WO2020107379A1

WO2020107379A1 - Reflectivity correction method for use in ranging apparatus, and ranging apparatus

Info

Publication number: WO2020107379A1
Application number: PCT/CN2018/118448
Authority: WO
Inventors: 陈涵; 张富; 洪小平
Original assignee: 深圳市大疆创新科技有限公司
Priority date: 2018-11-30
Filing date: 2018-11-30
Publication date: 2020-06-04
Also published as: CN111587383A

Abstract

A reflectivity correction method for use in a ranging apparatus, and a ranging apparatus. The reflectivity correction method for use in a ranging apparatus comprises: acquiring a real-time point cloud queue comprising a current detection point, the data of the current detection point comprising initial reflectivity; on the basis of the real-time point cloud queue, acquiring the angle of incidence of the current detection point; and, on the basis of the angle of incidence, correcting the initial reflectivity to obtain the corrected reflectivity of the current detection point. By means of correcting the reflectivity of the detection points, the present embodiments improve the accuracy of subsequent calculation results, and can reduce the occurrence of accidents, particularly in vehicle-mounted application scenarios. The number of detection points of the real-time point cloud queue in the present embodiments is relatively few, reducing the storage space and calculation resources required for the correction process and reducing the delay of the correction process, being particularly suitable for online correction application scenarios.

Description

Reflectance correction method applied to distance measuring device and distance measuring device

Technical field

The embodiments of the present invention relate to the technical field of data processing, and in particular, to a reflectance correction method and a distance measuring device applied to a distance measuring device.

Background technique

As a sensor, lidar can obtain the three-dimensional information of the scene. By emitting a laser pulse signal to the measured object and obtaining the reflected pulse signal, then calculate the distance of the measured object from the lidar according to the time difference between the transmitted signal and the received signal In-depth information. Moreover, based on the known launch direction of the lidar, the angle information of the measured object relative to the lidar is obtained; combining the depth information and the angle information, a detection point can be obtained. When the lidar scans the scene all over, a large number of detection points can be obtained to form a point cloud. Based on the point cloud, the spatial three-dimensional information of the measured object relative to the lidar can be reconstructed.

In some scenes, lidar not only outputs the spatial three-dimensional information of the measured object, but also outputs the reflectance of the measured object. When reconstructing the spatial three-dimensional information of the measured object, the existing laser radar defaults that the laser pulse signal is normally incident on the measured object, and the normal incidence of the measured object will result in inaccurate reflectance calculation results.

Summary of the invention

Embodiments of the present invention provide a reflectance correction method and a distance measuring device applied to a distance measuring device.

In a first aspect, an embodiment of the present invention provides a reflectance correction method applied to a distance measuring device, including:

Obtain a real-time point cloud queue containing the current detection point; the data of the current detection point includes the initial reflectance;

Obtaining the incident angle of the current detection point according to the real-time point cloud queue;

The initial reflectance is corrected according to the incident angle to obtain the corrected reflectance of the current detection point.

In a second aspect, an embodiment of the present invention provides a distance measuring apparatus, including a processor and a memory that stores executable instructions of the processor, and the processor communicates with the memory for reading from the memory. Execute instructions to achieve:

Correct the initial reflectance according to the incident angle to obtain the corrected reflectance of the current detection point.

In a third aspect, an embodiment of the present invention provides a readable storage medium that stores a number of computer instructions, and when the computer instructions are executed to implement the reflection applied to the distance measuring device according to the first aspect The steps of the rate correction method.

It can be seen from the above technical solution that, in this embodiment, the real-time point cloud queue corresponding to the current detection point is obtained; then, the incident angle of the current detection point can be obtained according to the real-time point cloud queue. Afterwards, the initial reflectivity in the current detection point data can be corrected according to the incident angle, thereby obtaining the corrected reflectivity. It can be seen that, in this embodiment, by correcting the reflectivity of the detection point, it is beneficial to improve the accuracy of the subsequent calculation results, especially in the vehicle-mounted application scenario, which can reduce the occurrence of accidents. In addition, the number of detection points of the real-time point cloud queue in this embodiment is relatively small, which can reduce the storage space and computing resources required for the correction process and reduce the delay of the correction process, and is particularly suitable for online correction application scenarios.

BRIEF DESCRIPTION

In order to more clearly explain the technical solutions in the embodiments of the present invention, the drawings required in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without paying any creative labor, other drawings can also be obtained based on these drawings.

1 is a schematic diagram of a scene of an incident angle provided by an embodiment of the present invention;

2 is a block diagram of a distance measuring device provided by an embodiment of the present invention;

3 is a schematic diagram of a distance measuring device using a coaxial optical path provided by an embodiment of the present invention;

4 is a schematic flowchart of a reflectance correction method applied to a distance measuring device provided by an embodiment of the present invention;

FIG. 5 is a schematic flowchart of obtaining an incident angle according to an embodiment of the present invention;

6 is a schematic flowchart of obtaining a normal vector according to an embodiment of the present invention;

7 is a schematic diagram of the effect of detecting a subsequence provided by an embodiment of the present invention;

FIG. 8 is another schematic flowchart of obtaining an incident angle according to an embodiment of the present invention;

FIG. 9 is a schematic flowchart of correcting reflectance provided by an embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative efforts fall within the protection scope of the present invention.

Considering that when reconstructing the spatial three-dimensional information of the measured object, the existing laser radar defaults that the laser pulse signal is normally incident on the measured object. For many scenes, the default normal incidence on the measured object will not affect the calculation result. However, if it is used as an in-vehicle device, the range of the lidar will be set lower, such as 1-100 meters. In this case, when the object to be measured is a lane line, street sign, etc., the normal incidence object will be used by default. Affect the calculation results and reflectance calculation results.

