CN113917473A - Pulse type polarized laser ranging method suitable for rain and fog environment - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/4861—Circuits for detection, sampling, integration or read-out
Abstract
The invention discloses a pulse type polarized laser ranging method suitable for a rain and fog environment, wherein laser is changed into emitting linearly polarized light in the vertical direction after passing through a polarizer, the linearly polarized light is depolarized due to the multiple scattering effect of particles when being transmitted in a typical interference environment, echo is changed into partial polarized light, the linearly polarized light is taken as the main light, and the original linear polarization direction is kept; the polarized light backscattered by the surface of the detection target is almost completely depolarized, the horizontal component and the vertical component of the echo are almost equal, the horizontal component is far larger than the horizontal component of the echo of a typical interference environment, 4 analyzers are respectively arranged at the positions of 0 degree, 45 degrees, 90 degrees and 135 degrees, the polarization degree of partial polarized light is calculated according to the atmospheric light intensity A, only when the polarization degree P is smaller than P0, the detection light intensity is regarded as target reflected light, the reflected echo of the typical interference environment and the reflected echo of the surface of the target are accurately distinguished, and the distance is measured by judging the echo reflected by the detection target.
Description
Technical Field
The invention relates to the technical field of laser ranging measurement, in particular to a pulse type polarized laser ranging method suitable for a rain and fog environment.
Background
Laser ranging is used as a means for measuring distance, and the ranging accuracy is an important index. The existing laser ranging methods include a pulse method, a phase method and a triangle method. The general principle of pulse type laser ranging is that a laser range finder emits a beam of ranging laser, after the ranging laser irradiates a target object, a target echo signal is reflected and received by the laser range finder, the laser range finder calculates the time difference of laser flight, and the distance from a laser emission point to the surface of the target is calculated according to the time difference and the propagation speed of light in the air.
The main difficulty of pulse laser ranging is to obtain the time difference between the sending of an optical signal and the receiving of the optical signal, wherein the time difference is obtained by subtracting the time of sending the laser signal from the time of receiving the laser signal, the time of sending the laser signal is determined to be known, and the key point is whether a pulse signal reflected back can be found from the received laser echo signal, the reflection time can be determined by finding the echo signal, and the laser pulse signal is influenced by factors such as environment, weather and the like when propagating and attenuating in the atmosphere, so that the echo signal can be accurately distinguished, the false alarm probability is reduced, and the measurement precision and the comprehensive performance can be improved.
Therefore, on the basis of the simple and feasible working principle of the pulse laser range finder, the pulse type polarized laser range finding method suitable for the rain and fog environment is provided, and the measurement precision and the comprehensive performance of the system are improved.
Disclosure of Invention
The invention aims to provide a pulse type polarized laser ranging method suitable for a rain and fog environment, solves the problem of high misjudgment rate of scattered echoes in pulse laser ranging under complex environmental interference in the prior art, accurately finds echo signals of a detection target and improves measurement precision.
In order to achieve the purpose, the invention provides the following technical scheme: under typical interference environments (cloud, rain, fog, snow and sand dust), the light intensity reaching the detector mainly comprises two parts: the reflected light of the detection target contains the intensity information of the detection target, and the light intensity of the part is mainly natural light; the other is stray light caused by particle scattering in a typical atmospheric interference environment, also called atmospheric light, which is a main interference factor of laser detection in the typical atmospheric interference environment, the partial light intensity is mainly partial polarized light, and the polarized light can be mistaken as reflected light of a detection target, so that a false ranging alarm can be caused.
