A measurement system and a measurement method thereof

Abstract

The application provides a measurement system and a measurement method thereof, and relates to the technical field of optoelectronic measurement, which aims to avoid the problem of affecting the measurement accuracy due to the linewidth of a laser, thereby improving the measurement accuracy. The measurement system comprises a mode-locked laser unit, a transmission emission unit and a detection processing unit. The mode-locked laser unit is configured to generate first laser and transmit second laser to the transmission emission unit. The transmission emission unit is configured to receive and emit the second laser to a to-be-measured moving target, generate reference light when transmitting the second laser, receive signal light generated after the to-be-measured moving target receives the second laser, and transmit the combined reference light and signal light to the detection processing unit. The detection processing unit is configured to receive and process the reference light and the signal light to obtain at least one Doppler frequency shift difference.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic measurement technology, and in particular to a measurement system and measurement method thereof. Background Technology

[0002] Doppler lidar is a powerful tool for measuring the velocity of moving objects. It features non-contact measurement, high precision, and strong anti-interference capabilities, and is widely used in fields such as national defense, meteorology, aviation, and environmental monitoring.

[0003] Traditional Doppler lidar typically uses a single-wavelength laser as its emission source. Its detection principle is that when the light emitted by the laser shines on the surface of a moving object being detected, a Doppler frequency shift occurs. The Doppler frequency shift is measured by coherent detection, thereby obtaining the motion information of the object.

[0004] However, single-wavelength Doppler lidar places stringent requirements on the linewidth of the laser. The linewidth of the laser must be smaller than the Doppler frequency shift in order to accurately measure the speed of moving objects. Further increasing the linewidth of the laser is very difficult, which poses a huge challenge to further improving measurement accuracy. Summary of the Invention

[0005] This invention provides a measurement system and method to avoid the problem of measurement accuracy being affected by the linewidth of the laser, thereby improving measurement accuracy.

[0006] This invention provides a measurement system for detecting the velocity of a moving target. The measurement system includes a mode-locked laser unit, a transmission and transmission unit, and a detection and processing unit. The transmission and transmission unit is connected to both the mode-locked laser unit and the detection and processing unit.

[0007] The mode-locked laser unit is configured to generate a first laser and transmit a second laser to the transmission unit; the first laser includes a preset number of N mode-locked lasers, 2≤N≤H, where N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0.

[0008] The transmission and transmission unit is configured to: receive and transmit the second laser to the moving target under test, generate a reference light while transmitting the second laser, receive the signal light generated by the moving target under test after receiving the second laser, and combine the reference light and the signal light and transmit them to the detection and processing unit.

[0009] The detection and processing unit is configured to receive and process the reference light and the signal light to obtain at least one Doppler frequency shift difference, wherein the Doppler frequency shift difference is the difference in the Doppler frequency shift corresponding to any two mode-locked lasers.

[0010] According to a measurement system provided by the present invention, the mode-locked laser unit includes: a mirror region, a gain region, and a saturable absorption region;

[0011] In the case of 2 < N < H, the saturated absorption region is configured to generate N1 mode-locked initial lasers, where N1 is a positive number and satisfies 2 < N < N1 ≤ H;

[0012] The reflector region is configured to: receive and generate reflection spectra with different spectral widths according to the driving signal, and select the first laser from the N1 mode-locked initial lasers;

[0013] The gain region is configured to provide lasing energy.

[0014] According to a measurement system provided by the present invention, the reflector region includes a distributed Bragg reflector.

[0015] According to a measurement system provided by the present invention, the reflector region, the gain region, and the saturable absorption region are integrated together.

[0016] According to a measurement system provided by the present invention, the measurement system is further used to detect the distance between the moving target to be measured and the measurement system; the measurement system further includes a signal generator; the signal generator is electrically connected to the gain region;

[0017] The signal generator is configured to provide a modulation signal to the gain region;

[0018] The gain region is further configured to receive and, based on the modulation signal, modulate the pulse amplitude of the initial laser generated in the saturation absorption region;

[0019] The reflector area is also configured to: select the initial laser after pulse amplitude modulation to obtain the first laser;

[0020] The detection processing unit is further configured to detect the pulse delay information of the signal light and the reference light.

