Laser ranging method, laser ranging system and laser radar system

Abstract

The present invention provides a laser ranging system, a laser radar system, and a ranging method therefor. The laser ranging method comprises the following steps: phase-modulating a laser beam to form a laser beam with a preset phase; splitting the modulated laser beam into a local oscillator beam and a probe beam. The probe beam is incident on a target to be measured and reflected as an echo beam; mixing the local oscillator beam and the echo beam to obtain a mixed optical signal; performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal; and analyzing the analog electrical signal to obtain the distance to the target to be measured. The present invention provides a novel laser ranging system, a laser radar system, and a ranging method therefor. These systems utilize the principle of coherent detection to improve the signal-to-noise ratio, enabling measurement of longer distances and improved resolution at low power. Phase modulation is also simple, and the phase modulation technology is easily implemented.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radar, and in particular relates to a laser ranging method, a laser ranging system and a laser radar system thereof. Background Art

[0002] LiDAR technology is a new product that combines lasers with traditional radar technologies, offering unique advantages. Leveraging the advantages of lasers' narrow emission angle, concentrated energy, and high coherence, LiDAR technology offers unique advantages not found in traditional radar. Compared to traditional radar systems, LiDAR collects data at a higher density, enabling the acquisition of diverse images. Furthermore, due to the laser's narrow emission angle and concentrated energy, LiDAR offers a longer detection range, higher resolution, and enhanced anti-interference capabilities. Combining different detection methods allows for simultaneous acquisition of distance and velocity information. Compared to traditional radar, LiDAR is compact and lightweight, making it easy to integrate with a variety of applications.

[0003] Common ranging methods used by lidar include pulse ranging, frequency-modulated continuous wave (FMCW), and phase-difference ranging. Pulse ranging is relatively mature and simple in principle, but it requires increased laser power to improve the signal-to-noise ratio when detecting longer distances. This presents significant challenges, such as eye safety concerns and incompatibility with some radar systems. Frequency-modulated continuous wave (FMCW) ranging uses mixing between the local oscillator (LO) signal and the echo signal, indirectly measuring the light's time of flight via the intermediate frequency (IF) signal. This method can achieve a sufficiently high signal-to-noise ratio even with low echo power, reducing the required transmit power. However, this method requires a narrow laser linewidth, high frequency modulation bandwidth, and high linearity, resulting in significant technical difficulties and high component costs, making it unsuitable for civilian use. Commonly available laser sources that meet these requirements cost tens of thousands of yuan, and the technology is relatively immature. Phase-difference ranging cannot achieve long-range measurements, and ranging accuracy is closely related to the phase quality of the echo signal. It often requires a cooperating target to achieve optimal ranging results, and is generally only used in handheld, short-range rangefinders. Summary of the Invention

[0004] 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.

[0005] The present invention provides a laser ranging method, comprising the following steps:

[0006] S1. Phase-modulate the laser beam to form a laser beam with a preset phase, and split the modulated laser beam into two parts: one part is used as a local oscillator beam, and the other part is used as a detection beam. The detection beam is incident on the target to be measured and is reflected to form an echo beam.

[0007] S2, mixing the local oscillator beam and the echo beam to obtain a mixed optical signal;

[0008] S3, performing photoelectric conversion on the mixed optical signal to obtain an analog electrical signal;

[0009] S4. Analyze the analog electrical signal to obtain the distance of the target to be measured.

[0010] Furthermore, in step S1, the preset phase is expressed as formula (1) and formula (2):

[0011]

[0012]

[0013] in, represents the preset phase, a and b represent unequal constants, t represents time, x represents an integer, and T represents a period.

[0014] Furthermore, step S4 is specifically as follows:

[0015] S401. Analyze the analog electrical signal according to formulas (3)-(6) to obtain the flight time. Formulas (3)-(6) are as follows:

[0016] I=I T +I R +A T A R cos[ω Ph τ+ab],(0+xT≤t<τ+xT) (3)

[0017]

[0018]

[0019]

[0020] Where, I represents the intensity of the mixed optical signal, I T Indicates the intensity of the local oscillator beam, I R Indicates the intensity of the echo beam, A T represents the amplitude of the local oscillator beam, A R represents the amplitude of the echo beam, ω Ph represents the optical frequency of the local oscillator beam, τ represents the flight time, which is the time interval between the detection beam and the echo beam;

[0021] S402: Substitute the flight time τ into formula (7) to obtain the distance of the target to be measured. Formula (7) is as follows:

[0022]

[0023] Where s represents the distance to the target to be measured.

