Study On Theories And Experiments Of Measuring The Milk Compositions With Near-infrared Spectroscopy

Tissue optics is introduced into the measurement of milk compositions. Theinteraction between the light and milk constituents and optical properties of milk arestudied. Compared with near infrared spectroscopy (NIRS), which apply "black box"method, the application of tissue optics begins to look from the "inner side", whichprovides a new tool and research method for measurement of milk components.Centering on propagation and distribution of light in turbid media, the theory andapplication of tissue optics to measurement of milk compositions are investigatedwith theoretical analysis, computer simulation and experiments. The physical modelof photons propagation in milk, comparison of experimental methods anddata-process methods, and measurement of the optical properties of milk are studied.The relation of optical properties to concentration of milk compositions is measured;the effect of the concentration of milk components on light distribution is simulated;and the solutions to measurement of milk components in reflection and transmissionway are given and compared.The main content of the dissertation involves:1. The propagation and distribution of light in turbid media is studied. TheBoltzmann transport equation and its diffuse approximation are introduced, andthe matching conditions for steady-state diffuse equation and its approximationsolutions are discussed. The Adding Doubling method, which is adopted to getthe optical properties of turbid media, is summarized and depicted systematically.2. The effect of Henyey-Greenstain and Mie scattering phase functions on theaccuracy of measuring the optical parameters is studied. It's found by MonteCarlo simulation that a large discrimination in angular single-scatteringdistribution for both phase functions exists, but reduces sharply when multiplescatterings occur.3. Design of experimental devices, comparison and selection of experimentalmethods and data-processing methods are performed. The experimental devicesare designed, and the error is analyzed in detail. The optical parameters of turbidmedia are measured with different devices. By Monte Carlo simulation andcomparison with experimental results, it's obtained that the doubleintegrating-sphere (DIS) device is more accurate and convenient. Comparison ofIAD (Inverse Adding Doubling) with IMC (Inverse Monte Carlo) is made. Ahybrid method of combining IAD and IMC is presented to ensure the efficiencyand accuracy of data process.4. The relationship of absorption and scattering coefficient to concentration of milkcomponents is quantitatively studied, which provide the first-hand data for studyof light distribution in milk and measurement of milk compositions.5. The relationship of light distribution to the concentration of milk components isstudied. Based on the measured optical properties of milk compositions, the effectof the concentration of milk components on diffuse reflectance and transmittanceis simulated with Monte Carlo. The optimal pathlength of glucose, protein and fatin milk are obtained.6. Assessment functions for optimal design of detector are presented to measure theconcentration of milk compositions with reflection and transmission spectroscopy.For absorbing matter, the evaluation function is presentedas S int 1= ???? ??μRa ???????? ??μRs????and S int 2=??μRs. For scattering particles, the function ispresented as S int 1= ???? ??μTa ???????? ??μTs????and S int 2=??μTs. The optimal pathlength isdefined as the solution to the above-mentioned equation while S int1 and S int2 ismaximal.7. The optimal pathlength for measurement of the concentrations of the glucose, fat,and protein in milk are obtained by Monte Carlo simulation in diffuse reflectionand transmission way, and then validated by experiments, respectively. The finalsolutions to measurement of different compositions in milk are presented.