Abstract: The optical-disk recording and reproducing apparatus is provided with an optical head, a reproduction circuit, a detector circuit, a servo circuit, a recording circuit, and a controller. The controller among them performs such control that information is recorded and reproduced on only either lands or grooves in a region where file management information is recorded and reproduced, while information is recorded and reproduced on both lands and grooves for a plurality of tracks or for every zone in a data region, in the case of a land and groove recording optical disk. In the case of a land or groove recording optical disk, the controller performs such control that information is recorded and reproduced at alternate tracks in a region where file management information is recorded and reproduced, while information is continuously recorded and reproduced in the data region.

Abstract: An optical recording medium which is constructed in a manner such that a plurality of recording areas in which an information signal is recorded along vortical spiral tracks are arranged in a ring shape on a recording surface and a vortex direction of the spiral track of the outside recording area among the plurality of recording areas differs from that of the spiral track of the inside recording area. When the information signal is recorded to the recording medium, the first writing device executes the writing operation from the outer rim side toward the inner rim side of the spiral track of the outside recording area and the second writing device executes the writing operation from the inner rim side toward the outer rim side of the spiral track of the outside recording area.

Abstract: A disc device accommodates a disc rotatably mounted therein, a plurality of first heads movable in a first direction radially of the disc, and a plurality of second heads movable in a second direction radially of the disc and perpendicular to the first direction. The disc has a first surface and a second surface opposite to each other, with an information area defined on at least one of the first and second surfaces. The information area is divided into an outer information region and an inner information region lying radially inwardly of the outer information region. The first heads are allowed to move within a limited distance across the outer information region so as to record or reproduce information on or from the outer information region, while the second heads are allowed to move within a limited distance across the inner information region so as to record or reproduce information on or from the inner information region.

Abstract: An information recording and reproducing apparatus comprises an optical device for causing a light beam to impinge upon a disc having a spiral guide groove along which a control signal is substantially recorded for scanning the spiral guide groove; a light beam modulating portion operative to intensity-modulate the light beam incident upon the disc in response to an information signal so that the information signal is intermittently recorded on the disc and operative further to cause the light beam to keep a relatively small intensity during a period in which the recording of the information signal is temporarily interrupted; a photo-detecting portion for detecting the light beam coming from the disc; a read signal processing portion operative to obtain, based on a detection output from the photo-detecting portion, a read output signal containing a read output of the control signal and a total amount signal corresponding to momentary total light amount of the light beam received by the photo-detecting portion

Abstract: The optical-disk recording and reproducing apparatus is provided with an optical head, a reproduction circuit, a detector circuit, a servo circuit, a recording circuit, and a controller. The controller among them performs such control that information is recorded and reproduced on only either lands or grooves in a region where file management information is recorded and reproduced, while information is recorded and reproduced on both lands and grooves for a plurality of tracks or for every zone in a data region, in the case of a land and groove recording optical disk. In the case of a land or groove recording optical disk, the controller performs such control that information is recorded and reproduced at alternate tracks in a region where file management information is recorded and reproduced, while information is continuously recorded and reproduced in the data region.

Abstract: A track on the disk is divided into plural concentric zones on the radial position thereof. During recording, the angular velocity varies according to the zones accessed for recording, and the disk is driven at a rotational velocity whereby the angular velocity is constant within any single zone but decreases as the radial position of the zone of the accessed track approaches the outside circumference of the disk. During reproducing, the disk is driven at a rotational velocity whereby the angular velocity is constant in all zones. The range of change in the relative linear velocity of the head to the track is thus smaller and the change in the recording conditions is less during recording. During reproducing, there is no delay time required for rotational control of the disk, and the desired track can be more quickly accessed.

Abstract: A receiver/recorder of television transmissions is disclosed which operates automatically on a stand-by basis to record continuously television transmissions from at least one channel onto a reusable large capacity recording medium such as a magnetooptic disk. The recording is accomplished without user intervention and the system includes an indexing for distinguishing a recent recording from an older recording which is partially overlapped by the recent recording.

