Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-02-17
2001-05-29
Faber, Alan T. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078110, C360S077030, C369S044260, C250S559010, C359S201100
Reexamination Certificate
active
06239938
ABSTRACT:
The present invention relates to the field of drive systems for the optics in a laser servowriting system for providing servo patterns on magnetic data storage disks. More particularly, the present invention provides drive systems and methods using multiple actuators to move the optics in the laser servowriting system.
BACKGROUND
Laser servowriting is used in connection with flexible magnetic data storage disks to increase the storage density of the magnetic media by allowing for more precise positioning of the read/write heads. The increased precision in positioning is provided by using an optical servo system that detects an optical servo pattern formed on or in the surface of the disc. The optical servo pattern can consist of a large number of equally spaced concentric tracks. Each track can be a single continuous groove, a plurality of equally spaced pits, or a plurality of relatively short equally spaced grooves or stitches.
The optical servo pattern is typically formed using light energy, e.g., a laser, that is focused into a spot having the desired width of the tracks to be formed on the disk. The focused spot of laser energy is typically translated across the radius of the media by moving a lens and mirror arrangement located on an optics sled. The optics sled is translated over the desired distance and along the direction of the laser energy, thereby causing the focused spot of laser energy to also move.
Control over movement of the optics sled is an important issue because the location of the focused spot of laser energy is critical in formation of the desired optical patterns. Variations in the size or location of the focused spot can cause corresponding variations in the optical contrast and/or location of the optical patterns. Such variations can be detrimental to the storage of data on the resulting magnetic data storage discs.
Among the causes of variations in the location and/or size of the focused spot size are deviations in the movement and orientation of the optics sled carrying the optics used to both redirect and focus the laser energy. Among those deviations are changes in the pitch and yaw of the optics sled with respect to the media, as well as errors in the location of the optics sled as it translates across the radius of the media.
In addition to deviations such as pitch and yaw, vibrations induced in the optics sled can also cause variations in the optical track pattern. Those vibrations may be caused by the alignment of the actuator or actuators used to move the optics sled. Where the resultant force produced by the actuators is not directed through the center of mass of the optics sled, moments can be induced that can cause the optics sled to vibrate about one or more axes. In some instances, the speed of the laser servowriting process can be limited by those vibrations.
One attempt to reduce vibrations caused by the resultant force includes mounting additional balancing masses on the optics sled in an attempt to move the center of mass of the optics sled. By adjusting the position of the balancing mass or masses, it may be possible to reduce vibration of the optics sled by moving the center of mass into alignment with the resultant force produced by the actuator or actuators. Balancing masses are, however, difficult to adjust initially and may required readjustment after use. In addition, the additional mass can reduce the acceleration of the optics sled, thereby increasing cycle time.
SUMMARY OF THE INVENTION
The present invention provides a drive system for moving an optics sled in a laser servowriting system used to provide a servo pattern on the media of a magnetic data storage disk. The drive system includes multiple actuators located about the centroidal axis of the optics sled. Moments induced by the multiple actuators acting on the optics sled can be balanced by varying the forces applied to the optics sled by the actuators. The invention also includes a control system for balancing the forces provided by the actuators by varying the gains on the signals driving the actuators.
In one aspect, the present invention provides a laser servowriting system for providing a servo pattern on a magnetic data storage disk, the system including a linear guide; an optics sled including laser optics, the optics sled mounted on the linear guide for translational movement, wherein the center of mass of the optics sled moves along a centroidal axis as the optics sled moves along the linear guide; three or more actuators operatively connected to the optics sled, wherein the actuators move the optics sled along the linear guide; a laser source directing laser energy at the laser optics on the optics sled; and a rotation system for rotating a magnetic data storage disk during servowriting of an optical stitch pattern thereon
In another aspect, the present invention provides a method of moving optics in a laser servowriting system during formation of a servo pattern on a magnetic data storage disk by providing an optics sled mounted on a linear guide for translational movement, wherein the center of mass of the optics sled moves along a centroidal axis as the optics sled moves along the linear guide; providing three or more actuators operatively connected to the optics sled, each of the actuators producing an actuator force to move the optics sled along the linear guide; and varying the actuator force provided by at least one of the actuators.
In another aspect, the present invention provides a drive system for moving the optics in a laser servowriting system for producing a servo pattern on a magnetic data storage disk, the system including a linear guide; an optics sled including laser optics, the optics sled mounted on the linear guide for translational movement, wherein the center of mass of the optics sled moves along a centroidal axis as the optics sled moves along the linear guide; and three or more actuators operatively connected to the optics sled, wherein the actuators move the optics sled along the linear guide.
As used in connection with the present invention, the term “centroidal axis” is the line along which the center of mass of an optics sled travels during laser servowriting.
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Boberg Arne B.
Bohlman Gary J
Faber Alan T.
Imation Corp.
Levinson Eric D.
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