Abstract: A first network device including modulation, transmit, front end, and phase modules. The modulation module amplitude or frequency modulates a data signal to generate a modulated signal. The transmit module transmits an output signal based on the modulated signal. The front end module obtains a phase of a point in a first cluster of index ratios. Each of the index ratios corresponds to a respective phase of a respective symbol period of the output signal. Each of the index ratios is based on a maximum amplitude, a minimum amplitude or a mean of amplitudes of the output signal over the symbol periods. The amplitudes for each of the means includes a corresponding one of the maximum amplitudes and a corresponding one of the minimum amplitudes. The phase module adjusts a phase of the output signal based on the phase of the point in the first cluster of index ratios.

Abstract: A method for controlling amplification factor of a receiver device includes: detecting a first variation of an equivalent length of a cable, detecting a second variation of amplification factor of a digital automatic gain controller (DAGC), determining a first update value of amplification factor of an analog automatic gain controller (AAGC) according to the first variation and the second variation, calculating a tuning ratio of the first update value to a current value of the amplification factor of the AAGC, calculating a second update value of the amplification factor of the DAGC according to the tuning ratio, updating a set value of the amplification factor of the AAGC according to the first update value, and updating a set value of the amplification factor of the DAGC according to the second update value.

Abstract: A method is provided for receiving and restoring data from an optical recording medium exhibiting strong asymmetry in the regenerated RF signal. The method provides digital partial response asymmetry compensation of a digital RF signal. The asymmetry of the digital RF signal is detected through the measurement of the envelopes of a short T pulse (xT pulse) and a long T pulse (yT pulse), where the T is the bit clock of the recovered bit stream. Through the evaluation of the xT upper and lower envelopes and the asymmetry factor, upper and lower thresholds are determined. Only the asymmetric parts of the digital RF signal are selected and compensated.

Abstract: According to one embodiment, there is provided a controller including an interference cancelling module, a boosting module, and a decoding module. The interference cancelling module generates a first correction signal by cancelling an interference component from an adjacent track in a signal read from a target track of a disk medium. The boosting module generates a second correction signal by boosting a low frequency component of a signal corresponding to the first correction signal. The decoding module decodes a signal based on the second correction signal.

Abstract: Asymmetry and offset compensation for a data signal may be performed by a compensation circuit as disclosed. A circuit can be configured to generate a compensated data signal from a data signal, and can include: an input node inputting the data signal, an offset coefficient feedback loop configured to calculate an offset coefficient based on the data signal, a scaling unit configured to scale the offset coefficient by a first predetermined value (the scaled offset coefficient representing an estimate of an asymmetry coefficient), an asymmetry coefficient feedback loop configured to calculate the asymmetry coefficient based on the data signal and an initial value, a signal selection unit that causes the circuit to calculate the compensated data signal using the asymmetry coefficient, and an output node that outputs the compensated data signal.

Abstract: A system with a nonlinear element processes a replay signal with a scaling factor into a signal compensated for asymmetry. The replay signal may include data from an optical disk. The scaling factor may be estimated based on the compensated signal and a scaling factor gain. The replay signal and the compensated signal may be converted into digital signals and processed digitally. In one embodiment, the compensated signal may be calculated as approximately the scaling factor multiplied by a square of an amplitude of the replay signal added to the amplitude of the replay signal. In another embodiment, the compensated signal may be calculated as approximately the scaling factor multiplied by an absolute value of an amplitude of the replay signal added to the amplitude of the replay signal. A related method is also disclosed. Other embodiments are provided, and each of the embodiments described herein can be used alone or in combination with one another.

Abstract: A data recovery device including an analog to digital converter (ADC), a filtering-equalizing unit, a zero crossing detector, a data phase locked loop, a data mapping unit and an estimation unit is provided. The ADC converts a radio frequency signal to a plurality of sampling data points. The sampling data points are converted to a plurality of retiming data points and a clock signal by the filtering-equalizing unit, the zero crossing detector and the data phase locked loop. The data mapping unit selects a plurality of maximum data points and minimum data points from the returning data points, and determines whether to map the maximum data points and the minimum data points to other levels for partially reconstructing the retiming data points. The estimation unit recovers the reconstructed retiming data points to a modulation signal.

