Wan Jingfang, Huang Yanan, Jhiang Sissy, Menq Chia-Hsiang
Department of Mechanical Engineering, The Ohio State University, 201 West 19th Avenue, Columbus, Ohio 43210, USA.
Appl Opt. 2009 Sep 1;48(25):4832-41. doi: 10.1364/AO.48.004832.
We present real-time in situ calibration of an optically trapped probing system. In the probing system, a micro/nanobead is stably trapped around the minimum of the field potential to serve as the measurement probe, whereas the random thermal force tends to destabilize it and causes Brownian motion around the equilibrium. The weighted recursive least-squares algorithm is applied to recursively update the system's parameters, such as the state transition coefficient, and to estimate specific system response and the unknown variance of the Gaussian white noise in real time according to the probe's motion. The real-time recursive algorithm was first applied to real-time calibration of measurement sensitivity and trapping stiffness for the case that the local temperature and the damping coefficient of the probe are known. It was then applied to estimate the probe's local temperature in real time. Two experiments were designed to illustrate the applicability of the real-time calibration method. The experimental results show that the recursive algorithm is able to real-time calibrate the trapping stiffness of the probing system and the measurement sensitivity of the back-focal-plane interferometry employed for position measurement. The experimental results also show that the method can estimate the probe's local temperature in real time.
我们展示了一种光学捕获探测系统的实时原位校准。在该探测系统中，一个微纳珠稳定地捕获在势场最小值附近，用作测量探针，而随机热力往往会使其不稳定并导致其在平衡位置周围做布朗运动。加权递归最小二乘算法被用于递归更新系统参数，如状态转移系数，并根据探针的运动实时估计特定的系统响应以及高斯白噪声的未知方差。该实时递归算法首先应用于在已知探针局部温度和阻尼系数的情况下对测量灵敏度和捕获刚度进行实时校准。然后将其应用于实时估计探针的局部温度。设计了两个实验来说明实时校准方法的适用性。实验结果表明，该递归算法能够实时校准探测系统的捕获刚度以及用于位置测量的背焦平面干涉测量法的测量灵敏度。实验结果还表明，该方法能够实时估计探针的局部温度。