In order to reduce the false alarm rate, the invention adopts a four-receiving type polarized laser ranging method, laser passes through a polarizer (assumed to be in the vertical direction) and then is changed into transmitting linearly polarized light in the vertical direction, the linearly polarized light is depolarized due to the multiple scattering effect of particles when being transmitted in a typical interference environment, echo is changed into partial polarized light, the linearly polarized light is taken as the main light, and the original linear polarization direction is kept; the polarized light backscattered by the surface of the detected target is almost completely depolarized (approximate to natural light), the horizontal component and the vertical component of the echo are almost equal, the horizontal component is far larger than the horizontal component of the typical interference environment echo (only partially depolarized), 1 to 4 analyzers are arranged at the receiving end, the 4 analyzers are respectively arranged at the positions of 0 degree, 45 degrees, 90 degrees and 135 degrees, and the total light intensity reaching the receiving end of the detector is the incoherent superposition of target reflected light intensity D (natural light) and atmospheric light intensity A (partially polarized light), which is represented as I ═ D + A. Calculating the polarization degree of partial polarized light according to the atmospheric light intensity A, setting the minimum polarization degree as a threshold value P0, regarding the detected light intensity as target reflected light only when the polarization degree P is less than P0, accurately distinguishing the reflected echo of a typical interference environment from the reflected echo of a target surface, and measuring the distance by judging the echo reflected by the detected target.
Advantageous effects
The invention provides a pulse type polarized laser ranging method suitable for a rain and fog environment, which has the following beneficial effects:
the invention adopts 1 to 4 receiving type analyzer at the receiving end, determines the echo of the detected target by polarization proportion, judges the depolarization degree of the echo signal, abandons the measuring signal with too weak or too strong echo signal, obtains more accurate target surface echo signal, and improves the measuring precision of laser ranging.
Drawings
FIG. 1 is a schematic diagram of a laser ranging structure of the present invention;
FIG. 2 is a schematic diagram of a 4-receive polarized pulsed laser receiving system of the present invention;
FIG. 3 is a schematic diagram of a 2-receive polarized pulsed laser receiving system of the present invention;
fig. 4 is a schematic diagram of a 1-receive polarized pulse laser receiving system of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-4, the present invention provides a technical solution: a pulse type polarized laser ranging method suitable for a rain and fog environment comprises the following steps:
step 1: firstly, a standard laser pulse is emitted by a laser emitting end and is changed into linearly polarized light after passing through a polarizer in the vertical direction, the linearly polarized light is divided into two beams through a beam splitter, one beam directly enters a receiving system as an initial signal, which is equivalent to an emitted pulse, the other beam sends the emitted standard laser pulse as a reference pulse into a main wave sampler, and the reference pulse is converted into an electric pulse through a photoelectric detector and is used as a timing initial signal;
step 2: because the linearly polarized light can be depolarized by multiple scattering of particles, part of the linearly polarized light depolarized in a typical interference environment becomes partial polarized light, the polarized light passing through the surface of a detection target almost completely depolarizes into natural light, the depolarized polarized light reflects an echo back to a receiving optical system, and the receiving optical system is divided into three receiving modes according to engineering and practical requirements, wherein the receiving modes comprise four analyzers for receiving, two analyzers for receiving and a single analyzer for receiving, and the specific working flows of the three modes are as follows:
four analyzers receive: with reference to fig. 2, there are four analyzers at the receiving end, each analyzer has a phase difference of 45 °, the total received light intensity is the incoherent superposition of the reflected light intensity of the detected target and the atmospheric light intensity, and the quantized value of the polarization degree of the received polarized light is represented by the polarization degree P:
wherein I represents the total intensity of light; q represents the difference between the linearly polarized light components of 0 ° and 90 °; u represents the difference between 45 ° and 135 ° linearly polarized light components; v represents the difference between the right-handed circularly polarized light component and the left-handed circularly polarized light component, and adopts a Stokes parameter I, Q, U, V; completely unpolarized light when the degree of polarization P is equal to 0; when the value of the polarization degree is closer to 1, the higher the polarization degree of the light is, namely the light is completely polarized; p0For the echo signal of the surface of the detection target with the polarization degree of 1, the energy is concentrated at 95 percent in combination with the actual situation, so that P0Set to 0.95, when only P is set0The threshold value of 0.95 can distinguish the echo of a typical interference environment from the echo of a detection target surface, and an environment interference signal and a noise signal are filtered by setting the threshold value, so that the method has the most accurate calculation but higher cost;
two analyzers receive: in combination with FIG. 3, the receiving end is provided with two analyzers which are perpendicular to each other, and the depolarization degree of the incident linearly polarized light is the intensity I of the scattered light in the direction perpendicular to the polarization direction of the incident light⊥Intensity I of scattered light in a direction parallel to the direction||The ratio between:
wherein, I||Light intensity in parallel direction, I⊥The intensity of light in the vertical direction.
