signal is multiple, and multiple second laser beams can be used to obtain multiple first laser beams respectively. Two high-frequency echo signals, and then the second high-frequency echo signal between each second high-frequency echo signal in the plurality of second high-frequency echo signals and the second reference signal corresponding to the second high-frequency echo signal can be obtained respectively. Phase difference, the second reference distance value is obtained according to a plurality of second phase differences and a first phase difference, for example, according to the third phase between each of the plurality of second phase differences and the first phase difference respectively difference, obtain a plurality of second reference distance values, and determine the measured distance value of the target object according to the first reference distance value and the plurality of second reference distance values.

In one embodiment, the first reference signal and the second reference signal are the first reference laser beam and the second reference laser beam, respectively, or the first reference electrical signal or the second reference electrical signal, respectively.

In one embodiment, the echo signal receiving unit 42 and the reference signal receiving unit 44 are further configured to: receive the first local oscillator high-frequency modulation signal; convert the first high-frequency echo signal into a corresponding electrical signal, and convert the first high-frequency The electrical signal corresponding to the high-frequency echo signal is mixed with the first local oscillator high-frequency modulation signal to obtain a first difference frequency ranging signal; the first reference laser beam is converted into a corresponding electrical signal and the first reference laser beam is converted into a corresponding electrical signal. The corresponding electrical signal is mixed with the first local oscillator high-frequency modulation signal, or the first reference electrical signal is mixed with the first local oscillator high-frequency modulation signal to obtain a first difference frequency reference signal; receiving the second local oscillator high frequency frequency modulation signal, convert the second high-frequency echo signal into a corresponding electrical signal, and mix the electrical signal corresponding to the second high-frequency echo signal with the second local oscillator high-frequency modulation signal to obtain a second difference frequency measurement distance signal; convert the second reference laser beam into a corresponding electrical signal and mix the electrical signal corresponding to the second reference laser beam with the second local oscillator high-frequency modulation signal, or mix the second reference electrical signal with the second local oscillator The high-frequency modulation signal is mixed to obtain a second difference frequency reference signal; wherein, the first high-frequency modulation signal is the high-frequency modulation signal of the first main vibration, and the second high-frequency modulation signal is the high-frequency modulation signal of the second main vibration , the frequency of the high-frequency modulation signal of the first main oscillator and the high-frequency modulation signal of the first local oscillator are different by a preset frequency, and the frequency of the high-frequency modulation signal of the second main oscillator and the high-frequency modulation signal of the second local oscillator are different by a preset frequency; The processing unit 50 is configured to obtain the first reference distance value of the target object according to the first phase difference between the first reference signal and the first high-frequency echo signal in the following manner: The difference frequency reference signal is compared to obtain a first phase difference, and the first reference distance value of the target object is obtained according to the first phase difference; the signal processing unit 50 is configured to obtain the target object according to the first phase difference and the second phase difference in the following manner. The second reference distance value of : compare the second beat frequency ranging signal with the second beat frequency reference signal to obtain the second phase difference; calculate the third phase difference between the second phase difference and the first phase difference; The third phase difference obtains the second reference distance value of the target object.

In this embodiment, the first local oscillator high frequency modulation signal is a local oscillator high frequency modulation signal corresponding to the first main oscillator high frequency modulation signal output by the modulation signal output unit 10, and the second local oscillator high frequency modulation signal is a modulation signal The output unit 10 outputs the local oscillator high frequency modulation signal corresponding to the second main oscillator high frequency modulation signal.

In this embodiment, the echo signal receiving unit 42 is configured to receive the high-frequency echo signal reflected by the target object, convert the high-frequency echo signal into a high-frequency electrical signal, and then convert the high-frequency electrical signal into a low-frequency electrical signal ; The signal processing unit 50 is set to convert the low-frequency analog electrical signal into a low-frequency digital signal, and then obtain the phase information by using the relevant algorithm, and then obtain the distance value of the target object.

Wherein, the echo signal receiving unit 42 and the reference signal receiving unit 44 actually use the difference frequency phase discrimination technology in the process of converting the high-frequency electrical signal into the low-frequency electrical signal. The difference frequency phase detection technology refers to the technology of converting high-frequency signals into low-frequency signals while keeping the phase information unchanged, and then using low-frequency signals for phase detection.

FIG. 5 is a schematic diagram of the principle of the difference frequency phase detection technology provided by an embodiment. Referring to Figure 5, the high-frequency modulation signal output unit in the optical transmitter module is equivalent to a high-frequency signal source, including a main oscillator and a local oscillator, and each group of high-frequency modulation signals output by the high-frequency signal source includes a main oscillator. High-frequency modulation signal and a local oscillator high-frequency modulation signal that differs from the main oscillator high-frequency modulation signal by a fixed frequency (eg 93.75MHZ). In this embodiment, the acquisition of the first phase difference in the above embodiment is taken as an example. The first main oscillator high-frequency modulation signal is loaded on the laser beam for modulation and the modulated laser beam is emitted (this embodiment mainly describes the entire optical path test The principle process of the distance, the specific laser modulation and amplification, please refer to the above description, which will not be repeated here), the emitted laser beam is divided into two parts, one part reaches the target object, and the target object then reflects the laser beam to the optical signal detection module. The receiver of the echo signal receiving unit receives the first high-frequency echo signal obtained by the laser beam reflected by the target object, and converts the first high-frequency echo signal into a high-frequency electrical signal. The ranging signal mixer in the signal receiving unit mixes the high-frequency electrical signal with the first local oscillator high-frequency modulation signal to obtain a low-frequency first difference frequency ranging signal.

The other part of the laser beam emitted as the first reference signal directly reaches the reference receiving signal receiving unit in the optical signal detection module through the internal optical path. The receiver of the reference signal receiving unit receives the first reference signal and converts the first reference signal. For a high-frequency electrical signal, the reference signal mixer in the reference signal receiving unit mixes the high-frequency electrical signal with the first local oscillator high-frequency modulation signal to obtain a low-frequency first difference frequency reference signal. The signal processing unit is configured to obtain the first phase difference by comparing the first beat frequency ranging signal with the first beat frequency reference signal, and then obtain the first reference distance value of the target object through the first phase difference.