[0021] According to a measurement system provided by the present invention, the measurement system further includes a radio frequency signal source and a voltage source; the radio frequency signal source and the voltage source are respectively electrically connected to the saturation absorption region;

[0022] The radio frequency signal source is configured to provide a radio frequency signal to the saturation absorption region;

[0023] The voltage source is configured to provide a reverse bias to the saturated absorption region.

[0024] According to a measurement system provided by the present invention, when M > 0, the mode-locked laser unit further includes: an amplifier;

[0025] The first laser beam is amplified M times by the amplifier and then transmitted to the transmission and transmission unit.

[0026] According to a measurement system provided by the present invention, the transmission unit includes: a circulator, a connector, and an antenna;

[0027] The second laser beam passes sequentially through the circulator, the connector, and the antenna before being emitted to the moving target to be measured.

[0028] The signal light generated by the moving target receiving the second laser light is transmitted to the detection and processing unit in sequence through the antenna, the connector and the circulator;

[0029] The connector is configured to generate a reference light when transmitting the second laser to the antenna; the reference light is transmitted to the detection and processing unit via the circulator.

[0030] According to a measurement system provided by the present invention, the detection and processing unit includes a photoelectric detection module and a data processing module; the photoelectric detection module and the data processing module are electrically connected.

[0031] The photoelectric detection module is configured to receive the reference light and the signal light and convert them into electrical signals;

[0032] The data processing module is configured to receive and process the electrical signal to obtain at least one of the Doppler frequency shift differences.

[0033] The present invention also provides a measurement method for any of the above-mentioned measurement systems, wherein the measurement method is at least applied to detecting the velocity of a moving target to be measured;

[0034] The measurement method includes:

[0035] The mode-locked laser unit generates a first laser and transmits a second laser to the transmission and transmission unit; the first laser includes a preset number of mode-locked lasers of number N, where 2≤N≤H, N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0.

[0036] The transmission and transmission unit receives and transmits the second laser to the moving target under test, generates a reference light while transmitting the second laser, transmits the reference light to the detection and processing unit, and receives and transmits the signal light generated by the moving target under test after receiving the second laser to the detection and processing unit.

[0037] The detection and processing unit receives and processes the reference light and the signal light to obtain at least one Doppler frequency shift difference, which is the difference in Doppler frequency shift corresponding to any two mode-locked lasers.

[0038] This invention provides a measurement system and method thereof. The measurement system is at least used for detecting the velocity of a moving target. The measurement system includes: a mode-locked laser unit, a transmission and transmission unit, and a detection and processing unit. The transmission and transmission unit is connected to both the mode-locked laser unit and the detection and processing unit. The mode-locked laser unit is configured to: generate a first laser and transmit a second laser to the transmission and transmission unit; the first laser includes a preset number of N mode-locked lasers, where 2 ≤ N ≤ H, N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes a laser amplified M times by the first laser, where M is a non-negative number greater than or equal to 0; the transmission and transmission unit is configured to: receive and transmit the second laser to the moving target, generate a reference light during the transmission of the second laser, receive the signal light generated by the moving target after receiving the second laser, and combine the reference light and the signal light before transmitting them to the detection and processing unit; the detection and processing unit is configured to: receive and process the reference light and the signal light to obtain at least one Doppler frequency shift difference, where the Doppler frequency shift difference is the difference in Doppler frequency shift corresponding to any two mode-locked lasers. This measurement system avoids the laser linewidth requirement in existing technologies and instead shifts the requirement to the linewidth of the dual-mode beat frequency microwave signal. This allows Doppler velocimetry radar to improve measurement accuracy without relying on narrow-linewidth lasers, thereby further enhancing measurement accuracy. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is one of the structural schematic diagrams of the measurement system provided by the present invention;

[0041] Figure 2 This is a schematic diagram of the mode-locked laser provided by the present invention;

[0042] Figure 3 This is the second schematic diagram of the measurement system provided by the present invention;

[0043] Figure 4 This is a flowchart illustrating the measurement method of the measurement system provided by the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0045] In the embodiments of the present invention, the terms "first", "second", "third" and other similar terms are used to distinguish the same or similar items with essentially the same function and effect, only for the purpose of clearly describing the technical solution of the embodiments of the present invention, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0046] In embodiments of the present invention, "a plurality of" means two or more, and "at least one" means one or more, unless otherwise explicitly specified.

