CN113917474A - Laser ranging method, laser ranging system and laser radar system thereof - Google Patents

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

Laser ranging method, laser ranging system and lidar system thereof

technical field

The invention belongs to the technical field of laser radar, and specifically relates to a laser ranging method, a laser ranging system and a laser radar system.

Background technique

Lidar technology is a new product with unique advantages that combines laser and traditional radar technology. Taking advantage of the advantages of small laser emission angle, concentrated energy, and high coherence, lidar technology can achieve special advantages that traditional radar technology does not have. Compared with traditional radar systems, lidars have higher data density and can obtain a variety of images; and due to the small emission angle of lasers and concentrated energy, lidars have longer detection distances, higher resolutions, and stronger anti-interference capabilities. ; Combined with different detection methods, the information of distance and speed can be obtained at the same time; compared with the size of traditional radar, lidar is small in size and light in weight, which is convenient to combine with various applications.

Commonly, the ranging methods used by lidar are pulse ranging method, frequency modulated continuous wave, phase difference ranging method, etc. Among them, the pulse ranging method is relatively mature and the principle is simple, but in order to improve the signal-to-noise ratio when detecting a long distance, the laser power must be increased, which brings some problems that cannot be ignored. For example, eye safety issues, incompatibility with some radar systems, etc. The FM continuous wave method is used as a ranging method, and the time of flight of light is indirectly measured by the intermediate frequency signal through the mixing between the local oscillator signal and the echo signal. In the case of low echo power, a sufficiently high signal-to-noise ratio can still be obtained, reducing the requirement for transmit power. However, this method requires the laser to have narrow linewidth, high frequency modulation bandwidth, high linearity, high technical difficulty, and high component cost, which makes it impossible to apply to the civilian market. The related technologies are relatively immature. The phase difference ranging method cannot achieve long-distance measurement, and the ranging accuracy has a great relationship with the phase quality of the echo signal. It often requires cooperative targets to achieve better ranging effects, and is often only used in hand-held short-distance rangefinders. .

SUMMARY OF THE INVENTION

The present invention overcomes the deficiencies of the prior art, and provides a laser ranging method, a laser ranging system and a laser radar system thereof.

The present invention provides a laser ranging method, comprising the following steps:

S1. The laser beam is phase-modulated into a laser beam with a preset phase, and the modulated laser beam is divided into beams, a part of which is used as a local oscillator beam, and the other part is used as a detection beam. After the detection beam is incident on the target to be ranged is reflected as an echo beam;

S2. Mix the local oscillator beam and the echo beam to obtain a mixed optical signal;

S3. Perform photoelectric conversion on the mixed-frequency optical signal to obtain an analog electrical signal;

S4, analyze the analog electrical signal to obtain the distance of the target to be measured.

Further, in step S1, the preset phase is expressed as formula (1) and formula (2):

表示预设相位，a，b分别表示不相等的常数，t表示时间，x表示整数，T表示周期。in,

Represents the preset phase, a and b represent unequal constants respectively, t represents time, x represents an integer, and T represents period.

Further, step S4 is specifically:

S401, analyze the analog electrical signal according to formulas (3)-(6) to obtain the flight time, formulas (3)-(6) are as follows:

I=I _T +I _R +A _T A _R cos[ω _Ph τ+ab], (0+xT≤t<τ+xT) (3)

Among them, I is the light intensity of the mixed optical signal, I _T is the light intensity of the local oscillator beam, IR is the light intensity of the echo beam, _{A T} is the amplitude of the local oscillator beam, _AR is the amplitude of the echo beam, ω _Ph represents the optical frequency of the local oscillator beam, and τ represents the flight time, which is the time interval between the probe beam and the echo beam;

S402. Substitute the flight time τ into formula (7) to obtain the distance of the target to be measured. Formula (7) is as follows:

Among them, s represents the distance of the target to be measured.

