Proceedings of the 6 th International Workshop on Adaptive Optics for Industry and Medicine. Ed. J.C. Dainty. Galway, June 2007. 1 CONVERGING AND DIVERGING LIQUID CRYSTAL LENSES A. K. KIRBY, P. J. W. HANDS, G. D. LOVE Durham University, Dept. of Physics, Durham, DH1 3LE, UK We report on recent work on the application of liquid crystals to variable lenses. We demonstrate the construction and operation of a novel and simple form of modal LC lens which offers both converging and diverging modes of operation, as well as tip/tilt and astigmatism. 1. Introduction Considerable work has been carried out in the field of electronically variable lenses (see, e.g. [1-3] and these proceedings). We have reported previously on the design and production of modal liquid crystal (LC) lenses [4-5] and their use as adaptive focus elements. We have recently developed a new LC device which overcomes some of the limitations of the modal LC lens; • The fabrication of the modal LC lens is complicated by the requirement for a high-resistance electrode, which is normally achieved by depositing an extremely thin layer of Indium Tin Oxide (ITO) onto a glass substrate. Producing the required thickness with good uniformity is problematic, and the deposition process typically has a low yield. The new LC device has a simple construction and requires only medium-resistance ITO coated glass substrates, which are rather easier to manufacture. • A normal modal LC lens can be driven to provide a positive (converging) lens of variable power. The new device can also be driven to provide a lens which can be varied from positive to negative optical powers. The effective optical throw of the lens, for a given cell thickness, is doubled compared to the modal lens. Correspondingly the relaxation time, for a given lens throw, is reduced by a factor of approximately 4.