Capillary Tube Refactometer: A Novel Method for Measuring the Refractive Index of Crude Oil

A novel method for measuring the refractive index of crude oils is described. The method involves the use of a simple optical capillary tube and is based on measuring transverse interference patterns in transmission permitting accuracy in the fringe spacing measurement of up to ½λ of the laser beam used. Because the diameter of the capillary tube is small the interference pattern becomes exceptionally visible in transmission making the method suitable for opaque liquids such as crude oils. The concept of the method and its theoretical model can be developed to operate in reflection as well which, in turn, makes it a promising tool in remote sensing applications such as the identification of crude oil spills based on their refractive indices.