WO2022062382A1

WO2022062382A1 - Lidar detection method and lidar

Info

Publication number: WO2022062382A1
Application number: PCT/CN2021/089527
Authority: WO
Inventors: 孙恺; 向少卿
Original assignee: 上海禾赛科技有限公司
Priority date: 2020-09-22
Filing date: 2021-04-25
Publication date: 2022-03-31
Also published as: CN114252866A

Abstract

Provided in the present invention is a detection method that uses a lidar. The lidar comprises a laser and a detection unit corresponding to the laser. The method comprises the following steps: within a time window, according to a pulse control parameter, driving the laser to emit a laser pulse so as to detect a target object, wherein the pulse control parameter is determined on the basis of an echo signal and a corresponding determination threshold; and/or according to the pulse control parameter, controlling the laser and/or the detection unit to turn on or off.

Description

Lidar detection method and lidar

technical field

The present invention generally relates to the technical field of lidar, and in particular, to a detection method of lidar and a lidar using the detection method.

Background technique

Lidar is a commonly used ranging sensor, which has the characteristics of long detection distance, high resolution, and little environmental interference. It is widely used in intelligent robots, unmanned aerial vehicles, unmanned vehicles and other fields. Lidar works by using the time it takes for a light wave to travel back and forth between the lidar and the target to assess the distance. The original lidar is a single-line lidar, that is, there is only one laser and a detector, and its scanning target range is limited, which is easy to cause the lack of detection targets. In order to make up for the shortcomings of single-line lidar, multi-line lidar has increasingly become the focus of research and commercial use. Multi-line LiDAR uses multiple lasers and corresponding detectors arranged in the vertical direction, which increases the detection range in the vertical direction. However, this type of lidar has the disadvantage of high cost, and the power of the lidar cannot be adjusted, which may cause waste. In addition, as a laser light source system, in order to avoid personal injury, the output laser power of lidar must meet the requirements of human eye safety.

Some mechanical radars can reduce the power consumption of lidar and avoid waste by allocating the power ratio according to the radar detection area. However, the modeling and power allocation algorithm in this way are more complicated, and once the model is determined, the allocation algorithm is fixed and cannot be adjusted adaptively. .

Single-photon detection technology has the advantages of ultra-high sensitivity and ultra-fast response speed, and can detect the smallest energy particles of light. It is an important detection method at present. The energy of a single photon is extremely small, and special optoelectronic devices must be used to detect a single photon. A single photon avalanche diode refers to an avalanche photodiode (Avalanche Photo Diode, APD) whose working voltage is higher than the breakdown voltage. An avalanche photodiode working in Geiger mode is also called a single photon avalanche diode (Single Photon Avalanche Photo Diode). , SPAD). SPAD has become the best device choice for single-photon detection due to its high avalanche gain, fast response speed, and low power consumption. SPAD amplifies the photocurrent based on the physical mechanisms of impact ionization and avalanche multiplication, thereby improving the detection sensitivity. In Geiger mode, the working voltage of the SPAD is greater than its avalanche breakdown voltage, which ensures that even a single photon incident and excited carriers can cause the avalanche effect. For a photodetector using a silicon photomultiplier (SiPM for short), the photodetector is usually implemented by using multiple SiPM units (or a pixel), and each SiPM unit uses multiple SiPM units. Parallel SPADs. And according to the total amount of photons received by the whole array at one time, the superimposed current outputs a pulse. However, at present, the utilization of single-photon detection technology is not enough, and the advantages of its high sensitivity are not fully reflected.

The contents in the Background section are merely technologies known to the disclosed person, and do not of course represent the prior art in the field.

SUMMARY OF THE INVENTION

In view of at least one defect of the prior art, the present invention provides a lidar solution that can save power consumption.

The present invention provides a detection method using a laser radar, the laser radar includes a laser and a detection unit corresponding to the laser, wherein the method includes the following steps:

Within the time window, the laser is driven to emit laser pulses to detect the target object according to a pulse control parameter, wherein the pulse control parameter is determined based on the echo signal and a corresponding decision threshold; and/or

The laser and/or the detection unit is controlled to be turned on or off according to the pulse control parameter.

According to one aspect of the present invention, wherein, the method further comprises:

driving the laser to emit laser pulses for detection according to the pulse control parameters;

Acquiring the echo signal of the laser pulse reflected on the detection target by the detection unit;

Pulse control parameters are updated according to the echo signal to control the laser and/or the detection unit to be turned off or on.

According to an aspect of the present invention, wherein the step of updating the pulse control parameter according to the echo signal further comprises:

a when the detection target changes, update the pulse control parameter according to the target information of the new detection target;

b controlling the emission of the laser according to the updated pulse control parameters to measure the changed detection target.

