Abstract: Apparatuses, systems, and methods for high-pass filtering pre-emphasis circuits. A device may use a pre-emphasis driver to provide a multi-level signal based on multiple binary signals. The pre-emphasis driver includes a primary driver coupled in parallel with at least one equalizer path, each of which includes an equalizer driver and a filtering element. The filtering element may be an AC filtering element, such as a capacitor. The equalizer paths may contribute equalized signal(s) which have a high-pass filtering behavior. The pre-emphasis circuit may combine the primary signal from the primary driver and the equalized signals to generate an overall output multi-level signal. In some embodiments, the pre-emphasis driver may be a pulse amplitude modulated (PAM) driver, such as a PAM4 driver with four levels of the multi-level driver.

Abstract: Systems and methods are disclosed for improving data channel design by applying transform domain analytics to more reliably extract user data from a signal. In certain embodiments, an apparatus may comprise a channel circuit configured to receive an analog signal at an input of the channel circuit, and sample the analog signal to obtain a set of signal samples. The channel circuit may further apply a filter configured to perform transform domain analysis to the set of signal samples to generate a first subset of samples, the first subset including fewer transitions and having a higher signal to noise ratio (SNR) than the set of signal samples. The channel circuit may detect first bit transform domain representation values from the first subset, and determine channel bit values encoded in the analog signal based on the set of signal samples and using the first bit transform domain representation values detected from the first subset as side information.

Abstract: Encoding and decoding systems are described for the provision of high quality digital representations of audio signals with particular attention to the correct perceptual rendering of fast transients at modest sample rates. This is achieved by optimising downsampling and upsampling filters to minimise the length of the impulse response while adequately attenuating alias products that have been found perceptually harmful.

Abstract: A header region evaluation circuit includes a difference signal detection unit that detects a difference signal proportional to a difference in amounts of received light from an optical disc, a high pass filter that switches a plurality of cutoff frequencies according to a passband control signal, removes a low frequency component from the difference signal, and generates a difference signal HPF output, a waveform shaping unit that generates a shaping signal to convert the difference signal HPF output into a pulse, and a physical header detection sequencer that generates a groove detection signal for evaluating whether the physical header region is either one of a groove and an inter-groove and generates a passband control signal for controlling the cutoff frequency to be reduced for a difference signal corresponding to at least a part of the physical header region.

Abstract: A demodulation circuit accurately demodulates a wobble signal of an optical disk without being affected by a phase shift induced by crosstalk. An A-D converter subjects wobble signal reproduced from an optical disk to A-D conversion and feeds a result of conversion to a zero-crossing detection circuit. The zero-crossing detection circuit detects zero-crossing points of the wobble signal. A sinusoidal wave generation circuit generates a sinusoidal wave by means of sequentially connecting sinusoidal wave elements whose periods are each equal to a time interval between zero-crossing points. A multiplier multiplies an original wobble signal by a sinusoidal wave signal. A slicer detects an HMW-modulated portion of the wobble signal, and another slicer detects an MSK-modulated portion of the wobble signal.

Abstract: An optical disc device including a high frequency band processing circuit for removing low frequency components of signals outputted from plural photodetectors of a pickup, and generating various kinds of signals required for recording/playback of an optical disc by digital processing after performing AD conversion by a high-speed low-bit AD converter; and a low frequency band processing circuit for removing high frequency components of the signals outputted from the respective photodetectors of the pickup, and generating various kinds of signals required for recording/playback of an optical disc by digital processing after performing AD conversion by a low-speed high-bit time-division AD converter.

Abstract: To determine the optimum amplitude of high frequency signal for the loaded disc with a simple configuration to achieve stable playing performance, there is provided an optical disc device comprising: a light source driven by a drive signal with a high frequency signal superimposed; a detector for detecting return light emitted from the light source; and a controller for controlling amplitude of the high frequency signal to be superimposed on the drive signal for the light source; the optical disc device being configured to read data on an optical disc loaded therein by a signal outputted from the detector, wherein the controller determines the amplitude of the high frequency signal to be superimposed on the drive signal based on asymmetry of the signal outputted from the detector.

