Thalhammer Gregor, Obmascher Lisa, Ritsch-Marte Monika
Opt Express. 2015 Mar 9;23(5):6112-29. doi: 10.1364/OE.23.006112.
Direct measurement of optical forces based on recording the change of momentum between the in- and outgoing light does not have specific requirements on particle size or shape, or on beam shape. Thus this approach overcomes many of the limitations of force measurements based on position measurements, which require frequent calibration. In this work we validate the achievable accuracy for direct force measurements in the axial direction for a single beam optical tweezers setup, based on numerical simulations and experimental investigations of situations, where the true force is known. We find that for typical experimental situations a good accuracy with an error of less than 1 % of the maximum force can be achieved, independent of particle size or refractive index, provided that the total amount of light scattered in the backward direction is also taken into account, which is easy to accomplish experimentally. Due to the inherent particle shape independence of the direct force measurement method, these findings support that it provides accurate results for 3D force measurements for particles of arbitrary shape.
基于记录入射光和出射光之间动量变化的光力直接测量方法，对粒子大小、形状或光束形状没有特定要求。因此，这种方法克服了基于位置测量的力测量方法的许多局限性，后者需要频繁校准。在这项工作中，我们基于数值模拟以及对已知真实力的情况进行的实验研究，验证了单光束光镊装置在轴向进行直接力测量时可达到的精度。我们发现，对于典型的实验情况，只要考虑向后散射的总光量（这在实验上很容易实现），就可以实现良好的精度，误差小于最大力的1%，且与粒子大小或折射率无关。由于直接力测量方法固有的与粒子形状无关的特性，这些发现支持了该方法能为任意形状的粒子提供准确的三维力测量结果。
