Hitachi, Ltd.

Hitachi Computer Peripherals Co., Ltd.

Hitachi Maxell, Limited

Toshiaki Tsuyoshi

Seiji Yonezawa

Norio Ohta

Masatoshi Ohtake

Harukazu Miyamoto

Hirofumi Sukeda

Keiji Kataoka

Hajime Aoi

Wasao Takasugi

Masahiko Takahashi

Toshio Niihara

Nobumasa Nishiyama

Kazuhisa Shiraishi

Kazuo Ichino

Yoshibumi Matsuda

Makoto Koizumi

Takashi Takeuchi

Takuji Ogawa

Tatsuo Horikoshi

Tetsuji Kameoka

Masaru Ito

Yosuke Seo

Yoshihiro Moribe

Harushige Nakagaki

Sumio Obata

Masatoshi Otake

Takeshi Maeda

Hisashi Takano

Makoto Saito

Toshimitsu Kaku

Yoshihiro Shiroishi

Yoshito Tsunoda

Hiromichi Fujisawa

Kazuo Shiiki

Takashi Yamaguchi

Yukio Fukui

Hideaki Amano

Katsuhiro Tsuneta

Fumio Kugiya

Futoshi Tomiyama

Toshihisa Okazaki

Yasuhiro Kato

Satoru Yamaura

Masuo Kasai

Yasunori Kanazawa

Tadashi Saitoh

Hiroshi Tooyama

Motoo Uno

Kazuyoshi Hanada

Haruhiko Hosokawa

Akio Takatsuka

Toshio Matsushita

Masaya Tanaka

Tetsji Kameoka

Sachio Kumagai

Takeshi Mada

In a magnetic recording drive having a plurality of magnetic heads each employing a magnetoresistive sensor for the purpose of averaging the time required for sense currents to be caused to flow through the respective magnetoresistive sensors to shorten the longest reproducing time and to suppress the degradation of the characteristics due to the electromigration, thereby improving the reliability of the magnetic recording drive, the magnetic recording drive includes circuits for averaging the useful life depending on the currents caused to flow through the respective magnetoresistive sensors among the plurality of magnetic heads, whereby the time required for the sense current to be caused to flow through one MR reproducing head is greatly shortened. Therefore, the levels of outputs of the MR reproducing heads can be increased without reduction of the reliability and thus the reliability of the magnetic recording drive can be improved.

Magnetic recording drive having arrangement for averaging useful life of

Magnetic recording drive

A magneto-optical data recording system comprises magnetic field pulse applying means for applying to a magneto-optic recording medium a magnetic field pulse of a polarity corresponding to code data to be recorded, and means for heating the recording medium in a pulsating manner at a predetermined frequency synchronous with the code data to be recorded. During recording, the magnetic field pulse applying means applies a magnetic field pulse of a polarity corresponding to code data along a track of the recording medium and the heating means continuously heats the recording medium in a pulsating manner at a predetermined frequency synchronous with the code data to thereby directly overwrite the code data. The magnetic field pulse applying means includes a magnetic coil driven by code data from a source of code data (data generator). The heating means includes an optical head which comprises a source of laser beam driven by a laser driver and an optical system which focuses the laser beam from the source of laser beam as a small light spot onto the recording medium.

Information recording medium with clock information therein

A magnetic disk apparatus includes a dual head equipped with an MR head for reading data and an inductive head for writing the data. One ID portion and one servo pattern are disposed in one sector and an unequal track pitch is formed. The ID portion is formed at the center of a radius of two positions to which the MR head is positioned at the time of reading the data and writing the data, respectively.

Magnetic disk apparatus

Information recording apparatus and method for modulated magneto-optical

Magneto optical recording medium apparatus and method utilizing light

A sensing current adjusting zone is formed in the outermost or innermost periphery of a magnetic disk and reference signals are recorded in a recording width corresponding to the width of a plurality of tracks in the sensing current adjusting zone so that the phases of the reference signals are the same and the radially adjacent reference signals overlap each other. When adjusting the sensing current, an MR head is moved forcibly into the sensing current adjusting zone to reproduce the reference signal and the sensing current is adjusted so that the difference between the respective absolute values of the plus peak and the minus peak of the reproduced reference signal is reduced to the least extent. Therefore, in a magnetic disk unit of a servo system or the like provided with an MR head for reproducing servo information, the sensing current to be supplied to the MR head can be adjusted to an optimum current, the sensing current can be correctly adjusted even in a process in which the servo system of the magnetic disk unit is unable to carry out positioning control. A feedback loop for sensing current adjustment is capable of always adjusting the sensing current to an optimum current even if the characteristics of the MR head varies with time.