Abstract: An optical disk reproducing device includes: a signal reproducing section configured to read and decode information recorded on an optical disk by an optical pickup unit, and reproduce the information, wherein the signal reproducing section includes a gain controlled amplifier circuit configured to amplify an radio frequency signal generated from a light receiving element, an automatic gain control circuit configured to control a gain of the gain controlled amplifier circuit, and a signal processing section configured to derive a part of an automatic gain control value generated in the automatic gain control circuit, and generate a control signal for adjusting one of an optical system path and a detection system path for controlling the optical pickup unit.

Abstract: An information recording medium according to the present invention includes an information recording layer on which information is recordable, and is evaluated using an evaluation index which is found based on a ratio of a center of an amplitude of a reproduction signal corresponding to a second shortest mark and a second shortest space, with respect to a center of an amplitude of a reproduction signal corresponding to a longest mark and a longest space.

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 recording apparatus for an optical disk drive is provided. The recording apparatus includes a driver, a servo signal generator, a filter, and a counter. The driver controls a recording speed of the optical disk drive. The servo signal generator generates at least a servo signal. The filter with a specific bandwidth filters the servo signal to generate a filtered servo signal. The counter generate a count value according to the filtered servo signal and instructs the driver to decrease the recording speed of the optical disk drive when the count value exceeds a trigger value, so as to record with the decreased recording speed.

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: According to one embodiment, a device includes a filter which limits a frequency bandwidth of a reproduced signal from an optical disc, an AD conversion module which converts an output signal from the filter into a multilevel digital signal, an equalizing module for equalizing a waveform of the multilevel digital signal based on a predetermined partial response class and generating an equalizing playback signal, a detection module for generating binary data corresponding to data recorded on the optical disc based on the equalizing playback signal, a module for determining an amplitude value of each of an input signal to and an output signal from the equalizing module with respect to each binary data sequence output from the detection module, and a module for adjusting a high-frequency amplification amount of the filter such that an amplitude value before waveform equalization and an amplitude value after waveform equalization satisfy a predetermined relationship.

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: Provided herein are hybrid laser diode drivers (LDDs) that drive a laser diode in response to receiving enable signals from a controller. In accordance with specific embodiments, a hybrid LDD includes a read channel to selectively output a read current, one or more write channel each to selectively output a write current, and an oscillator channel to selectively output an oscillator current. Additionally, in specific embodiments the hybrid LDD includes a state machine that receives the enable signals from the controller, and based on the enable signals, controls timing of the currents output by the read, write and oscillator channels.

Abstract: A data recovery device including an analog to digital converter (ADC), a filtering-equalizing unit, a zero crossing detector, a data phase locked loop, a data mapping unit and an estimation unit is provided. The ADC converts a radio frequency signal to a plurality of sampling data points. The sampling data points are converted to a plurality of retiming data points and a clock signal by the filtering-equalizing unit, the zero crossing detector and the data phase locked loop. The data mapping unit selects a plurality of maximum data points and minimum data points from the returning data points, and determines whether to map the maximum data points and the minimum data points to other levels for partially reconstructing the retiming data points. The estimation unit recovers the reconstructed retiming data points to a modulation signal.

Abstract: A hybrid LDD includes a read channel to selectively output a read current, a plurality of write channels, each to selectively output a different write current, and an oscillator channel to selectively output an oscillator current. Additionally, the hybrid LDD includes programmable LDD controller that receives the plurality of enable signals from the external controller, and based on the enable signals, controls timing of the currents output by at least the write channels. The programmable LDD controller can also control timing of the currents output by the read and oscillator channels, based on the enable signals. Further and alternative embodiments are also provided.

Abstract: A hybrid LDD includes a read channel to selectively output a read current, a plurality of write channels, each to selectively output a different write current, and an oscillator channel to selectively output an oscillator current. Additionally, the hybrid LDD includes programmable LDD controller that receives the plurality of enable signals from the external controller, and based on the enable signals, controls timing of the currents output by at least the write channels. The programmable LDD controller can also control timing of the currents output by the read and oscillator channels, based on the enable signals. Further and alternative embodiments are also provided.

Abstract: According to the present invention, whether recoding pits are larger or smaller than diffraction limit is determined. Then, a signal process suitable for processing of the recording pits larger than the diffraction limit and a signal process suitable for processing of the recording pits smaller than diffraction limit are divided to divisionally perform equalizer processing. The respective signals subjected to the divisional processing are synthesized to obtain a processed output signal. A reproduction signal with reduced impact of intersymbol interference is thus obtained.