According to one aspect of the present invention, wherein the target information includes reflectivity, the step a further comprises:

a11 updates the pulse control parameter according to the new reflectivity and the current determination threshold.

According to an aspect of the present invention, wherein the target information includes flight time, the step a further comprises:

a21 updates the transmission time of the pulse control parameter according to the new flight time and the current determination threshold.

According to an aspect of the present invention, wherein, the step a further comprises:

Whether the detection target has changed is determined according to at least one of the following parameters:

- the number of echo pulses received within the same time window;

- the flight time of the echo pulse;

- Detect the reflectivity of the target.

According to one aspect of the present invention, the method further comprises the following steps:

- Get the intensity of ambient light;

- setting the determination threshold according to the intensity of the ambient light.

According to one aspect of the present invention, wherein the detection unit includes one or more single-photon avalanche diodes, wherein the step of setting the determination threshold according to the intensity of ambient light further includes:

- measure the number of avalanches corresponding to the ambient light on the detection unit in a unit time;

- setting/updating the number determination threshold according to the number of avalanches of ambient light in the unit time.

- making measurements based on the detection information obtained by the detection unit.

According to an aspect of the present invention, the method further comprises: in the next time window, activating the laser and/or the detection unit.

According to one aspect of the present invention, wherein the laser is a vertical cavity surface emitting laser.

The present invention also provides a laser radar, comprising:

a laser configured to emit laser pulses for detecting the target;

a detection unit, corresponding to the laser, configured to receive echoes of the laser pulses reflected on the target and output echo signals;

a control unit, coupled to the laser and the detection unit and receiving the echo signal, the control unit is configured to: within a time window, drive the laser to emit laser pulses to detect a target object according to a pulse control parameter, Wherein, the pulse control parameter is determined based on the echo signal and the corresponding determination threshold; and the laser and/or the detection unit is controlled to be turned on or off.

According to an aspect of the present invention, wherein the control unit is further configured to:

Pulse control parameters are updated according to the indicated echo signals to control the laser and/or the detection unit to be turned off or on.

According to an aspect of the present invention, wherein the control unit further comprises:

an update module, configured to update the pulse control parameter according to the target information of the detection target when the detection target changes;

The emission module controls the emission of the laser according to the updated pulse control parameter, so as to measure the changed detection target.

According to an aspect of the present invention, wherein the target information includes reflectivity, the update module is further configured to:

- Updating the transmit power of the pulse control parameter according to the new reflectivity and the current decision threshold.

According to an aspect of the present invention, wherein the target information includes flight time, the update module is further configured to:

- Updating the firing time of the pulse control parameter according to the new flight time and the current decision threshold.

- the number of echo pulses received within the same time window;

- the flight time of the echo pulse;

- Detect the reflectivity of the target.

According to one aspect of the present invention, wherein the control unit is further configured to:

- Get the intensity of ambient light;

According to one aspect of the present invention, wherein the detection unit comprises one or more single-photon avalanche diodes, wherein the control unit is further configured to:

Measure the number of avalanches corresponding to the ambient light on the detection unit in a unit time;

The quantity determination threshold is set/updated according to the number of avalanches of ambient light in the unit time.

In the next time window, the laser and/or the detection unit are activated.

The preferred embodiment of the present invention provides a method of setting the determination threshold according to the ambient light, and then continuously updating the pulse control parameters during the detection process, so as to control the emission time of the laser within each time window, and/or the detection unit Receive time scheme. Through this solution, the power consumption of the overall solution can be effectively reduced. In the solution of the present invention, by using the highly sensitive characteristics of SPADs or SiPM, the ambient light information at the current moment can be easily obtained, and since ambient light and signal light are both detected by the same detector, the measurement standard is unified, so it can be Easily compare signal and ambient light intensities, avalanche counts, and more. Moreover, by reducing the number of pulses emitted in each fixed time window, the energy of the laser transmitter can be greatly saved and power consumption can be reduced while ensuring the detection quality. At the same time, it can also increase the protection of human eye safety, and reduce the risk of human eye safety caused by long-time laser pulse emission.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention. In the attached image:

FIG. 1 schematically shows a detection method of a lidar according to a preferred embodiment of the present invention;

Figure 2a schematically shows a laser according to a preferred embodiment of the present invention;

Figure 2b schematically shows a detection unit according to a preferred embodiment of the present invention.

