Summary of the invention
The objective of the invention is in order to solve above-mentioned the deficiencies in the prior art, a kind of liquid particles automatic detection device and detection method based on optical fiber coupling is provided, with solve the device complexity height in the full light scattering method particle sizing, refractive index to be measured is determined and reflection, the scattering problem of sample cell.
Basic thought of the present invention is: utilize the computer control high-precision optical to adjust platform, the two the end face of input optical fibre and the output optical fibre that is connected power meter that connects light source is controlled and is locked in the spacing of one 100 μ m, splash into solution to be measured and form sample pool structure, utilize multi-wavelength scanning then, in conjunction with the traditional MIE theory of Lorentz model refinement; Propose the multivariate genetic algorithm and realize real-time online detection.
Technical solution of the present invention is as follows:
A kind of grain testing apparatus based on the optical fiber coupling, characteristics are levied and are that its formation comprises: the high stable multi wave length illuminating source, input optical fibre, the automatically controlled optics of first high precision is adjusted platform, the CCD imaging system, the automatically controlled optics of second high precision is adjusted platform, output optical fibre, detected with high accuracy device and computing machine, one end of described input optical fibre links to each other with the output terminal of described high stable multi wave length illuminating source, the input end of the described detected with high accuracy device of one termination of described output optical fibre links to each other, the other end of described input optical fibre is fixed on the automatically controlled optics adjustment of described first high precision platform and extends outside the appearance, be called free end, the other end of described output optical fibre is fixed on the automatically controlled optics adjustment of described second high precision platform and extends outside the appearance, be called free end, the free end of described input optical fibre is relative in opposite directions with the free end of output optical fibre and be positioned at the camera watch region of described CCD imaging system, described computing machine respectively with described high stable multi wave length illuminating source, the automatically controlled optics of first high precision is adjusted platform, the CCD imaging system, the automatically controlled optics of second high precision is adjusted platform and is linked to each other with the detected with high accuracy device.
The wavelength of described high stable multi wave length illuminating source output and power are by described computer control.
The free-ended relative position of the free end of described input optical fibre and output optical fibre adjusts platform by the automatically controlled optics of described first high precision of described computer control and the automatically controlled optics of second high precision is adjusted platform, carries out precision adjustment under the monitoring of described CCD imaging system.
The signal that described computing machine receives the input of the described detected with high accuracy device line data of going forward side by side is handled.
A kind ofly utilize described grain testing apparatus based on optical fiber coupling to carry out the method for particle detection, its characteristics are levied and are that this method comprises the following steps:
(1) utensil cleans:
For avoiding artificial pollution, the utensil that will use for experiment must could use through strict cleaning process in advance;
(2) device preheating and initial adjustment:
In order to make light stability, described high stable multi wave length illuminating source and detected with high accuracy device must reach optimum performance through preheating, and be 30 minutes preheating time, measure temperature during experiment and are controlled at 20 ± 5 ℃; The precision of adjusting platform and the automatically controlled optics adjustment of second high precision platform by the automatically controlled optics of described first high precision of computer control moves, under the monitoring of described CCD imaging system, carry out precision adjustment, make the free end of described input optical fibre and the same optical axis of free end of output optical fibre;
(3) calibration solution is measured:
1. calibration solution adopts distilled pure water;
2. the free end face with described input optical fibre and output optical fibre cleans up on the free-ended end face of input optical fibre with isopropyl alcohol respectively, splash into an amount of pure water with glue head dropper, by surface tension effects, pure water liquid pearl can be attached on the end face of input optical fibre, stepper motor by the automatically controlled optics adjustment of computer control second high precision platform makes two free end faces close again, also touch until the output optical fibre end face with the liquid pearl, the spacing of regulating two end faces is 100 μ m and locking, forms the adjustable sample cell of pond spacing L;
3. successively export from wavelength 1000nm by the described high stable multi wave length illuminating source of computer control, be spaced apart 100nm, until 1300nm amounts to the light of 4 wavelength, described detected with high accuracy device writes down 4 I of corresponding optical power value
0, send computing machine to deposit array in;
(4) liquid to be measured is measured:
1. add particle to be measured in the solvent and place low speed rotation on the sol evenning machine, solution to be measured is fully stirred;
2. blow the calibration solution between the fiber end face off, the drop of drawing solution to be measured then is between two fiber end faces, the stepper motor that adjust platform by the automatically controlled optics of computer control second high precision this moment makes both ends of the surface close, also touch until the output optical fibre end face with the liquid pearl, the spacing of regulating two end faces is 100 μ m and locking, forms the adjustable sample cell of pond spacing L;
3. successively export from wavelength 1000nm by the described high stable multi wave length illuminating source of computer control, be spaced apart 100nm, until 1300nm amounts to the light of 4 wavelength, described detected with high accuracy device writes down 4 I of corresponding optical power value, send computing machine to deposit array in;
(5) data processing:
4 I that step (3) is obtained
0And 4 I obtaining of step (4), and 4 wavelength parameter, bring following formula into
Wherein:
B=10
-16* ω
0, C=10
-16* γ and
D
jFor getting from 0.1 to 20 successively, every 0.1 all values, the number of wavelengths 4 of M representative test, N representative diameter number of partitions: (20-0.1)/and 0.1+1=200, calculate mean grain size and distribution thus.
