Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.

Abstract: An optical pickup for writing information to and/or for reading information from an optical disc having at least two recording layers (dual layer) provided with first and second recording layers can prevent layer crosstalk resulting from disturbing a signal reproduced from the first recording layer by a reflected light beam reflected from the second recording layer during a writing operation for writing information to the first recording layer or a reading operation for reading information from the fist recording layer. An orthogonal polarization region forming component forms an orthogonal polarization region, in which respective directions of polarization of a first light beam focused on and reflected by a first recording layer of an optical disc and a second light beam reflected by a second recording layer of the optical disc are perpendicular to each other, in a region, in which the first and the second light beam overlap each other, on a light-receiving surface of a detector.

Abstract: An optical pickup module with enhanced aberration correctability is disclosed. This pickup includes more than two different types of laser light sources, an objective lens for collecting and focusing any one of the laser beams leaving the light sources onto an optical disc, and an aberration correction device of the liquid crystal (LC) type, which is disposed between the light sources and the objective lens. The aberration corrector has a surface on which multiple spaced-apart electrodes are patterned for enabling aberration correction relative to incident beams. The corrector controls the potential of a voltage being applied to each electrode in deference to incident beam properties and variations occurrable thereto, e.g., wavelength, effective beam diameter and relative incidence position offsets, thereby to optimally correct beam aberrations, such as coma aberration or wavefront aberration. An optical information reproduction apparatus using the pickup is also disclosed.

Abstract: The present invention provides a photodetector capable of generating highly accurate tracking and focusing error signals free of variations in light quantity caused by interference, in an optical pickup with a two-wavelength multilaser. The photodetector comprises first three light receiving areas arranged linearly to receive three light beams respectively resulting from splitting of a light beam emitted from a laser light source of a first wavelength and second three light receiving areas arranged linearly to receive three light beams respectively resulting from splitting of a light beam emitted from a laser light source of a second wavelength longer than the first wavelength. The distance between both-end light receiving areas out of the first three light receiving areas is longer than the distance between both-end light receiving areas out of the second three light receiving areas.

Abstract: An optical pickup device is provided which reduces variations in amplitude of a tracking error signal in a seek operation due to an installation error of the optical pickup device onto an optical disk apparatus, thereby generating the tracking error signal with high accuracy without any influence from stray lights, and which is high in productivity and low cost. Two sub-light beams are focused on at least one of forward and backward sides in a rotational direction of the disk with respect to a main light beam focused on the disk. When n is an integer number, and t is a distance between guide grooves of the disk, the two sub-light beams focused are spaced apart from each other by a distance of t×(n+0.5) in the radial direction of the optical disk. As splitting means for splitting the light beams into a plurality of beams, a diffraction grating is used which has grid grooves spaced apart at equal intervals, but having different angles at the upper and lower parts of an exiting surface of the light beam.

Abstract: An optical pickup and an optical information recording and reproducing device in which spherical aberration correction control after a disc is loaded can be efficiently made in a short time. Before an information recording medium is loaded into a drive, an optical axis direction position of a concave lens is preset to a state so as to optimize a converging spot on a recording surface of a single-layered medium of as a first recording medium or a predetermined layer (first layer having a substrate thickness of 0.1 mm) of a medium having two or more layers to which the recording/reproduction is executed by a laser light source. After the information recording medium is loaded, if it is determined to be a second (third) recording medium to which the recording/reproduction is executed by a laser light source, setting of the optical axis direction position of the concave lens is changed.

Abstract: 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.

Abstract: A rewritable optical disk apparatus, optical information recording and reproducing apparatus or the like is allowed to automatically and properly adjust the optical system to the optimum focal condition regardless of the readout signal detector's positional error and the residual aberration in the optical system. The spherical aberration and defocus are coarsely adjusted using the amplitude (PP amplitude) of the tracking error signal and then finely adjusted using the amplitude (RF amplitude) of the readout signal. Since the spherical aberration can properly be adjusted, it is possible to raise the reliability of the readout signal.

Abstract: 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.

Abstract: An optical pickup has a semiconductor laser having two laser sources of different wavelengths disposed in the same package, one diffraction grating and one optical detector. A plurality of light reception areas each having four divisional light reception planes of a -character shape are disposed at positions where light beams reflected from an optical disc are applied. A focus error signal is generated by an astigmatism method by using independently these light reception areas and a tracking error signal is generated by a differential phase detection method by using one or both the light reception areas.

Abstract: An optical pickup includes a diffraction grating partitioned into three areas, in which the phase of periodic grating groove structure in an area is successively shifted from that in the adjacent area by 90°. In the generation of a differential push-pull signal, an amplification factor K for sub push-pull signals is varied depending on the type of the optical disk. By such composition of the optical pickup, amplitude deterioration of the tracking error signal accompanying displacement of the object lens is reduced.

Abstract: 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.

Abstract: 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.

Abstract: Since the working distance of an objective lens for a high-density optical disk is short, in the case where an optical pick-up device in which a plurality of lenses including an objective lens for the high-density optical disk are installed in the same lens holder and an optical disk apparatus that uses the optical pick-up device are used to drive an objective lens to be used for the optical disk, there is high possibility that when one of the objective lenses is focus controlled, the other objective lens may collide with the optical disk, which presents a problem. To resolve the problem, in the optical pick-up device in which a plurality of objective lenses including the objective lens for the high-density optical disk are installed in the same lens holder and in an optical disk apparatus that uses it, relative positions of the objective lenses in the said lens holder in an optical-axis direction are set to predetermined positions.

Abstract: An optical pickup has a semiconductor laser having two laser sources of different wavelengths disposed in the same package, one diffraction grating and one optical detector. A plurality of light reception areas each having four divisional light reception planes of a -character shape are disposed at positions where light beams reflected from an optical disc are applied. A focus error signal is generated by an astigmatism method by using independently these light reception areas and a tracking error signal is generated by a differential phase detection method by using one or both the light reception areas.