Green S I, Zhao Z
Appl Opt. 1994 Feb 10;33(5):761-7. doi: 10.1364/AO.33.000761.
Double-pulsed holograms form the basis of holographic particle image velocimetry. This technique is becoming widely used for measuring three-dimensional velocity fields. The major deficiency of holographic particle image velocimetry is that the double-pulsed holograms must be painstakingly surveyed by a human observer for determination of the location of objects within the holographic volume. A system that automatically and efficiently analyzes double-pulsed holograms of microbubbles in water is developed that eliminates the need for a human surveyor. The system employs a three-part algorithm: (1) Holograms of microbubbles are scanned in the holographic (x-y) plane. Microbubbles within the scanned region are detected by a CCD-based fast object-detection system. (2) Bubble images thus detected are focused (in the z-direction) by an autofocusing technique. (3) In-focus bubble images are analyzed by a simple set of image-analysis techniques, including edge detection and patch correlation. The output of this alg rithm is the size, and the displacement between the two laser pulses, of microbubbles in the water.
双脉冲全息图构成了全息粒子图像测速技术的基础。该技术正被广泛用于测量三维速度场。全息粒子图像测速技术的主要缺陷在于，必须由人工仔细查看双脉冲全息图，以确定全息体积内物体的位置。现已开发出一种能自动且高效地分析水中微气泡双脉冲全息图的系统，从而不再需要人工查看。该系统采用了一个由三部分组成的算法：(1) 在全息（x - y）平面扫描微气泡的全息图。基于电荷耦合器件（CCD）的快速目标检测系统检测扫描区域内的微气泡。(2) 通过自动聚焦技术对如此检测到的气泡图像进行聚焦（在z方向）。(3) 利用包括边缘检测和块相关在内的一组简单图像分析技术分析聚焦后的气泡图像。该算法的输出结果是水中微气泡的大小以及两个激光脉冲之间的位移。
