2 March 2017 Fast axial scanning for 2-photon microscopy using liquid lens technology
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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, acousto-optics, 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 electro-wetting. We characterize the effects of the lens on attainable Z displacement, beam spectral characteristics, and pulse duration as compared with mechanical scanning.
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Kayvan Forouhesh Tehrani, Min Kyoung Sun, Lohitash Karumbaiah, Luke J. Mortensen, "Fast axial scanning for 2-photon microscopy using liquid lens technology", Proc. SPIE 10070, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XXIV, 100700Y (2 March 2017); doi: 10.1117/12.2252992; https://doi.org/10.1117/12.2252992

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