Abstract High-precision axial displacement tracking of trapped beads is an indispensable feature of optical tweezers in advanced single-molecule studies. Here, we demonstrate an alternative method that enables axial calibration and tracking to be carried out on the same sample to avoid unnecessary errors. This method works by applying a dynamic force balance on a bead trapped between a piezoelectrically driven glass slide and an optical trap; in this configuration, the bead can be stopped precisely in different positions and imaged by a camera. A simple gradient algorithm is used to process the images into calibration data. After optimization of the calibration method and samples, our method exhibited better than 5 nm experimental axial resolution, with a measurement range of +/-500 nm around the objective focus at video speed. Moreover, for the first time, the deviation of the focusing plane in dual-trap optical tweezers was measured. We confirmed the axial deviation between two optical traps in our setup to be ~10 nm, corresponding to a force spectroscopy gage error of ~1 pN. This approach offers a favorable solution for in-use setup updating, as it can be seamlessly integrated into any optical tweezers system without requiring new hardware updates.

中文翻译：

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光学捕获珠的轴向位移校准和跟踪

摘要 捕获微珠的高精度轴向位移跟踪是光镊在高级单分子研究中不可或缺的功能。在这里，我们展示了一种替代方法，该方法可以对同一样本进行轴向校准和跟踪，以避免不必要的错误。这种方法的工作原理是在压电驱动的载玻片和光阱之间捕获的珠上施加动态力平衡；在这种配置中，珠子可以精确地停在不同的位置并由相机成像。使用简单的梯度算法将图像处理成校准数据。在优化校准方法和样品后，我们的方法表现出优于 5 nm 的实验轴向分辨率，在视频速度下，在目标焦点周围的测量范围为 +/-500 nm。而且，首次测量了双阱光镊聚焦平面的偏差。我们确认我们设置中两个光阱之间的轴向偏差为 ~10 nm，对应于 ~1 pN 的力谱仪误差。这种方法为在用设置更新提供了一种有利的解决方案，因为它可以无缝集成到任何光镊系统中，而无需新的硬件更新。