In this embodiment, the acquisition principle of the second phase difference is the same as the acquisition principle of the first phase difference, and details are not repeated here. After obtaining the second phase difference, the third phase difference between the second phase difference and the first phase difference can be calculated, and then the second reference distance of the target object can be obtained, and the target object can be obtained according to the first reference distance and the second reference distance The measured distance of an object.

In one embodiment, before determining the measurement distance of the target object according to the first reference distance and the second reference distance, the signal processing unit 40 may be further configured to obtain a third reference distance value of the target object according to the second phase difference, and according to the first reference distance. The third reference distance value and the first reference distance value calculate a fourth reference distance value, and replace the first reference distance value with the fourth reference distance value.

In one embodiment, the average value of the third reference distance value and the first reference distance value may be used as the fourth reference distance value, or the fourth reference distance value may be determined by a table look-up or the like.

In this embodiment, the phase difference between the beat frequency ranging signal and the high frequency echo signal is the phase of the local oscillator high frequency modulation signal, and the phase difference between the main oscillator high frequency modulation signal and the beat frequency reference signal is also the local oscillator high frequency modulation signal Therefore, the phase difference between the beat frequency ranging signal and the beat frequency reference signal is equal to the phase difference between the high-frequency echo signal and the high-frequency modulation signal of the main oscillator, that is, since the phase information remains unchanged, the high-frequency signal can be converted into Low-frequency signal processing, using low-frequency signals for phase detection, reduces the requirements for analog-to-digital conversion chips, that is, reduces the bandwidth of the post-processing circuit. Because the narrower the bandwidth, the higher the phase detection accuracy is, so it is beneficial to improve the phase detection accuracy. , that is, to improve the processing accuracy of the high-frequency echo signal by the optical signal detection module. On the other hand, due to the reciprocal relationship between frequency and period, the difference frequency phase detection technology reduces the frequency of the signal to be measured, thereby broadening the period of the signal to be measured. At the same time, because the low-frequency signal processing technology is more mature than the high-frequency signal processing technology , so the high-frequency signal is converted into low-frequency signal processing, which can improve the resolution of phase measurement, thereby improving the accuracy of phase detection.

Exemplarily, the complete process of optical signal emission and detection shown in FIG. 5 is: the main oscillator and the local oscillator in the high-frequency signal source generate high-frequency modulation signals of the main oscillator respectively.

high frequency modulation signal with local oscillator

Both are high-frequency signals, but with different phases and frequencies, and the difference frequency is a low-frequency signal. Main oscillator high frequency modulation signal

Loaded on the laser beam, emitted to the target object, reflected by the target object, forming a high-frequency echo signal

received by the signal receiving unit. This high frequency echo signal

High frequency modulation signal with main oscillator

The frequency is the same, the phase changes, and the amount of the phase change is related to the distance of the target object. This high frequency echo signal

high frequency modulation signal with local oscillator

Mix the frequency, and then pass through a low pass filter (LPF) to generate a low frequency difference frequency ranging signal

The signal processing path for generating the difference frequency reference signal is: the main oscillator high frequency modulation signal

high frequency modulation signal with local oscillator

Mix the frequency, and then pass through the low-pass filter LPF to generate a low-frequency difference frequency reference signal

Then, the signal processing unit compares the low frequency difference frequency ranging signal

Difference frequency reference signal with low frequency

Detect the phase information of the beat frequency ranging signal and the beat frequency reference signal respectively and calculate the phase difference, the phase difference value and the high frequency main vibration high frequency modulation signal

with high frequency echo signal

the same phase difference. Therefore, the phase difference information carried by the high-frequency signal can be obtained by processing the low-frequency signal subsequently, so as to finally obtain the measured distance value of the target object.

In one embodiment, the signal processing unit uses a digital phase detection method to detect the phase information. The digital phase identification method is a method of digitizing the signal to be detected and then identifying the phase information of the signal. Exemplarily, FIG. 6 is a schematic flowchart of a digital phase identification method provided by an embodiment of the present application. Referring to FIG. 6 , the process of the digital phase detection method includes: converting the analog signal x(t) to be detected into a digital signal x(n) (wherein, n is a positive integer) through analog-to-digital conversion, and then going through a correlation algorithm Get phase information. In one embodiment, the core processing unit of the digital phase detection method may be a computer or a microprocessor. The above-mentioned digital phase detection method does not depend on the circuit, and the entire phase detection process is completely digital, which avoids the influence of electromagnetic interference in the circuit on the phase detection result, so it has good anti-interference ability and high phase detection accuracy. At the same time, the operation speed is fast and the volume is small. Applying the digital phase detection method to the lidar system can improve the speed and accuracy (also called resolution) of the distance measurement of the lidar system.

It should be noted that the "high frequency" mentioned in the above embodiments refers to the frequency with a unit level of 100 MHz (such as 100MHz or more), and the "low frequency" mentioned in this application refers to the frequency with a unit level of MHz (such as 1MHZ). ~10MHZ).

In one embodiment, both the echo signal receiving unit 42 and the reference signal receiving unit 44 include photodetectors.

This setting is equivalent to using two photodetectors to achieve three functions of receiving, converting and mixing the first reference signal, the second reference signal, the first high-frequency echo signal and the second high-frequency echo signal, thereby The number of components in the optical signal detection module is reduced, the structure of the optical signal detection module is simplified, and the volume of the optical signal detection module is reduced. The application of photoelectric detectors in lidar systems is beneficial to the miniaturized design of lidar systems.

