Abstract: An optical disc device capable of detecting a reference position of an optical disc in a rotating direction includes an optical disc rotation drive unit, an optical sensor, and a control circuit. The optical disc rotation drive unit rotates the optical disc provided with a rotation reference mark. The rotation reference mark is formed into a shape having a width changing in the radial direction of the optical disc. The optical sensor detects the rotation reference mark. The control circuit controls the optical disc rotation drive unit and the optical sensor, extracts a detection signal of the rotation reference mark as a pulse waveform from an output signal of the optical sensor with the optical disc being rotated, and specifies a rotation reference position of the optical disc in accordance with the pulse waveform.

Abstract: An optical storage system includes an optical head configured to split a light beam into a higher power main beam and at least one lower power side beam. The optical storage system also includes a controller configured to alter an optical medium, via modulation of the higher power main beam according to a writing strategy waveform that defines at least n pulses for every n bits of data to be written to the medium, while processing a first signal resulting from the at least one lower power side beam being reflected from the medium and a second signal indicative of the writing strategy waveform to remove noise from the first signal caused by the higher power main beam to generate output indicative of the data directly after writing.

Abstract: Embodiments are provided that include a memory device having a memory array including a plurality of access lines and data lines. The memory device further includes a circuit coupled to the plurality of access lines and configured to provide consecutive pulses to a selected one of the plurality of access lines. Each pulse of the consecutive pulses includes a first voltage and a second voltage. The first voltage is greater in magnitude than the second voltage, and the first voltage is applied for a shorter duration than the second voltage.

Abstract: Various examples are provided for feedback control of power systems. The feedback control can provide simultaneous frequency regulation and economic operation of a power system. In one example, a method includes obtaining a frequency difference associated with a generator of a power system; determining an output power adjustment based at least in part upon the frequency difference and a cost function associated with the generator; and providing a power command to a secondary frequency control of the generator, the power command based upon the output power adjustment. In another example, a generator control system includes a primary frequency controller configured to control frequency droop of a generator of a power system; and a secondary frequency controller configured to adjust output power of the generator based at least in part upon a frequency difference associated with the generator and a cost function associated with the generator.

Abstract: Methods, software, and apparatuses for reading from and/or writing to an optical storage medium. The methods generally include steps for reading a region of an optical storage medium to produce a readback signal, processing predetermined pattern data to produce one or more measurement instructions, measuring one or more characteristics of the readback signal in response to the measurement instructions to produce one or more measurement results, and further processing the readback signal in accordance with one or more of the measurement results. Thus, the ability to flexibly set test parameters and to quickly and accurately test the write characteristics of a recordable or re-writable optical storage medium is provided.

Abstract: An optical disk recording method includes the steps of: providing a multi-pulse chain from a recording wave; independently changing the pulse rise timing and pulse fall timing (pulse width) of the first pulse in the multi-pulse chain in accordance with a preceding space length and a recording mark length; changing the pulse rise timing and pulse fall timing (pulse width) in accordance with a following space length and the recording mark length in a predetermined timing or in independence; and in relation to the smallest mark recorded by irradiation with mono pulse, changing the rise timing in accordance with the preceding space length and the recording mark length and the fall timing (pulse width) in accordance with the following space length and recording mark length, compensating various optical disks different in recording material without change of the fundamental waveform.

Abstract: In an optical recording method, recording parameters (WU) to be used for recording are obtained using recommended recording parameter values (WR) read from an optical recording medium and previously obtained vector information (PC) and approximation coefficients (Ca, Cb) (S24). Writing to the optical recording medium is performed using the obtained recording parameters (S17). The vector information (PC) includes a vector component of the parameters obtained statistically with respect to parameter difference values (DF) between optimal recording parameter values (WO) and the recommended recording parameter values (WR) over a plurality of optical recording media so as to strengthen mutual correlation between the parameters.

Abstract: A recording apparatus characterized in that comprising a firmware configured to execute the following operation: performing a recording operation onto a rewritable optical recording medium with a recording speed selected from one of a plurality of recording speeds for an one-time optical recording medium; wherein the recording layer of the rewritable optical recording medium comprises at least four elements from Ge, In, Sb, Te, and Sn, wherein the component proportion of Sb/Te is ranged from 3 to 8, and the thickness of the recording layer is ranged from 3 nm to 25 nm.

