IMAGING PERFORMANCE OF THE LIQUID-CRYSTAL-ADAPTIVE LENS WITH CONDUCTIVE LADDER MESHING

The Liquid-crystal-adaptive lens (LCAL) is an electro-optical device t hat utilizes a graded index of refraction to bring light to focus. A s et of electrodes controls the index variation in a liquid-crystal thin film. One can vary the focal length of the LCAL by changing the volta ges applied to the device. The discrete nature of the electrodes cause s phase aberrations. We introduce a novel electrode architecture, call ed conductive ladder meshing (CLM), that we developed to greatly reduc e the static phase aberration (caused by the electrode structure). To reduce the dynamic phase aberration (associated with inaccurate voltag es), we used a simulated-annealing voltage-dithering technique. The co herent transfer function of the LCAL was derived so that the performan ce of the CLM LCAL could be predicted theoretically. Theoretical analy sis indicates that the CLM LCAL scatters less than 30% of incident lig ht compared with scattering of 65% in the previous version. The focal- spot performance of the spherical LCAL was measured under coherent ill umination for plane-wave illumination. Because of the improved quality of the spherical LCAL, true imaging experiments are demonstrated for a single incoming polarization under white-light illumination. Images formed by the spherical LCAL are comparable with those formed by a fix ed lens in terms of resolution, although the contrast is worse. (C) 19 97 Optical Society of America.