A two-dimensional simulation had been conducted to determine the thickness and orientation of a clear thin liquid film for both the multi-fiber and mono-fiber optic sensors developed recently. The multi-fiber sensor consists of a central light emitting fiber which is surrounded symmetrically by six light receiving fibers while the mono-fiber sensor has only one fiber which acts as both the light emitting and receiving sources. By analyzing the different patterns of light intensity reflected back at the liquid surface and collected by the receiving fibers, the thin film thickness and its orientation with respect to the measuring point can be determined. The present study suggests that the multi-fiber sensor is capable of measuring liquid thin film thicknesses, including orientation relative to the measuring point, within the range of 1-4 mm. Below the range of 1 mm, the use of mono-fiber sensor appears to be more effective. In both cases, limitation is mainly imposed by the numerical aperture of the fiber used. © 1995.
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