A great variety of reversible phase change optical recording materials have been extensively investigated. These alloy films are mainly composed of the IV-VI group (GeTe) and V group (Sb) in the periodic table. For achieving fast crystallization and stable cyclic operation, the excess Sb component of pseudo ternary alloy of GeTe-Sb2Te3-Sb has been investigated. At the melt-quenched process from the crystalline to the amorphous phase, the problem is to know if the laser pulse is essentially heating the sample which simply melts or if the electron-hole pairs created by the laser generate a new fluidlike state. The research on the electron-phonon interaction has shown that if a certain fraction of the valence-band electrons are excited into the conduction band, then the frequency of TA phonon, responsible for the stability of the crystal, goes to zero and crystal should become fluid. On the other hand, thin film surface becomes unstable before the bulk and the process of melting consists in the unstable surface at the film thickness of 10 - 50 nm. The inclusion of surface effects that self-consistently accounts for anharmonicity reduces the temperature at which an instability occurs. Both effects of electron-phonon instability and surface instability reduced the melting temperature of the phase change optical memory materials cooperatively. Therefore, the phase change optical disk is stable for the cyclic operation of 106 - 107.
Advanced phase-change optical disk technology has become matured products level. Reflectivity change recording function and the overwrite function of this technology has good affinity of the contents media as CD-ROM and interactive performance on the optical disk. The new concept `PD' system realized the multimedia optical disk, the first.
The dynamic properties of a Ge-Sb-Te phase-change optical disk with low writing power (5 - 13 mw) at 680 nm were investigated. The Carrier/Noise of the disk is about 45 approximately 60 dB and the Erase ratio is 23 approximately 28 dB.
This paper reviews bismuth-substituted ion garnet films for magneto-optical (MO) recording. The influences of doped ions on anisotropy (Ku), compensation temperature (Tcomp) and coercivity (Hc) are discussed. From the viewpoint of practical application the optimum design of disk structure such as reflective layers and thickness of garnet films is also described.
Effects of vacuum annealing on the coercivity in sputtered and evaporated Pt/Co multilayer films were detailedly investigated. Our experimental results showed that the coercivity experienced an initial increase and a subsequent decrease with the process of annealing. The saturation magnetization decreased slowly at initial annealing stage and then dropped drastically when the annealing temperature was further raised. The coercivity variation after vacuum annealing can be explained by the improvement of f.c.c. (111) texture and the reduction of Co layer thickness.
A magneto-optical (MO) video disk recorder with frequency modulation of video and audio signals has been developed. Using a 5.25' MO disk, analogic image recording time is about 20 minutes, and signal-to-noise ratio is more than 40 dB.
The use of organic compounds as optical storage materials have been receiving more and more attention due to their easy preparation, low cost and tunable properties. In this paper, research results on the application of organic dyes and organo-metallic compounds as optical recording media, such as write-once media, rewritable media, and photochromic media are presented, and preparation technologies of the recording thin films are outlined and discussed.
The optical discs which can quickly record, retrieve and read enormous numbers of documents, images, music are becoming new leading products in mass media industry now. Especially CDR discs which are following the booming CD-ROM sales are becoming more and more popular. CD-R discs are compatible to CD-ROM discs, and they can record information and preserve it for long periods without changing. Because organic-dye-laid discs are relatively low cost, the application of CD-R is extending to consumer areas. In addition, we believe that in the near future CD-R duplication will replace the standard injection molding and substrate finishing process for small volume CD-ROM distribution. There are about 50 kinds of recording materials that can be used for CD-R media as summarized in Figure 1. This paper concentrates on a recording media containing a cyanine dye, because of the following features: • compatible to Orange Book Standards and available licenses through Philips (including Taiyo Yuden), • recycling of dyes can be applied and thus low costs can be achieved.
A recordable compact disc with dye material has been researched. The disc realizes a high reflectivity satisfied with CD standard. A detailed theoretical analysis and a design of recordable compact discs configuration is given. Experimental results and the theoretical analysis shows that the reflectivity and read-write characteristics are suited for practical applications.
The enormous success of the CD-ROM has led to development of the CD-Recordable format and has resulted in a dramatic change in its market position. The CD-R media were introduced in the market place several years ago. The first media had stability problems. Since then, a series of improvements were developed, although incomplete, have resulted in the use of a wide variety of applications, in particular, CD-ROM editing. These applications favour higher data transfer speeds than that used for testing as defined in the Red Book. Recording higher than double the speed as defined in the Red Book creates both technological and compatibility problems. For that reason the CD-R standard, as described in the Orange Book, initially deals with single (lx) and double (2x)recording speeds.