It should be noted that the above-mentioned photodetector is only a design method for the echo signal receiving unit 42 and the reference signal 44 , and is not a limitation. In other embodiments, the above-mentioned functions of receiving, converting and mixing may also be implemented by two or three elements. At this time, the functions implemented by multiple components are relatively independent. When abnormal signal detection occurs, investigation can be carried out quickly, and the cost of replacing components is low.

FIG. 7 is a schematic diagram of an optical structure of a laser emitting unit and a signal receiving unit according to an embodiment. 7 , the echo signal receiving unit 42 and the reference signal receiving unit 44 may further include a receiving lens 213 and an optical filter 214, respectively, and the receiving lens 213, the optical filter 214 and the photodetector 211 are arranged in sequence along the propagation direction of the light beam ; Take the echo signal receiving unit 42 as an example, the receiving lens 213 is set to focus the first high frequency echo signal and the second high frequency echo signal to the photodetector 211; the filter 214 is set to pass the first high frequency echo signal The echo signal and the second high-frequency echo signal filter out interference signals of other wavelengths, that is, the interference signals will not be detected by the photodetector 211, thereby improving the signal-to-noise ratio of the optical signal detection module. Applying the filter 214 to the lidar system can increase the detection distance of the system under strong light.

Among them, due to the scattering on the surface of the target object, the echo signal generated by the reflection of the target object usually diverges, and the divergent echo signal is focused to the photodetector 211 by the receiving lens 213, which can enhance the echo signal received by the photodetector Strength of.

In one embodiment, the side of the receiving lens 213 close to the laser emitting unit 20 also includes a short-range optical path compensating mirror 2131 attached to the light-emitting surface of the receiving lens 213. The echo signal generated by the reflection is focused to the photodetector 211, thereby reducing the dead zone caused by the non-coaxial system. Exemplarily, in a lidar applied to a non-coaxial system, the blind zone of the lidar can be reduced to less than 20 cm.

In one embodiment, the signal processing unit 50 includes an operational amplifier, an analog-to-digital converter and a field programmable gate array; the input end of the operational amplifier is electrically connected to the signal receiving unit, and the output end of the operational amplifier is connected to the input end of the analog-to-digital converter. Electrical connection, the output end of the analog-to-digital converter is electrically connected with the field programmable gate array; the operational amplifier is set to respectively transmit the first difference frequency ranging signal, the first difference frequency reference signal, and the second difference frequency measurement signal transmitted by the signal receiving unit. Amplifying the distance signal and the second beat frequency reference signal; the analog-to-digital converter is set to respectively amplify the first beat frequency ranging signal, the first beat frequency reference signal, the second beat frequency ranging signal and the second beat frequency ranging signal amplified by the operational amplifier The beat frequency reference signal is converted from an analog signal to a digital signal; the field programmable gate array is set to compare the digital signal corresponding to the first beat frequency ranging signal with the digital signal corresponding to the first beat frequency reference signal to obtain the first beat frequency reference signal. a phase difference, and calculate the first reference distance value of the target object according to the first phase difference; compare the digital signal corresponding to the second frequency difference ranging signal with the digital signal corresponding to the second frequency difference Two phase differences; calculate the third phase difference between the second phase difference and the first phase difference, and calculate the second reference distance value of the target object according to the third phase difference; determine according to the first reference distance value and the second reference distance value The measured distance value of the target object.

In one embodiment, the optical signal detection module further includes: a power supply unit, a microprocessor unit and a high voltage adjustment unit; the power receiving end of the signal processing unit and the power receiving end of the microprocessor unit are respectively electrically connected to the power supply unit , the first control end of the microprocessor unit is electrically connected with the signal processing unit, and the second control end of the microprocessor unit is electrically connected with the signal receiving unit through the high voltage regulating unit; the power supply unit is set to send the signal processing unit and the microprocessor unit power supply; the microprocessor unit is configured to control the signal processing unit, and is also configured to adjust the voltage applied to the signal receiving unit through the high voltage adjusting unit, so that the signal receiving unit receives echo signals with different intensities.

In one embodiment, the optical signal detection module further includes a temperature detection unit, a high voltage detection unit and a standard voltage detection unit, the output end of the temperature detection unit, the output end of the high voltage detection unit and the output end of the standard voltage detection unit are respectively connected with the microcomputer. The input end of the processor unit is electrically connected; the temperature detection unit is set to the temperature value of the detection signal receiving unit, the high voltage detection unit is set to the high voltage value of the detection signal receiving unit, and the standard voltage detection unit is set to the standard voltage value of the detection signal receiving unit; The microprocessor unit is further configured to adjust the voltage output by the high voltage adjustment unit according to the temperature value, the high voltage value or the standard voltage value.

FIG. 8 is a structural block diagram of an optical system provided by an embodiment. Referring to FIG. 8 , the optical system provided in this embodiment may include the light emission module 60 provided in any of the foregoing embodiments and the optical signal detection module 70 provided in any of the foregoing embodiments, the optical signal detection module 70 and the light emission module 60 connect.

The principles of the optical emission module 60 and the optical signal detection module 70 in this embodiment are the same as those in the above-mentioned embodiments, and are not repeated here.

In an embodiment, the optical path layout between the optical transmitting module 60 and the optical signal detecting module 70 includes: a coaxial system and a single-transmitting dual-receiving system.

FIG. 9 is a schematic diagram of a hardware principle of a laser radar according to an embodiment. The following describes the principle of laser light emission and detection in combination with the hardware structure of the laser radar. Referring to FIG. 9 , the light transmitting module of the lidar includes two groups of phase-locked loops, each group of phase-locked loops includes four phase-locked loops, and the four phase-locked loops perform frequency switching through a switch . The two groups of phase-locked loops are controlled by field programmable gate arrays, and the high-frequency modulation signals output by the two groups of phase-locked loops respectively include the main oscillator high-frequency modulation signal and the local oscillator high-frequency modulation signal. In this way, 4 differential rulers can be generated, and the ranging range can reach 150 meters. Four sets of signals are generated, respectively, and one set of high-frequency modulated signals is selected in turn through two four-to-one switches at the same time. Each set of high-frequency modulated signal sources and lines are individually shielded and isolated to prevent mutual crosstalk.

