CN109116366B

CN109116366B - Multi-beam laser radar with non-uniform pulse energy

Info

Publication number: CN109116366B
Application number: CN201810681178.5A
Authority: CN
Inventors: 向少卿
Original assignee: Hesai Photonics Technology Co Ltd
Current assignee: Hesai Technology Co Ltd
Priority date: 2018-06-27
Filing date: 2018-06-27
Publication date: 2020-05-19
Anticipated expiration: 2038-06-27
Also published as: CN109116366A; WO2020001537A1

Abstract

The invention provides a multi-line beam laser radar with non-uniform pulses. The multi-beam laser radar comprises a control unit, a pulse driving unit and a pulse laser transmitting unit; the control unit controls the pulse driving unit to generate a driving signal; the pulse laser emission unit emits laser pulses under the driving of the driving signal; and adjusting the driving signal to enable the laser pulses to be distributed in a non-uniform mode in the field of view.

Description

Multi-beam laser radar with non-uniform pulse energy

Technical Field

The invention relates to the technical field of laser radars, in particular to a multi-beam laser radar with non-uniform pulse energy.

Background

The laser radar analyzes the turn-back time of the laser after encountering a target object by transmitting and receiving laser beams, calculates the relative distance between the target object and a vehicle, and quickly reconstructs a three-dimensional model of the target to be detected by utilizing information such as three-dimensional coordinates, reflectivity and the like of a large number of dense points on the surface of the target object, which is collected in the process, so as to achieve the purpose of environmental perception. In effect, the more the laser radar wire harnesses are, the more the number of points collected per second is, the higher the measurement precision is, and the higher the safety is. Commercially available multi-line beam lidar, such as the Velodyne HDL-64E, Pandar 40, includes a plurality of laser emitters having substantially uniform output pulse energy and pulse frequency, and thus substantially uniform detection range and horizontal angular resolution across the field of view.

The inventor has found that the existing multi-line beam lidar has substantially uniform detection range and horizontal angular resolution within the field of view due to the substantially uniform output pulse energy and frequency of the plurality of laser transmitters. The existing beam distribution setting mode has the problems that laser beams at the upper and lower edges of a vertical field range are mostly irradiated to the sky or the ground and wasted at a position far away from a laser radar, the horizontal sight of a vehicle which is focused on and the detection distance and horizontal angle resolution of the laser radar close to the ground are insufficient, and the obstacle identification accuracy is low.

Disclosure of Invention

In order to solve the technical problem, the invention provides a multi-beam laser radar with non-uniform pulse energy and a vehicle carrying the multi-beam laser radar.

In a first aspect of the present invention, a multi-line beam laser radar with non-uniform pulses is provided, which includes a control unit, a pulse driving unit, and a pulse laser emitting unit; the control unit controls the pulse driving unit to generate a driving signal; the pulse laser transmitting unit transmits multi-line beam laser pulses under the driving of the driving signals; the drive signals are adjusted such that the multi-line beam laser pulses are non-uniformly distributed over a field of view.

In a second aspect of the present invention, a vehicle is provided, the vehicle being equipped with the above-described laser radar.

By adopting the technical scheme, the invention has the following beneficial effects: the multi-beam laser radar provided by the invention has non-uniform pulse energy and pulse frequency and different pulse energy in each direction, and can improve the energy utilization rate and the overall performance of the laser radar by reasonably distributing the pulse energy and the pulse frequency of each laser.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of a multi-line beam lidar having non-uniform pulses according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a multi-line beam lidar having non-uniform pulses in accordance with an embodiment of the present invention;

FIG. 3 is a schematic diagram of a multi-line beam lidar having non-uniform pulses in accordance with an embodiment of the present invention;

FIG. 4 is a cloud point diagram of a multi-line beam lidar having non-uniform pulses according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a multi-line beam lidar having non-uniform pulses in accordance with an embodiment of the present invention;

FIG. 6 is a cloud point diagram of a multi-line beam lidar having non-uniform pulses according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a multi-line beam lidar having non-uniform pulses in accordance with an embodiment of the present invention;

FIG. 8 is a schematic diagram of a multi-line beam lidar having non-uniform pulses in accordance with an embodiment of the present invention;

FIG. 9 is a schematic diagram of a scanning pattern of a lidar according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of laser emission pulses provided by an embodiment of the present invention;

