A laser ranging method and a laser ranging sensor

Abstract

This application relates to the technical field of laser ranging, and specifically relates to a laser ranging method and a laser ranging sensor. The method includes: obtaining a laser pulse signal emitted by a laser sensor and an echo signal received; obtaining a spectrogram of the echo signal, and extracting candidate peak points and their peak intervals; determining whether each candidate peak point is a peak point; converting the frequency-domain signal within the peak interval of each peak point to obtain a characteristic echo signal; obtaining the interference index of the characteristic echo signal corresponding to each peak point; obtaining the local signal change degree of each characteristic echo signal in each filtering window; combining the endpoint differences of the peak intervals between peak points to obtain an optimal filtering window; filtering the characteristic echo signal of each peak point, and calculating distance data according to the phase difference between the laser pulse signal and the filtered characteristic echo signal. This application aims at the ranging accuracy and efficiency of the laser ranging sensor.

Description

Technical Field

[0001] This application relates to the technical field of laser ranging, and particularly relates to a laser ranging method and a laser ranging sensor. Background Art

[0002] Laser has very good directivity, coherence, and monochromaticity, and has important applications in fields such as aviation, aerospace, and medical treatment. A laser ranging sensor emits laser light, forms a reflection on the target object, then receives the reflected laser light, measures the reflection time, and half of the product of the speed of light and the round-trip time is the distance between the target object and the laser ranging sensor. The ranging accuracy is one of the most important performance indicators of the laser ranging sensor, reflecting the accuracy of the laser ranging sensor in measuring distance.

[0003] In a complex scene, the laser beam of the laser ranging sensor will not only be reflected back from the target surface, but may also be reflected onto surrounding objects or obstacles. These reflected signals may reach the sensor at the same time, resulting in the overlap of multiple echo signals. This overlap phenomenon makes it difficult for the laser ranging sensor to distinguish the specific time of each echo, thereby reducing the measurement accuracy and reliability. Summary of the Invention

[0004] In view of the above, it is necessary to provide a laser ranging method and a laser ranging sensor to solve the above problems.

[0005] The first aspect of this application provides a laser ranging method, and the method includes:

[0006] Obtain the laser pulse signal emitted by the laser sensor and the received echo signal;

[0007] Obtain the spectrogram of the echo signal, analyze the distribution of the signal amplitude within the neighborhood range of each spectral signal point, extract the candidate peak points and their peak intervals; judge whether each candidate peak point is a peak point by combining the amplitude distribution difference and frequency difference between each candidate peak point and the candidate peak point with the closest frequency to it, and the peak interval of each candidate peak point.

[0008] Convert the frequency-domain signal within the peak interval of each peak point to obtain the characteristic echo signal; obtain the interference index of the characteristic echo signal corresponding to each peak point according to the frequency and the distribution of the signal amplitude within the peak interval of each peak point; analyze the signal change characteristics of each characteristic echo signal within the filtering window, and combine the shape characteristics of the characteristic echo signal to obtain the local signal change degree of each characteristic echo signal in each filtering window.

[0009] Based on the interference index corresponding to the characteristic echo signal of each spike point and the local signal variation degree of each filtering window, combined with the endpoint difference of the spike interval between spike points, an optimal filtering window is obtained; the characteristic echo signal of each spike point is filtered, and the distance data is calculated according to the phase difference between the laser pulse signal and the filtered characteristic echo signal.

[0010] Preferably, the extraction of candidate spike points and their spike intervals is specifically as follows:

[0011] Taking each spectral signal point in the echo signal spectrogram as the center, the preset number of spectral signal points closest to it on its left and right sides are used as the neighborhood signal points of each spectral signal point;

[0012] If the signal amplitude of each spectral signal point is greater than the signal amplitude of its neighborhood signal points, the corresponding spectral signal point is used as a candidate spike point;

[0013] The signal interval composed of the minimum value points closest to the left and right sides of the candidate spike point is used as the spike interval of the candidate spike point.

