Sony Corporation

Kazuhiko Fujiie

Ryo Ando

Yasuaki Maeda

Tadao Yoshida

Nobuhiko Ando

Naohiro Netsu

Tetsu Watanabe

Yoshitaka Aoki

Hideo Obata

Takuya Kaeriyama

Hideki Nagashima

Hiroshi Mukawa

Hirotoshi Fujisawa

Tetsuhiro Sakamoto

Yasuhito Tanaka

Chiaki Nonaka

Goro Fujita

Takeshi Miki

Yasuyuki Takeshita

Akira Suzuki

Hiroshi Ogawa

Masashi Nakamura

Tsutomu Ishimoto

Takashi Ohmori

Ariyoshi Nakaoki

Katsuaki Tsurushima

Hajime Yano

Makoto Watanabe

Naoto Kojima

Osamu Kawakubo

Koji Sekiguchi

Kazutomo Miyata

Takashi Omori

You Yoshitoshi

Masahiro Hotori

Teruyuki Ota

Heitaro Nakajima

Tomohiro Koda

Yasunori Terayama

Yasushi Maeda

Yuichiro Hamada

Yoshiaki Haneda

Masanori Ohtawa

Directed to freely adjusting an emission period of a semiconductor laser. In the present invention, pulsed light serving as pulse-shaped laser light (LL) is emitted from a semiconductor laser (), and a laser drive voltage (DJ) that is generated on the basis of a pulse signal (SL) and that has pulse-shaped drive voltage pulses (DJw) is applied to the semiconductor laser (). At this time, a short-pulse light source () varies a voltage period (TV) corresponding to an interval between the drive voltage pulses (DJw), thereby varying a set period (TS) corresponding to an interval between generated signal pulses (SLw) in the pulse signal (SL).

Short-pulse light source, laser light emission method, optical device, optical disc device, and optical pickup

The present invention realizes the emission of a high-output short-pulse beam and a reduction in power consumption. A laser control unit () of a short-pulse light-source device () raises a gate pulse (PG) of a gate signal (SG) supplied to a power supply circuit () in such a manner that the gate pulse (PG) rises only for the duration of an extremely short pulse width (T) to include the rise time of a generated pulse (PL) of a pulse signal (SL) supplied to a driving circuit (). In this way, necessary power can be supplied at the rise timing of the generated pulse (PL), and the power consumption (Pa) can be greatly reduced from the standard power consumption (Pb).

Short-pulse light-source device, laser driving method, optical pickup, and optical disc apparatus

A signal detecting device includes: a semiconductor substrate; a near-field light generating section that is provided on the semiconductor substrate and generates near-field light near an interface with the semiconductor substrate; a light source that outputs light having wavelength corresponding to photon energy about a half as large as band-gap energy of a material of the semiconductor substrate; and a current detecting unit that detects a photocurrent generated in the semiconductor substrate when the near-field light is generated.

Signal detecting device and signal detecting method

The present invention proposes a method of controlling the laser power of a semiconductor laser that, in this method of controlling the laser power of a semiconductor laser by applying a power source voltage to between the collector and emitter of an output transistor and a serial circuit of the output transistor and a semiconductor laser, enables decreasing the power consumption of the output transistor. The present invention is arranged to apply a variable power source voltage Vcc to a serial circuit of an output transistor (Qb) and a semiconductor laser (SL) and thereby control the variable power source voltage Vcc such that a difference between the variable power source voltage Vcc and the peak hold voltage of an operating voltage of the semiconductor laser (SL) becomes substantially constant.

Optical recording, producing apparatus, and method with peak-hold voltage features

An optical recording medium is provided which has a substrate and a signal recording layer provided on the substrate and in which an information signal is recorded in the form of microscopic pits. A light beam is focused on the signal recording layer and some change of the light beam carried by a return light from the signal recording layer is detected to read the information signal recorded on the signal recording layer. The optical recording medium has a diameter of 65 mm or less and a thickness of 0.4 to 0.7 mm. An information signal recording area extends outwardly from a radial position of 12.5 mm or less from the center of the medium. The ratio in area between the information signal recording area and non-signal recording area is 3.4 or more. The storage capacity of this medium is 2 gigabytes or more. The optical recording medium has formed at the center thereof a center hole around which an annular table-abutment convexing to one side of the medium is formed. A magnetic-clamping hub is installed in the center hole and thus the medium is magnetically clamped to a rotation driving mechanism of an optical recording and/or reproducing apparatus. The compactness and high density of recording of the optical recording medium will contribute greatly to a further compact structure of a recording and/or reproducing apparatus in which the medium is to be used.

