Abstract: An optical system comprises an objective lens for moving along a recording face of an optical disk in the radial direction of the optical disk so that an optical axis thereof is almost perpendicular to the recording face, a reflecting mirror for moving together with the objective lens and whose reflecting axis extends in the radial direction, a detection optical unit, a movable mirror located to incline with respect to the optical axis extending almost parallel to the recording face from the detection optical unit and the reflecting axis of the reflecting mirror, and a mirror drive portion for rotating the movable mirror on an axis almost parallel to the recording face and shaking a light beam radiated from the objective lens onto the recording face in the radial direction. The mirror drive portion rotates the movable mirror on an axis almost parallel to an optical axis extending from the detection optical unit or on an axis almost parallel to a reflecting face of the movable mirror.

Abstract: The present invention generally relates to optical recording/reproducing apparatus, and relates particularly to a tracking system therefor. Tracking pit rows are provided on opposite sides of an information signal recording area. The frequencies of the tracking pit rows differ from each other, such that tracking servo normalizes a detected difference in amplitude between the reproduced signals of the tracking pit rows, resulting in improved tracking accuracy.

Abstract: Disclosed is a synchronizing signal switching system for synchronizing operations of a plurality of disk devices without stopping the system operation even when a currently used synchronizing signal is stopped or deviated from standard. To this end, each disk device comprises a disk unit and a synchronizing signal switching unit for generating a synchronizing signal to be supplied to the disk unit. One of the disk devices is a current master disk device for currently supplying a master synchronizing signal and another one of the disk devices is a next master disk device. The disk devices are connected in a sequence to form a loop through which the master synchronizing signal is transmitted. The synchronizing signal switching unit in each of the disk devices is provided with an inheritance order to become the current master disk device or the next master disk device.

Abstract: A magneto-optical signal detection device comprising a thin film type optical waveguide unit having a substrate on which a waveguide is formed. The unit has a coupling portion for coupling two polarization components simultaneously in a same plane of the waveguide as a TE mode and a TM mode. The modes TE and TM are included in reflection light reflected from a magneto-optical recording medium and perpendicular to each other. The unit also has a TE-TM mode separating portion having a taper boundary. A waveguide layer is gradually thinned in the taper boundary toward an outer end thereof.

Abstract: In the optical recording element of the invention, alignments of long thin pits inclined in various directions with respect to the track direction are formed on the tracks and information is recorded therein according to the different inclines of the pits, thereby performing higher-density and larger-volume recording without reducing the spacing between each pit and the track pitch. The invention also discloses an optical data retrieval system for use with the above optical recording element, which scans the pit alignments with a laser beam spot, detects the inclines of the pits by obtaining the distribution of the intensity of reflected light which is caused by light diffraction at the pits, and plays back information in accordance with the inclines. Therefore, not only can the substantially same structure as that of a standard type optical data retrieval system be applied to the invention without making any complicated change, but also cross-talk is less likely to be produced in the read out signals.

Abstract: An apparatus for attenuating optical crosstalk induced components of a focus error signal in an optical disk drive of the type having a grooved optical disk with servo tracks and tracking and focus servo systems controlled by a digital signal processor. A calibration operation is performed whenever a new disk is inserted into the track. During the calibration operation, the disk is scanned about a tracking axis at a track crossing frequency greater than the focus servo system bandwidth. The focus error signals produced when the disk is scanned are filtered about a pass band including the track crossing frequency. Crosstalk values equal to values of the filtered focus error signals are determined as a function of corresponding values of the tracking error signals, and are stored in memory. A correction operation is performed while reading and writing data on the disk.

Abstract: An optical disk recorder has a laser driven by a digital analog converter (DAC). During initialization a pair of comparators actuated at minimum and at maximum power levels for actuating a microprocessor to calibrate a DAC 23 between the minimum and maximum power levels rended of digital input changed to the DAC. The same comparators can be used during normal recording and reading operations for detecting under and over power conditions of the laser. Procedures for the calibration and over power and under power detection are described.

Abstract: An optical head which optically records and regenerates data by condensing light beams from a light source on the disk surface, wherein a plurality of piezoelectric elements are arranged to correct the tilt of a condensing lens or the tilt of optical system supporting means for making the optical axis of the condensing lens for condensing light beams on the disk surface or the light beams orthogonal to the disk surface.An optical disk drive provided with an optical head, wherein a plurality of piezoelectric elements are arranged to correct the tilt of the disk for making the optical axis of a condensing lens which condenses light beams on the disk surface orthogonal to the disk surface.

Abstract: An apparatus for selectively recording a baseband signal and a MUSE signal on a magnetic tape and for reproducing them at different speeds including: a magnetic head circuit having first and second groups of heads provided separately form each other. Each of the head groups includes four rotary heads for consecutively and helically scanning the tape to record and reproduce the baseband and MUSE signals.

Abstract: An optical head comprises a fixed optical casing and a movable optical casing accommodating a deflecting mirror and an objective lens which moves separately from the deflecting mirror. Windows are inserted in the boundary between the interior and exterior of an optical path to cover a light-exposed area of an optical system so as to prevent dust from entering into the optical casings. Each window is simple in its construction and makes a slight angle with a plane perpendicular to the optical axis of the optical system so that the windows do not become dusty. Each window can be coated with a conductive thin film which is grounded through a conductive area of each optical casing.

Abstract: The method of determining the last sector containing recorded information or the last recorded sector, of a writer-once and read-many optical disc, comprises dividing tracks of a write-once and read-many optical disc into a plurality of sectors, where each sector has a data part for recording data and a sector ID part in which ID information for identifying the sector is recorded in advance. The ID information of a sector is attached to the data part of the sector and is recorded in the data part of the sector. The ID information reproduced from the data part of the sector is then compared with the ID information reproduced from the sector ID part of the sector, and when the ID information from the ID part and the data part coincide, the sector is determined to be the last recorded sector.