Hitachi, Ltd.

Hitachi Maxell, Limited

Seiji Yonezawa

Toshiaki Tsuyoshi

Keiji Kataoka

Harukazu Miyamoto

Masatoshi Ohtake

Norio Ohta

Wasao Takasugi

Hirofumi Sukeda

Kazuo Shigematsu

Masahiko Takahashi

Toshio Niihara

Motoyasu Terao

Masahiro Ojima

Takashi Takeuchi

Kazuo Ichino

Keizo Kato

Takeshi Maeda

Hideki Saga

Kimio Tatsuno

Masaru Ito

Shinkichi Horigome

Yoshinori Miyamura

Tatsuo Horikoshi

Tsuneo Terasawa

Toshio Sugiyama

Yoshio Taniguchi

Harushige Nakagaki

Masatoshi Otake

Toshimitsu Kaku

Hirotada Ueda

Hiroshi Fukuda

Yoshito Tsunoda

Kiichi Ueyanagi

Toshiei Kurosaki

Yukio Fukui

Masuo Umemoto

Norio Yokozawa

Masuo Kasai

Soichi Katagiri

Yasunori Kanazawa

Teruichi Tomura

Fumiyuki Inose

Toshio Kaneko

Hajime Fukke

Hiroshi Tooyama

Tadashi Saitoh

Motoo Uno

Toshimitsu Miyauchi

Akira Fukuhara

Tsutomu Tawa

Ryoko Yamanaka

Klaus Kinstatter

Mahito Kohmoto

Takesi Maeda

Sachio Kumagai

An optical reproduction apparatus includes a light source which irradiates irradiation light onto a recording medium, the irradiation light being reflected by the recording medium to produce reflection light, a modulator which repetitively pulse modulates the irradiation light to produce irradiation light pulses, a photodetector which detects reflection light from the recording medium at more than two timings during each of the irradiation light pulses, and outputs detection signals respectively representative of the reflection light detected at the more than two timings during each of the irradiation light pulses, and an operation circuit which performs an operation between the detection signals outputted from the photodetector during each of the irradiation light pulses.

Optical reproduction method and optical information device

An optical reproduction method for reproducing information includes intermittently irradiating light to a moving optical medium, detecting reflected light from the moving optical medium while the light is irradiated intermittently when a moving distance of a light spot of the intermittently irradiated light on the moving optical medium is smaller than a diameter of the light spot, processing information based on the detected reflected light utilizing a differential operation, and obtaining a reproduction signal based on the differential operation.

An objective is to provide a technique capable of reproducing high-density recorded fine recording marks with excellent high output and excellent quality. To this end, with the present invention, light,is irradiated intermittently to an optical recording medium changeable in optical nature due to irradiation of light, permitting a differential amplifier,to perform differential processing of a signal as obtained by detection of reflection light rays at at least two time points during irradiation of the intermittent light to thereby obtain a reproduction signal. It is thus possible to effectively detect only a signal component of certain part whereat the reflection light is changed due to light irradiation during irradiation of the intermittent light, which in turn enables reproduction of fine record information with increased resolution while enabling suppression of those components other than the change component. This makes it possible to obtain a reproduction signal with good quality.

Optical reproduction method and optical information apparatus

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

Information recording apparatus and method for modulated magneto-optical

Magneto optical recording medium apparatus and method utilizing light

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

Magneto-optical data recording system continuously irradiating optical

A projection exposure apparatus has an effective source, a mask, a projection lens and an optical filter. The mask is illuminated with the light from the effective source having a substantially annular illumination distribution. The optical filter is disposed in the approximate position of the pupil plane of the projection lens. On the pupil plane, the transmittance of a first region is made lower than that of a second region, the first region being inside of the periphery of an annular region substantially conjugate with the effective source having the annular illumination distribution, the second region being outside of the periphery. Built in this manner, the apparatus forms fine patterns whose unit size is at least as small as the wavelength of the light used while maintaining high values of contrast and deep levels of focal length.

Projection exposure apparatus and pattern forming method for use

The present invention uses a magnetic recording medium equipped with those magnetically readable recording servo pits which are preformed on a magnetic recording medium and have different magnetic characteristics from those of a recording magnetic film, detects magnetically a tracking signal or preformat signals such as sync signals, address signals, and the like, from the magnetic flux distribution (leakage magnetic field) occurring at edges of each of the servo pits using a magnetic head, makes servo control of the position of the magnetic head by the detected tracking signal and records or reads magnetically the data along the center of a track. In the magnetic recording medium of the present invention, magnetically readable, wobbled servo pits or sync pits, track address pits and data pits are preformed on the magnetic recording medium, these pit portions have locally different magnetic characteristics from those of the recording magnetic film and have a magnetic film structure wherein saturated magnetization is smaller than at other portions or the magnetic film is removed locally. These preformed pits can be read magnetically by detecting the local magnetic field (leakage magnetic field) generated at their edges by the magnetic head.

Method of magnetically recording and reading data, magnetic recording

A magneto-optical data recording system includes 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 a heating 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 system

In the present invention, there is provided an optical disk medium wherein a ROM region having data already recorded therein and capable of only optically reproducing (reading) the data as well as a RAM region capable of optically recording and reading out therein and therefrom are interlacedly located in such a positional relationship that enables the substantially continuous and high-speed accessing operation to the read-only ROM and rewritable RAM data, and some of stationary data to be stored suitably in the ROM region are stored in positional relationship closer to some of additional data to be stored suitably in the RAM region which are especially closely related to the some of the stationary data.

Optical disk medium and its application method and system

An optical device for illuminating an object with a rectangular pattern having a uniform light intensity distribution includes n (n.gtoreq.1) polarization separating elements which a laser beam emitted from a laser source enters and each of which separates the laser beam into two beams in two directions. The angle of separation by the polarization separating element is set to be 2.sup.(n-1) times of the smallest one of the separation angles of the polarization separating elements used. At least one quarter-wave or half-wave plate is combined with the polarization separating elements. An imaging lens is provided for forming 2.sup.n beam spots on the object such as an optical laser disk plate.

Optical device for generating pattern having uniform light intensity

In a method of recording/reproducing information associated with an apparatus and recording medium, the medium has an alternate formation including tracks of first regions wherein at least an optical record of preformatted pits at a constant time interval is recorded and second regions in which information is recorded so that optical retrieval can be achieved. A clock signal is generated based on the readout signal of the preformatted pits to record an information signal in the second regions, and the clock signal is retarded and used to read out data pits that are the record of the information in the second regions.

Method and associated apparatus and medium for optical recording and

In a light spot position control system and method in which a control of the irradiation position of a light spot such as a focusing control, a jitter correction and/or a tracking control is made through a sampling control, a newly sampled error value is compared with a one-preceding sampled value. When a difference between both the values is within a range of a predetermined width, the newly sampled value is used as a new sample value as it is. When the difference exceeds the range of the predetermined width, a sum of the one-preceding sampled value and the predetermined width is used as a new sample value. Thereby, the influence of erroneous samples is reduced.

Light spot position control system and method by sampled servo

Growing community of inventors

Hachioji, Japan

Seiji Yonezawa