Abstract: A content reproducing method and system for performing seamless playback of contents between devices is provided. The contents reproducing system includes a portable device which, when a short distance communication with a remote control which is configured to control an electronic device occurs during reproducing of contents, generates data required by the electronic device for reproducing the contents that are being reproduced, and which transmits the generated data to the remote control; the remote control which receives the data from the portable device and which transmits the received data to the electronic device, in conjunction with the occurrence of the short distance communication with the portable device; and the electronic device for receiving the contents from a contents provider and reproducing the contents.

Abstract: Method for reading data from an optical disc comprising a substrate layer, a read-only data layer, and a nonlinear layer with a super-resolution structure disposed on the data layer, the read-only data layer including diffractive pits and lands having a length larger than the diffraction limit of the pickup and super-resolution pits and lands having a length smaller than the diffraction limit of the pickup, the method comprising the steps of using a pickup including a laser for providing a HF signal for retrieving of the data of the data layer, providing a constant laser power for retrieving of the data, and pulsing the laser at the end of a diffractive pit or land. The Apparatus comprises a pickup with a laser and a comparator responsive to a threshold level and to the HF signal, for providing a trigger signal for pulsing of the laser.

Abstract: An optical disk recording method includes the steps of: providing a multi-pulse chain from a recording wave; independently changing the pulse rise timing and pulse fall timing (pulse width) of the first pulse in the multi-pulse chain in accordance with a preceding space length and a recording mark length; changing the pulse rise timing and pulse fall timing (pulse width) in accordance with a following space length and the recording mark length in a predetermined timing or in independence; and in relation to the smallest mark recorded by irradiation with mono pulse, changing the rise timing in accordance with the preceding space length and the recording mark length and the fall timing (pulse width) in accordance with the following space length and recording mark length, compensating various optical disks different in recording material without change of the fundamental waveform.

Abstract: An optical information recording medium includes a recording layer in which a track is formed, the track having recording marks linearly arranged thereon. Each recording mark has a dimension corresponding to a reference mark length, which serves as a reference, in a track direction along which the track extends, the dimension being smaller than dimensions of the recording mark in two directions perpendicular to the track direction.

Abstract: Methods, software, and apparatuses for reading from and/or writing to an optical storage medium. The methods generally include steps for reading a region of an optical storage medium to produce a readback signal, processing predetermined pattern data to produce one or more measurement instructions, measuring one or more characteristics of the readback signal in response to the measurement instructions to produce one or more measurement results, and further processing the readback signal in accordance with one or more of the measurement results. Thus, the ability to flexibly set test parameters and to quickly and accurately test the write characteristics of a recordable or re-writable optical storage medium is provided.

Abstract: A recording adjustment method capable of controlling an edge position of a mark with high accuracy. Based on an acquired read-out signal waveform, a starting position of a last pulse is adjusted such that a so-called L-SEAT shift value for an end edge of the mark becomes minimum.

Abstract: In a optical disc system with constraint length equal to or greater than 5, under assumption that continuous 2T count included in a predetermined evaluation bit array is denoted by i and that length of evaluation bit array of interest is given by (5+2i), judgment is passed on whether binary bit arrays include the evaluation bit array. Previously prepared are the error vectors calculated on the basis of target signals corresponding to the evaluation bit arrays and the target signals derived from the binary bit arrays, and the selection of a desired error vector is performed depending on the result of the judgment. At the same time, an equalized error vector is calculated from the target signal derived from the binary bit array and the reproduced signal, and the inner product of the equalized error vector and the selected error vector is calculated.

Abstract: An optical disk recording method includes the steps of: providing a multi-pulse chain from a recording wave; independently changing the pulse rise timing and pulse fall timing (pulse width) of the first pulse in the multi-pulse chain in accordance with a preceding space length and a recording mark length; changing the pulse rise timing and pulse fall timing (pulse width) in accordance with a following space length and the recording mark length in a predetermined timing or in independence; and in relation to the smallest mark recorded by irradiation with mono pulse, changing the rise timing in accordance with the preceding space length and the recording mark length and the fall timing (pulse width) in accordance with the following space length and recording mark length, compensating various optical disks different in recording material without change of the fundamental waveform.