In practical applications, the physical model of reflectivity is:

In the formula, ρ is the reflectivity of the measured object, _Pr and _Pt are the received laser pulse energy and the emitted laser pulse energy, D _r is the receiving aperture, η is the atmosphere and lidar energy attenuation system, R is the The depth of the measured object from the lidar, α is the incident angle of the laser pulse hitting the measured object.

During the signal processing of a laser pulse transmission/reception, _Pr and _Pt can be estimated by the height (ie, amplitude) of the laser pulse information transmitted and received by Lidar, _Dr and η can be obtained by pre-measurement, and R can be It is calculated by the time difference between the pulse signal transmitted and received by the lidar. That is, in the physical model of reflectivity, only the incident angle α needs to be obtained separately. In addition, the subsequent embodiments of the present invention only describe how to obtain the incident angle, and other parameters can be obtained by referring to related technologies, which will not be repeated here.

The angle of incidence α refers to the angle between the normal vector of the measured object and the exit direction of the lidar. Referring to FIG. 1, the lidar 200 emits laser pulses to the measured object 301, where the normal vector of the measured object 301

The angle with the exit direction of the laser pulse is the incident angle α. In addition, when normal incidence α=0° (that is, cosα=1), the reflectance calculation result is not affected. But when cosα□1, the inaccurate angle α will cause the deviation of the reflectance calculation.

To this end, the embodiments of the present invention provide a reflectance correction method applied to a distance measuring device, which is suitable for a scene where lidar outputs detection points online. The inventive concept is to obtain the angle of incidence of the current detection point first, and then combine the incidence The relationship between the angle and the reflectivity is used to correct the initial reflectivity of the current detection point using the acquired incident angle, thereby improving the accuracy of the reflectivity of the detection point. Finally, the current detection point is output to the upper computer for use by the upper computer.

The reflectance correction methods provided by various embodiments of the present invention may be applied to a distance measuring device, and the distance measuring device may be an electronic device such as a laser radar or a laser distance measuring device. In one embodiment, the distance measuring device is used to sense external environment information, for example, distance information, azimuth information, reflection intensity information, speed information, etc. of the environmental target. In an embodiment, the distance measuring device may detect the time of light propagation between the distance measuring device and the measured object, that is, Time-of-Flight (TOF) to detect the distance between the measured object and the distance measuring device. distance. Alternatively, the distance measuring device may also detect the distance from the measured object to the distance measuring device through other techniques, such as a distance measuring method based on phase shift measurement, or a distance measuring method based on frequency shift measurement, There are no restrictions.

For ease of understanding, the following will describe the working process of distance measurement in conjunction with the distance measurement device 200 shown in FIG. 2.

Referring to FIG. 2, the distance measuring device 200 may include a transmitting circuit 210, a receiving circuit 220, a sampling circuit 230 and an arithmetic circuit 240.

The transmitting circuit 210 may transmit a sequence of light pulses (for example, a sequence of laser pulses). The receiving circuit 220 can receive the optical pulse sequence reflected by the object to be measured, and photoelectrically convert the optical pulse sequence to obtain an electrical signal, which can be output to the sampling circuit 230 after processing the electrical signal. The sampling circuit 230 may sample the electrical signal to obtain the sampling result. The arithmetic circuit 240 may determine the distance between the distance measuring device 200 and the measured object based on the sampling result of the sampling circuit 230.

Optionally, the distance measuring device 200 may further include a control circuit 250, which can control other circuits, for example, can control the working time of each circuit and/or set parameters for each circuit.

It is understandable that although the distance measuring device shown in FIG. 2 includes a transmitting circuit, a receiving circuit, a sampling circuit, and an arithmetic circuit for emitting a beam of light for detection, the embodiments of the present application are not limited thereto. The number of any one of the transmitting circuit, the receiving circuit, the sampling circuit, and the arithmetic circuit may also be at least two, for emitting at least two light beams in the same direction or respectively in different directions; wherein, the at least two light paths may be They are shot at the same time, or they can be shot at different times. In one example, the light-emitting chips in the at least two emission circuits are packaged in the same module. For example, each emitting circuit includes a laser emitting chip, and the laser emitting chips in the at least two emitting circuits are packaged together and housed in the same packaging space.

In some embodiments, in addition to the circuit shown in FIG. 2, the distance measuring device 200 may further include a scanning module 260 (not shown in the figure) for changing at least one laser pulse sequence emitted by the transmitting circuit to change the propagation direction.

Among them, the module including the transmitting circuit 210, the receiving circuit 220, the sampling circuit 230, and the arithmetic circuit 240, or the module including the transmitting circuit 210, the receiving circuit 220, the sampling circuit 230, the arithmetic circuit 240, and the control circuit 250 may be called a measurement For the distance module, the distance measuring module 250 may be independent of other modules, for example, the scanning module 260 (not shown in the figure).

