Collinear holography

A novel reading and writing technology for a holographic storage system called collinear holography is developed. With this method, two-dimensional page data can be recorded as volumetric holograms generated by a reference beam and a signal beam that are bundled on the same axis and irradiated on the recording medium through a single objective lens. The multiplex recording and reconstructing process is demonstrated, and it is presented that optical configuration and the dichroic media disk structure are suitable for a compact system. This method enables us to construct a small volumetric optical disk storage system with CD and DVD upper compatibility.     

Performance of a write-once multilayer optical disk that uses transparent recording material with an optical switching layer

A volumetric optical disk that has multiple transparent films with optical switching layers is used as a recording medium to increase the number of recording layers. In the disk the optical switching layer is adapted to reduce decay of laser energy and increase reading and recording sensitivity. Well-defined marks of approximately 100-nm depth can be placed precisely on the transparent films by a focused laser beam. Writing and reading of a four-layer recordable disk, fabricated by molding and spin bonding, have been demonstrated experimentally. The volumetric disk can achieve a high recording capacity with conventional optical pickups.     

Phase-change optical disks compatible with a two-wavelength laser beam

Three types of multiple-layer structure are proposed for a two-wavelength-compatible phase-change optical disk that uses an 830-nm beam for writing and erasing and a 670-nm beam for reading. Each disk with an optimized structure exhibits high-enough carrier-to-noise and erasing ratios at 830 nm and 670 nm for practical use. One of the disks has a lower erasing ratio at 670 nm than at 830 nm for the same erased marks. This difference is explained by optical characteristics that stem from the multiple-layer structure of the disks.     

Microholographic multilayer optical disk data storage

Micrometer-sized reflection holograms can be written into a rapidly rotating homogeneous photopolymer disk at the focus of a high-numerical-aperture beam and its retroreflection to implement high-capacity multilayer digital data storage. This retroreflection is generated by an optical system with positive unity magnification to ensure passive alignment of the counterpropagating beam. Analysis reveals that the storage capacity and transfer rate of this bit-based holographic storage system compare favorably with traditional page-based systems but at a fraction of the system complexity and cost. The analysis is experimentally validated at 532 nm by writing and reading 12 layers of microholograms in a 125-microm photopolymer disk continuously rotating at 3600 rpm. The experimental results predict a capacity limit of 140 Gbytes in a millimeter-thick disk or over 1 Tbyte with the wavelength and numerical aperture of Blu-Ray.     

A proposed beam-addressable memory

The feasibility of optical beam-operated magnetic storage systems is assessed. Recent advances in laser technology and in transparent magnetic materials are described along with methods for writing and reading information. In the writing process, thermomagnetic recording on thin films is considered and the writing speed and resolution is calculated, illustrating the large performance improvement obtainable compared with existing magnetic recording techniques. The progress in materials, beyond the previously used metals, has developed towards more transparent magnetic media while retaining large intrinsic magneto-optical rotation. Consequently, large signal-to-noise ratios are obtained which relax the material uniformity requirements. The properties of ferrites, garnets, and rare-earth compounds are compared with metals to illustrate this advance. At the present time, technical problems exist with a light beam in achieving random access to a large field. This limitation is alleviated, however, in certain types of memories where the access requirements combine sequential and random motions. As an example, a prototype memory is discussed for a computer input-output system having certain performance advantages. In this memory, sequential access is achieved with a rotating mirror and random access by means of a digital light-deflector.     

Enhancement of the switched phase conjugate reflectivity in a BaTiO3 crystal

We experimentally investigated the response of the photorefractive phase conjugation to a pulsed reading beam in an undoped BaTiO₃ crystal with a four-wave mixing geometry. A single longitudinal-mode Ar⁺ laser was used as a light source. The reading beam with a pulse width of ∼1 s was switched on after writing a steady-state grating in the crystal by two recording beams under a suitable condition and the generated phase conjugation was measured. The phase conjugate output was found to be increased by some factors of magnitude over the initial value for a given peak power and period of the reading pulses. A maximum of the enhanced reflectivity can be controlled by adjusting the interacting beam powers. An increase in the diffraction efficiency was also found with the same read-out process, which plays a key role to increase the phase conjugation as our knowledge.     

Analysis and Reduction of Ultrasonic Pitting Defects on Hard Disk Surfaces

It has become of paramount importance to be able to perform failure analysis of defects on hard disk surfaces quickly and accurately. In this study, ultrasonic pitting defects on hard disk surfaces were investigated. A new electrical tagging pattern system, which directly translated the channel bits to magnetic transitions during writing of the magnetic pattern around a defect, was used in the failure analysis of magnetic recording disks to mark defective sectors. With the help of the Kerr magneto-effect, the defective sectors were effectively located for further failure analysis. Results of the failure analysis revealed that there was 30% to 40% loss of the recorded magnetic bit signal due to an increase in the gap between a recording head and a hard disk surface with ultrasonic pitting defects. The experiments performed indicated that low ultrasonic power for disk cleaning could reduce the ultrasonic pitting defects significantly. The maximum failure rate due to single-type ultrasonic pitting defects was reduced from 33.4% to 16.7%, while the maximum failure rate due to cluster-type ultrasonic pitting defects was reduced from 11.1% to 5%.     

