Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: In a system using a pickup including a bifocal lens which is one lens having two focal points, mere judgment by the number of peaks of a focus error signal does not achieve a clear judgment of the type of an optical disc, especially whether it is a CD or a DVD. Therefore, it is required to perform a judgment based on a difference in recording density of the optical disc. According to the present invention, when detecting a tracking error by the phase difference method, a pulse width limit circuit 35 in a tracking error detecting circuit 7 provides such limitations that a pulse of a width larger than a predetermined pulse width should not appear in a pulse train of a phase error signal. Disc type judgment is then performed for discs having different recording densities, for instance, whether it is a CD or a DVD, based on the phase error signal after the pulse width limitation or that before and after the pulse width limitation.

Abstract: A disk-shaped recording medium includes a transparent substrate, and an optical recording layer formed on the transparent substrate. A light source emits light. An optical head is operative for applying the light to the optical recording layer from the light source via the transparent substrate, for focusing the light on the optical recording layer, and for reproducing information from the optical recording layer. A position detecting device is operative for detecting at least one of a pit depth and a physical position of information which has a first given relation with a specified address and which is recorded on the recording medium, and for generating first positional information representing at least one of the pit depth and the physical position. A previously-recorded secret code is reproduced from the recording medium. The secret code represents second positional information. The secret code is decoded into the second positional information.

Abstract: An electrical device, in particular a car radio, allows more user-friendly checking of access authorization is described. The electrical device includes a disc drive for a storage medium, a read device being provided for reading data stored on the storage medium placed in the disc drive. Device-specific data is stored in a memory assigned to the electrical device. Data read from the storage medium is compared with the device-specific data. The electrical device is only rendered operational if the data that has been read matches the device-specific data.

Abstract: An initialization method for a phase change type optical disc, including the steps of irradiating a laser beam of a predetermined power onto a specimen optical disc, increasing the power of the laser beam with constant rate, detecting a reflectivity of the laser beam reflected from the optical disc in accordance with the increasing laser power, detecting a saturated value of the reflectivity of the laser beam, detecting an optimal power of the laser beam where the reflectivity belongs 70% to 90% of the saturated value, and performing initialization by irradiating the laser beam having thus obtained optimal power onto the optical disc to be initialized which will be initialized with the adjusted laser beam can improve the recording characteristic and erase ratio.

Abstract: It is an object of the present invention to obtain a write condition detection index with improved stability for a variation in temperature and with improved detection sensitivity for a write condition so that the index can more appropriately follow a variation in write condition. A write pit reflected light level Sp and a write space reflected light level Ss are detected. On the basis of these detected values Sp and Ss and write power Pw1 with which laser beams from a semiconductor laser element exit an objective of an optical head during a write, an index Rm that is indicative of a write condition for an optical disk is determined using the equation Rm=Sp/Ss/(Pw1)2. Then, on the basis of the write condition detection index Rm, the write power Pw1 is controlled.

Abstract: A optical disk drive determines an optimum radiating power of laser for recording data in accordance with an asymmetry value or amplitude of a read signal. The optical disk drive includes an offset controller for changing a focus offset of laser in a direction of an optical axis to a focal point on an optical disk, a pre-test data recorder for recording pre-test data in a trial write area provided on the optical disk with the laser having a power kept in constant while the focus offset is changed by the offset controller, an offset detector for detecting a focus offset that minimizes an asymmetry value of a read signal of the pre-test data, a power controller for recording an Optimum Power Control (OPC) test data in the trial write area while changing the power of the laser, and an OPC operator for determining an optimum power of the laser in accordance with an asymmetry value of a read signal of the OPC test data.

Abstract: A data recording and/or reproducing method and apparatus. The apparatus may include one or more buffer memories, a recorder, a controller, and/or a reproducing unit. Continuous picture and/or speech data may be stored, recorded, and/or reproduced. The size of a recording unit may be controlled such that it corresponds to the amount of picture and/or speech data recorded by the recorder.

Abstract: It is an object of the invention to provide an integrating configuration of combined electronic equipment having circuit boards and a power supply circuit board which are arranged therein so as to render the combined electronic equipment comprising optical disc recording and reproducing unit and a video cassette recording and reproducing unit, which are disposed in parallel with each other, more compact. A DVD recording and reproducing unit and a video cassette recording and reproducing unit are arranged in parallel with each other on a bottom face frame, wherein the DVD recording and reproducing unit is supported by supporting members so that a height of a DVD insertion portion of the DVD recording and reproducing unit becomes substantially the same as that of a video cassette insertion portion of the video cassette recording and reproducing unit.