In this embodiment, the first main oscillator high-frequency modulation signal and the first local oscillator high-frequency modulation signal, and the second main oscillator high-frequency modulation signal and the second local oscillator high-frequency modulation signal are respectively output through two sets of phase-locked loops. Signal for example. First, a phase-locked loop is selected through a switch to output the first main oscillator high-frequency modulation signal and the first local oscillator high-frequency modulation signal. The high-frequency modulation signal of the first main oscillator can be loaded on the seed source of the laser emitting unit after being amplified by the amplifying circuit 1 . The first main oscillator high-frequency modulation signal is loaded on the seed source of the laser emitting unit and then emits a first laser beam frequency-modulated corresponding to the first main oscillator high-frequency modulation signal. The first laser beam is divided into two parts, and one part is After the external optical path reaches the target object, it will be reflected back, and the emitted laser beam is the first high-frequency echo signal. Since the emitted laser beam is modulated by a high-frequency modulation signal, the echo signal is also a high-frequency signal. After being amplified by the amplifying circuit 2, the first local oscillator high-frequency modulation signal can be loaded on the first photodetector and the second photodetector respectively.

After detecting the first high-frequency echo signal, the second photodetector first converts the first high-frequency echo signal into a high-frequency electrical signal, and the high-frequency electrical signal is vibrated by the first main oscillator. There is a delayed phase difference between the first laser beam modulated by the high-frequency modulation signal and the demodulated electrical signal after it travels back and forth to the target object and the high-frequency modulation signal of the first main oscillator. A low-frequency electrical signal (ie, the first difference frequency ranging signal in the above embodiment) is obtained by mixing the first high-frequency electrical signal with the first local oscillator high-frequency modulation signal. The low-frequency electrical signal is subjected to signal amplification and analog-to-digital converter conversion, and a low-frequency digital electrical signal (represented by eD) is output to a Field-Programmable Gate Array (FPGA).

For comparison, after the first main oscillator high-frequency modulation signal is loaded into the seed source of the laser emitting unit, another part of the first laser beam frequency modulated corresponding to the first main oscillator high-frequency modulation signal is emitted, which directly passes through the internal The optical path reaches the first photodetector to obtain a first reference laser beam, the first reference laser beam is photoelectrically converted by the first photodetector, and then mixed with the amplified first local oscillator high-frequency modulation signal A low-frequency first beat frequency reference signal is obtained by processing, and the low-frequency first beat frequency reference signal is also amplified and converted into a low-frequency reference digital electrical signal (represented by e0) as a phase comparison. Since e0 does not go through the round trip of the outer optical path, e0 does not have a phase delay like that produced in eD. Therefore, the field programmable gate array compares the phases of eD and e0 to obtain the first phase difference for obtaining the first reference distance value of the target object, and then obtains the first reference distance value.

By switching the switch, another phase-locked loop is selected, and the second main oscillator high-frequency modulation signal and the second local oscillator high-frequency modulation signal are output. Similarly, the field programmable gate array can obtain the second phase difference, and then calculate the third phase difference between the second phase difference and the first phase difference, obtain the second reference distance value according to the third phase difference, and then according to the first phase difference. The reference distance value and the second reference distance value obtain the measured distance value of the target object.

In this embodiment, the switch configured to select the phase-locked loop is controlled by the field programmable gate array, and the two sets of phase-locked loops can output at least four sets of different high-frequency modulation signals, and the four sets of high-frequency modulation signals The frequency values of the signals are relatively concentrated, that is, the difference between the two groups of frequency values is small, so that a unified high-frequency processing circuit can be used, which makes the design of the hardware circuit simple. Among them, the group with the highest frequency value (exemplarily, the frequency of the high-frequency modulation signal of the main oscillator is 1093.75MHZ, and the frequency of the high-frequency modulation signal of the local oscillator is 1000MHZ) is used as a precision ruler, which can ensure the measurement accuracy of the system. The other three groups (exemplarily, the frequency of the high-frequency modulation signal of the main oscillator is 1091.75MHZ, the frequency of the high-frequency modulation signal of the local oscillator is 998MHZ; the frequency of the high-frequency modulation signal of the main oscillator is 1081.75MHZ, the frequency of the high-frequency modulation signal of the local oscillator is 988MHZ and The frequency of the high-frequency modulation signal of the main oscillator is 1073.75MHZ, and the frequency of the high-frequency modulation signal of the local oscillator is 880MHZ) as the auxiliary ruler, and the difference frequency between the precision ruler and the three auxiliary rulers is used (exemplarily, the difference frequency can be 20MHZ respectively) and 6MHZ, etc.) can be used as two middle rulers and one thick ruler for extending the range to ensure the measurement range of the system. It can be understood that if only two phase-locked loops are set, the group with high frequency value is used as a fine ruler, and the other group is used as an auxiliary ruler. The difference frequency between the fine ruler and the auxiliary ruler can be used as a coarse ruler for extending the range.

On the one hand, while ensuring high precision and large range, the configuration time of the low-frequency measuring scale is reduced, thus improving the detection speed of the lidar. On the other hand, since the frequency of the modulated detection optical signal is relatively concentrated, it is convenient for the circuit to process signals of similar frequencies, so there is no need to separately design circuits for high-frequency signals and low-frequency signals, so the circuit design is less difficult and the circuit structure is simple.