Abstract: A recording wavelength generator selects control parameters of a recording pulse sequence, based on combinations of mark length, a first space length of a first space immediately before the mark, and a second space length of a second space immediately after the mark. A laser drive circuit records the marks by the recording pulse sequence. The first and second space lengths are classified into m and n types, respectively. An absolute value of a difference between two predetermined control parameters from among (m×n) control parameters selected during recording on a second information layer located on an incidence side of the laser beam with respect to a predetermined first information layer from among N information layers is equal to or greater than an absolute value of a difference between two predetermined control parameters from among the (m×n) control parameters selected during recording on the first information layer.

Abstract: A writing method for an optical disk drive includes receiving a command to write a disc; implementing an optimum power control (OPC) test for a predetermined data transfer rate to obtain a relation of a beta parameter to writing power; acquiring a writing power for the predetermined data transfer rate with a target beta parameter; calculating the energy area ratio of writing strategies for every data transfer rate; multiplying the energy area ratio by the writing power for the predetermined data transfer rate to produce the writing power for every data transfer rate; and compensating the writing power with automatic writing control.

Abstract: A signal processing device with dynamic phase detector switching includes a first phase detector of a first type, a second phase detector of a second type, and a mixing device to switch between using output from the first phase detector and output from the second phase detector in real time based on specified changes in an input signal being fed to the signal processing device.

Abstract: A recording apparatus includes a rotation driving portion that rotates and drives an optical disc master; and a recording portion that performs an information recording on the optical disc master, by performing a laser beam irradiation on the optical disc master, based on a recording waveform which has a land pulse of a first power, a recording waveform portion having a recording pulse of a second power higher than the first power, and a cooling pulse which has a third power lower than the first power and is inserted between the land pulse and the recording waveform portion.

Abstract: Provided are an optical disc recording device and a recording signal generating device which enable to correct displacement between a reproducing position of a reproduction signal from a concave-convex mark preformed in an optical disc, and a recording position of second information to be recorded in synchronism with the reproduction signal, and stably and speedily record the second information. A digital signal processor (202) specifies a reproducing position in the concave-convex mark, using a reproduction signal and a channel clock. A recording signal generator (211) generates a recording signal alternately including a plurality of additionally recordable data, each of which includes second information and has a predetermined length, and a plurality of dummy data.

Abstract: According to the present invention, a first error pattern caused by a shift of a bit relating to a recording mark or a space of a shortest length and a second error pattern caused by an edge shift of the recording mark are used. For each of a plurality of error patterns, a pattern shift obtained by normalizing a difference between a square of a Euclidean distance between the error pattern and a reproduction signal and a square of a Euclidean distance between a correct pattern and the reproduction signal, using a square of a Euclidean distance between the correct pattern and the error pattern is detected. Length and phase errors are calculated by a sum of, or a difference between, a first pattern shift amount obtained by normalization performed using the first error pattern and a second pattern shift amount obtained by normalization performed using the second error pattern.

Abstract: An optical disk recording method includes the steps of: providing a multi-pulse chain from a recording wave; independently changing the pulse rise timing and pulse fall timing (pulse width) of the first pulse in the multi-pulse chain in accordance with a preceding space length and a recording mark length; changing the pulse rise timing and pulse fall timing (pulse width) in accordance with a following space length and the recording mark length in a predetermined timing or in independence; and in relation to the smallest mark recorded by irradiation with mono pulse, changing the rise timing in accordance with the preceding space length and the recording mark length and the fall timing (pulse width) in accordance with the following space length and recording mark length, compensating various optical disks different in recording material without change of the fundamental waveform.

Abstract: In a medium of the phase change type, a power ratio and modulation degree for use in recording are determined from a recommended pulse width value in the recommended write strategy parameters recorded in the optical disk, the recommended power ratio value, the recommended recording power value, and the characteristics of the optical recording device, and recording is carried out on the optical disk according to the power ratio value and modulation degree value thus determined. Optimal recording can be carried out even on an optical disk for which the optimal write strategy information has not been determined in advance, without the need to store write strategy information suitable for each and every optical disk.

Abstract: An apparatus configured to write input data on an optical recording medium using a write pulse waveform including a first pulse, a last pulse and a multi-pulse train is provided.

