WO2021195831A1

WO2021195831A1 - Method and apparatus for measuring reflectivity in real time, and movable platform and computer-readable storage medium

Info

Publication number: WO2021195831A1
Application number: PCT/CN2020/082024
Authority: WO
Inventors: 张晓鹤; 陈涵
Original assignee: 深圳市大疆创新科技有限公司
Priority date: 2020-03-30
Filing date: 2020-03-30
Publication date: 2021-10-07

Abstract

Disclosed are a method (100) and apparatus (500, 630) for measuring reflectivity in real time, and a movable platform (600) and a computer-readable storage medium. The method (100) comprises: emitting an optical pulse signal to a measured object; receiving, in real time, a reflected pulse signal corresponding to the optical pulse signal; sampling the reflected pulse signal received in real time, so as to obtain a sampling result; and determining, on the basis of the sampling result, a feature value of the reflected pulse signal, acquiring an incident angle between the emitted optical pulse signal corresponding to the feature value and the measured object, and calculating, on the basis of the incident angle, the reflectivity of the measured object.

Description

Real-time reflectance measurement method, device, movable platform and computer readable storage medium

manual

Technical field

This application generally relates to the field of laser detection technology, and more specifically relates to a real-time reflectance measurement method, device, movable platform, and computer-readable storage medium.

Background technique

LiDAR is a perceptual sensor that actively emits laser pulse signals and obtains the pulse signals reflected by the measured object to obtain three-dimensional information of the scene.

Reflectance can provide important information about the surface of the measured object, thereby optimizing algorithms such as point cloud-based segmentation, clustering, and visualization.

Therefore, the measurement of reflectivity is very important, especially for oblique incidence. Obtaining accurate reflectivity can further help point cloud-based object detection and recognition, and high-precision map mapping. In addition, the current reflectance measurement is mostly calculated by offline point cloud data, rather than real-time online measurement, and there are many drawbacks.

Summary of the invention

The embodiment of the present application provides a reflectivity measurement solution, which can efficiently obtain accurate reflectivity measurement results. The following briefly describes the reflectance measurement scheme proposed in the present application, and more details will be described in the specific implementation in conjunction with the accompanying drawings.

According to one aspect of the present application, a method for real-time measurement of reflectance is provided, and the method includes:

Transmit light pulse signal to the measured object;

Receiving the reflected pulse signal corresponding to the optical pulse signal in real time;

Sampling according to the reflected pulse signal received in real time to obtain the sampling result;

Determine the characteristic value of the reflected pulse signal based on the sampling result, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and calculate the measured object's incident angle based on the incident angle Reflectivity.

According to another aspect of the present application, a device for real-time measurement of reflectance is provided. The device includes a transmitter, a receiver, a sampler, and a processor, wherein:

The transmitter is used to emit a light pulse signal to the object to be measured;

The receiver is configured to receive the reflected pulse signal corresponding to the optical pulse signal in real time;

The sampler is configured to sample the reflected pulse signal received in real time to obtain a sampling result;

The processor is configured to determine the characteristic value of the reflected pulse signal based on the sampling result, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and based on the incident angle Calculate the reflectance of the measured object.

According to another aspect of the present application, a movable platform is provided, the movable platform includes: a fuselage; a power system installed on the fuselage for providing flight power; the above-mentioned real-time reflectance measurement device, It is installed on the fuselage and used to perceive the environment where the movable platform is located and generate point cloud information.

According to yet another aspect of the present application, a computer-readable storage medium is provided, and a computer program is stored on the computer-readable storage medium, and the computer program executes the above-mentioned real-time measurement method of reflectance when running.

According to the real-time reflectivity measurement method, device, movable platform, and computer-readable storage medium of the embodiments of the present application, based on the characteristic value of the reflected pulse signal, the emitted light pulse signal corresponding to the characteristic value and the measured The incident angle between objects, and the reflectance of the measured object is calculated based on the incident angle. The reflectance measurement result can be obtained in real time and more accurately, and the real-time reflectance can be realized on the lidar sensor Calibration method.

Description of the drawings

Fig. 1 shows a schematic flow chart of a method for real-time measurement of reflectivity according to an embodiment of the present application;

2 shows a schematic flow chart of a method for calibrating a detection device that emits optical pulse signals in a method for real-time measurement of reflectance according to an embodiment of the present application;

3 shows a schematic diagram of a light reflection structure in a vertical incidence and oblique incidence scene in the method for real-time reflectance measurement according to an embodiment of the present application;

4 shows a schematic diagram of the structure of light reflection waveforms in a scene of vertical incidence and oblique incidence in the method for real-time reflectance measurement according to an embodiment of the present application;

Fig. 5 shows a schematic block diagram of a reflectance measuring device according to an embodiment of the present application;

Fig. 6 shows a schematic block diagram of a movable platform according to an embodiment of the present application;

Fig. 7 shows a schematic block diagram in which the movable platform according to an embodiment of the present application is a distance measuring device.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present application more obvious, the exemplary embodiments according to the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application, and it should be understood that the present application is not limited by the exemplary embodiments described herein. Based on the embodiments of this application described in this application, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of this application.

In the following description, a lot of specific details are given in order to provide a more thorough understanding of this application. However, it is obvious to those skilled in the art that this application can be implemented without one or more of these details. In other examples, in order to avoid confusion with this application, some technical features known in the art are not described.

It should be understood that this application can be implemented in different forms and should not be construed as being limited to the embodiments presented here. On the contrary, the provision of these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

The purpose of the terms used here is only to describe specific embodiments and not as a limitation of the present application. When used herein, the singular forms "a", "an" and "the/the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "composition" and/or "including", when used in this specification, determine the existence of the described features, integers, steps, operations, elements and/or components, but do not exclude one or more other The existence or addition of features, integers, steps, operations, elements, parts, and/or groups. As used herein, the term "and/or" includes any and all combinations of related listed items.