FIG. 11 is a schematic diagram of laser emission pulses provided in accordance with an embodiment of the present invention;

FIG. 12 is a schematic diagram of a pulse-coded laser emitting device according to an embodiment of the present invention;

FIG. 13 is a schematic circuit diagram of a charging unit of a pulse-coded laser transmitter according to an embodiment of the present invention;

FIG. 14 is a timing diagram of the triggering of the switch control signal and the switch trigger signal according to an embodiment of the present invention;

FIG. 15 is a timing diagram of the triggering of the switch control signal and the switch trigger signal according to an embodiment of the present invention;

FIG. 16 is a schematic diagram illustrating an echo identification principle of different laser pulse sequences according to an embodiment of the present invention;

FIG. 17 is a schematic diagram illustrating a ranging principle provided in an embodiment of the present invention;

FIG. 18 is a schematic diagram of a pulse code transmitting circuit according to an embodiment of the present invention;

FIG. 19 is a schematic diagram of a pulse code receiving circuit according to an embodiment of the present invention;

FIG. 20 is a schematic diagram illustrating a pulse transceiving principle according to an embodiment of the present invention;

FIG. 21 is a schematic diagram illustrating a pulse transceiving principle according to an embodiment of the present invention;

fig. 22 is an example of a pulse transceiving calculation principle according to an embodiment of the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the invention. In the description of the present invention, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein.

In one embodiment of the present invention, as shown in fig. 1, there is provided a multi-line beam lidar having non-uniform pulses, the multi-line beam lidar including a control unit, a pulse driving unit, and a pulse laser transmitting unit; the control unit controls the pulse driving unit to generate a driving signal; the pulse laser transmitting unit transmits multi-line beam laser pulses under the driving of the driving signals; the drive signals are adjusted such that the multi-line beam laser pulses are non-uniformly distributed over a field of view.

In an alternative embodiment, as shown in fig. 1, the non-uniform distribution of the multi-beam laser pulses over the field of view comprises: in a specific vertical emergent direction, the light source has stronger emergent pulse energy. In particular, the multi-line-beam lidar has several beams in the vertical direction, for example 40-line lidar forms 40 scanning beams by several lasers. The single scanning beam is formed by laser pulses emitted by the laser pulse emitting device, 40 scanning beams are arranged in the vertical emergent direction, and the arrangement intervals among the beams can be uniform or non-uniform. Whether the arrangement interval between the beams is uniform or not, the emergent pulse energy is stronger in some specific directions. For example, the laser pulse corresponding to the central portion of the field of view has a strong single pulse energy; the upper and lower edge laser pulses of the field of view have a lower single pulse energy. The laser pulse corresponding to the central part of the visual field has higher energy, longer flight time and long distance measurement; the laser pulse single pulse at the upper and lower edges of the visual field has low energy and the distance measurement is close, thereby avoiding the waste of irradiating the sky or the ground. For example: the laser pulse single pulse energy corresponding to the central part of the field of view is 150nJ, the flight time is 1.5 mu s, and the detection distance can reach 225m (d is ct/2); the laser pulse single pulse energy corresponding to the upper and lower edge parts of the visual field is 120nJ, the flight time is 1 mu s, the detection distance is 150m, the farther detection distance can be obtained at the horizontal sight line of the vehicle and the vicinity close to the ground, and the energy waste of the upper and lower edge parts of the visual field is avoided.

In the embodiment of fig. 1, the multi-beam laser pulse is realized by a plurality of lasers, but may also be realized by a single plurality of lasers through scanning or beam splitting without loss of generality. As a pulse laser, it emits a multi-line beam laser pulse under the drive of the drive signal.

As shown in fig. 2, in an alternative embodiment, the non-uniform distribution of the multi-beam laser pulses over the field of view comprises: the arrangement between the individual strands is non-uniform and has a strong outgoing pulse energy in certain specific directions. For example, the laser pulse corresponding to the central part of the field of view has stronger single pulse energy and denser laser beam distribution; the laser pulses at the upper and lower edges of the field of view have lower single pulse energy and the laser beams are distributed sparsely. The dense wiring harness distribution in the center of the view field can ensure higher vertical resolution, and the stronger monopulse energy can ensure longer pulse flight time, thereby ensuring the effective range of distance measurement; the laser pulse single pulse at the upper and lower edges of the visual field has low energy and the distance measurement is close, thereby avoiding the waste of irradiating the sky or the ground. It can be seen that, in combination with the non-uniformly distributed vertical angular resolution, the horizontal line of sight and the close vicinity of the ground of the vehicle with the important attention can obtain better ranging and vertical angular resolution.

