Patents by Inventor Tehri S. Lee

Tehri S. Lee has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8787125
    Abstract: A disk drive is disclosed comprising a disk, a head comprising a laser operable to heat the disk while writing data to the disk, and a fly height actuator (FHA) operable to actuate the head vertically over the disk. A setting is applied to the FHA to maintain a fly height of the head. An approximately zero bias laser power is applied to the laser during a non-write mode, and a first write laser power is calibrated during a write mode. A non-zero bias laser power is applied to the laser during the non-write mode, and a second write laser power is calibrated during the write mode. When the second write laser power is different than the first write laser power, the setting of the FHA is adjusted to adjust the fly height of the head.
    Type: Grant
    Filed: March 13, 2013
    Date of Patent: July 22, 2014
    Assignee: Western Digital Technologies, Inc.
    Inventor: Tehri S. Lee
  • Patent number: 7859782
    Abstract: A method is disclosed for demodulating a spiral servo track recorded on a disk of a disk drive. The spiral servo track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. A demodulation window is enabled relative to a spiral servo track crossing, and a plurality of sync marks are detected in a sync mark window of the demodulation window. A reliability metric is generated for each of the detected sync marks, wherein the reliability metrics are evaluated to select one of the detected sync marks. A clock is synchronized in response to the selected sync mark.
    Type: Grant
    Filed: May 18, 2008
    Date of Patent: December 28, 2010
    Assignee: Western Digital Technologies, Inc.
    Inventor: Tehri S. Lee
  • Patent number: 7499236
    Abstract: A method is disclosed for writing product servo sectors to the disk of a disk drive by demodulating spiral tracks recorded on the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The high frequency signal is demodulated into a plurality of servo burst signals, and a position error signal is generated from the servo burst signals. A correlation between the position error signal and an off-track displacement of a head is calibrated, for example, by moving the head radially over the disk until the servo burst signals attain a first predetermined relationship, and then calibrating the correlation in response to the corresponding position error signal.
    Type: Grant
    Filed: April 8, 2005
    Date of Patent: March 3, 2009
    Assignee: Western Digital Technologies, Inc.
    Inventors: Tehri S. Lee, Siri S. Weerasooriya, Harry S. Hvostov
  • Patent number: 7468855
    Abstract: A method is disclosed of writing product servo sectors to a disk of a disk drive to define a plurality of product servo wedges, the disk comprising a plurality of spiral tracks. The spiral tracks are spaced apart circumferentially by a substantially equal spacing, and the number of spiral tracks equals a non-integer multiple of product servo wedges. The head internal to the disk drive is used to read the spiral tracks to generate a read signal, and the sync marks are detected from the read signal to generate a sync mark detect signal. A timing recovery measurement is generated in response to the sync mark detect signal, and a frequency control signal is generated in response to the timing recovery measurement. A servo write clock is generated in response to the frequency control signal which is used to write the product servo sectors to the disk.
    Type: Grant
    Filed: February 9, 2007
    Date of Patent: December 23, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventors: Siri S. Weerasooriya, Tehri S. Lee
  • Patent number: 7440210
    Abstract: A method of writing spiral tracks on a disk of a disk drive is disclosed. The disk drive comprises control circuitry and a head disk assembly (HDA) comprising the disk, an actuator arm, a head coupled to a distal end of the actuator arm, and a voice coil motor for rotating the actuator arm about a pivot to position the head radially over the disk. A write clock is synchronized to the rotation of the disk, and a plurality of spiral tracks are written on the disk at a predetermined circular location determined from the write clock. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a multi-bit sync mark, and each multi-bit sync mark comprises a plurality of bits.
    Type: Grant
    Filed: June 23, 2004
    Date of Patent: October 21, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventor: Tehri S. Lee
  • Patent number: 7433143
    Abstract: A method and apparatus is disclosed for adjusting the track density by changing the slope of spiral tracks used to servo write a disk drive. A target track density is established for a disk surface, and a plurality of spiral tracks are written to the disk surface in response to the target track density. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark, and a slope of the spiral tracks is selected in response to the target track density. The head internal to the disk drive is used to read the spiral tracks in order to write product servo sectors to the disk to define a plurality of data tracks, wherein the slope of the spiral tracks determines the density of the data tracks.
