CN204575674U - Based on the laser Doppler speed measuring device of rotating grating - Google Patents
Based on the laser Doppler speed measuring device of rotating grating Download PDFInfo
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- CN204575674U CN204575674U CN201520270510.0U CN201520270510U CN204575674U CN 204575674 U CN204575674 U CN 204575674U CN 201520270510 U CN201520270510 U CN 201520270510U CN 204575674 U CN204575674 U CN 204575674U
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Abstract
Based on the laser Doppler speed measuring device of rotating grating, comprise: detection probe, the detection signal of detection probe collected by concentric cable, transfers to the signal processing circuit board for the speed of settling accounts, and signal processing circuit board connects display screen and shown on a display screen by detection signal, described detection probe comprises a laser instrument, laser device laser path is arranged the collimating mirror for collimating, rotating grating is provided with after collimating mirror, two total reflective mirror Parallel Symmetrics are arranged in the laser path after rotating grating diffraction, and the detect aperture making laser from detection probe after laser reflection is penetrated, collecting lens is positioned at detect aperture, collect the laser of testee scattering, laser reflexes to plus lens through angled downward-sloping total reflective mirror, the laser of plus lens collected by photodetector, and signal is spread out of detection probe by the front end circuit carrying out signal amplification and filtering through concentric cable.
Description
Technical field
The utility model relates to laser and Technology of Precision Measurement field, particularly a kind of laser Doppler speed measuring device based on rotating grating.
Background technology
The ultimate principle of Laser Doppler Velocimeter is: when beam of laser incides on relative motion object, and the frequency of its scattered light and the frequency of incident light are not identical, and both differences are exactly Doppler frequency, and it is directly proportional to the movement velocity of object.Therefore the movement velocity of object can be measured by detection Doppler frequency.
The common measurement pattern of Laser Doppler Velocimeter has three kinds: reference light pattern, from mixed mode and twin-beam differential mode.Wherein reference light pattern, its Doppler signal is relevant with receive direction, and the size of detector aperture also can affect the measuring accuracy of signal; From mixed mode, because it is undertaken measuring by the vibration frequency of detection laser light intensity, so when working current and ambient temperature change, light intensity also can correspondingly change, this is also very large on the impact of doppler accuracy; And twin-beam differential mode, its Doppler signal and receive direction have nothing to do, and the aperture of detector can increase arbitrarily, and the fluctuation of laser intensity only can affect the signal to noise ratio (S/N ratio) of signal, can't affect measuring accuracy.The plurality of advantages of twin-beam differential laser Doppler anemometer makes the multiple occasions such as the measurement of its fluid-velocity survey at gas, liquid and solid surface movement velocity be widely used.
But also there is many deficiencies in twin-beam differential laser Doppler anemometer shaping at present both at home and abroad: (1) wave length shift.In typical twin-beam differential laser Doppler anemometer, Doppler frequency is not only relevant with the movement velocity of object, also relevant with the wavelength of incoming laser beam.But the wavelength of laser beam all exists drift usually, thus introduce measuring error; (2) laser instrument.Existing instrument adopts helium-neon laser or semiconductor laser as light source usually, and on the one hand helium-neon laser volume is large, needs high-voltage power supply to power, therefore all laser instrument and its power supply is contained in one independently in cabinet, and volume is large, heaviness, dangerous; The live width of semiconductor laser is wider on the other hand, thus the measuring accuracy of influential system; (3) direction identification.Domestic and international most product does not all have the function of direction identification.Even if small part product has the function of direction identification, be also all adopt acousto-optic crsytal or electro-optic crystal shift frequency to realize.But acousto-optic crsytal or electro-optic crystal all need complicated control system, volume is comparatively large, expensive.In addition, the Radio frequency interference (RFI) that control system is introduced can have a strong impact on Doppler signal, is unfavorable for extracting Doppler frequency; (4) signal processor.Current existing system all adopts the method for fast fourier transform (FFT) usually, but directly FFT peak value is composed corresponding frequency as Doppler frequency value, then there is the problem that precision is low.Because frequency resolution is Δ f=f
s/ N, wherein f
sfor sample frequency, N is for analyzing data length.And the two kinds of methods (reduce sample frequency and increase data analysis and count) improving frequency resolution are intuitively all infeasible, this is because: on the one hand, because the dynamic range of object under test movement velocity is larger, want the whole dynamic range of coverage speed, can not sample frequency be reduced; On the other hand, the operand of FFT and data analysis are counted closely related, and increase data analysis points N, the calculated amount of whole signal processing algorithm can be made greatly to increase, and the system resource of consumption increases, and real-time is deteriorated.