Further, in an alternative embodiment, the lidar may have more than 3 detection ranges, implemented by the laser control module.

As shown in fig. 3 and 4, in an alternative embodiment, the non-uniform distribution of the multi-beam laser pulses over the field of view includes: the specific direction has a higher outgoing pulse frequency. The laser pulse corresponding to the central part of the field of view has higher pulse frequency; the laser pulse frequency of the upper and lower edges of the field of view is low. And for the case that the multi-line beam laser radar is arranged on the top of the vehicle, the central part of the visual field corresponds to the horizontal sight line of the vehicle and the vicinity close to the ground. This ensures that a higher horizontal angular resolution is obtained for the vehicle's horizontal line of sight and near the ground. Since the laser pulse corresponding to the central part of the field of view has high pulse frequency, namely, in the scanning process of the multi-line laser radar, the central part of the field of view has more point cloud data in time. Taking fig. 4 as an example, the laser pulses corresponding to the central portion of the field of view have a high pulse frequency; the upper and lower edges of the field of view have a low pulse frequency. The central part of the view field is corresponding to the point cloud data with larger quantity, and the point cloud data corresponding to the middle part of the figure 4 is dense. The edge part of the field of view is correspondingly obtained with a smaller amount of point cloud data, and the point cloud data corresponding to the edge part of fig. 4 is sparse, so that a higher horizontal angular resolution (more scanning points in the horizontal direction) can be obtained when the laser radar is horizontally in the sight line and near the ground.

As shown in fig. 5 and 6, in an alternative embodiment, the non-uniform distribution of the multi-beam laser pulses over the field of view includes: the specific direction has higher outgoing pulse beam density. The laser pulse corresponding to the central part of the field of view has denser beam density; the line beam density at the upper and lower edges of the field of view is lower. And for the case that the multi-line beam laser radar is arranged on the top of the vehicle, the central part of the visual field corresponds to the horizontal sight line of the vehicle and the vicinity close to the ground. This ensures that more scanning beams are available for the horizontal line of sight of the vehicle and near the ground, thereby increasing vertical resolution (more scanning points in the vertical direction).

Of course, in an alternative embodiment, the density of the scanning beams and the frequency of the scanning beams may be increased in one direction. This can improve both the horizontal direction resolution and the vertical direction resolution of the scanning direction.

As shown in fig. 7, in an alternative embodiment, the non-uniform distribution of the laser pulses over the field of view includes: in different azimuthal directions, there are different outgoing pulse energies. In a real scene, the detection requirements of the laser radar on different azimuth directions are different, so that the emitting energy of the laser radar on each azimuth direction is not required to be uniform, and the detection of a specific area can be enhanced through the uneven distribution of laser pulse capacity in different directions. Fig. 7 shows that different detection energies are used for the front and rear sides of the laser radar, and the detection distance L1 is larger due to the higher energy of the front laser pulse, and the detection distance L2 is smaller due to the lower energy of the front laser pulse. For example: during forward detection of the laser radar, the single pulse energy of the laser pulse is 150nJ, the flight time is 1.5 mu s, and the detection distance can reach 225m (d is ct/2); the backward (and lateral) laser pulse single pulse energy is 120nJ, the flight time is 1 Mus, the detection distance is 150m, and the farther detection distance can be obtained in the forward direction of the vehicle, so that the energy waste of the laser radar is avoided. Further, in combination with the non-uniform distribution of vertical angular resolution, the horizontal line of sight and the close proximity to the ground of the vehicle of significant interest may result in better ranging and vertical angular resolution.

In an alternative embodiment, as shown in fig. 8, different scanning beam numbers and scanning frequency distribution settings can be implemented at different orientations. For example, in the forward direction, the middle of the scan field has higher pulse energy, pulse frequency and denser scan beam, thus achieving enhanced detection in front of the scan field. Meanwhile, in the back direction, the middle part of the scanning view field has higher pulse energy, pulse frequency and denser scanning beam, thereby realizing the reinforcement of the detection in front of the scanning view field. Of course, fig. 8 is only an example, and actually, the pulse energy, the pulse frequency, and the beam density at different positions in the direction may be adjusted according to the control of the control unit. For example, a uniform scan beam density in the middle and peripheral regions of the field of view is used in the posterior direction.

