Technologies for removability in a near-field optical disc system

Approach of Improving Disk Performance to High-Quality Gap Control in Near-Field Optical Disk Drive System

“…5) To achieve a highly accurate gap performance, we have expanded the bandwidth of a gap servo system to 13 kHz and also introduced a learning servo system. 4) Consequently, we have successfully demonstrated the control of the gap with an accuracy of 6 nm for a disk with a run-out of 45 mm at 3,000 rpm. To improve the gap servo quality further, both the gap servo system and the disk mechanical performance should be improved from the viewpoint of gap servo system stability.…”

“…3) We have also demonstrated its removable performance toward the practical use. 4) In the NFDD, the gap performance has detrimental effects on the RF amplitude vibration of 2.0%/nm in a reading channel and the signal laser peak power vibration of 1.2%/ nm in a writing channel. 5) To achieve a highly accurate gap performance, we have expanded the bandwidth of a gap servo system to 13 kHz and also introduced a learning servo system.…”

Recording characteristics of high-density thin optical disk using near-field optical recording

“…[27][28][29] Although the NFR optical disk has a fourfold higher data capacity per recording layer than that of Blu-ray disk, the 20 nm gap servo control between the SIL optical head and the disk surface meant that there were difficulties with obtaining a high disk rotational speed for high-data transfer rate recording when the conventional method was used. [30][31][32][33][34] We have proposed a precise gap servo system of reducing harmonics of an axial run-out disturbance-feed-forward control (RHD-FFC) system for the NFR drive. 35) We have also proposed a high-density thin optical disk with a narrow track pitch for NFR with an SIL, and also have reported and indicated the feasibility of high-data transfer rate recording corresponding to 252 Mbps and indicated less than 2 nm of high-precision gap servo control with a small axial run-out between 1 and 10 m p-p , and obtained sufficient carrier-to-noise ratio characteristics at a high disk rotational speed.…”

High-Speed Tracking Servo Using Zero Phase Error Tracking-Feed-Forward Method for Professional-Use Optical Disks over 10000 rpm

“…For example, the employment of repetitive control techniques to the gap servo for near-field recording systems was reported. 4,5) We have proposed a high-speed tracking control system that combines a feedback (FB) control system with a feed-forward (FF) control system, which was based on the zero phase error tracking (ZPET) method [6][7][8][9][10] (referred to as the ZPET-FF control). This system has been shown to reduce residual tracking error far better than conventional FB control or repetitive control, 7) and has demonstrated the capability to reduce the residual tracking error on an optical disk rotated at a high speed with an optical system with an objective lens of a numerical aperture (NA) of 0.65.…”