[0047] Embodiments of the present invention provide a measurement system, at least for detecting the velocity of a moving target, with reference to... Figure 1 As shown, the measurement system includes: a mode-locked laser unit 1, a transmission and transmission unit 2, and a detection and processing unit 3. The transmission and transmission unit 2 is connected to both the mode-locked laser unit 1 and the detection and processing unit 3.

[0048] Among them, reference Figure 1 As shown, the mode-locked laser unit 1 is configured to generate a first laser and transmit a second laser to the transmission and transmission unit 2; the first laser includes a preset number of N mode-locked lasers, 2≤N≤H, where N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0.

[0049] refer to Figure 1 As shown, the transmission and transmission unit 2 is configured to: receive and transmit a second laser to the moving target 4 under test, generate a reference light while transmitting the second laser, receive the signal light generated by the moving target 4 under test after receiving the second laser, and combine the reference light and the signal light and transmit them to the detection and processing unit 3.

[0050] refer to Figure 1As shown, the detection and processing unit 3 is configured to receive and process the reference light and the signal light to obtain at least one Doppler frequency shift difference, which is the difference in the Doppler frequency shift corresponding to any two mode-locked lasers.

[0051] The specific structure of the aforementioned mode-locked laser unit is not limited. This mode-locked laser unit may include a semiconductor mode-locked laser; a semiconductor mode-locked laser is an integrable pulsed light source capable of generating short pulses with repetition frequencies ranging from several GHz to hundreds of GHz, and pulse widths reaching the picosecond level; it also possesses advantages such as high integration, compact structure, low cost, and ease of mass production.

[0052] Research has shown that, based on mode-locked lasers, by measuring the difference in Doppler frequency shift between any two phase-locked laser wavelengths, and then applying δ² - δ¹∝s... t Δf, where δ1 and δ2 correspond to the Doppler shifts in the two modes, δ2-δ1 is the Doppler frequency shift difference between the two modes, and S t Let v1 be the velocity of the moving target to be measured, and Δf = v1 - v2 be the frequency difference between the two modes, where v1 and v2 are the frequencies corresponding to the two lasing modes, respectively; then the velocity of the moving target to be measured can be calculated.

[0053] Based on this speed measurement principle, the requirement for laser linewidth in existing technologies can be avoided. Instead, the requirement for laser linewidth is shifted to the requirement for the linewidth of the dual-mode beat frequency microwave signal. This allows Doppler velocimeters to improve measurement accuracy without relying on narrow-linewidth lasers, thereby further improving measurement accuracy.

[0054] Meanwhile, existing single-wavelength Doppler lidar technologies are affected by speckle noise caused by target roughness, leading to linewidth broadening of the Doppler frequency shift signal and thus limiting velocity measurement accuracy. The measurement system provided in this invention, compared to systems using single-wavelength Doppler lasers for velocity measurement, significantly reduces interference from surface noise of the moving target, thereby greatly mitigating the linewidth broadening problem caused by the roughness of the moving target surface and further improving velocity measurement accuracy.

[0055] The speed measurement principle of the measurement system provided by this invention will be explained in detail below.

[0056] Taking any two lasing modes (v1 and v2) generated by a mode-locked laser as an example, the lasers corresponding to the two modes will undergo a Doppler frequency shift after detecting the moving target. The output light field of the mode-locked laser can be expressed as:

[0057]

[0058] Where A1, A2, v1, v2, These represent the electric field intensity, frequency, and phase corresponding to the two lasing modes, respectively.

