CN111999739A - Coherent laser radar method and device for measuring distance and speed by phase modulation - Google Patents

Coherent laser radar method and device for measuring distance and speed by phase modulation Download PDF

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CN111999739A
CN111999739A CN202010633321.0A CN202010633321A CN111999739A CN 111999739 A CN111999739 A CN 111999739A CN 202010633321 A CN202010633321 A CN 202010633321A CN 111999739 A CN111999739 A CN 111999739A
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phase
light beam
signal
target
echo
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职亚楠
孙建锋
潘卫清
戴恩文
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Sun Jianfeng
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Hangzhou Ilidar Technology Co ltd
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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
    • G01S17/50—Systems of measurement based on relative movement of target
    • G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • 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
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • 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

Abstract

The invention discloses a coherent laser radar method and device for phase modulation distance measurement and speed measurement.A light beam output is divided into a local oscillator light beam and an emission light beam by a first beam splitter; the emission light beam is transmitted to the second beam splitter and is divided into a detection light beam and a reference light beam, the detection light beam is emitted to a target, and an echo light beam is received; the local oscillation light beam is divided into a local oscillation first light beam and a local oscillation second light beam through a third beam splitter; carrying out coherent light frequency mixing on the local oscillator first light beam and the echo light beam to obtain first sampling data; carrying out coherent light frequency mixing on the local oscillator second light beam and the reference light beam to obtain second sampling data, and respectively processing the first sampling data and the second sampling data by using a field programmable gate array to obtain an echo phase sequence and a reference phase sequence; and processing the echo phase sequence and the reference phase sequence to respectively obtain the motion vector speed and the distance of the target. The invention can reduce the hardware requirement of the laser radar, realize high resolution and high precision distance and speed measurement, and has miniaturized whole system and easy operation.

Description

Coherent laser radar method and device for measuring distance and speed by phase modulation
Technical Field
The invention relates to the technical field of laser radars, in particular to a phase modulation ranging and speed measuring coherent laser radar method and device.
Background
The laser radar can acquire information such as distance and speed of a target with high precision and high accuracy, can realize 3D high-resolution imaging of a long-distance target, and has an important effect in the fields of surveying and mapping, navigation and the like. Laser radars can be divided into two main categories according to the difference of the transmitted signals: pulsed lidar and continuous wave lidar.
The pulse laser radar adopts a pulse light signal as a detection signal, and obtains target distance information by accurately measuring the flight time of a reflected light pulse. The pulse laser radar adopts a direct detection system, the resolution ratio is relatively low, short pulses with low time delay jitter, an ultrafast optoelectronic device and the like are required to be used for improving the distance resolution ratio, independent Doppler velocity measurement cannot be carried out, and the higher pulse power also puts requirements on the device performance and the human eye safety.
The continuous wave laser radar adopts continuous light signals as detection signals and has the characteristics of low peak power, high resolution and the like. Continuous wave lidar is further classified into phase-type lidar, pseudo-random code modulated lidar and frequency modulated continuous wave lidar. The phase type laser radar is based on a phase laser ranging technology, adopts single-frequency signals to modulate laser, and finally obtains target distance information by phase discrimination of reflected light signals. The disadvantage of this method is that there is a phase measurement error, and the phase measurement error increases with decreasing frequency of the modulation signal, thus the contradiction between increasing the measurement distance and improving the accuracy. In order to realize long-distance and high-precision measurement, several different modulation signal frequencies can be used at the same time, namely several different measuring rulers are used, the shortest measuring ruler is used for ensuring the measurement precision, and the longest measuring ruler is used for ensuring the distance measurement range, so that the system is more complex and does not have the Doppler velocity measurement capability. The pseudo-random code modulation laser radar modulates the amplitude or the phase transmitted by the laser radar by the pseudo-random code modulation code, and a receiving end uses a method of solving a correlation function by a received signal and the modulation pseudo-random code to realize the measurement of a target distance, so that higher distance resolution can be obtained under the condition of wide pulse width. However, the range resolution of the pseudo-random code modulation laser radar is inversely proportional to the transmission signal bandwidth, and the larger the transmission signal bandwidth is, the higher the range resolution is, which puts high requirements on receiving hardware. In addition, the modulation process of the pseudo-random code makes the echo signal be a continuous sine wave only at the position of the "1" code, so that the doppler signal cannot be sampled at equal intervals, and the spectrum analysis cannot be directly performed by adopting fast fourier transform. The frequency modulation continuous wave laser radar performs linear modulation on the frequency of transmitted laser, coherent reception is performed on echo signals and local oscillation signals, distance measurement of a target is achieved by acquiring heterodyne frequency, and Doppler velocity measurement can be achieved through waveform modulation. The frequency modulation continuous wave laser radar has the advantages that when the laser works in a wide pulse width and low peak power state, the pulse repetition detection frequency can be greatly improved, so that the spatial resolution is improved; in addition, higher sensitivity can be obtained with coherent detection. However, the cost is high due to the limitation of the hardware condition of the laser, the pulse repetition frequency is limited, and the frequency modulation nonlinearity is still an unsolved problem.
Disclosure of Invention
The invention aims to provide a coherent laser radar method and a coherent laser radar device for measuring distance and speed by phase modulation. The invention can reduce the requirements on hardware such as a laser light source, detection receiving and the like, realizes high-resolution and high-precision distance measurement and speed measurement, has miniaturized whole system and easy operation, and has good development prospect in the field of distance measurement and speed measurement of vehicle-mounted, airborne and satellite-mounted laser radars.
The technical scheme of the invention is as follows: in the method, a narrow-linewidth single-frequency continuous laser light source in a radar platform generates an output light beam which is polarized and then divided into a local oscillation light beam and an emission light beam by a first beam splitter; the emission beam is amplified after phase modulation and then transmitted to a second beam splitter to be divided into a detection beam and a reference beam, the detection beam is emitted to a target, and an echo beam carrying target distance and motion Doppler information is received; the local oscillation light beam is divided into a local oscillation first light beam and a local oscillation second light beam through a third beam splitter; the local oscillator first light beam and the echo light beam are subjected to coherent light frequency mixing through a first optical bridge, a first intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the first intermediate frequency signal to obtain first sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained first sampling data to obtain an echo phase sequence containing a target distance and a target speed; the local oscillator second light beam and the reference light beam are subjected to coherent light frequency mixing through a second optical bridge, a second intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the second intermediate frequency signal to obtain second sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained second sampling data to obtain a reference phase sequence; subjecting the echo phase sequence to deskew processing and quadrature phase demodulation processing; subjecting the reference phase sequence to quadrature phase demodulation processing; and then carrying out phase difference processing on the processed echo phase sequence and the reference phase sequence to finally obtain the motion vector speed and the distance of the target.