The present invention also provides a laser ranging system, comprising: a laser, a phase modulator, a signal generator, a beam splitting unit, a coupler, a photodetector, and a data acquisition and analysis unit; wherein,

The laser is used to emit the laser beam; the phase modulator is used to phase modulate the laser beam; the signal generator is used to control the phase modulator to generate a phase modulation signal and output a preset phase; the beam splitting unit is used to divide the laser beam into a local vibrating beam and detection The beam, the local oscillator beam is incident on the coupler, the detection beam is incident on the target to be ranged and then reflected as an echo beam, and the echo beam is incident on the coupler; the coupler is used to mix the local oscillator beam and the echo beam, and the optoelectronic The detector is used to convert the optical signal into an analog electrical signal, and the data acquisition and analysis unit is used to collect and analyze the analog electrical signal, and obtain the distance between the laser ranging system and the target to be ranging.

Further, it also includes a fiber amplifier 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;

The laser beam output by the phase modulator is incident on the beam splitter and is divided into a local oscillator beam and a probe beam. The local oscillator beam is incident on the coupler, and the probe beam is incident on the circulator. The probe beam emitted from the circulator is collimated by the collimator. It is incident on the target to be ranged, and is reflected by the target to be measured to form an echo beam, which is incident to the collimator for collimation, and then incident to the coupler for mixing with the local oscillator beam.

Further, the laser ranging system also includes a galvanometer for scanning, thereby realizing the establishment of a laser radar system. The probe beam split by the beam splitting unit is incident on the galvanometer, and the probe beam emitted by the galvanometer is incident on the target to be ranged. After being reflected by the target to be measured, an echo beam is formed, which is incident on the galvanometer and then incident on the coupler.

The present invention also provides a laser radar system, comprising: a laser, a beam splitting unit, an optical phased array chip, a signal generator, a coupler, a photodetector, and a data acquisition and analysis unit; wherein,

The laser is used to emit a laser beam; the beam splitting unit is used to divide the laser beam into a local oscillator beam and a probe beam; the local oscillator beam and the probe beam are incident on the optical phased array chip, and the optical phased array chip outputs the laser beam for scanning; The signal generator is used to send a phase modulation signal to the optical phased array chip, and control the optical phased array chip to output a preset phase; the local oscillator beam is incident on the coupler, and the detection beam is incident on the target to be ranged and then reflected as an echo beam , the optical phased array chip receives the echo beam, the echo beam is transmitted to the beam splitting unit, and is incident on the coupler through the beam splitting unit, and the coupler is used to mix the local oscillator beam and the echo beam into a frequency mixing optical signal; The photodetector is used to convert the mixed optical signal into an analog electrical signal, and the data acquisition and analysis unit is used to collect and analyze the analog electrical signal to obtain the distance between the laser ranging system and the target to be measured.

The present invention also provides a laser radar system, comprising a laser, a beam splitting unit, an optical phased array chip, a signal generator, a phase modulator, a coupler, a photodetector, and a data acquisition and analysis unit,

The laser is used to emit a laser beam; the laser beam is phase-modulated by the phase modulator; the signal generator is used to control the phase modulator to generate a phase modulation signal and output a preset phase; the laser beam output by the phase modulator is divided into a resonant beam by a beam splitting unit and the detection beam; the local oscillator beam and the detection beam are incident on the optical phased array chip, and the optical phased array chip outputs the laser beam for scanning; the local oscillator beam is incident on the coupler, and the detection beam is incident on the target to be measured and then reflected It becomes the echo beam, the optical phased array chip receives the echo beam, the echo beam is transmitted to the beam splitting unit, and then enters the coupler through the beam splitting unit, and the local oscillator beam and the echo beam are mixed in the coupler to become a mixed beam. The photoelectric detector is used to convert the mixed frequency optical signal into an analog electrical signal; the data acquisition and analysis unit is used to collect and analyze the analog electrical signal to obtain the distance between the laser ranging system and the target to be measured.

