CN113917474A - Laser ranging method, laser ranging system and laser radar system thereof - Google Patents
Laser ranging method, laser ranging system and laser radar system thereof Download PDFInfo
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Abstract
The invention provides a laser ranging system, a laser radar system and a ranging method thereof, wherein the laser ranging method comprises the following steps: modulating the phase of the laser beam into a laser beam with a preset phase, splitting the modulated laser beam into a local oscillator beam and a probe beam, wherein the probe beam is incident to a target to be measured and then reflected into an echo beam; mixing the local oscillator light beam and the echo light beam to obtain a mixed light signal; performing photoelectric conversion on the mixed optical signal to obtain an analog electric signal; and analyzing the analog electric signal to obtain the distance between the object to be measured and the target. The invention provides a novel laser ranging system, a laser radar system and a ranging method thereof, which improve the signal-to-noise ratio by utilizing the principle of coherent detection, measure longer distance under the condition of low power and improve resolution; meanwhile, the phase modulation is simple, and the phase modulation technology is easy to realize.
Description
Technical Field
The invention belongs to the technical field of laser radars, and particularly relates to a laser ranging method, a laser ranging system and a laser radar system thereof.
Background
Lidar technology is a new product with unique advantages that combines laser with traditional radar technology. By utilizing the advantages of small laser emission angle, concentrated energy and high coherence, the laser radar technology can realize special advantages which are not possessed by the traditional radar technology. Compared with the traditional radar system, the laser radar has higher data acquisition density and can obtain various images; moreover, the emission angle of the laser is small, the energy is concentrated, the detection distance of the laser radar is longer, the resolution is higher, and the anti-interference capability is stronger; distance and speed information can be obtained simultaneously by combining different detection methods; compared with the size of the traditional radar, the laser radar is small in size, light in weight and convenient to combine with various applications.
The common ranging methods adopted by the laser radar are a pulse ranging method, a frequency modulation continuous wave method, a phase difference ranging method and the like. The pulse ranging method is relatively mature and simple in principle, but the laser power must be increased for increasing the signal-to-noise ratio when the distance is far away, which brings some non-negligible problems. Such as eye safety issues, problems with not adapting to some radar systems, etc. The frequency modulation continuous wave mode is used as a distance measurement method, and the optical flight time is indirectly measured through intermediate frequency signals by mixing between local oscillation signals and echo signals. Under the condition of lower echo power, a sufficiently high signal-to-noise ratio can be still obtained, and the requirement on the transmission power is reduced. However, the method requires a narrow line width of the laser, a high frequency modulation bandwidth, high linearity, great technical difficulty and high component cost, so that the method cannot be applied to the civil market, the price of the common laser light source meeting the requirements on the market reaches tens of thousands of yuan, and the related technology is relatively immature. The phase difference distance measurement principle cannot realize long-distance measurement, the distance measurement precision has a great relationship with the phase quality of echo signals, a better distance measurement effect is often realized by cooperation with a target, and the method is often only applied to a handheld short-distance measuring instrument.
Disclosure of Invention
The invention overcomes the defects of the prior art and provides a laser ranging method, a laser ranging system and a laser radar system thereof.
The invention provides a laser ranging method, which comprises the following steps:
s1, modulating the laser beam into a laser beam with a preset phase after phase modulation, splitting the modulated laser beam into a local oscillator beam and a probe beam, wherein the probe beam is incident to a target to be measured and then reflected into an echo beam;
s2, mixing the local oscillator light beam and the echo light beam to obtain a mixing optical signal;
s3, performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;
and S4, analyzing the analog electric signal to obtain the distance between the object to be measured and the target.
Further, in step S1, the preset phase is expressed as formula (1) and formula (2):
wherein,
representing a preset phase, a, b respectively representing unequal constants, T representing time, x representing an integer, and T representing a period.
Further, step S4 is specifically:
s401, analyzing the analog electric signal according to the formulas (3) to (6) to obtain the flight time, wherein the formulas (3) to (6) are as follows:
I＝IT+IR+ATARcos[ωPhτ+a-b]，(0+xT≤t<τ+xT) (3)
wherein I represents the intensity of the mixed optical signal, ITIndicating the light intensity of the local oscillator beam, IRRepresenting the intensity of the echo beam, ATIndicating the amplitude of the local oscillator beam, ARRepresenting the amplitude, omega, of the echo beamPhRepresenting the optical frequency of the local oscillator light beam, and tau representing the flight time, which is the time interval between the detection light beam and the echo light beam;
s402, substituting the flight time tau into a formula (7) to obtain the distance to the target to be measured, wherein the formula (7) is as follows:
where s represents the distance to the target to be measured.
