光镊轴向阱位操控及器件安装误差对径向阱位操控的影响

Influences of axial position manipulation and misalignments of optical elements on radial trap position manipulation

光镊利用光学梯度力捕获和操控微小粒子,已经成为深入研究生物分子间相互作用等微观机制的独特技术.光镊光束操控系统一般由扩束输入镜、扩束输出镜、调焦透镜、耦合透镜和压电转镜等光学元器件组成,以保证物镜后瞳充满的前提下实现光镊阱位操控.光镊阱位的三维精确操控是实现光镊位钳和力钳模式的基本条件.本文根据矩阵光学,对基于无穷远校正显微镜的光镊操控光路进行计算,分析扩束输入镜、调焦透镜和物镜轴向位置调整,以及压电转镜、调焦透镜和耦合透镜安装位置误差对光镊径向阱位操控精度的影响,得到了物镜高度调整基本不会影响光镊径向位置操控,压电转镜和调焦透镜的安装位置误差对光镊径向阱位操控精度影响最大等结论,提出了能够实现径向阱位精确操控的轴向阱位动态操控范围,为光镊设计和操控提供理论和实验指导.

Optical tweezers in which a tightly focused laser beam is used to trap micron-sized or nanometer-sized particles have become indispensable tools for measuring the forces and displacements associated with molecular biomechanical events in a noninvasive manner. A complete beam manipulation system is composed of a beam expander input lens, beam expander output lens, focusing lens, piezoelectric translator mirror to control the trap position, with the overfilling degree of the objective entrance aperture retained. The accurate manipulations of trap position in three dimensions are the bases for the realization of the position clamp and force clamp. The optical path of optical tweezers based on infinity corrected conjugate microscope is calculated using matrix optics. The influences on radial trap position manipulation caused by axial position adjustment of focusing lens and objective, and by the installation location error of focusing lens and piezoelectric translator mirror are analyzed. The result shows that axial position adjustment of objective introduces a nominal error in radial trap position manipulation. The misalignments of focusing lens and piezoelectric translator mirror have a greater influence on optical tweezers performances. The theory points out the accurate dynamic axial position adjustment range, which is useful to optical tweezers design and experiments.