To sum up, speed instrument of the prior art, all exists: responsive to wave length shift, volume large, complex structure, interference are strong, signal processor poor performance, expensive shortcoming.
Summary of the invention
For overcoming the above-mentioned shortcoming of existing Laser Doppler Velocimeter, the purpose of this utility model is to provide a kind of laser Doppler speed measuring device based on rotating grating, rotating grating is utilized beam splitter and shift frequency to be integrated in one, the centre wavelength achieving Doppler frequency and laser beam on the one hand in principle has nothing to do, and eliminates the drift of laser beam centre wavelength to the impact of measuring accuracy; On the other hand, control system volume, do not introduce other interference prerequisites under, realize the function of direction identification.Fully use frequency spectrum refinement technology and Spectrum Correction technology in frequency domain in signal processing algorithm, the accuracy of raising spectral resolution and Doppler frequency, thus substantially reduce the error that classical signal Processing Algorithm causes.The utility model provide a kind of insensitive to optical maser wavelength, can distinguish that velocity reversal, integration degree are high, structure is simple, volume is little, sensitive reliable, measuring accuracy is high.It has insensitive to optical maser wavelength, can distinguish that velocity reversal, integration degree are high, structure is simple, volume is little, sensitive reliable, advantage that measuring accuracy is high.
For achieving the above object, the technical solution of the utility model is:
A kind of laser Doppler speed measuring device based on rotating grating, comprise: detection probe, the detection signal of detection probe collected by concentric cable, transfers to the signal processing circuit board for the speed of settling accounts, and signal processing circuit board connects display screen and shown on a display screen by detection signal, described detection probe comprises a laser instrument, laser device laser path is arranged the collimating mirror for collimating, rotating grating is provided with after collimating mirror, two total reflective mirror Parallel Symmetrics are arranged in the laser path after rotating grating diffraction, and the detect aperture making laser from detection probe after laser reflection is penetrated, collecting lens is positioned at detect aperture, collect the laser of testee scattering, laser reflexes to plus lens through angled downward-sloping total reflective mirror, the laser of plus lens collected by photodetector, and signal is spread out of detection probe by the front end circuit carrying out signal amplification and filtering through concentric cable.
Further, described laser instrument is single longitudinal mode solid state laser or semiconductor laser.
Further, the laser that described laser instrument is launched forms ± 1 order diffraction light through rotating grating.
Further, in described detection probe ± angle of 1 order diffraction light is θ, utilize two total reflective mirrors to change direction of beam propagation and carry out conjunctions bundle, the angle closing two-beam when restrainting is θ equally.
Further, first Fast Fourier Transform (FFT) FFT is carried out to the signal that detection probe exports in described signal processing circuit board, and then use frequency spectrum refinement technology to improve spectral resolution, finally recycle Spectrum Correction technology to revise the frequency spectrum after refinement, thus extract Doppler frequency, calculate the movement velocity of testee.
Relative to prior art, the beneficial effects of the utility model are:
(1) utilize rotating grating beam splitter and shift frequency to be integrated in one dexterously, the centre wavelength achieving Doppler frequency and laser beam on the one hand in principle has nothing to do, and eliminates the drift of laser beam centre wavelength to the impact of measuring accuracy; On the other hand, control system volume, do not introduce other interference prerequisites under, efficiently solve the difficult problem that velocity reversal is fuzzy.
(2) fully use frequency spectrum refinement technology and Spectrum Correction technology in frequency domain, the accuracy of raising spectral resolution and Doppler frequency, thus substantially reduce the error that classical signal Processing Algorithm causes.
(3) traditional He-Ne laser instrument or semiconductor laser diode is replaced with single longitudinal mode solid state laser, make laser instrument have line width simultaneously, the plurality of advantages such as the large and volume of power is little, are conducive to the noise when spatial resolution improving Doppler signal.
Accompanying drawing explanation
Fig. 1: general structure block diagram of the present utility model
Fig. 2: theory diagram of the present utility model
Fig. 3: the utility model signal processing flow block diagram
Fig. 4: the utility model velocity test schematic diagram.
Wherein: detection probe-1, concentric cable-2, signal processing circuit board-3, display screen-4, testee-5, laser instrument-6, collimating mirror-7, rotating grating-8, total reflective mirror-9, total reflective mirror-10, collecting lens-11, total reflective mirror-12, convergent lens-13, photodetector-14, front end circuit-15.
