Laser ranging method and laser ranging sensor

Abstract

The invention relates to the technical field of laser ranging, in particular to a laser ranging method and a laser ranging sensor, and the method comprises the steps: obtaining a laser pulse signal transmitted by the laser sensor and a received echo signal; obtaining a spectrogram of the echo signal, and extracting candidate peak points and peak intervals thereof; judging whether each candidate peak point is a peak point or not; converting the frequency domain signal in the peak interval of each peak point to obtain a characteristic echo signal; obtaining an interfered index of the characteristic echo signal corresponding to each peak point; obtaining a local signal change degree of each characteristic echo signal in each filtering window; obtaining an optimal filtering window by combining the endpoint difference of the peak interval between the peak points; and 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. The invention aims to improve the ranging precision and efficiency of the laser ranging sensor.

Description

Technical Field

[0001] The present application relates to the technical field of laser ranging, and in particular to a laser ranging method and a laser ranging sensor. Background Art

[0002] Lasers have very good directivity, coherence, and monochromaticity, and have important applications in aviation, aerospace, medical and other fields. Laser ranging sensors emit lasers, which are reflected on the target object, and then receive the reflected lasers and measure the reflection time. 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. Distance measurement accuracy is the most important performance indicator of laser ranging sensors, reflecting the accuracy of the laser ranging sensor in measuring distance.

[0003] In complex scenarios, the laser beam of the laser ranging sensor will not only be reflected from the target surface, but may also be reflected from surrounding objects or obstacles. These reflected signals may arrive at the sensor at the same time, causing multiple echo signals to overlap. This overlapping phenomenon will make 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 the present application provides a laser ranging method, the method comprising: 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.

[0006] Preferably, 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.

[0007] Preferably, 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; The mergeability corresponding to all candidate peak points is normalized, and the average of the normalized mergeability values ​​corresponding to all candidate peak points is used as the merge threshold. Each candidate peak point with a mergeability greater than or equal to the merge threshold is merged with the candidate peak point closest to its frequency to obtain a peak point; each remaining candidate peak point is used as a peak point.

[0008] Preferably, the step of obtaining the mergibility 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; Obtain the frequency difference and signal amplitude difference of each candidate peak point and the candidate peak point closest to its frequency respectively; 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.

[0009] Preferably, the step of merging each candidate peak point whose mergeability is greater than or equal to a 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.

[0010] Preferably, the interference index of the characteristic echo signal corresponding to each peak point is obtained, specifically: 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.

[0011] Preferably, 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.

[0012] Preferably, the obtaining of the optimal filtering window is specifically 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.

[0013] Preferably, the obtaining 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.

[0014] In a second aspect, an embodiment of the present application further provides a laser ranging sensor, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0015] 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

[0016] Figure 1A flowchart of a laser ranging method provided in accordance with an embodiment of the present application; Figure 2 A schematic diagram of obtaining an optimal filtering window provided in one embodiment of the present application. DETAILED DESCRIPTION

[0017] 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.

[0018] 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.

[0019] It should also 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. The method disclosed in the embodiments of the present application or the method shown in the flow chart includes one or more steps for implementing the method. Without departing from the scope of protection of the present application, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0020] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0021] The following is a detailed description of a laser ranging method and a specific solution of a laser ranging sensor provided by the present application in conjunction with the accompanying drawings.

[0022] See also Figure 1 , which shows a step flow chart of a laser ranging method provided by an embodiment of the present application, the method comprising the following steps: The first step is to obtain the laser pulse signal emitted by the laser sensor and the received echo signal.

[0023] In complex environments, when a laser ranging sensor is measuring distance, the echo signal is easily interfered by the outside world, resulting in problems such as echo signal overlap, thereby reducing the accuracy of laser ranging. Therefore, the present application improves the efficiency and accuracy of laser ranging by processing the echo signal received by the laser ranging sensor.

[0024] 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 is irradiated to 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.

[0025] The second step: obtain the spectrum of the echo signal, analyze the distribution of signal amplitude in 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.

[0026] First, the echo signal is Fourier transformed to obtain the spectrum of the echo signal. In a complex environment, when multiple objects are located in the same ranging direction, the echo signals of different objects or surfaces will arrive at the receiver at the same time. Since the laser ranging sensor can usually only receive one echo signal, these echo signals may overlap, resulting in confusion in the ranging results.

[0027] 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 in the spectrum diagram, and the height of this peak is proportional to the amplitude of the reflected signal. However, in actual situations, due to factors such as the complexity of the reflecting surface, the existence of multipath effects, and differences in the material of the object, the signal reflected by the object may show a slightly expanded peak range in the spectrum diagram. The width and shape of this peak range are related to the degree of interference to the signal. The stronger the interference, the more significant the expansion of the peak. In addition, the echo signals of different objects may have different amplitudes and frequency characteristics, resulting in the echo signals of multiple objects showing different characteristics in the spectrum, so that their echo signals do not completely overlap, which may affect the accuracy of the measurement.

