Man Fai Cheung

US Patent:

6476998, Nov 5, 2002

Filed:

Nov 16, 1998

Appl. No.:

09/192876

Inventors:

Man F. Cheung - Campbell CA

Assignee:

Maxtor Corporation - Longmont CO

International Classification:

G11B 5596

US Classification:

360 7806, 360 7804

Abstract:

A method for improving servo seek settling performance by selectively activating a gain enhancement control signal during settling. As an actuator approaches a target location, absolute position and velocity of the read/write transducer head are monitored. If the absolute position changes absolute values (positive to negative or vice-versa) or the velocity approaches zero, the gain enhancement control signal is activated and combined with a nominal actuator control signal to further urge the actuator towards the target location. The gain enhancement control signal decays exponentially so as not to excite mechanical resonance of the actuator arms.

US Patent:

6912235, Jun 28, 2005

Filed:

Jul 31, 2002

Appl. No.:

10/210039

Inventors:

Douglas W. Anthon - El Cerrito CA, US
Jill D. Berger - Los Gatos CA, US
Alexander A. Tselikov - Fremont CA, US
Stephen J. Hrinya - San Jose CA, US
Howard S. Lee - San Jose CA, US
Alan A. Fennema - San Jose CA, US
Man F. Cheung - Campbell CA, US

Assignee:

Iolon, Inc. - San Jose CA

International Classification:

H01S003/098
H01S003/13

US Classification:

372 2902, 372 18, 372 19, 372 32

Abstract:

An apparatus and method for controlling the phase of a tunable laser is provided. Stabilization of the mode of a laser beam is provided as the laser is tuned to a target frequency. For one embodiment, a laser generates a reference beam and an output beam. The power of each of beam is measured by optical detectors, and a ratio thereof is utilized to detect when a mode hop occurs as the laser is coarsely tuned. The average of the pre and post mode hop ratios is utilized as a control setpoint while finely tuning the laser to the target frequency. Wavelength lockers, optical power dividers and optical detectors are utilized to determine power levels of the reference and output beams while also monitoring frequency characteristics thereof. A control unit utilizes the outputs from the wavelength locker to control the operation of the extended cavity laser during and after tuning.

US Patent:

7411758, Aug 12, 2008

Filed:

Jan 23, 2006

Appl. No.:

11/337360

Inventors:

Man Cheung - Campbell CA, US
Perry Neos - Los Altos CA, US

Assignee:

Marvell International Ltd. - Hamilton

International Classification:

G11B 21/02

US Classification:

360 75, 360 51, 360 7707

Abstract:

A servo control system includes a peak detection module that detects peak times of spiral signals generated by reading spirals prewritten on a magnetic medium. The servo control system includes a control module that determines positions of the spirals based on the peak times, stores the positions of the spirals, seeks and tracks the spirals using the positions, and writes servo on the magnetic medium based on the positions of the spirals.

US Patent:

7646559, Jan 12, 2010

Filed:

Sep 26, 2007

Appl. No.:

11/904117

Inventors:

Man Cheung - Campbell CA, US
Pantas Sutardja - Los Gatos CA, US

Assignee:

Marvell International Ltd. - Hamilton

International Classification:

G11B 21/02
G11B 5/09
G11B 5/596

US Classification:

360 75, 360 51, 360 7704

Abstract:

A control system includes a write head that writes servo data on a rotating medium. A control module signals the write head to write a servo test track on the rotating medium and subsequent to a reference servo track. The reference servo track is written prior to an interrupt event. The control module detects a position of the servo test track relative to the reference servo track and signals the write head to write a new servo track based on the position after the interrupt event.

US Patent:

7764457, Jul 27, 2010

Filed:

Aug 7, 2008

Appl. No.:

12/188118

Inventors:

Perry Neos - Los Altos CA, US
Luan Ton-That - San Jose CA, US
Man Cheung - Campbell CA, US

Assignee:

Marvell International Ltd. - Hamilton

International Classification:

G11B 21/02
G11B 5/596

US Classification:

360 75, 360 7707

Abstract:

Methods, systems and computer program products for detecting an end of a reference spiral band are described. A first portion of servo information may be written on a disk using the reference spiral band. By detecting an end of a reference spiral band, a new reference spiral band may be launched. A read/write head of a hard disk drive may subsequently use the new spiral band to write the remaining portion of the servo information, which aids the writing of data tracks on the disk.

US Patent:

7773335, Aug 10, 2010

Filed:

Aug 15, 2008

Appl. No.:

12/192981

Inventors:

Jason Adler - Fremont CA, US
David Rutherford - San Jose CA, US
Man Cheung - Campbell CA, US
Perry Neos - Los Altos CA, US
Luan Ton-That - San Jose CA, US

Assignee:

Marvell International Ltd. - Hamilton

International Classification:

G11B 21/02
G11B 5/596
G11B 5/09

US Classification:

360 75, 360 51, 360 7707

Abstract:

Methods, systems, and apparatus, including computer program products, are described for calibrating servos, and in some implementations for calibrating spiral servos for use in self-servo-write processes. In one aspect, a method is provided that includes determining a measured slope of a spiral, and calibrating radial spacing between servo tracks using the measured slope and a target slope.

US Patent:

7791832, Sep 7, 2010

Filed:

Jan 11, 2010

Appl. No.:

12/685264

Inventors:

Man Cheung - Campbell CA, US
Pantas Sutardja - Los Gatos CA, US

Assignee:

Marvell International Ltd. - Hamilton

International Classification:

G11B 21/02
G11B 5/09
G11B 5/596

US Classification:

360 75, 360 51, 360 7704

Abstract:

A control system includes a write head and a control module configured to signal the write head to write a servo test track on a rotating medium at a position relative to a reference servo track on the rotating medium. The servo test track is written on the rotating medium subsequent to an interrupt event. The reference servo track having been written to the rotating medium prior to the interrupt event, detects the position of the servo test track relative to the reference servo track and signals the write head to write a new servo track on the rotating medium based on the detected position of the servo test track relative to the reference servo track.

US Patent:

7869158, Jan 11, 2011

Filed:

Aug 15, 2008

Appl. No.:

12/192931

Inventors:

Man Cheung - Campbell CA, US
Perry Neos - Los Altos CA, US
David Rutherford - San Jose CA, US

Assignee:

Marvell International Ltd. - Hamilton

International Classification:

G11B 5/596
G11B 21/02
G11B 15/12
G11B 5/09

US Classification:

360 7707, 360 75, 360 51, 360 61

Abstract:

A recording medium can include multiple helicoid patterns arranged in multiple helicoid groups, e. g. , first and second helicoid groups. Operating a disk drive can include switching between helicoid groups to maintain the alignment of the head with respect to a target track of the rotating recording medium. Enabling a switch can include receiving a waveform produced by a head operated with respect to a rotating recording medium, generating first information from one or more portions of the waveform corresponding to the helicoid patterns of the first helicoid group; generating second information from one or more portions of the waveform corresponding to the helicoid patterns of the second helicoid group; and analyzing the second information with respect to the first information to generate calibration information. The calibration information can compensate for operational differences between using the helicoid patterns of the first helicoid group and the helicoid patterns of the second helicoid group.