Abstract: A disk drive unit is disclosed, which comprises a recording medium having more than two disk-shaped recording faces disposed on each other with an interval; information tracks disposed along the periphery on the more than two recording faces and servo signal fields on the recording faces, in the peripheral direction for different recording faces; more than two heads reading out servo information from the servo signal fields on the more than two recording faces; head moving means for moving the heads in the radial direction of the recording faces, linked with each other; means for obtaining position signals on the recording faces at different points of time for different heads on the basis of the servo signals; means for obtaining information on the relative velocity of the heads to the recording faces from the position signals at different points of time for different recording faces, and control means for effecting the velocity control by means of the head moving means on the basis of the information on the

Abstract: A magnetic-disk drive includes: a magnetic disk having a ridge pattern consisting of at least one ridge extending in the circumferential direction; a recording/reproduction head arranged over the surface of the magnetic disk and having a track width larger than the width of the ridge of the pattern and smaller than the pattern pitch; a device for rotating the magnetic disk; and a recording/reproduction circuit.

Abstract: In a method of recording/reproducing information associated with an apparatus and recording medium, the medium has an alternate formation including tracks of first regions wherein at least an optical record of preformatted pits at a constant time interval is recorded and second regions in which information is recorded so that optical retrieval can be achieved. A clock signal is generated based on the readout signal of the preformatted pits to record an information signal in the second regions, and the clock signal is retarded and used to read out data pits that are the record of the information in the second regions.

Abstract: In a light spot position control system and method in which a control of the irradiation position of a light spot such as a focusing control, a jitter correction and/or a tracking control is made through a sampling control, a newly sampled error value is compared with a one-preceding sampled value. When a difference between both the values is within a range of a predetermined width, the newly sampled value is used as a new sample value as it is. When the difference exceeds the range of the predetermined width, a sum of the one-preceding sampled value and the predetermined width is used as a new sample value. Thereby, the influence of erroneous samples is reduced.

Abstract: A tracking servo system includes in addition to a composite servo system composed of a push-pull track deviation detecting loop operative with pregrooves formed in an optical disc and a wobbling track deviation detecting loop operative with intermittently provided wobbled tracking marks, an offset correcting loop for detecting offset component possibly produced due to tilt, deformation and eccentricity of a recording medium or change in optical and mechanical parameters in the course of time lapse to drive forcibly a light spot by applying an electrical offset to cancel out the offset component. In the offset correcting loop, light reflected by wobbled tracking marks provided intermittently or mirror areas formed by interrupting intermittently the pregroove is utilized for detecting the offset component.

Abstract: An optical information recording and reproducing apparatus of a sampling servo system which effects the tracking by holding the differential output of the reproduced signals of tracking pits that are wobbled toward the right and left relative to the track of the optical disk. Reproduced signals of a plurality of pits arranged maintaining a distance on the track and wobbled toward the right or left in a servo signal region, are compared with each other to detect any abnormal condition in the tracking pits. When the abnormal condition is detected, the tracking signal that is sampled is not used, but instead the tracking signal sampled under the normal condition is continuously used to perform the tracking control.

Abstract: A method of beam-track alignment in an optical disk apparatus comprises detecting the velocity v of a beam spot moving in parallel to the surface of an optical disk and traversing a target track in a direction orthogonal with respect to the track, detecting the displacement x given by the distance between the center of the target track and the present position of the beam spot, and starting tracking control (position control) when the detected values of v and x satisfies a predetermined condition.

Abstract: A light spot position control system of the invention uses an optical disc in which a servo area and a data area are alternately formed along a rotating direction of a rotary recording medium, wherein error signals obtained from the servo areas are sampled, the latest sample value is compared with at least one-preceding sample value, a check is made to see if the latest sample value is correct or incorrect, and when the latest sample value is decided to be incorrect, the preceding error signal held is directly used as a light spot position control signal without updating the current error signal holding value.