In one embodiment, the signal amplifying circuit is an operational amplifier that amplifies weak signals, thereby improving the signal-to-noise ratio of the signals. Exemplarily, the operational amplifier may use a multi-stage signal amplification circuit, the former stage is for current mode signal and voltage mode signal processing, and the latter stages use low noise, high speed, high precision signal amplification processing. In this embodiment, a switch is set after the first photodetector and the second photodetector, and the signal received by the first photodetector and the second photodetector is selectively switched by the switch, and transmitted to the three-stage Signal amplifier circuit. Which stage of signal amplifying circuit is selected according to the needs. For example: when the signal output by the first photodetector or the second photodetector is relatively weak, a signal amplification circuit with a 2-stage amplification can be used. If the 2-stage amplification is still too small, a 3-stage amplification signal can be selected. amplifying circuit. In addition, the limit is that if the signal amplifying circuit with a 3-level amplification factor is used to saturate the signal, a 2-level signal amplifying circuit can be used instead. amplifying circuit. Generally speaking, these groups of circuits can basically cover most measurement environments.

The input end of the operational amplifier is electrically connected to the output end of the photodetector, the output end of the operational amplifier is electrically connected to the input end of the analog-to-digital converter, and the output end of the analog-to-digital converter is electrically connected to the field programmable gate array .

In one embodiment, the analog-to-digital converter is set to quickly acquire signals, and the field programmable gate array is set to perform high-speed phase and frequency calculation on the signals acquired by the analog-to-digital converter (exemplarily, a smoothing filter sub may be integrated on the FPGA. unit and 260-point fast Fourier transform sub-unit), thus, the lidar measurement speed is fast, the anti-interference ability is strong, and the precision is high. At the same time, the field programmable gate array can discard unstable data and only collect stable data for processing, so that the data consistency is good and the data stability is high.

In addition, the analog-to-digital converter set for high-speed signal acquisition and the FPGA set for high-speed phase calculation used by the lidar can adopt professional tape-out technology, so that the product has a high integration level, a small area, reliability and stability. higher, resulting in lower cost and ease of miniaturization. At the same time, the use of the boundary scan test technology of the Joint Test Action Group (JTAP) can reduce the test cost and test time, thereby shortening the time to market.

Continuing to refer to Fig. 9, the lidar also includes a power supply unit, a microprocessor (Microcontroller Unit, MCU) and a high-voltage adjustment unit; the power supply unit is electrically connected to the microprocessor, FPGA, laser emission unit, etc. to achieve power supply, and the first part of the microprocessor A control terminal is electrically connected to the FGPA to realize a variety of data interaction and program control, and the second control terminal of the microprocessor is electrically connected to the photodetector through a high-voltage adjustment unit to adjust the voltage of the photodetector, thereby allowing the photodetector to be detected. The amplifier can amplify a variety of different reflected echo signals.

In one embodiment, the power supply unit can convert the external power supply into the voltage required by the multiple components of the module according to the requirements of the module, and supply power to the multiple components respectively. In addition, the microprocessor can control the power supply unit to realize the independent power supply of multiple components in the lidar.

In one embodiment, the high voltage adjustment unit can adjust the magnitude of the high voltage (High voltage, HV) applied to the photodetector by means of Pulse Width Modulation (PWM).

Exemplarily, in the high voltage process of pulse width modulation, the larger the duty cycle, the higher the voltage value.

Continuing to refer to FIG. 9 , the lidar further includes a temperature detection unit (AD_NTC), a high voltage detection unit (AD_HV) and a standard voltage detection unit (AD_VBAS). The output end of the temperature detection unit, the output end of the high voltage detection unit and the The output ends are respectively electrically connected with the input ends of the microprocessor; the temperature detection unit is set to detect the temperature value of the photodetector, the high voltage detection unit is set to detect the high voltage value of the photodetector, and the standard voltage detection unit is set to detect the temperature value of the photodetector. Standard voltage value; the microprocessor is also set to adjust the output voltage according to the temperature value and various feedback signals.

In this embodiment, in order to make the lidar applicable to different environments, a temperature detection unit, a high-voltage detection unit and a standard voltage detection unit are designed to monitor the use environment of the photodetector, and according to the environmental information (including temperature value, high-voltage value and standard voltage value) to adjust the voltage value applied to the photodetector.

Exemplarily, according to the influence of temperature on the photodetector, the change of the echo signal received by the photodetector caused by the temperature change is compensated by the voltage difference. Exemplarily, according to the intensity of the echo signal generated by the surface emission of the target object, the change in the echo signal received by the photodetector caused by the change in the intensity of the echo signal is compensated by the voltage difference. Therefore, the optical signal detection module can be applied to a variety of different environments.

In this embodiment, a constant current, constant voltage and constant power drive circuit (not shown in FIG. 9 ) is also used to provide a stable power supply system for the laser emitting unit. At the same time, the laser emitting unit’s own voltage feedback is used to stabilize the operation of the laser emitting unit. point.

In one embodiment, switching is performed by a high-speed switching switch, which greatly improves the frequency switching time. Applying high-speed switch (SW) to lidar can effectively improve measurement accuracy.

In one embodiment, the optical path system layout of the lidar includes: a coaxial system and a single-transmitting dual-receiving system.

In one embodiment, the lidar further includes an angle detection unit, which is electrically connected to the signal processing unit in the optical signal detection module; the angle detection unit is configured to detect the angle value of the rotation of the lidar; the signal processing unit is further configured to The amount of change in the distance value is associated with the amount of change in the angle value.

In one embodiment, the light emitting module can be rotated within a range of 360 degrees, and the angle detection unit is set to detect the angle of rotation of the light emitting module, so that the lidar can achieve a horizontal 360-degree two-point range within a range of at least 0.01 meters (m) to 150 m. Dimensional scanning detection, so as to obtain the two-dimensional position information of the surrounding environment. In one embodiment, the detection accuracy of the lidar can be as high as millimeters, so that the lidar can be widely used in laser scanning systems, monitoring systems, space mapping (space modeling), collision avoidance, robotics, environmental detection, and military reconnaissance, etc. field.

In one embodiment, the rotation transmission mode of the lidar includes: a brushed motor, a brushless motor, or wireless power supply.

In one embodiment, the lidar further includes a communication unit; the communication unit is electrically connected to the signal processing unit in the optical signal detection module; the communication unit is configured to compare the distance value, the angle value and the variation of the distance value obtained by the signal processing unit with the change amount of the distance value. At least one of the correlations of the variation of the angle value is transmitted to a feedback signal receiving unit.

