International Business Machines Corporation

Wen-Wei Chiang

Chih-Kung Lee

Steven Robert Hetzler

John Stewart Best

Donald E Horne

Vincent Marrello

A non-invasive servo-write system for use in a data recording disk drive. The system measures actuator position and generates a reference clock using semiconductor lasers. Internal position references are provided by reflective diffraction gratings affixed to the actuator arm and the spindle hub. Wavefront reconstruction optics correct for aberrations in the gratings. Optical sensors detect differential changes in the diffraction patterns created by the gratings, eliminating sensitivity to frequency drift. Decode electronics convert optical sensor data into an actuator position measurement. Control electronics drive the voice coil motor within the disk drive, which positions the write transducer to record servo information provided in a servo pattern generator. Transparent windows in the head-disk-assembly cover allow the servo-writer to write drives which are completely assembled and sealed.

Servo-writing system for use in a data recording disk drive

An optical measurement system for use in a data recording disk drive includes wavefront reconstruction optics which correct and compensate for aberrations in laser beams reflected from radial and linear diffraction gratings. The reconstruction optics include two spherical lenses and two reflectors, one of each positioned on each side of a diffraction grating. Light directed from a laser beam toward the grating diffracts into a +1 order component directed at the first set of reconstruction optics and into a -1 order component directed at the second set of reconstruction optics. The reconstruction optics compensate for the variable yaw angle caused by a linear grating and for the optical wavefront aberrations caused by a radial grating. Use of the reconstruction optics permits an optical measurement system in a data recording disk drive to accurately measure the position of either a linear or rotary actuator and to generate a precise reference clock for use in timing the recording of servo information to the data recording disk.

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San Jose, CA, United States of America

Wen-Wei Chiang