In this paper the gray scale fidelity of images retrieved from photorefractive volume holographic memories is studied in detail. We propose, for the first time to our knowledge, to use the correlation coefficient between the original and the retrieved images as one of the measures for proper assessment of the gray-scale fidelity. The influence of recording object-reference beam ratio on the fidelity is investigated by using these quantities, and the dynamic evolution of the gray scale fidelity during hologram recording is calculated and experimentally measured.
Compact Disc Recordable (CD-R) and Digital Versatile Disc Recordable (DVD-R) are discs where enormous mounts of digital data can be recorded. The reflection, absorption and transmission rate of laser beam in the layer of CD-R at 780 nm and DVD-R at 650 nm with no reflecting layer were numerically calculated and optical properties of a dye film was measured. The results indicate that it is preferable to use dye as the recording media with n and k value in the range of 2.0 to 2.8 and 0.02 to 0.22, respectively. Thermal properties of these dye materials were analyzed by Differential Scanning Calorie method. The decomposition temperature of dyes were varied from 200 to 300 degree(s)C resulted from different methine length, substitutes and counter anions. The optical recording mechanism of CD-R and DVD-R were also briefly discussed based on the above results.
A multi-valued photochromic optical disk written by different flux irradiation based on the photon-mode recording property is presented to obtain high density and high speed. A four-valued (2-bit) photochromic storage is carried out by static testing on pyrrl fulgide derivative. A new nondestructive read out method--dual-beam compensation readout--is proposed and discussed.
For the bismuth substituted yttrium ion garnet (Bi-YIG), it is considered that the 6p orbits of Bi3+, 2p orbits of O2+, and 3d orbits of Fe3+ are overlapped one another into hybridized molecular orbits. The number of hybridized orbits is quantitative related with the ion concentration of Bi3+. When (omega) equals 2.3 eV or (omega) equals 2.8 eV. The (theta) F varied with the spin- orbit splitting energies (Delta) is calculated respectively, in Y3-xBixFe5O12 on x equals 0, 0.1, 0.3, 0.5. The results indicate that the large enhancement of Faraday rotation, with the enhancement of spin-orbit splitting of excited state, is dominated by the substitution of bismuth.
This paper lays emphasis on the mechanisms of optical bistabilities in thin films (TF) or organic dye solutions (OS). The absorption of laser beam in these materials strongly depends upon not only their detailed electronic structures but also the photon energy (HBAR (omega) ) of laser beam. The third-order nonlinear optical characteristics of TF or OS are presented and discussed.
Near-field Recording Optical Disc is a new optical disc recording technique. It has two characteristics: (1) ultra high recording density; (2) very high tracking speed. The paper introduces characteristic of near-field optical disc recording technique. The paper presents energy problem of read-writing system with dynamic state in near-field optical disc recording technique; and does simulating calculations for energy transporting problem between of flying head and optical disc.
With the terabyte demands of storage in many applications, the improvement of the speed of optical disk, especially the write performance will definitely extend the scope of their applications and enhance the overall performance of computer system. One effective way to improve the speed is to use a plurality of optical disk drivers together to construct an optical storage array similar to Redundant Arrays of Independent Disks (RAID). According to the typical architecture of RAID, the most common fault tolerant RAID architecture is RAID level 1 or RAID level 5. Both are not suitable for optical storage array because RAID level 1 architecture has the most redundancy, while the write performance of RAID level 5 architecture is one-fourth of that of RAID level 0 architecture especially for the small- write problem. In this paper, we propose a high performance and high reliability optical disk array architecture with less redundancy, called Mirror Striped Disk Array (MSDA). It is a novel solution to a small write problem for disk array. MSDA stores the original data in two ways, one in a single optical disk and the other in a plurality of optical disks in the way of RAID level 0. The redundancy of whole system is less than RAID level 1 architecture but with the same reliability as RAID level 5. As the performance of RAID level 0 part of optical storage system is much higher than that of RAID level 5 in ordinary disk array, thus it avoids the write performance loss when using Mirror Striped Disk Array architecture. Because it omits the parity generation procedure when writing the new data, thus the overall performance of Mirror Striped Disk Array is the same as that of RAID level 0 architecture. Using this architecture, we can achieve the high reliability and high performance optical storage system without adding any extra redundancy and without losing any performance compared with RAID level 0 architecture but with the reliability much higher than that of RAID level 5.