Embodiment
Below in conjunction with accompanying drawing, the utility model is described in further detail:
As shown in Figure 1, 2, a kind of laser Doppler speed measuring device based on rotating grating, comprise: detection probe 1, the detection signal of detection probe 1 collected by concentric cable 2, transfer to the signal processing circuit board 3 for the speed of settling accounts, signal processing circuit board 3 connects display screen 4 and is shown on the display screen 4 by detection signal, described detection probe 1 comprises a laser instrument 6, laser instrument 6 laser path is arranged the collimating mirror 7 for collimating, rotating grating 8 is provided with after collimating mirror 7, two total reflective mirror 9 and 10 Parallel Symmetrics are arranged in the laser path after rotating grating 8 diffraction, and the detect aperture making laser from detection probe 1 after laser reflection is penetrated, collecting lens 11 is positioned at detect aperture, collect the laser of testee scattering, laser reflexes to plus lens 13 through angled downward-sloping total reflective mirror 12, the laser of plus lens 13 collected by photodetector 14, and signal is spread out of detection probe 1 by the front end circuit 15 carrying out signal amplification and filtering through concentric cable 2.
Further, described laser instrument 6 is single longitudinal mode solid state laser or semiconductor laser.
Further, the laser that described laser instrument 6 is launched forms ± 1 order diffraction light through rotating grating 8.
Further, in described detection probe 1 ± angle of 1 order diffraction light is θ, utilize two total reflective mirrors 9,10 to change direction of beam propagation and carry out conjunctions bundle, the angle closing two-beam when restrainting is θ equally.
Further, first Fast Fourier Transform (FFT) FFT is carried out to the signal that detection probe exports in described signal processing circuit board 3, and then use frequency spectrum refinement technology to improve spectral resolution, finally recycle Spectrum Correction technology to revise the frequency spectrum after refinement, thus extract Doppler frequency, calculate the movement velocity of testee.
Fig. 3 is the utility model signal processing flow block diagram.After light signal is converted to electric signal by photodetector 14, front end circuit 15 amplifies original Doppler signal, tracking filter carries out tracking filter to the signal after amplification, suppress the impact that DC terms and noise bring, then the frequency spectrum of Doppler signal is obtained based on the method for fast fourier transform, use frequency spectrum refinement and the frequency spectrum of Spectrum Correction technology to signal to revise again, finally in revised frequency spectrum, extract Doppler frequency, try to achieve the movement velocity of object under test.
Single longitudinal mode solid state laser also can be replaced by semiconductor laser, but line width of semiconductor laser is wider can affect measuring accuracy.
Principle of work of the present utility model is:
In real work, as shown in Figure 2, in detection probe 1, single longitudinal mode solid state laser 6 sends beam of laser bundle, after collimating mirror 7 collimates, incide on rotating grating 8, due to diffraction effect, symmetrical ± 1 order diffraction light is via total reflective mirror 9, 10 change the direction of propagation, incide in moving object 5 to be measured symmetrically with same angle theta, then collecting lens 11 collects the scattered light from moving object, total reflective mirror 12 changes the direction of propagation of scattered light, converged on the photosurface of photodetector 14 via convergent lens 13, last front end circuit 15 amplifies original Doppler signal and is sent to signal processing circuit board 3 by concentric cable 2 after filtering and processes, extract Doppler frequency, thus calculate the movement velocity of object under test, result is shown by display screen 4.Laser Doppler speed measuring device based on rotating grating detects from the Doppler shift of moving object scattered light by optic probe, to amplify and the front end circuit of filtering and optical detection are popped one's head in and integrated, remaining circuit is integrated in one piece of circuit board and carries out LDA signal processor, by display screen display measurement result.As shown in Figure 1, wherein tested moving object 5, integrated detection probe 1, concentric cable 2, signal processing circuit board 3, display screen 4 connects its general structure successively.
In order to eliminate the impact of drift on measuring accuracy of laser beam centre wavelength, the utility model utilizes the characteristic of optical grating diffraction to carry out beam splitting to laser beam, recycle symmetrical catoptron and carry out conjunction bundle, the centre wavelength that principle achieves Doppler frequency and laser beam has nothing to do.Specific as follows: from diffraction properties
dsinα＝λ (1)
Wherein d is the spacing of diffraction grating, and α is the angle of diffraction light and incident light, and λ is the wavelength of laser beam.And the principle formula of traditional double light beam differential laser knotmeter is
Wherein f
dbe Doppler frequency, θ is the two symmetrical beam angles for closing light, and v is the movement velocity of object under test.Be not difficult to find, θ=2 α, in conjunction with (1) formula, (2) formula can abbreviation be
As can be seen from (3) formula, the centre wavelength of Doppler frequency and laser beam and the angle of two light beams have nothing to do, and this obviates the impact of drift on measuring accuracy of laser beam centre wavelength.