The present invention also provides a laser ranging system, comprising: the device comprises a laser, a phase modulator, a signal generator, a beam splitting unit, a coupler, a photoelectric detector and a data acquisition and analysis unit; wherein,
the laser is used for emitting laser beams; the phase modulator is used for modulating the phase of the laser beam; the signal generator is used for controlling the phase modulator to generate a phase modulation signal and outputting a preset phase; the beam splitting unit is used for splitting the laser beam into a local oscillator beam and a detection beam, the local oscillator beam is incident to the coupler, the detection beam is reflected into an echo beam after being incident to the target to be measured, and the echo beam is incident to the coupler; the coupler is used for mixing the local oscillation light beam and the echo light beam, the photoelectric detector is used for converting the optical signal into an analog electric signal, and the data acquisition and analysis unit is used for acquiring and analyzing the analog electric signal; and obtaining the distance between the laser ranging system and the target to be measured.
Further, the optical fiber amplifier is used for amplifying the power of the laser beam emitted by the laser.
Further, a collimator for collimating the probe beam and the echo beam is also included.
Further, the beam splitting unit includes a beam splitter and a circulator;
laser beams output by the phase modulator are incident to the beam splitter and are divided into local oscillation beams and detection beams, the local oscillation beams are incident to the coupler, the detection beams are incident to the circulator, the detection beams emitted by the circulator are collimated by the collimator and then incident to a target to be measured, echo beams are formed after being reflected by the target to be measured, are incident to the collimator and then are incident to the coupler and are mixed with the local oscillation beams.
Furthermore, the laser ranging system also comprises a galvanometer for scanning, so that the establishment of the laser radar system is realized. The detection light beam split by the beam splitting unit is incident to the vibrating mirror, the detection light beam emitted by the vibrating mirror is incident to the target to be measured, and the detection light beam is reflected by the target to be measured to form an echo light beam which is incident to the vibrating mirror and then is incident to the coupler.
The present invention also provides a laser radar system comprising: the device comprises a laser, a beam splitting unit, an optical phased array chip, a signal generator, a coupler, a photoelectric detector and a data acquisition and analysis unit; wherein,
the laser is used for emitting laser beams; the beam splitting unit is used for splitting the laser beam into a local oscillation beam and a detection beam; the local oscillation light beam and the detection light beam are incident to the optical phased array chip, and the optical phased array chip outputs a laser light beam for scanning; the signal generator is used for sending a phase modulation signal to the optical phased array chip and controlling the optical phased array chip to output a preset phase; the optical phased array chip receives the echo light beam, the echo light beam is transmitted to the beam splitting unit and enters the coupler through the beam splitting unit, and the coupler is used for mixing the local oscillator light beam and the echo light beam to form a mixing optical signal; the photoelectric detector is used for converting the mixing optical signal into an analog electrical signal, and the data acquisition and analysis unit is used for acquiring and analyzing the analog electrical signal to obtain the distance between the laser ranging system and the target to be measured.
The invention also provides a laser radar system, which comprises a laser, a beam splitting unit, an optical phased array chip, a signal generator, a phase modulator, a coupler, a photoelectric detector and a data acquisition and analysis unit,
the laser is used for emitting laser beams; the laser beam is subjected to phase modulation through a phase modulator; the signal generator is used for controlling the phase modulator to generate a phase modulation signal and outputting a preset phase; the laser beam output by the phase modulator is divided into a local oscillation beam and a detection beam by a beam splitting unit; the local oscillation light beam and the detection light beam are incident to the optical phased array chip, and the optical phased array chip outputs a laser light beam for scanning; the local oscillator light beam is incident to the coupler, the detection light beam is reflected into an echo light beam after being incident to a target with a distance to be measured, the optical phased array chip receives the echo light beam, the echo light beam is transmitted to the beam splitting unit and is incident to the coupler through the beam splitting unit, and the local oscillator light beam and the echo light beam are mixed in the coupler to form a frequency mixing optical signal; the photoelectric detector is used for converting the mixing optical signal into an analog electric signal; the data acquisition and analysis unit is used for acquiring and analyzing the analog electric signal to obtain the distance between the laser ranging system and the target to be measured.
