Laser measurement method, laser radar and autonomous vehicle

Abstract

The invention provides a laser measurement method, a laser radar and an autonomous vehicle, and relates to the field of laser radar measurement. The method comprises the steps that a first laser beam and a second laser beam are generated, and the frequency change directions of the first laser beam and the second laser beam are opposite in a frequency sweeping period; multiplexing the first and second laser beams into a swept-frequency beam; splitting the sweep-frequency light beam into a signal light beam and a local oscillator light beam; transmitting a signal light beam; receiving a reflected light beam; performing in-phase orthogonal coherent demodulation on the local oscillation light beam and the reflection light beam so as to obtain scalar values of beat frequency in a frequency raising stage and beat frequency in a frequency lowering stage; and detecting the beat frequency of the up-conversion phase and the beat frequency of the down-conversion phase to determine the speed and / or distance of the object. According to the scheme, a measurement blind area can be avoided, and the measurement precision is improved.

Description

Technical Field

[0001] The present application relates to the field of lidar measurement, and particularly to a lidar measurement method, a lidar, and a vehicle including the lidar, which are applied to a lidar. Background Art

[0002] A lidar can accurately measure the position (distance and angle), motion state (speed, vibration, and attitude), and shape of a target object, and detect, identify, distinguish, and track the target object. The lidar can be classified into a pulsed lidar and a frequency-modulated continuous-wave (FMCW) lidar according to the working mode. A typical FMCW lidar emits a laser beam and uses a detector to receive the reflected beam of the target object from the nearby environment, so as to calculate information such as the distance and speed of the target object. Due to the Doppler shift and the lidar system, to accurately obtain the speed signal and distance signal of the target object at a certain moment, the up-sweeping frequency information and the down-sweeping frequency information are required simultaneously. When the frequency shift caused by the Doppler effect is greater than the frequency offset caused by the flight time of the reflected beam, it will lead to calculation errors of the short-distance information, thereby resulting in a measurement blind area. In addition, the related FMCW lidar can only obtain one up-sweeping frequency information and one down-sweeping frequency information in each sweep cycle. When the Doppler broadening causes the up-sweeping frequency signal and the down-sweeping frequency signal to be indistinguishable, one or both of these two signals will have detection errors, resulting in a low detection probability. Summary of the Invention

[0003] In view of this, the present application provides a lidar measurement method, a lidar, and a vehicle including the lidar, which are applied to a lidar, so as to solve the problem that the Doppler effect causes calculation errors of short-distance information, thereby resulting in a measurement blind area, and solve the problem that the Doppler broadening causes a low detection probability.

[0004] In a first aspect, the present disclosure provides a lidar measurement method applied to a lidar. The method includes: generating a first laser beam and a second laser beam, where each of the first laser beam and the second laser beam is a frequency-modulated laser, has the same sweep cycle and different wavelengths, and the frequency change directions of the first laser beam and the second laser beam are opposite within the sweep cycle; multiplexing the first laser beam and the second laser beam into a sweep beam; splitting the sweep beam into a signal beam and a local oscillator beam; emitting the signal beam; receiving the reflected beam generated after the signal beam encounters an object; performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam, so as to obtain scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; and detecting the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam, so as to measure the speed of the object and / or the distance between the object and the lidar.

[0005] Optionally, the scalar value of the beat frequency in the up-conversion stage includes a positive value or a negative value of the beat frequency in the up-conversion stage; the scalar value of the beat frequency in the down-conversion stage includes a positive value or a negative value of the beat frequency in the down-conversion stage.

[0006] Optionally, before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam, the method further includes: performing time delay or frequency shift on at least one of the signal beam, the reflected beam, and the local oscillator beam.

[0007] Optionally, performing time delay on at least one of the signal beam, the reflected beam, and the local oscillator beam includes: performing time delay on the signal beam and the reflected beam, or performing time delay on the local oscillator beam, so as to increase or decrease the scalar values of the beat frequencies in the up-conversion stage and the down-conversion stage between the local oscillator beam and the reflected beam.

[0008] Optionally, performing frequency shift on at least one of the signal beam, the reflected beam, and the local oscillator beam includes: performing frequency shift on the frequency of the signal beam or the local oscillator beam, so as to increase or decrease the scalar values of the beat frequencies in the up-conversion stage and the down-conversion stage between the local oscillator beam and the reflected beam.

[0009] Optionally, performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam includes: inputting the reflected beam and the local oscillator beam into a 90-degree mixing unit to perform in-phase quadrature coherent demodulation.

[0010] Optionally, the beat frequencies in the up-conversion stage and the down-conversion stage are located on both sides of the frequency of the ranging zero point position without Doppler frequency shift in the ranging spectrum of the lidar.

[0011] Optionally, the opposite directions of frequency change of the first laser beam and the second laser beam include one of the following two cases: in the first half cycle of the frequency sweep period, the first laser beam sweeps from zero frequency, and the second laser beam sweeps from the maximum frequency; in the second half cycle of the frequency sweep period, the first laser beam sweeps from the maximum frequency, and the second laser beam sweeps from zero frequency; or in the first half cycle and the second half cycle of the frequency sweep period, the first laser beam sweeps from zero frequency, and the second laser beam sweeps from the maximum frequency.

[0012] Second aspect, the present application provides a lidar, the lidar comprising: a first laser source configured to generate a first laser beam; a second laser source configured to generate a second laser beam, wherein each of the first laser beam and the second laser beam is a frequency-modulated laser, having the same sweep period and different wavelengths, and the frequency change directions of the first laser beam and the second laser beam are opposite within the sweep period; a wavelength division multiplexer configured to multiplex the first laser beam and the second laser beam into a swept-frequency beam; a beam splitter configured to split the swept-frequency beam into a signal beam and a local oscillator beam; an optical transceiver configured to transmit the signal beam and receive a reflected beam generated after the signal beam encounters an object; an in-phase quadrature coherent demodulator configured to perform in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam so as to obtain scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; and a detector configured to detect the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam to measure the speed of the object and / or the distance between the object and the lidar.

[0013] Optionally, the scalar value of the beat frequency in the up-frequency stage includes a positive value or a negative value of the beat frequency in the up-frequency stage; the scalar value of the beat frequency in the down-frequency stage includes a positive value or a negative value of the beat frequency in the down-frequency stage.

[0014] Optionally, the lidar further comprises: a time delay device configured to perform time delay on at least one of the signal beam, the reflected beam and the local oscillator beam before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam; and / or a frequency shifter configured to perform frequency shifting on at least one of the signal beam, the reflected beam and the local oscillator beam before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam.

