CN103411905A - Measuring method for participation property medium radiation characteristics based on short-pulse laser radiation and multi-information inverse problem solution algorithm - Google Patents

Abstract

The invention relates to a measuring method for participation property medium radiation characteristics based on a short-pulse laser radiation and multi-information inverse problem solution algorithm. The measuring method is used for solving the problems of insufficient experimental measurement information content and large measuring result error in the participation property medium radiation parameter measurement based on the inverse problem solution. The measuring method is realized by the following steps of (1) acquiring a time-domain hemisphere reflected signal curve R(t) of a test piece; (2) acquiring the time-domain hemisphere reflected signal curves Ri, mea(t) of the test piece under N groups of working conditions; (3) acquiring radiation intensity fields in a computational domain; (4) acquiring an estimated value Ri, est(t) of a time-domain hemisphere reflected signal on the left side border of the test piece, wherein x is equal to 0; (5) acquiring an objective function value Fobj in an inverse problem algorithm; (6) acquiring an absorption coefficient Ka and a scattering coefficient Ks of a to-be-measured medium. The measuring method can be applied to the technical field of physical property measurement of participation property medium.

Description

A kind of participating medium radiation characteristic measuring method based on short-pulse laser irradiation and many information inverse problem derivation algorithm

Technical field

This patent relates to participating medium radiation physical property field of measuring technique, relates in particular to a kind of participating medium radiation characteristic measuring method based on short-pulse laser irradiation and many information inverse problem derivation algorithm.

Background technology

Participating medium heat radiation physical parameter is the important parameter to participating medium is analyzed in its application process, Design and optimization is required.In recent years, along with the develop rapidly of the modern high technologies such as the infrared characteristic of Aero-Space, infrared acquisition, target and environment, laser, electron device, biomedicine, the thermal physical property parameter of participating medium in the situations such as high temperature, multidimensional, non-homogeneous, anisotropic scattering becomes particularly important.The research of carrying out participating medium heat radiation physical property and related discipline is all significant for dual-use field.

Absorption coefficient and scattering coefficient are the important parameters that characterizes participating medium heat radiation physical property.Deeply understand this thermal physical property parameter and it is carried out to experiment measuring and theoretical analysis, the significant and using value for fields such as metal processing, medical imaging technology, harmless laser therapy technology, particle detection research, infrared remote sensing technology, material science and environmental monitorings.

In the actual measurement process, there is certain measuring error in experimental facilities, and some working condition measuring signal is fainter, single information can not complete the measurement of radiation physical property, the measuring method that the present invention proposes introduces by changing the measuring conditions such as sample thickness, sample border side blackness, pulse laser incident angle, pulse width the time domain hemisphere reflected signal that many groups solve for inverse problem, thereby improved the inverse problem solving precision, can rebuild comparatively exactly absorption coefficient and the scattering coefficient of medium inside.

Summary of the invention

The present invention will solve to have now in the participating medium radiation parameter measurement solved based on inverse problem, the experiment measuring quantity of information is not enough and the larger problem of measuring result error, has proposed the participating medium absorption coefficient and the scattering coefficient measurement method that based on many information inverse problem, solve.

Participating medium absorption coefficient and the scattering coefficient measurement method solved based on many information inverse problem of the present invention, the concrete steps of the method are:

Step 1, participating medium is made to the flat test specimen that thickness is x, establish its upper surface thickness x=0, upper surface, to the thickness x=L of lower surface, coats to a side of test specimen to be measured the opaque coating that blackness is ε, utilizes pulse width to be t _pThe Gauss pulse laser instrument produce Gauss pulse laser, the Gauss pulse laser beam is along with Specimen Method, inciding without coating one side surface to degree into θ angle, adopt single photon counter to measure the time domain hemisphere reflected signal on the participating medium surface-boundary, obtain the time domain hemisphere reflected signal curve R (t) of test specimen;