Compared with the prior art, the invention has the beneficial effects that:
the laser ranging method, the laser ranging system and the laser radar system effectively solve the problem of eye safety caused by overhigh instantaneous power in the traditional pulse ranging method; the problems of high difficulty and high cost of the frequency modulation continuous wave technology are solved; and the method can realize remote detection and make up for the defects of a phase difference detection method. The laser ranging method, the laser ranging system and the laser radar system thereof provide a novel phase modulation laser ranging system and a ranging method, namely, the signal-to-noise ratio is improved by utilizing the principle of coherent detection, and the longer distance is measured and the resolution is improved under the condition of lower power; meanwhile, the laser ranging system provided by the invention is simple in phase modulation, and the phase modulation technology is easy to realize.
Drawings
Fig. 1 is a schematic view of a first structure of a laser ranging system in embodiment 1 of the present invention;
fig. 2 is a schematic view of a second structure of a laser ranging system in embodiment 1 of the present invention;
fig. 3 is a schematic diagram of the structure of a laser radar system in embodiment 2 of the present invention;
FIG. 4 is a schematic diagram showing the structure of a lidar system according to embodiment 3 of the present invention
Fig. 5 is a schematic view of a flow of a laser ranging method in embodiment 4 of the present invention;
fig. 6 is a schematic diagram of a phase modulation signal in embodiment 4 of the present invention;
fig. 7 is a schematic diagram of a mixed optical signal in embodiment 4 of the present invention.
Wherein the reference numerals are as follows:
the device comprises a laser 1, a phase modulator 2, a signal generator 3, a beam splitter 4, a circulator 5, a target 6 to be measured, a coupler 7, a photoelectric detector 8, a data acquisition and analysis unit 9, an amplifier 10, a collimator 11, a vibrating mirror 12, an optical phased array chip 13 and a local oscillation light beam LOProbe beam TXEcho light beam RX。
Detailed Description
The embodiments of the present invention will be described in further detail with reference to the drawings and examples. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. 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.
Example 1:
fig. 1 shows a schematic structural diagram of a laser ranging system in embodiment 1 of the present invention.
As shown in fig. 1, an embodiment of the present invention provides a laser ranging system, including: the device comprises a laser 1, a phase modulator 2, a signal generator 3, a beam splitter 4, a circulator 5, a coupler 7, a photoelectric detector 8 and a data acquisition and analysis unit 9.
The laser 1 is used for emitting laser beams, the laser beams are subjected to phase modulation through the phase modulator 2, and the signal generator 3 is used for controlling the phase modulator 2 to generate phase modulation signals and outputting preset phases. The signal generator is connected with the electrode of the phase modulator, outputs a designated signal, controls the laser beam to have a preset phase, and can adopt an electro-optical modulator such as a lithium niobate phase modulator. The laser beam output by the phase modulator 2 is incident on the beam splitter 4 and is divided into a local oscillation beam LOAnd a probe beam TXLocal oscillator beam LOIncident to the coupler 7 and the echo beam RXMixing the frequency, detecting the light beam TXIncident on the circulator 5, and the probe beam T emitted from the circulator 5XThe light is collimated by the collimator 11 and then enters the target 6 to be measured, and is reflected by the target 6 to be measured to form an echo light beam RXThe light beam enters the collimator 11 for collimation and then enters the coupler 7 and the local oscillator light beam LOMixing is performed to form a mixed optical signal. Probe beam TXWhen encountering a target 6 with a distance to be measured, the target is reflected to generate an echo signal, and an echo light beam R is formedX. The mixed optical signal is converted into an analog electrical signal by the photoelectric detector 8, and the data acquisition and analysis unit 9 acquires and analyzes the analog electrical signal to obtain the distance between the laser ranging system and the target 6 to be measured. The data acquisition and analysis unit 9 in the embodiment of the present invention may use a TDC time-to-digital converter to directly time, so as to measure the pulse width of the analog electrical signal, or use an ADC analog-to-digital converter to count and time, so as to acquire the pulse waveform of the analog electrical signal and then analyze the pulse waveform; the coupler 7 uses a 2 x 2 fiber coupler 7 for mixing. The principle of phase modulation in embodiment 1 of the present invention is not limited, and may be thermo-optic modulation, for example: heating the waveguide, changing the temperature, changing the refractive index of the waveguide, changing the optical phase, and also electro-optical modulation, for example: the waveguide is doped with P type and N type, PN junction voltage is adjusted, the number of carriers in the waveguide is adjusted, refractive index is adjusted, phase is adjusted, and the light beam can be modulated externally, such as: a lithium niobate phase modulator is added. Can be based on the practiceThe case is selected, and the present invention is not limited to this case in example 1.
