Abstract: A disk reading apparatus includes a binarizing unit 5 for binarizing a tracking error signal 21 with a hysteresis width and for generating a track count signal 22, a jump unit 8 for causing track-jump on the basis of the track count signal 22, a malfunction detecting unit 9 for transmitting a malfunction signal 24 when level inversion occurs to the track count signal 22 while follow of the track is being implemented, and a control unit 15 for widening the hysteresis width when the pickup 1 is caused to follow the track, and for narrowing the hysteresis width when the pickup 1 is caused to track-jump.

Abstract: An optical disc system for efficiently controlling a sled motor is provided. The optical disc system has a sled motor for moving an optical pick-up; a digital servo core to generate a first and a second sled control signal; a microcomputer for generating a selecting signal, a third and a fourth sled control signal for controlling the sled motor; a first and a second selecting unit for receiving the selecting signal and selecting and outputting one of the first and third sled control signals and selecting and outputting one of the second and fourth sled control signals, respectively; and a third and a fourth selecting unit for respectively receiving the outputs of a first and second digital-to-analog converters and generating the respective outputs of the first and second digital-to-analog converters in response to the selecting signal to the sled motor.

Abstract: An optical disk device reproduces an RF signal by projecting a light beam on an optical disk and detecting a reflected light therefrom. On the optical disk, information is recorded by forming a pit on a track determined according to a groove having a wobble signal recorded thereon. The optical disk device comprises a comparator comparing the RF signal with a threshold value so as to output a binary signal, a first band-pass filter filtering a frequency band of the wobble signal from the binary signal so as to extract a wobble signal component, and a first adder obtaining a value by adding the wobble signal component to a fixed reference value so as to supply the value to the comparator as the threshold value.

Abstract: A light-pickup device has a constitution in which a microcomputer executes control for applying offset voltage to a focus error signal by changing over connection of an FE offset circuit when a servo-processor kicks focus drive voltage for acceleration in order to change over information recording layers of an optical disk having two information recording layers on a plane thereof. Then, a signal output level at a zone in which no focus error signal is occurred, does not coincide with focus zero cross. Owing to this constitution, the servo-processor detects focus zero cross point of the focus error signal even in a simple circuit structure.

Abstract: An optical disk apparatus includes: a light irradiator operable to converge a light beam and irradiate an information carrier with the converged light beam; a moving means operable to move the light beam in a direction traversing a track formed on a surface of the information carrier; and a tracking controller operable to control the moving means to scan the track with the light beam. The tracking controller includes a deviation detector operable to generate a detection signal, a tracking driving means operable to generate a driving signal, an integrator operable to integrate a magnitude of a signal corresponding to the driving signal over a predetermined time period and an abnormal state detector operable to detect an abnormal state of the moving means based on an output of the integrator.

Abstract: An apparatus for scanning optical recording media, having a detection unit with a photodetector and a reference voltage associated therewith, an evaluation unit having an input, and a connection disposed between the detection unit and the input of the evaluation unit. In such scanning apparatuses, voltage coupling is usually provided between the detection unit and the input of the evaluation unit. Such a coupling arrangement has the disadvantage that the two units must operate in approximately the same voltage range. In the scanning apparatus according to the present invention it is not necessary for the detection unit and the evaluation unit to operate in substantially the same voltage range. According to the present invention, the evaluation unit has a controller, that holds the input of the connection at the value of a reference voltage of the detection unit.

Abstract: A system for detecting a tracking error comprises a two-divided type light detector (2), LPFs (4a, 4b), first and second waveform generator (5a, 5b), first and second delay circuits (6a, 6b), first and second adders (7a, 7b) and a phase comparator (8). The detector (2) has two photo detecting elements (2a, 2b) disposed separately in the radius direction of an optical disc. The LPFs (4a, 4b) remove high frequency components from the outputs of the elements (2a, 2b). The first waveform generator (5a) generates a sine wave (B1) with amplitude corresponding to the output level of a signal (A1), which passed the LPF (4a). The second waveform generator (5b) generates a sine wave (B2) having the identical frequency to the wave (B1), with amplitude corresponding to the output level of a signal (A2), which passed the LPF (4b). The first delay circuit (6a) delays the wave (B1) by the prescribed amount of delay to form a sine wave (C1).

