CN112034437A - Laser detection system and detection method for pulse emission coherent reception - Google Patents

Abstract

The invention relates to the field of detectors, in particular to a laser detection system and a detection method for pulse emission coherent reception; the laser detection system comprises a laser seed source, a beam splitter, a time delay optical fiber, a light receiving component, a scanner, a frequency mixer, a signal processing component and a main control unit; the invention designs a laser detection system and a detection method for pulse emission coherent reception, sets a pulse signal with bias and combines a coherent reception mode, realizes the combination of pulse direct ranging and a coherent reception system, not only utilizes the advantages of high coherent reception sensitivity and strong external interference resistance, effectively reduces the minimum detectable distance, but also avoids expensive modulation devices in the existing coherent detection system, and effectively reduces the system cost; meanwhile, the pulse power of the emitted laser can be effectively reduced in a pulse emission coherent receiving mode, continuous modulation laser does not need to be emitted continuously, the average laser power of the system is effectively reduced, and the power consumption of the system is further reduced.

Description

Laser detection system and detection method for pulse emission coherent reception

Technical Field

The invention relates to the field of detectors, in particular to a laser detection system and a detection method for pulse emission coherent reception.

Background

Laser radar is a radar system for detecting characteristic quantities such as position, speed and the like of a target by emitting laser beams, and currently common laser detection can be divided into direct detection and coherent detection according to different detection modes.

The direct detection scheme mainly comprises two schemes, wherein one scheme is that one or a plurality of laser pulse signals are emitted in the working process, when the emitted pulses irradiate a target object, a part of energy is correspondingly reflected so as to be received by a detection system, the detection system realizes distance detection by measuring the time difference between the emitting time and the receiving time, the other scheme is that an amplitude-modulated continuous sine/cosine modulation signal or a square wave modulation signal is emitted, the receiving system receives the energy reflected by the target object by the emitted signals, and the target distance detection is realized by measuring the phase difference between the emitting time and the receiving time; the direct detection system has a simple structure and a mature signal processing technology, but because the detector has limited responsiveness and strong interference of external noise signals, accurate detection is realized by a high signal-to-noise ratio, high laser emission energy is often needed, and high optical power often means high power consumption and eye injury.

The coherent detection scheme includes mainly frequency modulated continuous wave mode and phase modulated continuous wave mode, in the frequency modulated continuous wave detection system, the emitting end emits frequency modulated continuous signal, the target reflects back partial laser energy to be received by the detection system, the local oscillation signal and the received signal are coherent processed to output the received signal, the processing system calculates the distance and relative radial speed of the target via detecting the direct frequency difference between the emitted signal and the received signal, in the phase modulated continuous wave detection system, the emitting end emits phase modulated continuous optical signal, the target reflects back partial laser energy to be received by the detection system, the local oscillation signal and the received signal are coherent processed to output the received signal, the processing system analyzes and recovers the received signal code, and calculates the distance of the target via comparing the time delay between the received sequence and the emitted sequence, calculating Doppler frequency shift through signal processing to obtain the relative radial velocity of the target object; the existing coherent detection system has high detection sensitivity and strong anti-interference capability, so that compared with direct detection, the equivalent or stronger detection effect can be achieved only by using lower laser power, but expensive frequency modulation or phase modulation devices are required in the detection process, and a complex algorithm is required at a signal processing end to analyze signals.

Therefore, it is important to design a new laser detection system and detection method that combines the simple signal processing method of direct detection and the high sensitivity of coherent detection system.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a laser detection system and a detection method for pulse emission coherent reception, which overcome the defects that the direct detection system in the prior art has limited responsivity, is easily interfered by external noise and needs high laser emission energy, and the coherent detection system in the prior art needs an expensive modulation device and needs a complex algorithm to perform signal analysis.