From the above, the laser ranging system provided by the invention adopts the characteristic that the phase modulator 2 and the signal generator 3 can control the phase of the laser beam, so as to realize the detection of the phase modulation laser on the target 6 to be measured. The embodiment of the invention provides no high requirements on the line width, the frequency modulation bandwidth and the linearity of the laser 1 in the laser ranging system, so that the cost is reduced compared with that of a frequency modulation continuous wave mode as a ranging method. The related technology of the high laser 1 with narrow line width, high frequency modulation bandwidth and high linearity is not mature, and the laser ranging system provided by the embodiment of the invention effectively avoids hidden troubles caused by using an immature technology. The laser ranging system provided by the invention utilizes the principle of coherent detection and uses a local oscillator signal (namely a local oscillator light beam L)O) With echo signals (i.e. echo beam R)X) Mixing, i.e. echo-light beam RXWeak but due to local oscillator beam LOThe power is enough, so that the signal to noise ratio can still be guaranteed to be high. The power of the laser beam emitted by the laser 1 does not need to be improved in the remote detection, so that the safety problem of human eyes does not exist. The laser ranging system provided by the invention utilizes the local oscillator light beam LOAnd an echo light beam RXAnd the frequency mixing is carried out, so that higher signal-to-noise ratio can be realized even if the remote measurement is carried out, the feasibility of the remote measurement is ensured, and the defect problem of a phase difference detection method is solved.
In the preferred embodiment 1 of the present invention, the laser ranging system further includes an optical fiber amplifier 10 for amplifying the power of the laser beam emitted by the laser 1. If the power of the laser 1 in the laser ranging system is not high enough, the optical fiber amplifier 10 may be used for amplification, so that in the embodiment provided by the present invention, not only the laser 1 with high power may be used, but also the optical fiber amplifier 10 may be used to cooperate with the laser 1 with low power to complete ranging.
In an embodiment 1 of the present invention, a preferable scheme is provided, and the laser ranging system further includes a system for transmitting the probe beam and the echo beam RXA collimator 11 for performing collimation.
Fig. 2 is a second schematic structural diagram of the laser ranging system in embodiment 1 of the present invention.
The embodiment 1 of the invention provides a preferable scheme, and the laser ranging system further comprises a galvanometer for scanning, so that the establishment of the laser radar system is realized. As shown in FIG. 2, the laser ranging system further includes a galvanometer 12 for scanning, and a probe beam T divided by the beam splitting unitXA detection beam T incident on the galvanometer 12 and emitted through the galvanometer 12XIncident to the target 6 to be measured and reflected by the target 6 to be measured to form an echo light beam RXThe light enters the polarizer 12 and then enters the coupler 7. By combining the scheme of the galvanometer 12 to perform scanning, the laser ranging system provided by embodiment 1 of the invention not only can measure distance, but also has a scanning function.
Example 2:
fig. 3 is a schematic structural diagram showing a laser radar system in embodiment 2 of the present invention.
As shown in fig. 3, embodiment 2 of the present invention provides a laser radar system including: the device comprises a laser 1, an optical fiber amplifier 10, a beam splitting unit, an optical phased array chip 13, a signal generator 3, a coupler 7, a photoelectric detector 8 and a data acquisition and analysis unit 9.
The laser device 1 is used for emitting laser beams, the beam splitting unit is used for splitting the beams, the optical phased array chip 13 outputs laser beams for scanning, the signal generator 3 is used for emitting phase modulation signals to the optical phased array chip 13 and controlling the optical phased array chip 13 to output preset phases, the coupler 7 is used for mixing different beams, the photoelectric detector 8 is used for converting optical signals into analog electric signals, and the data acquisition and analysis unit 9 is used for acquiring and analyzing the analog electric signals. This embodiment 2 provides a preferred technical solution for an optical fiber amplifier 10 for amplifying the power of a laser beam emitted from a laser 1. If the power of the laser 11 in the laser radar system is not high enough, the optical fiber amplifier 10 may be used for amplification, so that in the embodiment provided by the present invention, not only the laser 11 with high power may be used, but also the optical fiber amplifier 10 may be used to cooperate with the laser 11 with low power to complete ranging.