Further, the lidar may have a plurality of directionally different detection ranges, implemented by the laser control module. As shown in fig. 9, which is a top view of the scanning process of the multi-beam radar, a polar coordinate system is established on the plane, and the angle a of the scanning position is the polar coordinate angle, the control unit can control the intensity of the outgoing pulse of the laser radar to be S ═ Acos (a/2) + B, so that the scanning light intensity at the position where a is 0 ° is the maximum, and the scanning light intensity at the position where a is 180 ° is the minimum. It can be seen that in the azimuth direction, the lidar may have different energy distributions, which are not only in sine or cosine distribution, but may also be scanned in the following pattern:

x(θ)＝a sinθ；

wherein n is not less than 1 and

n is called the parameter of the curve and is the ratio of the frequencies of the two sinusoidal vibrations.

If the ratio is rational number, then

The parametric equations can be written as x (O) -a sin (pO),

theta is more than or equal to 0 and less than or equal to 2 pi, wherein theta is a scanning variable, and other parameters are constants.

In addition to spatially varying the inhomogeneity of the laser radar exit beam, the drive signal may also be encoded in the time domain, the encoded drive signal encoding the excitation laser pulses with a temporal sequence. As shown in fig. 10 and 11, different laser emitting devices emit laser pulses with different intensities, and the emission frequencies of the laser pulses are the same, and in fact, the emission frequencies may be different.

In an alternative embodiment, the laser firing pulses have different codes, the codes may have different frequencies and/or intensities, and the different laser firing pulse intensities may be determined by different driving signals, such as:

the first drive signal: [1,0,1,1,1,1,0,1,1, 1], where signal strength "1" indicates 1 unit signal strength and "0" indicates that there is no pulse at that time.

The second drive signal: [1.5,1.5,1.5,1.5,1.5,1.5,0,1.5,1.5,1.5,1.5 ], signal strength "1.5" indicates 1.5 unit signal strength, and "0" indicates that there is no pulse at that time.

In an alternative embodiment, the laser pulses having a timing sequence with non-uniform pulse energy in timing sequence, such as:

third drive signal: [0,1,2,3,2,1,0,1,2,3,2,1,0]

Fourth drive signal: [0, sin (0.1 π), sin (0.2 π), sin (0.3 π), sin (0.4 π), sin (0.5 π), sin (0.4 π), sin (0.3 π), sin (0.2 π), sin (0.1 π),0]

In an alternative embodiment, the pulse driving signal may be a pulse excitation signal with time sequence interval, a pulse signal with time sequence different width, or a pulse signal with time sequence interval different width. The laser pulse transmitting unit transmits a coded laser pulse sequence based on the first coding signal; the encoded laser pulse sequence is in time sequenceA sequence of laser pulses with a spacing therebetween, or a sequence of pulses with a temporal pulse intensity modulation, or a sequence of pulses with a temporal spacing and a temporal pulse intensity modulation. The laser pulse train includes at least two laser pulses, such as a first laser pulse and a second laser pulse. Of course, without loss of generality, the laser pulse train may further include a plurality of laser pulses, such as a first laser pulse, a second laser pulse, … …, and an nth laser pulse, and the plurality of lasers have a time sequence relationship, such as a first time interval t between the first laser pulse and the second laser pulse₂-t₁With a time interval t between the Nth laser pulse and the N-1 th laser pulse_n-t_n-1. The time intervals describe the timing relationship of the laser pulse train.

In a possible embodiment, when the first coded signal is the same as the pulse echo signal, the laser pulse train echo is determined as the echo signal of the first coded signal, the signal is retained, and the information carried by the signal is extracted. And when the first coding signal is different from the pulse echo signal, judging the laser pulse sequence echo as a laser pulse transmitted by other laser pulse transmitting units, and discarding the laser pulse sequence echo.