[0014] Preferably, the process of determining whether each candidate spike point is a spike point is as follows:

[0015] Through the frequency difference between each candidate spike point and the candidate spike point with the closest frequency to it, combined with the amplitude distribution difference of their respective neighborhood signal points, the mergability between each candidate spike point and the candidate spike point with the closest frequency to it is obtained;

[0016] Normalize the mergabilities corresponding to all candidate spike points, take the mean of the normalized values of the mergabilities corresponding to all candidate spike points as the merging threshold, merge each candidate spike point with the candidate spike point with the closest frequency to it whose mergability is greater than or equal to the merging threshold to obtain spike points; take the remaining each candidate spike point as a spike point.

[0017] Preferably, the steps of obtaining the mergability between each candidate spike point and the candidate spike point with the closest frequency to it are as follows:

[0018] Obtain the similarity of the signal amplitude distribution of the neighborhood signal points of each candidate spike point and the candidate spike point with the closest frequency to it;

[0019] Respectively obtain the frequency difference and signal amplitude difference between each candidate spike point and the candidate spike point with the closest frequency to it;

[0020] Based on the similarity, the frequency difference, and the signal amplitude difference corresponding to each candidate spike point, obtain the mergability between each candidate spike point and the candidate spike point with the closest frequency to it; wherein, the mergability is positively correlated with the similarity and negatively correlated with the signal amplitude difference and the frequency difference.

[0021] Preferably, merging each candidate spike point with a mergibility greater than or equal to the merging threshold with the candidate spike point closest to its frequency specifically includes:

[0022] For two candidate spike points to be merged, select the candidate spike point with the largest signal amplitude as the spike point;

[0023] If the signal amplitudes of the two candidate spike points are the same, obtain the union of the spike intervals of the two candidate spike signals to be merged, and select the candidate spike point closest to the center position of the union as the spike point.

[0024] Preferably, obtaining the interference index of the characteristic echo signal corresponding to each spike point specifically includes:

[0025] Obtain the length of the spike interval of each spike point; calculate the chaos degree and dispersion degree of all signal intensity values within each spike interval respectively; fuse the length of each spike interval, the chaos degree, and the dispersion degree to obtain the interference index of the characteristic echo signal corresponding to each spike point.

[0026] Preferably, the process of obtaining the local signal change degree of each characteristic echo signal in each filtering window specifically includes:

[0027] For each signal point in the characteristic echo signal, record the interval formed by the two closest zero points on both sides of the signal point as the signal interval; record the signal point with the largest absolute signal amplitude within the signal interval corresponding to each signal point as the symmetric point; obtain the time interval between each signal point and the symmetric point; record the signal point at the same time interval on the other side of the symmetric point as the corresponding point of each signal point;

[0028] Obtain the maximum absolute value of the difference between all adjacent signal points in each filtering window of the characteristic echo signal;

[0029] Calculate the signal amplitude difference between each signal point and its corresponding point in each filtering window of the characteristic echo signal, and record it as the change degree;

[0030] Fuse the maximum absolute value of the difference and all the change degrees in the filtering window to obtain the local signal change degree of the characteristic echo signal in each filtering window.

[0031] Preferably, obtaining the optimal filtering window specifically includes:

[0032] According to the endpoint difference of the spike interval between each spike point and its adjacent spike point, obtain the associated feature of each spike point, denoted as cd;

[0033] The normalized value of the product of the local signal variation degree of the characteristic echo signal corresponding to each spike point in each filtering window and the interference index is used as the adjustment factor of the characteristic echo signal corresponding to each spike point in each filtering window, denoted as s;

[0034] The adjusted window size is: ; where represents the size of the filtering window after the current adjustment; represents the size of the filtering window before the current adjustment; represents the ceiling function; and are the first preset value and the second preset value respectively, where the second preset value is greater than the first preset value;

[0035] When the sizes of the filtering windows before and after adjustment are the same, the optimal filtering window is obtained.

[0036] Preferably, the obtaining of the associated feature of each spike point is specifically:

[0037] If there is a common point in the spike intervals between each spike point and its adjacent spike points, the reciprocal of the frequency difference between each spike point and its adjacent spike points is used as the association value between each spike point and its adjacent spike points, and the normalized value of the sum of all association values of each spike point is used as the associated feature of each spike point;

[0038] Otherwise, 0 is used as the associated feature of each spike point.