If I⊥＝I||When Dep is 1, the scattered light is natural light, the detected echo is a probe target echo, and if I is⊥When Dep is 0, the scattered light is linearly polarized and no depolarization occurs. If 0 < I⊥＜I||Then, 0<Dep<1, the scattered light is partially polarized light, and both the scattered light and the partially polarized light are echoes generated by typical environmental interference. In this case, the echo of the typical interference environment and the echo of the target surface can be distinguished by setting a threshold value with Dep of 1 in the horizontal analyzer and the vertical analyzer.
A single analyzer receives: with reference to fig. 4, 1 analyzer at the receiving end almost completely depolarizes the polarized light passing through the surface of the detected target into natural light, the horizontal component and the vertical component of the echo are almost equal, and the horizontal component is much larger than the horizontal component of the echo in the typical interference environment (only partially depolarized), so that the echo in the typical interference environment and the echo on the surface of the target can be distinguished by only detecting the horizontal component by the analyzer and then prejudging as the echo in the typical interference environment. This method is not accurate, but is low cost.
The three methods can distinguish the detection target echo from the typical environment interference echo, reduce the false alarm rate, filter the typical environment interference signal and the noise signal, and can be reasonably selected according to the engineering requirements.
And step 3: when signal processing and calculation are carried out, photoelectric signals cannot be directly used, so that the optical signals need to be subjected to photoelectric conversion, the optical signals are converted into echo waveforms in an electric signal form corresponding to the optical signal waveforms, the echoes are subjected to photoelectric conversion through an APD photoelectric detector, echo pulse signals reflected by a detection target are converged through an echo receiving optical system, and then the echo pulse signals are amplified and then subjected to high-speed sampling through a high-speed sampling plate.
And 4, step 4: stopping counting by a counter for judging the echo peak value reflected by the detection target; calculating the distance according to the time t required by the pulse measurement of the timing module by using an initial moment identification method, reading and storing data through an upper computer controller, and finishing single high-frequency distance measurement; if the signal is passed through the pulse semiconductor laser driver again, continuous high-frequency distance measurement can be carried out.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. A pulse type polarized laser ranging method suitable for a rain and fog environment is characterized by comprising the following steps:
step 1: firstly, a standard laser pulse is emitted by a laser emitting end and is changed into linearly polarized light after passing through a polarizer in the vertical direction, the linearly polarized light is divided into two beams through a beam splitter, one beam directly enters a receiving system as an initial signal, which is equivalent to an emitted pulse, the other beam sends the emitted standard laser pulse as a reference pulse into a main wave sampler, and the reference pulse is converted into an electric pulse through a photoelectric detector and is used as a timing initial signal;
step 2: linearly polarized light is depolarized due to multiple scattering of particles, a part of polarized light depolarized after passing through a typical interference environment becomes partial polarized light, polarized light passing through the surface of a detection target is nearly completely depolarized into natural light, and echoes are reflected back to a receiving optical system by the depolarized polarized light;
and step 3: when signal processing and calculation are carried out, photoelectric signals cannot be directly used, so that the optical signals need to be subjected to photoelectric conversion, converted into echo waveforms in an electric signal form corresponding to the optical signal waveforms, the echoes are subjected to photoelectric conversion through an APD photoelectric detector, echo pulse signals reflected by a detection target are converged through an echo receiving optical system, and after the echo pulse signals are amplified, the echo signals are subjected to high-speed sampling through a high-speed sampling plate;
and 4, step 4: stopping counting by a counter for judging the echo peak value reflected by the detection target; calculating the distance according to the time t required by the pulse measurement of the timing module by using an initial moment identification method, reading and storing data through an upper computer controller, and finishing single high-frequency distance measurement; if the signal is passed through the pulse semiconductor laser driver again, continuous high-frequency distance measurement can be carried out.