The distance measuring device 200 may use a coaxial optical path, that is, the light beam emitted by the distance measuring device and the reflected light beam share at least part of the optical path in the distance measuring device. For example, after at least one laser pulse sequence emitted by the transmitting circuit is emitted by the scanning module to change the propagation direction, the laser pulse sequence reflected by the object to be measured passes through the scanning module and enters the receiving circuit. Alternatively, the distance measuring device may also adopt an off-axis optical path, that is, the light beam emitted by the distance measuring device and the reflected light beam are respectively transmitted along different optical paths in the distance measuring device. 3 is a schematic diagram of a distance measuring device using a coaxial optical path provided by an embodiment of the present invention. See Figure 3:

The distance measuring device 300 includes a distance measuring module 310. The distance measuring module 310 includes a transmitter 303 (which may include the above-mentioned transmitting circuit), a collimating element 304, and a detector 305 (which may include the above-mentioned receiving circuit, sampling circuit, and arithmetic circuit) and Optical path changing element 306. The ranging module 310 is used to emit a light beam, and receive back light, and convert the back light into an electrical signal. Among them, the transmitter 303 can be used to transmit a sequence of optical pulses. In one embodiment, the transmitter 303 may emit a sequence of laser pulses. Optionally, the laser beam emitted by the transmitter 303 is a narrow-bandwidth beam with a wavelength outside the visible light range. The collimating element 304 is disposed on the exit light path of the emitter, and is used to collimate the light beam emitted from the emitter 303, and collimate the light beam emitted from the emitter 303 into parallel light to the scanning module. The collimating element is also used to converge at least a part of the return light reflected by the measured object. The collimating element 304 may be a collimating lens or other element capable of collimating the light beam.

In the embodiment shown in FIG. 3, the optical path changing element 306 is used to combine the transmitting optical path and the receiving optical path in the distance measuring device before the collimating element 304, so that the transmitting optical path and the receiving optical path can share the same collimating element, so that the optical path More compact. In other embodiments, the transmitter 303 and the detector 305 may use respective collimating elements, and the optical path changing element 306 may be disposed on the optical path behind the collimating element.

In the embodiment shown in FIG. 3, since the beam aperture of the light beam emitted by the transmitter 303 is small and the beam aperture of the return light received by the distance measuring device is large, the light path changing element can use a small-area mirror to emit The optical path and the receiving optical path are merged. In other embodiments, the optical path changing element may also use a reflector with a through hole, where the through hole is used to transmit the outgoing light of the emitter 303, and the reflector is used to reflect the return light to the detector 305. This can reduce the shielding of the small mirror's bracket to the return light in the case of using a small mirror.

In the embodiment shown in FIG. 3, the optical path changing element is offset from the optical axis of the collimating element 304. In other embodiments, the optical path changing element may also be located on the optical axis of the collimating element 304.

The distance measuring device 300 further includes a scanning module 302. The scanning module 302 is placed on the exit optical path of the distance measuring module 310. The scanning module 302 is used to change the transmission direction of the collimated light beam 319 emitted through the collimating element 304 and project it to the external environment, and project the return light to the collimating element 304 . The returned light is converged on the detector 305 via the collimating element 304.

In one embodiment, the scanning module 302 may include at least one optical element for changing the propagation path of the light beam, wherein the optical element may change the propagation path of the light beam by reflecting, refracting, diffracting, etc. the light beam. For example, the scanning module 302 includes a lens, a mirror, a prism, a galvanometer, a grating, a liquid crystal, an optical phased array (Optical Phased Array), or any combination of the above optical elements. In one example, at least part of the optical element is moving, for example, the at least part of the optical element is driven to move by a driving module, and the moving optical element can reflect, refract, or diffract the light beam to different directions at different times. In some embodiments, multiple optical elements of the scanning module 302 may rotate or vibrate about a common axis 309, and each rotating or vibrating optical element is used to continuously change the direction of propagation of the incident light beam. In one embodiment, the multiple optical elements of the scanning module 302 may rotate at different rotation speeds, or vibrate at different speeds. In another embodiment, at least part of the optical elements of the scanning module 302 can rotate at substantially the same rotational speed. In some embodiments, the multiple optical elements of the scanning module may also rotate around different axes. In some embodiments, the multiple optical elements of the scanning module may also rotate in the same direction, or rotate in different directions; or vibrate in the same direction, or vibrate in different directions, which is not limited herein.

In one embodiment, the scanning module 302 includes a first optical element 314 and a drive 316 connected to the first optical element 314. The drive 316 is used to drive the first optical element 314 to rotate about a rotation axis 309 to change the first optical element 314 Collimate the direction of beam 319. The first optical element 314 projects the collimated light beam 319 to different directions. In one embodiment, the angle between the direction of the collimated light beam 319 changed by the first optical element and the rotation axis 309 changes as the first optical element 314 rotates. In one embodiment, the first optical element 314 includes a pair of opposing non-parallel surfaces through which the collimated light beam 319 passes. In one embodiment, the first optical element 314 includes a prism whose thickness varies along at least one radial direction. In one embodiment, the first optical element 314 includes a wedge-angle prism, aligning the straight beam 319 for refraction.

In one embodiment, the scanning module 302 further includes a second optical element 315. The second optical element 315 rotates about a rotation axis 309. The rotation speed of the second optical element 315 is different from the rotation speed of the first optical element 314. The second optical element 315 is used to change the direction of the light beam projected by the first optical element 314. In one embodiment, the second optical element 315 is connected to another driver 317, and the driver 317 drives the second optical element 315 to rotate. The first optical element 314 and the second optical element 315 may be driven by the same or different drivers, so that the rotation speed and/or rotation of the first optical element 314 and the second optical element 315 are different, thereby projecting the collimated light beam 319 to the outside space Different directions can scan a larger spatial range. In one embodiment, the controller 318 controls the

drivers

316 and 317 to drive the first optical element 314 and the second optical element 315, respectively. The rotation speeds of the first optical element 314 and the second optical element 315 may be determined according to the area and pattern expected to be scanned in practical applications.