[0024] 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 photoelectric detector, and a data acquisition and analysis unit; wherein,

[0025] The laser is used to emit a 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 split the laser beam into a local oscillator beam and a detection beam, the local oscillator beam is incident on the coupler, the detection beam is incident on the target to be measured and reflected to become 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, the photodetector 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; the distance between the laser ranging system and the target to be measured is obtained.

[0026] Furthermore, it also includes an optical fiber amplifier for amplifying the power of the laser beam emitted by the laser.

[0027] Furthermore, it also includes a collimator for collimating the detection beam and the echo beam.

[0028] Further, the beam splitting unit includes a beam splitter and a circulator;

[0029] The laser beam output by the phase modulator is incident on the beam splitter and is divided into a local oscillator beam and a detection beam. The local oscillator beam is incident on the coupler, and the detection beam is incident on the circulator. The detection beam emitted by the circulator is collimated by the collimator and then incident on the target to be measured. After being reflected by the target to be measured, an echo beam is formed and incident on the collimator. After collimation, it is incident on the coupler to mix with the local oscillator beam.

[0030] Furthermore, the laser ranging system also includes a galvanometer for scanning, thus completing the construction of a laser radar system. The detection beam split by the beam splitting unit is incident on the galvanometer, and the detection beam emitted by the galvanometer is incident on the target to be measured. After being reflected by the target to be measured, the echo beam is incident on the galvanometer and then on the coupler.

[0031] 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 photoelectric detector, and a data acquisition and analysis unit; wherein,

[0032] The laser is used to emit a laser beam; the beam splitting unit is used to split the laser beam into a local oscillator beam and a 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 a 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 reflected after being incident on the target to be measured to become an echo beam, and the optical phased array chip receives the echo beam, and the echo beam is transmitted to the beam splitting unit, and is incident on the coupler through the beam splitting unit. The coupler is used to mix the local oscillator beam and the echo beam into a mixed light signal; the photodetector is used to convert the mixed light 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.

[0033] 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.

[0034] The laser is used to emit a laser beam; the laser beam is phase-modulated by a 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 split into a local oscillator beam and a detection beam by a beam splitting unit; the local oscillator beam and the detection beam are incident on the optical phased array chip, and the optical phased array chip outputs a laser beam for scanning; the local oscillator beam is incident on the coupler, and the detection beam is reflected after being incident on the target to be measured to become an echo beam, and the optical phased array chip receives the echo beam, and the echo beam is transmitted to the beam splitting unit, and is incident on 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 optical signal; the photodetector is used to convert the mixed 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.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The laser ranging method, laser ranging system, and laser radar system provided by the present invention effectively address the eye safety issues associated with traditional pulse ranging methods due to excessive instantaneous power, as well as the difficulty and high cost of frequency-modulated continuous wave technology. They also enable long-distance detection, compensating for the shortcomings of phase-difference detection methods. The laser ranging method, laser ranging system, and laser radar system provide a new phase-modulated laser ranging system and ranging method, utilizing the principle of coherent detection to improve the signal-to-noise ratio, enabling measurement of longer distances and improved resolution at lower power levels. Furthermore, the laser ranging system provided by the present invention features simple phase modulation, and the phase modulation technology is easily implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of a first structure of a laser ranging system in Example 1 of the present invention;

[0038] Figure 2 is a schematic diagram of a second structure of the laser ranging system in Example 1 of the present invention;

[0039] Figure 3 is a schematic diagram of the structure of the laser radar system in Example 2 of the present invention;

[0040] Figure 4 Schematic diagram of the structure of the laser radar system in Example 3 of the present invention

[0041] Figure 5 Schematic diagram of the process of the laser ranging method in Example 4 of the present invention;

[0042] Figure 6 is a schematic diagram of a phase modulation signal in Example 4 of the present invention;

[0043] Figure 7 Schematic diagram of the mixed optical signal in Example 4 of the present invention.

[0044] The reference numerals therein are as follows:

[0045] 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 DESCRIPTION

[0046] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and examples. It should be noted that the embodiments of the present invention and the features therein can be combined with each other in the absence of conflict. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0047] Example 1:

[0048] Figure 1 The figure shows a schematic structural diagram of the laser ranging system in Example 1 of the present invention.

