Liquid crystal-based planar optical elements destined for control of direction of light propagation are investigated. There are diffractive active lenses, dynamic diffraction gratings, tuneable prisms, etc. Among the attractive features of such optical elements are non-mechanical tunability, low driving voltage, relatively low cost, and small sizes. In fact, they can be much smaller and have less weight that conventional glass and plastic analogues [1-3]. The key role in achieving the needed optical properties plays a liquid crystal due to its unique features - electric and optical anisotropies coupled with high fluidity. A certain distribution of an external electric field or inhomogeneous boundary conditions leads to a spatial distribution of the liquid crystal molecules (director) that, in turn, forms an optically inhomogeneous medium. This medium affects the light propagation in the required way.
In the present work, we study formation of a desired liquid crystal director distribution by the use of inhomogeneous alignment, i.e. non-uniform distributions of anchor energy or the pre-tilt angle. Such an approach enables one to control the optical element by a uniform electric field when only two continues electrodes are needed. This means that there are no constructive regularities, e.g. a periodic arrangement of the electrodes or thickness, which often have undesired impact on diffractive characteristics of the optical elements. Moreover, periodicity and diffraction efficiency of such kind of the optical elements can be higher than the optical elements controlled by an inhomogeneous electric field [1-3].
As examples of practical applications, a reflective lens utilising cholesteric liquid crystal and a projection optical system for hypothetic near eye displays that can be built into a contact lens or glasses will be reported.
 S. Valyukh, I. Valyukh, V. Chigrinov, H. S. Kwok, and H. Arwin, “Liquid crystal light deflecting devices based on nonuniform anchoring,” Appl. Phys. Lett. 97, 231120 (2010).
 S. Valyukh, V. Chigrinov, “Optimization of Liquid-Crystal Phase Arrays,” SID Symposium Digest 42, pp. 1691-1694 (2011).
 S. Valyukh, V. Chigrinov, H. S. Kwok, and H. Arwin, “On liquid crystal diffractive optical elements utilizing inhomogeneous alignment, ” Optics Express, 20, pp. 15209-15221 (2012).
4th Workshop on Liquid Crystals for Photonics 2012, 9-11 December, 2012, Hong Kong