Fig. 3 schematically shows a pulse signal waveform diagram according to a preferred embodiment of the present invention;

Figure 4a schematically shows a histogram diagram of the number of photons output by a single-photon avalanche diode;

Fig. 4b schematically shows the waveform diagram of the output pulse of the silicon photomultiplier tube;

FIG. 5 schematically shows a schematic block diagram of the structure of a lidar according to a preferred embodiment of the present invention.

detailed description

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "top", "bottom", "front", " Or The positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be understood as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined as "first", "second" may expressly or implicitly include one or more of said features. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection Connection, or integral connection: it can be a mechanical connection or an electrical connection or can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal communication of two elements or the interaction of two elements relation. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include direct contact between the first and second features, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "above" the second feature includes that the first feature is directly above and diagonally above the second feature, or simply means that the first feature is level higher than the second feature. The first feature "below", "below" and "beneath" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature has a lower level than the second feature.

The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are only examples and are not intended to limit the invention. Furthermore, the present disclosure may repeat reference numerals and/or reference letters in different instances for the purpose of simplicity and clarity and not in itself indicative of a relationship between the various embodiments and/or arrangements discussed. In addition, the present disclosure provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the application of other processes and/or the use of other materials.

The embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

According to a preferred embodiment of the present invention, the present invention provides a method 100 for detecting a target object by using a laser radar 10. The laser radar 10 includes a laser 11 and a detection unit 12 corresponding to the laser 11 (as shown in FIG. 5 ) . The laser 11 corresponds to the detection unit 12 , which means that when the laser pulse emitted by the laser 11 is irradiated on the target object at infinity and diffusely reflected, the reflected echo will be received by the detection unit 12 . Each laser 11 and its corresponding detection unit 12 constitute a detection channel, and the lidar 10 may include multiple detection channels, such as 8, 16, 32, 40, 64, or 128 detection channels.

Wherein, the laser 11 according to the present invention can be realized by using a vertical cavity surface emitting laser (Vertical Cavity Surface Emitting Laser, VCSEL) or an edge-emitting laser EEL (edge-emitting laser, EEL).

Preferably, the laser 11 according to the present invention can be implemented using a VCSEL.

More preferably, the laser radar according to the present invention is an area array flash (FLASH) type laser radar realized by using a VCSEL area array (Array).

More preferably, the transmitting end of the FLASH lidar is realized by VCSEL area array, and the receiving end is realized by using SPADs array or SiPM array.

The detection method according to an embodiment of the present invention includes step S100.

In step S100, within a time window, the laser is driven to emit laser pulses to detect a target object according to a pulse control parameter, wherein the pulse control parameter is determined based on an echo signal and a corresponding decision threshold; and/or according to the A pulse control parameter controls the turning on or off of the laser and/or the detection unit.

Wherein, the time window can be determined based on at least any one of the following:

1) Scanning frequency; for example, a single frame scan time is a time window.

2) Predetermined scanning interval, etc.

Wherein, the pulse control parameter is used to indicate the number of pulses emitted by the laser within the time window; or, the pulse control parameter is used to indicate the turn-on time of the laser and/or the detection unit within the time window.

Specifically, the pulse control parameter is determined based on the echo signal and the corresponding decision threshold. For example, the flight time of the echo signal, another example, the light intensity information of the echo signal, etc.

Preferably, the determination threshold can be determined according to the strength of the echo signal.

Refer to Figures 1-3. According to a preferred embodiment of the present invention, as shown in FIG. 1 , the method for determining the pulse control parameter includes step S101 , step S102 and step S103 .

Continuing to refer to Figures 2a and 2b. A laser area array is illustrated in Figure 2a. Each unit shown in FIG. 2a corresponds to one laser, such as laser 11-1, laser 11-2, and so on. Preferably, the laser can be a VCSEL light-emitting channel or an EEL laser. When the laser is implemented with a VCSEL light-emitting channel, a VCSEL light-emitting channel may include an array formed by one or more photocells. Each photovoltaic cell is realized by including a quantum well that can emit a laser beam and its resonant cavity. One luminescent channel can be excited and emit detection pulses simultaneously.

Figure 2b illustrates a detection unit area array. Each cell in FIG. 2b corresponds to an individually addressable detection unit 12, wherein the detection unit 12 may comprise an array of SPADs formed by at least one SPAD; alternatively, the detection unit 12 may correspond to a SiPM unit.

FIG. 3 schematically shows a pulse diagram of a detection signal. As shown in FIG. 3 , the detection signal continuously transmits pulses at a certain pulse interval to perform detection.

Specifically, the method 100 according to the present invention includes steps S101, S102, and S103:

In step S101, the laser radar drives the laser 11 to emit laser pulses to detect the target.

Specifically, at the beginning of a time window, the driving laser 11 emits laser pulses at normal power for detection. The lidar 10 usually has an emission lens, and the laser 11 is located on the focal plane of the emission lens, so the laser pulses emitted by the laser 11 are collimated by the emission lens and then emitted into the surrounding environment as parallel light to detect the target object.

