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- International Symposium on Optical Memory and Optical Data Storage
International Symposium on Optical Memory and Optical Data Storage
Deep-UV mastering with a write compensation technique realizing over 20-GB/layer capacity disk
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Recent progress in blue laser diodes requires the development of ultra-high density mastering corresponding to several times higher density than the digital versatile disc (DVD).
Recent developments in optical disk mastering technology
G. J. Verhaart
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The first step in the production process of both pre-recorded and recordable optical discs is mastering. In this process, the relief structure containing pre-recorded data and/or servo information is created in a master disc. The required structures can vary considerably in appearance and size.
Very small track mastering for higher-density optical disk memory
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For achieving higher density optical discs, it is quite important to decreasing a track pitch without deteriorating the signal to noise ratio. For this purpose, an optical disc of the land recording type having a very small groove width has already been proposed.
Near-field optical head on disk mastering process
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The focus-servo system on optical disc mastering conventionally used to be with the off-axis optical setup. As Fig.l shows, a laser beam which does not expose photo-resist, like a red He-Ne laser, leads to an objective from a point off of the optical axis, reflects on the surface ofthe photo-resist and returns in the direction of the incident beam. The reflected beam changes the beam angle from the optical axis according to the working distance of the objective, and is detected as a position with a PSD(Position Sensor Diode). The position-signal from PSD feeds back to the VCM and controls the working distance statically. The focus-servo error remains normally 30nmPP. In the near field operation, however, the working distance should be less than the wavelength The fluctuation caused by that error has a risk of collision between the objective and the glass master. The requirement must be one order of magnitude below like lOnmPP. So a new type of focusservo system had been required.
Fast-access optical drive
J. Wals,
Jadranko Dovic,
Arnold J. Niessen,
et al.
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Low media price and removability have always been unique selling features of CD and DVD. Nowadays, all kinds of affordable and removable storage media are available that have the additional capacity of high-speed accessing. Whereas the latter emerges from the computer industry, CD and DVD historically stem from the consumer industry where access time has never been a critical factor, since audio and video data are predominantly read sequentially rather than randomly. However, there is an increasing demand of both the consumer and the computer market for fast random-access optical drives, which requires the development of new radial access mechanisms. We have achieved 11 ms average seek time for a 120-mm optical disc by applying a three-phase commuting linear motor in combination with a split-optical head resulting in 25 ms total average access time for a DVD-ROM spinning at 100 Hz (10X).
Track center servo and radial tilt servo system for DVD-RAM disk
Shin-ichi Yamada,
Seiji Nishiwaki,
Atsushi Nakamura,
et al.
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To increase optical disc capacity, the track pitch becomes narrower. This necessitates a higher-accuracy for track servo. However, with the push-pull track error detection, the standard error detection for rewritable optical disc, detection error occurs due to disc radial tilt. The authors propose new method of a track center detection method that detects track center more accurately than the push-pull track error detection method, and develop a track center servo and radial tilt servo system based on this detection method.
Development of tilt servo system using 4-axis lens actuator for disk tilt compensation
Y. Motegi,
M. Nagasato,
Yoriyuki Ishibashi,
et al.
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High-Definition DVD 15 GB/side recording capacity is realized by using violet laser diodes, and it is expected to be the next generation optical disc. However, the shortening in the wavelength of laser diode and increase in recording density lead to a tighter margin for allowable disc tilt due to the wavefront aberration. Therefore, a tilt servo system using a 4-axis lens actuator has been developed. It controls the object lens not only in tracking and focusing directions but also in two axes tilt directions corresponding to disc tilt. This paper describes features of the tilt servo system and the experimental results of its tilt compensation effect.
Recording laser power control method based on wobble signal amplitude detection
Chikashi Inokuchi,
Toshiya Akagi,
Seiji Nishiwaki,
et al.
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The DVD-RAM, now a world standard among rewritable high-capacity optical disks, is expected to have wide applications in the PC and AV fields. However, when a recording and reproducing optical disk’s surface is soiled with fingerprints or dust, generally some writing error can be happened. As a solution to this problem, this paper presents the method for controlling recording laser power to improve recording reliability.
Cross talk cancellation with a quadrant cell detector
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An effective method of cross talk cancellation involves the use of a signal formed from a quadrant pupil detector placed in the collimated portion of the reflected light, as shown in Fig 1.
Lens shift correction for DVD-RAM tracking servo
Tetsuya Shihara,
Katsuya Watanabe,
Shin-ichi Kadowaki,
et al.
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Generally, push-pull tracking detection, necessary for read/write type optical disk, is sensitive to tracking lens-shift caused by eccentric disk rotation or track jump acceleration /deceleration. The lens-shift yields tracking offset easily, which makes record or reproduction information signal jitters get worse. The tracking offset versus to the lens-shift tends to be large, as an optical pick-up becomes small. Furthermore, in consideration of mobile application, not only the lens-shift but also the lens droops in a vertical posture increases.
Optical pickup employing a hologram-laser-photodiode unit
Yukio Kurata,
Shinya Yoshida
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A conventional optical pickup consists of various kinds of optical components, which makes it difficult to improve the environmental stability of the pickup with reduced size and weight. To solve this difficulty several works have been reported.
Flat intensity lens with high optical efficiency and small spot size for use in optical disk
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The optical system in recordable optical disc must satisfy both a reduction in spot size for a high data capacity, and an increase in optical energy for high data transfer rate. We have devised one simple optical element that converts the Gaussian intensity distribution into the flat intensity distribution by refraction without optical energy loss or aberrations.
Optical head with coaxial dual-beam cross talk canceller
Kenichi Kasazumi,
Kazuhisa Yamamoto,
Makoto Kato
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A type of optical head with crosstalk canceller (CTC)[1] investigated so far increased considerably the storage density of the optical disks. This type of the CTC, however, required off-axis beams to detect signals from adjacent tracks, and also additional electronics to compensate for time delay between the main-beam and the sub-beams. Such beam separation caused the system unstable, because the delay time fluctuates due to the change in the wavelength, and also because the decentering of the disk resulted radial positioning error of sub-beams. To overcome these problems, we have proposed a new typed crosstalk canceller using coaxial dual beams which are orthogonally polarized[2.] In this paper, we demonstrate a practical configuration of an optical head with the CTC, and some experimental results with play back characteristics.
Superresolution by spatial filtering of high-order Laguerre-Gaussian mode vertical-cavity surface-emitting lasers
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In the competitive industry of optical data storage, larger disk capacities are constantly being sought. One way to increase the data density in an optical disk is to decrease the spot size of the reading and writing beam. Decreasing the spot size by conventional means is diffraction limited by the numerical aperture of available lens technologies and the wavelength of light used. Superresolution, or manipulation of the input beam profile, can be used to further decrease the size of the spot on the disk surface to below its classical diffraction limit. The current method of superresolution in optical memory m suffers from a low signal-to-noise ratio and only decreases the spot diameter by 80%. This method uses a shading band to perform spatial filtering on the fundamental Gaussian beam created by a collimated laser diode. An alternative method is suggested in this paper, which generates a superresolved spot by introducing a mask function into the Fourier plane of a Vertical Cavity Surface Emitting Laser (VCSEL) that exhibits a high-order Laguerre-Gaussian output mode. Theoretical results show a decrease in spot size by up to 47% in two dimensions.
Is a round focus spot better than an oval shaped spot?
Ivan Prikryl
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It is well recognized that the smaller the focused spot size the higher the data density that can be stored on an optical disk. Together, the optical disk and an optical head define the optical system for reading data from and writing data on the disk.