Abstract: A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation to provide a sector, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in the header field in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted by the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot traversing the wobbled track marks. The push-pull tracking error signal is corrected on the basis of the wobbled tracking error signal to attain the tracking control with higher accuracy, thereby eliminating an undesirable track offset attributable to tilting or eccentricity of the optical disc.

Abstract: In an optical disk, one turn of a recording track is divided into a number of sectors. Each of these sectors is composed of a servo field, which is stored in advance with servo information for tracking, and a data recording area which is to be written with data. A predetermined number of these sectors are joined together to form a plurality of blocks. Each of these blocks is recorded at the data recording areas of its predetermined sectors with identification information for identifying the blocks and phase synchronization loop pull-in information for read out clocks.

Abstract: An optical system for recording and reproducing optical information. A line of synchronization pits for tracking and an information recording area are disposed alternately in advance. At the time of recording, a tracking signal is detected from the line of synchronization pits and while tracking in the information recording area by utilizing this signal, the information signal is recorded in the information recording area. Tracking control in tracking in the information recording area is stabilized by holding the tracking signal which is detected from the synchronization signal and by compensating for an electrical phase delay caused by the holding.

Abstract: A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in each of the header fields in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted from the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot passing the wobbled track marks. After attenuating the gain of the wobbled tracking error signal by a low-pass filter so that the gain of the wobbled tracking error signal becomes equal to that of the push-pull tracking error signal at a frequency fe satisfying the relation1/50.multidot.N.multidot.fd<fe<1/5.multidot.N.multidot.

Abstract: A record carrier has a circular disc-shaped substrate on which a recording layer capable of optically writing information therein is disposed, and is so constructed that a plurality of circumferential reference tracks extending in a rotating direction are provided at radial intervals, the reference track being put into an optically detectable structure so as to function as an optical guide for recording information between the adjacent reference tracks. A first light beam and a second light beam are condensed by an identical objective lens so as to be respectively focused on the recording layer of the record carrier. As one of the reference tracks is being tracked by the first light beam, the second light beam is diffracted by a light diffracter so as to be spaced from the first light beam on the record carrier by desired track pitches in the radial direction thereof.

Abstract: An information recording and reproducing apparatus wherein a light beam is applied onto an optical disk having pits previously formed in optical manner thereon. A tracking signal is detected from the light beam which has been modulated by the pits, and information is recorded by applying a record beam modulated by an information signal onto an area between one pit and the succeeding pit while tracking is effected by using the tracking signal.

Abstract: A device for optically tracking information recorded on an optical disc wherein a photodetector is disposed on the optical axis of an optical system for guiding diffracted waves to the photodetector. The origin of a fictitious X-Y coordinate system at the photodetector is placed on the above-mentioned optical axis, X- and Y-axes of the coordinate system are made parallel to and perpendicular to an information track having the information pits on the rotating recording medium, and the photodetector is divided into four equal parts. A first summation signal indicating the sum of output signals from the four parts of the photodetector is converted into a binary signal, and a difference signal between second summation signals each indicating the sum of output signals from a pair of photodetector parts facing each other with the origin of the coordinate system therebetween is converted into another binary signal.

Abstract: An optical information tracking apparatus for reproducing information by applying light beam onto a track on a rotating record medium, sensing the diffracted light beam thus generated by means of a photodetector and transforming the diffracted light beam into electrical signals, wherein the origin of said photodetector is aligned with the light axis of the optical system, the X axis is placed in parallel with the direction of said track, the Y axis is placed perpendicular to said track. Electrical signals are taken out respectively from photodetector elements which exist respectively in the first, second, third and fourth quadrants. A difference signal representing the difference between a signal which is the sum of the output signal from the first quadrant and that from the third quadrant and a signal which is the sum of the output signal from the second quadrant and that from the fourth quadrant as well as a sum signal representing the sum of output signals from the first to fourth quadrants are calculated.