The spectrum characteristic and photostability of three near-infrared absorbing cyanine dyes with typical structure have been studied. The results show that the stability of three dyes with molecular structure of heterocyclic stem nuclei against photooxidation is in such order: benzoxazole > benzothiazole > benselenazole. It was found through quenching experiments that the photooxidation of cyanine dyes not only relates to the singlet oxygen but also to the superoxide anoin, however single oxygen plays a dominant role. We have succeeded in drastically improving the photostability of three cyanine dyes by using a dithiol nickel chelate as a singlet oxygen quencher.
Optical recording performance of phthalocyanine thin films as write-once read-many recording media has ben investigated. The retrieval of information from the disk utilizing a phthalocyanine thin film has been successfully realized.
Phthalocyanine dyes with various central metal atoms and different substituents showing improved spectroscopic properties to match the output of GaAs diode-laser have been synthesized. Smooth thin films have been prepared by spin- coating technique. Solvent-vapor induced crystallization of VOPc(OC3H7)4 has also been studied. The results showed that the VOPc(OC3H7)4 primarily deposited on glass substrate as an amorphous form. However, the dyes were changed to crystalline form by exposure to appropriate solvent vapors. The polymorphs of the VOPc(OC3H7)4 were investigated by visible absorption and IR spectroscopy, X-ray diffraction and high resolution electron microscopy. The optical recording performances of the thin films were also reported.
A cyanine-in-polymer film was prepared by spin-coating process on pregrooved polycarbonate substrate, and its optical storage performance was studied. The reflectance and absorbance of the film at 830 nm wavelength are high enough for optical storage. With optimum recording condition, 58 dB of carrier-to-noise ratio was obtained for single layer disk. Both of carrier-to-noise ratio and carrier signal level are proportional to log of the reflectivity change of the film before and after laser recording.
Investigation on the recorded areas of phthalocyanine thin films shows that bubbles emerge after laser irradiation. It is demonstrated that microstructural information is very important to the improvement of disk performance.
Mechanical and thermal properties of UV-cured acrylate film have been measured, which presents Young's module and glass transition temperature. Based on CDs' structure, temperature field simulation are carried out, influential factors are also discussed.
CD-Audio is broadly seen as a success-story. For good reasons. The CD-Audio is a worldwide recognized standard; the underlying Red Book (1 982) its carefully and well protected by Philips and Sony. The industrial involvement of third parties is promoted by a non-discriminatory licensee policy. All this has led to an annual market volume of more than three billion discs involving a family of CD type application standards: CD-Audio, CD-ROM, CD-i, CD-R and CD-E. All these applications are based on the mechanical, opto-electronical, disc-layout and data encoding specifications described in the Red Book of 1 980. Since then a variety of technological improvements were developed leading to proposals for a new "Red Book". These trials were unsuccessful (for good reasons) until a broad consortium of companies went for a massive support towards the Digital Video Disc, DVD, standard. The DVD standard presents a challenging update of the Red Book for its technology as well as for its applications. Referring to the large variety of publications and press releases, the DVD product is certainly the most widely supported and most optimistically forecasted medium since the introduction of the CD. It happens that the optical industry has quite some experience with optimistically forecasts. These overestimations were partially attributable to inappropriate product positioning, to inadequate market volume assumptions and due to wrong assumptions on the time it would take to commercialize a new product. In looking back to this past and learning form the history of magnetic recording as well, we have to recognize that a variety of factors co-determine the success or failure in the market place. The purpose of this contribution is to evaluate the position of DVD. After summarizing the functionalities of the DVD standard, the growth factors will be summarized by evaluating the initial growth of the CD-Audio, the CD-ROM and the CD-R markets. Based on these experiences the prospects of the DVD will be discussed in terms of their most potential applications and their most relevant factors for their market growth.
International Standards of Optical disks: CD-ROM, CD-R, CD- E, magneto-optical disk and heat-mode phase-change optical disk are presented. DVD-RAM based on photon excited effects: electron-hole pair generation and recombination in nonlinear materials is discussed.
Persistent spectral hole burning with multiplicity was realized at room temperature for Nile blue molecules-doped polymeric dielectric spherical microparticles based on morphology-dependent resonances. Hole parameters depending on burning conditions were studied. Dynamical characteristic behavior of hole formation was measured and analyzed with a model based on rate equations. The effective hole formation rate was obtained by simulation. Photophysical and photochemical mechanisms of the room temperature hole burning for this system was discussed.