[0039] In a second aspect, an embodiment of the present application further provides a laser ranging sensor, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the method described in any one of the above are implemented.

[0040] In the above scheme, by analyzing the spectrum of the echo signal, candidate peak points in the spectrum are extracted, and the peak points are screened and merged based on the local signal characteristics of the candidate peak points to eliminate false peak points. The beneficial effect is that it can help distinguish the characteristic frequencies of different targets, thereby improving the target recognition ability. In addition, by extracting the peak points, noise can be removed from the spectrum in the subsequent process, and the target echo signal can be enhanced, thereby providing help for the accuracy and reliability of ranging; the frequency domain signal in the peak interval of each peak point is converted to obtain a characteristic echo signal, which can extract finer-grained target features, thereby improving the target recognition and classification capabilities; according to the distribution of the frequency and signal amplitude in the peak interval of each peak point, the interference index of the characteristic echo signal corresponding to each peak point is obtained. The method evaluates the quality, detection capability and reliability of echo signals in complex environments by analyzing the signal change characteristics of each characteristic echo signal in the filtering window, and obtains the local signal change degree of each characteristic echo signal in each filtering window in combination with the shape characteristics of the characteristic echo signal, so as to help the filter adapt to different signal characteristics more accurately and avoid over-smoothing the signal or missing important details. The method adaptively completes the filter window adjustment based on the interference index of the characteristic echo signal corresponding to each peak point and the local signal change degree of each filtering window, and obtains the optimal filtering window in combination with the endpoint difference of the peak interval between the peak points, thereby improving the filtering accuracy and efficiency of the median filter, reducing the interference of the echo signal in complex environments, and improving the ranging accuracy and efficiency of the laser ranging sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flowchart of a laser ranging method provided in accordance with an embodiment of the present application;

[0042] Figure 2 A schematic diagram of obtaining an optimal filtering window provided in one embodiment of the present application. DETAILED DESCRIPTION

[0043] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0045] In addition, it should be noted that the terms "first" and "second" in this application and the accompanying drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. For the methods disclosed in the embodiments of this application or the methods shown in the flowcharts, including one or more steps for implementing the methods, without departing from the scope of protection of this application, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs.

[0047] The following specifically describes the specific solutions of a laser ranging method and a laser ranging sensor provided by this application in conjunction with the accompanying drawings.

[0048] Please refer to Figure 1 , which shows a flowchart of the steps of a laser ranging method provided by an embodiment of this application. The method includes the following steps:

[0049] The first step: Obtain the laser pulse signal emitted by the laser sensor and the received echo signal.

[0050] In a complex environment, when the laser ranging sensor performs ranging, the echo signal is easily affected by external interference, resulting in problems such as overlapping of echo signals, thereby reducing the accuracy of laser ranging. Therefore, this application processes the echo signal received by the laser ranging sensor to improve the efficiency and accuracy of laser ranging.

[0051] The laser pulse signal emitted by the laser ranging sensor is a pre-modulated periodic sine wave signal. The laser pulse signal obtained in this application is a time series. When the laser pulse signal irradiates the surface of an object, reflection occurs, and the reflected laser pulse signal is received by the ranging sensor to form an echo signal. The echo signal is also a time series, recording the changes in the reflected signal.

[0052] The second step: Obtain the spectrogram of the echo signal, analyze the distribution of signal amplitudes in the neighborhood range of each spectral signal point, extract candidate peak points and their peak intervals; judge whether each candidate peak point is a peak point by combining the amplitude distribution difference and frequency difference between each candidate peak point and the candidate peak point with the closest frequency to it, and the peak interval of each candidate peak point.

[0053] First, perform a Fourier transform on the echo signal to obtain the spectrogram of the echo signal. In a complex environment, when multiple objects are in the same ranging direction, the echo signals of different objects or surfaces will reach the receiver simultaneously. Since the laser ranging sensor usually can only receive one echo signal, these echo signals may overlap, resulting in confusion in the ranging results.