[0059] The laser generated by the mode-locked laser is transmitted and emitted to the moving target. The laser undergoes a Doppler frequency shift on the surface of the moving target, thus scattering signal light. This signal light can be represented as:

[0060]

[0061] Among them, v 12 =v1+δ1,v 22 = v² + δ², where τ is the delay of the signal light relative to the reference light, B i =A i / α(B i (where α is an intermediate parameter), and α is the total loss during the scattering process. and The phase noise generated by the two modes on the surface of the moving target due to roughness is δ1 = 2s. t v1 / c and δ2 = 2s t v² / c represents the Doppler frequency shift corresponding to the two modes, c is the speed of light in a vacuum, and s is the speed of light in a vacuum. t The velocity of the moving target to be measured.

[0062] The transmission unit combines the signal light and the reference light and transmits them to the detection and processing unit. The detection and processing unit processes the signal light and the reference light to obtain the Doppler frequency shift signals v1 and v2, respectively:

[0063]

[0064]

[0065] Then, by further mixing I1(t) and I2(t), the Doppler frequency shift signal generated by the dual-wavelength laser beat frequency microwave signal can be obtained as follows:

[0066]

[0067] Among them, C i =RA i B i R is the responsivity of the detection and processing unit; the Doppler frequency shift difference between the two modes is δ1-δ2=2s. t (v1-v2) / c; Due to the coherence of the mode-locked laser modes, and Compared to using a single-wavelength Doppler laser for velocities, this method significantly reduces the interference of surface noise caused by the roughness of the moving target surface, thereby greatly mitigating the linewidth broadening problem of the Doppler signal caused by the roughness of the moving target surface and further improving the velocities measurement accuracy.

[0068] The velocity of the moving target to be measured is expressed as:

[0069] s t =(δ1-δ2)c / 2Δf

[0070] Where δ1-δ2 represents the difference in Doppler frequency shift between the two modes, Δf = v1-v2 is the frequency of the beat frequency signal between the two modes, and c is the speed of light in vacuum. Based on this formula, the velocity of the moving target can be calculated as long as δ1-δ2 is obtained. Furthermore, for the same moving target, the Doppler frequency shift difference under different Δf values ​​can be obtained, thus yielding multiple velocity information values. Processing these multiple velocity information values ​​yields more accurate velocity information, further improving the measurement accuracy, sensitivity, and robustness of the measurement system.

[0071] In the measurement system provided by the embodiments of the present invention, the preset number N of mode-locked lasers generated by the mode-locked laser unit can be 2. In this case, the detection and processing unit can obtain one Doppler frequency shift difference, and the system belongs to a dual-wavelength mode-locked laser Doppler velocimetry system. The preset number N of mode-locked lasers generated by the mode-locked laser unit can also be 3. In this case, the detection and processing unit can obtain three Doppler frequency shift differences, and the system belongs to a multi-wavelength mode-locked laser Doppler velocimetry system. Of course, the preset number N of mode-locked lasers generated by the mode-locked laser unit can also be other values, which are not specifically limited here.

[0072] In the measurement system provided by the embodiments of the present invention, the structure of the mode-locked laser unit, the transmission and emission unit, and the detection and processing unit is not limited, as long as they can meet the relevant functions.

[0073] The aforementioned mode-locked laser unit transmits a second laser to the transmission and transmission unit. The second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0. When M equals 0, it means the amplification factor of the first laser is 0, i.e., the first laser has not been amplified. When M is greater than 0, it means the first laser has been amplified, and the amplification factor is M. The value of M can be selected according to system requirements. For example, if the power of the mode-locked laser unit is large enough and the emitted laser can meet the requirements of the backend system, then amplification is not required, i.e., M = 0. If the power of the mode-locked laser unit is insufficient and the emitted laser cannot meet the requirements of the backend system, then amplification is required. In this case, M can be selected as a value of 1, 2, 3, or 4.

[0074] It should be noted that in the measurement system provided in the embodiments of the present invention, the detection and processing unit obtains at least one Doppler frequency shift difference; to obtain the velocity value of the moving target to be measured, further manual calculation or automatic calculation by a calculation unit is required, which is not limited here. For example, if automatic calculation is required, the measurement system may further include a calculation unit electrically connected to the detection and processing unit, configured to calculate the velocity of the moving target to be measured based on at least one Doppler frequency shift difference.