The manufacturing of the latest High Density Optical Disc, the Digital Versatile Disc, requires modified mastering and replication equipment. A new mastering system and dedicated manufacturing equipment will be introduced.
Differing from the storage of image on the optical disk in series, a new method for realizing image parallel storage is presented, based on the theory of holographic optical disk storage. The image parallel readout architecture is described, and the specified optical disk holograms are designed by our proposed iterative search algorithm. The experiment results have demonstrated the image parallel storage technique.
The optical properties of GeSb2Te4 thin films prepared by vacuum RF-sputtering method at the wavelength region of 400 - 830 nm were studied. A comparatively large absorption was observed in the wavelength range 400 - 600 nm, which matches with the wavelengths of Argon laser. The optical storage characterizations of GeSb2Te4 thin film demonstrate clearly that larger reflectivity contrast can be obtained at lower power Argon laser (514.5 nm) irradiation. The erasing contrast is relatively lower but can be improved by multi-layer films match.
Based on the analyses of holographic optical disk storage theory and the technological issues, the parallel addressing/tracing technology are discussed in detail. The optical comparison parallel addressing and tracing servo/track-search systems are described and experimentally demonstrated.
Several improvements to the optical disk drive and key parts have been carried out to enhance their function, storage density, capacity, data rate and reduce access time in recent years in the Optical Memory National Engineering Research Center (OMNERC). Approach for research on both of optical system and mechanic-electronic servo system are also reported in this paper. OMNERC of China started research and development on optical disk drive in the early 80's. In the past 15 years, many kinds of drives as phase-change erasable disk drive, CD-ROM drive, V-CD player etc. have been finished and some results of them have been playing important role in optical storage products manufacturing industry. In recent 5 years OMNERC has made the new optical drive model and some major technology research and development from the China national 8th five years science and technology development plan. The objective of this major subject is to make research and development on new generation multifunctional optical disk drive, especially on photo/thermo effect read, write and erase technology and drive as well as application systems. They are following projects: designing larger numerical aperture of objective lens used to enhance resolution and storage density, simplifying moving part of optical head to reduce its weight with holographic and other diffraction elements, increasing autofocusing and seeking precision, speed and proper frequency width of driving system, developing dual laser beams multifunctional optical head which is suitable for various inorganic and organic write once or erasable media, improving the data rate and reliability of storage data.
Recent research and development efforts in digital versatile disc mastering using dye-polymer media and direct-read- after-write technology are discussed. A comparison of this implementation to that of photoresist technology is given.
A dual beam recorder for high density format has been developed. The recorder features remote control of size and mutual distance of both recording spots, a special beam pointing control system, and a high accuracy, laser interferometer controlled, radial drive. The recorder can switch between very dissimilar formats without intermediate alignment. The performance of the recorder has been shown for DVD, MO, and even higher density formats. Track pitches down to 0.7 micrometers have been realized.
Mastering refers to the process of forming the original pattern for replicating structures to provide the specified opto-electronic signals. Several technologies have been explored since the start of the optical storage industry. Mechanical cutting, as used in the conventional audio industry, turned out to be unpractical. Mastering dynamics could be best reached by laser beam recording. Literature reveals two types of possible processes for laser beam recording; photo-resist based and non-photoresist (ablative) based technology. The photo-resist technology is based upon a process using well established lithographic technologies. The master disc is composed of a glass substrate on which a layer of photo-resist material has been applied. The submicron sized portions of this photo-resist layer, exposed by the focused laser beam, give the requested opto-electronic structure after development and rinsing of the master substrate. The photo-resist based process is a microscopically localized process. The pit shape depends on the exposure of that area only and no contributions from adjacent spot positions are present. The photo-resist process has proven flexibility towards a large variety of groove and pit shapes. The final pit structure is controlled during the development process by pit-formation monitoring. Non photo-resist mastering deals with forming structures by local heating of specific areas of a substrate covered with an ablative material. The pit formation and the shape of the pit depend strongly on the temperature profile. This pit-formation process depends not only on the (heat) exposure of the laser beam for that given minute portion but also on the heat flow from neighbouring areas. If a nearby area has just been heated, heat will diffuse to that given area and cause a different pit shape. This highly unwanted phenomenon is known in optical recordable systems as "inter symbol interference". In order to prevent uncontrolled pit formation due to this interference from adjacent pits, complex write strategies have to be used. These write strategies are strongly dependent on recording speeds, layer thickness, spot quality and layer quality. In order to certify the performance of this process for its pit characteristics, the pit formation has to be verified by a second read beam. This read laser adds to the systems complexity while its reliability has to be certified systematically. This explains why more complex pit structures, e.q. MO, are preferably realized by the photoresist mastering process.
