Measurement of Refractive Indices of Semi-transparent Oils Using LFI Method
LFI法测量半透明油的折射率(英文)

Lens fiber interference(LFI) method was used to measure refractive indices of fiber with big radius. A capillary tube, half filled liquid and half air, replaced fiber and was illuminated by focused laser sheet of light. Interferograms of liquid and air were produced at the same time. By the fringe of air, a parameter b was determined. And by the interference fringe patterns of a set of standard samples, anther parameter c was determined. A curve between the refractive indices and the deviation angles of the external fringes of the standard liquids was established. For the sample unknown refractive index, once the deviation angle of the external fringe was measured, the refractive index could be read from the standard curve. Using this method, the refractive indices of a set of semi-transparent oils were measured. The results are approximate to that of Abbe refractometer.