CN1844844A - Device and method for measuring micro displacement by femtosecond laser speckle correlation method - Google Patents
Device and method for measuring micro displacement by femtosecond laser speckle correlation method Download PDFInfo
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- CN1844844A CN1844844A CN 200610026621 CN200610026621A CN1844844A CN 1844844 A CN1844844 A CN 1844844A CN 200610026621 CN200610026621 CN 200610026621 CN 200610026621 A CN200610026621 A CN 200610026621A CN 1844844 A CN1844844 A CN 1844844A
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- 238000006073 displacement reaction Methods 0.000 title claims abstract description 29
- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000005259 measurement Methods 0.000 claims description 18
- 230000003993 interaction Effects 0.000 abstract description 2
- 238000012545 processing Methods 0.000 abstract description 2
- 238000005314 correlation function Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 238000005311 autocorrelation function Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000010365 information processing Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000010606 normalization Methods 0.000 description 1
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Abstract
A device and a method for measuring micro displacement by using a femtosecond laser speckle correlation method. The device mainly comprises a femtosecond laser source, a CCD camera and a computer control and processing system, wherein the method uses the device to record the speckle fields before and after the object moves by using a CCD detector respectively and stores the recorded speckle fields in a computer, and the speckle fields before and after the object moves are subjected to correlation operation to determine the moving amount of the field; the invention can measure the speckle field shift action in real time; to sub-pixel size. The generation of speckles caused by the interaction of the femtosecond laser with molecules and organisms is a common phenomenon, and the method has important significance in obtaining the spatial motion information of the scatterer by utilizing the information of the femtosecond speckles.
Description
Technical field
The invention belongs to the planar measurement of micro-displacement of object, particularly relate to apparatus and method with micro-displacement in the femtosecond laser speckle correlation measurement plane.
Background technology
Laser speckle belongs to the holographic interference phenomenon, and it is prevalent in the process of optical imagery, and speckle has carried many information of the object that light beam and light beam passed through, so produced many application.For example measure the roughness of reflecting surface, utilize the speed of the current intelligence Measuring Object motion of speckle, utilize speckle to carry out optical information processing, even utilize speckle optometry or the like with the contrast of speckle.Laser speckle can be measured with the way of exposure, but up-to-date measuring method is to utilize CCD and computer technology, because avoided the process of development and photographic fixing, can realize the purpose measured in real time in the research and production process, obtaining increasingly extensive application with this technology.
The present invention determines moving of field with femtosecond laser speckle correlation method, speckle field before and after the movement of objects is noted and is stored in the computing machine with ccd detector respectively, speckle field after moving preceding speckle field and moving is carried out correlation operation, just can determine the amount of movement that appears on the scene, it does not need to carry out fringe analysis, also do not need photographic plate is dealt with, this just makes this method to move speckle field and does to measure in real time that the precision of Displacement Measurement can reach sub-pixel.More simple to operate than traditional speckle interference the Schlieren method [J.C.Dainty, " Laser Speckle and Related Phenomena ", Springer-Verlag, 1984].It is common phenomena [Wenjun Liu and Changhe Zhou that the interaction of femtosecond laser and molecule, biosome causes the generation of speckle, " Femtosecond laser speckles ", APPLIED OPTICS_Vol.44, No.30, p6506-6510,2005].The present invention learns that by utilizing the information of femtosecond speckle the spatial movement information of scatterer has application value.
Summary of the invention
Technical matters to be solved by this invention provides a kind of apparatus and method of femtosecond laser speckle correlation measurement object micro-displacement, and it should have true-time operation, and method is easy, and precision can reach the requirement of sub-pixel.
Technical solution of the present invention is as follows:
A kind of device with femtosecond laser speckle correlation measurement micro-displacement, comprise a femto-second laser, be provided with first lens, second lens, body to be measured, ccd detector successively in the light beam working direction of this femto-second laser, the focus of described first lens, second lens overlaps, the output terminal of described ccd detector links to each other with an input end and computer, the femtosecond laser of described femto-second laser emission is converged to focus through first lens, become directional light through second lens then, shine the surface of body to be measured.
A kind of method of femtosecond laser speckle correlation measurement micro-displacement, it mainly is:
(1) note body to be measured and move with ccd detector before and move after speckle field, the speckle field before moving is as with reference to a F
1, the speckle field after scatterer moves is as moving field F
2,
(2) from F
1And F
2(X Y) moves to the displacement that S ' (X+ Δ X, Y+ Δ Y) is taken place from S to calculate body to be measured with related algorithm.
