Abstract: An ADIP demodulation method and apparatus, which are used in an optical disk driver to generate the ADIP information according to a wobble signal. The apparatus includes a slicing unit for receiving the wobble signal and generating a wobble pulse, a phase locked loop for generating a reference wobble signal with the same frequency and phase as the wobble pulse and a reference clock with frequency higher than the wobble pulse, a channel bit generator for generating a channel bit signal according to the reference wobble signal and the wobble pulse, and a decoder for decoding to ADIP information according to the channel bit signal. The channel bit generator generates a difference signal between the wobble pulse and the reference wobble signal, and outputs the channel bit signal according to the difference signal.

Abstract: An apparatus and method detecting synchronization of address in pre-groove (ADIP), allowing an optical storage device to write data to an accurate location of a disc includes a bit synchronization detecting unit and a word synchronization detecting unit. The bit synchronization detecting unit determines synchronization of bits of the ADIP to be in a bit synchronization locked state when synchronization of raw bits is detected within a bit synchronization window having a first predetermined period a first predetermined number of consecutive times. The word synchronization detecting unit determines synchronization of words of the ADIP to be in a word synchronization locked state when synchronization of raw words is detected within a word synchronization window having a second predetermined period the first predetermined number of consecutive times.

Abstract: A tilt compensating device and method of performing normal tilt compensation in the event of a servo emergency which may occur during reproduction of data from an optical recording medium are provided. The tilt compensating device includes: an optical pickup; a tilt adjusting unit that adjusts a tilt angle of the optical pickup; a jitter detecting unit that detects an amount of jitter in a reproduction signal output from the optical pickup; and a controlling unit that monitors speed at which the optical recording medium operates using a phase-locked loop (PLL) signal generated from the reproduction signal and the degree of focus of the optical pickup, performs an operation to return to a normal state if any abnormality occurs, and controls operation of the tilt adjusting unit by comparing an amount of jitter detected at regular intervals against a reference.

Abstract: Stable playback performance is assured and data loss due to out-of-step synchronization is reduced even when playback signal quality deteriorates due to such cause as a recording medium defect. The playback method applies to a recording medium to which data is recorded in block units containing multiple fixed-length frames together with block address information. The data and the block address information are acquired from the recording medium. The recording position of each frame in a block is then predicted from the acquired block address information. Synchronization is then set to the frame level based on the acquired data, and the memory address for storing the acquired data is determined based on the predicted recording position. The acquired data is then stored at the determined memory address.

Abstract: A control circuit for an optical disk drive includes a frequency detector, a phase detector, a low pass filter, a voltage-controlled oscillator (VCO), and a controller. The frequency detector and the phase detector both receive an eight-to-fourteen modulation (EFM) signal and a data phase-locked loop (DPLL) signal. The controller can calculate a target frequency and control the VCO to output the DPLL signal according to the target frequency. During a non-seek mode, the VCO outputs the DPLL signal according to output of the frequency detector, phase detector, and low pass filter. During a seek mode or when spindle speed of the optical disk drive changes, the VCO outputs the DPLL signal according to the target frequency. The controller further outputs charge pump currents for the frequency detector and the phase detector and sets an RF equalizer signal and a differential phase detector (DPD) equalizer signal according to the target frequency.

Abstract: The present invention relates to a method of searching for a recordable position of a writable disk, the method comprising the steps of (a) reading data recording information of the writable disk, the data recording information indicating a position of a last track recorded and a recordable position for data to be recorded; (b) examining whether or not an area after the recordable position indicated by the read data recording information has recorded data; and (c) determining whether to change the recordable position to another position for new input data based on the examination result.

Abstract: A frame synchronization signal detection apparatus includes a synchronization signal detector, a main frame synchronization signal generator, a sub frame synchronization signal generator, and an output unit. The synchronization signal detector detects and outputs a synchronization signal from a digital data signal. The main frame synchronization signal generator detects and outputs a first valid synchronization signal from the synchronization signal, as an internal frame synchronization signal, and generates and outputs a first insertion synchronization signal, as the internal frame synchronization signal, if the first valid synchronization signal is not detected in a predetermined first time period. The sub frame synchronization signal generator detects and outputs a second valid synchronization signal from a synchronization signal. The output unit outputs a frame synchronization signal.