Compared with the prior art, the beneficial effects of the present invention are:

The laser ranging method, laser ranging system and laser radar system provided by the present invention effectively solve the problem of human eye safety caused by the traditional pulse ranging method due to excessive instantaneous power; and the frequency modulation continuous wave technology is difficult and costly. problem; and can realize long-distance detection to make up for the defects of the phase difference detection method. The laser ranging method, laser ranging system and its lidar system provide a new phase modulation laser ranging system and ranging method, that is, the principle of coherent detection is used to improve the signal-to-noise ratio, and in the case of low power At the same time, the laser ranging system provided by the invention has simple phase modulation, and the phase modulation technology is easy to realize.

Description of drawings

1 is a schematic diagram of a first structure of a laser ranging system in Embodiment 1 of the present invention;

2 is a schematic diagram of a second structure of the laser ranging system in Embodiment 1 of the present invention;

3 is a schematic diagram of the structure of the lidar system in Embodiment 2 of the present invention;

FIG. 4 is a schematic diagram of the structure of a lidar system in Embodiment 3 of the present invention

5 is a schematic diagram of the flow of the laser ranging method in Embodiment 4 of the present invention;

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.

The reference numbers are as follows:

Laser 1, phase modulator 2, signal generator 3, beam splitter 4, circulator 5, target to be measured 6, coupler 7, photodetector 8, data acquisition and analysis unit 9, amplifier 10, collimator 11 , galvanometer 12 , optical phased array chip 13 , local oscillator beam L _O , detection beam T _X , echo beam R _X .

Detailed ways

The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts 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: a laser 1 , a phase modulator 2 , a signal generator 3 , a beam splitter 4 , a circulator 5 , a coupler 7 , and a photodetector 8 , Data acquisition and analysis unit 9 .

The laser 1 is used to emit a laser beam, and the laser beam is phase-modulated by the phase modulator 2, and the signal generator 3 is used to control the phase modulator 2 to generate a phase modulation signal and output a preset phase. The electrode of the phase modulator is connected by a signal generator, and a specified signal is output to control the laser beam to have a preset phase. Electro-optic modulators such as lithium niobate phase modulators can be used. The laser beam output by the phase modulator 2 is incident on the beam splitter 4 and is divided into a local oscillator beam _LO and a probe beam _TX . The local oscillator beam _LO is incident on the coupler 7 and mixed with the echo beam _RX . The probe beam T _X is incident on the circulator 5 , and the probe beam T _X emitted by the circulator 5 is collimated by the collimator 11 and then incident on the target 6 to be _ranged . After the collimator 11 is collimated, it is incident on the coupler 7 and mixed with the local oscillator light beam _LO to form a mixed optical signal. After the detection beam T _X encounters the target 6 to be ranged, it will be reflected to generate an echo signal, thereby forming an echo beam R _X . The mixed optical signal is converted into an analog electrical signal by the photodetector 8, and the data acquisition and analysis unit 9 collects and analyzes the analog electrical signal to obtain the distance between the laser ranging system and the target 6 to be ranging. The data acquisition and analysis unit 9 in the embodiment of the present invention can use a TDC time-to-digital converter to directly time the time, and then measure the pulse width of the analog electrical signal, or can use the ADC analog-to-digital converter to count and time, and then collect the analog electrical signal. The pulse waveform of the signal is analyzed again; the coupler 7 uses a 2*2 fiber coupler 7 for frequency mixing. The principle of phase modulation in Embodiment 1 of the present invention is not limited, and it can be thermo-optical modulation, such as heating the waveguide, changing the temperature, changing the refractive index of the waveguide, changing the optical phase, or electro-optical modulation, such as: the waveguide performs P-type and N-type modulation. Doping, adjusting the PN junction voltage, adjusting the number of carriers in the waveguide, adjusting the refractive index, adjusting the phase, or modulating the beam externally, such as adding a lithium niobate phase modulator. The selection can be made according to the actual situation, which is not limited in Embodiment 1 of the present invention.