In order to thoroughly understand this application, detailed steps and detailed structures will be presented in the following description to explain the technical solutions proposed by this application. In addition to the implementation exceptions described in detail in this application, this application may also have other implementation modes.

The reflectance measurement is based on the following basic physical model:

Where ρ is the reflectivity of the measured object, Pr and Pe are the received and emitted laser pulse energy respectively, Dr is the receiving aperture, η is the energy attenuation of the atmosphere and the system, L is the depth of the measured object from the lidar, and α is the laser shot The angle of incidence on the measured object.

In the signal processing process of a laser emission/reception, Pr, Pe can be estimated by the height of the laser radar transmitting and receiving pulse signal, Dr, η can be obtained by pre-measurement, and L is calculated by the time difference between the laser radar transmitting and receiving the pulse signal get. Only α needs to be obtained with additional technology. When normal incidence is α=0°(cosα=1), but oblique incidence, especially large angle oblique incidence, cosα<<1, inaccuracy of α will cause reflectivity calculation deviation, which we call "reflection under oblique incidence Rate calculation deviation".

Most of the reflectance information provided by the existing lidar ignores "the reflectance calculation deviation under oblique incidence", that is, α=0°. However, when actually surveying the point cloud, the measured plane is not completely perpendicular to the incident laser. For example, for a vehicle application scenario, the typical oblique incident object to be measured is the ground and the lane line on the ground. At this time, the lidar for vehicle applications is required to calibrate/correct the reflectance calculation deviation caused by the oblique incident.

Some work has used offline data processing to fit the surface normal vector of the measured object based on one or several frames of offline point cloud data, and then calculate the angle between the normal vector and the laser emission direction to obtain α. However, the method is only seen in offline point cloud data processing solutions, and has not been applied to online implementation on the sensor side. Since this method needs to be based on massive offline point cloud data and perform surface fitting on the neighborhood of each point, it requires huge storage space and computing power. Lidar is a sensor module and obviously does not have the storage space and computing power required by the above methods. On the other hand, real-time acquisition of pulse waveforms at the bottom of the sensor is also information that is not included in offline point cloud data.

In order to solve the above-mentioned problems, the first aspect of the present application provides a real-time reflectance measurement method. The following describes a schematic flowchart of the reflectance real-time measurement method 100 according to an embodiment of the present application with reference to FIG. 1. As shown in FIG. 1, the method 100 for real-time reflectance measurement may include the following steps:

Step S110, transmitting a light pulse signal to the measured object;

Step S120, receiving the reflected pulse signal corresponding to the optical pulse signal in real time;

Step S130, sampling according to the reflected pulse signal received in real time to obtain a sampling result;

Step S140: Determine the characteristic value of the reflected pulse signal based on the sampling result, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and calculate the measured object based on the incident angle The reflectivity of the measured object.

Each step in the real-time measurement method 100 will be described in detail below.

First, in the embodiment of the present application, in the steps S110 and S120, a detection device may be used to transmit a light pulse signal to the object to be measured, and receive a reflected pulse signal corresponding to the light pulse signal. Wherein, the detection device includes, but is not limited to, laser radar, electromagnetic wave radar, millimeter wave radar, or ultrasonic radar. The detection device will be described in detail below. For details, please refer to the relevant description in the following embodiments.

Further, in step S130, the reflected pulse signal received in real time is sampled. It should be noted that in the real-time measurement method of the present application, both steps S120 and S130 are online real-time operations, that is, the reflected pulse signal corresponding to the optical pulse signal is received in real time, and the reflected pulse signal corresponding to the optical pulse signal is received in real time. Sampling in the reflected pulse signal is not an offline data processing method in the prior art to calculate the angle between the normal vector and the laser emission direction to obtain α. In this application, the data is received and sampled in real time to achieve online and real-time reflectivity calculation and calculation. Correction, with relatively little computing power, real-time online correction of the oblique incident example, real-time calibration of the reflectance deviation caused by the incident laser and the reflection plane of the measured object are not perpendicular, so as to obtain the reflectance more quickly and accurately Numerical value.

In a specific embodiment of the present application, the reflected pulse signal can be sampled based on a time-to-digital converter (TDC). Among them, the sampling of the reflected pulse signal based on the time-to-digital converter is to set multiple trigger voltage thresholds, for example, expressed as {V1,V2,V3,...,Vn} (where n is a natural number), and each channel is sampled on the rising edge of the signal and Sampling is triggered when the falling edge voltage reaches the set voltage threshold, and the corresponding time information is recorded, for example, expressed as {(t11,t12),(t21,t22),...,(tn1,tn2)}, so as to obtain the sampling result p = {(V1, t11, t12), (V2, t21, t22),..., (Vn, tn1, tn2)}. Therefore, sampling the reflected pulse signal based on the time-to-digital converter may include: multi-channel sampling of the reflected pulse signal, each sampling obtains a rising edge sampling point and a falling edge sampling point, the rising edge sampling point and The falling edge sampling points have the same voltage value and different time values.

In another embodiment of the present application, the reflected pulse signal can be sampled based on an analog-to-digital converter (ADC). Among them, the sampling of the reflected pulse signal based on the analog-digital converter is equal time interval sampling, that is, the reflected pulse signal is sampled every fixed time, and the voltage information corresponding to each time point is recorded, for example, expressed as {V1,V2,V3 ,...,Vn} (where n is a natural number), so as to obtain the sampling result p={(t1,V1),(t2,V2),(t3,V3),...,(tn,Vn)}. Therefore, sampling the reflected pulse signal based on the analog-digital converter may include: sampling the reflected pulse signal at equal intervals to obtain multiple sampling points, and the equal interval sampling refers to sampling the reflected pulse signal at regular intervals. Once, each sampling point corresponds to a voltage value and a time value.