Drives

316 and 317 may include motors or other drives.

In one embodiment, the second optical element 315 includes a pair of opposed non-parallel surfaces through which the light beam passes. In one embodiment, the second optical element 315 includes a prism whose thickness varies along at least one radial direction. In one embodiment, the second optical element 315 includes a wedge angle prism.

In one embodiment, the scanning module 302 further includes a third optical element (not shown in the figure) and a driver for driving the third optical element to move. Optionally, the third optical element includes a pair of opposed non-parallel surfaces through which the light beam passes. In one embodiment, the third optical element includes a prism whose thickness varies along at least one radial direction. In one embodiment, the third optical element includes a wedge angle prism. At least two of the first, second and third optical elements rotate at different rotational speeds and/or turns.

The rotation of each optical element in the scanning module 302 can project light into different directions, such as directions 311 and 313, so as to scan the space around the distance measuring device 300. When the light 311 projected by the scanning module 302 hits the object 301 to be measured, a part of the light object 301 is reflected to the distance measuring device 300 in the direction opposite to the projected light 311. The reflected light 312 reflected by the measured object 301 passes through the scanning module 302 and enters the collimating element 304.

The detector 305 is placed on the same side of the collimating element 304 as the emitter 303. The detector 305 is used to convert at least part of the returned light passing through the collimating element 304 into an electrical signal.

In one embodiment, each optical element is coated with an antireflection coating. Optionally, the thickness of the AR coating is equal to or close to the wavelength of the light beam emitted by the emitter 303, which can increase the intensity of the transmitted light beam.

In one embodiment, a filter layer is coated on the surface of an element on the beam propagation path in the distance measuring device, or a filter is provided on the beam propagation path to transmit at least the wavelength band of the beam emitted by the transmitter, Reflect other bands to reduce the noise caused by ambient light to the receiver.

In some embodiments, the transmitter 303 may include a laser diode through which laser pulses in the order of nanoseconds are emitted. Further, the laser pulse receiving time may be determined, for example, by detecting the rising edge time and/or the falling edge time of the electrical signal pulse. In this way, the distance measuring device 300 can calculate the TOF 307 using the pulse reception time information and the pulse emission time information, thereby determining the distance between the measured object 301 and the distance measuring device 300.

The distance and orientation detected by the distance measuring device 300 can be used for remote sensing, obstacle avoidance, mapping, modeling, navigation, and the like. In one embodiment, the distance measuring device of the embodiment of the present invention can be applied to a mobile platform, and the distance measuring device can be installed on the platform body of the mobile platform. A mobile platform with a distance measuring device can measure the external environment, for example, measuring the distance between the mobile platform and obstacles for obstacle avoidance and other purposes, and performing two-dimensional or three-dimensional mapping on the external environment. In some embodiments, the mobile platform includes at least one of an unmanned aerial vehicle, a car, a remote control car, a robot, and a camera. When the distance measuring device is applied to an unmanned aerial vehicle, the platform body is the fuselage of the unmanned aerial vehicle. When the distance measuring device is applied to an automobile, the platform body is the body of the automobile. The car may be a self-driving car or a semi-automatic car, and no restriction is made here. When the distance measuring device is applied to a remote control car, the platform body is the body of the remote control car. When the distance measuring device is applied to a robot, the platform body is a robot. When the distance measuring device is applied to a camera, the platform body is the camera itself.

FIG. 4 is a schematic flowchart of a reflectance correction method applied to a distance measuring device provided by an embodiment of the present invention. For convenience of description of subsequent embodiments, the distance measuring device is a laser radar. Referring to FIG. 4, a method for correcting the reflectance of a distance measuring device includes steps 401 to 403, in which:

401. Obtain a real-time point cloud queue containing the current detection point; the data of the current detection point includes the initial reflectance.

In this embodiment, the laser radar emits the laser pulse signal according to a preset mode, and the preset mode may include at least one of the following: a straight line, a curve, a spiral line, and an "8"-shaped line. Of course, the preset method can also be adjusted according to the specific scenario, which is not limited here.

The laser pulse information hits the measured object to form echo information, and the lidar samples the echo information to form a detection point. The data of each detection point includes at least one of the following: the initial reflectance and spatial coordinates of the detection point. The initial reflectivity is the uncorrected reflectivity.

Then, the detection points stored by the lidar can form a real-time point cloud queue. The real-time point cloud queue includes the current detection point, and the current detection point can be at any position in the real-time point cloud queue.

In this embodiment, the current detection point is set at an intermediate position, that is, there are m detection points before the current detection point, and there are m detection points after the current detection point, where m is a positive integer. It should be noted that the current detection point "before" or "after" refers to the sampling sequence, that is, the detection points of the real-time point cloud queue are detection points related to the time domain. To facilitate understanding, subsequent embodiments will be described in real-time point cloud queues in the time domain.

In addition, it should be noted that in some real-time requirements that are low, even in offline scenarios, each detection point in the real-time point cloud queue can also be a detection point related to the spatial domain, that is, the lidar scans the area on both sides of the current detection point Detection points, wherein the detection points on both sides of the area can be obtained by scanning the entire object after scanning in the above time domain scheme.

In this embodiment, two methods are used for the value of m:

In the first way, the m value is a fixed value, and the setting method is preset by the user or the lidar.

In this mode, the value of m is related to the performance parameters of the lidar. The performance parameters include at least one of the following: sampling speed and delay of the output detection point.