In one embodiment, the feedback signal receiving unit may be an optical transmitting module, and the optical transmitting module adjusts the intensity of the transmitted detection optical signal through the received information, so as to be suitable for different detection environments.

In an embodiment, the feedback signal receiving unit may also be a microcontroller, and the microcontroller is configured to further process the detected data, so as to monitor the surrounding environment or realize automatic control.

In an embodiment, the communication mode of the communication unit may include: optical communication, Bluetooth communication or WIFI communication.

In this way, data transmission through wireless transmission can reduce the number of external interfaces of the lidar, which simplifies the structure of the lidar on the one hand; or water environment.

Exemplarily, FIG. 10 is a schematic diagram of a workflow of a lidar provided by an embodiment of the present application. Referring to FIG. 10 , the working flow of the lidar includes the following steps.

Step S5110, the motor is powered on and rotated.

Among them, the rotation of the motor (motor) can drive the rotation module (mainly including the light emission module and the light signal detection module) to rotate, so that the lidar can realize scanning and detection within a 360-degree range.

Step S5120, transmitting a detection light signal.

Wherein, the detection light signal may be an infrared laser beam modulated by a high frequency modulation signal. The detection light signal is sent out by the laser emitting unit.

Step S5130, receiving an echo signal.

The echo signal is a reflected light signal formed after the detection light signal sent by the light emitting module is reflected by the target object. The echo signal is received by the signal receiving unit in the optical signal detection module.

Step S5140: Calculate the distance according to the phase difference.

The phase difference between the detection light signal and the echo signal is related to the distance of the target object.

Exemplarily, the formula for distance measurement using the phase method is:

where D is the distance to be detected, c is the speed of light,

is the detected phase difference, and f is the modulation frequency of the detected optical signal. Therefore, as long as the phase difference between the detection light signal and the echo signal is detected, the distance to be detected can be calculated. The optical signal detection module provided by the above embodiments can realize high-speed data calculation, thereby realizing fast processing of the optical signal, and thus quickly obtaining the distance to be detected.

Step S5150, upload data.

Wherein, this step may include feeding back the data obtained in step S5140 to the light emitting module performing step S5120 and the optical signal detecting module performing step S5130. Thus, a closed-loop self-feedback adjustment system is formed, and the intensity of the detection light signal and the echo signal is adjusted, so that the detection result is more accurate.

Meanwhile, this step may further include uploading the data obtained in step S5140 to a feedback signal receiving unit, that is, performing step S5160.

Step S5160, data output.

Among them, this step can realize the display of the two-dimensional detection point cloud image data, and can also use the output data as a control command to realize automatic control.

Exemplarily, FIG. 11 is a schematic flowchart of an algorithm of a lidar provided by an embodiment of the present application. Referring to FIG. 11 , the workflow of the lidar includes the following steps.

Step S5200, start the measurement.

Wherein, to realize this step, the start button in the lidar can be pressed, the start button on the lidar screen can be clicked, or the remote control can be performed by means of wireless transmission.

Step S5210, frequency configuration.

Wherein, this step is performed by the light emitting module, and the high-frequency modulated signal output by the high-frequency modulated signal output unit is loaded into the laser emitting unit to modulate a detection light signal with a frequency that meets the requirements.

Step S5220, temperature, high voltage, and bias (Bias) point detection.

Among them, this step is performed by the optical signal detection module. By detecting the application environment of the laser radar, such as the application environment parameters of the signal receiving unit, the voltage applied to the signal receiving unit is adjusted subsequently, that is, step S5230 is executed, which can improve the different usages. The accuracy of the detection results in the environment, so that the lidar can be applied to more test environments.

After step S5200 and before step S5220, the following three steps may be included in order to realize the rotation of the lidar.

Step S5310, start the radar motor.

Wherein, the rotation of the motor can drive the light transmitting module and the signal receiving unit (or the entire light signal detection module) in the lidar system to rotate.

Step S5320, controlling the rotational speed.

Among them, the rotation speed can be adjusted to a preset range according to the density of detection points within each 360-degree range or the actual needs of the detection range.

Exemplarily, when the requirement for the density of detection points per 360 degrees is low, a higher rotation speed can be used; when the requirements for the density of detection points per 360 degrees are higher, a lower rotation speed can be used.

Exemplarily, the control of the rotational speed can be realized by adjusting the knob for controlling the rotational speed or inputting a desired rotational speed value.

Step S5330, measure the code wheel signal.

Wherein, this step is performed by the angle detection unit. By performing this step, the detection of the rotation angle and the monitoring of the rotational speed can be realized.

After step S5220, step S5230 is performed.

Step S5230, high pressure adjustment.

Among them, this step can be realized by pulse width modulation. After step S5230 is completed, the receiving unit is in a working state suitable for the use environment, and starts to send and receive signals at this time, including the following steps.

Step S5410, frequency selection 1. The choice of frequency can be realized by FPGA controlling the switch to select the phase-locked loop.

Step S5420, switch to the inner optical path. The switching between the inner optical path and the outer optical path can also be realized by a switch.

Step S5430, collecting the inner optical path signal.

Step S5440, signal processing, calculating the phase of the inner optical path.

Step S5450, switch to the external optical path.

Step S5460, collect external optical path signals.

Step S5470, signal processing, calculating the phase of the external optical path.

Step S5480, calculate the phase difference 1.

Step S5490: Calculate the distance measured by the measuring ruler 1.

Usually, due to the phase method for distance measurement, the distance measured by one measuring ruler is not accurate enough, and multiple measuring rulers are required to cooperate. Therefore, the detection of the distance to the target object by at least one detection light signal with a frequency different from the frequency of step S5410 is also included, including the following: step.

Step S5510, frequency selection 2. The frequency selection can also be achieved through the FPGA control switch to select the phase-locked loop.