Abstract: A robust Artificial Neural Network controller is proposed for the motion control of a magnetic disk drive voice coil motor (voice coil motor). The neural controller is used to approximate the nonlinear functions (actuator electromechanical dynamics) of the voice coil motor while having on line training. One main advantage of this approach, when compared with standard adaptive control, is that complex dynamical analysis is not needed. Using this design, not only strong robustness with respect to uncertain dynamics and non-linearities can be obtained, but also the output tracking error between the plant output and the desired reference can asymptotically converge to zero. Additionally, standard offline training, utilizing training vectors to stimulate the voice coil motor, is not required.

Abstract: A disk apparatus includes a DSP (digital signal processor), and a DSP core of the DSP receives a feedback input from a pick-up, and generates a focus control pulse and a tracking control pulse. That is, a focus servo loop and a tracking servo loop are formed. The DSP core detects a phase difference between a sine wave of a target frequency and a sine wave superposed on an input signal, and adjusts a gain of the servo loop so as to bring a DC component of a correlation signal correlated with the phase difference to a 0 level. More specifically, if the DC component of the correlation signal exceeds a predetermined threshold value, an adjusting amount of the gain is rendered large, and greatly brought closer to the 0 level. On the other hand, if the DC component of the correlation signal is equal to or less than the predetermined threshold value, the adjusting amount of the gain is rendered small, and gradually brought to the 0 level.

Abstract: Apparatus and method for scanning a surface. An optical system generates a light beam to illuminate a surface. A carrier supports the surface for reciprocating motion with respect to the light beam to form one axis of a raster. A propulsion system moves the carrier at a substantially constant speed and a position sensor provides an output signal representing the surface position with respect to the light beam. A control system responsive to the output signal modulates a sample period reciprocally to carrier speed to achieve substantially constant scan length per sample and to control data acquisition timing.

Abstract: An optical disk apparatus capable of suppressing displacement of a servo system from a track even when a track defect is caused on an optical disk and achieving appropriate data recording and reproduction. In the case where any track defect is detected on an optical disk, a pulse width modulation signal, rather than a tracking servo signal created based on a tracking error signal, is used as a servo signal to drive an optical pick-up. The pulse width modulation signal is modulated such that its DC level becomes identical to a DC level of a tracking servo signal obtained immediately before detection of the track defect.

Abstract: Disclosed is a method of tracking control for an optical disc recorder and reproducer, which includes the steps of detecting a land/groove switching position, storing tracking error signals for a predetermined time if the land/groove switching position is detected, obtaining a mean value of the stored tracking error signals, and judging whether the mean value is larger than a predetermined permissible tracking level, and if it is judged that the mean value is larger than the predetermined tracking level, determining a direction of a track center, correcting the track center, and compensating for a DC offset.

Abstract: An apparatus for determining an information record medium is provided. The apparatus includes an emitting device, a light receiving device and a determining device. The emitting device respectively emits a plurality of light beams whose wave lengths are different from each other. Then, the light receiving device receives respective reflection lights from an information record medium of the emitted respective light beams, and outputs light reception signals respectively corresponding to the received reflection lights. After that, the determining device determines a type of the information record medium in accordance with a ratio between the outputted respective light reception signals.

Abstract: An optical disk device in which data is written to or reproduced from an optical disk having an area which contains a header section and another area which does not contain a header section. When a track deviation of an optical pickup occurs, it is detected whether or not a signal representing the header section is contained in the return light signal from the optical disk. When a signal representing the header section is contained in the return light signal, it is determined that the optical pickup is located in an area which contains a header section and tracking is controlled through a push-pull method etc. On the other hand, when a signal representing the header section is not contained in the return light signal from the optical pickup, it is determined that the optical pickup is located in an area which does not contain a header section and tracking is controlled through differential phase detection etc.

Abstract: An optical information recording medium according to the present invention includes at least one groove track and at least one land track allowing information to be recorded on or reproduced from the groove track and the land track, the groove track and the land track adjoining each other. The optical information recording medium further includes: an identification signal region including a pre-pit array, the pre-pit array indicating identification information concerning the groove track and the land track; and a servo control region disposed ahead of the identification signal region along the groove track and the land track, the servo control region including wobble pits positioned so as to shift to opposite sides of a center line of either the groove track or the land track.

