Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1997-10-09
2001-07-24
Tran, Thang V. (Department: 2753)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
Reexamination Certificate
active
06266306
ABSTRACT:
MICROFICHE APPENDIX
This application contains Microfiche Appendix A and B consisting of five (5) slides and 289 frames.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to data storage systems of the type that include a housing having an opening for receipt of a removable disc cartridge in which an information recording medium is mounted for protection. More particularly, it relates to a system for rapidly encoding and writing information onto optical disks in a high density format, and for reading and decoding the information written thereon. The present invention is further directed to the specific technical areas discussed below.
CMOS Logic and Current Switching: Another problem that arises in disc handling systems, such as compact disc, laser disc, or magneto-optical player/recorder devices, is dealing with laser switching designs to mitigate the effects of undesired thermal problems. Previous laser switching designs have consumed considerable power, even when not writing. ln addition, there has been a desire to achieve faster rise and fall times in switching the lasers.
Oscillator Ringing: A further problem that arises in disc handling systems, such as compact disc, laser disc, or magneto-optical player/recorder devices, is dealing with preamplifier designs to mitigate the effects of oscillator ringing. While previous oscillator designs have provided sufficient amplitude modulation into the laser to reduce noise, such designs typically ring every time a write pulse is supplied.
Focus Capture: Another problem that arises in disc handling systems, such as compact disc, laser disc, or magneto-optical player/recorder devices, is dealing with focus capture whereby false captures and consequent loss of reliability, accuracy and efficiency are mitigated.
Mechanical Isolation: Still another problem that arises in disc handling systems, such as compact disc, laser disc, or magneto-optical player/recorder devices, is dealing with mechanical isolation to mitigate the effects of compressive forces and vibration.
Blank Sector Check: Another problem that arises in disc handling systems, such as compact disc, laser disc, or magneto-optical player/recorder devices, is dealing with detection of blank sectors.
Analog to Digital Converter: Those concerned with the design and development of optical disc systems have also sought improved analog to digital converters for normalizing servo error signals and for multiplexing reference voltage inputs and digital outputs. Accordingly, those concerned with the design, development and use of disc drive systems have long recognized the need for new and improved systems which obviate the above-described difficulties. The present invention is directed to satisfying these needs.
2. Description of the Related Art: Overview
The demand for mass data storage continues to increase with expanding use of data processing systems and personal computers. Optical data storage systems are becoming an increasingly popular means for meeting this expanding demand. These optical data systems provide large volumes of relatively low-cost storage that may be quickly accessed.
In optical disc systems, coded video signals, audio signals, or other information signals are recorded on a disc in the form of information tracks on one or both planar surfaces of the disc. At the heart of an optical storage system is at least one laser (or other light source). In a first operating mode, the laser generates a high-intensity laser beam that is focused on a small spot on an information track of a rotating storage disc. This high-intensity laser beam raises the temperature of the recording surface of the material above its Curie Point—the point at which the material loses its magnetization and accepts the magnetization of the magnetic field in which the disc is placed. Thus, by controlling or biasing this surrounding magnetic field, and allowing the disc to cool below its Curie Point in a controlled magnetic environment, information may be recorded on the disc in the form of magnetic domains referred to as “pits” on the recording medium.
Subsequently, when the operator desired to reproduce or read the previously recorded information, the laser enters a second operating mode. In this mode, the laser generates a low-intensity laser beam that is again focused on the tracks of the rotating disc. This lower intensity laser beam does not heat the disc above its Curie Point. The laser beam is, however, reflected from the disc surface in a manner indicative of the previously recorded information due to the presence of the previously formed pits, and the previously recorded information may thereby be reproduced. Since the laser may be tightly focused, an information processing system of this type has advantages of high recording density and accurate reproduction of the recorded information.
The components of a typical optical system include a housing with an insertion port through which the user inserts the recording media into the drive. This housing accommodates, among other items, the mechanical and electrical subsystems for loading, reading from, writing to, and unloading an optical disc. The operation of these mechanical and electrical subsystems is typically within the exclusive control of the data processing system to which the drive is connected.
Within the housing of a conventional system that uses disc cartridges, a turntable for rotating a disc thereon is typically mounted on the system baseplate. The turntable may comprise a spindle having a magnet upon which a disc hub is mounted for use. The magnet attracts the disc hub, thereby holding the disc in a desired position for rotation.
In optical disc systems, as discussed above, it is necessary to magnetically bias the disc during a writing operation by applying a desired magnetic field to at least the portion of the disc being heated by the laser during the writing (recording or erasing) operation. Thus, it is necessary to mount a magnetic field biasing device where it may be conveniently placed in close proximity to the disc surface when the disc is held in position by the magnet associated with the spindle.
A variety of media or disc types are used in optical data storage systems for storing digital information. For example, standard optical disc systems may use 5¼ inch disks, and these optical disks may or may not be mounted in a protective case or cartridge. If the optical disc is not fixedly mounted in a protective cartridge, an operator manually removes the disc from the protective case. The operator would then manually load the disc onto a loading mechanism, using care to prevent damage to the recording surface.
Alternatively, for purposes of convenience and protection, a disc may be mounted within an enclosure or a cartridge that is itself inserted into the insertion port of the drive and is then conveyed to a predetermined position. These disc cartridges are well known in the computer arts. The disc cartridge comprises a cartridge housing containing a disc upon which data may be recorded.
Cartridge Loading
To protect the disc when the cartridge is external from the drive, the disc cartridge typically includes at least one door or shutter that is normally closed. The cartridge shutter may have one or more locking tabs associated with it. The corresponding disc drive includes a mechanism for opening the door or shutter on the cartridge as the cartridge is pushed into the system. Such a mechanism may comprise a door link that makes contact with a locking tab, thereby unlocking the shutter. As the cartridge is inserted further into the drive, the shutter is opened to partially expose the information recording medium contained therein. This permits a disc hub to be loaded onto a spindle of a motor or other drive mechanism, and permits entry of a read-write head and a bias magnetic into the protective cartridge. The disc, when rotated by the drive mechanism, permits the read-write head to access all portions of the disc media.
To conserve space in optical storage systems, it is desirable
Crupper Randolph Scott
Davis Marvin B.
Getreuer Kurt W.
Grassens Leonardus J.
Lewis David E.
Discovision Associates
Masaki Keiji
Tran Thang V.
Wenskay Donald L.
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