Abstract: Disclosed is an optical disk barcode forming method wherein, as information to be barcoded, position information for piracy prevention, which is a form of ID, is coded as a barcode and is recoded by laser trimming on a reflective film in a PCA area of an optical disk. When playing back the thus manufactured optical disk on a reproduction apparatus, the barcode data can be played back using the same optical pickup.

Abstract: An optical disk is provided which includes a rewritable first recording area and a read-only second recording area. The first recording area includes groove tracks and land tracks divided into first sectors. Each first sector has a header region with identification data and a data region for recording user data. The second recording area includes tracks formed with physical bit rows, the tracks being divided into second sectors. Each second sector includes a header region and a data region having read-only data recorded as the bit rows. The header regions in the first sectors include pits the width of groove tracks and wobbled from a center line of the groove track. The header regions in the second sectors include pits having a width smaller than the groove tracks and formed along the center line of a track.

Abstract: According to the present invention, an optical disk recording method for recording data on an optical disk including a land and a groove by forming a mark representing the data on the optical disk by irradiating a light beam onto the optical disk is provided. In this method, conditions for irradiating the light beam are varied depending upon whether a position at which the mark representing the data is formed on the land or on the groove so that a size of the mark formed on the land is equal to a size of the mark formed on the groove.

Abstract: An information recording apparatus for continuously recording information without losing any information even if the apparatus temporarily falls into a recording-disable state owing to the shock externally applied, etc. is provided. A disability detector for detecting the recording-disable state is provided in the information recording apparatus, thereby interrupting the recording operation and the reading operation from the buffer memory under the recording-disable state, and making a coding rate reduction controller instruct a coder to temporarily reduce the coding rate of the input information. A remaining capacity detector is provided for monitoring the remaining capacity in the buffer memory and instructing the coder to temporarily reduce the coding rate of the input information when the remaining capacity becomes a predetermined value or less. As a result, the reduction in the remaining capacity of the buffer memory under the recording-disable state is prevented.

Abstract: A digital information playback apparatus comprises A/D converter that converts a playback signal into digital data, a maximum likelihood decoder that decodes the quantized data output from the A/D converter to obtain the original digital information, and a timing signal extractor that generates a sampling clock used in the A/D converter, and wherein the maximum likelihood decoder detects the response characteristic of the record/playback system and obtains level fluctuations contained in the playback signal, based on the survival path obtained as a maximum likelihood decoding result, to control the expected multilevel equalized values used in the maximum likelihood decoder, the timing signal extractor obtains level fluctuations, based on the survival path obtained as a maximum likelihood decoding result, and obtains the component of the level fluctuations due to phase shifts of the sampling clock of the VCO to control the phase of the sampling clock of the VCO.

Abstract: A method for controlling intensities of a plurality of laser beams respectively emitted on a track of an optical disk by a plurality of laser diodes according to the present invention includes a step of performing focusing servo control for focusing one of the plurality of laser beams emitted by one of the plurality of laser diodes onto the track, and concurrently controlling an intensity of the laser beam emitted by each of plurality of laser diodes to be within a predetermined range by comparing a signal which is in accordance with an intensity of the laser beam emitted by that laser beam with a reference signal. A period during which the one of the plurality of laser diodes used for the focusing does not emit the one laser beam is shorter than a response time of the focus servo control.

Abstract: A first current source applies a first current to an anode of a semiconductor laser, and a second current source either draws a second current from the anode of the semiconductor layer or supplies the second current to the anode of the semiconductor layer. A switched current source connected to the anode of the semiconductor layer selectively draws a third current from the anode of the semiconductor laser. The third current has a value corresponding to a difference between a peak value and a minimum value of a pulse current flow in the semiconductor laser during a recording operation. By drawing the third current from the anode of the semiconductor laser according to recording data, a high speed and high power recording operation can be effected.

