Design of a four-sided magnetic circuit for an optical pickup actuator for multilayer high-density optical disks

Abstract

Large-capacity optical storage materials have reached a stage of relative maturity, but progress in the design of optical pickup actuators is currently slow. To improve the reading and writing capabilities of optical recording systems, we propose a design for a four-sided magnetic circuit for an optical pickup actuator for multilayer high-density optical disks that make full use of the space around the actuator. The basic magnetic circuit model in this design, which is derived by the equivalent magnetic charge method, can be applied to the design of all such actuators. The static and dynamic magnetic circuit evaluation parameters established in this paper can be used conveniently and directly to improve the magnetic circuit performance of the actuator. The design was verified by finite element simulation, and linear working ranges of ±2.6 mm, ±0.6 mm, and ±16° were found in the focusing, tracking, and tilting degrees of freedom. This is sufficient to compensate for errors in phase-change optical disks with more than 50 layers in high-speed rotation. The theoretical servo accuracy of the actuator can reach tens of nanometers. This can be used with a dual-objective-lens layout that can support layer-skip reading and writing of optical disks with an effective working bandwidth greater than 10 000 Hz.