The method of described femtosecond laser speckle correlation measurement micro-displacement, its concrete steps are as follows:
(1) sets up the device of micro-displacement in the femtosecond laser speckle correlation measurement plane;
(2) note the speckle field F of body original state to be measured by ccd detector
1Deposit computing machine in, after the state of body to be measured changes, note the speckle field F of this moment again with ccd detector
2And deposit computing machine in;
(3) utilize computing machine to initial speckle field F
1Carry out auto-correlation computation, asking autocorrelative peak value coordinate is (x
1, y
1) pixel, coordinate (x
1, y
1) be the initial position of scatterer;
(4) to initial speckle field F
1With the speckle field F after the body variation to be measured
2Carry out computing cross-correlation, the peak value coordinate of simple crosscorrelation is (x
2, y
2) pixel, then (x
2, y
2) be the position after the object trace moves;
(5) amount of movement of speckle field is (Δ x, Δ y), Δ x=x
2-x
1, Δ y=y
2-y
1, the size of each pixel is the μ micron, and the magnification of CCD is M, and then the displacement of body to be measured is (μ Δ x/M, μ Δ y/M) micron.
Principle of work of the present invention is:
Suppose that the speckle light distribution on any 2 of the sightingpiston is I (x
1, y
1), I (x
2, y
2), the autocorrelation function of light distribution is:
G(x
1，y
1；x
2，y
2)＝<I(x
1，y
1)I(x
2，y
2)> (1)
I (x wherein
1, y
1) expression sightingpiston on any point Q
1Light intensity, I (x
2, y
2) light intensity on the expression sightingpiston on another Q,＜the expression assembly average.
I(x，y)＝U(x，y)U*(x，y) (2)
U in the formula (x, y) complex amplitude of expression light field.Can obtain following formula according to the statistical theory of speckle:
G(x
1，y
1；x
2，y
2)＝<I(x
1，y
1)I(x
2，y
2)>+|U(x
1，y
1)U*(x
2，
y
2)|
2＝<I>[1+μ(x
1，y
1；x
2，y
2)] (3)
μ (x in the formula
1, y
1x
2, y
2)=|＜U (x
1, y
1) U* (x
2, y
2) |
2/＜I 〉
2Be called complex phase responsibility number.Because the hot spot of laser emitting is a Gaussian distribution, can releases complex phase responsibility number according to diffraction theory and be:
μ(x
1，y
1；x
2，y
2)＝exp[-(Δx
2+Δy
2)/S
2] (4)
Δ x=(x in the formula
2-x
1), Δ y=(y
2-y
1), substitution (3) formula turns to
G(x
1，y
1；x
2，y
2)＝<I>
2[1+μ(x
1，y
1；x
2，y
2)]＝<I>
2{1+
exp[-(Δx
2+Δy
2)/S
2]} (5)
Wherein the meaning of S is promptly represented the mean radius of speckle.
Suppose any 1 Q of sightingpiston
1On the speckle light distribution be I (x
1, y
1), after scatterer changes, as scatterer a small translation d=(d takes place
ξ+ d
η)
1/2, any 1 Q of sightingpiston
2On the speckle light distribution be I ' (x
2, y
2), the cross correlation function of light distribution is:
GC(x
1，y
1；x
2，y
2)＝<I(x
1，y
1)I’(x
2，y
2)> (6)
Equally have with top
I(x，y)＝U(x，y)U*(x，y) (7)
I’(x，y)＝U’(x，y)U’*(x，y) (8)
U in the formula (x, y) and U ' (x y) represents the complex amplitude of two speckle light fields respectively.The cross correlation function that we can obtain two speckle fields according to the statistical theory of speckle is:
Owing to utilize CCD and computing machine, what therefore measure is one group of discretize, digitized light intensity value (each CCD pixel obtains 8 binary numbers) in actual measurement, I (i, j), i=1,2 ... n
xJ=1,2 ...., n
yn
xAnd n
yBe the pixel number of area array CCD in level and vertical direction, N
0=n
x* n
yBe total pixel number.After finishing, sampling calculates the normalization sampled correlation function of speckle field.Sampled correlation function is defined as
N=(n wherein
x-l) (n
y-m).Order:
Then
g(l，m)＝G(l，m)/<I>
2，
(l m) is called normalized sampled correlation function to this g.Therefore we can obtain the displacement information of scatterer again by the variation that CCD measures and speckle is measured in the calculating of sampled correlation function from the variation of speckle.
Our experiments show that: the inventive method can Measuring Object micro-displacement planar, true-time operation, and method is easy, and measuring accuracy can reach sub-pixel.
Description of drawings
Fig. 1 is the synoptic diagram of apparatus of the present invention
Among the figure: the 1-femto-second laser 2-first convergent lens 21-second convergent lens 3-scatterer 4-CCD detector 5-computer control and the disposal system
Embodiment
The invention will be further described below in conjunction with embodiment.