Abstract: An optical recording and/or reproducing apparatus is operable to transmit at a high speed a long-play program comprising video and/or audio signals and has a capability of recording the program during a playback mode at a normal reproducing speed of the program. At a transmitter side, a digital data of the program is divided on a time-sharing basis and is then reproduced from an optical disc at a high transfer rate simultaneously with a plurality of channels of optical read/write heads so that, when the digital data is transmitted, the length of time during which the transmission occupies a transmission line can be reduced. On the other hand, at a receiver side, the transmitted signals are recorded on the optical disc at a high transfer rate simultaneously using plural channels of optical read/write heads.

Abstract: An analog-to-digital converter executes analog-to-digital conversion of a first analog video signal at a predetermined sampling frequency "fs". A time base converter converts a time base of an output signal from the analog-to-digital converter at a predetermined time base conversion frequency "ftci". A digital output signal from the time base converter is converted into a corresponding second analog video signal in response to a clock signal of a frequency corresponding to the frequency "ftci". The second analog video signal is converted into an FM video signal recorded on a video region of an optical disk. A binary audio digital signal is converted into a multi-level form digital audio signal. The binary audio digital signal has a data rate corresponding to the frequency "ftci". The multi-level form digital audio signal has a data rate "ftci/n" and 2.sup.n discrete amplitude levels where "n" denotes a predetermined integer.

Abstract: In an optical recording disk having groove-like guide tracks, a rotation index mark is provided to indicate a rotation starting point where the rotation index mark is constructed of a grooved-like phase structure. The rotation index mark may be formed in a track which is located separated from the information recording tracks, and may be detected optically without using a laser light beam. The rotation index mark is used to control the rotation of the disk as well as writing and reading operation of an optical disk recording/reproducing apparatus so that various information, such as video signals, can be accurately recorded and reproduced. In the case of recording digital signals, the guide tracks may be divided into a plurality of sector regions, and sector index marks corresponding to respective sector regions may also be formed together with the rotation index mark. Furthermore, an address index mark indicative of the position of track address region radially formed in the guide tracks may also be added.

Abstract: Herein disclosed is a semiconductor laser control circuit in which: (i) the peak and bottom values of a pulse light can be controlled independently and precisely and set at an optical power value necessary for a high speed; and (ii) the abnormality of the output light of the semiconductor laser can be detected to prevent the stored content of an optical disc, for example, from being broken.

Abstract: An optical recording and reproducing apparatus which records information on the optical disc to reproduce the information from the optical disc. It is necessary to detect the abnormal condition, when the abnormal condition has been caused while the information is recording on the optical disc, to change the optical power level of the laser light source into the non-recording condition so that the abnormal data may not be recorded on the optical disc. The track skipping which is not intended, unnecessary during the recording operation, the condition which is not the record power with the record power level being set, the motor which is rotating the optical disc causes the abnormal rotation, are the abnormal condition during the recording operation.

Abstract: A track skipping detection and control arrangement for an optical recording and reproducing disc formed with guide tracks for use in an optical information recording and reproducing apparatus. According to the track skipping detection and control arrangement of the present invention, any sudden track skipping which may take place during recording can be instantaneously detected by the track traversing signal so as to reduce the recording power for the prevention of erroneous recording to neighboring tracks. Moreover, by distinguishing the track traversing signal detected during the jumping operation for repeated continuous reproduction of the particular one track of the optical disc having spiral tracks, from the traversing signal due to the track skipping, erroneous recording may be similarly prevented also with respect to the optical disc having the tracks in the spiral configuration.

Abstract: A drive circuit for a semiconductor laser in an apparatus for recording/playback of data utilizing an optical recording medium includes circuit elements for establishing recording and playback operating conditions respectively in which output light levels from the laser are set to suitable values for recording and playback, and for controlling the laser output light levels during recording and playback operation at fixed values, and moreover for modulating the laser output light in accordance with a recording signal during recording operation. A changeover control signal which executes changeover between the recording and playback conditions is derived such as to begin in coincidence with the start of a leading pulse of a series of recording signal pulses, and to end immediately following the final recording signal pulse, to thereby avoid excessive laser drive current levels following changeover between playback and recording operating conditions.

