CN105606566A - Transparent medium film refractive index and thickness on-line measuring method - Google Patents

Abstract

The invention discloses a transparent medium film refractive index and thickness on-line measuring method. The method comprises the following steps: obtaining a film surface reflection spectrum: using an on-line spectrum measuring apparatus for measuring a film surface reflection spectrum of a predetermined wavelength scope of a film sample to be measured; setting Cauchy optical model parameters: according to the characteristic of the film surface reflection spectrum and influence of the parameter in the Cauchy optical model to a refractive index dispersion relation, performing initial setting of the thickness and Cauchy optical model parameters to form an initial value; performing a genetic algorithm: by using the genetic algorithm and combining the film surface reflection spectrum, through the initial value, controlling a genetic process by setting the parameters of the genetic algorithm, and finally obtaining the film refractive index and film thickness. By establishing the film Cauchy optical model and fully combining the genetic algorithm, reasonable parameters can be set according to the spectrum characteristic of the practical films, so that analysis convergence speed can be faster, and result can be more accurate.

Description

A kind of transparent medium rete refractive index and thickness On-line Measuring Method

Technical field

The present invention relates to coated glass field, particularly a kind of transparent medium rete refractive index and thickness On-line Measuring Method.

Background technology

Off-line Low-E (low radiation) coated glass has good energy-efficient performance, has been widely used in door and window, curtain wall etc. and has builtBuild field, but off-line Low-E coated glass membrane system complex structure, rete is more than 5 layers, and the optical property of every one deck is all by shadowRing the final quality to product, thereby cause the product design and development cycle long, production process technology control complexity.

For making the design of film system and technology controlling and process there is directionality, reduce exploitation and debugging cost, utilize film is at present design software moreSet up model, the performance to deisgn product and process debugging scheme are assessed in advance, but the key that use film is design software existsIn the film material optical constant and the unit power depositional coating thickness data that accurately and timely obtain actual production, Film Optics constantCan use ellipse folk prescription method to measure, but ellipsometer equipment cost is higher, professional also stronger in the use, the data-analysis time is long;Film thickness can be measured with step instrument, but test sample manufacturing cycle is long.

Existing these professional measuring instruments facilitate simple and direct not for factory's actual production control, therefore general factory is difficult to timelyObtain accurate rete optical constant and the thickness of actual production, while causing using film to be design software, input parameter disconnects with actual.

Summary of the invention

The object of the embodiment of the present invention is the defect for above-mentioned prior art, provides one to test transparent medium accurately and rapidlyThin-film refractive index and thickness On-line Measuring Method.

The technical scheme that the present invention takes is to achieve these goals:

A kind of transparent medium rete refractive index and thickness On-line Measuring Method, comprising:

S101: obtain face reflectance spectrum:

The face that the online spectral measurement device of tested plated film sample utilization that is coated with transparent medium rete is recorded to predetermined wavelength range is anti-Penetrate spectrum;

S102: carry out the setting of Cauchy's optical model parameter:

Carry out thickness according to the impact of each parameter refractive index dispersion relation in film face reflectance spectrum feature and Cauchy's optical modelAnd the initial setting up of Cauchy's optical model parameter, form initial value;

S103: genetic algorithm:

Utilize genetic algorithm, by initial value, in conjunction with face reflectance spectrum, by genetic algorithm parameter, control genetic process be set,Finally obtain thin-film refractive index and thicknesses of layers.

