FLUORESCENT CONFOCAL MICROSCOPY EXPLORATION OF 3D LIQUID CRYSTAL STRUCTURES

液晶显示器是显示信息的低功耗方法的前沿。由于巨大的平面屏幕市场，许多关于液晶在光学显示器中的应用的研究仍在进行中，一些最新一代的设备使用了一种与传统扭曲向列显示完全不同的方法。该器件不需要维持电压来产生暗（或光）状态，而是由表面起伏光栅基板构成，其产生在二维甚至三维上变化的定向排列。这导致两个不同的光学稳定状态在零施加电压，一个出现在交叉偏振光下暗，而另一个，光。电源只需要在这些状态之间切换。目前正在开发用于商业应用的两种这样的结构是ZBD显示器开发的顶顶双稳器件（ZBD）和惠普开发的后对齐双稳器件（PABN）。为了充分了解液晶导向在这些新结构中的行为，我们建议使用荧光共聚焦显微镜（FCM）。对于传统的平移不变结构，解开定向结构的最佳技术是埃克塞特大学首创的光波导技术。然而，在基板平面上的分辨率受到探测激光束直径的限制，只有几微米，而且它不能用于探测新周期结构中发现的完整三维轮廓。当用于控制液晶材料的结构从一维移动到二维时，我们在这里提出了一种研究它们所需的表征技术。

Liquid crystal displays are at the forefront of low power methods for displaying information. Because of the massive flat screen market place much research is still going on into the use of liquid crystals in optical displays, and some of the latest generation of devices use a radically different approach to that of the conventional twisted nematic displays. Instead of requiring a voltage to be maintained to produce the dark (or light) state, the devices are constructed from surface relief grating substrates that produce a director alignment that varies in two or even three dimensions. This results in two optically distinct stable states at zero applied voltage, one appearing dark under crossed polarisers, and the other, light. Power only needs to be applied to switch between these states. Two such structures currently in development for commercial applications are the zenithal bistable device (ZBD), developed by ZBD displays, and the post aligned bistable device (PABN) developed by Hewlett-Packard. To understand fully the behaviour of the liquid crystal director in these new structures we here propose to use Fluorescence confocal microscopy (FCM). For conventional translationally invariant structures the best techniques for unravelling the director structure are optical waveguide techniques, pioneered in Exeter. However, the resolution in the plane of the substrate is limited by the diameter of the probing laser beam to a few microns and further it cannot be used to probe the full three dimensional profile found in the new periodic structures. As the structures used to control the liquid crystal material move from one-dimension to two-dimensions we here propose a characterisation technique required to study them which follows suit.