Method for screening validity of laser ranging data

Abstract

The invention provides a laser ranging data validity screening method, which can effectively solve the problem of inaccurate data caused by difficulty in distinguishing a laser ranging effective signal from an interference signal in a complex environment. Comprising the following steps: calibrating a relation between echo signal intensity and signal pulse width, and constructing a first relation comparison table between the echo signal intensity and the signal pulse width; calibrating the relation between the echo signal intensity and the ranging distance, and constructing a second relation comparison table between the echo signal intensity and the ranging distance; real-time signal acquisition and preliminary preprocessing; and judging the signal validity based on the first relation comparison table and the second relation comparison table.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, specifically a method for screening the validity of laser ranging data. Background Technology

[0002] Traditional laser rangefinders utilize time-of-flight ranging, precisely measuring the time difference between the emitted and received laser signals and multiplying it by the speed of light to determine the distance between the object and the rangefinder. However, during signal reception, due to the use of highly sensitive receiving components such as avalanche diodes (APDs) or electron multipliers, a large amount of interference signals are received in addition to the valid return signal. These interference signals, such as backscattered light and spatial astigmatism, have the same wavelength and polarization direction as the emitted laser signal. Therefore, these interference signals cannot be effectively filtered out by conventional narrowband filters. Furthermore, in some special scenarios, such as when the emitted laser signal is split into two beams—one a valid signal and the other a interference signal—both of which have received return signals, the traditional method of determining the valid signal based on signal amplitude thresholds cannot effectively distinguish between the valid and interference signals. This poses a significant challenge to the filtering of ranging data, severely affecting the accuracy and reliability of laser ranging and restricting its application in many fields with high accuracy requirements. Summary of the Invention

[0003] To address the above problems, this invention provides a method for filtering the validity of laser ranging data, which can effectively solve the problem of inaccurate data caused by the difficulty in distinguishing between valid and interference signals in laser ranging under complex environments.

[0004] This invention adopts the following technical solution: a method for screening the validity of laser ranging data, comprising the following steps:

[0005] S1. The rangefinder performs multiple laser ranging operations on the object under different attenuation coefficients. The echo signal intensity and the corresponding signal pulse width are recorded each time the ranging is performed. Based on the recorded data, a mathematical relationship between the echo signal intensity and the signal pulse width is established using a data fitting method, and a first relationship reference table between the echo signal intensity and the signal pulse width is constructed.

[0006] S2. Perform multiple laser ranging measurements at different ranging distances. Record the echo signal intensity and the corresponding ranging distance for each ranging measurement. Based on the recorded data, use data fitting methods to establish a mathematical relationship between the echo signal intensity and the ranging distance, and construct a second relationship comparison table between the echo signal intensity and the ranging distance.

[0007] S3. In actual ranging, the received echo signal is preprocessed and the preprocessed signal is converted into a digital signal to obtain the current echo signal strength, signal pulse width and ranging distance.

[0008] S4. Determine the current echo signal strength value based on the current signal pulse width and the first relationship lookup table;

[0009] Based on the current ranging distance and in conjunction with the second relationship lookup table, determine the echo energy value at the current ranging distance;

[0010] S5. Based on the obtained echo signal strength value and echo energy value, determine whether the echo signal strength value and echo energy value meet the preset conditions. If they meet the conditions, the signal is considered valid; otherwise, it is considered an interference signal.

[0011] Furthermore, in step S1, an adjustment mechanism capable of adjusting the attenuation coefficient is installed between the rangefinder and the object being measured. Multiple laser emission and reception measurements are performed under different attenuation coefficients to obtain a mathematical relationship model between the echo signal intensity and the signal pulse width, namely: E1 = aW 2 +bW+c;

[0012] Where E1 is the echo signal intensity; W is the signal pulse width; and a, b, and c are known fitting coefficients.