[0054] The laser pulse signal in this application is a sine wave. In ideal laser ranging, the echo signal reflected by an object or surface usually appears as a sharp peak on the spectrogram, and the height of this peak is proportional to the amplitude of the reflected signal. However, in actual situations, due to factors such as complex reflecting surfaces, multipath effects, and differences in object materials, the signal reflected by the object may present a slightly extended peak interval on the spectrogram. The width and shape of this peak interval are related to the degree of interference the signal receives. The stronger the interference, the more significant the peak expansion. In addition, the echo signals of different objects may have different amplitude and frequency characteristics, resulting in different characteristics of the echo signals of multiple objects on the spectrum, so that their echo signals do not completely overlap, which may affect the measurement accuracy.

[0055] For the spectrogram, due to the existence of multiple objects (i.e., reflection sources) in a complex environment, and due to different materials of the reflection sources and different propagation paths of the echo signals, multiple frequency components appear in the spectrum of the echo signals. Therefore, first, according to the distribution of signal amplitudes in the neighborhood of each spectral signal point in the echo signal spectrogram, candidate spike points are extracted to reflect the complex situation of the environment in the actual laser ranging process, and then the overlapping situation of the echo signals is judged: taking each spectral signal point in the echo signal spectrogram as the center, the preset number of spectral signal points closest to it on its left and right sides are used as the neighborhood signal points of each spectral signal point. If the signal amplitude of each spectral signal point is greater than the signal amplitudes of its neighborhood signal points, the corresponding spectral signal point is used as a candidate spike point. In this embodiment, the preset number is 6, and the implementer can adjust it according to the actual situation.

[0056] Since the echo signal is interfered by the environment during the receiving process, the extracted candidate peak points may not be the actual reflection signals, but the wrong peaks mislead by the interference sources; therefore, through the corresponding amplitude distribution and frequency difference of the neighborhood signal points between each candidate spike point and the candidate spike point with the closest frequency to it, the mergibility between each candidate spike point and the candidate spike point with the closest frequency to it is obtained: obtaining the similarity of the signal amplitude distribution of the neighborhood signal points between each candidate spike point and the candidate spike point with the closest frequency to it; respectively obtaining the frequency difference and signal amplitude difference between each candidate spike point and the candidate spike point with the closest frequency to it; based on the similarity, the frequency difference, and the signal amplitude difference corresponding to each candidate spike point, the mergibility between each candidate spike point and the candidate spike point with the closest frequency to it is obtained; wherein, the mergibility is positively correlated with the similarity and negatively correlated with the signal amplitude difference and frequency difference.

[0057] In this embodiment, the similarity is calculated using the Pearson correlation coefficient, and the sum value of the first preset value and the similarity is obtained, where the first preset value is 1, and after summation, it is used to ensure that the numerator is not negative; the signal amplitude difference and the frequency difference are measured using the absolute value of the difference; the product result of the signal amplitude difference and the frequency difference is calculated; the ratio of the sum value to the product result is used as the mergibility of each candidate peak point. It should be noted that to avoid the denominator being 0, a second preset value greater than zero needs to be added to the denominator, and the value in this embodiment is 0.1.

[0058] For the mergibility corresponding to all candidate peak points, the maximum-minimum normalization method is used, and the mean value of the normalized values of the mergibility corresponding to all candidate peak points is used as the merging threshold. Each candidate peak point with a mergibility greater than or equal to the merging threshold is merged with the candidate peak point with the closest frequency to it. It should be understood that the greater the mergibility, the greater the possibility that the two candidate peak points are echo signals reflected by the same object. Therefore, it is necessary to merge the candidate peak points with large mergibility to obtain peak points, and the candidate peak points that do not participate in the merging are used as peak points.

[0059] The merging method adopted in this embodiment is as follows: If two candidate peak points can be merged, the candidate peak point with the largest signal amplitude is selected as the peak point; if the signal amplitudes of the two candidate peak points are the same, the union of the peak intervals of the two candidate peak signals is obtained, and the candidate peak point closest to the center position of the union is used as the peak point. Among them, the peak interval is specifically the signal interval composed of the two closest minimum value points on the left and right sides of the candidate peak point.