See also Fig. 1 earlier, Fig. 1 is the synoptic diagram of apparatus of the present invention, as seen from the figure, the device of femtosecond laser speckle correlation measurement micro-displacement of the present invention, comprise a femto-second laser 1, light beam working direction at this femto-second laser 1 is provided with first lens 2 successively, second lens 21, body 3 to be measured, ccd detector 4, the focus of described first lens 2 and second lens 21 overlaps, the output terminal of described ccd detector 4 links to each other with the input end of computing machine 5, the femtosecond laser of described femto-second laser 1 emission is converged to focus through first lens 2, become directional light through second lens 21 then, shine the surface of body 3 to be measured.Body 3 to be measured is used for producing speckle, and before ccd detector 4 is used to note body 3 to be measured and moves and the speckle field after moving, computing machine 5 is used for data processing.
A kind of method of femtosecond laser speckle correlation measurement micro-displacement mainly is:
(1) note body 3 to be measured and move with ccd detector 4 before and move after speckle field, the speckle field before moving is as with reference to a F
1, the speckle field after scatterer 3 moves is as moving field F
2,
(2) (X, Y) essence that moves to the process of the displacement that S ' (X+ Δ X, Y+ Δ Y) taken place is: from F from S to calculate body 3 to be measured from F1 and F2 with related algorithm
1And F
2In intercept a number of sub images S respectively
1And S
2, calculate subimage S with related algorithm
1And S
2Between the approximation of statistical property, be similar to and use reference field S
1To moving field S
2Scan, when scanning S
2In certain regional statistical property and reference field S
1Statistical property when identical, this zone is exactly subimage S
1Field S after moving
1', the peak of related operation is exactly subimage S
1From (X Y) moves to S
1' displacement that (X+ Δ X, Y+ Δ Y) taken place.
The method of micro-displacement in the described femtosecond laser speckle correlation measurement plane, feature is that its concrete steps are as follows:
(1) sets up the device of femtosecond laser speckle correlation measurement micro-displacement;
(2) note the speckle field F of body 3 original states to be measured by ccd detector 4
1Deposit computing machine 5 in, after the state of body 3 to be measured changes, note the speckle field F of this moment again with ccd detector 4
2And deposit computing machine 5 in;
(3) utilize 5 couples of initial speckle field F of computing machine
1Carry out auto-correlation computation, asking autocorrelative peak value coordinate is (x
1, y
1) pixel, coordinate (x
1, y
1) be the initial position of scatterer;
(4) to initial speckle field F
1With the speckle field F after body 3 variations to be measured
2Carry out computing cross-correlation, the peak value coordinate of simple crosscorrelation is (x
2, y
2) pixel, then (x
2, y
2) be the position after the object trace moves;
(5) amount of movement of speckle field is (Δ x, Δ y), Δ x=x
2-x
1, Δ y=y
2-y
1, the size of each pixel is the μ micron, and the magnification of CCD is M, and the displacement of body 3 then to be measured is (μ Δ x/M, μ Δ y/M) micron.
Our experiments show that: the inventive method can Measuring Object micro-displacement planar, true-time operation, and method is easy, and measuring accuracy can reach sub-pixel.
Claims (3)
1, a kind of device with femtosecond laser speckle correlation measurement micro-displacement, it is characterized in that comprising a femto-second laser (1), light beam working direction at this femto-second laser (1) is provided with first lens (2) successively, second lens (21), body to be measured (3), ccd detector (4), described first lens (2), the focus of second lens (21) overlaps, the output terminal of described ccd detector (4) links to each other with the input end of computing machine (5), the femtosecond laser of described femto-second laser (1) emission is converged to focus through first lens (2), become directional light through second lens (21) then, shine the surface of body to be measured (3).
2, a kind of method of femtosecond laser speckle correlation measurement micro-displacement is characterized in that:
(1) note body to be measured (3) and move with ccd detector (4) before and move after speckle field, the speckle field before moving is as with reference to a F1, the speckle field after scatterer (3) moves is as moving field F2,
(2) (X Y) moves to the displacement that S ' (X+ Δ X, Y+ Δ Y) is taken place from S to calculate body to be measured (3) by F1 and F2 with related algorithm.
