Mitsuru Irie

Investigation on Life Expectancy of High-Speed Recordable Optical Disks

This study is intended to establish a standard technique for measuring high-density optical disk life expectancy. The life expectancy of archival performance for high-speed recordable optical disks [digital versatile disc-recordable (DVD-R) disk] was examined using two acceleration test models, namely, the Arrhenius and Eyring models, and an analysis of statistical techniques based on the ISO method. Results demonstrate that the statistical distribution of failure time using both acceleration test models follows a lognormal distribution. Thus, we can estimate a standard life expectancy of 95% survival probability with a 95% confidence level for each acceleration test model.

Statistical Analysis of Lifetime Distribution for Optical Recordable Disks

In this study, we examine the criteria for lifetime measurements using the Eyring acceleration test model and statistical analyses to evaluate high-density recordable optical disks. Two criteria are commonly used to determine disk lifetimes. One is the parity inner (PI) error number of the error correction code (ECC). The other is the jitter value (the channel clock to data). The results have demonstrated that the statistical distribution of lifetime data using jitter is a lognormal distribution. Using this criterion, we can estimate the standard life expectancy of high-density recordable optical disks as the minimum lifetime of 95% survival probability at a 95% confidence level.

Simple Estimation Method for Life Expectancy of Optical Disks Using Resampling Statistical Analysis

In this paper, we present and discuss a simple estimation method for the life expectancy of optical disks using resampling (bootstrap) statistical analysis in order to roughly estimate the lifetime of archival-grade disks. The performance of this method was examined experimentally using the Eyring acceleration test with four stress conditions. Results demonstrated the capability of this bootstrap analysis for estimating life expectancy compared with conventional statistical analysis using the Eyring acceleration test.

1.0 W High-Power Small-Sized Nd: Yttrium Aluminum Garnet (YAG) Laser Optical Head for a Laser-induced Printing System

A high-power small-sized optical head which adopts a laser diode (LD) pumped Nd: yttrium aluminum garnet (YAG) laser (maximum power: 16 W) for a laser-induced thermal-transfer printing system was developed. The size of the developed optical head is 10 cm (width) × 15 cm (depth) × 3 cm (height); the maximum power of an optical spot that can be obtained is 1.2 W. Stable characteristics of pulse width modulation and rise-time using the acousto/optic modulator (AOM) are confirmed experimentally. Digital high-definition image printing was evaluated at the 3 µs laser pulse by the developed head. The system achieved a more than 10-fold speed increase over our previous system which adopted a 100 mW laser diode. In addition, a good high-definition digital image was confirmed. In this paper, we describe the optical design and optical characteristics of the high-power small-sized optical head, which adopts a laser diode pumped Nd:YAG laser; we also present experimental results of the digital high-definition image.

Optical design of laser unit with polarized holographic element for digital versatile disc pickup

The laser unit that adopts a polarized hologram element and a front laser diode (LD) monitor of 10.4 mm (width)×4.8 mm (depth)×5.5 mm (height) for digital versatile disc pickup was developed. By optimizing the phase transfer function of the hologram element and the division ratio of six segments of the photodetector, suitable characteristics of sensing signals, which were used in the spot-size-detection (SSD) method for the focusing sensor and the differential-phase-detection (DPD) method for the tracking sensor, were confirmed experimentally. The front monitor method using the reflective hologram was developed for stable control of the laser beam. The developed laser unit achieved an optical efficiency of more than 90%, and a wavefront aberration of 0.014λ rms. This paper describes the optical design of the laser unit system that adopts the polarized hologram element (PHOE) and optical characteristics of the PHOE laser unit.

Control mechanism of an optical head for 130-mm read/write disk drives

To cope with the trend of high-speed access, a high-performance optical head with a sliding and rotary-type of lens actuator has been developed. An advantage of this type of lens actuator is that the moving part of the actuator is dynamically well balanced so that the objective lens is not shaken by acceleration or deceleration during seeking. As a result, the stability of the velocity control during seeking has been improved and the waiting time when the operation mode changes from the seek mode to the tracking mode has been reduced. To cope with the trend of high-speed transfer, we have increased driving efficiency and set the frequency of the parasitic resonance sufficiently high. Also, the rotational latency, which is an important factor of the access time, has been shortened. As a result, a data transfer rate of 7.4 Mbits/s and average access time of 48 ms have been attained in a 130-mm rewritable optical disk drive.

Pumping Configuration for Small-Sized Diode-Pumped Nd:YAG Laser

diode-pumped lasers using a miniature NdYAG slab without focusing lenses is proposed. Using total reflection on the slab surfaces, the pump light is confmed to the laser mode volume. In the fundamental oscillation, a TEMoo output power of 210 mW is obtained with a laser diode power of 890 mW. Furthermore, we realized a small-sized (10 mm Φ x 17.5 mm) diode-pumped green laser using this configuration. An output power of 4.4 mW is obtained with a laser diode power of 440 mW.

New tracking method for two-beam optical heads using continuously grooved disks

A new composite tracking method suitable for a two-beam split-type optical head is suggested. Using twin spot and push-pull tracking method, and with ana auxiliary actuator combined, this method is designed so as to be applied, in particular, to optical disks having continuous grooves. In this method, a read-out spot is controlled by the twin-spot method, and moreover an auxiliary actuator for write spot positioning is driven by a differential signal of two push-pull tracking error signals derived from read-out and write beams. To examine tracking performance of this method, we constructed a two-beam optical head and successfully confirmed that the two spots could be easily positioned on the same track center independent of +/- 100 micrometers objective lens shift.