    Type: Grant
    Filed: September 17, 2004
    Date of Patent: October 7, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventors: Wing Ying, Jack M. Chue, Siri S. Weerasooriya, Tehri S. Lee
  • Patent number: 7391583
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The read signal from the head is processed to detect a plurality of the sync marks in a spiral track crossing. A timing recovery measurement is generated in response to a selected one of the sync marks based on reliability metrics, wherein a servo write clock is synchronized in response to the timing recovery measurement. The read signal representing the high frequency signal in the spiral track crossing is processed to generate a position error signal (PES) used to maintain the head along a substantially circular target path while using the servo write clock to write product servo sectors along the circular target path.
    Type: Grant
    Filed: July 27, 2006
    Date of Patent: June 24, 2008
    Assignee: Western Digital Technologies, Inc.
    Inventors: Edgar D. Sheh, Tehri S. Lee
  • Patent number: 7301717
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The head internal to the disk drive is used to read the spiral tracks to generate a read signal. The read signal is integrated to generate a ramp signal, wherein a position error signal is generated from the ramp signal. The position error signal is used to maintain the head internal to the disk drive along a servo track while writing product servo sectors along the servo track.
    Type: Grant
    Filed: December 20, 2004
    Date of Patent: November 27, 2007
    Assignee: Western Digital Technologies, Inc.
    Inventors: Tehri S. Lee, Siri S. Weerasooriya
  • Patent number: 7248426
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The sync marks in the spiral tracks are detected to synchronize a servo write clock used to open a demodulation window during which the high frequency signal in the spiral tracks is demodulated to generate a position error signal for maintaining the head along a first servo track while writing product servo sectors along the first servo track. The demodulation window is then shifted by an integer number of sync mark intervals to initiate a seek to a second servo track. The head is then used to write product servo sectors along the second servo track.
    Type: Grant
    Filed: July 30, 2004
    Date of Patent: July 24, 2007
    Assignee: Western Digital Technologies, Inc.
    Inventors: Siri S. Weerasooriya, Tehri S. Lee
  • Patent number: 7212364
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. A plurality of spiral tracks are written to the disk, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. During the product servo writing process, the sync marks in the spiral tracks are detected and a sync mark reliability metric is generated, wherein the sync mark reliability metric represents a probability that the sync mark was detected accurately. A timing recovery measurement is generated in response to the detected sync marks and the sync mark reliability metrics. A servo write clock is synchronized in response to the timing recovery measurement and used to write the product servo sectors to the disk while serving on the spiral tracks.
    Type: Grant
    Filed: January 31, 2004
    Date of Patent: May 1, 2007
    Assignee: Western Digital Technologies, Inc.
    Inventor: Tehri S. Lee
  • Patent number: 7113362
    Abstract: A disk drive is disclosed having a disk comprising a plurality of spiral tracks, a head actuated over the disk, and control circuitry operable to process the spiral tracks in an interleaved manner to write a plurality of product servo sectors to the disk to define a plurality of radially spaced, concentric data tracks.
    Type: Grant
    Filed: August 19, 2005
    Date of Patent: September 26, 2006
    Assignee: Western Digital Technologies, Inc.
    Inventors: Tehri S. Lee, Siri S. Weerasooriya
  • Patent number: 7068459
    Abstract: A method and apparatus is disclosed for writing product servo sectors to a disk of a disk drive to define a plurality of data tracks. The disk drive comprises the disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks which are read using the head to synchronize a write clock and to generate a position error signal (PES) according to a PES algorithm used to maintain the head along a first servo track while writing product servo sectors along the first servo track. The PES algorithm is adjusted to seek the head to a second servo track, and the head is used to write product servo sectors along the second servo track.
    Type: Grant
    Filed: September 20, 2004
    Date of Patent: June 27, 2006
    Assignee: Western Digital Technologies, Inc.
    Inventors: Robert L. Cloke, Siri S. Weerasooriya, Tehri S. Lee, Edgar D. Sheh, Wing Ying
  • Patent number: 7068461
    Abstract: A disk drive is disclosed comprising a disk having a plurality of servo bursts written using perpendicular magnetic recording, wherein each servo burst is written at a servo burst frequency. A fill pattern is written between the servo bursts using perpendicular magnetic recording at a frequency substantially equal to an even harmonic of the servo burst frequency, and a phase shift occurs at the transition between the servo burst and the fill pattern. A head is actuated over the disk, and a sampling device samples a read signal emanating from the head to generate a sequence of read signal sample values. Control circuitry demodulates the servo bursts from the sequence of read signal sample values by computing a single-point Discrete Fourier Transform (DFT) at the servo burst frequency.
