A laser detection device and method

Abstract

The application discloses a kind of laser detection device and method, belong to laser detection technical field, the device includes beam output module, light splitting module, optical path multiplexing module, two coherent mixing modules and signal processing module;Beam output module outputs the positive and negative double-chirp laser of frequency-modulated time sequence synchronization of different wavelength, chirp rate absolute value equal, after light splitting, optical path multiplexing, get local light and echo light, two coherent mixing modules generate four-way quadrature beat frequency signal, signal processing module does product subtraction and addition operation to four-way beat frequency signal and constructs complex signal, offset Doppler broadening interference introduced by rotating polygon mirror, again Fourier transform, peak searching obtains intermediate frequency parameter and calculates target vector velocity, the application can completely eliminate the influence of Doppler broadening on speed measurement, significantly improve speed measurement precision.

Description

Technical Field

[0001] This invention relates to the field of laser detection technology, and specifically to a laser detection device and method. Background Technology

[0002] In the evolution of laser detection from mechanical rotation to hybrid solid-state, the adoption of a combined rotating mirror and galvanometer scanning scheme—a rotating-galvanometer scanning scheme—is a key technological advancement. The core of this scheme lies in its dual-axis scanning system: one dimension is handled by a high-speed rotating multifaceted mirror, enabling continuous scanning of the beam across a large azimuth angle; the other dimension is handled by one or more galvanometers, the core of which is a rotor with miniature reflective mirrors. Electromagnetic force drives the rotor and mirrors to precisely reciprocate around an axis at a limited angle, thereby changing the beam's elevation angle. A stationary laser emits the beam to the galvanometer mirrors, which reflect it before it reaches the rotating mirror. Finally, the coordinated motion of the two mirrors synthesizes a two-dimensional scanning field of view.

[0003] Although rotary scanning has advantages such as high control precision, fast response, and large scanning field of view, scanning schemes based on this device still have a series of inherent defects. In particular, the high-speed rotating mirror introduces a new physical challenge: the Doppler broadening effect. Figure 1 As shown, the high-speed rotating mirror itself has a very high linear velocity, such as an angular velocity of ω. At different incident positions, the angular velocities are V1, V2, or V3, which causes a significant Doppler frequency shift in the reflected laser beam. Because the velocity vectors differ at different parts of the mirror and the velocity changes continuously during the scanning process, the beat frequency peak of the received echo light and the local oscillator light is broadened. The spectral peaks before and after the Doppler broadening introduced by the high-speed rotation of the rotating polygonal mirror are shown below. Figure 2 As shown, the Doppler broadening effect severely reduces the signal-to-noise ratio of coherent detection lidar on the one hand, and seriously degrades the velocity measurement accuracy on the other, becoming one of the main limiting factors for the application of high-precision, high-resolution coherent lidar. Summary of the Invention

[0004] This invention provides a laser detection device and method to solve the technical problem of deteriorated velocity measurement accuracy due to the Doppler broadening effect.

[0005] In a first aspect, the present invention provides a laser detection device, comprising: The beam output module is used to output a first modulated light and a second modulated light with different wavelengths. The first modulated light and the second modulated light are frequency-modulated timing synchronous positive and negative double-chilled lasers with the same frequency modulation period, and the absolute values ​​of their chirp rates are equal. A beam splitting module is used to split the first modulated light into a first emitted light and a first local oscillator light, and to split the second modulated light into a second emitted light and a second local oscillator light; The optical path multiplexing module is used to combine the first emitted light and the second emitted light and then emit them to the target, and to receive the first echo light returned based on the first emitted light and the second echo light returned based on the second emitted light; The first coherent mixing module is used to generate a first orthogonal beat frequency signal through the first local oscillator light and the first echo light. The first orthogonal beat frequency signal includes a first beat frequency signal and a second beat frequency signal that are orthogonal to each other. The second coherent mixing module is used to generate a second orthogonal beat frequency signal through the second local oscillator light and the second echo light. The second orthogonal beat frequency signal includes a third beat frequency signal and a fourth beat frequency signal that are orthogonal to each other. The signal processing module is used to obtain a cosine component by subtracting the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals, and to obtain a sine component by adding the product of the second and third beat frequency signals to the product of the first and fourth beat frequency signals. A first complex signal is generated based on the sine and cosine components, the peak position of the spectrum of the first complex signal is extracted to obtain a first intermediate frequency parameter, and the vector velocity of the target is calculated based on the first intermediate frequency parameter.

[0006] In one optional implementation, the first coherent mixer module includes: The first optical mixer is used to receive the first local oscillator light output from the beam splitter module and the first echo light output from the optical path multiplexing module. It generates four mixing signals with a relative phase shift of 90 degrees in sequence: the first mixing signal, the second mixing signal, the third mixing signal, and the fourth mixing signal. The first photoelectric balance detector is used to receive the first mixing signal and the third mixing signal output by the first optical mixer, and to obtain the first beat frequency signal by subtracting the first mixing signal and the third mixing signal. The second photoelectric balance detector is used to receive the second mixing signal and the fourth mixing signal output by the first optical mixer, and to obtain the second beat frequency signal by subtracting the second mixing signal and the fourth mixing signal. The second coherent mixer module includes: The second optical mixer is used to receive the second local oscillator light output from the beam splitter module and the second echo light output from the optical path multiplexing module. It generates four mixing signals, namely the fifth, sixth, seventh, and eighth mixing signals, with a relative phase shift of 90 degrees in sequence, through the second local oscillator light and the second echo light. The third photoelectric balance detector is used to receive the fifth and seventh mixing signals output by the second optical mixer, and to obtain the third beat frequency signal by subtracting the fifth and seventh mixing signals. The fourth photoelectric balance detector is used to receive the sixth and eighth mixing signals output by the second optical mixer, and to obtain the fourth beat frequency signal by subtracting the sixth and eighth mixing signals.

[0007] In one optional implementation, the first coherent mixer module further includes: The first filter is used to perform low-pass filtering on the first beat frequency signal output by the first photoelectric balance detector; The first analog-to-digital converter is used to perform analog-to-digital conversion on the first beat frequency signal after low-pass filtering. The second filter is used to perform low-pass filtering on the second beat frequency signal output by the second photoelectric balance detector. The second analog-to-digital converter is used to perform analog-to-digital conversion on the low-pass filtered second beat frequency signal; The second coherent mixer module also includes: The third filter is used to perform low-pass filtering on the third beat frequency signal output by the third photoelectric balance detector; The third analog-to-digital converter is used to convert the low-pass filtered third beat frequency signal into an analog-to-digital signal; The fourth filter is used to perform low-pass filtering on the fourth beat frequency signal output by the fourth photoelectric balance detector; The fourth analog-to-digital converter is used to perform analog-to-digital conversion on the low-pass filtered fourth beat frequency signal.