Abstract: A method and apparatus to reproduce and/or record data from and/or to an optical recording medium. The method includes detecting a wobble signal from the optical recording medium, predicting a wobble channel state from the detected wobble signal, detecting an information signal from the optical recording medium, predicting an information channel state from the detected information signal. If a damaged section is discovered from the optical recording medium, the information signal is decoded based on the information on the wobble channel state or the information on the information channel state. Accordingly, data can be reproduced more effectively by predicting a channel state of an information (RF) signal and a channel state of a wobble signal.

Abstract: A defect signal detecting apparatus for an optical recording/reproducing apparatus that includes a maximum value detecting unit for detecting a highest amplitude among signals input during a maximum value detection period as a maximum value, a minimum value detecting unit for detecting a lowest amplitude among signals input during a minimum value detection period as a minimum value, an asymmetry detecting unit for calculating an amount ? of asymmetry by detecting a maximum value ILmax and a minimum value ILmin of a signal IL having a maximum periodicity among the signal input, and a maximum value ISmax and a minimum value ISmin of a signal IS having a minimum periodicity among the signal input, and a defect determining unit for determining whether there is a defect in the signal input, using the maximum value, the minimum value and the amount ? of asymmetry.

Abstract: An apparatus and method to detect an LPP sync signal on an optical storage medium include a frame sync bit detection unit detecting frame sync bits from the LPP sync signal on the optical storage medium and a sync detection unit determining whether continuity exists in the detection of the frame sync bits and detecting a 6-bit sector sync or a 3-bit sector sync using a 6-bit long window or a 3-bit long window, respectively, in response to a result of the determination. The apparatus further includes a sync detection result output unit outputting a sector sync detection period when continuity exists in the detection of frame sync bits and in the detection of the 3-bit sector sync or 6-bit sector sync and counting a sync detection signal and a new sync detection period when a sector sync signal is detected by the sync detection unit.

Abstract: A disc recording and reproducing device disclosed herein comprises: a resuming section which resumes writing of record data; a first reproduction synchronization signal output section which reproduces the record data recorded on a recorded data region, sequentially extracts a synchronization signal from the reproduced record data, and outputs a first reproduction synchronization signal; a reliability judging section which only detects a frame having a period in accordance with a predetermined standard from the first reproduction synchronization signal, and outputs the frame as a reliability synchronization signal; a synchronization signal phase retaining section which outputs a retained phase signal that retains a phase of the frame of the reliability synchronization signal; a second reproduction synchronization signal output section which reproduces the record data recorded on an additional data region, sequentially extracts the synchronization signal, and outputs a second reproduction synchronization signal

Abstract: The invention advantageously provides an apparatus and method for recovering clock signals extracted from prerecorded wobbled grooves formed in an optical storage medium such as a compact disk (CD), mini disk (MD) or digital video disk (DVD). A preferred embodiment of the method according to the invention primarily comprises the steps of extracting a series of wobble signals from the prerecorded information, demodulating the wobble signals for generating a series of demodulated clock signals, detecting a period for the clock signals, dividing each of the clock signals for acquiring a series of synchronization frames, generating compensating phases, and respectively adjusting the synchronization frames with the compensating phases for generating a series of phase compensated frames.

Abstract: A recording and reproducing apparatus of the present invention includes a photo-detector having light receiving sections divided along the track direction of an optical disk. The apparatus also includes a wobble signal processing circuit for generating a wobbling polarity judging signal used in judging a wobbling polarity of a track being tracked by comparing phases of a first wobble signal detected from a difference signal of the outputs of the light receiving sections and a second wobble signal detected from a sum signal of the outputs of the light receiving signals. Consequently, whether the wobbled side wall of the track being tracked is the inner or outer radius of track can be judged in real time by a simple structure using one laser beam.