In step S102 , the laser radar acquires the echo signal reflected by the laser pulse on the target through the detection unit 12 .

The laser pulse is diffusely reflected on the target, and part of the reflected echo returns to the lidar, and is received by the detection unit 12 corresponding to the laser 11. The detection unit 12 usually includes a photodiode, which can convert the optical signal into an electrical signal to for subsequent signal processing.

In step S103, the laser radar updates the pulse control parameters according to the echo signal, so as to control the laser 11 and/or the detection unit 12 to be turned off or turned on.

Specifically, the lidar updates the pulse control parameters according to the light intensity information and/or the flight time of the echo signal.

Preferably, the laser radar obtains the pulse control parameters according to the determination threshold. Wherein, the determination threshold includes a quantity determination threshold. The number decision threshold is used to indicate the number of received echo signals. Preferably, the determination threshold further includes a light intensity determination threshold, and the light intensity determination threshold is used to determine an available echo signal.

Wherein, the pulse control parameter includes pulse emission duration. More preferably, the pulse control parameter further includes pulse transmission power.

The light intensity information can be represented in different forms according to the device used by the actual detection unit 12 . Preferably, according to an embodiment of the present invention, the detection unit 12 is implemented by a single-photon avalanche diode.

More preferably, the detection unit according to an embodiment of the present invention is a SPAD array or a SiPM unit. Wherein, when the detection unit 12 is implemented with different devices, the corresponding light intensity determination threshold may have different expressions.

For example, when the detection unit 12 is implemented with a SPAD array, the light intensity determination threshold can be expressed as the number of photons. The SPAD array counts each time an echo signal is detected, and when the count result is greater than the light intensity determination threshold, it is determined that the light intensity information of the current echo signal is greater than the light intensity determination threshold.

For another example, when the detection unit 12 is implemented with a SiPM unit, the light intensity determination threshold may be expressed as a peak voltage. The peak voltage of the SiPM unit is measured each time an echo signal is detected, and when the peak voltage of the echo pulse is greater than the light intensity determination threshold, it is determined that the light intensity information of the current echo signal is greater than the light intensity determination threshold.

According to a preferred embodiment of the present invention, the lidar performs the steps S101 to S103 in at least one time window. More preferably, the lidar performs the steps S101 to S103 in each time window.

In addition, "turning off" the laser 11 and/or the detection unit 12 in the context of the present invention includes, but is not limited to, disconnecting the driving circuit of the laser 11 and/or the detection unit 12, etc., only in fact, the laser 11 and/or The detection unit 12 enters a mode that cannot work normally so as to save power consumption, which falls within the protection scope of the present invention.

According to an embodiment of the present invention, the step S103 further includes step S1031 and step S1032.

In step S1031, when the detection target changes, the laser radar updates the pulse control parameter according to the target information of the detection target.

Specifically, the laser radar can update the transmission duration of the pulse control parameter according to the flight time to make it meet the quantity judgment threshold in the judgment threshold; or, the laser radar can update the pulse according to the reflectivity and/or light intensity information of the echo signal The emission light intensity information of the control parameter is controlled to satisfy the light intensity determination threshold in the determination threshold.

Wherein, the target information of the detection target includes at least any one of the following information:

1) Ranging information corresponding to the detection target: The ranging information includes any information that can indicate its relative distance from the lidar, for example, the distance information relative to the lidar; another example, the time-of-flight information of the detection target, etc.

2) Detect the reflectivity information corresponding to the target.

Wherein, the target information of the detection target can be determined through echo signals obtained by at least one detection.

Wherein, whether the detection target has changed is determined according to at least one of the following parameters:

1) The number of echo pulses received within the same time window;

2) The flight time of the echo signal;

3) Detect the reflectivity of the target.

According to a preferred embodiment, when the target information includes the flight time, step S1031 further includes: updating the pulse control parameter according to the new flight time and the current determination threshold.

According to the first example of the present invention, the pulse interval is 20 ns, the time window is 1 μs, the flight time TOF1 = 60 ns corresponding to the current detection target, the pulse control parameter includes the emission time length of 120 ns, and the determination threshold includes the quantity determination threshold of 4 times/cycle. That is, in a time window, pulses are continuously emitted only in the first 120 ns, and then the laser 11 is turned off. Meanwhile, the detection unit 12 is required to obtain at least 4 echo signal pulses in each time window period.

In this embodiment, since the dead time of a device using a SiPM or SPAD array is usually several nanoseconds, such as about 5ns, when the pulse interval is 20ns, each reflected echo signal can be received, while will not be affected.