Abstract: Various embodiments of the present invention provide systems and methods for reduced latency feedback in a data processing system. For example, some embodiments provide a data processing system that includes a variable gain amplifier, a processing circuit, a data detector, and an error signal calculation circuit. The variable gain amplifier amplifies a data input signal and provides an amplified signal. The processing circuit generates a signal output corresponding to the amplified signal, and includes a conditional multiplication circuit. The conditional multiplication circuit conditionally multiplies the signal output by a gain correction signal and provides the result as an interim output. The data detector applies a data detection algorithm to the signal output and provides an ideal output. The error signal calculation circuit generates a gain correction signal based at least in part on the interim output and a derivative of the ideal output.

Abstract: Provided is an optical disk apparatus which has high read retry ability and high compatibility by performing a proper verify for other apparatuses. The optical disk apparatus includes a playback system capable of arbitrarily changing playback performance, and means which detects and determines a factor causing a read error. Moreover, a read retry is performed by use of playback parameters corresponding to the factor causing the read error. Furthermore, a verify is performed with the playback performance of the playback system lowered.

Abstract: There is provided an optical information recording/reproducing apparatus capable of obtaining a high super-resolution effect using an optical information recording medium in which a super-resolution thin film is formed. An optical information recording medium 1 having a super-resolution layer is irradiated with a laser light in a light emission pattern such that a bias light emission portion that does not cause the super-resolution layer to be in the state of super-resolution and a pulse light emission portion that causes the super-resolution layer to be in the state of super-resolution alternatively appear, and reflected light is detected. A reproduction signal based on the pulse light emission portion and a reproduction signal based on the bias light emission portion are acquired.

Abstract: The gain controlling portion sets a gain of an RF amplifier to a maximum range when an activation process starts for an optical disk. The binary process condition setting portion sets an upper threshold level and a lower threshold level corresponding to 80% of upper and lower levels of the maximum range as the binary process condition for the binary process portion. A vacant part without a signal between the upper threshold level and the lower threshold level corresponds to a part of a CAPA signal. The binary signal ratio calculating portion measures a time period of a binary signal from a binary process portion that performs a binary process on the vacant part, and it calculates a binary signal ratio indicating a ratio of the time period of the binary signal to a time period corresponding to one rotation of the optical disk. The disk discriminating portion determines that the loaded optical disk is a DVD-RAM if the binary signal ratio is a value within the range of 4±1 %.

Abstract: Provided herein are hybrid laser diode drivers (LDDs) that drive a laser diode in response to receiving enable signals from a controller. In accordance with specific embodiments, a hybrid LDD includes a read channel to selectively output a read current, one or more write channel each to selectively output a write current, and an oscillator channel to selectively output an oscillator current. Additionally, in specific embodiments the hybrid LDD includes a decoder that receives the enable signals from the controller, and based on the enable signals, controls timing of the currents output by the read, write and oscillator channels.

Abstract: Provided herein are hybrid laser diode drivers (LDDs) that drive a laser diode in response to receiving enable signals from a controller. In accordance with specific embodiments, a hybrid LDD includes a read channel to selectively output a read current, one or more write channel each to selectively output a write current, and an oscillator channel to selectively output an oscillator current. Additionally, in specific embodiments the hybrid LDD includes a state machine that receives the enable signals from the controller, and based on the enable signals, controls timing of the currents output by the read, write and oscillator channels.

Abstract: In three consecutive cells consisting of a preceding cell, a center cell, and a subsequent cell, a possible change rate of the amplitude of a reproduced signal for the center cell with respect to the sum of the multiple values of the preceding and subsequent cells is obtained in advance. Then, for reproduction, the sum of the multiple values of the adjacent preceding and subsequent cells is obtained with respect to each cell. The amplitude of the reproduced signal obtained at the center cell is corrected to be closer to a reference value on the basis of the obtained change rate and sum.

Abstract: In an optical disk apparatus, for reproducing information recorded on a recording surface of an optical disk, by setting such a focus condition that a tracking servo-error level comes to be maximum with a reflection light from the recording surface, while irradiating a light beam of a semiconductor laser, within a signal processor portion 300 for amplifying a RF signal reproduced from the optical disk is provided an equalizer 330 for lifting up high-frequency region of the RF signal, wherein an optimal control is made on an amount of lifting (i.e., EQ Boost Value) by the equalizer, depending upon a difference (?AF) between a focus offset amount at which the RF signal reproduced comes to be maximum and a focus offset amount at which jitter of the RF signal reproduced come to be minimum.

