Yu Haitao, Shen Jianqi, Tropea Cameron, Xu Feng
Opt Lett. 2019 Feb 15;44(4):823-826. doi: 10.1364/OL.44.000823.
A model is proposed to compute the salient optical caustic partitions occurring in the primary rainbow for oblate spheroidal drops. By computing the boundary limits of outgoing rays, the optical caustic structures (termed rainbow and hyperbolic umbilic fringes) for tilted drops are calculated and compared with those for aligned (untilted) drops. The curvature of the rainbow fringe and the shifts of cusp caustics are discussed as well. The observed properties of the caustics can potentially be used for drop measurements. The model could also be applied to compute the optical caustics for drops with arbitrary shape, arbitrary orientation, and shaped beam illumination.
提出了一个模型来计算扁球体液滴在主虹中出现的显著光学焦散分区。通过计算出射光线的边界极限，计算了倾斜液滴的光学焦散结构（称为彩虹条纹和双曲脐条纹），并与对齐（未倾斜）液滴的光学焦散结构进行了比较。还讨论了彩虹条纹的曲率和尖点焦散的位移。所观察到的焦散特性可能可用于液滴测量。该模型还可应用于计算任意形状、任意取向和成形光束照明的液滴的光学焦散。