When the detection target changes, according to the time when the detection unit 12 obtains the echo signal pulse in the time window, it can be known that the flight time TOF2=80ns of the new detection target. At this time, according to the current control pulse parameters, only 3 can be obtained in the current time window echo signal pulse. At this time, according to the quantity determination threshold of 4/cycle, combined with the new flight time of 80ns, a new launch duration is obtained.

Among them, the launch duration can be obtained based on the following formula:

Launch duration = flight time + pulse interval time * (quantity determination threshold - 1);

Then the new transmission duration=80ns+20ns*3=140ns at this time.

That is, in subsequent time windows, pulses are fired continuously for the first 140 ns of each window, after which the laser 11 is turned off.

Similarly, when the detection target distance becomes shorter and the flight time becomes shorter, considering the power saving, the transmission time can also be shortened, and only the time for acquiring 4 echo pulses is reserved.

According to a preferred embodiment, when the target information includes a reflectivity, the step S1031 further includes: updating the pulse control parameter according to the new reflectivity.

According to the second example of the present invention, the pulse interval is 15ns, the time window is 1μs, the detection unit 12 adopts SiPM, the light intensity determination threshold is 30mv, the reflectivity of the current detection target is 90%, and the peak value of the echo signal is 45mv; When the detection target is changed to a new detection target with a reflectivity of 50%, the obtained echo signal peak value is 25mv, which is less than the light intensity judgment threshold. At this time, the transmit power can be increased by updating the power control parameter of the pulse control parameter, so that the echo signal strength can still be maintained in the optimal detection range with a peak value of about 45mv.

Among them, those skilled in the art should understand that when the detection target changes, the ranging information and the reflectivity often change at the same time. Therefore, it may be necessary to adjust the transmission duration and transmission power information at the same time. This method should also be included in the present invention. range, and will not be repeated here.

Next, in step S1032, the laser radar controls the emission of the laser according to the updated pulse control parameter, so as to measure the changed detection target.

According to a preferred embodiment of the present invention, the method 100 further includes the following step S104 (not shown): setting/updating the number determination threshold (Nth) of the determination thresholds according to the ambient light.

The ambient light can be obtained through the detection result of the detection unit 12 or through an external sensor.

Preferably, the determination threshold further includes a light intensity determination threshold for determining whether the signal light is suitable. Wherein, the light intensity can be characterized in different ways based on different detection units 12, instead of directly using units such as lux.

For example, when the detection unit 12 is a single-photon avalanche diode (SPAD), the number of received photons of each SPAD array can be used to characterize the light intensity; for another example, when the detection unit 12 is a silicon photomultiplier (SiPM), The output voltage of the SiPM cell is used to characterize the light intensity, etc.

Specifically, the detection unit determines the ambient light intensity according to the number of photons obtained during the predetermined initial detection period, and determines/updates the determination threshold of the signal light based on the determined ambient light.

Preferably, the processor may set/update the quantity determination threshold Nth of the signal light according to the unit number of avalanches of ambient light according to a predetermined rule.

For example, the predetermined rule can be set as the following formula (1)

Nth=n*S; (1)

Wherein, Nth is the threshold for determining the quantity of signal light, S is the number of avalanches in the average unit time of the detected ambient light, and n is a preset multiple. That is, the threshold for determining the quantity of signal light may be set to n times the average number of avalanches of ambient light.

More preferably, n can be adjusted according to the average intensity of ambient light.

Specifically, when the average light intensity of ambient light is small, n can be set to a small value; and when the average light intensity of ambient light is large, n can be set to a large value. Therefore, when the ambient light is weak, the measurement can be completed with fewer pulses, and when the ambient light is strong, the accurate measurement can be ensured by increasing the number of pulses.

According to a preferred embodiment of the present invention, the time of 100 μs after the laser radar is started and before the laser pulse is emitted is set as its predetermined detection period, and the predetermined rule is Nth=5*S. The time window is 1 μs, and one cycle is a time window. The detection unit 12 detects 70 avalanches within the 100 μs period, and the lidar processor determines that the number of avalanches of ambient light in one cycle is 0.7. Next, the processor determines, according to a predetermined rule, that the intensity threshold of the signal light is:

Nth=5*S=5*0.7(pieces/cycle)=3.5(pieces/cycle).

It should be noted that those skilled in the art should understand that the foregoing formula (1) is only an example, rather than the only way to determine the threshold. Any method of obtaining the decision threshold value of signal light based on the average light intensity should be included in the predetermined rules described in the present invention, for example, other formula relations, such as multiplying by multiples and then rounding, etc., and for example, other light intensities Correspondence with the threshold, etc.

