Fujitsu Corporation

Takahisa Ueno

Tomoyoshi Yamada

Susumu Hasegawa

Nobuyuki Suzuki

Kazuhiko Takaishi

Iwao Okamoto

Keiji Aruga

Shuichi Hashimoto

Seigo Igaki

Yukihiro Uematsu

Tohru Horie

After a measurement apparatus records a magnetization state of a reference pattern on at least one specific track of a recording medium, it generates a leakage magnetic field of a demagnetization pattern and demagnetizes the magnetization state of the reference pattern using the leakage magnetic field. Then, the measurement apparatus calculates a difference between the read output of a reference pattern before demagnetization and the read output of a reference pattern after demagnetization on the specific track and obtains a leakage magnetic field of a recording head from the obtained difference.

Apparatus and method of measuring write magnetic field of recording head

An object of the present invention is to implement head position control in a disk drive for the case in which a disk is assembled into the disk drive after a precise track is recorded onto it using an external apparatus, which is capable of high-speed access even if there is eccentricity between a track defined by servo information and the center of rotation of the track. Two phase servo bursts consisting of servo information are recorded onto each of the servo information regions of a disk surface, in mutual alternation, the strength ratio between signals detected from these two phase servo bursts being used to determine to which side the head is displaced. By performing control so that this strength ratio is a prescribed value at each angular position, control is achieved so that the head moves along a circular path of rotation, even if there is eccentricity in the servo circular path defined by the recorded servo information with respect to the center of rotation.

Head position control for a disk drive which performs recording about the rotational center even if the recorded servo information is eccentric

A disk device includes a magnetic disk carrying servo information and rotatable about a rotational axis, a magnetic head for reading information from the magnetic disk, a positioning unit for positioning the magnetic head radially over the magnetic disk, and a control unit for controlling the positioning unit according to the servo information. The control unit separately measures a rotational frequency component of the magnetic disk and a high-order frequency component which has frequencies higher than the rotational frequency component, and thereafter controls the positioning unit so as to follow the rotational frequency component while eliminating the high-order frequency component. When the magnetic head is positioned along a circular pattern about the rotational axis of the magnetic disk, the magnetic head is prevented from vibrating while compensating for an eccentricity of the magnetic disk.

Method of positionally controlling a recording/reproducing head so as to

Head position control is implemented in a disk drive for the case in which a disk is assembled into the disk drive after a precise track is recorded onto it using an external apparatus, which is capable of high-speed access even if there is eccentricity between a track defined by servo information and the center of rotation of the track. Two phase servo bursts consisting of servo information are recorded onto each of the servo information regions of a disk surface, in mutual alternation, the strength ratio between signals detected from these two phase servo bursts being used to determine to which side the head is displaced. By performing control so that this strength ratio is a prescribed value at each angular position, control is achieved so that the head moves along a circular path of rotation, even if there is eccentricity in the servo circular path defined by the recorded servo information with respect to the center of rotation.

Head position control for a disk drive which performs recording about

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Kawasaki, Japan

Takahisa Ueno