Experimental validation of non-sphericity effect on monochromatic rainbow measurement

摘要

Monochromatic rainbow measurement, as a laser based interference detecting technique, is always used to measure particle refractive index. However, the accuracy of this method is effected by particle non-sphericity. In this paper, the non-sphericity effect is analyzed from both simulation and experiment. The non-sphericity effect for both prolate and oblate spheroid is studied. The simulation result shows that the axial ratio greatly effects the rainbow angle position, and eventually effect the refractive index evaluation. An experiment is also taken. The refractive indexes of ethanol solutions with different concentration are measured by monochromatic rainbow method. A comparison is taken between the results measured from the rainbows formed by a liquid cylinder and rainbows of free falling droplets.