Abstract: An information reproducing apparatus (1) is provided with: an offset adding device (19-1, 19-2) for adding a first offset value (OFS) which can be set to be variable, to a read signal (RRF) read from a recording medium (100); a correcting device (18) for correcting waveform distortion occurring in a read signal corresponding to a long mark, of the read signal to which the first offset value is added; an offset subtracting device (19-2, 19-3) for subtracting a second offset value (OFS) which can be set to be variable, from the read signal in which the waveform distortion is corrected; and a waveform equalizing device (15) for performing a waveform equalization process on the read signal in which the second offset value is subtracted.

Abstract: A high-speed mixed analog/digital PRML data detection and clock recovery apparatus and method. The high-speed mixed analog/digital PRML data detection and clock recovery apparatus includes a variable gain amplifier, an analog equalizer, an analog-to-digital (A/D) converter, a DC offset remover, a level error detector, a Viterbi decoder, and an adaptive digital controller. The adaptive digital controller separately stores the level error values by predetermined frequencies, calculates predetermined coefficient values by each frequency component based on the level error values, and D/A-converts and applies the calculated predetermined coefficient values to the variable gain amplifier and the analog equalizer.

Abstract: A multi-level information reproducing method is provided which can increase the degree of separation between distributions of cell boundary values to thereby improve the accuracy of reproduction. Specifically, in a method of reproducing multi-level information recorded on a track of an optical information recording medium by virtually providing cells at equal intervals and by varying a width of an information pit in a track direction or an area of an information pit, a cell boundary value (a value obtained by sampling a reproduced signal when a center of a light spot is located at a boundary of cells) is corrected based on cell center values of two cells adjacent to the boundary (a value obtained by sampling a reproduced signal when the center of the light spot is located at a center of a cell), and the multi-level information is reproduced based on the corrected cell boundary value.

Abstract: The present invention provides a recording pulse generating apparatus capable of forming a recording pit having a proper shape even at the time of ultra-high-speed recording of, for example, 8×recording or higher. A recording controller 10 for generating recording pulse signals having lengths corresponding to ten kinds of lengths of pits formed at the time of recording information has a recording controller 10 for generating the recording pulse signals so that the amplitude of a recording pulse signal corresponding to a pit having a length of 4T changes from a first amplitude to a second amplitude, and generating the recording pulse signals so that the amplitude of a recording pulse signal corresponding to a pit having a length of 5T or longer changes from a third amplitude to a fourth amplitude and further changes to a fifth amplitude.

Abstract: A signal processing circuit for adjusting an input signal and generating a corresponding digital output signal in an optical disk driver is provided. The signal processing circuit includes an attenuator for receiving and attenuating the input signal and then generating an attenuated output signal; a gain controllable amplifier for receiving and amplifying the input signal and then generating an amplified output signal; a control unit providing a control signal and a select signal, the control signal is directed to the attenuator and the gain controllable amplifier for enabling/disabling the attenuator and the gain controllable amplifier and for controlling their gains such that one of the attenuator and gain controllable amplifier is enabled at a time; and a waveform adjuster circuit for adjusting the amplified/attenuated output signal delivered from the gain controllable amplifier or the attenuator so as to generate the digital signal related to the input signal.

Abstract: An optical disc apparatus includes: a read unit for outputting an RF signal, which is a read signal of data recorded in an optical disc, by irradiating a laser beam to the optical disc and detecting reflected light in a photo detector; an equalize unit for performing equalize adjustment on the RF signal, which is an output from the read unit; a playback unit for generating a playback signal from the RF signal having undergone the equalize adjustment by the equalize unit and outputting the playback signal; a parameter storage unit for storing initial values of parameters used for the equalize adjustment by the equalize unit; and a parameter detection unit for detecting a value of at least one parameter at which jitter of the RF signal having undergone the equalize adjustment by the equalize unit becomes optimal during playback of the optical disc.

Abstract: A method and apparatus for signal equalization in a light storage system is disclosed. The method includes observing run length of an RF signal read from the optical disc; classifying run lengths into sets; calculating the mean of certain run lengths; comparing the values with expected values of said run lengths to generate an error value; and adjusting equalizing parameters of boost and frequency if the error value lies outside an expected range.

