CN1027557C - Optic frequency shift separation method for three-dimensional laser Doppler signal and three-dimensional laser Doppler speed measuring device - Google Patents
Optic frequency shift separation method for three-dimensional laser Doppler signal and three-dimensional laser Doppler speed measuring device Download PDFInfo
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- CN1027557C CN1027557C CN 92114234 CN92114234A CN1027557C CN 1027557 C CN1027557 C CN 1027557C CN 92114234 CN92114234 CN 92114234 CN 92114234 A CN92114234 A CN 92114234A CN 1027557 C CN1027557 C CN 1027557C
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Abstract
The present invention relates to an optic method and an instrument for the three-dimensional measurement of flow speed, particularly to an optic frequency shift separation method for a three-dimensional laser Doppler signal and a three-dimensional laser Doppler speed measuring device. Three optic frequency shifts are used as the carrier frequencies of the three-dimensional measured speed signal, and a scattered light signal is detected by a single photoelectric receiver and is separated by a frequency selection filter with different pass bands. The formed three-dimensional speed measuring device has the advantages of simple structure, easy adjustment and low fabrication cost and can be widely used for the speed measurement of the three-dimensional flow fields of fields, such as fluid mechanics, chemical industry, water conservancy, biomedical engineering, etc.
Description
The present invention relates to a kind of optical means and instrument that three-dimensional flow is measured that be used for.
Laser Doppler Velocimeter (be called for short LDA) has become indispensable fluid-velocity survey means in the numerous areas such as fluid mechanics, Aero-Space, combustion diagnosis, chemical industry, water conservancy and biomedical engineering with its outstanding feature (as not interference flowing field, spatial discrimination height, response is fast, precision is high).The flow field problem that modern age, fluid mechanics and many engineerings were run in using belongs to three-dimensional flow mostly.When the relevant and calculating shear stress parameters of studying between each speed component such as (eddy stresses), must obtain three all velocity components simultaneously.In this case, the three-dimensional speed measurement instrument is absolutely necessary completely.
Early stage in LDA development, people have just proposed to constitute the scheme of three dimension system.These schemes all are based on reference beam type light path.This three dimension system biggest advantage is the signal that each detector receives one-component, does not have the Signal Separation problem.But be worth owing to existing problems such as light path dispersed placement and difficult adjustment and spatial resolution are low to greatly reduce its practicality, thereby this three dimension system fails to be developed fully and use.
Existing three-dimensional LDA system all grows up on twin-beam LDA basis.Have signal to noise ratio (S/N ratio) and spatial resolution advantages of higher, but the Signal Separation between the friction speed component then becomes a key issue.The method of existing separation three-dimension signal comprises: with the multiline laser look partition method of light source, and color separation and the method for dividing polarization (or frequency displacement) to combine, and frequency displacement is in conjunction with the separation method of polarization.There is following shortcoming in the three-dimensional LDA that constitutes with said method:
1. colour splitting system needs the laser instrument of multiline output, all is to use Argon ion laser at present.The Argon ion laser price is very high, makes the cost of total system increase substantially, and is unfavorable for applying.In addition, the life-span of Argon ion laser is also shorter.
2. the complicated and difficult adjustment of optical emitting part-structure.When adopting the look isolation technics, need a cover beam split light path that the light of different wave length is separated from the mixed light of Argon ion laser output, through focusing on measurement point (some system even adopt two diversing lens) after the beam splitting, frequency displacement, its light path arrangement is very complicated again for the light of each wavelength.For example, the 9100-11 of U.S. Technical Sourcing Internation type three dimension system, only its optical emitting part just has 27 optical elements, and its processing charges and adjustment difficulty are well imagined.When adopting the polarization separation method, also need a cover light path system that the polarization state of incident laser is accurately transformed to required state.The problems such as " cross interference " between the different components numerous and diverse and that cause by the change of scatter light polarization attitude adjusted be polarization separation type LDA intrinsic shortcoming.