Abstract: A DVD seamless playback system has a first timer, a second timer, a register, a processor, a buffer, and a decoder. The processor is capable of parsing bit-streamed data and of setting count initial values of the first and the second timers alternatively if the data stored in the register is updated.

Abstract: An adjusting method for a synchronous signal in an optical storage device is disclosed. The optical storage device produces a predetermined synchronous signal, and the predetermined synchronous signal normally is matched with the data synchronous signal of the data on the optical disc. The predetermined synchronous signal includes a number of predetermined synchronous impulses, and the data synchronous signal includes a number of data synchronous impulses. In the method, when the data synchronous signal is not matched to the predetermined synchronous signal, it is searched that whether or not a data synchronous impulse is outside of the predetermined window and another consecutive data synchronous impulse detected later by a distance of an image frame is detected. Also and, according to the data synchronous impulse, the predetermined synchronous impulse is adjusted, so that the data synchronous impulse is matched with the predetermined synchronous impulse.

Abstract: A controller for an optical disk drive includes a modulator configured to modulate a record data to be recorded on a optical disk based on a record clock that is a reference clock in recording, and to generate a modulation data and an address information of the modulation data. A prepit decoder is configured to generate a prepit clock from a prepit signal detected from the optical disk, and a decision circuit is configured to determine whether or not recording in accordance with a standard is performed, from phase characteristic based on the address information and the prepit clock, and to control a frequency of the record clock.

Abstract: Without waiting for the rotational speed of an optical disk reaches a rotational speed (Vb) for a reproduction process, a cutoff frequency (Fca) of an RF signal and a boost amount (Bt) for an equalizer circuit are detected, and, with using the rotational speed (Va) of the optical disk at this detection, the cutoff frequency (Fc) by which jitter of the RF signal is optimized when the optical disk is rotated at the rotational speed (Vb) for the reproduction process is calculated by the equation of Fc=Fca+k(Vb?Va), and then set. Therefore, the time between the timing when the user conducts an input operation for starting reproduction, and that when reproduction is actually started can be shortened, and the usability can be improved.

Abstract: An optical disk apparatus for driving an optical disk having formed therein sawtooth wobbles of +STW and ?STW. A pickup receives a laser beam reflected from the optical disk and supplies a reproduced signal to a wobble signal processing section. The wobble signal processing section differentiates the reproduced signal and binarizes the differential signal with reference to a zero level. A pulse length of the binary signal achieved during a positive period is compared with that of the binary signal achieved during a negative period. When the pulse length achieved during the positive period is longer than that achieved during the negative period, the binary signal is determined to be a +STW. In contrast, when the pulse length achieved during the negative period is longer than that achieved during the positive period, the binary signal is determined to be a ?STW, whereby a wobble signal is demodulated.

Abstract: A method and apparatus for detecting information recorded as a phase-modulated wobble along a track of an optical disk, whereby a reference phase section is recorded with wobble having a predetermined reference phase and whereby respective polarities of phase integration values obtained by synchronous detection of phase-modulated unit sections following the reference phase section, in a playback wobble signal, are compared with the polarity of a reference phase integration value obtained for the reference phase section, to thereby detect respective bit states expressed by the phase-modulated unit sections.

Abstract: A pre-pit signal decoder includes a shift register, a pattern comparator, a counting unit, an in-sync signal generating unit and a protection unit. The register receives serial pre-pit bits and converts them into a parallel pre-pit byte. The comparator generates an odd sync bit, an even sync bit, a low bit, and a high bit according to the pre-pit byte and receives a disable signal to operate when the disable signal is not enabled. The counting unit generates a counting value, which marks oddness/evenness of frames of the pre-pit bits and sequence of wobble signals in the frames, according to the odd sync, even sync, low and high bits. The signal generating unit generates an in-sync signal according to the odd sync, even sync, low, and high bits. The protection unit receives the counting value and the in-sync signal to thereby enable the disable signal at positions where the pre-pit bits impossibly exist according to the counting value.