Step 2, thickness x, coating blackness ε by changing test specimen, the pulse width t of laser instrument _pAnd the incident angle θ of laser designs the operating mode that N group is different, obtain respectively the time domain hemisphere reflected signal curve R of test specimen under N group operating mode according to the measuring method of step 1 _{I, mea}(t), wherein i=1,2 ..., N-1, N;

Step 3, utilize the inverse problem derivation algorithm, suppose the absorption coefficient κ of testing medium _aScattering coefficient κ with testing medium _s, by the solving of radiation transfer equation, obtain the radiation intensity field in computational fields;

Step 4, utilize the radiation intensity field in the computational fields that step 3 obtains, according to formula:

Obtain the estimated value R of the time domain hemisphere reflected signal on test specimen x=0 left border _{I, est}(t); I in formula ₀The radiation intensity peak value of Gauss pulse laser, I _i(0, θ, t) is at i, to organize under operating mode on test specimen x=0 left border, the t moment, the radiation intensity on the θ direction; θ is the radiation direction angle;

Step 5, utilize the estimated value R of the time domain hemisphere reflected signal that step 4 obtains _{I, est}(t) with step 1 and step 2 in the employing single photon counter measure the borderline time domain hemisphere of participating medium reflected signal R _{I, mea}(t), by many information inverse problem derivation algorithm, according to formula:

Obtain the target function value F in the inverse problem algorithm _obj

Whether the target function value in step 6, determining step five is less than setting threshold ξ, if, by the absorption coefficient κ of the testing medium that obtains in step 3 _aScattering coefficient κ with testing medium _sAs a result of, complete based on the absorption coefficient of many information inverse problem derivation algorithm and the measurement of scattering coefficient, otherwise return to step 3, proceed computing.

The present invention includes following beneficial effect:

1, the present invention by set up the radiation physical measurement just, the inverse problem solving model, application many information inverse problem derivation algorithm has overcome metrical information quantity not sufficient and the larger problem of measuring result error in the actual measurement process;

2, compared with prior art, the present invention can measure absorption coefficient and the scattering coefficient of participating medium comparatively accurately, and accuracy rate has improved respectively 10%～25% and 15%～28%.

The accompanying drawing explanation

Fig. 1 is the radiation transmission schematic diagram that the described participating medium of embodiment one is subject to the incident of a Gauss pulse laser; In figure, solid arrow is Gauss pulse laser parallel incident direction, and the empty direction of arrow is hemisphere otdr signal direction.

Embodiment

For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, the present invention is further detailed explanation below in conjunction with Fig. 1 and embodiment.

Embodiment one, described participating medium absorption coefficient and the scattering coefficient measurement method solved based on many information inverse problem of present embodiment, the concrete operation step of the method is:

Step 1, participating medium is made to the flat test specimen that thickness is x, establish its upper surface thickness x=0, upper surface, to the thickness x=L of lower surface, coats to a side of test specimen to be measured the opaque coating that blackness is ε, utilizes pulse width to be t _pThe Gauss pulse laser instrument produce Gauss pulse laser, the Gauss pulse laser beam is along with Specimen Method, inciding without coating one side surface to degree into θ angle, adopt single photon counter to measure the time domain hemisphere reflected signal on the participating medium surface-boundary, obtain the time domain hemisphere reflected signal curve R (t) of test specimen;

Step 2, thickness x, coating blackness ε by changing test specimen, the pulse width t of laser instrument _pAnd the incident angle θ of laser designs the operating mode that N group is different, obtain respectively the time domain hemisphere reflected signal curve R of test specimen under N group operating mode according to the measuring method of step 1 _{I, mea}(t), wherein i=1,2 ..., N-1, N;

Step 3, utilize the inverse problem derivation algorithm, suppose the absorption coefficient κ of testing medium _aScattering coefficient κ with testing medium _s, by the solving of radiation transfer equation, obtain the radiation intensity field in computational fields;