Abstract: An optical recording/reproducing apparatus comprises a light beam emitting unit which emits a plurality of light beams to the recording medium, a photodetection unit which detects the reflected light beams and output detection signals, a detection signal selection unit which selects one of the detection signals according to one of a plurality of tracks which is selected in order to record or reproduce data, the tracks being formed on at least one of the land and the groove, and a tracking control unit which make one of the light beams trace the track which is selected in order to record or reproduce data, according to the selected detection signal.

Abstract: An optical disk device for driving an optical disk having an emboss section and a data section comprises an optical pickup for replaying address information by irradiating a laser beam onto the emboss section of an optical disk and writing data by irradiating the laser beam onto the data section of the optical disk, and a control unit for controlling the focus position when address information is replayed at the emboss section and the focus position when data are written onto the data section to a common focus position. By using the common focus position as the focus position when the emboss section is replayed and as the focus position when the data are written to the data section, it is possible to eliminate any need for rapidly switching the focus position at the boundary between the emboss section and the data section.

Abstract: A disk apparatus includes a DSP core, and executes processing for focal point positioning when turning on the power to the apparatus main body or exchanging the MO disk. The DSP core detects maximum and minimum values of outputs (focus error signal) of an FE signal detector circuit while moving the objective lens from an uppermost position of not contacted with a disk surface to a lowermost position. The DSP core calculates a middle position using positions of the objective lens upon fetching maximum and minimum values (uppermost and lowermost positions). Subsequently, the DSP core determines a range narrower than a range to be determined by the uppermost and lowermost positions, by the use of the middle point and amount of surface deflection of the MO disk. Then, the DSP core wobbles the objective lens within the narrow range and detects a focal point based on a level of the focus error signal.

Abstract: Focusing balance adjustment of adjusting a servo mechanism is executed so that reproduction quality is optimum in a state where a focusing servo is active (#5). Thereafter, tracking balance adjustment of adjusting the servo mechanism is executed so that a tracking balance deviation is cancelled which is an amplitude difference between the upper side and lower side relative to a reference level of a waveform generated in a tracking error signal when the focal point of a light beam applied to the disk crosses a track of the disk (#7).

Abstract: An optical disc drive equipped with a TLN signal generating apparatus is disclosed. The TLN signal generating apparatus includes a TLN signal generating circuit for generating a TLN signal (track loss signal) based on signals obtained from an optical pick-up; a digitizing circuit for digitizing the TLN signal by comparing it with a reference level; and a correction circuit for correcting the TLN signal so that it is accurately digitized by the digitizing circuit irrespective of an offset component which is a direct current component contained in the TLN signal.

Abstract: A focal detecting means (35) of a controller (25) controls an actuator driver (38) to actuate an actuator (12) to vibrate an objective lens (3) in a direction along an optical axis. An output of a focus error signal from a signal generator (27) is checked by a signal detecting means (46) and presence of a workpiece is determined when the signal is detected. When the presence of the workpiece is detected, the focal detecting means (35) moves the objective lens (3) along the optical axis by the actuator (12) and a focus position is recognized with reference to a position signal from a position detecting means (49) together with the focus error signal, where the objective lens (3) is moved to the focus position for focusing.

Abstract: A recording/reproducing medium having grooves, a land formed between the grooves, and land prepits formed on the land in which each of said land prepits has a most optimum design condition where a ratio (LLP Level/offset) between a voltage amplitude (LLP Level) of a land prepit detection signal and an offset level (offset) of an RF signal becomes more than about 10 or where an amplitude change of an RF signal through the land prepit becomes minimum. The recording/reproducing medium can be one of a DVD-R and a DVD-RW.

Abstract: Through a provision of a level holding circuit in a focus servo mechanism for an optical disk reproducing device, a detection signal level with regard to a focusing position error, when a detection signal corresponding to a received optical beam amount shows a maximum value under a condition when not being changed over to an automatic focus loop, is sampled as an offset amount and, is held in advance in the level holding circuit, and the thus held level is utilized for effecting an automatic focusing under a just focusing servo condition.

Abstract: Writing predetermined data pattern to an allocated segment of a disk drive and appropriately reading that one data pattern while varying the read focus characteristics provides for efficient and effective read focus optimization in an optical disk drive. In order to produce helpful data, the read focus offset is varied while reading the different segments of the data pattern, thus producing read out signals with different peak to peak amplitudes. This is compared to data which is obtained by reading the same data pattern while the offset is held constant. Optimization of the read focus offset is carried out and made possible by appropriate analysis of the waveforms produced when reading the predetermined data pattern in these two reading passes. By appropriately tracking the results of the various read focus offsets, an optimum read focus offset can be easily determined.