In the phase modulation distance measurement and speed measurement coherent laser radar method, the laser light source in the radar platform generates unmodulated single-frequency single-mode continuous coherent laser as an output beam, and the output beam is polarized by the polarizer, so that the polarization degree is improved, and the method is represented as follows:
E0(t)＝E0exp[j2πf0t+jφN0+jφ0]；
in the formula (f)0Is the frequency of the laser light source; phi is a0Is the output beam initial phase; phi is aN0Is the noise phase of the output beam; e0Is the output beam amplitude, t is the time,
Figure RE-GDA0002688408720000041
exp is an exponential function with a natural constant e as the base.
In the phase modulation distance measurement and speed measurement coherent laser radar method, after the output light beam is split by the first beam splitter, a small part of energy is used as a local oscillator light beam, the local oscillator light beam is split by the third beam splitter into the same local oscillator first light beam and local oscillator second light beam, and the light fields of the local oscillator first light beam and the local oscillator second light beam are uniformly expressed as:
ELO(t)＝ELOexp[j2πf0t+jφLO+jφ0]；
in the formula, ELOIs the local oscillator beam amplitude, phiLOIs the noise phase of the local oscillator beam; f. of0Is the frequency of the laser light source, phi0To output the initial phase of the beam, t is time,
Figure RE-GDA0002688408720000042
exp is an exponential function with a natural constant e as the base;
most of the energy is used as a radiation beam, and the radiation beam becomes:
EM(t)＝E0exp{j2πf0t+jAcos[2πfEOMt+φN-EOM(t)+φ0-EOM]+jφN+jφ0}；
in the formula (f)EOMIs the modulation frequency of the phase modulator; phi is aN-EOM(t) is the noise phase of the modulated signal; phi is a0-EOMFor the initial phase of the modulated signal, A is the phase modulation factor, E0Is the output beam amplitude, f0Which is the frequency of the laser light source, t is the time,
Figure RE-GDA0002688408720000043
exp is an exponential function, φ, based on a natural constant e0Is the output beam initial phase; phi is aNIs the noise phase of the output beam.
In the phase modulation distance measurement and speed measurement coherent laser radar method, the emitted light beam is subjected to phase modulation, then is subjected to laser amplification and then is split by the second beam splitter, a small part of energy in the emitted light beam is used as a reference light beam, and a large part of energy is used as a detection light beam;
the reference beam is represented as:
Figure RE-GDA0002688408720000051
in the formula: time delay
Figure RE-GDA0002688408720000052
L0Is the transmission path of a single pass of the reference beam, ES-rIs the amplitude of the reference beam, c is the speed of light, phiN_rIs the noise phase of the reference beam;
the probe beam is transmitted to a target through the optical circulator, the optical scanner and the optical telescope, and an echo beam of the target is received by the optical telescope, wherein the echo beam is expressed as:
Figure RE-GDA0002688408720000053
wherein E isSIs the amplitude of the echo beam, phiSIs the noise phase of the echo beam; echo beam time delay
Figure RE-GDA0002688408720000054
L is the single pass optical path length of the target, c is the speed of light, V is the radial velocity of the target relative to the radar platform, phiN_sFor detecting the phase of the noise received by the optical path0-EOMFor modulating the initial phase of the signal, phiN-EOM(t) is the noise phase of the modulated signal;
the optical field after the echo light beam of the target and the local oscillator light beam are combined is represented as follows:
Figure RE-GDA0002688408720000061
the four outputs after being mixed by the 2 × 490 ° first optical bridge are respectively:
Figure RE-GDA0002688408720000062
in the formula ISIs a direct current quantity related to the echo beam; i isLOIs the direct current quantity related to the local oscillator beam; for the purpose of remote detection of the object,
Figure RE-GDA0002688408720000063
therefore, the method of firstly solving the mean value and then differentiating is adopted for eliminating; to obtain
Figure RE-GDA0002688408720000064
fDopplerThe Doppler frequency is caused by the relative motion radial velocity of the radar platform and the target;
the light field after the reference beam and the local oscillator two beams are combined is represented as follows:
Figure RE-GDA0002688408720000071
the four outputs after being mixed by the 2 × 490 ° second optical bridge are respectively:
Figure RE-GDA0002688408720000072
in the formula IS_rIs a direct current quantity related to the reference beam; i isLOIs the direct current quantity related to the local oscillator beam; due to the fact that
Figure RE-GDA0002688408720000073
Eliminating by adopting a method of firstly calculating the mean value and then differentiating;
synchronous receiving of the outputs of the first optical bridge and the second optical bridge is realized through an external trigger circuit;
the in-phase signal and the quadrature signal with the quadrature characteristic output by the first optical bridge are respectively received by the first photoelectric balanced detector to obtain a first intermediate frequency signal, and the in-phase signal and the quadrature signal in the first intermediate frequency signal output by the first photoelectric balanced detector are respectively:
Figure RE-GDA0002688408720000081
in the formula: k is a radical ofinIs the first photoelectric balanced detector responsivity, k, of the received in-phase signalquIs the first photo-balance detector responsivity receiving the quadrature signal;
if the response rates of the first photoelectric detectors for receiving the in-phase signals and the orthogonal signals are kept consistent, the in-phase signals and the orthogonal signals in the first intermediate frequency signals are respectively subjected to analog-to-digital conversion, collected by a field programmable gate array and obtained by arc tangent phase-splitting:
Figure RE-GDA0002688408720000082
then reconstructing the echo phase sequence of the target by a unwrapping algorithm due to phiN_S-φLOIs a slowly varying quantity that can be considered as a direct current quantity for one sequence duration, and is therefore eliminated by high-pass filtering, resulting in:
Figure RE-GDA0002688408720000083
the in-phase signal and the quadrature signal with the quadrature characteristic output by the second optical bridge are respectively received by the second photoelectric balanced detector to obtain a second intermediate frequency signal, and the in-phase signal and the quadrature signal in the second intermediate frequency signal output by the second photoelectric balanced detector are respectively:
Figure RE-GDA0002688408720000091
in the formula: k is a radical ofinIs the response rate, k, of a second photoelectric balanced detector receiving an in-phase signalquIs the second photo-balance detector responsivity receiving the quadrature signal;
if the response rates of the second photoelectric detectors for receiving the in-phase signals and the orthogonal signals are kept consistent, the in-phase signals and the orthogonal signals in the second intermediate frequency signals are respectively subjected to analog-to-digital conversion, collected by a field programmable gate array and obtained by arc tangent phase-splitting:
Figure RE-GDA0002688408720000092
then reconstructing the reference phase sequence by a unwrapping algorithmN_r-φLOIs a slowly varying quantity that can be considered as a direct current quantity for one sequence duration, and is therefore eliminated by high-pass filtering, and therefore:
Figure RE-GDA0002688408720000093
according to the coherent laser radar method for measuring distance and speed by phase modulation, an echo phase sequence is subjected to deskew processing and orthogonal phase demodulation processing; subjecting the reference phase sequence to quadrature phase demodulation processing; and then carrying out phase difference processing on the processed echo phase sequence and the reference phase information to finally obtain the motion vector speed and the distance of the target respectively, wherein the phase difference processing specifically comprises the following steps:
first, to echo phase sequence
Figure RE-GDA0002688408720000094
The slope K is obtained by deskewing, and the doppler frequency:
Figure RE-GDA0002688408720000101