Optical disk system for digital video recording
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Recently, a storage capacity of 9 to 10 GB on a 12 cm optical disc was demonstrated using a red laser (650 nm) and a dual-lens objective with a numerical aperture of 0.85 in combination with a thin transparent cover layer.
Progress in optically assisted Winchester (OAW) recording
J. E. Davis,
A. A. Fennema,
King L. Wong,
et al.
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Optically Assisted Winchester (OAW) recording refers to a data storage architecture that employs several optical technologies in a Winchester hard disk drive platform. The strategy is to preserve the inherent advantages ofthe Winchester architecture (such as fast seek time, multiple recording heads and disks, high linear density, high data transfer rate, and low cost) while incorporating the advantages of optical recording (such as vertical recording media with immunity to superparamagnetic effects, preformatted substrates that eliminate servo track writing and allow very high track densities, and plastic substrates for low cost). As published in previous papers, this was accomplished by introducing four new technologies into the conventional hard disk drive. The first is a light delivery system that transmits light from a laser diode to any one ofseveral recording heads by employing a 1 x n optical switch and optic fibers. The second is a unique recording head that contains micro-optics, a micro-machined mirror, and a writing coil that creates a vertical magnetic field. The third is a two-stage servo system that consists of a coarse actuator as the first stage, and the micro-machined mirror as the second stage. The fourth is pre-formatted first-surface M-0 media that allows recording on both top and bottom surfaces and is relatively immune from the superparamagnetic effects impacting conventional longitudinal recording media in the range of 20-40 Gb/in2.
High-frequency wobbles: a write clock generation method for rewritable DVD that enables near drop-in compatibility with DVD-ROMs
Daniel Abramovitch,
David K. Towner,
Craig Perlov,
et al.
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This paper presents an overview of a new method of write clock generation on rewritable DVD drives that eliminates many of the problems associated with reading rewritable disks in DVD-ROM drives. It is believed that such a format will provide tremendous benefits to the end user, making it possible to edit content on a rewritable DVD disk and then play that same disk in a conventional DVD-ROM player.
Synchronous trigger detection for pulse laser readout on superresolution erasable optical disks
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Pulse readout technique is viewed as a way to improve the CNR ofreadout signal on super resolution disks, such as Magneto-optical Super Resolution Center Aperture Detection disk (MSR-CAD), Erasable Phase change Super Resolution disk (EPSR), Thermal distribution generated by pulse readout scheme results in more regular shape apertures and narrower wall width on those super resolution disks which leads to better signal quality.
Experiments of noble optical floppy disk drive using phase-change optical medium and quasi-near-field optical head
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A lensless optical floppy disk drive which does’t have any optical lens between the optical head and the phase change (PC) type optical floppy disk medium have been developed. The head is a contact type, which had already been adopted in higher density magnetic floppy disk drives such as the LS120. The main point of this optical head is an antireflection (AR) coating technology of very low reflectivity on an output facet of a low cost laser diode which is as same as the laser diode installed in a commercial CD player. The AR coat of the laser diode and also the optical floppy disk medium are deposited on to both laser diode facet and to thin polyimid floppy disk substrate using an electron cyclotron resonance sputtering (ECR) method.
0.04-um domain expansion readout for the MAMMOS
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Magneto-Optical (MO) disk possesses a very high advantage of high density recording compared to non magnetic optical disk, because MO recording is almost same as a perpendicular magnetic recording However, the high density recording is recorded by very tiny domains, so the readout MO signal decreases and the correct data reproduction becomes impossible. In order to amplify the small MO signal, one new idea has been proposed.
L/G recording with 0.45-um track pitch in CAD-MSR disk
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A 6 GB user-capacity disk with a 120 mm-diameter single side substrate was realized by the use of a center aperture detection (CAD) type of magnetically induced super resolution (MSR) disk through the AS-MO (Advanced Storage Magneto Optical) activity. It utilized a practical optics which consists of a 640 nm wavelength laser and a 0.6 numerical aperture (NA) lens, and land and groove (L/G) recording with an effective track pitch of 0.6 pm was realized. The areal bit density reached to 4.6 Gbit/in2 with available system margins. In this report, we present improved CADMSR performance at narrower pitch tracks and at higher linear density with the same optics.
Applying an objective lens of 0.7 NA to a CAD-MSR disk
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We developed the magneto-optical disk system with 6 Gbyte-user capacity that is called AS-MO (Advanced Storage Magneto-Optical).
Greater than 15-GB-capacity DWDD-MO recording using a DVD dimensional optical head
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A new class of super resolution method was proposed for magneto-optical recording by T. Shiratori et.al. The method called DWDD (Domain Wall Displacement Detection) is principled on momentary magnetic wall displacement during a read-out.
DVD copy protection issues: technology, consensus, and implementation
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Shortly after the initial higher density proposals were put forth for the 120 mm optical disk ROM, analysis and comment on proposed capacity, modulation code, error correction coding, performance, disk handling, volume and file structure, and application requirements were given by an ad hoc computer industry technical working group. As the initial proposals evolved into the DVD Specification, the motion picture industry raised the issue of copy protection for movies. To assist in finding acceptable solutions, the technical working group was expanded by consensus to a larger ad hoc group, the Copy Protection Technical Working Group (CPTWG), with participation from the motion picture (MPAA), consumer electronics (CEMA), and computer (IT) industries. Subgroups were formed to study promising areas, e.g. the Data Hiding Sub Group (DHSG) for watermarking of the video, and the Data Transmission Discussion Group for encryption of 1394 transmissions. Proceeding on a voluntary and open basis, the DHSG developed a request for proposals and undertook analysis of the multiple proposals received from many companies including Digimarc, Hewlett-Packard, Hitachi, IBM, MacroVision, NEC, Philips, Pioneer, Sony, and others.
IPR protection features for optical disks to promote superdistribution
Makoto Yoshioka
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In the industrial age the mass production system was developed and people bought products through physical distribution channels. In this age, the value of the products was attained by physically possessing the products.
Evaluation of DVD-R for archival applications
Michael D. Martin,
Jason J. Hyon
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For more than a decade, CD-ROM and CD-R have provided an unprecedented level of reliability, low cost and cross-platform compatibility to support federal data archiving and distribution efforts. However, it should be remembered that years of effort were required to achieve the standardization that has supported the growth of the CD industry. Incompatibilities in the interpretation of the ISO-9660 standard on different operating systems had to be dealt with, and the imprecise specifications in the Orange Book Part II and Part III led to incompatibilities between CD-R media and CD-R recorders. Some of these issues were presented by the authors at Optical Data Storage ’95. The major current problem with the use of CD technology is the growing volume of digital data that needs to be stored. CD-ROM collections of hundreds of volumes and CD-R collections of several thousand volumes are becoming almost too cumbersome to be useful.
High-speed optical library system using DVD-RAM
Takaya Tanabe,
Tetsuya Ura,
Manabu Yamamoto
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Optical disk drives are relatively high-capacity random access storage devices that use removable storage media. Therefore, besides their use as back-up systems for magnetic disks, we considered their potential for random-access storage of infrequently used files.
Rewritable holographic memory
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With a photorefractive crystal sitting on top of silicon, a read/write compact holographic memory module is a potential competitive data storage technique. The main advantages of a holographic memory are to store more data with smaller silicon area and lower cost than the traditional silicon Dynamic Random Access Memory (DRAM), and to readout data with faster access time than the magnetic storage.