Abstract: A wobbling signal demodulation method is disclosed that is capable of fast and precisely demodulating a wobbling signal without increasing cost of the circuit. The wobbling signal is obtained based on light reflected from a recording surface of an optical disk having a wobbling track formed thereon, and includes a carrier portion having a predetermined basic period and a phase demodulated wave portion including predetermined information.

Abstract: A method of adjusting a condition for at least one of a recording operation and a reproducing operation includes the following steps. At least first and second asymmetry values is found. The first asymmetry value is defined based on a first signal combination selected from at least three signals different in cycle from each other. The second asymmetry value is defined based on a second signal combination selected from the at least three signals. The second signal combination is different from the first signal combination. The condition is set with reference to the at least first and second asymmetry values.

Abstract: An optical disk apparatus for recording data on an optical disk. Prior to recording data on the optical disk, a controller records test data in a test area of the optical disk, thereby optimizing write power. After having recorded the test data, the controller computes a difference between jitter or an error rate obtained when test data are overwritten at write power higher than that used for recording test data and jitter or an error rate obtained when test data are overwritten at write power lower than that used for recording the test data. A jitter or error rate difference is detected while write power is changed. Write power at which the jitter or error rate difference is smaller than or equal to a predetermined threshold value is selected as optimum write power, and data are recorded in a data area.

Abstract: A laser power selecting method includes the steps of recording an asymmetry measuring recording pattern in an optical disk trial-writing area while a laser power is being changed, reproducing a signal from the trial-writing area to calculate an asymmetry value from the waveform of the reproduced signal, determining the change rate of asymmetry from the relation between a laser power when the recording pattern is recorded and the calculated asymmetry value, and setting a laser power, at which the determined change rate of an asymmetry value is maximum, as a recording power used when recording on an optical disk.

Abstract: A control circuit for an optical disk drive includes a frequency detector, a phase detector, a low pass filter, a voltage-controlled oscillator (VCO), and a controller. The frequency detector and the phase detector both receive an eight-to-fourteen modulation (EFM) signal and a data phase-locked loop (DPLL) signal. The controller can calculate a target frequency and control the VCO to output the DPLL signal according to the target frequency. During a non-seek mode, the VCO outputs the DPLL signal according to output of the frequency detector, phase detector, and low pass filter. During a seek mode or when spindle speed of the optical disk drive changes, the VCO outputs the DPLL signal according to the target frequency. The controller further outputs charge pump currents for the frequency detector and the phase detector and sets an RF equalizer signal and a differential phase detector (DPD) equalizer signal according to the target frequency.

Abstract: Creation and detection of synchronization marks for a multilevel data storage medium is disclosed. A sequence of symbols is generated and the sequence of symbols is written to the multilevel data storage medium. A corresponding sequence may be generated by a detector and correlated with read data to detect the synchronization mark.

Abstract: A block synchronization detection apparatus and method. Block synchronization for discriminating one error correction code (ECC) block from another is detected, even when a first sector of the ECC block is not detected in a system having a decoder that decodes an ECC in units of ECC blocks. The block synchronization detection apparatus includes an operator performing an operation on a predetermined last sector number, an n-th sector number, and an (n?1)-th sector number contained in a block, based on a predetermined operation relation; and a comparator comparing a result of the operation output from the operator with a predetermined threshold value and outputting the result of the comparison as a block synchronization signal.

Abstract: A disk type record playback device having a wobble signal extracting bandpass filter for controlling a filter's center frequency according to a frequency follow-up control loop including a dummy filter identical in configuration to a filter to be controlled, and a phase comparator is capable of controlling the center frequency of the bandpass filter with satisfactory accuracy. A frequency variable lowpass filter is provided in a preceding stage of the phase comparator constituting a frequency follow-up circuit and supplies a signal obtained by eliminating harmonic components from a frequency follow-up clock signal to the phase comparator. A cutoff frequency of the lowpass filter is changed in cooperation with a center frequency of the bandpass filter, based on a signal outputted from the frequency follow-up control loop.