Polymer materials show their impact on optical storage technology for developing high information density and fast access-type memories. A new push-pull azo dye-doped polymer material has been developed by a spin coating process and used for write-once optical media in this paper. The absorption spectrum of the spin-coated thin film show a strong and broad absorption region at the 400 - 550 nm, which matched with the wavelengths of Ar-laser. The optical recording performance of the azo dye-doped polymer thin film show that higher reflectivity contrast can be obtained at lower writing power and writing pulse width using an Ar- laser (514.5 nm) irradiation.
In this paper, a writing and reading method of 3D optical digital storage is presented. The novel method is based on dual photon-absorption effective and multi-layer distribution of data. The potential problems of the method are discussed and analyzed.
This paper introduces the design and implementation of a Multimedia Data Repository served as a multimedia information system, which provides users a Web accessible, platform independent interface to query, browse, and retrieve multimedia data such as images, graphics, audio, video from a large multimedia data repository. By integrating the multimedia DBMS, in which the textual information and samples of the multimedia data is organized and stored, and Web server together into the Microsoft ActiveX Server Framework, users can access the DBMS and query the information by simply using a Web browser at the client-side. The original multimedia data can then be located and transmitted through the Internet from the tertiary storage device, a 400 CDROM optical jukebox at the server-side, to the client-side for further use.
In this paper, design of the OAH-M7 Optical RAID system is discussed. Scatter/Gather method is used in data stripping and data reconstruction to improve the data transfer rate. In addition, the function of each model is described.
This paper describes the probabilities of concurrent access to an optical jukebox in a hierarchical VOD system, it also explains some fundamental principles for the retrieval and storage of video data. Using a simplified general framework, both singled and multiple video streams playback are discussed. As a result, there are three ways to support more users to access an optical jukebox directly.
Slow access speed is still the problem to limit applications of rewritable optical disk drives. Dual stage actuators with a coarse and a fine actuator are used in optical disk drives. In this paper, the two-actuator cooperative seek control method, based on time optimal seek control, is presented, and the average seek time is analyzed theoretically.
In this paper, principle and design of high spatial frequency rectangular phase optic grating used as high- efficiency, micro energy beam-splitter are discussed. By using Fourier integration, lightwave electromagnetic vector diffraction model for high spatial frequency grating is made, and with the help of computer, grating structure parameters' effect upon beam-slitting efficiency is simulated. In order to evaluate the design effect of grating, an evaluation function is introduced. Finally, the design of grating laser beam-slitting system is optimized.
The energy loss of fiber tapered is an important problem in research of Near-Field Optical disc technique. To calculate accurately energy loss, laser waveguide model in fiber tapered should be made. The paper discusses the problem of waveguide of fiber tapered with three layers medium (core, clad and air). The paper makes a model that transforms waveguide problem to problem of a series equation. If boundary condition is confirmed, numerical solution of waveguide in fiber tapered can be got by using the model. In the condition of column-symmetry field the paper provides an example.
In this paper, a high speed data recording system based on optical disk array is presented on the basis of careful analyses of the techniques to improve the data recording speed of the commercial optical drives. An ultra high speed and mass storage capacity are achieved in this system. Flexibility and portability are also gained by the design.
In this 1D model of Magneto-Optical read channel, the isolated step response is modeled to be a Q function, and an equalizer parameter designing method based on the least square error criterion is given, which is suitable for both linear equalizers and feedback equalizers. The detection method can adopt the threshold detection and Viterbi detection. Although the model is linear, it is easy to simulate the non-linear characteristics like bloom or jitter in Magneto-Optical recording.
An optical recording static tester with high performance but low cost based on a commercial optical disk drive is introduced. Its schematic diagram and optical system are described. A quasi-linear-region focusing search method is proposed and carried out. It is a simple reliable focusing search method based on the positive and negative feedback characteristics of the focusing error curve.
