Abstract: A method for demodulating a focusing error signal in an optical disc system, comprising the steps of (A) generating a beam strength signal and the focusing error signal, (B) sampling the beam strength signal and the focusing error signal at an appropriate sampling rate, (C) removing a static offset from the beam strength signal and the focusing error signal, (D) calibrating a peak-to-peak value of the beam strength signal and the focusing error signal, and (E) determining an appropriate phase to (i) demodulate the focusing error signal and (ii) calculate a vertical position of a lens in relation to a disc.

Abstract: A signal generator generates a track traversing signal, and a driver causes a pick-up to traverse across tracks of a disc in accordance with the track traversing signal. An error signal generator generates a tracking error signal from the pick-up traversing across the tracks of the disc in accordance with the track traversing signal. A parameter calculator determines a value of a calibration parameter from the tracking error signal that is generated without delay and without signal distortion from low frequency components.

Abstract: A track-crossing signal generator includes a bottom envelope detecting unit, a defect detector, an auto gain control unit, and an amplifier. The bottom envelope detecting unit receives a radio frequency signal, and outputs a bottom envelope signal. The defect detector is electrically connected to the bottom envelope detecting unit for receiving the bottom envelope signal and generating a defect signal when a defect area is formed on a disc track. The auto gain control unit is electrically connected to the bottom envelope detecting unit for receiving the bottom envelope signal and dynamically adjusting a gain value according to the amplitude of the bottom envelope signal. The amplifier is electrically connected to the bottom envelope detecting unit and the auto gain control unit for receiving the bottom envelope signal and dynamically adjusting the bottom envelope signal according to the gain value, thereby amplifying the bottom envelope signal as a track-crossing signal.

Abstract: An information reproducing apparatus has a light source for generating linearly polarized light, a medium having linear marks disposed in overlapping relation to one another, and an optical head disposed between the light source and the medium and having a fine aperture. A polarized light control portion in the light source controls the linearly polarized light to pass through the fine aperture of the optical head to generate near-field light having a preselected polarization direction and to irradiate the linear marks of the medium with the near-field light so that the preselected polarization direction of the near-field light is orthogonal to a longitudinal axis of each of the linear marks. A detector detects light scattered by the linear mark irradiated with the near-field light.

Abstract: A position control method is disclosed that is capable of precisely and stably controlling a position of an object lens relative to a recording medium. When controlling the position of the object lens in the tracking direction, first, an attempt is made to read address information recorded on the recording medium, and if the address information is not readable, the polarity of the tracking error signal used for servo control is reversed. As a result, even for a recording medium of a low quality or a nonstandard recording medium, which are treated as invalid media in the related art, it is possible to locate the object lens to the target position.

Abstract: A phase difference detection circuit that is formed by digital circuits having a small circuit area. In the phase difference detection circuit, the circuits for generating a tracking error signal are structured by digital circuits, and a digital tracking error signal TE is generated from digital signals output from comparators. The latest previous phase difference data are stored in a phase difference memory, and a phase difference window PW is defined from the average phase difference calculated from the stored phase differences.

Abstract: A method and apparatus for controlling a focus servo of an optical disk drive is provided. The focus servo controlling method includes the operations of, when an operating mode enters into a focus pull-in mode, detecting a period of time that satisfies a first threshold condition, the first threshold condition set to determine a duration in which a focal point of an optical signal emitted from a pickup is passing through a cover layer of a disk, the determination made by using a first signal proportional to a detected portion of an optical signal reflected by the disk, and preventing focus servo control from being performed during a detected period of time that first satisfies the first threshold condition since the operating mode entered into the focus pull-in mode.

Abstract: A method controls an assembly using an oscillating wave, such that the assembly moves in an oscillated manner in relation to a surface of an optically writable medium in correspondence with oscillation of the oscillating wave. The assembly generates a beam towards the surface of the optically writable medium. A proximity signal is detected in response to the beam being generated towards the surface of the optical medium, and denotes closeness of the assembly to the surface. A number of peaks within the proximity signal are determined. The time at which each peak within the proximity signal occurs is correlated with a value of the oscillating wave at that time, yielding a number of time-value pairs. The topology of the surface of the optical medium is approximated from these time-value pairs.

