Mark Edge Recording Research Articles

Consideration of Jitter on Mark-Edge Recording

Almost all optical disks have adopted a mark edge recording standard to increase the data capacity. The interchangeability of drives and media is important because an optical disk is exchangeable media. This paper focuses on a jitter characteristic that is important for estimating this interchangeability. The deviation factors of jitter are analyzed and an analysis equation of jitter regarding the probability of generating a mark and space is deduced. In addition, a method to measure the remaining-edge shift in these factors is reported.

Phase-Change Optical Disks for a High Data Transfer Rate

We studied a phase-change optical disk structure suitable for high linear velocity, red laser source, and mark edge recording conditions in order to realize high data transfer rate recording. On the conventional disk with a metal reflective layer suitable for pit position recording, it was found that the increase in overwrite jitter at low linear velocity conditions is small because “preceding crystallization” functions effectively. It was proved that absorption control between amorphous marks and crystalline erased area is indispensable for high linear velocity conditions. Based on these studies, we designed an absorption-controlled disk with a Si reflective layer and confirmed low overwrite jitter at a wide range of linear velocity conditions up to 17.4 m/s.

Optimum Recording Conditions of Direct Overwrite Magneto-Optical Disk Drive for the Widest Power Margin

The write laser power margin of magneto-optical (MO) disks is determined by, for example, the disk sensitivity and various conditions of MO drive. Especially when the multipulse writing method is used for mark edge recording, the drive conditions influence the writing power margin. The drive conditions include both the write channel conditions, such as the writing waveform and the writing power, and the read channel conditions, such as the readout equalizer. When these conditions are optimal, the drive has the widest power margin possible for the object disk. We used the multipulse writing method on direct overwrite (DOW) MO disks and examined the optimum write power condition and the optimum readout equalizer condition. As a result, the correlation between those parameters has been clarified.

Phase Change Optical Disks Having Recording Marks with Large Optical Phase Difference Suitable for Mark Edge Recording

We have developed a novel absorptivity control method for phase change optical disks with the aim of reducing overwriting jitter in mark edge recording without degradation of overwriting cyclability. To control absorptivity more easily, we have designed a disk with a small difference in reflectivity between the amorphous and the crystalline states, and with a large optical phase difference between the reflected light from those two states, which produces a high carrier-to-noise ratio. We have obtained significantly reduced overwriting jitter, down to 2.5 ns for the leading edge, as well as a sufficient overwriting cyclability of up to 105 times.

Modeling magneto-optical domain for mark edge recording

A theoretical model for domain dynamics in magneto-optical recording is described. In this model, domain dynamics is interpreted in terms of a model comprising of initial magnetization reversal nucleation followed by a wall displacement process. Domain simulations are compared to experiments on a moving disk with a rectangular laser pulse, teardrop-like domains were reproduced and understood. Application of the model to control domain shape is discussed, and optimal shape of laser pulses was presented for mark edge recording.

Partial-Response Maximum-Likelihood Channel for Mark Edge Recording on Magneto-Optical Disks

We have developed a partial-response maximum-likelihood (PRML) read channel for mark edge recording on magneto-optical disks. In this paper, we report the results of a computer simulation and an actual experiment using this method and compare them with those of a conventional (level slice [bit-by-bit]) detection method in a leading/trailing-edge-independent reproduction. The PRML read channel can decrease the error rates of signal detection in terms of two factors (phase margin characteristics and error rate characteristics of the carrier-to-noise ratio [CNR]). We found that the PR(1, 1) ML detection method improved the CNR by 1.7 dB over the conventional detection method. With these improvements, we achieved a 30% phase margin at a density of 0.57 µm/mark ( 0.43 µm/bit). Therefore, we improved the capacity of MO disks using the PRML read channel, which decreased the error rates of signal detection for mark edge recording.

PHASE-CHANGE RECORDING

The phase-change optical disc is one of the most promising candidates for the next generation rewritable, optical discs. For multimedia and video applications, high capacity and high data-rate are required. The choice of the phase-change material, usually a Ge-Sb-Te compound, becomes extremely important since data rate is related to the minimum time for crystallization of the recording material. The availability of high-power, red laser diodes combined with an objective lens with high NA and the application of the mark-edge recording technique, offer the possibility to increase the storage density. We realized a capacity of 2.6 GByte continuous data on a pregrooved disc with a diameter of 12 cm. More than 105 direct overwrite cycles at a bit rate of 18 Mbit/sec were achieved by optimizing the disc structure and recording strategy.