For example, when the performance parameter includes the sampling speed, the lidar has a large number of sampling detection points per unit time. Due to the close proximity of these detection points, the calculation accuracy may be affected. Therefore, the greater the sampling speed, the greater the value of m. That is, the m value can be increased when the sampling speed is increased, and the m value can be decreased when the sampling speed is decreased.

For another example, the performance parameters include the time delay of the output detection point. Considering the relationship between the data processed by the lidar and the time delay, if the real-time point cloud queue contains more detection points (that is, the larger the m value), the The greater the amount of data, the greater the delay of the output probe point. Conversely, if the real-time point cloud queue contains fewer detection points (that is, the smaller the m value), the smaller the amount of data processed by the lidar and the smaller the delay in outputting the detection points. Therefore, Lidar can adjust the value of m according to the time delay requirement of the output detection point. If the lidar detects that the delay of the output detection point increases, the m value can be reduced; if the delay decreases, the m value can be increased. In this way, dynamically adjusting the value of m in the case of meeting the delay requirement is beneficial to improve the accuracy of the detection point.

As another example, the performance parameters include the sampling speed and the time delay of the output detection point. You can select a compromise value for the m value through the change of the sampling speed and the m value, and the change of the delay and the m value.

It should be noted that the above sampling speed and delay are the performance parameters of the lidar itself, and the sampling speed and delay have been set for each use, so a fixed value of m can be obtained. Of course, you can also choose performance parameters related to lidar, such as reflectivity accuracy. In the case of higher reflectivity accuracy requirements, the greater the amount of data required by lidar, so the larger the value of m; the other hand, in the reflection When the rate accuracy requirement is lower, the amount of data required by lidar is smaller, so the smaller the m value. The scheme of the present application can also be realized, and the corresponding scheme falls within the protection scope of the present application.

In this way, the real-time point cloud queue is relatively simple, lidar processing is also more convenient and can ensure the consistency of the calculation results.

Method 2: The m value is a dynamic value, and the setting method is set dynamically by the lidar.

In this mode, the value of m is related to at least one of the incident angle of the previous detection point, whether the current detection point and the previous detection point belong to the same object to be measured, and the scanning density at different positions in space.

In this manner, the incident angle of the previous detection point refers to the incident angle of a detection point calculated by the subsequent step 402, and the one detection point is a detection point before the current detection point in sampling timing. The smaller the incident angle at the previous detection point, the smaller the angle between the measured object and the laser pulse signal exit direction, that is, the closer to the normal incident measured object. In order to cover the same area, the larger the number of sampled detection points, the larger the m value needs to be. In other words, the smaller the incident angle of the previous detection point, the larger the value of m; the larger the incident angle of the previous detection point, the smaller the value of m.

In this mode, whether the current detection point and the previous detection point belong to the same object to be measured refers to whether the current detection point and the previous detection point are on the same object, that is, whether the current detection point and the previous detection point are lasers The radar emits laser light to the same measured object and samples it on the echo signal. If the current detection point and the previous detection point belong to the measured object, and the two detection points are very close, so that the current detection point can have the same or similar expression effect as the previous detection point, in this case, the m value can be reduced. In other words, if the real-time point cloud queue of the previous detection point and the real-time point cloud queue of the previous detection point belong to the same object to be measured, the value of m is smaller; otherwise, if the real-time point cloud queue of the current detection point is the same as the previous If the real-time point cloud queue of points does not belong to the same object to be measured, the value of m is larger.

In this method, the scanning density at different positions in space refers to the density of point clouds at different positions in space. The greater the scanning density of the lidar at different positions in space, the more detection points used to cover the same area. Therefore, the greater the scanning density at different positions in space, the greater the value of m. Conversely, the lower the scanning density at different positions in space , The smaller the value of m.

It should be noted that the lidar can dynamically adjust the m value according to at least one of the incident angle including the previous detection point, whether the current detection point and the previous detection point belong to the same object to be measured, and the scanning density at different positions in space. For the value, if this solution can be realized, the corresponding solution falls into the protection scope of this application.

It should also be noted that the technician can choose the setting method of the m value according to the specific scenario, and can choose the fixed method, the dynamic method, or a combination of the fixed method and the dynamic method, which is not limited herein.

For convenience of description, in this embodiment, the solution of the present invention is described in a manner that the m value is a fixed value. In this scenario, the real-time point cloud queue formed by lidar can include:

Scenario 1: If the current detection point is the first detection point after the lidar is turned on, the lidar samples 2m+1 detection points, and uses the m+1 detection point as the current detection point. Relative to the last detection point, the current detection point is delayed by m detection points output.

Scenario 2: If the current detection point is not the first detection point, lidar discards the first m detection points in the real-time point cloud queue. Then, the lidar continues to sample the echo information of the laser pulse signal to obtain m new detection points and add them to the real-time point cloud queue. The m+1th probe point in the new point cloud queue becomes the new current probe point. Correspondingly, in the updated real-time point cloud queue, the current detection point and the last detection point are also delayed by m detection points. In this way, in this embodiment, by discarding part of the detection points, the storage space is not occupied, and storage resources are saved.

402. Obtain the incident angle of the current detection point according to the real-time point cloud queue.

In an embodiment, the lidar can obtain the incident angle of the current detection point according to the real-time point cloud queue. Referring to FIG. 5, the lidar can obtain the normal vector at the current detection point according to the real-time point cloud queue (corresponding to step 501). When obtaining the normal vector, see Figure 6:

Lidar first divides the real-time point cloud queue to obtain the detection point subsequences that belong to the same continuous surface as the current detection point (corresponding to step 601). The segmentation result is shown in Figure 7, which includes a total of four detection point subsequences indicated by dotted boxes , Including probing point subsequence a, probing point subsequence b, probing point subsequence c and probing point subsequence d. Among them, the detection point sub-sequence b belongs to the same connection plane as the current detection point. Then, the lidar can obtain its corresponding surface (corresponding to step 602) according to the determined sub-sequence of detection points, where the surface includes at least one of the following: a plane and a high-order curved surface. Finally, the lidar acquires the normal vector of the surface at the current detection point (corresponding to step 603).

