Abstract: An optical pickup including a light source for radiating a light beam, a diffraction element for separating a light beam radiated from the light source into at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a four-segment first light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions arranged on both sides of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, and a calculation unit for generating a first tracking signal based on respective outputs of the first light receiving portion and for generating a second tracking signal based on outputs of the second and third light receiving portions.

Abstract: An optical pickup including a light source for radiating a light beam, a diffraction element for separating a light beam radiated from the light source into at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a four-segment first light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions arranged on both sides of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, and a calculation unit for generating a first tracking signal based on respective outputs of the first light receiving portion and for generating a second tracking signal based on outputs of the second and third light receiving portions.

Abstract: An objective lens, a reproducing apparatus and a reproducing method using a single objective lens for a DVD which can also read a CD without adding any peripheral member can be obtained. In an objective lens which is arranged so that a light beam emitted form a common light source (11) may be focused through a common objective lens (8) on respective signal recorded surfaces (1a), (2a) of a DVD (2) and a CD (1) having light transmitting layers (1c), (2c) of different thicknesses, an area of the objective lens (8) for the DVD (2) in a range of a numerical aperture NA from 0 to 0.3-0.4 from the light axis is worked to form correcting lens surface 8a for correcting the aberration caused when reading the CD (1) through the objective lens for the DVD (2), thereby allowing the CD to be read through the objective lens for the DVD.

Abstract: A disk reproducing apparatus capable of improving the feeding accuracy of a pickup, reducing the cost of a feeding portion of the pickup, and realizing a small-sized skew adjustment mechanism at low cost, wherein the disk producing apparatus comprises: a disk driving unit for rotating a disk; a pickup having a first guide portion provided on one side portion and a guide face provided on the other side portion; a base member having a guide member for receiving the guide face, the guide member having a length shorter than the sliding distance of the pickup in the guiding direction; a driving unit for driving the pickup in the radial direction of the disk; and a signal processing unit for applying a specified processing to a signal reproduced from the pickup. Preferably, the first guide portion comprises: a guide shaft supported on the base; and a guide bearing provided on the one side portion of the pickup in such a manner as to be slidably inserted around the guide shaft.

Abstract: A laser diode applies a laser beam through a grating, a beam splitter, and an objective to a compact disc. A laser beam reflected by the compact disc is applied through the objective and the beam splitter to a photodiode. The objective has a large numerical aperture of 0.6 in order to be able of play back a digital video disc that has a thin substrate and contains information recorded at a high density. To prevent the photodiode from suffering aberrations caused due to the large numerical aperture of the objective, the photodiode has a relatively small photodetector unit having a normalized detector size ranging from 3 .mu.m to 16 .mu.m, for detecting only returning light up to a numerical aperture of 0.3 and not detecting light of greater numerical aperture values.

Abstract: An optical pickup and a reproducing apparatus includes an objective lens having a hologram lens formed over the entire area of one surface thereof. A central portion of the hologram lens and peripheral portions of the hologram lens are formed differently, so that a laser beam diffracted by the central portion of the hologram lens is focused at plane A, and a laser beam diffracted by the peripheral portion is directed outward. As a result of this, the light intensity distribution after light has passed through the objective lens becomes substantially uniform, so that almost no primary ring is produced, thus preventing cross talk caused by reflected light from an adjacent track.

Abstract: The type of optical disc having different track pitch is identified simply. A light emitted from the LED 21 is irradiated through a condenser lens 22 onto an optical disc 1. The incident light is diffracted and reflected by the pit 3. When, if the optical disc 1 is a CD, the first order diffracted light is received by the first light receiver 10, on the other hand, if the optical disc 1 is a DVD having a smaller track pitch Pt, the first order diffracted light is received by the second light receiver 11. Therefore, the type of the optical disc 1 is identified based on a light receiving signal of the first light receiver 10 and the second light receiver 11.

Abstract: An objective lens having at least two regions of different numerical apertures is configured for focusing a light beam through the regions of the different numerical apertures on two different signal recording surfaces of at least two optical discs having light transmitting layers of different thicknesses. Since the objective lens is integrally formed by at least two lens portions, a light beam outgoing from a common light source is focused on signal recording surfaces of at least two optical discs having the light transmitting layers of different thicknesses.

