International Business Machines Corporation

Wai Cheung Leung

Hal Jervis Rosen

Milton Russell Latta

Anthony Juliana

Wayne Isami Imaino

Charles H Lee

Shanlin Duan

Thomas Young Chang

Terence Tin-Lok Lam

James Hammond Brannon

Steven W Meeks

Timothy Carl Strand

Richard Sonningfeld

Charles Chung Lee

Andrew Ching Tam

Randall George Simmons

Yan Liu

Clinton David Snyder

John Martin Burns

Li Tang

Bob Clyde Robinson

Walter Crooks

Wei-Ming Lee

Paul Marion Green

Victor T Pan

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In one embodiment of the invention, the incident beam is directed onto the surface to be inspected at an angle slightly offset from perpendicular so that the reflected beam is physically separated from the incident beam. The reflected beam is routed to a detector which converts the intensity of the reflected into an analog signal. The analog signal is sampled and digitized to generate pixel data stored in a buffer. Various analyses are performed on the data including calculating a rate of change in the pixel data. If the rate of change in the pixel data exceeds a selected threshold that indicates a possible defect if it occurs in the data area of the disk.

Surface inspection tool

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In an embodiment of the invention, light reflected from the surface at an angle slightly offset from perpendicular is routed through a telecentric lens to a detector which converts the intensity of the reflected beam into an analog signal. The analog signal is sampled and digitized to generate pixel data. A data acquisition system sequentially stores the pixel data in a buffer. A median filter and derivative analysis can be applied to the pixel data to detect deviations indicating defects. An optional calibration system periodically reflects the scanning beam back to a detector to form a reference signal for use in absolute reflectivity measurements.

An inspection system using laser light directed at an off-axis parabolic mirror which focuses the beam on the surface being inspected and also serves as the collector for scattered and specular light returned from the surface is described. Specular and scattered light returned from the surface onto the parabolic mirror is divided into appropriate fields and directed onto detectors. In the preferred embodiment a polarized laser is used in conjunction with a polarizing beam splitter and a quarter-wave plate to route the reflected beam to a detector while allowing the original beam to be directed through the same optics. The parabolic mirror and selected additional components may be commonly mounted on a translatable stage which is moved along a radius of the disk when the optical inspection is being performed. Other components of the system such as the laser can remain in a fixed position. The system of the invention can be used to inspect one or both planar surfaces of the disk by providing duplication of selected components appropriately oriented with respect to the second surface.

Surface inspection tool using a parabolic mirror

The present invention is a read/write head for writing information to magnetic media and reading information from magnetic media. It includes a write head element for writing information onto magnetic media, a read head element for reading information from the magnetic media, and an electromagnetic field shield element that is disposed between the write head element and the read head element. The shield functions to shield the read head from electromagnetic field energy created by the write head element. An enhanced second embodiment includes an electrical circuit element that is disposed proximate the read head element that functions to generate an electromagnetic field at the read head element that is generally oppositely directed to the electromagnetic field generated by the write head element to reduce the total electromagnetic field that the read head element is exposed to during a writing operation. The method for operating the read/write head in a hard disk drive, includes the steps of writing data onto a hard disk and reading data from the hard disk simultaneously with the data writing. This is accomplished by shielding the read head from the electromagnetic field energy generated during the data writing by utilizing the electromagnetic field shield element that is disposed between the write head element and the said read head element. The electrical circuit element of the second embodiment is preferably interconnected with the write head electric circuit.

Magnetic recording transducer with electronic shield

The present invention is a read/write head for writing information to magnetic media and reading information from magnetic media. It includes a write head for writing information onto magnetic media, a read head for reading information from the magnetic media, and an electrical circuit element that is disposed proximate the read head that functions to generate an electromagnetic field at the read head that is generally oppositely directed to the electromagnetic field generated by the write head. The method for operating the read/write head in a hard disk drive, includes the steps of writing data onto a hard disk, while simultaneously generating an electromagnetic field at the read head that is directed oppositely to the electromagnetic field generated by the write head.

Magnetic read/write head having electromagnetic field cancellation element

The burnishing head for hard disk processing includes a solid body having generally rectangular surfaces, including an upper surface, a burnishing pad surface, a front surface, a rear surface and two side surfaces. A plurality of burnishing pads are disposed upon the burnishing pad surface. The pads are shaped such that each pad has a burnishing edge that is generally parallel to said front surface and therefore orthogonal to the direction of media travel. The burnishing pads are preferably configured such that one frontward leading pad is centrally disposed proximate the front surface of the head, followed by two middle pads that are disposed in a spaced apart relationship. A single centrally disposed rear middle pad is formed behind the two middle pads, and two rear pads are disposed in a spaced apart relationship at the rear surface of the head. In the preferred embodiment the pads are generally triangular in shape and the outer surface of the leading and rearward pads is tapered. The method for manufacturing the burnishing head, includes the steps of making a series of parallel cuts in a surface of a solid body of material. The burnishing pads result from material that remains following the cuts.

Hard disk burnishing head

The hard disk testing and certifying device of the present invention includes a spin stand to rotate a disk to be tested. A single read/write head, including both a write head and a read head is mounted upon an armature which movably supports the read/write head. The device includes a computerized control system and signal processing system that provides write signals to the write head and receives and processes read head signals from the read head. In the preferred embodiment the read/write head simultaneously provides write signals to the disk and receives read signals from the disk. Preferably, the read/write head functions continually and the certification testing is conducted utilizing a spiral path. In the preferred read/write head the read head is disposed behind the write head and an electromagnetic field shield is disposed between them to reduce electromagnetic field interference between the write head and the read head during simultaneous operation. The read/write head may also include an electromagnetic field interference element to further reduce signal interference at the read head.

