Sharp Kabushiki Kaisha Corporation

Other

Junsaku Nakajima

Akira Takahashi

Kenji Ohta

Yoshiteru Murakami

Junji Hirokane

Junichiro Nakayama

Hitoshi Takeuchi

Masaru Nomura

Naoyasu Iketani

Michinobu Mieda

Hiroyuki Katayama

Go Mori

Takeshi Yamaguchi

An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit stringof pits of different depths is formed in the lead in region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof. The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

Optical recording medium recorded with information in depth direction, and method and apparatus of reproduction therefrom

On an optical disk, a string of a plurality of pits having two different depths is formed. Quantity of light reflected from the pit string is detected by a photoreceptor element, and based on the detected quantity of reflected light, a pit depth detecting unit detects depth of each pit. Based on the detected quantity of reflected light, a servo signal generating unit generates a tracking servo signal. An output control unit supplies the generated tracking servo signal when a pit of such depth that is to be reproduced is tracked, and holds and supplies an immediately preceding tracking servo signal when a pit of different depth is being tracked, based on the result of detection by the pit depth detecting unit.

Optical disk having pits of different depths formed therein, optical disk reproducing apparatus for reproducing the optical disk, and method of tracking the optical disk

On an optical disc including a substrate on which pits having at least two different depths are formed, main information is recorded by the shape of the pits and additional information is recorded by the depth of the pit. It is possible to reverse polarity of a tangential push-pull signal dependent on the depth of the pit, and therefore it becomes possible to record information utilizing the depth of the pit. This improves recording density of the optical disc. Further, when information of the optical disc is to be copied, the information recorded by the depth of the pit cannot be copied. Therefore, unauthorized reproduction can be prevented.

Optical disc having pits of different depth formed therein, optical disc device for reproducing the same, and method of reproduction

An optical disk has a lead-in region provided at the inner circumference side and a user region provided at the outer circumference side. Pit stringof pits of different depths is formed in the lead-in region. Light beam reflected from the pit string is detected by detector and TPP and RF signals are output by differential amplifier and addition amplifier. A ternary signal is restored from pits based on the TPP and RF signals. Information is recorded by pits of the same depth in the user region. Recording information in the depth direction in the lead-in region increases the recording capacity thereof. The information recorded in the depth direction in the lead-in region cannot be transferred to a user region of another optical disk.

An optical device to control the output power of a laser on recording and reproduction without expensive high-speed circuits is provided. The optical disk device of the present invention comprises monitor portion for monitoring the power of laser light, averaged light quantity calculating portion for calculating the averaged light quantity of the power of the laser light, memory portion for memorizing the averaged light quantity, error quantity calculated portion for calculating the difference between the output signals of the averaged light quantity calculating portion and the memory portion, and laser power control portion for controlling the power of the laser light in response to the output signal from the error quantity calculating portion.

Optical disk device

Featured is a recording and reproducing method of a magneto-optical recording medium including a recording layer for recording thereon information magneto-optically and a readout layer which has in-plane magnetization at room temperature and where a transition occurs from in-plane magnetization to perpendicular magnetization as temperature raises. The method includes projecting a light beam onto such a magneto-optical recording medium so as to form a perpendicularly magnetized area in the readout layer by duplication of the magnetization of said recording layer to the area. In further embodiments, the recording medium further includes an intermediate layer made of non-magnetic film formed between the readout and recording layers and the readout and recording layers are composed of rare-earth transition metal alloys such as TbFeCo (recoding layer) readout layer, made of GdFeCo (readout layer).

Magneto-optical recording medium and recording and reproducing method and optical head designed for the magneto-optical recording medium

A magneto-optical head device includes a light source, an objective lens which condenses a light beam emitted from the light source, an auxiliary lens which converts an effective numerical aperture of the light beam condensed by the objective lens to irradiate a recording medium with the light beam, and a magnetic reproducing head which is integrated into the auxiliary lens. The magneto-optical head device can thus be decreased in size and information can be reproduced from both surfaces of a disk since the magnetic reproducing head is integrated into the auxiliary lens. Further, when a thermomagnetic recording medium is employed as the recording medium, the magneto-optical head device can reproduce information recorded at a high track density and a high line density.

Magneto-optical head device having integrated auxiliary lens and magnetic reproducing head and recording and reproducing device using magneto-optical head device

Optical recording medium having prepits deeper than grooves

In an optical recording medium in which marks are allowed to be written at grooves and information has been recorded beforehand in the form of prepits in a prepit area, the medium is constructed so that the groove width, Wg, the land width, Wl, and the prepit width, Wp, satisfy the relationships of either Wl<Wg, and Wp<Wg, or Wl>Wg, and Wp>Wg. Alternatively or additionally to the above, a sum of lengths of pit-presence portions in the prepit area is larger than a sum of lengths of pit-absence portions in the prepit area.