[0075] Traditional mode-locked lasers have a large number of locked modes, each with low comb energies, requiring significant optical amplification. Using all modes for measurement necessitates high-gain optical amplification to boost the energy of individual spectral lines for each mode, hindering system miniaturization, cost reduction, and integration. However, in practical applications of mode-locked lasers in Doppler velocimetry systems, only a limited number of modes are needed for high-precision measurements, eliminating the need to use all modes.

[0076] To meet the requirements of miniaturization and integration, while minimizing costs as much as possible, in one or more embodiments, optionally, refer to... Figure 2 As shown, the mode-locked laser unit includes: a mirror region 11, a gain region 12, and a saturable absorption region 13.

[0077] In the case of 2 < N < H, the saturated absorption region is configured to generate N1 mode-locked initial lasers, where N1 is a positive number and satisfies 2 < N < N1 ≤ H; the mirror region is configured to receive and generate reflection spectra with different spectral widths according to the driving signal, and select the N1 mode-locked initial lasers to obtain the first laser; the gain region is configured to provide lasing energy.

[0078] The aforementioned gain region (also known as the gain area) can be injected with current to provide the energy required for laser lasing. The aforementioned saturable absorber (SA) includes a saturable absorber that can enter a hybrid mode-locked state after reverse bias and modulation by an RF signal source. The aforementioned mirror region can be located in the same cavity as the gain region and saturable absorber; or the mirror region can be located in one cavity, while the gain region and saturable absorber are located in another cavity; other structures are also possible and are not limited here. The aforementioned mirror region, gain region, and saturable absorber together form a mode-locked laser.

[0079] In the aforementioned mode-locked laser unit, the reflecting mirror region can select the initial laser light generated in the saturated absorption region, and the number of lasing modes can be selected by controlling the reflection spectral width. For example, the center wavelength of the reflection spectrum can be adjusted by changing the injection current, thereby selecting multiple phase-locked modes. By setting the reflecting mirror region, the aforementioned mode-locked laser unit can select a limited number of modes for Doppler velocimetry, which is beneficial for system miniaturization, low cost, and integration.

[0080] For ease of implementation, the reflector region may optionally include a distributed Bragg reflector (DBR). The DBR, acting as a bandpass reflector, can be placed in the same cavity as the gain region and saturable absorption region. A mode-locked laser incorporating a DBR can concentrate energy on fewer modes within the DBR's reflection band, resulting in higher energy distribution per comb tooth. This allows for more efficient use of laser energy and significantly reduces the gain requirements of the amplifier. It also provides selection and control over the lasing mode.

[0081] In one or more embodiments, to reduce system complexity, the mirror region, gain region, and saturable absorption region can optionally be integrated together to form a three-segment semiconductor mode-locked laser. This way, the mirror region, gain region, and saturable absorption region are located in the same cavity, avoiding the need to place the mirror region outside the gain region and saturable absorption region. This reduces system complexity and allows energy to be concentrated on fewer modes within the reflection band through the mirror region, resulting in higher energy distribution per comb tooth. This leads to more efficient use of laser energy and significantly reduces the gain requirement for the amplifier. It also provides selection and control of the lasing mode. After multiple modes within the reflection band of the mirror region are locked, the mode-locked laser can output a narrow pulse laser with high pulse energy and a narrow pulse width, which is beneficial for long-distance velocimetry.

[0082] Traditional time-of-flight ranging systems and Doppler velocity measurement systems operate independently. To improve system utilization and compatibility, the measurement system can optionally also be used to detect the distance between the moving target and the measurement system; Reference Figure 3 As shown, the measurement system also includes a signal generator 5; the signal generator 5 is electrically connected to the gain region 12.

[0083] The signal generator is configured to provide a modulation signal to the gain region; the gain region is further configured to receive and, based on the modulation signal, modulate the pulse amplitude of the initial laser generated in the saturation absorption region; the mirror region is further configured to select the initial laser after pulse amplitude modulation to obtain a first laser; the detection processing unit is further configured to detect the pulse delay information of the signal light and the reference light.