Laser beams are incident to the optical phased array chip 13 through the beam splitting unit and output after phase modulation, the laser beams output by the optical phased array chip 13 comprise local oscillator beams and detection beams, the local oscillator beams are incident to the coupler 7, the detection beams are reflected into echo beams after being incident to the target 6 to be measured, the optical phased array chip 13 receives the echo beams, the echo beams are transmitted to the beam splitting unit and are incident to the coupler 7 through the beam splitting unit, the local oscillator beams and the echo beams are subjected to frequency mixing in the coupler 7 to form frequency mixing optical signals, the frequency mixing optical signals are converted into analog electric signals through the photoelectric detector 8, the data acquisition and analysis unit 9 acquires and analyzes the analog electric signals, and the distance between the laser radar system and the target 6 to be measured is obtained. The beam splitting unit in the embodiment of the present invention is a circulator 5, and a coupler 7 adopts a 2 × 2 fiber coupler 7 for frequency mixing. The principle of phase modulation in embodiment 2 of the present invention is not limited, and may be thermo-optic modulation, for example: heating the waveguide, changing the temperature, changing the refractive index of the waveguide, changing the optical phase, and also electro-optical modulation, for example: the waveguide is doped with P type and N type, PN junction voltage is adjusted, the number of carriers in the waveguide is adjusted, refractive index is adjusted, phase is adjusted, and the light beam can be modulated externally, such as: a lithium niobate phase modulator 2 is added. The selection can be made according to the actual situation, which is not limited in embodiment 2 of the present invention.
From the above, the laser radar system provided by the present invention adopts the characteristics that the optical phased array chip 13 and the signal generator 3 can control the phase of the laser beamAnd further, the detection of the target 6 to be measured by the phase modulation laser is realized. The embodiment of the invention provides no high requirements on the line width, the frequency modulation bandwidth and the linearity of the laser 1 in the laser radar system, so that the cost is reduced compared with a frequency modulation continuous wave mode as a distance measurement method. The related technology of the high laser 1 with narrow line width, high frequency modulation bandwidth and high linearity is not mature, and the laser radar system provided by the embodiment of the invention effectively avoids hidden troubles brought by using an immature technology. The laser radar system provided by the invention utilizes the principle of coherent detection and uses local oscillator signals (namely local oscillator light beams L)O) With echo signals (i.e. echo beam R)X) Mixing, i.e. echo-light beam RXWeak but due to local oscillator beam LOThe power is enough, so that the signal to noise ratio can still be guaranteed to be high. The power of the laser beam emitted by the laser 1 does not need to be improved in the remote detection, so that the safety problem of human eyes does not exist. The laser radar system provided by the invention utilizes the local oscillator light beam LOAnd an echo light beam RXAnd the frequency mixing is carried out, so that higher signal-to-noise ratio can be realized even if the remote measurement is carried out, the feasibility of the remote measurement is ensured, and the defect problem of a phase difference detection method is solved.
This embodiment 2 provides a preferred technical solution for an optical fiber amplifier 10 for amplifying the power of a laser beam emitted from a laser 1. If the power of the laser 11 in the laser radar system is not high enough, the optical fiber amplifier 10 may be used for amplification, so that in the embodiment provided by the present invention, not only the laser 1 with high power may be used, but also the optical fiber amplifier 10 may be used to cooperate with the laser 1 with low power to complete ranging.
Example 3:
fig. 4 is a schematic structural diagram showing a laser radar system in embodiment 3 of the present invention.
An embodiment 2 of the present invention provides a preferable scheme, and as shown in fig. 4, a laser radar system includes a laser 1, a phase modulator 2, an optical fiber amplifier 10, a beam splitting unit, an optical phased array chip 13, a signal generator 3, a coupler 7, a photodetector 8, and a data acquisition and analysis unit 9. The beam splitting unit is a circulator 5. LaserThe laser beam emitted by the device 1 is subjected to phase modulation through the phase modulator 2, the signal generator 3 is used for controlling the phase modulator 2 to generate a phase modulation signal and output a preset phase, the laser beam output by the phase modulator 2 is incident to the optical phased array chip 13 through the circulator 5 and is output after being subjected to phase modulation again, and the laser beam output by the optical phased array chip 13 comprises a local oscillator beam LOAnd a probe beam TXLocal oscillator beam LOIncident on the coupler 7, the probe beam TXIs reflected into an echo light beam R after being incident on a target 6 with a distance to be measuredXThe optical phased array chip 13 receives the echo beam RXEcho light beam RXTransmitted to the beam splitting unit, and then incident on the coupler 7 via the beam splitting unit to generate local oscillation light beam LOAnd an echo light beam RXThe mixed optical signal is mixed by the coupler 7. The photodetector 8 is used for converting the optical signal into an analog electrical signal, and the data acquisition and analysis unit 9 is used for acquiring and analyzing the analog electrical signal. This embodiment 3 provides a preferred technical solution for an optical fiber amplifier 10 for amplifying the power of a laser beam emitted from a laser 1. If the power of the laser 11 in the laser radar system is not high enough, the optical fiber amplifier 10 may be used for amplification, so that in the embodiment provided by the present invention, not only the laser 11 with high power may be used, but also the optical fiber amplifier 10 may be used to cooperate with the laser 11 with low power to complete ranging.