Magnetic tester for disk surface scan

A method and apparatus for precise measurement of pressure dependence of head fly height using transitional thermal signals is disclosed. A slider is positioned relative to a rotating a disk having at least one laser bump. Calibration data is gathered by decreasing the pressure and measuring the fly height until a contact positive TA signal is detected. A non-contact negative TA signal is then normalized using the gathered calibration data. The TA signal amplitude may then be used to ascertain the fly height and pressure for a head.

Method and apparatus for precise measurement of pressure dependence of head fly height using transitional thermal signals

A method of making a calibration disk for a laser based inspection tool (LIT) for inspecting planar surfaces is described. The calibration disk has a plurality of overlapping bumps forming a circular ring with a width of one bump. The circular ring of bumps forms a feature of a known width and position on a disk which can be used to adjust one or more LIT's to yield calibrated results. The ring of overlapping bumps is preferably formed by rotating a disk substrate under a stationary pulsing laser beam.

Method of producing a calibration disk

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In an embodiment of the invention, the incident beam is directed onto the surface to be inspected at an angle slightly offset from perpendicular so that the reflected beam is physically separated from the incident beam. Although slightly offset the reflected beam is routed back through the telecentric lens and scanner which are used for the incident beam. Preferably an aperture mask is placed in the path of the reflected beam and the incident beam to limit the cone of scattered light. Since the incident and reflected beams are physically separated, there may be an aperture for each beam, but the two masks may be physically connected. The aperture masks may also be used for alignment adjustments of the beams.

The hard disk drive manufacturing method of the present invention includes an initial determination of the orientation of the individual hard disks during the various processing steps and disk drive assembly steps. Specifically, the orientation of the hard disks in the assembled disk drive is ascertained, such that the direction of arcuate writing paths on the disk surface is known. Additionally, the orientation of non-random arcuate micro-scratches that appear on the disk surface during disk processing is ascertained. Where the arcuate path of the micro-scratches corresponds to the arcuate writing paths on a disk surface, the disk process is altered to effectively reorient the disk in its mounting in the hard disk drive. The result of the process alteration is that there is no longer a correspondence between the arcuate path of the micro-scratches and the arcuate written data paths, and a significant reduction in the number of defects on the surface of the hard disk is obtained.

Thin film disk media using optimum surface orientation to written data

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. In one embodiment of the invention, a disk is moved into an inspection subcompartment between a pair of air knives which blow partially ionized air onto the planar sides of the disk to remove loose particles adhering thereto. After the disk moves through the air knife streams, the two laser beams scan the two sides of the disk. Preferably the scan occurs after the air knives have been turned off and as the disk moves out of the inspection subcompartment. The subcompartment may optionally have an air source which forces air to flow out of the subcompartment to aid in maintaining a clean environment for inspection.

A glass disk substrate inspection tool uses a polarized laser beam that is directed to the first surface of the disk substrate at Brewster's angle and is then transmitted through the disk substrate to a light detector that generates a signal representative of the intensity of the light received. Because the light polarized parallel to the plane of incidence, i.e., the plane formed by the line of the incident beam and a line perpendicular to the surface of the disk substrate, is completely transmitted, there is no surface reflection at either the first or second surfaces of the disk substrate. The polarized beam is directed by a first rotating scanner to the input of a telecentric lens assembly that provides an output beam parallel to its optical axis as the beam is being scanned. The beam is then directed by a first fixed mirror to strike the first surface of the disk substrate at Brewster's angle as the beam is scanned along a line across the first disk surface. The beam is then transmitted through the substrate to the second surface of the disk substrate to a second fixed mirror that redirects the beam to a second telecentric lens assembly. The light passes through the second telecentric lens assembly in the direction reverse to the direction of passage through the first telecentric lens assembly so that the output beam from the second telecentric lens assembly is directed to its focal point. This focal point coincides with the point of contact of a second rotating scanner synchronized for rotation with the first scanner. The second scanner directs the transmitted beam to the light detector.

Glass substrate inspection tool having a telecentric lens assembly

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. The choice of a polygon scanner is preferred, but other scanning means such as a galvonometer mirror could be used. A separate polygon scanner is used for each side of the disk. The polygons are arranged in a common plane, but rotate in opposite directions to reduce the inteference which might otherwise result when the beams pass through the central hole in the disk and impinge on the detection channel for the other side. Preferably the rotation of the polygons is synchonized and angularly offset so that the two beams are synchonized and offset. The rotating polygons may conveniently be included in a system which scans each of the two laser beams through a telecentric lens assembly onto the surface and which routes the reflected light which passes back through the telecentric lens and is reflected from the polygons to the detection component.

A laser based inspection tool (LIT) for inspecting planar surfaces is described. In a preferred embodiment the LIT can simultaneously inspect both planar surfaces of disks for use in disk drives. The LIT uses a mechanical lifter which moves the disk through the laser scan lines (i.e. perpendicular to the scan lines) to allow the entire surface on each side of the disk to be scanned. The light reflected from the surface is routed to a detector which converts the intensity of the reflected beam into an analog signal. The analog signal is sampled and digitized to generate pixel data. A data acquisition system sequentially stores the pixel data in a buffer. The edges of the planar surface in the pixel data are determined for each scan line while data acquisition is in progress. A mask is applied to direct the defect detection only to meaningful areas of the disk while data acquisition is in progress. A median filter and derivative analysis can be applied to the pixel data to detect deviations indicating defects.

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San Jose, CA, United States of America

Wai Cheung Leung