Abstract: A reproduction apparatus is capable of reproducing information recorded on information recording media including at least a super RENS recording medium. The reproduction apparatus includes: an optical head that receives laser light that has been reflected or transmitted by the information recording medium and photoelectrically converts the laser light to an electric signal; a signal processing circuit that extracts an AC component from the electric signal and attenuates the AC component by a predetermined attenuation; an amplitude controlling circuit that controls an amplitude of an electric signal outputted from the signal processing circuit so as to become a predetermined amplitude; and a reproduction circuit that reproduces information recorded on the medium based on an electric signal outputted from the amplitude controlling circuit. An information recording medium testing apparatus includes the reproduction apparatus and a test information generating circuit that generates test information.

Abstract: An apparatus for controlling a monitor photo diode (PD) of an optical pickup system monitors an optical power signal output for writing data on or reading data from a disk. The apparatus includes a comparator which compares a voltage signal corresponding to the optical power signal output from the LD with a predetermined reference voltage signal, and a gain selector which selectively issues a gain output from the comparator depending on the type of the optical power signal output from the LD.

Abstract: Disclosed here is an apparatus and method for realizing write/read of mass information by reducing cross-talk components that are apt to increase in narrow tracks when various disturbances and variations are recognized. In order to achieve the above object, the apparatus is provided with a plurality of equalizers for correcting frequency characteristics of signals reproduced from a plurality of spots, then outputs from those equalizers are subjected to a computing process to correct tap coefficients of the equalizers sequentially so as to minimize the influence of the subject cross-talk, thereby realizing stable reduction of the cross-talk components.

Abstract: The invention provides an automatic gain controller processing an input signal for wobble detection circuit. An exemplary embodiment of the automatic gain controller comprises an envelope detection module, an analog to digital converter, a digital control module, a digital to analog converter, and a variable gain amplifier. The envelope detection module detects an envelope magnitude of an amplified signal. The analog to digital converter converts the envelope magnitude from analog to digital to obtain a digital envelope signal. The digital control module determines a digital gain signal for amplification of the input signal according to the digital envelope signal. The digital to analog converter converts the digital gain signal to an analog gain signal. The variable gain amplifier then amplifies the input signal according to the analog gain signal to obtain the amplified wobble signal.

Abstract: Provided is an optical disk apparatus which has high read retry ability and high compatibility by performing a proper verify for other apparatuses. The optical disk apparatus includes a playback system capable of arbitrarily changing playback performance, and means which detects and determines a factor causing a read error. Moreover, a read retry is performed by use of playback parameters corresponding to the factor causing the read error. Furthermore, a verify is performed with the playback performance of the playback system lowered.

Abstract: Provided are an optical information reproducing method capable of determining multi-level information with high precision, and an apparatus for the method. Specifically, a cell having a reduced multi-level is provided in a portion of a data region to perform the level correction or the AGC. For example, a cell recorded with an M-value for each group including a plurality of cells, each of which is recorded with an N-value (N?3, M<N), is provided. A reproduction signal level of a cell recorded with the N-value, which follows the cell recorded with the M-value, is corrected based on a difference between a cell center value of a reproduction signal sampled when a center of a light spot is moved to a center of the cell recorded with the M-value and a reference value obtained from learning information.

Abstract: An RF signal that is a disk reproduction signal is binarized through an equalizer and a slicer, followed by data demodulation, and an error rate of the reproduction signal is detected in an error detection circuit. If the error rate in the error detection circuit is higher than a prescribed value, a slice balance adjustment circuit performs slice balance adjustment for the slicer and a boost adjustment circuit performs boost adjustment for the equalizer.

Abstract: A feedback loop structure including an operational amplifier unit (1) for amplifying a reproduction signal of recorded information and a gain/offset control unit (6) for controlling an amplitude and an offset of an output of the operational amplifier unit (1) so that each of the amplitude and the offset becomes a predetermined value is adopted, and accurate information for an asymmetry amount is obtained by a binarization unit (7) for receiving the output of the operational amplifier unit (1) and performing binarization while adjusting a slice level by feedback control so that a duty ratio after the binarization substantially becomes a predetermined value. Based on the asymmetry amount information, a judgment level of a Viterbi decoding unit (15) is changed, thereby reducing a reproduction error rate.

