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

用于对卷云中的冰晶进行成像的新型 3D 数字全息仪器

• 批准号: 9261712
• 负责人: R. Paul Lawson
• 金额: $ 4.99万
• 依托单位: STRATTON PARK ENGINEERING CO INC
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-01-01 至 1993-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9261712&HistoricalAwards=false
• 关键词: Novel; Digital; Holographic; Instrument; Imaging

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.

卷云持续覆盖近40%的地球表面，现在已知对全球辐射收支有重大影响。例如，热带风暴产生的卷云砧被吹到数百公里的顺风处，限制了海面的变暖。这反过来又可能影响随后产生的热带风暴，甚至可能在控制南方涛动（即厄尔尼诺事件）方面发挥作用。利用晶体收集器和复制器进行的有限的飞机观测表明，卷云主要由形状复杂的冰晶组成，大小从10微米到1毫米不等。然而，在这些研究中使用的收集器和复制器仅限于进行粗略的空间观察，不能提供晶体浓度的良好测量。目前的飞机光学成像探头不能很好地测量尺寸约为150微米的晶体浓度。这是传统光学系统固有的局限性，因为景深（DOF），因此样品体积，减少与晶体半径的平方。在这里，PI提出了一种使用新型数字全息成像系统（DHIS）的新型光学仪器，与传统成像系统相比，DOF增加了100多倍。在第一阶段，气象研究所进行数值模拟和DHIS实验室测试，以提供卷云冰晶的三维信息。该机载仪器将在第二阶段进行建造和测试，能够以高达100赫兹的速率提供直径从5微米到2.5毫米的冰晶的数字化3-D全息图。