[0015] Optionally, the time delay device is specifically configured to perform time delay on the signal beam and the reflected beam, or perform time delay on the local oscillator beam, so as to increase or decrease the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; the frequency shifter is specifically configured to perform frequency shifting on the frequency of the signal beam or the local oscillator beam, so as to increase or decrease the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

[0016] Optionally, the in-phase quadrature coherent demodulator is specifically configured to receive the reflected beam and the local oscillator beam to obtain scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

[0017] Optionally, the beat frequencies in the up - frequency stage and the down - frequency stage are located on both sides of the frequency corresponding to the ranging zero - point position without Doppler frequency shift in the ranging spectrum of the lidar.

[0018] Optionally, the opposite directions of frequency change of the first laser beam and the second laser beam include one of the following multiple cases: within the first half - period of the frequency - sweeping period, the first laser beam sweeps from zero frequency and the second laser beam sweeps from the maximum frequency; within the second half - period of the frequency - sweeping period, the first laser beam sweeps from the maximum frequency and the second laser beam sweeps from zero frequency; or within the first half - period and the second half - period of the frequency - sweeping period, the first laser beam sweeps from zero frequency and the second laser beam sweeps from the maximum frequency.

[0019] In a third aspect, the present application provides an autonomous vehicle, which includes the lidar according to the second aspect.

[0020] The solution of the present application can obtain the scalar values of the beat frequencies in the up - frequency stage and the down - frequency stage of the local oscillator signal and the reflected signal, can expand the measurement spectrum range of the lidar, avoid the measurement blind area caused by Doppler frequency shift, and improve the measurement accuracy. In addition, the solution of the present application uses a dual - wavelength combined laser as the detection optical signal, can obtain the beat frequency in the up - frequency stage and the beat frequency in the down - frequency stage simultaneously at one sampling moment, can accurately obtain the speed and distance information of the target object, improve the angular scanning accuracy of the lidar, solve the problem that Doppler broadening makes it impossible to distinguish the beat frequency in the up - frequency stage and the beat frequency in the down - frequency stage, can obtain the direction of the target speed, improve the signal - to - noise ratio, and solve the problem of point cloud trailing. Description of the Drawings

[0021] Figure 1 Shows a schematic diagram of the working principle of a related frequency - modulated continuous - wave lidar;

[0022] Figure 2 Shows a schematic diagram of measuring a target object using related technologies to obtain the beat frequency in the up - frequency stage and the beat frequency in the down - frequency stage;

[0023] Figure 3A and Figure 3B Shows a schematic diagram of Doppler frequency shift causing the beat frequencies in the up - frequency stage and the down - frequency stage to be outside the measurement spectrum of the lidar;

[0024] Figure 4 Shows a schematic diagram of obtaining the scalar values of the beat frequencies in the up - frequency stage and the down - frequency stage using the in - phase IQ coherent demodulation method of the present application;

[0025] Figure 5 Shows a schematic diagram of the flow of the laser ranging method of the present application;

[0026] Figure 6A Shows the waveform schematic of the local oscillator beam and the signal beam of the present application Figure 1 ;

[0027] Figure 6B Shows the use of Figure 6A The waveform of the beat frequency in the up - frequency stage and the down - frequency stage is obtained; Schematic diagram

[0028] Figure 7A Shows the waveform schematic of the local oscillator beam and the signal beam of the present application Figure 2 ;

[0029] Figure 7B Shows the use of Figure 7A The waveform of the beat frequency in the up - frequency stage and the down - frequency stage is obtained; Schematic diagram

[0030] Figure 8A And Figure 8B Shows the schematic diagram of the time delay of the signal beam and the reflected beam by using the laser measurement method of the present application;

[0031] Figure 9A And Figure 9B Shows the time - frequency domain schematic diagram of the time delay of the local oscillator beam by using the laser measurement method of the present application;

[0032] Figure 10 Shows the schematic diagram of the frequency shift of the local oscillator beam by using the laser measurement method of the present application;

[0033] Figure 11 Shows the schematic diagram of the frequency shift of the signal beam by using the laser measurement method of the present application;

[0034] Figure 12 Shows the schematic diagram of the expanded measurement spectrum of the lidar by using the laser measurement method of the present application;

[0035] Figure 13 Shows the structural schematic of the lidar of the present application Figure 1 ;

[0036] Figure 14A Shows the structural schematic of the lidar of the present application Figure 2 ;

[0037] Figure 14B Shows the third structural schematic diagram of the lidar of the present application;

[0038] Figure 15A And Figure 15B Shows the schematic diagram of an autonomous vehicle including the lidar of the present application. Detailed implementation mode

[0039] Next, specific embodiments of the present application will be described in detail with reference to the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the following exemplary embodiments, the described embodiments are not all embodiments of the present application. Instead, they are merely examples of devices and methods that are consistent with some aspects of the present application as detailed in the appended claims. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0040] Reference Figure 1 , Figure 1 , is a schematic diagram of the working principle of a related Frequency Modulated Continuous Wave (FMCW) lidar. The related frequency modulated continuous wave lidar 1 adopts the working principle of coherent reception. By comparing the instantaneous frequency relationship between the reflected light beam reflected from the target object 2 and the local oscillator light beam of the lidar 1, information such as the distance between the target object 2 and the lidar 1 and the speed of the target object can be given simultaneously. The related frequency modulated continuous wave lidar can use a periodic triangular wave or sawtooth wave waveform as the signal light beam.

[0041] Reference Figure 2 , Figure 2 shows a schematic diagram of measuring a target object using the related technology to obtain the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage. In Figure 2 , the solid triangular wave is the instantaneous time-frequency relationship of the signal light beam or the local oscillator light beam of the lidar, and the dashed triangular wave is the instantaneous real frequency relationship of the reflected light beam of the target object, where τ is the delay of the reflected light beam of the target object, and f1 and f2 are the beat frequency of the reflected light beam of the target object in the up-sweeping part and the down-sweeping part (i.e., the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the reflected light beam and the local oscillator light beam), T is the period including one up-sweeping and one down-sweeping, and f B is the swept bandwidth of linear frequency modulation, and f d =(f2 - f1) / 2. Figure 2 , the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage of the reflected light beam are respectively:

[0042]

[0043]

[0044] Assume that the distance between the target object and the lidar is R, then R = τ * c / 2, where c is the speed of light and λ is the laser wavelength. Then in the Figure 2 time-frequency relationship diagram, the distance R and speed ν of the target object are as follows:

[0045]

[0046] When f1 = 0, the relationship between the above distance and speed can be expressed as follows:

[0047]

[0048] In the above formula 2, the absolute values of f1 and f2 are required, that is, it is required that both f1 and f2 are greater than 0, and the actual distance between the lidar and the target object needs to be greater than the value of R calculated by the above formula, R m , that is to say, it is necessary to ensure that the value of R, R > R m , that is less than the above value of R m will cause calculation errors in speed and distance. In addition, it can be seen from formula 3 that R is proportional to the speed ν of the target object. When the speed ν of the target object is larger, the above value of R is larger. When the true speed ν of the target object is relatively fast, the frequency shift caused by the Doppler effect may be greater than the frequency offset caused by the flight time of the reflected light beam, resulting in the actual value of the beat frequency f1 in the up-frequency stage between the local oscillator light beam and the received reflected light beam being negative, as shown in Figure 3. Although the beat frequency f1 in the up-frequency stage between the local oscillator light beam and the received reflected light beam is actually negative (less than 0), the lidar judges this frequency f1 as positive (greater than 0). Therefore, when using the above formulas 1-3 to calculate the distance and speed of the target object, calculation errors in distance and speed will occur, resulting in a measurement blind area.

