Direct Servo Error Signal Detection Method from Recorded Micro-Reflectors

Micro-reflector data storage is a practical candidate for post Blu-ray optical memory. It is based on bit-wise recording in a monolithic recording medium with a reference layer. In our conventional drive system, the objective lens position is controlled by servo error signals obtained from the reference layer. However, this servo system is not sufficiently robust against recording medium tilt and decentering because the servo error signals are not directly obtained from recorded marks. Here, we present a novel direct three-dimensional servo method to resolve this problem. In this servo method, the objective lens position is controlled by servo error signals directly obtained from recorded marks, or micro-reflectors. We verified the validity of the novel servo method by simulations. Furthemore, we demonstrated the improvement of the envelope and the jitter of a RF signal by the novel servo method experimentally.