CN110361752B - Heterodyne interference-based moving object motion characteristic measurement method - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/50—Systems of measurement based on relative movement of target
- G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
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Abstract
本发明公开了一种外差干涉的运动目标运动特征测量方法，涉及一种新型的激光测量技术。该方法利用一种纵模频率锁定的多纵模脉冲激光器作为探测用激光，一种频率与多纵模脉冲激光器相互锁定的单频激光作为本地参考激光，一个宽带的光电探测器作为外差干涉用的信号接收探测器。利用多纵模脉冲激光照射待测运动目标后得到的散射激光与本地连续波单频激光的外差干涉信号，实时获得回波信号携带的微多普勒信息，并由此得到待测目标的微运动特征。本发明所述技术具有测量速度快、精度高、可探测距离远、性能可靠等特点，能够广泛应用于各类运动目标特征测量。
The invention discloses a method for measuring the motion characteristics of a moving target by heterodyne interference, and relates to a novel laser measuring technology. The method utilizes a longitudinal-mode frequency-locked multi-longitudinal-mode pulsed laser as the detection laser, a single-frequency laser whose frequency is mutually locked with the multi-longitudinal-mode pulsed laser as the local reference laser, and a broadband photodetector as the heterodyne interference The signal receiving detector used. Using the multi-longitudinal mode pulsed laser to irradiate the moving target to be measured, the heterodyne interference signal between the scattered laser and the local continuous wave single-frequency laser is used to obtain the micro-Doppler information carried by the echo signal in real time. Micro-motion features. The technology of the invention has the characteristics of fast measurement speed, high precision, long detectable distance, reliable performance and the like, and can be widely used in the measurement of various moving targets.
Description
Technical Field
The invention relates to a novel laser measurement technology, in particular to a heterodyne interference-based moving object motion characteristic measurement method.
Background
Laser measurement techniques for moving objects have been rapidly developed, and related techniques include measurement of distances, coordinates, shapes, moving speeds, etc. of moving objects, wherein the measurement of the moving object speeds is often performed using the amount of change in laser frequency. According to the Doppler principle, when relative motion exists between a measuring main body and a target to be measured, a laser beam emitted from the measuring main body to the target to be measured irradiates the target to be measured, part of the laser beam is reflected or scattered and returns to an optical receiving system where the measuring main body is located, the laser beam is converged to a photoelectric detector for photoelectric conversion by the optical receiving system, and the collected reflected or scattered light carries Doppler information containing the speed characteristic of the moving target. If a reference laser is applied to the photodetector at the same time, a heterodyne interference signal is generated between the echo laser and the reference laser. A properly designed detection laser and reference laser and corresponding photoelectric conversion detector will give a valuable target doppler signal which will help to resolve the motion characteristics of the target.
The conventional laser active illumination target feature resolution technology is a coherent detection technology based on continuous single-frequency laser irradiation. A beam of continuous wave single-frequency laser is transmitted to a target through an optical telescope system, part of the laser irradiated to the target is scattered, and a small part of the scattered laser signals can be collected by a signal receiving optical system. The signal and local single-frequency laser (intrinsic signal) are subjected to heterodyne coherent detection, so that Doppler frequency shift information in a target echo can be extracted, and the motion characteristic of the target can be distinguished. The technology is widely applied to speed measurement of various targets, such as speed measurement of automobiles and airplanes and even speed measurement of air flow, and vibration measurement in various occasions, such as remote laser monitoring.
However, conventional coherent detection techniques based on continuous single frequency laser illumination have more limitations in certain applications. When the speed of the moving target to be detected is high, the Doppler frequency shift carried by the detection laser becomes very large, which brings great challenges to the photoelectric detector and the processing bandwidth of the electric signal at the rear end of the photoelectric detector, and the laser heterodyne interference system cannot work normally even due to the excessively large bandwidth. In addition, the laser power amplification of the continuous single-frequency laser has certain difficulties, and when the high-efficiency fiber laser is used for laser power amplification, the maximum continuous laser power is limited by the threshold of stimulated brillouin scattering of the fiber material, so that the farthest measurement distance is greatly restricted during laser measurement.