[0084] The aforementioned signal generator can include an arbitrary waveform generator. For example, this signal generator can be used to generate a square wave signal with a certain duty cycle, which can be used as a modulation signal. The specific value of the duty cycle can be selected according to the actual situation. It should be noted that the specific principle of pulse amplitude modulation can be obtained by referring to relevant technologies, and will not be elaborated here.

[0085] The principle of ranging is explained below. The principle of ranging technology is as follows: A laser outputs a light pulse. The pulse is reflected from the surface of the target object. The detector detects the time interval between the emitted pulse and the received reflected pulse, and then calculates the distance using a ranging formula. The ranging formula is as follows:

[0086] L=cΔt / 2

[0087] Where L is the distance between the moving target and the measurement system, c is the speed of light in a vacuum, and Δt is the time interval between the emitted pulse and the reflected pulse.

[0088] In the measurement system provided by the embodiments of the present invention, the initial laser pulse amplitude is modulated by the gain region of the mode-locked laser unit, and the pulse delay information of the signal light and the reference light is detected by the detection processing unit. The distance value can then be calculated manually according to the ranging formula or automatically by the calculation unit. For example, if automatic calculation is required, the measurement system may further include a calculation unit electrically connected to the detection processing unit, configured to calculate the distance between the moving target and the measurement system based on the pulse delay information of the signal light and the reference light. The measurement system provided by the embodiments of the present invention can simultaneously perform ranging and velocity measurement, has strong compatibility, and high equipment utilization.

[0089] To ensure the normal and stable operation of the saturated absorption region, refer to Figure 3 As shown, the measurement system also includes an RF signal source 6 and a voltage source 7; the RF signal source 6 and the voltage source 7 are electrically connected to the saturated absorption region 13, respectively.

[0090] The radio frequency signal source is configured to provide a radio frequency signal to the saturation absorption region; the voltage source is configured to provide a reverse bias voltage to the saturation absorption region.

[0091] The specific form of the aforementioned radio frequency signal is not limited; for example, a sinusoidal radio frequency signal can be used. The saturation absorption region can be modulated by a sinusoidal radio frequency signal and then reverse biased, thereby enabling the laser to operate in a hybrid mode-locked state.

[0092] Optionally, to ensure that the laser generated by the mode-locked laser unit meets the requirements of the back-end system, when M > 0, refer to Figure 3As shown, the mode-locked laser unit 1 further includes an amplifier 14; wherein the first laser is amplified M times by the amplifier and then transmitted to the transmission and transmission unit.

[0093] Optionally, for the purpose of simplifying the structure and facilitating implementation, refer to Figure 3 As shown, the transmission unit 2 includes a circulator 21, a connector 22, and an antenna 23. The second laser is transmitted to the moving target under test by passing through the circulator, connector, and antenna in sequence. The signal light generated by the moving target under test after receiving the second laser is transmitted to the detection and processing unit by passing through the antenna, connector, and circulator in sequence. The connector is configured to generate a reference light when transmitting the second laser to the antenna. The reference light is transmitted to the detection and processing unit through the circulator.

[0094] The aforementioned circulator may include a three-port circulator, see reference. Figure 3 As shown, the three ports of the three-port circulator are labeled a, b, and c. The connector described above may include a fiber optic connector, and the antenna may include an optical transceiver antenna; for example, the optical transceiver antenna may include a lens. Of course, the circulator, connector, and antenna may also include other structures, which will not be listed here.

[0095] The antenna described above can transmit multi-wavelength light signals and receive light signals scattered by moving objects.

[0096] Optionally, to simplify the structure and facilitate implementation, the detection and processing unit includes a photoelectric detection module and a data processing module; the photoelectric detection module and the data processing module are electrically connected; the photoelectric detection module is configured to receive and convert the reference light and the signal light into electrical signals; the data processing module is configured to receive and process the electrical signals to obtain at least one Doppler frequency shift difference.

[0097] refer to Figure 3 As shown, the above-mentioned photoelectric detection module may include a photodetector 31, which can receive reference light and signal light, and convert the Doppler frequency shift signal of the multi-wavelength beat frequency signal into an electrical signal.