Abstract: A disk drive stores multimedia data in long spiral data tracks. The tracks on opposite surfaces of the disk spiral in opposite directions, so that a track on one surface can be read as the actuator sweeps in, and a track on the opposite surface can be read as the actuator sweeps out. Because the actuator only follows spiral tracks without performing long seek operations, the actuator motor can be reduced in size and stresses on actuator bearings and other parts are reduced. Additionally, due to reduced disturbances associated with seeks, it is possible to follow tracks more closely and therefore reduce the width of individual tracks. Further cost reductions are accomplished by spinning the disks at a slower speed and reducing the size of the spin motor accordingly. Finally, data density can be increased simply because multimedia data does not require the same low error rate as conventional data. Preferably, a group of disk drives optimized for multimedia data is used to form a video-on-demand system.

Abstract: An optical disc has a recording surface on which a spiral track having a predetermined track pitch is formed. A plurality of information units are formed on the track each of which has a predetermined unit length in a circumferential direction and a radial direction of the optical disc respectively. The information is converted in a shape and a disposed position of an information pit, which is formed in each of the plurality of information units. A method of reproducing the information includes the steps of: irradiating a reading light to form a light spot on the information pit; detecting an outer light portion, which corresponds to an outer circumferential side domain, among a reflective light shaped in a spot from the information pit, which is projected on an imaginary plane including a light receiving surface of a light detecting apparatus to output a light detection signal indicating the detected outer light portion; and reproducing the information on the basis of the light detection signal.

Abstract: An optical recording medium on which information data is to be recorded and on which an n-th recording track is located at a distance from the (n-1)th recording track preceding the n-th recording track in a recording region which is narrower than the diameter of a spot of a light beam radiated on the recording area, with recording data obtained on logical processing with recording data recorded on the (n-1)th recording track being recorded on the n-th recording track for increasing the storage capacity of information data, is disclosed. A return beam of a light beam radiated across two neighboring recording tracks on the optical recording medium is detected by a detector having first and second light receiving sections having a boundary line extending parallel to the recording track of the optical recording medium for reading out the information recorded on the optical recording medium based on the level of a sum or difference signal of the output signals of the first and second light receiving sections.

Abstract: A disc device accommodates a disc rotatably mounted therein, a plurality of first heads movable in a first direction radially of the disc, and a plurality of second heads movable in a second direction radially of the disc and perpendicular to the first direction. The disc has a first surface and a second surface opposite to each other, with an information area defined on at least one of the first and second surfaces. The information area is divided into an outer information region and an inner information region lying radially inwardly of the outer information region. The first heads are allowed to move within a limited distance across the outer information region so as to record or reproduce information on or from the outer information region, while the second heads are allowed to move within a limited distance across the inner information region so as to record or reproduce information on or from the inner information region.

Abstract: An optical scanning device for realizing in a recording layer of an optical tape a longitudinal path (i.e. pattern) of substantially parallel tracks. The device includes an optical system for focusing a radiation beam at the recording layer, which radiation beam causes a scanning spot to develop on the recording layer. The tracks are formed by the optical tape being cyclically scanned, through use of a polygon mirror, via the scanning spot and displaced relative to the optical system in a direction transverse to the scanning direction. The device further includes an optoelectrical measuring unit for deriving a measuring signal indicative of the track pitch of the successively produced tracks. The velocity of the displacement of the optical tape is controlled as a function of the measuring signal.

Abstract: An optical recording medium on which information data is to be recorded and on which an n-th recording track is located at a distance from the (n-1)th recording track preceding the n-th recording track in a recording region which is narrower than the diameter of a spot of a light beam radiated on the recording area, with recording data obtained on logical processing with recording data recorded on the (n-1)th recording track being recorded on the n-th recording track for increasing the storage capacity of information data, is disclosed. A return beam of a light beam radiated across two neighboring recording tracks on the optical recording medium is detected by a detector having first and second light receiving sections having a boundary line extending parallel to the recording track of the optical recording medium for reading out the information recorded on the optical recording medium based on the level of a sum or difference signal of the output signals of the first and second light receiving sections.

