Enhancing the Perfomance of a Submersible Holographic Camera and Automating Analysis for Determining Particle Location and Turbulance in the Ocean

9909170 Katz这个海洋科学技术开发项目建立在之前工作的基础上，开发和测试一种使用激光产生全息图的潜水全息相机系统，从中可以研究小颗粒的运动和分布。目前，一种用于在海洋中记录原位全息图的潜水式全息系统以串联模式运行，使用红宝石激光器作为其光源。它由车载电池供电，并通过两根光缆控制，这两根光缆还提供来自其他车载环境传感器的实时数据。该系统旨在将系统对采样水量的影响降至最低。目前的工作重点是提高全息相机的性能，并继续开发全息分析程序。全息术是一种独特的工具，可以在大样本体积上提供微观颗粒的瞬时位置，以及每个颗粒的形状、大小和方向。一系列全息图也可以用来确定该样品体积内液体的全部三维速度场，以及较大颗粒的相对速度。数据分析程序包括重建记录的全息图，以创建原始样本体积的3-D定格图像。通过以高倍率扫描重建的图像，人们可以在大约1000 cm3的样本体积内观察和测量所需的细节，其精度低于10 mm。将通过整合和开发软件工具来自动化和提高分析程序的效率，这些工具将执行1)使用各种基于直方图的、非线性和形态过滤器的图像增强；2)使用斑点分析子例程的颗粒检测；以及3)基于大小和形状的颗粒分类。进一步的改进将为全息粒子图像测速提供能力，为全息摄像机提供单独的离轴参考光束，以及插入样品体积和胶片之间的空间高通过滤器。将使用实验室应用的方法开发测量海洋中三维液体速度分布和选定颗粒的相对运动的能力，在实验室应用中，使用小颗粒的位移来测量液体流场。将开发一种原位方法，通过使用粒子在空间中的准确位置(粒子跟踪)准确确定粒子的轴向位移，并使用能够根据其他两个速度分量的空间分布计算轴向分量的连续性方程，从一张全息图中获得所有三个速度分量。提出了解决同轴全息术和离轴全息术重叠问题的方法。现场测试将与港湾分院海洋研究所的研究人员一起进行。他们的研究需要关于浮游生物尺度上的局部剪切应变(即三维速度分布)的数据，以及桡足类丰度与海洋雪和/或其他资源丰度之间的相关性。两者都可以由全息摄像机同时提供。该传感器可以应用于其他物理和生物海洋学问题，如小尺度湍流、生物的微尺度斑块、捕获食物颗粒，以及描述气泡的大小和运动，包括那些比多频声学技术可以测量的气泡更小的气泡。

9909170KatzThis ocean sciences technology development project builds on previous work to develop and test a submersible holographic camera system using lasers to produce holograms, from which the motion and distribution of small particles can be studied. A submersible "holocamera" system for recording in-situ holograms in the ocean presently operates in an in-line mode utilizing a ruby laser as its light source. It is powered by onboard batteries and is controlled via two fiber optic cables, which also provide real time data from other onboard environmental sensors. The system is designed to minimize the effect the system has on the sampled water volume. The present effort focuses on enhancing the performance of the holocamera and continuing the development of hologram analysis procedures. Holography is a unique tool that can provide the instantaneous location of microscopic particles over a large sample volume as well as the shape, size and orientation of each particle. A series of holograms can also be used to determine the full 3 -D velocity field of the liquid in that sample volume and the relative velocities of larger particles. The data analysis procedure consists of reconstructing a recorded hologram to create a 3 - D frozen image of the original sample volume. By scanning the reconstructed image at high magnification, one can observe and measure desired details down to less than 10 mm within a sample volume of about 1000 cm3. Work will be undertaken to automate and improve the efficiency of the analysis procedures by incorporating and developing software tools that will perform 1) image enhancement using a variety of histogram-based, non-linear and morphological filters; 2) particle detection involving use of blob analysis subroutines; and 3) particle classification based on size and shape. A further enhancement will provide the capability for Holographic Particle Image Velocimetry by providing the holocamera with a separate, off-axis reference beam, and a spatial, high pass filter inserted between the sample volume and the film. The ability to measure the 3-D liquid velocity distribution in the ocean and the relative motion of selected particles will be developed using methods used for laboratory applications where the liquid flow field is measured using the displacement of small particles. In situ methods will be developed to obtain all three velocity components from a single hologram by determining the axial displacement of particles accurately using their exact location in space (particle tracking); and by using the continuity equation that enables computation of the axial component from the spatial distribution of the other two. Methods to address the overlap problem for in-line holography and for off-axis holography are proposed.Field tests will be performed in conjunction with investigators from Harbor Branch Oceanographic Institute. Their research requires data on the local shear strains (i.e. 3 - D velocity distribution) in the scale of planktonic organisms as well as correlation between copepod abundance and marine snow and/or other resource abundance. Both can be simultaneously provided by the holocamera. This sensor could be applied to other physical and biological oceanographic problems such as small scale turbulence, microscale patchiness of organisms, capture of food particles, and describing the size and motion of bubbles including those smaller than multi-frequency acoustical techniques can measure.