[0008] In one alternative implementation, the beam output module includes: First frequency-modulated continuous wave light source; The first driving module is used to drive the first frequency-modulated continuous wave light source to output the first modulated light; The first optical amplifier is used to amplify the first modulated light output from the first frequency-modulated continuous wave light source; Second frequency-modulated continuous wave light source; The second driving module is used to drive the second frequency-modulated continuous wave light source to output the second modulated light. The second optical amplifier is used to amplify the second modulated light output from the second frequency-modulated continuous wave light source.

[0009] In one alternative implementation, the beam splitting module includes: The first optical beam splitter is used to split the first modulated light output by the beam output module to obtain the first emitted light and the first local oscillator light. The second beam splitter is used to split the second modulated light output from the beam output module to obtain the second emitted light and the second local oscillator light.

[0010] In one optional implementation, the optical path multiplexing module includes: A beam combiner is used to combine the first and second emitted beams output from the beam splitter to obtain a combined beam. An optical circulator is used to output the combined beam to an optical scanner and receive the echo light returned by the optical scanner, and output the echo light to a wave splitter. The optical scanner includes a rotating multifaceted mirror for directing the combined beam to the transceiver telescope and receiving the echo light returned from the transceiver telescope. A transceiver telescope is used to send a beam of combined light to a target and receive the returning echo light. A wavelength divider is used to divide the echo light based on wavelength to obtain a first echo light and a second echo light, wherein the first echo light and the first emitted light have the same wavelength, and the second echo light and the second emitted light have the same wavelength.

[0011] In a second aspect, the present invention provides a laser detection method, applied to a laser detection device as described in any of the first aspects of the present invention, the method comprising: Acquire the first beat frequency signal and the second beat frequency signal output by the first coherent mixer module, as well as the third beat frequency signal and the fourth beat frequency signal output by the second coherent mixer module; The cosine component is obtained by subtracting the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals. The sine component is obtained by adding the product of the first and fourth beat frequency signals to the product of the second and third beat frequency signals. The first complex signal is generated based on the sine and cosine components. Extract the peak position of the spectrum of the first complex signal to obtain the first intermediate frequency parameter; The target's vector velocity is calculated based on the first intermediate frequency parameter.

[0012] In one optional implementation, generating a first complex signal based on a first beat frequency signal, a second beat frequency signal, a third beat frequency signal, and a fourth beat frequency signal includes: Subtracting the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals yields the cosine component. Add the product of the second and third beat frequency signals to the product of the first and fourth beat frequency signals to obtain the sinusoidal component; The first complex signal is obtained by complexifying the sine and cosine components.

[0013] In one optional implementation, the peak position of the spectrum of the first complex signal is extracted to obtain the first intermediate frequency parameter, including: Perform a Fast Fourier Transform on the first complex signal to obtain the first spectral distribution; The first intermediate frequency parameter is obtained by extracting the position corresponding to the spectral peak of the first spectral distribution using the centroid method.

[0014] In one optional implementation, the laser detection method further includes: A second complex signal is generated based on the first and second beat frequency signals, and a third complex signal is generated based on the third and fourth beat frequency signals. The second complex signal is subjected to a Fast Fourier Transform to obtain a second spectral distribution. The position corresponding to the spectral peak of the second spectral distribution is extracted by the centroid method to obtain the second intermediate frequency parameter. The third complex signal is subjected to a Fast Fourier Transform to obtain a third spectral distribution. The position corresponding to the spectral peak of the third spectral distribution is extracted by the centroid method to obtain the third intermediate frequency parameter. The reference target velocity and reference target range are calculated based on the second and third intermediate frequency parameters. The vector velocity of the target calculated based on the first intermediate frequency parameter is taken as the ideal target velocity. The measurement accuracy of the ideal target velocity, the measurement accuracy of the reference target velocity, and the measurement accuracy of the reference target distance are obtained. The product of the measurement accuracy of the ideal target velocity and the measurement accuracy of the reference target velocity is divided by the measurement accuracy of the reference target distance to obtain the measurement accuracy of the ideal target distance. The first intermediate frequency correction value is obtained by subtracting the reference target velocity from the ideal target velocity. The second intermediate frequency correction value is calculated based on the first intermediate frequency correction value, the measurement accuracy of the ideal target velocity, the measurement accuracy of the reference target velocity, the measurement accuracy of the reference target distance, and the measurement accuracy of the ideal target distance. The ideal target distance is calculated based on the second intermediate frequency correction value and the reference target distance, and then used as the optimized target distance.

[0015] The present invention has the following beneficial effects: The laser detection device of this invention includes a beam output module, a beam splitting module, an optical path multiplexing module, a first coherent mixing module, a second coherent mixing module, and a signal processing module. The beam output module outputs a frequency-modulated, timing-synchronized positive and negative double-chirped laser. After passing through the beam splitting module and the optical path multiplexing module, it generates a local oscillator beam and an echo beam. The local oscillator beam and the echo beam are then processed by the first and second coherent mixing modules to generate a first orthogonal beat frequency signal containing a first beat frequency signal and a second beat frequency signal, and a second orthogonal beat frequency signal containing a third beat frequency signal and a fourth beat frequency signal, respectively. The signal processing module performs product, subtraction, and addition operations on the four beat frequency signals to construct a complex signal to cancel Doppler broadening interference. The intermediate frequency parameters are then obtained through Fourier transform and peak finding, and used to calculate the target's vector velocity. This invention requires no additional hardware or cumbersome post-processing, has strong real-time performance, effectively eliminates the influence of Doppler broadening on velocity measurement, and significantly improves velocity measurement accuracy.

[0016] This invention can measure speed and distance simultaneously. Speed ​​measurement is completely unaffected by Doppler broadening, while distance measurement, although still affected by Doppler broadening, can be optimized and corrected to further improve distance measurement accuracy.

[0017] Existing technologies all use single-wavelength lasers for coherent laser detection. This invention is the first to use a combination of dual-wavelength positive and negative dual-chirped lasers, utilizing the complementarity of chirp rates to cancel out Doppler broadening interference terms.

[0018] Existing technologies only use simple Fourier transforms or filtering to process beat frequency signals. This invention is the first to use product-subtraction / addition operations of four beat frequency signals to construct complex signals, completely eliminating Doppler broadening at the signal processing level without the need for additional hardware.