Abstract: An optical recording medium on which information data is to be recorded and on which an n-th recording track is located at a distance from the (n-1)th recording track preceding the n-th recording track in a recording region which is narrower than the diameter of a spot of a light beam radiated on the recording area, with recording data obtained on logical processing with recording data recorded on the (n-1)th recording track being recorded on the n-th recording track for increasing the storage capacity of informer, ion data, is disclosed. A return beam of a light beam radiated across two neighboring recording tracks on the optical recording medium is detected by a detector having first and second light receiving sections having a boundary line extending parallel to the recording track of the optical recording medium for reading out the informer, ion recorded on the optical recording medium based on the level of a sum or difference signal of the output signals of the first, and second light receiving sections.

Abstract: On an optical disk, information is recorded on both grooves and lands as guide tracks for guiding a light beam. The width of each groove and that of each land are set substantially equal to each other. A plurality of series of pits representing address information are formed in the grooves so that the series of pits in a groove and the series of pits in the adjacent grooves are located in different radial directions of the optical disk. Address pits are not formed in any of the tracks formed by the lands. When the light beam scans the track on the land, the address information is obtained by crosstalk of the series of address pits formed in the track on the groove. This structure enables the management of the addresses of tracks having thereon no address pits. When obtaining the address information by reproducing the series of address pits on the groove, since no crosstalk occurs, accurate address information is obtained.

Abstract: In a laser power controller, a part of laser beam emitted from a laser diode 1 is detected with a photodetector 2. The operational processor 3 controls a driver 5 so that the light-emitting power of the laser diode 1 has prescribed values, and the driver 5 drives the laser diode 1. The record powers are set beforehand in one or more gap sections existing between record areas, and the operational processor 3 stores the results of the operation in an external memory 4. On recording, the results stored in the external memory 4 are read by the operational processor 3 so as to set the record powers. Thus, the record powers can be set stably even for a fast recording rate.

Abstract: An optical disc includes a signal recording track spirally formed on the surface of the optical disc, information pits formed on the signal recording track, and a plurality of non-signal regions periodically formed on the signal recording track, wherein no information pit is formed on the non-signal region.

Abstract: Disclosed is an optical information recording and/or reproducing system for recording or reproducing information in parallel from a first point towards a second point in which at least (N+1) numbers of track turns are herein provided between the first and second points on a helical track by converging, when N is an integer being two or larger than two, N numbers of light beams respectively at N numbers of track turns adjacent to each other in the radial direction of the helical track on an optical information recording medium and positioning the light beams to form N numbers of beam spots through an optical system. Any portion of the information by N numbers of beam spots is recorded or reproduced from a third point between the first and second points towards the second point. The beam spots are moved from the second point in the radial direction of the helical track so that at least one or more beam spots of N numbers of beam spots come in front of the first point in a scanning direction of the beam spots.

Abstract: A method of optically reproducing information from an optical recording medium on which concave or convex signal pits are formed, is provided with the steps of: irradiating each of pit edge portions of one signal pit which are opposed to each other, with a reading light respectively; detecting a reflection light from each of pit edge portions, separately, to output two detection signals indicating detected positions of the pit edge portions with respect to one signal pit; and reproducing one information recorded in one signal pit on the basis of the two detection signals.

Abstract: An optical recording and reproducing apparatus records two rows of a plurality of pit patterns with respect to one track by modulating two light beams and by converging the modulated two light beams in parallel onto the track. The plurality of pit patterns are detected and judged by a multiple hologram on which reflected object waves of all kinds of pit patterns are recorded, thereby enabling to carry out recording of information. With the arrangement, since multiple values recording and reproducing can be carried out with respect to a magneto-optical disk, the recording capacity becomes greater than the conventional case and the reproduced signal having little crosstalk can be obtained according to the present way of reproducing.