2. The pulsed polarized laser ranging method suitable for the rain and fog environment according to claim 1, wherein the receiving optical system is divided into three receiving modes, namely four analyzer receiving, two analyzer receiving and single analyzer receiving, and the three modes specifically work as follows:
four analyzers receive: four analyzers are arranged at a receiving end, the phase difference of each analyzer is 45 degrees, the total received light intensity is the incoherent superposition of the reflected light intensity of a detection target and the atmospheric light intensity, and the quantized value of the polarization state degree of the received polarized light is represented by the polarization degree P:
wherein I represents the total intensity of light; q represents the difference between the linearly polarized light components of 0 ° and 90 °; u represents the difference between 45 ° and 135 ° linearly polarized light components; v represents the difference between the right-handed circularly polarized light component and the left-handed circularly polarized light component, and adopts a Stokes parameter I, Q, U, V; completely unpolarized light when the degree of polarization P is equal to 0; when the value of the polarization degree is closer to 1, the higher the polarization degree of the light is, namely the light is completely polarized; p0For the echo signal of the surface of the detection target with the polarization degree of 1, the energy is concentrated at 95 percent in combination with the actual situation, so that P0Set to 0.95, when only P is set0The threshold value of 0.95 can distinguish the echo of a typical interference environment from the echo of a detection target surface, and an environment interference signal and a noise signal are filtered by setting the threshold value, so that the method has the most accurate calculation but has higher cost;
two analyzers receive: the receiving end is provided with two analyzers which are vertical to each other, and the depolarization degree of the incident linearly polarized light is the intensity I of scattered light in the direction vertical to the polarization direction of the incident light⊥Intensity I of scattered light in a direction parallel to the direction||The ratio between:
wherein, I||Light intensity in parallel direction, I⊥Light intensity in the vertical direction;
if I⊥＝I||When Dep is 1, the scattered light is natural light, the detected echo is a probe target echo, and if I is⊥When Dep is 0, the scattered light is still linearly polarized light and no depolarization occurs; if 0 < I⊥＜I||Then, 0<Dep<1, the scattered light is partially polarized light, and both the scattered light and the partially polarized light are echoes generated by typical environmental interference. At the moment, the echo of a typical interference environment and the echo of a target surface can be distinguished by setting a threshold with the Dep of 1 on the horizontal analyzer and the vertical analyzer;
a single analyzer receives: the receiving end is 1 analyzer, the polarized light passing through the surface of the detected target is almost completely depolarized into natural light, the horizontal component and the vertical component of the echo are almost equal, the horizontal component is far larger than the horizontal component of the echo of the typical interference environment, and the echo of the typical interference environment and the echo of the surface of the target can be distinguished by judging as the echo of the detected target in advance as long as the analyzer detects the horizontal component to be large.
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| US20200233063A1 (en) * | 2017-08-14 | 2020-07-23 | Hangzhou Ole-Systems Co., Ltd. | High-speed laser distance measuring device |
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| CN1641339A (en) * | 2004-11-20 | 2005-07-20 | 中国科学院安徽光学精密机械研究所 | Metre scattering polarization micro-pulse laser radar control method and device |
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| US20200233063A1 (en) * | 2017-08-14 | 2020-07-23 | Hangzhou Ole-Systems Co., Ltd. | High-speed laser distance measuring device |
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