[0049] like Figure 1As shown, 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, a photodetector 8, and a data acquisition and analysis unit 9.

[0050] The laser 1 is used to emit a laser beam, which 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 signal generator is connected to the electrodes of the phase modulator to output a specified signal to control the laser beam to have a preset phase. An electro-optical modulator such as a lithium niobate phase modulator 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 L O and the probe beam T X , local oscillator beam L O The beam incident on the coupler 7 and the return beam R X Mixing is performed, and the detection beam T X The detection beam T is incident on the circulator 5 and emitted by the circulator 5 X After being collimated by the collimator 11, it is incident on the target 6 to be measured and reflected by the target 6 to form an echo beam R X The incident beam is collimated by the collimator 11 and then incident on the coupler 7 and the local oscillator beam L O Mixing is performed to form a mixed optical signal. X When encountering the target 6 to be measured, reflection will occur 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 measured. 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 and then measure the pulse width of the analog electrical signal, or use an ADC analog-to-digital converter for counting and timing, and then collect the pulse waveform of the analog electrical signal and then analyze it; the coupler 7 uses a 2*2 optical fiber coupler 7 for frequency mixing. The principle of phase modulation in Example 1 of the present invention is not limited, and can be thermo-optical modulation, such as heating the waveguide, changing the temperature, changing the refractive index of the waveguide, changing the light phase, or electro-optical modulation, such as P-type and N-type doping of the waveguide, adjusting the PN junction voltage, adjusting the number of carriers in the waveguide, adjusting the refractive index, and adjusting the phase. The light beam can also be modulated externally, for example, by adding a lithium niobate phase modulator. It can be selected according to actual conditions, and Example 1 of the present invention does not limit this.

[0051] From the above content, it can be seen that the laser ranging system provided by the present invention adopts the characteristics of 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 measured by the phase-modulated laser. The embodiment of the present invention provides a laser ranging system that does not have high requirements on the line width, frequency modulation bandwidth, and linearity of the laser 1, so it reduces the cost compared with the frequency modulated 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. The laser ranging system provided by the embodiment of the present invention effectively avoids the hidden dangers brought about by the use of immature technology. The laser ranging system provided by the present invention utilizes the principle of coherent detection, and the local oscillator signal (that is, the local oscillator beam L O ) and the echo signal (i.e. the echo beam R X ) for mixing, even if the echo beam R X Weak, but due to the local oscillator beam L O The power is sufficient, so 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 eye safety problem. The laser ranging system provided by the present invention uses the local oscillator beam L O and the echo beam R X By performing frequency mixing, a higher signal-to-noise ratio can be achieved even for long-distance measurements, ensuring the feasibility of long-distance measurements and making up for the defects of the phase difference detection method.

[0052] Embodiment 1 of the present invention provides a preferred solution, wherein the laser ranging system further comprises 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 can be used to amplify it. Thus, in the embodiment provided by the present invention, not only a high-power laser 1 can be used, but also the optical fiber amplifier 10 can be used in conjunction with a low-power laser 1 to complete ranging.

[0053] Embodiment 1 of the present invention provides a preferred solution, wherein the laser ranging system further comprises a device for combining the detection beam and the echo beam R X A collimator 11 performs collimation.

[0054] Embodiment 1 of the present invention provides a preferred solution, wherein 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 split into a local oscillator beam L O and the probe beam T X , local oscillator beam L O The beam incident on the coupler 7 and the return beam R X Mixing is performed, and the detection beam T X The detection beam T is incident on the circulator 5 and emitted by the circulator 5 XAfter being collimated by the collimator 11, it is incident on the target 6 to be measured and reflected by the target 6 to form an echo beam R X The incident beam is collimated by the collimator 11 and then incident on the coupler 7 and the local oscillator beam L O Perform mixing.

[0055] Figure 2 A second structural schematic diagram of the laser ranging system in Example 1 of the present invention is shown.