Optical recording medium and disc cartridge

A method for manufacturing a magneto-optical recording medium in which reading of recorded information is performed through domain wall displacement in a reproduction layer is provided, in which magnetic separation of groove side-wall portions is performed more reliably; as a result a magneto-optical recording medium with satisfactory recording and reproduction characteristics can be provided. The method is to manufacture a magneto-optical recording medium in which on a substratehaving groovesat least a reproduction layer and a recording layer, each of which is formed of magnetic layers, are deposited and recorded information is reproduced through domain wall displacement in the reproduction layer; and the method includes a first annealing process in which, after depositing at least the reproduction layer and recording layer on the substrateon which are formed landsand grooves, only side-wall portionsbetween adjacent landsand groovesare irradiated with laser light L, and a second magnetization annealing process in which regions including adjacent side-wall portionsand lands between side-wall portionsare irradiated with laser light Lhaving a spot diameter greater than the spot diameter of the laser light in the first annealing process, while applying an external magnetic field H.

Method for manufacturing magneto-optical recording medium

A magneto-optical recording medium includes a first magnetic layer (reproduction layer), a second magnetic layer (control layer), a third magnetic layer (blocking layer), and a fourth magnetic layer (recording layer) having respective Curie temperatures T, T, Tand T. The Curie temperatures of the layers satisfy the relationships T&#x3e;T&#x3e;Tand T&#x3e;T. In addition, the magnetic anisotropy of the third magnetic layer Kis greater than that of the second magnetic layer K. A magnetic domain wall in the first magnetic layer in front of the spot irradiated by the reproduction light in the direction of travel is displaced toward the peak temperature portion so that a recorded domain is expanded. Displacement in the spot direction of a domain wall in the first magnetic layer behind the reproduction light spot in the direction of travel is suppressed. The second and third magnetic layers control the magnetic exchange coupling between the first and fourth magnetic layers.

Magneto-optical recording medium and signal reproduction method

A magneto-optical recording/reproducing method is disclosed which causes a laser beam to be emitted to a disc recording medium having information recorded thereon earlier by magnetic field modulation, the laser beam causing the disc recording medium to develop a temperature distribution such as to generate a driving force for moving a domain wall of a magnetic domain in the medium so that the magnetic domain smaller in diameter than a spot of the laser beam is expanded sufficiently to let information recorded in the domain be detected. The method comprises the steps of: recording information to the disc recording medium while rotating the medium in a first rotating direction; and reproducing the information that was recorded to the disc recording medium in the recording step while rotating the medium in a second rotating direction reverse to the first rotating direction.

Method for reproducing information data from a magneto-optical storage medium in reverse direction with recording

Read-only optical recording medium and disc cartridge

A magnetic head device comprising a head section for applying a magnetic field to a disk. The head section includes a magnetic field generating section and a slider . The slider supports the magnetic field generating section and may be set in sliding contact with the disk. The magnetic field generating section has a magnetic core and a coil wound around the magnetic core . The section is designed to generate the magnetic field and embedded in and formed integral with the slider . The head section excels in heat-radiating property.

Magnetic head device and recording/reproducing apparatus using the magnetic head device

An optical recording medium is provided which has a substrate and a signal recording layer provided on the substrate and in which an information signal is recorded in the form of microscopic pits. A light beam is focused on the signal recording layer and some change of the light beam carried by a return light from the signal recording layer is detected to read the information signal recorded on the signal recording layer. The optical recording medium has a diameter of 65 mm or less and thickness of 0.4 to 0.7 mm. An information signal recording area extends outwardly from a radial position of 12.5 mm or less from the center of the medium. The ratio in area between the information signal recording area and non-signal recording area is 3.4 or more. The storage capacity of this medium is 2 gigabytes or more. The optical recording medium has formed at the center thereof a center hole around which an annular table-abutment convexing to one side of the medium is formed. A magnetic-clamping hub is installed in the center hole and thus the medium is magnetically clamped to a rotation driving mechanism of an optical recording and/or reproducing apparatus. The compactness and high density of recording of the optical recording medium will contribute greatly to a further compact structure of a recording and/or reproducing apparatus in which the medium is to be used.

Optical recording medium and disc cartridge having 2 GB capacity

An optical pickup device that is able to record/reproduce information signals for first and second optical discs with different recording capacities. The optical pickup device includes an objective lens for converging first and second light beams of different wavelengths on the signal recording layers of first and second optical discs having different substrate thicknesses, a beam splitter having the same transmittance to the first and second light beams and configured for separating the first and second light beams radiated by first and second light sources to fall on the beam splitter via a first objective lens or a second objective lens, and a hologram element arranged between the objective lens and the beam splitter for limiting the aperture of one of the first light beam and the second light beam and for correcting the spherical aberration caused by difference in the disc substrate thickness of the first and second optical discs. This configuration enables various optical elements, such as objective lens or beam splitter, to be used in common for the optical disc of different recording capacities.

Optical pickup with a hologram to limit the aperture of two light beams with different wavelengths

Growing community of inventors

Kanagawa, Japan

Kazuhiko Fujiie