[0013] Furthermore, the adjusting element is a variable attenuator or a variable aperture;

[0014] Furthermore, in step S2, the ranging distance between the rangefinder and the object being measured is gradually increased according to the set distance value, and multiple laser ranging measurements are performed at each ranging distance. Subsequently, a mathematical relationship model between the echo energy and the ranging distance is obtained based on the recorded data, namely: E2 = k / L 2 +m;

[0015] Where E2 is the echo energy; L is the ranging distance; k and m are known fitting coefficients;

[0016] Furthermore, the preset condition in step S5 is: E1∈[[γ min ×E2,γ max [×E2], where γ min The minimum value of the target reflectivity γ, γ max This represents the maximum value of the target reflectivity γ; and γ = 10%–90%.

[0017] Furthermore, in step S5, a correlation judgment is made based on the obtained current echo signal strength and signal pulse width. If any abnormal fluctuation or discontinuity occurs in the echo signal strength or signal pulse width, it is judged to be an interference signal.

[0018] Furthermore, in step S5, the ranging data that is determined to be a valid signal is smoothed, output, and stored in the database; the ranging data that is determined to be an interference signal is marked and stored.

[0019] The beneficial effects of this invention are that it can effectively solve the problem of difficulty in distinguishing between effective signals and interference signals when laser ranging is performed in complex environments, significantly improve the quality and reliability of laser ranging data, provide strong support for the widespread application of laser ranging technology in the field of high-precision measurement, and has good practical value. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the present invention;

[0021] Figure 2 This is a structural layout diagram of the laser ranging experiment of this invention;

[0022] Figure 3 This is a curve showing the fitting of experimental data on the relationship between attenuation coefficient and signal pulse width in this invention. Detailed Implementation

[0023] like Figures 1-3 As shown, a laser ranging data validity screening method of the present invention includes the following steps:

[0024] S1. The rangefinder 1 performs multiple laser ranging measurements on the object 3 under different attenuation coefficients, and the distance between the object 3 and the rangefinder 1 remains constant. The echo signal intensity and the corresponding signal pulse width are recorded each time the ranging is performed. Based on the recorded data, a mathematical relationship between the echo signal intensity and the signal pulse width is established using a data fitting method. A first relationship reference table between the echo signal intensity and the signal pulse width is constructed to achieve the calibration of the relationship between the echo signal intensity and the signal pulse width.

[0025] Further, in step S1, an adjustment component 2 capable of adjusting the attenuation coefficient is set between the rangefinder 1 and the object being measured 3. The adjustment component 2 is a variable attenuator or a variable aperture. Multiple laser emission and reception measurements are performed under different attenuation coefficients to obtain a mathematical relationship model between the echo signal intensity and the signal pulse width, namely: E1 = aW 2 +bW+c;

[0026] Where E1 is the echo signal intensity; W is the signal pulse width; and a, b, and c are known fitting coefficients.

[0027] The mathematical model of the relationship between echo signal strength and signal pulse width can reflect the influence of echo signal strength changes on signal pulse width.

[0028] S2. Perform multiple laser ranging measurements at different ranging distances. Record the echo signal intensity and the corresponding ranging distance for each measurement. Based on the recorded data, establish a mathematical relationship between the echo signal intensity and the ranging distance using a data fitting method, and construct a second relationship comparison table between the echo signal intensity and the ranging distance. The second relationship comparison table can reflect the variation law of echo signal intensity with ranging distance under ideal interference-free conditions, providing an important basis for judging the effectiveness of the signal in actual measurement.

[0029] Furthermore, in step S2, the ranging distance between the rangefinder and the object being measured is gradually increased according to the set distance value, and multiple laser ranging measurements are performed at each ranging distance. Subsequently, a mathematical relationship model between the echo energy and the ranging distance is obtained based on the recorded data, namely: E2 = k / L 2 +m;

[0030] Where E2 is the echo energy; L is the ranging distance (unit: meters); k and m are known fitting coefficients;

[0031] S3. In actual ranging, the received echo signal is preprocessed to improve the signal quality and stability, and the preprocessed signal is converted into a digital signal to obtain the current echo signal strength, signal pulse width and ranging distance.