This paper brings in focus the quality control issues during data handling in the CD production process. By warning for the problems that can occur at different points in the production chain, many costly, damaging and time-consuming errors can be prevented. Errors can happen anywhere along the line at various points and logistic interfaces. So it is important to identify what can go wrong from the authoring/pre-mastering stage all the way to shipping the final product to the customer.
Multimedia consumes a vast amount of storage, even when compressed. This requirement couples with the continual explosion of media availability and the human desire to access more information, makes multimedia servers the inevitable repository for many applications. In this paper we describe technology for multimedia data storage. We discuss: the choice of storage media, disk scheduling, data placement in the media, the file system of the storage server, and the reliability and availability of the multimedia storage server. As a summary, we give an implementation of our project ATM-Based Multimedia Storage System in the final part of this paper.
Optical array and special data arrangement affect data sharing feature of Video-on-Demand system significantly. Some aspects related to maximum user number have been analyzed in theory and verified in experiment.
Video CD playback board is a built-in card for a conventional audio CD player that allows users to play back high quality full-motion video and stereo sound. The board is made up of the CL480 MPEG-1 audio/video decoder, the Bt851 NTSC/PAL video encoder and the CS4331 stereo D/A converter. By connecting the board to the DSP's serial data output of a audio CD player. Video CD discs can be played back by using the Subcode PQ search mode of the CD player. Audio CD players will simply evolve into Video CD player.
The CD-R, a recordable disc that can be played on CD and CD-ROM drives, is emerging as the ideal device for small-scale data distribution and pre-master editing of CD-ROMs. Several media manufacturers have plans to add CD-R to their product line and need to become familiar with the new testing requirements. Testing of recordable media such as CD-R has very different aspects from the testing of CDs. The CD-R system description is given in the Orange Book, Part Two published by Sony and Philips. Since the CD-R has to be playable on a regular CD (-ROM) player it must meet both the regular Red Book specifications for CD and the additional requirements that allow recording on a CD-R drive. CD manufacturers are intimately familiar with the Red Book requirements and with the test methods used to ensure compliance. The CD-R is posing new and interesting challenges to an industry largely used to non-destructive read-only testing. In the following a review will be given of the CD-R, its specifications and testing requirements, together with testing approaches. Special attention will be given to the measurement of jitter.
In this paper, introductions are focused on the principle, structure and precision of the laser-cutting machine, which has been used to etch servo-grooves and preformat information for making the master optical disk.
The theory and experimental analysis has been made in this paper for the change of phase retardation in optical disk substrates when light beams pass through them from different incident angles. We tested the PC and glass substrate by using a polarization phase modulation method with Polarizer- Modulation-Compensator-Specimen-Analyzer structure.
We have developed a testing system with 514.5 nm argon ion laser to test the static properties of optical disks. The whole testing system is controlled by a computer. The laser power, pulse duration time and external applied magnetic field can be adjusted in a wide range. The focused spot size is less than 1 micrometers on the recording layer which allows high laser power irradiation, up to 30 mW. This testing system can evaluate the writing and erasing characteristics of phase-changes and magneto-optical disks. The design idea and experimental results of this testing system are presented.
We have developed a dual-beam magneto-optical (MO) recording system to test the dynamical properties of MO disks. Magnetic field modulated direct overwrite is realized on this system. The effect of light intensity, linear velocity of disk, modulating frequency and magnetic field intensity on carrier-to-noise ratio is investigated.
The average distance between different data will decrease through reasonable data distribution. Redundant MacroBlock data strategy is such a way to reduce seeking distance, and improve seeking efficiency, which is presented in theory and experiment.
This paper reports our study of a novel image sequence coding scheme based on 3D image segmentation. The intervals between successive reference frames are adaptively adjusted to increase the compensability of image sequences. The bit rate allocation takes the advantage of the temporal masking of human vision system.
An analysis of the RLL (1,7)-PWM method for magneto-optical disks and the RLL (2,7)-PPM method for phase-change disks is presented. The reasons why they exist simultaneously is the light of the characteristics of recording media are discussed.
This paper introduces a new method to simulate the pre- formatted information on optical disk cartridges. Using personal computer and a few data output circuits, pre- formatted information on magneto-optical disks specified by ISO/IEC 13549 standard can be generated continuously at a high rate.