Abstract: A semiconductor laser drive circuit functioning as a light source of an optical recording/reproducing apparatus using an optical disk. In the recording mode, the input light of a semiconductor laser is modulated by a recording signal, the output light of the semiconductor laser is detected as a monitor signal by a photo sensitive device, the peak value of this monitor signal is held by a peak-hold circuit, a differential compensation control signal is obtained from the output of the peak-hold circuit and is fed back, and a photo control system to control the output light to a constant level is constituted, thereby controlling in such a way that the output light of the semiconductor laser becomes a certain constant modulation amplitude. Even upon recording, the output light can be stably controlled within a wide temperature range even if the characteristic of the semiconductor laser changes with the elapse of time. Also, this drive circuit can be realized by a simple arrangement.

Abstract: A light beam emitted from a semiconductor laser passes through optical elements which include a condenser lens, a magnifier prism, and a focussing lens to obtain a substantially circular spot of light on a disc. The magnifier prism is constructed such that only the narrower cross-section of the elliptical light beam emitted from the condenser lens is magnified by the incidence surface of the magnifier prism to obtain a substantially circular light beam. The light beam thus obtained is reflected by the prism so that it becomes substantially perpendicular to the beam emitted from the condenser lens. After reflection by the disc, the light passes through a splitter prism. The splitter prism has a reflecting surface and a transmitting surface which spatially bisect the light beam reflected from the disc, a lens and other components. The bisected portions of the beam fall on a photodetector for focussing control and a photodetector for tracking control.

Abstract: An optical recording and reproducing apparatus in which a laser beam is converged to a tiny beam spot and projected onto an optical disc to change thermally the optical disc, thereby effecting recording and reproducing of a signal and which detects a mark (17) for determining a recording polarity of the optical disc which is provided on an optical disc or a disc jacket and effects switching between analog gate switches (23a), (23b) in accordance with the result of the detection thereby to control a polarity of a signal to be recorded or reproduced in a positive or negative direction, whereby it is made possible to stably effect recording and reproduction of signals on optical discs which provide reproduced signals of different polarities because of the characteristics of their recording materials, such as erasable optical discs and unerasable optical discs, by using one and the same recording and reproducing apparatus.

Abstract: An optical and reversible recording and reproducing apparatus providing a practical apparatus in which information signals can be recorded, reproduced and erased by irradiating a laser beam and the like on the substrate to be optically recorded. More practically, there is provided such an apparatus wherein two light sources such as lasers having different wavelengths are used, and a first almost circular micro-lightspot is produced by one light source, while a second elliptic light spot having a longitudinal diameter in the tangential direction of a guide track on a disc is produced by the other light source. These first and second light spots are closely irradiated on one and the same guide track of an optical recording disc. The recording and reproducing of the signals are performed using the first light spot while the erasure of the recorded signals can be made by using the second light spot or using both first and second light spots in combination.

Abstract: An optical recording and reproducing head wherein light beams emitted from two light sources are combined and applied to a recording medium and the light beams reflected from the recording medium are drawn out in such a way that they are separated from each other. The wavelengths of the light beams from both light sources are different from each other, i.e., .lambda..sub.1, .lambda..sub.2, and the light beams from the light sources are combined by means of a polarization beam splitter, two quarter wave plates and optical filters, and are then simultaneously focussed by a single focussing lens substantially along the optical axis thereof, thereby allowing microspots of focussed light to be disposed on a disc close to each other. The light beams reflected from the disc are drawn out so as to be completely separated from each other by the polarization beam splitter owing to the difference in polarization direction.

Abstract: An optical data recording and reproducing apparatus for recording digital data in a recording track on an optical recording disc. The apparatus includes a light illuminating unit for condensing an output light beam from a light source and for illuminating the disc, a recording-reproducing unit for recording and reproducing the digital data by a recording light beam and a reproducing light beam from the light illuminating unit, a dropout detecting and inspecting unit, and a recording-prohibited sector detecting unit to produce an output signal identifying a recording-prohibited sector where recording is prohibited responsive to an output signal from the dropout detecting and inspecting unit. The sector address of a recording-prohibited sector is recorded at least until recording of digital data in the recording track on the optical disc is begun. A comparator unit compares the sector address of the recording-prohibited sector with a sector address read continuously from the disc.