Dual-Layer-Compatible Optical Head: Integration with a Liquid-Crystal Panel

A liquid-crystal (LC) panel was integrated into a two-axis electromagnetic actuator in order to realize a dual-layer-compatible optical head for “Blu-ray Disc” systems. This head configuration can actively compensate the cover layer difference of up to nearly 40 μm thickness. Our novel driving method of mixing the controlling signals into four metal wire suspensions can maintain the dynamic performance of the optical head and has achieved a servo bandwidth beyond 5 kHz both in the focusing and in the tracking directions. We also confirmed its optical performance by recording and reproducing 17PP signals on a dual-layer phase-change disc and verified a 46.6 GB storage capacity. In addition, our optical head has interlayer accessibility within 20 ms and satisfies the requirement for a dual-layer disc system. By using this integrated optical head instead of a beam expander, a compact optical pickup for a dual-layer storage system can be realized.