We study dynamical Newton-ring like fringes created by interfering Fresnel reflections of an evaporating sessile liquid droplet, which acts as a miniature convex lens. We show that conventional thin-film interference theory cannot be applied to explain the physical phenomenon. Because of the large thickness and curvature of the liquid droplet, the geometrical light paths of the reflected beams become very complicated and can no longer be considered approximately collimated. This results in interference fringes of concentric circles with different directional motion depending on the observation plane. The change in the interference pattern as a function of time is demonstrated by both simulation and experiment. This investigation allows us to fully understand the formation of interference patterns of an optical system having arbitrary thickness and curvature. In addition, by analyzing the high-contrast dynamic rings, we demonstrate nanoscale sensitivity to surface height changes of an evaporating water drop.

中文翻译：

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由水平表面上的蒸发液滴产生的干涉图案

我们研究了通过干涉蒸发的固着液滴的菲涅耳反射产生的动态牛顿环状条纹，该液滴充当微型凸透镜。我们表明传统的薄膜干涉理论不能用于解释物理现象。由于液滴的厚度和曲率很大，反射光束的几何光路变得非常复杂，不能再认为是近似准直的。这导致同心圆的干涉条纹根据观察平面具有不同的方向运动。模拟和实验都证明了干涉图案随时间的变化。这项研究使我们能够充分了解具有任意厚度和曲率的光学系统的干涉图案的形成。此外，通过分析高对比度动态环，我们证明了对蒸发水滴表面高度变化的纳米级敏感性。