A Novel 3-D Digital Holographic Instrument for Imaging Ice Crystals in Cirrus

卷云持续覆盖着地球近40%的面积 表面和现在已知有重大影响的 全球辐射收支 例如，热带风暴产生 卷云铁砧被吹到数百公里的下风处， 限制了海面的升温。 这反过来可能会影响 甚至有可能在 在控制源振荡（即，厄尔尼诺现象）。 使用晶体收集器进行有限的飞机观测， 复制者认为卷云主要由冰晶组成 具有尺寸范围从约10 μ m到1 mm的复杂形状。 然而，这些研究中使用的收集器和复制器是 仅限于进行粗略的空间观测，不提供 晶体浓度的良好测量。 当前飞行器 光学成像探头不能进行良好的测量 晶体浓度约为150 μ m。 这是一 传统光学系统的固有限制， 景深（DOF）以及因此的样品体积减小 与晶体半径的平方成正比 在这里，PI提出了一种新的光学仪器， 增加自由度的数字全息成像系统 与传统成像系统相比， 100. 在第一阶段，PI进行数值模拟， DHIS的实验室测试将提供三维 关于卷云中冰晶的信息 机载仪器， 在第二阶段建造和测试，可以提供数字化的3D 以高达100 Hz的速率拍摄的直径为 5 μ m至2.5 mm。

Cirrus clouds continuously cover nearly 40% of the earth's surface and are now known to have a significant influence on the global radiation budget. For example, tropical storms generate cirrus anvils that are blown hundreds of kilometers downwind and limit warming of the sea surface. This in turn may influence the subsequent generation of tropical storms and may even play a role in controlling the Sourthern Oscillation (i.e., the El Nino event). Limited aircraft observations using crystal collectors and replicators suggest that cirrus are composed mostly of ice crystals with complex shapes that range in size from about 10 um to 1 mm. However, the collectors and replicators used in these studies are limited to making coarse spatial observations and do not provide good measurements of crystal concentration. The current aircraft optical imaging probes are not capable of making good measurements of crystal concentrations for sizes about 150 um. This is an inherent limitation of conventional optical systems because the depth of field (DOF), and consequently the sample volume, decreases with the square of the crystal radius. Here, the PI proposes a new optical instrument using a novel digital holographic imaging system (DHIS) which increases DOF compared to conventional imaging systems by more than a factor of 100. In Phase I, the PI performs numerical simulations and laboratory tests of a DHIS which will provide three-dimensional information on ice crystals in cirrus. The airborne instrument, to be built and tested in Phase II, could provide digitized 3-D holograms at rates up to 100 Hz of ice crystals with diameters from 5 um to 2.5 mm.