Trends and features of mass storage subsystems in network are surveyed and their key technologies spotlighted. Storage subsystems are becoming increasingly important in new network systems in which communications and data processing are systematically combined. These systems require a new class of high-performance mass-information storage in order to effectively utilize their processing power. The requirements of high transfer rates, high transactional rates and large storage capacities, coupled with high functionality, fault tolerance and flexibility in configuration, are major challenges in storage subsystems. Recent progress in optical disk technology has resulted in improved performance of on-line external memories to optical disk drives, which are competing with mid-range magnetic disks. Optical disks are more effective than magnetic disks in using low-traffic random-access file storing multimedia data that requires large capacity, such as in archive use and in information distribution use by ROM disks. Finally, it demonstrates image coded document file servers for local area network use that employ 130mm rewritable magneto-optical disk subsystems.

The National Aeronautics and Space Administration (NASA) is proceeding with an evolutionary approach to creating integrated muIti discipline image management systems. A goal of this development is an integrated Astrophysics Data System (ADS). The system will allow astrophysics research teams to' correlate spectral images from multiple research satellites. The ADS is the first large scale integrated research data system planned at NASA. The Earth Observing System Data and Information System (EosDlS) will create a similar system for earth sciences research. These two programs will store and retrieve more than 1 0 terabytes of satellite image data per day. Ford Aerospace is actively involved in the design and development of both the ADS and EosDlS. This paper reviews the role of optical storage technology in supporting these image storage and retrieval systems. It explores system limits based upon the current state of optical storage technology. Also discussed, are those advances in optical storage technology that could increase the role for optical storage in NASA's image management systems.

The Automated Patent System (APS) was designed, among other things, to assist the patent examiner in performing the patent search. It is a fully distributed system that uses custom-built high-resolution dual-display intelligent workstations, optical file servers, mainframes, and support computers networked together using Ethernet technology. The system is composed of two parts which are highly integrated: a full text search system and a patent image retrieval system. When fully deployed, APS will have an image data base of up to 30 terabytes being accessed from over 1000 workstations. The U.S. Patent and Trademark Office (PTO) has had problems with their optical drives, and although they are fairly stable today, we still experience a moderately high hardware failure rate. The optical drive problems include media instability, hardware design errors, vendor problems, and configuration control failures. We intend to purchase additional drives in the future, and are re-evaluating the exclusive use of optical storage in light of recent advances in magnetic storage technology.

Front illumination is the fastest type of optical disk. Front illumination also allowed us to design a very small and light head with a beam size of 1 mm. It also allowed us to use an opaque aluminum substrate, which can rotate at high speeds. If optical disks are mounted in an enclosure like those for hard disks, they are protected from contamination and front illumination would be practical.

The read and write transfer rates for large image files are studied as a function of various system parameters and file sizes for a magneto-optic (MO) drive/microcomputer system. In particular, the transfer rate performance of two erase strategies are explored as a function of parameters accessible to the image application developer. Empirical studies have shown that a feature within the magneto-optic (MO) device called pre-erase used in conjunction with the Erase command can increase performance (through-put) by almost a factor of two.

The possibility of direct overwriting in magneto-optical (MO) disk is demonstrated. By a modfied frequency modulation technique of laser pulse, erasing of recorded bits could be accomplished on the rotating disk. We measured the erasure characteristics for GdTbFe films prepared by RF magnetron sputtering, and found that erasure performance depended on the frequency and the power of the laser pulse and on the magnetic field. We also found that there was an optimum power for erasing the recorded bits. Our experiment produced almost the same rewriting carrier-to-noise ratio (CNR) as the original CNR under a weak constant magnetic field. We confirmed that direct overwriting in MO disk is possible by using a two-beam technique and that read-before-write scheme which makes a drive complex is unnecessary.

Hoechst Celanese's proprietary naphthalocyanine record-ing layer materials exhibit excellent performance for a write-once read many (WORM) optical data storage media. This pit-forming medium shows a CNR greater than 50 dB and a bit error rate less than 1 x 10 for data recorded at either 780 or 830 nm. The stability under accelerated aging conditions is superior to that for coririercial media.