[0060] The third step: Convert the frequency-domain signal within the peak interval of each peak point to obtain a characteristic echo signal; according to the frequency and signal amplitude distribution within the peak interval of each peak point, obtain the interference index of the characteristic echo signal corresponding to each peak point; analyze the signal change characteristics of each characteristic echo signal within the filtering window, and combine the shape characteristics of the characteristic echo signal to obtain the local signal change degree of each characteristic echo signal in each filtering window.

[0061] The number of peak points can reflect the number of objects obtained by laser ranging in a complex environment. At the same time, the frequency offset condition within the peak interval can describe the interference degree of the complex environment on the echo signal.

[0062] Extract the frequencies within the spike intervals corresponding to the spike points through a band-pass filter, and obtain the corresponding time-domain signal through inverse Fourier transform, denoted as the characteristic echo signal. This process is to filter out the frequency components related to the spike intervals in the spectrum and then inverse-transform these components into the time-domain signal, thereby obtaining the echo signal reflecting the object characteristics. This characteristic echo signal contains the signal information within this frequency range and can be used to analyze the specific response or reflection characteristics of the object. Among them, both the band-pass filter and the inverse Fourier transform are well-known technologies and will not be elaborated here in detail.

[0063] According to the frequencies within the spike intervals of each spike point and the distribution of signal amplitudes, obtain the interference index of the characteristic echo signal corresponding to each spike point: Obtain the length of the spike interval of each spike point; calculate the degree of chaos and the degree of dispersion of all signal amplitude values within each spike interval respectively; fuse the length of each spike interval, the degree of chaos, and the degree of dispersion to obtain the interference index of the characteristic echo signal corresponding to each spike point. In this embodiment, the degree of chaos of multiple data can be measured by the entropy value; the degree of dispersion of multiple data can be measured by the range value; multiple variables are fused by the method of multiplication.

[0064] It should be understood that if the spike interval corresponding to the spike point is wider, it means that the frequency offset phenomenon is more obvious, usually indicating that the signal is strongly interfered by the environment. Specifically, the larger the width of the spike interval, the greater the expansion of the frequency components of the signal, reflecting that the environmental factors have a more significant impact on the signal frequency. And if the signal amplitude within the spike interval changes greatly, it means that the signal amplitude within this frequency band is unstable, and there may be large fluctuations or interferences, which usually means that the characteristic echo signal is affected by more external interferences or noise. In short, the increase in the width of the spike interval and the change in amplitude indicate an increase in the interference degree of the signal, resulting in a decrease in the quality of the characteristic echo signal.

[0065] Since the laser pulse signal emitted by the laser ranging sensor is a sine wave, in the case of no interference, the echo signal received by the laser ranging sensor should also be a sine wave, and the sine wave has symmetry; therefore, analyze the shape characteristics of the characteristic echo signal and obtain the corresponding points of each signal point in the characteristic echo signal: For each signal point in the characteristic echo signal, record the interval formed by the two nearest zero points on both sides of the signal point as the signal interval; record the signal point with the largest absolute value of the signal amplitude within the signal interval corresponding to each signal point as the symmetric point; obtain the time interval between each signal point and the symmetric point; record the signal point at the same time interval on the other side of the symmetric point as the corresponding point of each signal point.

[0066] Use a filtering algorithm to denoise the characteristic echo signal obtained for each spike point to eliminate noise interference. In this embodiment, the median filtering method is used, and the initial median filtering window size is The implementer can adjust the size of the initial median filter window according to the actual situation; analyze the signal change characteristics of each characteristic echo signal within the filter window, and combine the shape characteristics of the characteristic echo signal to obtain the local signal change degree of each characteristic echo signal corresponding to each peak point within each filter window: obtain the absolute value of the maximum difference between all adjacent signal points of the characteristic echo signal within each filter window; calculate the signal amplitude difference between each signal point of the characteristic echo signal within each filter window and its corresponding point, which is denoted as the change degree; fuse the absolute value of the maximum difference with all the change degrees within the filter window to obtain the local signal change degree of the characteristic echo signal within each filter window.