It should be noted that the segmentation method in this embodiment may include at least one of the following: clustering algorithm based on curvature, clustering algorithm based on spatial distance, clustering algorithm based on multi-pulse echo, clustering based on Mahalanobis distance Algorithm, clustering algorithm based on graduation. Of course, the technician can choose the appropriate segmentation method according to the specific scenario, for example, directly use the depth information for the segmentation, and in the case where the detection point sub-sequence can be obtained, the corresponding partitioning scheme falls within the protection scope of the present application.

It should be further noted that, in step 602, when determining the surface corresponding to the detection point subsequence, if the laser radar emits a laser pulse signal in a straight line, and the object to be measured is a larger plane (or a larger curved surface), such as the ground, The effect is better. If the measured object is a small volume object in space, the number of detection points in the detection point sub-sequence is too small, so that there can be countless faces determined based on the detection point sub-sequence, so that there are countless normal vectors determined subsequently, which affects Subsequent calculation accuracy. Therefore, in this scenario, the laser pulse signal can be emitted using a curve, a helix, or an "8" shape line to form a certain spatial angle in space, so that the effect of determining the surface will be better.

Continuing to refer to FIG. 5, the lidar can obtain the exit direction of the lidar at the current detection point, and the angle between the normal vector and the exit direction can be calculated. Angle (corresponding to step 502). Continuing to refer to FIG. 1, the lidar can obtain the vector OS, and then using the cosine theorem, the vector OS and the vector can be obtained

Angle (acute angle).

In another embodiment, referring to FIG. 8, the lidar determines whether the current detection point and the previous detection point are on the same continuous surface (corresponding to step 801). If they belong to the same connection surface, the lidar acquires the incident angle of the previous detection point as the incident angle of the current detection point (corresponding to step 802). If they do not belong to the same connection surface, lidar uses the method shown in Figure 5 to obtain the angle of incidence.

It should be noted that in some scenes, the measured object and the lidar are in a static state. Since the change of the laser emission point and the exit direction of the two laser pulses is negligible, the incident angle can be directly obtained as shown in FIG. 8 method.

In other scenes, considering that the measured object and/or lidar exhibit a high-speed motion state, in this case, the lidar emission time interval between the two laser pulse signals before and after the determination is very short (for example, nanoseconds, microseconds) , And when the motion of the measured object and the lidar (such as millimeters, centimeters, or even meters) is negligible in the two transmission time intervals, the angle of incidence of the previous detection point is used as the angle of incidence of the current detection point.

In this way, in this embodiment, the same continuous surface can reduce the calculation amount, improve the calculation efficiency, and help reduce the delay of the output detection point.

403. Correct the initial reflectance according to the incident angle to obtain the corrected reflectance at the current detection point.

In this embodiment, the lidar can correct the initial reflectance according to the angle of incidence to obtain the corrected reflectance at the current detection point. The correction method includes:

Method 1: Based on the physical model of reflectivity, LiDAR can use the physical model to directly calculate the corrected reflectivity when other parameters are known.

Method two, a calibration model can be set in advance as follows:

In this way, referring to FIG. 9, the lidar acquires the cosine value cosα _{n of the} incident angle (corresponding to step 901). Since the initial reflectivity ρ _{raw, n} has been obtained in step 401 and is a known quantity. The lidar can calculate the quotient of the initial reflectivity ρ _raw,n and the cosine value cosα _n , which is taken as the corrected reflectivity ρ _corr,n (corresponding to step 902).

It should be noted that, in this embodiment, the lidar needs to integrate the storage amount of detection points, the amount of data calculation, and the reflectance accuracy to determine the number of detection points that need to be stored and calculated. As the accuracy of the reflectance is higher, the storage amount of the detection point is more and the calculation amount of data is larger. In some scenarios, the true value of the reflectance can be set in advance, and then the accuracy of the reflectance, the storage amount of the detection point, and the data calculation amount can be determined through continuous adjustment, which will not be repeated here.

So far, in this embodiment, the real-time point cloud queue corresponding to the current detection point is obtained; then, the incident angle of the current detection point can be obtained according to the real-time point cloud queue. Afterwards, the initial reflectivity in the current detection point data can be corrected according to the incident angle, thereby obtaining the corrected reflectivity. It can be seen that, in this embodiment, by correcting the reflectivity of the detection point, it is beneficial to improve the accuracy of the subsequent calculation results, especially in the vehicle-mounted application scenario, which can reduce the occurrence of accidents. In addition, the number of detection points of the real-time point cloud queue in this embodiment is relatively small, which can reduce the storage space and computing resources required for the correction process, reduce the delay of the correction process, and is suitable for the application scenario of online correction.

2 and FIG. 3, a distance measuring device provided by an embodiment of the present invention may further include a memory that stores executable instructions, and the arithmetic circuit 240 may be connected to the memory through a communication bus for reading from the memory. Execute instructions to achieve:

In this embodiment, by correcting the reflectivity of the detection point, it is beneficial to improve the accuracy of subsequent calculation results, especially in the vehicle-mounted application scenario, which can reduce the occurrence of accidents. In addition, the number of detection points of the real-time point cloud queue in this embodiment is relatively small, which can reduce the storage space and computing resources required by the correction process, reduce the delay of the correction process, and is suitable for the application scenario of online correction.

