Dynamic information storage or retrieval – Storage medium structure – Adjuncts or adapters
Reexamination Certificate
1998-04-28
2002-12-03
Klimowicz, William (Department: 2652)
Dynamic information storage or retrieval
Storage medium structure
Adjuncts or adapters
C360S133000
Reexamination Certificate
active
06490242
ABSTRACT:
TECHNICAL FIELD
The present invention relates to data storage and, more particularly, to cartridge structures for housing data storage disks.
BACKGROUND INFORMATION
Data storage is an important aspect of today's information technology. A great deal of effort has been made by the storage industry to increase the areal data density of a storage medium in order to meet the ever increasing demand for higher capacity storage devices.
Magnetic storage devices such as fixed or removable magnetic disks and tapes are widely-used conventional storage devices. The state-of-art conventional magnetic hard drive systems can achieve extremely high linear bit densities, especially with the new MR and GMR magnetic heads. For example, the areal density of many hard disk drives is on the order of magnitude of about one gigabit per square inch. One limitation in increasing areal data density in a magnetic device is the particle size or the characteristic dimension of a typical magnetic domain of the magnetic recording materials. Other limitations include the width of the magnetic read/write head and the limitations of mechanical tracking. Therefore, these hard drives are typically limited to less than 10,000 tracks per inch.
Optical storage devices are emerging as an alternative technology to the conventional magnetic technology because of their potential for high density data storage. In optical recording, data is represented as an optically readable domain on a recording medium such as an optical disk. Optically readable data can be recorded on a disk using a variety of mechanical or optical techniques. For example, CD disks typically are prerecorded using mechanical stamping and molding steps. So-called “rite-once” media, such as CD-R disks, can be recorded permanently with optical techniques to record particular data. As an alternative to permanent recording, magneto-optic and phase change disks allow data to be recorded in an “erasable” or “rewritable” manner. DVD disks, for example, can provide prerecorded content or be configured for rewritable recording by an end user.
Optical storage disks and, in particular, magneto-optical disks offer greatly increased data storage capacity relative to other disk media, such as magnetic disks. The storage capacity for a given optical disk depends on the recording area of the disk and the areal density of domains recorded over the recording area. The recording area of a disk ordinarily is limited by physical requirements such as size and weight for minimal footprint and ease of portability. Accordingly, the pursuit of greater storage capacity has focused primarily on increased areal density over a given recording area. Optical recording offers relatively high areal density capabilities, but has been limited by the spot size of the optical beam used for read and write operations. In other words, areal density remains a function of the ability of the write and read beams to address increasingly smaller domains on the disk surface.
The areal density of an optical storage device, in principle, is only limited by the diffraction limit of an illuminating optical beam for reading or writing. One type of commercial optical storage technology is based on magneto-optical materials. These materials can currently produce an areal data density of about one gigabit per square inch. One well-known approach to increase the areal data density in an optical storage system is using smaller beam size. Due to the diffraction limit, this may be achieved by using a light source with shorter wavelengths such as those toward the blue end of the spectrum. For example, one application for the industrial development of compact blue lasers is aimed at the optical storage. Alternatively, one may increase the numerical aperture of the objective lens in the system to focus a beam at a given wavelength to a smaller spot within the diffraction limit.
SUMMARY
The present invention is directed to a data storage disk cartridge having a dual housing structure, and to techniques for limiting the effects of debris in a data storage system. The disk cartridge includes an inner housing that contains the disk, and an outer housing that contains the inner housing. The inner housing is at least partially removable from the outer housing for insertion into a disk drive. The outer housing remains external to the disk drive, however, except for a portion that is inserted into the drive to provide a docking channel for removal of the inner housing. A shutter on the inner housing covers a portion of the disk, and is manipulable by the disk drive to uncover the disk and allow access by the drive head. The dual housing structure of the cartridge can significantly improve disk and drive reliability, especially for recording applications that require higher areal recording densities or reduced air gaps between the disk and the drive head. In particular, the disk cartridge reduces the accumulation of debris on the disk and drive components. The reduced amounts of debris contribute to more consistent performance of the disk and drive, and thereby enhance data storage reliability. For optical disks and drives, in particular, reduced amounts of debris are important for reliable optical and mechanical performance.
Debris is a significant concern in data recording systems. Debris can degrade the optical performance of an optical disk or the components of an optical drive. Debris that accumulates on the optical components of a drive, for example, can attenuate the intensity of the beams used for read or write operations. Consequently, the optical components can deliver a beam with insufficient energy, imprecise spot size, or misregistered addressing. Accumulation of debris on the disk can cause loss of tracking as well as attenuation of read and write beam energy. Debris can also cause disk tilt and, in some cases, drive head crashes. With substantial amounts of debris, disk or drive failure can occur, leading to data loss and repair costs.
The debris problem becomes more pronounced as areal density increases in an optical recording system. Optical disks with lower areal densities ordinarily tolerate some degree of optical error, and therefore are not as greatly impacted by debris. Also, to the extent that optical error is a concern, conventional recording drives typically make use of focus adjustment, interleaved data formats, and error correction. At higher areal densities, however, debris can impair the ability of the drive laser to consistently write and read to and from individual domains on the disk despite such measures. In other words, the more aggressive areal densities required by newer recording techniques may offer very little tolerance for optical error induced by debris. Accordingly, the absence of debris is a critical concern in high density optical recording applications.
An example of an optical recording application with extremely high areal density requirements is near field recording. Near field recording is one form of optical recording that is capable of producing extremely small spot sizes, for example, on magneto-optic disk media. For near field recording, a solid immersion lens (SIL) can be used to transmit an optical beam across an extremely thin air bearing, and through the top of the recording medium to the recording layer. The beam is “air-incident” in the sense that it does not pass through the disk substrate before it reaches the recording layer. This aspect of near field recording differs from the substrate-incident techniques used in conventional magneto-optic recording, in which the beam passes through the substrate. A SIL can be integrated with a flying magnetic head assembly that hovers above the disk during operation and provides the magnetic bias for magneto-optic recording. For near-field recording, the thickness of the air gap is less than one wavelength of the recording beam. Transmission of the beam is accomplished by a phenomenon known as evanescent coupling, which results in extremely small spot sizes.
As an example, the near field recording technique is expected
Bonn Brian T.
Dalziel Warren L.
Fairchild Scot C.
Hector Wayne M.
Maiers Michael A.
Klimowicz William
Shumaker & Sieffert PA
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