because the Doppler frequency is in direct proportion to the radial velocity of the relative movement of the radar platform and the target, the positive frequency and the negative frequency of the Doppler frequency are related to the direction of the radial velocity of the relative movement of the radar platform and the target, the positive frequency represents that the radar platform and the target move in the opposite direction, and the negative frequency represents that the radar platform and the target move in the opposite direction; thus, the radial velocity V of the target relative to the radar platform relative to the target is expressed as:
Figure RE-GDA0002688408720000102
in the formula: lambda [ alpha ]0Is the laser wavelength;
obtaining the magnitude and the direction of the radial velocity V of the radar platform relative to the target by solving the magnitude and the positive and negative of the slope K;
after the deskew treatment, the linear terms are eliminated, and the following can be obtained:
Figure RE-GDA0002688408720000103
in the formula: a is the phase modulation factor, fEOMThe modulation frequency of the phase modulator, t is the time, L is the transmission optical path length of a single pass of the object, c is the speed of light, phiN-EOM(t) is the noise phase of the modulated signal, phi0-EOMIs the initial phase of the modulated signal;
then separately aligning the echo phase sequences
Figure RE-GDA0002688408720000104
And a reference phase sequence
Figure RE-GDA0002688408720000105
Performing quadrature demodulation processing:
in the echo phase sequence
Figure RE-GDA0002688408720000106
In the orthogonal demodulation process of (2), will
Figure RE-GDA0002688408720000107
And modulation signal cos 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000108
the same-phase baseband signal can be obtained after low-pass filtering
Figure RE-GDA0002688408720000109
Figure RE-GDA0002688408720000111
Then, will
Figure RE-GDA0002688408720000112
And modulation signal sin 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000113
the quadrature baseband signal can be obtained after low-pass filtering
Figure RE-GDA0002688408720000114
Figure RE-GDA0002688408720000115
Finally, the phase inversion by arctangent can be obtained:
Figure RE-GDA0002688408720000116
in reference phase sequence
Figure RE-GDA0002688408720000117
In the orthogonal demodulation process of (2), will
Figure RE-GDA0002688408720000118
And modulation signal cos 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000119
the same-phase baseband signal can be obtained after low-pass filtering
Figure RE-GDA00026884087200001110
Figure RE-GDA00026884087200001111
Then, will
Figure RE-GDA00026884087200001112
And modulation signal sin 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000121
the quadrature baseband signal can be obtained after low-pass filtering
Figure RE-GDA0002688408720000122
Figure RE-GDA0002688408720000123
Finally, the phase inversion by arctangent can be obtained:
Figure RE-GDA0002688408720000124
respectively obtained by orthogonal solution
Figure RE-GDA0002688408720000125
And
Figure RE-GDA0002688408720000126
then, take the difference
Figure RE-GDA0002688408720000127
Figure RE-GDA0002688408720000128
In the formula: l is0Is the transmission optical path of the reference beam one way; l is the target single pass transmission path length due to the noise phase phi of the modulated signalN-EOM(t) and phi0-EOMAnd eliminating by difference, and finally obtaining the distance R between the laser radar transmitting end and the target point as:
Figure RE-GDA0002688408720000129
in the formula: c is the speed of light, fEOMIs the modulation frequency of the phase modulator;
the range resolution is expressed as:
Figure RE-GDA00026884087200001210
in the formula:
Figure RE-GDA00026884087200001211
is the differential dephasing resolution.
The device for realizing the coherent laser radar method for measuring the distance and the speed by phase modulation comprises a linear frequency modulation continuous wave laser light source, wherein the output end of the linear frequency modulation continuous wave laser light source is sequentially connected with a polarizer and a first beam splitter, and the first beam splitter is connected with a phase modulator and a third beam splitter; the output end of the phase modulator is sequentially connected with a laser amplifier and a second beam splitter; the output end of the second beam splitter is sequentially connected with an optical circulator, an optical scanner and an optical telescope;
the third beam splitter and the optical circulator are connected with a first optical bridge together, and the first optical bridge is connected with a first analog-to-digital converter through a first photoelectric balance detector;
the second beam splitter and the third beam splitter are connected with a second optical bridge together, and the second optical bridge is connected with a second analog-to-digital converter through a second photoelectric balance detector;
the first analog-to-digital converter and the second analog-to-digital converter are connected with a field programmable gate array together, and the output end of the field programmable gate array is connected with a main control computer; the main control computer is connected with an external trigger circuit, and the external trigger circuit is connected with the phase modulator through a radio frequency driver; the external trigger circuit is respectively connected with the first analog-to-digital converter and the second analog-to-digital converter; the main control computer is also connected with the optical scanner.
Compared with the prior art, the output light beam generated by the linear frequency modulation continuous wave laser light source in the radar platform is polarized and then divided into the local oscillation light beam and the emission light beam by the first beam splitter; the emission beam is amplified after phase modulation and then transmitted to a second beam splitter to be divided into a detection beam and a reference beam, the detection beam is emitted to a target, and an echo beam carrying target distance and motion Doppler information is received; the local oscillation light beam is divided into a local oscillation first light beam and a local oscillation second light beam through a third beam splitter; the local oscillator first light beam and the echo light beam are subjected to coherent light frequency mixing through a first optical bridge, a first intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the first intermediate frequency signal to obtain first sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained first sampling data to obtain an echo phase sequence containing a target distance and a target speed; the local oscillator second light beam and the reference light beam are subjected to coherent light frequency mixing through a second optical bridge, a second intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the second intermediate frequency signal to obtain second sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained second sampling data to obtain a reference phase sequence; subjecting the echo phase sequence to deskew processing and quadrature phase demodulation processing; subjecting the reference phase sequence to quadrature phase demodulation processing; and then carrying out phase difference processing on the processed echo phase sequence and the reference phase sequence to finally obtain the motion vector speed and the distance of the target. Compared with the traditional phase ranging, the ranging resolution depends on the differential dephasing resolution and the modulation frequency, so that the ranging resolution can be improved by improving the dephasing resolution or increasing the modulation frequency, the requirements on hardware such as a laser light source, detection receiving and the like can be reduced, the dependence of a frequency modulation continuous wave technology on the modulation linearity of the laser light source is avoided, and the coherent ranging and speed measurement of a long-distance target are realized; the invention can independently obtain the Doppler frequency of the target without depending on distance measurement, thereby obtaining the radial speed and the direction of the radar platform relative to the target, being beneficial to the integration miniaturization, reducing the complexity of the system and the volume of the whole device, and having the advantages of small volume, light weight, high resolution, high precision and the like. The invention has good development prospect in the fields of vehicle-mounted, airborne and satellite-mounted laser radars.
