Decoupled direct tracking control system based on use of a virtual track for multilayer disk with a separate guide layer

Abstract

We developed a decoupled direct tracking control system for multilayer optical disk that uses a separate guide layer. Data marks are recorded on a recording layer immediately above the guide layer by using two spatially separated spots with different wavelengths. Accurate data mark recording requires that the relative positions of the corresponding spots on the recording layer and guide layer are maintained. However, a disk tilt can shift their relative positions and cause previously recorded data marks to be overwritten. Additionally, a two-input/two-output control system is susceptible to mutual interference phenomenon between the two outputs, which can destabilize tracking control. A tracking control system based on use of data marks previously recorded as a virtual track has been developed that prevents spot shifting and mutual interference even if the disk tilt reaches 0.7°, thereby preventing overwriting.

High-speed focus servo control system using Nyquist aperture mounted on a triaxial actuator for holographic disc drive system

“…One solution to this problem is to use a separate guide layer with a groove structure and multiple recording layers without a groove structure. [6][7][8] This simple disc structure reduces the disc fabrication cost because the process of forming a groove structure on the recording layers is eliminated. However, the practical data transfer rate is thought to be around megabits per second 9 because recorded data are accessed sequentially (bit-by-bit).…”