Abstract: A write/read device includes two optical heads for writing data on an optical disk. The two heads are moved simultaneously after data is written in a track, the written data is read and checked for writing errors. This write verify is performed by the two optical heads in parallel, and data can be written on an optical disk at a fast rate.

Abstract: An optical data storage system comprises a multiple data surface medium and optical head. The medium comprises a plurality of substrates separated by a light transmissive medium. Data surfaces are located on the substrate surfaces which lie adjacent a light transmissive medium. The data surfaces are substantially light transmissive. The optical head includes an aberration compensator to allow the head to focus onto the different data surfaces and a filter to screen out unwanted reflected light.

Abstract: A recording medium is provided for use with a device for recording data on and reading data from the recording medium using first and second recording and reading methods. A first recording region of the recording medium stores data recorded using the first method and includes blocks having a first data storage capacity. A second recording region of the recording medium stores data recorded using the second method and includes blocks having a second data storage capacity. The first and second recording regions may be, for example, first and second offset helical grooves formed on the recording medium. A device for recording and reading data on the recording medium using the first and second recording methods in accordance with identification data identifying the methods is also provided.

Abstract: A plurality of tracks are spirally arranged in a group on an optical disc. The tracks in the group are simultaneously radiated by laser beams. Adjacent tracks in the group are disposed at a radial distance d1, and adjacent spots of the laser beams on the tracks are disposed at a radial distance ds which is smaller than the distance d1.

Abstract: An optical head system designed to accomplish an information recording and/or reproduction from opposite disc surfaces of an optical disc with the use of a single light source. The optical head system comprises a source of light for providing a linearly polarized beam of light; a collimator lens for collimating the linearly polarized beam of light into a collimated beam of light; a polarizing direction rotating unit for arbitrarily varying a direction of linear polarization of said beam of light; a polarizing beam splitter for dividing the beam, whose direction of linear polarization has been varied, into first and second beam components; and objective lenses for focusing the first and second beam components into respective penciles of light which are projected onto first and second, opposite disc surfaces of an optical disc or one disc surfaces of respective first and second optical discs.

Abstract: An optical disk includes a recording medium having a disk shape, and a plurality of signal pit strings formed on the recording medium and arranged in a circumferential direction of the optical disk. Each of the signal pit strings includes a plurality of signal pits arranged in a line in a radial direction of the optical disk. An optical pickup apparatus includes a photodetector having a plurality of photoelectric elements. A light spot is sequentially projected onto the signal pit strings, and a reflected light therefrom is converged by an objective lens. An image formed by the objective lens is detected by the photodetector located in an image forming position of the objective lens. The unit information pieces contained in one of the signal pit strings are simultaneously read by the photoelectric elements. In this manner, the signal pit strings are sequentially read while the optical disk is being rotated.

Abstract: An information recording/reproducing method in which a recording area is divided into a plurality of zones in the radial direction of a disk so that the lengths of recording pits become the same in the entire recording area of the disk and the recording/reproduction of information is effected with the number of revolutions of the disk changed in each zone from the inner peripheral zone toward the outer peripheral zone. The method includes the step of effecting the recording or reproduction of the information without changing the number of revolutions if the amount of information to be recorded or reproduced is equal to or smaller than a predetermined amount when seeking is effected from a zone in which a recording/reproducing head is in a standby state to a different zone to effect the recording or reproduction.

Abstract: A recording and reproducing apparatus of an optical recording medium has a plurality of light sources. A plurality of light beams are radiated by a laser diode array to a track of the optical recording medium, and each of the plurality of light beams reflected by the track is detected by a photodiode and converted into an electrical signal. The laser diode array is arranged such that the beam spots of adjacent ones of the plurality of light beams cross a track direction of the optical recording medium and a track width direction perpendicular to the track direction. The signal detected by the photodiode is converted into an electrical signal and recorded in a frame memory as data corresponding to the signal. The digital data stored in the frame memory is read out by a two-dimensional decoder.