Relationship between Overwrite Characteristics and Linear Velocity in Mark Edge Recording with Phase-Change Media

In this paper, we describe the relationship between overwrite characteristics and linear velocity in mark edge recording with phase-change media. Overwrite jitter is reduced for a disk in which the absorptivity of the crystalline state (A c) has been designed to be higher than that of the amorphous state (A a). When linear velocity is lower than 6 m/s, however, overwrite jitter is suppressed even in disks with A a higher than A c. This jitter suppression at low linear velocity cannot be explained simply in terms of thermal diffusion or critical cooling rate. This paper presents a “preceding crystallization” model for a jitter-suppression mechanism in which a previously recorded amorphous mark crystallizes before the scanning laser spot reaches it. Computer simulation confirms the feasibility of this mechanism at linear velocities lower than 6 m/s.

Dynamics of the domain collapse in the true direct overwrite magneto-optic disk

To achieve faster access time in magneto-optical (MO) recording, direct overwrite (DOW) is critical. In single layer direct overwrite media, it was previously shown that domain width modulation limits the CNR. In this report, date collected with a high speed Kerr microscope system and a MO spin stand show that if is possible to collapse the center of a stripe domain using only low power P/sub L/. It is believed that the thermal gradient shrinks and collapses a domain. The fact that a sufficiently high P/sub L/ can collapse a stripe domain in the center suggests that the problem of domain width modulation may be solved by developing a writing scheme which eliminates the thermal interference from P/sub H/. Mark-edge recording may then be possible in single layer DOW media.

ON THE RECORDING CODE WHICH IMPROVES THE GROOVE PARAMETER

In order to increase the recording capacity the mark edge recording and (1, 7)RLL code are employed in the second generation ISO/IEC optical disk standard. However this recording method degrades groove parameter at ROM area because (1, 7)RLL code has long Tmax which causes recording pattern of combination of long pits and short spaces. New (2, 5)RLL code whose Tmax is small were developed. Because Tmax/Tmin gets close to unity, the information capacity of the code is small so that detection window width becomes narrow. Because narrow band signal to noise ratio is large and jitter is small in ROM area, the window margin of (2, 5)RLL code written in ROM area is same as that of (1, 7)RLL code written in MO area when both codes are recorded in the same recording density. The window width of (2, 5)RLL code is 0.4Tb and Tmin is 1.2Tb where Tb is one bit length of information bit.

Write/erase cyclability of TbFeCo for mark edge recording

Domain size changes due to thermal relaxation after high laser power irradiation on amorphous TbFeCo films were studied. In order to achieve mark edge recording for high-density magneto-optical memory, accurate domain size recording is required even after a million erase/write cycles. Highly accelerated erase/write test was performed on typical recording media, rare-earth (RE) -rich and transition-metal (TM) -rich disks. The elongation of the domain size written on the TM-rich film after erase/write cycles was clearly evident; however, the change in the domain size of RE-rich films was small. The small domain size change of the RE-rich disk can be explained in terms of the rapid increase in the coercive force with decreasing temperature and the smaller domain-wall driving force at recording temperature than those for the TM-rich disk, even though both have the same level of structural relaxation.

Jitter improvement in mark edge recording for phase change optical disks with optical phase encoding

We have developed a novel absorptivity control method for phase change optical disks for improving overwriting jitter in mark edge recording. In order to control absorptivity more easily, we have designed a disk with a small difference in reflectivity between the amorphous and the crystalline states, and with a large optical phase difference between the reflected light from those two states, which produces a high carrier to noise ratio. We have obtained remarkably reduced overwriting jitter, down to 2.47 ns from 5.69 ns for the leading edge, and this has meant greatly increased applicability of mark edge recording to phase change optical disks.