Partial response equalization for gray-scale volume holographic data storage
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Digital volume holographic storage is being investigated as a potential technology with the ability to provide high storage densities as well as data rates. While the page-based access makes the high data rates possible, the ability to multiplex several data pages in the same storage volume enables the high densities. A goal in any data storage system is to increase the density.
Multilayer holographic data multiplexing with random encoded reference beam
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In this paper we demonstrate the scheme for volume holographic data multiplexing by using the features of shift selectivity of a random encoded speckle reference wave. The proposed recording method results in a more efficient use of the recording medium volume and increases the storage density in comparison with spherical or plane-wave reference beams. The mechanism of lateral and longitudinal shift selectivity are described theoretically and shown to agree with experimental measurements for holographic data multiplexing in the volume of the FetLiNbCE crystal.
High-density erasable three-dimensional optical bit data storage in a photorefractive polymer using two-photon excitation
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Multi-layered (or three-dimensional) optical memories have increasingly become a field of interest of interest in the development of a high density optical data storage devices. Systems that utilise multiple layer recording can achieve recording densities from 100 to 10,000 times higher than conventional optical data storage devices.
Crescent geometry for an optical ribbon recorder
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Several geometries have been presented in the literature for optical tape recorders. In this paper, we address a new scanning architecture called crescent scanning. The primary features of this architecture include a new scanning mechanism and the resulting crescent-like pattern of tracks across the width of the ribbon. In addition, the ribbon is contained in a sealed or semi-sealed cartridge where the optical surface of the ribbon does not come into contact with any surface other than rolling upon the tape itself. This paper will primarily discuss concepts related to scanning the ribbon.
Rewritable dual-layer phase-change optical disk
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Various technologies enabling to increase the storage capacity of rewritable phase-change optical disk have been proposed.
New 3.5-in. magneto-optical disk system: 1.3-GB GIGAMO technology, reliability, and performance
Kenichi Ito,
Hiroshi Yoshimura,
Koichi Ogawa
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Since the introduction of 128 MB system in 1991, 3.5” MO has been accepted as a large capacity, high performance removable storage for personal computers. The capacity was enhanced to 540/640 MB in 1996, but larger capacity and higher speed have always been requested to cope with the progress of PC system and increasing needs for multimedia information storage.
Crystallization behavior of sputter-deposited nitrogren-doped amorphous Ge2Sb2Te5 thin films
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Recently, the demand of high-speed and high-density optical recording media using a direct overwrite scheme is very high.
Polarization effect on signal from optical ROM using SIL
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In high NA imaging systems such as Solid Immersion Lens ,incident angle is so large, and the polarization of incident beam is disturbed by passing through the SIL surface and by diffraction from the recording medium. Previously (ISOM'98) we reported the influence of polarization disturbance to the readout signals in phase change medium^. Here the same problem on the embossed mark is studied.
Experimental study of image formation in a magneto-optical apertureless scanning near-field microscope
H. Wioland,
O. Bergossi,
S. Hudlet,
et al.
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In this paper, we present an apertureless Scanning Near-field Optical Microscope (SNOM) configuration in transmission mode, adapted to image magnetic samples using the Faraday and Magnetic Circular Dichroism (MCD) effects. We analyze different parameters which influence the image formation. The artefacts observed in the images depending on the collection configuration are discussed.
Characteristics of R-MSR on groove recording
Toshifumi Kawano,
Naoyuki Uchida,
Akio Okamuro
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Magnetically induced super resolution (MSR) is one of the most promising way to achieve high recording density for MO. We reported a unique MSR method called R-MSR, that utilized magnetization reversal at high temperature area. In the R-MSR, super resolution effect can be achieved by signal enhancement at mark edge (Fig.l). The reversal can be realized by magneto-static coupling between readout layer and writing layer as shown in Fig.2. It can give high resolution that comparable to FAD or RAD without readout field. Since the edge signal is enhanced, the readout signal becomes first differentiation of ordinary MO signal, like magnetic media. Recently, groove recording type media was developed in conventional MO. It is said that the groove recording has lower noise level because of its U-shape groove. In this report, performance of R-MSR on groove recording was investigated.
Rewritable optical disk with a new addressing method for increasing recording density and random accessibility
Sang-Woon Suh,
Dae-Young Kim,
Il-Yong Jong,
et al.
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Rewritable optical disks require higher recording density in order to record HD-Video signal. Improvement in random accessibility is also highly recommended for realizing RTRW (real time recording requirement). In this paper, we propose a new addressing method which employs phase modulated(PM) wobble signal to encode a physical address for land/groove recording. We call this method as address in Phase modulated wobble (APMW). By using proposed new addressing method, we could increase recording density as compared with a pit addressed method such as applied in DVD-RAM and improve random accessibility as compared with that of DVD-RW.
Quality discrimination method for write-once optical disk
Hyung-Kyu Kim,
Woon-Seong Yeo,
Dongseok Bae
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The conventional inspection method for write-once optical disk such as CD-R is mostly dependent on sampling and visual inspection. The sampling inspection can comparatively analyze disk quality in physical, optical and signal characteristics. Also, the visual inspection method by photo-scanning is not sufficient to detect disk defects. Furthermore, the sampling method has destructive characteristics that prevent disks from whole inspection in fabrication process because CD-R is write-once disk. On the other hands, our new method can do the whole and non-destructive inspection and discriminate exactly whether a disk is good or bad by recording and reading signals in outer area of disk. It has shorter process time than that of the conventional method. Our method does not hurt the international standards because ofusing an outer area rather than an user area of a disk i.e., beyond of Φ 118mm. The disk inspected by our new method has perfect compatibility with existing CD-R or CD-RW drives. Consequently, our new method is able to apply into CD-R fabrication process and duplication process by discriminating quality of CD-R disk, in manufacturing and before duplicating respectively.
Automated analysis of data mark microstructure in high-density optical disks
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We describe a computerized method to measure the geometry of nanometer-scale data marks from AFM images. By compiling measurements of hundreds offeatures, we obtain statistically robust results, not only for mean values ofstructural parameters, but also for the standard deviations, so that process windows can be determined. On DVDs, we measured the following parameters: track pitch, bump height, bump width and length (at various threshold levels), bump length, and four sidewall slope angles, in each case reporting mean, standard deviation and other statistics. For each 10x10 pm image of a DVD stamper, containing about 100 bumps, we tabulated over 1000 values. In a plot of bump width vs. bump length, we found that width at half height increased from 328 nm for the shortest bumps (440 nm long) to about 385 nm for bumps longer than 800 nm; this matches the increase seen for corresponding optical signals produced when a finished disc is played. Where sidewall angle deviated from the norm, we were able to review the image data to identify the specific nature of the defect. Thus, feature geometry will no longer be a hidden variable in the path between controlling production equipment and observing the good or bad electrical performance of a finished disc.
Effects of magnetic properties and layers thickness on the readout performance of MAMMOS disks
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The needs of recording media for high density are increasing for huge data base and the digital TV environment in near future. A lot of technologies are developed and being developed to achieve a high recording density in MO media. It is a principal approach to circumvent the limit of the spot size of laser due to the diffraction.
Suppression of jitter bump for GeSbTe phase-change optical disk
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For the phase change optical disk, the jitter value of recorded signal during the early several times of direct overwrite is usually much larger than that of initial writing.