[0049] This application adopts the method of in-phase quadrature (IQ) coherent demodulation to obtain the true values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the reflected light beam and the local oscillator light beam, that is, scalar values (positive or negative values, that is, values greater than 0 or less than 0), as Figure 4 shown. The solution of this application can obtain the true value, rather than the absolute value of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage (only values greater than 0), and can effectively avoid the ranging blind area. Since the negative frequency information is obtained, the solution of this application can also increase the width of the ranging spectrum of the lidar.

[0050] Specifically, when using the in-phase IQ coherent demodulation method of this application to obtain the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage, the calculation method used is also different from the above formulas 1-2. When the target object moves towards the lidar, the frequency of the reflected light beam increases relative to the frequency of the local oscillator light beam. At this time, the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage of the reflected light beam are respectively:

[0051]

[0052] The distance and speed of the target object are as follows:

[0053]

[0054] When the target object moves away from the lidar, the frequency of the reflected light beam decreases relative to the frequency of the local oscillator light beam. At this time, the beat frequencies in the up-frequency stage and the down-frequency stage of the reflected light beam are respectively:

[0055]

[0056]

[0057] The distance and speed of the target object are as follows:

[0058]

[0059] By using the above formulas 4-7, the scalar values (true values) of the beat frequencies in the up-frequency stage and the down-frequency stage can be accurately obtained, the measurement spectrum of the lidar can be extended, and the ranging blind area caused by the Doppler frequency shift can be avoided.

[0060] The solution of the present application also adopts a dual-wavelength modulation method. In addition to obtaining the true frequency information of the beat frequencies in the up-frequency stage and the down-frequency stage, the beat frequencies in the up-frequency stage and the down-frequency stage can be obtained simultaneously at the same detection moment (fast Fourier transform FFT time window), which can improve the detection success rate, improve the angle scanning accuracy of the lidar, solve the problem that the up-sweeping frequency (beat frequency in the up-frequency stage) and the down-sweeping frequency (beat frequency in the down-frequency stage) caused by Doppler broadening cannot be distinguished, and can obtain the velocity direction of the target, and improve the signal-to-noise ratio SNR of the detection signal. The specific embodiments of the present application are described below.

[0061] In some embodiments, the present disclosure provides a laser measurement method. The laser measurement method can be applied to a frequency-modulated continuous-wave (FMCW) lidar, such as Figure 5 shown, the laser measurement method includes the following steps S501-S506.

[0062] Step S501: Generate a first laser beam and a second laser beam.

[0063] Specifically, the first laser beam and the second laser beam can be generated by a first laser source and a second laser source respectively. The first laser source and the second laser source can be directly modulated by a chirp signal of an optical signal. For example, the driving signal of the laser light source can be input to the laser light source with an intensity that changes over time, so that the laser light source generates and outputs a laser beam, that is, a beam with a frequency varying within a predetermined range.

[0064] In some embodiments, each of the first laser source and the second laser source may further include a modulator that receives a modulation signal. The modulator may be configured to modulate the light beam based on the modulation signal to generate and output a laser beam, and the frequency of the laser beam varies within a predetermined range. The principle of generating a laser beam by an FMCW lidar is well known to those skilled in the art. For the sake of saving space, it will not be further described herein.

[0065] Wherein, each of the first laser beam and the second laser beam is a frequency-modulated continuous-wave laser beam, having the same sweep period T and different wavelengths λ1 and λ2.

[0066] Optionally, in each sweep period T, both the first laser beam and the second laser beam may be triangular-wave sweep waveforms, that is, a detection signal whose sweep waveform is triangular, or a detection signal whose time-frequency waveform is triangular. Wherein, the modulation depth of the first laser beam is the same as that of the second laser beam. The modulation depth refers to the ratio between the maximum value and the minimum value when the laser is modulated, and is usually expressed in decibels (dB). The modulation slope of the first laser beam is the same as that of the second laser beam, for example, both are 2f B / T. Wherein, within the sweep period T, the frequency change directions of the first laser beam and the second laser beam are opposite. Specifically, as shown in 6A, the start time of the first laser beam and the start time of the second laser beam may differ by half a period. The first laser beam may start scanning from zero frequency, and the second laser beam may start scanning from the maximum frequency f B start scanning. In Figure 6A the moment when the first laser beam is at zero frequency is also the moment when the second laser beam is at the maximum frequency f B of.

[0067] Optionally, as Figure 7A shown, in each sweep period T, both the first laser beam and the second laser beam may be periodic sweep waveforms. The modulation depth of the first laser beam is the same as that of the second laser beam; the modulation slope of the first laser beam is the same as that of the second laser beam, for example, both are 2f B / T. Different from Figure 6A in, in Figure 7A each of the first laser beam and the second laser beam is a sawtooth waveform. Within the first half period and the second half period of the sweep period T, the frequency change directions of the first laser beam and the second laser beam are opposite. The first laser beam may linearly increase from zero frequency to the maximum frequency f B , and the second laser beam may linearly decrease from the maximum frequency f B to zero frequency; or the second laser beam both linearly increases from zero frequency to the maximum frequency f B , and the first laser beam both starts from the maximum frequency f BLinearly decrease to zero frequency.

[0068] Step S502: Multiplex the first laser beam and the second laser beam into a frequency-swept beam.

[0069] Specifically, a wavelength division multiplexer can be used to multiplex the first laser beam and the second laser beam into a frequency-swept beam. The frequency-swept beam carries two optical signals with two different wavelengths λ1 and λ2. The wavelength division multiplexer can be common to those skilled in the art, for example, it can be a dense wavelength division multiplexer or an optical splitter, etc.

[0070] Step S503: Split the frequency-swept beam into a signal beam and a local oscillator beam.

[0071] In some examples, an optical splitter (also called a beam splitter) can be used to split the frequency-swept beam into a signal beam and a local oscillator beam. The signal beam and the local oscillator beam have the same frequency, the same modulation depth, the same waveform, and the same slope at any time point. Each of the signal beam and the local oscillator beam simultaneously carries two optical signals with two different wavelengths λ1 and λ2. In some examples, the optical splitter can specifically be a specific wavelength coupler (optical splitter) for wavelengths of 445 - 2100 nm, such as a 1×2 optical splitter on an optical chip and an optical splitter of the SMC series. In other examples, other optical splitters known to those skilled in the art that can split the frequency-swept beam into a signal beam and a local oscillator beam can also be used.