[0028] For the spectrum diagram, since there are 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, the spectrum of the echo signal has multiple frequency components. Therefore, firstly, according to the distribution of the signal amplitude in the neighborhood range of each spectrum signal point in the echo signal spectrum diagram, the candidate peak points are extracted to reflect the complex conditions of the environment in the actual laser ranging process, and then the overlapping conditions of the echo signals are judged: each spectrum signal point in the echo signal spectrum diagram is taken as the center, and the preset number of spectrum signal points closest to it on both sides are taken as the 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 neighborhood signal point, the corresponding spectrum signal point is taken as the candidate peak point. In this embodiment, the preset number is 6, and the implementer can adjust it according to the actual situation.

[0029] Since the echo signal is interfered by the environment during the receiving process, the extracted candidate peak points may not be actual reflected signals, but erroneous peaks mistakenly induced by the interference source; therefore, the mergeability between each candidate peak point and the candidate peak point closest to its frequency is obtained through the corresponding amplitude distribution and frequency difference of the neighborhood signal points between each candidate peak point and the candidate peak point closest to its frequency: the similarity of the signal amplitude distribution of the neighborhood signal points of each candidate peak point and the candidate peak point closest to its frequency is obtained; the frequency difference and signal amplitude difference of each candidate peak point and the candidate peak point closest to its frequency are obtained respectively; 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.

[0030] In this embodiment, the similarity is calculated using the Pearson correlation coefficient to obtain the sum of a first preset value and the similarity, wherein the first preset value is 1, and the sum is used to ensure that the numerator is not a negative number; the signal amplitude difference and the frequency difference are measured using the absolute value of the difference; the multiplication result of the signal amplitude difference and the frequency difference is calculated; the ratio of the sum to the multiplication result is used as the mergibility of each candidate peak point. It should be noted that in order 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.

[0031] The maximum and minimum normalization method is used for the mergibility corresponding to all candidate peak points, and the average of the normalized values ​​of the mergibility corresponding to all candidate peak points is used as the merging threshold, and 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. 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 merger are used as peak points.

[0032] The merging method adopted in this embodiment is: 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 consistent, 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 selected as the peak point. The peak interval is specifically the signal interval composed of the minimum value points closest to the left and right sides of the candidate peak point.

[0033] The third step: 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 distribution of the frequency and signal amplitude within the peak interval of each peak point; analyze the signal change characteristics of each characteristic echo signal in 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.

[0034] The number of peak points can reflect the number of objects obtained by laser ranging in complex environments. At the same time, the frequency offset within the peak interval can characterize the interference of complex environments on echo signals.

[0035] The frequency in the peak interval corresponding to the peak point is extracted through a bandpass filter, and the corresponding time domain signal is obtained through inverse Fourier transform, which is recorded as a characteristic echo signal. This process is to obtain an echo signal reflecting the characteristics of the object by filtering out the frequency components related to the peak interval in the spectrum, and then inversely transforming these components into time domain signals. This characteristic echo signal contains signal information within the frequency range and can be used to analyze the specific response or reflection characteristics of the object. Among them, bandpass filters and inverse Fourier transforms are both well-known technologies and will not be described in detail here.

[0036] 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 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 merged to obtain the interference index of the characteristic echo signal corresponding to each peak point. In this embodiment, the degree of confusion of multiple data can be measured by entropy value; the degree of discreteness of multiple data can be measured by extreme difference value; multiple variables are merged by multiplication method.

[0037] It should be understood that if the peak interval corresponding to the peak point is wider, it means that the frequency offset phenomenon is more obvious, which usually indicates that the signal is subject to strong environmental interference. Specifically, the wider the peak interval, the greater the expansion of the frequency component of the signal, reflecting that the environmental factors have a significant impact on the signal frequency. If the signal amplitude changes greatly within the peak interval, it means that the signal amplitude in the frequency band is unstable, and there may be large fluctuations or interference, which usually means that the characteristic echo signal is subject to more external interference or noise. In short, the increase in the width of the peak interval and the amplitude change indicate that the interference level of the signal has increased, resulting in a decrease in the quality of the characteristic echo signal.

[0038] Since the laser pulse signal emitted by the laser ranging sensor is a sine wave, the echo signal received by the laser ranging sensor should also be a sine wave without interference, and the sine wave is symmetrical; therefore, the shape characteristics of the characteristic echo signal are analyzed to obtain the corresponding points of each signal point in the characteristic echo signal: 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.