As shown in fig. 12, the encoding unit includes: a plurality of charging units and an energy storage device; the charging unit sequentially carries out continuous charging action on the energy storage device under the control of a switch control signal (GATE1, GATE2, …, GATEN) and a switch TRIGGER signal (TRIGGER), and emits a coded laser pulse sequence. The sequential continuous charging action on the energy storage device comprises that after the previous charging unit charges the energy storage device according to corresponding switch control signals (GATE1, GATE2, … and GATEN), the energy storage device discharges under the control of a switch TRIGGER signal (TRIGGER) so that the laser pulse emitting unit emits light pulses; and continuing the light emitting action of the laser pulse emitting unit, and charging the energy storage device by the latter charging unit according to corresponding switch control signals (GATE1, GATE2, … and GATEN).

As shown in fig. 13, the charging unit includes a switching tube, an inductor, and a diode, the switching tube is controlled by a switching tube control signal (GATE1, GATE2, …, GATE), the control signal has a time length, the time length of the control signal is used for controlling the charging amount of the charging unit to the capacitor, and the charging amount determines the intensity of the emitted light pulse. In a specific embodiment, the time length of the control signal may be a pulse width of the control signal.

In one possible embodiment, the energy storage device is a capacitive device, and the width of the control signal is controlled by controlling the switch tube, so that the charging time of the energy storage device by the charging unit can be controlled, the single-charging electric quantity of the energy storage device is controlled, and the pulse intensity emitted by the laser pulse emitting device is further controlled.

And the light-emitting control switch (N1), the light-emitting control switch (N1) is controlled by a switch TRIGGER signal (TRIGGER), the switch TRIGGER signal (TRIGGER) is triggered by a switching tube control signal (GATE1, GATE2, … …), and the switch TRIGGER signal (TRIGGER) is triggered once when each switch control signal (GATE1, GATE2, … …) is ended, so that the next charging-light-emitting process can be started immediately after the previous charging light-emitting process is ended.

By controlling the length of the GATE signal and the intensity of the modulation pulse, because the encoding is in tandem, the emitted laser pulses cannot be overlapped in time sequence, and the laser pulses emitted by different radars can be distinguished through the intensity of the pulse modulated by the GATE signal.

In one possible embodiment, the signal accuracy of the switch control signals (GATE1, GATE2, … …) is ensured to be in the order of nanoseconds by controlling the crystal oscillator of the switch tube control signal to be 1G or higher, and the width of each GATE signal is in the order of nanoseconds or tens of nanoseconds. Thereby ensuring that the entire pulse train is within a short time frame.

Since the plurality of charging units are independent of each other, when a certain charging circuit is charged and emits light, no influence is exerted on other charging circuits. The continuous charging can be carried out until the previous charging-light emitting process is finished, and the next charging-light emitting process can be started immediately. The minimum time interval of the two pulses is in the order of tens of ns, so that the encoding takes only a small amount of time of flight. It is also possible to control the different radar emission intervals to be more than 500ns, so that the pulses emitted by the lasers do not overlap with each other.

Fig. 13 also includes a switch control signal generating unit (CLK1) for controlling the charging amount of the energy storage device by controlling the timing length of the switch control signals (GATE1, GATE2, …, GATEN), thereby controlling the intensity of the single pulse emitted by the laser pulse emitting unit. The timing of the control signals (GATE1, GATE2, …, GATEN) themselves control the timing of the pulses emitted by the laser pulse emitting unit. The charging unit comprises a power supply (BAT), an inductor (L1), a one-way conduction diode (D2) and a switch control tube (M1); the positive electrode of the power supply (BAT) is connected with the first end of the inductor (L1); the second end of the inductor (L1) is connected with the first end of the unidirectional conducting diode (D2); the second end of the unidirectional conducting diode (D2) is connected with the first pole of an energy storage device (C2); a second pole of the energy storage device (C2) is connected to the negative pole of the power source; the switch control tube (M2) is connected between the second end of the inductor (L1) and the second pole of the energy storage device (C2) in a bridging mode and is switched on or off under the control of the switch control signals (GATE1, GATE2, …, GATEN).

Of course, in fig. 13, the energy storage device is implemented by using capacitors, and a single capacitor in the figure is only one possible embodiment, and is also implemented by using a plurality of capacitors, or an LC circuit and other energy storage elements.

Also, the circuit in fig. 13 is not the only implementable manner for the charging unit, but the circuit may also be implemented using timing generation means such as edge triggering.