Abstract: The present invention relates to an apparatus for reading from and/or writing to optical recording media capable of playback of an optical recording medium based on one single focus search cycle. The apparatus distinguishes between the types of optical recording media on the basis of the focus error signal and the data signal obtainable during focus search operation. An S-CurveOK signal, derived from the focus error signal, is the indication whether at all an optical medium is loaded. When a FocusOK signal, derived from the data signal, is active with dedicated settings for a high-reflectivity medium, this means that a high-reflectivity medium is loaded. However, when the FocusOK signal is not active, the apparatus deduces that a low-reflectivity medium is loaded. The operation mode for the second type of optical recording medium is adapted during the focus search cycle based on the combination of the S-CurveOK and FocusOK signals.

Abstract: A recording device (1T or the like) is provided with (i) recording means (50, 40) for recording data by irradiating a recording medium with laser beams; (ii) driving means (33T, 33F, 55T, 55F, 54) for performing tracking process or focusing process; (iii) a servo means (31T, 31F) for automatically controlling the driving means based on an error signal; (iv) specifying means (21, 22) for specifying an area where a recording medium characteristic (core eccentricity or the like) is not good, based on a high frequency component included in the error signal; and (v) a control means (10) for (v-i) controlling the servo means to change the gain in the automatic control, and for (v-ii) controlling the recording means to change the recording power of the laser beams, in the specified area

Abstract: An optical disk apparatus includes a light focusing element arranged to face a disk and to focus light emitted from a light source on the disk, an actuator to move the light focusing element towards and away from the disk according to an actuator driving voltage, a light intensity detection unit to detect an intensity of light reflected by the light focusing element and generate a gap error signal based on the detected intensity, a servo unit to generate the actuator driving voltage and a predetermined threshold voltage based on the gap error signal generated by the light intensity detection unit and to provide the actuator driving voltage to the actuator, a distance detection unit to detect a first distance at which the actuator driving voltage is maintained when the threshold voltage is detected using the gap error signal and to detect a second distance at which a gap between the light focusing element and the disk is shorter than the first distance and at which a gap servo operation is started based on the

Abstract: In a method for adjusting a focus position for an optical disc, onto/from which in formation is recorded or reproduced, while adjusting the focus position of an optical reproducing means, upon a recording surface of an optical information recording medium having an area where information of the optical information recording medium is recorded in advance, comprising the following steps of: memorizing plural numbers of information relating to focus positions determined appropriately, which can be obtained from the area where the information of the optical information recording medium is recorded in advance; and adjusting the focus position for the optical disc loaded into an apparatus, from at lease one (1) signal relating to the focus position, which can be obtained from the optical disc, with utilizing a relationship between the plural numbers of information relating to the focus positions determined appropriately, memorized in advance, when reproduction of the information is impossible when the optical disc

Abstract: An optical disk device includes an optical pickup, a focus drive section, a detection section, a time measurement section and a disk identification section. The detection section detects reflected light reflected from an optical disk while the focus drive section moves a focus position of the optical pickup. The time measurement section measures a focus search time between when the reflected light reflected from a disk surface of the optical disk is detected and when the reflected light reflected from an information recording layer of the optical disk is detected. The time measurement section measures a false reflection search time between when the reflected light reflected from the disk surface is detected and when false reflection light is detected. The disk identification section calculates a ratio of the focus search time to the false reflection search time, and identifies a type of the optical disk based on the ratio.

Abstract: An optical disc machine initially identifies a disc positioned in it by moving the focal point of its optical pick-up unit between an outer surface and an interior reflective data carrying surface. The time required for the focal point to travel between the two reflective layers, proportional to the distance between the layers, is compared with one or more thresholds to identify the type of disc present. Example types are CDs and DVDs that can be distinguished from each other because of different distances between their two layers. Variations in the velocity of a motive source that drive the focal point to traverse the disc are compensated in order to avoid erroneous measurements of the distance between reflective layers, and thus to avoid misidentifying the disc types. Different types of DVDs or CDs may also be identified by measurement of reflected light intensity with respect to a threshold that is updateable.