[0019] This invention is not only applicable to rotary scanning, but can also be extended to other laser coherent detection scenarios with Doppler broadening, possessing versatility and practicality. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A schematic diagram illustrating the introduction of Doppler broadening into a rotating polyhedron; Figure 2 A schematic diagram comparing the spectral peaks before and after the Doppler broadening introduced by the high-speed rotation of the rotating multifaceted mirror; Figure 3 This is a schematic diagram of the structure of the laser detection device according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the waveform of the positive and negative double-chirped sawtooth wave according to an embodiment of the present invention; Figure 5 This is a waveform diagram of a positive and negative double-chirped symmetrical triangular wave according to an embodiment of the present invention; Figure 6 This is a schematic flowchart of the laser detection method according to an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1. Beam output module; 2. Beam splitting module; 3. Optical path multiplexing module; 41. First coherent mixer module; 42. Second coherent mixer module; 5. Signal processing module; 6. Host computer; 101. First frequency-modulated continuous wave source; 102. First drive module; 103. First optical amplifier; 104. Second frequency-modulated continuous wave source; 105. Second drive module; 106. Second optical amplifier; 201. First optical beam splitter; 202. Second optical beam splitter; 301. Beam combiner; 302. Optical circulator; 303. Optical scanner 304. Transceiver telescope; 305. Wavelength divider; 411. First optical mixer; 412. First photoelectric balance detector; 413. Second photoelectric balance detector; 414. First filter; 415. Second filter; 416. First analog-to-digital converter; 417. Second analog-to-digital converter; 421. Second optical mixer; 422. Third photoelectric balance detector; 423. Fourth photoelectric balance detector; 424. Third filter; 425. Fourth filter; 426. Third analog-to-digital converter; 427. Fourth analog-to-digital converter. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection of two components. The terms "parallel," "perpendicular," and "equal" include the described situation and situations that are similar to the described situation, where the range of similarity is within an acceptable deviation range, which is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, "parallel" includes absolute parallelism and approximate parallelism, where the acceptable deviation range for approximate parallelism can be, for example, within 5°; "perpendicular" includes absolute perpendicularity and approximate perpendicularity, where the acceptable deviation range for approximate perpendicularity can also be, for example, within 5°; "equal" includes absolute equality and approximate equality, where the acceptable deviation range for approximate equality can be, for example, the difference between the two equals being less than or equal to 5% of either one. For a person skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0025] Among the relevant schemes, the Doppler broadening suppression / compensation schemes mainly include the following: 1. Reduce the linear velocity of the rotating mirror surface. This is the most direct technical approach, specifically including reducing the spot size, shrinking the size of the rotating mirror's surface, or lowering its rotation speed. However, this approach essentially involves a trade-off between system performance: reducing the linear velocity directly suppresses Doppler shift, but at the cost of sacrificing signal-to-noise ratio and scanning field of view. To achieve a better balance in this trade-off, related technologies employ beam shaping techniques, aiming to compress the size of the transmitting and receiving spots in the rotating mirror's direction. This effectively reduces the equivalent linear velocity of the acting mirror surface without significantly sacrificing too much optical power, thereby suppressing the Doppler effect. The main drawback of this approach is that it leads to spatial asymmetry in the transmitting / receiving spots, which may introduce optical aberrations such as astigmatism, pose challenges to subsequent optical path calibration and point cloud quality, and increase the complexity of the transmitting / receiving optical path.

[0026] 2. Real-time pre-compensation. A high-precision encoder monitors the position and instantaneous velocity of the rotating mirror in real time and calculates the Doppler frequency shift introduced by the mirror at the current moment. Subsequently, an equal-magnitude, opposite-direction frequency offset is pre-applied to the laser's modulation signal, thus canceling out the effect at the transmitting end. Although theoretically accurate, this method places extremely high demands on the system's real-time computing power, sensor accuracy, and control system latency, making it complex and costly to implement.

[0027] 3. Backend Signal Processing and Calibration. In the signal processing stage, the Doppler frequency shift introduced by the rotating mirror is modeled as a known systematic error. Digital signal processing algorithms are used to eliminate or smooth the Doppler effect in the digital domain. The advantage is high flexibility, requiring no hardware modifications. However, its effectiveness heavily depends on the accuracy of the model; when dealing with dynamic targets and complex scenes, computational complexity and performance degradation are possible.

[0028] In view of this, embodiments of the present invention provide a laser detection device and method that eliminates the influence of Doppler broadening introduced by high-speed rotating multi-mirror on velocity measurement, significantly improves velocity measurement accuracy, and can simultaneously perform distance measurement.

[0029] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] According to an embodiment of the present invention, a laser detection device is provided, such as... Figure 3 As shown, the laser detection device includes: Beam output module 1 is used to output a first modulated light and a second modulated light with different wavelengths. The first and second modulated lights are frequency-modulated synchronous positive and negative double-chilled lasers with the same frequency modulation period, and their absolute chirp rates are equal. Beam output module 1 is responsible for generating and outputting beams with specific characteristics, namely the first and second modulated lights. The first modulated light is a positively chirped laser with a wavelength of λ1, and the second modulated light is a negatively chirped laser with a wavelength of λ2. The absolute values ​​of the chirp rates of the positive and negative chirped lasers are equal. Figure 4 and Figure 5 As shown, the first and second modulated lights can be positive and negative double-chirped sawtooth waves or positive and negative double-chirped symmetrical triangular waves, wherein... Figure 4 The horizontal axis represents time t, and the vertical axis represents frequency f. The first modulated light is a positively chirped laser, and the second modulated light is a negatively chirped laser. The two are frequency-modulated synchronously, have the same frequency modulation period, and have equal absolute chirp rates. Figure 5 The horizontal axis represents time t, and the vertical axis represents frequency f. The two have synchronous frequency modulation timing with opposite chirps, the same frequency modulation period, and equal absolute chirp rates.

[0031] Beam splitter 2 is used to split the first modulated light into a first emitted light and a first local oscillator light, and to split the second modulated light into a second emitted light and a second local oscillator light. Beam splitter 2 can split the first and second modulated lights according to a set ratio. Generally, most of the energy in the first modulated light is used as the first emitted light, and a small portion is used as the first local oscillator light. Similarly, most of the energy in the second modulated light is used as the second emitted light, and a small portion is used as the second local oscillator light. The first and second emitted lights enter optical path multiplexing module 3, and the first and second local oscillator lights enter first coherent mixing module 41 and second coherent mixing module 42, respectively.

[0032] The optical path multiplexing module 3 is used to combine the first emitted light and the second emitted light and emit them to the target, and to receive the first echo light and the second echo light reflected back from the first emitted light. After the first emitted light and the second emitted light are emitted to the target through the optical path multiplexing module 3, the optical path multiplexing module 3 receives the echo light reflected from the target. The echo light includes the first echo light and the second echo light reflected back from the first emitted light. The wavelength of the first echo light is the same as the wavelength of the first emitted light, and the wavelength of the second echo light is the same as the wavelength of the second emitted light.

[0033] The first coherent mixing module 41 is used to generate a first orthogonal beat frequency signal through the first local oscillator light and the first echo light. The first orthogonal beat frequency signal includes a first beat frequency signal and a second beat frequency signal that are orthogonal to each other. The first local oscillator light and the first echo light are coherently mixed to obtain the first beat frequency signal and the second beat frequency signal that are orthogonal to each other. Both the first beat frequency signal and the second beat frequency signal contain the target's distance and vector velocity information.