[0067] In this embodiment, the change degree is the absolute value of the difference in signal amplitude between two points; the product of the sum value of all change degrees within each filter window and the absolute value of the maximum difference is used as the local signal change degree.

[0068] It should be understood that the larger the absolute value of the maximum difference, the greater the local signal change amplitude and the change degree of the characteristic echo signal; at the same time, the greater the signal amplitude difference between the signal points of the characteristic echo signal within the filter window and their corresponding points, the more the signal waveform within the filter window does not conform to the symmetry of the sine wave, and the greater the waveform deformation degree, that is, the greater the local signal change degree.

[0069] The fourth step: Based on the interference index of each characteristic echo signal corresponding to each peak point and the local signal change degree of each filter window, combined with the endpoint difference of the peak interval between peak points, obtain the optimal filter window; filter the characteristic echo signal of each peak point, and calculate the distance data according to the phase difference between the laser pulse signal and the filtered characteristic echo signal.

[0070] In a complex environment, due to the different distances of the reflection signals of each object, there will be a frequency difference between the echo signal and the transmitted signal. When the objects are far apart, different objects will produce significantly different frequency offsets. If the objects are close to each other, similar frequency offsets may occur.

[0071] According to the endpoint difference of the peak interval between each peak point and its adjacent peak point, obtain the associated feature of each peak point: if there is a common point in the peak interval between each peak point and its adjacent peak point, take the reciprocal of the frequency difference between each peak point and its adjacent peak point as the associated value between each peak point and its adjacent peak point, and take the normalized value of the sum value of all associated values of each peak point as the associated feature of each peak point; otherwise, take 0 as the associated feature of each peak point. In this implementation, normalization uses the maximum-minimum normalization method.

[0072] For a spike point with an associated feature of 0, it can be understood that the frequency feature corresponding to this signal point is the inherent frequency of the echo signal reflected by the object, that is, the corresponding spike interval represents the reflection response of the object or surface at a specific frequency, which is usually related to the physical characteristics of the object. The frequency position of this spike point reveals the frequency information of the reflected signal and can be used to analyze features such as the presence or position of the object.

[0073] Based on the interference index of the characteristic echo signal corresponding to each spike point and the local signal variation degree of each filtering window, combined with the associated feature of the spike point, the filtering window is adjusted: The normalized value of the product of the local signal variation degree of the characteristic echo signal corresponding to each spike point in each filtering window and the interference index is used as the adjustment factor of the characteristic echo signal corresponding to each spike point in each filtering window, denoted as s; in this embodiment, the normalization uses the sigmoid function; the associated feature of each spike point is denoted as cd; the adjusted window size is: ; where represents the size of the filtering window after the current adjustment; represents the size of the filtering window before the current adjustment, and is the initial median filtering window size for the first adjustment; represents the ceiling function; and are the first preset value and the second preset value respectively; in this embodiment, they are respectively set to 0.3 and 0.6.

[0074] When the sizes of the filtering windows before and after the adjustment are the same, the optimal filtering window is obtained. Filter the characteristic echo signal of each spike point according to the obtained optimal filtering window, and calculate the distance data according to the phase difference between the laser pulse signal and the filtered characteristic echo signal. Among them, calculating the distance through the phase difference is a well-known prior art. Among them, the schematic diagram of obtaining the optimal filtering window is as Figure 2 shown.

[0075] Based on the same inventive concept as the above method, an embodiment of the present application further provides a laser ranging sensor, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above laser ranging methods.