This paper provides a method to test some parameters of CDs. These parameters show the quality of the disks directly. The method is based on a commercial CD-ROM and a common computer. Some necessary circuits and software are added in. The analytic results can be provided.
Magneto optical (MO) disks have shown great advantages in performance, reliability, price per bit, portability, rewrite cycles, high-density recording, and achieve life. For a 3.5' ISO standard MO media, the capacity of 1X-density disks is 128 MB, and 5X density disks have 540 MB/640 MB capacity, with track and bit density increased. Media testing is very important in research and manufacture of the disks. A media testing system for the characteristics of the recording layer of the 5X capacity MO disks is introduced in this paper. Many features and techniques are discussed such as to achieve high accuracy testing, flexibility to upgrade the system.
According to detailed analysis of dynamic process in electron capture material, we suggest a theoretical model in which the electron transfer from electron traps to luminescent centers through conduction band and tunnel are considered simultaneously. A group of equations is set up based on this model and an expression describing the read process is gained. A kind of electron capture material, BaFCl:Eu2+, is fired and a serial of spectra is measured. The theoretical results are compared with the experiments in terms of decay process, the difference between two kinds of electron traps and the relationship between irradiation dose and luminescent intensity.
The luminescence of BaFCl:Eu2+ after ultraviolet under different temperature is studied in this paper. According to the spectra, the temperature effects of two kinds of electron traps is compared and the electron transfer process in read process is discussed.
The thermal stability of amorphous TbFeCo films covered with the protected AlN films prepared by the RF magnetron sputtering system was studied, in order to understand the degradation kinetics in rare-earth transition metal films. The changes of anisotropy Ku, Kerr rotation angle (theta) k and coercivity Hc with annealing time were measured with the automatic magnetic torque apparatus and the automatic measurement system of MO Kerr effect, respectively. Data clearly show that stress relaxation is responsible for the decrease in the magneto-optical properties after thermal annealing. Furthermore, annealing studies reveal that the thermal stability of magneto-optical properties improves with increasing Ar sputtering pressure-- a trend that is in conflict with the tendency for films sputtered under low Ar pressure to be more oxidation resistant. This trend is attributed to the large stress component that exists at low Ar pressures and its tendency to decrease as a result of annealing.
The analytical expression for the relationship between the eigenvalue and the total value of the Kerr rotation angle is given by adopting the superposion principle of the interference of light in the bilayer-structure coating with transparent dielectric. The mechanism for the enhancement of the Polar Kerr effect can be discussed. Moreover, comparisons with J. Zak' method and discussions of suitability for the expression have enabled the method validation.
In this paper, optical properties of Eu3+:Y2SiO5 have been investigated. 7FJ(J equals 0,1,2,3,4)$ARLR5D0,1,2 transitions of Eu3+- doped in Y2SiO5 crystal were studied by transmission spectra, fluorescence spectra, photoluminescence excitation (or absorption) spectra and site selective fluorescence spectra. Nearly fifty Stark energy levels are recorded in our experiments. The results show that the Eu3+ ions occupy two inequivalent sites whose spectral lines of 5D0$ARLR7F0 transitions are about 0.2 nm from each other in Y2SiO5 crystal. By analyzing these spectra we also find that both sites are centers of low symmetry. The X-ray powder diffraction pattern of Eu3+:Y2SiO5 shows that the crystal is monoclinic, and lattices constants a, b, c and (beta) is obtained by a simulation with the measured diffraction angles. The lattice constants a, b, c is found slightly larger but very close to those of undoped Y2SiO5 crystal.
