Pioneer Corporation

Pioneer Electronic Corporation

Hoya Corporation

Katsuhiro Koike

Takanori Maeda

Ikuya Kikuchi

Makoto Sato

Masakazu Ogasawara

Takuma Yanagisawa

Koichi Maruyama

Shuichi Takeuchi

Takamasa Yoshikawa

Yoshitsugu Araki

Tetsuya Iida

Yoshiyuki Tsukai

A pickup device includes an irradiation optical system including an object lens for focusing light flux on a track of a recording surface of an optical recording media having a plurality of recording layers stacked while a spacer layer is interposed between the recording layers to form a spot and a detection optical system including an photo detector having a plurality of light receiving parts for receiving returning light reflected from the spot through the object lens to perform photoelectric conversion. The pickup device controls a position of the object leans according to an electrical signal calculated from outputs of the light receiving parts. The pickup device further includes an astigmatic device for providing astigmatism to the returning light directed to the light receiving parts and a division device, having divisional regions divided by a division line extending in an astigmatic direction about an optical axis of the returning light, for dividing the returning light having the astigmatism into a plurality of partial light fluxes divided for the respective divisional regions along the optical axis of returning light. The neighboring divisional regions provide the partial light fluxes with an optical action so that interference between the corresponding partial light fluxes does not occur on the light receiving parts.

Pickup device

An optical element () includes a spherical aberration correction hologram () and a color aberration correction hologram (). For a first laser light requiring the greatest valid diameter, no affect is given to the wave front in either of the aberration correction holograms. However, for a second laser light requiring the second greatest valid diameter, the valid diameter is narrowed down by the spherical aberration correction hologram (). For a third laser light requiring the smallest valid diameter, the valid diameter is narrowed down to a predetermined amount by the diffusion light coming and the spherical aberration correction hologram () and further the valid diameter is narrowed down by the selective diffraction of the light flux incident in the annular area B of the color aberration correction hologram () and its diffusion.

Optical element having aberration correction and optical pickup and optical information recording and/or reproducing apparatus equipped therewith

An optical pickup has a light source for emitting a plurality of laser beams with different wavelengths; and an objective lens for focusing the laser beams emitted from the light source on recording surfaces of plural types of information recording media. A diffractive lens structure is provided in a light path of the laser beam, the structure including ring zone areas divided by a plurality of phase steps for correcting a wavefront aberration of the laser beam, a diameter of an outermost phase step of the diffractive lens structure is smaller than a second largest effective diameter of effective diameters required for reproduction of the plural types of information recording media.

Optical pickup, optical element, and information reproducing apparatus configured for use with any of plural types of recording media

The hologram () for spherical aberration correction is formed in optical element (). With respect to the first laser light which requires the largest effective diameter, the hologram does not have effect on wavefront. With respect to the second laser light which requires the second largest effective diameter, the spherical aberration is corrected by the holograms () which are formed in a concentric and zonal pattern and construct the hologram, and the effective diameter is converged. With respect to the third laser light which requires the smallest effective diameter, only the hologram () has the effect of the correction for the spherical aberration. The hologram () is formed such that its diameter is associated with the effective diameter required by the third laser light, and the effective diameter is converged due to the combination with the incidence of the diffused laser light

Optical element, optical pickup, and optical information recording/reproducing apparatus

An objective lens module includes a light-converging lens that is coaxially disposed with respect to an optical axis of first laser light having a first wavelength, and a transmission-type diffractive optical element that is coaxially disposed to cause diffracted light of first laser light to be incident on the light-converging lens. The diffractive optical element has an incident surface and an emergent surface, and first, second, and third regions that are provided on at least of the incident surface and the emergent surface in the vicinity of the optical axis, and are sequentially defined according to different radius distances from the optical axis to have different diffraction gratings of different diffraction angles, respectively. The first region diffracts odd-order diffracted light of first laser light to the light-converging lens, the second region diffracts even-order diffracted light of first laser light to the light-converging lens, and the third region diffracts even-order or zero-order diffracted light of first laser light to the light-converging lens, such that the light-converging lens converges diffracted light from the first, second, and third regions with a predetermined numerical aperture.