Initialization process by induction heating for phase-change optical disks
Woon-Seong Yeo,
Hyung-Kyu Kim,
Chang-Jong Kim
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Phase change media have to be initialized prior to recording in order to satisfy the current standards for example CD-RW, PD and DVD-RAM. Initialization for phase change optical disks is the process of crystallization of as-deposited amorphous recording film by sputtering method. The Initialization process is basically similar to erasing process in phase change media by laser and current process adopts high power large beam laser for the heating the recording film in order to reduce the process time. But the process time of current initialization is quit long compared to the time required for other manufacturing process by one order. So the Induction Heating method is studied in order to reduce the process time resulting low production cost which is very important for commercializing phase change optical disks. Induction heating is well known process technology for metallurgical industry and others due to its effective indirect and focused heating performance. The induced current by external alternate magnetic field flow in the conductive material internally and develops Ohmic heat. By the internal heating, the surround materials are free from thermal damage which is inevitable in external heating.
Terminal attractor optical associative memory for pattern recognition
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Optical associative memory for pattern recognition using the Hopfield model has the advantage of simplicity for its network structure. But further investigation reveals that the basins of the attractors for stored patterns are small in the Hopfield model and the recalling ability is not so great. Moreover, the memory capacity is low because there are many spurious states and oscillations in the network. In order to obviate the spurious states and low storage capacity in the Hopfield model, a type of attractor called a terminal attractor (TA), which represents singular solutions of a neural dynamic system, was introduced. These terminal attractors are characterized by having finite relaxation times, no spurious states, and infinite stability.
New way to improve the reliability of high-speed and mass data recording optical disk array
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Optical recording has some inborn advantages over magnetic recording. Under some circumstances where magnetic recording can not meet the specific requirements, optical recording can play an important role. In this paper, an optical disk array was designed to record successive data with high speed and mass capacity under the circumstances where air-pressure is fairly low and with high electromagnetic interference.
Model of photochromic mask layer for optical storage
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With the development of the computer science and multimedia technology, high-density and high-speed storage media is demanded.
Optical storage properties of novel azo-dye-doped polymer thin films
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The research and development of high density optical data storage technology has become one of the most important objectives of the current data storage research activities.
Characteristics of super-RENS disks with various thickness of thermal protective layers
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Recently a super-resolution near-field structure (Super-RENS) has been proposed. A storage density of a conventional optical disk has been limited by the diffraction limit of the light. During the readout process of a Super-RENS, a small aperture is formed in a masklayer by a readout laser power. The mask layer is laid very close to a recording layer, and the aperture produced in the mask layer acts as an optical near-field probe. We have retrieved marks as small as 60 nm.
Transmitted signal properties of super-RENS disks
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Near-field optics has been applied to optical data storage systems with a high recording density beyond the diffraction limit. However, the actual data storage has not been realized, yet. The difficulty applying a near-field optics to optical data storage is caused by a narrow space between a near-filed probe and a recording medium.
Improvement of performance of a tracking servo system for an optical disk drive
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This paper describes a high speed and precise tracking servo system for an optical disk drive. For efficient production of television programs, an optical video disk recording system with high data transfer rate and large capacity is being developed. To realize a high data transfer rate, a high disk rotation speed is needed. Together with the utilization of short-wavelength lasers and an objective lens with a high numerical aperture, the track pitch on the disk must be reduced to enlarge the recording capacity.
Performance comparison of detectors for DVD channel impaired by bloom and transition noise
Srinivasan Gopalaswamy,
Ng See Kee,
B. Farhang-Boroujeny
Show abstract
Bloom, which is an increase (positive bloom) or decrease (negative bloom) of the size of a written mark, is a nonlinear effect prevalent in optical recording systems. Two kinds of bloom are possible. The first kind is data dependent, and can be (at least partially) compensated for during writing. The second kind of bloom is caused by over- or under-etching during mastering, thermal sensitivity of the media, or by laser power variations. This can be negative or positive, and cannot be avoided while writing.
Equalizer design based on diffraction analysis
Yoshinori Honguh
Show abstract
The recording densities of optical disks have been increasing, and the system design has become much more complicated, because the relations among various parts in the system have become closer. It is necessary to take various characteristics into account in the system design. For example, design of the signal processing circuit requires knowledge of signal qualities determined by the readout optics and mechanical allowances, as well as the modulation characteristics.
Superresolution rewritable optical disk having a mask layer composed of thermochromic organic dye
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Some super-resolution (SR) techniques are proposed on optical disks for a breakthrough to the recording density limit restricted by wavelength.
Optical disk readout analysis using an extended point-spread function
Kiyoshi Toyota,
Satoshi Hineno,
Yoshiyuki Matsumoto,
et al.
Show abstract
troduction The scalar diffraction theory represented by the Hopkins’ method has been widely used for simulating the readout signals from optical pickups. This method is based on the partially coherence theory, and was well improved by previous works, for example the classification into the two types of scanning microscopes,2< extension for MO pickups, and so on. Furthermore, various super-resolution techniques and the crosstalk reduction technique were analyzed theoretically by using this scalar diffraction theory. On the use of this theory, the light amplitude distribution on the exit pupil of the objective lens or the modulation transfer function (MTF) is usually employed for the explanation of the functions of optics. Meanwhile, the method we present here is based on the work by Velzel. His method is basically an approximation of the scalar theory and concentrates on the point spread function (PSF) of the illumination optics in the pickup. And it provides a simple and practical way for computations and understanding of the readout process. For example, Kubota presented in his study the influences of wave front aberrations on the readout characteristics by using jitter calculations, in which the readout signal was calculated as a convolution of the pits on the disk and the PSF. In this paper, we present a method using an extended point spread function (EPSF) that can be applied for the case when the detector has an arbitrary shape and information pits are recorded on a groove. After that, two examples, differential phase detection (DPD) method and jitter analysis of the readout signal from pits on a groove, will be shown. Although our method is also an approximation, physical and intuitive considerations will be acquired even under such complex cases.
Jitter simulation of readout signal including adjacent track mark profile variations of optical disks
Yeonsoo Park,
Soonchul Jo
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The crosstalk, which is defined as interference noises and jitters as well as signal decrease due to adjacent tracks can become a major contributor to total noise, as track pitches get reduced in order to achieve higher track density. To increase the track density, land • groove recording method is used, which can increase the recording density by a factor of two if the crosstalk and crosserasing problems can be avoided. Also, mark edge recording method can cause considerable jitters if the mark profile variations are significant.
High-density holographic memory and its applications to optical pattern recognition
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To date, optical correlator has been extensively developed and applied for pattern recognition.
Tilt servo using modal wavefront actuator
Hsiao-Wen Lee
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Correcting disk tilt aberrations have been studied extensively in recent years. One example is using LCD phase shift modulating devices. Another example is using a comatic lenses. The other example is combined tracking position and tilt sensor for actuator. Method 1 has the advantage ofless space, lower cost; but disadvantage of low wavefront resolution. Method 2 and 3 has the disadvantage of precise mechanical control.
Overview and the future of phase-change optical disk technology
Takeo Ohta
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Information data storage now takes two main forms: magnetic memory and optical memory. Up to now, the leading type has been magnetic memory such as hard disk drives and floppy disks. The recording density of magnetic media has increased by 60% per year and by a factor of 100 in the past decade. Initially, when laser optical memory arrived on the scene, it was expected to rapidly replace magnetic memory. Paradoxically, though, the new challenger appears to have spurred the growth of the recording density of magnetic media.
AgInSbTe materials for high-speed phase-change recording
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Currently applied phase change rewritable optical discs are mainly based on two families of phase change materials.
Large-capacity and high-data-rate phase-change disks
Yuji Kuroda,
Yutaka Kasami,
Masumi Ono,
et al.
Show abstract
In recent days, Post VTR is one of the key phrases often heard in development scenes of the rewritable optical discs. However, in order to make it possible to introduce an optical disc for the consumer video application we have to get over several barriers. For example, to store a 6.7Mbps digital video data of 3-hour long, the disc must have a user capacity of 9GB.