In an embodiment of the present application, real-time sampling of the reflected pulse signal is implemented based on a time-to-digital converter (TDC), but it is not limited to this example, and can be selected according to actual needs.

In step S140, the characteristic value of the reflected pulse signal is determined based on the sampling result, the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object is obtained, and the incident angle is calculated based on the incident angle. The reflectivity of the measured object.

Wherein, when determining the characteristic value of the reflected pulse signal based on the sampling result, the value of any parameter of the echo corresponding to the sampling result can be selected, that is, a parameter value is selected as the characteristic of the reflected pulse signal value.

In addition, the values of multiple parameters of the echo corresponding to the sampling result can be selected, and the characteristic value of the reflected pulse signal can be determined based on the combination of the values of the multiple parameters, that is, after a combination of multiple parameters is selected As the characteristic value of the reflected pulse signal.

Specifically, the parameter of the characteristic value in this application must include at least the pulse width. The pulse width can be a baseline pulse width, a pulse width at a special position such as a half-height width, or a pulse width at any waveform height. Wide, not limited here. In addition to the pulse width, other parameters related to the pulse width may also be included, such as the echo height and the pulse width corresponding to the echo height, the ratio of the pulse width to the corresponding height, and so on. Therefore, the parameters of the echo include but are not limited to the following parameters: pulse width, echo height, and one or more of the pulse width corresponding to the echo height or the ratio of the pulse width to the corresponding height.

For example, in an embodiment of the present application, the characteristic value of the reflected pulse signal can extract any parameter of the echo that has a monotonic mapping relationship with different incident angles (such as the pulse width (wave width) at the characteristic height, etc.) Or the value combination of multiple parameters of the echo (such as the ratio of the pulse width (wave width) to the corresponding height, etc.).

Wherein, the change of the angle of incidence will cause the shape of the echo to change, and the angle of incidence can be obtained from the shape of the echo. Therefore, the parameter of the characteristic value must at least include the pulse width. A detailed description is given below:

Specifically, the light pulse signal (laser) emitted in this application has a certain divergence angle, and the pulse has a time length. For the standard waveform of normal incidence, it is considered that the difference in the size of the light spot at different distances caused by the divergence angle can be ignored. And the resulting optical path difference is different. Based on this, the change of the standard echo waveform is only reflected in the amplitude, and its time constant remains unchanged. That is, after the amplitude is normalized, the truncation and distortion caused by circuit saturation on the analog signal are not considered, and the standard waveforms of all normalized analog signals are the same.

For oblique incident events, the relationship between pulse width and echo energy no longer conforms to the law under normal incidence (for example, for more important ground echoes in autonomous driving scenarios, or terrain such as slopes in surveying and mapping scenarios). As shown in Figure 3, in the oblique incident scene, when there is an angle between the incident direction and the normal direction of the reflecting surface, the optical path difference between the return lights increases, which causes the return time to increase, that is, the waveform broadens. The larger the incident angle α, the more obvious the broadening effect.

Taking the light spot expansion in the one-dimensional direction x as an example, the maximum optical path difference Δl at this time is:

Where d is the distance from the emitting point to the reflecting surface when the laser divergence angle is 0.

Wherein, the optical path difference refers to the fact that not all photons are incident perpendicularly when they are incident. When the photons are incident perpendicularly or obliquely, after the photons are reflected on the surface of the object to be measured, there is a difference between the incident angle and the reflection angle, so the detection device receives the reflection after the reflection. There will be differences in the distance of the photon, where the maximum optical path difference Δl is the distance difference between the first and last received photons after reflection, that is, the product of the time difference and the speed of light.

Assuming that the statistical broadening of the photons reflected in dx at the receiving end of the lidar is 0, the time broadening of the corresponding echo is:

Where c is the speed of light.

Synthesizing the change of echo intensity in dx caused by the change of optical path and the decrease of echo energy caused by oblique incidence, assuming that the function of echo intensity in the time domain is Pr(t), at the same time, the laser emission intensity is Pe(t ), the circuit response is R(t), then the final output electrical signal strength Q(t) is:

Q(t)=(P _r +P _e +R)(t) formula (4);

According to formula (4), the final electrical signal Q of the reflected pulse signal is a function related to Pr(t). The angle of incidence α will affect the shape of Pr, and the reflectivity and distance of the reflecting plane will affect the overall intensity of Pr. .

The shape of the final electrical signal Q of the reflected pulse signal expands when it is incident obliquely, that is, the maximum height of the waveform of the final electrical signal Q decreases and the width at the baseline increases, as shown in FIG. 4. The change of its shape is caused by the change of the incident angle, that is, the incident angle α will affect the shape of Pr. The larger the incident angle α, the more obvious the shape widening effect of the final electrical signal Q. For a given system, it can be considered that Pe and R are known, so that the angle between the reflecting surface and the incident light pulse signal can be calculated by calculating the characteristic value of the waveform. Therefore, the parameter of the echo that the characteristic value must include is the pulse width.

Further, the parameters of the echo can select the pulse width at any height of the echo waveform of the reflected pulse signal. The method selects the pulse width at a specific height, that is, the obtained value is a single point value. Yes, the ratio of the pulse width at any height of the echo waveform of the reflected pulse signal to the corresponding height can also be selected.

In addition to the above-mentioned selection method of eigenvalues, in order to improve the accuracy, the pulse width at all heights of the echo waveform can also be selected, that is, comprehensive value selection, and the pulses at all heights of the echo waveform of the reflected pulse signal can also be selected. The ratio of the width to the corresponding height.

Wherein, in the step S140, after determining the characteristic value of the reflected pulse signal, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and calculate based on the incident angle The reflectivity method of the measured object includes at least the following two methods, which will be described in detail below.