[0056] Embodiment 1 of the present invention provides a preferred solution, wherein the laser ranging system further includes a galvanometer for scanning, thereby realizing the establishment of a laser radar system. Figure 2 As shown, the laser ranging system also includes a galvanometer 12 for scanning, and the detection beam T split by the beam splitting unit X The detection beam T is incident on the galvanometer 12 and emitted from the galvanometer 12 X The beam is incident on the target 6 to be measured and reflected by the target 6 to form an echo beam R X The light is incident on the galvanometer mirror 12 and then incident on the coupler 7. By combining the scheme of the galvanometer mirror 12 for scanning, the laser ranging system provided by the embodiment 1 of the present invention can not only measure distance but also has the function of scanning.

[0057] Example 2:

[0058] Figure 3 A schematic structural diagram of the laser radar system in Example 2 of the present invention is shown.

[0059] like Figure 3 As shown, embodiment 2 of the present invention provides a laser radar system, including: 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 photodetector 8, and a data acquisition and analysis unit 9.

[0060] The laser 1 is used to emit a laser beam, the beam splitting unit is used to split the beam, the optical phased array chip 13 outputs a laser beam for scanning, the signal generator 3 is used to send a phase modulation signal to the optical phased array chip 13 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 collect and analyze the analog electrical signal. This embodiment 2 provides a preferred technical solution, which is 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 a high-power laser 11 can be used, but also a fiber amplifier 10 can be used in combination with a low-power laser 11 to complete ranging.

[0061] The laser beam is incident on the optical phased array chip 13 through the beam splitting unit and is phase-modulated before being output. 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. The probe beam is incident on the target 6 to be measured and reflected to become an echo beam. The optical phased array chip 13 receives the echo beam, which is transmitted to the beam splitting unit and then incident on the coupler 7 through the beam splitting unit. The local oscillator beam and the echo beam are mixed in the coupler 7 to form a mixed optical signal. 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 to obtain the distance between the laser radar system and the target 6 to be measured. In this embodiment of the present invention, the beam splitting unit is a circulator 5, and the coupler 7 uses a 2*2 fiber coupler 7 for mixing. The principle of phase modulation in Example 2 of the present invention is not limited. It can be thermo-optical modulation, for example, heating the waveguide, changing the temperature, changing the waveguide refractive index, and changing the optical phase. It can also be electro-optical modulation, for example, performing P-type and N-type doping on the waveguide, adjusting the PN junction voltage, adjusting the number of carriers in the waveguide, adjusting the refractive index, and adjusting the phase. The light beam can also be modulated externally, for example, by adding a lithium niobate phase modulator 2. The selection can be made based on actual conditions and is not limited in Example 2 of the present invention.

[0062] From the above content, it can be seen that the laser radar system provided by the present invention adopts the characteristics of the optical phased array chip 13 and the signal generator 3 that can control the phase of the laser beam, thereby realizing the detection of the target 6 to be measured by phase-modulated laser. The embodiment of the present invention provides a laser radar system that does not have high requirements on the line width, frequency modulation bandwidth, and linearity of the laser 1, so it reduces the cost compared to the frequency modulated 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. The laser radar system provided by the embodiment of the present invention effectively avoids the hidden dangers brought about by the use of immature technology. The laser radar system provided by the present invention utilizes the principle of coherent detection, and the local oscillator signal (that is, the local oscillator beam L O ) and the echo signal (i.e. the echo beam R X ) for mixing, even if the echo beam R X Weak, but due to the local oscillator beam L O The power is sufficient, so 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 eye safety issue. The laser radar system provided by the present invention utilizes the local oscillator beam L O and the echo beam R X By performing frequency mixing, a higher signal-to-noise ratio can be achieved even for long-distance measurements, ensuring the feasibility of long-distance measurements and making up for the defects of the phase difference detection method.

[0063] This embodiment 2 provides a preferred technical solution, 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 to amplify it. In this way, in the embodiment provided by the present invention, not only a high-power laser 1 can be used, but also the fiber amplifier 10 can be used in conjunction with a low-power laser 1 to complete ranging.

[0064] This embodiment 3:

[0065] Figure 4 A schematic structural diagram of the laser radar system in Example 3 of the present invention is shown.