[0098] The aforementioned data processing module may include, for example: Figure 3 The oscilloscope 32 or data acquisition device shown can receive the Doppler frequency shift signal detected by the photodetector and display the Doppler frequency shift difference after processing; it can also record the pulse delay modulated by the square wave signal.

[0099] by Figure 3 The measurement system shown is used as an example to illustrate the structural relationships and working process of the system. (Reference) Figure 3As shown, the output of the mode-locked laser 10 is connected to the input of the amplifier 14. Port a of the three-port circulator 21 is connected to the output of the amplifier 14, port b is connected to the connector 22, and port c is connected to the photodetector 31. One end of the connector 22 is connected to port b, and the other end is connected to the antenna 23. The real-time oscilloscope 32 or the data acquisition unit is connected to the photodetector 31. The first laser generated by the mode-locked laser is amplified by the amplifier to become the second laser. The second laser is sent to port a of the three-port circulator, and port b is connected to the antenna through the connector. The antenna emits a multimode laser and receives the signal light scattered by the moving target to be detected. The laser emitted through the connector has a certain amount of reflection at the connector joint. This reflected light (i.e., the reflected light from the end face where the connector is connected to the antenna) serves as the reference light for the system. The connector combines the signal light and the reference light, and the combined beam is sent from port b of the circulator to the photodetector via port c. The photodetector detects the Doppler frequency shift signal of the multi-wavelength optical beat frequency signal, which is recorded by a real-time oscilloscope or data acquisition unit. The speed of the moving target can be calculated using the aforementioned velocity measurement formula. Additionally, the oscilloscope or data acquisition unit can record the pulse delay modulated by the square wave signal; the distance between the object and the measurement system can be calculated using the aforementioned distance measurement formula.

[0100] Embodiments of the present invention also provide a measurement method for any of the above-described measurement systems, wherein the measurement method is at least applied to detecting the velocity of a moving target to be measured.

[0101] refer to Figure 4 As shown, the measurement methods include:

[0102] S01, the mode-locked laser unit generates a first laser and transmits a second laser to the transmission and transmission unit; the first laser includes a preset number of mode-locked lasers of number N, 2≤N≤H, where N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0.

[0103] S02, the transmission and transmission unit receives and transmits a second laser to the moving target under test, generates a reference light while transmitting the second laser, transmits the reference light to the detection and processing unit, and receives and transmits the signal light generated by the moving target under test after receiving the second laser to the detection and processing unit.

[0104] S03. The detection and processing unit receives and processes the reference light and the signal light to obtain at least one Doppler frequency shift difference, which is the difference in the Doppler frequency shift corresponding to any two mode-locked lasers.

[0105] It should be noted that the relevant descriptions of the above measurement system can be found in the foregoing embodiments, and will not be repeated here.

[0106] By executing steps S01-S03, at least one Doppler frequency shift of the moving target can be obtained with high precision, thereby determining the velocity of the moving target. This measurement method avoids the laser linewidth requirements of existing technologies, instead shifting the requirement to the linewidth of the dual-mode beat-frequency microwave signal. This eliminates the need for narrow-linewidth lasers to improve measurement accuracy in Doppler velocimetry radar, thus further enhancing measurement accuracy. Furthermore, compared to ranging methods using single-wavelength Doppler lasers, this method significantly reduces interference from surface noise of the moving target, thereby greatly mitigating the linewidth broadening problem caused by surface roughness of the Doppler signal and further improving velocity measurement accuracy.

[0107] The terms "an embodiment," "embodiment," or "one or more embodiments" as used herein mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. Furthermore, please note that the examples of the phrase "in one embodiment" do not necessarily all refer to the same embodiment.

