Abstract: Disclosed is an optical disk player capable of suppressing the influence of side lobes of an irradiated spot on the reflected light from an optical disk, thereby ensuring an improved recording/reproducing characteristic. The optical disk player comprises an optical irradiation system for focusing a laser beam as a spot along an information recording portion of an optical disk, and an optical detection system for guiding reflected light from the spot to a photosensor, whereby recorded information is reproduced based on an output signal from the photosensor. The information recording portion is formed of a reflection film whose reflectance increases gradually or stepwise in accordance with an increase in intensity of incident light. The optical irradiation system has an amplitude filter or a phase filter.

Abstract: An optical recording medium in which tracks are constructed by a plurality of combination tracks and-the distance between tracks is narrowed so that data is recorded at a high density, and a playing apparatus for such a medium. The recording medium has a plurality of combination tracks whose track pitch is smaller than a spot diameter of a reading beam of an optical pickup. A track gap which is larger than an optical cut-off wavelength of the optical pickup and is larger than the track pitch is provided for each combination track. The playing apparatus includes a reading which generates beam spots which are equal in number to the tracks constructing the combination track of the recording medium, and a tracking error detecting section for detecting a level difference between two reading signals obtained from tracks at both inner and outer peripheries of the combination track by the reading means, thereby detecting a tracking error.

Abstract: An optical recording medium in which tracks are constructed by a plurality of combination tracks and the distance between tracks is narrowed so that data is recorded at a high density, and a playing apparatus for such a medium. The recording medium has a plurality of combination tracks whose track pitch is smaller than a spot diameter of a reading beam of an optical pickup. A track gap which is larger than an optical cut-off wavelength of the optical pickup and is larger than the track pitch is provided for each combination track. The playing apparatus includes a reading device which generates reading beam spots which are equal in number to the tracks constructing the combination track of the recording medium, and a tracking error detecting section for detecting a level difference between two reading signals obtained from tracks at both inner and outer peripheries of the combination track by the reading means, thereby detecting a tracking error.

Abstract: A disk recording and reproducing apparatus in which the recorded information is read by using a pair of heads alternately. When recording information, the minimum recording time for each group is controlled to be longer than the maximum seek time. When reproducing information, the minimum reading time required for a reading operation is controll to be longer than the maximum seek time, in order that the seek operation will be completed during the reading operation.

Abstract: An optical recording medium, including a substrate and a recording film disposed thereon, wherein an optical shutter layer is disposed in front of the recording film with respect to the direction of an incident reading light beam or recording light beam which is to be supplied to the optical recording medium; and the optical shutter layer comprises, as a main component, a substance having a shutter property such that the substance is in a state where it develops a color thereof until the substance is irradiated with a reading light beam, but when the substance is irradiated with the reading light beam, the substance irradiated with the reading light beam is heated up over a certain temperature so that the substance is decolored and a central portion of the optical shutter layer irradiated with the reading light beam is caused to have a light transmission.

Abstract: A duty factor control circuit for use in an optical disk apparatus has first and second delay circuits for synchronously extending or shortening the width of an input pulse by equal amounts. The operation of the circuit is such that an output pulse center is synchronized with a center of a falling edge of a clock timing pulse, to compensate for time base errors.

Abstract: A disk recording/reproducing apparatus includes a spindle control device in which phase control is performed when spindle motor speed is within a predetermined range, and a synchronizing mark detection signal is detected normally. For a composite video signal, a signal synchronization signal may be produced in response to detection of a synchronizing signal within that composite video sinal; phase control may be performed in response to that signal synchronization signal as well. In the absence of one or more of these signals for less than a predetermined time, phase control may be performed based on predetermined phase-difference information. Additionally, an error may be generated if one or more of the above-mentioned signals is absent for longer than a predetermined time.

Abstract: In a disk recording/reproducing apparatus, phase control of a spindle servo system is made to be smaller than a range of time base control of a time base servo system, so as to obtain spindle servo phase jitter equivalent to that obtained using a horizontal synchronizing signal, which may not be available under all circumstances. Preferably, the range of phase control is no more than 1/10 of the range of variation of a variable delay line used to provide a time base reference signal.

Abstract: A pulse width adjustment circuit for an optical disk recording system selectively adjusts the width of pulses to be recorded in dependence upon an input control signal, which in turn is dependent upon the width of the pulse to be adjusted. In one embodiment a minimum bit length pulse is widened and all other pulses are narrowed. This is useful in recording on the inner portions of a CAV optical disk. In another embodiment a selectable control signal determines whether the minimum bit length signal is to be narrowed or widened.

Abstract: A duty factor control circuit for use in an optical disk apparatus has first and second delay circuits for synchronously extending or shortening the width of an input pulse by equal amounts. The operation of the circuit is such that an output pulse center is synchronized with a center of a falling edge of a clock timing pulse, to compensate for time base errors.