First, calculate the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object according to the response function between the characteristic value and the incident angle.

Among them, as described above, a change in the incident angle α causes a change in the shape Q(t), so α can be obtained from Q(t) inversely.

Specifically, the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object may be calculated according to the response function between the characteristic value of the reflected pulse signal and the incident angle. Wherein, the response function refers to the functional relationship between the eigenvalue and the incident angle, that is, when the eigenvalue is obtained, the corresponding incident angle can be obtained.

Wherein, the method for obtaining the response function is: directly performing curve or surface fitting on the relationship between the characteristic value of the received pulse signal Q(t) and the incident angle α, so as to obtain a calculation model for α. Commonly used curve fitting models include polynomial curves, splines, and one-dimensional tables, and surface fitting models include two-dimensional tables and polynomial surfaces.

Optionally, in practical applications, the response function is a preset response function obtained by calibrating the detection device that emits light pulse signals. The preset response function is stored in the detection device. When the detection device is working, when the reflected pulse signal corresponding to the optical pulse signal is received and the characteristic value of the reflected pulse signal is determined, it can be obtained in real time according to the characteristic value and the preset response function stored in advance. The size of the incident angle, and then calculate the reflectivity of the measured object.

Wherein, as shown in FIG. 2, the method 110 for calibrating a detection device that emits a light pulse signal includes:

Step S111: Transmit a light pulse signal to the calibration board;

Step S112: Collect the reflected pulse signals reflected by the calibration plate under different energies and different incident angles;

Step S113: sampling according to the received reflected pulse signal to obtain a sampling result;

Step S114: Count the relationship between the eigenvalue at each sampling point and the incident angle, and fit the relationship curve and/or curved surface to obtain the preset response function.

In an embodiment of the present application, when performing calibration, the reflected echo signals of the tested calibration plate at different incident angles α are collected, and the waveform height is normalized according to the maximum amplitude. Then extract the eigenvalues that have a monotonic mapping relationship with different incident angles (such as including parameters such as the width of the waveform at the characteristic height) or combination of eigenvalues (such as parameters including the ratio of the waveform width to the corresponding height), and fit the corresponding α Thereby, the model function is obtained.

Specifically, in the step S111, the radar laser is emitted at a single point during calibration, wherein the reflective surface of the calibration plate is flat within the coverage area of the light spot, and various effects caused by the non-planar reflective surface are eliminated.

In the step S112, by adjusting the calibration plate, the reflected echo signals of the measured calibration plate at different energies and different angles α are collected.

Specifically, the distance between the detection device and the calibration board can be adjusted, the incident angle between the optical pulse signal of the detection device and the calibration board can be adjusted, and the calibration board itself can be replaced with a different The reflectivity material can adjust the incident energy of the detection device by changing one or more of the above parameters, and then collect the reflected echo signals of the tested calibration plate under different energies. Of course, the adjustment of the incident energy is not limited to the above example.

In the step S113 and the step S114, the pulse width at any height of the echo waveform of the reflected pulse signal can be selected, for example, the pulse width at a specific height is selected, that is, a single point value is obtained, The ratio of the pulse width at any height of the echo waveform of the reflected pulse signal to the corresponding height can also be selected.

In a specific embodiment, if the bottom width w of the waveform is selected, that is, the width at the baseline, the curve function model α=u(w) can be obtained by fitting the calibration data. In addition to selecting the width at the baseline, you can further select the half-height width and so on.

In a specific embodiment, integrating the data of all the widths at all heights and fitting with α, a curved surface function model α=v(w,h) can be obtained. Specifically, in this embodiment, after the waveform height is normalized (the height of the data point divided by the estimated total echo height), the relationship between the waveform width w, the normalized height h and the angle α at each data point is calculated , And then fitting to obtain the curved surface function α=v(w,h).

In this application, unless otherwise specified, the height of the waveform is the normalized height obtained by dividing the height of the sampling point by the total echo height, and the normalized height is obtained after the height is normalized. Waveform graphs can overlap each other.

After the curve function or the curved surface function is obtained, it is stored in the detection device as a preset response function. When the detection device is in use, the value of the incident angle can be obtained according to the characteristic value of the echo obtained in real time.

Specifically, during sampling in practical applications, multiple sampling points are selected for the reflected pulse signal, and the incident angle of each sampling point is calculated; the average value of the incident angles of all the sampling points is calculated to obtain the average incident angle.

Specifically, when sampling, each echo signal is composed of N data points. Calculate echo signal corresponding to the data point i and W _i h _i, so that the above-described calibration results calculated using the corresponding α _i.

Further, in order to reduce the error, the α _i obtained from the data points is averaged to obtain the average value of α. Take this as the angle between the reflection surface corresponding to this echo and the laser, and use the average value of the angle α to correct the calculated reflectivity.

The second method of calculating the reflectivity of the measured object based on the incident angle will be described in detail below. The second method is based on the functional relationship between the characteristic value of the reflected pulse signal and the incident angle. The incident angle corresponding to the characteristic value is directly calculated.

In the method, the functional relationship between the characteristic value of the reflected pulse signal and the angle of incidence of _{Q (t) = (P r} + P e + R) (t) Equation (4).

Among them, a change in the incident angle α will cause a change in the shape Q(t), and α can be inversely calculated from Q(t). Specifically, Pr(t) can be obtained by deconvolution calculation by formula (4). Combining with the spatial distribution of the instantaneous emission spot, α can be calculated according to the width characteristic value of Pr.