Abstract: The present invention concerns an arrangement for reading an optically readable carrier having a substrate with diffractive tracks with respective longitudinal axes and formed of a succession of irregularities with respect to a smooth reference surface. The irregularities have a width of at most two microns and a variable length equal to or greater than their width and these irregularities have closed contours in the reference surface. The closed contours are diffractive along the entire extent in order to provide for a diffraction of light of a particular light spot focused and centered on a single one of the tracks and substantially occupying the width of the single track. Each of the irregularities has a data element stored along the entire length of the contour and successive irregularities along a track are separated by clearance spaces at least as long as the width of the irregularities in the reference surface.

Abstract: An information recording disc having at least two bands of information provided thereon. Each of the bands contain at least one track with one of the at least two bands being a read-only area band or a write area band along the one track of the one band. Another of the at least two bands is a mixed area band having at least one read-only area and at least one write area at different portions along the track of the mixed area band. An information system utilizes the disc for writing and reading information to and from the disc.

Abstract: This invention relates to a crosstalk detecting apparatus for detecting crosstalk which can occur when an image signal FM-modulated and recorded on a recording medium is read. The crosstalk detecting apparatus calculates a valve indicative of the amount of crosstalk originating from an adjacent track based on a signal read by a pickup, utilizing a simple construction. The cross-talk detecting apparatus according to the present invention is adapted to detect crosstalk during a period in which an identification signal recorded on the medium is being read therefrom, and comprises an FM-demodulator for demodulating the signal read from the medium, an AM-demodulator for demodulating the signal read from the medium, a multiplier circuit for multiplying the signal output from the FM-demodulator with the signal output from the AM-demodulator and an averaging circuit for averaging the values output by the multiplier circuit.

Abstract: A disc drive device has a head mounted on a head carriage with a head moving support mechanism which is capable of moving the head to the extent of one track pitch. The device is arranged to advance the head for a plurality of recording tracks on a disc-shaped recording medium at the pitch of two frame-recording tracks. At each moving position of the head carriage, the head is moved from one track position to an adjacent track by the head moving support mechanism.

Abstract: An optical recording medium, typically an optical disc, has a recording region of a laser medium extending thicknesswise thereof, and a reference region positioned radially inwardly of the recording region for emitting reference light. The recording region has pits and lands formed on a surface thereof as representing recorded information. The pits and lands having respective first surfaces parallel to corresponding second surfaces on an opposite surface of the recording region. The first and second surfaces provide different thicknesses of the recording region. When pumping light emitted from a semiconductor laser, for example, is applied to the recording region, the recording region operates as optical resonators between the first and second surfaces for emitting laser signal light of a variable frequency depending on the recorded information. The optical resonators have respective optical axes extending thicknesswise of the recording region.

Abstract: A self-timing optic lathe, comprising a turntable for rotating an object disc, an offset code track carried by the turntable and embodying an encoded control signal, a read laser for optically reading the encoded control signal from the code track, a write laser for optically recording an information signal on the object disc, an optical carriage for moving the write laser and the read laser in a radial direction across the turntable relative to the code track, and a timing and control circuit connected to the write laser and the read laser for reading the control signal and in response controlling rotation of the turntable and operation of the write laser to record the information signal independently of the speed of rotation of the turntable.

Abstract: The beginning of a segment within a track of a record carrier, having a plurality of frames in each segment, is identified by detecting the presence of a control mark at a given position near the beginning of a frame, and the absence of a control mark at an adjoining position at which a control mark will be found in all other frames of the segment. The other frames of each segment are free from a mark at the given position. The next bit position containing a mark, after the given position and its adjoining position, is the clock bit position used for bit clock synchronization. An apparatus for reading these marks may include a qualification circuit for evaluating the magnitude of the difference in detector output at the given bit position and the adjoining bit position.