Abstract: An optical pickup device or an optical disk device includes: a light source 11 that emits a laser beam toward an optical disk 25; an optical receiver 18 that detects light reflected from the optical disk 25; and an astigmatism-generating element 31 that generates light used for focus control in a condition where a focusing position on one of two perpendicular cross sections including an optical axis of the light reflected from the optical disk 25 is located ahead of the optical receiver 18 and a focusing position on the other cross section is located behind the optical receiver 18. The astigmatism-generating element is a Fresnel mirror 31a configured to include a plurality of reflecting mirrors, and an imaginary surface 31d that connects the tips of the reflecting mirrors is curved in a concave shape toward a light incidence side.

Abstract: An optical data processing apparatus reads and/or writes data from/on a data storage medium, in which first and second data storage layer are stacked. The apparatus includes: a light detector including at least one photodetector for generating a light quantity signal; a detecting optical system for guiding reflected light beams from a storage layer; and a signal processor for generating a layer sensing signal from the light quantity signal and determining, by the layer sensing signal, the type of data storage medium. The light detector includes a layer sensing photodetector arranged in view of an of an area of the light detector, and further includes a photodetector which is different from the layer sensing photodetector which receives the reflected light beam to generate a focus signal.

Abstract: A method and apparatus for compensating tilt. The tilt compensation method includes: obtaining one of a jitter best, an RF envelope, and a focus DC offset (FODC) from a detection signal of the ROM data region and determining whether the obtained value is within a tolerance range; and obtaining an initial skew compensation value using the obtained value when the obtained value is within the tolerance, changing the magnitude of current applied to an actuator designed to perform driving in at least three-axis directions to drive an objective lens of an optical pickup assembly in a radial tilt direction when the obtained value is not within the tolerance range, and repeating the obtaining of one of the jitter best, the RF envelope, and the FODC and changing the magnitude of the current until the obtained value is within the tolerance range.

Abstract: Disclosed is a tilt controlling method and apparatus in which an FE signal track at a point where an RF signal is the maximum or an RE signal track at a point where a jitter is the minimum is detected as a tilt control signal to induct a DC component according to the disk shape and an AC component according to the surface vibration of the disk. Further, the fact is used that an RF envelope has a maximum value when the disk is parallel to an object lens or there is no tilt. Thus, in a tilt initialization step, a tilt track as the RF Max. is obtained for one rotation and the central potential of this track is set as a tilt control reference voltage, and when the RF envelope becomes a phase corresponding to a condition of a controller or a differential value of the RF envelope in the tilt window signal becomes a desired phase, tilt control is started so that the RF envelope always has the maximum value.

Abstract: An optical disk apparatus according to the present invention is an optical disk apparatus for performing at least one of: recording data to a plurality of types of optical disks including a recordable optical disk and a read-only optical disk which are produced according to the BD specifications; and reproducing data from the optical disks. This apparatus includes: a means (506, 507) for irradiating a management area 502 of an optical disk 501 with a light beam while not performing tracking control, and generating a track position signal (push-pull TE or phase difference TE) from light which is reflected by the management area 502; and a disk determination means for determining, based on the track position signal obtained from the management area 502, whether the optical disk 501 mounted in the optical disk apparatus is a recordable optical disk or a read-only optical disk.

Abstract: A high density optical disc that can be driven changeably with the existent optical disc by the same driving apparatus. On the recording surface of the optical disc, a light transmissive layer with a thickness of about 0.2 to 0.4 mm is formed. The recording face is accessed by allowing a light beam with a wavelength of 395 to 425 nm in a spot shape to be irradiated onto it. Also, the light beam is converged in a spot shape by an objective lens having the numerical aperture of about 0.62 to 0.68.