The technical scheme adopted by the invention for solving the technical problems is as follows: a laser detection system for pulse transmission coherent reception is provided, and the preferable scheme is as follows: the laser detection system comprises a laser seed source, a beam splitter, a time delay optical fiber for performing time domain delay on an optical signal, an optical receiving component, a scanner for light deflection scanning, a frequency mixer, a signal processing component for converting the optical signal into a digital signal and a main control unit;

the main control unit controls the laser seed source to emit a pulse signal with power bias, the pulse signal is divided into a local oscillator signal and a detection signal through the beam splitter, the local oscillator signal directly enters the frequency mixer, the detection signal enters the time-delay optical fiber for time-domain delay and then enters the scanner for deflection scanning, an echo signal is generated after the detection signal detects a target, the echo signal enters the frequency mixer after being received by the optical receiving assembly, the frequency mixer sends the local oscillator signal and the echo signal to the signal processing assembly after coherent reception, and the signal processing assembly converts the signal after coherent processing into a digital signal and sends the digital signal back to the main control unit so as to calculate the target distance.

Wherein, the preferred scheme is: the laser detection system further comprises a frequency shifter for performing frequency offset on the optical signal, wherein the frequency shifter is arranged in the local oscillator signal path and is used for performing frequency offset on the local oscillator signal and then injecting the local oscillator signal into the frequency mixer, or the frequency shifter is arranged in the detection signal path and is used for performing frequency offset on the detection signal and then injecting the detection signal into the scanner.

Wherein, the preferred scheme is: the signal processing assembly comprises a photoelectric detector and an analog-digital converter, the photoelectric detector is used for converting an optical signal subjected to coherent processing by the frequency mixer into a current signal and sending the current signal to the analog-digital converter, and the analog-digital converter is of a current input type and is used for converting the current signal into a digital signal.

Wherein, the preferred scheme is: the signal processing assembly comprises a photoelectric detector, a TIA device and an analog-digital converter, the photoelectric detector is used for converting an optical signal subjected to coherent processing by the frequency mixer into a current signal and sending the current signal to the TIA device, the TIA device is used for converting the current signal into a voltage signal and sending the voltage signal to the analog-digital signal converter, and the analog-digital converter is used for converting the voltage signal into a digital signal.

Wherein, the preferred scheme is: the light receiving component is one or a combined structure of at least two of a collimating lens, a circulator, a collecting lens and a beam expanding lens.

Wherein, the preferred scheme is: the optical receiving assembly comprises a circulator and a beam expander used for optical beam expansion, the circulator is an optical fiber circulator, the detection signal is output to the beam expander through the optical fiber circulator, and the echo signal is converged to the optical fiber circulator through the beam expander and then input to the mixer.

Wherein, the preferred scheme is: the light receiving component comprises a collimating lens for light path collimation, a collecting lens for light path convergence and a circulator, the circulator is a space light path component comprising a PBS (polarizing beam splitter) sheet, a half glass sheet or a half glass sheet, the detection signal enters the circulator after being collimated by the collimating lens, and the echo signal enters the circulator after being condensed by the collecting lens.

Wherein, the preferred scheme is: the laser detection system further comprises an optical power amplifier, wherein the optical power amplifier is arranged between the laser seed source and the beam splitter, or between the beam splitter and the delay optical fiber, or between the delay optical fiber and the light receiving component.

In order to solve the problems in the prior art, the present invention further provides a laser detection method for pulse emission coherent reception, and a preferred scheme thereof is that the laser detection method is implemented by the laser detection system, and the laser detection method specifically includes the following steps:

outputting a laser power pulse signal with bias power;

splitting a laser power pulse signal to obtain a detection signal and a local oscillation signal;

carrying out time delay output on the detection signal;

receiving and performing coherent processing on the local oscillator signal and an echo signal obtained by reflecting the detection signal by a target;

converting the optical signal after the coherent processing into a digital signal;

carrying out spectrum analysis on the digital signal to obtain speed information of a target object;

and calculating the flight time of the laser pulse according to the digital signal to acquire the distance of the target object.

Preferably, the laser detection method further includes the following steps:

acquiring pointing information of a scanning real-time light beam;

acquiring radial speed information of a target relative to a detection system;

calculating target azimuth information according to the distance and the pointing information of the target object;

and calculating the relative speed information of the target according to the plurality of target azimuth information to acquire the motion state of the target.

