采用玻尔兹曼统计法分析光阱刚度的测量精度

朱春丽; 李静

doi:doi:10.3788/ope.20162408.1834

光学精密工程, 2016, 24 (8): 1834, 网络出版: 2016-10-19

采用玻尔兹曼统计法分析光阱刚度的测量精度

Analysis of stiffness measurement precision of optical trap with Boltzmann statistics method

论文大纲

朱春丽 ^*李静

作者单位

中国科学技术大学精密机械与精密仪器系, 安徽合肥 230027

光镊近红外光镊系统光阱刚度测量玻尔兹曼统计法 optical tweezer near-infrared optical tweezer system optical trap stiffness measurement Boltzmann statistics method

摘要

考虑高精度的光阱刚度测量是光阱力测量的关键, 本文提出了采用玻尔兹曼统计法来分析光阱刚度的测量精度。首先, 描述了实验室搭建的近红外光镊系统, 并将其搭建在暗室中的气垫平台上, 以便隔离光干扰和振动干扰。然后, 用四象限光电探测器探测被光镊捕获的微球向后散射的光, 并选用与溶液黏度无关的玻尔兹曼统计法计算样品池底面附近的光阱刚度。最后,分析和讨论了溶液温度的变化、四象限光电探测器的灵敏度、采样频率以及采样时间对光阱刚度测量精度的影响。理论分析及实验计算显示: 溶液温度的变化对光阱刚度的测量影响很小, 但四象限光电探测器的灵敏度对光阱刚度测量精度影响较大。考虑采样的完整性和数据处理速度, 采样频率通常取为被捕获颗粒拐角频率的5~10倍。对于本文搭建的近红外光镊测量系统, 采样时间取为1~7 s时, 可以保证高精度地测量光阱刚度。

Abstract

The stiffness measurement precision of an optical trap is a key in optical force measurement, so this paper proposes a method based on Boltzmann statistics to analyze the stiffness measurement precision of the optical trap. Firstly, a near infrared optical tweezer was introduced and it was built on an air cushion platform in a dark room to isolate light interference and vibration interference. Then, a quadrant photodiode was used to detect the backscatter light of a microsphere captured by the tweezer and the Boltzmann statistics method having no relation with solution viscosity was adopted to calculate the optical trap stiffness near the bottom surface of the sample cell. Finally, the influences of the solution temperature, the sensitivity of the quadrant photodiode, sampling frequency, and the sampling time on the accuracy of the optical trap stiffness measurement were analyzed and discussed. Theoretical analysis and practical calculation results indicate that the solution temperature has a little effect on the measurement, but the sensitivity of the quadrant photodiode influences on the measurement precision greatly. In consideration of complete sampling and higher data processing speeds, the sampling frequency is set 5 to 10 times as great as the knee frequency of the optically trapped microsphere. For the measurement setup proposed in this paper, the sampling time is set in the range 1-7 s, which ensures the higher measurement precision of the optical trap.

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朱春丽, 李静. 采用玻尔兹曼统计法分析光阱刚度的测量精度[J]. 光学精密工程, 2016, 24(8): 1834. ZHU Chun-li, LI Jing. Analysis of stiffness measurement precision of optical trap with Boltzmann statistics method[J]. Optics and Precision Engineering, 2016, 24(8): 1834.

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