Abstract: An optical pickup device capable of correcting an off-tracking which is ascribable to a phase shift of a differential push-pull signal waveform, even when an optical disk or an objective lens is tilted along a radial direction of the optical disk, so that stable tracking control can be performed; and, an optical disk apparatus comprising such an optical pickup device.

Abstract: The invention relates to a method for optimized tracking of an optical scanner along a track of an optical recording medium, the track having information markings arranged in dense succession, and also having fundamental changes in properties in significantly lower density. The method has the following steps: formation of a track error signal, detection of the occurrence of fundamental changes in properties of the track, formation of an offset value from the comparison of the value of the track error signal that occurs shortly before and shortly after the fundamental change in properties, formation of the track error signal, taking account of the offset value and repetition of the aforementioned steps.

Abstract: An optical data processing apparatus reads and/or writes data from/on a data storage medium, in which first and second data storage layer are stacked, by radiating light from the second layer. The processor includes: a light detector including at least one photodetector for generating a light quantity signal; a detecting optical system for guiding first and second reflected light beams from the first and second layers to the light detector; and a signal processor for generating a layer sensing signal from the light quantity signal and determining, by the layer sensing signal, whether the focal spot is now located near the first layer or the second layer. The detecting optical system includes an optical element that produces astigmatism to the first and second reflected beams.

Abstract: A method for adjusting a focus bias in an optical disc drive comprises the steps of: rotationally driving an optical disc in a state that only focus servo is engaged without engaging tracking servo; driving an actuator of an optical pick-up so that a laser beam projected from the optical pick-up is moved in a tracking direction to obtain an HF signal; and determining a focus bias by which a proper focusing point can be obtained based on the HF signal. The driving of the actuator is carried out by supplying an actuator drive control signal to a tracking actuator of the optical pick-up in a state that tracking servo is not engaged.

Abstract: Whether an optical disc is a first optical disc or not is determined with reference to at least one of first and second focus error signal amplitude values. Then, if a sum value of the addition of a first focus balance signal value (CD-FBAL signal value) to a second focus balance signal value (DVD-FBAL signal value) is equal to or more than a predetermined threshold value, the signal surface of the optical disc is determined to be a CD signal surface of a dual disc. On the other hand, if the sum value is smaller than the predetermined threshold value, the signal surface of the optical disc is determined to be a DVD signal surface of a DVD or a DVD signal surface of a dual disc.

Abstract: The invention relates to a method of optimizing an optical drive system 101 capable of recording and/or reproducing data to and from an optical carrier 102, such as the high number of different types present e.g. a CD, DVD-SL, DVD-DL, HD-DVD or BD carrier More specifically, the invention relates to improved radial tracking error signal in the optical drive system and thereby alternatively or additionally also improved carrier recognition in the optical drive system. Disc recognition may be a cumbersome procedure due to influences such as the high number of carrier types present, the tolerances specified for and quality of the carriers, the tolerances within the optical system. E.g.

Abstract: The present invention relates to a focus control apparatus and method of controlling focus of a radiation beam onto a first spatial level of a record carrier, wherein a focus control loop is locked onto a reflection signal obtained from a second spatial level located at a predetermined distance from said first spatial level, and is then opened to move an objective means towards the second spatial level by a predetermined amount related to the predetermined distance. This stepwise procedure enlarges the margin for mechanical overshoot and hence reduces the risk of bumping into the disc. Additionally, no ambiguous focus error signals are detected and robustness of initial focusing is improved if a thin transparent cover layer is present.