[0034] The second coherent mixing module 42 is used to generate a second orthogonal beat frequency signal through the second local oscillator light and the second echo light. The second orthogonal beat frequency signal includes a third beat frequency signal and a fourth beat frequency signal that are orthogonal to each other. The second local oscillator light and the second echo light are coherently mixed to obtain the third beat frequency signal and the fourth beat frequency signal that are orthogonal to each other. Both the third beat frequency signal and the fourth beat frequency signal contain the target's range and vector velocity information.

[0035] Signal processing module 5 is used to obtain a cosine component by subtracting the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals, and to obtain a sine component by adding the product of the second and third beat frequency signals to the product of the first and fourth beat frequency signals. A first complex signal is generated based on the sine and cosine components, and the peak position of the spectrum of the first complex signal is extracted to obtain the first intermediate frequency parameter. The target's vector velocity is then calculated based on the first intermediate frequency parameter. Specifically, signal processing module 5 can employ a field-programmable gate array (FPGA) or a microcontroller. Signal processing module 5 performs subtraction and addition operations on the products of the first, second, third, and fourth beat frequency signals to obtain two output signals. Based on these two output signals, a first complex signal is constructed, which can cancel the Doppler broadening interference introduced by the rotating multi-mirror on the velocity measurement. Then, a fast Fourier transform and peak finding are performed on the first complex signal to obtain the first intermediate frequency parameter, and the target's velocity is calculated using the first intermediate frequency parameter.

[0036] The laser detection device of this invention obtains a first local oscillator beam, a second local oscillator beam, a first echo beam, and a second echo beam through a beam output module 1, a beam splitting module 2, and an optical path multiplexing module 3. A first coherent mixing module 41 and a second beat frequency signal generate a first orthogonal beat frequency signal and a second orthogonal beat frequency signal based on the first local oscillator beam, the second local oscillator beam, the first echo beam, and the second echo beam. A first complex signal is generated based on each signal in the first orthogonal beat frequency signal and the second orthogonal beat frequency signal, so that the interference of Doppler broadening introduced by the rotating polygon mirror of different signals cancels each other out. Then, the peak position of the spectrum is extracted based on the first complex signal to obtain a first intermediate frequency parameter. The vector velocity of the target is calculated based on the first intermediate frequency parameter, which can eliminate the influence of Doppler broadening introduced by the rotating polygon mirror on the velocity measurement and significantly improve the velocity measurement accuracy.

[0037] In some embodiments, the beam output module 1 includes: First frequency-modulated continuous wave light source 101; The first driving module 102 is used to drive the first frequency-modulated continuous wave light source 101 to output the first modulated light; The first optical amplifier 103 is used to amplify the first modulated light output from the first frequency-modulated continuous wave light source 101; Second frequency-modulated continuous wave light source 104; The second driving module 105 is used to drive the second frequency-modulated continuous wave light source 104 to output the second modulated light; The second optical amplifier 106 is used to amplify the second modulated light output from the second frequency-modulated continuous wave light source 104.

[0038] Specifically, the first driving module 102 drives the first frequency-modulated continuous wave light source 101 to output the first modulated light, and the second driving module 105 drives the second frequency-modulated continuous wave light source 104 to output the second modulated light. The two modulated light signals are frequency-modulated and time-synchronized positive and negative double-chirped lasers with wavelengths of λ1 and λ2, respectively. The first modulated light and the second modulated light are amplified by the first optical amplifier 103 and the second optical amplifier 106, respectively.

[0039] In this system, the first modulated light is a positively chirped laser, the second modulated light is a negatively chirped laser, and the optical field of the first modulated light... The light field of the second modulated light Represented as:

[0040] in, The amplitude of the light field of the first modulated light; The amplitude of the optical field of the second modulated light; The starting frequency of the first modulated light; This is the starting frequency of the second modulated light; The chirp rate of the first modulated light. , Let T be the bandwidth of the first modulated light, and T be the frequency modulation period. The frequency modulation periods of the first and second modulated lights are the same. The chirp rate of the second modulated light. , The bandwidth of the second modulated light; The noise phase of the first modulated light; This is the noise phase of the second modulated light; This represents the initial phase of the first modulated light; The initial phase of the second modulated light; ; It is an exponential function with the natural constant e as the base, and t is time.

[0041] In the above scheme, the combination of frequency-modulated continuous wave light source, driving module and optical amplifier can stably output the first modulated light and the second modulated light that meet the requirements, so as to ensure the normal operation and stable performance of the entire laser detection device.

[0042] In some embodiments, the beam splitting module 2 includes: The first optical beam splitter 201 is used to split the first modulated light output by the beam output module 1 to obtain the first emitted light and the first local oscillator light. The second beam splitter 202 is used to split the second modulated light output by the beam output module 1 to obtain the second emitted light and the second local oscillator light.

[0043] Specifically, the first optical beam splitter 201 and the second optical beam splitter 202 can use devices such as prism beam splitters, planar beam splitters, or fiber beam splitters to split the light beam. Most of the energy in the first modulated light, such as 80%, is used as the first emitted light, and a small portion, such as 20%, is used as the first local oscillator light. Similarly, most of the energy in the second modulated light, such as 80%, is used as the second emitted light, and a small portion, such as 20%, is used as the second local oscillator light.

[0044] The first book on the light field of Zhenguang Represented as:

[0045] in, This is the amplitude of the first oscilloscope.

[0046] The second book, "The Light Field of Zhenguang" Represented as:

[0047] in, This is the amplitude of the second oscillator.

[0048] In the above scheme, the beam splitting module 2 uses an optical beam splitter to achieve the beam splitting function. It has a simple structure and the beam splitting ratio can be precisely controlled. It can stably split the first modulated light and the second modulated light into the emitted light and the local oscillator light respectively, which provides a guarantee for subsequent optical path multiplexing and beat frequency signal generation.

[0049] In some embodiments, the optical path multiplexing module 3 includes: The beam combiner 301 is used to combine the first emitted light and the second emitted light output from the beam splitter 2 to obtain a combined beam. The optical circulator 302 is used to output the combined light to the optical scanner 303, receive the echo light returned by the optical scanner 303, and output the echo light to the wave splitter 305. The optical scanner 303 includes a rotating polygonal mirror for outputting combined light to the transceiver telescope 304 and receiving the echo light returned by the transceiver telescope 304. The transceiver telescope 304 is used to send the combined beam of light to the target and receive the returned echo light; Wavelength divider 305 is used to divide the echo light based on wavelength to obtain a first echo light and a second echo light, wherein the first echo light and the first emitted light have the same wavelength, and the second echo light and the second emitted light have the same wavelength.