采用图像格式的IDE硬盘直写记录

介绍一种采用IDE硬盘的高速图像记录系统的设计方法。该方法去掉了大量的软件编程代 之以硬盘直写图像文件的模式,将图像数据记录到硬盘的同时直接以文件形式存放。实验效果表明,采用该设计方法的记录设备做到了记录完全脱机,事后将硬盘通过USB接口直接与计算机相连,即可对图像进行访问,达到了预期的目的。     

声学环境对硬盘读写性能影响的实验研究

伴随着笔记本电脑的小型化,机械硬盘也朝着小体积、高存储密度的方向发展,近年来硬盘对系统扬声器播放音频产生振动的敏感性表现出增加的趋势。采用实验研究的手段,通过纸盆扬声器,考察声学环境对硬盘读写性能的影响。首先,通过编写程序实现对硬盘读写速率长时间有效的监测;其次,改变声音输入的声压及频率特性,得到硬盘失效模式与声学环境之间的关系;第三,考察硬盘在无阻尼自由边界、无阻尼刚性边界、有阻尼刚性边界三种状态下读写速率的变化情况,分析边界条件对硬盘读写速率的影响,从而为笔记本电脑内部硬盘安装的优化提供依据。     

Integrated magnetic recording heads

A new type of integrated magnetic recording head has been developed. The head is made completely from thin films by vacuum deposition through a mask. This technology enables us to make many heads in one vacuum cycle. A special study has been carried out on the geometrical forms and on the anisotropic magnetic material. The demagnetizing fields require that we make magnetostatic coupling layers for each magnetic leg of the head. Also, the results indicate that the heads can be used for writing and reading.     

Analytic determination of overwrite capability in magnetic recording systems

Analytic design criteria are provided to determine if a digital magnetic recording system can overwrite under worst-case conditions. The worst-case condition is taken to be a bubble of reversed magnetization in an otherwise saturated medium, written by applying current to a stationary recording head. A leading and a trailing transition are formed, creating a large demagnetizing field opposing the head field. Although the leading transition is commonly thought to be unimportant in saturation writing, its demagnetizing field can significantly hamper the writing of the trailing transition. First, self-consistent numerical calculation shows the characteristics of the bubble and its associated fields. Then the bubble is approximated analytically by a biquadratic form, and the demagnetizing field at the bubble center is compared with the field necessary to saturate the medium. A rapid loss of overwrite ability with decreasing gap-length is demonstrated. The importance of including image fields for thin-film heads is discussed. Graphical representations are given for the minimum gap-length necessary for overwrite. A relation between media parameters, bit density, and magnetic energy/bit in commercial disk drives is discussed.     

Thin-film inductive heads for perpendicular recording

A modified thin-film magnetic head for perpendicular recording in rigid disk drives with improved read/write characteristics, especially at high areal bit densities, is presented. The head on which the modified design is based is described. It combines the advantages of single-pole heads and thin-film heads, writing with the sharp field edge of the leading pole and reading like a thin-film head. To increase the writing efficiency and improve the yield, the sequence of magnetic layers in the head is changed; the second layer of the four-layer head is embedded in the substrate, where it can be placed much closer to the pole tip of the first layer. The improved write capability depends mainly on the position of the embedded layer. In addition, there results an improved magnetic flux guidance from the embedded layer into the pole tip layer, providing the potential for a significant improvement in fabrication yield. The embedded-layer approach also allows a further increase in areal density. The results of read/write tests and the write-wide and read-narrow characteristics are presented     

Large scale model studies of vertical recording

A large scale magnetic recording model (5000x) has been used to study writing and reading using a film ring head on a medium which can be configured in either a horizontal or vertical recording mode. Field measurements from the written transitions indicate that a narrower transition is written on the vertical medium configuration than on the horizontal.     

Optical-disk media fabrication for high data-transfer rate

Two media fabrication methods are developed in order to improve the data-transfer rate of optical disks. One is a beam-scanning method for multispiral pregroove recording. A sixfold spiral pregroove with a 1.6-μm spacing can be recorded with this method. The other is a method for fabrication of phase-change optical-disk media that provides signal reading at 670 nm, writing at 830 nm, and high erasability at high linear velocity. The linear recording density of disks fabricated in this way is 1.2 times higher than that of optical disks read at 830 nm, and the erasability is more than 25 dB at 40 m/s. These methods offer the possibility of a data transfer rate 10 times higher than with conventional methods.     

