Hitachi, Ltd.

Other

Hitachi Maxell, Limited

Hitachi Media Electronics Co., Ltd.

Hitachi Heating Appliances Co., Ltd.

Yukio Fukui

Masayuki Inoue

Kunikazu Ohnishi

Takeshi Shimano

Shigeru Nakamura

Makoto Miyamoto

Toshio Sugiyama

Shinji Fujita

Hidenori Shinohara

Masaji Ishigaki

Yasuyuki Sugi

Nobuo Imada

Motoyasu Terao

Yoshio Suzuki

Akemi Hirotsune

Tetsuya Nishida

Yasushi Miyauchi

Nobuhiro Tokushuku

Motoyuki Suzuki

Keikichi Andoo

Takashi Takeuchi

Yoshio Miura

Norio Goto

Mitsuhiko Ota

Katunobu Takeda

Koichi Moritani

Takeshi Maeda

Takao Arai

Tohru Sasaki

Akira Arimoto

Toshimitsu Kaku

Seiji Yonezawa

Masuo Oku

Toshiaki Tsuyoshi

Tetsu Ohishi

Takeshi Nakao

Masafumi Nakamura

Masaaki Kurebayashi

Yoshimichi Kudo

Masatoshi Ohtake

Shigeki Inoue

Harushige Nakagaki

Yoshie Kodera

Tooru Sasaki

Keikichi Ando

Kazuo Ichino

Reiji Tamura

Takehiko Yorozu

Hideo Suenaga

Yoshihiro Ikari

Isao Saito

Tatsuo Baba

Junji Nakajima

Hiroshi Nogami

Hisamitsu Tanaka

Hideo Onuki

Nobuhiro Tokusyuku

An optical head having a semiconductor laser and a generation of a plurality of reflected light beams from an optical disk which have polarities of intensity distribution variations which are substantially inverted to each other when a periodic structure of the optical disk crosses at least one focused spot on the disk. An optical detection system splits the plurality of reflected light beams and detects the split reflected light beams. An electrical circuit provides a focus error signal of the at least one focused spot and a tracking error signal from the plurality of reflected light beams. The electrical circuit adds focus error signals provides a difference signal between the focus error signals, amplifies tracking error signals with a gain, and obtains a difference between amplified tracking error.

Optical head

An information reproducing method for reproducing information recorded on a medium by irradiating a laser beam and detecting a reflected light beam from the medium. The method includes detecting a plurality of reflected light beams in which the polarities of variations in reflected light beam intensity distributions are substantially inverted to each other, the distribution variation being produced when a light spot of the laser beam crosses a track on the medium, generating components of a focus error signal and components of a tracking error signal, adding the components of the focus error signal of the plurality of reflected light beams to generate a focus error signal, and taking a difference between the components of the tracking error signal of the plurality of reflected light beams to generate a tracking error signal.

Information reproducing method which reproduces plural components of a focus error signal and a tracking error signal from plural detection regions of plural reflected light beams

An optical detector for detecting at least three optical beams reflected by an optical information recording medium and outputting an electric signal, the optical detector having three light receiving areas each of which receives a respective one of the three optical beams and each of which has four light receiving surfaces, twelve signal lines to transmit an electric signal obtained on respective ones of the four light receiving surfaces of the three light receiving areas, selected ones of the twelve signal lines connected to the four light receiving surfaces of different ones of the three light receiving areas being joined together within the optical detector, and less than nine signal output lines formed by joining the selected ones of the twelve signal lines extend from the optical detector to a signal processing circuit.

Optical detector having three light receiving areas

It is desirable to greatly reduce the disturbance that arises in a focusing error signal by a astigmatic detection method and offset that arises in the tracking error signal by a push-pull method when reproducing various information storing disks, such as a DVD-RAM disk. It is also desirable to provide an optical disk apparatus which is able to reproduce a variety of high density optical disks, such as DVD-RAM and DVD-ROM disks, as well as conventional disks, such as CD, CD-ROM, CD-R disks, by using a simple optional head. For this purpose, an optical disk apparatus irradiates three optical beams produced by a diffraction grating on the specified position of an optical disk and detects reflected light using a specified optical detector divided into twelve parts.

Optical detector, signal processing circuit and optical information reproduction apparatus thereof

An optical head eliminates an disturbance which occurs in a focus error signal in association with the decentering of an optical disk when an optical spot crosses a track on a storage film surface, and in addition the optical head cancels an off-set which occurs in a tracking error signal in association with the movement of an objective lens. In the constitution of the optical head, phases of wave surfaces of &plusmn; st order diffracted lights are shifted by an amount of &lgr;/2 with a common period by using a phase-inverted diffraction grating the phase of which is inverted with a period of D &lgr;/(2P . NA) in a radial direction of the optical disk, thus causing, on the optical disk, sub-spots to be located on the same track as a main-spot. Taking advantage of this location, focal point shift error signals of the main-spot and the sub-spots are added to each other with an appropriate gain ratio, thereby making it possible to cancel the disturbance which occurs in the focus error signal. Meanwhile, tracking error signals of the main-spot and the sub-spots according to a push-pull method are subtracted from each other with an appropriate gain ratio, thereby making it possible to cancel the off-set.