Abstract: An optical recording medium is provided, the optical recording medium including a plurality of zones configured to store data corresponding to an adaptive write pulse, the adaptive write pulse including a first pulse, a last pulse, and a multi-pulse train, the adaptive write pulse being different for each of the plurality of zones, the plurality of zones being reflected by a grouping table, the grouping table being configured to generate an adaptive write pulse waveform by varying a position of a rising edge of a first pulse of a mark to be written according to a length of the mark to be written and a leading space, the adaptive write pulse waveform being generated without regard for a trailing space of a present mark being written using the adaptive write pulse waveform, the adaptive write pulse being configured to correspond to the adaptive write pulse waveform, and store rising edge data of the first pulse of the adaptive write pulse waveform varying according to corresponding stored values of lengths of m

Abstract: An optical recording medium is provided, the optical recording medium including a plurality of zones respectively corresponding to width data of first and/or last pulses of an adaptive write pulse waveform stored in a grouping table, the grouping table being configured to group a magnitude of a present mark of input data and magnitudes of leading and/or trailing spaces of the present mark into a short pulse group, a middle pulse group, and a long pulse group using grouping pointers, store data configured to calculate a width of a write pulse, an adaptive write pulse being generated in response to the calculated width, generate the adaptive write pulse waveform by varying a position of a rising edge of a first pulse of a mark to be written according to the magnitudes of the present mark and the leading space, the adaptive write pulse waveform being generated without regard for the trailing space of the present mark being written using the adaptive write pulse waveform, the adaptive write pulse being configured

Abstract: An apparatus configured to write input data on an optical recording medium using a write pulse waveform, the write pulse waveform including a first pulse, a last pulse and a multi-pulse train, is provided.

Abstract: Provided are a variable delay circuit, a recording apparatus, and a delay amount calibration method. The variable delay circuit includes a delay line in which a delay amount is variably set, a delay setting unit that performs delay setting of the delay line using a unit delay control value, in a calibration period, overlaps a test pulse with the input signal, and generates a comparison pulse, and a unit delay determining unit that sets the delay of the unit delay amount in the delay line by providing the unit delay control value to the delay setting unit in the calibration period, determines the unit delay control value equivalent to the unit delay amount based on a phase comparison result between the comparison pulse and the test pulse, and provides, to the delay setting unit, the determined unit delay control value as the unit delay control value of a calibration result.

Abstract: There is provided an optical recording method for directing a recording pulse train to an optical disc medium to form marks thereon and for recording information as information about the edge positions of said marks and the spaces between marks, the recording pulse train having been created by modulating laser light into plural power levels. The method includes: coding to-be-recorded data into coded data consisting of the combination of marks and spaces; classifying said marks within said coded data on the basis of the mark length and the preceding or succeeding space lengths of the marks; shifting the position of the second pulse edge counted from the end portion of the recording pulse train for forming said marks, depending on the result of said classification, to adjust said recording pulse train; and directing said recording pulse train to the optical disc medium to form said marks thereon.

Abstract: A recording and reproducing apparatus includes: an optical head unit irradiating a laser beam on an optical recording medium and performing writing and readout of information represented by marks and spaces on the medium; a laser-driving-pulse generating unit generating and supplying a laser driving pulse to the head unit, and causing the head unit to execute laser beam irradiation; an evaluation-value measuring unit measuring an evaluation value representing an error of an edge position of the mark; and a control and calculating unit causing the apparatus to separately execute, concerning mark lengths to be adjusted among mark lengths of the laser driving pulse, for each set of mark lengths grouped in advance, trial writing with shift amounts of edge positions of a laser driving pulse concerning the lengths belonging to the set changed, causing the apparatus to execute readout of a signal recorded by the execution of the trial writing, causing the measuring unit to measure an evaluation value under setting o

Abstract: An information recording medium according to the present invention includes a track on which a data sequence including a plurality of recording marks and a plurality of spaces provided between the plurality of recording marks is recordable; and a recording condition recording area in which a recording condition for recording the data sequence on the track is recordable.

Abstract: The invention relates to write strategy modification, and in particular, to dynamic write strategy modification. A dynamic write strategy modification apparatus comprises a measurement module, a write strategy development module, and a write laser module. The measurement module measures a plurality of different parameters. The write strategy development module calculates or chooses an optimal parameter from the plurality of different parameters and modifies a default strategy to generate a modified write strategy. The write laser module drives to write data onto an optical disc. A write strategy modification will be repeated until writing is finished.

Abstract: An optical disc device and an adjusting method for a recording condition for use with the optical disc device that records data into an optical disc medium by using codes whose shortest run length is 2T and reproduces the recorded data by using an adaptive equalizing procedure and a PRML procedure, wherein the recording condition is so adjusted that a reproduced signal with desired quality can be obtained, by using, as the adaptive equalizing procedure, a procedure in which a tap coefficient Cn is set to a value obtained by averaging values of a tap coefficient an renewed by a LMS method, located symmetrically with each other along the time axis.