As shown in fig. 14, the falling edge of the switch TRIGGER signal (TRIGGER) is triggered by the end of the switch control signal (GATE1, GATE2, …, GATEN), such as the timing falling edge of the switch control signal (GATE1, GATE2, …, GATEN) shown in the figure; without loss of generality, if the end of the switch TRIGGER signal (TRIGGER) is the rising edge of the timing signal, the rising edge is used as the TRIGGER of the switch control signal to ensure that the light-emitting process is started after the end of charging, and the next charge-light-emitting process can be started immediately after the end of the previous charge-light-emitting process.

In the embodiment shown in fig. 14, the switch control signals (GATE1, GATE2, …, GATEN) are of equal temporal width, thus ensuring that the pulse widths in the transmitted pulse train are substantially identical.

As shown in fig. 15, control of the transmit pulse intensity can be achieved by controlling the width of the switch control signal in different pulse sequences. As shown in fig. 15, if the switch control signal GATE1 and the switch control signal GATE2 have different signal durations, the amount of charge in the energy storage device (C2) is different, and the intensity of the emitted single pulse is different.

According to the duration of different switch control signals, the control on the transmission pulse intensity can be controlled, the echo signals can be distinguished, and the interference among different transmission signal sequences is avoided.

Without loss of generality, each transmit pulse in the same pulse transmit queue may also be modulated by different pulse width modulation signals, for example, in the embodiment shown in fig. 15, the pulse intensity is in direct proportion to the duration width of the driving signal, the widths of the switch control signals (GATE1, GATE2, …, GATEN) are kA1, kA2, kA3, and the pulse intensities corresponding thereto are a1, a2, A3.

In this embodiment, the switch TRIGGER signal (TRIGGER) is triggered using a switch control signal (GATE1, GATE2, …, GATEN). In some possible embodiments, the switch control signal (GATE1, GATE2, …, GATEN) may also be triggered by a switch TRIGGER signal (TRIGGER).

In one possible embodiment, as shown in fig. 16, the laser emitting device comprises a plurality of laser emitting devices, and the plurality of laser emitting devices emit laser pulses with different codes. As shown in fig. 16, for example, two or more laser emitting devices (not shown) respectively emit pulsed laser light having different codes.

The emitted laser pulses are reflected at obstacles in the area to be detected and produce reflected echoes. Fig. 16 shows that the echoes emitted by two different laser emitters partially overlap at the laser receiver, which can identify the pulse sequences emitted by the different pulsed lasers by their intensities.

Meanwhile, the two pulses can also respectively have the same or different codes, and the pulse sequence can be judged by the codes to be transmitted by which pulse transmitting device.

In one possible embodiment, since the entire coded pulse sequence is captured for each range measurement, the coding allows the pulse sequence to last longer than if the laser pulse emitting device emitted a single pulse, while including intensity modulation, thereby making the pulse more easily identifiable. The laser pulse emitting device can continuously emit a plurality of pulses, and based on the continuous charging, the interval between the pulses is very small so as to prevent the flight time from spending longer in the same ranging range.

In one possible embodiment, the pulse flight distance is calculated using the encoded laser pulse sequence and the laser pulse sequence echoes.

In one possible embodiment, as shown in fig. 17, the laser emitting device comprises a plurality of laser emitting devices, and the plurality of laser emitting devices emit laser pulses with different codes. And judging whether an error pulse time calculation exists or not by calculating the standard deviation of the flight time of the laser pulse sequence. Since if a wrong pulse is introduced into the time of flight calculation it will cause the standard deviation to be greater than zero, whereas normally the standard deviation of the time of flight for each pulse train is substantially zero.

Meanwhile, the flight time may be obtained by calculating the average value of the flight times of a plurality of coded pulses, respectively, and the distance calculation is performed based on the TOF. For example, fig. 17 includes two pulse sequences, which pass the flight times T1, T2, T3, and T4, and T1 ', T2', T3 ', and T4' respectively during the ranging process. By bringing the time of flight of the pulse into the formula:

k is a pulseAnd calculating to obtain the distance for ranging based on the pulse laser, wherein c is the speed of light.

