Tehrani Kayvan Forouhesh, Sun Min Kyoung, Karumbaiah Lohitash, Mortensen Luke J
Regenerative Bioscience Center, Rhodes Center for ADS, University of Georgia, Athens, GA 30602, USA.
College of Engineering, University of Georgia, Athens, GA 30602, USA.
Proc SPIE Int Soc Opt Eng. 2017 Mar;10070. doi: 10.1117/12.2252992.
Scanning microscopy methods require movement of the focus in Z coordinates to produce an image of a 3-dimensional volume. In a typical imaging system, the optical setup is kept fixed and either the sample or the objective is translated with a mechanical stage driven by a stepper motor or a piezoelectric element. Mechanical Z scanning is precise, but its slow response and vulnerability to mechanical vibrations and stress make it disadvantageous to image dynamic, time-varying samples such as live cell structures. An alternative method less susceptible to these problems is to change the focal plane using conjugate optics. Deformable mirrors, acoustooptics, and electrically tunable lenses have been experimented with to achieve this goal and have attained very fast and precise Z-scanning without physically moving the sample. Here, we present the use of a liquid lens for fast axial scanning. Liquid lenses have a long functional life, high degree of phase shift, and low sensitivity to mechanical stress. They work on the principle of refraction at a liquid-liquid interface. At the boundary of a polar and an apolar liquid a spherical surface is formed whose curvature can be controlled by adjusting its relative wettability using electrowetting. We characterize the effects of the lens on attainable Z displacement, beam spectral characteristics, and pulse duration as compared with mechanical scanning.
扫描显微镜方法需要在Z坐标中移动焦点以生成三维体积的图像。在典型的成像系统中，光学装置保持固定，样品或物镜通过由步进电机或压电元件驱动的机械载物台进行平移。机械Z扫描精确，但响应速度慢，且易受机械振动和应力影响，这使得它不利于对动态、随时间变化的样品（如实细胞结构）进行成像。一种不太受这些问题影响的替代方法是使用共轭光学器件改变焦平面。人们已经对变形镜、声光器件和电可调透镜进行了实验以实现这一目标，并且在不实际移动样品的情况下实现了非常快速和精确的Z扫描。在此，我们展示了一种用于快速轴向扫描的液体透镜的应用。液体透镜具有较长的功能寿命、高相位偏移度以及对机械应力的低灵敏度。它们基于液 - 液界面处的折射原理工作。在极性液体和非极性液体的边界处形成一个球面，其曲率可以通过使用电润湿调节其相对润湿性来控制。与机械扫描相比，我们表征了该透镜对可实现的Z位移、光束光谱特性和脉冲持续时间的影响。