For example, presetting the corresponding relationship between the light intensity of the ambient light and the determination threshold, and searching according to the currently obtained light intensity of the ambient light to obtain the corresponding determination threshold should also be included in the solution described in the present invention. middle.

Figure 4a shows a waveform diagram of the output of the detection unit during a predetermined detection period when a single photon avalanche diode (SPAD) is used as the detection unit. The output of the SPAD is a photon count, that is, a digital signal, and Figure 4b shows a silicon photomultiplier When the tube (SiPM) is the detection unit, the output waveform when it receives photons.

It should be noted that, for SiPM, its actual output is the accumulated voltage of the outputs of multiple SPADs, which is an analog signal. At the weak light signal level, the output photocurrent of SiPM is proportional to the incident optical power, and the SiPM exhibits a linear response; as the incident optical power increases, due to the limitation of the number of SiPM pixels, its output photocurrent begins to deviate from the linear response region, and Eventually saturation occurs. Therefore, when a large number of photons are received by the SiPM, its output waveform exhibits a pulse waveform with a linear response similar to that of the APD within a certain stage.

The quantity determination threshold Nth can be obtained based on the measurement of ambient light or ambient noise in the early stage. For example, the quantity determination threshold Nth can be set by performing a single measurement of the ambient light, or the number determination threshold Nth can also be set by performing multiple measurements of the ambient light. A certain number of decision thresholds Nth.

Setting the quantity determination threshold Nth by taking a single measurement of ambient light includes, for example:

Measure the number of photons of ambient light incident on the detection unit 12 in unit time;

The number determination threshold Nth is set so that the number determination threshold Nth is greater than the number of photons of ambient light incident on the detection unit 12 within the unit time.

For the lidar, for example, the intensity of ambient light can be measured according to a preset period, and the set quantity determination threshold Nth can be updated according to the measurement result. In addition, for each detection unit 12 has its fixed detection time slot, the echo should return to the detection unit 12 within the detection time slot, and the time period outside the detection time slot of this detection unit 12 can be used to measure the ambient light , because the photons received by the detection unit 12 at this time should belong to ambient light.

Setting the quantity determination threshold Nth by performing multiple measurements of ambient light includes, for example:

The number of avalanches in the average unit time of the ambient light is obtained by multiple measurements;

The number determination threshold Nth is set so that the number determination threshold Nth is greater than the average number of avalanches of the ambient light.

Same as the above, the ambient light can be measured according to a preset period, or can be measured in a time period other than the detection time slot of the detection unit 12 .

According to a preferred embodiment of the present invention, in the method 100, only the detection unit 12 may be turned off to reduce the photon detection efficiency of the detection unit 12. Preferably, the detection unit 12 is a single-photon avalanche diode, and the avalanche occurs in the detection unit 12. The number is reduced, thereby avoiding the waste of power at the receiving end. It is also possible to turn off only the laser 11. Since the currently detected optical signal is sufficient to calculate the target distance, the laser 11 is temporarily turned off during this pulse period, which saves the transmitting power of the transmitter and avoids threats to human eye safety. Those skilled in the art can easily understand that when the number of received echo pulses is greater than the number determination threshold Nth, it is completely feasible to turn off the laser 11 and the corresponding detection unit 12 at the same time, and these are all within the protection scope of the present invention. .

According to a preferred embodiment of the present invention, the method 100 further includes: starting the laser 11 and/or the detection unit 12 in the next time window, so that the laser 11 and/or the detection unit 12 are in a normal working state.

According to this solution, by turning off the laser for a period of time in a time window, the energy emitted by the laser in each time window is reduced, thereby saving the energy of the laser, reducing the power consumption, and improving the eye safety of the lidar. performance.

Those skilled in the art should understand that the above examples are only used to illustrate the process of how to compare the determination thresholds and turn off the laser and/or the detection unit, rather than actual values.

According to a preferred embodiment of the present invention, the lidar 10 includes a plurality of lasers 11 and a plurality of detection units 12 corresponding to the plurality of lasers 11, and the method 100 further includes:

When the number of pulses of the echo signal received by the detection unit 12 exceeds the number determination threshold Nth, the corresponding laser 11 is turned off.

Those skilled in the art can easily understand that when the number of photons received by the detection unit 12 exceeds the threshold Nth, the detection unit 12 can be turned off, the laser 11 can be turned off, or both can be turned off at the same time. In the next time window, whether to turn on the laser 11 can be determined according to whether the detection unit 12 is turned on (the last time window was turned off or in the dead time of the photodiode). Judgment can also be made according to whether the adjacent lasers 11 of the laser 11 are turned on. In order to ensure that obstacles are not missed, all lasers 11 cannot be stopped emitting within a certain range. It can also be judged according to the map drawn by the sensor module or the current detection results of the lidar. When the surrounding environment is complex (for example, on a noisy road, there are various types of objects in the surrounding environment, such as vehicles, pedestrians, buildings, etc.), turn on The detection unit 12 may temporarily turn off the laser 11 when the surrounding environment is simple, such as in a field with few obstacles.

