High-density recording systems using PRML with blue LD

In high-density optical disk recording systems using blue laser diodes, a NA 0.85 thin cover layer disk system (I. Ichimura et al., Jpn. J. Appl. Phys., vol. 39, pt. 1, no. 2B, pp. 937-942, 2000) and a 0.6 mm-thick substrate disk system (S. Ohkubo et al., Optical Data Storage 2000, PD5, 2000) have been developed. However, the demand for huge capacity with higher data bit rate recording for HD-video recording, and PC application requests (e.g. no cartridge and easy compatibility with DVD/CD-ROM) have been growing rapidly. In this paper, we describe our newly developed two high-density recording systems, which are System 1 (0.6 mm substrate disk system with NA 0.65 objective lens) and System 2 (0.1 mm cover layer disk system with NA 0.85 objective lens), with advanced PRML technology respectively. Moreover, we examined a fingerprint influence and arranged various advantages and disadvantages over each high-density recording system, and considered future applications.