Abstract: The reference character 5 denotes a supporting shaft holding base, which holds the lower end of a supporting shaft 103 coated with fluororesin with a small frictional coefficient. The reference characters 107a and 107b are tracking magnets bipolar-magnetized in the right and left direction, which are fixed to a fixing base 1 by bonding. The character 108 denotes a mirror for reflecting a light beam 2 incident from the front in the vertical upward direction. The character 6 denotes a lens holder formed of a plastic material, or the like, with light weight and high stiffness, which holds objective lenses 3 and 4 corresponding to a plurality of optical information recording media with different substrate thicknesses and different recording densities at positions eccentrically displaced by almost equal distances from the supporting shaft 103.

Abstract: The second harmonic wave of a solid laser light which is emitted from a second harmonic wave light source is divided into a plurality of laser beams by a diffraction grating. The divided laser beams are converged on a record carrier into a plurality of light spots by an optical head. Magnetic field generating coils for applying magnetic fields to the respective light spots in accordance with the recording signals from a signal line are disposed under the record carrier. Part of the solid laser light is reflected and input to a beam splitter. Since part of the light input to the beam splitter is taken out, a stabilizer controls the output of the solid laser light from the second harmonic wave light source, parallel recording/reproduction using the plurality of light spots which are arranged on the record carrier is enabled and the formation of the plurality of light spots is effectively controlled.

Abstract: An optical recording apparatus which reduces light loss by expanding the laser beam diameters irradiated from a plurality of beam sources, and reducing the expanded beam diameters immediately before focusing the beams onto an information recording/reproducing medium to make the beams circular, thereby minimizing deviation of the laser beam from the optical axis.An optical system for use in recording apparatus with a multi-beam optical head provided with a plurality of laser beam sources in a fixed unit which reduces light loss by minimizing deviation of the laser beam from the optical axis, and also by maintaining the laser power of each laser beam at a predetermined intensity independent of changes in distance between the fixed unit half and the moving unit half of the optical system by detecting intensities of the laser beams focused on a recording medium.

Abstract: An optical recording and reproducing apparatus uses a laser to form one or more spots on an information recording medium preformatted with wobbling guide grooves, and detects tracking error. If the differential push-pull method of detecting tracking error is used, a center spot is flanked by satellite spots distant by an odd multiple of half the repeating period of tile wobble. If the three-beam method is used, the distance is an odd multiple of one-fourth the repeating period of the wobble. If the push-pull method is used, a split photodetector generates a pair of electrical signals. The sum and difference of these signals are filtered, then synchronously detected, and the result is combined with the difference signal to generate a corrected tracking error signal.

Abstract: An optical recording and reproducing apparatus uses a laser to form one or more spots on an information recording medium preformatted with wobbling guide grooves, and detects tracking error. If the differential push-pull method of detecting tracking error is used, a center spot is flanked by satellite spots distant by an odd multiple of half time repeating period of tile wobble. If tile three-beam method is used, the distance is an odd multiple of one-fourth the repeating period of the wobble. If the push-pull method is used, a split photodetector generates a pair of electrical signals. The sum and difference of these signals are filtered, then synchronously detected, and the result is combined with the difference signal to generate a corrected tracking error signal.

Abstract: A multi-beam optical recording-reproducing device is capable of detecting the focusing and tracking errors of respective beams independently of each other by means of a simple optical system. The optical system for independent tracking error detection may include a wedge prism 39 and a four-partitioned photosensor 42, and that for the independent focusing error detection may include a half prism 33 for dividing the beams into reflected and transmitted portions, first and second knife-edges 34 and 19 for the reflected and transmitted beams, respectively, and a first and second two-partitioned photosensors 35 and 20 for receiving the beams via the first and the second knife-edge, respectively (FIG. 7). Alternatively, the optical system for independent focusing error detection may include a single knife-edge plate 61 having two knife-edges, and a four-partitioned photosensor 64 (FIG. 10), or a wedge prism 71 and an eight-partitioned photosensor 74 (FIG. 12).

Abstract: An optical recording apparatus which reduces light loss by expanding the laser beam diameters irradiated from a plurality of beam sources, and reducing the expanded beam diameters immediately before focusing the beams onto an information recording medium to make the beams circular, thereby minimizing deviation of the laser beam from the optical axis. An optical system for use in recording apparatus with a multi-beam optical head provided with a plurality of laser beam sources in a fixed unit which reduces light loss by minimizing deviation of the laser beam from the optical axis, and also by maintaining the laser power of each laser beam at a predetermined intensity independent of changes in distance between the fixed unit half and the moving unit half of the optical system by detecting intensities of the laser beams focused on a recording medium.

Abstract: An optical recording and reproducing apparatus uses a laser to form one or more spots on an information recording medium preformatted with wobbling guide grooves, and detects tracking error. If the differential push-pull method of detecting tracking error is used, a center spot is flanked by satellite spots distant by an odd multiple of half the repeating period of the wobble. If the three-beam method is used, the distance is an odd multiple of one-fourth the repeating period of the wobble. If the push-pull method is used, a split photodetector generates a pair of electrical signals. The sum and difference of these signals are filtered, then synchronously detected, and the result is combined with the difference signal to generate a corrected tracking error signal.

Abstract: An optical recording/reproducing apparatus capable of detecting recording defects on an information recording medium comprises a beam irradiation device for irradiating a first beam, by which information pits are recorded on/reproduced from the information track on the information recording medium, a second beam preceding the first beam and a third beam following the first beam, along the information track; an optical detector having a plurality of light receiving surfaces for individually detecting the reflected light of the first beam, the second beam and the third beam, which have been reflected from the information recording medium; a monitoring device for, in a recording mode, monitoring the condition of the information track prior to and after recording in response to amount-of-light signals which respectively correspond to the reflected light of the second beam and the third beam; and a signal generator for, in a reproducing mode, producing a tracking error signal in response to the amount-of-light sig

Abstract: In a semiconductor laser apparatus driving system, forward or/and backward beams from a plurality of semiconductor laser beam sources are detected, and arithmetic operations are provided for the detection outputs to determine the light outputs of the respective ones of the semiconductor laser beam sources. The use of a condenser lens which has been used in conventional system is eliminated and, as a result, precise positioning of such lens is avoided, and the semiconductor laser apparatus driving system can be mass-produced.

Abstract: An optical information recording and reproducing apparatus which radiates a plurality of beams onto an information recording medium to optically record information on the medium as well as reproduce the information just recorded. The apparatus includes a beam generator for radiating a plurality of beams of the same wavelength; an optical system for radiating the plurality of beams onto the information recording medium in such a manner that spots formed by the beams are arranged in the direction in which the information is being recorded, and for extracting the plurality of beams reflected by the information recording medium; and an optical detector for detecting each of the plurality of beams after they have been extracted by the optical system.