Application of a Liquid Crystal Lens to an Optical Disc Memory Device

光学头由于其对物镜进行调焦的机械控制，显示出其小型化和高速接入的局限性。这个研究项目的目的是将一个液晶透镜应用到光学头上，其焦距可以通过施加电压来控制。在具有孔型电极和折射率径向分布的液晶电池中产生轴对称非均匀电场；也就是说，液晶微透镜可以通过在非均匀电场中的分子取向效应得到。本文研究了具有非对称电极结构的平面电极和空穴电极的均匀排列和混合排列液晶微透镜的光学特性和响应特性。在电极结构不对称的均匀排列液晶微透镜中，在垂直于分子取向的方向上，电极结构产生的偏斜线使透镜性能恶化。这种偏斜线通过采用杂交排列的分子取向来消除。然而，由于透镜中心的移位效应，透镜的性能并没有得到很大的改善。然后，通过抑制这些恶化因素，可以预期更显著的改善。在此基础上，制备了具有小孔图案的均匀排列的液晶微透镜，并对其光学性能进行了研究。由于分子倾斜方向均匀，可以获得折射率的同心圆形和无缺陷分布特性；即消除了迄今所制备的透镜中对透镜性能的一些不利影响，透镜性能得到了不断的改善。当在微透镜上突然施加高电压时，即使采用对称电极结构的液晶微透镜，在施加电压后也会立即出现偏斜线。在卸除电压后，偏斜线不会消失，而且会持续很长时间。采用施加偏置电压的方法可以改善响应特性，抑制偏斜线的产生。外加电压在偏置电压和目标电压之间变化。这样就不会观察到偏斜线，提高了液晶微透镜的光学性能和再现性。此外，采用施加偏置电压的方法可以改善液体微透镜的响应特性，抑制偏斜线的产生。采用施加偏置电压的方法可以抑制T偏斜线。然后将微透镜应用于光学头的要求今天似乎得到了满足。目前对光学头应用微透镜的要求似乎得到了满足。讨论了液晶微透镜在光学头上应用的可能性。少

An optical head shows a limitation of its miniaturization and highspeed accessions because of its mechanical control of an object lens for focus adjustment. The aim of this research project is applying a liquid crystal lens, of which focal length can be controlled by applying voltage, to an optical head.An axially symmetric nonuniform electric field is produced in a liquid crystal cell with a hole-patterned electrode, and radial distribution of refractive indices; that is, a liquid crystal microlens can be obtained by a molecular orientation effect in a nonuniform electric field. Optical properties and response properties of a homogeneously aligned or a hybrid-aligned liquid crystal microlens with an asymmetric electrode structure of a hole-patterned electrode and a flat electrode have been investigated. In the homogeneously aligned liquid crystal microlens with the asymmetric electrode structure, electrode structure, a disclination line which worsens the lens properties, is observed i … More n the direction perpendicular to the molecular orientation. Such a disclination line is eliminated by adopting a hybrid-aligned molecular orientation. However, the lens properties are not improved very much since a shifting effect of the lens center appears. Then more significant improvements can be expected by suppressing such deteriorating factors. Then, a homogeneously aligned liquid crystal microlens with hole patterns on both surfaces of the substrates is prepared and its optical properties are investigated. Concentrically circular and defect-free distribution properties of refractive indices can be obtained as a result of uniform tilt direction of the molecules; that is, some detrimental effects of lens properties in hitherto prepared lenses are eliminated and the lens properties are eceedingly improved. When a high voltage is suddenly applied across the microlens, the disclination lines appear immediately after the voltage is applied even if the liquid crystal microlens with the symmetrical electrode structure is used. The disclination lines does not disappear and it remains for a long period of time after voltage is removed.The response properties can be improved and the creation of the disclination lines can be suppressed by using a method of bias voltage application. The applied voltage is changed between the bias voltage and the target voltage. Then no disclination lines are observed, and the optical properties of the liquid crystal micro-lens and their reappearance can be improved. In addition, the response properties of the liquid microlens can be improved and the creation of the disclination lines can be suppressed by using the method of the bias voltage application. T disclination lines can be suppressed by using the method of the bias voltage application. Then a requirement for applying the microlens to the optical head today are seemed to be satisfied. requirement for applying the microlens to the optical head today are seemed to be satisfied.The possibility of application of the liquid crystal microlens to the optical head is discussed. Less