Specifically, because the maximum optical path difference of the emitted light pulse signal is calculated according to the incident angle between the emitted light pulse signal and the measured object, the characteristic value can be calculated according to the maximum optical path difference, as in the formula ( 1). In addition, after obtaining the waveform of the echo, the width w of Pr at the height of the arbitrary waveform (for example, the baseline) can be used as the characteristic value for calculation. Therefore, the width w has a functional relationship with Pr and the incident angle α, so:

The second method is the direct calculation method. In this method, it is assumed that the model of each part of the given system is known, for example, when the emission spot, emission pulse width, circuit response, noise, etc. are all fixed, and the reflective surface is assumed The coverage area of the light spot is a plane to eliminate the influence of the uneven plane. Only when the variables in the above model are determined, the incident angle can be estimated analytically.

Therefore, the second method is suitable for the ideal situation where the model of each part of the system is known. In practical applications, when it is difficult to obtain all the information for the actual system for forward analytical calculation, the first method can be used to calculate the incident angle, which can be based on the actual Need to make a choice.

In addition to the measurement method described in this application that can obtain the reflectance of the surface of the object to be measured for the laser used, the method may further include at least one of the following steps: according to the time difference between the transmitted signal and the received signal, combined with the speed of light , Can calculate the depth information of the distance detector of the measured object; based on the known emission direction of the lidar, obtain the angle information of the measured object relative to the lidar. The collection of detection points obtained by combining the above information is the point cloud. Based on the point cloud, the spatial three-dimensional information relative to the lidar can be reconstructed and provide data for further calculations.

In this application, by receiving data and real-time sampling, online real-time calculation and correction of reflectance can be realized. Relatively little computing power can be used to make real-time online corrections to cases of oblique incidence. Real-time calibration is due to the reflection of incident laser light and the measured object. The reflectivity deviation caused by the plane is not vertical, so that the reflectivity value can be obtained more quickly and accurately.

The second aspect of the present application provides a real-time reflectance measurement device 500. The composition of the reflectance real-time measurement device 500 will be described in detail below with reference to the accompanying drawings. As shown in Figure 5, the device includes a transmitter 510, a receiver 520, a sampler 530, and a processor 540, where:

The transmitter 510 is used to emit a light pulse signal to the object to be measured;

The receiver 520 is configured to receive the reflected pulse signal corresponding to the optical pulse signal in real time;

The sampler 530 is configured to sample the reflected pulse signal received in real time to obtain a sampling result;

The processor 540 is configured to determine the characteristic value of the reflected pulse signal based on the sampling result, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and based on the incident Calculate the reflectance of the measured object.

The solutions provided by the various embodiments of the present application can be applied to a distance measuring device, and the distance measuring device may be electronic equipment such as lidar and laser distance measuring equipment. In one embodiment, the distance measuring device is used to sense external environmental information, for example, distance information, orientation information, reflection intensity information, speed information, etc. of environmental targets. In one implementation, the distance measuring device can detect the distance from the probe to the distance measuring device by measuring the time of light propagation between the distance measuring device and the probe, that is, the time-of-flight (TOF). Alternatively, the ranging device can also detect the distance from the detected object to the ranging device through other technologies, such as a ranging method based on phase shift measurement, or a ranging method based on frequency shift measurement. This is not limited.

In order to facilitate understanding, the following will describe with an example the working process of the real-time measurement device 500 shown in FIG. 5.

Exemplarily, the real-time measurement device 500 may include a transmitter 510, a receiver 520, a sampler 530, and a processor 540. The transmitter 510 is used to emit light pulses; the receiver 520 is used to receive reflections from objects. Return at least part of the light pulses, and determine the distance of the object relative to the distance measuring device according to the received at least part of the light pulses.

The transmitter 510 may emit a light pulse sequence (for example, a laser pulse sequence). The receiver 520 may receive the light pulse sequence reflected by the object to be detected, and perform photoelectric conversion on the light pulse sequence to obtain an electrical signal, and then process the electrical signal and output it to the sampler 530. The sampler 530 may sample the electrical signal to obtain the sampling result. The processor 540 may obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object based on the sampling result of the sampler 530, and calculate the reflectance of the measured object based on the incident angle.

Further, in addition to calculating the reflectance of the measured object, the processor is also used to calculate the distance between the other measuring device and the measured object based on the sampling result of the sampler 530, for example, according to the emission The time difference between the signal and the received signal, combined with the speed of light, can calculate the depth information of the distance detector of the measured object; based on the known emission direction of the lidar, obtain the angle information of the measured object relative to the lidar; and by calculating the echo light Strong, the reflectivity of the surface of the object to be measured for the laser used can be obtained. The collection of detection points obtained by combining the above information is the point cloud. Based on the point cloud, the spatial three-dimensional information relative to the lidar can be reconstructed and provide data for further calculations.

Among them, the steps and methods performed by the transmitter 510, the receiver 520, the sampler 530, and the processor 540 in the measurement device 500 described in this application can refer to the real-time reflectance measurement method described in the first aspect of this application. The description of each step in the corresponding step will not be repeated here. Only the specific structure of the measuring device 500 will be described in detail below.

Optionally, the real-time measurement device 500 may further include a control circuit, which can control other circuits, for example, can control the working time of each circuit and/or set parameters for each circuit.

It should be understood that although the distance measuring device shown in FIG. 5 includes a transmitter, a receiver, a sampler, and a processor for emitting a beam for detection, the embodiment of the present application is not limited to this, the transmitter The number of any one of the receiver, the sampler, and the processor can also be at least two, which are used to emit at least two beams in the same direction or in different directions; wherein, the at least two beams can be emitted simultaneously. , It can also be launched at different times. In an example, the light-emitting chips in the at least two transmitting circuits are packaged in the same module. For example, each emission processor includes a laser emission chip, and the dies in the laser emission chips in the at least two emission circuits are packaged together and housed in the same packaging space.

In some implementations, in addition to the circuit shown in FIG. 5, the measuring device 500 may also include a scanning module for changing the propagation direction of at least one light pulse sequence (for example, a laser pulse sequence) emitted by the transmitter circuit to perform the field of view. scanning. Exemplarily, the scanning area of the scanning module in the field of view of the distance measuring device increases with the accumulation of time.