According to a preferred embodiment of the present invention, the laser 11 is a vertical cavity surface emitting laser (VCSEL). The lidar 10 can calculate the distance of the obstacle according to the flight time of the transmitted pulse and the echo signal, or calculate the reflectivity of the obstacle in the target space according to the power of the transmitted pulse and the echo signal.

As shown in FIG. 5 , according to a preferred embodiment of the present invention, the present invention provides a lidar 10 , including: a laser 11 , a detection unit 12 and a control unit 13 . The laser 11 is configured to emit laser pulses for detecting the target object. The detection unit 12 corresponds to the laser 11 . As shown in FIGS. 2 a and 2 b , the detection unit 12 and the laser 11 form a one-to-one correspondence. Only one laser 11 and one detection unit 12 are schematically shown in FIG. 5 , and those skilled in the art can easily understand that the lidar 10 may include any number of pairs of lasers 11 and detection units 12 . The detection unit 12 is configured to receive echoes of the laser pulses reflected on the target and output echo signals. The control unit 13 is coupled to the laser 11 and the detection unit 12 and receives the echo signal, and the control unit 13 is configured to have the following function: within the time window, drive the laser to emit laser pulses to detect the target object according to the pulse control parameters, wherein, The pulse control parameter is determined based on the echo signal and the corresponding decision threshold; and/or controls the laser and/or the detection unit to be turned on or off.

1) Scanning frequency; for example, a single frame scan time is a time window.

2) Predetermined scanning interval, etc.

Wherein, the pulse control parameter is used to indicate the number/power of pulses emitted by the laser within the time window; or, the pulse control parameter is used to indicate the ON time of the laser and/or the detection unit within the time window.

Specifically, the pulse control parameter is determined based on the echo signal and the corresponding decision threshold.

According to a preferred embodiment of the present invention, the control unit 13 is further configured to have the following functions:

1. Drive the laser 11 to emit laser pulses according to the pulse control parameters to detect the target.

2. Obtain the echo signal reflected by the laser pulse on the target through the detection unit 12 .

The laser pulse is diffusely reflected on the target, and part of the reflected echo returns to the lidar 10 and is received by the detection unit 12 corresponding to the laser 11. The detection unit 12 usually includes a photodiode, which can convert the optical signal into an electrical signal, for subsequent signal processing.

3. Update the pulse control parameters according to the echo signal to control the laser 11 and/or the detection unit 12 to be turned off or on.

According to a preferred embodiment of the present invention, the control unit 13 is further configured to have the following modules:

The updating module is configured to update the pulse control parameter according to the target information of the detection target when the detection target changes.

Specifically, the update module can update the transmission duration of the pulse control parameters according to the flight time to make it meet the number judgment threshold of the judgment threshold; or can update the transmission of the pulse control parameters according to the reflectivity and/or light intensity information of the echo signal Light intensity information to make it meet the light intensity judgment threshold of the judgment threshold.

The ranging information corresponding to the detection target:

Wherein, the ranging information includes any information that can indicate the relative distance from the laser radar, for example, the distance information relative to the laser radar; another example, the time-of-flight information of the detected target, and the like.

The reflectivity information corresponding to the detection target:

The target information of the detection target may be determined through at least one detection.

1) The number of echo pulses received within the same time window;

2) The flight time of the echo signal;

3) Detect the reflectivity of the target.

Get the intensity of ambient light;

The determination threshold is set according to the intensity of the ambient light.

According to a preferred embodiment of the present invention, wherein the detection unit 12 includes one or more single-photon avalanche diodes, the control unit 13 is further configured to:

According to a preferred embodiment of the present invention, the control unit 13 is further configured to:

The measurement is performed according to the detection information obtained by the detection unit.

In the next time window, the laser and/or the detection unit are activated.

A preferred embodiment of the present invention provides a method of setting the signal light judgment threshold according to the ambient light, and then setting the pulse control parameters, and in each time window, according to the pulse control parameters to adjust the laser and/or the detection unit on/off The method for turning off (preferably also including the transmit power of the laser), and the lidar for detection using the method, saves the power consumption of lidar transmit/receive, avoids waste, and reduces the threat to human eye safety from transmitting laser pulses .