Step 4, utilize the radiation intensity field in the computational fields that step 3 obtains, according to formula:

Obtain the estimated value R of the time domain hemisphere reflected signal on test specimen x=0 left border _{I, est}(t); I in formula ₀The radiation intensity peak value of Gauss pulse laser, I _i(0, θ, t) is at i, to organize under operating mode on test specimen x=0 left border, the t moment, the radiation intensity on the θ direction; θ is the radiation direction angle;

Step 5, utilize the estimated value R of the time domain hemisphere reflected signal that step 4 obtains _{I, est}(t) with step 1 and step 2 in the employing single photon counter measure the borderline time domain hemisphere of participating medium reflected signal R _{I, mea}(t), by many information inverse problem derivation algorithm, according to formula:

Obtain the target function value F in the inverse problem algorithm _obj

Whether the target function value in step 6, determining step five is less than setting threshold ξ, if, by the absorption coefficient κ of the testing medium that obtains in step 3 _aScattering coefficient κ with testing medium _sAs a result of, complete based on the absorption coefficient of many information inverse problem derivation algorithm and the measurement of scattering coefficient, otherwise return to step 3, proceed computing.

The present invention includes following beneficial effect:

1, the present invention by set up the radiation physical measurement just, the inverse problem solving model, application many information inverse problem derivation algorithm has overcome metrical information quantity not sufficient and the larger problem of measuring result error in the actual measurement process;

2, compared with prior art, the present invention can measure absorption coefficient and the scattering coefficient of participating medium comparatively accurately, and accuracy rate has improved respectively 10%～25% and 15%～28%.

At first present embodiment designs the physical model of translucent medium Transient Radiative Transfer of Ultra, change the corresponding mathematical model of rear foundation and method for solving, by changing operating mode, obtain many group time domain hemisphere reflected signals, the method that many information inverse problem of utilization solves reconstructs absorption coefficient and the scattering coefficient of participating medium accurately.The width of pulse laser is very short, be far smaller than the response time of temperature variation in medium, pulsed laser energy is lower simultaneously, ignore its heat effect to medium, so the reflected signal measuring process of measured medium can be considered to be a pure Radiation Transfer Problems of one dimensional transient.

Embodiment two, present embodiment are that the described inverse problem algorithm of step 3 and step 5 adopts ant group algorithm to realize to the further illustrating of the described participating medium absorption coefficient solved based on many information inverse problem of embodiment one and scattering coefficient measurement method.

Embodiment three, present embodiment are that the method that step 3 obtains the radiation field intensity in computational fields is to the further illustrating of the described participating medium absorption coefficient solved based on many information inverse problem of embodiment one and scattering coefficient measurement method:

Utilize radiation transfer equation:

$\frac{\∂I_i(x,\mathrm{\θ},t)}{c\∂t}+\frac{\∂I_i(x,\mathrm{\θ},t)}{\∂x}=-({\mathrm{\κ}}_a+{\mathrm{\κ}}_s)I_i(x,\mathrm{\θ},t)+\frac{{\mathrm{\κ}}_s}{2}{\∫}_0^{\mathrm{\π}}{I}_i(L,\mathrm{\θ}\′,t)\mathrm{\Φ}(\mathrm{\θ}\′,\mathrm{\θ})\sin \mathrm{\θ}\′\mathrm{d\θ}\′;$

$I_i(0,\mathrm{\&theta;},t)=(1-{\mathrm{\&rho;}}_0)I_c(t,{\mathrm{\&theta;}}_i)+2{\mathrm{\&rho;}}_1{\&Integral;}_{\mathrm{\&pi;}/2}^{\mathrm{\&pi;}}{I}_i(0,\mathrm{\&theta;}\&prime;,t)\cos \mathrm{\&theta;}\&prime;\sin \mathrm{\&theta;}\&prime;\mathrm{d\&theta;}\&prime;,0\&le;\mathrm{\&theta;}<\mathrm{\&pi;}/2;$