[0066] Embodiment 2 of the present invention provides a preferred solution, such as Figure 4 As shown, the laser radar 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 coupler 7, a photodetector 8, and a data acquisition and analysis unit 9. The beam splitting unit is a 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 optical phased array chip 13 through the circulator 5 and is phase modulated again before being output. The laser beam output by the optical phased array chip 13 includes a local oscillator beam L O and the probe beam T X , local oscillator beam L O The detection beam T is incident on the coupler 7. X After being incident on the target 6 to be measured, it is reflected and becomes an echo beam R X , the optical phased array chip 13 receives the echo beam R X , echo beam R X It is transmitted to the beam splitting unit and incident on the coupler 7 through the beam splitting unit. The local oscillator beam L O and the echo beam R X Frequency mixing is performed 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. This embodiment 3 provides a preferred technical solution, which is an optical 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 optical fiber amplifier 10 can be used for amplification. In this way, in the embodiment provided by the present invention, not only a high-power laser 11 can be used, but also an optical fiber amplifier 10 can be used in combination with a low-power laser 11 to complete ranging.

[0067] Example 4:

[0068] Figure 5The figure shows a flow chart of the laser ranging method in embodiment 4 of the present invention.

[0069] like Figure 5 As shown, embodiment 4 of the present invention provides a laser ranging method, which specifically includes the following steps:

[0070] S1, the laser beam is phase modulated to become a laser beam with a preset phase, and the modulated laser beam is split, a part of which is used as the local oscillator beam L O The other part is phase modulated to become a detection beam T with a preset phase. X , the detection beam is incident on the target to be measured and then reflected to become the echo beam T X .

[0071] The laser beam generated by the laser 1 is phase modulated to become a laser beam with a preset phase, and then split into two parts, which are divided into the local oscillator beam L O and the probe beam T X , the detection beam T X After being incident on the target 6 to be measured, it is reflected and becomes an echo beam R X , where the echo beam R X Carrying echo signal.

[0072] S2, the local oscillator beam L O and the echo beam T X Frequency mixing is performed through the coupler 7 to obtain a mixed optical signal.

[0073] S3. In the fourth embodiment of the present invention, the mixed optical signal is subjected to photoelectric conversion by the photodetector 8 to obtain an analog electrical signal.

[0074] S4. Analyze the analog electrical signal to obtain the distance of the target to be measured. The data acquisition and analysis unit 9 acquires and analyzes the analog electrical signal to obtain the distance of the target to be measured.

[0075] The laser ranging method provided in Example 4 of the present invention utilizes the principle of coherent detection, where the local oscillator beam L O With the echo beam R X Mixing, even if the echo beam R X However, due to the local oscillator beam L O The power is sufficient, so the signal-to-noise ratio can still be guaranteed. This eliminates the need to increase the power of the emitted light during long-distance detection, and eliminates eye safety issues.

[0076] Figure 6 Schematic diagram of the phase modulation signal in embodiment 4 of the present invention is shown. The embodiment of the present invention provides a preferred solution, in step S1, as Figure 6As shown, 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):

[0077]

[0078]

[0079] Where a and b represent unequal constants, t represents time, x represents an integer, and T represents a period.

[0080] Embodiment 4 of the present invention provides a preferred solution. In step S4, the analog electrical signal converted after mixing is analyzed according to formulas (3)-(6) to obtain the flight time. Formulas (3)-(6) are as follows:

[0081] I=I T +I R +A T A R cos[ω Ph τ+ab],(0+xT≤t<τ+xT) (3)

[0082]

[0083]

[0084]

[0085] Where, I represents the intensity of the mixed optical signal, I T Represents the local oscillator beam L O The light intensity, I R Represents the echo beam R X The light intensity, A T Represents the local oscillator beam L O The amplitude, A R Represents the echo beam R X The amplitude, ω Ph Represents the local oscillator beam L O The optical frequency, τ represents the flight time, and T is the detection beam X and the echo beam R X Where τ represents the time of flight and T is the time interval of the detection beam. X and the echo beam R X time interval.

[0086] The following is a detailed description of the detection principle involved in the technical solution provided in Example 4 of the present invention. The local oscillator beam L O The light field E Tx , the light field E of the echo beam Rx RxAs shown in formula (7) and formula (8) respectively:

[0087]

[0088]

[0089] Among them, A T and A R are all constants, Represents the local oscillator beam L O The preset phase, ω Ph Represents the local oscillator beam L O The optical frequency, t represents time, τ is the detection beam T X and the echo beam R X total time.