Compared with the prior art, the invention has the beneficial effects that by designing a pulse transmitting coherent receiving laser detection system and a detection method, setting a pulse signal with bias and combining a coherent receiving mode, the combination of pulse direct ranging and a coherent receiving system is realized, the advantages of high coherent receiving sensitivity and strong external interference resistance are utilized, the minimum detectable distance is effectively reduced, an expensive modulation device in the existing coherent detection system is avoided, and the system cost is effectively reduced; meanwhile, the pulse power of the emitted laser can be effectively reduced in a pulse emission coherent receiving mode, continuous modulation laser does not need to be emitted continuously, the average laser power of the system is effectively reduced, and the power consumption of the system is further reduced.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic diagram of a first embodiment of a laser detection system for pulse transmission coherent reception according to the present invention;

FIG. 2 is a schematic structural diagram of a pulse-emitting coherent-receiving laser detection system according to the present invention;

FIG. 3 is a schematic structural diagram III of a laser detection system for pulse transmission coherent reception according to the present invention;

FIG. 4-1 is a schematic structural diagram of a laser detection system for pulse transmission coherent reception according to the present invention;

FIG. 4-2 is a schematic structural diagram of a laser detection system for pulse transmission coherent reception according to the present invention;

FIG. 5 is a first schematic diagram of a signal processing module according to the present invention;

FIG. 6 is a second schematic structural diagram of a signal processing module according to the present invention;

FIG. 7 is a first schematic view of a light receiving element according to the present invention;

FIG. 8 is a second schematic structural view of a light receiving element according to the present invention;

FIG. 9 is a third schematic view of the structure of the light receiving element of the present invention;

FIG. 10 is a first flowchart of a laser detection method for pulse transmission coherent reception according to the present invention;

FIG. 11-1 is a diagram of a pulse signal in the present invention;

FIG. 11-2 is a diagram of an amplitude modulated signal in the present invention;

FIGS. 11-3 are graphs of echo pulse signals in the present invention;

FIGS. 11-4 are graphs of echo pulse signals in the present invention;

FIGS. 11-5 are graphs of echo pulse signals in the present invention;

fig. 12 is a flow chart of a laser detection method of pulse transmission coherent reception in the invention.

Detailed Description

The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in fig. 1-4, the present invention provides a preferred embodiment of a laser detection system for coherent reception of pulse emissions.

A laser detection system for pulse emission coherent reception, and referring to fig. 1, the laser detection system includes a laser seed source 1, a beam splitter 2, a delay fiber 3 for performing time-domain delay on an optical signal, an optical receiving component 4, a scanner 5 for optical deflection scanning, a mixer 6, a signal processing component 7 for converting the optical signal into a digital signal, and a main control unit 8;

the main control unit 8 controls the laser seed source 1 to emit a pulse signal with power offset, the pulse signal is divided into a local oscillation signal and a detection signal through the beam splitter 2, the local oscillation signal is directly emitted into the frequency mixer 6, the detection signal enters the time-delay optical fiber 3 for time-domain delay and then enters the scanner 5 for deflection scanning, an echo signal is generated after the detection signal detects a target, the echo signal enters the frequency mixer 6 after being received by the optical receiving component 4, the frequency mixer 6 performs coherent reception on the local oscillation signal and the echo signal and then sends the signals to the signal processing component 7, and the signal processing component 7 converts the signals after coherent processing into digital signals and sends the digital signals back to the main control unit 8 so as to calculate the target distance.