[0032] Preprocessing includes conventional signal preprocessing operations such as amplification and filtering;

[0033] S4. Based on the current signal pulse width and referring to the first relationship lookup table, determine the current echo signal intensity value; for example, if the ranging target is 1km and the echo signal pulse width is 50ns, according to the echo signal intensity relationship formula: E1=aW 2 +bW+c, we can obtain the echo signal strength as:

[0034] E1 = a × 50 2 +b×50+c

[0035] Based on the current ranging distance and referring to the second relationship table, determine the echo energy value at the current ranging distance; for example, when measuring a target at 1km, the estimated echo energy should be:

[0036]

[0037] S5. Based on the obtained echo signal strength value and echo energy value, determine whether the echo signal strength value and echo energy value meet the preset conditions. If they meet the conditions, the signal is considered valid; otherwise, it is considered an interference signal.

[0038] That is, the preset condition is: E1∈[γ] min ×E2,γmax [×E2], where γ min The minimum value of the target reflectivity γ, γ max This represents the maximum value of the target reflectivity γ; and γ = 10%–90%.

[0039] In other words, if E1∈[[0.1×E2,0.9×E2], then it is judged to be a valid signal;

[0040] Furthermore, in step S5, the correlation judgment is also made based on the obtained current echo signal strength and signal pulse width. If either the echo signal strength or the signal pulse width shows abnormal fluctuations or discontinuities, such as a sudden large change in the strength of an echo signal and no reasonable logical relationship with the preceding and following signals, or a jump change in the signal pulse width, it is judged to be an interference signal.

[0041] In step S5, the ranging data that is determined to be a valid signal is smoothed to remove minor fluctuations and then stored in the database in a specified data format for use by subsequent application systems; the ranging data that is determined to be an interference signal is marked and stored for reference when analyzing interference source characteristics and optimizing ranging algorithms.

[0042] Figure 3 In the graph, the horizontal axis represents the attenuation coefficient, which actually indicates the echo intensity. The attenuation coefficient and the echo intensity have a linear relationship.

[0043] Based on the above, the present invention will be further described with reference to the following embodiments:

[0044] In a high-precision topographic mapping laser ranging project, the laser ranging data validity screening method of this invention is used to process the ranging data:

[0045] First, the relationship between echo signal intensity and signal pulse width was calibrated in a laboratory environment: The rangefinder was fixed, and a standard target plate with known reflectivity (i.e., the object being measured) was used as the reflective target. The attenuation coefficient in the optical path was changed using a variable attenuator or variable aperture. 100 laser emission and reception measurements were performed at each attenuation coefficient. The echo signal intensity and signal pulse width were recorded for each measurement. All measurement data were then fitted using existing data fitting methods to obtain the following relationship model between echo signal intensity (E1) and signal pulse width (W): E1 = aW 2 +bW+c, and then the echo signal intensity values ​​corresponding to different signal pulse width values ​​are made into the corresponding first relationship lookup table and stored in the rangefinder;

[0046] Next, the relationship between echo signal strength and ranging distance was calibrated: starting from 10 meters away from the rangefinder, the target distance was gradually increased to 200 meters at 5-meter intervals. 100 laser emission and reception measurements were performed at each distance point, and the received signal strength at each ranging distance point was recorded. The relationship model between echo energy (E2) and ranging distance (L) was obtained as: E2 = k / L 2 +m, and then the echo signal intensity values ​​corresponding to different ranging distances are made into a corresponding second relationship lookup table and stored in the rangefinder;

[0047] Then, at the actual terrain surveying site, the laser rangefinder measured the distance to different terrain targets. When the echo signal was received, the echo signal was first amplified by 1000 times and filtered using a low-pass filter with a bandwidth of 100kHz. Then, the analog signal was converted into a digital signal by a 12-bit high-speed ADC with a sampling rate of 1MHz. The measured current echo signal strength was 50μJ, the signal pulse width was 10ns, and the ranging distance was 1500m.

[0048] By consulting the second relationship table (i.e., the relationship table between echo energy and ranging distance), the expected echo energy range at a ranging distance of 1500 meters is calculated to be 45μJ~55μJ. Therefore, it can be determined that the current echo energy deviation is within an acceptable range.