Example 4:
fig. 5 is a schematic flow chart illustrating a laser ranging method in embodiment 4 of the present invention.
As shown in fig. 5, embodiment 4 of the present invention provides a laser ranging method, which specifically includes the following steps:
s1, phase modulating the laser beam into a laser beam with a preset phase, splitting the modulated laser beam into partial local oscillation beam LOThe other part of the probe beam is phase-modulated to become a probe beam T with a preset phaseXThe probe beam is reflected to become an echo beam T after being incident on the target to be measuredX。
Laser beam generated by the laser 1, phase-shiftedThe modulated light is divided into two parts, namely local oscillation light beam LOAnd a probe beam TXProbe beam TXIs reflected into an echo light beam R after being incident on a target 6 with a distance to be measuredXWherein the echo beam RXCarrying an echo signal.
S2, local oscillation light beam LOAnd an echo beam TXThe mixed optical signal is obtained by mixing through the coupler 7.
S3, in embodiment 4 of the present invention, the mixed optical signal is subjected to photoelectric conversion by the photodetector 8, and an analog electrical signal is obtained.
And S4, analyzing the analog electric signal to obtain the distance between the object to be measured and the target. The data acquisition and analysis unit 9 acquires and analyzes the analog electrical signal to obtain the distance to be measured from the target.
The laser ranging method provided by the embodiment 4 of the invention utilizes the principle of coherent detection and uses the local oscillator light beam LOAnd the echo light beam RXMixing, i.e. echo beams RXBut due to local oscillator beam LOThe power is enough, so the signal-to-noise ratio can still be guaranteed. This eliminates the need to increase the power of the emitted light at long range detection, and thus eliminates the eye safety problem.
Fig. 6 shows a schematic diagram of a phase modulation signal in embodiment 4 of the present invention. In step S1, as shown in fig. 6, the signal generator 3 controls the phase modulator 2 to generate a phase modulation signal and output a preset phase, where the preset phase is expressed as formula (1) and formula (2):
wherein a and b respectively represent unequal constants, T represents time, x represents an integer, and T represents a period.
I＝IT+IR+ATARcos[ωPhτ+a-b]，(0+xT≤t<τ+xT) (3)
wherein I represents the intensity of the mixed optical signal, ITIndicating the local oscillator beam LOLight intensity of (1)RRepresenting an echo beam RXLight intensity of (A)TIndicating the local oscillator beam LOAmplitude of (A)RRepresenting an echo beam RXAmplitude of (a), ωPhIndicating the local oscillator beam LOIs the probe beam T, and tau represents the time of flightXAnd an echo light beam RXWherein τ represents the time of flight, is the probe beam TXAnd an echo light beam RXThe time interval of (c).
The following detailed description of the technical solution provided by embodiment 4 of the present invention relates to the detection principle, and the local oscillator light beam LOLight field E ofTxLight field E of the echo light beam RxRxAs shown in equation (7) and equation (8):
wherein A isTAnd ARAre all constant and are all provided with the same power,
indicating the local oscillator beam LOPredetermined phase of (a), omegaPhIndicating the local oscillator beam LOT denotes time, τ is the probe beam TXAnd an echo light beam RXThe total time of (c).
The local oscillator beam LOA new light field E generated after coherent superposition with the echo light beam RxGeneral assemblyAs shown in formula (9):
since the light intensity is proportional to the square of the light field, the local oscillator light beam L is further generatedOThe light intensity I after coherent superposition with the echo light beam Rx is shown in formula (10):
since the light intensity is proportional to the square of the light field, the local oscillator beam LOLight intensity ofTAnd an echo light beam RXLight intensity ofRRespectively shown in formula (11) and formula (12):
the formula (10) is arranged through the formula (11) and the formula (12), and the arrangement is shown as the formula (13):
the light intensity I of equation (13) is transformed using the trigonometric function equation, as shown in equation (14):
due to the fact that
Is a term with extremely high frequency, to which the photodetector 8 cannot respond, and therefore can be ignored, and the obtained light intensity I is shown in formula (15):
the preset phase formula (1) and the preset phase formula (2) are arranged to obtain a formula (16) and a formula (17):
substituting the formula (16) and the formula (17) into the formula (17) for arrangement to obtain the formula (3) -the formula (6).