[0072] Step S504: Emit the signal beam and receive the reflected beam generated after the signal beam encounters an object.

[0073] In some examples, an optical transmitter and a receiver or an optical transceiver are used to emit the signal beam at a predetermined angle, and an optical receiver or the optical transceiver is used to receive the reflected light reflected by the target object.

[0074] Specifically, a polarization beam splitter (e.g., polarizationsplitter-rotator (PSR)), a circulator (e.g., a three-port circulator), a lens assembly, a beam scanning guiding device, etc. can be included between the optical transceiver and the target object. The lens assembly is configured to collimate the signal beam and focus the reflected beam to couple it into the optical transceiver. The beam scanning guiding device is configured to achieve the deflection and scanning of light.

[0075] Step S505: Perform in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam to obtain the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

[0076] In an embodiment of the present application, a method of in-phase IQ (In-phase and Quadrature) coherent demodulation is used to measure a moving target object, and a scalar value (i.e., a value with a plus or minus sign) of the beat frequency f1 (i.e., the frequency difference) in the up-frequency stage between the rising edge of the local oscillator beam and the rising edge of the reflected beam and the beat frequency f2 (i.e., the frequency difference) in the down-frequency stage between the falling edge of the local oscillator beam and the falling edge of the reflected beam can be obtained. Thus, the frequency range of the negative frequency band can be fully utilized, and the measurement spectrum of the lidar can be extended. The measurement spectrum of the lidar refers to the frequency range of the beat frequency f1 in the up-frequency stage and the beat frequency f2 in the down-frequency stage that the lidar can measure, as shown in Figure 3B In the related FMCW lidar, the range of this measurement spectrum can be [0, +f max , where f max is the maximum value of the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam of the lidar. Therefore, the related FMCW lidar can only obtain the absolute values (positive values) of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage. Due to the influence of the Doppler effect, when the distance between the target object and the lidar is close enough or the relative speed is fast enough, the true value of the beat frequency f1 between the rising edge of the local oscillator beam and the rising edge of the reflected beam or the true value of the beat frequency f1 between the falling edge of the local oscillator beam and the falling edge of the reflected beam may be negative. Therefore, if the measurement spectrum of the related lidar is used, the true value of the beat frequency f1 in the up-frequency stage may be outside the range of this measurement spectrum, resulting in errors in the calculation of the speed and distance of the target object and causing a measurement blind spot.

[0077] Specifically, a 90-degree mixing unit can be used to obtain the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage of the local oscillator beam and the reflected beam. The 90-degree mixing unit can perform 90-degree mixing on the local oscillator beam and the reflected beam, and input the mixed signal into the first balanced detector and the second balanced detector for detection. The 90-degree mixing unit is configured to perform coherent mixing on the local oscillator light and the reflected light, so that the relative phase differences of the four output ports are 0°, 90°, 180°, and 270° respectively. The 90-degree mixing unit can be a 90-degree mixing unit known to those skilled in the art. The present application will not describe it in detail here.

[0078] In some embodiments, before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam, the method further includes: performing time delay or frequency shift on at least one of the signal beam, the reflected beam, and the local oscillator beam.

[0079] In some embodiments, performing a time delay on at least one of the signal beam, the reflected beam, and the local oscillator beam includes: performing a time delay on the signal beam and the reflected beam, or performing a time delay on the local oscillator beam, so that the beat frequencies in the up-conversion stage and the down-conversion stage between the local oscillator beam and the reflected beam move in a first direction or a second direction of the ranging spectrum of the lidar. The first direction of the ranging spectrum is the direction in which the beat frequencies in the up-conversion stage and the down-conversion stage gradually increase, for example, the direction in which the frequency axis extends to the right. The second direction of the ranging spectrum is the direction in which the beat frequencies in the up-conversion stage and the down-conversion stage gradually decrease, for example, the direction in which the frequency axis extends to the left. Therefore, by performing a time delay on at least one of the signal beam, the reflected beam, and the local oscillator beam, the scalar values of the beat frequencies in the up-conversion stage and the down-conversion stage can be increased or decreased.

[0080] Taking the triangular wave of the first laser beam as an example, as Figure 8A shown, when a time delay Δt is performed on both the signal beam and the reflected beam, when the target object moves away from the lidar, the beat frequencies in the up-conversion stage and the down-conversion stage of the reflected beam are respectively:

[0081]

[0082]

[0083] The distance and speed of the target object are as follows:

[0084]

[0085] When the target object moves towards the lidar, the frequency of the reflected beam increases relative to the frequency of the local oscillator beam. At this time, the beat frequencies in the up-conversion stage and the down-conversion stage of the reflected beam are respectively:

[0086]

[0087]

[0088] The distance and speed of the target object are as follows:

[0089]

[0090] As Figure 8BAs shown, when Δt increases, the beat frequency f1 in the up - frequency stage and the beat frequency f2 in the down - frequency stage between the local - oscillator beam and the reflected beam move in opposite directions, so that the spacing increases. Vice versa, when Δt decreases, the beat frequency f1 in the up - frequency stage and the beat frequency f2 in the down - frequency stage between the local - oscillator beam and the reflected beam move in opposite directions, so that the spacing increases. When Δt continues to decrease, the beat frequency f1 in the up - frequency stage and the beat frequency f2 in the down - frequency stage can cross each other and move in opposite directions, so that the spacing increases.

[0091] Taking the triangular - wave signal of the first laser beam as an example, as Figure 9A shown, in this embodiment, a time delay Δt is performed on the local - oscillator signal. When the target object moves away from the lidar, the beat frequencies in the up - frequency stage and the down - frequency stage of the reflected beam are respectively:

[0092]

[0093]

[0094] The distance and speed of the target object are as follows:

[0095]

[0096] When the target object moves towards the lidar, the frequency of the reflected beam increases relative to the frequency of the local - oscillator beam. At this time, the beat frequencies in the up - frequency stage and the down - frequency stage of the reflected beam are respectively:

[0097]

[0098]

[0099] The distance and speed of the target object are as follows:

[0100]

[0101] As Figure 9B shown, when Δt increases, the beat frequency f1 in the up - frequency stage and the beat frequency f2 in the down - frequency stage between the local - oscillator beam and the reflected beam move in opposite directions, so that the spacing decreases. When Δt continues to increase, the beat frequency f1 in the up - frequency stage and the beat frequency f2 in the down - frequency stage can cross each other and move in opposite directions, so that the spacing increases. Vice versa, when Δt decreases, the beat frequency f1 in the up - frequency stage and the beat frequency f2 in the down - frequency stage between the local - oscillator beam and the reflected beam move in opposite directions, so that the spacing increases.