Abstract: A method for recognizing at least two types of optical discs, which are associated with multiple different numerical apertures, includes the step of setting the numerical aperture of a focusing mechanism equal to a first one of the multiple different numerical apertures. The focusing mechanism is used to focus a light beam on a data storage layer of a given optical disc. The first numerical aperture is smaller than any of the other numerical apertures. The method further includes the step of recognizing the type of the given optical disc by the first numerical aperture that has been selected in the step of setting the numerical aperture.

Abstract: From an optical disc on which physical address information is recorded in the form of phase modulation of a groove wobble, a wobble signal is optically obtained which is affected by the groove wobble. The wobble signal is phase detected by a phase detector and then fed into a low-pass filter. In a jitter calculator the value of &sgr;/T is calculated from the standard deviation &sgr; of a jitter distribution obtained from the output of the low-pass filter and the period T of a symbol clock for the phase modulation to evaluate the recorded physical address information.

Abstract: There is provided a phase-change type optical recording medium, including: a substrate; a recording layer formed on the substrate, phase condition of the recording layer being changed when a laser beam is radiated thereonto, to thereby record, erase or reproduce data into or from the recording layer; and a reflection layer formed on the recording layer for reflecting a laser beam having been radiated onto the recording layer. The recording layer is formed so that the following equation is established: Rc>Rm>Ra wherein Rc indicates a reflectivity to be obtained when the recording layer is in crystal condition, Ra indicates a reflectivity to be obtained when the recording layer is in amorphous condition, and Rm indicates a reflectivity to be obtained when the recording layer is in mixed condition of molten condition and crystal or amorphous condition.

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 recorded 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: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: A method of optimal power calibration adapted to an optical storage medium such as a rewritable (CD-RW) disk is disclosed. The method takes the advantages of rewritable characteristic defined in the Orange Book to perform a plurality of optimal power calibration (OPC) processes on the power calibration area allocated in inner track and several recording positions on the rewritable disk. The OPC processes write erasable patterns such as the “Sub Q mode 0” pattern define in Orange Book on data written area(s) of the rewritable disk so that these erasable patterns will be overwritten by sequentially recording data. A relation curve, which indicates the relationships between optimal recording powers of a recording position and the distance from the center of the rewritable disk to the recording position, is then established by using the optimal recording powers measured from the aforementioned OPC processes.

Abstract: An optical head reproduces optical disks of different disk plate thickness t1 (0.6 mm) or t2 (1.2 mm) by using light beams of two wavelengths and one object lens. An converging element comprises a central portion and outer portion, wherein the central portion has optimum design plate thickness of 0.6*t1 to t1 and the outer portion has optimum design plate thickness of 0.6 mm. By providing a step difference in the converging element, information can be recorded or reproduced for an information medium of disk plate thickness t1 and for an information medium of disk plate thickness t2, in a state having small side lobes. Alternatively, a step difference is provided in the object lens, and optical distance L2 from a second light source to a condensing optical system is set to 80 to 95% of optical distance L1 from a first light source to the condensing optical system. Alternatively, only light of first wavelength is shielded or diffracted in a ring-like shape.

Abstract: A blank detection circuit and method which detects a blank of a reproduced signal read from a recording medium such as are optical disc and which includes an edge detector which detects edges of the reproduced signal and detects an interval between the detected edges, a maximum value/minimum value detector which detects an amplitude of the reproduced signal in response to the detected edges and provides a maximum value or a minimum value of the detected amplitude, and a determiner which determines whether the reproduced signal is the blank according to the inter-edge interval detected in the edge detector and/or the maximum value or minimum value detected in the maximum value/minimum value detector. Since a blank component of the reproduced signal read from the optical disc is quickly detected, and a blank signal is generated at an accurate point in time, reliability of the entire system is enhanced.

Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: A calibration processing unit executes a calibration when calibration operative conditions are satisfied. Irrespective of satisfaction of the calibration operative conditions during the processing of sequential data, a calibration invalidation unit temporarily invalidates the execution of the calibration and permits the execution thereof after termination of the sequential data processing. Upon the occurrence of an error, an error recovery unit makes a recovery for canceling the error and then a retry, allowing the execution of the calibration when the error recovery is normally terminated. If the sequential data processing is in process at that time, then the execution of the calibration is temporarily invalidated.