I＝IT+IR+ATARcos[ωPhτ+a-b]，(0+xT≤t<τ+xT) (3)
Fig. 7 shows a schematic diagram of a waveform diagram of the mixed optical signal obtained according to formula (3) -formula (6) in the present embodiment. As shown in fig. 7, the waveform diagram of the photodetection signal (it should be noted that fig. 7 is a schematic diagram for convenience of explanation only) and the equations (3) to (6) of the light intensity I are shown, IT+IRIs a detectable local oscillator beam LOAnd the sum of the light intensity of the echo light beam Rx as a detectable parameter; a. theT、ARThe waveform is the relative amplitude, which is the parameter that can be obtained by the method shown in FIG. 7; omegaPhτ, a, b are all constants, and the time of flight τ can be obtained by reading the width of the mixed optical signal pulse in fig. 7. Acquiring the flight time tau, and acquiring distance data between the laser ranging system and the target 6 to be measured through a formula (18), wherein the formula (18) is as follows:
where c is the speed of light and s represents the distance between the laser ranging system and the target 6.
In the laser ranging method provided in embodiment 4 of the present invention, the distance of the target 6 to be measured can be obtained according to the above formula, that is, the signal-to-noise ratio is improved by using the principle of coherent detection, a longer distance can be measured even if the echo signal is weak, and high resolution is maintained. The waveform of the phase modulation in the laser ranging method provided by embodiment 4 of the present invention is easier to implement, the phase modulation in the laser ranging method provided by embodiment 4 of the present invention is a modulation in which the waveform is a square wave, and for changing the phase of the laser beam, the phase modulation can be implemented only by applying a square wave electric signal. While the phase modulation in the prior art is generally a quadratic waveform, the waveform requires a more complex electrical signal and many calibration procedures to achieve the desired phase modulation. Therefore, the phase modulation of the laser ranging method provided by the embodiment 4 of the invention is simple and easy to realize.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be taken as limiting the invention. Variations, modifications, substitutions and alterations of the above-described embodiments may be made by those of ordinary skill in the art without departing from the scope of the present invention.
The above embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A laser ranging method is characterized by comprising the following steps:
s1, modulating the laser beam into a laser beam with a preset phase after phase modulation, splitting the modulated laser beam into a local oscillator beam and a probe beam, wherein one part of the local oscillator beam and the other part of the local oscillator beam are reflected into an echo beam after the probe beam is incident to a target to be measured;
s2, mixing the local oscillator light beam and the echo light beam to obtain a mixed light signal;
s3, performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;
and S4, analyzing the analog electric signal to obtain the distance of the target to be measured.
2. The laser ranging method according to claim 1, wherein the preset phase is expressed as formula (1) and formula (2) in the step S1:
wherein,
representing a preset phase, a, b respectively representing unequal constants, T representing time, x representing an integer, and T representing a period.
3. The laser ranging method according to claim 1, wherein the step S4 specifically comprises:
s401, analyzing the analog electric signal according to formulas (3) - (6) to obtain the flight time, wherein the formulas (3) - (6) are as follows:
I＝IT+IR+ATARcos[ωPhτ+a-b]，(0+xT≤t<τ+xT) (3)
wherein I represents the light intensity of the mixed optical signal, ITRepresenting the light intensity, I, of the local oscillator beamRRepresenting the light intensity of said echo beam, ATRepresenting the amplitude, A, of the local oscillator beamRRepresenting the amplitude, ω, of said echo beamPhRepresenting the optical frequency of the local oscillator light beam, and representing the flight time by tau, wherein the flight time is the time interval between the detection light beam and the echo light beam;
s402, substituting the flight time tau into a formula (7) to obtain the distance between the target to be measured and the target, wherein the formula (7) is as follows:
wherein s represents the distance of the target to be measured.
4. A laser ranging system, comprising: the device comprises a laser, a phase modulator, a signal generator, a beam splitting unit, a coupler, a photoelectric detector and a data acquisition and analysis unit; wherein,
the laser is used for emitting laser beams; the phase modulator is used for performing phase modulation on the laser beam; the signal generator is used for controlling the phase modulator to generate a phase modulation signal and outputting a preset phase; the beam splitting unit is used for splitting the laser beam into a local oscillator beam and a probe beam, the local oscillator beam is incident to the coupler, the probe beam is reflected into an echo beam after being incident to a target to be measured, and the echo beam is incident to the coupler; the coupler is used for mixing the local oscillator light beam and the echo light beam; the photoelectric detector is used for converting the optical signal into an analog electrical signal; the data acquisition and analysis unit is used for acquiring and analyzing the analog electric signal to obtain the distance between the laser ranging system and the target to be measured.
