Seagate Technology Incorporated

Seagate Removable Storage Solutions LLC

Jianmin Wang

Jason L Pressesky

Jing Gui

Li-Ping Wang

Huan H Tang

Shih-Fu Lee

An optical profiler for an ultra-smooth surface, such as a magnetic recording disk, provides for a normally incident beam deflection against the target surface to be profiled. A linearly polarized laser light of a first polarization is focused on the target surface in a normally incident direction. The beam is reflected back along its original path from the focal point. Optics are provided that change the polarization of the reflected beam to a second polarization. A reflected beam, with a second polarization, is directed onto a position sensitive detector for evaluation.

Method and optical profiler

An arrangement and method for reliably finding the wave form extrema of interference signals produced by a quadrature phase shift interferometer (QPSI) takes advantage of the quadrature property of I and Q signals. The zero-crossing points in the I and Q signals are determined. Peak detection is performed for peaks and valleys in the Q signal in close proximity to the zero-crossing points in the I signal, and for peaks and valleys in the I signal in close proximity to the zero-crossing points in the Q signal. These represent the maximum and minimum points of the I and Q signals. From these points, intensity envelopes are created and QPSI phase wrapping is performed to determine the phase angle and ultimately, out-of-plane displacement may be determined.

Quadrature phase shift interferometer (QPSI) decoder and method of decoding

An arrangement and method of measuring head-media spacing modulation (HMS_Wq) removes the portion of out-of-plane motion caused by disk modes from the dynamic measurements of hard disk surface topography. Employing time-domain measurement techniques, circumferential surface topographical measurements are made for a hard disk surface. A boundary wavelength is determined, and a first partial HMS_Wq value is determined based upon measurements taken at a first disk rotational speed. A second partial HMS_Wq value is determined based upon measurements taken at a second disk rotational speed. The first and second partial HMS_Wq values are combined to provide a complete and accurate HMS_Wq value, taking advantage of the principle that the disk mode location in the spatial domain topography spectrum converted from the measured time-domain data shifts when the disk rotation speed is changed during the measurement.

Method and arrangement for topographically characterizing a surface of a hard disk with distortion due to disk modes removed

A method and arrangement for measuring head-media spacing modulation (HMS_Wq) employs a profilometer to measure the surface topography of a disk. A cumulative power spectral density (PSD) distribution is generated from the measured surface topography. Discontinuities and steps are identified in the PSD distribution. The discontinuities and steps are removed to create a corrected PSD distribution. A noise free spectrum is then reconstructed from the corrected PSD distribution.

Method and arrangement for removing noise and measurements of head-media spacing modulation for digital recording

A method and apparatus for using a dual-beam interferometer to test surface flatness is provided. The interferometer directs two beams focused at distinct points on a testing surface, such as the surface of a magnetic recording disc. An offset distance 'd' between the two beams is provided on the target surface. In the present invention, the separation distance 'd' is adjustable. The feature of adjustable separation distance in the interferometer allows the interferometer to meet the different spatial frequency requirements of various applications. In operation, first and second reflected beams are returned to an intensity beam splitter, where they are split and then recombined into two new beams of substantially equal intensity. The second of the two new light beams is constructed by the interference of half intensity of the first and half intensity of second beams, and is sent to a photodiode. The photodiode generates signals in response to the changing interference fringes caused as a result of the modulation of the optical path length difference between the original first and second beams. A local height difference on the reflective surface is calculated relative to the separation distance &#x201c;d&#x201d;.

Dual-beam interferometer for ultra-smooth surface topographical measurements

A method and apparatus for interferometnc measurement of a medium surface is disclosed. More particularly, a quadrature phase shift interferometer and a process for unwrapping phase are described. The interferometer has a reduced number of optical components though yields results sufficient to measure surface of a hard disc for final inspection. Defects on such a surface are characterized by their out-of-plane displacement with nanometer resolution.

Quadrature phase shift interferometer with unwrapping of phase

A tape head assembly for high-speed and high-density multi-channel read-while-writing (RWW) operation comprises two modules bonded together. The modules are initially formed on an integral unit and gapped in pair, to produce a good reference surface, which insures that the finished head assembly will meet tight azimuth and gap tolerances. The unit is then machined to two separate the modules. Further processing involves individually machining the head surface of each module to achieve desired contours. The machined modules are tested and brought together in the positional arrangement required to form the final head assembly. In disclosed embodiments, the overall contour enables the assembly to skive air and debris off a surface of the magnetic tape before passage of the tape over the transducers. The contour allows the tape to fly over outriggers, but contacts regions at or around the transducers with a low constant contact pressure during RWW operation.

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Fremont, CA, United States of America

Jianmin Wang