[0050] Specifically, the transceiver telescope 304 includes a transmitting telescope and a receiving telescope.

[0051] The first and second emitted beams are combined by a combiner 301, and then the combined beam is transmitted to the target via an optical circulator 302, an optical scanner 303, and a transmitting telescope. The first and second echo beams returning from the target are then split by a wavelength division multiplexer 305. Due to the coaxial common optical path transmission and reception, the first and second echo beams are linear frequency modulated beams with the same time delay. The optical field of the first echo beam... The light field of the second echo They are represented as follows:

[0052] The first and second echoes are time-delayed. Represented as:

[0053] in, The amplitude of the first echo. The amplitude of the second echo. This represents the radial distance to the target, i.e., the distance to the target. The radial velocity of the target, i.e., the velocity of the target. The amount of displacement introduced by rotating the mirror. It is the speed of light.

[0054] By combining devices such as beam combiner 301, optical circulator 302, optical scanner 303 and transceiver telescope 304, the beam combining, transmission, scanning, reception and beam splitting functions are realized. It can accurately transmit the beam to the target and receive the echo light, while separating the echo light of different wavelengths to provide the required signal input for subsequent beat frequency signal generation.

[0055] In some embodiments, the first coherent mixing module 41 includes: The first optical mixer 411 is used to receive the first local oscillator light output by the beam splitting module 2 and the first echo light output by the optical path multiplexing module 3, and to generate four mixing signals with a relative phase shift of 90 degrees in sequence: a first mixing signal, a second mixing signal, a third mixing signal, and a fourth mixing signal. The first photoelectric balance detector 412 is used to receive the first mixing signal and the third mixing signal output by the first optical mixer 411, and to obtain the first beat frequency signal by subtracting the first mixing signal and the third mixing signal. The second photoelectric balance detector 413 is used to receive the second mixing signal and the fourth mixing signal output by the first optical mixer 411, and to obtain the second beat frequency signal by subtracting the second mixing signal and the fourth mixing signal.

[0056] The second coherent mixer module 42 includes: The second optical mixer 421 is used to receive the second local oscillator light output by the beam splitting module 2 and the second echo light output by the optical path multiplexing module 3. It generates four mixing signals, namely the fifth, sixth, seventh and eighth mixing signals, with a relative phase shift of 90 degrees in sequence, through the second local oscillator light and the second echo light. The third photoelectric balance detector 422 is used to receive the fifth and seventh mixing signals output by the second optical mixer 421, and to obtain the third beat frequency signal by subtracting the fifth and seventh mixing signals. The fourth photoelectric balance detector 423 is used to receive the sixth and eighth mixing signals output by the second optical mixer 421, and to obtain the fourth beat frequency signal by subtracting the sixth and eighth mixing signals.

[0057] Specifically, both the first optical mixer 411 and the second optical mixer 421 are 2×4 90-degree optical mixers.

[0058] The first optical mixer 411 receives the first local oscillator light and the first echo light as inputs. After coherent mixing, it outputs a first mixed signal, a second mixed signal, a third mixed signal, and a fourth mixed signal. The first mixed signal... Second mixing signal Third mixing signal and the fourth mixing signal They are represented as follows:

[0059] The second optical mixer 421 receives the second local oscillator light and the second echo light as inputs. After coherent mixing, it outputs a fifth, sixth, seventh, and eighth mixing signal. The fifth mixing signal... Sixth mixing signal 7th Mixer Signal and the eighth mixing signal They are represented as follows:

[0060] in, For the target radial Doppler frequency shift, , The carrier wavelength; The time delay is caused by the displacement introduced by the rotating mirror. ; The noise phase after mixing the first local oscillator beam and the first echo beam. This is the noise phase after the second local oscillator light and the second echo light are mixed.

[0061] First mixing signal and the third mixing signal After being received by the first photoelectric balance detector 412, the difference is calculated to obtain the first beat frequency signal. Second mixing signal and the fourth mixing signal After being received by the second photoelectric balance detector 413, the difference is calculated to obtain the second beat frequency signal. .

[0062] Fifth mixing signal and the seventh mixing signal After being received by the third photoelectric balance detector 422, the difference is calculated to obtain the third beat frequency signal. The sixth mixing signal and the eighth mixing signal After being received by the fourth photoelectric balance detector 423, the difference is calculated to obtain the fourth beat frequency signal. .

[0063] Furthermore, the first coherent mixer module 41 also includes: The first filter 414 is used to perform low-pass filtering on the first beat frequency signal output by the first photoelectric balance detector 412. The first analog-to-digital converter 416 is used to perform analog-to-digital conversion on the first beat frequency signal after low-pass filtering; The second filter 415 is used to perform low-pass filtering on the second beat frequency signal output by the second photoelectric balance detector 413. The second analog-to-digital converter 417 is used to perform analog-to-digital conversion on the low-pass filtered second beat frequency signal; The second coherent mixer module 42 also includes: The third filter 424 is used to perform low-pass filtering on the third beat frequency signal output by the third photoelectric balance detector 422. The third analog-to-digital converter 426 is used to perform analog-to-digital conversion on the low-pass filtered third beat frequency signal; The fourth filter 425 is used to perform low-pass filtering on the fourth beat frequency signal output by the fourth photoelectric balance detector 423; The fourth analog-to-digital converter 427 is used to perform analog-to-digital conversion on the low-pass filtered fourth beat frequency signal.

[0064] The high-frequency terms in the corresponding beat frequency signal are filtered out by the first filter 414 and the second filter 415, resulting in the filtered first beat frequency signal. Second beat frequency signal Third beat frequency signal and the fourth beat frequency signal They are represented as follows:

[0065] in, It is the responsivity of the first photoelectric balanced detector 412 in the in-phase channel; It is the responsivity of the second photoelectric balance detector 413 in the positive traffic channel; It is the responsivity of the third photoelectric balance detector 422 in the in-phase channel; This is the responsivity of the fourth photoelectric balance detector 423 in the positive traffic channel. Each responsivity satisfies:

[0066] in, It is a constant.

[0067] Because dual-wavelength wavelength division multiplexing and demultiplexing are used, there is a certain wavelength difference between the first and second modulated light, and the frequency difference is much greater than the detection bandwidth, thus achieving crosstalk suppression between channels.

[0068] After analog-to-digital conversion, digital signal processing is performed. If a Fourier transform is directly performed on the above beat frequency signal and peak finding is attempted, the time delay caused by the vibration term, i.e., the displacement introduced by the rotating polygonal mirror, will be encountered. The presence of this phenomenon leads to broadening of the beat frequency spectrum peaks. Therefore, a signal processing module is needed to process the first, second, third, and fourth beat frequency signals by subtracting and adding their products to obtain two output signals. Based on these two output signals, a first complex signal is constructed, which can cancel the interference of Doppler broadening introduced by the rotating polygonal mirror on the velocity measurement. Then, a fast Fourier transform and peak finding are performed on the first complex signal to obtain the first intermediate frequency parameter. The velocity of the target is calculated using the first intermediate frequency parameter, thus eliminating the interference of Doppler broadening on the velocity measurement.