Abstract: An adaptive equalization circuit (105) operates for PR-equalization of the reproduced signal that is subjected to an A/D conversion by an A/D converter (103) and shaped by a waveform shaping circuit (104). An ideal-waveform generation circuit (110) generates an ideal waveform that corresponds to the reproduced signal that is binarized by a Viterbi-decoding circuit (108). A mark-length/space-length calculation circuit (112) calculates the actual mark length/space length relative to the mark length/space length to be formed, based on the equalization error that arises when the ideal waveform assumes a central reference level as calculated by an equalization-error calculation circuit (111) and the intervals of polarity inversions of binarized data detected by a 0-cross detection circuit (109). A system controller (114) adjusts the edge shift quantity of the recording waveform when forming a mark based on the calculated mark length/space length.

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: In a recording system in which linear velocity during the write operation changes, it is difficult to obtain write strategy parameters in every linear velocity with trial writing. The optimum write strategy condition under the high speed or low speed operation is obtained with trial writing or the like and a value of power compensation is obtained from the frequency characteristic stored in the table. Fluctuation in performance of optical disk drive, deterioration by aging, and temperature characteristic can be compensated.

Abstract: A method of writing a mark to an optical disc includes receiving data to be written and generating a control signal for a laser pulse having a melt period that transitions to a growth period wherein the melt period is characterized by a melt power and the growth period is characterized by a growth power.

Abstract: A data reproduction device for equalizing a reproduced digital signal. A signal reproduced using a reproduction head is sequentially processed by an analogue filter, an A/D, and an interpolator before being supplied to a digital equalizer. The digital equalizer digitally equalizes an input digital signal to output to a subsequent Viterbi decoder, or the like. The digital equalizer comprises a variable BPF, and a variable FIR filter, and the filtering characteristic is variably adjusted.

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 equalizer for a high density optical disc reproducing apparatus and an equalizing method therefore are provided. The equalizer includes: a non-linear transformer, which transforms an input signal according to predetermined threshold levels; a cosine transform filter, which inverts phases of high frequency spectrum components of an output signal of the non-linear transformer; a high boost filter, which increases amplitudes of high frequency spectrum components of the input signal; and an adder, which adds an output signal of the cosine transform filter with an output signal of the high boost filter. Therefore, the equalizer can increase recording density of the optical disc in the high density optical disc reproducing apparatus and accordingly increase recording amount of information, by reducing inter-signal interference (ISI) and increasing a signal-to-noise ratio in the output signal of the equalizer. Also, the equalizer has a simple configuration.

Abstract: A multi-layered disc (D1, D2, D3) is provided with a plurality of recording layers laminated with each other in a direction of a normal line of the recording layers, in each of which an information data recording area (2, 4) for recording information data and a control data recording area (1, 3) for recording control data to control an operation of recording and/or reproducing the information data are disposed on a same plane, the control data being recorded by a CAV method over a plurality of tracks in the control data recording area. The control data recording area in each of the recording layers is disposed such that the control data recording area (1) of one of the recording layers is not superimposed with the control data recording area (3) of another of the recording layers in the direction of the normal line.

Abstract: An analog filter is placed at a stage previous to an analog-digital converter (ADC), and a waveform equalizer is placed at a stage subsequent to the ADC. The sampling frequency of the ADC is determined by a clock generation section according to the relationship between the bit rate of an input reproduction signal and the characteristic of the analog filter. The number of taps is changed according to the relationship between the bit rate of the input reproduction signal and the characteristic of the analog filter. Further, the tap coefficients of a waveform equalizer are changed according to the height of the frequency band of the input reproduction signal. A waveform evaluation section generates a signal that evaluates a waveform equalization signal transmitted from the waveform equalizer to a Viterbi decoder, whereby adaptive waveform equalization is realized.

