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。由于巨大的平板屏幕市场，许多关于液晶在光学显示器中的使用的研究仍在进行中，一些最新一代的设备使用了与传统扭曲向列相显示器完全不同的方法。这些器件不需要维持电压来产生暗(或亮)状态，而是由产生在两个甚至三个维度上变化的导向器对准的表面浮雕光栅衬底构造而成。这导致在零电压下产生两个光学上截然不同的稳定状态，一个在交叉偏振器下看起来很暗，而另一个看起来很亮。只需通电即可在这些状态之间切换。目前正在为商业应用开发的两种这样的结构是由ZBD Display开发的天顶双稳器件(ZBD)和由惠普开发的后对准双稳器件(PABN)。为了充分了解液晶指向矢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，解开导向器结构的最佳技术是由埃克塞特首创的光波导技术。然而，由于探测激光的直径只有几微米，基片平面上的分辨率受到限制，不能用来探测新的周期结构中发现的完整的三维轮廓。随着用于控制液晶材料的结构从一维转移到二维，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.