Abstract: An optical disk apparatus includes a rotary driving unit rotating an optical disk which is flexible, an optical pickup irradiating light upon a recording surface of the optical disk on which writing/reading of information is performed, a stabilizing unit stabilizing vibration of the optical disk in a rotary axial direction by using pressure difference of air flow at least on a portion where writing/reading is performed, and being disposed on a side of the optical disk opposite to a side on which the recording surface is provided, and a control-adjustment unit analyzing a value of a tracking error signal of the optical disk obtained by scanning along a groove of the optical disk with use of the optical pickup, comparing the analyzed value of the tracking error signal of the optical disk and a value priorly obtained by scanning along a groove of a standard disk prepared beforehand, and adjusting a positional relation between the optical disk and the stabilizing member in a three dimensional space according to t

Abstract: A method for detecting whether vertical deviation of an optical disc occurs is provided. First, before a pickup head is successfully focused on the optical disc, a pickup head is actuated based on an input control signal so as to generate a focus error signal with a plurality of S-curves. Then, a plurality of zero crossing points of the S-curves in the focus error signal is identified and a plurality of input control values respectively corresponding to the zero crossing points is obtained. A variation of the input control values is then calculated. Whether vertical deviation of the optical disc occurs can be determined according to the variation of the input control values.

Abstract: A method of identifying an optical disc is disclosed. The method includes enabling an optical pick-up unit to emit a first laser beam having a first wavelength to the optical disc; controlling the optical pick-up unit to move a focus point of the first laser beam in a direction of thickness of the optical disc; obtaining a first focus error (FE) signal corresponding to the first laser beam; counting a first s-curve number corresponding to s-curve occurring in the first FE signal; and identifying the optical disc according to the first s-curve number.

Abstract: A calibration of a focus error signal gain in a focus servo system of an optical disk drive is presented. The focus error signal gain can be calibrated by oscillating an optical pick-up unit in a focus direction through a focus point and determining a focus sum threshold. The optical pick-up unit can then be oscillated around a focus control effort that results in a sum signal equal to the focus sum threshold and the peak-to-peak value of a focus error signal can be measured. The focus error signal gain can be determined from the peak-to-peak value of the focus error signal.

Abstract: The invention relates to a disc discriminating method and an optical disc information reproducing apparatus wherein DVD-RAM which is DVD-RAM1 or DVD-RAM2 and DVDRW which is DVD-RW or DVD+RW which cannot be respectively determined based upon distance from the surface of a disc to the recording face, the number of recording faces and the reflectance can be discriminated. In case an optical disc is DVD-RAM or DVDRW, the amplitude of a push-pull tracking error signal is measured by a microcomputer in a state in which servo control is executed based upon a focus error signal. Determination is performed based upon the amplitude of the push-pull tracking error signal, when the amplitude of the push-pull tracking error signal is larger than a predetermined value, the optical disc is judged as DVD-RAM and when the amplitude is smaller than the predetermined value, the optical disc is judged as DVDRW.

Abstract: An optical head with excellent optical characteristics even when using a light source that substantially has a wavelength broadening is provided. The optical head includes a light source, an objective lens for focusing a light beam emitted from the light source on an information recording medium and a photodetector for detecting the light beam reflected from the information recording medium, wherein defocusing correction means and spherical aberration correction means are provided in an optical path between the light source and the information recording medium. Since both the defocusing correction means and the spherical aberration correction means are provided, while defocusing of a focused spot on the information recording medium caused by a wavelength broadening of the light source and chromatic aberration of the optical system can be corrected, the spherical aberration of the optical system caused by wavelength difference between a design wavelength and an incident wavelength also can be corrected.

Abstract: An optical disk apparatus includes a light emitting unit, a light detecting unit, a tracking error signal generating unit, and a tracking control unit. The light emitting unit emits a single light beam onto an optical disk. The light detecting unit includes at least three light detecting portions, each being configured to receive light reflected off the optical disk and produce corresponding output. The at least three light detecting portions are arranged in a track direction of the optical disk. The tracking error signal generating unit generates at least two types of the tracking error signal using the outputs from the at least three light detecting portions. The tracking control unit performs tracking control on the optical disk on the basis of the tracking error signal.

Abstract: An optical disc reading and reproducing apparatus includes reading means for reading data recorded on an optical disc by applying laser light through an objective lens and detecting its reflected light, focus control means for performing focus control for moving the objective lens based on a focus error signal indicating an amount of deviation of a focusing position, focus bias adjustment means for adjusting a focus bias used in the focus control to a voltage in which amplitude of an acquired RF signal is maximized, and detection means for detecting that the amplitude becomes smaller than a predetermined threshold level. The focus bias adjustment means samples the RF signal and acquires the amplitude, sets the focus bias to the amount in which the amplitude of the RF signal is maximized, and stops sampling of the RF signal when the amplitude is detected to be smaller than the predetermined threshold level.

