8 February 2018 Method of preparing a tunable-focus liquid-crystal (LC) lens
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A liquid crystal (LC) lens is prepared by controlling the alignment of a LC using a homogeneous polyimide (PI) layer and a homeotropic PI layer. The rubbed homogeneous PI layer has a concave surface and the homeotropic PI layer is flat. The LC sandwiched between the two PI layers obtains a hybrid alignment which has the largest gradient of refractive index (GRIN) distribution. The LC layer exhibits a lens character because of its convex shape. Since the effective refractive index of the LC is larger than that of the homogeneous PI, the LC lens can focus a light with the shortest focal length in the voltage-off state. By applying an external voltage, the LC molecules can be reoriented along the electric field. As a result, the focal length of the LC lens is reduced. The focal length of the LC lens can be tuned from ~30 to ~120 μm when the voltage is changed from 0 to 7 Vrms. This LC lens has the advantages of no threshold, low operating voltage, and simple fabrication.
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Xiaolong Li, Xiaolong Li, Zuowei Zhou, Zuowei Zhou, Hongwen Ren, Hongwen Ren, } "Method of preparing a tunable-focus liquid-crystal (LC) lens", Proc. SPIE 10555, Emerging Liquid Crystal Technologies XIII, 105551A (8 February 2018); doi: 10.1117/12.2286584; https://doi.org/10.1117/12.2286584

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