[0069] Furthermore, the signal processing module 5 is also connected to the host computer 6, outputting the calculation results to the host computer 6 and receiving instructions from the host computer 6.

[0070] Secondly, the present invention also provides a laser detection method, applied to the laser detection device as described in the embodiments of the present invention, such as... Figure 6 As shown, the method includes: Step S601: Obtain the first beat frequency signal and the second beat frequency signal output by the first coherent mixing module 41, and the third beat frequency signal and the fourth beat frequency signal output by the second coherent mixing module 42. Step S602: Subtract the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals to obtain the cosine component; add the product of the second and third beat frequency signals to the product of the first and fourth beat frequency signals to obtain the sine component; and generate the first complex signal based on the sine and cosine components. Step S603: Extract the peak position of the spectrum of the first complex signal to obtain the first intermediate frequency parameter; Step S604: Calculate the target's vector velocity based on the first intermediate frequency parameter.

[0071] Specifically, the laser detection method of this embodiment of the invention is executed by the signal processing module 5. The signal processing module 5 performs subtraction and addition operations on the products of the first beat frequency signal, the second beat frequency signal, the third beat frequency signal, and the fourth beat frequency signal to obtain two output signals. Based on these two output signals, a first complex signal is constructed, which can cancel the interference of Doppler broadening introduced by the rotating polygonal mirror on the velocity measurement. Then, the first complex signal is processed by fast Fourier transform and peak finding to obtain the first intermediate frequency parameter. The velocity of the target is calculated through the first intermediate frequency parameter.

[0072] In step S602, the first beat frequency signal is... Second beat frequency signal Third beat frequency signal and the fourth beat frequency signal The operation of pairwise multiplication is represented as:

[0073] in, and All are noise phases.

[0074] Because it satisfies Then, through pairwise addition and subtraction operations, two output signals are obtained, namely the cosine components. Sine component , respectively represented as:

[0075] The first complex signal is obtained by complexification of the sine and cosine components. Represented as:

[0076] When the absolute values ​​of positive and negative chirp rates are equal, i.e. , This item can be completely eliminated, simplifying it to:

[0077] Therefore, by measuring velocity based on this first complex signal, the effect of Doppler broadening introduced by the rotating polygonal mirror can be eliminated.

[0078] In some embodiments, step S603, extracting the peak position of the spectrum of the first complex signal to obtain the first intermediate frequency parameter, includes: Step S6031: Perform a fast Fourier transform on the first complex signal to obtain the first spectral distribution; Step S6032: Extract the position corresponding to the spectral peak of the first spectral distribution using the centroid method to obtain the first intermediate frequency parameter.

[0079] Specifically, a Fast Fourier Transform is performed on the first complex signal to eliminate the Doppler broadening introduced by the rotating polygonal mirror, and the spectral peak position is extracted using the centroid method to obtain the first intermediate frequency parameter. Represented as:

[0080] In the formula, This is the carrier wavelength. Then, based on the first intermediate frequency parameters... Obtain the target radial velocity The size and direction are represented as:

[0081] Among them, the target radial velocity A positive value indicates that the laser detection device is moving towards the target, while a negative value indicates that the laser detection device is moving away from the target.

[0082] Furthermore, laser detection methods also include: Step S6051: Generate a second complex signal based on the first beat frequency signal and the second beat frequency signal, and generate a third complex signal based on the third beat frequency signal and the fourth beat frequency signal; Step S6052: Perform a Fast Fourier Transform on the second complex signal to obtain a second spectral distribution. Extract the position corresponding to the spectral peak of the second spectral distribution using the centroid method to obtain the second intermediate frequency parameter. Perform a Fast Fourier Transform on the third complex signal to obtain a third spectral distribution. Extract the position corresponding to the spectral peak of the third spectral distribution using the centroid method to obtain the third intermediate frequency parameter. Step S6053: Calculate the reference target velocity and reference target distance based on the second and third intermediate frequency parameters; Step S6054: The vector velocity of the target calculated based on the first intermediate frequency parameter is taken as the ideal target velocity. The measurement accuracy of the ideal target velocity, the measurement accuracy of the reference target velocity, and the measurement accuracy of the reference target distance are obtained. The product of the measurement accuracy of the ideal target velocity and the measurement accuracy of the reference target velocity is divided by the measurement accuracy of the reference target distance to obtain the measurement accuracy of the ideal target distance. Step S6055: Subtract the reference target velocity from the ideal target velocity to obtain the first intermediate frequency correction value. Calculate the second intermediate frequency correction value based on the first intermediate frequency correction value, the measurement accuracy of the ideal target velocity, the measurement accuracy of the reference target velocity, the measurement accuracy of the reference target distance, and the measurement accuracy of the ideal target distance. Step S6056: Calculate the ideal target distance based on the second intermediate frequency correction value and the reference target distance, and use the ideal target distance as the optimized target distance.

[0083] Specifically, the first orthogonal beat frequency signal is complexed to obtain the second complex signal. The second complex signal is represented as:

[0084] Perform a Fast Fourier Transform on the second complex signal, and extract the peak positions of the spectrum using the centroid method to obtain the second intermediate frequency parameters. :

[0085] in, It is the mid-frequency peak-finding error introduced by Doppler broadening in the second complex signal.

[0086] The second orthogonal beat frequency signal is complexized to obtain the third complex signal. The third complex signal is represented as follows:

[0087] Perform a Fast Fourier Transform on the third complex signal, and extract the peak positions of the spectrum using the centroid method to obtain the third intermediate frequency parameters. :

[0088] in, It is the mid-frequency peak-finding error introduced by Doppler broadening in the third complex signal.

[0089] Due to the existence of mid-frequency peak finding error, the obtained reference target velocity Distance from reference target They are represented as follows:

[0090]

[0091] in, This is the first intermediate frequency correction value. This is the second intermediate frequency correction value.

[0092] By performing multiple measurements, the reference target velocity can be obtained. Measurement accuracy and reference target distance Measurement accuracy .

[0093] If we disregard factors such as laser linewidth, the speed and distance required to overcome Doppler broadening, i.e., the ideal target velocity, are... Distance from ideal target They can be represented as follows:

[0094]

[0095] Furthermore, the aforementioned target radial velocity To overcome Doppler broadening at speed and distance, i.e., the ideal target speed, without considering factors such as laser linewidth. It can also be expressed as:

[0096] By performing multiple measurements, the ideal target speed can be obtained. Measurement accuracy .