Abstract: This invention provides an optical disc device and method for discriminating between DVD and HD-DVD more rapidly. After an optical pickup has been stopped above a data region on the optical disc, a tracking error signal generator acquires amplitude “Vdpp” based on a DPP method and amplitude “Vdpd” based on a DPD method as tracking error signals. A disc discriminator discriminates the kind of optical disc by comparing the acquired “Vdpp” and “Vdpd” data with a threshold level “Vth”. Alternatively, the optical pickup is stopped above the data region and a system lead-in region on the optical disc, and then amplitude values “Vdata” and “Vlead” of tracking error signals are acquired and compared.

Abstract: An optical disc reading and reproducing apparatus includes reading means for reading data recorded on an optical disc by applying laser light to the disc through an objective lens and detecting reflected light, focus control means for performing focus control for moving the lens based on a focus error signal, and focus bias adjustment means for adjusting a focus bias to a voltage in which amplitude of an RF signal acquired by the reading means is maximized. When a difference between addresses of a focus bias adjustment information and at which data is read exceeds a predetermined amount, and amplitude of the RF signal is smaller than the amplitude of the RF signal stored, the focus bias is readjusted and the stored focus bias adjustment information is updated to the amplitude of the RF signal after this readjustment and the address of the track to which the focus bias is adjusted.

Abstract: A method of discriminating an optical disc type and an apparatus thereof. The method for an optical disc system of recording and/or reproducing an optical disc that includes an optical pickup having a laser diode, an object lens, and a light receiving device, checks a track error signal while moving the object lens to upward/downward, and discriminates an optical disc type by using the magnitude of the checked track error signal. The method and apparatus discriminate the disc type in the initial stage of focusing where the object lens moves to upward/downward.

Abstract: A focusing controller and the method thereof for an optical disk drive. The focusing controller includes a filter, a coupler and a focus compensator. The filter filters out a high-frequency component of the track error signal and derives an adjusted signal, while the coupler eliminates the adjustment signal from the focusing error signal so as to generate a coupled signal. The focus compensator generates a focus control signal used for controlling a position of the pick up head of the optical disk drive according to the coupled signal during a focusing operation.

Abstract: While reproducing information on an optical disc, an optical disc apparatus varies a focus balance value in both positive and negative directions from a currently set value thereof by ±a which will not affect reproduction operation, measures jitter levels c and d of a reproduced signal when the focus balance value is varied in the positive and negative directions, and calculates a difference e=c?d between the measured jitter levels. If this difference e exceeds a threshold value f, the optical disc apparatus varies the focus balance value by a specified amount g in a direction in which the difference e approaches 0, thereby updating the current focus balance value.

Abstract: When a type of an optical disc is discriminated by disc type discriminating processing, search operation by a CD light beam is carried out in CD discriminating processing, and a distance from a position xf where a large signal change of a first time is detected as a fake phenomenon to a position xs where the large signal change of a second time corresponding to a recording layer is detected as a moving distance d3. Based on the moving distance d3, whether the optical disc is a CD medium is determined. In this manner, whether the optical disc is the CD medium or not can be determined correctly with high precision.

Abstract: Plural grooves or lands formed in an information recording carrier include at least a wobbling region and data is recorded wobblingly in this wobbling region by phase shift modulation while recorded digitally with a single or multiple waves as a channel bit.

Abstract: In a multilayer optical disc having information layers conforming to a plurality of different optical disc standards, because the type of each information layer is not recorded in the other information layers, in read and write operations by a compatible optical disc device conforming to a plurality of optical disc standards, every time the information layer being accessed changes, it has been necessary to read the type of the information layer and select a method of generating a tracking error signal adapted to the type of information layer, so access has taken time. In order to solve the above problem, in the optical multilayer disc according to the present invention, having information layers conforming to a plurality of different optical disc standards, in an area in one of the information layers, information about the other information layers is recorded. The time required to access the other information layers can be reduced by using this information to select a tracking error signal generating method.

