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

摘要

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 read both DVD information layers simultaneously. For fast and near diffraction limited performance, a new circular electrode structure with 64 ring electrodes was studied. Short response times of 50 ms for blazed Fresnel lens profiles and less than 10 ms for binary lens profiles could be realized using the transient nematic effect. Both lens types were characterized in terms of diffraction limited operation, focus efficiency and switching time.