Step S5520, switch to the inner optical path.

Step S5530, collecting the inner optical path signal.

Step S5540, signal processing, calculating the phase of the inner optical path.

Step S5550, switch to the external optical path.

Step S5560, collecting external optical path signals.

Step S5570, signal processing, calculating the phase of the external optical path.

Step S5580, calculate the phase difference 2.

Step S5590: Calculate the distance measured by the measuring ruler 2.

Based on the distance measured by the measuring ruler 1 in the above step S5490 and the distance measured by the measuring ruler 2 in the above step S5590, step S5610 is executed.

Step S5610, the measuring ruler is connected.

Among them, the linking of measuring rulers on the one hand refers to combining the distance measured by the above-mentioned measuring ruler 1 with the distance measured by measuring ruler 2; distance value.

Exemplarily, the measuring ruler 1 and the measuring ruler 2 are used as the rough ruler by the difference frequency of the software algorithm, the distance calculated by the rough ruler is 100m, the measuring ruler 2 is the fine ruler, and the distance measured by the fine ruler is 0.8m, then the connection is made. The resulting distance is 100.8m.

It should be noted that the specific numerical values of the above distances are only illustrative and not limiting.

Step S5620, calculate the final distance.

Wherein, the distance obtained in step S5610 is usually a relative distance value, and there is a distance error value. There is a one-to-one correspondence between the relative distance value and the absolute value of the distance. Therefore, the absolute value of the distance can be obtained by looking up the table. value as the final distance.

Step S5630, end the measurement.

Exemplarily, corresponding to step S5200, the measurement can be ended by means of buttons, keys or remote control; or the measurement can be automatically ended after the threshold range set by the lidar detection is set. When the measurement is finished, the lidar can be in a standby state or powered off.

It should be noted that the work flow of the lidar system shown in FIG. 10 and the algorithm flow of the lidar shown in FIG. 11 are both executed based on the lidar provided by the embodiment of the present application, and the parts that are not described in detail in the steps are: It can be understood with reference to the working principles of the multiple components of the lidar in the above-mentioned embodiments, and details are not repeated here.

In addition, Figure 11 is only an illustration of the algorithm flow based on the feasibility of the principle. In actual operation, other procedures can also be used. For example, without switching the internal and external optical paths, the modulated beam can be directly divided into the internal optical path and the external optical path through optical components. . For another example, the inner optical path of all beams of different frequencies is directly measured and then switched to the outer optical path.

Claims

A light emitting module, comprising:

a high-frequency modulation signal output unit, configured to output preset high-frequency modulation signals of at least two different frequencies;

a laser emitting unit, connected to the high-frequency modulation signal output unit, and configured to emit at least two laser beams of different frequencies modulated by the at least two high-frequency modulation signals of different frequencies respectively;

And, the laser emitting unit includes a laser, the laser includes a seed source and a fiber amplifier, and the fiber amplifier is configured to amplify the optical signal emitted by the seed source.
The light emitting module according to claim 1, wherein the wavelength of the laser beam emitted by the laser is a 1550 nm band or a 2000 nm band.
The light emission module according to claim 2, wherein the fiber amplifier is an erbium-doped fiber amplifier or a thulium-doped fiber amplifier or an erbium-ytterbium co-doped fiber amplifier.
The light emitting module according to claim 1, wherein each high frequency modulation signal is a main oscillator high frequency modulation signal;

The high-frequency modulation signal output unit is further configured to output at least two local oscillator high-frequency modulation signals of different frequencies to the signal receiving unit, wherein the at least two local oscillator high-frequency modulation signals are one with the at least two main oscillator high-frequency modulation signals. One-to-one correspondence, and each local oscillator high-frequency modulation signal differs from the corresponding main oscillator high-frequency modulation signal by a preset frequency.
The light emitting module according to claim 1, wherein the preset frequency range is 0-100 MHz.
The optical transmitter module according to claim 4, wherein the high-frequency modulation signal output unit comprises at least two groups of phase-locked loops, and each group of phase-locked loops is respectively configured to output a high-frequency modulation signal of a main oscillator and The local oscillator high-frequency modulation signal corresponding to the high-frequency modulation signal.
The light emitting module according to claim 1, wherein the laser emitting unit further comprises a collimating lens, the laser and the collimating lens are arranged in sequence along the propagation direction of the light beam, and the collimating lens is arranged to The laser beam emitted by the laser is collimated.
An optical signal detection module, comprising:

The echo signal receiving unit is configured to receive a first high-frequency echo signal and a second high-frequency echo signal, where the first high-frequency echo signal is a laser beam after the first laser beam is reflected by the target object, the The second high-frequency echo signal is the laser beam after the second laser beam is reflected by the target object;

The reference signal receiving unit is configured to receive a first reference signal and a second reference signal, wherein the first reference signal is a reference signal modulated by a first high frequency modulation signal, and the second reference signal is a reference signal modulated by a second high frequency modulation signal. The reference signal modulated by the frequency modulated signal;

The first laser beam is a laser beam modulated by the first high-frequency modulation signal, and the second laser beam is a laser beam modulated by the second high-frequency modulation signal; the first high-frequency modulation signal the frequency of the modulation signal is greater than the frequency of the second high frequency modulation signal;