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: An equalizer and an equalizing method of optical recording/reproducing apparatus capable of enhancing equalizing performance and equalizing speed are disclosed. The equalizer includes a FF unit having a feedforward filter for removing pre-cursor from inter-symbol interference of input signal, a FB unit having a feedback filter for predicting post-cursor of the inter-symbol interference and outputting it, a first adder and a second adder for adding the signal from the FF unit and the signal from the FB unit, to remove the inter-symbol interference, a slicer for deciding the level of the signal from the first adder to be a predetermined level and feeding back the level-decided signal to the FB unit, and a signal detection unit for outputting the signal having the inter-symbol interference removed by the second adder as a predetermined signal using at least one of a trellis structure method and a tree structure method.

Abstract: A multi-layered disc (D1, D2, D3) is provided with a plurality of recording layers laminated with each other in a direction of a normal line of the recording layers, in each of which an information data recording area (2, 4) for recording information data and a control data recording area (1, 3) for recording control data to control an operation of recording and/or reproducing the information data are disposed on a same plane, the control data being recorded by a CAV method over a plurality of tracks in the control data recording area. The control data recording area in each of the recording layers is disposed such that the control data recording area (1) of one of the recording layers is not superimposed with the control data recording area (3) of another of the recording layers in the direction of the normal line.

Abstract: A PRML detector includes a waveform equalizer for equalizing a waveform of a reproduction signal obtained by reproducing marks and non-marks recorded on a recording medium, and a decoder for generating binary-coded data of the reproduction signal based on the waveform equalized by the waveform equalizer. The decoder outputs a temporary data string which is obtained before the binary-coded data is obtained. The waveform equalizer includes an equalizer that includes a delay element that delays propagation of the reproduction signal, a plurality of multipliers that multiply predetermined coefficients by the reproduction signal and the delayed signal from the delay element, and an adder that adds outputs from the plurality of multipliers.

Abstract: A waveform equalizer for equalizing a waveform of a reproduction signal. A delay element delays a propagation of the reproduction signal. A plurality of multipliers multiply predetermined coefficients by the reproduction signal and the delayed propagation reproduction signal. A detector detects an asymmetry of the reproduction signal arising from physical profiles of each of the marks and the non-marks, and outputs a detection signal representing an amount of asymmetry. A discriminator outputs a discrimination signal in response to a discrimination of the marks and the non-marks. A calculator calculates a first coefficient multiplied by the reproduction signal of the marks based on the outputted detection signal, and calculates a second coefficient multiplied by the reproduction signal of the non-marks. A selector selects either the first or second coefficient, based upon the outputted discriminating signal.

Abstract: A semiconductor laser driving apparatus for directing light to an optical disc for recording a recording mark based on a recording current and reproducing the recording mark to generate a reproduction signal. The apparatus includes a reproduction current generation section; a high frequency current generation section for generating a current including a high frequency component for reducing semiconductor laser noise in the reproduction; a recording current generation section, the recording current including a pulse corresponding to the recording mark and including a plurality of multi-pulses; and a current driving section for amplification. The apparatus further includes a filter to attenuate the enhanced high frequency components in the high frequency current and in the enhanced high frequency component; and a switching section for switching the filter so that the enhanced component in the recording current is superposed on at least one of the multi-pulses.

Abstract: A defect protecting circuit and a method for data slicer in an optical drive is disclosed. As a defect occurs in a disk, the gain of the data slicer is switched to a high gain. After the defect does not occur further, the gain is switched back to a normal gain. Therefore the slicing level can return back to a correct slicing level for reducing incorrect data after the defect terminates, and the jitter in the output data is also reduced.

