Phase modulation laser Doppler velocity measurement system and velocity measurement method

A technology of Doppler speed measurement and phase modulation, which is applied in the phase modulation laser Doppler speed measurement system and the field of speed measurement, can solve the problems of multiple structures of components, narrow measurement range, complex sensitivity, etc., and achieve high measurement sensitivity, wide measurement range, Parts Simple Effects

Inactive Publication Date: 2015-10-21
HARBIN NORMAL UNIVERSITY
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  • Abstract
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  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The present invention solves the problem that the existing phase-modulated laser Doppler velocity measurement system must have an energy detector, resulting in many components and complex structures, and solves the problem that the existing phase-modulated laser Doppler velocity measurement method has low sensitivity and narrow measurement range The problem

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  • Phase modulation laser Doppler velocity measurement system and velocity measurement method
  • Phase modulation laser Doppler velocity measurement system and velocity measurement method
  • Phase modulation laser Doppler velocity measurement system and velocity measurement method

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specific Embodiment approach 1

[0037] combine figure 1To illustrate this embodiment, a phase-modulated laser Doppler velocimetry system includes: a laser 1, a polarization beam splitter 2, a mechanical switch 3, a first convex lens 4, a rotating target 5, a second convex lens 6, a multimode optical fiber 7, a third Convex lens 8, polarizer 9, fourth convex lens 10, optical fiber phase modulator 11, fifth convex lens 14, beam expander 15, F-P interferometer 16, sixth convex lens 17, photomultiplier tube 18, driver 12, signal generator 13 , data acquisition card 19, output card 20 and computer 21;

[0038] When the mechanical switch 3 is turned on, the laser 1 emits signal light, passes through the polarization beam splitter 2 and then passes through the center of the first convex lens 4;

[0039] The center of the first convex lens 4 is arranged on the optical path passing through the polarizing beam splitter 2;

[0040] After the signal light passes through the center of the vibration beam splitter 2 and...

specific Embodiment approach 2

[0053] The method for realizing speed measurement by using the phase modulation laser Doppler speed measurement system comprises the following steps:

[0054] Step 1: When the mechanical switch 3 is in the closed state, use the computer 21 to control the output card 20 to adjust the output frequency of the laser 1, i.e. the frequency ω of the signal light, and use the computer 21 to collect the output frequency of the different laser frequencies collected by the data acquisition card 19. Output current i(t), draw the frequency shift change curve of nA(ω);

[0055] Step 2: When the mechanical switch 3 is closed, under the normal working condition of the phase modulation laser Doppler velocimetry system, the computer 21 collects the output current i(t) from the data acquisition card 19, and calculates nA(ω 0 ); Use the frequency shift curve of nA(ω) to determine the frequency ω of the outgoing signal light 0 value;

[0056] Step 3: When the mechanical switch 3 is turned on, th...

specific Embodiment approach 3

[0058] The field strength of the single-frequency signal light after sinusoidal phase modulation is expressed as

[0059] E. in =E 0 exp[j(ωt+βsinΩt)] (1)

[0060] Among them, E 0 is the incident signal light field intensity; ω is the frequency of the incident signal light; Ω is the phase modulation frequency; β is the phase modulation depth; j is a complex number; t is time;

[0061] Properly adjust the magnification of the driver 12 to make the phase modulation depth β≤0.9, and the signal light after sinusoidal phase modulation produces positive and negative first-order sidebands (second-order and above sidebands can be ignored), the field strength can be expressed as:

[0062] E. in =E 0 {J 0 (β)exp(jωt)+J 1 (β)exp[j(ω+Ω)t]-J 1 (β)exp[j(ω-Ω)t]} (2)

[0063] Among them, J 0 and J 1 are zero-order and first-order Bessel functions, respectively;

[0064] F-P interferometer transmittance curve as figure 2 As shown, after passing through the F-P interferometer 16,...

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Abstract

The invention discloses a phase modulation laser Doppler velocity measurement system and a velocity measurement method, so as to solve the problems of many parts and complicated structure as the existing phase modulation laser Doppler velocity measurement system needs to have an energy detector, and low sensitivity and narrow measurement range of the prior phase modulation laser Doppler velocity measurement method. The phase modulation laser Doppler velocity measurement system comprises a laser, a polarized beam-splitting plate, a mechanical switch, a first convex lens, a rotating target, a second convex lens, a multi-mode optical fiber, a third convex lens, a polarized plate, a fourth convex lens, an optical fiber phase modulator, a fifth convex lens, a beam expander, an F-P interferometer, a sixth convex lens, a photomultiplier, a driver, a signal generator, a data acquisition card, an output card and a computer. The phase modulation laser Doppler velocity measurement system is used for realizing velocity measurement on a moving object. The system and the method of the invention are applied to velocity measurement on a moving object.

Description

technical field [0001] The invention relates to a Doppler speed measuring system and a speed measuring method. Background technique [0002] A beam of laser with a stable frequency is irradiated on the moving target. Due to the Doppler effect, the backscattered light of the target will produce a certain frequency shift. By measuring the Doppler frequency shift of the backscattered light, the moving target can be obtained. Velocity information along the beam direction, this is the basic principle of the laser Doppler velocimeter. Due to the unparalleled measurement accuracy of the laser Doppler velocimeter, it has broad application prospects in various fields such as military affairs and industry. At present, laser Doppler velocimeter mainly adopts two methods of measuring Doppler frequency shift, coherent detection and direct detection. Although these two methods each have significant advantages, they also have disadvantages that are difficult to overcome. Coherent detect...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01S17/58
CPCG01S17/58
Inventor 杜军刘靖宇杨娜张海波邱琳吴莹
Owner HARBIN NORMAL UNIVERSITY
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