If aiming at the measurement of a moving target, the method is only used for measuring the micro-motion state characteristic of the moving target to be measured relative to the mass center of the moving target, and then a heterodyne interference technology irradiated by a multi-longitudinal mode pulse laser can be considered. In this case, the use of a multi-longitudinal mode pulse laser operating in pulses as a detection laser instead of a single-frequency laser operating in continuous waves has significant advantages. Firstly, for a target moving at a high speed, a large-magnitude doppler frequency shift exists, and a micro-doppler frequency shift signal caused by the movement of the target moving at a high speed, such as rotation, vibration, precession, and the like, is included in the large-magnitude doppler frequency shift, so that the micro-doppler frequency shift signal must be eliminated, the receiving bandwidth of a signal processing system is significantly reduced, and the detection of the micro-doppler signal can be realized. The elimination of a large number of levels of doppler frequency shift signals is generally realized by optical frequency shift of a local signal, and heterodyne processing is performed on a local single-frequency laser after frequency shift and an echo signal modulated by a target, so that it is possible to shift a high-frequency doppler signal to a low-frequency region, on the premise that speed information of a high-speed moving target needs to be grasped. In practical operation, it is very difficult to realize stable frequency shift of the local single-frequency intrinsic laser in a short time, and the technical feasibility is greatly questioned. In contrast, when the mode-locked laser is used for irradiating the target, the echo signal actually contains a plurality of laser longitudinal modes of the multi-longitudinal-mode pulse laser, and the laser longitudinal modes are subjected to heterodyne interference with local single-frequency laser, so that the large-magnitude doppler frequency shift signal does not cause the generation of high frequency in a heterodyne signal. At this time, in the heterodyne signal, the high-frequency signal with the maximum bandwidth is still limited by the pulse width and the pulse repetition frequency of the multi-longitudinal mode pulse laser pulse itself, which brings great convenience to the processing of the heterodyne signal. Second, the power amplification capability of single frequency continuous lasers is significantly limited, limiting the range of targets that can be detected. The energy of the multi-longitudinal-mode pulse laser is concentrated in time, the signal-to-noise ratio is high, target detection is facilitated, meanwhile, amplification of the multi-longitudinal-mode pulse laser is easy to achieve, and higher laser peak power can be obtained. Thus, the detection of a long-distance target is more facilitated.
Disclosure of Invention
The invention aims to provide a laser heterodyne interference method which adopts a multi-longitudinal-mode pulse laser with longitudinal-mode frequency locking as detection laser aiming at the motion characteristic measurement of a long-distance high-speed moving target, and can obtain micro Doppler information containing the motion characteristic of the moving target in real time. The method of the invention can make the related measurement fast and real-time, and realize the purpose of remote measurement. The heterodyne interference measurement method has the characteristics of high measurement speed, high precision, long distance, compact system structure, reliable performance and good environmental stability, and can be widely applied to the characteristic measurement of various moving targets.
The technical scheme of the invention is realized by the following modes: a heterodyne interference moving target motion characteristic measuring method includes the steps that a multi-longitudinal-mode pulse laser and a single-frequency laser are locked mutually in frequency, laser pulses of the multi-longitudinal-mode pulse laser are amplified in power through a subsequent laser power amplifier, the amplified multi-longitudinal-mode laser pulses are emitted to a moving target after passing through an optical system, partial laser pulses reflected or scattered by the moving target are collected by the optical system and focused on a photoelectric detector, partial single-frequency laser of the single-frequency laser is always incident on the photoelectric detector, heterodyne interference is conducted on the multi-longitudinal-mode laser pulses on the photoelectric detector and the single-frequency laser, micro Doppler information of moving target motion characteristics is output, and Fourier transform processing is conducted through a signal processing system to obtain the motion characteristics of the moving target.
Further, the multi-longitudinal mode pulse laser is an active mode-locked or passive mode-locked solid laser or fiber laser, and the wavelength range of the multi-longitudinal mode pulse laser is 1.02-1.12 μm, 1.53-1.65 μm or 1.9-2.1 μm.
Further, the multi-longitudinal mode pulse laser is an acousto-optic frequency-shifted multi-longitudinal mode pulse laser, and the wavelength range of the multi-longitudinal mode pulse laser is 1.02-1.12 mu m, or 1.53-1.65 mu m, or 1.9-2.1 mu m.
Further, the pulse width of the multi-longitudinal mode pulse laser is between 100fs and 100ns, and the pulse repetition frequency is between 100kHz and 5 GHz.
Furthermore, the single-frequency laser is a semiconductor laser, a solid laser or a fiber laser which works in a continuous wave single frequency mode, the wavelength range of the single-frequency laser is matched with the wavelength range of the multi-longitudinal mode pulse laser, and the laser frequency is mutually locked with the longitudinal modes of the multi-longitudinal mode pulse laser.
Further, the laser power amplifier is a solid or optical fiber laser power amplifier, and the gain characteristic of the laser power amplifier is matched with the wavelength of the pulse working laser of the multi-longitudinal mode pulse laser.
Compared with the prior art, the invention has the beneficial effects that: firstly, the technical difficulty that the micro-motion characteristic of a high-speed moving target cannot be measured by the laser heterodyne interference technology based on the continuous wave single-frequency laser in the current laser heterodyne interference technology is solved. This scheme utilizes the stable many longitudinal mode pulsed laser of longitudinal wave to interfere with stable single-frequency laser for many longitudinal mode laser pulse is when shining the target of high-speed motion, because high-speed motion produces large-range Doppler's translation, though arouse many longitudinal mode laser pulse laser frequency great frequency shifts appear, but this many longitudinal mode pulsed laser still can interfere with single-frequency laser, and it is fast to have the measuring speed, the precision is high, the distance is far away, compact system structure, dependable performance, the characteristics that environmental stability is good, the novel laser heterodyne interference measurement system who constructs in view of the above can effectively be applied to the measurement to all kinds of moving target characteristics.