Abstract: Methods for maximizing recording efficiency when recording data from a source to an optical media are provided. In one example, a method includes identifying a list of files to be recorded, and then generating a plurality of recording orders for the list of files. A plurality of writing speeds supported by a target optical media recording device are determined, and then each of the plurality of recording orders for the list of files at each of the plurality of writing speeds are evaluated to determine the amount of system cache required and the projected recording time for recording the data. The method selects a single recording order and a single writing speed that minimizes system cache utilization and minimizes actual recording time to record the data from the source to the optical media.

Abstract: A disk-shaped recording medium includes a transplant substrate, and an optical recording layer formed on the transparent substrate. A light source emits light. An optical head is operative for applying the light to the optical recording layer from the light source via the transparent substrate, for focusing the light on the optical recording layer, and for reproducing information from the optical recording layer. A position detecting device is operative for detecting at least one of a pit depth and a physical position of information which has a first given relation with a specified address and which is recorded on the recording medium, and for generating first positional information representing at least one of the pit depth and the physical position. A previously-recorded secret code is reproduced from the recording medium. The secret code represents second positional information. The secret code is decoded into the second positional information.

Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: An apparatus and method to detect the boundary between a recorded region and a recordable region. When data is recorded on fixed length packets, with each packet comprised of a plurality of blocks, the boundary is determined by a block in which a reading error has occured and that is located at a position distant from a track head by an integral multiple of the packet length. Alternatively, when the blocks are identifiable from among a plurality of block types, the boundary is determined by using the block type of the eroneous block.

Abstract: Optimum power control also known as OPC is performed while changing a recording speed and a recording laser power level. Signal recorded through the optimum power control is reproduced for measurement of reproduced signal quality. Recording speed achieving a recording laser power level that can provide reproduced signal quality falling within a predetermined acceptable range is displayed as a recommendable recording speed so that a user can set the displayed speed as a recording speed for use in actual recording.

Abstract: An optical information recording apparatus, an optical information recording method, and an optical information recording medium that enable information signals to be recorded precisely by determining recording conditions such as recording power, edge positions of recording pulses, and the like suitably before recording information signals. An edge test signal generation circuit supplies a test signal for optimizing edge positions of recording pulses. In order to suppress the variation in intervals between edges due to mark distortion caused by overwriting, test recording is carried out using this test signal in a plurality of sectors on the optical information recording medium with a test recording start point being shifted at random in each sector by a recording start point shifting circuit.

Abstract: When a migration is predicted and judged of continuous recording and regeneration to an adjacent next optimum condition effective area in the course of data sequential processing for recording or regenerating data continuous in a certain optimum condition effective area, a setting control unit performs optimum condition setting processing (erase, recording, regeneration) of the next optimum condition effective area under the control of an optimum condition setting processing unit, to thereby previously determine the optimum emission power and the optimum magnetic field.

Abstract: A disc-shaped information recording medium in which the recording density can be increased to secure a large storage capacity and in which there is no risk of an address section being mistakenly detected by cross-talk from a neighboring track, is disclosed. Specifically, an optical disc of a continuous servo system in which tracking is controlled using a pre-groove and in which information is recorded and/or reproduced with constant angular velocity using clocks of a sole frequency, is disclosed. On the disc is formed a spiral track made up of a data portion for recording data and an address section for recording management information for recording/reproducing data. Both a groove and a land are used as a recording/reproducing track. Odd tracks are formed on the land, while even tracks are formed on the groove.

Abstract: An optical information medium is made up of a transparent substrate for a reproducing laser beam to penetrate therethrough, a recording layer formed on the transparent substrate and a reflective layer for reflecting the reproducing laser beam thereupon, thereby enabling the recording of optically readable signals by a recording laser beam incident upon the transparent substrate. This optical information medium has a spiral-like tracking guide on a side surface of the transparent substrate, on which the recording layer is formed, and on lands defined between the spiral-like tracking guide are formed land pre pits indicative of the sector information, including the address and so on, wherein the length of the land pre pits is selected to be from 50% to 83% of the length of the minimum pit and to be from 1.5 to 2.5 times the length of the channel clock.