Described step S1031 comprises:

S1031: generate initial population:

Utilizing genetic algorithm, has been dot generation initial population by initial value;

S1032: admittance matrix spectrum calculates:

Initial population obtains calculating spectrum individual in population according to Cauchy's optical model and admittance matrix spectrum computational methods, and withThe face reflectance spectrum that actual measurement obtains compares sequence according to evaluation function; Described evaluation function is for calculating spectrum RfJ (λ)And mean square deviation MSE between measure spectrum RfC (λ):

$\mathrm{MSE}={\left({\mathrm{\Σ}}_{\mathrm{\λ}=380}^{\mathrm{\λ}=780}{(R{f}_{J\left(\mathrm{\λ}\right)}-R{f}_{C\left(\mathrm{\λ}\right)})}^2\right)}^{1/2};$

S1032: hereditary end condition:

If meeting MSE, genetic process is less than 10^-3Or 40 iteration, just stop genetic process, obtain rete refraction nowRate and thicknesses of layers, if do not meet, proceed genetic process, Population Size that genetic process is arranged by genetic algorithm, repeatedlyGeneration number, elite's quantity, cross-ratio parameter determine, and generate new population, then carry out the calculating of admittance matrix spectrum, until fullThe end condition that foot evaluation function requires, and obtain thin-film refractive index and thicknesses of layers.

Described predetermined wavelength range is 380～780nm.

The beneficial effect that the technical scheme that the embodiment of the present invention provides is brought is:

1. adopt online spectral measurement device, this device is installed and filming equipment products export end, adopts CCD (ChargeCoupledDevice, charge-coupled image sensor) spectral measurement methods, measuring speed is much better than spectrophotometer measurement mode, measuresRete 380nm～780nm range of spectra required time is less than 260 milliseconds;

2. utilize rete face reflectance spectrum as the foundation of analyzing thin-film refractive index and thickness, avoid due to building float glassAbsorb the impact on result, more can embody the optical signature of rete essence;

3. set up rete Cauchy optical model can with the abundant combination of genetic algorithm, according to the spectral signature setting of actual production reteIt is faster that rational parameter will make to analyze convergence rate, and result is more accurate.

Brief description of the drawings

Fig. 1 is the structural representation of the online spectral measurement device that provides of the embodiment of the present invention;

Fig. 2 is a kind of transparent medium rete refractive index of providing of the embodiment of the present invention and the flow chart of thickness On-line Measuring Method;

Fig. 3 is the analysis process figure of the genetic algorithm that provides of the embodiment of the present invention;

Fig. 4 is the affect figure of the Population Size that provides of the embodiment of the present invention on result;

Fig. 5 is the affect figure of the Population Size that provides of the embodiment of the present invention on convergence process

Fig. 6 is the affect figure of elite's quantity of providing of the embodiment of the present invention on result;

Fig. 7 is that the cross-ratio that the embodiment of the present invention provides affects figure to result;

Fig. 8 is the reflectance spectrum of the different refractivity same thickness film that obtains of Cauchy's optical model that the embodiment of the present invention providesFigure;

Fig. 9 is the situation of change figure of the SiNx media coating face reflectance spectrum that provides of the embodiment of the present invention with thickness.

Detailed description of the invention

For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing to embodiment of the present invention do intoOne step ground is described in detail.

Referring to Fig. 1, a kind of online spectral measurement device, comprises support 3, and support 3 is provided with guide rail 4, and guide rail 4 is provided with surveyAmount probe 5, the support 3 of guide rail 4 one sides is provided with primary importance sensor 6, and the support 3 of opposite side is provided with the second place and passesSensor 7, in the time that primary importance sensor 6 and second place sensor 6 detect tested plated film sample 2 simultaneously, measuring probe 5Above tested plated film sample 2, test along guide rail 4 step motion point by point scannings, for testing the each point film of tested plated film sample 2Face reflectance spectrum, guide rail 4 belows are provided with multiple conveying rollers 1, and multiple conveying rollers 1 are for delivery of the tested plated film being placed on itSample.

Measurement mechanism of the present invention is arranged on off-line Low-E coating film production line plated film chamber outside manufacture slice-feeding end, tested plated film sampleFor the plated film sample after having produced; In the time that tested plated film sample 2 is transferred to primary importance sensor 6, on-line measurement deviceSend the signal that carries out system optics, position correction, on-line measurement device is carried out to system and automatically detect, to avoid because of deviceThe measurement that fault causes is inaccurate; When tested plated film sample 2 is transferred to second place sensor 7, primary importance sensing simultaneouslyDevice 6 has under RST, illustrates under measuring probe and has tested plated film sample, and now measuring probe 5 is on tested plated film sample 2Side is along guide rail 4 step motion point by point scanning tests; Measurement mechanism is to go along with sb. to guard him by support 3, is fixed, protects.