A single beam overwrite optical disk memory using a rewritable phase change medium has been developed for digital data storage. The overwrite function was realized by using the same simple optical head as that of write-once memory. An 86mm pregrooved disk has the large capacity of 280MB on both sides. A higher data transfer rate of 6Mbps was achieved. A split type optical head having a 9gr. moving portion realized 42ms seek time with low power consumption. Overwrite operation is done by making amorphous marks and crystallized (erased) area with single laser beam. As the read-out signal is obtained from the difference of their reflectivities in the same way as write-once media, the optical head has become simple and compact. The overwriting temperature of the active layer is much higher than the operating temperature. This optical disk memory can execute reliable write and read operations with a wide tolerance for the operating temperature. Rewritable media were evaluated under practical perating conditions and could be overwritten more than 100,000 cycles on the same physical sectors. Implementing effective defect management, the practical or logical cyclability of the optical disk memory was improved up to one million cycles.

Co/Pt and Co/Pd multilayers were prepared by two source dc-magnetron sputtering. Magneto-optical properties of these multilayers were affected by total film thickness, and a perfect squareness of Kerr loop and an enhancement of Kerr rotation angle weresimultaneously achieved when the film thickness was below several hundred angstroms. The improvement of Kerr remanence ratio can be explained by the change in domain structure from a stripe domain to a single domain, d the enhancement of Kerr rotation is due to the optical interference effect with the multiple reflection. The ultrathin films have high corrosion resistance, large Kerr rotation and strong perpendicular magnetic anisotropy even in very thin film thickness. A hermomagnetic writing was successfully made in the magneto-optical disks using these ultrathin media,and the C/N ratio showed 53 dB and 46 dB for Co/Pt and Co/Pd disks,respectively.The figure of merit becomes larger at shorter wavelength, and thus the ultrathin multilayers can be new promising magneto-optical recording media, especially for higher density recording using a shorter wavelength laser.

Miniaturization of optical disk pickups is very important for higher data rate, faster access and lower cost, which are all required in future computer data storage systems. Various proposals that have been made along this direction in Japan for the last few years are reviewed. Proposed pickups for miniaturization are divided into the following four ones: (1) Conventional type pickups: these are miniaturized further by reducing the size and weight of each component as well as the number of components. (2) A laser/photodiode chip pickup: the laser is optically switched by relief of external recording medium, and the pickup is mounted on a flying slider, which eliminates the focus servo system. (3) Pickups with holographic optical elements: HOEs are used for replacement of discrete components. Since a single hologram can have several functions such as beam splitting and focusing, the number of those components can be reduced. Various types of complicated HOEs are proposed for tracking/focusing error detection. (4) A waveguide-type pickup: several optical components such as focusing grating, splitting grating and four photodiode are integrated on a single waveguide chip. These miniaturization research activities will become more important for future development of disk systems.

A flying optical head has been developed to attain high speed accessing, the important issue in applying optical disks for computer file memories, because the head weight could be ultimately reduced. And it was successfully applied for writing and reading of optical disks for the first time. The moving part of the head consists of an objective lens, mirror, flying slider and moving coil of a voice coil motor and a linear bearing, which total weight is as light as 3.6gr. The flying slider makes the objective lens follow on a disk surface, so the variation of the distance between the lens and the optical disk caused by the axial runout of the disk is largely reduced. Autofocusing is done by axial moving of relay lenses which are placed in the fixed part of the head. The resonant frequency of the moving part has been improved to more than 10kHz by reducing its weight, which enables it to do track-following as well as track-seeking. Seek time of less than 20 ms for a 130mm disk was achieved with the flying optical head.

We have developed a new digital servo controller for a 5"hard disk drive which has average access time of 10 ms for a 25 mm stroke. To obtain this fast access speed, we used a state estimator with a new acceleration irajectory model. The estimator and trajectory generator are implemented using a digital signal processor. There are two problems for fast access control: motor coil inductance and the mechanical resonance of the actuator and disk enclosure. To solve these problems and to achieve precise head positioning, we developed the following control method. To solve the voice coil motor inductance and actuator resonance problems, we used a new acceleration trajectory model which is not affected by the coil inductance when the head moves quickly. This design is based on an optinial control theory which minimizes the square of differentiated acceleration. By using this new trajectory model, the high harmonics of actuator drive are damped and the residual vibration ofactuator immediately after access is decreased.