[0076] In summary, in the embodiments of the present application, by analyzing the spectrogram of the echo signal, candidate spike points in the spectrogram are extracted, and the spike points are screened and merged based on the local signal characteristics of the candidate spike points to eliminate false spike points. The beneficial effects are that it can help distinguish the characteristic frequencies of different targets, thereby improving the target recognition ability. In addition, by extracting the spike points, it helps to remove noise from the spectrum, enhance the target echo signal, and thus improve the accuracy and reliability of the ranging system. The frequency-domain signals within the spike intervals of each spike point are converted to obtain characteristic echo signals, which can extract finer-grained target features, thereby improving the target recognition and classification abilities. According to the frequency and signal amplitude distribution within the spike intervals of each spike point, the interference index of the characteristic echo signal corresponding to each spike point is obtained to evaluate the quality, detection ability, and reliability in a complex environment of the echo signal. By analyzing the signal change characteristics of each characteristic echo signal within the filtering window and combining the shape characteristics of the characteristic echo signal, the local signal change degree of each characteristic echo signal in each filtering window is obtained, which helps the filter to more accurately adapt to different signal characteristics, avoid over-smoothing the signal or missing important details. Based on the interference index of the characteristic echo signal corresponding to each spike point and the local signal change degree of each filtering window, combined with the endpoint differences of the spike intervals between the spike points, the filtering window is adaptively adjusted to obtain the optimal filtering window, improving the filtering accuracy and efficiency of the median filtering, reducing the interference received by the echo signal in a complex environment, and improving the ranging accuracy and efficiency of the laser ranging sensor.

[0077] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems, methods, and computer program products according to embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions marked in the block may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. In the descriptions corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different blocks may also occur in a different order than disclosed in the descriptions. Sometimes, there is no specific order between different operations or steps. For example, two consecutive operations or steps may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. Each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or actions, or can be implemented by a combination of dedicated hardware and computer instructions.

[0078] For those skilled in the art, it is obvious that the present application is not limited to the details of the above-described exemplary embodiments, and the present application can be implemented in other specific forms without departing from the basic characteristics of the present application. Therefore, from any point of view, the above-described embodiments of the present application should be regarded as exemplary and non-restrictive; modifying the technical solutions recorded in the foregoing embodiments, or equivalently replacing some of the technical features therein, does not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application, and should all be included within the protection scope of the present application.

Claims

1. A laser ranging method, characterized in that: The method comprises the following steps: Obtain the laser pulse signal emitted by the laser sensor and the received echo signal; Obtain the spectrum of the echo signal, analyze the distribution of the signal amplitude within the neighborhood of each spectrum signal point, and extract candidate peak points and their peak intervals; determine whether each candidate peak point is a peak point by comparing the amplitude distribution difference and frequency difference between each candidate peak point and the candidate peak point closest to its frequency, combined with the peak interval of each candidate peak point; The frequency domain signal in the peak interval of each peak point is converted to obtain a characteristic echo signal; according to the distribution of the frequency and signal amplitude in the peak interval of each peak point, the interference index of the characteristic echo signal corresponding to each peak point is obtained; the signal change characteristics of each characteristic echo signal in the filtering window are analyzed, and the local signal change degree of each characteristic echo signal in each filtering window is obtained in combination with the shape characteristics of the characteristic echo signal; Based on the interference index of the characteristic echo signal corresponding to each peak point and the local signal change degree of each filtering window, combined with the endpoint difference of the peak interval between the peak points, the optimal filtering window is obtained; the characteristic echo signal of each peak point is filtered, and the distance data is calculated according to the phase difference between the laser pulse signal and the filtered characteristic echo signal; The optimal filtering window is obtained as follows: According to the endpoint difference of the peak interval between each peak point and its adjacent peak point, the associated feature of each peak point is obtained, which is recorded as cd; The normalized value of the product of the local signal variation degree of the characteristic echo signal corresponding to each peak point in each filtering window and the interference index is used as the adjustment factor of the characteristic echo signal corresponding to each peak point in each filtering window, which is recorded as s; The adjusted window size is: ;in, Indicates the filter window size after current adjustment; Indicates the filter window size before the current adjustment; represents the ceiling function; , are respectively a first preset value and a second preset value, wherein the second preset value is greater than the first preset value; When the filter window sizes before and after adjustment are consistent, the optimal filter window is obtained.