Technique effect of the present invention is as follows:
Particle automatic testing method and device based on the optical fiber coupling provided by the invention have improved the deficiency that existing full light scattering method carries out particle detection from mechanism.Remarkable result of the present invention shows with conventional method and compares, solve it and pre-estimated the error that refractive index to be measured is brought, and well solved the problem of the reflection and the scattering of sample cell, utilize continuous spectrum to carry out multi-wavelength scanning, adopt genetic algorithm to carry out optimization computation, finally finish calculating such as particle test and size distribution, operability and accuracy have been significantly improved, improved the accuracy of online particle test effectively, reduced the error that bring in the experience sum of errors common sample pond estimated, have the conveniently moving of carrying simultaneously, adjust quick, the precision advantages of higher.Help realizing real-time online particle detection fast and accurately.
The grain testing apparatus that the present invention is based on optical fiber coupling have volume little, be convenient to move, it is little influenced by vibration interference, need not in advance liquid to be measured to be carried out detecting refractive index, do not need external independent high power laser light source, and there are not the reflection and the scattering of traditional sample pool structure pool wall, the control accuracy height of sample cell, measurement mechanism main body are optical fiber, change cheaply easy.The deficiency of existing optical scatter method of testing can be effectively solved, the real-time online particle detection can be realized.
Embodiment
The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit protection scope of the present invention with this.
One, ultimate principle of the present invention:
One particle size distribution function is the polydispersion granular system of N (D), and multiple different mean grain size define method can be arranged.In light total scattering method, define the average extinction coefficient K of polydispersion granular system according to the principle of equivalent extinction coefficient
mWith mean diameter D
32As follows:
(1)
(2)
(3)
Wherein: I
0Be respectively incident intensity with I and reach by the projection light intensity behind the sample, L is the thickness of sample measurement district (sample cell), and D is an actual particle size, D
32Be called Sauter mean diameter.
By formula (1) as can be known, K
mNumerical value should be relevant with distribution of particles function N (D), but according to existing research, in the scope of particle diameter parameter α (α=D π/λ (lambda1-wavelength))<4, the K that obtains by different particle size distribution function N (D)
mWith press D
32The extinction coefficient K that obtains
ExtNumerically differ very little, promptly little with the shape correlation of particle size distribution function.Can use by D for this reason
32The K that tries to achieve
ExtReplace K
mActual computation shows that this scope can expand α=30 to.Formula (1) and formula (2) substitution formula (3) can be got:
(4)
Wherein: N is the total number of particles of granular system, and n is a refractive index.So just the measurement of a polydispersion granular system is changed into and be equivalent to have single diameter D
32The measurement of monodisperse particles system, and provide the mean grain size D of this granular system
32Formula (4) is carried out numerical solution can be changed into:
(5)
In the formula: M
2Be the stepping number of particle diameter, f (D
j) and K
Ext(D
j) be respectively j particle diameter stepping [D
j, D
J+1] particle diameter volume frequency distribution function and the mean value of extinction coefficient, Δ D be the particle diameter stepping at interval.
Introduce the multi-wavelength method of testing, then formula (5) becomes:
(6)
(7)
Wherein: M
1Be the number of wavelengths of measuring, M
2Interval number for the particle division.(6) (7) two formula simultaneous can be got:
(8)
Introducing has the Lorentz dispersion equation of pervasive meaning:
(9)
In the formula: N
eBe the resonance subnumber in the granule medium unit volume, q is an electron charge, ε
0Be permittivity of vacuum, m is an electron mass, and γ is a ratio of damping, ω
0Be natural frequency, ω=2 π c/ λ are light wave circular frequency, χ
rAnd χ
iBe respectively the real part and the imaginary part of electric polarization coefficient.