Optimization of mark edge recording waveform for a phase change rewritable optical disk using a 680 nm laser diode

A high density mark edge recording method on a phase change rewritable disk is reported. A carrier-to-noise ratio of 55 dB for a mark length of 0.55,μm is obtained by using a 680 nm, NA 0.6 head and a phase change rewritable disk. In mark edge recording, it is necessary to record each mark in correct length. A new laser power modulation pattern is proposed. This pattern consists of a first-pulse, a multi-pulse chain and a last-pulse. Both positions of the first-ptilse and the last-pulse are movable. By adjusting these positions, a jitter, σ/Tw (Tw is window margin), is improved to 6.5% in high density EFM (Eight to Fourteen Modulation) recording of 0.4 μm/bit.

High speed and high density recording in a phase change rewritable disk system

A Phase Change Rewritable optical disk system with a high density of 0.57 μm/bit and high transfer rate up to 46.3 Mbps is presented. In this system, the Mark Edge Recording method is used to attain the total capacity of 19 GB in a double-sided 300 mm-diameter disk. Since this method requires precise recording mark length, a write compensation method, disk media and read data detection method suitable for a wide range of scanning linear velocities ranging from 10.7 to 27.4 m/s have been developed.

Improvement in Jitter Characteristics in Mark Edge Recording for Phase Change Media

This paper describes improvement in jitter characteristics in mark edge recording (MER) for phase change media at a high linear velocity. Jitter of the mark edge position, usually caused by thermal and/or intersymbol interference, can also increase due to overwrite when MER is used with phase change media. We have found that the main cause of jitter increase due to overwrite is the difference in absorptivity between the amorphous and the crystalline states. We were able to reduce jitter significantly by controlling absorptivity through the use of a Si reflective layer. It was also confirmed that this improvement in jitter characteristics can achieve high recording density of 0.59 µm/bit.

Digital Video Disc Recorder Using Second Harmonic Generation Green Laser

A prototype of a digital video disc recorder (D-VDR) with laser-disc-quality video and compact-disc-quality audio is developed and demonstrated using a second harmonic generation (SHG) green laser, narrow-track magneto-optical disk (MOD), mark edge recording and data compression.

Write-Once Optical Disk Using Ge-Sb-Te/Bi-Te Bilayer Film for Mark-Edge Recording

The Ge-Sb-Te/Bi-Te bilayer has been developed as a recording layer for a write-once optical medium. Mark-edge recording is carried out using the bilayer, and the (1, 7) run-length-limited code is employed for mark-edge recording. Without waveform equalization, the bilayer has a wide recording power tolerance of ±33% with a linear density of 0.68 µm/bit. This linear density corresponds to ∼9 Gbytes for both sides of a 300-mm disk with a modified constant angular velocity mode. Furthermore, the alloying states along the cross section of the bilayer are measured by energy-dispersive X-ray spectroscopy after laser recording at 9 and 15 mW.

2 GB/130 mm Capacity Direct-Overwrite Magneto-Optical Disk

Precise mark-edge recording on a high signal-to-noise ratio (S/N) exchange-coupled direct overwrite magneto-optical (MO) disk provides 2 GB capacity on a 130 mm disk with a sufficient edge jitter margin. Write compensation technology was proven to be effective for both non- and direct-overwrite MO disks.

Write/Erase Cyclability of TbFeCo for Mark-Edge Recording

Write/erase cyclability for mark-edge recording is studied using rare-earth element[RE]-rich TbFeCo media. Mark-edge jitter for the (1-7) random pattern is small enough even after millions of cycles of data writing and erasing.

Extended Capacity and High Speed Magnetic Field Modulation Recording for 3.5" Magnetooptical Disk

The authors attempted recording by magnetic field modulation overwriting with a flying magnetic head, using a (1,7) RLL code, mark-edge recording, write precompensation, equalization, and the ZCAV format. A flying magnetic head for high-speed magnetooptic recording was developed. It was confirmed that the magnetic head has a magnetic efficiency of 1.38 Oe/mA at a spacing of 18 ?m and a modulation frequency of 8.16 MHz. Under these conditions, a linear recording density of 0.55 ?m/bit and an overwrite power margin in excess of ±25% were achieved. A 3.5 magnetooptic disk drive with a storage capacity greater than 300 MB and a high data transfer rate of 2.7 MB/s at the outermost track was realized.