[0108] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A measurement system, characterized in that, The measurement system, which is at least used for detecting the velocity of a moving target, includes: a mode-locked laser unit, a transmission and transmission unit, and a detection and processing unit; the transmission and transmission unit is connected to both the mode-locked laser unit and the detection and processing unit. The mode-locked laser unit is configured to: generate a first laser and transmit a second laser to the transmission and emission unit; the first laser includes a preset number N mode-locked lasers, 2≤N≤H, where N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0; the mode-locked laser unit includes: a mirror region, a gain region, and a saturation absorption region; when 2<N<H, the saturation absorption region is configured to: generate N1 mode-locked initial lasers, where N1 is a positive number and satisfies 2<N<N1≤H; the mirror region is configured to: receive and generate reflection spectra of different spectral widths according to the driving signal, and select the N1 mode-locked initial lasers to obtain the first laser; the gain region is configured to: provide lasing energy. The transmission and transmission unit is configured to: receive and transmit the second laser to the moving target under test, generate a reference light while transmitting the second laser, receive the signal light generated by the moving target under test after receiving the second laser, and combine the reference light and the signal light and transmit them to the detection and processing unit. The detection and processing unit is configured to receive and process the reference light and the signal light to obtain at least one Doppler frequency shift difference, wherein the Doppler frequency shift difference is the difference in Doppler frequency shift corresponding to any two mode-locked lasers.

2. The measurement system according to claim 1, characterized in that, The reflector region includes: a distributed Bragg reflector.

3. The measurement system according to claim 1, characterized in that, The mirror region, the gain region, and the saturable absorption region are integrated together.

4. The measurement system according to claim 1, characterized in that, The measurement system is also used to detect the distance between the moving target and the measurement system; the measurement system also includes a signal generator; the signal generator is electrically connected to the gain region. The signal generator is configured to provide a modulation signal to the gain region; The gain region is further configured to receive and, based on the modulation signal, modulate the pulse amplitude of the initial laser generated in the saturation absorption region; The reflector area is also configured to select the initial laser after pulse amplitude modulation to obtain the first laser; The detection processing unit is further configured to detect the pulse delay information of the signal light and the reference light.

5. The measurement system according to claim 1, characterized in that, The measurement system further includes a radio frequency signal source and a voltage source; the radio frequency signal source and the voltage source are respectively electrically connected to the saturated absorption region; The radio frequency signal source is configured to provide a radio frequency signal to the saturation absorption region; The voltage source is configured to provide a reverse bias to the saturated absorption region.

6. The measurement system according to any one of claims 1-5, characterized in that, When M > 0, the mode-locked laser unit further includes: an amplifier; The first laser beam is amplified M times by the amplifier and then transmitted to the transmission and transmission unit.

7. The measurement system according to claim 1, characterized in that, The transmission unit includes: a circulator, a connector, and an antenna; The second laser beam passes sequentially through the circulator, the connector, and the antenna before being emitted to the moving target to be measured. The signal light generated by the moving target receiving the second laser light is transmitted to the detection and processing unit in sequence through the antenna, the connector and the circulator; The connector is configured to generate a reference light when transmitting the second laser to the antenna; the reference light is transmitted to the detection and processing unit via the circulator.

8. The measurement system according to claim 1, characterized in that, The detection and processing unit includes a photoelectric detection module and a data processing module; the photoelectric detection module and the data processing module are electrically connected. The photoelectric detection module is configured to receive the reference light and the signal light and convert them into electrical signals; The data processing module is configured to receive and process the electrical signal to obtain at least one of the Doppler frequency shift differences.

9. A measurement method for a measurement system as described in any one of claims 1-8, characterized in that, The measurement method is at least applied to detecting the velocity of a moving target; The measurement method includes: The mode-locked laser unit generates a first laser and transmits a second laser to the transmission and transmission unit; the first laser includes a preset number of mode-locked lasers of number N, where 2≤N≤H, N and H are both positive numbers, and H is the maximum number of mode-locked lasers that the mode-locked laser unit can generate; the second laser includes the first laser amplified by M times, where M is a non-negative number greater than or equal to 0. The transmission and transmission unit receives and transmits the second laser to the moving target under test, generates a reference light while transmitting the second laser, transmits the reference light to the detection and processing unit, and receives and transmits the signal light generated by the moving target under test after receiving the second laser to the detection and processing unit. The detection and processing unit receives and processes the reference light and the signal light to obtain at least one Doppler frequency shift difference, which is the difference in Doppler frequency shift corresponding to any two mode-locked lasers.

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