Ellipsometric measurement of skin refractive index in vivo
This technique measures two angles (ψ and ∆) of a light beam, and the changes in these angles because of the surface reflection. ψ is a trigometric ratio function of the parallel and perpendicular beam amplitudes (relative to the plane of incidence). ∆ is the related phase shift between these two orthogonal beam components. After the beam strikes a surface these two values change according to the electrical properties of the material. Measurement of these two parameters can be accomplished by various techniques and in this investigation measurement was performed using phase-modulated ellipsometry. These two values can be used to determine the real and imaginary components of the refractive index which in turn describes both the light-bending and lightabsorption properties of the medium. With continued experimentation this instrument will enable non-invasive detailed exploration to be made of skin thickness, changes due to sun damage, and effectiveness of various cosmetic preparations.
KeywordsRefractive Index Stratum Corneum Quarter Wave Plate Refractive Index Measurement ELLIPSOMETRIC Measurement
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