Abstract: There is disclosed a method of playing back information from an optical multilayer disk having a plurality of recording disks stacked on top of each other, by the use of an optical pickup device. In order to switch the focused recording layer from a first one to a second one so that data is read from the second recording layer, the focus balanced condition of the pickup device is switched from a setting providing a focus error characteristic adapted for the first recording layer to a reference setting providing a neutral focus error characteristic. Then, the focal point of the pickup device is moved from the first recording layer. Subsequently, the pickup device is focused onto the second recording layer, and data is read from the second recording layer. Thereafter, the focus balanced condition of the pickup device is switched to a setting adapted to the second recording layer.

Abstract: A disk player has a guide member for guiding an optical pickup carrier along both sides of a double-sided disk. In order to prevent interference between the pickup carrier and the periphery of the disk during turning movement of the pickup carrier around the periphery of the disk from one of the upper and lower sides of the disk to the other side, the guide member is shaped like a horseshoe. The guide member includes upper and lower straight sections for guiding the pickup carrier, respectively, along the upper and lower sides of the disc, and an arched section extending vertically around the periphery of the disk and connecting the outer ends of the upper and lower straight sections. The upper and lower straight sections are not parallel to each other, but rather they are inclined in such a fanlike manner that the outer ends are wider apart.

Abstract: A signal reproducing system for use in an optical disc player comprises a photodetector including at least first and second photodetecting elements which are so disposed that a beam spot is formed on the first and second photodetecting elements by a light beam caused to impinge upon and reflected at an optical record disc and are aligned along a direction of movement of a diffraction pattern appearing in the beam spot in accordance with a record track on the optical record disc, a phase shifter for varying at least a phase of one of first and second output signals obtained respectively based on detection outputs of the first and second photodetecting elements, a switch for causing the first and second output signals selectively to pass through the phase shifter in response to a direction of movement of the record track in relation to the light beam incident upon the optical record disc, and a mixer operative to add one of the first and second output signals derived from the phase shifter to the other of the f

Abstract: In an optical information reproducing apparatus for reproducing an information recorded on a recording surface of a disc-shaped record medium and which includes an optical pick up device mounted on a tiltable optical block and having a laser beam source for generating a laser beam and a photo detector for detecting the reflected beam from the recording surface and for reading the recorded information, a skew error detector mounted on the tiltable optical block for detecting skewing of the record medium and a skew error corrector controlled by the output of the skew error detector for controlling the optical block so that an optical axis of the pick up device is maintained perpendicular to the recording surface; the skew error detector includes diffused light source, a divided photo detector and a lens, the light source and the divided photo detector being arranged symmetrically with respect to an axis parallel with the optical axis of the optical pick up device, the light irradiated from the diffused light so

Abstract: A compact skew or skewness detector conventiently applicable for an optical information reproducing apparatus and so forth. The skew detector includes a light source and at least a pair of photo sensors arranged side-by-side with the light source. A transparent detector housing houses the light source and photo sensors. The detector housing is provided with a deflector section for deflecting the light from the light source in such a manner that an annular or circular image of the light reflected from the surface of the object about which the skewness is to be detected is formed around the light source.

Abstract: A releasable cover locking device associated with a cover of a record player of the type in which a record disk is rotated during a reproduction operation when power is supplied to the record player, includes a locking mechanism having a locking lever biased about a shaft to a locking position to lock the cover into a closed position; a first release mechanism including a release link rotatably mounted on the shaft for biasing the locking lever to an unlocked position, a reciprocable rod connected to the release link and an electromagnetic plunger for actuating the reciprocable rod when power is supplied to the apparatus and when the rotational speed of the record disk falls below a predetermined value wherein the release link biases the locking lever to the unlocked position; and a second release mechanism including an arm rotatably mounted on the shaft for biasing the locking lever to the unlocked position, a stop lever connected to the arm through an operating link, a positioning mechanism for positioning