Gholami Mahmoodabadi Reza, Taylor Richard W, Kaller Martin, Spindler Susann, Mazaheri Mahdi, Kasaian Kiarash, Sandoghdar Vahid
Opt Express. 2020 Aug 31;28(18):25969-25988. doi: 10.1364/OE.401374.
Interferometric scattering (iSCAT) microscopy is an emerging label-free technique optimized for the sensitive detection of nano-matter. Previous iSCAT studies have approximated the point spread function in iSCAT by a Gaussian intensity distribution. However, recent efforts to track the mobility of nanoparticles in challenging speckle environments and over extended axial ranges has necessitated a quantitative description of the interferometric point spread function (iPSF). We present a robust vectorial diffraction model for the iPSF in tandem with experimental measurements and rigorous FDTD simulations. We examine the iPSF under various imaging scenarios to understand how aberrations due to the experimental configuration encode information about the nanoparticle. We show that the lateral shape of the iPSF can be used to achieve nanometric three-dimensional localization over an extended axial range on the order of 10 µm either by means of a fit to an analytical model or calibration-free unsupervised machine learning. Our results have immediate implications for three-dimensional single particle tracking in complex scattering media.
干涉散射（iSCAT）显微镜是一种新兴的无标记技术，专为纳米物质的灵敏检测而优化。先前的iSCAT研究通过高斯强度分布来近似iSCAT中的点扩散函数。然而，最近在具有挑战性的散斑环境中以及在扩展的轴向范围内追踪纳米颗粒迁移率的努力，需要对干涉点扩散函数（iPSF）进行定量描述。我们提出了一个用于iPSF的稳健矢量衍射模型，并结合实验测量和严格的有限时域差分（FDTD）模拟。我们在各种成像场景下研究iPSF，以了解由于实验配置引起的像差如何编码有关纳米颗粒的信息。我们表明，通过拟合解析模型或无校准无监督机器学习，iPSF的横向形状可用于在约10 µm的扩展轴向范围内实现纳米级三维定位。我们的结果对复杂散射介质中的三维单粒子追踪具有直接影响。
