Dynamic Tilt Control of SIL with 4-axis Actuator in NFR System

Abstract

In the near field recording (NFR) system, tilt margin between disc and solid immersion lens (SIL) is affected by the geometric features of the SIL. If the tilt angle is larger than the allowable tolerance, SIL can touch the surface of a disc and stable read-out of the recorded data or data writing may be difficult. Because tangential as well as radial tilt angle of real disc is so considerable in NFR system with low tilt tolerance, we propose a 4-axis actuator for active tilt compensation to diminish radial and tangential tilt errors as well as focusing and tracking errors between disc and SIL in this paper. Disc tilt and tilt detectable gap error signal (GES) are measured simultaneously and compared to examine the relation of two signals. For this, we newly designed and tested a 4-axis actuator and also established GES-based tilt error detecting test-bed. As a result, we confirmed the mechanical characteristics of the 4-axis actuator and the decrease of tilt errors in radial and tangential tilt directions. We expect that this tilt error reduction can improve the productivity and reliability of this NFR system and relieve disc manufacturing tolerance towards SOOGB capacity.