The online spectral measurement device that the present invention uses is easy fast, and this system can be applied to monitoring product glass surface, face simultaneouslyReflection and see through other quality testing processes such as spectrum and color.

Referring to Fig. 3, the present invention also provides a kind of transparent medium rete refractive index and thickness On-line Measuring Method, comprising:

S101: obtain face reflectance spectrum 1-3:

The online spectral measurement device of tested plated film sample utilization is recorded to the face reflectance spectrum of predetermined wavelength range; Predetermined wavelength modelEnclosing is 380～780nm;

S102: carry out Cauchy's optical model parameter 1-4 is set:

According to the impact of each parameter refractive index dispersion relation in film face reflectance spectrum feature (Fig. 9) and Cauchy's optical model(Fig. 8) carry out thickness and the initial setting up of Cauchy's optical model parameter, form initial value;

Reflectance spectrum feature of the present invention mainly refers to maximum and the residing peak position of maximum of reflectance spectrum, referring to Fig. 9, and canFind out that wavelength corresponding to the thicker reflectance spectrum maximum of thickness is larger; The impact of the each parameter of Cauchy's optical model is embodied in refractive indexThe impact of size, referring to Fig. 8, can find out that coefficient is larger, and refractive index is larger; Dispersion relation refers to the change of refractive index with wavelengthChange relation.

S103: genetic algorithm 1-6:

Utilize genetic algorithm, by initial value, in conjunction with face reflectance spectrum, by genetic algorithm parameter, 1-5 is set and controls heredityProcess, finally obtains thin-film refractive index and thicknesses of layers.

Genetic algorithm specifically comprises:

S1031: generate initial population:

Utilizing genetic algorithm, has been dot generation initial population by initial value;

S1032: admittance matrix spectrum calculates:

Initial population obtains calculating spectrum individual in population according to Cauchy's optical model and admittance matrix spectrum computational methods, and withThe face reflectance spectrum that actual measurement obtains compares sequence according to evaluation function; Described evaluation function is for calculating spectrum RfJ (λ)And mean square deviation MSE between measure spectrum RfC (λ):

$\mathrm{MSE}={\left({\mathrm{\Σ}}_{\mathrm{\λ}=380}^{\mathrm{\λ}=780}{(R{f}_{J\left(\mathrm{\λ}\right)}-R{f}_{C\left(\mathrm{\λ}\right)})}^2\right)}^{1/2};$

S1032: hereditary end condition:

If meeting MSE, genetic process is less than 10^-3Or 40 iteration, just stop genetic process, obtain rete refraction nowRate and thicknesses of layers, if do not meet, proceed genetic process, Population Size that genetic process is arranged by genetic algorithm, repeatedlyGeneration number, elite's quantity, cross-ratio parameter determine, and generate new population, then carry out the calculating of admittance matrix spectrum, until fullThe end condition that foot evaluation function requires, and obtain thin-film refractive index and thicknesses of layers.

Sample of the present invention is produced and is adopted off-line Low-E coating film production line, and production line completes a slice in a continuous manner for every 45～60 secondsCoating film on glass is produced, and a slice transparency area maximum area can reach 2540 × 3660mm conventionally², because speed of production is fast continuously, because ofThis test and analysis speed to properties of product has proposed very high requirement; Online spectral measurement device 2 is arranged on production line plated filmChamber outside manufacture slice-feeding end, can be with measurement products normal orientation optical transmission spectra and 8 ° of direction glass surfaces, face reflectance spectrum, shouldSystem adopts CCD spectral measurement methods, the luminous intensity of each wavelength within the scope of measure spectrum simultaneously, and measuring speed is much better than light splitting lightDegree meter metering system, measures rete 380nm～780nm range of spectra required time and is less than 260 milliseconds; The present invention only utilizes onlineThe face reflectance spectrum 1-3 that measurement mechanism 1-2 actual measurement obtains is the building float glass process glass using due to off-line Low-E coated glassGlass all has faint absorption, thereby to seeing through and the certain influence of glass surface reflectance spectrum formation, therefore face reflectance spectrum (Rf) canThe better optical property that embodies rete essence.

