Developments in waveguide studies of director profiles

The most powerful optical procedures for characterising in detail the direc tor profile in liquid crystal cells are based on the excitation of guided m odes. Over the past ten to fifteen years a variety of cell geometries have been used. Most of these are not particularly suitable for the study of rea l commercial cells. In this study we briefly review the earlier techniques and go on to discuss recent developments. The implementation of the fully-l eaky guided wave technique which uses low index coupling prisms and involve s monitoring both reflected and transmitted signals with real commercial ce lls is discussed. In addition a further very recent modification using a co nvergent-beam geometry together with the fully-leaky arrangement is conside red. This very latest development paves the way for detailed dynamic studie s of commercial devices as well as giving potential for the exploration of single pixels.