Abstract: A recording/reproducing apparatus including an optical pickup compatible with a plurality of optical recording media each using light of a different wavelength. The optical pickup includes at least one light source, an objective lens having a function of focusing light emitted from the light source into the optimal light spot on an information recording surface of one of the plurality of the optical recording media, and a light detector to detect light transmitted through the objective lens after being reflected from the information recording surface of the optical recording medium on which the light spot is formed. The objective lens has an inner area, an annular lens area and an outer area such that the annular lens area divides the inner area from the outer area and has a ring shape centered at a vertex. The inner area, the annular lens area and the outer area have aspherical surface shapes.

Abstract: A disk cartridge includes a case which contains a disk, and a shutter which opens/closes at least one opening formed in the case. The shutter is configured to be foldable around upper and lower surfaces of the case, and slides on the upper and lower surfaces of the case to open/close the opening. Since the shutter opens/closes the opening while being folded around the upper and lower surfaces of the case, a movable distance of the shutter for opening/closing the opening can be fully accommodated even though the size of the disk cartridge is reduced. In addition, applying the configuration of the shutter to a double-sided disk cartridge prevents an inflow of dust from entering into the double-sided disk cartridge since the shutter closes an opening, which is not in use, during a recording/reproducing operation.

Abstract: An optical disc includes a substrate having micro-embossments, in which flat portions referred to as lands, and track guides, referred to as hills, and which protrude from the surfaces of the flat portions are formed. A reflective layer is formed on the substrate, a dielectric layer is formed on the reflective layer, a recording layer is formed on the dielectric layer, and a protective layer is formed on the recording layer. Thus, the lands and hills on the substrate of the optical disc enable disc fabrication to more easily facilitate manufacturing of the optical disc. Accordingly, tracks of the disc can be narrowed, to thereby enhance a recording density of the optical disc.

Abstract: An optical disc apparatus and a wobble signal detection method in which a light beam projected onto an optical disc and reflected by the optical disc is divided into at least four light regions in the direction corresponding to the radial direction of the optical disc to detect the light regions, and a wobble signal is detected by performing a subtraction on first and second difference signals, the first difference signal obtained by performing a subtraction on detection signals for the inner light regions of the divided and/or detected light beam and the second difference signal obtained by performing a subtraction on detection signals for the outer light regions of the divided and/or detected light beam.

Abstract: An error signal detection apparatus for an optical recording/reproducing system which detects a tilt error signal and/or tracking error signal, based on the phase characteristics of light reflected and diffracted from a recording medium, and a method therefor. The error signal detection apparatus includes multiple photodetectors and a circuit unit for detecting an error signal by processing detection signals generated by each photodetector The the photodetectors are arranged in a matrix wherein a row or column of the matrix is parallel to a direction corresponding to a direction of an information stream on the recording medium. A circuit unit compares the phases of the detection signals of the inner and/or outer light receiving portions arranged in the same row or of detection signals from diagonal positions on the matrix to output at least one of a tilt error signal and a tracking error signal based on the phase comparison.

Abstract: An optical recording medium having groove tracks and land tracks, first wobbles formed along both sidewalls of each of the groove tracks, second wobbles formed along both sidewalls of each of the land tracks and which are independent of the formation of the first wobble. A middle portion is formed at a predetermined position on each of the sidewalls between adjacent pairs of the land and groove tracks. This optical recording medium can significantly reduce the non-recordable area as compared to conventional optical recording media, resulting in a great improvement in recording density.

Abstract: A method of detecting a reproduction signal from an optical disc. A light beam reflected from a recording surface of an optical disc is divided into a central light beam portion and outer light beam portions in a direction corresponding to a radial direction of the optical disc. The central light beam portion and outer light beam portions are detected and a first detection signal from the central light beam portion and a second detection signal from at least one of the outer light beam portions are output. The amplitude of at least one of the first and second detection signals is adjusted and the reproduction signal is detected by subtraction between the first detection and second detection signals so that where reproduction is carried out on an optical disc having a varying track width the reproduction signal is improved.

Abstract: A land/groove discriminating method and an optical recording and/or reproducing apparatus employing the method are provided. The land/groove discriminating method emits a light beam onto an optical disc having lands and grooves through an optical element capable of causing and varying an effect of thickness variation of the optical disc, detects a light beam reflected/diffracted from the optical disc by dividing the reflected/diffracted light beam into inner and outer light beam portions, and discriminates between a land and a groove of the optical disc by detecting variation in a difference signal between detection signals from the inner and outer light beam portions while varying the degree of the effect of thickness variation of the optical disc by driving the optical element.

Abstract: A method of detecting a servo error, an apparatus therefor, a disk which maintains quantity of a servo error signal, a method of controlling a servo of an apparatus for recording data on and reproducing data from a disk, a method of detecting the tracking error, and a method of detecting tilt error of the apparatus.

Abstract: An optical pick-up apparatus for recording and reproducing information from recording media using a first, second, and third light source to emit light beams having various wavelengths corresponding to a first, second and third recording media, respectively. A dichroic beam splitter has a first, second, and third input surface for receiving the light beams emitted from the first, second and third light sources, respectively, and an output surface through which the light beams received through the input surfaces is transmitted toward the first, second, and third recording media. A converging device converges the light beams transmitted through the output surface of the dichroic beam splitter toward the first, second, and third recording media, and a photodetector receives light beams reflected from the first, second, and third recording media that has been transmitted through the dichroic beam splitter.