Make three unknown numbers:
B=10
-16* ω
0, C=10
-16* γ and
Then (9) formula can be rewritten into:
(10)
Consider the multi-wavelength test, adopt the multivariate genetic algorithm for solving, evaluation function is defined as:
(11)
Wherein: K
ExtBeing extinction coefficient, is the function of wavelength, refractive index and particle diameter; F (D) is a particle diameter volume distributed median frequency function, and its expression formula is:
Be zero dimension distribution parameter k and characteristic dimension parameter
Function.
Therefore have here five unknown numbers be k,
A, B, C utilize multi-wavelength and can calculate particle grain size distribution in conjunction with the multivariate genetic algorithm.
The same continuation found the solution with identical method mitscherlich's law, can obtain corresponding mean grain size formula:
(12)
Two, emulated data:
Improve the genetic algorithms use binary coding, roulette is selected, 2 crossover operators, and discrete variation, crossover probability are 0.8, the variation probability is 0.7/ chromosome length, initial population size 100,400 generations of evolutionary generation.With three parameter substitutions of A, B, C (11) formula that genetic algorithm is obtained, obtain refractive index.Analog result is as shown in table 1, than adopting average refractive index method inverting parameter to be measured, considered the caused variations in refractive index of effect of dispersion after, inversion result and setting value are more approaching.When reality is tested, because factors such as instrument error, environment temperature can cause certain measuring errors, in order to verify the reliability of this method, respectively at first of NO.7 place, added 2% random noise on the delustring measured value of the 5th wavelength to represent measuring error, the result shows that inversion error is lower than 1%, and in fact 2% random noise is very big.This shows that the relative medium refraction index with it of mean grain size that adopts the method count particles is fully feasible.
The genetic algorithm evolutionary generation changed for 200 generations into, and other parameter is provided with constant.Analog result is as shown in table 2, and inversion result and setting value are quite approaching as can be seen, introduces 2% random noise on the delustring measured value of first, the 3rd wavelength at NO.4 place, and inversion error is lower than 10%, and is more more accurate than average refractive index method.Consider as can be seen can be finally inversed by particle grain size distribution more accurately after the situation of variations in refractive index, though after having added 2% random noise and theoretical distribution still can coincide relatively goodly.
The inversion result of table 1 mean grain size and refractive index
The inversion result that R-R distributes under table 2 non-standalone mode
Three, the liquid particles pick-up unit that is coupled based on optical fiber
Based on the grain testing apparatus of optical fiber coupling as shown in Figure 1, Fig. 2 has then shown the enlarged image of two fiber end faces, and the structural equivalents in the circle is in the sample cell of conventional particles tester.As seen from the figure, the formation that the present invention is based on the grain testing apparatus of optical fiber coupling comprises: high stable multi wave length illuminating source 1, input optical fibre 2, the automatically controlled optics of first high precision is adjusted platform 3, CCD imaging system 4, the automatically controlled optics of second high precision is adjusted platform 5, output optical fibre 6, detected with high accuracy device 7 and computing machine 8, one end of described input optical fibre 2 links to each other with the output terminal of described high stable multi wave length illuminating source 1, the input end of the described detected with high accuracy device 7 of one termination of described output optical fibre 6 links to each other, the other end of described input optical fibre 2 is fixed on the automatically controlled optics adjustment of described first high precision platform 3 and extends outside the appearance, be called free end, the other end of described output optical fibre 6 is fixed on the automatically controlled optics adjustment of described second high precision platform 5 and extends outside the appearance, be called free end, the free end of the free end of described input optical fibre 2 and output optical fibre 6 is relative in opposite directions and be positioned at the camera watch region of described CCD imaging system 4, described computing machine 8 respectively with described high stable multi wave length illuminating source 1, the automatically controlled optics of first high precision is adjusted platform 3, CCD imaging system 4, the automatically controlled optics of second high precision is adjusted platform 5 and is linked to each other with detected with high accuracy device 7.
The wavelength of described high stable multi wave length illuminating source 1 output and power are by described computing machine 8 controls.
The free-ended relative position of described input optical fibre 2 and output optical fibre 6 adjusts platform 3 by the automatically controlled optics of described computing machine described first high precision of 8 controls and the automatically controlled optics of second high precision is adjusted platform 5, carries out precision adjustment under the monitoring of described CCD imaging system 4.
The signal that described computing machine 8 the receives described detected with high accuracy device 7 inputs line data of going forward side by side is handled.
