Fast switching liquid crystal lenses for a dual focus digital versatile disc pickup

We investigated two types of liquid crystal (LC) lenses, the convex LC lens and the adaptive LC lens. Both lens types were designed and fabricated for integration in a novel pickup head for dual layer digital versatile discs (DVDs). The polarization dependent focal length of LC lenses was used to re ad both DVD information layers simultaneously. For fast and near diffractio n limited performance, a new circular electrode structure with 64 ring elec trodes was studied. Short response times of 50 ms for blazed Fresnel lens p rofiles and less than 10 ms for binary lens profiles could be realized usin g the transient nematic effect. Both lens types were characterized in terms of diffraction limited operation, focus efficiency and switching time. (C) 2001 Elsevier Science B.V. All rights reserved.