Drawings
Fig. 1 is a structural schematic diagram of a coherent laser radar for measuring distance and speed by phase modulation.
FIG. 2 is a schematic diagram of an echo phase sequence deskew process.
The labels in the figures are:
1. a laser light source; 2. a polarizer; 3. a first beam splitter; 4. a phase modulator; 5. a third beam splitter; 6. a laser amplifier; 7. a second beam splitter; 8. an optical circulator; 9. an optical scanner; 10. an optical telescope; 11. a first optical bridge; 12. a first photoelectric balance detector; 13. a first analog-to-digital converter; 14. a second optical bridge; 15. a second photoelectric balance detector; 16. a second analog-to-digital converter; 17. a field programmable gate array; 18. a main control computer; 19. an external trigger circuit; 20. a radio frequency driver.
Detailed Description
The invention is further illustrated by the following figures and examples, which are not to be construed as limiting the invention.
Example 1: a coherent laser radar method for measuring distance and speed by phase modulation is characterized in that a narrow-linewidth single-frequency single-mode continuous laser light source in a radar platform generates an output light beam which is divided into a local oscillation light beam and an emission light beam by a first beam splitter after polarizing; the emission beam is amplified after phase modulation and then transmitted to a second beam splitter to be divided into a detection beam and a reference beam, the detection beam is emitted to a target, and an echo beam carrying target distance and motion Doppler information is received; the local oscillation light beam is divided into a local oscillation first light beam and a local oscillation second light beam through a third beam splitter; the local oscillator first light beam and the echo light beam are subjected to coherent light frequency mixing through a first optical bridge, a first intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the first intermediate frequency signal to obtain first sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained first sampling data to obtain an echo phase sequence containing a target distance and a target speed; the local oscillator second light beam and the reference light beam are subjected to coherent light frequency mixing through a second optical bridge, a second intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the second intermediate frequency signal to obtain second sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained second sampling data to obtain a reference phase sequence; subjecting the echo phase sequence to deskew processing and quadrature phase demodulation processing; subjecting the reference phase sequence to quadrature phase demodulation processing; and then carrying out phase difference processing on the processed echo phase sequence and the reference phase sequence to finally obtain the motion vector speed and the distance of the target.
The device for realizing the method comprises a laser light source 1, wherein the output end of the linear frequency modulation continuous wave laser light source 1 is sequentially connected with a polarizer 2 and a first beam splitter 3, and the first beam splitter 3 is connected with a phase modulator 4 and a third beam splitter 5; the output end of the phase modulator 4 is sequentially connected with a laser amplifier 6 and a second beam splitter 7; the output end of the second beam splitter 7 is sequentially connected with an optical circulator 8, an optical scanner 9 and an optical telescope 10;
the third beam splitter 5 and the optical circulator 8 are connected together with a first optical bridge 11, and the first optical bridge 11 is connected with a first analog-to-digital converter 13 through a first photoelectric balance detector 12;
the second beam splitter 7 and the third beam splitter 5 are connected together with a second optical bridge 14, and the second optical bridge 14 is connected with a second analog-to-digital converter 16 through a second photoelectric balance detector 15;
the first analog-to-digital converter 13 and the second analog-to-digital converter 16 are connected with a field programmable gate array 17 together, and the output end of the field programmable gate array 17 is connected with a main control computer 18; the main control computer 18 is connected with an external trigger circuit 19, and the external trigger circuit 19 is connected with the phase modulator 4 through a radio frequency driver 20; the external trigger circuit 19 is respectively connected with the first analog-to-digital converter 13 and the second analog-to-digital converter 16; the host computer 18 is also connected to the optical scanner 9.
Example 2: a coherent laser radar method for measuring distance and speed by phase modulation is shown in figure 1 and comprises a laser light source 1, a 1550nm single-mode narrow-linewidth single-mode continuous optical fiber laser which is safe to human eyes is adopted, the linewidth of the laser is 10kHz, the output power is 20mW, and the optical fiber output has isolation protection; the laser light source generates unmodulated single-frequency single-mode continuous coherent laser as an output light beam, the output light beam is polarized by the polarizer 2, the polarization degree is improved, and the polarization extinction ratio is ensured to be larger than 25dB, which is expressed as:
E0(t)＝E0exp[j2πf0t+jφN0+jφ0]；
in the formula (f)0Is the frequency of the laser light source; phi is a0Is the output beam initial phase; phi is aN0Is the noise phase of the output beam; e0, output beam amplitude, t time,
Figure RE-GDA0002688408720000171
exp is an exponential function with a natural constant e as the base.