Abstract: A signal of a run-length-limited code is reproduced from a recording medium. The reproduced signal is sampled to generate a sampling-resultant signal. An odd-sample signal and an even-sample signal are generated in response to the sampling-resultant signal. A first transversal filter subjects the odd-sample signal to first partial-response waveform equalization to generate an equalization-resultant odd-sample signal. The first partial-response waveform equalization depends on first tap coefficients. The first tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant odd-sample signal. A second transversal filter subjects the even-sample signal to second partial-response waveform equalization to generate an equalization-resultant even-sample signal. The second partial-response waveform equalization depends on second tap coefficients. The second tap coefficients are controlled on a feedback basis to minimize an error of the equalization-resultant even-sample signal.

Abstract: An apparatus and method for generating a radio frequency (RF) signal and control signals are provided. In an apparatus for generating a radio frequency (RF) signal and control signals in which the current output from a plurality of light receiving elements is converted into voltage signals and the RF signal and the control signals are generated in response to the voltage signals, the apparatus includes an input data processing unit, a digital filter, a servo signal generating unit, a digital RF data generating unit, and a reference comparator. The input data processing unit performs time-sharing sampling on the voltage signals and converts the voltage signals into first digital signals in response to an analog/digital conversion clock signal having a predetermined period and a sequentially applied selection signal. The digital filter filters each of the first digital signals to modify the shape of the waveforms of the first digital signals and outputs the modified waveforms as second digital signals.

Abstract: To correct a bit shift of binary data read from a medium and further enable correction of a bit error caused by mis-correction of the bit shift, a data recovery apparatus according to the present invention comprises: circuits for respectively correcting time at an intersection of a read signal and a slice signal; and a circuit for generating gray bits representing a time cell including an intersection, the time of the intersection being uncorrected and a time cell adjacent to the time cell, positioned in the direction of the intersection being shifted for correction.

Abstract: The reproduction method includes steps of: performing an addition operation on a detection signal obtained by the first light-detecting element group and a detection signal obtained by the second light-detecting element group so as to generate a summation signal and outputting the summation signal to a signal processing section; performing a difference operation on a detection signal obtained by the first light-detecting element group and a detection signal obtained by the second light-detecting element group so as to generate a differential signal and outputting the differential signal to the signal processing section; digitalizing the summation signal so as to generate a binary signal, and generating a binary signal edge pulse; when an amplitude which is equal to or greater than a predetermined value of the differential signal is detected, outputting the binary signal edge pulse as a reproduction edge pulse from the signal processing section; and generating the reproduction data.

Abstract: A clock generator in a recorded information reproduction apparatus for reproducing recorded information from a recording medium includes a pickup that produces a reading signal by reading a recording track of the recording medium. The reading signal is sampled by a sampling circuit at timing corresponding to a clock signal to produce a reading sample value sequence. A crosstalk removing circuit removes crosstalk components which are present in recording tracks adjacent to the recording track read by the pickup from the reading sample value sequence and produces a crosstalk-removed reading sample value sequence. A phase detecting circuit detects a phase error existing in the reading signal based on the crosstalk-removed reading sample value sequence. A clock signal generating circuit generates the clock signal based on the phase error.

Abstract: A first multiplier 251 multiplies a reproduced RF signal rf(t) by a DC component of an APC monitoring output signal m(t), which component is an output signal from an LPF 252, and then supplies a signal resulting from the multiplication to an arithmetic unit 255. A second multiplier 254 multiplies the reproduced RF signal rf(t) by a laser noise component of the APC monitoring output signal m(t), which component is an output signal from an HPF 253, and then supplies a signal resulting from the multiplication to the arithmetic unit 255. The arithmetic unit 255 subtracts the signal from the multiplier 254 from the signal from the multiplier 251 to thereby remove both an additive noise component and a modulated noise component of laser noise.