In a possible embodiment, a lidar is also proposed, which comprises a plurality of the aforementioned laser emitting devices based on time-series pulse coding. Because the crosstalk problem among different laser radar echoes can be effectively solved based on time sequence pulse coding, only a single laser receiving device can be used, and the reception of the echoes of a plurality of laser transmitting devices is realized. The measurement accuracy of the laser radar can be improved. The laser radar system comprises a plurality of lasers, and each time of detection, the coding unit controls the laser pulse transmitting unit to transmit a plurality of laser pulses in a very short first time, and the triggering of the plurality of pulses can be completed in a very short time by utilizing the triggering circuit and the triggering principle of the embodiment, so that the transmission of the whole detection pulse is maintained in a very short time period, for example, under a system clock of 1GHz, a pulse sequence can be controlled in tens of nanoseconds. Controlling multiple pulses per ranging over a certain time, e.g. 500ns, may also ensure that different ranging processes are not correlated with each other.

The receiving circuitry and processor of the lidar take a time measurement of multiple echo pulses in a range.

In one possible embodiment, as shown in fig. 18, in one possible embodiment, a plurality of energy storage modules are connected to the power supply module, each energy storage module is connected to a control switch, and the control switch is responsible for controlling the on/off of the energy storage module and the laser emitting unit. When a control switch between one energy storage module and the laser emission unit is closed, the charge stored in the energy storage module drives the laser emission unit to emit light pulses. Specifically, the respective unit switches shown in fig. 18 may be independent of each other, and the control switches are independently controlled by the control unit, respectively, and at the same time in terms of timing, the control unit may control the control switches to be independently opened or closed. When a plurality of control switches are closed at the same time, the energy of the emitted laser pulse is the sum of the energy storage modules. By simultaneously closing a plurality of control switches at the same time to emit high energy pulses, detection of distant objects can be achieved. The pulse shape emitted in time sequence can be controlled by controlling the number and time points of the control switches closed in time sequence. For example, at a certain time, only 1 control switch is closed, and the intensity of the pulse emitted at that time is 1 unit, while at a subsequent time, N control switches are closed, and the intensity of the pulse emitted at the corresponding time is N units. The timing and intensity of the transmitted pulses can be controlled by the control unit controlling the number of switches closed at different times.

In one possible embodiment, as shown in fig. 19, the receiving device receives the echo signal, passes through the compensation amplifier, then through the high-precision ADC, and continues to process the echo signal. The control unit may also be used to control the control switches in fig. 18 individually.

As shown in fig. 20, the pulse emitted from the laser radar is attenuated to some extent in consideration of the spatial reflection loss and the spatial propagation loss in the obstacle. Making the echoes difficult to distinguish. In particular, there is a problem that different lasers cannot be distinguished when they are received at the same time. Thus, using a modulation scheme such as that of fig. 21, the middle pulse is stronger than the side pulses in successive pulses, and is proportional to the side pulses. In particular, the middle pulse of the continuous laser pulses emitted by the laser radar can be several times of the side pulse, so that the middle strong pulse can realize the detection of a long-distance object. Furthermore, the method is simple. When continuous pulse echoes are received, the pulse signals arriving at the same moment can be distinguished more easily according to the comparison relation between the middle pulse and the pulses at the two sides.

In one embodiment, as shown in FIG. 22, two differently encoded sets of probe pulse echoes are aliased at the detector. The detector detects the intensity of the two sets of pulse echoes after superposition, as shown by the dashed line in fig. 22. In the usual case, the two groups of pulse echoes are indistinguishable according to the rayleigh criterion, due to the occurrence of aliasing. In embodiments using coded pulses, the echo signals detected by the detector may be calculated based on the coding at the time of transmission, in combination with the aliased signals detected by the detector. For example, in fig. 22, Am1, Am2, Am3 are pulse signal intensities where aliasing does not occur; am4, Am5, Am6 are pulse signal intensities at which aliasing occurs. In the actual determination process, it cannot be determined which part of Am1, Am2, Am3 and Am4, Am5, Am6 is subjected to aliasing. The processing unit can therefore make the following logical decisions:

the number of pulses of Am1, Am2, Am3, Am4, Am5, Am6 exceeds the maximum length of the transmission pulse, and thus it is determined that aliasing occurs.

The intensity difference of the coded pulses is then obtained, for example the difference between the maximum intensity and the minimum intensity. By comparing the difference with the intensity of the received pulse sequence, the position where aliasing occurs is judged.