Two optical fiber are installed in two automatically controlled optics of high precision respectively and adjust on the platform.The automatically controlled optics of high precision is adjusted platform and is controlled the position of three directions and lockable position by computing machine.The CCD imaging system monitoring optical fiber endface position and the drop situation that side-looking are arranged simultaneously and overlook both direction.The high stability multi wave length illuminating source is in order to providing the light signal of stable a plurality of wavelength, and the detected with high accuracy device is surveyed the light intensity signal of different wave length, and sends into computing machine and finish data processing.High stability light source, photo-detector, the automatically controlled adjustment platform of high precision all are connected with computing machine by gpib interface, realize adjusting control, the locking of platform position by software programming, the conversion of optical source wavelength, the data acquisition of photo-detector, and final data is handled.The algorithm of system uses MATLAB to carry out simulating, verifying, and finally uses VB to carry out program composition.Two high-precision opticals that computerized control are adjusted platform, and the plane lapping FC/PC end face that can make two optical fiber is to each other apart from being controlled at 40-100 μ m; When splashing into calibration solution and liquid to be measured, because surface tension effects makes drop form connection between two fiber facet, constituted theoretic sample pool structure, promptly be equivalent to the sample cell of conventional particles checkout equipment, as Fig. 2.
Working of an invention process and result thereof:
1, the parameter study of sample under different spacing:
The nominal diameter that confirmatory experiment uses is respectively the U.S. Du Ke company polystyrene latex ball standard particle of 1.00m (sample 1) and 2.00m (sample 2), and base liquid is a pure water, and the concentration of two kinds of samples is respectively 0.5% and 1.0%.Particle proportion is about 1, can guarantee even suspension after 30 minutes magnetic stirs, and measures fast then.The optical fiber that constitutes sample cell is that commercially available optical communication is with band FC/PC wire jumper and by the single mode silica fibre of plane lapping.Having selected 4 centre wavelengths for use, is respectively 1000nm, 1100nm, 1200nm and 1300nm.Each sample repeated test 6 times, the extinction value I/I that surveys
0Average and classify as shown in table 3, the table 4.
Table 3 sample 1 test value.
Table 4 sample 2 test values
2, carry out algorithm process:
Utilize genetic algorithm to handle, calculate the particle mean grain size D of two kinds of samples under the spacing of different ponds respectively
32, shown in the table 5.
Table 5 particle diameter calculated value
Pond spacing (μ m) |
Mean grain size (sample 1) |
Mean grain size (sample 2) |
10 |
2.477 |
4.614 |
20 |
1.645 |
2.951 |
80 |
0.974 |
1.972 |
100 |
0.981 |
1.985 |
180 |
0.689 |
1.546 |
300 |
0.564 |
1.278 |
3, interpretation of result:
By the actual measurement situation shown in table 3, the table 4 as can be known, when sample cell spacing difference, promptly measuring distance not simultaneously, the result difference that records is very big.Under situation with a kind of sample (the maintenance sample concentration is constant), extinction value I/I
0Increase with measuring distance reduces.In the measuring distance scope of 10 μ m to 20 μ m, extinction value is very high, and this is because the end face of incident optical and outgoing optical fiber is very near from getting, and makes most of scattered light also can be received by outgoing optical fiber, I is that the light intensity sum by a part of scattered light and transmitted light constitutes, and makes I become bigger.Increase along with measuring distance, the end face of incident optical and outgoing optical fiber gradually away from, what outgoing optical fiber can receive also reduces gradually through the scattered light behind the particulate samples, when both ends of the surface are enough far away, scattered light all can't be received by outgoing optical fiber basically, outgoing optical fiber receptible nearly all be pure transmitted light, this moment measurement comparatively accurate.Along with both ends of the surface further away from each other, a part of transmitted light can't be received by outgoing optical fiber, like this, make I become less, extinction value I/I
0Become very low.As can be seen from Table 5, as preceding described, when sample cell spacing during at 80 μ m and 100 μ m, the sample particle diameter and the normal diameter that record are comparatively identical.This paper experimental results demonstrate in the scope of 80 μ m to 100 μ m, can both comparatively be met the measurement result of its nominal diameter for two kinds of standard particles of experiment usefulness.When distance is excessive or too small, bigger measuring error will be had.
In order further to verify the accuracy of refractive index disposal route described herein, sample thief pond spacing L=100 μ m surveys institute grain diameter and adopts conventional refractive index technique of estimation relatively, adopts the valuation of conventional refractive index estimation method refractive index to get 1.57, ignores chromatic dispersion.Corresponding Suo Taier mean grain size D
32, mean bias and repeatability lists in table 6, as can be seen, the mean bias of this paper method and repeatability is all less than 5%, and is better than conventional refractive index estimation method.