Automated optical mass storage system with 3-beam magneto-opticaldisk drives

An automated optical mass storage system (optical MSS) with high-speed magnetooptical (MO) disk drives has been developed. It features a high data transfer rate for writing with the use of the 130-mm ISO standard MO disk, and disk cartridges with high storage efficiency. As the key device, a high-speed MO disk drive has been developed. It provides a high-speed data writing capability of about ten times that of conventional MO disk drives. The optical MSS provides a data transfer rate for reading and writing of 2.1 MB/s, a storage capacity of 250 GB to 1 TB, and an average cartridge handling time of 5 s. From performance simulations, the optical MSS is proved to be applicable to a low-traffic random-access file that stores multimedia data and a high-speed direct-access storage device (DASD) backup file     

Partial-response signaling for phase-change optical data storage without electronic equalization

We describe the application of partial-response (PR) signaling in rewritable phase-change optical data storage. No electronic filter is necessary to shape the readout signal to a certain PR target. A PR-like waveform at the output of the read channel is directly achieved by optical recording. A genetic algorithm is used to optimize the parameters for writing and therefore to minimize the difference between the actual readout signal and the ideal PR waveform. With a laser wavelength of 0.66 microm and an objective lens with a numerical aperture of 0.6, four linear densities were examined: 0.4, 0.3, 0.25, and 0.2 microm/bit (without modulation). Results showed that the linear density of 0.25 microm/bit can be realized on a rewritable digital-versatile disk.     

基于HVD包络谱瞬态能量曲率的井架钢结构损伤识别

针对复杂工作环境下井架钢结构损伤识别问题,提出了一种基于希尔伯特振动分解(HVD)包络谱瞬态能量曲率的井架钢结构损伤识别方法。已知非平稳、非线性的复杂信号,利用结构低阶信息,利用HVD法将其分解为拥有缓慢变化多个信号分量之和,选取主分量提取信号特征;对于井架钢结构损伤识别,利用HVD法提取振动信号的损伤特征,将HVD包络谱瞬态能量曲率作为损伤敏感指标;计算井架钢结构振动信号包络谱瞬态能量曲率完成损伤识别,以ZJ70井架钢结构为例,通过损伤识别仿真计算,得出该指标对井架钢结构损伤敏感,能够准确识别单损伤和多损伤位置;将该方法应用于ZJ70井架钢结构实验模型,成功地识别了单损伤和两损伤,验证了该方法的可行性和准确性。     

Study and implementation of a hybrid diffractive/refractive lens and a color inkjet head on high density data storage

Traditional optical storage technology focuses a laser beam on the surface of a disk using objective lenses. The storage capacity is limited. It entirely depends on the effective disk size. Using colored storage technology to increase the storage capacity is a novel approach. Color is used to store information. After the spectrometer reads the data, the original color is computed and the stored information is read. In this study, a color is used to write colors; optical transmission with a hybrid diffractive/refractive lens produces a transmission spectrum, and then the fiber-optic spectrometer reads and analyzes the color and then decodes the information. Based on a 2.4?μm reading spot size and the implementation of tricolor ink, ～4.561 Gbytes can be stored. If the tricolor ink dripping and laser size can be reduced to 1.80?μm, each disk can store data up to 8.1?GB.     

Electron-beam writing system and its application to large and high-density diffractive optic elements

An electron-beam writing system that is chartacterized by a stationary electron beam and a continuously spinning table is proposed and developed for diffractive optic elements with axisymmetric patterns. This system allows us to fabricate continuously concentric or radialized high-density microgratings with effective areas over the electron-beam deflection limits. For a fine electron-dose distribution, we adopted multiple-revolution writing and electron-beam modulation. Several test gratings, including a rotary encoder disk with a 1.57-μm grating pitch and a 15-mm diameter and a blazed micro-Fresnel lens with a 4.5-mm diameter and a N.A. of 0.45, are successfully demonstrated with real-time data processing.     

5.25 inch floppy disk drive using perpendicular magnetic recording

5.25 inch high density perpendicular magnetic recording floppy disk drive has beer developed by employing new types of high saturation magnetization ring head, Co-Cr single layer medium with Ge underlayer, head slider with ellipsoidal surface configuration to assure intimate head to medium contact, and signal equalization. By these combination, recording density D50 of 145 kFCI, peakshift of 28 % at 100 kFCI, signal to noise ratio of 40.4 dB for cut-off frequency 4.25 MHz, overwrite signal to noise ratio of 27 dB, measured by writing signals at 48 kFCI over previously written 100 kFCI signals were obtained as typical recording characteristics. These results would indicate that floppy disk drive with 100 kFCI recording density has enough system margin by above-mentioned combination. In this paper, design and performance of newly developed floppy disk drive are described.