In some embodiments, the real-time point cloud queue includes a current detection point, there are m detection points before the current detection point, and m detection points after the current detection point, m is a positive integer.

In some embodiments, the m value is a fixed value.

In some embodiments, the m value is related to the performance parameter of the distance measuring device.

In some embodiments, the performance parameter includes at least one of the following: sampling speed, time delay of the output detection point.

In some embodiments, the performance parameter includes a sampling speed, and the larger the sampling speed, the larger the value of m.

In some embodiments, the performance parameter includes a delay of outputting the detection point. The greater the delay, the smaller the value of m.

In some embodiments, the m value is a dynamic value.

In some embodiments, the value of m is related to at least one of the incident angle of the previous detection point, whether the current detection point and the previous detection point belong to the same object to be measured, and the scanning density at different positions in space.

In some embodiments, the smaller the incident angle of the previous detection point, the larger the value of m.

In some embodiments, the real-time point cloud queue of the current detection point and the real-time point cloud queue of the previous detection point belong to the same object to be measured, and the smaller the value of m.

In some embodiments, the greater the scanning density at different locations in space, the greater the value of m.

In some embodiments, the operation circuit 240 is configured to obtain the incident angle of the current detection point according to the real-time point cloud queue includes:

Acquiring the normal vector at the current detection point according to the real-time point cloud queue;

The angle between the normal vector and the exit direction of the distance measuring device is calculated to obtain the angle of incidence of the current detection point.

In some embodiments, the operation circuit 240 for acquiring the normal vector at the current detection point according to the real-time point cloud queue includes:

Dividing the real-time point cloud queue to obtain a sub-sequence of detection points that belong to the same continuous surface as the current detection point;

Acquiring the face corresponding to the probing point sub-sequence;

Obtain the normal vector of the surface at the current detection point.

In some embodiments, the method for the arithmetic circuit 240 to segment the real-time point cloud queue includes at least one of the following: a clustering algorithm based on curvature, a clustering algorithm based on spatial distance, and a clustering based on multi-pulse echo Class algorithm, clustering algorithm based on Mahalanobis distance, clustering algorithm based on graduation.

In some embodiments, the surface includes at least one of the following: a flat surface, a high-order curved surface.

In some embodiments, during the process of acquiring the real-time point cloud queue containing the current detection point, the laser pulse signal is emitted according to a preset method, the preset method includes at least one of the following: straight line, curve, spiral line, "8" Zigzag line.

In some embodiments, the detection points of the real-time point cloud queue are detection points related to the time domain, or the detection points of the real-time point cloud queue are detection points related to the space domain.

In some embodiments, the operation circuit 240 for correcting the initial reflectance according to the incident angle includes:

Obtaining the cosine value of the incident angle;

A quotient of the initial reflectance and the cosine value is calculated, and the quotient is used as the corrected reflectance.

An embodiment of the present invention also provides a readable storage medium that stores a number of computer instructions, and when the computer instructions are executed, the reflectance applied to the distance measuring device shown in FIGS. 1 to 9 is realized The steps of the calibration method.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations There is any such actual relationship or order. The terms "include", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also others that are not explicitly listed Elements, or also include elements inherent to such processes, methods, objects, or equipment. Without more restrictions, the element defined by the sentence "include one..." does not exclude that there are other identical elements in the process, method, article or equipment that includes the element.

The devices and methods provided by the embodiments of the present invention have been described in detail above. Specific examples are used in the present invention to explain the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the methods and methods of the present invention. The core idea; for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be construed as limiting the present invention.

Claims

A reflectivity correction method applied to a distance measuring device, which is characterized by including:

Obtain a real-time point cloud queue containing the current detection point; the data of the current detection point includes the initial reflectance;

Obtaining the incident angle of the current detection point according to the real-time point cloud queue;

Correct the initial reflectance according to the incident angle to obtain the corrected reflectance of the current detection point.
The reflectance correction method according to claim 1, wherein the real-time point cloud queue includes a current detection point, there are m detection points before the current detection point, and m detection points after the current detection point, m is Positive integer.
The reflectance correction method according to claim 2, wherein the m value is a fixed value.
The reflectance correction method according to claim 2, wherein the m value is related to the performance parameter of the lidar.
The reflectance correction method according to claim 4, wherein the performance parameter includes at least one of the following: sampling speed and time delay of the output detection point.
The reflectance correction method according to claim 5, wherein the performance parameter includes a sampling speed, and the larger the sampling speed, the larger the value of m.
The reflectance correction method according to claim 5, wherein the performance parameter includes a delay of outputting the detection point, and the greater the delay, the smaller the value of m.
The reflectance correction method according to claim 2, wherein m value is a dynamic value.
The reflectance correction method according to claim 8, wherein the value of m and the angle of incidence of the previous detection point, whether the current detection point and the previous detection point belong to the same object to be measured, and the scan density at different positions in space At least one of the related.
The reflectance correction method according to claim 9, wherein the smaller the incident angle of the previous detection point, the larger the value of m.
The reflectance correction method according to claim 9, wherein the real-time point cloud queue of the current detection point and the real-time point cloud queue of the previous detection point belong to the same object to be measured, and the smaller the m value.
The reflectance correction method according to claim 9, wherein the greater the scanning density at different positions in space, the larger the value of m.
The reflectance correction method according to claim 1, wherein obtaining the incident angle of the current detection point according to the real-time point cloud queue includes:

Acquiring the normal vector at the current detection point according to the real-time point cloud queue;

The angle between the normal vector and the exit direction of the lidar is calculated to obtain the incident angle of the current detection point.
The reflectance correction method according to claim 13, wherein obtaining the normal vector at the current detection point according to the real-time point cloud queue includes:

Dividing the real-time point cloud queue to obtain a sub-sequence of detection points that belong to the same continuous surface as the current detection point;

Acquiring the face corresponding to the probing point sub-sequence;

Obtain the normal vector of the surface at the current detection point.
The reflectance correction method according to claim 14, wherein the method for segmenting the real-time point cloud queue includes at least one of the following: a clustering algorithm based on curvature, a clustering algorithm based on spatial distance, and a multi-pulse response Wave clustering algorithm, clustering algorithm based on Mahalanobis distance, clustering algorithm based on division.
The reflectance correction method according to claim 14, wherein the surface includes at least one of the following: a flat surface and a high-order curved surface.
The reflectance correction method according to claim 1, characterized in that, in the process of acquiring the real-time point cloud queue containing the current detection point, the laser pulse signal is emitted in a preset manner, and the preset manner includes at least one of the following: Straight line, curve, spiral line, "8" shape line.
The reflectance correction method according to claim 1, wherein the detection points of the real-time point cloud queue are detection points related to the time domain, or the detection points of the real-time point cloud queue are related to the space domain Detection point.
The reflectance correction method according to claim 1, wherein correcting the initial reflectance according to the incident angle comprises:

Obtaining the cosine value of the incident angle;

A quotient of the initial reflectance and the cosine value is calculated, and the quotient is used as the corrected reflectance.
A distance measuring device, characterized in that it includes a processor and a memory storing executable instructions of the processor, and the processor communicates with the memory for reading executable instructions from the memory to implement:

Obtain a real-time point cloud queue containing the current detection point; the data of the current detection point includes the initial reflectance;

Obtaining the incident angle of the current detection point according to the real-time point cloud queue;

Correct the initial reflectance according to the incident angle to obtain the corrected reflectance of the current detection point.
The distance measuring device according to claim 1, wherein the real-time point cloud queue includes a current detection point, there are m detection points before the current detection point, and m detection points after the current detection point, m is positive Integer.
The distance measuring device according to claim 21, wherein the m value is a fixed value.
The distance measuring device according to claim 21, wherein the m value is related to a performance parameter of the distance measuring device.
The distance measuring device according to claim 23, wherein the performance parameter includes at least one of the following: sampling speed and time delay of the output detection point.
The distance measuring device according to claim 24, wherein the performance parameter includes a sampling speed, and the larger the sampling speed, the larger the value of m.
The distance measuring device according to claim 24, wherein the performance parameter includes a delay of outputting the detection point, and the greater the delay, the smaller the value of m.
The distance measuring device according to claim 21, wherein the m value is a dynamic value.
The distance measuring device according to claim 27, wherein the value of m and the angle of incidence of the previous detection point, whether the current detection point and the previous detection point belong to the same object to be measured, and among the scanning densities at different positions in space At least one item is relevant.
The distance measuring device according to claim 28, wherein the smaller the incident angle of the previous detection point, the larger the value of m.
The distance measuring device according to claim 28, wherein the real-time point cloud queue of the current detection point and the real-time point cloud queue of the previous detection point belong to the same object to be measured, and the smaller the m value.
The distance measuring device according to claim 28, wherein the larger the scanning density at different positions in space, the larger the value of m.
The distance measuring device according to claim 20, wherein the processor is configured to obtain the incident angle of the current detection point according to the real-time point cloud queue includes:

Acquiring the normal vector at the current detection point according to the real-time point cloud queue;

The angle between the normal vector and the exit direction of the distance measuring device is calculated to obtain the angle of incidence of the current detection point.
The distance measuring device according to claim 32, wherein the processor is configured to obtain the normal vector at the current detection point according to the real-time point cloud queue including:

Dividing the real-time point cloud queue to obtain a sub-sequence of detection points that belong to the same continuous surface as the current detection point;

Acquiring the face corresponding to the probing point sub-sequence;

Obtain the normal vector of the surface at the current detection point.
The distance measuring device according to claim 33, wherein the method for the processor to segment the real-time point cloud queue includes at least one of the following: a clustering algorithm based on curvature, a clustering algorithm based on spatial distance, Clustering algorithm based on multi-pulse echo, clustering algorithm based on Mahalanobis distance, clustering algorithm based on division.
The distance measuring device according to claim 33, wherein the surface includes at least one of the following: a flat surface and a high-order curved surface.
The distance measuring device according to claim 20, characterized in that, in the process of acquiring the real-time point cloud queue containing the current detection point, the laser pulse signal is emitted in a preset manner, the preset manner including at least one of the following: a straight line , Curve, spiral line, "8" shape line.
The distance measuring device according to claim 20, wherein the detection points of the real-time point cloud queue are detection points related to the time domain, or the detection points of the real-time point cloud queue are related to the space domain Probe point.
The distance measuring device according to claim 20, wherein the processor for correcting the initial reflectance according to the incident angle comprises:

Obtaining the cosine value of the incident angle;

A quotient of the initial reflectance and the cosine value is calculated, and the quotient is used as the corrected reflectance.
A readable storage medium, characterized in that a plurality of computer instructions are stored on the readable storage medium, and when the computer instructions are executed, the reflectance applied to the distance measuring device according to any one of claims 1 to 19 is realized The steps of the calibration method.