Yasunori Sugimoto

High-Speed Recording up to 15,000 rpm Using Thin Optical Disks

We propose a high-speed optical disk system using thin flexible optical disks (HS-FOD) recording up to 15,000 rpm. The thin optical disk system is composed of three technical elements: media employing a thin and flexible substrate 0.1 mm thick, a mechanical stabilizer, and a high-speed tracking servo employing a feed-forward control with zero phase error tracking (ZPET-FF control). The HS-FOD system has an optical head with numerical aperture (NA) of 0.85 and is compatible with the optical system of a Blu-ray disc or a broadcast-use optical disk. We have successfully performed disk rotation stably and have performed precisely a focus servo and a tracking servo at 15,000 rpm. We also achieved writing and reading data at 15,000 rpm and recording 252 Mbps of random pattern data and could get small values of jitter below the tolerance. These results are enough to record professional high-definition television (HDTV) video signals in formats such as HD-D5 for broadcast-use.

A 252-Mb/s Recording Experiment Using Flexible Optical Disks for Broadcast Use

Flexible optical disks (FOD) have a feasibility of their high data-transfer rate and large capacity for archival storage. We have been developing the FOD in order to replace as the media with a current professional video cassette recorder (VCR) of HD-D5 format which have a data-transfer rate of more than 250 Mb/s. Here, we developed the FOD with the high recording sensitivity for high-speed recording, and succeeded to record the 252 Mb/s data with the high-speed tracking control method and optimized write strategy. We also employed the partial response maximum likelihood (PRML) read channel for playback data. We could get and achieve the low byte-error rate (BER) below 2 times 10-4 at the recording speed of 252 Mb/s, enough to record the video signals of HD-D5 VTR for professional broadcast use.

High Speed Flexible Optical Disk with Cylindrically Concaved Stabilizer

We developed a brand-new stabilizer with a cylindrically concaved active surface for a flexible optical disk system. The unique design enabled extremely stable driving of the flexible disk at rotational speeds over 10,000 rpm. We actually demonstrated the driving at rotational speeds of up to 15,000 rpm, the spindle motor limit of our optical disk tester. This highest rotational speed promises a maximum data transfer rate of more than 600 Mbps for the recording density of a Blu-ray Disc. This stable state was achieved using a simple control that just adjusts the relative axial position of the stabilizer against the flexible disk. Once the adjustment was made, high stability was maintained over a wide rotational speed, ranging from 4,000 to 15,000 rpm. In this stable state, the axial runout on the pickup scanning line was suppressed to less than 10 µm at all rotational speeds. By achieving this high performance with simplified stabilizer control, we have come close to putting our system into practical use.

Improvement of Aerodynamic Stability in Flexible Optical Disk System with Cylindrically Concaved Stabilizer

To improve the aerodynamic stability in a flexible optical disk system with a cylindrically concaved stabilizer, the effects of the curvature of the stabilizer, disk thickness, and disk materials on aerodynamic stability were investigated. We clarified that these factors affect the effective working area of the stabilizer. This result shows that the effective working area of the stabilizer could be expanded by adjusting the curvature of the stabilizer, disk thickness, and disk material. We also demonstrated recording and reproduction at 4× speed for Blu-ray disc density using flexible optical disks with various thicknesses.