[0090] The local oscillator beam L O The new light field E generated by the coherent superposition of the echo beam Rx 总 As shown in formula (9):

[0091]

[0092] Since the light intensity is proportional to the square of the light field, the local oscillator beam L O The light intensity I after coherent superposition with the echo beam Rx is shown in formula (10):

[0093]

[0094] Since the light intensity is proportional to the square of the light field, the local oscillator beam L O Light intensity I T and the echo beam R X Light intensity I R As shown in formula (11) and formula (12) respectively:

[0095]

[0096]

[0097] Formula (10) is sorted out by formula (11) and formula (12), and the sorted formula is shown in formula (13):

[0098]

[0099] The light intensity I in formula (13) is transformed using the trigonometric function relationship formula, as shown in formula (14):

[0100]

[0101] because It is a very high frequency term, and the photodetector 8 cannot respond to it, so it can be ignored. The light intensity I is obtained as shown in formula (15):

[0102]

[0103] Arrange the preset phase formula (1) and formula (2) to obtain formula (16) and formula (17):

[0104]

[0105]

[0106] Substitute formula (16) and formula (17) into formula (17) and sort them out to obtain formula (3)-formula (6).

[0107] I=I T +I R +A T A R cos[ω Ph τ+ab],(0+xT≤t<τ+xT) (3)

[0108]

[0109]

[0110]

[0111] Figure 7 FIG. 1 is a schematic diagram showing the waveform of the mixed optical signal obtained according to formula (3) to formula (6) in this embodiment. Figure 7 As shown, the waveform of the photoelectric detection signal (it should be noted that, Figure 7 It is only a schematic diagram for the convenience of explanation) and the formula (3)-formula (6) of the light intensity I, I T +I R is the detectable local oscillator beam L O The sum of the light intensities of the echo beam Rx is the detectable parameter; A T 、A R The waveform is represented by the relevant amplitude, which can be Figure 7 The parameter to be obtained; ω Ph τ, a, and b are all constants, and the flight time τ can be read Figure 7 The width of the mixed optical signal pulse is obtained. The flight time τ is obtained, and the distance data between the laser ranging system and the target 6 to be measured can be obtained through formula (18). Formula (18) is as follows:

[0112]

[0113] Wherein, c is the speed of light, and s represents the distance between the laser ranging system and the target 6 to be measured.

[0114] In the laser ranging method provided in Example 4 of the present invention, the distance to the target 6 to be measured can be obtained according to the above formula. That is, the principle of coherent detection is utilized to improve the signal-to-noise ratio. Even when the echo signal is weak, it is possible to measure longer distances while maintaining high resolution. The phase modulation waveform in the laser ranging method provided in Example 4 of the present invention is easier to implement. The phase modulation in the laser ranging method provided in Example 4 of the present invention is for modulation of a square wave waveform. To change the phase of the laser beam, only a square wave electrical signal needs to be applied to achieve phase modulation. However, the phase modulation in the prior art is generally a quadratic waveform. This waveform requires a more complex electrical signal and many calibration processes to achieve the required phase modulation. Therefore, the phase modulation of the laser ranging method provided in Example 4 of the present invention is simple and easy to implement.

[0115] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0116] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0117] The above specific embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A laser ranging method, characterized in that: The following steps are involved: S1. Phase-modulate the laser beam to obtain a laser beam with a preset phase. The preset phase is expressed as formula (1) and formula (2): （1） （2） in, represents a preset phase, a and b represent unequal constants, t represents time, x represents an integer, and T represents a period; the modulated laser beam is split, with one part serving as a local oscillator beam and the other part serving as a detection beam. The detection beam is incident on the target to be measured and is reflected to form an echo beam; 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; S4. Analyze the analog electrical signal to obtain the distance of the target to be measured; The step S4 is specifically as follows: S401. Analyze the analog electrical signal according to formulas (3)-(6) to obtain the flight time. Formulas (3)-(6) are as follows: （3） （4） （5） （6） Wherein, I represents the intensity of the mixed optical signal, I T represents the intensity of the local oscillator beam, I R represents the intensity of the echo beam, A T represents the amplitude of the local oscillator beam, A R represents the amplitude of the echo beam, represents the optical frequency of the local oscillator beam, represents the flight time, which is the time interval between the detection beam and the echo beam; The waveform of the mixed light signal is obtained according to formula (3) to formula (6), the width of the mixed light signal pulse in the waveform of the mixed light signal is read to obtain the flight time, and the distance of the target to be measured is obtained based on the flight time.

