Technique for local pretilt measurement in nematic liquid crystals

We propose a simple technique for local measurement of the nematic pretilt on a solid substrate, using standard planar orientation on the opposite sur face. We obtain the pretilt from the variation of the cell birefringence un der weak electric field. We apply experimentally the proposed technique to measure the pretilt of the nematic 5CB on various substrates, We discuss th e advantages and the limitations of our technique.