I _i(L, θ, t)=0, pi/2≤θ<π obtains the radiation intensity field in computational fields, I in formula _i(x, θ, t) is under i group operating mode, the t moment, and the radiation intensity at θ direction through-thickness x place, x is position in radiation field to be asked, θ radiation direction to be asked, t is for waiting to ask the moment, k _aFor the absorption coefficient of testing medium, κ _sScattering coefficient for testing medium; I _i(L, θ ' are t) under i group operating mode, the t moment, the radiation intensity at θ ' direction through-thickness x place; θ ' is incident direction, and Φ (θ ', be θ) from θ ' direction incident the Scattering Phase Function that scatters out from the θ direction, I _i(L, θ, t) is under i group operating mode, the t moment, the radiation intensity on the right side boundary at θ direction through-thickness x=L place; C is the light velocity in medium; ρ ₀It is the reflectivity while entering medium by environment; ρ ₁Reflectivity for by the medium entered environment time; I _c(t, θ _i) be that t is constantly along θ _iThe radiation intensity of the Gauss pulse laser of angle incident, I _c(t) be the radiation intensity of the Gauss pulse laser of t incident constantly.

Embodiment four, present embodiment are to the further illustrating of the calculating of radiation intensity field in the described computational fields of embodiment three, the radiation intensity I of the Gauss pulse laser of t incident constantly _c(t) pass through formula:

Calculate I in formula ₀For the radiation intensity peak value of Gauss pulse laser, t _pFor the pulse width of gauss laser, H (t) is extra large gloomy Saden function, as t>H (t)=1 0 time, H (t)=0 when t<0.

Claims (4)

1. participating medium radiation characteristic measuring method based on short-pulse laser irradiation and many information inverse problem derivation algorithm is characterized in that it realizes by following steps:

Step 1, participating medium is made to the flat test specimen that thickness is x, establish its upper surface thickness x=0, upper surface, to the thickness x=L of lower surface, coats to a side of test specimen to be measured the opaque coating that blackness is ε, utilizes pulse width to be t _pThe Gauss pulse laser instrument produce Gauss pulse laser, the Gauss pulse laser beam is along with Specimen Method, inciding without coating one side surface to degree into θ angle, adopt single photon counter to measure the time domain hemisphere reflected signal on the participating medium surface-boundary, obtain the time domain hemisphere reflected signal curve R (t) of test specimen;

Step 2, thickness x, coating blackness ε by changing test specimen, the pulse width t of laser instrument _pAnd the incident angle θ of laser designs the operating mode that N group is different, obtain respectively the time domain hemisphere reflected signal curve R of test specimen under N group operating mode according to the measuring method of step 1 _{I, mea}(t), wherein i=1,2 ..., N-1, N;

Step 3, utilize the inverse problem derivation algorithm, suppose the absorption coefficient κ of testing medium _aScattering coefficient κ with testing medium _s, by the solving of radiation transfer equation, obtain the radiation intensity field in computational fields;

Step 4, utilize the radiation intensity field in the computational fields that step 3 obtains, according to formula:

Obtain the estimated value R of the time domain hemisphere reflected signal on test specimen x=0 left border _{I, est}(t); I in formula ₀The radiation intensity peak value of Gauss pulse laser, I _i(0, θ, t) is at i, to organize under operating mode on test specimen x=0 left border, the t moment, the radiation intensity on the θ direction; θ is the radiation direction angle;

Step 5, utilize the estimated value R of the time domain hemisphere reflected signal that step 4 obtains _{I, est}(t) with step 1 and step 2 in the employing single photon counter measure the borderline time domain hemisphere of participating medium reflected signal R _{I, mea}(t), by many information inverse problem derivation algorithm, according to formula:

Obtain the target function value F in the inverse problem algorithm _obj

Whether the target function value in step 6, determining step five is less than setting threshold ξ, if, by the absorption coefficient κ of the testing medium that obtains in step 3 _aScattering coefficient κ with testing medium _sAs a result of, complete based on the absorption coefficient of many information inverse problem derivation algorithm and the measurement of scattering coefficient, otherwise return to step 3, proceed computing.