[0097] Passing the ideal target speed Subtract the reference target speed The first intermediate frequency correction value can be calculated. However, because and All are random quantities and cannot be obtained from the first intermediate frequency correction value. Directly obtain the second intermediate frequency correction value To correct the reference target distance .

[0098] To obtain the optimized reference target distance First, the measurement accuracy of the ideal target distance is derived from the following steps. , is represented as:

[0099] Therefore, the measurement accuracy of the ideal target velocity can be determined. , Measurement accuracy of the reference target velocity Measurement accuracy of distance to reference target To obtain the measurement accuracy of the ideal target distance. , is represented as:

[0100] because Determine the first intermediate frequency correction value Scope Determine the second intermediate frequency correction value The range, therefore, the second intermediate frequency correction value It can be approximated as:

[0101] Furthermore, the ideal target distance is expressed as:

[0102] Therefore, the embodiments of the present invention can achieve simultaneous ranging and speed measurement. Speed ​​measurement is completely unaffected by Doppler broadening, while ranging, although still affected by Doppler broadening, can be optimized and corrected by the above methods to improve ranging accuracy.

[0103] The laser detection device and method of the present invention will be described below with reference to specific application examples.

[0104] The first frequency-modulated continuous wave (FMMC) light source 101 uses a 1530nm DFB laser with a linewidth of 100kHz, an output power of 20mW, a symmetrical triangular waveform, a positive chirp bandwidth of 2GHz, a modulation period of 5µs, a negative chirp bandwidth of 2GHz, and a modulation period of 5µs. The second FMMC light source 104 uses a 1550nm DFB laser with a linewidth of 100kHz, an output power of 20mW, a symmetrical triangular waveform, a positive chirp bandwidth of 2GHz, a modulation period of 5µs, a negative chirp bandwidth of 2GHz, and a modulation period of 5µs. The signal processing module uses a 5-field-programmable gate array (FPGA) to synchronously trigger the first and second driving signals, thereby achieving modulation timing synchronization between the two light sources.

[0105] The light output from the first frequency-modulated continuous wave light source 101 first passes through an optical amplifier, where an erbium-doped fiber amplifier is used to amplify the beam to 200mW. Then, it passes through a 1×2 fiber beam splitter (splitting ratio of 1 / 99) to split the light into the first local oscillator light and the first emitted light. A small portion of the energy is used as the first local oscillator light, and most of the energy is used as the first emitted light.

[0106] The light output from the second frequency-modulated continuous wave light source 104 first passes through an optical amplifier, where an erbium-doped fiber amplifier is used to amplify the beam to 200mW. Then, it passes through a 1×2 fiber beam splitter (splitting ratio of 1 / 99) to split the light into the second local oscillator and the second emitted light. A small portion of the energy is used as the second local oscillator, and most of the energy is used as the second emitted light.

[0107] The first and second emitted beams are combined by a combiner 301, then emitted through an optical circulator 302 and an optical fiber collimator, and finally emitted to the target by a rotating optical scanner 303, where two echo beams are received. The galvanometer-type galvanometer has a frequency of 10Hz. The rotating mirror is a five-sided gold-plated rotating mirror with an outer diameter of 60mm and a rotation speed of 2400 rpm.

[0108] At the receiving end of the laser detection device, the returned first and second echo beams, after passing through the wave splitter 305, enter the first coherent mixing module 41 and the second coherent mixing module 42, respectively. The first echo light and the first local oscillator light are input to a first optical mixer 411 at a 2×4 90-degree angle to achieve quadrature coherent reception. The mixed output light includes a first mixed signal, a second mixed signal, a third mixed signal, and a fourth mixed signal, which are detected by a first photoelectric balance detector 412 and a second photoelectric balance detector 413. The bandwidth is 500MHz, and the signal is AC coupled. The second echo light and the second local oscillator light are input to a second optical mixer at a 2×4 90-degree angle to achieve quadrature coherent reception. The mixed output light includes a fifth mixed signal, a sixth mixed signal, a seventh mixed signal, and an eighth mixed signal, which are detected by a third photoelectric balance detector 422 and a fourth photoelectric balance detector 423. The bandwidth is 500MHz, and the signal is AC coupled.

[0109] The photoelectric balanced detector obtains orthogonal beat frequency analog signals containing target distance and vector velocity information, namely the first, second, third, and fourth mixing signals. These signals are then converted into digital signals by an analog-to-digital converter with a 1 GHz sampling rate (14 bits). An FPGA is used as the signal processing module 5 to perform digital signal processing on the obtained samples, completely eliminating the influence of Doppler broadening introduced by the rotating polygon mirror on the velocity measurement. Then, fast Fourier transform processing (4096 points) and centroid peak finding are performed to realize the parallel and simultaneous measurement of distance and vector velocity between the laser detection device and the target.

[0110] The laser detection device has a ranging resolution of 7.5 cm, a velocity resolution of 0.3 m / s, and a velocity accuracy of 0.1 m / s, with a point cloud output frequency of 200 kHz. Therefore, this embodiment of the invention eliminates the influence of Doppler broadening introduced by the high-speed rotating polygonal mirror on velocity measurement, significantly improving velocity measurement accuracy, achieving simultaneous velocity and ranging measurement, and also increasing the point cloud output frequency.

[0111] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A laser detection device, characterized in that, include: The beam output module is used to output a first modulated light and a second modulated light with different wavelengths. The first modulated light and the second modulated light are frequency-modulated timing synchronous positive and negative double-chilled lasers with the same frequency modulation period, and the absolute values ​​of their chirp rates are equal. A beam splitting module is used to split the first modulated light into a first emitted light and a first local oscillator light, and to split the second modulated light into a second emitted light and a second local oscillator light; An optical path multiplexing module is used to combine the first emitted light and the second emitted light into a beam and emit it to the target, and to receive the first echo light returned based on the first emitted light and the second echo light returned based on the second emitted light; The first coherent mixing module is used to generate a first orthogonal beat frequency signal through the first local oscillator light and the first echo light. The first orthogonal beat frequency signal includes a first beat frequency signal and a second beat frequency signal that are orthogonal to each other. The second coherent mixing module is used to generate a second orthogonal beat frequency signal through the second local oscillator light and the second echo light. The second orthogonal beat frequency signal includes a third beat frequency signal and a fourth beat frequency signal that are orthogonal to each other. The signal processing module is used to subtract the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals to obtain a cosine component, add the product of the second and third beat frequency signals to the product of the first and fourth beat frequency signals to obtain a sine component, generate a first complex signal based on the sine and cosine components, extract the spectral peak position of the first complex signal to obtain a first intermediate frequency parameter, and calculate the target's vector velocity based on the first intermediate frequency parameter.

