International Business Machines Corporation

Charles H Lee

Wayne Isami Imaino

Hal Jervis Rosen

Milton Russell Latta

Wai Cheung Leung

Anthony Juliana

Steven W Meeks

James Hammond Brannon

Richard Sonningfeld

Hoa-Binh Thi Tu

Manoj Chopra

Jay Allan Merz

Thorsten Lohmeyer

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.

Burnishing tape testing method and device

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.

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 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.

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. An optional calibration mirror is taught which is positioned to reflect substantially all of the incident beam during a segment of the scan line as the reflected calibration beam which is converted to an analog signal, sampled and digitized similarly to the reflected beam from the surface being inspected. By comparing the intensity of the calibration beam to the reflected beam the reflectivity of the surface can be measured.

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.

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San Jose, CA, United States of America

Charles H Lee