Among them, a module including a transmitter 510, a receiver 520, a sampler 530, and a processor 540, or a module including a transmitter 510, a receiver 520, a sampler 530, a processor 540, and a control circuit may be referred to as a ranging Module, the ranging module can be independent of other modules, for example, the scanning module.

According to the third aspect of the present application, a movable platform is also provided. The following describes a schematic block diagram of a movable platform 600 provided according to another aspect of the present application in conjunction with FIG. 6. As shown in FIG. 6, the movable platform 600 may include a body 610, a power system 620, and a reflectance measuring device 630. Wherein, the power system 620 may be installed on the fuselage 610 to provide flight power. The reflectance measuring device 630 can be installed on the fuselage 610 for sensing the environment where the movable platform 600 is located and generating point cloud information. The reflectance measuring device 630 may be the reflectance measuring device 630 described above. Illustratively, the movable platform 600 may be a drone. Exemplarily, the reflectance measuring device 630 may include, but is not limited to, a distance measuring device, electromagnetic wave radar, millimeter wave radar, or ultrasonic radar.

In an embodiment of the present application, the measuring device 630 includes a distance measuring device. The distance measuring device may be shown in FIG. At least part of the optical path is shared within the device. For example, after at least one laser pulse sequence emitted by the transmitter circuit changes its propagation direction and exits through the scanning module, the laser pulse sequence reflected by the probe passes through the scanning module and then 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 transmitted along different optical paths in the distance measuring device. FIG. 7 shows a schematic diagram of an embodiment in which the distance measuring device of the present application adopts a coaxial optical path.

The ranging device 200 includes a ranging module 210, which includes a light source, that is, a transmitter 203 (which may include the above-mentioned transmitting circuit), a collimating element 204, and a detector 205 (which may include the above-mentioned receiving circuit, sampling circuit, and Arithmetic circuit) and optical path changing element 206. The ranging module 210 is used to emit a light beam, receive the return light, and convert the return light into an electrical signal. Among them, the transmitter 203 can be used to transmit a light pulse sequence. In one embodiment, the transmitter 203 may emit a sequence of laser pulses. Optionally, the laser beam emitted by the transmitter 203 is a narrow-bandwidth beam with a wavelength outside the visible light range. The collimating element 204 is arranged on the exit light path of the emitter, and is used to collimate the light beam emitted from the emitter 203, and collimate the light beam emitted from the emitter 203 into parallel light and output to the scanning module. The collimating element is also used to condense at least a part of the return light reflected by the probe. The collimating element 204 may be a collimating lens or other elements capable of collimating a light beam.

In the embodiment shown in FIG. 7, the light path changing element 206 is used to combine the transmitting light path and the receiving light path in the distance measuring device before the collimating element 204, so that the transmitting light path and the receiving light path can share the same collimating element, so that the light path More compact. In some other implementations, it is also possible that the emitter 203 and the detector 205 use their respective collimating elements, and the optical path changing element 206 is arranged on the optical path behind the collimating element.

In the embodiment shown in FIG. 7, since the beam aperture of the light beam emitted by the transmitter 203 is small, and the beam aperture of the return light received by the distance measuring device is relatively large, the optical path changing element can use a small area mirror to The transmitting light path and the receiving light path are combined. In some other implementations, the light path changing element may also use a reflector with a through hole, where the through hole is used to transmit the emitted light of the emitter 203 and the reflector is used to reflect the return light to the detector 205. In this way, the shielding of the back light by the support of the small reflector in the case of using the small reflector can be reduced.

In the embodiment shown in FIG. 7, the optical path changing element deviates from the optical axis of the collimating element 204. In some other implementation manners, the optical path changing element may also be located on the optical axis of the collimating element 204.

The distance measuring device 200 further includes a scanning module 202, which is used to sequentially change the light beams emitted by the light source to different propagation directions and exit to form a scanning field of view. The scanning module 202 is placed on the exit light path of the distance measuring module 210. The scanning module 202 is used to change the transmission direction of the collimated beam 219 emitted by the collimating element 204 and project it to the external environment, and project the return light to the collimating element 204 . The returned light is collected on the detector 205 via the collimating element 204.

Wherein, the scanning module 202 can refer to the corresponding description of the scanning module in the foregoing embodiment, which will not be repeated here.

The detector 205 and the transmitter 203 are placed on the same side of the collimating element 204, and the detector 205 is used to convert at least part of the return light passing through the collimating element 204 into electrical signals.

In one embodiment, an anti-reflection coating is plated on each optical element. Optionally, the thickness of the antireflection coating is equal to or close to the wavelength of the light beam emitted by the emitter 203, which can increase the intensity of the transmitted light beam.

In one embodiment, a filter layer is plated on the surface of an element located on the beam propagation path in the distance measuring device, or a filter is provided on the beam propagation path for transmitting 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 203 may include a laser diode through which nanosecond laser pulses are emitted. Further, the laser pulse receiving time can be determined, for example, the laser pulse receiving time can be determined by detecting the rising edge time and/or the falling edge time of the electrical signal pulse. In this way, the distance measuring device 200 can calculate the TOF using the pulse receiving time information and the pulse sending time information, so as to determine the distance between the probe 201 and the distance measuring device 200. The distance and orientation detected by the distance measuring device 200 can be used for remote sensing, obstacle avoidance, surveying and mapping, modeling, navigation, and the like.

According to the fourth aspect of the present application, there is also provided a computer-readable storage medium with a computer program stored on the computer-readable storage medium. Measurement methods. The computer-readable storage medium may include, for example, a memory card of a smart phone, a storage component of a tablet computer, a hard disk of a personal computer, a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a portable compact disk Read only memory (CD-ROM), USB memory, or any combination of the above storage media. The computer-readable storage medium may be any combination of one or more computer-readable storage media.