[0102] In the above embodiments, time delays can be applied to both the signal beam and the reflected beam, and / or a time delay can be applied to the local oscillator beam. By applying time delays to one or more of the signal beam, the reflected beam, and the local oscillator beam, the positions of the beat frequencies f1 in the up-conversion stage and f2 in the down-conversion stage between the local oscillator beam and the reflected beam on the measurement spectrum of the lidar can be changed, and the speed of the target object and the distances and speeds between the lidar and the target object can be correctly calculated according to the above formulas, avoiding measurement blind spots and improving measurement accuracy. In addition, due to the adoption of time delays, the time delay system can be used as a measurement scale for the lidar measurement system to accurately obtain the position of the measurement zero point.

[0103] In some embodiments, a time delay device can be used to shift the waveforms of the signal beam and the reflected beam. The number of time delay devices can be one or more (for example, multiple serially connected time delay devices, such as delay optical fibers) so that one or more of the signal beam, the reflected beam, and the local oscillator beam all pass through time delays. The parameters of the time delay device can be defined according to the performance of the lidar system and the maximum moving speed of the target object, and details are not described in this application.

[0104] In the embodiment shown in FIG. 6, the start time of the triangular wave waveform of the second laser beam is half a cycle different from the start time of the triangular wave of the first laser beam. The methods for the beat frequencies in the up-conversion stage and the down-conversion stage of the triangular wave waveform of the first laser beam and the distance and speed of the target object are also applicable to the beat frequencies in the up-conversion stage and the down-conversion stage of the triangular wave of the second laser beam. For detailed content, refer to the above description, and details are not described in this application.

[0105] For the case where both the first laser beam and the second laser beam are sawtooth wave waveforms, as Figure 7A and Figure 7B shown, within each frequency sweep period, the up-conversion stage of the first laser beam and the down-conversion stage of the second laser beam form a triangular waveform, and the down-conversion stage of the second laser beam and the up-conversion stage of the first laser beam form an inverted triangular waveform. Within each frequency sweep period, the first laser beam only corresponds to the beat frequency f1 in the up-conversion stage, and the second laser beam only corresponds to the beat frequency f2 in the down-conversion stage. Therefore, within each frequency sweep period, the calculation formulas for the speed and distance of the target object are similar to the above formulas 8-15, with the difference that the first laser beam only corresponds to the beat frequency f1 in the up-conversion stage and the second laser beam only corresponds to the beat frequency f2 in the down-conversion stage. For detailed content, reference can be made to the above description, and details are not described in this application.

[0106] In some embodiments, frequency shifting at least one of the signal beam, the reflected beam, and the local oscillator beam includes: frequency shifting the frequency of the signal beam or the local oscillator beam so that the beat frequencies in the up - frequency stage and the down - frequency stage between the local oscillator beam and the reflected beam are shifted in a first direction or a second direction of the measurement spectrum.

[0107] The first direction of the ranging spectrum is the direction in which the beat frequencies in the up - frequency stage and the down - frequency stage gradually increase, such as Figure 10 and 11 the direction in which the frequency axis points to the right in. The second direction of the ranging spectrum is the direction in which the beat frequencies in the up - frequency stage and the down - frequency stage gradually decrease, such as Figure 10 and 11 the direction in which the frequency axis points to the left in. Therefore, by introducing a time delay to at least one of the signal beam, the reflected beam, and the local oscillator beam, the scalar values of the beat frequencies in the up - frequency stage and the down - frequency stage can be increased or decreased.

[0108] In some embodiments, when frequency - shifting the frequency of the local oscillator beam, the frequency of the local oscillator beam can be increased or decreased as a whole. Taking the triangular wave of the first laser beam as an example, as Figure 10 shown, the frequency of the local oscillator beam is increased by Δf as a whole. When the target object moves away from the lidar, the beat frequencies in the up - frequency stage and the down - frequency stage are respectively:

[0109]

[0110]

[0111] The distance and speed of the target object are as follows:

[0112]

[0113] When the target object moves towards the lidar, the beat frequencies in the up - frequency stage and the down - frequency stage are respectively:

[0114]

[0115]

[0116] The distance and speed of the target object are as follows:

[0117]

[0118] In some embodiments, when frequency - shifting the frequency of the signal beam, the frequency of the signal can be increased or decreased as a whole. For example, as Figure 11As shown, the frequency of the signal beam is increased by Δf as a whole. When the target object moves away from the lidar, the beat frequencies in the up-frequency stage and the down-frequency stage are respectively:

[0119]

[0120]

[0121] The distance and speed of the target object are as follows:

[0122]

[0123] When the target object moves towards the lidar, the beat frequencies in the up-frequency stage and the down-frequency stage are respectively:

[0124]

[0125]

[0126] The distance and speed of the target object are as follows:

[0127]

[0128] In some embodiments, the minimum value of the scalar values of the beat frequencies in the up-frequency stage and the down-frequency stage is equal to the maximum negative frequency shift amount caused by the Doppler effect.

[0129] In some embodiments of the present application, the start time of the triangular wave waveform of the second laser beam differs from the start time of the triangular wave of the first laser beam by half a cycle. The above calculation methods for the beat frequencies in the up-frequency stage and the down-frequency stage of the triangular wave waveform of the first laser beam and the distance and speed of the target object are equally applicable to the beat frequencies in the up-frequency stage and the down-frequency stage of the triangular wave of the second laser beam. For detailed content, refer to the above description, and the present application will not describe it in detail herein.

[0130] For the case where both the first laser beam and the second laser beam are sawtooth wave waveforms, as Figure 7A and Figure 7B shown, within each frequency sweep period, the up-frequency stage of the first laser beam and the down-frequency stage of the second laser beam form a triangular waveform, and the down-frequency stage of the second laser beam and the up-frequency stage of the first laser beam form an inverted triangular waveform. Therefore, within each frequency sweep period, the first laser beam only corresponds to the beat frequency f1 in the up-frequency stage, and the second laser beam only corresponds to the beat frequency f2 in the down-frequency stage. Therefore, within each frequency sweep period, the calculation formulas for the speed and distance of the target object are similar to the above formulas 16-23, with the difference that the first laser beam only corresponds to the beat frequency f1 in the up-frequency stage, and the second laser beam only corresponds to the beat frequency f2 in the down-frequency stage. For detailed content, reference can be made to the above description, and the present application will not describe it in detail herein.

[0131] By performing frequency shift on the local oscillator beam and / or the signal beam, the positions of the beat frequencies in the up - frequency stage and the down - frequency stage on the measurement spectrum of the lidar system can be changed. Combining with the in - phase quadrature coherent demodulation method of the present application, the range of the measurement spectrum of the lidar system can be expanded from [0, f max to [-f max , f max , thus avoiding the measurement blind area.

[0132] Step S506: Detect the beat frequencies in the up - frequency stage and the down - frequency stage between the local oscillator beam and the reflected beam to measure the speed of the object and / or the distance between the object and the lidar.

[0133] Specifically, a balanced detector can be used to measure the beat frequency between the local oscillator beam and the reflected beam. The balanced detector can be a photodetector.