Diffractive optical element, objective lens module, optical pickup, and optical information recording and reproducing apparatus

The present invention relates to an optical multi-layer information recording medium for recording information therein and/or retrieving information therefrom upon radiation of a convergent beam of light. The recording medium includes at least two pairs of recording layer and light-transmissive layer stacked one after another. A first recording layer proximal to a beam radiation side and a second recording layer distal from the beam radiation side are made from a material that satisfies a function including the following parameters; transmissivity and absorptance of the first recording layer, absorptance of the second recording layer, a numerical aperture on the first recording layer, a numerical aperture of the second recording layer, and transmissivity of between the first and second recording layers. Even if the numerical apertures change with spherical aberration compensation made to respective recording layers, a power density of a light spot does not change. Thus, recordation can be performed with consistent recording characteristics.

Optical multi-layer information recordating medium

Provided is an optical recording medium whose surface is not easily injured, particularly an optical recording medium which is not required to be put into a cartridge. The optical recording medium comprises a recording layer, a covering layer comprising a polymer material, and a protective layer which are successively deposited, recording or reproducing wavelength for the medium being 420 nm or less, the numerical aperture of an optical system for the medium being 0.74 or more, and light being radiated to the side of the protective layer to read out data in the recording layer. In the medium, the protective layer has a hardness of 1000 kg/mm or more and a thickness of 4.66 &mgr;m or less.

Optical recording medium

An aspherical objective lens and its manufacturing method are disclosed which allows for forming an optical spot with fewer side lobes on optical discs having a continuous lens plane and substrates different in thickness. The aspherical objective lens is characterized by converging first and second beams of light of first and second wavelengths individually on a first optical disc having a first substrate thickness and on a second optical disc having a second substrate thickness greater than the first substrate thickness at approximately a valid first numerical aperture and a second numerical aperture smaller than the first numerical aperture, respectively. A difference between average values of variations in wavefront aberration corresponding to an inner circumference portion and outer circumference portion, when the first beam of light converges on the first optical disk of the first substrate thickness, is approximately equal to one wavelength of a beam of light of the first wavelength.

Aspherical objective lens for reading information from optical disks of different thickness and manufacturing method therefor

The present invention relates to an optical pickup having a constant numerical aperture even if spherical aberration is compensated for. The optical pickup is used in an information recording and/or reproducing machine. The information recording and/or reproducing machine records and/or reproduces information in a recording medium upon radiation of a light beam from a light source. The optical pickup includes a condensing optical system for condensing the light beam from the light source onto a recording layer of the recording medium. The condensing optical system includes an object lens. The condensing optical system also includes an aperture positioned about a focal length of the object lens apart from a position of a principal incidence plane of the object lens toward the light source along an optical axis of the condensing optical system.

Optical pickup

A lens made of at least one of a resin and glass includes a lens effective diameter area, a peripheral area formed integral with the lens effective diameter area and located at a periphery of the lens effective diameter area, and at least one marker area located in the peripheral area and formed on a circle whose center is a center of the lens effective diameter area.

Lens and production method therefor

An objective lens for condensing a light beam, has at least one of annular grooves and ridges producing a phase difference. Each of the annular groove and ridge is formed concentrically on at least one of an incident surface which said light beam is introduced, and an emission surface which said light beam is emitted.

Objective lens and optical pickup device

An objective lens that allows spherical aberration to be suppressed during the reproduction of a CD without sacrificing reproduction characteristics of a DVD, has a first numerical aperture comprising a refracting surface that is in rotatory symmetry about an optical axis. A part of the refracting surface is displaced along the optical axis as an annular concave (or convex) portion centered on the optical axis. The annular concave (or convex) portion has a certain inner diameter r.sub.1 and a certain outer diameter r.sub.2 that reduce RMS aberration V to a value close to a minimum value. The annular portion has a certain depth (or height).

Objective lens

A bifocal crystal optic lens made of a uniaxial crystal comprising two surfaces having a same axis, at least one of the two surfaces being a spherical surface or an aspherical surface. An optical system for an optical pickup device includes; a crystal optic lens consisting of a first lens body made of a transparent uniaxial crystal and a second lens body made of a transparent optical material selected from a second uniaxial crystal and an optical isotropic material, the first and second lens bodies joining via a spherically or aspherically curved interface; and an objective lens aligned with the crystal optic lens in a same optical axis of an incident ray. This optical system for the optical pickup device is capable of making simultaneously two focal points in the same axis, so as to simplify preferably the structure of the compatible video optical disc player for CD and SD to minimize the size thereof, thereby providing a relatively low cost for the manufacture thereof.

Growing community of inventors

Tsurugashima, Japan

Katsuhiro Koike