Abstract: A PLL circuit is disclosed which extracts phase difference information of a high S/N ratio from a readout signal uses the phase difference information for PLL control. An A/D converter samples the input signal to produce a digital signal. A pattern string detector identifies a type of an input pattern string formed from a plurality of successive sample values successively outputted from the A/D converter and outputs pattern string identification information which indicates an identification result. A phase difference generator outputs phase difference information which indicates a phase error of the output of the A/D converter based on the pattern string identification information and the output of the A/D converter. A loop filter, a D/A converter and a voltage controlled oscillator generate a clock signal from the phase difference information to control the sampling timing of the A/D converter.

Abstract: An equalizer for a high density optical disc reproducing apparatus and an equalizing method therefore are provided. The equalizer includes: a non-linear transformer, which transforms an input signal according to predetermined threshold levels; a cosine transform filter, which inverts phases of high frequency spectrum components of an output signal of the non-linear transformer; a high boost filter, which increases amplitudes of high frequency spectrum components of the input signal; and an adder, which adds an output signal of the cosine transform filter with an output signal of the high boost filter. Therefore, the equalizer can increase recording density of the optical disc in the high density optical disc reproducing apparatus and accordingly increase recording amount of information, by reducing inter-signal interference (ISI) and increasing a signal-to-noise ratio in the output signal of the equalizer. Also, the equalizer has a simple configuration.

Abstract: An analog filter is placed at a stage previous to an analog-digital converter (ADC), and a waveform equalizer is placed at a stage subsequent to the ADC. The sampling frequency of the ADC is determined by a clock generation section according to the relationship between the bit rate of an input reproduction signal and the characteristic of the analog filter. The number of taps is changed according to the relationship between the bit rate of the input reproduction signal and the characteristic of the analog filter. Further, the tap coefficients of a waveform equalizer are changed according to the height of the frequency band of the input reproduction signal. A waveform evaluation section generates a signal that evaluates a waveform equalization signal transmitted from the waveform equalizer to a Viterbi decoder, whereby adaptive waveform equalization is realized.

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: An equalizer and an equalizing method of optical recording/reproducing apparatus capable of enhancing equalizing performance and equalizing speed are disclosed. The equalizer includes a FF unit having a feedforward filter for removing pre-cursor from inter-symbol interference of input signal, a FB unit having a feedback filter for predicting post-cursor of the inter-symbol interference and outputting it, a first adder and a second adder for adding the signal from the FF unit and the signal from the FB unit, to remove the inter-symbol interference, a slicer for deciding the level of the signal from the first adder to be a predetermined level and feeding back the level-decided signal to the FB unit, and a signal detection unit for outputting the signal having the inter-symbol interference removed by the second adder as a predetermined signal using at least one of a trellis structure method and a tree structure method.

Abstract: Device and method for detecting a non-writable region of an optical recording medium, wherein a read channel 1 signal and a read channel 2 signal are sliced at respective slice levels to produce header mask signals, and a header region which is a non-writable region is determined for the header mask signal taking the slice levels and written/unwritten regions ion the disk, whereby permitting stabilization of servos because servo error signals, such as a tracking error signal, and a focus error signal can be held exactly at a header region even if the servos are not stable, that prevents deterioration of a data quality in writing and reading, and permitting to shift an optical pickup to a desired position and accurate measurement of an amount of eccentricity because there is no influence of the header in a track jump and a disk eccentricity measurement.

Abstract: A method of reproducing information by scanning information marks, disposed with a predetermined mark pitch therebetween and recorded on tracks inside a predetermined information recording region, by an optical spot. The method includes detecting the size of the optical change resulting from the information mark, calculating a plurality of equalization coefficients used for an equalization processing for the size of the optical change detected for each of the information marks, and reducing the inter-symbol interference on the basis of the equalization coefficients by the equalization processing. The equalization coefficient used for the equalization processing of the size of the optical change by a first information mark is greater than said equalization coefficient used for the equalization processing of the size of said optical change by a second information mark which is longer than the first information mark.