3, the method for femtosecond laser speckle correlation measurement micro-displacement according to claim 2 is characterized in that concrete steps are as follows:
(1) sets up the device of femtosecond laser speckle correlation measurement micro-displacement;
(2) note the speckle field F of body to be measured (3) original state by ccd detector (4)
1Deposit computing machine (5) in, after the state of body to be measured (3) changes, use again ccd detector (4) note this moment speckle field F2 and deposit computing machine (5) in;
(3) utilize computing machine (5) to initial speckle field F
1Carry out auto-correlation computation, asking autocorrelative peak value coordinate is x
1, y
1Pixel, coordinate x
1, y
1Initial position for scatterer;
(4) the speckle field F2 after initial speckle field F1 and body to be measured (3) variation is carried out computing cross-correlation, the peak value coordinate of simple crosscorrelation is x
2, y
2Pixel, then x
2, y
2Be the position of body to be measured trace after moving;
(5) amount of movement of speckle field is Δ x, Δ y, Δ x=x
2-x
1, Δ y=y
2-y
1, the size of each pixel is the μ micron, and the magnification of CCD is M, and the displacement of body then to be measured (3) is μ Δ x/M, μ Δ y/M micron.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101788269A (en) * | 2010-03-22 | 2010-07-28 | 西安交通大学 | Displacement measuring device with reference and measuring method |
| CN102135413A (en) * | 2010-12-14 | 2011-07-27 | 河南科技大学 | Phase vortex based digital speckle correlation measurement method |
| CN106247952A (en) * | 2016-08-31 | 2016-12-21 | 昆明理工大学 | A kind of speckle pattern photography in-plane displacement quantity algorithm based on Fourier transformation phase place |
| CN106771349A (en) * | 2016-12-26 | 2017-05-31 | 浙江科聪智能科技有限公司 | Contactless water speed measurement sensor, Intelligent pipe net, the intelligent network of rivers |
| CN108050939A (en) * | 2017-12-06 | 2018-05-18 | 柳州市融智科技服务有限公司 | A kind of displacement detector |
| CN108981585A (en) * | 2017-06-01 | 2018-12-11 | 上海砺晟光电技术有限公司 | It can accurately measure the laser displacement sensor of curved surface displacement of targets |
| CN110307785A (en) * | 2019-07-11 | 2019-10-08 | 清华大学 | The method, apparatus and system of facula position precise positioning based on memory effect |
| CN110631487A (en) * | 2019-11-08 | 2019-12-31 | 济南大学 | Method for measuring transverse micrometric displacement by utilizing laser speckle autocorrelation technology |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5299035A (en) * | 1992-03-25 | 1994-03-29 | University Of Michigan | Holographic imaging through scattering media |
| US5489984A (en) * | 1994-04-01 | 1996-02-06 | Imra America, Inc. | Differential ranging measurement system and method utilizing ultrashort pulses |
| CN2551982Y (en) * | 2002-06-14 | 2003-05-21 | 中国科学院上海光学精密机械研究所 | Flying laser pulse autocorelation measurer |
-
2006
- 2006-05-17 CN CNB2006100266212A patent/CN100378432C/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101788269A (en) * | 2010-03-22 | 2010-07-28 | 西安交通大学 | Displacement measuring device with reference and measuring method |
| CN101788269B (en) * | 2010-03-22 | 2012-03-28 | 西安交通大学 | Displacement measuring device with reference and measuring method |
| CN102135413A (en) * | 2010-12-14 | 2011-07-27 | 河南科技大学 | Phase vortex based digital speckle correlation measurement method |
| CN102135413B (en) * | 2010-12-14 | 2012-08-22 | 河南科技大学 | Phase vortex based digital speckle correlation measurement method |
| CN106247952A (en) * | 2016-08-31 | 2016-12-21 | 昆明理工大学 | A kind of speckle pattern photography in-plane displacement quantity algorithm based on Fourier transformation phase place |
| CN106247952B (en) * | 2016-08-31 | 2018-11-27 | 昆明理工大学 | A kind of speckle pattern photography in-plane displacement quantity algorithm based on Fourier transformation phase |
| CN106771349A (en) * | 2016-12-26 | 2017-05-31 | 浙江科聪智能科技有限公司 | Contactless water speed measurement sensor, Intelligent pipe net, the intelligent network of rivers |
| CN108981585A (en) * | 2017-06-01 | 2018-12-11 | 上海砺晟光电技术有限公司 | It can accurately measure the laser displacement sensor of curved surface displacement of targets |
| CN108050939A (en) * | 2017-12-06 | 2018-05-18 | 柳州市融智科技服务有限公司 | A kind of displacement detector |
| CN110307785A (en) * | 2019-07-11 | 2019-10-08 | 清华大学 | The method, apparatus and system of facula position precise positioning based on memory effect |
| CN110631487A (en) * | 2019-11-08 | 2019-12-31 | 济南大学 | Method for measuring transverse micrometric displacement by utilizing laser speckle autocorrelation technology |
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