Optical head including electrical circuit which produces focus error signal and tracking error signal unaffected by variations in intensity distributions of reflected light beams

A dichroic mirror of a polarized beam splitter is installed between a mirror and an objective lens as a beam synthesize/split means, in an optical system corresponding to a second dick and an optical system corresponding to a first disk arranged so as to form a two-layer structure. The dimension of the optical head in the width, length, and thickness directions are designed moderately.

Compact optical head including two light emitters having parallel optical axes

An information recording medium having recording, reproducing, and rewriting characteristics better than those of prior art media. The media has a recording layer made of a material represented by the following formula: Ge Sb Te M , wherein 0.13&lE;x&lE;0.22, 0.20&lE;y&lE;0.32, 0.53&lE;z&lE;0.60, 0&lE;w&lE;0.06, x&plus;y&plus;z&equals;1, and M is any one of Na, Mg, Al, P, S, Cl, L, Ca, Sc, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nb, Ru, Rh, Cd, In, Sn, I, Cs, Ba, La, Hf, Ta, Re, Os, Ir, Hg, Tl, Pb, Th, U, Ag, Cr, W, Mo, Pt, Co, Ni, Pd, Si, Au, Cu, V, Mn, Fe, Ti and Bi.

Information recording medium

An information recording medium which includes at least a recording layer, and first and second metallic layers disposed on an opposite side of an energy beam incident side of the recording layer and having different compositions, and in which the first one of the first and second metallic layers located closer to the recording layer contains Al, Ag, Au, Pt and Pd as its main components and a sum of contents of these atoms is 60% or more. Thereby recording and reproducing of information can be realized with a high reliability.

Information recording medium and information recording and reproducing apparatus using the same

Information recording medium and information recording and reproducing

Disclosed is an optical pickup and an optical disc device using the same, each including a laser diode, a photo-detector having a region divided into at least six photo-detection areas, and a diffraction grating disposed between the laser diode and the photo-detector and having a region divided into four areas by cross-shaped division lines. The diffraction grating divides a light beam reflected from an optical disc into four diffracted light beams. A focus error signal in accordance with a knife edge method and two kinds of tracking error signals in accordance with a push-pull method and a differential phase detection method are detected by irradiating the light beams diffracted at the areas of the diffraction grating on the detection areas of the photo-detector and/or at boundary lines therebetween, and arithmetically operating light intensity signals obtained from the detection areas of the photo-detector. As a result, there can be realized an optical pickup and an optical disc device, each of which can be matched with various optical discs different in structure by detecting a tracking error signal in accordance with the push-pull method and a tracking error signal suitable for a read only disc using only one photo-detector. Further, in the present invention, a holographic element can be used as the diffraction grating.

Optical pickup for optical disk apparatus

The dichroic mirror or a polarized beam splitter is installed between a mirror and an objective lens as a beam synthesize/split means, in an optical system corresponding to a second disk and an optical system corresponding to a first disk arranged so as to form a two-layer structure. The dimension of the optical head in the width, length, and thickness directions are designed moderately.

Compact optical head including two light emitters having parallel

The present invention comprises an arrangement with removable optical element having a predetermined focal distance in the light path between a light source and an objective lens, so as to insert said optical element into the light path between the light source and the objective lens for playing back or recording onto one type of thickness of disk plates, as well as to remove it therefrom for playing back or recording onto another type of thickness of disk plates. Alternatively, by retaining variably the distance between the light source and the collimator lens, the distance between the light source and the collimator lens along with the light path is variably changed according to the thickness of the disk plate being inserted. Then by determining the type of the disk inserted and accordingly selectably inserting/removing the optical element, only one objective lens may be used to conform to the disk plates having different thicknesses.

Optical disk apparatus and optical head thereof

A bidirectional optical transmission and receiving module of a simplified structure and an optical communication system using the same. The optical transmission and receiving module includes a light emitting device and a light receiving device disposed with in a same package having an opening covered with a cover glass sheet, and a holographic diffraction grating provided on a top or lower surface of the glass sheet. In transmitting operation, a light beam emitted from the light emitting device passes through the diffraction grating to be concentrated onto an end face of an optical fiber by a lens. In receiving operation, a received light beam emanated from the end face of the optical fiber reaches the diffraction grating via the lens to be thereby diffracted. A plus-sign primary diffracted light beam resulting from the diffraction is concentrated onto a light detecting surface of the light receiving device. Signal as transmitted through the optical fiber in the form of signal light can thus be received.

Optical transmission and receiving module and optical communication

A masking type light control layer for decreasing its reflection factor in a high-temperature region is formed on phase pits of an optical disc, and the phase pit depth is set to a predetermined value. A light spot for reproduction is shaped to an elliptical form and two sub-flux beams on the optical disc are spaced by 5/4 track pitch from a principal flux beam in the radial direction of the optical disc. The kind of optical disc is discriminated and reproduction laser power and characteristics of an equalizer circuit are switched in accordance with the type of an optical disc. Through this, a stable servo signal detection can be ensured and repetitive reproduction characteristics can be improved.

Optical disc with phase pits and a reproducing apparatus for data

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Machida, Japan

Yukio Fukui