Abstract: An optical disk drive for accessing data stored on a compact disc has a housing, a sled sliding inside the housing, a driving device for driving the sled, an actuator installed on the sled, a servo device for providing a push force to drive the actuator, a control circuitry for controlling operations of the optical disk drive, an adaptive compensator, and an error signal generation circuit. The actuator can move within a predetermined range on the sled, wherein the predetermined range includes a linear region and a non-linear region. It is desirable to keep the actuator within the linear region of the predetermined range. For this, an adaptive compensator is used to provide a supplementary force to the sled when the actuator is near the non-linear region.

Abstract: An optical disc playback apparatus selectively plays back a plurality of optical discs having different numbers of recording layers and/or different positions of recording layers in the thickness direction of the optical disc. In the optical disc playback apparatus, a light beam is applied to a loaded optical disc, and reflected light from the optical disc upon application of the light beam is detected. A signal is generated based on the reflected light which is detected, and the number of peaks of the generated signal and timings at which the peaks are outputted are detected. The type of the loaded disc is determined based on the detected number of peaks and/or the detected timings.

Abstract: The present invention provides a method for guiding a pick-up head to follow an information track. The method comprises the steps of sensing and sending notification of displacement between the pick-up head and the center of the information track, generating a first correction directly proportional to the displacement, generating a second correction non-proportional to the displacement and generating a driving force proportional to the sum of the first and second correction, driving the pick-up head to follow the information track.

Abstract: An optical pickup actuator circuit includes: a lens holder 2 supported so as to be slidable along a support shaft and rotatable around the support shaft and for holding an objective lens 8 so that the objective lens 8 forms an image of a light beam on a desired track on an information recording surface of an optical disk; a focusing coil 7 attached to the lens holder 2; and a focusing magnet fixedly disposed so as to be opposite to the focusing coil 7; wherein two diodes D1 and D2 are parallel-connected in a forward direction between an input end 7a of the focusing coil 7 and the ground so that an input voltage not lower than a predetermined voltage is led to the ground by the two diodes D1 and D2.

Abstract: An apparatus and method for controlling tracking for an optical recording/reproducing apparatus is disclosed. A track center level is determined at a point where a high width of a TE signal generated during free-running or traverse is equal to its low width. Alternatively, a TE detection level at a TZC point of the TE signal in which asymmetry is adjusted is determined as the track center level. The determined track center level is used for normal recording/reproduction, so that the tracking servo is activated at the actual track center position. Thus, initial stable tracking performance can be obtained, and bias of the tracking can be avoided during tracking control by estimating the exact track center value.

Abstract: An optical disk apparatus comprising a device for moving a focal point of a light beam for reproducing information recorded on an information face of a disk, in the direction perpendicular to the information face; a device for detecting a reflected light from the disk; and a device for discriminating whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate. In this apparatus, a maximum value AS1Lmax of an output signal from the reflected light detecting device and a maximum value ENVmax of an amplitude of an information reproducing signal are detected while driving the focal point moving device so that the focal point passes through the information face, and the discriminating device discriminates whether the disk set in the apparatus is a disk having a thick base substrate or a disk having a thin base substrate, on the basis of the ratio of ENVmax to AS1Lmax.

Abstract: An optical head eliminates an disturbance which occurs in a focus error signal in association with the decentering of an optical disk when an optical spot crosses a track on a storage film surface, and in addition the optical head cancels an off-set which occurs in a tracking error signal in association with the movement of an objective lens. In the constitution of the optical head, phases of wave surfaces of ±1st order diffracted lights are shifted by an amount of &lgr;/2 with a common period by using a phase-inverted diffraction grating the phase of which is inverted with a period of D &lgr;/(2P . NA) in a radial direction of the optical disk, thus causing, on the optical disk, sub-spots to be located on the same track as a main-spot. Taking advantage of this location, focal point shift error signals of the main-spot and the sub-spots are added to each other with an appropriate gain ratio, thereby making it possible to cancel the disturbance which occurs in the focus error signal.