2. The laser detection device according to claim 1, characterized in that, The first coherent mixer module includes: The first optical mixer is used to receive the first local oscillator light output by the beam splitting module and the first echo light output by the optical path multiplexing module, and to generate four mixing signals with a relative phase shift of 90 degrees between them: a first mixing signal, a second mixing signal, a third mixing signal, and a fourth mixing signal. A first photoelectric balance detector is used to receive the first mixing signal and the third mixing signal output by the first optical mixer, and to obtain the first beat frequency signal by subtracting the first mixing signal and the third mixing signal. The second photoelectric balance detector is used to receive the second mixing signal and the fourth mixing signal output by the first optical mixer, and to obtain the second beat frequency signal by subtracting the second mixing signal and the fourth mixing signal. The second coherent mixer module includes: The second optical mixer is used to receive the second local oscillator light output by the beam splitting module and the second echo light output by the optical path multiplexing module, and to generate four mixing signals, namely the fifth mixing signal, the sixth mixing signal, the seventh mixing signal and the eighth mixing signal, which are sequentially spaced by a 90-degree relative phase shift, through the second local oscillator light and the second echo light. The third photoelectric balance detector is used to receive the fifth mixing signal and the seventh mixing signal output by the second optical mixer, and to obtain the third beat frequency signal by subtracting the fifth mixing signal and the seventh mixing signal. The fourth photoelectric balance detector is used to receive the sixth mixing signal and the eighth mixing signal output by the second optical mixer, and to obtain the fourth beat frequency signal by subtracting the sixth mixing signal and the eighth mixing signal.

3. The laser detection device according to claim 2, characterized in that, The first coherent mixer module further includes: The first filter is used to perform low-pass filtering on the first beat frequency signal output by the first photoelectric balance detector; The first analog-to-digital converter is used to perform analog-to-digital conversion on the first beat frequency signal after low-pass filtering; The second filter is used to perform low-pass filtering on the second beat frequency signal output by the second photoelectric balance detector; The second analog-to-digital converter is used to perform analog-to-digital conversion on the second beat frequency signal after low-pass filtering; The second coherent mixer module further includes: The third filter is used to perform low-pass filtering on the third beat frequency signal output by the third photoelectric balance detector; The third analog-to-digital converter is used to perform analog-to-digital conversion on the third beat frequency signal after low-pass filtering; The fourth filter is used to perform low-pass filtering on the fourth beat frequency signal output by the fourth photoelectric balance detector; The fourth analog-to-digital converter is used to perform analog-to-digital conversion on the low-pass filtered fourth beat frequency signal.

4. The laser detection device according to claim 1, characterized in that, The beam output module includes: First frequency-modulated continuous wave light source; The first driving module is used to drive the first frequency-modulated continuous wave light source to output the first modulated light; The first optical amplifier is used to amplify the first modulated light output from the first frequency-modulated continuous wave light source; Second frequency-modulated continuous wave light source; The second driving module is used to drive the second frequency-modulated continuous wave light source to output the second modulated light; The second optical amplifier is used to amplify the second modulated light output from the second frequency-modulated continuous wave light source.

5. The laser detection device according to claim 1, characterized in that, The beam splitting module includes: The first beam splitter is used to split the first modulated light output by the beam output module to obtain the first emitted light and the first local oscillator light. The second beam splitter is used to split the second modulated light output by the beam output module to obtain the second emitted light and the second local oscillator light.

6. The laser detection device according to claim 1, characterized in that, The optical path multiplexing module includes: A beam combiner is used to combine the first emitted light and the second emitted light output from the beam splitter to obtain a combined beam. An optical circulator is used to output the combined beam to an optical scanner, receive the echo light returned by the optical scanner, and output the echo light to a wave demultiplexer. The optical scanner includes a rotating multifaceted mirror for projecting the combined beam to a transceiver telescope and receiving the echo light returned by the transceiver telescope. The transceiver telescope is used to output the combined beam to the target and receive the returned echo light; A wavelength divider is used to divide the echo light based on wavelength to obtain a first echo light and a second echo light, wherein the first echo light and the first emitted light have the same wavelength, and the second echo light and the second emitted light have the same wavelength.

7. A laser detection method, characterized in that, The laser detection device as described in any one of claims 1 to 6 comprises: Acquire the first beat frequency signal and the second beat frequency signal output by the first coherent mixer module, as well as the third beat frequency signal and the fourth beat frequency signal output by the second coherent mixer module; The cosine component is obtained by subtracting the product of the second and fourth beat frequency signals from the product of the first and third beat frequency signals. The sine component is obtained by adding the product of the second and third beat frequency signals to the product of the first and fourth beat frequency signals. The first complex signal is generated based on the sine component and the cosine component. Extract the peak position of the spectrum of the first complex signal to obtain the first intermediate frequency parameter; The target's vector velocity is calculated based on the first intermediate frequency parameter.

8. The laser detection method according to claim 7, characterized in that, Extracting the peak position of the spectrum of the first complex signal to obtain the first intermediate frequency parameters includes: Perform a Fast Fourier Transform on the first complex signal to obtain the first spectral distribution; The first intermediate frequency parameter is obtained by extracting the position corresponding to the spectral peak of the first spectral distribution using the centroid method.

9. The laser detection method according to claim 7, characterized in that, Also includes: A second complex signal is generated based on the first beat frequency signal and the second beat frequency signal, and a third complex signal is generated based on the third beat frequency signal and the fourth beat frequency signal; The second complex signal is subjected to a Fast Fourier Transform to obtain a second spectral distribution. The position corresponding to the spectral peak of the second spectral distribution is extracted by the centroid method to obtain the second intermediate frequency parameter. The third complex signal is subjected to a Fast Fourier Transform to obtain a third spectral distribution. The position corresponding to the spectral peak of the third spectral distribution is extracted by the centroid method to obtain the third intermediate frequency parameter. The reference target velocity and reference target distance are calculated based on the second intermediate frequency parameter and the third intermediate frequency parameter. The vector velocity of the target calculated based on the first intermediate frequency parameter is taken as the ideal target velocity. The measurement accuracy of the ideal target velocity, the measurement accuracy of the reference target velocity, and the measurement accuracy of the reference target distance are obtained. The product of the measurement accuracy of the ideal target velocity and the measurement accuracy of the reference target velocity is divided by the measurement accuracy of the reference target distance to obtain the measurement accuracy of the ideal target distance. Subtracting the reference target velocity from the ideal target velocity yields a first intermediate frequency correction value. A second intermediate frequency correction value is then calculated based on the first intermediate frequency correction value, the measurement accuracy of the ideal target velocity, the measurement accuracy of the reference target velocity, the measurement accuracy of the reference target distance, and the measurement accuracy of the ideal target distance. The ideal target distance is calculated based on the second intermediate frequency correction value and the reference target distance, and the ideal target distance is used as the optimized target distance.

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