Table 6 particle diameter test result
The basic operation flow process describes in detail:
(1) utensil cleans
For avoiding artificial pollution, the utensil that will use for experiment must could use through strict cleaning process in advance, clean synoptic diagram as shown in Figure 3, the utensil that can use in the experiment comprises large beaker, cucurbit, blender jar, spirit lamp, drop bottle, glue head dropper, dry ball, cotton rod etc.The utensil that wherein needs to clean is a large beaker, blender jar and cucurbit, and drop bottle, glue head dropper, cleaning process is all finished in ultrasonic cleaning machine.Now be example with the large beaker, concrete utensil cleaning step is as shown in Figure 3 following.
(2) instrument preheating
In order to make light stability, laser instrument and power meter must reach optimum performance through preheating, and be 30 minutes preheating time, measure temperature during experiment and are controlled at 20 ± 5 ℃.
(3) calibration solution is measured
In the experiment, calibration solution adopts distilled pure water, in order to eliminate the influence of calibration solution, does not add particle to be measured earlier and measures.One end of input optical fibre is connected to high stability multi-wavelength light source output terminal, and the other end is connected to the end that the automatically controlled optics of high precision is adjusted the platform support; Simultaneously an end of output optical fibre is connected to the input end of detected with high accuracy device, the other end is connected to the other end that the automatically controlled optics of high precision is adjusted the platform support; Two fiber end faces are cleaned up with isopropyl alcohol respectively.On the end face of input optical fibre, splash into an amount of pure water with glue head dropper, by surface tension effects, pure water liquid pearl can be attached on the end face of input optical fibre, the stepper motor that adjust platform by the automatically controlled optics of computer control high precision this moment makes both ends of the surface close, also touch until the output optical fibre end face, regulate the spacing and the locking of two end faces, form the adjustable sample cell of pond spacing L with the liquid pearl.Pass through spacing computer controlled built in 100 μ m.Then by the computer control multi wave length illuminating source, light source is successively exported from wavelength 1000nm, be spaced apart 100nm, until 1300nm amounts to the light of 4 wavelength, corresponding detection also along with receiving from wavelength 1000nm to 1300nm, is spaced apart the optical power value of the different wave length of 100nm.These 4 values are 4 I0 corresponding to different wave length in the formula, obtain data by computing machine by the GPIB communication interface and deposit array in, to treat the computing in later stage.
(4) liquid configuration to be measured
Liquid to be measured is placed on the sol evenning machine, adds and stir particle (cleaning) low speed rotation, liquid to be measured is fully stirred.Blow the calibration solution between the fiber end face off, draw drop to be measured then between two fiber end faces, same as (3) calibration solution is measured described step and is surveyed, control by computer program, by the optical power value of GPIB communication interface acquisition under different wave length, i.e. 4 I in the formula corresponding to different wave length;
(5) data processing
4 I that 4 I0 that will obtain by step (3) and step (4) obtain, and 4 wavelength parameter bring in the formula (11), and convolution (10) can obtain A, B, C, k and
Calculate mean grain size and distribution thus.
Because a lot of parameters and function are implicit functions in the formula (11), therefore in computing machine by software programming a series of equations, in order to passing through 4 I0 and 4 I, and 4 λ, can calculate A, B, C, k and
For convenience's sake: all formula is as follows by the iteration sequence identification:
(13)
(14)
Wherein: Dj is for getting from 0.1 to 20 successively, every 0.1 all values.
The number of wavelengths (4) of M representative test
N representative diameter number of partitions: (20-0.1)/0.1+1=200
Can see and also have a Kext function here, this function is an implicit function, and just a function of functions that is formed by a lot of combination of function is listed the correlated expression formula below, all these expression formulas all program, and realize automatic computing by computer program.
Wherein:
This shows extinction ratio direct and an and two functional dependences of bn.
Then write out the expression formula of an and bn below successively, these two expression formulas neither directly can be listed as the function of writing certainly, still need further recursive resolve.
Here still need further recurrence:
In the formula: Z can be α and m α in the following formula, and m is a refractive index here, just the m in the formula (13).Wherein Jn+1/2 (z) and Hn+1/2 (z) are the semi-integer order Bessel function and the second class Hankel function.As can be seen from the above equation, as long as derive n (z) and n (z).Recursion formula just can be obtained the value of an and bn.And Bessel's function and Hankel function all satisfy following recursion formula:
(19) are taken back (18) can get:
In conjunction with starting condition:
ψ
0(z)=sin?z
ζ
0(z)=sin?z+i?cos?z
This shows, by Computerized Editing a comprehensive function that comprises all formula between formula (13)-(21) handle subfunction, this operating function program only need provide 4 wavelength, 4 I0 and 4 I, five parameters to be asked be can obtain, and then required mean grain size and distribution obtained.