Specifically, the laser seed source is used for generating a pulse signal with a certain power bias, the number of pulses of the pulse signal can be one or more, and when a plurality of pulses are selected to be transmitted, different pulse amplitudes or time intervals can be set, so that the coding standard of self-transmitting pulses is realized, and the capability of the system for resisting the interference of other laser radars is effectively improved; the beam splitter is used for splitting the input laser into two or more paths according to a set proportion for output, and in the embodiment, the beam splitter is used for splitting the input laser into a local oscillator signal with low success rate and a detection signal with high power; the delay optical fiber is arranged at the rear end of the detection signal output by the beam splitter and is used for delaying the detection signal relative to the local oscillator signal in a time domain, so that the position of the local oscillator signal can be judged in time, and detection interference caused by introduction of the local oscillator pulse signal is avoided; the light receiving component is mainly used for receiving echo signals of detection signals reflected by an external target; the frequency mixer is mainly used for performing coherent receiving processing on a local oscillator signal and an echo signal reflected by an external target, and sending the optical signal after the coherent receiving processing to the signal processing component, in this embodiment, the frequency mixer may be a 90-degree frequency mixer, a 180-degree frequency mixer, or another type, or may be composed of devices such as a discrete mirror, a lens, a PBS, or an optical fiber or optical waveguide integrated device; the scanner is used for deflection scanning of detection signals, covers a large range of FOV, and realizes three-position detection, and can adopt a vibrating mirror, a rotating mirror, an MEMS scanning mirror, OPA or liquid crystal and the like.

The laser detection system for pulse emission coherent reception combines pulse direct ranging in a direct detection system and a coherent reception mode in the coherent detection system, has the advantages of high sensitivity and strong external interference resistance of the coherent detection system, avoids the defects of expensive modulation devices and high system cost of the traditional coherent detection system, does not need high laser power of the direct detection system, does not need to continuously emit high-power modulated laser, reduces the power consumption of the system, and protects the human eye safety of operators, wherein the pulse amplitude and the offset of a laser power pulse signal with offset power output by a laser seed source can be adjusted in real time according to needs, so as to avoid the influence of the pulse signal in a local oscillator signal on detection, the detection signal is output in a delayed manner, and when the delay guarantees that the detection signal is transmitted to the outside of the system within an effective distance detection range, the echo signal of reflection can not cause the confusion with the local oscillator signal, when the detection signal produced echo signal and returned light receiving component through the target reflection, the power of the detection signal of transmission is compared to the power of echo signal and will be reduced a lot, this moment, because the existence of outside light noise and the inside photoelectric noise of system, can't extract effective signal with direct detection system, and this scheme has adopted coherent reception, the local oscillator signal has been introduced and has been strengthened the processing gain, can detect the laser pulse that traditional direct detection system can't respond down, and, because local oscillator light has irrelevance with photoelectric noise, consequently can effectively improve the SNR.

Further, the laser detection system further includes a frequency shifter 9 for performing frequency shift on the optical signal, referring to fig. 2, the frequency shifter 9 is disposed in the local oscillator signal path and is configured to perform frequency shift on the local oscillator signal and then inject the local oscillator signal into the mixer 6, referring to fig. 3, or the frequency shifter 9 is disposed in the detection signal path and is configured to perform frequency shift on the detection signal and then inject the detection signal into the scanner 5.

Specifically, the frequency shifter is mainly used for outputting the local oscillator signal or the detection signal after generating a frequency offset, and aims to enable the local oscillator signal and the detection signal to generate a fixed frequency difference, the frequency shifter may be an electro-optical frequency shifter or an acousto-optical frequency shifter, and the frequency shifter may be configured in a local oscillator signal path or a detection signal path.

Further, the laser detection system further includes an optical power amplifier 10, referring to fig. 4-1, the optical power amplifier 10 is disposed between the laser seed source 1 and the beam splitter 2, or referring to fig. 4-2, the optical power amplifier 10 is disposed between the delay fiber 3 and the optical receiving component 4, and further, the optical power amplifier 10 may also be disposed between the delay fiber 3 and the optical beam splitter 2.

Specifically, the optical power amplifier is configured to amplify and output the input laser power, and it should be noted that the optical power amplifier may be configured in the detection signal path or at the front end of the beam splitter, and when the laser power of the laser seed source is large enough, the optical power amplifier may not be used.

As shown in fig. 5 and 6, the present invention provides a preferred embodiment of the signal processing assembly.