Abstract: An optical head device for recording and/or reproducing information by using an optical recording medium includes a light source, an objective lens, a photo detector, an optical system including a collimator lens, a beam splitter, a convergent lens and a cylindrical lens, a housing for accommodating the light source, the photo detector and the optical system, and an optical glass plate for reducing aberration of the optical system and the objective lens. A light beam from the light source is turned to a parallel beam flux by the collimator lens to irradiate the objective lens, which provided drivably converges the parallel beam flux on the optical recording medium. The light beam reflected from the optical recording medium passes through the objective lens and reflected by the beam splitter in the optical system toward the photo detector. The light beam reflected by the beam splitter is converged on the photo detector by the convergent lens and the cylindrical lens.

Abstract: An optical scanning system for a compact disc having a sinusoidal data track radially meandering, at a selected frequency, about the axis of rotation of the disc includes a first laser beam for reading data from the data track. A +1 level laser beam and a -1 level laser beam respectively track the opposite edges of the data track and generate a tracking error signal. The +1 level laser beam and the -1 level laser beam are separated, with respect to the disc, by a distance equal to an odd integer multiple of one half the wavelength corresponding to the selected frequency. The +1 and -1 laser beams are not modulated by the sinusoidal data track and standard tracking circuitry can be used to track the data track.

Abstract: An optical disk includes a spiraling guide track embedded in a surface of the disk on either side of which is positioned a different information track. Apparatus for both tracking and reading the disk includes a source providing two light beams directed to the disk surface and spaced apart such as to nominally illuminate respective ones of the information tracks and part of the intermediate guide track. Detectors are positioned to receive reflected light from the disk to both provide signals corresponding to information on the disk and to track the beams relative to the disk so that they are located properly with respect to the location of the information tracks on the disk.

Abstract: A display apparatus for a multidisk player including a memory for storing data of titles and disk kinds for a plurality of disks, and a controller for reading all the stored data and displaying the title and the disk kind of each disk on a display in accordance with the read data. Accordingly, a user can acknowledge the content of each disk at a glance without actually playing the disks. Furthermore, the user can conveniently distinguish an audio disk from a ROM disk and select a desired one of these disks.

Abstract: A method of reproducing optical information by utilizing an optical information recording medium is disclosed, in which a timing mark is formed on each information track in the recording medium; an information mark is formed on each information track with a predetermined cycle at a predetermined distance from the timing mark, which is a starting point of the information mark; comprising the steps of (a) scanning the information track at a specified scanning speed using a light spot; (b) detecting physical changes caused by the timing marks and information marks in the light reflected or transmitted from the optical information recording medium; and (c) reproducing the optical information by determining the presence or absence of an information mark by performing particular calculations as described in the specification.

Abstract: An optical waveguide recording medium has optical waveguides on which minute refractive-index discontinuous portions for generating multiple reflected waveguide lights of different amplitudes and phases can be aligned in accordance with information to be recorded. A recorded-information reproducing apparatus splits a light beam from a light-emitting element into two, guides one of the split beams to the optical waveguides, and causes interference between a signal light reflected after modulation of the amplitude and phase of part of the guided beams and a light acquired by applying a frequency shift to the other beam to obtain an optical heterodyne output, thereby reproducing information recorded as a time-series signal waveform.

Abstract: An apparatus and method for erasing data from optical media in dual beam systems. The erase spot is focused to have a diameter equal to three times the track pitch of the medium. The larger erase spot eases spot alignment requirements since even beam misalignments of half a track width still supply enough energy to the medium to erase the data bump. The larger erase spot heats a larger area more gradually than a single track width erase beam and thereby also enables a more complete erasure of the medium.

Abstract: A track access control method and apparatus for an optical disk apparatus are disclosed. Where a locus of movement of an object lens through which a write beam and a read beam are projected onto an optical disk upon track accessing is offset from a straight line which passes the center of the optical disk, the positional relationship of the read beam and the write beam is controlled relatively in accordance with a track position so that, at any track position, the read beam and the write beam can be positioned on the same track.