After the output light beam is split by the first beam splitter 3, a small part of energy is used as a local oscillation light beam, the local oscillation light beam is split into a first local oscillation light beam and a second local oscillation light beam by the third beam splitter, and here, the optical fields of the first local oscillation light beam and the second local oscillation light beam are uniformly expressed as:
ELO(t)＝ELOexp[j2πf0t+jφLO+jφ0]；
in the formula, ELOIs the local oscillator beam amplitude, phiLOIs the noise phase of the local oscillator beam; f. of0Is the frequency of the laser light source, phi0To output the initial phase of the beam, t is time,
Figure RE-GDA0002688408720000172
exp is an exponential function with a natural constant e as the base;
most of the energy is taken as a radiation beam, which first passes through a phase modulator 4 driven by a radio frequency driver 20, with sinusoidal modulation, with a modulation rate of 100MHz/s, becoming:
EM(t)＝E0exp{j2πf0t+jAcos[2πfEOMt+φN-EOM(t)+φ0-EOM]+jφN+jφ0}，
in the formula (f)EOMIs the modulation frequency of the phase modulator; phi is aN-EOM(t) is the noise phase of the modulated signal; phi is a0-EOMFor initial phase of the modulation signal, A is the phase modulation factor, E0 is the output beam amplitude, f0Which is the frequency of the laser light source, t is the time,
Figure RE-GDA0002688408720000173
exp is an exponential function, φ, based on a natural constant e0Is the output beam initial phase; phi is aNIs the noise phase of the output beam;
the emitted light beams are subjected to phase modulation, amplified to 350mW by a laser amplifier 6 (erbium-doped fiber amplifier), and split by a second beam splitter 8, wherein a small part of energy in the emitted light beams is used as a reference beam, the reference beam is about 1mW, most of energy is used as a probe beam, and the probe beam is about 300 mW;
the reference beam is represented as:
Figure RE-GDA0002688408720000181
in the formula: time delay
Figure RE-GDA0002688408720000182
L0Is the transmission path of a single pass of the reference beam, ES-rIs the amplitude of the reference beam, c is the speed of light, phiN_rIs the noise phase of the reference beam;
the probe beam is transmitted to the target through an optical circulator 8 (a three-port optical fiber circulator), an optical scanner 9, and an optical telescope 10, and an echo beam of the target is received by the optical telescope 10, the echo beam being expressed as:
Figure RE-GDA0002688408720000183
the phase term of the above formula contains the speed and distance information of the target, and the target can be considered to be in a substantially uniform motion within a microsecond-order measurement period, and the target distance is a constant value, so that the phase change caused by the change of the target distance can be eliminated. Wherein E isSIs the amplitude of the echo beam, phiSIs the noise phase of the echo beam; echo signal time delay
Figure RE-GDA0002688408720000191
L is the single pass optical path length of the target, c is the speed of light, V is the radial velocity of the target relative to the radar platform, phiN_sFor detecting the phase of the noise received by the optical path0-EOMFor modulating the initial phase of the signal, phiN-EOM(t) is the noise phase of the modulated signal;
the optical field after the echo light beam of the target and the local oscillator light beam are combined is represented as follows:
Figure RE-GDA0002688408720000192
the four outputs after being mixed by the 2 × 490 ° first optical bridge are respectively:
Figure RE-GDA0002688408720000193
in the formula ISIs a direct current quantity related to the echo beam; i isLOIs a direct current quantity related to the local oscillator beam, and for long-distance detection,
Figure RE-GDA0002688408720000194
the method of firstly solving the mean value and then differentiating can be adopted for elimination;
Figure RE-GDA0002688408720000195
are also eliminated here; to obtain
Figure RE-GDA0002688408720000196
fDopplerIs the relative movement of the radar platform and the targetRadial velocity induced doppler frequency;
the light field after the reference beam and the local oscillator two beams are combined is represented as follows:
Figure RE-GDA0002688408720000201
the four outputs after being mixed by the 2 × 490 ° second optical bridge 14 are:
Figure RE-GDA0002688408720000202
in the formula IS_rIs a direct current quantity related to the reference beam; i isLOIs the direct current quantity related to the local oscillator beam; due to the fact that
Figure RE-GDA0002688408720000203
Eliminating by adopting a method of firstly calculating the mean value and then differentiating;
synchronous reception of the outputs of the first optical bridge 11 and the second optical bridge 14 is achieved by an external trigger circuit 19;
the in-phase signal and the quadrature signal with the quadrature characteristic output by the first optical bridge 11 are respectively received by a first photo-balance detector 12 (with a bandwidth of 100MHz, ac-coupled) to obtain a first intermediate frequency signal, and the in-phase signal and the quadrature signal in the first intermediate frequency signal output by the first photo-balance detector 12 are respectively:
Figure RE-GDA0002688408720000211
in the formula: k is a radical ofinIs the first photoelectric balanced detector responsivity, k, of the received in-phase signalquIs the first photo-balance detector responsivity receiving the quadrature signal;
if the response rates of the first photodetectors receiving the in-phase signals and the orthogonal signals are kept consistent, the in-phase signals and the orthogonal signals in the first intermediate frequency signals are subjected to analog-to-digital conversion by the first analog-to-digital converter 13 and then collected by the field programmable gate array 17, and the in-phase signals and the orthogonal signals are obtained by arc tangent phase-splitting:
Figure RE-GDA0002688408720000212
then the echo phase sequence of the target can be reconstructed through a unwrapping algorithm, because of phiN_S-φLOIs a slowly varying quantity that can be considered as a direct current quantity for one sequence duration, and is therefore eliminated by high-pass filtering, and therefore:
Figure RE-GDA0002688408720000213
the in-phase signal and the quadrature signal with the quadrature characteristic output by the second optical bridge 14 are respectively received by a second photo balance detector 15 (with a bandwidth of 100MHz, ac-coupled) to obtain a second intermediate frequency signal, and the in-phase signal and the quadrature signal in the second intermediate frequency signal output by the second photo balance detector 15 are respectively:
Figure RE-GDA0002688408720000221
in the formula: k is a radical ofinIs the response rate, k, of a second photoelectric balanced detector receiving an in-phase signalquIs the second photo-balance detector responsivity receiving the quadrature signal;
if the response rates of the second photodetector 15 receiving the in-phase signal and the quadrature signal are kept consistent, the in-phase signal and the quadrature signal in the second intermediate frequency signal are respectively subjected to analog-to-digital conversion by a second analog-to-digital converter 16, and then collected by a field programmable gate array 17, and the following results are obtained by arctan solution:
Figure RE-GDA0002688408720000222
the reference phase sequence can be reconstructed by unwrapping algorithm due to phiN_r-φLOIs a slowly varying quantity that can be considered as a direct current quantity for one sequence duration, and is therefore eliminated by high-pass filtering, and therefore:
Figure RE-GDA0002688408720000223
in the main control computer 18, the echo phase sequence is successively processed by deskew processing and orthogonal phase demodulation processing, the reference phase sequence is processed by orthogonal phase demodulation processing and phase difference processing of the two parts, and finally the motion vector speed and the distance of the target are respectively obtained. The method comprises the following steps:
first, to echo phase sequence
Figure RE-GDA0002688408720000224
The slope K is obtained by deskewing, and the doppler frequency:
Figure RE-GDA0002688408720000231
because the Doppler frequency is in direct proportion to the radial velocity of the relative movement of the radar platform and the target, the positive frequency and the negative frequency of the Doppler frequency are related to the direction of the radial velocity of the relative movement of the radar platform and the target, the positive frequency represents that the radar platform and the target move in the opposite direction, and the negative frequency represents that the radar platform and the target move in the opposite direction; thus, the radial velocity V of the target relative to the radar platform relative to the target is expressed as:
Figure RE-GDA0002688408720000232
in the formula: lambda [ alpha ]0Is the laser wavelength;
obtaining the magnitude and the direction of the radial velocity V of the radar platform relative to the target by solving the magnitude and the positive and negative of the slope K;
after the deskew treatment, the linear terms are eliminated, and the following can be obtained:
Figure RE-GDA0002688408720000233
in the formula: a is the phase modulation factor, fEOMThe modulation frequency of the phase modulator, t is the time, L is the transmission optical path length of a single pass of the object, c is the speed of light, phiN-EOM(t) is the noise phase of the modulated signal, phi0-EOMIs the initial phase of the modulated signal;
then separately aligning the echo phase sequences
Figure RE-GDA0002688408720000234
And a reference phase sequence
Figure RE-GDA0002688408720000235
Performing quadrature demodulation processing:
in the echo phase sequence
Figure RE-GDA0002688408720000236
In the orthogonal demodulation process of (2), will
Figure RE-GDA0002688408720000237
And modulation signal cos 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000238
the same-phase baseband signal can be obtained after low-pass filtering
Figure RE-GDA0002688408720000239
Figure RE-GDA0002688408720000241
Then, will
Figure RE-GDA0002688408720000242
And modulation signal sin 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000243
the quadrature baseband signal can be obtained after low-pass filtering
Figure RE-GDA0002688408720000244
Figure RE-GDA0002688408720000245
Finally, the phase inversion by arctangent can be obtained:
Figure RE-GDA0002688408720000246
in reference phase sequence
Figure RE-GDA0002688408720000247
In the orthogonal demodulation process of (2), will
Figure RE-GDA0002688408720000248
And modulation signal cos 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000249
the same-phase baseband signal can be obtained after low-pass filtering
Figure RE-GDA00026884087200002410
Figure RE-GDA00026884087200002411
Then, will
Figure RE-GDA00026884087200002412
And modulation signal sin 2 pifEOMt]Multiplication, the following can be obtained:
Figure RE-GDA0002688408720000251
the quadrature baseband signal can be obtained after low-pass filtering
Figure RE-GDA0002688408720000252
Figure RE-GDA0002688408720000253
Finally, the phase inversion by arctangent can be obtained:
Figure RE-GDA0002688408720000254
respectively obtained by orthogonal solution
Figure RE-GDA0002688408720000255
And
Figure RE-GDA0002688408720000256
then, take the difference
Figure RE-GDA0002688408720000257
Figure RE-GDA0002688408720000258
In the formula: l is0Is the transmission optical path of the reference optical path one way;
taking into account the noise phase phi of the modulated signalN-EOM(t) and phi0-EOMCan be eliminated by difference;
the distance R between the laser radar transmitting end and the target point is finally obtained and can be expressed as:
Figure RE-GDA0002688408720000259
in the formula: c is the speed of light, fEOMIs the modulation frequency of the phase modulator;
the range resolution is expressed as:
Figure RE-GDA00026884087200002510
in the formula:
Figure RE-GDA00026884087200002511
is the differential dephasing resolution.
In this embodiment, the length of the transmission sequence is 1000 sine cycles, 10 μ s, the repetition frequency is 100kHz, the differential de-phasing precision reaches 10mrad, and the ranging resolution can reach 2.38 mm.
In conclusion, the ranging resolution depends on the differential dephasing resolution and the modulation frequency, so that the ranging resolution can be improved by improving the dephasing resolution or increasing the modulation frequency, the requirements on hardware such as a laser light source, detection receiving and the like can be reduced, the dependence of the frequency modulation continuous wave technology on the modulation linearity of the laser light source is avoided, and the coherent ranging and speed measurement of a long-distance target are realized; in addition, the differential phase-solving processing of the two paths of light beams is adopted, so that the phase-solving error can be greatly reduced after the differential phase-solving processing, the phase-solving precision is improved, and the distance measuring precision is correspondingly and greatly improved; the invention can independently obtain the Doppler frequency of the target without depending on distance measurement, thereby obtaining the radial speed and the direction of the radar platform relative to the target. The invention has good development prospect in the fields of vehicle-mounted, airborne and satellite-mounted laser radars.

Claims (6)

1. The coherent laser radar method for measuring distance and speed by phase modulation is characterized in that: an output light beam generated by a narrow-linewidth single-frequency continuous laser light source in the radar platform is polarized and then divided into a local oscillation light beam and an emission light beam by a first beam splitter; the emission beam is amplified after phase modulation and then transmitted to a second beam splitter to be divided into a detection beam and a reference beam, the detection beam is emitted to a target, and an echo beam carrying target distance and motion Doppler information is received; the local oscillation light beam is divided into a local oscillation first light beam and a local oscillation second light beam through a third beam splitter; the local oscillator first light beam and the echo light beam are subjected to coherent light frequency mixing through a first optical bridge, a first intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the first intermediate frequency signal to obtain first sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained first sampling data to obtain an echo phase sequence containing a target distance and a target speed; the local oscillator second light beam and the reference light beam are subjected to coherent light frequency mixing through a second optical bridge, a second intermediate frequency signal is obtained through balanced receiving, sampling processing is carried out on the second intermediate frequency signal to obtain second sampling data, and an on-site programmable gate array is used for carrying out arc tangent depacketization and unwrapping operation on the obtained second sampling data to obtain a reference phase sequence; subjecting the echo phase sequence to deskew processing and quadrature phase demodulation processing; subjecting the reference phase sequence to quadrature phase demodulation processing; and then carrying out phase difference processing on the processed echo phase sequence and the reference phase sequence to finally obtain the motion vector speed and the distance of the target.
2. The phase modulation distance measurement and speed measurement coherent laser radar method according to claim 1, characterized in that: laser light source produces the continuous coherent laser of unmodulated single-frequency single mode as output beam among the radar platform, and polarizer polarizing improves the polarization degree, shows as:
E0(t)＝E0 exp[j2πf0t+jφN0+jφ0]；
in the formula (f)0Is the frequency of the laser light source; phi is a0Is the output beam initial phase; phi is aN0Is the noise phase of the output beam; e0Is the output beam amplitude, t is the time,
Figure RE-FDA0002688408710000021
exp is an exponential function with a natural constant e as the base.
3. The phase modulation distance measurement and speed measurement coherent laser radar method according to claim 1, characterized in that: the output light beam is split by the first beam splitter, a small part of energy is used as a local oscillation light beam, the local oscillation light beam is split into a first local oscillation light beam and a second local oscillation light beam by the third beam splitter, and the light fields of the first local oscillation light beam and the second local oscillation light beam are uniformly expressed as follows:
ELO(t)＝ELO exp[j2πf0t+jφLO+jφ0]；
in the formula, ELOIs the local oscillator beam amplitude, phiLOIs the noise phase of the local oscillator beam; f. of0Is the frequency of the laser light source, phi0To output the initial phase of the beam, t is time,
Figure RE-FDA0002688408710000022
exp is an exponential function with a natural constant e as the base;
most of the energy is used as a radiation beam, and the radiation beam becomes:
EM(t)＝E0 exp{j2πf0t+jAcos[2πfEOMt+φN-EOM(t)+φ0-EOM]+jφN+jφ0}；
in the formula (f)EOMIs the modulation frequency of the phase modulator; phi is aN-EOM(t) is the noise phase of the modulated signal; phi is a0-EOMFor the initial phase of the modulated signal, A is the phase modulation factor, E0Is the output beam amplitude, f0Which is the frequency of the laser light source, t is the time,
Figure RE-FDA0002688408710000023
exp is an exponential function, φ, based on a natural constant e0Is the output beam initial phase; phi is aNIs the noise phase of the output beam.