Abstract: A method and apparatus to dynamically adjust the amplitude of a signal comprising information read from an information storage medium. The method first forms (N) digital signals comprising information read from an information storage medium. The method provides a first signal comprising information read an information storage medium, wherein that first signal is one of the (N) digital signals. The method provides a first gain level, and calculates a first gain adjusted signal comprising the multiplication product of the first signal and the first gain level. To dynamically adjust that gain level, Applicants' method determines a gain error. Using that gain error, Applicants' method then calculates a second gain level by multiplying the gain error times a multiplier coefficient, and adding that multiplication product to the first gain level.

Abstract: Disclosed is a PLL circuit having a voltage-controlled oscillator, to which a difference voltage across non-inverting and inverting input terminals is input as a control voltage, for oscillating at a frequency in accordance with the control voltage; a phase comparator for comparing the phase of an output signal obtained by frequency-dividing the output of the voltage-controlled oscillator by a frequency-divider, with the phase of an input signal and outputting the result of this phase comparison; first and second loop filters connected at output terminals thereof to the non-inverting and inverting input terminals, respectively, of the voltage-controlled oscillator; and a charge pump, which is responsive to receipt of an UP signal supplied from the phase comparator, for supplying a first charging current from a PMOS transistor to a capacitor of the first loop filter and supplying a first discharge current from an NMOS transistor to a capacitor of the second loop filter, and which is responsive to receipt of a

Abstract: A method for adjusting a reference level of an analog signal from a plurality of periodically sampled points includes the following steps. Firstly, a first level shift from an preliminary reference level to the last second sampled point within a specified period and a second level shift from the preliminary reference level to the last sampled point within the specified period is determined when one of a first level of the last second sampled point and a second level of the last sampled point is higher than the preliminary reference level and the other is lower than the preliminary reference level. Then, the preliminary reference level is moved toward the first level when an absolute value of the first level shift is greater than an absolute value of the second level shift, and the preliminary reference level is moved toward the second level when the absolute value of the first level shift is less than the absolute value of the second level shift, thereby defining an adjusted reference level.

Abstract: The waveform equalizer (6) for obtaining a corrected signal S? by performing a waveform equalization to a read signal S read out from an information carrier (1). The waveform equalizer (6) has a first filter (61) able to perform a filtering process to said read signal S, and an amplitude limiting means (62) able to obtain an amplitude limited read signal SLIM by limiting an amplitude level of said read signal S by a predetermined amplitude limitation value. A second filter (63) is provided which is able to perform a filtering process to said amplitude limited read signal SLIM. Further, an adder (64) is present which is able to add the signals obtained by performing the filtering process by each of said first (61) and second filters (63), able to generate an addition result as said corrected read signal S?.

Abstract: In the disclosed pulse shape modulation method, an amplitude modulation gain for a reproduced signal from an information recording medium that makes the jitter of the reproduced signal become the minimum is specified. Then, it is determined whether the amplitude modulation gain corresponding to the minimum jitter resides within a prescribed range. If the amplitude modulation gain corresponding to the minimum jitter is outside the prescribed range, the pulse shape of the pulsed laser beam is modulated.

Abstract: An information recording apparatus includes a pickup which irradiates a recording light to a disc on which prepits are formed and which outputs return light quantity data, a period determination circuit which determines a data obtaining period in which return light quantity is not affected by the prepit, a sample-hold circuit which obtains the return light quantity in the data obtaining period, and a microcomputer which controls a recording power based on the return light quantity data. The microcomputer obtains the return light quantity data in the data obtaining period in which the return light quantity is not affected by the prepit, and executes control including the recording power control based on the return light quantity data. As a sample-hold circuit detects a pit level and the like in a 9T to 11T period which is hardly affected by the LPP and controls the recording power based on the result, proper recording power control can be executed.

Abstract: A write clock generation circuit is provided that can detect wobble signal in high accuracy and can appropriately generate write clock with only small jitter even when the operation is switched from reproduction to recording. The wobble signal is obtained by changing stepwise the gain of a variable gain amp in the rear stage of a divided photo detector using a gain control circuit in a predetermined time period just after the beginning of recording. The write clock signal is generated using the above wobble signal. According to this arrangements, the change in wobble signal just before and after the beginning of recording can be reduced, and the gain change of a wobble signal amplitude regulation AGC is made slow. As a result, high frequency deviation of the wobble signal can be reduced even when the operation is switched from reproduction to recording, and the write clock with only small jitter can be generated.