Scheme one

Referring to fig. 5, the signal processing component 7 includes a photodetector 71 and an analog-to-digital converter 72, the photodetector 71 is configured to convert the optical signal subjected to the coherent processing by the mixer 6 into a current signal and send the current signal to the analog-to-digital converter 73, and the analog-to-digital converter 73 is configured to convert the current signal into a digital signal.

Specifically, the photodetector is mainly used for converting a coherent signal output by the mixer into a current signal, and the photodetector may be specifically configured as a single PD or a balanced detector; the analog-digital converter is specifically an ADC chip, and the ADC chip is of a current input type and is mainly used for collecting current signals, converting the collected current signals into digital signals and sending the digital signals to the main control unit for signal processing.

Scheme two

Referring to fig. 6, the signal processing assembly 7 includes a photo detector 71, a TIA device 72, and an analog-to-digital converter 73 ', the photo detector 71 is configured to convert an optical signal subjected to coherent processing by the mixer 6 into a current signal and send the current signal to the TIA device 72, the TIA device 72 is configured to convert the current signal into a voltage signal and send the voltage signal to the analog-to-digital signal converter 73 ', and the analog-to-digital converter 73 ' is configured to convert the voltage signal into a digital signal.

Specifically, the photodetector is mainly used for converting a coherent signal output by the mixer into a current signal, and the photodetector may be specifically configured as a single PD or a balanced detector; the TIA device is mainly used for converting a current signal output by the photoelectric detector into a voltage signal, the analog-digital converter is specifically an ADC chip, and the ADC chip is of a voltage input type and is mainly used for collecting the voltage signal, converting the collected voltage signal into a digital signal and sending the digital signal to the main control unit for signal processing.

As shown in fig. 7-9, the present invention provides a preferred embodiment of a light receiving module.

Referring to fig. 7 to 9, the light receiving component 4 is one or a combination of at least two of a collimating lens 41, a circulator 43, a collecting lens 44 and a beam expanding lens 45.

Scheme one

Referring to fig. 7, the light receiving component 4 includes a collimating lens 41 for collimating the light path and a collecting lens 44 for converging the light path, the detection signal enters the scanning component 5 for deflection scanning after being collimated by the collimating lens 41, and the echo signal enters the mixer 6 after being condensed by the collecting lens 44.

In particular, the scheme is suitable for the case of not adopting a coaxial optical system.

Scheme two

Referring to fig. 8, the light receiving module includes a circulator 43 and a beam expander 45 for expanding light, the detection signal is output to the beam expander 45 through the circulator 43, and the echo signal is converged to the circulator 43 through the beam expander 45 and then input to the mixer 6.

Specifically, the circulator is an optical fiber circulator, when the optical fiber circulator is used as a receiving device, an output optical path may not be collimated by a collimating lens, and a receiving optical path may not be converged by a collecting lens.

Scheme three

Referring to fig. 9, the light receiving component 4 includes a collimator 41 for collimating the light path, a condenser 44 for converging the light path, and a circulator 43, the detection signal enters the circulator 43 after being collimated by the collimator 41, and the echo signal enters the mixer 6 after being condensed by the condenser 44.

Specifically, the circulator is a spatial optical path component with a circulator function and including elements such as a PBS plate, a quarter-wave plate, a half-wave plate, and the like, and is mainly used for enabling the transmitted optical signal and the received optical signal to be in the same optical path in most of paths, so as to conveniently design a coaxial optical path system.

As shown in fig. 10-12, the present invention also provides a preferred embodiment of a laser probing method of pulse transmission coherent reception.

A laser detection method for pulse emission coherent reception, referring to fig. 10, the laser detection method is implemented by the laser detection system as described above, and the laser detection method specifically includes the following steps:

s1, outputting a laser power pulse signal with bias power;

s2, splitting the laser power pulse signal to obtain a detection signal and a local oscillation signal;

s3, carrying out time delay output on the detection signal, and carrying out frequency offset on the local oscillation signal or the detection signal;

s4, receiving and coherently processing the local oscillation signal and an echo signal obtained by reflecting the detection signal by a target;

s5, converting the optical signal after the coherent processing into a digital signal;

s6, carrying out spectrum analysis on the digital signal to obtain speed information of the target object;

and S7, calculating the flight time of the laser pulse according to the digital signal to acquire the distance of the target object.

