Abstract: A cartridge case for containing a disk-shaped recording medium has a shutter attached slidably thereon. The shutter is U-shaped sectionally and the edge sections where the shutter contacts the surface of the cartridge case are rounded so that friction therebetween is reduced when the shutter slides on the surface of the cartridge case. The cartridge case is provided with a notch and an indentation on at least one of its side surfaces corresponding to protruding pieces in the device into which the cartridge case is inserted such that a sensor in the device can be activated only when a cartridge case compatible with the device is inserted and these protruding pieces properly engage with the notch and the indentation on the cartridge case.

Abstract: An optical disk recording/reproducing device for recording or reproducing information on or from an optical disk while rotatively driving the optical disk at a constant angular velocity. The disk has pre-recorded information cyclically formed along a track so as to provide rotation control at a constant linear velocity. The device, which includes a clock generating circuit for generating a clock signal for recording or reproducing in accordance with a recording frequency of the pre-recorded information derived from signals reproduced by an optical head, is designed to perform recording or reproducing operations with a recording frequency according to the clock signal. The device further includes a magnetic filed control circuit and a recording light power control circuit whereby a magnetic field and light power to be applied to the optical disk is varied according to the recording frequency during recording operations.

Abstract: The invention provides an improvement of the conventional laser driving circuit mainly including a control logic circuit, a reproducing power producing circuit, and a recording power producing circuit for preventing a recording film of a disk from being damaged by a laser in a reproducing mode. The improved respect is addition of a voltage monitoring circuit and a bypass transistor for an abnormal signal. The voltage monitoring circuit monitors a voltage drop caused in the control logic circuit and supplies a voltage abnormality indicating signal, thereby causing the bypass transistor to be conductive for allowing the abnormal signal to be flown therethrough.

Abstract: A digital signal reproduction apparatus includes a first differential circuit for differentiating a reproduction signal reproduced from a recording medium. This differential circuit outputs a first order differential signal. A second differential circuit differentiates the first order differential signal of the reproduction signal and outputs a second order differential signal. A comparator compares the second order differential signal with a predetermined level to produce a window signal. A peak detecting circuit detects zero-cross points in the first order differential signal and outputs a peak detecting signal. A gate gates the peak detecting signal with the window signal to output a reproduction data signal.

Abstract: A recording/reproducing device performs the recording/reproduction on a recording medium having an information recording area and a table of contents area. The recording medium is provided with guiding grooves that snake in cycles corresponding to values of absolute addresses. The device divides the information recording area into a plurality of domains. Each domain corresponds to a single sampling frequency with respect to the information being recorded. An electromagnet and an optical head record information in the domain that corresponds to its sampling frequency and records additional information concerning the division in the table of contents. A spindle motor drives the disk which is adjusted such that the velocity of the disk is changed for each domain during recording and reproduction. A demodulator obtains the absolute addresses through demodulation by comparing frequencies determined from the snaking cycles of the guiding grooves with a reference frequency.

Abstract: The optical recording/reproducing device of the present invention has an AGC circuit that emits an AGC voltage to be used for controlling the amplification of a reproduced signal in accordance with the amplitude of the reproduced signal, and a controller where permissible ranges for the AGC voltage value is set for recording operation, for erasing operation and for reproduction operation, that, when an optical recording medium is loaded and when one of the recording operation, erasing operation or reproduction operation is instructed, compares the AGC voltage with the permissible range corresponding to the instructed operation and determines whether the AGC voltage is comprised within the permissible range for the instructed operation, and that sets the conditions for the instructed operation for each optical recording medium being loaded in the device.

Abstract: A track access operation system for an optical recording and reproducing apparatus using a medium having a plurality of guide grooves and ID sections utilized for identifying a particular guide groove. The intensity of reflected light and transmitted light from each of a plurality of light beams projected on the recording medium is monitored for determining the location of the beam on the disk. The system is designed such that at least either the plurality of light beams or the plurality of ID sections of the guide grooves are so arranged such that more than half of the light beams or more than half of the ID sections do not overlap in a parallel direction along the guide grooves whereby the number of light beams simultaneously projected on the ID sections is limited to less than half of the total number of light beams projected on the recording medium.

Abstract: An optical memory device has grooves for guiding a light spot and pits for serving as track number indicators. The width W.sub.1 and depth d.sub.1 of the grooves and the width W.sub.2 and depth d.sub.2 of the pits are so selected that 2D(W.sub.1, d.sub.1)=1+D(W.sub.2, d.sub.2) where D(W.sub.1, d.sub.1) and D(W.sub.2, d.sub.2) are respectively the reflectivity of the groove and the pit.

Abstract: An optical disk recording/reproducing device in accordance with the present invention has a controller that, during recording, performs the rotation control of the optical disk in Constant Linear Velocity according to reproduced signals of pre-recorded information that was pre-recorded on the optical disk, during reproduction, performs the rotation control according to reproduced signals of recorded information, and when the rotation control based on the reproduced signals of the recorded information is infeasible, switches the rotation control and performs the rotation control based on the reproduced signals of the pre-recorded information during reproduction also. As a result, a suitable and appropriate CLV control may be executed during recording and during reproduction.