A 16.8GB double-decker phase-change disc
Kotora Kurokawa,
Mitsuo Naito,
Koichi Yasuda,
et al.
Show abstract
Possibilities to increase the data capacity of a phase change optical disc by doubling the recording stack within one disc have been explored and the results were presented by several authors.
High-data-rate phase-change media for the digital video recording system
B. Tieke,
Martijn K. Dekker,
Nicola Pfeffer,
et al.
Show abstract
Today’s major trends in optical recording are the increase in storage capacity per disc and the increase in data-rate, both for reading and for writing. To enlarge the capacity, there are two straightforward means to reduce the optical spot size: increase of the numerical aperture of the objective lens (NA) and reduction in laser wavelength λ.
Crystallization process in thin films of GeSbTe
Show abstract
Phase-change (PC) rewritable optical recording uses a focused laser beam to reversibly switch a submicron-sized area of a thin chalcogenide film between its amorphous and crystalline states. Information is generally stored in these media in the form of melt-quenched amorphous marks on a crystalline background.
Analysis of thermomagnetic recording by using magnetic field microscopy
Hiroaki Nemoto,
Hideki Saga,
Yukio Honda,
et al.
Show abstract
We have developed a new recording scheme that combines thermomagnetic recording (used in magneto-optical disks) and magnetic-flux detection (in magnetic disks).
Crystallization and amorphization studies on a Ge2Sb2Te5 thin film sample using a two-laser static tester
Show abstract
In phase-change (PC) optical data storage, information bits are recorded as amorphous marks on a crystalline film of GeSbTe alloy (hereinafter referred to as GST). This is achieved by raising the local temperature of the film above its melting point (approximately 600°C) using a high power laser pulse, and allowing the film to cool down rapidly to below its glass transition temperature. The crystalline-to-amorphous transition (or vice-versa) is accompanied by a large change in the optical constants of the GST material, which provides a mechanism for optical readout. Thus, crystallization, melting, and amorphization of thin GST films are of fundamental significance in PC optical recording technology. Several such studies have been undertaken in the past, using a single laser beam to both trigger the transformation and monitor its progress. In the present paper we describe the results obtained in a novel, two-laser static tester, which allows real-time monitoring of the crystallization/amorphization processes both during the laser pulse and in the cooling period following the pulse.
Imaging of phase-change optical disk by the reflection-mode scattering-type scanning near-field optical microscope
Mitsushiro Yamaguchi,
Yasuo Sasaki,
Hiroko Sasaki,
et al.
Show abstract
Recent advancement of recording technologies provides us higher density, huge capacity memory devices, such as digital video disks and magneto-optical disks. The higher density is realized for making the recording marks smaller. The size of the recording marks became smaller in the DVD media. In the development of these media, direct observation of the recording marks is important, because the memory performance strongly depends on the shape or the size of them.
Instrument to measure tilt of the objective lens of a near-field recording head
Show abstract
A typical head-lens configuration for near-field recording consists of an objective lens followed by a solid immersion lens (SIL) as shown in Fig. la. The SIL is a hemispherical lens element and its purpose is to produce a focal spot which is smaller than that produced by the objective lens alone.
In-situ identification of material property values for phase-change optical recording
Show abstract
As phase-change optical recording technology matures, partnerships emerge between companies to provide a complete optical data storage solution. A supplier of optical media and a optical disk drive supplier must exchange information, based on prototype evaluations, to establish media and drive specifications which optimize overall performance. For example, in the development of write strategies which result in acceptable jitter and media life, testing is important. But it can be very time-consuming to explore the effects of the many design parameters by iterating on media configurations in the laboratory. Therefore, simulation becomes an attractive option, if it (a) is verifiable using laboratory measurements, (b) requires a minimum number of media parameters, and (c) provides sufficient accuracy to enable good design decisions for both media and drive. For optimal jitter and media life, the simulation should point the way to a write strategy which precisely controls media temperature and cooling rate.
Variation in optical disk birefringence measurements
Show abstract
Optical disc birefringence affects playback performance in a variety of ways and is routinely measured as part of the manufacturing process. However, many disc manufacturers have observed significant variation in birefringence measurements when using commercially available instrumentation. To quantify the reliability of these tools, the Optical Disc Manufacturing Association (ODMA) and NIST performed a round robin intercomparison of optical disc retardance measurements. In this paper, we report that remarkably large measurement variation among instruments indeed exists. We discuss some sources of this variation to show that a substantial part is due to instrument uncertainty, and describe possible error source in one class of polarimetric instruments.
Optical disk recording using a GaN blue laser diode
Show abstract
Both over 20 GB of capacity and higher data transfer rate more than 25 Mbps are required for the optical data storage in the era of digital broadcasting to record high-definition digital video stream.
27.4-GB read-only dual-layer disk for blue laser
Takanobu Higuchi,
Shogo Miyanabe,
Makoto Okano
Show abstract
Our colleagues and the authors earlier reported on a 15 Gbyte read only disc playback system and the disc manufacturing method. The authors are calling a prototype of the next generation DVD system as HD-DVD. A lot of technologies were devised in our proposal: including the new signal processing such as a cross talk canceler (CTC) and a “limit equalizer”, a tilt servo system with a liquid crystal panel and a disc mastering process employing photobleachable organic dye. In the following paragraphs, the authors will mainly report on a dual layer disc system for a blue laser. The recording capacity of 27.4 Gbytes on a 12 cm disc has been achieved with sufficient playback margin.
Magneto-optical disk for blue lasers
Y. Sabi,
K. Kawase,
Kazunori Yamaguchi,
et al.
Show abstract
Recent progress on blue laser diodes promises us a high areal density in the next generation optical disks. For the magneto-optical (MO) disks, however, overcoming the decrease of Kerr rotation angle in blue region had been a long discussion, and several materials were proposed.
New method of readout signal generation to reduce the adjacent track cross talk
Show abstract
To realize more than 15GB data capacity using blue laser diode, suppression of the adjacent track crosstalk may be one of the key technology. Several methods have been proposed for the adjacent track crosstalk cancellation using 2 beams or 3 beams. Kasazumi et.al. have proposed one method with coaxial dual beams. Although they can reduce the adjacent track crosstalk, it is not easy to get enough optical power from the objective lens for recording. In this paper, we propose new method of the readout signal generation to reduce the adjacent track crosstalk.
Miniaturized SHG blue laser without coupling lenses
Y. Kitaoka,
T. Yokoyama,
K. Mizuuchi,
et al.
Show abstract
High-density optical disk systems with storage capacity of over 10GB are focused on as next DVD system. Several high-density optical disk technologies have been reported, such as cross talk canceller technology, magnet super-resolution technology, and use of higher numerical aperture of objective lens and shorter wavelength light source. We have concentrated our attention to development of the shorter wavelength coherent light source. It is required for the light source to gain continuous wave with low noise and good focusing characteristics, and also pulsed power of over 10mW at frequency of maximum modulation frequency of over 10 MHz.
Dual-level optical disks
Show abstract
Digital Versatil Disc (D.V.D.) is now established on the media market. In order to increase the capacity of this format, dual level technology is very attractive as a second generation. We report here our last results on this topic, and particularly analyze the requirements for a hybrid ROM/RAM disc, but also a dual RAM optical disc.
PRML (partial response maximum likelihood) simulator with nonlinearity compensated channel model
Hyung-Nam Kim,
Seong-Keun Ahn,
SeongYun Jeong,
et al.
