Study On The Influence Of The Contact Pressure In Near Infrared Spectroscopic Measurement Applied On Human

Diabetes,as a chronic disease,has become a serious threat to the public health.To control diabetes,certain continuous measurements of blood glucose levels are utilized,however the traditional method of blood sampling has the disadvantages of great pain and high risk of infection.Near-infrared spectroscopy emerged as the most promising blood glucose detection method because of its speediness noninvasive examination,plentiful information and so on.In order to improve the measurement stability,nearinfrared spectroscopy often used the method that making an optical fiber probe contact with human skin tissue.Nevertheless,the skin tissue will deform during the contact measurement,affecting the spectral measurement results.For purpose of optimizing the contact measurement method,this paper studies the effect of fiber probe pressure on earlobe diffusion and transmission spectra from theoretical model simulation and human experiment verification.And on this base,this paper proposes a solution that utilizing the low sensitivity range of contact pressure which provides a reference for the measurement of human blood glucose near-infrared spectroscopy.Firstly,this paper selected earlobe as the measurement according to the requirement of blood glucose detection,meanwhile,studies the optical parameters and mechanical property of ear tissue.Then,based on the solid-liquid two-phase mechanic properties of skin tissue,the deformation regularity of skin tissue under different contact pressures is found.and the quantitative relationship between contact pressure and absorption coefficient and scattering coefficient under certain assumptions is deduced.Secondly,a five-layer skin tissue model is established which based on the anatomical characteristics of the earlobe tissue.The change of the structure parameters of each layer with the contact pressure is calculated by finite element simulation.On the basis of this,the influence of the contact pressure on the near-infrared spectroscopy is analyzed by using the Monte Carlo model which simulate the diffuse reflectance and transmittance spectra.Then,to analyze the spectra of the earlobe under different contact pressures,the system which can collects diffuse reflectance and transmittance spectra is used.,Comparing with experimental and simulation results,the variation law of the diffuse reflectance and transmittance spectra under pressure is verified,namely,the energy of the diffuse reflectance spectra gradually decreases,and the diffuse transmittance spectra gradually increases as the contact pressure between the optical fiber probe and the skin tissue increases.Finally,for the sake of improving the accuracy and stability of near-infrared spectroscopy,a superior detection scheme is designed on account of the study about influence of contact pressure on the spectra.According to the simulation and experimental results,it is shown that when the contact pressure is within 15-20 kpa,the spectroscopy is insensitive to the pressure variation,which is helpful to ensure the accuracy of spectral modeling.