For example, in fig. 22, it can be determined that aliasing has occurred at the Am6 and Am5 positions by determining (Am6-Am2) and (Am5-Am3) to be equal. The two sequences can then be specifically identified according to where aliasing occurs.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A multi-line beam laser radar with non-uniform pulses is characterized by comprising a control unit, a pulse driving unit and a pulse laser transmitting unit;

the control unit controls the pulse driving unit to generate a driving signal;

the pulse laser transmitting unit transmits multi-line beam laser pulses under the driving of the driving signals;

adjusting the drive signals such that the multi-line beam laser pulses are non-uniformly distributed over a field of view;

wherein the driving signal is encoded in a time domain, so that the pulse laser emission unit emits laser pulses with a time sequence under the driving of the driving signal, and the intensity and the frequency of the laser pulses are determined by the driving signal;

the pulse driving unit includes:

a plurality of charging units and an energy storage device; the plurality of charging units are independent of each other;

a plurality of charging units charge the energy storage device under the control of switch control signals (GATE1, GATE2, …, GATEN);

the energy storage device is used for continuous discharging under the control of a switch TRIGGER signal (TRIGGER) so that the laser pulse emitting unit emits a single pulse;

a switch control signal generation unit (CLK1) for controlling signal intervals and signal widths of the switch control signals (GATE1, GATE2, …, GATEN).

2. The lidar of claim 1, wherein the non-uniform distribution of the multi-line beam laser pulses over the field of view comprises: in a specific vertical emergent direction, the light source has stronger emergent pulse energy.

3. The lidar of claim 2, wherein having a relatively strong emergent pulse energy in a particular vertical emergent direction comprises: the laser pulse corresponding to the central part of the visual field has stronger single pulse energy; the upper and lower edge laser pulses of the field of view have a lower single pulse energy.

4. The lidar of claim 1, wherein the non-uniform distribution of the multi-line beam laser pulses over the field of view comprises: in a specific vertical emergent direction, the emergent pulse frequency is higher.

5. The lidar of claim 4, wherein having a higher fire pulse frequency in a particular vertical fire direction comprises: the laser pulse corresponding to the central part of the visual field has high pulse frequency; the upper and lower edges of the field of view have a low pulse frequency.

6. The lidar of claim 1, wherein the non-uniform distribution of laser pulses over the field of view comprises: in different azimuthal directions, there are different outgoing pulse energies.

7. The lidar of claim 1, wherein the non-uniform distribution of laser pulses over the field of view comprises: in different azimuth directions, with different outgoing pulse frequencies.

8. The lidar of claim 1, wherein the non-uniform distribution of laser pulses over the field of view comprises: there is a higher outgoing pulse energy or frequency in a particular vertical outgoing direction and a different outgoing pulse energy or frequency in a different azimuthal outgoing direction.

9. The lidar of claim 1, wherein the laser pulses having a timing sequence have a non-uniform pulse energy in timing sequence.

10. Lidar according to claim 1, wherein the energy storage means is sequentially discharged under control of a switch TRIGGER signal (TRIGGER) such that the laser pulse emitting unit emits a single pulse comprises:

after the Mth charging unit finishes charging the energy storage device according to the corresponding switch control signals (GATE1, GATE2, …, GATEN), triggering a switch TRIGGER signal (TRIGGER) to control the energy storage device to discharge immediately so that the laser pulse emitting unit emits a single light pulse;

the M +1 th charging unit charges the energy storage device according to the corresponding switch control signals (GATE1, GATE2, …, GATEN);

wherein M is a natural number and is less than the number N of the charging control switches.

11. Lidar according to claim 1, wherein said charging unit comprises a power supply (BAT), an inductor (L1), a unidirectional diode (D2), a switching control transistor (M1);

the positive electrode of the power supply (BAT) is connected with the first end of the inductor (L1);

the second end of the inductor (L1) is connected with the first end of the unidirectional conducting diode (D2);

the second end of the unidirectional conducting diode (D2) is connected with the first pole of an energy storage device (C2);

a second pole of the energy storage device (C2) is connected to the negative pole of the power source;

the switch control tube (M1) is connected between the second end of the inductor (L1) and the second pole of the energy storage device (C2) in a bridging mode and is switched on or off under the control of the switch control signals (GATE1, GATE2, …, GATEN).

12. A vehicle carrying a lidar according to any of claims 1 to 11.