DC Modulation noise was studied in thin film magnetic recording disk media as a function of magnetic layer thickness for plated, longitudinal, low-noise, 900 Oe to 1 100 Oe, Co-alloy disk media from a controlled fabrication runs. This noise is generated when a reverse longitudinal DC field is applied to a uniformly magnetized disk. This noise provides information on the uniformity of the disk for high density recording. Noise measurements using electronic detection via a spectrum analyzer provide resolution and sensitivity that is not obtainable from conventional microscopic observation. This noise was deduced to be caused by vanations in coercivity associated with defects in the medium, and not to surface roughness as has been conjectured previously. A new model was developed which allows autocorrelation functions and noise spectra to be calculated. The model agrees with measured spectral noise data with correlations greater than 0.99. The model treats the noise as effective transitions with an average magnetization less than saturation across the track width, an associated variance, and a linear distribution with Weibull process statistics, which generalizes previous work using the Poisson process for AC-erased noise. Data indicate that as the reverse field increases from zero, the distance between effective transitions peaks and then decreases as the field increases further. As the magnetic layer thickness increases from 25 nm to 60 nm, the maximum distance between effective transitions decreases from 2.8 im to 1 jim. The maximum average transition amplitude is bounded by 0.001 of the saturation magnetization and is independent of thickness.

In a magnetic disk system, the distance between the head and the disk is reduced as much as possible to increase the recording density. As the distance decreases, contact between the head and the disk becomes more and more likely. We have studied conditions leading to contact between head and disk in an effort to decrease the likelihood of contact. We experimented with a piezoelectric transducer on the back of the head slider as a contact sensor. We also construct a contamination system which issues glassbead particles at a controllable rate. We studied the relation between particle concentration and head/disk contact using this system. We also evaluated head flying characteristics over particle-contaminated disk surfaces, and tested contaminated disk surfaces in high-velocity head sliding contact.

In magnetic recording on hard disks, coated with particulate media, the maietic panicles are oriented circumferentially to provide a higher signal amplitude for the read/write head. The degree of anisotropy is termed the orientation ratio. It is the value of the magnetic remanence measured in the easy axis direction or circumferential direction, divided by the rnaietic remanence measured in the hard axis direction or radial direction. It is preferred that this ratio he uniform from the inner-most recording track of the disk (ID) to the outermost recording track of the disk (01)). Additionally, it is preferred that this ratio be uniform circumlerentially around the disk surface. Magnetic performance in terms of uniform signal modulation is more satisfactory when the orientation ratio is uniform radially and circumlerentially compared to when this ratio varies someway in either or both of these directions. j\ nondestructive optical technique, which allows the radial and circumferential orientation uniformity to be rapidly measured on a disk after coating application and orientation, is described. The methods make use of a Cross Polarizing Microscope. This rapid measuring technique allows parameters to be changed quickly, should the orientation ratio he nonuniform in any way during disk development. This convenient method ensures that disks tested at sinJe disk test do not tini because of particle orientation problems.

A decision to implement an optical storage system raises a number of issues, some of which relate directly to the current capabilities of technology and some of which are operational. The determinants for success include a thorough analysis of existing operations, a clear requirements definition, and a careful mapping of the requirements to a configuration for the system. Although these steps are materially similar to the analysis required for any automation project, they have been less than well understood in the context of this storage technology. This paper will identify and discuss these tasks as they relate to the design of a complete system, using case studies to highlight the effects of work flows, storage algorithms, and communication requirements. In the process, the paper distills design experience in optical disk data management systems with hundreds of workstations and Terabytes of on-line storage.

The National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) is developing a permanent archive for the astronomical images that will be collected by the Hubble Space Telescope (HST) spacecraft. Initially this archive will hold 30 terabytes ofdata and is expected to grow to 68 terabytes. The stellar observations and the additional ancillary information needed to fully interpret the image data will be stored in a central facility, the HST Data Archive and Distribution Service (DADS). The HST DADS will collect and archive over three gigabytes of image data per day plus support data during the 15-year lifetime ofthe spacecraft. The archive will provide astronomical researchers around the world with electronic access to the images. Prior to the HST Program, researchers usually submitted written or verbal requests for data which was then mailed to them several weeks later. HST DADS will provide almost instantaneous access to all HST data. The HST DADS functionality, the modular architecture, and the key components of the system are presented herein. The HST DADS will support over 140 simultaneous users accessing the system via a variety of wide area network and local area network connections. An online catalog will be available to assist in identifying the desired set or sets of data from amongst the eventual 68 terabytes of online data. HST DADS will support retrieval and distribution ofthe data via a variety ofelectronic and physical media.