Optical recording medium

Featured is a recording and reproducing method for recording and reproducing information on and from a recording medium. The medium includes a base having a property that a light can be transmitted therethrough, a readout layer formed on the base, which has an in-plane magnetization at room temperature, whereas, a transition occurs from in-plane magnetization to perpendicular magnetization as temperature rises and a recording layer formed on said readout layer for recording thereon information magneto-optically. A groove for guiding a light beam is formed on a readout layer side of the base and a groove width is set substantially equal to a land width formed between grooves. The recording layer on the grooves and the recording layer on lands are used in recording and reproducing information. Further a light beam is incident on a converging lens of an optical head, the light beam having a larger diameter &ohgr; than an aperture &agr; of the converging lens for converging the light beam on a predetermined position of the magneto-optical recording medium.

Magneto-optical recording method using the relation of beam diameter and an aperture of converging lens

An optical recording medium capable of obtaining a large reproduced signal from the recoded mark, a large reproduced signal of a pre-pit and a large tracking signal both in an area of the grooves and an area of the pre-pits, which provides a sufficient time allowance for switching tracking to that suitable for the area of the grooves or to that suitable for the area of the pre-pits. An optical recording medium comprising a substrate whereon tracks each comprising at least of writable grooves and pre-pits deeper than or equal to the grooves are formed and areas of a relatively shallow pits are each provided between an area of the deep pits and an area of the grooves. The depth Dg of the grooves, the depth Dsp of the shallow pits and the depth Ddp of the deep pits satisfy the following conditions: Dg<&lgr;/(8n), &lgr;/(8n)<Ddp<&lgr;/(4n) and Dg&lE;Dsp<Ddp. Tracking method is switched over in the shallow pit area when recording or reproducing information on the optical recoding medium.

Optical recording medium, media tracking method and recording/reproducing apparatus

Light emitted from a light source is converged by an objective lens, and an auxiliary lens increases an effective numerical aperture to project the light on a recording medium. The temperature of a recording mark recording on the recording medium is increased by the projection of the light, and saturation magnetization which is in accordance with the information is generated, thus generating magnetic flux. There is a reproducing magnetic layer, which is provided on the auxiliary lens. Magnetization generated on the reproducing magnetic layer has an effect on the polarization direction of the reflected light at the reproducing magnetic layer. Reflected light from the reproducing magnetic layer reaches a photodetector to generate a reproduced signal.

Magneto-optical device and recording/reproducing method

A thermomagnetic recording and reproducing head includes a floating slider, and a heating head, a reproduction-use magnetic head as an MR head and a recording-use magnetic head as a thin-film inductive head mounted on the floating slider in this order from an upstream side of a track. The heating section of the heating head is formed by boron nitride or ruthenium oxide, and has a width narrower than the widths of the reproduction-use magnetic head and recording-use magnetic head. Moreover, the recording layer of a disk medium is made from an N-type ferrimagnetic material, the coercive force of the recording layer at a recording temperature and saturation magnetization thereof at a reproduction temperature are adjusted, and the compensation temperature of the recording layer is adjusted to be substantially room temperature. The thermomagnetic recording and reproducing head can realize a narrow track without decreasing the widths of the recording-use magnetic head and reproduction-use magnetic head, thereby increasing the track density.

Thermomagnetic recording and reproducing head having a heating head with a width narrower than the magnetic heads, a recording and reproducing device with such a heating head and methods related thereto

A magneto-optical memory medium according to the present invention comprises a reproducing layer, which has in-plane magnetization at room temperature and perpendicular magnetization when heated to above a predetermined temperature by a reproducing light beam; a recording layer, which is magnetostatically coupled to the reproducing layer; and an in-plane magnetized layer, provided adjacent to the recording layer, which has a Curie temperature at the above-mentioned predetermined temperature. In this medium, at temperatures below the predetermined temperature, signals recorded at high density in the recording layer are masked, and the above-mentioned magnetostatic coupling is suppressed, by magnetic masking by the in-plane magnetized layer. At temperatures above the predetermined temperature, however, within a domain forming part of the in-plane magnetized layer, the recording layer and the reproducing layer are magnetostatically coupled, and a recording bit of the recording layer is copied and expanded to a magnetic domain in the reproducing layer. Accordingly, with this medium, by reproducing from an expanded magnetic domain of the reproducing layer, even information from recording bits recorded at high density can be reproduced with high signal quality.

Growing community of inventors

Kashihara, Japan

Junsaku Nakajima