Abstract: Disclosed are an information outputting apparatus, an information outputting method and a presentation medium, wherein the information outputting apparatus having an extracting device for extracting a program clock reference and a transport packet from an input stream, a clock generating device for generating a clock signal synchronized with the program clock reference extracted by the extracting device, a time-stamp generating device for generating a time stamp in synchronization with the clock signal generated by the clock generating device, and an information generating device for generating information representing continuity of time stamps. As a result, a stream can be played back correctly and continuously even if discontinuity of time stamps exists.

Abstract: A method is described for determining a set of recording pulse series parameters for recording information on an optical record carrier. First a series of test patterns is written on the record carrier with a values of the parameters. On reading the test patterns, the jitter values of each read signal is determined. The optimum values of the parameters are derived from a linear dependence between the set of recording pulse series parameters and the relative jitter values. The invention relates also to a device arranged to perform the method. The invention further relates to an optical record carrier comprising the optimum recording power as determined by the method according to the invention.

Abstract: A jitter detection apparatus includes an A/D conversion section for converting an input analog signal into a plurality of discrete multiple value digital signals; a binarization section for performing binarization of the plurality of multiple value digital signals to generate a binary signal; a jitter calculation section for calculating a jitter amount based on an error between a value of a prescribed multiple value digital signal sampled at a time which is substantially the same as a time when the value of the binary signal is changed and a prescribed threshold value; a pattern detection section for detecting patterns of the binary signal before and after the time when the prescribed multiple value digital signal is sampled; and a correction section for correcting the jitter amount based on the detected pattern.

Abstract: A record carrier (1) has a servo track (4) indicating an information track (9) intended for recording information blocks represented by marks, this servo track (4) having a periodic variation of a physical parameter. Due to cross-talk, there exists a variation in the wobble signal called wobble beat. The track pitch t and the wobble period p, p being the length of a wobble period, are chosen in such a way that 2?t/p?n+½ where n is integer. The choice results in a reduced wobble beat. A recording and/or playback device has apparatus for recording/reading the information blocks and for generating a wobble signal.

Abstract: Method and apparatus for reducing effect of jitter is described. More particularly, one or more taps of a delay line are selected for a reference clock signal. These selected taps each have an associated index, which is stored, and stored indices are statistically processed to select a tap of another delay line.

Abstract: The present invention discloses a disk player for recording information on a disk and/or reproducing recorded information thereon. The disk player includes a wobble detection unit for detecting a wobble signal corresponding to a wobbling pattern formed along a track of the disk; and an information processing unit for detecting a pre-pit signal recorded on the disk using the wobble signal output from the wobble detection unit and a clock signal obtained by multiplying the wobble signal a predetermined number of times, and for processing the information recorded on the disk or the information to be recorded thereon according to the detected pre-pit signal. Since the detection of a synchronization signal can be performed more precisely, this disk player can reduce error in the recording and reproduction of data.

Abstract: A method and apparatus for normalized bit counting is described. The method comprising incrementing a bit counter using a first clock, and adjusting a target bit based on a difference in frequency between the first clock and a second clock. The method further comprising determining when the bit counter reaches the adjusted target bit.

Abstract: To provide a method for optimizing the optical output from an optical head when recording data onto an optical disk, each time a suspension of data recording onto the disk is determined, the optical head reads data recorded onto the disk before the suspension, and recording state of this data is judged. Based on the judged recording state, the optical output from the optical head to be emitted when resuming the data recording is controlled. A timing at which to suspend data recording can be desirably set, so that the recording state of the recorded data in the disk can be judged at desirable timing in data recording operation, so that the optical output from the optical head is controlled based on the judged recording state.