Abstract: A feedback control apparatus in an optical recording and reproducing device for recording, reproducing and/or erasing data from an optical recording medium projects a light beam emitted from an optical head onto the optical recording medium. The apparatus includes an actuator for controlling the illuminating conditions of the light beam projected onto the optical recording medium, a detection unit for detecting the illuminating conditions of the light beam projected onto the optical recording medium, and a control amplifier for driving the actuator in accordance with a detection signal outputted from the detection unit, thereby controlling the illuminating conditions of the light beam projected onto the recording medium.

Abstract: A magneto-optical head wherein a light flux, which is reflected from a recording medium, is separated into its central portion and remaining portion. The central light flux portion is only used as a magneto-optical signal while the remaining light flux portion is only used as an optical servo signal.

Abstract: A recording and reproducing device providing control data recording area on erasable type optical recording medium wherein control data are recorded thereof, characterized in that there is provided a control data recording area forming device for forming control data recording areas having more than two control recording blocks which in turn have more than one recording unit. The control data can be recorded independently. A control data updating device records new control data in the control data recording blocks which were the ones not previously being updated with control data, thereby allowing this device to minimize damage caused by electrical power failure.

Abstract: An apparatus for operating a magneto-optic medium includes a magnetic biasing field developing device for developing a magnetic biasing field which is applied to the magneto-optic medium when the magneto-optic medium erases or records data. Additionally, a neutral-position controller is provided for positioning permanent magnets of the magnetic biasing field developing device in a neutral position with respect to the medium when the magnetic biasing field developing device is switched off. Thereby, the neutral-position controller maintains the medium at the neutral position with respect to the permanent magnets until the magnetic biasing developing device is switched on and the permanent magnets are placed in a field applying position.

Abstract: An apparatus for recording and reproducing information on and from an optical disk includes a first control for producing a first control signal for controlling the rotational speed of a rotational driving apparatus, on the basis of the detected radial position; a judging apparatus which judges whether or not the reproduced signals are reproduced from a recorded region of the optical disk; a second control for producing a second control signal for controlling the rotational speed of the rotational driving apparatus, on the basis of the signals reproduced from the disk; and a switch apparatus which switches the circuit so that the rotational driving apparatus is controlled by the first control signal when the reproduced signals are not reproduced from a non-recorded region, and controlled by the second control signal when the reproduced signals are reproduced from a recorded region.

Abstract: A semiconductor laser driving apparatus for supplying a driving current to a semiconductor laser device of an optical disk recording and reproducing system, the level of which is changed to adjust the optical output of the laser device to one of plural levels corresponding to positions of an optical disk which is irradiated by a laser beam emitted from the laser device.

Abstract: A recording and reproducing apparatus is provided which includes a recording condition control device for controlling recording conditions during recording of a binary-coded original recording signal on a recording medium, a signal recording device for recording the original recording signal onto the recording medium according to recording conditions set by the recording condition control device, a reproducing signal output device for outputting binary-coded reproducing signals by detecting the recording signal as recorded on the recording medium by the signal recording device, and a recording condition setting device for obtaining the recording conditions to provide a reproducing signal approximately equal to the original recording signal through a comparison between the reproducing signal outputted from the reproducing signal output device and the original recording signal.

Abstract: The track counter for optical disk in accordance with the present invention, that counts the number of tracks a light beam passes upon when an optical head moves over an optical disk in the radial direction, comprises a passage signal generating circuit for detecting based on a reflected light of the light beam from the optical disk, that the light beam passed upon a track and for releasing a passage signal on that occasion, a counter that counts the passage signals released by the passage signal generating circuit, a count suspending circuit for forecasting that the light beam will pass upon a specific position of a track and for suspending the count by the aforementioned counter of the passage signals during this forecasted period, and a count value compensating circuit for assuming, when the count of the passage signals is suspended by the count suspending circuit, the number of tracks the light beam passed upon during that period, and for adding this assumed number to the count value of the counter.

Abstract: A disk recording checking method in which recording is performed on a disk having radially different recording tracks each divided circumferentially into a plurality of sectors. The method employs a continuous writing device for continuously writing data onto a predetermined number of the sectors, and a continuous checking device for checking the data, while continuously reading the data from the predetermined number of the sectors. The method utilized checks both the number of errors in each code sequence and the total number of errors in each sector to determine if the data in the sector is valid.

Abstract: A digital signal reproduction apparatus includes a first differential circuit for differentiating a reproduction signal reproduced from a recording medium. This differential circuit outputs a first order differential signal and second differential circuit differentiates the first order differential signal of the reproduction signal and outputs a second order differential signal. A comparator compares the second order differential signal with a predetermined level to produce a window signal. A peak detecting circuit detects zero-cross points in the first order differential signal and outputs a peak detecting signal. A gate gates the peak detecting signal with the window signal to output a reproduction data signal.

Abstract: An optical magnetic memory device includes an optical magnetic recording medium such as a disc having recording magnetic film at least on one side thereof and initialized in a certain direction in advance, a recording section for recording data in such a manner that data-recorded portions and non-recorded portions are alternately formed, and a reproducing section for reproducing data from the recording medium by detecting the interval between the recorded or non-recorded portions. The reproducing section comprises a detector for detecting positive and negative peaks of signals reproduced from the recorded or non-recorded portion and a selector for selecting either of the detection outputs from the detector according to a control signal.