In S3, the frequency offset of the local oscillator signal or the probe signal is selectively performed, and the frequency offset may be optionally not performed.

Specifically, because the power of the echo signal obtained after the detection signal is reflected by the target is much smaller than the power of the transmitted detection signal, the local oscillator signal is introduced to enhance the processing gain of the echo signal, so that the comparison is performed according to the strength of the transmitted detection signal, the strength of the local oscillator signal and the strength of the echo signal, an electric pulse signal with obvious discrimination can be output, then the flying time of the laser signal can be calculated according to the sampling time of the electric pulse signal, and the distance of the target object can be calculated by combining the light speed.

The distance detection comprises the following calculation steps: comparing the strength of the transmitted probe signal, the strength of the local oscillator signal, and the strength of the echo signal, and outputting an electrical pulse signal with a distinct degree of discrimination (refer to fig. 11-1, where a1 is a driving pulse signal sent by the main control unit, a2 is a laser seed source pulse signal, A3 is a local oscillator signal, a4 is a delayed probe signal, a5 is an echo signal, a6 is a coherent signal after coherent processing, a1 is a bias voltage, a2 is a laser seed source bias light intensity, A3 is a local oscillator bias light intensity, a5 is an echo signal light intensity, and a6 is a coherent signal light intensity), and because there is relative motion between the target and the laser probe system, a doppler shift is introduced in the received echo signal, so there is a corresponding frequency difference between the local oscillator signal and the echo signal, and the signal output by the optical signals with different frequencies during coherent probing is not a simple form of direct current plus pulse, instead, an amplitude modulation signal is formed according to the originally transmitted detection signal intensity and frequency difference signal (refer to fig. 11-2, where B1 is idle signal amplitude, and B2 is pulse signal intensity), and further, the original pulse signal needs to be recovered for distance detection, and corresponding signal processing needs to be performed on the amplitude modulation signal.

Scheme one

By means of digital signals.

Scheme two

And a hardware processing mode is utilized.

The specific amplitude modulation signal processing step includes: specifically, the method comprises the steps of obtaining a digitized echo pulse signal through half-wave rectification (refer to fig. 11-3), or obtaining a digitized echo pulse signal through full-wave rectification (refer to fig. 11-4), and obtaining a digitized echo pulse signal through low-pass filtering and the like; or directly obtain the original pulse modulation signal by rectifying and filtering the echo signal through hardware and the like (refer to fig. 11-5).

After the echo pulse signal is recovered, the flight time of the laser pulse can be calculated according to the sampling time by using methods such as a fixed threshold value or constant ratio timing method, and the target distance can be calculated according to the light speed.

Further, referring to fig. 12, the laser detection method further includes the steps of:

s8, acquiring real-time beam pointing information of the scanning beam;

s9, acquiring radial speed information of the target relative to the detection system;

s10, calculating target azimuth information according to the distance and the pointing information of the target object;

and S11, calculating the relative speed information of the target according to the plurality of target azimuth information to acquire the motion state of the target.

Specifically, the FFT processing may be directly performed on the amplitude modulation signal to obtain doppler shift information including information about doppler shift caused by direct relative motion with the target object, and the relative velocity information of the target may be further analyzed; the target azimuth information can be calculated by combining the distance information of the target and the real-time pointing information of the scanner light beam, the relative speed information of the target can be obtained by combining a plurality of azimuth information, the type of the target can be further judged, and the information such as the motion state of the target can be further analyzed.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, but rather as embodying the invention in a wide variety of equivalent variations and modifications within the scope of the appended claims.