Abstract: A known film becomes transparent when heated from a first temperature (for example, room temperature) to a second temperature and non-transparent when heated to a third temperature. These changes are reversible. A film of this type is to be used as a record carrier for optical information. The film (A) is passed continuously or stepwise past an erasing device (L), a cooling device (K), a preheating device (V) and a writing device (S). The film (A) can be made either transparent or non-transparent by heating it to different predetermined temperatures. The information can be recorded on the film in either its transparent form in non-transparent surroundings or in its non-transparent form in transparent surroundings. The device can be used together with the film to obtain a "paperless" office, because the recordings can be erased from the films, which can therefore be constantly re-used.

Abstract: This invention is intended for MCAV-based information processing which records and/or reproduces data. A disc-shaped recording medium having a record area formed in a plurality of concentric tracks is rotated at a constant angular velocity, the record area is partitioned into a plurality of zones depending on the radial position, base clock frequencies are assigned to the zones so that an outer zone has a higher clock frequency than an inner zone, and data is recorded and reproduced in each zone in accordance with the base clock of the assigned frequency. In recording and reproducing data, a VFO signal recorded together with the unit block data of recording and reproduction (sector) is reproduced thereby to produce a VFO clock which is synchronous with the reproduced VFO signal by means of a phase lock circuit (VFO), and, in introducing reproduced data which follows the VFO signal into the reproduced data introduction circuit, synchronization disorder (sync-disorder) of the VFO clock is detected.

Abstract: The present invention concerns an arrangement for reading an optically readable light reflective carrier on which data is stored in form of diffractive elements which are deviations from a reference surface. The data elements each have a plurality of adjacent tracks located on the carrier with data elements being positioned on adjacent tracks. The system utilizes an illumination system for projecting a concentrated light spot onto the carrier along a track wherein the diffraction is such that the light emerging from the diffractive track has a spatial distribution representing an amount of track misregistration between the spot and the axis of the track.

Abstract: The present invention concerns an arrangement for reading an optically readable light reflective carrier on which data is stored in the form of diffractive elements which are deviations from a reference surface. The data elements each have a plurality of adjacent tracks located on the carrier with data elements being positioned on adjacent tracks. The system utilizes an illumination device for projecting a concentrated light spot onto the carrier in order to obtain diffraction of light along the entire length of each of the data elements with an optical arrangement collecting light reflected from a carrier in such a way that the light energy which is received when a projected light spot impinges on the reference surface is greater than the light energy received when the projected light spot impinges on a data element.

Abstract: A recording medium in which one sector is divided into a plurality of segments and information is recorded in the segments, uses a reproducing method in which information is reproduced optically from this medium. The recording medium has an area in which no embossed pit is formed beforehand comprising at least one segment among a plurality of segments, and embossed pits indicative of the head of the sector which is formed in correspondence to the head position of the sector. Clocks are reproduced by detecting the pit for clock reproduction on the basis of the area in the recording medium in which no embossed pit is formed beforehand. The head position of the sector is detected by detecting whether the pit indicative of the head of the sector is present or not at a timing based on the clock. With this method, the head position of the sector can be detected correctly even if information was recorded by a modulating system in which all signal patterns can exist according to the modulating rule.

Abstract: An optical recording apparatus employing a plurality of modulated laser beams as means for recording information on an optical recording medium, comprising a laser beam source which emits a laser beam, a plurality of carrier sources which generate carriers respectively of different frequencies, a plurality of switching circuits respectively connected to the carrier sources to interrupt the carriers intermittently for modulation according to information data signals applied respectively thereto to provide driving signals, an acoustooptic reflector which splits the laser beam into a plurality of discrete laser beam intermittently interrupted respectively according to the driving signals, a focusing lens for focusing the plurality of discrete laser beams on spots on the recording surface of a recording medium, and a polygonal rotating mirror disposed between the acoustooptic deflector and the focusing lens to reflect the plurality of discrete laser beams so as to sweep the recording surface of the recording medi

Abstract: A rotary actuator for an optical head comprises a pair of reflectors mounted respectively on the end of the arm and on the pivot axis to define an optical path via the arm to an optical disk for an external beam directed along the pivot axis. Special arm geometry reduces variable head skew and consequent image rotation. A multiple platter design features optical switches effectively aligned on the pivot axis.