Abstract: In an optical disk recording/reproducing apparatus, a spindle control device in which a vertical synchronizing mark is detected so as to generate a synchronizing mark detection signal. A time base reference signal is generated at the same time, that signal being delayed by a variable delay circuit so as to perform phase control on a spindle motor for rotating the optical disk in accordance with a phase difference of the synchronizing mark detection signal from the delayed time base reference signal. Accordingly, it is easy to adjust, electrically, the relative position on the time base between the vertical synchronizing mark detection timing and a composite video signal to be recorded, by adjusting suitably the amount of delay of the variable delay circuit, without having to adjust the vertical synchronizing mark detector positionally.

Abstract: A clock signal producing circuit for a data storing and reproducing system in which a reference clock signal having a predetermined frequency is generated, a first sync-signal detection signal is generated when the time between two adjacent pulses in the input signal which is measured by the reference clock signal becomes equal to the predetermined reference value, the clock edge pulse is separated from the input signal using the first sync-signal detection signal and then outputted, and a reproducing clock signal having a predetermined frequency coinciding with the generating timing of the separated clock edge pulse is generated.

Abstract: An optical disc with pregrooves arranged circumferentially so as to define a track area, and recording method and apparatus using an optical disc of that type. The disc is characterized by horizontal sync signal formed regions in which the pregrooves are formed in an intermittent manner along a circumference. The recording method and apparatus are characterized by performing a recording operation by irradiating a recording light beam modulated by a video format signal on a track area of an optical disc with pregrooves, generating a sync pulse signal having pulses corresponding to the horizontal sync signal forming area, from an electric signal obtained by a photo-electric conversion of a reflection signal from the optical disc, detecting the phase difference between the sync pulse signal and a horizontal sync pulse signal in the video format signal, and delaying the video format signal in accordance with the magnitude of the phase difference.

Abstract: An optical disc recording and playing apparatus records a video format signal on an optical disc on which an address signal is recorded in the form of prepits, while controlling the rotation of the optical disc on the basis of a phase difference between a synchronizing signal in the video format signal to be recorded and the address signal read-out from the optical disc, and reproduces the recorded video format signal. During the playing operation the apparatus generates a synchronizing signal which is synchronized with the reproduced video format signal and the generated synchronizing signal is outputted in place of the video format signal for the period of sections of the video format signal corresponding to the address signal. With this feature, generation of disturbances in the reproduced picture is surely prevented.

Abstract: A recording-reproducing clock generator circuit generates a reproduced clock having a predetermined frequency from a read out signal including such pulses that the interval between two successive pulses thereof at a predetermined length is to be used as a synchronizing signal region. The circuit generates a reference clock of a predetermined frequency, generates a first sync signal detection signal when the distance between two successive pulses in the input signal measured by means of the clock pulses is equal to a predetermined reference value, separates a clock edge pulse from the input signal by using the first sync signal detection signal, and generates the reproduced clock having the predetermined frequency and synchronized with the separated clock edge pulse.

Abstract: Identification of a tracking servo system type with which a recording disc is to be used. Data is provided to inform a recording/reproducing apparatus that user data is recorded for reproduction by either a sample servo system or a continuous reproduction servo system. Identification data is recorded in a constant angular velocity (CAV) format, in which the data, recorded a plurality of times in a predetermined region of the disc, is located in the same circumferential but a different radial location on the disc. The predetermined region may be in an inner or outer portion of the disc, and has a width greater than the eccentricity of the disc.

Abstract: A clock pulse generating circuit is provided which is capable of generating a stabilized clock pulse without being effected by disturbance due to the vertical equalizer pulse. The clock pulse generating circuit includes a PLL circuit for generating a clock pulse which is phase-synchronized with an input signal. The circuit further includes a synchronizing circuit for generating a window pulse synchronized with the horizontal synchronizing signal by being operated with a clock pulse generated by the PLL circuit as a reference. The synchronization condition is judged with respect to the composite synchronizing signal and a gate circuit which permits passage of the composite synchronizing signal only during the period of existence of the window signal. Accordingly, the signal is constructed so as to select the composite synchronizing signal before passage through the gate in an asynchronous condition of the synchronizing circuit.

Abstract: An optical recording apparatus of the type employing a read/write laser adapts the recording light beam to various linear speeds of the recording disk by jointly controlling both the beam power and the duty ratio of the recording signal in accordance with the radial position of the beam spot on the disk.

Abstract: A tracking error signal generating apparatus for use in a recording and reproducing system employing a disk on which is formed an information track comprising a pair of tracking markers and a time-division servo signal including a sync signal. An error is calculated from any two of the tracking marker data obtained from the disc and a series of error data is generated. Furthermore, a series of corrected error data is generated by respectively inserting at least one neighboring value of adjacent two data between the adjacent two data of the error data, and each of the corrected error data are converted to form an analog signal.

Abstract: A phase-locked loop circuit (PLL) to which a phase-synchronization signal is intermittently supplied, both of the natural angular frequency of the PLL and the damping factor of the same are so determined as to prevent a phase difference produced at the next sampling point from exceeding the linear property range of a phase comparator even when the extraneous electrical disturbance enters the PLL. In addition, when the level of a clock control signal supplied to a variable frequency oscillator which varies the clock signal of the PLL in phase and frequency exceeds a predetermined value, the level of the clock control signal is limited to the predetermined value. As a result, it is possible to prevent the output signal of the phase difference from having any discontinuity.