[0134] In some embodiments, step S506 specifically includes: mixing the received reflected beam with the local oscillator beam to obtain a mixed - frequency signal. Specifically, the local oscillator beam of the present application is two optical signals including two different wavelengths λ1 and λ2, and the reflected beam is also two optical signals including two different wavelengths λ1 and λ2. Mixing the reflected beam and the local oscillator beam can simultaneously obtain the mixing results of the first reflected light and the first local oscillator light with wavelength λ1 and the mixing results of the second reflected light and the second local oscillator light with wavelength λ2. Therefore, at the same moment, the information of the beat frequency in the up - frequency stage and the beat frequency information in the down - frequency stage can be obtained simultaneously, which can improve the detection accuracy, solve the problem that the up - sweep frequency and the down - sweep frequency signals cannot be distinguished caused by Doppler broadening, obtain the direction of the target speed, and enhance the signal - to - noise ratio.

[0135] Among them, a mixer can be used to mix the local oscillator beam with the received reflected beam to obtain a mixed - frequency signal. The mixing device can be a coupler, such as a 2×2 coupler, and the mixed - frequency signal is a coherent signal generated by the interference of the local oscillator beam and the corresponding reflected beam. The mixer or coupler can be the mixers and couplers well - known to those skilled in the art. For the sake of saving space, the present application will not describe it in detail.

[0136] The above - mentioned solution of the present application uses the in - phase IQ coherent demodulation method to obtain the true value of the beat frequency in the up - frequency stage between the local oscillator beam and the reflected beam, and can simultaneously obtain the beat - frequency signal in the up - frequency stage and the beat - frequency signal in the down - frequency stage distributed on both sides of zero at one detection moment (i.e., within the same time window), expand the measurement spectrum of the lidar, avoid the measurement blind area, and improve the measurement accuracy and angular resolution.

[0137] Optionally, the beat frequencies in the up - frequency stage and the down - frequency stage are located on both sides of the frequency of the ranging zero - point position without Doppler frequency shift in the ranging spectrum of the lidar.

[0138] The lidar provided by the present disclosure is described in detail below. Figure 13 The structural schematic of the lidar of the present application is shown Figure 1 . In this embodiment, the lidar 1300 includes a first laser source 1301 configured to generate a first laser beam; and a second laser source 1302 configured to generate a second laser beam.

[0139] The first laser source 1301 and the second laser source 1302 can be directly modulated by a chirp signal of an optical signal. For example, the drive signals controlling the laser sources can be input into the first laser source and the second laser source with intensities varying over time, such that the first laser source and the second laser source generate and output the first laser beam and the second laser beam. The first laser beam and the second laser beam are frequency - modulated continuous - wave laser beams with frequencies varying within a predetermined range, having the same sweep period T and different wavelengths λ1 and λ2. Optionally, in each sweep period T, the first laser beam and the second laser beam can both be triangular - wave sweep waveforms or saw - tooth - wave sweep waveforms. Optionally, each of the first laser source 1301 and the second laser source 1302 can include a modulator for receiving a modulation signal. The modulator can be configured to modulate the light beam based on the modulation signal to generate and output a laser beam with a frequency varying within a predetermined range.

[0140] Among them, the modulation depths of the first laser beam and the second laser beam are the same, and the modulation slopes are the same. The frequency change directions of the first laser beam and the second laser beam are opposite within the sweep period T. Specifically, in each sweep period T, the start times of the first laser beam and the second laser beam can differ by half a period. The first laser beam can start scanning from zero frequency, and the second laser beam can start scanning from the maximum frequency f B ; or within the first half - period and the second half - period in each sweep period T, the first laser beam linearly increases from zero frequency to the maximum frequency f B , and the second laser beam linearly decreases from the maximum frequency f B to zero frequency; or the second laser beam linearly increases from zero frequency to the maximum frequency f B , and the first laser beam linearly decreases from the maximum frequency f B to zero frequency.

[0141] In some embodiments, the lidar further includes a wavelength division multiplexer 1303 configured to multiplex the first laser beam and the second laser beam into a swept-frequency beam. The swept-frequency beam carries two optical signals having different wavelengths λ1 and λ2; a first beam splitter 1304 configured to split the swept-frequency beam into a signal beam and a local oscillator beam, where the signal beam and the local oscillator beam have the same frequency at any point in time, that is, the frequency modulation waveforms of the signal beam and the local oscillator beam are exactly the same, and each of the signal beam and the local oscillator beam simultaneously carries two optical signals of two different wavelengths λ1 and λ2; an optical transceiver 1305 configured to emit the signal beam and receive the reflected beam generated after the signal beam encounters a target object.

[0142] Optionally, the lidar 1300 further includes: a polarization beam splitter (e.g., polarization splitter-rotator (PSR)): disposed between the optical transceiver 1305 and the target object 1306, configured to change the polarization direction of the beam or combine multiple beams into a polarized beam; a lens assembly configured to collimate the signal beam and focus the reflected beam to couple it into the optical transceiver; and a beam scanning and guiding device configured to achieve deflection and scanning of light.

[0143] In some embodiments, the lidar further includes: an in-phase quadrature coherent demodulator 1307 configured to perform in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam to obtain scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; and a first detector 1308 and a second balanced detector 1309 configured to detect the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam to determine the speed of the object and / or the distance between the object and the lidar.

[0144] Wherein, the scalar value of the beat frequency in the up-frequency stage includes the positive or negative value of the beat frequency in the up-frequency stage; the scalar value of the beat frequency in the down-frequency stage includes the positive or negative value of the beat frequency in the down-frequency stage.

[0145] Specifically, the in-phase quadrature coherent demodulator 1307 can be a 90-degree mixing unit, specifically including: a second beam splitter 13071, a third beam splitter 13072, a first 2×2 coupler 13073, and a second 2×2 coupler 13074. Among them, the second beam splitter 13071 is configured to receive the local oscillator light beam from the first beam splitter 13042. The local oscillator light beam is split into two light beams, and these two light beams are respectively input into the first 2×2 coupler 13073 and the second 2×2 coupler 13074. The third beam splitter 13072 is configured to receive the reflected light beam from the optical transceiver 1305. The reflected light beam is split into two light beams, and these two light beams are respectively input into the first 2×2 coupler 13073 and the second 2×2 coupler 13074. The first 2×2 coupler 13073 is configured to couple the two light beams from the second beam splitter 13071 and the third beam splitter 13072 into two light beams with phases of 0° and 180° respectively, and input these two light beams into the first balanced detector 1308 through the first output port and the second output port. The second 2×2 coupler 13074 is configured to couple the two light beams from the second beam splitter 13071 and the third beam splitter 13072 into two light beams with phases of 90° and 270° respectively, and input these two light beams into the second balanced detector 1309 through the third output port and the fourth output port.

