Phase modulation direct detection laser Doppler velometer and velocity measuring method thereof

A Doppler velocimeter and laser detection technology, which is applied to instruments, measuring devices, radio wave measurement systems, etc., can solve the problems of low measurement accuracy, achieve high measurement signal-to-noise ratio, improve measurement accuracy, and narrow working bandwidth Effect

Inactive Publication Date: 2013-06-19
HARBIN INST OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] The purpose of the present invention is to solve the problem of using the edge filter such as FP interferometer in the current direct detection method to convert the frequency change of the backscattered light into the change of the transmittance so as to obtain the Doppler frequency shift. For the problem of low measurement accuracy of the detection method, the present invention provides a phase modulation direct detection laser Doppler velocimeter and its velocity measurement method

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  • Phase modulation direct detection laser Doppler velometer and velocity measuring method thereof
  • Phase modulation direct detection laser Doppler velometer and velocity measuring method thereof
  • Phase modulation direct detection laser Doppler velometer and velocity measuring method thereof

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specific Embodiment approach 1

[0030] Specific implementation mode one: combine figure 1 Describe this embodiment, the phase modulation direct detection laser Doppler velocimeter described in this embodiment,

[0031] It includes single longitudinal mode frequency stabilized laser 1, polarization beam splitter 2, mechanical switch 3, first convex lens 4, second convex lens 6, multimode fiber 7, third convex lens 8, polarizer 9, beam expander 11, splitter Beam sheet 12, FP interferometer 13, fourth convex lens 14, fifth convex lens 15, first detector 16, second detector 17 and computer 22, it also includes electro-optic phase modulator 10, driver 18, phase shifter 19 , multiplier 20 and low-pass filter 21;

[0032] The laser light emitted by the single longitudinal mode frequency-stabilized laser 1 sequentially passes through the polarization beam splitter 2, the mechanical switch 3 and the first convex lens 4 and is incident on the moving target. 4. The converged light enters the polarization beam splitte...

specific Embodiment approach 2

[0040] Specific embodiment two: the phase modulation described in this embodiment directly detects the velocity measuring method of laser Doppler velocity measuring instrument, and it comprises the following steps:

[0041] Step 1: When the mechanical switch 3 is in the closed state, the laser light emitted by the single longitudinal mode frequency-stabilized laser 1 is irradiated onto the switch wall of the mechanical switch 3 at rest, and then the Doppler-free switching of the switch wall of the mechanical switch 3 The frequency shifted backscattered light is used for frequency measurement to obtain a frequency measurement value;

[0042] The described method that obtains a frequency measurement value is: utilize FP interferometer 13 and electro-optical phase modulator 10 to produce the beat frequency signal that amplitude changes with the Doppler frequency shift of measured moving target; And by phase shifter 19, multiplier 20 and low-pass filter 21 to extract the amplitude...

specific Embodiment approach 3

[0075] Specific embodiment three: this embodiment is a further limitation of the speed measurement method of the phase modulation direct detection laser Doppler velocimeter described in specific embodiment two, and the step one also includes:

[0076] The frequency of the laser light emitted by the single longitudinal mode frequency stabilized laser 1 is adjusted by the computer 22 so that the frequency of the emitted laser light coincides with the frequency corresponding to the transmittance peak point of the FP interferometer 13 .

[0077] Adjust the frequency of the output light of the single longitudinal mode frequency-stabilized laser 1 by a computer, so that the amplitude term of the double modulation frequency obtained by the final system is zero, even if the frequency of the outgoing light coincides with the peak transmittance point of the FP interferometer, this can Make the system have the best measurement range.

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Abstract

The invention discloses a phase modulation direct detection laser Doppler velometer and a velocity measuring method thereof, and relates to a direct detection laser Doppler velometer. In order to solve the problem that a method of converting frequency change of back scattering light into the change of transmittance by utilizing edge filters of a Fabry-Perot (F-P) interferometer in the current direct detection mode to obtain Doppler frequency shift is low in measuring accuracy relative to a coherent detection mode, the invention provides the phase modulation direct detection laser Doppler velometer and the velocity measuring method thereof. According to the method, a beat frequency signal of which the vibration amplitude is changed with the Doppler frequency shift of a moving target is generated by an electric-optical phase modulator and the FP interferometer; a vibration amplitude item is extracted by a phase shifter, a multiplying unit and a low-pass filter, and optical wave frequency information is identified by utilizing the vibration amplitude item; and the frequency of emitted laser and target back scattering light is measured by utilizing the turning-on state and turning-off state of a mechanical switch, and difference of two-time frequency measuring values is used as a measuring value of the Doppler frequency shift. According to the phase modulation direct detection laser Doppler velometer, the influence of the change of light intensity on a measuring result is removed by the energy detection of backward waves, so that the phase modulation direct detection laser Doppler velometer is used for measuring the movement velocity of targets in the field of optics.

Description

technical field [0001] The invention relates to a direct detection laser Doppler velocimeter, in particular to a phase modulation direct detection laser Doppler velocimeter and a speed measurement method thereof. Background technique [0002] When a beam of laser light with stable frequency is irradiated on the moving target, the backscattered light of the target will produce a certain frequency shift due to the Doppler effect. By measuring the Doppler frequency shift of the backscattered light, the moving target along the This is the basic principle of the 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. According to the measurement principle, laser Doppler velocimeters can be mainly divided into two types: direct detection and coherent detection. Coherent detection is to use the beat frequency of intrinsic light and backscattered ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01S17/58
Inventor 杜军曲彦臣赵卫疆任德明耿利杰
Owner HARBIN INST OF TECH
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