3. receiving unit needs many photelectric receivers and complicated beam splitting system.Because three speed components are to be distinguished by different optical maser wavelength or polarization state,, and a cover and the similar beam splitting system of radiating portion to be arranged so the scattered light signal of each component will be surveyed with a photelectric receiver.
In a word, with the three-dimensional LDA complex structure that existing method is constituted, be difficult for adjusting, commercial instrument appropriate litigation fees costliness is difficult to apply.
Purpose of the present invention just provides a kind of method and a kind of three-dimensional laser Doppler speed measuring device that constitutes with this method that relies on optic frequency shift to distinguish whole three-dimensional velocity components fully.
The signal separating method that the present invention relates to is to utilize three kinds of fixing optic frequency shifts respectively as the carrier frequency of three-dimensional tested speed, and the Doppler shift choosing that these three kinds of frequency displacements and corresponding speed component are produced adds the back is positioned at non-overlapping copies on frequency spectrum frequency band.Scattered light signal utilizes three kinds of parallel frequency-selecting filters to isolate frequency signal corresponding to the tested speed component of three-dimensional from same photo-signal after opto-electronic conversion.
Accompanying drawing 1 is the frequency displacement divergence type three-dimensional laser Doppler speed measuring device that constitutes according to the method for the invention.
In the accompanying drawing, [1] He-Ne laser instrument, [2] [4] beam splitter prism, [3] [5] [6] acousto-optic frequency shift device, [7] [9] wedge, [8] right-angle prism is right, [10] diversing lens, [11] photelectric receiver, [12] signal distributor, [13] [14] [15] frequency-selecting filter mixes circuit, [19] [20] [21] doppler signal processor under the frequency of [16] [17] [18].
The laser beam of being sent by laser instrument [1] is divided into two bundles behind beam splitter prism [2], a branch of frequency shifter [3] that enters; Another bundle enters another beam splitter prism [4] along incident direction, is divided into the aplanatic directional light of two bundles, enters frequency shifter [5] [6] respectively.Frequency shifter [3] is f by frequency
3Signal drive, the first-order diffraction light of generation is told [8] after wedge incides lens [10] by prism.The zero order light of frequency shifter [3] (not frequency shifted portion) is directly incident on lens [10].Frequency shifter [5] [6] is f by frequency respectively
1And f
2Signal drive, the first-order diffraction light that their produce incides lens [10] through wedge.Four bundle incident lights (represent with A by wherein a branch of not frequency displacement; Three beams is distinguished frequency displacement f in addition
1, f
2And f
3, represent with B, C, D respectively) all be parallel to the optical axis of emission coefficient, focus on measurement point P through lens [10].Light beam B and A combination, light beam C and A combination be two speed components of measuring vertical in the systematic optical axis plane respectively; Light beam D and A multiple measurement are along the speed component of system axial.The photo-signal that is produced by photelectric receiver [11] is divided into three the tunnel through divider [12], selects frequency signal corresponding to the three-dimensional velocity component respectively by frequency-selecting filter [13] [14] [15].The local oscillation signal mixing that this three road signal produces through mixting circuit [19] [20] [21] and frequency synthesizer of phase locking respectively, difference frequency signal is admitted to the triple channel doppler signal processor and handles, and obtains three-dimensional tested velocity amplitude.
The three-dimensional laser Doppler speed measuring device that consists of with the method has the following advantages:
1. lasing light emitter can use mono-colour laser, such as the He-Ne laser instrument. Compare its price with argon ion laser low, and the life-span is long.
2. owing to do not relate to color separation or polarisation of light problem, no longer need baroque optical filtering/beam split or polarization spectro light path with the scattered light receiving unit in the optical emitting part.This simplification not only can be saved expensive optics processing charges, and makes light path be convenient to adjust, and the instrument resistance to overturning is able to basic improvement.
3. receiving unit has only just been finished the detection of whole three-dimensional velocity informations with a photelectric receiver, and does not need any color separation or polarization spectro light path.
4. there be not " cross interference " between the different component signals that cause because of the variation of scatter light polarization attitude.