As can be seen from the above content, the laser ranging system provided by the present invention adopts the phase modulator 2 and the signal generator 3 to control the phase of the laser beam, thereby realizing the detection of the target 6 to be ranged by the phase-modulated laser. The embodiment of the present invention provides that the laser ranging system does not have high requirements on the line width, frequency modulation bandwidth, and linearity of the laser 1 , so the cost is reduced compared to the FM continuous wave method as a ranging method. The related technology of the 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 present invention effectively avoids the hidden dangers caused by using immature technology. The laser ranging system provided by the present invention uses the principle of coherent detection to mix the local oscillator signal (ie the local oscillator beam L _O ) and the echo signal (ie the echo beam R _X ), even if the echo beam R _X is weak, However, since the power of the local oscillator beam L _O is sufficient, the signal-to-noise ratio can still be guaranteed to be high. There is no need to increase the power of the laser beam emitted by the laser 1 during long-distance detection, so there is no problem of human eye safety. In addition, the laser ranging system provided by the present invention uses the local oscillator beam L _O and the echo beam R _X to perform frequency mixing, which can achieve a higher signal-to-noise ratio even if a long-distance measurement is performed, which ensures the feasibility of the long-distance measurement and makes up for the Defects of the phase difference detection method.

Embodiment 1 of the present invention provides a preferred solution. The laser ranging system further includes a 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 fiber amplifier 10 can be used for amplification. In this way, in the embodiment provided by the present invention, not only the high-power laser 1 can be used, but also the fiber amplifier 10 can be used to match the power Low laser 1 to complete ranging.

Embodiment 1 of the present invention provides a preferred solution. The laser ranging system further includes a collimator 11 for collimating the probe beam and the echo beam _RX .

Embodiment 1 of the present invention provides a preferred solution. The beam splitting unit includes a beam splitter 4 and a circulator 5; the laser beam output by the phase modulator 2 is incident on the beam splitter 4 and is divided into a local oscillator beam L _O and a probe beam T _X , the local oscillator beam _LO is incident on the coupler 7 and the echo beam _RX is mixed, the probe beam _TX is incident on the circulator 5, and the probe beam _TX emitted by the circulator 5 is collimated by the collimator 11 and then incident After reaching the target 6 to be measured, the echo beam R _X is formed after being reflected by the target 6 to be measured, and is incident on the collimator 11 and then incident on the coupler 7 for mixing with the local oscillator beam _LO .

FIG. 2 shows a second schematic structural diagram of the laser ranging system in Embodiment 1 of the present invention.

Embodiment 1 of the present invention provides a preferred solution. The laser ranging system further includes a galvanometer for scanning, thereby realizing the establishment of a laser radar system. As shown in FIG. 2 , the laser ranging system also includes a galvanometer 12 for scanning, the detection beam _TX split by the beam splitting unit is incident on the galvanometer 12, and the detection beam _TX emitted by the galvanometer 12 is incident on the to-be-measured The distance target 6 is reflected by the to-be-measured target 6 to form an echo beam R _X which is incident on the galvanometer 12 and then incident on the coupler 7 . Combining with the solution of the galvanometer 12 for scanning, the laser ranging system provided in Embodiment 1 of the present invention can not only measure the distance, but also have the function of scanning.

Example 2:

FIG. 3 shows a schematic structural diagram of a lidar system in Embodiment 2 of the present invention.

As shown in FIG. 3, Embodiment 2 of the present invention provides a lidar system, including: a laser 1, a fiber amplifier 10, a beam splitting unit, an optical phased array chip 13, a signal generator 3, a coupler 7, and a photodetector 8. Data acquisition and analysis unit 9.

The laser 1 is used to emit a laser beam, the beam splitting unit is used to split the beam, the laser beam output by the optical phased array chip 13 is used for scanning, and the signal generator 3 is used to send out phase modulation to the optical phased array chip 13 signal, and control the optical phased array chip 13 to output a preset phase, the coupler 7 is used to mix different light beams, the photodetector 8 is used to convert the optical signal into an analog electrical signal, and the data acquisition and analysis unit 9 is used to The analog electrical signal is collected and analyzed. This embodiment 2 provides a preferred technical solution for a fiber amplifier 10 for amplifying the power of the laser beam emitted by the laser 1 . If the power of the laser 11 in the lidar system is not high enough, the fiber amplifier 10 can be used for amplification. In this way, in the embodiment provided by the present invention, not only the high-power laser 11 can be used, but also the fiber amplifier 10 can be used in conjunction with a low-power laser. The laser 11 is used to complete the ranging.

