Design and control of high precision 3D pickup actuators for near field recording system

In the NFR system, since the gap between SIL and disc is under 100 nm, the precise control of actuator is required. For the stable gap control, performance of actuator should be improved. When the mass center and centroid of actuator is not coincide with each other, coupling between linear and rotational motion appears and in near field recording system, it affects directly readout performance. Therefore, by constructing general mathematical model of actuator which can reflect coupling motion, quantity of coupling was analyzed. Moreover, by sensitivity analysis, critical variables which affect coupling motion were selected and by applying optimal value to the system, coupling effect was decreased effectively. By measuring transfer function of actuator, analytic approach was verified.