Media servowriting system

Abstract

A system and methods for efficiently performing media writing functions is disclosed. The system and methods include: detecting media movement with respect to a base and heads during reading and writing, and moving the heads in response; using an interferometer, such as a dual beam differential interferometer, to dynamically monitor disk position and address perceived errors; and minimizing repeatable and non repeatable runout error by writing data, such as servo bursts, in multiple revolutions to average adverse runout conditions. The present system has the ability to use an interferometer to enhance media certification and perform on line, in situ monitoring of the media, and includes shrouding, head mounting, disk biasing, and related mechanical aspects beneficial to media writing.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 367,046, filed Mar. 23, 2002.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to the field of data storage media, and more specifically to systems and methods for efficiently initializing, certifying or otherwise reading data from or writing data to such media. [0004] 2. Description of the Related Art [0005] Disk drives are magnetic recording devices used for the storage of digital information. The digital information is recorded on substantially-concentric tracks on either surface of one or more magnetic recording disks. The disks are rotatably mounted on a spindle motor, and information is accessed by read / write heads mounted to actuator arms rotated by a voice coil motor. The voice coil motor rotates the pivoting arms and moves the heads radially over the surface of the disk or disks. During servowriting and / or initialization of ...

AI Technical Summary

Benefits of technology

[0025] According to a second aspect of the present design, there is provided a method for minimizing likelihood of a head within a servowriting apparatus contacting a disk located therein. The method comprises sensing sound intensity in a predetermined frequency range from a first sensor positioned at a first location within the servowriting apparatus, determining the existence of a pending head crash based on the sound intensity; and moving an element of the servowriting apparatus upon determining the existence of the pending head crash.

[0030] According to a seventh aspect of the present design, there is provided a system for accurately positioning a head over rotating media, the rotating media able to spin about a center axis. The system comprises an interferometer having the ability to emit light energy and measure an effective distance between the head and the spindle, and means for computing a correction factor to be applied to the spindle to correct for any perceived distance errors related to the head measurement.

[0032] According to a ninth aspect of the present design, there is provided a method for increasing magnetic disk yield during the manufacturing process. The method comprises initially writing a first complete set of servo data to a magnetic disk, subsequently writing at least one additional set of servo data to the magnetic disk, evaluating the quality of the servo data written, and removing the lowest quality servo data and retaining the highest quality servo data.

[0037] According to a fourteenth aspect of the present design, there is provided a method for biasing a disk attached to a spindle, comprising applying a biasing lateral force to the disk fixedly attached to the spindle thereby tightly interfacing the disk with the spindle at one portion of the disk.

Problems solved by technology

Previously available servowriters suffer from a variety of shortcomings and system performance issues.

Most, if not all, of the previously available systems suffer from an inability to support custom read / write heads, or provide accurate micro-move and settle times or track holding accuracy.

One particular problem with currently available disk drives and servowriters is the complexity associated with knowing the location of a head over a disk, and detecting and utilizing relative movements of disks, positioners, heads, and related equipment with respect to a reference point or plane.

Current systems do not physically track disk position nor compensate for movement or irregularities resulting from real world conditions, including the aforementioned conditions and non-repeatable run out movement.

A servowriter without the ability to track disk position and compensate for positional or movement irregularities may introduce or otherwise suffer from errors while heads are reading from or writing to the disks.

This error introduction may limit the spin rate and / or track density of the disks.

Another problem with currently available disk drives and servowriters is that of accurate head positioning.

Errors in servo track accuracy can occur whenever the system does not maintain head position in a controlled radius as the media disk spins below the head.

Head position errors may also occur if the entire optical encoder fails to precisely track head position.

The entire positioning device can translate or vibrate with respect to the spinning disk, or flexing of any components connecting the head to the optical encoder can produce positional errors.

In a disk having a track pitch below one micron, the rigid positional linkage performance between the optical encoder and the head as well as the optical encoder and spindle axis can be compromised by various factors, such as wobble or translation of the spindle axis within its bearing mount, causing radial runout.

Other potentially problematic factors may include tiny distortions of the shape of any hardware that mechanically references the head to the spindle axis.

One particular problem with currently available servowriters is the equipment used to format a disk writes a set of servo sectors to the disk, and the presence of relatively significant servo sector errors can cause the servowriter to indicate the disk is bad during verification testing.

Alternately, when writing to a formatted disk, the presence of relatively significant errors in the servo sectors causes the disk drive to mark those sectors as unusable for data storage, either by detecting excessive servo errors while track following or excessive errors detected during data writing and reading, with the result that the data storage capacity of the disk would be reduced.

These drawbacks decrease yield and reduce available storage capacity.

Furthermore, most, if not all, of the previously available systems suffer from an inability to support custom read / write heads, or provide accurate micro-move and settle times or track holding accuracy.

However, as disk areal data density has increased, many Hard Disk Drives today utilize only one disk, decreasing the usefulness of the aforementioned technique.

This increased number of tracks results in a dramatic increase in the time required to write the servo tracks.

If this clearance is too large, the disk or disks will move laterally and possibly axially during high RPM rotation.

This clearance, if not addressed in some manner, creates an uncertainty with regard to the concentricity of servo tracks to disk ID, and can in certain circumstances result in significant eccentricity errors introduced when removing disks from the MTW and installed into a disk drive HAD.

If uncontrolled, these errors can in certain circumstances exceed 4000 microinches, or millionths of an inch.

Excessive eccentricity, or servo track “runout”, can cause servo capture and performance problems for the HDD, in that the head can be mislocated above the disk and can run outside a track, or begin in one track and end in another.

These jaw-type locking devices tend to be imprecise in holding the hub or other cylindrical piece.

This prying tends to damage the hub and / or maintaining device and is generally unacceptable.

Thus the previous devices could be characterized as easily pried open, with poor repeatability, and highly subject to movement of the piece.

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