[0049] Simultaneously, by consulting the first relationship lookup table (i.e., the signal strength and signal pulse width relationship lookup table), the expected signal pulse width range corresponding to a 50μJ echo signal strength is found to be 8ns to 12ns. Therefore, it can be determined that the current signal pulse width is also within a reasonable range. Furthermore, by analyzing the returned signals from multiple consecutive measurements, it was found that the echo signal strength and signal pulse width showed stable trends with no abnormal fluctuations. Based on preset conditions, the returned signal was determined to be a valid signal. The corresponding ranging data was then smoothed, output, and stored in the database for use by subsequent topographic mapping data processing software.

[0050] As can be seen from this embodiment, the laser ranging data validity screening method of the present invention can effectively screen out valid laser ranging data in actual high-precision measurement scenarios, improve data quality, and provide reliable data support for applications such as topographic mapping.

[0051] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0052] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for screening the validity of laser ranging data, characterized in that: Includes the following steps: S1. The rangefinder performs multiple laser ranging operations on the object under different attenuation coefficients. The echo signal intensity and the corresponding signal pulse width are recorded each time the ranging is performed. Based on the recorded data, a mathematical relationship between the echo signal intensity and the signal pulse width is established using a data fitting method, and a first relationship reference table between the echo signal intensity and the signal pulse width is constructed. S2. Perform multiple laser ranging measurements at different ranging distances. Record the echo signal intensity and the corresponding ranging distance for each ranging measurement. Based on the recorded data, use data fitting methods to establish a mathematical relationship between the echo signal intensity and the ranging distance, and construct a second relationship comparison table between the echo signal intensity and the ranging distance. S3. In actual ranging, the received echo signal is preprocessed and the preprocessed signal is converted into a digital signal to obtain the current echo signal strength, signal pulse width and ranging distance. S4. Determine the current echo signal strength value based on the current signal pulse width and the first relationship lookup table; Based on the current ranging distance and in conjunction with the second relationship lookup table, determine the echo energy value at the current ranging distance; S5. Based on the obtained echo signal strength value and echo energy value, determine whether the echo signal strength value and echo energy value meet the preset conditions. If they meet the conditions, the signal is considered valid; otherwise, it is considered an interference signal.

2. The laser ranging data validity screening method according to claim 1, characterized in that: In step S1, an adjustable attenuation coefficient is placed between the rangefinder and the object being measured. Multiple laser emission and reception measurements are performed at different attenuation coefficients to obtain a mathematical model relating the echo signal intensity and the signal pulse width, namely: E1 = aW 2 +bW+c; Where E1 is the echo signal intensity; W is the signal pulse width; and a, b, and c are known fitting coefficients.

3. The laser ranging data validity screening method according to claim 2, characterized in that: The adjustment element is a variable attenuator or a variable aperture.

4. The laser ranging data validity screening method according to claim 2, characterized in that: In step S2, the distance between the rangefinder and the object is gradually increased according to the set distance value, and multiple laser ranging measurements are performed at each distance. Then, based on the recorded data, a mathematical relationship model between the echo energy and the ranging distance is obtained: E2 = k / L 2 +m; Where E2 is the echo energy; L is the ranging distance; and k and m are known fitting coefficients.

5. The laser ranging data validity screening method according to claim 4, characterized in that: The preset condition in step S5 is: E1∈[γ] min ×E2,γ max [×E2], where γ min The minimum value of the target reflectivity γ, γ max This represents the maximum value of the target reflectivity γ; and γ = 10%–90%.

6. The laser ranging data validity screening method according to claim 1, characterized in that: In step S5, the correlation judgment is also performed based on the obtained current echo signal strength and signal pulse width. If any abnormal fluctuation or discontinuity occurs in the echo signal strength or signal pulse width, it is judged to be an interference signal.

7. The laser ranging data validity screening method according to claim 1, characterized in that: In step S5, the ranging data determined to be valid signals are smoothed, output, and stored in the database; the ranging data determined to be interference signals are marked and stored.

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