Hitachi-high-technologies Corporation

Yukio Yamamoto

Yoshihiro Sakurai

Kunihito Higa

Shigeo Nakamura

Kimihiko Sudo

Yasuhiro Matsuda

Toshinori Sugiyama

Hitoshi Otani

The present invention realizes reduction of position information demodulation errors caused by the eccentricity of the magnetic disk and improvement of position signal detection accuracy, as well as enabling quick eccentricity clock correction for arbitrary clock frequencies. An inspection device in accordance with the present invention comprises: a servo demodulation unit which demodulates servo information; a PLL clock generating unit which generates a reference clock and supplies the reference clock to the servo demodulation unit; and a tester control unit. The PLL clock generating unit includes an eccentricity correction circuit for correcting the frequency of the reference clock depending on the eccentricity of the magnetic disk. The tester control unit generates correction data for correcting the frequency of the reference clock, multiplies the correction data by the inverse of a transfer function of the PLL clock generating unit, and supplies the product to the eccentricity correction circuit.

Inspection device and inspection method for inspecting magnetic disk or magnetic head

Drive waveforms with which extension and contraction characteristics of an actuator corresponding to a number of track eccentricity amounts are stored as data. By reading servo information written in a disk is obtained as a signal indicating a head displacement amount from a track. The head is moved in a direction in which the track is displaced by obtaining an amplitude corresponding to a slip amount of the head position and a rotation angle of maximum eccentricity, reading drive waveforms which is optimal in driving the actuator from the memory and driving the actuator with a drive waveform matched with the rotation angle at which the eccentricity is maximum.

Head positioning method for eccentric track and head positioning control device

A magnetic head-positioning servo system is provided to accurately test a magnetic disk with a track written in advance, by providing two fine actuators. The second fine actuator, to which a magnetic head is attached, is mounted on the first fine actuator. The second fine actuator has a larger generating displacement than a generating displacement of the first fine actuator, and lets the magnetic disk to follow the eccentricity of the track. In this way, the positioning accuracy can be increased.

Magnetic head-positioning servo system, magnetic head test system and magnetic disk test system

A mark information is recorded in an area which is on a circumference of a magnetic disk corresponding to a last track in which a servo information write is ended or a track, which is one or two in front of the last track in which servo information is not written and the mark information is detected by returning a magnetic head in a radial direction of the magnetic disk by a fine movement stage after the magnetic head is moved to a next aimed track by a coarse movement stage. The servo information write position is detected by the magnetic head and the servo information is written in a servo information write position of a next track by positioning the magnetic head therein by using the fine movement stage.

Servo information writing method, magnetic head tester and magnetic disk tester using the servo information writing method

A magnetic head position control method is provided to control a magnetic head to follow the track on a DTM (discrete-track magnetic) disk by accurately detecting the eccentricity compensation amount through a simple process. An angle detection unit detects &#x3b8;at which the relative displacement between the magnetic head and the tracks on the DTM (discrete-track magnetic) disk has a peak with no vibration data added. A vibration data calculation unit calculates first vibration data with first vibration amplitude, so that the displacement has a peak at &#x3b8;displaced from &#x3b8;by a predetermined value. The angle detection unit detects &#x3b8;at which the relative displacement has a peak with the first vibration data added. A compensation data calculation unit calculates compensation data for the eccentricity of the tracks, from the detected angles &#x3b8;, the first vibration amplitude, and &#x3b8;. The position of the magnetic head is compensated according to the correction data.

Growing community of inventors

Kokubunji, Japan

Yukio Yamamoto