[0039] The filtering algorithm is used to denoise the characteristic echo signal obtained at each peak 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 in the filter window, and combine the shape characteristics of the characteristic echo signal to obtain the local signal change degree of each peak point corresponding to the characteristic echo signal in each filter window: obtain the maximum absolute value of the difference between all adjacent signal points of the characteristic echo signal in each filter window; calculate the signal amplitude difference between each signal point and its corresponding point in each filter window of the characteristic echo signal, and record it as the degree of change; merge the maximum absolute value of the difference with all the degrees of change in the filter window to obtain the local signal change degree of the characteristic echo signal in each filter window.

[0040] In this embodiment, the degree of change is the absolute value of the difference in signal amplitude between two points; the product of the sum of all degree of change in each filtering window and the absolute value of the maximum difference is taken as the local signal degree of change.

[0041] It should be understood that the larger the absolute value of the maximum difference, the greater the amplitude of the local signal change of the characteristic echo signal and the greater the degree of change; at the same time, the greater the difference in signal amplitude between the signal point in the filtering window and its corresponding point, the greater the signal waveform in the filtering window does not conform to the symmetry of the sine wave, and the greater the degree of waveform variation, that is, the greater the degree of local signal variation.

[0042] The fourth step: 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.

[0043] In a complex environment, the reflected signal of each object will cause a frequency difference between the echo signal and the transmitted signal due to its different distance. 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 be produced.

[0044] 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: if there is a common point between the peak intervals of each peak point and its adjacent peak point, the inverse of the frequency difference between each peak point and its adjacent peak point is used as the associated value between each peak point and its adjacent peak point, and the normalized value of the sum of all the associated values ​​of each peak point is used as the associated feature of each peak point; otherwise, 0 is used as the associated feature of each peak point. In this implementation, the normalization adopts the maximum and minimum normalization method.

[0045] For a peak point with a correlation feature of 0, it can be understood that the frequency feature corresponding to the signal point is the natural frequency of the echo signal reflected by the object, that is, the corresponding peak interval represents the reflection response of the object or surface at a specific frequency, which is usually related to the physical properties of the object. The frequency position of this peak point reveals the frequency information of the reflected signal, which can be used to analyze features such as the existence or location of the object.

[0046] Based on the interference index of the characteristic echo signal corresponding to each peak point and the local signal variation of each filtering window, combined with the correlation characteristics of the peak points, the filtering window is adjusted: the normalized value of the product of the local signal variation 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, denoted as s; in this embodiment, the normalization adopts the sigmoid function; the correlation characteristics of each peak point are denoted as cd; the adjusted window size is: ;in, Indicates the filter window size after current adjustment; Indicates the filter window size before the current adjustment. The first adjustment is the initial median filter window size. represents the ceiling function; , They are respectively the first preset value and the second preset value; in this embodiment, the values ​​are 0.3 and 0.6 respectively.

[0047] When the filter window sizes before and after adjustment are consistent, the optimal filter window is obtained. The characteristic echo signal of each peak point is filtered according to the obtained optimal filter window, and the distance data is calculated according to the phase difference between the laser pulse signal and the filtered characteristic echo signal. Calculating the distance by phase difference is a well-known technology. The schematic diagram of obtaining the optimal filter window is shown in FIG. Figure 2 shown.

[0048] Based on the same inventive concept as the above method, an embodiment of the present application also provides a laser ranging sensor, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above laser ranging methods are implemented.

[0049] In summary, the embodiment of the present application analyzes the spectrum diagram of the echo signal to extract candidate peak points in the spectrum diagram, and screens and merges the peak points 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, it helps to remove noise from the spectrum and enhance the target echo signal, thereby improving the accuracy and reliability of the ranging system; 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 characteristic echo signal corresponding to each peak point is obtained. The interference index evaluates the quality, detection capability, and reliability of the echo signal in complex environments; analyzes the signal change characteristics of each characteristic echo signal in the filtering window, and combines the shape characteristics of the characteristic echo signal to obtain the local signal change degree of each characteristic echo signal in each filtering window, helping the filter to adapt to different signal characteristics more accurately and avoid over-smoothing the signal or missing important details; 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 filter window adjustment is adaptively completed to obtain the optimal filtering window, which improves the filtering accuracy and efficiency of the median filter, reduces the interference of the echo signal in complex environments, and improves the ranging accuracy and efficiency of the laser ranging sensor.

[0050] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the function marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two continuous boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and the block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two continuous operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0051] For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the basic features of the present application. Therefore, no matter from which point of view, the above embodiments of the present application should be regarded as exemplary and non-restrictive; the technical solutions recorded in the above embodiments are modified, or some of the technical features are replaced by equivalents, which does not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and should be included in 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.

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 mergibility 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; Obtain the frequency difference and signal amplitude difference of each candidate peak point and the candidate peak point closest to its frequency respectively; 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 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.

9. A laser distance measurement method as claimed in claim 8, 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.

10. 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 9 are implemented.

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