4. The phase modulation ranging speed measuring coherent laser radar method according to claim 3, wherein: the emitted light beams are subjected to phase modulation, then are subjected to laser amplification and then are split by a second beam splitter, a small part of energy in the emitted light beams is used as a reference light beam, and a large part of energy is used as a detection light beam;
the reference beam is represented as:
Figure RE-FDA0002688408710000031
in the formula: time delay
Figure RE-FDA0002688408710000032
L0Is the transmission path of a single pass of the reference beam, ES-rIs the amplitude of the reference beam, c is the speed of light, phiN_rIs the noise phase of the reference beam;
the probe beam is transmitted to a target through the optical circulator, the optical scanner and the optical telescope, and an echo beam of the target is received by the optical telescope, wherein the echo beam is expressed as:
Figure RE-FDA0002688408710000033
wherein E isSIs the amplitude of the echo beam, phiSIs the noise phase of the echo beam; echo beam time delay
Figure RE-FDA0002688408710000034
L is the single pass optical path length of the target, c is the speed of light, V is the radial velocity of the target relative to the radar platform, phiN_sFor detecting the phase of the noise received by the optical path0-EOMFor modulating the initial phase of the signal, phiN-EOM(t) is the noise phase of the modulated signal;
the optical field after the echo light beam of the target and the local oscillator light beam are combined is represented as follows:
Figure RE-FDA0002688408710000041
the four outputs after being mixed by the 2 × 490 ° first optical bridge are respectively:
Figure RE-FDA0002688408710000042
in the formula ISIs a direct current quantity related to the echo beam; i isLOIs the direct current quantity related to the local oscillator beam; for the purpose of remote detection of the object,
Figure RE-FDA0002688408710000043
therefore, the method of firstly solving the mean value and then differentiating is adopted for eliminating; to obtain
Figure RE-FDA0002688408710000044
fDopplerThe Doppler frequency is caused by the relative motion radial velocity of the radar platform and the target;
the light field after the reference beam and the local oscillator two beams are combined is represented as follows:
Figure RE-FDA0002688408710000051
the four outputs after being mixed by the 2 × 490 ° second optical bridge are respectively:
Figure RE-FDA0002688408710000052
in the formula IS_rIs a direct current quantity related to the reference beam; i isLOIs the direct current quantity related to the local oscillator beam; due to the fact that
Figure RE-FDA0002688408710000053
Eliminating by adopting a method of firstly calculating the mean value and then differentiating;
synchronous receiving of the outputs of the first optical bridge and the second optical bridge is realized through an external trigger circuit;
the in-phase signal and the quadrature signal with the quadrature characteristic output by the first optical bridge are respectively received by the first photoelectric balanced detector to obtain a first intermediate frequency signal, and the in-phase signal and the quadrature signal in the first intermediate frequency signal output by the first photoelectric balanced detector are respectively:
Figure RE-FDA0002688408710000061
in the formula: k is a radical ofinIs the first photoelectric balanced detector responsivity, k, of the received in-phase signalquIs the first photo-balance detector responsivity receiving the quadrature signal;
if the response rates of the first photoelectric detectors for receiving the in-phase signals and the orthogonal signals are kept consistent, the in-phase signals and the orthogonal signals in the first intermediate frequency signals are respectively subjected to analog-to-digital conversion, collected by a field programmable gate array and obtained by arc tangent phase-splitting:
Figure RE-FDA0002688408710000062
then reconstructing the echo phase sequence of the target by a unwrapping algorithm due to phiN_S-φLOIs a slowly varying quantity that can be considered as a direct current quantity for one sequence duration, and is therefore eliminated by high-pass filtering, resulting in:
Figure RE-FDA0002688408710000063
the in-phase signal and the quadrature signal with the quadrature characteristic output by the second optical bridge are respectively received by the second photoelectric balanced detector to obtain a second intermediate frequency signal, and the in-phase signal and the quadrature signal in the second intermediate frequency signal output by the second photoelectric balanced detector are respectively:
Figure RE-FDA0002688408710000071
in the formula: k is a radical ofinIs the response rate, k, of a second photoelectric balanced detector receiving an in-phase signalquIs the second photo-balance detector responsivity receiving the quadrature signal;
if the response rates of the second photoelectric detectors for receiving the in-phase signals and the orthogonal signals are kept consistent, the in-phase signals and the orthogonal signals in the second intermediate frequency signals are respectively subjected to analog-to-digital conversion, collected by a field programmable gate array and obtained by arc tangent phase-splitting:
Figure RE-FDA0002688408710000072
then reconstructing the reference phase sequence by a unwrapping algorithmN_r-φLOIs a slowly varying quantity that can be considered as a direct current quantity for one sequence duration, and is therefore eliminated by high-pass filtering, and therefore:
Figure RE-FDA0002688408710000073
5. the phase modulation distance measurement and speed measurement coherent laser radar method according to claim 1, characterized in that: subjecting the echo phase sequence to deskew processing and quadrature phase demodulation processing; subjecting the reference phase sequence to quadrature phase demodulation processing; and then carrying out phase difference processing on the processed echo phase sequence and the reference phase information to finally obtain the motion vector speed and the distance of the target respectively, wherein the phase difference processing specifically comprises the following steps:
first, to echo phase sequence
Figure RE-FDA0002688408710000074
The slope K is obtained by deskewing, and the doppler frequency:
Figure RE-FDA0002688408710000081
because the Doppler frequency is in direct proportion to the radial velocity of the relative movement of the radar platform and the target, the positive frequency and the negative frequency of the Doppler frequency are related to the direction of the radial velocity of the relative movement of the radar platform and the target, the positive frequency represents that the radar platform and the target move in the opposite direction, and the negative frequency represents that the radar platform and the target move in the opposite direction; thus, the radial velocity V of the target relative to the radar platform relative to the target is expressed as:
Figure RE-FDA0002688408710000082
in the formula: lambda [ alpha ]0Is the laser wavelength;
obtaining the magnitude and the direction of the radial velocity V of the radar platform relative to the target by solving the magnitude and the positive and negative of the slope K;
after the deskew treatment, the linear terms are eliminated, and the following can be obtained:
Figure RE-FDA0002688408710000083
