Development of a free-drifting submersible digital holographic imaging system
Development of a free-drifting submersible digital holographic imaging system
复制标题
自由漂潜式数字全息成像系统的研制
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
J. Katz
中科院分区：
文献类型：
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作者：
D. Pfitsch;E. Malkiel;Y. Ronzhes;S. King;J. Sheng;J. Katz
潜水胶片全息系统已经证明了全息术的独特能力，可以提供海洋生物的高分辨率、三维、原位图像。本质上，胶片的使用限制了帧率和全息图的总数。本文介绍了一种具有实时光纤通信链路的水下自由漂流数字全息摄影系统。该系统以每秒15帧的速率收集双视图数字全息图，使用户能够观察海洋浮游生物的行为，并区分运动生物和非生物颗粒。为了及时跟踪粒子，样品相对于相机的运动应该尽可能少。为了实现这一目标，潜水器具有中性浮力，并且在样品体积的高度具有高阻力产生元件。此外，样品周围的组件是流线型设计，以尽量减少局部流动干扰。来自两个数码相机和其他传感器的数据通过1公里长、直径250 /spl mu/m的光纤电缆以120mb /s的速度传输到位于科考船上的采集系统。当潜水器远离船只时，光纤通过动力机构从潜水器中绕出，以大于漂移速度的速度释放光纤，使通过电缆的力传输最小化，有效地将潜水器与电缆和船只动力学解耦。可变浮力系统提供垂直位置控制，同时仍允许系统随周围流体垂直漂移，即跟随内波。双视角全息相机记录两个垂直方向的直线全息图，每个全息图的体积为40.5 cm/sup /。在没有透镜的情况下，在光束相互交叉的3.4 cm/sup /体积内，三个方向的分辨率约为7.4 /spl mu/m。在重叠区域之外，光束轴向分辨率较低，但横向分辨率仍为7.4 /sup /。可选的2/spl倍/镜头使分辨率加倍，但减少了样本量。该系统的首次现场部署于2005年6月在西班牙的Ria de Pontevedra进行。它被用来检查有害藻华的薄层。
Submersible film-based holographic systems have demonstrated the unique ability of holography to provide high resolution, three-dimensional, in-situ images of marine organisms. Inherently, use of film limits the frame rate and total number of holograms. This paper describes a submersible, free-drifting, digital holographic cinematography system that has a real-time fiber optic communication link. This system collects dual-view digital holograms at a rate of 15 frames per second, enabling the user to observe the behavior of marine plankton and distinguish motile organisms from abiotic particles. In order to follow the particles in time, the sample should have as little motion relative to the cameras as possible. To achieve this goal, the submersible is neutrally buoyant, and has high drag generating elements at the height of the sample volume. In addition, the components surrounding the sample are streamlined and designed to minimize the local flow disturbance. The data from the two digital cameras and other sensors are transmitted at 120 MB/s through a 1 km long, 250 /spl mu/m diameter, fiber optic cable to an acquisition system located on a research vessel. The optical fiber is spooled out from the submersible by a powered mechanism, as the submersible drifts away from the vessel Releasing the fiber out at a rate greater than that of the drifting speed minimizes the transmission of forces through the cable, effectively decoupling the submersible from the cable and vessel dynamics. A variable buoyancy system provides vertical position control while still allowing the system to drift vertically with the surrounding fluid, i.e., follow internal waves. The dual-view holo-camera records two in-line holograms from orthogonal directions, each with a volume of 40.5 cm/sup 3/. Without lenses, the resolution in the 3.4 cm/sup 3/ volume where the beams cross each other, is about 7.4 /spl mu/m in all three directions. Outside of the overlapping region, the resolution in the beam axial direction is lower, but the lateral resolution remains 7.4 /sup 3/. An optional 2/spl times/ lens doubles the resolution, but reduces the sample volume. The first field deployment for this system took place in June 2005, in the Ria de Pontevedra, Spain. It was used for examining thin layers of harmful algal blooms.