2. A laser ranging method as claimed in claim 1, characterized in that: The extracting of candidate peak points and their peak intervals is specifically as follows: Taking each spectrum signal point in the echo signal spectrum graph as the center, a preset number of spectrum signal points closest to the left and right sides thereof are taken as neighborhood signal points of each spectrum signal point; If the signal amplitude of each spectrum signal point is greater than the signal amplitude of its neighboring signal points, the corresponding spectrum signal point is taken as a candidate peak point; The signal interval composed of the minimum value points closest to the left and right sides of the candidate peak point is taken as the peak interval of the candidate peak point.

3. A laser ranging method as claimed in claim 2, characterized in that: The process of determining whether each candidate peak point is a peak point is as follows: The mergibility between each candidate peak point and the candidate peak point closest to its frequency is obtained by combining the frequency difference between each candidate peak point and the candidate peak point closest to its frequency and the amplitude distribution difference of the respective neighboring signal points; Normalize the mergeability corresponding to all candidate peak points, take the average of the normalized mergeability values ​​corresponding to all candidate peak points as the merge threshold, merge each candidate peak point whose mergeability is greater than or equal to the merge threshold with the candidate peak point closest to its frequency, and obtain the peak point; Each remaining candidate peak point is regarded as a peak point.

4. A laser ranging method as claimed in claim 3, characterized in that: The step of obtaining the commensurability between each candidate peak point and the candidate peak point closest to its frequency is: Obtaining the similarity of signal amplitude distribution between each candidate peak point and the neighboring signal points of the candidate peak point closest to its frequency; Respectively obtain the frequency difference and signal amplitude difference of each candidate peak point and the candidate peak point closest to its frequency; Based on the similarity corresponding to each candidate peak point, the frequency difference and the signal amplitude difference, the mergeability of each candidate peak point and the candidate peak point closest to its frequency is obtained; wherein the mergeability is positively correlated with the similarity and negatively correlated with the signal amplitude difference and the frequency difference.

5. A laser ranging method as claimed in claim 3, characterized in that: The step of merging each candidate peak point whose mergeability is greater than or equal to the merge threshold with the candidate peak point whose frequency is closest to the candidate peak point is specifically as follows: For two candidate peak points to be merged, the candidate peak point with the largest signal amplitude is selected as the peak point; If the signal amplitudes of the two candidate peak points are consistent, a union of the peak intervals of the two candidate peak signals to be merged is obtained, and the candidate peak point closest to the center position of the union is taken as the peak point.

6. A laser ranging method as claimed in claim 1, characterized in that: The interference index of the characteristic echo signal corresponding to each peak point is obtained as follows: The length of the peak interval of each peak point is obtained; the degree of confusion and the degree of discreteness of all signal values ​​in each peak interval are calculated respectively; the length of each peak interval, the degree of confusion and the degree of discreteness are integrated to obtain the interference index of the characteristic echo signal corresponding to each peak point.

7. A laser ranging method as claimed in claim 1, characterized in that: The process of obtaining the local signal variation degree of each characteristic echo signal in each filtering window is specifically as follows: For each signal point in the characteristic echo signal, the interval formed by the nearest zero points on both sides of the signal point is recorded as the signal interval; the signal point with the largest absolute value of the signal amplitude in the signal interval corresponding to each signal point is recorded as the symmetrical point; the time interval between each signal point and the symmetrical point is obtained; the signal point located at the same time interval on the other side of the symmetrical point is recorded as the corresponding point of each signal point; Obtain the maximum absolute value of the difference between all adjacent signal points of the characteristic echo signal in each filtering window; Calculate the signal amplitude difference between each signal point and its corresponding point in each filtering window of the characteristic echo signal, and record it as the degree of change; The maximum difference absolute value is merged with all the change degrees in the filtering window to obtain the local signal change degree of the characteristic echo signal in each filtering window.

8. A laser distance measurement method as claimed in claim 1, characterized in that: The acquisition of the associated features of each peak point is specifically as follows: If there are common points between the peak intervals of each peak point and its adjacent peak points, the inverse of the frequency difference between each peak point and its adjacent peak points is used as the correlation value between each peak point and its adjacent peak points, and the normalized value of the sum of all correlation values ​​of each peak point is used as the correlation feature of each peak point; Otherwise, 0 is used as the associated feature of each peak point.

9. A laser ranging sensor, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

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