    Type: Grant
    Filed: November 29, 2004
    Date of Patent: June 27, 2006
    Assignee: Western Digital Technologies, Inc.
    Inventors: Jack M. Chue, Siri S. Weerasooriya, Tehri S. Lee
  • Patent number: 6989954
    Abstract: A method of manufacturing a disk drive by demodulating product servo sectors and spiral tracks written on a disk of the disk drive is disclosed. An external spiral servo writer writes a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The spiral tracks are used to write product servo sectors to the disk during a fill operation. Common circuitry, such as burst demodulation circuitry, is used to demodulate the high frequency signal in the spiral tracks during the fill operation as well as demodulate the product servo sectors.
    Type: Grant
    Filed: January 31, 2004
    Date of Patent: January 24, 2006
    Assignee: Western Digital Technologies, Inc.
    Inventors: Tehri S. Lee, Robert L. Cloke, Siri S. Weerasooriya
  • Patent number: 6987636
    Abstract: A method and apparatus is disclosed for adjusting the track density over the disk radius by changing the slope of spiral tracks used to servo write a disk drive. A plurality of spiral tracks are written to the disk wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. A slope of the spiral tracks over a first radial segment of the disk is substantially steeper than the slope of the spiral tracks over a second radial segment of the disk. The head internal to the disk drive is used to read the spiral tracks in order to write product servo sectors to the disk to define a plurality of data tracks. The steeper slope of the spiral tracks over the first radial segment causes a track density of the data tracks to be lower over the first radial segment compared to the track density of the data tracks over the second radial segment.
    Type: Grant
    Filed: September 17, 2004
    Date of Patent: January 17, 2006
    Assignee: Western Digital Technologies, Inc.
    Inventors: Jack M. Chue, Siri S. Weerasooriya, Tehri S. Lee
  • Patent number: 6967799
    Abstract: A disk drive is disclosed servo written from spiral tracks by generating a time-stamped sync mark detect signal processed by timing recovery firmware. A plurality of spiral tracks are written to the disk, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. The head internal to the disk drive is used to read the spiral tracks, and a time-stamped sync mark detect signal is generated when one of the sync marks is detected. The time-stamped sync mark detect signal represents a time when the sync mark was detected relative to a servo write clock. A difference between the time-stamped sync mark detect signal and an expected time is computed in firmware to generate a coarse timing recovery measurement used to synchronize the servo write clock. The servo write clock and the head internal to the disk drive are used to write product servo sectors along a substantially circular target path.
    Type: Grant
    Filed: May 28, 2004
    Date of Patent: November 22, 2005
    Assignee: Western Digital Technologies, Inc.
    Inventor: Tehri S. Lee
  • Patent number: 6965489
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. An external spiral servo writer writes a plurality of reference servo sectors at an outer diameter of the disk and a plurality of spiral tracks that spiral from an outer diameter to an inner diameter of the disk. At the beginning of the product servo writing process, the reference servo sectors are demodulated to initially synchronize a servo write clock. The spiral tracks are then demodulated to maintain synchronization of the servo write clock as well as maintain the head along a target circumferential path while writing product servo sectors to the disk.
    Type: Grant
    Filed: January 31, 2004
    Date of Patent: November 15, 2005
    Assignee: Western Digital Technologies, Inc.
    Inventors: Tehri S. Lee, Robert L. Cloke, Siri S. Weerasooriya
  • Patent number: 6943978
    Abstract: A method of writing product servo sectors to a disk of a disk drive is disclosed. A plurality of spiral tracks are written to the disk, wherein each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark. During the product servo writing process, the sync marks in the spiral tracks are read to generate a coarse timing recovery measurement, and the high frequency signal in the spiral tracks is read to generate a fine timing recovery measurement. The coarse and fine timing recovery measurements are processed to synchronize a servo write clock used to write the product servo sectors to the disk. In one embodiment the control circuitry within the disk drive synchronizes the servo write clock by reading the spiral tracks, and in an alternative embodiment an external product servo writer synchronizes the servo write clock by reading the spiral tracks.
    Type: Grant
    Filed: January 31, 2004
    Date of Patent: September 13, 2005
    Assignee: Western Digital Technologies, Inc.
    Inventor: Tehri S. Lee