Abstract: A disk drive apparatus drives, by means of a motor, a disk mounted thereon so as to reproduce signals recorded in the disk. The disk drive apparatus has an edge detecting unit for generating an edge signal XEG indicating a timing of phase switching, in accordance with a plurality of signals CU, CV and CW induced when the motor is driven. The disk drive apparatus further has a drive voltage controlling unit for controlling, in accordance with the edge detection signal XEG, the maximum value of a drive voltage VS for driving said motor. This arrangement implements optimal motor control, while reducing circuit scale and cost and, at the same time, enhancing adaptability of the disk drive apparatus.

Abstract: The present invention relates to a method of changing a recording mode from CAV (Constant Angular Velocity) mode to CLV (Constant Linear Velocity) mode in the middle of recording data to a disk recording medium. A method according to the present invention reads ATIP-framed data encoded in a wobble signal formed along a spiral physical track while recording input data to a recording medium, and detects a sync signal contained in the read ATIP-framed data. Another method measures the frequency of a low-frequency component of the wobble signal instead of reading ATIP-framed data. These two methods determine, in common, when to change the recording mode from CAV to CLV based on the period of the detected sync signal or the measured frequency. The present invention makes it possible to record input data to an entire area of a disk more rapidly without fatal errors such as imperfect writing. As a result, total recording time can be reduced with stable recording guaranteed.

Abstract: A wobble demodulator for reproducing digital information from an optical recording medium in which a track is formed in accordance with a wobble signal that is MSK-modulated so as to contain the digital information by a carrier signal with a predetermined frequency and a sine wave signal with a frequency different from that of the carrier signal, includes: a wobble signal detector for detecting a wobble signal of the track from the optical recording medium; a wobble PLL for detecting the carrier signal based on the wobble signal detected by the wobble signal detector; a multiplier for multiplying the carrier signal detected by the wobble PLL by the wobble signal detected by the wobble signal detector and outputting a multiplied output; a MSK detector for detecting a MSK modulation mark having a phase or a frequency different from that of the carrier signal, based on an integrated value obtained by integrating the multiplied output from the multiplier on a predetermined section basis; and a MSK synchronization

Abstract: A method and device for controlling a rotation speed of a spindle of an optical disk drive includes a frequency detector, two phase detectors, a frequency divider, a low pass filter, a switch circuit, and a drive circuit. The method uses a wobble signal, an encoder EFM frame synchronization (EEFS) signal, an encoder subcode frame synchronization (ESFS) signal, and other related signals to generate five control signals for controlling the rotation speed of a motor connected to the spindle of the optical disk drive. Using the five control signals, the method limits the phase difference between the Absolute Time in Pre-groove (ATIP) sync and the ESFS to be within a predetermined value, and thus improves an update rate and a writing efficiency.

Abstract: An optical recording method for an optical medium including a disk-like substrate, a spiral or concentric-shaped groove structure along a track formed on the disk-like substrate, the groove structure being wobbled in a radial direction of the optical medium, the track being divided into a plurality of units in the track direction by at least one radial boundary line, at least two adjacent units in the radical direction of the medium comprise one zone, the optical medium including a plurality of zones, and the groove structure included in the adjacent units within at least one zone having substantially a same number of wobbling. The method includes providing the optical medium, and recording information on the optical medium by irradiating an optical spot thereon.

Abstract: An apparatus and a method for detecting address information are provided. The apparatus for detecting address information from an optical disc on which a plurality of sectors are arranged and pre-pit data are recorded on each sector, includes: a window generation circuit for generating a detection window for detecting the pre-pit data; a data detection circuit for detecting the pre-pit data based on the generated detection window; a latch for latching the data detected by the data detection circuit to a larger number of bits than a pre-allotted number of bits; a synch information extraction circuit for generating synch information informing a time to refer to the latched data; and an address information extraction circuit for detecting address information by reading the latched data based on the generated synch information. Therefore, the address information recorded on an optical recording medium as land pre-pit (LPP) data can be efficiently detected.