in the formula: a is the phase modulation factor, fEOMThe modulation frequency of the phase modulator, t is the time, L is the transmission optical path length of a single pass of the object, c is the speed of light, phiN-EOM(t) is the noise phase of the modulated signal, phi0-EOMIs the initial phase of the modulated signal;
then separately aligning the echo phase sequences
Figure RE-FDA0002688408710000085
And a reference phase sequence
Figure RE-FDA0002688408710000086
Performing quadrature demodulation processing:
in the echo phase sequence
Figure RE-FDA0002688408710000088
In the orthogonal demodulation process of (3), first, the orthogonal demodulation process of (2) will be performed
Figure RE-FDA0002688408710000087
And modulation signal cos 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-FDA0002688408710000084
the same-phase baseband signal can be obtained after low-pass filtering
Figure RE-FDA0002688408710000097
Figure RE-FDA0002688408710000091
Then, will
Figure RE-FDA0002688408710000098
And modulation signal sin 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-FDA0002688408710000092
the quadrature baseband signal can be obtained after low-pass filtering
Figure RE-FDA00026884087100000912
Figure RE-FDA0002688408710000093
Finally, the phase inversion by arctangent can be obtained:
Figure RE-FDA0002688408710000094
in reference phase sequence
Figure RE-FDA0002688408710000099
In the orthogonal demodulation process of (3), first, the orthogonal demodulation process of (2) will be performed
Figure RE-FDA00026884087100000910
And modulation signal cos 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-FDA0002688408710000095
the same-phase baseband signal can be obtained after low-pass filtering
Figure RE-FDA00026884087100000911
Figure RE-FDA0002688408710000096
Then, will
Figure RE-FDA00026884087100000913
And modulation signal sin 2 pi fEOMt]Multiplication, the following can be obtained:
Figure RE-FDA0002688408710000101
the quadrature baseband signal can be obtained after low-pass filtering
Figure RE-FDA0002688408710000107
Figure RE-FDA0002688408710000102
Finally, the phase inversion by arctangent can be obtained:
Figure RE-FDA0002688408710000103
respectively obtained by orthogonal solution
Figure RE-FDA0002688408710000109
And
Figure RE-FDA00026884087100001010
then, take the difference
Figure RE-FDA00026884087100001011
Figure RE-FDA0002688408710000104
In the formula: l is0Is the transmission optical path of the reference beam one way; l is the target single pass transmission path length due to the noise phase phi of the modulated signalN-EOM(t) and phi0-EOMAnd eliminating by difference, and finally obtaining the distance R between the laser radar transmitting end and the target point as:
Figure RE-FDA0002688408710000105
in the formula: c is the speed of light, fEOMIs the modulation frequency of the phase modulator;
the range resolution is expressed as:
Figure RE-FDA0002688408710000106
in the formula:
Figure RE-FDA0002688408710000108
is the differential dephasing resolution.
6. Device for implementing the phase modulation ranging velocimetry coherent lidar method according to any of claims 1-5, characterized in that: the linear frequency modulation continuous wave laser device comprises a laser light source (1), wherein the output end of the linear frequency modulation continuous wave laser light source (1) is sequentially connected with a polarizer (2) and a first beam splitter (3), and the first beam splitter (3) is connected with a phase modulator (4) and a third beam splitter (5); the output end of the phase modulator (4) is sequentially connected with a laser amplifier (6) and a second beam splitter (7); the output end of the second beam splitter (7) is sequentially connected with an optical circulator (8), an optical scanner (9) and an optical telescope (10);
the third beam splitter (5) and the optical circulator (8) are connected with a first optical bridge (11), and the first optical bridge (11) is connected with a first analog-to-digital converter (13) through a first photoelectric balance detector (12);
the second beam splitter (7) and the third beam splitter (5) are connected with a second optical bridge (14), and the second optical bridge (14) is connected with a second analog-to-digital converter (16) through a second photoelectric balance detector (15);
the first analog-to-digital converter (13) and the second analog-to-digital converter (16) are connected with a field programmable gate array (17) together, and the output end of the field programmable gate array (17) is connected with a main control computer (18); the main control computer (18) is connected with an external trigger circuit (19), and the external trigger circuit (19) is connected with the phase modulator (4) through a radio frequency driver (20); the external trigger circuit (19) is respectively connected with the first analog-to-digital converter (13) and the second analog-to-digital converter (16); the main control computer (18) is also connected with the optical scanner (9).
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CN112285684A (en) * 2020-12-29 2021-01-29 南昌大学 Relative motion speed tracking method and device, readable storage medium and electronic equipment
CN112684465A (en) * 2020-12-28 2021-04-20 昂纳信息技术（深圳）有限公司 Detection system and detection method based on phase modulation coded pulse
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WO2022119973A1 (en) * 2020-12-02 2022-06-09 Waymo Llc Dynamic sensing channel multiplexing for lidar applications
WO2022132822A1 (en) * 2020-12-14 2022-06-23 Waymo Llc Lidar devices with frequency and time multiplexing of sensing signals
CN115210603A (en) * 2021-10-20 2022-10-18 深圳市速腾聚创科技有限公司 Laser radar and laser radar control method
CN115685235A (en) * 2022-10-13 2023-02-03 南京工业大学 Optical phase tracking system for measuring fast time-varying signals
CN115685235B (en) * 2022-10-13 2024-05-03 南京工业大学 Optical phase tracking system for measuring fast time-varying signals

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022119973A1 (en) * 2020-12-02 2022-06-09 Waymo Llc Dynamic sensing channel multiplexing for lidar applications
CN112230238A (en) * 2020-12-09 2021-01-15 武汉光谷航天三江激光产业技术研究院有限公司 Laser intensity modulation distance and speed measuring method and system, terminal device and storage medium
CN112230238B (en) * 2020-12-09 2021-04-23 武汉光谷航天三江激光产业技术研究院有限公司 Laser intensity modulation distance and speed measuring method and system, terminal device and storage medium
WO2022132822A1 (en) * 2020-12-14 2022-06-23 Waymo Llc Lidar devices with frequency and time multiplexing of sensing signals
CN112684460B (en) * 2020-12-21 2024-03-22 武汉光目科技有限公司 Area array sweep frequency measuring device and method
CN112684460A (en) * 2020-12-21 2021-04-20 武汉光目科技有限公司 Area array sweep frequency measuring device and method
CN112684465A (en) * 2020-12-28 2021-04-20 昂纳信息技术（深圳）有限公司 Detection system and detection method based on phase modulation coded pulse
CN112285684B (en) * 2020-12-29 2021-03-16 南昌大学 Relative motion speed tracking method and device, readable storage medium and electronic equipment
CN112285684A (en) * 2020-12-29 2021-01-29 南昌大学 Relative motion speed tracking method and device, readable storage medium and electronic equipment
CN115210603A (en) * 2021-10-20 2022-10-18 深圳市速腾聚创科技有限公司 Laser radar and laser radar control method
CN115210603B (en) * 2021-10-20 2023-06-23 深圳市速腾聚创科技有限公司 Laser radar and laser radar control method
CN115685235A (en) * 2022-10-13 2023-02-03 南京工业大学 Optical phase tracking system for measuring fast time-varying signals
CN115685235B (en) * 2022-10-13 2024-05-03 南京工业大学 Optical phase tracking system for measuring fast time-varying signals

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