Abstract: In a signal processing device, a 3-beam TE signal generation circuit generates a tracking error signal by a 3-beam method (3-beam tracking error signal), and a DPD TE signal generation circuit generates a tracking error signal by a DPD method (DPD tracking error signal). A TE signal variation detection circuit detects a variation in 3-beam tracking error signal. A TE signal generation method switch circuit selects and outputs the 3-beam tracking error signal initially, and if the TE signal variation detection circuit detects a variation, selects and outputs the DPD tracking error signal.

Abstract: The invention is disclosed a method for promptly protecting a voice coil motor in an optical disk drive. A step (A) allows a data signal processor (DSP) to execute a protect module of the voice coil motor every preset time interval. In a step (B), the DSP executes following further steps during executing the protect module. A step (b1) reads tracking error (TE)/focusing error (FE) and determines if the TE/FE is over a safety range. A step (b2) starts a gain decrease operation of a signal amplifier if the TE/FE in step (b1) has been over the safety range for more than the first preset number of times so as to lower the control current outputting to the voice coil motor. A step (b3) starts an operation of speed reduction and a low current operation of a controller to secure the voice coil motor being safe if the TE/FE in step (b1) has been over the safety range for more than a second preset number of times.

Abstract: An optical disc apparatus according to the present invention steadily performs a focus jump operation and a track-crossing seek operation relative to an optical disc having a plurality of recording layers. A signal processing section generates a focus error signal based on a conventional astigmatism detection (CAD) system and a focus error signal based on a differential astigmatism detection (DAD) system from a detection signal generated by an optical detector. When a focus jump is to be performed from one recording layer of the optical disc to another recording layer, a focus drive signal that is generated from the focus error signal based on the CAD system is used. When a read/write operation is to be performed in relation to one recording layer, a focus drive signal that is generated from the focus error signal based on the DAD system is used.

Abstract: A plurality of types of writable discs on which wobbles having a predetermined frequency containing absolute addresses and/or various pieces of information on the writable discs can be discriminated by controlling only focusing and using an amplitude of a wobble signal or a wobble PLL lock signal that has passed through a phase locked loop. Accordingly, a discrimination time can be reduced and a disc in an unrecorded state can also be discriminated.

Abstract: A push-pull signal Spp fetched with tracking open is smoothed to a smoothing signal Spp to remove signal components generated wobbling due to radial runout, and the smoothing signal is binarized to compute an autocorrelation value in the autocorrelation computing circuit 210. This computing is made by multiplying the binarized signal by a signal delayed by the half cycle and sign-negated to compute the integrated value, and the integrated value output signal Dint is generated. A maximum value of the integrated value output signal Dint within a predetermined period of time is computed by the maximum value holding circuit 220 to output a maximum value output signal Dout. Depending on the amplitude of the maximum value signal Dout, the CPU 105 determines whether the recording medium is a writable one or read only one. Wobble determination can be made keeping tracking open, and a type of a recording medium is carried out accurately.

Abstract: A method for calibrating a center error signal in an optical disc system, comprising the steps of (i) measuring a peak-to-peak value of the center error signal, (ii) computing a nominal peak-to-peak value of the center error signal after locking to a particular track of an optical disc, (iii) computing the nominal peak-to-peak value of the center error signal for a run-out condition, and (iv) defining a calibration gain for the current value for the center error signal.

Abstract: An adjustment apparatus for adjusting an optical pickup capable of recording and/or reproducing optical discs of different sorts. The adjustment apparatus is an adjustment optical disc having a first signal recording layer of a physical format in common with a CD and a second signal recording layer of a physical format in common with a DVD. On the first and second signal recording layers, there are concentrically recorded EFM modulated data. The respective signal recording layers are provided with recording areas that are not overlapped with each other.