[0146] The first balanced detector 1308 includes a photodetector 1 and a photodetector 2. The photodetector 1 and the photodetector 2 are connected in series. The photodetector 1 is configured to receive the output light of 0°, and the photodetector 2 is configured to receive the output light of 180°. The second balanced detector 1309 includes a photodetector 3 and a photodetector 4. The photodetector 3 and the photodetector 4 are connected in series. The photodetector 3 is configured to receive the output light of 90°, and the photodetector 4 is configured to receive the output light of 270°. Among them, the DC components of the photocurrents obtained by the balanced detectors for the light beams of 0° and 180°, and 90° and 270° are respectively equal.

[0147] In this application Figure 13The laser measurement device shown can obtain the scalar values of the beat frequencies in the up - frequency stage and the down - frequency stage of the local oscillator signal and the reflected signal, can expand the measurement spectrum range of the lidar, avoid the measurement blind area caused by Doppler frequency shift, and improve the measurement accuracy. In addition, the device uses a dual - wavelength combined laser as the detection optical signal, can obtain the beat frequency in the up - frequency stage and the beat frequency in the down - frequency stage simultaneously at one sampling moment, can accurately obtain the speed and distance information of the target object, improve the angular scanning accuracy of the lidar, solve the problem that Doppler broadening makes it impossible to distinguish the beat frequency in the up - frequency stage from the beat frequency in the down - frequency stage, can obtain the direction of the target speed, improve the signal - to - noise ratio, and solve the problem of point cloud trailing points. The laser measurement device can implement the method steps described above. The relevant content of the lidar 1300 can be referred to the above description about Figure 5 for the relevant description. It will not be repeated here.

[0148] Reference Figure 14A and Figure 14B , Figure 14A is a detailed structural schematic diagram of the lidar of the present application Figure 2 , Figure 14B is the third detailed structural schematic diagram of the lidar of the present application. In this embodiment, the lidar 1400 includes a first laser source 1401 configured to generate a first laser beam; a second laser source 1402 configured to generate a second laser beam; a wavelength - division multiplexer 1403 configured to multiplex the first laser beam and the second laser beam into a frequency - swept beam. The frequency - swept beam carries two optical signals with different wavelengths λ1 and λ2; a first beam splitter 1404 configured to split the frequency - swept beam into a signal beam and a local oscillator beam, where the signal beam and the local oscillator beam have the same frequency at any time point, that is, the frequency - modulation waveforms of the signal beam and the local oscillator beam are exactly the same, and each of the signal beam and the local oscillator beam simultaneously carries two optical signals with two different wavelengths λ1 and λ2; an optical transceiver 1405 configured to emit the signal beam and receive the reflected beam generated after the signal beam encounters a target object; an in - phase quadrature coherent demodulator 1407 configured to perform in - phase quadrature coherent demodulation on the local oscillator beam and the reflected beam to obtain the scalar values of the beat frequencies in the up - frequency stage and the down - frequency stage between the local oscillator beam and the reflected beam; and a first balanced detector 1408 and a second balanced detector 1409 configured to detect the beat frequencies in the up - frequency stage and the down - frequency stage between the local oscillator beam and the reflected beam to measure the speed of the object and / or the distance between the object and the lidar.

[0149] The functions, principles, and structures of the first laser source 1401, the second laser source 1402, the wavelength division multiplexer 1403, the first beam splitter 1404, the optical transceiver 1405, the in-phase quadrature coherent demodulation 1407, the first detector 1408, and the second detector 1409 are the same as those of the first laser source 1301, the second laser source 1302, the wavelength division multiplexer 1303, the first beam splitter 1304, the optical transceiver 1305, the in-phase quadrature coherent demodulation 1307, the first detector 1308, and the second detector 1309 above. For detailed content, reference can be made to the above description, and the present application will not repeat the description here.

[0150] Further, the lidar 1400 further includes a first time delay device or a first frequency shifter 1410 and a second time delay device or a second frequency shifter 1411.

[0151] In some embodiments, as Figure 14A shown, the first time delay device or the first frequency shifter 1410 is disposed between the first beam splitter 1404 and the second beam splitter 14071. The first time delay device 1410 is configured to perform time delay on the local oscillator beam, and the first frequency shifter 1410 is configured to perform frequency shift on the local oscillator beam; the second time delay device or the second frequency shifter 1411 is disposed between the first beam splitter 1404 and the third beam splitter 14072. The second time delay device 1411 is configured to perform time delay on the signal beam and the reflected beam, and the second frequency shifter 1411 is configured to perform frequency shift on the signal beam and the reflected beam.

[0152] In some embodiments, as Figure 14B shown, the first time delay device or the first frequency shifter 1410 is disposed between the first beam splitter 1404 and the second beam splitter 14071. The first time delay device 1410 is configured to perform time delay on the local oscillator beam, and the first frequency shifter 1410 is configured to perform frequency shift on the local oscillator beam; the second time delay device 1411 is disposed between the first beam splitter 1404 and the optical transceiver 1405. The second frequency shifter 1411 is configured to perform frequency shift on the signal beam.

[0153] Through time delay and / or frequency shift, the beat frequencies in the up-frequency stage and the down-frequency stage between the local oscillator beam and the reflected beam can be shifted in the positive or negative direction of the measurement spectrum, thereby expanding the range of the measurement spectrum and avoiding the measurement blind area caused by the beat frequencies in the up-frequency stage and the down-frequency stage between the local oscillator beam and the reflected beam being outside the measurement spectrum range of the lidar, improving the measurement accuracy. For the principle of shifting the beat frequencies in the up-frequency stage and the down-frequency stage through time delay and / or frequency shift, reference can be made to the relevant description above in the present application. To avoid repetition, the present application will not describe it in detail here.

[0154] Optionally, the lidar 1400 further includes: a polarization beam splitter (e.g., polarization splitter-rotator (PSR)) disposed between the optical transceiver 1305 and the target object 1306 and configured to change the polarization direction of the light beam or combine multiple light beams into a polarized light beam; a lens assembly configured to collimate the signal light beam and focus the reflected light beam to couple it into the optical transceiver; and a beam scanning guiding device configured to achieve deflection and scanning of the light.

[0155] Figure 15A and Figure 15B FIG. illustrates an example autonomous vehicle 1500 according to an embodiment of the present application, which may include any components of the lidar LIDAR device shown in FIG. 4 of the present application. The illustrated autonomous vehicle 1500 includes a sensor array configured to capture one or more objects in the external environment of the autonomous vehicle and generate sensor data related to the captured one or more objects for controlling the operation of the autonomous vehicle 1500. Figure 13-1 Sensors 1501, 1502, 1503, 1504, and 1505 are shown. Figure 15A Sensors 1501, 1502, 1503, 1504, 1505, 1506, 1507, 1508, and 1509 are illustrated. Figure 15B Shown is a top view of the autonomous vehicle 1500. Any one of sensors 1501, 1502, 1503, 1504, 1505, 1506, 1507, 1508, and 1509 may include the lidar device shown in FIG. 4 of the present application, and the device includes any LIDAR component of the present application. The autonomous vehicle may include a powertrain that includes a prime mover powered by an energy source and capable of powering a transmission system. The autonomous vehicle may further include a control system that includes direction control, powertrain control, and braking control. The autonomous vehicle may be implemented as any number of different vehicles, including vehicles capable of transporting people and / or goods and capable of traveling in various different environments. It should be understood that the above components can vary widely based on the type of vehicle that utilizes these components. Figure 15B The detailed content of this embodiment of the present application may refer to the description of the foregoing method embodiment. To avoid repetition, the present application does not repeat the description here. Figure 13-1

[0156]

[0157] ​​Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0158] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0159] In several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be electrical, mechanical, or other forms.