Show abstract
As linear recording density of optical discs increases, the channel non-linearity grows larger. And narrowing of track pitch also makes the read-out signals affected by large crosstalk from adjacent tracks. These non-linearity and crosstalk degrade the performance of the disc read-out systems. So we need to design equalizers and detecting methods - especially MLSD(Maximum Likelihood Sequence Detector) - considering those deteriorating factors.
Examination of tungsten-oxide-based thin films for optical memory
Show abstract
Because of its well known electrochromic and photochromic properties, and its relative ease of large scale manufacture, tungsten oxide has long been a candidate for display applications. This use was first suggested by Deb in 1973, and numerous patents and papers in the primary literature followed. Tungsten oxide based electrochromic processes have been reviewed by Granquist. We are currently exploring the medium’s photochromic and electrochromic properties for memory and switching purposes. Photochromism refers to the fact that exposing the medium to light causes the material to change color. The light is thought to induce the formation of free charge carriers which can be mobile oxygen ions and radicals as well as electrons that initiate the chemistry leading to the color change. The process we have studied is represented by the chemical reaction below. This process is distinct from chemistry originally described by Deb and reviewed by Granquist in that subbandgap exploitation can be employed.
Electro-optic scanner for an optical head fine actuator
Jinhui Zhai,
Yuhong Huang,
Steve Schroeck,
et al.
Show abstract
Optical disks are widely used in data storage system as well as in audio disk and video disk systems. Rapid progress is now being achieved in toms of recording density and data capacity. Ultra-high density magneto-optical recording has been obtained using recently developed magnetic field modulation (MFM) recording and magnetic super resolution (MSR) and magnetic domain expansion readout techniques.
Optical field study in solid immersion lens
Show abstract
Solid Immersion Lens (SIL)[1,2,3] is a candidate to improve areal density in optical data storage. To design efficient SIL systems, better knowledge ofthe optical field and physical understanding is required. In this paper, a new method for the estimation of the optical field is developed[4]. With this method, a number of physical phenomena are modeled, including the observation that light polarization rotation angle oscillates as the air gap varies.
Physical properties of volume holographic recording utilizing photoinitiated polymerization for nonvolatile digital data storage
Show abstract
Volume holographic recording of information is an attractive solution for the next generation of digital storage systems, for the ability to optically record and retrieve, independently, multiple superimposed holograms, transferring in parallel the corresponding page-formated digital data representations.
Design of a near-field probe for optical recording using a three-dimensional finite-difference time-domain method
Show abstract
The data density of the optical recording medium depends on the focused beam spot size, which is limited by diffraction. Near-field optical techniques using evanescent light have been developed to overcome the diffraction limit of the far-field optics. In particular, Betzig et al. have applied a scanning near-field optical microscope (SNOM) for magneto-optical recording. The resolution of the metal coated tapered SNOM probe is limited by the aperture size and not by the farfield diffraction limit. A resolution less than 60nm was demonstrated. However, low efficiency of the throughput of this probe limits the speed of read-out and recording. In other research, Terris et al. have developed near-field optical recording optics using the solid immersion lens (SIL). The advantage of SIL is a high optical throughput which is larger than that of conventional SNOM probe. However, there is technical difficulty in keeping the position of the relatively large flat bottom of the SIL in the near-field of the recording medium. Recently, Ghislain et al. developed a tapered SIL whose bottom is a sharp conical shape to improve the positioning of the SIL probe. We designed an alternative tapered probe whose bottom is flat, table shaped and 1/n wavelength in diameter. This diameter is large enough to propagate the incident light without significant decay of the amplitude. This probe shape also can be easily made by using a conventional lithography technique and can be applied to the flying—head for nearfield optical recording. The probe shapes and optical configurations are schematically illustrated in Fig.l. In this study, we employed three dimensional (3D) FDTD model to compute the electromagnetic field of this probe optics. A full-vector computation method of electromagnetic field, which based on the Maxwell’s equations, is necessary to design a practical near-field probe. Arbitrary probe shapes and geometries can be modeled using the 3D-FDTD method.
Subsampled digital retiming for optical disk
G. Feyh,
James M. Graba
Show abstract
As profit margins and market windows shrink, it becomes desireable to design as much of the optical storage electronics with digital CMOS. By using CMOS processes, the drive designer ensures the cheapest silicon possible. Unfortunately, the analog CMOS designer faces a greater challenge when designing in CMOS. For highest yield and quickest design cycles the percentage of drive functions implemented with digital blocks should be as high as possible.
Comparison of timing recovery schemes for optical storage systems
Show abstract
Timing recovery (also called bit synchronization) is indispensable for the signal processing in recording systems. As readback signals always suffer from unknown time-varying delays due to mechanical disturbances, timing recovery is needed to keep track of those delays and provide correct time instants for sampling and bit detection. Timing recovery is usually implemented with a phase-locked loop containing a timing error detector (TED), a loop filter and a voltage control oscillator (VCO). Three timing schemes can be seen in data storage channels. Among them, binary logic method dominates optical storage systems such as CD-ROM and DVD-ROM. It is comparatively simple, but degrades in high intersymbol interference (ISI) situations.
Multitrack storage of 10,000 holograms in a disk-type photorefractive crystal
Show abstract
Volume holographic storage has attracted intensive attention during the past decades, owing to mainly the potential high storage capacity and fast data transfer rate. Thick media such as photorefractive materials allow a large number of holograms to be multiplexed in a common volume of the material, resulting in high storage capacity.
Recrystallization velocity of phase-change material
Cyril Trappe,
Bernard Bechevet,
Berangere Hyot,
et al.
Show abstract
Fast recrystallization is a decisive factor to achieve high recording data rates in phase change recording. Recrystallization velocities can be determined by observing the reflected laser power in real time during the interaction of the laser with the sample.
Multilevel reflection modulation recording for phase-change optical disks
Show abstract
Phase change (PC) optical disk is one important type of rewritable optical disk available currently. In PC optical recording, a bit of information is written by using a laser beam to heat the disk which has been initialized to the crystalline state.
Experimental model of the sled system in optical disk drive
Jinsong Han,
Kai Meng Hock,
Wenhua Li,
et al.
Show abstract
In an optical disk drive, seeking and following servo guarantees correct track jumps and continuous read-out signals mainly through controlling the sled movement. Till now there are much more works and publications contributed to focusing and tracking servo than to seeking and following servo, which involves non-linear effects such as friction of the sled and thus is difficult to characterise. However, to enhance the performance of an optical disk drive, a close study of the sled system is necessary to improve the seeking and following control strategy. In this paper, experiments are conducted on a SONY CD-ROM drive and a physical model of the sled system is drawn from experiment data.
Three-dimensional FDTD analysis of optical disk storage system
Show abstract
With the development of high density optical disk storage, the characteristic size of the interaction object is comparable to the wavelength of the light which is used to read/write the disk. In this resonance region, the conventional scalar diffraction theory can not be applied to analyze the system anymore. Vector diffraction theories have been proposed to address this problem: thin film theory for treatment of the multilayer structure of flat surface, rigorous grating theory for treatment of the pre-grooved multilayer coated disk, finite methods for treatment of the pre-grooved multilayer coated disk with the presence of irregular data marks. Among the various finite methods, finite-difference time-domain (FDTD) method can treat the complex disk structure and is relatively easy to implement.5,6* But when treating focusing problem, the incident focusing beam was approximated as Gaussian plane beam previously. This is not the case in high NA optical storage system. In this paper, we propose a three dimensional FDTD method which can be used to analyze the high NA optical disk storage system.
