Improving the spatial dynamic range of digital inline particle holography.
Improving the spatial dynamic range of digital inline particle holography.
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DOI：
10.1364/ao.58.000a65
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发表时间：
2018-12
期刊：
影响因子：
1.9
通讯作者：
Z. Falgout;Yi Chen;D. Guildenbecher
中科院分区：
文献类型：
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作者：
Z. Falgout;Yi Chen;D. Guildenbecher
数字同轴全息术已经被证明可以用单个相机提供三维液滴位置、尺寸和速度分布。这些数据对于理解多相流至关重要。在这项工作中，我们研究了这种诊断在非常小的颗粒的限制下的性能，在直径和更小的像素的数量级上，并提出了一种后处理方法来改善它们：Lanczos插值。Lanczos插值内核是Whittaker sinc滤波器的数字实现，并且在保持原始数字图像的空间频率上限和插值的计算成本之间达成了折衷。在没有Lanczos插值或超插值的情况下，最终可检测的颗粒尺寸下限大约为四个像素宽度。在这项工作中，我们表明，这一限制可以减少50%或更多的superspeed，这取决于所需的直径精度，并检查superspeed对所得到的准确性提取的大小和位置的球形颗粒的效果。扩展该分辨率极限增加了诊断的总体检测效率。由于这增加了诊断的空间动态范围，因此它还可以允许用相同的颗粒尺寸底捕获更大的视场。
Digital inline holography has been proven to provide three-dimensional droplet position, size, and velocity distributions with a single camera. These data are crucial for understanding multiphase flows. In this work, we examine the performance of this diagnostic in the limit of very small particles, on the order of a pixel in diameter and smaller, and propose a postprocessing method to improve them: Lanczos interpolation. The Lanczos interpolation kernel is the digital implementation of the Whittaker sinc filter and strikes a compromise between maintaining the spatial frequency ceiling of the original digital image and computational cost of the interpolation. Without Lanczos interpolation, or supersampling, the ultimate detectable particle size floor is on the order of four pixel widths. We show in this work that this limit can be reduced by 50% or more with supersampling, depending upon the desired diameter accuracy, and examine the effect of supersampling on the resulting accuracy of the extracted size and position of spherical particles. Extending this resolution limit increases the overall detection efficiency of the diagnostic. Since this increases the spatial dynamic range of the diagnostic, it can also allow a larger field of view to be captured with the same particle size floor.