Claims (10)

1. A laser detection system for pulse transmission coherent reception, comprising: the laser detection system comprises a laser seed source, a beam splitter, a time delay optical fiber for performing time domain delay on an optical signal, an optical receiving component, a scanner for light deflection scanning, a frequency mixer, a signal processing component for converting the optical signal into a digital signal and a main control unit;

the main control unit controls the laser seed source to emit a pulse signal with power bias, the pulse signal is divided into a local oscillator signal and a detection signal through the beam splitter, the local oscillator signal directly enters the frequency mixer, the detection signal enters the time-delay optical fiber for time-domain delay and then enters the scanner for deflection scanning, an echo signal is generated after the detection signal detects a target, the echo signal enters the frequency mixer after being received by the optical receiving assembly, the frequency mixer sends the local oscillator signal and the echo signal to the signal processing assembly after coherent reception, and the signal processing assembly converts the signal after coherent processing into a digital signal and sends the digital signal back to the main control unit so as to calculate the target distance.

2. The laser detection system of claim 1, wherein: the laser detection system further comprises a frequency shifter for performing frequency offset on the optical signal, wherein the frequency shifter is arranged in the local oscillator signal path and is used for performing frequency offset on the local oscillator signal and then injecting the local oscillator signal into the frequency mixer, or the frequency shifter is arranged in the detection signal path and is used for performing frequency offset on the detection signal and then injecting the detection signal into the scanner.

3. The laser detection system of claim 1, wherein: the signal processing assembly comprises a photoelectric detector and an analog-digital converter, the photoelectric detector is used for converting an optical signal subjected to coherent processing by the frequency mixer into a current signal and sending the current signal to the analog-digital converter, and the analog-digital converter is of a current input type and is used for converting the current signal into a digital signal.

4. The laser detection system of claim 1, wherein: the signal processing assembly comprises a photoelectric detector, a TIA device and an analog-digital converter, the photoelectric detector is used for converting an optical signal subjected to coherent processing by the frequency mixer into a current signal and sending the current signal to the TIA device, the TIA device is used for converting the current signal into a voltage signal and sending the voltage signal to the analog-digital signal converter, and the analog-digital converter is used for converting the voltage signal into a digital signal.

5. The laser detection system of claim 1, wherein: the light receiving component is one or a combined structure of at least two of a collimating lens, a circulator, a collecting lens and a beam expanding lens.

6. The laser detection system of claim 1, wherein: the optical receiving assembly comprises a circulator and a beam expander used for optical beam expansion, the circulator is an optical fiber circulator, the detection signal is output to the beam expander through the optical fiber circulator, and the echo signal is converged to the optical fiber circulator through the beam expander and then input to the mixer.

7. The laser detection system of claim 1, wherein: the light receiving component comprises a collimating lens for light path collimation, a collecting lens for light path convergence and a circulator, the circulator is a space light path component comprising a PBS (polarizing beam splitter) sheet, a half glass sheet or a half glass sheet, the detection signal enters the circulator after being collimated by the collimating lens, and the echo signal enters the circulator after being condensed by the collecting lens.

8. The laser detection system of claim 1, wherein: the laser detection system further comprises an optical power amplifier, wherein the optical power amplifier is arranged between the laser seed source and the beam splitter, or between the beam splitter and the delay optical fiber, or between the delay optical fiber and the light receiving component.

9. A laser detection method for pulse transmission coherent reception, wherein the laser detection method is implemented by the laser detection system according to any one of claims 1 to 8, and the laser detection method specifically includes the following steps:

outputting a laser power pulse signal with bias power;

splitting a laser power pulse signal to obtain a detection signal and a local oscillation signal;

carrying out time delay output on the detection signal;

carrying out frequency offset on the local oscillation signal or the detection signal;

receiving and performing coherent processing on the local oscillator signal and an echo signal obtained by reflecting the detection signal by a target;

converting the optical signal after the coherent processing into a digital signal;

carrying out spectrum analysis on the digital signal to obtain speed information of a target object;

and calculating the flight time of the laser pulse according to the digital signal to acquire the distance of the target object.

10. The laser detection method of claim 9, further comprising the steps of:

acquiring pointing information of a scanning real-time light beam;

acquiring radial speed information of a target relative to a detection system;

calculating target azimuth information according to the distance and the pointing information of the target object;

and calculating the relative speed information of the target according to the plurality of target azimuth information to acquire the motion state of the target.

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