Abstract: A Fuzzy Inference System (FIS) algorithm capable of discriminating among various disc types including double-layer DVD, single-layer DVD, CD-ROM/CD-Audio, CD-R, and CD-RW is used to identify disc type in an optical drive. This FIS optical disc determination algorithm relies on the physical properties of the reflecting layer of an optical disc, using a DVD and CD photo diode outputs, to discriminate among several disc types. Focus error and quad sum data from both DVD and CD lasers is provided as eight inputs to a nineteen rule Sugeno FIS which outputs a value corresponding to drive type.

Abstract: An information recording apparatus capable of forming a fine mark reliably and highly precisely through compensation for thermal interference and heat accumulation. The information recording apparatus is provided with a recording energy irradiating unit for generating at least two recording waveforms when marks of the same length or spaces of the same length in a channel data sequence are recorded. The information recording apparatus constructed as above can realize highly reliable recording/reproducing operations and can be made compact at a low cost with a large storage capacity.

Abstract: A disc-shaped information recording medium in which the recording density can be increased to secure a large storage capacity and in which there is no risk of an address section being mistakenly detected by cross-talk from a neighboring track, is disclosed. Specifically, an optical disc of a continuous servo system in which tracking is controlled using a pre-groove and in which information is recorded and/or reproduced with constant angular velocity using clocks of a sole frequency, is disclosed. On the disc is formed a spiral track made up of a data portion for recording data and an address section for recording the management information for recording/reproducing the data. Both a groove and a land are used as a recording/reproducing track. Odd tracks are formed on the land, while even tracks are formed on the groove.

Abstract: An information recording apparatus capable of forming a fine mark reliably and highly precisely through compensation for thermal interference and heat accumulation. The information recording apparatus is provided with a recording energy irradiating unit for generating at least two recording waveforms when marks of the same length or spaces of the same length in a channel data sequence are recorded. The information recording apparatus constructed as above can realize highly reliable recording/reproducing operations and can be made compact at a low cost with a large storage capacity.

Abstract: Additional recording data is written continuously with data already recorded on a disk and writing of additional data is started in synch with recorded data. The optical head 1 reads data recorded on the disk just before recording is halted every time the record decision unit 22 judges that recording is to be halted. The record-status detection unit 25 detects the formation status of the recorded data. The head output control unit 14 sets the luminous output of the optical head 1 at the beginning of additional writing according to the recording state judged by the record-state detection unit 25. Thus, the formation status of data recorded on a disk is detected to allow the luminous output of the optical head 1 to be set to an optimum record level.

Abstract: A system and method for encoding servo sector information in a nonvolatile data storage and retrieval system using rotating recording disks. Servo sectors are angularly-spaced approximately radial regions reserved for position reference and tracking adjustment information. Servo timing marks including means for detecting defects on the recording surface, encoded track address and sector address data, and position error signal blocks are permanently fabricated into a number of servo sectors. The present invention helps the storage system controller locate, certify, and follow any particular track and sector while maximizing the amount of disk surface area available for data storage and retrieval.

Abstract: This invention provides a recording apparatus, a recording method, a playback apparatus, a playback method, a recording/playback apparatus, a recording/playback method, a recording medium and a presentation medium. In this invention, information on the album is recorded only into a chief disc, one of the discs composing the album. The other discs simply include an identification of the chief disc. Accordingly it is possible to allow a plurality of recording media to be handled as a unit with ease and to allow each of the recording media to pertain to a plurality of such units.

Abstract: A disc-shaped information recording medium in which the recording density can be increased to secure a large storage capacity and in which there is no risk of an address section being mistakenly detected by cross-talk from a neighboring track, is disclosed. Specifically, an optical disc of a continuous servo system in which tracking is controlled using a pre-groove and in which information is recorded and/or reproduced with constant angular velocity using clocks of a sole frequency, is disclosed. On the disc is formed a spiral track made up of a data portion for recording data and an address section for recording management information for recording/reproducing data. Both a groove and a land are used as a recording/reproducing track. Odd tracks are formed on the land, while even tracks are formed on the groove.

Abstract: An optical information recording apparatus detects an irradiated position by a laser beam, and modulating additional information in accordance with a track address and angular information as the results of the position detecting to record the modulated additional information at a prescribed position on an optical information recording medium.

Abstract: A dye record disc has a disc shape substrate having a track-forming surface divided into a read-only area and a recordable area. A reproducing track is formed on the track-forming surface in the read-only area, and has a plurality of pits, each of the pits comprising a dye material, and having a shape corresponding to the reproducing information. A recording/reproducing track is formed on the track-forming surface in the recordable area, and extends continuously, the recording/reproducing track comprising the same dye material as each of the pits.