In Low-E film system, often use SiN_x、SnO_x、TiO_xDeng extinction coefficient k=0 in the optical constant of transparent medium rete,Refractive index n can be used Cauchy (Cauchy) model representation (suc as formula 1), wherein A with the dispersion relation of wavelength_nEmbody refractionThe minimum of a value of rate, B_n、C_nEmbodied the situation of change of refractive index with wavelength, its value is larger, and refractive index increases in shortwave directionMore obvious.

(λ is wavelength, for visible-range value 380～780nm) (1)

Referring to Fig. 8 and Fig. 9, according to each parameter refractive index dispersion relation in film reflectance spectrum 1-3 feature and Cauchy's optical modelThickness and Cauchy's optical model parameter initial setting up 1-4 are carried out in impact, thereby form initial value 1-5, and initial value is that genetic algorithm is searchedSeek the starting point of optimum value, the direction of convergence is played to important impact. Genetic algorithm has its intrinsic programming mode, at the beginning of passing throughInitial value 1-5 has been dot generation initial population 2-1, by genetic algorithm parameter, 1-6 is set and controls genetic process 2-4, and parameter comprises:Population Size, genetic process are set by Population Size, iterations, elite's quantity, cross-ratio, the direct shadow of these parametersRing operand and convergence rate.

Genetic algorithm essence is that a kind of iteration cycle process finally obtains thin-film refractive index and thickness 1-8 optimum value. In Fig. 3 heredityIn the analysis cycle process of algorithm, initial population 2-1 obtains in population individual according to optical model and admittance matrix spectrum computational methodsThe calculating spectrum of body, and compare sequence with the face reflectance spectrum 1-3 that actual measurement obtains according to evaluation function 2-5, commentValency function 2-5 is to calculate spectrum and the direct mean square deviation of measure spectrum (MSE) as foundation (suc as formula 2), and MSE gets over brief summary fruit precisionHigher.

$\mathrm{MSE}={\left({\mathrm{\Σ}}_{\mathrm{\λ}=380}^{\mathrm{\λ}=780}{(R{f}_{J\left(\mathrm{\λ}\right)}-R{f}_{C\left(\mathrm{\λ}\right)})}^2\right)}^{1/2}---\left(2\right)$

Heredity end condition 2-6 is the desired value of MSE, and desired value is that MSE is less than 10^-3, or constraint genetic iteration maximumNumber of times is 40 times, avoids invalid cycle calculations, obtains thin-film refractive index and thickness 1-8 now if meet end condition 2-6Optimum solution, if do not meet and proceed 2-4 genetic process, Population Size that genetic process is arranged by genetic algorithm 1-6, repeatedlyGeneration number, elite's quantity, cross-ratio parameter determine, and generate new population 2-3, starts new once circulation until meet and evaluateThe end condition that function 2-5 requires, and obtain thin-film refractive index and thickness 1-8 optimum solution.

Genetic algorithm (GA:GeneticAlgorithm) is one effective search algorithm in optimal combinatorial search application, stillOnly have according to concrete physical model and actual product state and carry out genetic process and initial parameter setting, just can obtain significantCorrect result.