a signal processing unit, which is electrically connected to the echo signal receiving unit and the reference signal receiving unit at the same time; the signal processing unit is configured to: according to the first reference signal and the first high frequency echo signal A first reference distance value of the target object is obtained by a phase difference; a second reference distance value of the target object is obtained according to the first phase difference and the second phase difference, and a second reference distance value of the target object is obtained according to the first reference distance value and the The second reference distance value determines the measured distance value of the target object; wherein, the second phase difference is the phase difference between the second reference signal and the second high frequency echo signal.
The optical signal detection module according to claim 8, wherein the first reference signal and the second reference signal are respectively a first reference laser beam and a second reference laser beam, or a first reference electrical signal or The second reference electrical signal.
The optical signal detection module according to claim 9, wherein the first reference signal is a first reference laser beam; the second reference signal is a second reference laser beam; the echo signal receiving unit and the The reference signal receiving unit is further configured to: receive the first local oscillator high-frequency modulation signal; convert the first high-frequency echo signal into a corresponding electrical signal, and convert the electrical signal corresponding to the first high-frequency echo signal with the electrical signal corresponding to the first high-frequency echo signal. The first local oscillator high-frequency modulation signal is mixed to obtain a first difference frequency ranging signal; the first reference laser beam is converted into a corresponding electrical signal and the electrical signal corresponding to the first reference laser beam mixing with the first local oscillator high-frequency modulation signal, or mixing the first reference electrical signal with the first local oscillator high-frequency modulation signal to obtain a first difference frequency reference signal; receiving a second reference signal The local oscillator high-frequency modulation signal; converting the second high-frequency echo signal into a corresponding electrical signal, and performing the electrical signal corresponding to the second high-frequency echo signal with the second local oscillator high-frequency modulation signal. frequency mixing to obtain a second difference frequency ranging signal; converting the second reference laser beam into a corresponding electrical signal and combining the electrical signal corresponding to the second reference laser beam with the second local oscillator high-frequency modulation signal mixing, or mixing the second reference electrical signal with the second local oscillator high-frequency modulation signal to obtain a second difference frequency reference signal; wherein the first high-frequency modulation signal is the first main A high-frequency modulation signal, the second high-frequency modulation signal is the second main oscillator high-frequency modulation signal, and the frequency of the first main oscillator high-frequency modulation signal and the first local oscillator high-frequency modulation signal differs by a preset frequency frequency, the frequency of the second main oscillator high-frequency modulation signal and the frequency of the second local oscillator high-frequency modulation signal differs from the preset frequency;

The signal processing unit is configured to obtain the first reference distance value of the target object according to the first phase difference between the first reference signal and the first high-frequency echo signal in the following manner: Comparing the first beat frequency ranging signal with the first beat frequency reference signal to obtain a first phase difference, and obtaining a first reference distance value of the target object according to the first phase difference;

The signal processing unit is configured to obtain the second reference distance value of the target object according to the first phase difference and the second phase difference by: combining the second difference frequency ranging signal with the second comparing the difference frequency reference signals to obtain a second phase difference; calculating a third phase difference between the second phase difference and the first phase difference; obtaining a second phase difference of the target object according to the third phase difference Reference distance value.
The optical signal detection module according to claim 8, wherein the echo signal receiving unit and/or the reference signal receiving unit both comprise photodetectors.
The optical signal detection module according to claim 11, wherein the echo signal receiving unit and/or the reference signal receiving unit further comprises a receiving lens and an optical filter, the receiving lens, the optical filter and the The photodetectors are arranged in sequence along the propagation direction of the light beam;

the receiving lens is configured to focus the first high frequency echo signal and the second high frequency echo signal to the photodetector;

The filter is configured to filter out interference signals of other wavelengths through the first high-frequency echo signal and the second high-frequency echo signal.
The optical signal detection module according to claim 8, wherein the signal processing unit comprises an operational amplifier, an analog-to-digital converter and a field programmable gate array;

The input end of the operational amplifier is electrically connected to the echo signal receiving unit and the reference signal receiving unit, the output end of the operational amplifier is electrically connected to the input end of the analog-to-digital converter, and the analog-to-digital converter is electrically connected. the output terminal is electrically connected with the field programmable gate array;

The operational amplifier is configured to respectively transmit the first beat frequency ranging signal, the first beat frequency reference signal, and the second beat frequency ranging signal transmitted by the echo signal receiving unit and the reference signal receiving unit and amplifying the second difference frequency reference signal;

The analog-to-digital converter is configured to respectively convert the first beat frequency ranging signal, the first beat frequency reference signal, the second beat frequency ranging signal and the first beat frequency ranging signal amplified by the operational amplifier. The two-difference frequency reference signal is converted from an analog signal to a digital signal;

The field programmable gate array is configured to compare the digital signal corresponding to the first beat frequency ranging signal with the digital signal corresponding to the first beat frequency reference signal to obtain a first phase difference, and obtain a first phase difference according to the The first phase difference calculates the first reference distance value of the target object; the digital signal corresponding to the second beat frequency ranging signal is compared with the digital signal corresponding to the second beat frequency reference signal to obtain the first Two phase differences; calculating a third phase difference between the second phase difference and the first phase difference, and calculating a second reference distance value of the target object according to the third phase difference; The reference distance value and the second reference distance value determine the measured distance value of the target object.
The optical signal detection module according to claim 13, wherein the operational amplifier adopts a three-stage signal amplifying circuit.
An optical system, comprising: the optical signal detection module according to any one of claims 8-13, and an optical emission module connected to the optical signal detection module;

The light emission module includes a high-frequency modulation signal output unit and a laser emission unit, the high-frequency modulation signal output unit is configured to output preset high-frequency modulation signals of at least two different frequencies; the laser emission unit is configured to emit At least two laser beams of different frequencies modulated by at least two high-frequency modulation signals of different frequencies respectively;

A part of the at least two laser beams of different frequencies is emitted and reflected by the target object and received by the echo signal receiving unit; the other part of the two laser beams of different frequencies is directly received by the reference signal as a reference signal unit receives;

The laser emitting unit includes a laser, the laser includes a seed source and a fiber amplifier, and the fiber amplifier is configured to amplify the optical signal emitted by the seed source.
The optical system according to claim 15, wherein the wavelength of the laser beam emitted by the laser is in the 1550 nm band or the 2000 nm band.
The optical system according to claim 16, wherein the fiber amplifier is an erbium-doped fiber amplifier or a thulium-doped fiber amplifier or an erbium-ytterbium co-doped fiber amplifier. 18. A lidar system comprising the optical system according to any one of claims 15 to 17.