The laser beam is incident on the optical phased array chip 13 through the beam splitting unit and is output after phase modulation. The laser beam output by the optical phased array chip 13 includes a local oscillator beam and a probe beam. The local oscillator beam is incident on the coupler 7 and the probe beam is incident. After reaching the target 6 to be measured, it is reflected as an echo beam, the optical phased array chip 13 receives the echo beam, the echo beam is transmitted to the beam splitting unit, and is incident on the coupler 7 through the beam splitting unit. The wave beam is mixed in the coupler 7 to become a mixed optical signal, and the mixed optical signal is converted into an analog electrical signal by the photodetector 8. The data acquisition and analysis unit 9 collects and analyzes the analog electrical signal, and obtains the laser radar system and the analog electrical signal. The distance between the targets 6 to be measured. The beam splitting unit in the embodiment of the present invention is the circulator 5, and the coupler 7 uses 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 it can be thermo-optical modulation, such as heating the waveguide, changing the temperature, changing the refractive index of the waveguide, changing the optical phase, or electro-optical modulation, such as: the waveguide performs P-type and N-type modulation. Doping, adjusting the PN junction voltage, adjusting the number of carriers in the waveguide, adjusting the refractive index, adjusting the phase, or modulating the beam externally, for example: adding a lithium niobate phase modulator 2. The selection can be made according to the actual situation, which is not limited in Embodiment 2 of the present invention.

It can be seen from the above content that the laser radar system provided by the present invention adopts the optical phased array chip 13 and the signal generator 3 to control the phase of the laser beam, thereby realizing the detection of the target 6 to be ranged by the phase-modulated laser. The embodiment of the present invention provides that the laser radar system does not have high requirements on the line width, frequency modulation bandwidth, and linearity of the laser 1, so the cost is reduced compared with the frequency modulation continuous wave method as a ranging method. The related technology of the 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 present invention effectively avoids the hidden dangers caused by using immature technology. The laser radar system provided by the present invention uses the principle of coherent detection to mix the local oscillator signal (ie the local oscillator beam L _O ) and the echo signal (ie the echo beam R _X ), even if the echo beam R _X is weak, but Since the power of the local oscillator beam L _O is sufficient, the signal-to-noise ratio can still be guaranteed to be high. There is no need to increase the power of the laser beam emitted by the laser 1 during long-distance detection, so there is no problem of human eye safety. In addition, the laser radar system provided by the present invention uses the local oscillator beam _LO and the echo beam _RX to perform frequency mixing, and even if a long-distance measurement is performed, a higher signal-to-noise ratio can be achieved, which ensures the feasibility of the long-distance measurement and compensates for the phase. The defect problem of poor detection method.

This embodiment 2 provides a preferred technical solution for a fiber amplifier 10 for amplifying the power of the laser beam emitted by the laser 1 . If the power of the laser 11 in the lidar system is not high enough, the fiber amplifier 10 can be used for amplification. In this way, in the embodiment provided by the present invention, not only the high-power laser 1 can be used, but also the fiber amplifier 10 can be used in conjunction with a low-power laser. the laser 1 to complete the ranging.

This Example 3:

FIG. 4 shows a schematic structural diagram of a lidar system in Embodiment 3 of the present invention.