Abstract: A reproducing apparatus for reproducing information recorded on an optical recording medium including a disk-like substrate, a spiral or concentric-shaped groove structure along a track formed on the substrate, wherein the groove structure is wobbled in a radial direction of the medium. The wobbled groove structure is utilized for recording of recording data, and the track is divided into a plurality of recording units in the track direction by at least one radial boundary line. The apparatus includes an irradiation source for irradiating a light spot on the optical recording medium, an optical detector for detecting a reflected light from the medium, and a reproducer for reproducing information by using a signal from the detector.

Abstract: A recording clock generating apparatus for a data recording system includes a wobble signal sampler which samples a wobble signal, from wobble grooves of an optical disk. A first phase comparator provides a first phase-difference signal based on a difference in phase between the wobble signal and a first recording clock signal. A prepit detector detects a prepit signal from prepits of the optical disk. A second phase comparator provides a second phase-difference signal based on a difference in phase between the prepit signal and the first recording clock signal. A phase control signal generator provides a phase control signal based on a sum of the first phase-difference signal and the second phase-difference signal. A clock generator provides a second recording clock signal having a phase corrected in response to the phase control signal provided by the phase control signal generator.

Abstract: On an optical disk medium according to the present invention, address information is recorded along a wobbling track groove 2. The track groove 2 is made up of a plurality of unit sections 22, 23. Each of these unit sections 22, 23 has side faces that are displaced periodically in a disk radial direction. This displacement oscillates at a single period in a tracking direction. However, the displacement pattern differs depending on “each bit of address information (subdivided information)” allocated to each of the unit sections 22, 23.

Abstract: A VCO, which good temperature characteristics, high frequency accuracy, and high phase accuracy is provided as an LSI, without making its master clock frequency operate the VCO high. The VCO includes a digital VCO, a phase modulator, and a frequency band limiting element. The digital VCO outputs an oscillating frequency clock and a phase difference lower than an output cycle resolution at the same timing as the output of the oscillating frequency clock. The phase modulator makes side-band components of the output from the digital VCO move from positions near the fundamental frequency to farther bands by modulating the phase of the output from the digital VCO based on the phase difference.

Abstract: A tuned circuit is used to detect wobble clock inversions. The tuned circuit reacts to a wobble inversion with a change in amplitude that may be detected by a threshold detector. A bandpass tuned circuit is used to detect wobble clock inversions. The output of the bandpass tuned circuit is input to a saturating high-gain amplifier such as a comparator. The output of the saturating high-gain amplifier reacts to wobble inversions with a half-cycle that has an increased duration as compared to half-cycles without wobble inversions.

Abstract: A PLL circuit for generating a clock signal using a reference signal, the frequency of which is relatively low. The PLL circuit includes a first loop circuit for generating a first clock signal which is synchronized with a first reference signal. A second loop circuit generates a second clock signal which is synchronized with a second reference signal. The frequency of the second reference signal is sufficiently lower than the frequency of the first reference signal. The first reference signal is compared with the first clock signal to generate a first control voltage. The second reference signal is compared with the second clock signal to generate a second control voltage. The second loop circuit generates the second clock signal in accordance with the first control voltage and the second control voltage.

Abstract: An optical disk apparatus and methods for controlling the same are provided. The operational reference is switched between a writing clock signal and a playback signal to generate a playback clock signal. The switching of the operation is executed when the playback of test-writing data is initiated.

Abstract: A method for compensating for tilt in reproducing an optical reproducing medium is performed by determining an initial tilt driving direction so as to not interrupt a reproducer when tilt compensation is performed on the optical recording medium. The tilt compensation method involves comparing the amount of jitter detected over a certain period of time when the optical recording medium is reproduced with a reference value; determining the direction of tilt compensation in the direction of reproducing a track of the optical recording medium, before performing tilt compensation, when the amount of jitter detected, according to a comparison result of the comparator, exceeds a reference value; and resuming reproduction of the optical recording medium after performing tilt compensation so that the jitter decreases in the direction of the determined tilt compensation.