Although the exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above-described exemplary embodiments are merely exemplary, and are not intended to limit the scope of the present application thereto. Those of ordinary skill in the art can make various changes and modifications therein without departing from the scope and spirit of the present application. All these changes and modifications are intended to be included within the scope of the present application as required by the appended claims.

A person of ordinary skill in the art may realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether these functions are executed by hardware or software depends on the specific application and design constraint conditions of the technical solution. Professionals and technicians can use different methods for specific applications to implement the described functions, but such implementation should not be considered beyond the scope of this application.

In the several embodiments provided in this application, it should be understood that the disclosed device and method may be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components may be combined or It can be integrated into another device, or some features can be ignored or not implemented.

In the instructions provided here, a lot of specific details are explained. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures, and technologies are not shown in detail, so as not to obscure the understanding of this specification.

Similarly, it should be understood that, in order to simplify this application and help understand one or more of the various aspects of the invention, in the description of the exemplary embodiments of this application, the various features of this application are sometimes grouped together into a single embodiment or figure. , Or in its description. However, the method of this application should not be interpreted as reflecting the intention that the claimed application requires more features than those clearly stated in the claims. More precisely, as reflected in the corresponding claims, the point of the invention is that the corresponding technical problems can be solved with features that are less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are thus clearly incorporated into the specific embodiment, wherein the claims themselves are all regarded as separate embodiments of the present application.

Those skilled in the art can understand that in addition to mutual exclusion between the features, any combination of all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and any method or device disclosed in this manner can be used. Processes or units are combined. Unless expressly stated otherwise, the features disclosed in this specification (including the accompanying claims, abstract and drawings) may be replaced by alternative features that provide the same, equivalent or similar purpose.

In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments means that they are within the scope of the present application. Within and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

The various component embodiments of the present application may be implemented by hardware, or by software modules running on one or more processors, or by a combination of them. Those skilled in the art should understand that a microprocessor or a digital signal processor (DSP) may be used in practice to implement some or all of the functions of some modules according to the embodiments of the present application. This application can also be implemented as a device program (for example, a computer program and a computer program product) for executing part or all of the methods described herein. Such a program for implementing the present application may be stored on a computer readable storage medium, or may have the form of one or more signals. Such a signal can be downloaded from an Internet website, or provided on a carrier signal, or provided in any other form.

It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be constructed as a limitation to the claims. The application can be realized by means of hardware including several different elements and by means of a suitably programmed computer. In the unit claims listing several devices, several of these devices may be embodied in the same hardware item. The use of the words first, second, and third, etc. do not indicate any order. These words can be interpreted as names.

The above are only specific implementations of this application or descriptions of specific implementations. The scope of protection of this application is not limited to this. Anyone familiar with the technical field within the technical scope disclosed in this application can easily Any change or replacement should be covered within the scope of protection of this application. The protection scope of this application shall be subject to the protection scope of the claims.

Claims

A real-time measurement method of reflectivity, characterized in that the method includes:

Transmit light pulse signal to the measured object;

Receiving the reflected pulse signal corresponding to the optical pulse signal in real time;

Sampling according to the reflected pulse signal received in real time to obtain the sampling result;

Determine the characteristic value of the reflected pulse signal based on the sampling result, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and calculate the measured object's incident angle based on the incident angle Reflectivity.
The method according to claim 1, wherein the incident angle between the emitted light pulse signal corresponding to the eigenvalue and the measured object is calculated according to the response function between the eigenvalue and the incident angle.
The method according to claim 2, wherein a relationship curve and/or curved surface are fitted based on the different incident angles and the eigenvalues of the reflected pulse signal corresponding to the incident angle to obtain the response function .
The method according to claim 2, wherein the response function is a preset response function obtained by calibrating a detection device that emits an optical pulse signal.
The method according to claim 4, wherein the method of calibrating the detection device emitting the optical pulse signal comprises:

Transmit light pulse signals to the calibration board;

Collect the reflected pulse signal reflected by the calibration plate under different energy and different incident angle;

Sampling according to the received reflected pulse signal to obtain the sampling result;

The relationship between the characteristic value and the incident angle at each sampling point is counted, and the relationship curve and/or the curved surface are fitted to obtain the preset response function.
The method according to claim 5, characterized in that by changing the distance between the detection device and the calibration plate, the material of the calibration plate, the optical pulse signal of the detection device and the calibration plate At least one of the incident angles between the two to change the energy of the light pulse signal emitted by the detection device.
The method according to claim 1, wherein the reflective surface of the measured object is a flat surface.
The method according to any one of claims 1-7, wherein the determining the characteristic value of the reflected pulse signal based on the sampling result comprises:

Determine the value of any parameter of the echo corresponding to the sampling result based on the sampling result as the characteristic value of the reflected pulse signal; or

The values of multiple parameters of the echo corresponding to the sampling result are determined based on the sampling result, and the characteristic value of the reflected pulse signal is determined based on the combination of the values of the multiple parameters.
The method according to claim 8, wherein the parameters of the echo include: pulse width, echo height, and one of the pulse width corresponding to the echo height or the ratio of the pulse width to the corresponding height or Many kinds.
The method according to claim 8 or 9, wherein the parameters of the echo include the pulse width at any height of the echo corresponding to the sampling result or the pulse width at any height and the corresponding height. Ratio; and/or

The characteristic value includes the pulse width at all heights of the echo corresponding to the sampling result or the ratio of the pulse width at all heights to the corresponding height.
The method according to claim 10, wherein the height is a normalized height obtained by dividing the height of the sampling point by the total height of the echo.
The method according to claim 10, wherein the characteristic value is the pulse width at the baseline of the echo or the half-width of the echo.
The method according to claim 1, wherein the incident angle corresponding to the eigenvalue is directly calculated according to the functional relationship between the eigenvalue of the reflected pulse signal and the incident angle.
The method according to claim 13, wherein the functional relationship between the characteristic value of the reflected pulse signal and the incident angle is:

The maximum optical path difference of the emitted light pulse signal is calculated according to the incident angle between the emitted light pulse signal and the measured object, and the characteristic value is calculated according to the maximum optical path difference.
The method according to any one of claims 1-14, wherein the sampling according to the reflected pulse signal received in real time is implemented based on a time-to-digital converter.
The method according to any one of claims 1-14, wherein multiple sampling points are selected for the reflected pulse signal;

Calculate the incident angle of each sampling point;

Calculate the average of the incident angles of all sampling points to obtain the average incident angle.
The method according to claim 16, wherein the reflectance of the measured object is calculated based on the average incident angle.
The method according to any one of claims 1-17, wherein the method further comprises: after calculating the reflectance of the measured object based on the pulse energy value, according to the measured object Reflectivity for object detection and recognition, or for map surveying and mapping.
A reflectance measuring device, characterized in that the device includes a transmitter, a receiver, a sampler and a processor, wherein:

The transmitter is used to emit a light pulse signal to the object to be measured;

The receiver is configured to receive the reflected pulse signal corresponding to the optical pulse signal in real time;

The sampler is configured to sample the reflected pulse signal received in real time to obtain a sampling result;

The processor is configured to determine the characteristic value of the reflected pulse signal based on the sampling result, obtain the incident angle between the emitted light pulse signal corresponding to the characteristic value and the measured object, and based on the incident angle Calculate the reflectance of the measured object.
The measurement device according to claim 19, wherein the processor is configured to calculate the difference between the emitted light pulse signal corresponding to the characteristic value and the measured object according to the response function between the characteristic value and the incident angle. Angle of incidence.
The measurement device according to claim 20, wherein the processor is configured to fit a relationship curve and/or a curved surface based on the different incident angles and the characteristic values of the reflected pulse signals corresponding to the incident angles, To get the response function.
22. The measurement device according to claim 20, wherein the response function is a preset response function obtained by calibrating a detection device that emits an optical pulse signal.
The measurement device according to claim 22, wherein the method of calibrating the detection device emitting the optical pulse signal comprises:

The transmitter is used to emit a light pulse signal to the calibration board;

The receiver is used to receive the reflected pulse signal of the measured object;

The sampler is used to collect reflected pulse signals reflected by the calibration plate under different energies and different incident angles;

The processor is configured to perform sampling according to the received reflected pulse signal to obtain a sampling result;

The processor is also used to count the relationship between the characteristic value at each sampling point and the incident angle, and fit the relationship curve and/or the curved surface to obtain the preset response function.
The measuring device according to claim 23, characterized in that by changing the distance between the detection device and the calibration plate, the material of the calibration plate, the optical pulse signal of the detection device and the calibration plate At least one of the incident angles between the two to change the energy of the light pulse signal emitted by the detection device.
The measuring device according to claim 19, wherein the reflective surface of the measured object is a flat surface.
The measurement device according to any one of claims 19-25, wherein the processor determining the characteristic value of the reflected pulse signal based on the sampling result comprises:

Determine the value of any parameter of the echo corresponding to the sampling result based on the sampling result as the characteristic value of the reflected pulse signal; or

The values of multiple parameters of the echo corresponding to the sampling result are determined based on the sampling result, and the characteristic value of the reflected pulse signal is determined based on the combination of the values of the multiple parameters.
The measurement device according to claim 26, wherein the parameters of the echo include: pulse width, echo height, and one of the pulse width corresponding to the echo height or the ratio of the pulse width to the corresponding height Or multiple.
The measurement device according to claim 26 or 27, wherein the parameters of the echo include the pulse width at any height of the echo corresponding to the sampling result or the pulse width at any height and the corresponding height Ratio; and/or

The characteristic value includes the pulse width at all heights of the echo corresponding to the sampling result or the ratio of the pulse width at all heights to the corresponding height.
The measuring device according to claim 28, wherein the height is a normalized height obtained by dividing the height of the sampling point by the total height of the echo.
The measurement device according to claim 28, wherein the characteristic value is the pulse width at the baseline of the echo or the half-width of the echo.
The measurement device according to claim 19, wherein the processor is configured to directly calculate the incident angle corresponding to the characteristic value according to the functional relationship between the characteristic value of the reflected pulse signal and the incident angle .
The measurement device according to claim 31, wherein the functional relationship between the characteristic value of the reflected pulse signal and the incident angle is:

The maximum optical path difference of the emitted light pulse signal is calculated according to the incident angle between the emitted light pulse signal and the measured object, and the characteristic value is calculated according to the maximum optical path difference.
The measurement device according to any one of claims 19-32, wherein the sampling based on the reflected pulse signal received in real time is implemented based on a time-to-digital converter.
The measurement device according to any one of claims 19-32, wherein the sampler is further configured to select multiple sampling points for the reflected pulse signal;

The processor is also used to calculate the incident angle of each sampling point;

The processor is also used to calculate the average value of the incident angles of the sampling points to obtain the average incident angle.
The measurement device according to claim 34, wherein the processor is further configured to calculate the reflectance of the measured object based on the average incident angle.
A movable platform, characterized in that, the movable platform includes:

body;

The power system is installed on the fuselage to provide flight power;

The measurement device according to any one of claims 19-35, installed on the fuselage, for sensing the environment in which the movable platform is located and generating point cloud information.
The movable platform according to claim 36, wherein the reflectance measuring device comprises laser radar, electromagnetic wave radar, millimeter wave radar, or ultrasonic radar.
A computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, and the computer program executes the reflectance measurement method according to any one of claims 1-18 during operation. Measurement methods.