5. be used for surveying and do not have along optical axis direction incident along the detection light of system axial (optical axis direction) speed component, but incide measurement point from axle with wide-angle, eliminate existing three-dimensional laser tachometer because of adopting the symmetrical structure light path, adjusted the angular deviation of the axial velocity component that error brings by light path.
6. eliminated " direction is fuzzy " of each speed component, can determine the positive negative direction of velocity component.
Claims (4)
1, the optic frequency shift separation method of three-dimensional laser Doppler signal, wherein step comprises: the laser beam of being sent by lasing light emitter is through the Amici prism beam split, carry out frequency displacement by the acousto-optic frequency shifter, light beam arrives measurement point through lens focus, it is characterized in that utilizing three kinds of fixing optic frequency shifts respectively as the carrier frequency of three-dimensional tested rate signal, scattered light signal is surveyed by single photelectric receiver, the photo-signal that is produced is delivered to the frequency-selecting filter with different passbands of three-channel parallel, and the frequency-selecting filter of three-channel parallel is isolated the frequency signal corresponding to the tested speed component of three-dimensional from photo-signal.
2, three-dimensional laser Doppler speed measuring device according to the described method formation of claim 1, this device comprises light path part and signal processing, wherein light path part has He-Ne laser instrument [1], beam splitter prism [2] [4], acousto-optic frequency shift device [3] [5] [6], wedge [7] [9], right-angle prism is to [8], diversing lens [10], photelectric receiver [11], signal processing has signal distributor [12], frequency-selecting filter [13] [14] [15], mix circuit [16] [17] [18] under the frequency, doppler signal processor [19] [20] [21], it is characterized in that lasing light emitter is a mono-colour laser, adopt a photelectric receiver [11] to receive three-dimensional velocity information.
3, according to the described three-dimensional laser Doppler speed measuring device of claim 2, it is characterized in that acousto-optic frequency shifter [3] [5] [6] is driven by three kinds of different fixed frequencies respectively, produce three kinds of fixing optic frequency shifts, the photo-signal of photelectric receiver [11] output is sent into frequency-selecting filter [13] [14] [15] through signal distributor [12].
4, according to the described three-dimensional laser Doppler speed measuring device of claim 2, the light beam that it is characterized in that being used to measuring axial velocity component incides measurement point from the direction that departs from optical axis.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 92114234 CN1027557C (en) | 1992-12-12 | 1992-12-12 | Optic frequency shift separation method for three-dimensional laser Doppler signal and three-dimensional laser Doppler speed measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 92114234 CN1027557C (en) | 1992-12-12 | 1992-12-12 | Optic frequency shift separation method for three-dimensional laser Doppler signal and three-dimensional laser Doppler speed measuring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1077798A CN1077798A (en) | 1993-10-27 |
| CN1027557C true CN1027557C (en) | 1995-02-01 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN 92114234 Expired - Fee Related CN1027557C (en) | 1992-12-12 | 1992-12-12 | Optic frequency shift separation method for three-dimensional laser Doppler signal and three-dimensional laser Doppler speed measuring device |
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| JP4093971B2 (en) * | 2004-02-12 | 2008-06-04 | シャープ株式会社 | Optical movement information detection apparatus, movement information detection system, electronic apparatus and encoder |
| CN105589253B (en) * | 2016-03-18 | 2019-05-07 | 京东方科技集团股份有限公司 | Color membrane substrates and preparation method thereof, display device, exposure sources |
| CN108549086B (en) * | 2018-03-20 | 2022-04-12 | 天津大学 | Laser Doppler signal filter band self-adaptive selection and test method |
| CN110988380A (en) * | 2019-12-12 | 2020-04-10 | 华中科技大学 | Structured light interferometry method and device |
| CN112716472B (en) * | 2020-12-25 | 2023-01-17 | 杭州电子科技大学 | Three-dimensional laser Doppler blood flow instrument based on optical frequency division |
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- 1992-12-12 CN CN 92114234 patent/CN1027557C/en not_active Expired - Fee Related
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