Optical coherence tomography: state of the art

Our setup has been devised in which the spatial focus and the interference condition coincide at an assumed average refractive index of the sample, independently of the position Δz_Fiber,, of the fiber tip which causes the depth scanning. Local deviations in refractive index on the order of 25 μm can be tracked by small position changes ΔZ_L1 of one lens within the sample arm. Depending on the type of skin, refractive indices can be evaluated down to 400 μm. The hydration level could clearly be delineated as it was demonstrated in the vicinity of a sweatgland duct in a palm. Images with a resolution of around 5 μm have been obtained from various sites of the body. Beyond high resolution morphology in OCT images, additional local physical parameters can be desired for cosmetics/pharmaceutical and medical applications. Spatially confined refractive indices have been shown to provide a distribution map of moisture levels. Further studies (not shown) exhibit effects of hydration cremes. In skin disease characterization refractive index distribution may supplement clinical diagnosis.