Drawings
FIG. 1 is a schematic diagram of the principle of the laser heterodyne interference method of the multi-longitudinal mode pulse laser of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
Fig. 1 is a schematic diagram of a principle of a laser heterodyne interference method of a multi-longitudinal mode pulse laser, which is a moving object motion characteristic measurement method based on heterodyne interference of multi-longitudinal mode pulse laser and single-frequency laser, and the method is implemented by using a frequency-locked multi-longitudinal mode pulse laser 1 as a laser pulse for detection, using a single-frequency laser 2 with a frequency mutually locked with the multi-longitudinal mode pulse laser 1 as a local reference laser, and using a broadband photoelectric detector 6 as a signal receiving detector for heterodyne interference. The frequency of a multi-longitudinal mode pulse laser 1 with longitudinal mode frequency locking and a single-frequency laser 2 working with continuous waves are mutually locked, the laser pulse of the multi-longitudinal mode pulse laser 1 is amplified by a subsequent laser power amplifier 3, the amplified multi-longitudinal mode laser pulse is emitted to a moving target 5 after passing through an optical system 4, and part of the laser pulse reflected or scattered by the moving target 5 is collected by the optical system 4 and focused into a photoelectric detector 6. Part of laser light of the laser 2 working at a continuous wave single frequency is always incident on the photoelectric detector 6, heterodyne interference is carried out on multi-longitudinal mode laser pulses on the photoelectric detector 6 and single-frequency laser light, micro Doppler information of motion characteristics of a moving target is output, and the motion characteristics of the moving target are obtained through Fourier transform processing by the signal processing system 7.
The frequency-locked multi-longitudinal-mode pulse laser 1 can be a mode-locked solid laser or a fiber laser, the wavelength range of the frequency-locked multi-longitudinal-mode pulse laser is 1.02-1.12 mu m or 1.53-1.65 mu m or 1.9-2.1 mu m, the longitudinal mode of the mode-locked laser and a continuous wave single-frequency laser 2 used as reference laser are mutually locked, the pulse width of the mode-locked laser is between 100fs and 100ns, and the pulse repetition frequency is between 100kHz and 5 GHz.
The frequency-locked multi-longitudinal-mode pulse laser 1 can be an acousto-optic frequency-shifted solid laser or an optical fiber laser, the wavelength of the frequency-locked multi-longitudinal-mode pulse laser can be 1.02-1.12 mu m or 1.53-1.65 mu m or 1.9-2.1 mu m, the longitudinal mode of the acousto-optic frequency-shifted laser and a continuous wave single-frequency laser used as reference laser are mutually locked, the pulse width of the acousto-optic frequency-shifted laser is 100ps-100ns, and the pulse repetition frequency is 100kHz-5 GHz.
The continuous wave single-frequency laser 2 can be a semiconductor laser, a solid laser or a fiber laser which works in a continuous wave single-frequency mode, the wavelength range of the laser is matched with a mode-locked laser, and the laser frequency is mutually locked with the longitudinal modes of the multi-longitudinal-mode pulse laser.
The laser power amplifier 3 is a solid or optical fiber laser power amplifier, and the gain characteristic of the laser power amplifier is matched with the pulse working laser wavelength of the multi-longitudinal mode pulse laser.
The optical system 4 is a conventional optical telescope and can transmit laser light or receive laser echo signals.
The target 5 is a moving target to be detected.
The photoelectric detector 6 is a photoelectric detector with a large bandwidth, the spectral response range of the photoelectric detector is adaptive to the working wavelength of the multi-longitudinal-mode pulse laser, and the bandwidth of the photoelectric detector meets the requirement of quick response to the pulse width of the multi-longitudinal-mode pulse laser.
The signal processing system 7 is an electrical signal processing system with a large bandwidth, can sample the heterodyne interference signal output from the photodetector 6 in real time, and has a corresponding spectrum analysis function.
The method for measuring the motion characteristics of the moving target by heterodyne interferometry can be widely applied to capturing the motion states of remote satellites and missiles, has the characteristics of high measurement speed, high precision, long distance, compact system structure, reliable performance and good environmental stability, and the novel laser heterodyne interferometry system constructed in accordance with the method can be effectively applied to measurement of various motion target characteristics.
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| CN102236092A (en) * | 2010-04-29 | 2011-11-09 | 西安近代化学研究所 | Doppler signal period distribution demodulation method of laser Doppler velocimeter |
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