Abstract: A reproduction signal evaluation method according to the present invention relates to adjustment of an edge portion between a shortest mark and a shortest space in a data sequence including marks and spaces in combination that is recordable on an information recording medium. In a pattern including a shortest mark and a shortest space adjacent before or after the shortest mark, a shift amount of an edge of the shortest mark is obtained from a differential metric calculated regarding one of a first pattern in which a space adjacent to the shortest mark and not adjacent to the shortest space is longer than the shortest space; and a second pattern in which a mark adjacent to the shortest space and not adjacent to the shortest mark is longer than the shortest mark.

Abstract: There is provided an optical recording method for directing a recording pulse train to an optical disc medium to form marks thereon and for recording information as information about the edge positions of said marks and the spaces between marks, the recording pulse train having been created by modulating laser light into plural power levels. The method includes: coding to-be-recorded data into coded data consisting of the combination of marks and spaces; classifying said marks within said coded data on the basis of the mark length and the preceding or succeeding space lengths of the marks; shifting the position of the second pulse edge counted from the end portion of the recording pulse train for forming said marks, depending on the result of said classification, to adjust said recording pulse train; and directing said recording pulse train to the optical disc medium to form said marks thereon.

Abstract: The present invention provides a measure for getting read/write control information stored within a space of a predetermined size in a format that ensures compatibility with media of a lower order or an older generation even if the size of the read/write control information increases significantly as the storage densities of information storage media rise in the near future. On an information storage medium, a data sequence is writable as a combination of marks and spaces. The medium has at least one information storage layer, which has an information storage area to store information and a control information area for use to perform a read/write operation on the at least one information storage layer. The control information area stores at least one set of control information, which includes a first kind of write pulse information including information to be used as a reference value and a second kind of write pulse information including information to be used as an offset value.

Abstract: According to a method of the present invention for recording data on an optical disk, a recording pulse corresponding to a long mark includes a combination of a leading pulse and a subsequent intermediate pulse. Further, a level of the leading pulse indicates a first recording power, and a level of the intermediate pulse indicates a second recording power. When an optical disk includes a plurality of recording layers, a ratio of the second recording power to the first recording power is determined for each recording layer. When the recording speed is variable, the ratio of the second recording power to the first recording power is determined for each recording speed.

Abstract: A method and apparatus for writing data to an optical storage medium are disclosed. A write signal indicating power levels of a laser diode is generated by encoding and decoding codewords. The codewords are generated and decoded according to a specific requirement proposed by the present invention. By doing so, toggling (i.e. state changing) times occurring in channels transferring the codewords can be significantly reduced to avoid the problems of pulse distortion and disappearance in high frequency transmission. Alternatively, toggles appearing in the respective channels can be spread to avoid interference between the channels. Further, a phase adjustment device for adjusting a phase of each codeword is disclosed.

Abstract: A reproduction signal evaluation method according to the present invention relates to adjustment of an edge portion between a shortest mark and a shortest space in a data sequence including marks and spaces in combination that is recordable on an information recording medium. In a pattern including a shortest mark and a shortest space adjacent before or after the shortest mark, a shift amount of an edge of the shortest mark is obtained from a differential metric calculated regarding one of a first pattern in which a space adjacent to the shortest mark and not adjacent to the shortest space is longer than the shortest space; and a second pattern in which a mark adjacent to the shortest space and not adjacent to the shortest mark is longer than the shortest mark.

Abstract: A reproduction signal evaluation method according to the present invention relates to adjustment of an edge portion between a shortest mark and a shortest space in a data sequence including marks and spaces in combination that is recordable on an information recording medium. In a pattern including a shortest mark and a shortest space adjacent before or after the shortest mark, a shift amount of an edge of the shortest mark is obtained from a differential metric calculated regarding one of a first pattern in which a space adjacent to the shortest mark and not adjacent to the shortest space is longer than the shortest space; and a second pattern in which a mark adjacent to the shortest space and not adjacent to the shortest mark is longer than the shortest mark.

Abstract: A tracking signal generating apparatus includes a phase detector and a digital phase controller. The phase detector generates an up signal and a down signal which contain information regarding a phase difference between a plurality of square wave signals that have been generated from an optical signal. The digital phase controller generates an up limit signal or a down limit signal whose logic levels are controlled so that a phase difference between the up limit signal and the down limit signal is reduced.

