International Business Machines Corporation

Other

Fior D Sargent

Steven W Meeks

Thao Anh Nguyen

Christopher S Gudeman

Andrew Ching Tam

Peter Michael Baumgart

Prakash Kasiraj

Donald E Horne

Douglas J Krajnovich

Gerard H Vurens

Controlled laser texturing of a magnetic recording disk is accomplished by use of a textured test band on the disk and an analyzing laser system to provide feedback to the texturing laser. The analyzing laser system determines, from diffracted laser light, the average height of the laser-induced bumps formed in the test band by the texturing laser. The analyzing laser beam is directed to the substrate surface and overlaps a group of individual bumps formed in a repetitive pattern. A scanning linear photodector array receives light diffracted from the surface. The digitized output of the array is the angular distribution of diffracted light intensities and is used to compute the average height of the bumps in the test band. The disk is then translated radially so that the texturing laser is aligned with the region of the disk where the textured landing zone is to be placed. Then, in response to the computed value of average bump height in the test band, a correction signal or signals is output to modify one or more parameters of the texturing laser so that the texturing laser can form bumps of the correct average height in the textured landing zone.

Process and apparatus for controlled laser texturing of magnetic

An analyzing laser system determines a physical characteristic of a repetitive texture pattern formed on a substrate surface. In one embodiment the system uses diffracted laser light to compute the average height of texturing bumps on a substrate surface. A laser beam is directed to the substrate surface and overlaps a group of individual marks or bumps formed in a repetitive pattern. A scanning linear photodector array receives light diffracted from the surface. The digitized output of the array is the angular distribution of diffracted light intensities. In the preferred embodiment for determining the average height of laser-induced bumps formed on a specular magnetic recording disk substrate, the angular positions of the first and second diffraction peaks or rings are determined and the intensities are integrated around those diffraction peaks or rings. These position and integrated intensity values are then compared to position and integrated intensity values for bumps of known height on calibration disk substrates. If the individual marks or bumps making up the repetitive pattern are also symmetrical then the angular distribution of diffracted light intensities is the square of the absolute value of the Fourier transform of the cross sectional profile of the bumps. Mathematical operations, including an inverse Fourier transform, are then performed on the digitized array output to yield the average cross sectional shape of the bumps illuminated by the analyzing laser.

Process and apparatus for laser analysis of surface having a repetitive

At the wafer level, a conventional write signal is applied to a pre-selected thin film head. Thereafter, first and second constant amplitude, differing frequency sine wave signals are applied to the head along with a DC bias signal whose magnitude is varied. The level of frequency mixing in the output signal of the head is detected at each level of magnitude of the DC bias signal and this data is utilized in predicting the level of noise in the read-back signal of the thin film head during normal read and write operations in connection with a rotating storage disk.

Method and apparatus for measuring nonlinearity in thin film heads

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San Jose, CA, United States of America

Fior D Sargent