The quantity of calculative individuality when Population Size is each genetic iteration in genetic process control parameter, therefore Population SizeDetermine total operand with genetic iteration number of times. Fig. 4 is the MSE situation of change of optimum individual after 100 genetic iteration, computingTo carry out under the same conditions (initial value thickness 65nm, A_n＝1.9、B_n＝0.002、C_n=0.0001,4 of elite's quantity, friendshipFork ratio 0.2), can find out that MSE with the increase result of individual amount in population is in rapid reduction, due to genetic process have withMachine variation is individual, and therefore in the time that Population Size reaches more than 25, MSE tends towards stability and has certain fluctuation. Fig. 5 is not for of the same raceGenetic iteration convergence process under group's size cases, can find out that the less convergence of population is faster, but final result is poorer, this and heredityCalculation ratio juris is correlated with, and increase quantity individual in population and just improved the possibility of evolving, favourable and acquisition globally optimal solution,Can find out and select 40 genetic iteration, 30～40 individual population computational efficiency the bests from Fig. 4, Fig. 5.

In each iteration, the fitness result (being the MSE value of the calculating spectrum of each individuality) of each individuality in meeting computing population,The line ordering of going forward side by side, is elite by the forward individuality of the high rank of little MSE precision, directly retains and enters filial generation, and this mode improvesThe possibility of convergence, it is long that the little meeting of elite's quantity causes restraining time of needs, and quantity conference causes Premature Convergence. Fig. 6 isInitial value thickness 65nm, A_n＝1.9、B_n＝0.002、C_n=0.0001,35 of population at individuals, genetic iteration 40 times, the ratio that intersectsUnder example 0.2 condition, the MSE of result under different elite's quantity, can find out when result MSE in the time that elite's quantity exceedes 20 aobviousWork increases, and this is due under identical Population Size, and what directly elite's quantity increase of heredity caused making a variation in genetic process canCan property reduce, cause population to evolve and be absorbed in locally optimal solution, therefore general elite's quantity is no more than population at individual numberHalf.

Progeny population is in the elite that directly hands down by heredity from parent, parent, between individuality, to intersect and individual summation that variation forms,Cross-ratio be in population except elite's number, the individual ratio being produced by cross method, Fig. 7 be under above the same terms notThe impact on result with cross-ratio and elite's quantity, can find out that result will be tight in the time that the increase of elite's quantity, cross-ratio become largeHeavily worsen, therefore explanation need to ensure to have in population the quantity of suitable variation individuality, and cross-ratio should be less than 0.5, to promote kindGroup's evolution, avoids being absorbed in the situation of locally optimal solution.

From what has been discussed above determine that Population Size is that 35 individualities, genetic iteration 40 times, elite's quantity are 8, cross-ratio0.2 is best hereditary condition, sets with this understanding different initial values, analyzes and obtains thin-film refractive index, thickness and calculate filmFace reflectance spectrum Rfy obtains face thickness, refractive index and face reflectance spectrum Rft by sample with Ellipsometry Measurement, comparison simultaneouslyMSE between Rft and Rfy, as shown in table 1.

The impact of table 1 initial value on analysis result

The initial value of given genetic algorithm and measured value are more approaching as can be seen from Table 1, calculate spectral results and more approach actual measurementAs a result, precision is higher, therefore needs to estimate reasonable initial value according to actual measurement situation. The face reflection spectrum characteristic master of reteTo be that refractive index and thickness determine by optical thickness, if Fig. 8 is that Cauchy model obtains the anti-of different refractivity same thickness filmPenetrate spectrum, more high reflectance is higher can to find out refractive index, A_n、B_n、C_nInfluence to reflectivity size reduces successively;Because the dielectric layer refractive index using in Low-E film system is all higher than glass, therefore reflectivity is greater than the reflectivity of glass own, and anti-Penetrate spectrum and present sinusoidal version with thickness increase. Because Low-E film is optical property demand, and technique andDevice-restrictive, dielectric layer thickness in monolayer is generally no more than 80nm, and Fig. 9 is silicon nitride SiN_xRete face reflectance spectrum is with thicknessSituation of change, according to principle of interference, under same interference periods along with thickness increase interfere produce reflectivity maximum position toLong wave direction moves. Therefore can utilize feature shown in Fig. 9, by adjusting glass movement velocity, can estimate that film is at 50～80nmThickness size in scope utilizes feature shown in Fig. 8 can rationally set the each coefficient magnitude of Cauchy according to reflectivity size simultaneously.