Abstract: Test pattern data is recorded on a track of the optical disc, and the other pattern data is recorded on the neighboring track. A focus bias value providing the minimum jitter amount when the test pattern data is reproduced with varying the focus bias, is obtained. Just focusing condition is attained by the focus servo using the focus bias. When the test pattern data is reproduced, the data of these neighboring track is also reproduced simultaneously because the pattern data of the type different from the test pattern data is also recorded on the neighboring track. Particularly, under the defocusing condition, crosstalk amount becomes larger because the beam shape is distorted. With reference to jitter amount, such a mistake that the defocusing condition is erroneously determined as the just focusing condition can be eliminated. That is, the focus servo signal providing the accurate just focusing condition can be obtained.

Abstract: An optical pickup device comprises a semiconductor laser, an optical system which converges light projected by the semiconductor laser onto an optical disk and directs reflected light from the optical disk to a photoreceptor element, and a photoreceptor element which detects the reflected light; the photoreceptor element including at least two main photoreceptive domains divided from one another by a dividing line, which receive reflected light corresponding to a focusing error of the light projected onto the optical disk, and at least one auxiliary photoreceptive domain which detects reflected light which exceeds the main photoreceptive domains in a defocused state; in which the auxiliary photoreceptive domain is provided adjacent to an end of said main photoreceptive domains in the direction of the dividing line.

Abstract: A method and apparatus for controlling reproduction of an optical recording medium is disclosed. According to the method and apparatus, a moving direction of an object lens on a disc is detected from a slope of a differential phase detection (DPD) error signal in case that the tracking control of the disc is performed by the DPD error signal, and the tracking control is performed using the detected moving direction of the object lens. Thus, the proceeding direction of the object lens can be easily and accurately detected in the disc from which the detection of a mirror signal is not facilitated, i.e., in the disc whose tracking is controlled by the DPD error signal during reproduction. Since it can be easily discriminated whether the phase of the tracking error signal to be in a track-on state when a track servo is turned on is a land or a groove, the stability of the servo can be secured, and an automatic breaking can be achieved.

Abstract: Apparatus and method for scanning a surface. An optical system generates a light beam to illuminate a surface. A carrier supports the surface for reciprocating motion with respect to the light beam to form one axis of a raster. A propulsion system moves the carrier at a substantially constant speed and a position sensor provides an output signal representing the surface position with respect to the light beam. A control system responsive to the output signal modulates a sample period reciprocally to carrier speed to achieve substantially constant scan length per sample and to control data acquisition timing.

Abstract: For reproducing information recorded on an optical disc, a pickup is used to detect a target track on the disc through an optical beam. In carriage servo control, movement of the pickup is servo-controlled in the radial direction of the optical disc. In this control, a tracking error signal is produced by a preamplifier. A pulse signal is produced, in which the period of the pulse signal is set to a constant amount corresponding to the accuracy of movement of the pickup. The duty ratio of the pulse signal is changed based on characteristic of the error signal, so that a changed pulse signal is produced. The changed pulse signal is multiplied by the tracking error signal, so that a carriage control signal is produced. The carriage control signal is supplied to a carriage motor by a driver, so that the pickup is moved.

Abstract: In order to reproduce signals from a double-layer optical disc having two signal recording surfaces, a focus jump that the focusing of an objective lens from the one signal recording surface to the other signal recording surface is quickly achieved, is necessary. When a focus error signal (FE) from a pickup (60, 70) reaches a predetermined threshold value (Vcomp), a deceleration signal for decelerating the objective lens (42) is supplied to an actuator (47). Preferably, a deceleration pulse voltage is lowered step by step. The deceleration pulse voltage is determined in accordance with the maximum value (DFEmax) of a differential focus error signal (DFE) generated by differentiating the focus error signal (FE). Preferably, the address seeking is done simultaneously with the focus jump. The focus jump is performed in accordance with the layer-to-layer distance which is measured beforehand. The focus jump is performed by using a lens (143) having a controllable focal distance.

Abstract: A control unit positions a laser beam toward a target track on a medium on the basis of a tracking error signal (TES) Y indicative of a positional deviation amount from a track center as a zero point on the basis of return light from the medium. A position signal correcting unit executes a correcting arithmetic operation using a non-linear function such as a quadratic polynomial, a quadratic monomial equation, or the like to the TES Y and outputs a corrected TES Z obtained by correcting detection sensitivity characteristics to desired characteristics so that a feedback is sufficiently performed when a lead-in control to the track center by the control unit is executed.