2. The laser ranging method according to claim 1, characterized in that: S402, the flight time Substitute into formula (7) to obtain the distance of the target to be measured. Formula (7) is as follows: （7） Wherein, s represents the distance to the target to be measured.

3. A laser ranging system, characterized in that: include: Laser, phase modulator, signal generator, beam splitting unit, coupler, photodetector, data acquisition and analysis unit; wherein, The laser is used to emit a laser beam; the phase modulator is used to perform phase modulation on the laser beam; the signal generator is used to control the phase modulator to generate a phase modulation signal and output a preset phase, and the preset phase is expressed as formula (1) and formula (2): （1） （2） in, represents a preset phase, a and b represent unequal constants respectively, t represents time, x represents an integer, and T represents a period; the beam splitting unit is used to split the laser beam into an LO beam and a detection beam, the LO beam is incident on the coupler, the detection beam is incident on the target to be measured and reflected to become an echo beam, and the echo beam is incident on the coupler; the coupler is used to mix the LO beam and the echo beam; the photodetector is used to convert the 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, and the analog electrical signal is analyzed according to formulas (3)-(6) to obtain the flight time. Formulas (3)-(6) are as follows: （3） （4） （5） （6） Wherein, I represents the intensity of the mixed optical signal, I T represents the intensity of the local oscillator beam, I R represents the intensity of the echo beam, A T represents the amplitude of the local oscillator beam, A R represents the amplitude of the echo beam, represents the optical frequency of the local oscillator beam, represents the flight time, which is the time interval between the detection beam and the echo beam; The waveform of the mixed light signal is obtained according to formula (3) to formula (6), the width of the mixed light signal pulse in the waveform of the mixed light signal is read to obtain the flight time, and the distance of the target to be measured is obtained based on the flight time.

4. The laser ranging system according to claim 3, characterized in that: It also includes an optical fiber amplifier for amplifying the power of the laser beam emitted by the laser.

5. The laser ranging system according to claim 3, characterized in that: Also included is a collimator for collimating the probe beam and the echo beam.

6. The laser ranging system according to claim 5, characterized in that: 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 the local oscillator beam and the detection beam. The local oscillator beam is incident on the coupler, and the detection beam is incident on the circulator. The detection beam emitted by the circulator is collimated by the collimator and then incident on the target to be measured. After being reflected by the target to be measured, the echo beam is formed and is incident on the collimator. After collimation, it is incident on the coupler to be mixed with the local oscillator beam.

7. The laser ranging system according to claim 3, characterized in that: It also includes a galvanometer for scanning, the detection light beam split by the beam splitting unit is incident on the galvanometer, the detection light beam emitted by the galvanometer is incident on the target to be measured, and the echo light beam formed after being reflected by the target to be measured is incident on the galvanometer and then on the coupler.

8. A laser radar system, characterized in that: It includes laser, beam splitting unit, optical phased array chip, signal generator, phase modulator, coupler, photodetector, and data acquisition and analysis unit; among them, 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, and the preset phase is expressed as formula (1) and formula (2): （1） （2） in, represents a preset phase, a and b represent unequal constants respectively, t represents time, x represents an integer, and T represents a period; the laser beam output by the phase modulator is divided into a local oscillator beam and a detection beam by the beam splitting unit; the local oscillator beam and the detection beam are incident on the optical phased array chip, and the optical phased array chip outputs a laser beam for scanning; the local oscillator beam is incident on the coupler, and the detection beam is reflected after being incident on the target to be measured to become an echo beam, and the optical phased array chip receives the echo beam, and the echo beam is transmitted to the beam splitting unit and incident on 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 optical signal; the photodetector is used to convert the mixed 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 radar system and the target to be measured, and the analog electrical signal is analyzed according to formulas (3)-(6) to obtain the flight time. Formulas (3)-(6) are as follows: （3） （4） （5） （6） Wherein, I represents the intensity of the mixed optical signal, I T represents the intensity of the local oscillator beam, I R represents the intensity of the echo beam, A T represents the amplitude of the local oscillator beam, A R represents the amplitude of the echo beam, represents the optical frequency of the local oscillator beam, represents the flight time, which is the time interval between the detection beam and the echo beam; The waveform of the mixed light signal is obtained according to formula (3) to formula (6), the width of the mixed light signal pulse in the waveform of the mixed light signal is read to obtain the flight time, and the distance of the target to be measured is obtained based on the flight time.

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