Liquid Crystal Microlenses

Fixed focal length microlenses and arrays with lens diameters of a few to several hundred micrometers are extensively used in many optical systems such as projection lithography [1-3], optical coherence microscopy (OCM) [4], Shack-Hartmann sensors [5], and back lighting for projection liquid crystal displays (LCDs) [6]. 

Unlike traditional glass lenses, focal lengths of microlenses can be tuned electrically or mechanically by various mechanisms. In this chapter we will describe a series of electrically tuned microlenses (1) liquid lenses covered with a thin polymer film and driven by electrostatic forces (2) lens arrays utilizing dielectrophoretic effect (3) electrochemically activated liquid lenses (4) tunable liquid lenses actuated by electrowetting and (5) liquid crystal (LC) lenses. 

The use of nematic liquid crystals (LCs) for making tunable focus microlenses was described as early as 1979 by Sato. He showed that LC cells shaped into planoconvex or planoconcave lenses could be controlled electrically to form microlenses [1]. In 1984, Kowel et al. used a simple parallel electrode structure in a uniform thickness LC cell. Each electrode was subjected to different voltages to demonstrate the optical focusing ability of LC microlenses [2,3]. 

Unlike traditional glass lenses, focal lengfhs of microlenses can be tuned by various electrical and mechanical techniques. Chapter 5, Electrically Driven Tunable Microlenses, describes several examples of electrically tuned microlenses including liquid-crystal-based lenses and liquid lenses driven by electrostatic forces, dielecfrophorefic forces, electrowetting, and electrochemical reactions. 

The commercial application of polymer blend technology has grown significantly such that, today, compositions are available with properties that once were substantially unattainable with homopolymers. To date, polymer blends have been applied in optical fibers [13,14], microlenses [15], liquid crystal display components [16,17], solar cells [18-20], nonionizing radiation detection [21] and polymer light-emitting diodes [22-24]. In particular, the use of developed polymer blends in optoelectronics applications appears unlimited. Polymer blends may also provide model systems in statistical physics when studying the fundamental aspects of equilibrium and nonequilibrium properties [3], optical properties [25], and mechanical and electrical properties [26]. 

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