Abstract: The present invention realizes stable and more proper data reproduction even when a reproduced signal varies locally due to a noise or includes a steady distortion. In a data reproduction control method and apparatus, and an optical disk unit that adjust sampled values, in sampling a signal reproduced from a recording medium recorded with data, the frequencies of the levels of quantized data are counted, a histogram of the frequencies of the levels is created based on the counting results, and more accurate reproduced data is obtained by means of a distribution of the frequencies of the levels in the histogram.

Abstract: A method and apparatus in an optical disk system employing a decision feedback equalization (DFE) technique to provide a boosted signal resolution at a data slicer input while minimizing noise. In one embodiment, an optical equalizer includes a feed forward equalizer (FFE) that equalizes the signal from the optical disk and provides an equalized signal and a feedback equalizer (FBE) that generates a feedback signal. The feedback signal is subtracted from the equalized signal to provide a signal having increased resolution and low noise, which is then applied to a data slicer. In one embodiment, the boost provided by the FFE is lower than in conventional equalizers to minimize noise. As the boost of the FFE is reduced, the number of taps in the FBE is increased to provide optimized system performance.

Abstract: Even with an asymmetric reproduction waveform, or under the noisy environment, an accurate equalizing error is found and temporary judgment value for adaptively controlling the coefficient of FIR filter is accurately outputted. A waveform equalizer for equalizing a waveform of a reproduction signal obtained by reproducing marks and non-marks recorded on a recording medium is provided. The equalizer includes: a detector which detects asymmetry of the reproduction signal arising from physical profiles of the marks and non-marks and outputs a detection signal representing asymmetric amount; a discriminator which discriminates the marks and non-marks based on the reproduction signal to output a discriminated signal; and a selector which calculates a first and second coefficient multiplied by the reproduction signal of the marks and non-marks based on the detection signal, which are different. The selector selects one of the first and second coefficients based on the discriminating signal.

Abstract: The invention relates to a digital-signal processing apparatus for playing back a digital signal recorded on a recording medium, wherein the digital signal is recorded onto the recording medium by delimiting the digital signal at predetermined time intervals into blocks and then processing each of the blocks to convert the digital signal into at least first coefficient data prescribing the amplitude of the digital signal or first coefficient data prescribing the amplitude of a component obtained as a result of conversion of the digital signal and second coefficient data for prescribing the waveform of the digital signal in conjunction with the first coefficient data, and the digital-signal processing apparatus selectively updates the first coefficient data of the digital signal recorded on the recording medium.

Abstract: An optical disc having marks for dispersed addresses that can be easily detected with high precision.

Abstract: The present invention realizes stable and more proper data reproduction even when a reproduced signal varies locally due to a noise or includes a steady distortion. In a data reproduction control method and apparatus, and an optical disk unit that adjust sampled values, in sampling a signal reproduced from a recording medium recorded with data, the frequencies of the levels of quantized data are counted, a histogram of the frequencies of the levels is created based on the counting results, and more accurate reproduced data is obtained by means of a distribution of the frequencies of the levels in the histogram.

Abstract: The signal processor includes an analog filter, an analog-to-digital (A-D) converter, an adaptive equalization filter, a quality value calculating circuit, and a control circuit. The analog filter removes high-frequency noises of a played-back signal from a recording medium and amplifies a specific frequency band of the played-back signal. The A-D converter converts the played-back signal from the analog filter into a digital signal. The adaptive equalization filter performs waveform equalization of the played-back signal from the A-D converter while adjusting a tap coefficient of the adaptive equalization filter so as to reduce a difference between an output of the adaptive equalization filter and a target value. The quality value calculating circuit calculates a quality value based on the difference between the output of the adaptive equalization filter and the target value.

Abstract: An information reproducing device for reproducing digital signals with an optical head from an optical disk includes a first equalizer for waveform-equalizing a reproduction signal, an adaptive learning device for renewing the equalization properties of the first waveform equalizer with an adaptation algorithm, a memory for storing a reproduction signal, a second waveform equalizer that reads signals from the memory and performs waveform equalization after an adaptive learning operation for the first waveform equalizer has been terminated, and a demodulator for demodulating the output of the second waveform equalizer. Thus, adaptive equalization processing can be performed with constantly superior equalization properties and without sacrificing data capacity.