Finally, it should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still possible to Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

A method for detection using a lidar, the lidar comprising a laser and a detection unit corresponding to the laser, wherein the method comprises the following steps:

Within the time window, the laser is driven to emit laser pulses to detect the target object according to a pulse control parameter, wherein the pulse control parameter is determined based on the echo signal and a corresponding decision threshold; and/or

The laser and/or the detection unit is controlled to be turned on or off according to the pulse control parameter.
The method of claim 1, wherein the method further comprises:

driving the laser to emit laser pulses for detection according to the pulse control parameters;

Acquiring the echo signal of the laser pulse reflected on the detection target by the detection unit;

Pulse control parameters are updated according to the echo signal to control the laser and/or the detection unit to be turned off or on.
The method according to claim 1 or 2, wherein the step of updating the pulse control parameter according to the echo signal further comprises:

a when the detection target changes, update the pulse control parameter according to the target information of the new detection target;

b controlling the emission of the laser according to the updated pulse control parameters to measure the changed detection target.
The method according to claim 3, wherein the target information includes reflectivity, and the step a further comprises:

a11 updates the pulse control parameter according to the new reflectivity and the current determination threshold.
The method according to claim 3, wherein the target information includes flight time, and the step a further comprises:

a21 updates the transmission time of the pulse control parameter according to the new flight time and the current determination threshold.
The method according to claim 4 or 5, wherein the step a further comprises:

Whether the detection target has changed is determined according to at least one of the following parameters:

- the number of echo pulses received within the same time window;

- the flight time of the echo pulse;

- Detect the reflectivity of the target.
The method of claim 1 or 2, further comprising the steps of:

- Get the intensity of ambient light;

- setting the determination threshold according to the intensity of the ambient light.
The method of claim 7, wherein the detection unit comprises one or more single-photon avalanche diodes, wherein the step of setting the determination threshold according to the intensity of ambient light further comprises:

- measure the number of avalanches corresponding to the ambient light on the detection unit in a unit time;

- setting/updating the number determination threshold according to the number of avalanches of ambient light in the unit time.
The method of claim 1 or 2, wherein the method further comprises:

- making measurements based on the detection information obtained by the detection unit.
The method of claim 1 or 2, further comprising: in the next time window, activating the laser and/or the detection unit.
The method of claim 1 or 2, wherein the laser is a vertical cavity surface emitting laser.
A lidar comprising:

a laser configured to emit laser pulses for detecting the target;

a detection unit, corresponding to the laser, configured to receive echoes of the laser pulses reflected on the target and output echo signals;

a control unit, coupled to the laser and the detection unit and receiving the echo signal, the control unit is configured to: within a time window, drive the laser to emit laser pulses to detect a target object according to a pulse control parameter, Wherein, the pulse control parameter is determined based on the echo signal and the corresponding determination threshold; and the laser and/or the detection unit is controlled to be turned on or off.
The lidar of claim 12, wherein the control unit is further configured to:

driving the laser to emit laser pulses for detection according to the pulse control parameters;

Acquiring the echo signal of the laser pulse reflected on the detection target by the detection unit;

Pulse control parameters are updated according to the indicated echo signals to control the laser and/or the detection unit to be turned off or on.
The lidar of claim 12 or 13, wherein the control unit further comprises:

an update module, configured to update the pulse control parameter according to the target information of the detection target when the detection target changes;

The emission module controls the emission of the laser according to the updated pulse control parameter, so as to measure the changed detection target.
The lidar of claim 14, wherein the target information includes reflectivity, and the update module is further configured to:

- Updating the transmit power of the pulse control parameter according to the new reflectivity and the current decision threshold.
The lidar of claim 14, wherein the target information includes time of flight, and the update module is further configured to:

- Updating the firing time of the pulse control parameter according to the new flight time and the current decision threshold.
The lidar of claim 15 or 16, wherein the control unit is further configured to:

Whether the detection target has changed is determined according to at least one of the following parameters:

- the number of echo pulses received within the same time window;

- the flight time of the echo pulse;

- Detect the reflectivity of the target.
The lidar of claim 12 or 13, wherein the control unit is further configured to:

- Get the intensity of ambient light;

- setting the determination threshold according to the intensity of the ambient light.
19. The lidar of claim 18, wherein the detection unit comprises one or more single photon avalanche diodes, wherein the control unit is further configured to:

Measure the number of avalanches corresponding to the ambient light on the detection unit in a unit time;

The quantity determination threshold is set/updated according to the number of avalanches of ambient light in the unit time.
The lidar of claim 12 or 13, wherein the control unit is further configured to:

- making measurements based on the detection information obtained by the detection unit.
The lidar of claim 12 or 13, wherein the control unit is further configured to:

In the next time window, the laser and/or the detection unit are activated.
The lidar of claim 12 or 13, wherein the laser is a vertical cavity surface emitting laser.