The Tracker Data Acquisition System, TDAS is a system architecture for a high speed data recording and analysis system. The device utilizes dual Direct Memory Access (DMA), parallel Small Computer System Interface (SCSI) interface channels and multiple SCSI hard drives. Video rate data capture and storage is accomplished on 16 bit digital data at video rates to 15 Megahertz. The average data rate is approximately 1 Megabyte per second to the current hard disk drives, with instantaneous rates to 5 Megabytes per second. Message protocol enables symbology and frame data to be stored concurrently with the windowed image data. Dual parallel image buffers store 512 Kilobytes of raw image data for each frame and pass windowed data to the storage drives via the SCSI interfaces. Microcomputer control of DMA, Counter Input/Output, Serial Communications Controller and FIFO's is accomplished with a 16 bit processor which efficiently stores the video and ancillary data. Off-line storage is accomplished on 60 Megabyte streaming tape units for image and data dumps. Current applications mclude real-time multimode tracker performance recording as well as statistical post processing of system parameters. Data retrieval is driven by a separate microcomputer, providing laboratory frame-by-frame analysis of the video images and symbology. The TDAS can support 80 Megabytes of on-line storage presently, but can be simply expanded to 400 Megabytes. Phase 2 of the TDAS will include real-time playback of video images to recreate recorded scenarios. This paper describes the system architecture and implementation of the Tracker Data Acquisition system (TDAS), with current applications.

A nass image storage and retrieval system is described that utilizes digital tape for image storage, and provides fast retrieval of image batches from a tape archive through use of multiple retrieval tape drives in parallel. Suitable applications are described and system cost is compared with alternative storage media.

A memory card camera, which captures still video images in an IC memory card, has many potential applications. Digital image transmission is one of the most important functions for the development of digital still video systems. Here an experimental ISDN transmitter for digital images, recorded by the memory card camera FUJIX DS-1P, is presented.

The space programs of the 90's and beyond will employ sophisticated I with high resolution and high data rates . Temporary storage of this data on-board the satellites is an important function. The NASA Spaceflight Optical Disk Recorder (SODR) , currently under development for these future space missions, utilizes advanced techniques and concepts to satisfy these needs.

A significant advancement in law enforcement tools has been made possible by the rapid and innovative development of electronic imaging for criminal identification systems. In particular, development of optical disks capable of high-capacity and random-access storage has provided a unique marriage of application and technology. Fast random access to any record, non-destructive reading of stored images, electronic sorting and transmission of images and an accepted legal basis for evidence are a few of the advantages derived from optical disk technology. This paper discusses the application of optical disk technology to both Automated Fingerprint Identification Systems (AFIS) and Automated Mugshot Retrieval Systems (AMRS). The following topics are addressed in light of AFIS and AMRS user requirements and system capabilities: Write once vs. rewritable, gray level and storage requirements, multi-volume library systems, data organization and capacity trends.

As image processing technology advances, its application in developing management information systems (MISs) will increase. Effectively integrating this technology into large-scale information system development efforts requires advances in development tools, particularly software development tools. The development of MIS software has become more sophisticated and efficient due to the availability of powerful tools; however, these tools have not kept pace with the tremendous progress made in image processing technology. The availability of software tools is key to the success of electronic imaging --the broader the software support, the larger the potential marketplace. Standards already exist for the interchange of image information, i.e., how to move images from Point A to Point B. For example, CCITT Group 4 deals with formats for compression/decompression techniques. The tagged image file format (TIFF) has become an industry-accepted file structure. These structures do not address the problems of preserving quality, extracting information through enhancement or restoration techniques, or manipulating the image once it has been delivered to the imaging application. These and other image processing operations are becoming more widely performed, especially as the image content of information management systems increases.

The optical memory card manufactured and marketed by Drexier Technology Corporation under the LaserCard®trademark, is a credit card-sized optical data storage device presently configured to hold up to 4.11 Mbytes of WORM (Write Once Read Many) data. The availability of a portable storage medium with this data capacity has stirred the interest of applications developers in such diverse fields as security access/ID, database publishing and distribution, vehicle maintenance logs and consumer electronic coupons. The application of the LaserCard as a portable, personal medical record is currently the most fully developed and as such is being evaluated in numerous field trials worldwide. Before describing some of these field trials, it is worthwhile to discuss several contributing factors that have made these field trials possible. These factors include, 1) evolution of a manufacturing facility of high-quality LaserCards, 2) availability of production-level read/write drives from several sources, 3) emergence of standards for optical memory cards and read/write drives, and 4) perceived value of a portable medical record in the medical care field.