[0160] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment solutions of this application.

[0161] In addition, the functional units in each embodiment of this application can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0162] When the above-mentioned functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the related technology, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs.

[0163] The computer-readable storage medium mentioned in this application can be volatile or non-volatile.

[0164] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A laser measurement method applied to lidar, characterized in that, The method includes: generating a first laser beam and a second laser beam, where each of the first laser beam and the second laser beam is a frequency-modulated laser, having the same sweep period and different wavelengths, and the frequency change directions of the first laser beam and the second laser beam are opposite within the sweep period; multiplexing the first laser beam and the second laser beam into a swept-frequency beam; beam-splitting the swept-frequency beam into a signal beam and a local oscillator beam; transmitting the signal beam; receiving a reflected beam generated by reflection of the signal beam after encountering an object; performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam so as to obtain a scalar value of the beat frequency in the up-frequency stage and a scalar value of the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; and detecting the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam to measure the speed of the object and / or the distance between the object and the lidar.

2. The laser measurement method according to claim 1, wherein The scalar value of the beat frequency in the up-frequency stage includes a positive value or a negative value of the beat frequency in the up-frequency stage; The scalar value of the beat frequency in the down-frequency stage includes a positive value or a negative value of the beat frequency in the down-frequency stage.

3. The laser measurement method according to claim 1, characterized in that, Before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam, the method further includes: performing time delay or frequency shift on at least one of the signal beam, the reflected beam, and the local oscillator beam.

4. The laser measurement method according to claim 3, characterized in that, Performing time delay on at least one of the signal beam, the reflected beam, and the local oscillator beam includes: performing time delay on the signal beam and the reflected beam, or performing time delay on the local oscillator beam, so as to increase or decrease the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

5. The laser measurement method according to claim 3, wherein Performing frequency shift on at least one of the signal beam, the reflected beam, and the local oscillator beam includes: performing frequency shift on the frequency of the signal beam or the local oscillator beam, so as to increase or decrease the scalar values of the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

6. The laser measurement method according to claim 1 or 2, characterized in that, Performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam includes: inputting the reflected beam and the local oscillator beam into a 90-degree mixing unit to perform in-phase quadrature coherent demodulation.

7. The laser measurement method according to claim 4 or 5, characterized in that, The beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage are located on both sides of the frequency of the ranging zero point position without Doppler frequency shift in the ranging spectrum of the lidar.

8. The laser measurement method according to claim 1, characterized in that, The opposite frequency change directions of the first laser beam and the second laser beam include one of the following two cases: In the first half period of the sweep period, the first laser beam starts sweeping from zero frequency, and the second laser beam starts sweeping from the maximum frequency; in the second half period of the sweep period, the first laser beam starts sweeping from the maximum frequency, and the second laser beam starts sweeping from zero frequency; or In each of the first half period and the second half period of the sweep period, the first laser beam starts sweeping from zero frequency, and the second laser beam starts sweeping from the maximum frequency.

9. A lidar, characterized in that, The lidar includes: A first laser source configured to generate a first laser beam; A second laser source configured to generate a second laser beam, wherein each of the first laser beam and the second laser beam is a frequency-modulated laser, having the same sweep period and different wavelengths, and the frequency change directions of the first laser beam and the second laser beam are opposite within the sweep period; A wavelength division multiplexer configured to multiplex the first laser beam and the second laser beam into a swept-frequency beam; A beam splitter configured to split the swept-frequency beam into a signal beam and a local oscillator beam; An optical transceiver configured to transmit the signal beam and receive a reflected beam generated by reflection after the signal beam encounters an object; An in-phase quadrature coherent demodulator configured to perform in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam so as to obtain a scalar value of the beat frequency in the up-frequency stage and a scalar value of the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; and A detector configured to detect the beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam to measure the speed of the object and / or the distance between the object and the lidar.

10. The lidar according to claim 9, wherein, The scalar value of the beat frequency in the up-frequency stage includes a positive value or a negative value of the beat frequency in the up-frequency stage; The scalar value of the beat frequency in the down-frequency stage includes a positive value or a negative value of the beat frequency in the down-frequency stage.

11. The lidar according to claim 9, characterized in that, The lidar further includes: A time delay device configured to perform time delay on at least one of the signal beam, the reflected beam, and the local oscillator beam before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam; and / or A frequency shifter configured to perform frequency shift on at least one of the signal beam, the reflected beam, and the local oscillator beam before performing in-phase quadrature coherent demodulation on the local oscillator beam and the reflected beam.

12. The lidar according to claim 11, wherein, The time delay device is specifically configured to perform time delay on the signal beam and the reflected beam, or perform time delay on the local oscillator beam, so as to increase or decrease the scalar value of the beat frequency in the up-frequency stage and the scalar value of the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam; The frequency shifter is specifically configured to perform frequency shift on the frequency of the signal beam or the local oscillator beam, so as to increase or decrease the scalar value of the beat frequency in the up-frequency stage and the scalar value of the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

13. The lidar according to claim 9 or 10, characterized in that, The in-phase quadrature coherent demodulator is specifically configured to receive the reflected beam and the local oscillator beam to obtain a scalar value of the beat frequency in the up-frequency stage and a scalar value of the beat frequency in the down-frequency stage between the local oscillator beam and the reflected beam.

14. The lidar according to claim 12, wherein The beat frequency in the up-frequency stage and the beat frequency in the down-frequency stage are located on both sides of the frequency of the ranging zero point position without Doppler frequency shift in the ranging spectrum of the lidar.

15. The lidar according to claim 9, characterized in that, The opposite frequency change directions of the first laser beam and the second laser beam include one of the following multiple situations: In the first half cycle of the frequency sweep period, the first laser beam sweeps from zero frequency, and the second laser beam sweeps from the maximum frequency; in the second half cycle of the frequency sweep period, the first laser beam sweeps from the maximum frequency, and the second laser beam sweeps from zero frequency; or In each of the first half cycle and the second half cycle of the frequency sweep period, the first laser beam sweeps from zero frequency, and the second laser beam sweeps from the maximum frequency.

16. An autonomous vehicle, comprising: A lidar according to any one of claims 9 to 15.

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