New additional layer to realize initialization-free function for DVD-RAM disk
Show abstract
The phase-change media, such as GeSbTe and AglnSbTe, are widely applied in rewritable DVD-RAM, CD-RW, and PD optical disks. Before information can be recorded on these disks, the initialization process that changes phase-change media from as-deposited amorphous state to crystalline state must be completed.
Comparison of two coding schemes for generating dc-free RLL sequences
Show abstract
A variety of CD and DVD recordable and rewritable disc formats have or shortly will transition into mass market products. Apart from the inherent manufacturing complexity, this development has created very demanding requirements on unit manufacturing cost, production yields, and quality. The dynamic storage marketplace has placed additional, constantly evolving demands on product capabilities. All of this is reflected in the current approach to optical disc manufacturing equipment through their emphasis on modularity, flexibility, and upgradeability. The developments in the CD-R arena encapsulate and serve to highlight these issues and will be used as a case study.
Theoretical analysis of recording light distribution in phase-change near-field recording using SIL
Show abstract
Recently, the near field recording using a Solid Immersion Lens (SIL) is getting much attention to be a promising candidate of super high density optical recording. The high density recording is achieved by introducing a highindex SIL between the recording medium and the objective lens, thereby increasing the numerical aperture (NA) of the optical system and reducing the focal spot size. The SIL lens is usually a hemisphere or a super-hemisphere. The preliminary analyses of readout signal in this case have been reported.
Aspherical supersphere solid immersion lens for near-field optical recording
Show abstract
Near-field optical recording is a potential way to get higher recording density. In this technology, the Solid Immersion Lens is used to increase optical system numerical aperture, thus reduce the focused beam spot.
Finite element analysis of structural resonance of actuator in optical pickup head
J. P. Yang,
Gaoqiang Yuan,
Z. J. Liu,
et al.
Show abstract
Vibration analysis is an integral part of the design process for precise components, especially for higher density optical disk drives (e.g. DVD ROM/RAM). The designer often encounters challenges arising due to undesirable vibration modes in the components. The demands for precise track accessing and focusing are of importance in higher density optical disk drives. However, structural resonant vibration of mechanical components in the optical pickup head limits the tracking and focusing servo performances. Such tighter design specifications require the designer to have in-depth understanding of how structured resonance of the actuator in the optical pickup head responds to its tracking or focusing mechanism.
Three-dimensional thermal modeling and analysis of near-field rewritable phase-change optical disks
Show abstract
The data density of the optical recording disk is mainly dependent on the light beam spot size. In conventional optical recording system, the beam spot size, which is limited by the optical diffraction limit, can be reduced by using a shorter wavelength light source or objective lens with larger NA. Recently, near-field optical techniques have been developed to overcome the diffraction limit. In particular, Betzig et al have applied the scanning near-field optical microscope (SNOM) optics, which as a tapered fiber prove with sub-micron aperture, for use in the recording of magneto-optical (MO) media. However, the low optical coupling efficiency ofthis fiber prove need further improvement before it is practical for application in data storage. Terris et al have developed another near-field optical recording optics using the solid immersion lens that has been developed as the optics for a microscope by Mansfield and Kino. They have demonstrated the recording of the 350nm diameter mark on MO media by using the truncated spherical shaped Solid Immersion Lens (SIL).
Superlattice-like phase-change optical recording disks
Show abstract
Phase-change recording is an emerging technology for achieving high-density data storage and is compatible with CD- or DVD-ROM.
Computer-aided design and analysis of rewritable phase-change optical disk
Show abstract
The development of phase change recording is spurred by the demand of high capacity, low cost and rewritable optical data storage. In phase change optical disk, recording and erasing are achieved by laser heating that induces the crystallographic structural changes in the media. The difference in reflectivities of crystalline and amorphous states determines the information stored. Hence the dependence of optical and thermal effects arising from the laser irradiation on the disk needs to be thoroughly investigated. In today’s competitive marketplace, companies are looking into ways of producing better product at lower cost and shorter development time. Thus the capability of performing interactive computer modeling and analyses of the optical disk becomes inevitable to achieve these ends.
Neural network-aided pixel alignment in digital holographic storage
Cheng-Chiang Phua,
Jingfeng Liu,
Jun Li,
et al.
Show abstract
In view of the potential advantages of digital holographic data storage, such as the large storage capacity, high data transfer rate and fast access time as compared to other data storage technologies, there is intense interest in making holographic data storage technology a reality.
Multichannel response estimation for digital holographic data storage
Show abstract
Digital holographic data storage, featuring high capacity and fast data transfer rate, has been investigated extensively in the past few years as one of the potential candidates for next generation high density data storage.
Mechanism of the superresolution optical near-field structure
Show abstract
A new technique for recording and retrieving small marks beyond the optical diffraction limit was recently proposed by Tominaga et al. Carrier to noise ratio (CNR) of more than 10 dB was demonstrated with an estimated recorded marks of 90 nm at a constant linear velocity of 2.0 m/s using a laser wavelength of 686 nm and a numerical aperture of 0.6.
Recent advances in optical media manufacturing technology
Brian Josef Bartholomeusz
Show abstract
A variety of CD and DVD recordable and rewritable disc formats have or shortly will transition into mass market products. Apart from the inherent manufacturing complexity, this development has created very demanding requirements on unit manufacturing cost, production yields, and quality. The dynamic storage marketplace has placed additional, constantly evolving demands on product capabilities. All of this is reflected in the current approach to optical disc manufacturing equipment through their emphasis on modularity, flexibility, and upgradeability. The developments in the CD-R arena encapsulate and serve to highlight these issues and will be used as a case study.
10-year overview and future prospects of write-once organic recordable media
Emiko Hamada
Show abstract
More than 10 years have passed since CD-R was developed in 1988. Back then, annual sales in 1998 were reported to be 600M units and sales for 1999 were projected to be over 1 billion units. CD-R has clearly become the most popular recordable optical media in the world today. The reasons for this success are related to the fact that, from its inception, CD-R was highly feasible, which was directly related to its function, its format and its production methods, all of which are very similar to those for CD Audio and CD-ROM.
Cover-layer technology for the high-NA digital video recording system
M. M. J. Decre,
P. H.G.M. Vromans,
J. M.J. den Toonder,
et al.
Show abstract
A well-known way of achieving larger optical disc capacity is to reduce tire laser spot size, either increasing tire numerical aperture (NA) of the optical pick-up unit, and/or working at a smaller laser wavelength. Yamamoto et al.
Computation of the effective depth of grooves in an optical disk using vector diffraction theory
Show abstract
The technique of land-groove recording has been proposed to increase the storage density of optical disks.
Approach for high-speed recording of 4.7-GB DVD-R
T. Fujii,
Takayoshi Yajima,
Ryo Negishi,
et al.
Show abstract
DVD-R, which has a capacity of 4.7GB, was developed using thermal design technology extended from CD-R. The quality of recording on DVD-R is governed mainly by thermal accumulation and diffusion in the layers, which causes interference that restricts the recording density and recording speed. In an attempt to reduce thermal interference and extend the range of recording speed from IX to 4X, we carried out both theoretical and experimental simulations. This paper describes the results of actual IX- and 2x-speed recordings and discusses the possibility of 4X-speed recording.
Signal processing for 15/27-GB read-only disk system
Fumihiko Yokogawa,
Shogo Miyanabe,
Masakazu Ogasawara,
et al.