The density of states and orbital energies of (Y3+Fe3+6O2-8)5+ cluster of YIG and (Bi3+Fe36O2-8)5+ cluster of Bi-YIG are calculated by using DV-X(alpha) method. The wavefunctions of some orbits of clusters are given. From total density of state and wavefunctions, it is found that the spin-orbit interaction is increased by the formation of molecular orbit between 3d orbital in Fe3+ and 6p orbital in Bi3+ having a large spin-orbit interaction coefficient and the oscillator strengths of transitions are increased because of bismuth substitution. There are two types of charge transfer transition between -3.2 approximately 3.2 eV on the basis of the total density of energy states of YIG and Bi-YIG films. The optical absorption spectra of Bi-YIG are calculated while x equals 0, 0.4, 1.0 in the wavelength from 0.5 micrometers to 0.9 micrometers . The dependence of absorption coefficient (alpha) on transition linewidths (Gamma) , and spin-orbit splitting energies (Delta) i of coupling orbits are investigated respectively. The influence of Bi3+ ion on optical absorption is obtained.
A thiol-terminated phenylazonaphthalene derivative, namely 1-mercapto-6-[1-(4-phenylazonaphthoxy)]hexane 1, was synthesized by diazo coupling of aniline with 1-naphthol, etherification with 1,6-dibromohexane and thiol derivatization, subsequently. By self-assembly technology, the compound was spontaneously absorbed in thin, optically transparent gold film and formed stable self-assembled monolayer (SAM). The self-assembly course was monitored by UV-visible absorption spectra which gave direct evidence for the self-assembly mechanism of self-assembled monolayer, i.e., chemically adsorbed firstly, then came through a long- time orientation. Meanwhile, cyclic voltammogram was employed to study the electrochemical reduction and oxidation of the immobilized phenylazonaphthalene. The single molecular area obtained using the two methods was almost the same: ca. 0.9 nm2. The irreversibility of the electrode process, sluggish reaction and reduction peak splitting all were originated from the well molecular orientation, not the dense packing in the SAM. This implied the process of oxidation and reduction accompanied the molecular conformation change which needed more free space for the movement of the molecular chain during the electrode processes.
Thin films of TNPPcZn (tetra-neopentoxy phthalocyanine zinc) were prepared by methods of spin-coating and vacuum evaporation. The absorption spectra and X-ray diffraction of both types of thin films were measured at various temperature or after annealing at various temperature. Phase changes were found in the TNPPcZn spin-coating film while the evaporating thin film hardly showed any changes.
The optical parameters of two type vacuum stabilized vanadium oxide phthalocyanine (VOPc) thin film samples were measured by a spectroscopic ellipsometer system. The results were obtained over the spectral from 270 nm to 1700 nm, and the thickness of each VOPc film was determined.
The current 3.5' MO disk has a capacity of 640 MB. To increase capacity/recording density, we investigated magnetically induced super resolution. Double mask rear aperture detection is described, resulting in two to four times increase in capacity. In future we want to achieve 15 GB or 20 Gb/in2 five years later from now and 150 GB ten years later. Various technologies to achieve them are surveyed. To increase performance we proposed multi-beam optical head. Laser-assisted magnetic recording will be a breakthrough to the density limitation of magnetic recording caused by thermal fluctuation.
Within a few years development in read-out technology will enable optical disc formats with linear densities of almost 2.5 times the DVD linear density. Mastering these format set very tight requirements for the resolution and the mechanical stability of the equipment. Mastering for these formats will be possible by a combination of deep UV recording wavelength, high contrast photoresist processes and the evolution of existing servo mechanical systems. The experimental work in under way at the time of submission, the results will be presented at the conference.
This paper describes one of the most successful application of digital video on Compact Disc (CD) so far, namely Video- CD and the basic format characteristics for the proposed next generation Video-CD, now called HQ-VCD. The paper starts with a survey of the different CD formats that has been introduced since Compact Disc Digital Audio was introduced in 1983. The CD has proven to be a very suitable media for publishing of all sorts of content; audio, video, text and data.
At the rate which areal density is advancing, the drive designer expects to encounter the superparamagnetic limit somewhere between 20 and 40 Gbpsi. In this paper, we review several new near-field magneto-optical recordings for high- capacity storage technology and their optical characteristics. We also will present novel head designs. The HGA (Head Gimbal Assembly) consists of a miniature slider body, objective, solid-immersion lens and a planar writing coil mounted underneath the slider in a flying height of few micro inches above the media. We will discuss aspects of the near field optical recording technology, along with some physics.