The present invention utilizes online spectral measurement system fast detecting product face reflectance spectrum, adopts on this basis genetic algorithm baseIn Cauchy's optical model analysis Low-E film system, refractive index and the thickness of transparent medium rete, can meet actual production to reteRefractive index and thickness are analyzed demand accurately and rapidly; In genetic algorithm there is zone of reasonableness in genetic process parameter, and the present invention setsPopulation Size is that 35 individualities, genetic iteration 40 times, elite's quantity are 8, and cross-ratio 0.2 is the most efficient hereditary barPart; According to rete face reflection spectrum characteristic estimation thicknesses of layers and Cauchy's optical model coefficient of actual production, set up reasonablyInitial value, will make result more accurate.

It is media coating optical signature that face reflectance spectrum of the present invention more can be reacted Low-E film compared with transmitted spectrum; Genetic algorithmBetter with rete optics Cauchy optical model combination degree, actual in the reasonable setting of algorithm parameter in conjunction with producing, can be quickRestrain and obtain globally optimal solution, therefore adopting the present invention can obtain fast and accurately rete optical constant and thickness data,Greatly simplify product design and development and production control process, be more suitable for the actual production conditions in factory, reduce business equipment and invest intoThis.

The foregoing is only preferred embodiment of the present invention, not in order to limit the present invention, all the spirit and principles in the present invention itIn, any amendment of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (3)

1. transparent medium rete refractive index and a thickness On-line Measuring Method, is characterized in that, comprising:

S101: obtain face reflectance spectrum:

The online spectral measurement device of tested plated film sample utilization is recorded to the face reflectance spectrum of predetermined wavelength range;

S102: carry out the setting of Cauchy's optical model parameter:

Carry out thickness according to the impact of each parameter refractive index dispersion relation in film face reflectance spectrum feature and Cauchy's optical modelAnd the initial setting up of Cauchy's optical model parameter, form initial value;

S103: genetic algorithm:

Utilize genetic algorithm, by initial value, in conjunction with face reflectance spectrum, by genetic algorithm parameter, control genetic process be set,Finally obtain thin-film refractive index and thicknesses of layers.

2. transparent medium rete refractive index according to claim 1 and thickness On-line Measuring Method, is characterized in that, described inStep S1031 comprises:

S1031: generate initial population:

Utilizing genetic algorithm, has been dot generation initial population by initial value;

S1032: admittance matrix spectrum calculates:

Initial population obtains calculating spectrum individual in population according to Cauchy's optical model and admittance matrix spectrum computational methods, and withThe face reflectance spectrum that actual measurement obtains compares sequence according to evaluation function; Described evaluation function is for calculating spectrum RfJ (λ)And mean square deviation MSE between measure spectrum RfC (λ):

$\mathrm{MSE}={\left({\mathrm{\Σ}}_{\mathrm{\λ}=380}^{\mathrm{\λ}=780}{({\mathrm{Rf}}_{J\left(\mathrm{\λ}\right)}-{\mathrm{Rf}}_{C\left(\mathrm{\λ}\right)})}^2\right)}^{1/2};$

S1032: hereditary end condition:

If meeting MSE, genetic process is less than 10^-3Or 40 iteration, just stop genetic process, obtain rete refraction nowRate and thicknesses of layers, if do not meet, proceed genetic process, Population Size that genetic process is arranged by genetic algorithm, repeatedlyGeneration number, elite's quantity, cross-ratio parameter determine, and generate new population, then carry out the calculating of admittance matrix spectrum, until fullThe end condition that foot evaluation function requires, and obtain thin-film refractive index and thicknesses of layers.

3. transparent medium rete refractive index according to claim 1 and 2 and thickness On-line Measuring Method, is characterized in that,Described predetermined wavelength range is 380～780nm.