Hu Chunguang, Su Chenguang, Yun Zelin, Wang Sirong, He Chengzhi, Gao Xiaoqing, Li Shuai, Li Hongbin, Hu Xiaodong, Hu Xiaotang
Appl Opt. 2018 Feb 10;57(5):1241-1246. doi: 10.1364/AO.57.001241.
Beads trapped in optical tweezers are aligned along the optical propagation direction, which makes it difficult to determine the number of beads with bright-field microscopy. This problem also dramatically influences the measurement of the optical trapping based single-molecule force spectroscopy. Here, we propose a video processing approach to count the number of trapped micro-objects in real time. The approach uses a normalized cross-correlation algorithm and image enhancement techniques to amplify a slight change of the image induced by the entry of an exotic object. As tested, this method introduces a ∼10% change per bead to the image similarity, and up to four beads, one-by-one falling into the trap, are identified. Moreover, the feasibility of the above analysis in a moving trap is investigated. A movement of the trap leads to a fluctuation of less than 2% for the similarity signal and can be ignored in most cases. The experimental results prove that image similarity measurement is a sensitive way to monitor the interruption, which is very useful, especially during experiments. In addition, the approach is easy to apply to an existing optical tweezers system.
被光镊捕获的珠子会沿着光传播方向排列，这使得用明场显微镜确定珠子数量变得困难。这个问题也极大地影响了基于光镊的单分子力谱测量。在此，我们提出一种视频处理方法来实时计数被捕获的微物体数量。该方法使用归一化互相关算法和图像增强技术来放大由外来物体进入引起的图像微小变化。经测试，此方法给图像相似度引入了每个珠子约10%的变化，并且能识别多达四个珠子逐个落入陷阱的情况。此外，还研究了上述分析在移动陷阱中的可行性。陷阱的移动导致相似度信号的波动小于2%，在大多数情况下可以忽略不计。实验结果证明，图像相似度测量是监测中断的一种灵敏方法，这非常有用，尤其是在实验过程中。此外，该方法很容易应用于现有的光镊系统。
