Hiromi Honma

High-Density Land/Groove Recording for Digital Video File System

High-density land/groove recording technology for magnetooptical (MO) disks, using a high-speed crosstalk canceller which eliminates crosstalk from adjacent tracks, has been developed. A 0.50 µm/bit linear density with a 0.8 µm track pitch has been confirmed with a bit error rate (BER) less than 10-5. A digital video file system using this technology has also been developed. As a result, the authors confirmed the validity for the high-density land/groove recording technology in realizing larger capacity for digital video file systems.

High-density land/groove recording using PRML technology

High density land/groove recording, using partial response maximum likelihood (PRML) technology, which corrects errors in the readout signal for exploiting readout channel characteristics, has been developed. By this detection method, both land area and groove area can be used for data storage tracks without a crosstalk cancellation technique. Applying this method with a red laser, 8 times the storage capacity, compared with the conventional method, has been achieved.

Signal-to-Noise Ratio in a Partial-Response Maximum-Likelihood Detection

In this paper we describe a derivation of general expression of signal-to-noise ratio (SNR) in a partial-response maximum-likelihood (PRML) detection system. Because of media noise, as well as difference of transfer function between target PR and the actual channel, the noise at the Viterbi detector is no longer white but colored. The conventional expression of SNR is not appropriate for evaluating signal quality for the colored noise. We have shown how to calculate the variance of the colored noise in the PRML system. The derived SNR can be easily calculated using hardware and is very useful for evaluating signal quality under high-density recording conditions where jitter cannot be accurately measured. We have confirmed that the bit error rate (bER) predicted by the SNR correlates well with the actual bER, regardless of bit density.

Optimization of Write Strategy in a Partial-Response-Maximum-Likelihood System for High-Density Recording

It is difficult to optimize the write strategy by conventional methods in high-density recording systems with very severe intersymbol interference. We have proposed a new method using the index accounting for the linearity of the channel, which is very important in the partial-response-maximum-likelihood detection scheme. It has been confirmed that the minimum bit error rate can be obtained when the linearity of the channel becomes maximum. We have shown the feasibility of a recording capacity of over 20 GB with 120-mm-diameter phase-change media using the blue-violet laser diode with an objective lens whose numerical aperture is 0.65.

Optimization of write strategy in a PRML system for high density recording

Recently, there has been much research on high density recording using an NA = 0.85 objective lens . The use of PRML (partial response-maximum-likelihood) is an efficient way to handle inter-symbol interference (ISI) that degrades the bit-error-rate at a very high recording density. We have shown that the recording capacity of about 32 GB is achieved with the use of PR channel with a constraint length of 5, i.e., PR (12221) and Viterbi detection in the NA = 0.85 system. This paper describes the method for optimizing a write strategy in the PRML system. We have confirmed that the write strategy can be optimized in terms of a linearity of the channel. It has been found that the recording density near the optical cut-off frequency can be achieved by using the optimized write strategy and PRML.

High-Density Recording Systems Using Partial Response Maximum Likelihood (PRML) with Blue Laser Diode (LD)

This paper describes our two newly developed high-density recording systems, which consist of a 35 GB system and a 20 GB system using partial response maximum likelihood (PRML) with blue laser diode (LD), and their respective evaluation systems. The 20 GB system consists of a 0.6 mm substrate disk system (System #1) with a numerical aperture (NA) 0.65 objective lens. On the other hand, the 35 GB system consists of a 0.1 mm cover layer disk system (System #2) with a NA0.85 objective lens. Moreover, we considered the two advantages and disadvantages, and future technical progress. Consequently, we considered that System #1 is fit for personal computer (PC) applications, and System #2 is fit for video disk recorder applications, such as prolonged high definition (HD) video recording of broadcasting satellite (BS) digital broadcasting.

Optimization of write conditions with a new measure in high-density optical recording

We defined a new measure called the partial response signal-to-noise ratio (PRSNR) to evaluate signal quality in partial response maximum likelihood (PRML) detection, instead of measuring jitter. This PRSNR was adapted to optimize the write conditions of high-density optical recording in a PR(12221)ML system with blue laser detection. We confirmed that optimum power control (OPC) with PRSNR was able to accurately search for the optimum power of discs and that it was able to do this in a short time occupying less disc area. These results denote that it was sufficiently useful for actual optical disc drives. We also confirmed the feasibility of adjusting a write strategy with PRSNR.

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.