Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1998-10-09
2001-04-10
Edun, Muhammad (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S044150, C369S044140
Reexamination Certificate
active
06215755
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the recording and playback of data on an optical medium. More particularly, the present invention teaches a novel technology which enables the creation and retrieval of optically stored data at speeds approaching those attained by current magnetic hard drive technology.
BACKGROUND ART
Original mass storage devices for use with computers were generally serial type devices. Examples of these serial devices include the well-known punched paper tape and magnetic recording tape. These early serial storage devices were the norm until the advent of direct access storage devices (DASD). Examples of direct access storage devices include the well-known computer hard drive adapters. With the exception of the hard and floppy disk drives, mass storage devices, particularly those found in microcomputer applications, have historically tended to be formed from, or be adaptations of, serial entertainment storage devices. Examples of such storage devices include cassette tapes and CD-ROM drives. The access time for such devices suffers from their inherently serial nature.
The advent of the digital video disk (DVD) bodes well for increasing the storage capacity of the both removable and fixed computer drives. This increase in optical storage capacity has not heretofore been coupled with a concomitant decrease in access time. This is because, at their core technology, both CD-ROM and DVD drives are essentially serial storage devices, with all the inherent limitations thereof. And these limitations specifically included slow access times. Because of the relatively slow access times inherent in prior art CD-ROM and DVD technology, their utilization as direct access storage devices has not been realized.
The well-known CD-ROM drive is based on electro-optical device typically mounted on a truck or carriage which is actuated linearly to provide access to the information stored on the optical media, a rotating optical disk. The problem with this design is that the electro-optical device and the carriage (sled or sledge) which actuates it are relatively massive devices, ill-suited for rapid access speeds.
Hard disk access times are now routinely less than 10 msec. This is accomplished by mounting a very lightweight read/write head on a pivoting arm. The arm pivots substantially parallel to the surface of the magnetic media, and is positioned by means of voice-coil motors or other electrical positioning devices. The head typically flies at a height measured in millionths of an inch. The combination of the lightweight head pivoting under the impetus of a relatively powerful voice-coil motor enables the very fast access speeds currently attained by hard disk drives.
Heretofore, the mass of the CD-ROM electro-optical device and the truck on which it is mounted have precluded the attainment of access times approaching those currently attained by hard disks. This is because of the enormous forces the voice-coil motor would have to generate to achieve the desired accelerations of the massive carriage and optical assembly.
What is clearly needed is an optical, or magneto optical, drive technology which combines the reliability, removeability, and replaceability of CD-ROM or DVD technology with the low access times currently attained by hard drive technology.
What is further needed is a methodology which decreases the mass of the optical read/write assembly.
What is still further needed is a methodology which increases the data storage capacity of removable disk drives.
DISCLOSURE OF THE INVENTION
The present invention teaches a pivoting arm to move the objective lens of the DVD head, somewhat like the arm used for standard magnetic recording heads. The advantage of the rotating arm is that if it has low rotational inertia it can be swung across the disk much quicker than prior art carriage can be translated.
In order to keep the arm mass and rotational inertia low, the focus and tracking functions have been removed from the objective lens. In other words, the objective lens is now fixed rigidly to the tip of the arm.
The focusing function of the present invention is performed in two stages. High frequency, short dynamic range focusing motion is imparted to the first lens collecting light from the laser using a voice coil driven by a servo feedback loop. Low frequency, high dynamic range focusing motion is imparted by piezoelectrically articulating the arm to which the objective lens is attached. This articulation is again driven by the servo feedback loop.
Other features of the present invention are disclosed or apparent in the section entitled “BEST MODE OF CARRYING OUT THE INVENTION”.
REFERENCES:
patent: 4761774 (1988-08-01), Ishibashi et al.
patent: 4959824 (1990-09-01), Ueda et al.
patent: 5199020 (1993-03-01), Kim et al.
patent: 5982733 (1999-11-01), Yanagawa et al.
Handbook of Magneto-Optical Data Recording: Materials, Subsystems, Techniques (1996), edited by Terry W. McDaniel and Randall Victora, pp. 148-156.
Johnston Ross
Kwiatkowski Stephen L.
Snyder James J.
Blue Sky Research
Edun Muhammad
LaRiviere Grubman & Payne, LLP
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