Abstract: An optical disk used for writing and reading data in units of an error correction block containing a plurality of sectors by means of a light beam and comprising land and groove tracks arranged adjacent to one another and a plurality of emboss pits formed on a boundary between the land and the groove tracks to detect respective positions of the error correction blocks.

Abstract: A recording medium has first and second areas on which first and second information signals are recorded respectively. The first information signal has a size Ya. The second information signal has a size Yb. A head operates for reproducing the first and second information signals from the first and second areas of the recording medium and transmitting the reproduced first and second information signals on a time sharing basis and at a predetermined constant transfer rate Rp while moving between the first and second areas of the recording medium. A buffer memory operates for receiving the first and second information signals from the head at the predetermined constant transfer rate Rp, for temporarily storing the first and second information signals, and for outputting the first and second information signals at first and second transfer rates Ra and Rb respectively. The first and second transfer rates Ra and Rb are lower than the predetermined constant transfer rate Rp.

Abstract: By reducing the number of seek operations in an operation to play back a signal from a recording medium, the amount of data temporarily stored in a read buffer memory employed in a signal recording/playback apparatus is large enough to be output as a playback signal during a seek operation, allowing a continuous playback operation to be carried out. In order to reduce the number of seek operations, a signal is always recorded onto the recording medium in continuous free areas each having a size equal to or larger than a predetermined recording/playback time length which is typically set at 1 minute. If it is necessary to insert an additional signal having a length smaller than the predetermined recording/playback time length into a point of insertion in an area already occupied by an existing signal, a continuous free area with a size equal to or larger than the predetermined recording/playback time length is newly allocated to the additional signal.

Abstract: Method and arrangement for controlling the data stream in a vibration-resistant playback device. In vibration-resistant playback devices, it is known to write the data to a buffer memory continually at a doubled rate and to read out the said data at a normal data rate. If no vibrations occur, artificial returns must be effected. This leads to an increased power consumption. The present invention enables a reading rate which can be adapted to the averaging of the periods of time when the information medium can and cannot be read. In order to enable processing of the data stream with such a variable reading rate, reading from a memory is switched over between a normal and doubled data rates and the processing stages are likewise correspondingly switched over. As a result, only information data is stored in a downstream buffer memory, so that a lower capacity is sufficient or, with the existing capacity, a longer time span can be bridged during which no data can be read.

Abstract: A disc-shaped information recording medium in which the recording density can be increased to secure a large storage capacity and in which there is no risk of an address section being mistakenly detected by cross-talk from a neighboring track, is disclosed. Specifically, an optical disc of a continuous servo system in which tracking is controlled using a pre-groove and in which information is recorded and/or reproduced with constant angular velocity using clocks of a sole frequency, is disclosed. On the disc is a formed spiral track made up of a data portion for recording data and an address section for recording management information for recording/reproducing data. Both a groove and a land are used as a recording/reproducing track. Odd tracks are formed on the land, while even tracks are formed on the groove.

Abstract: A disk-shaped recording medium includes a transparent substrate, and an optical recording layer formed on the transparent substrate. A light source emits light. An optical head is operative for applying the light to the optical recording layer from the light source via the transparent substrate, for focusing the light on the optical recording layer, and for reproducing information from the optical recording layer. A position detecting device is operative for detecting at least one of a pit depth and a physical position of information which has a first given relation with a specified address and which is recorded on the recording medium, and for generating first positional information representing at least one of the pit depth and the physical position. A previously-recorded secret code is reproduced from the recording medium. The secret code represents second positional information. The secret code is decoded into the second positional information.

Abstract: In recording, onto a disc, data continuously reproduced such as picture data or speech data, etc., minimum continuous recording unit Ba is set. Picture data, etc. is divided into minimum continuous recording units Ba to record such divided data, on real time basis, into space areas existing in a distributed manner on the disc. Ba is expressed as follows: Ba=[Ri×Ro×{(N−1)×Tr+N×Tj}]/(Ri−Ro) Ri: input rate to buffer memory, Ro: output rate from the buffer memory, N: total number of continuous reproduction data simultaneously recorded and reproduced in carrying out reproduction, Tj: maximum seek time of reproduction head, and Tr: minimum read time from the disc.