Magnetic disk drive with sensing current adjustment of MR head

In a magnetic disk apparatus of high-speed data transfer, in order to cover an uncompensable section of the thermal asperity by error code correction to shorten the uncompensable section, upper and lower envelopes of a reproduced waveform are detected to obtain a level variation waveform due to the thermal asperity and subtract it from the reproduced signal. A thermal asperity processing circuit shown in FIG. 1 for compensating for the thermal asperity is used. In an envelope detection circuit in the thermal asperity processing circuit, a forced charge and discharge current control circuit is used in the thermal asperity portion to thereby be able to improve the follow-up characteristic to level variation of the thermal asperity and shorten the uncompensable section.

Magnetic recording and reproducing apparatus with thermal asperity

Increased memory capacity for a magnetic disk device is realized without degrading information error rate, by making the number of sectors at a given circumference of the disk variable in accordance with a radial direction of a disk. The number of sectors is made variable by deciding a predetermined information error rate from a ratio of reproduced signal output to noises of head, disk and amplifier at a maximum recording and reproducing frequency at a certain radial position along a disk.

Method and apparatus for optimizing the recording and reproducing of

A magneto-optical data recording system comprises magnetic field pulse applying apparatus for applying to a magneto-optic recording medium a magnetic field pulse of a polarity corresponding to code data to be recorded, and apparatus for heating the recording medium in a pulsating manner at a predetermined frequency synchronous with the code data to be recorded. During recording, the magnetic field pulse applying apparatus applies a magnetic field pulse of a polarity corresponding to code data along a track of the recording medium and the heating apparatus continuously heats the recording medium in a pulsating manner at a predetermined frequency synchronous with the code data to thereby directly overwrite the code data. The magnetic field pulse applying apparatus includes a magnetic coil driven by code data from a source of code data (data generator). The heating apparatus includes an optical head which comprises a source of laser beam driven by a laser driver and an optical system which focuses the laser beam from the source of laser beam as a small light spot onto the recording medium.

Magneto-optical data recording apparatus using a sample-servo system for

Magnetic recording drive having arrangements for average useful life of

Magneto-optical data recording system continuously irradiating optical

A magnetic recording and reproducing apparatus, comprising a magnetic recording medium, a head arrangement for reading data from or writing data on the magnetic recording medium including an inductive recording head and a magnetoresistive reproducing head, and a phase discriminating circuit for discriminating data `1` from peaks of a waveform reproduced by the head. The phase discriminating circuit has a differential circuit for differentiating the waveform, a pulse circuit for producing a zero cross pulse from a zero-level crossing point of the differentiated waveform, a discriminating circuit for discriminating `1` and `0` of the data with use of pulses output from the pulse circuit and a discriminating window needed for judgment of `1` and `0` of the data, and a decoding circuit for decoding and feeding out the data output of the discriminating circuit. The head comprises a recording head of inductive type, and a reproducing head of magnetoresistive type. The phase discriminating circuit comprises a circuit for controlling a magnetic bias level for the magnetoresistive reproducing head so that a change of resistance of the magnetoresistive reproducing head due to magnetic field is made virtually equal both at positive and negative polarity waveform peaks.

Magnetic recording and reproducing apparatus with reproducing head of

A waveform equalizer for processing a signal read by a magnetic head from a magnetic written medium includes a slimming circuit which, in turn, has a first delay unit for delaying the read signal, a first attenuator connected in parallel with the first delay unit, a first differentiating circuit for receiving the output from the first delay unit and the output from the first attenuator, and a resistor connected to a first delay unit side input of the first differential circuit; and a pseudo-peak elimination circuit connected in series with the slimming circuit and including a circuit for separating the from the read signal the read signal or a signal reverse in phase to the read signal, a second delay unit for delaying the separated signal, a second attenuator for attenuating the amplitude of the separated signal, and a second differential circuit for receiving the read signal and the separated, delayed and attenuated signal.

Digital magnetic writing and reading apparatus

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Kawasaki, Japan

Toshiaki Tsuyoshi