Stimulable phosphor cassettes, personal computers, optical discs and optical data cards permit the design of a filmiess radiographic system. X-ray cassettes are read by a laser scanner and images are displayed and stored at the small computer. More than 100 images can be stored on the computer hard disk and recalled by the radiologist for interpretation. Four high resolution monitors permit the system to be used in the same way as a radiographic alternator (multiple viewer). A report can be prepared, the images annotated and the results stored on an optical disc used by the clinic/hospital as a permanent archive. Individual records and images can be copied to credit card-size optical data cards for use by the referring physician or surgeon. The data cards can be displayed on an inexpensive independent viewer. The computer can be coupled to external medical imaging systems, CT, MRI, etc., via an Ethernet port or an ACRINEMA interface. The first system is being developed for the US Army Medical Research and Development Command under Contract DAMD17-88C-8058.

CD-ROM represents a novel and relatively effective way to store and retrieve images in a PC environment. Indeed it may be the only current method to have real utility. This paper reviews the basics of this method and the various format options available. The advantage of the CD format and, more critically, its' very real limitations are reviewed. From this analysis a set of application 'ground rules' will be developed that attempt to defme what are potentially good (i.e. successful) applications and what are not likely to succeed in the market place. Finally the evolution trends for newer image related laser based read only formats are discussed and some possible R & D routes outlined.

Traditionally, medical imaging has required large capital investments into workstations and storage subsystems. Many vendors have chosen to offer proprietary systems which are expensive to develop and costly to the institutions which purchase them. Our experience has been that this is unnecessary; most traditional imaging functions in the digital modalities of computed tomography (CT) and magnetic resonance imaging (MM) can be performed using off-the-shelf hardware with relatisely inexpensive software. In order to reduce the cost of medical imaging, our approach has been to choose computers and storage subsystems that are efficient, inexpensive, and easy-to-use (after all, the users are interested in practicing medicine, not computer science.) With these goals in mind, we chose to use a general purpose computer (the Apple Macintosh Ilci) with two types of high-capacity optical storage devices (both magneto-optical and write once, read multiple (WORM) disc subsystems.) We have developed a powerful, yet user-friendly medical imaging workstation oriented towards radiologists, orthopadic surgeons, neurosurgeons, and other users of medical images. In addition to providing inexpensive storage, the workstation is capable of multiplanar reformatting (MPR), 3D MM angiography, and other image processing functions. The resulting images may be annotated, windowed, and filmed on to 14x17" radiology film for presentation to the referring physicians and their patients. This system can be considered to be a picture archiving and communication system (PACS) for private physicians and small clinics; further, it is small enough for desktop environments and inexpensive enough for clinicians to purchase.

Several factors work together to make the publishing industry among the most demanding environments for extremely high performance mass storage systems. The first factor is the size and volume of the images, text sources, and other data that must be gathered, considered, selected and altered as a publication is produced. Mother factor is the speed with which these operations must be performed in order to support a publishing staff in its fast paced and time critical work. A third factor is the intensive level of interpersonal collaboration that is a fundamental part of the publication process. The requirements of the publishing industry are only beginning to be addressed by currently available technologies. Examples of some typical publishing processes are presented with an analysis of the storage and computational capabilities that would be required to support them at their current level of flexibility. An examination of existing storage and network technologies points out that there is much need for improvement in the areas of shared storage and retrieval systems for publishing. Data rates of existing systems remain inadequate for the needs of image intensive publication work.

Because graphic files can be stored in a number ofdifferent file formats, it has traditionally been difficult to create a graphics database from which users can open, copy, and print graphic files, where each file in the database may be in one ofseverai different formats. HyperCard Graphics Database Toolkit has been designed and written by Apple Computer to enable software developers to facilitate the creation of customized graphics databases. Using a database developed with the toolkit, users can open, copy, or print a graphic transparently, without having to know or understand the complexities of file formats. In addition, the toolkit includes a graphic user interface, graphic design, on-line help, and search algorithms that enable users to locate specific graphics quickly. Currently, the toolkit handles graphics in the formats MPNT, PICT, and EPSF, and is open to supporting other formats as well. Developers can use the toolkit to alter the code, the interface, and the graphic design in order to customize their database for the needs oftheir users. This paper discusses the structure ofthe toolkit and one implementation, Apple Graphics Source (AGS). AGS contains over 2,000 graphics used in Apple's books and manuals. AGS enables users to find existing graphics of Apple products and use them for presentations, new publications, papers, and software projects.