In order to ensure that system bulk is less and realize the function of direction identification under not introducing prerequisites of other interference, the utility model is utilizing rotating grating to carry out shift frequency, and diffraction light at different levels with the frequency difference between incident light is
f
g＝mωN
g(4)
Wherein m is the order of diffraction time, and ω is grating rotating angular velocity, N
git is grating number of buses.The utility model utilizes ± 1 order diffraction light to carry out conjunction bundle, and therefore the offset frequency of two light beams is
f
0＝2f
g＝2mωN
g(5)
This just utilizes rotating grating to realize optic frequency shift, thus efficiently solves the fuzzy problem of velocity reversal, and controls the volume of system, does not also introduce other interference.
As shown in Figure 4, first Fast Fourier Transform (FFT) (FFT) is carried out to the signal that detection probe exports in signal processing circuit board 3, and then use frequency spectrum refinement technology to improve spectral resolution, finally recycle Spectrum Correction technology to revise the frequency spectrum after refinement, thus extract Doppler frequency, calculate the movement velocity of testee.In order to reduce the error that conventional laser LDA signal processor method (FFT) is brought, the utility model uses frequency spectrum refinement technology to improve frequency resolution on the basis of FFT, and use Spectrum Correction technology to revise Doppler frequency, make it more close to actual value.
Claims (5)
1. the laser Doppler speed measuring device based on rotating grating, it is characterized in that, comprise: detection probe, the detection signal of detection probe collected by concentric cable, transfer to the signal processing circuit board for the speed of settling accounts, signal processing circuit board connects display screen and is shown on a display screen by detection signal, described detection probe comprises a laser instrument, laser device laser path is arranged the collimating mirror for collimating, rotating grating is provided with after collimating mirror, two total reflective mirror Parallel Symmetrics are arranged in the laser path after rotating grating diffraction, and the detect aperture making laser from detection probe after laser reflection is penetrated, collecting lens is positioned at detect aperture, collect the laser of testee scattering, laser reflexes to plus lens through angled downward-sloping total reflective mirror, the laser of plus lens collected by photodetector, and signal is spread out of detection probe by the front end circuit carrying out signal amplification and filtering through concentric cable.
2. the laser Doppler speed measuring device based on rotating grating according to claim 1, is characterized in that: described laser instrument is single longitudinal mode solid state laser or semiconductor laser.
3. the laser Doppler speed measuring device based on rotating grating according to claim 1, is characterized in that: the laser that described laser instrument is launched forms ± 1 order diffraction light through rotating grating.
4. the laser Doppler speed measuring device based on rotating grating according to claim 1, it is characterized in that: in described detection probe ± angle of 1 order diffraction light is θ, utilize two total reflective mirrors to change direction of beam propagation and carry out conjunction bundle, the angle closing two-beam during bundle is θ equally.
5. the laser Doppler speed measuring device based on rotating grating according to claim 1, it is characterized in that: in described signal processing circuit board, first Fast Fourier Transform (FFT) FFT is carried out to the signal that detection probe exports, and then use frequency spectrum refinement technology to improve spectral resolution, finally recycle Spectrum Correction technology to revise the frequency spectrum after refinement, thus extract Doppler frequency, calculate the movement velocity of testee.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106645777A (en) * | 2016-11-10 | 2017-05-10 | 华东师范大学 | Spatial filtering speed measurer based on digital micro mirror |
| CN104833816B (en) * | 2015-04-29 | 2018-04-10 | 中国人民解放军国防科学技术大学 | Laser Doppler speed measuring device and its speed-measuring method based on rotating grating |
| CN109407110A (en) * | 2018-10-12 | 2019-03-01 | 湖南波恩光电科技有限责任公司 | Vehicle-mounted laser Doppler anemometer based on scanning galvanometer |
-
2015
- 2015-04-29 CN CN201520270510.0U patent/CN204575674U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104833816B (en) * | 2015-04-29 | 2018-04-10 | 中国人民解放军国防科学技术大学 | Laser Doppler speed measuring device and its speed-measuring method based on rotating grating |
| CN106645777A (en) * | 2016-11-10 | 2017-05-10 | 华东师范大学 | Spatial filtering speed measurer based on digital micro mirror |
| CN106645777B (en) * | 2016-11-10 | 2023-10-27 | 华东师范大学 | Spatial filtering speed measuring device based on digital micromirror |
| CN109407110A (en) * | 2018-10-12 | 2019-03-01 | 湖南波恩光电科技有限责任公司 | Vehicle-mounted laser Doppler anemometer based on scanning galvanometer |
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| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20150819 Termination date: 20160429 |