2. a kind of participating medium radiation characteristic measuring method based on short-pulse laser irradiation and many information inverse problem derivation algorithm as claimed in claim 1, is characterized in that the described inverse problem algorithm of step 3 and step 5 adopts ant group algorithm to realize.

3. a kind of participating medium radiation characteristic measuring method based on short-pulse laser irradiation and many information inverse problem derivation algorithm as claimed in claim 1 is characterized in that the method that step 3 obtains the radiation field intensity in computational fields is:

Utilize radiation transfer equation:

$\frac{\&PartialD;I_i(x,\mathrm{\&theta;},t)}{c\&PartialD;t}+\frac{\&PartialD;I_i(x,\mathrm{\&theta;},t)}{\&PartialD;x}=-({\mathrm{\&kappa;}}_a+{\mathrm{\&kappa;}}_s)I_i(x,\mathrm{\&theta;},t)+\frac{{\mathrm{\&kappa;}}_s}{2}{\&Integral;}_0^{\mathrm{\&pi;}}{I}_i(L,\mathrm{\&theta;}\&prime;,t)\mathrm{\&Phi;}(\mathrm{\&theta;}\&prime;,\mathrm{\&theta;})\sin \mathrm{\&theta;}\&prime;\mathrm{d\&theta;}\&prime;;$

$I_i(0,\mathrm{\&theta;},t)=(1-{\mathrm{\&rho;}}_0)I_c(t,{\mathrm{\&theta;}}_i)+2{\mathrm{\&rho;}}_1{\&Integral;}_{\mathrm{\&pi;}/2}^{\mathrm{\&pi;}}{I}_i(0,\mathrm{\&theta;}\&prime;,t)\cos \mathrm{\&theta;}\&prime;\sin \mathrm{\&theta;}\&prime;\mathrm{d\&theta;}\&prime;,0\&le;\mathrm{\&theta;}<\mathrm{\&pi;}/2;$

I _i(L, θ, t)=0, pi/2≤θ<π obtains the radiation intensity field in computational fields, I in formula _i(x, θ, t) is under i group operating mode, the t moment, and the radiation intensity at θ direction through-thickness x place, x is position in radiation field to be asked, θ radiation direction to be asked, t is for waiting to ask the moment, κ _aFor the absorption coefficient of testing medium, κ _sScattering coefficient for testing medium; I _i(L, θ ' are t) under i group operating mode, the t moment, the radiation intensity at θ ' direction through-thickness x place; θ ' is incident direction, and Φ (θ ', be θ) from θ ' direction incident the Scattering Phase Function that scatters out from the θ direction, I _i(L, θ, t) is under i group operating mode, the t moment, the radiation intensity on the right side boundary at θ direction through-thickness x=L place; C is the light velocity in medium; ρ ₀It is the reflectivity while entering medium by environment; ρ ₁Reflectivity for by the medium entered environment time; I _c(t, θ _i) be that t is constantly along θ _iThe radiation intensity of the Gauss pulse laser of angle incident, I _c(t) be the radiation intensity of the Gauss pulse laser of t incident constantly.

4. a kind of participating medium radiation characteristic measuring method based on short-pulse laser irradiation and many information inverse problem derivation algorithm as claimed in claim 3, is characterized in that the radiation intensity I of the Gauss pulse laser of t incident constantly _c(t) pass through formula:

Calculate I in formula ₀For the radiation intensity peak value of Gauss pulse laser, t _pFor the pulse width of gauss laser, H (t) is extra large gloomy Saden function, as t>H (t)=1 0 time, H (t)=0 when t<0.

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