Embodiment 2 of the present invention provides a preferred solution. As shown in FIG. 4 , the lidar system includes a laser 1, a phase modulator 2, a fiber amplifier 10, a beam splitting unit, an optical phased array chip 13, a signal generator 3, a coupling 7, photodetector 8, data acquisition and analysis unit 9. The beam splitting unit is the circulator 5 . The laser beam emitted by the laser 1 is phase modulated by the phase modulator 2. The signal generator 3 is used to control 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 on the circulator 5. The optical phased array chip 13 is output after phase modulation again. The laser beam output by the optical phased array chip 13 includes a local oscillator beam _LO and a detection beam _TX . The local oscillator beam _LO is incident on the coupler 7, and the detection beam _TX After being incident on the target 6 to be measured, it is reflected as an echo beam R _X , the optical phased array chip 13 receives the echo beam R _X , the echo beam R _X is transmitted to the beam splitting unit, and is incident on the coupler through the beam splitting unit 7. The local oscillator beam L _O and the echo beam R _X are mixed in the coupler 7 to form a mixed optical signal. The photodetector 8 is used to convert the optical signal into an analog electrical signal, and the data acquisition and analysis unit 9 is used to collect and analyze the analog electrical signal. Embodiment 3 provides a preferred technical solution for a fiber amplifier 10 for amplifying the power of the laser beam emitted by the laser 1 . If the power of the laser 11 in the lidar system is not high enough, the fiber amplifier 10 can be used for amplification. In this way, in the embodiment provided by the present invention, not only the high-power laser 11 can be used, but also the fiber amplifier 10 can be used in conjunction with a low-power laser. The laser 11 is used to complete the ranging.

Example 4:

FIG. 5 shows a schematic flowchart of the 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. The laser beam is phase-modulated into a laser beam with a preset phase, and the modulated laser beam is split into beams, a part of which is used as a local oscillator beam L _O , and the other part is phase-modulated into a detection with a preset phase. For the light beam T _X , the detection beam is incident on the target to be ranged and then reflected as the echo beam T _X .

The laser beam generated by the laser 1 is phase-modulated into a laser beam with a preset phase, and then split into two parts, which are divided into a local oscillator beam L _O and a probe beam T _X , and the probe beam T _X is incident on the to-be-measured beam. After being away from the target 6, it is reflected as an echo beam R _X , wherein the echo beam R _X carries the echo signal.

S2. Mix the local oscillator light beam _LO and the echo light beam _TX through the coupler 7 to obtain a mixed frequency optical signal.

S3. In the fourth embodiment of the present invention, the photoelectric detector 8 performs photoelectric conversion on the mixed optical signal to obtain an analog electrical signal.

S4, analyze the analog electrical signal to obtain the distance of the target to be measured. The data collection and analysis unit 9 collects and analyzes the analog electrical signal to obtain the distance of the target to be measured.

The laser ranging method provided in Embodiment 4 of the present invention utilizes the principle of coherent detection. The local oscillator beam L _O is mixed with the echo beam R _X. Even if the echo beam R _X , the power of the local oscillator beam L _O is sufficient. Therefore, the signal-to-noise ratio can still be guaranteed. In this way, there is no need to increase the power of the emitted light during long-distance detection, and there is no eye safety problem.

FIG. 6 shows a schematic diagram of a phase modulation signal in Embodiment 4 of the present invention. The embodiment of the present invention provides a preferred solution. 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. The preset phase is expressed as formula (1) and Formula (2):

Among them, a and b represent unequal constants respectively, t represents time, x represents an integer, and T represents period.

Embodiment 4 of the present invention provides a preferred solution. In step S4, the frequency converted into an analog electrical signal is analyzed according to formulas (3)-(6), and the flight time is obtained, and formulas (3)-(6) are as follows shown:

I=I _T +I _R +A _T A _R cos[ω _Ph τ+ab], (0+xT≤t<τ+xT) (3)

Among them, I represents the light intensity of the mixed optical signal, IT represents the light intensity of the local oscillator beam _LO , IR represents the light intensity of the echo beam R _X , A _T represents the amplitude of the local oscillator beam _LO , and A _{R represents} the echo beam _. The amplitude of the wave beam R _X , ω _Ph is the optical frequency of the local oscillator beam L _O , τ is the time of flight, is the time interval between the probe beam T _X and the echo beam R _X where, τ is the flight time, is the probe beam T _X and the time interval of the echo beam _RX .