Abstract: [Object] To Reduce Read Errors. [Solving Means] Where new data recording is started from LRA (old) and a record error is detected, at position P0, an extent is closed and the record position is made to jump from the position P0 to position P1. Further, a new extent is set, at the position P1 so that the data recording is continued. Further, a range from the position P0 where the record error was detected to the position P1 where the new data recording was started is registered, as a defect sector. The present invention can be used for a Blu-Ray-Disc-capable recording-and-reproducing system.

Abstract: It is to provide an optical disc recording apparatus and a recording power control method that are adapted to high-speed recording and can set an optimal erasing power with high accuracy. A test writing signal detector reproduces a test writing signal of a predetermined mark length or space length with varied power, and detects the number of error mark signals and an amplitude value of an envelope. A controller obtains a first threshold Pe0 of the erasing power based on the number of error mark signals in a region where laser power is low, and obtains a second threshold Pe1 of the erasing power based on the amplitude value in a region where the laser power is high. Then, the controller sets an optimal value of the erasing power from an average value of the first and second thresholds.

Abstract: A recording parameter setting device including a trial recording parameter setting section and a reproduced signal quality judging section. The reproduced signal quality judging section judges whether or not a reproduced signal obtained by reproduction of the trial recording carried out in accordance with the trial recording parameter satisfies a predetermined reproduced signal quality. If no, the recording parameters of the predetermined recording mark length or longer are further classified into detailed groups and trial recording is carried out again. If the reproduced signal satisfies the predetermined reproduced signal quality, the reproduced signal quality judging section sets the trial recording parameters as a recording parameter. This makes it possible to form a recording mark capable of surely providing a good reproduced signal quality while the number of recording parameters to be used is reduced.

Abstract: A recording and reproducing apparatus includes optical head means for writing and reading information expressed by a mark and a space on an optical recording medium by irradiating laser light to the optical recording medium, laser-drive pulse generating means for creating and supplying a laser-driving pulse in accordance with information to write to the optical head means and causing the optical head means to perform the irradiation of laser light for writing, mark edge error detecting means for detecting an error of the edge position of the mark from a signal read out from the optical recording medium by the optical head means; and adjustment control means for defining the adjustment on a laser-driving pulse generated by the laser-driving pulse generating means.

Abstract: To compensate for edge shifts varying largely in accordance with preceding mark lengths. Provided are a method and a recorder in which a duration of a cooling pulse in each recording pulse string to form a mark having a length of nT is determined on the basis of an edge shift amount of a front edge of a mark whose preceding mark has a length of nT, where n is an integer and T is a channel bit length.

Abstract: The system and method is used for CAV (Constant Angular Velocity) control format recording, whereas the existing disk data is recorded under CLV (Constant Linear Velocity) control format recording. When the PUH receives a laser driver signal, it generates a feed signal and a wobble signal. The feed signal is received by the automatic power control; thereafter the automatic power control generates a first control signal used for causing the laser driver to adjust the laser driver signal. After the ATIP decoder receives the wobble signal, the ATIP decoder generates and outputs ATIP decoded data to the CLV value detector. The CLV value detector receives ATIP decoded data and generates a CLV decoded data to the laser power control. The laser power control receives the CLV decoded data and generates a second control signal used for causing the automatic power control to adjust the first control signal.

Abstract: A record carrier has substantially parallel tracks having first variations of a first physical parameter and second variations of a second physical parameter of the track. The first variations represent information recorded on the record carrier, this information being recoverable by a controllable type of data processing. A modulation pattern of the second variations represents a code for controlling the type of data processing. In respect of a code track that includes the modulation pattern, the modulation pattern in the left neighboring track is aligned to the modulation pattern in the right neighboring track. Thereby crosstalk due to the second variations is decreased, and at least two tracks have the same modulation pattern. The playback device has a demodulator (50) and a control unit (56) for retrieving the code from at least two tracks.

Abstract: An optical recording method for recording mark length-modulated information on a recording medium by using a plurality of recording mark lengths. The optical recording method comprises the steps of: when a time length of one recording mark is denoted nT (T is a reference clock period equal to or less than 25 ns, and n is a natural number equal to or more than 2), (i) dividing the time length of the recording mark nT into ?1T, ?1T, ?1T, ?2T, ?2T, . . . , ?iT, ?iT, . . .