Abstract: The present invention realizes stable and more proper data reproduction even when a reproduced signal varies locally due to a noise or includes a steady distortion. In a data reproduction control method and apparatus, and an optical disk unit that adjust sampled values, in sampling a signal reproduced from a recording medium recorded with data, the frequencies of the levels of quantized data are counted, a histogram of the frequencies of the levels is created based on the counting results, and more accurate reproduced data is obtained by means of a distribution of the frequencies of the levels in the histogram.

Abstract: An equalizer for producing an equalized signal from an input signal. The input signal has a DC component. The equalizer includes a programmable filter and equalizer. A detector for generating a threshold signal from a preprocessed signal. The preprocessed signal is generated from the equalized signal. A comparator for comparing the preprocessed signal to the threshold signal to produce an output signal. A tracking device for tracking the DC component from the output signal.

Abstract: An optical disc playback apparatus that performs appropriate waveform equalization according to a difference in characteristics of reproduced signals between land parts and groove parts in an optical disc to which high-density recording is performed using a land/groove recording method. The optical disc playback apparatus includes a reproduction means 102, an A/D conversion circuit 103 for sampling a reproduced signal to be converted into a multi-bit digital signal, a filter 105 for subjecting the multi-bit digital signal to digital equalization, a filter coefficient learning means 106 for adaptively controlling filter coefficients for the filter 105 corresponding to the land part and the groove part to minimize an equalization error, and a switch signal generation means 107 for generating a signal for switching between land and groove, thereby changing the filter coefficient adaptively to the land or the groove.

Abstract: A data processing apparatus having a partial response forward equalizer (filter) with sufficient number of taps to result in 7-tap target response, designed by jointly optimizing the target response and the target coefficients to maximize an appropriate signal-to-noise ratio (SNR) at the detector input, followed by a new post-processing scheme enhances performance of the threshold based bit-by-bit detector designed for the d=2 optical channels. The resulting performance of the proposed scheme over a range of channel densities of 4.5 and below (used on EFM/EFMPlus coded channels for CD/DVD), is close to maximum-likelihood bound (MLB), and it is better than that of other schemes at channel densities of 4.5 and higher. Advantageously, the detector of the invention is simple in structure compared to conventional partial response Viterbi detector schemes. By processing the detected data in accordance with a set of data correction rules, the invention provides advantageous enhanced detection capacity.

Abstract: Even with an asymmetric reproduction waveform, or under the noisy environment, an accurate equalizing error is found and temporary judgment value for adaptively controlling the coefficient of FIR filter is accurately outputted. A waveform equalizer for equalizing a waveform of a reproduction signal obtained by reproducing marks and non-marks recorded on a recording medium is provided. The equalizer includes: a detector which detects asymmetry of the reproduction signal arising from physical profiles of the marks and non-marks and outputs a detection signal representing asymmetric amount; a discriminator which discriminates the marks and non-marks based on the reproduction signal to output a discriminated signal; and a selector which calculates a first and second coefficient multiplied by the reproduction signal of the marks and non-marks based on the detection signal, which are different. The selector selects one of the first and second coefficients based on the discriminating signal.

Abstract: A multi-layered disc (D1, D2, D3) is provided with a plurality of recording layers laminated with each other in a direction of a normal line of the recording layers, in each of which an information data recording area (2, 4) for recording information data and a control data recording area (1, 3) for recording control data to control an operation of recording and/or reproducing the information data are disposed on a same plane, the control data being recorded by a CAV method over a plurality of tracks in the control data recording area. The control data recording area in each of the recording layers is disposed such that the control data recording area (1) of one of the recording layers is not superimposed with the control data recording area (3) of another of the recording layers in the direction of the normal line.