The technical solution provided in Embodiment 4 of the present invention involves a detailed description of the detection principle below. The optical field E _Tx of the local oscillator beam _LO and the optical field E Rx of the echo beam _Rx are as shown in formula (7) and formula (8), respectively. Show:

表示本振光束L_O的预设相位，ω_Ph表示本振光束L_O的光频，t表示时间，τ为探测光束T_X和回波光束R_X的总时间。where A _T and A _R are both constants,

represents the preset phase of the local oscillator beam _LO , ω _Ph represents the optical frequency of the local oscillator beam _LO , t represents the time, and τ represents the total time of the probe beam _TX and the echo beam _RX .

The new light field E generated by coherently superposing the local oscillator beam L _O and the echo beam Rx is _always shown in formula (9):

Since the light intensity is proportional to the square of the light field, the light intensity I after coherent superposition of the local oscillator beam L _O and the echo beam Rx is shown in formula (10):

Since the light intensity is proportional to the square of the light field, the light intensity I _T of the local oscillator beam _LO and the light intensity IR of the echo beam _{R X} are shown in formula (11) and formula (12), respectively:

Formula (10) is sorted by formula (11) and formula (12), and the sorting is shown in formula (13):

The light intensity I of formula (13) is deformed by using the trigonometric function relation formula, as shown in formula (14):

是一个频率极高的项，光电探测器8对此无法响应，故而可以被忽略，得到光强I如公式(15)所示：because

is a very high frequency term, and the photodetector 8 cannot respond to this, so it can be ignored, and the light intensity I is obtained as shown in formula (15):

Arrange the preset phase formula (1) and formula (2) to obtain formula (16) and formula (17):

Substitute formula (16) and formula (17) into formula (17) for sorting, and obtain formula (3)-formula (6) after sorting.

I=I _T +I _R +A _T A _R cos[ω _Ph τ+ab], (0+xT≤t<τ+xT) (3)

FIG. 7 shows a schematic diagram of the waveform diagram of the mixed optical signal obtained according to the formula (3)-formula (6) in this embodiment. As shown in Figure 7, the waveform diagram of the photoelectric detection signal (it should be noted that Figure 7 is only a schematic diagram for convenience of description) and the formula (3)-formula (6) of the light intensity I can know that I _T + I _R can be The sum of the light intensities of the detected local oscillator beam _LO and the echo beam Rx is a detectable parameter; A _T and _AR are the relevant amplitudes in the waveform diagram, which are parameters that can be obtained through Fig. 7; ω _Ph τ, a, and b are all constants, and the flight time τ can be obtained by reading the width of the mixed optical signal pulse in Fig. 7 . To obtain the flight time τ, the distance data between the laser ranging system and the target 6 to be ranged can be obtained by formula (18). The formula (18) is as follows:

Among them, c is the speed of light, and s is the distance between the laser ranging system and the target 6 to be ranged.

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 principle of coherent detection is used to improve the signal-to-noise ratio, even if the echo signal is weak Longer distances can also be measured while maintaining high resolution. The waveform of phase modulation in the laser ranging method provided in Embodiment 4 of the present invention is easier to implement. The phase modulation in the laser ranging method provided in Embodiment 4 of the present invention is for the modulation of the waveform as a square wave, and for changing the phase of the laser beam In other words, phase modulation can be achieved only by applying a square wave electrical signal. The phase modulation in the prior art is generally a quadratic waveform, which requires more complex electrical signals and many calibration processes to achieve the desired phase modulation. Therefore, the phase modulation of the laser ranging method provided by Embodiment 4 of the present invention is simple and easy to implement.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed 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, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Although the embodiments of the present invention have been shown and described above, it is to be understood that the above-described embodiments are exemplary and should not be construed to limit the present invention. Variations, modifications, substitutions, and alterations to the above-described embodiments can be made by those of ordinary skill in the art within the scope of the present invention.

The above specific embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made according to the technical concept of the present invention shall 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＝I_T+I_R+A_TA_Rcos[ω_Phτ+a-b]，(0+xT≤t<τ+xT) (3)

wherein I represents the light intensity of the mixed optical signal, I_TRepresenting the light intensity, I, of the local oscillator beam_RRepresenting the light intensity of said echo beam, A_TRepresenting the amplitude, A, of the local oscillator beam_RRepresenting the amplitude, ω, of said echo beam_PhRepresenting 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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