Abstract: An optical pickup for a recording medium includes a light beam division and detection unit including receiving portions dividing an incident light beam reflected on the recording medium into a first light beam portion and a second light beam portion around the first light beam portion and converting the first and second light beam portions into first and second detection signals, respectively. A thickness variation detection circuit detects a variation in thickness of the recording medium according to the first and second detection signals and outputs a thickness variation signal indicative thereof.

Abstract: An objective lens device and an optical pickup employing the objective lens device. The objective lens device is formed of three lenses including a lens having a negative power and formed of material having an Abbe number which is 45 or less in line d. At least one surface of surfaces of the three lenses is formed to be aspherical. Thus, in the objective lens device, a high numerical aperture of 0.70 or more is realized and chromatic aberration is corrected with respect to blue light enabling improved recording and/or reproduction using blue light.

Abstract: A high-density focusing objective lens having a high numerical aperture (NA), which can be easily manufactured by an existing technique, and an optical pickup using the objective lens for high-density recording.

Abstract: An optical pickup is provided for a recording medium, including: a light source generating and emitting a light beam; a light beam division and detection unit dividing a particular light beam portion of the light beam after being reflected/diffracted from the recording medium into sub-divided light beams portions, and detecting the sub-divided light beam portions; and a spherical aberration detection circuit processing the sub-divided light beam portions to detect spherical aberration caused by thickness variation of the recording medium.

Abstract: An error signal detection apparatus for an optical recording/reproducing system including a light source emitting a light beam and an objective lens focusing the light beam to form a light spot on a recording medium, the apparatus including: a photodetecting unit dividing at least a part of the light beam passed through the objective lens after being reflected/diffracted from an information stream of the recording medium into light beam portions, and detecting the light beam portions; and a signal processor detecting phase differences between detection signals from the light beam portions to detect a tangential error signal, a defocus error signal, and/or a radial tilt error signal.

Abstract: An optical pickup device includes a light source to emit light, an objective lens to focus the light incident from the light source on a recording medium to form a light spot, an optical path changer disposed on an optical path between the light source and the objective lens to change the path of incident light, a chromatic aberration correction lens disposed on an optical path between the light source and the objective lens, and a photodetector to receive light which is reflected from the recording medium and is then incident thereon through the optical path changer. The chromatic aberration correction lens corrects a chromatic aberration occurring due to a change in the wavelength and/or due to an increase in a wavelength bandwidth of light emitted from the light source. The chromatic aberration correction lens includes at least two lenses such that a lens having a positive power and a lens having a negative power are adjacent to each other.

Abstract: An apparatus for and a method of detecting a defocus error signal. First, second and third light receiving regions of a photodetector are arranged in a radial direction of a recording medium to independently perform photoelectric conversion with respect to incident light which is reflected/diffracted by the recording medium. A subtractor subtracts a sum signal of detection signals from the first and third light receiving regions and a detection signal of the second light receiving region to output a defocus error signal, to detect defocus and/or a change in thickness of the recording medium. The defocus error signal and a push-pull tracking error signal are compared in a state in which a predetermined amount of defocus is applied to a light spot to detect a seek direction of the recording medium having a land/groove structure.

Abstract: An optical pickup in which a light receptor and a light transmitter are integrated with a catadioptric objective lens. The optical pickup includes a unit for emitting laser light to a recording medium and detecting the light reflected from the recording medium. The catadioptric objective lens includes a first reflective area for reflecting the light incident from the unit, a focusing area for focusing the light incident from the unit as a focused spot, and a second reflective area for reflecting the light reflected from the first reflective area toward the focusing area. The first reflective area and the focusing area form a first surface of the catadioptric objective lens while the second reflective area is a part of a second surface of the catadioptric objective lens located in the vicinity of the unit.

Abstract: An optical pickup including a light detection element to divide light reflected from an optical recording medium into first through fourth light beam portions in a radial direction of the optical recording medium. From detection signals from the light detection element, a reproduction signal detection portion detects an information signal, and a tracking error signal detection portion detects a tracking error signal. The light source emits light that is focused as a single light spot on a main track of the optical recording medium. The tracking error signal detection portion gain controls and sums push-pull signals from the detection signals to detect, during a recording operation, a tracking error signal with reduced push-pull offset without erasing existing signals on adjacent tracks. The reproduction signal detection portion sums and gain controls the detection signals to detect an information signal containing reduced crosstalk from adjacent tracks.

Abstract: An optical pickup includes an aberration correction element to correct chromatic aberration caused by variation of power from a light source when changing between operating modes in a recording medium. The aberration correction includes a first retardation member, which includes a stepped convex pattern with a plurality of steps at one side, and a second retardation member combined with the first retardation member. The second retardation member includes a stepped concave pattern with a plurality of steps at one side facing the first retardation member, the stepped concave pattern corresponding to the stepped convex pattern. The first and the second retardation members include different refractive indices for a light beam, which allows the first and the second retardation members to selectively create a phase difference of an incident light beam according to a polarization of the incident light beam.