Show abstract
In order to realize 15/27 GB Read-Only disk system using blue laser, new signal processing is required. We have realized 15/27 GB system by using the 2 dimensional adaptive equalizer. The 2 dimensional equalizer was composed of the cross-talk cancel system, the asymmetry compensation type tangential adaptive equalizer and the limit equalizer. By using these signal-processing systems we could reduce the bottom jitter more than 3 % and we could expand the tilt margin.
Error modeling and performance analysis of error-correcting codes for the digital video recording system
Show abstract
The ’’Digital Video Recording system (DVR)” has achieved the storage capacity of 9.2GByte on 12cm optical disc with a red laser by a high numerical aperture (NA=0.85) lens and thin cover layer.
Concatenated codes and iterative (turbo) decoding for PRML optical recording channels
Laura L. McPheters,
Steven W. McLaughlin
Show abstract
Turbo codes, or parallel concatenated codes with iterative decoding, were shown to achieve remarkable, near-capacity performance on AWGN channels.
Linear modeling and nonlinearity compensation of the high-density disk channel
Seong-Keun Ahn,
Hyung-Nam Kim,
SeongYun Jeong,
et al.
Show abstract
As the recording density increases, the linear convolution model, which expresses the time-dependent readout signal as a convolution of unit optical stylus with a data sequence, does not simulate the readout signal well enough to be used for performance analysis.
Optically equalized PRML channels for high-density optical data storage
Show abstract
The use of optical super-resolution techniques to improve the performance of conventional far-field readout systems in optical data storage has generated much recent interest. The insertion of amplitude shading bands in the illumination (incident) path and the collection (reflection) path has been investigated by various researchers as a means for reducing inter-symbol and/or cross-track interference. Phase-shifting apodizers have also proved useful in a variety of storage formats. All of these methods modify in some way the optical transfer function of readout head. From this point of view optical super-resolution can be thought of as a form of optical equalization. This opens up the possibility for designing the readout head to incorporate optically some of the equalization/filtering functions that are normally performed electronically. A particularly exciting prospect would be a readout head that generated directly a partial response type readout waveform, without the need for electronic equalization. In this paper we show that this is indeed possible, using simple rectangular shading bands inserted into the collection path to equalize optically to PR(a,b,b,a) type targets.
Optical near-field aperture storage technology (ONFAST) for high-density high-performance data storage applications
Afshin Partovi
Show abstract
Optical near-field aperture storage technique (ONFAST) is based on using a beam of light exiting a sub-wavelength size aperture (size d←λ) in an opaque screen to record on a media within its close proximity (<d/2).
Near-field phase-change optical recording over 1.2 numerical aperture
Show abstract
Recently, solid immersion lenses (SILs) have yielded a great interest in near-field optical data storage. However, convincing data on areal recording density have yet to be reported. The difficulty is attributed to the fact that an air-bearing slider needs to be kept optically contacted and also that a tiny SIL is vulnerable to aberrations caused by an air gap between a lens and a disk. The air-bearing system cannot easily achieve the condition above because its linear velocity changes the air gap. We have developed a new SIL device mounted on an actuator, which allows the air gap to be varied arbitrarily and enables optical contact independent of disk rotation. The obtained eyepattern of (l,7)-coded data on a phase-change disk demonstrates near-field recording over 1.2- numerical-aperture (NA).
Evanescent coupling in magneto-optical and phase-change disk systems based on the solid immersion lens (SIL)
Show abstract
Through the coupling of evanescent waves into the recording medium, the size ofthe marks that a SIL-based optical system is able to write and read is substantially reduced. This promises a significant increase in the storage density and data rate of optical storage devices. However, without properly controlling the flight height ofthe SIL above the spinning disk, the available optical energy for recording as well as the readout resolution are severely compromised. Here we present results of numerical simulations pertaining to evanescent coupling for magneto-optical (MO) and phase-change (PC) disks through a solid immersion lens.
Near-field phase-change optical recording using a GaP hemispherical lens
Show abstract
The data density ofthe optical recording medium depends on the focused beam spot size, which is limited by diffraction. The beam spot size can be reduced by using a shorter wavelength light source or a larger NA objective lens. Recently, near-field optical techniques using evanescent light, have been developed to overcome the diffraction limit of far-field optics.
Proposal of a near-field optical head using a new solid immersion mirror
Kiichi Ueyanagi,
Takao Tomono
Show abstract
The near field optical recording technologies using a solid immersion lens (SIL) or solid immersion mirror (SIM) have been proposed as promising candidates to overcome the density limit of conventional optical recordings with far field optics. These devices are also suitable for the OAM (optically-assisted magnetic) recording technologies with avoiding the super paramagnetic problem in HDD.
Signal characteristics from a catadioptric system for near-field application
Chul Woo Lee,
Seung Tae Jung,
Joong Eon Seo
Show abstract
Technologies related to optical memory using near field optical phenomena have been developed.
New technique for readout of superdensity data storage beyond the diffraction limit
Show abstract
An approach for high speed optical near-field recording and detection is shortly reviewed, and the basic near-field scattering by super-resolution near-field structure(Super-RENS) is discussed.
Aperture formation and mechanism of super-RENS
Show abstract
The formation and mechanism of nanometer sized apertures of super-resolution nearfield structure (Super-RENS) was thermally, mechanically and optically investigated. An aperture of an antimony film forced in a high compressive stress showed the resolution of less than 100 nm, whereas the film forced in a tensile stress did not. An aperture formation mechanism is proposed by balance between the aperture formation energy and the surface energy including the internal stresses.
Pupil plane filtering for improved signal detection in an optical data storage system incorporating a solid immersion lens
Show abstract
Solid immersion lens (SIL) technology is a promising way to increase the data density of an optical storage system by decreasing the spot size.
Focusing the solid immersion lens
Show abstract
When the solid immersion lens (SIL) is used for magneto-optical storage, the SIL is normally followed by an air gap and then one or more layers of material on top of the magneto-optic layer.
Grating-assisted superresolution for scanning optical systems
Show abstract
ntroduction Super-resolution is the eternal dream of the researchers in the field of optics. It is almost surprising that many new techniques for super-resolution have come in the field of optical storage recently. In the case of optical disc systems, one can modify the recorded mark on the disc so as to give the optimum result to the detected signal. This feature of optical systems makes it relatively easier to come up with a new super-resolution technique in comparison with microscopy where the image must be similar to the object. In addition, it is a great advantage to use scanning optical systems for read-out because finite time is necessary to form a scanned image, which allows us to make ’trick of time’. Therefore, it is relatively easier to figure out a new super-resolution technique in the field of optical storage compared with that of optical lithography where scanning optical systems have not been applied. However, it is well worth trying to introduce good concepts for super-resolution from historical work of microscopy. Sometimes a gem is hidden among them.
How high an NA is too high?
Ivan Q. Prikryl
Show abstract
An increasing density of data stored on an optical disk requires better writing and reading control, more sophisticated data processing, and smaller laser beam stylus. An optical head can produce a smaller beam stylus by using a shorter wavelength laser diode and/or by increasing the numerical aperture (NA) of an objective lens. While the usage of a shorter wavelength is clearly curtailed by availability of short wavelength diodes, the upper limit on the NA may not be determined by constraints associated with the lens design and manufacturing. Particularly, when the recording surface of an optical disk is protected with a substrate, the upper NA limit may be dependent on disk tolerances and on the capability of a drive servo control. When the solid immersion lens (SIL) technique is used, the upper NA limit depends more on the optical system design ingenuity and on the magnitude of the refractive index n of a SIL lens. In the SIL case the disk without substrate suffers with far less flaws. Our interest here will be in optical heads working with substrate furnished disks displaced more than one millimeter from a biaspheric objective lens.