5. The laser ranging system of claim 4, further comprising a fiber amplifier for amplifying the laser beam power emitted by the laser.
6. The laser ranging system of claim 4, further comprising a collimator for collimating the probe beam and the echo beam.
7. The laser ranging system of claim 6, wherein the beam splitting unit comprises a beam splitter and a circulator;
the laser beam output by the phase modulator is incident to the beam splitter and is divided into the local oscillator beam and the detection beam, the local oscillator beam is incident to the coupler, the detection beam is incident to the circulator, the detection beam emitted by the circulator is collimated by the collimator and then is incident to the target to be measured, and the detection beam is reflected by the target to be measured to form the echo beam, is incident to the collimator for collimation and then is incident to the coupler to be mixed with the local oscillator beam.
8. The laser ranging system according to claim 4, further comprising a galvanometer for scanning, wherein the detection beam split by the beam splitting unit enters the galvanometer, the detection beam emitted by the galvanometer enters the target to be measured, and the detection beam reflected by the target to be measured forms the echo beam and enters the galvanometer and then enters the coupler.
9. A lidar system, comprising: the device comprises a laser, a beam splitting unit, an optical phased array chip, a signal generator, a coupler, a photoelectric detector and a data acquisition and analysis unit; wherein,
the laser is used for emitting laser beams; the beam splitting unit is used for splitting the laser beam into a local oscillation beam and a detection beam; the local oscillator light beam and the detection light beam are incident to the optical phased array chip, and the optical phased array chip outputs a laser light beam for scanning; the signal generator is used for sending a phase modulation signal to the optical phased array chip and controlling the optical phased array chip to output a preset phase; the local oscillator light beam is incident to the coupler, the probe light beam is incident to a target to be measured and then reflected to be an echo light beam, the optical phased array chip receives the echo light beam, the echo light beam is transmitted to the beam splitting unit and is incident to the coupler through the beam splitting unit, and the coupler is used for mixing the local oscillator light beam and the echo light beam to form a mixing optical signal; the photoelectric detector is used for converting the mixing optical signal into an analog electric signal; the data acquisition and analysis unit is used for acquiring and analyzing the analog electric signal to obtain the distance between the laser ranging system and the target to be measured.
10. A laser radar system is characterized by comprising a laser, a beam splitting unit, an optical phased array chip, a signal generator, a phase modulator, a coupler, a photoelectric detector and a data acquisition and analysis unit; wherein,
the laser is used for emitting laser beams; the laser beam is subjected to phase modulation by the phase modulator; the signal generator is used for controlling the phase modulator to generate a phase modulation signal and outputting a preset phase; the laser beam output by the phase modulator is divided into a local oscillation beam and a detection beam by the beam splitting unit; the local oscillator light beam and the detection light beam are incident to the optical phased array chip, and the optical phased array chip outputs a laser light beam for scanning; the local oscillator light beam is incident to the coupler, the probe light beam is incident to a target to be measured and then reflected to be an echo light beam, the optical phased array chip receives the echo light beam, the echo light beam is transmitted to the beam splitting unit and is incident to the coupler through the beam splitting unit, and the local oscillator light beam and the echo light beam are mixed in the coupler to be a mixed frequency optical signal; the photoelectric detector is used for converting the mixing optical signal into an analog electric signal; the data acquisition and analysis unit is used for acquiring and analyzing the analog electric signal to obtain the distance between the laser ranging system and the target to be measured.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114646940A (en) * | 2022-03-15 | 2022-06-21 | 中国科学院微电子研究所 | Laser frequency sweep distance measuring device and method |
| CN117233783A (en) * | 2023-11-14 | 2023-12-15 | 中国科学院长春光学精密机械与物理研究所 | Laser radar optical communication integrated system |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114646940A (en) * | 2022-03-15 | 2022-06-21 | 中国科学院微电子研究所 | Laser frequency sweep distance measuring device and method |
| CN117233783A (en) * | 2023-11-14 | 2023-12-15 | 中国科学院长春光学精密机械与物理研究所 | Laser radar optical communication integrated system |
| CN117233783B (en) * | 2023-11-14 | 2024-01-12 | 中国科学院长春光学精密机械与物理研究所 | Laser radar optical communication integrated system |
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