Super-resolution optical microscopy using transmissive micro structures

高分辨率的物体细节检测对于许多研究、开发和制造领域都是必不可少的。一个简单的选择是经典的光学显微镜。然而，这种方法的分辨率受到阿贝所描述的分辨率限制的限制。因此，过去人们一次又一次地研究克服这一限制的方法。提高分辨率的一种方法是将微球应用到对象的表面。可实现的分辨率主要取决于微球的直径和微球与周围介质之间的折射率差。在文献中，用标准光学显微镜来分辨间隔为&lt；100 nm的物体，其对应的分辨率比波长小得多。目前，还没有通用的模型来解释这种实验观察到的效应。然而，广泛的理解对于评估该方法的局限性和潜力以及优化所使用的微结构的成像特性是至关重要的。在文献中，实验数据仅限于对球形微结构的研究，这些微结构既没有显示无失真的图像，也没有显示更大的视场。对偏离球面形状的微结构的研究仅限于对其聚焦特性的模拟，没有实验结果。因此，该项目有两个目标：1.发展一个理论模型来解释低于阿贝衍射极限的分辨率的影响(以下称为超分辨率)：与文献相反，这里提出的模型不是基于麦克斯韦方程的解，而是基于标量衍射理论的更简单的原理，特别是为了理解超分辨率的扩展惠更斯-菲涅尔方法。这一方法将被用来以一种简化的方式描述逝去的场与微结构的耦合。上面概述的过程导致了计算时间的减少，并允许根据成像特性迭代优化微结构。2.理论研究结果的实验实现：虽然到目前为止，文献中只对球形结构进行了实验研究，非球面结构仅通过模拟来描述，但在我们的建议中，球面结构和自由曲面微结构是通过直接激光写入来制备的，并进行了光学表征，从而验证了超分辨的效果。因此，提出的项目使得有可能获得一个有充分基础的理论理解来解释超分辨率的影响。它还将直接激光写入球面和非球面微结构的超分辨光学显微镜带入实际应用。

The examination of object details with high resolution is essential for many areas of research, development and fabrication. A simple option is the classical light microscopy. The resolution of this approach is, however, restricted by the resolution limit described by Abbe. Therefore, approaches have been investigated again and again in the past to overcome this limit. One way to increase the resolution is the application of microspheres to the surface of the object. The achievable resolution essentially depends on the diameter of the microsphere and the refractive index difference between the microsphere and the surrounding medium. In the literature, objects with a separation <100 nm were resolved with a standard light microscope, which corresponds to a resolution much smaller than the wavelength. Presently, no general model is available to explain this experimentally observed effect. However, a broad understanding is essential for the evaluation of the limits and potential of the method as well as for optimizing the imaging properties of the microstructures used. In the literature, experimental data are limited to studies on spherical microstructures, which neither show distortion-free images nor larger fields of view. Investigations of microstructures that deviate from a spherical shape are limited to simulations of their focussing properties; experimental results are not available.Therefore, the proposed project has two objectives: 1. Development of a theoretical model to explain the effect of a resolution below the Abbe diffraction limit (in the following termed super-resolution): In contrast to the literature, the model proposed here is not based on the solution of Maxwell's equations, but on the simpler principles of scalar diffraction theory, specifically an extended Huygens-Fresnel approach in order to understand the effects of super-resolution. This approach will be employed in the project to describe the coupling of evanescent fields into the microstructure in a simplified way. The procedure outlined above leads to a reduction of the computation time and allows an iterative optimization of the microstructures in term of imaging properties. 2. Experimental implementation of the theoretical findings: While in the literature so far only spherical structures were investigated experimentally and aspheric structures were only described by simulations, in our proposal spheres and freeform-microstructures are fabricated by direct laser writing, optically characterized and in this way the effect of the super-resolution will be verified. The proposed project thus makes it possible to obtain a well-grounded theoretical understanding to explain the effect of super-resolution. It also brings the super-resolution optical light microscopy using spherical and aspherical microstructures fabricated by direct laser writing to a practical application.