Abstract: A light receiving element (7) receiving return light from an optical disk has main light receiving sections (7a, 7b) and sub light receiving sections (7e, 7f). A focus error signal is found by computing (Sa+Sf )−(Sb+Se), where Sa, Sb, Se, and Sf represent output signals of the light receiving sections (7a, 7b, 7e, 7f), respectively. Each of the sub light receiving sections (7e, 7f) has a smaller area than each of the main light receiving sections (7a, 7b) has. With the foregoing arrangement, upon access to a multilaminate optical disk in which distances between recording layers are small, respective focus error signals from the recording layers do not interfere with each other, and occurrence of an offset can be suppressed even in the case where an assembly error of the optical element or the like exists.

Abstract: An optical beam (8) in a scanning device is focused on an information layer (3) of a multi-layer optical record carrier. A focus control circuit (22) keeps the focal point (9) of the beam on the information layer. When the focal point jumps to another information layer, the focus control circuit does not monitor the so-called central aperture signal in order not to depend on the presence of information in the information layers. During the jump the characteristics of the feedback loop of the focus control unit are modified to avoid instabilities in the movement of the focal point during the jump. When the focal point is captured on the designated information layer, the characteristics of the feedback loop are restored.

Abstract: In this invention, track address information is recorded at a portion different from a recording track along user data by a land pre-pit, wobbled groove interrupt, wobble stop, or a projecting portion formed at a land/groove boundary. With the address information, the track position can be detected at least once per data length of the minimum recording unit. To increase the recording frequency of tracking error detection information, instead of recording the absolute address value of a track, information representing a position in tracks divided into groups is recorded.

Abstract: A focusing bias adjusting apparatus in an optical recording medium playing apparatus, in which a focusing bias adjustment is executed to remove an offset component in a focusing error signal based on each output signal of a split type photodetector in an optical pickup and, thereafter, a tilt adjustment is executed to an optical system so as to maximize a read signal serving as a sum signal of the output signals of the photodetector in order to compensate a tilt angle which is defined by a normal at the irradiating position of a laser beam from the optical pickup on the recording surface of an optical recording medium and the optical axial direction of the laser beam. When the tilt adjusting operation of the optical system of the optical pickup is performed after completion of the focusing bias adjustment, the focusing bias adjustment is executed again.

Abstract: An optical pickup provided opposed to an optical disc D is moved in the optical axis direction with a drive signal from a focus search circuit to detect, with an amplitude detecting circuit, the character “S” shape waveform of large amplitude corresponding to the recording surface of optical disc of the focus error signal FE obtained from the optical pickup and such detected output is counted by a counter. When the character “S” shape waveform of large amplitude appears twice, an interval thereof is measured with a time measuring circuit and width of interval is detected with an interval detecting circuit. The counted value of counter and detected output of the interval detecting circuit are supplied to a microcomputer to automatically detect a type of optical disc. Thereby, a reproducing device which can be used for a plurality of reflection type optical discs may be structured.

Abstract: An optical disk apparatus includes an optical disk, a laser source, an objective lens, an astigmatic element, and a photodetector. Recording tracks are formed in both grooves and lands of the optical disk. The laser source emits a laser beam. The objective lens focuses the laser beam emitted by the laser source to form a fine spot on a recording track of the optical disk. The astigmatic element is placed in a convergent optical system for focusing the beam reflected by the optical disk, to receive the beam reflected by the optical disk and emit an astigmatic beam. The photodetector detects the astigmatic beam emerging from the astigmatic element. The optical disk apparatus serves to perform at least focal adjustment of the objective lens by using a detection signal from the photodetector. A relation 0.8<&lgr;/(Tp·NA)<1.1 is satisfied where &lgr; is a wavelength of the laser beam emitted by the laser source, NA is a numerical aperture of the objective lens, and Tp is a pitch size of the grooves.

Abstract: An apparatus and method for controlling tracking for an optical recording/reproducing apparatus is disclosed. A track center level is determined at a point where a high width of a TE signal generated during free-running or traverse is equal to its low width. Alternatively, a TE detection level at a TZC point of the TE signal in which asymmetry is adjusted is determined as the track center level. The determined track center level is used for normal recording/reproduction, so that the tracking servo is activated at the actual track center position. Thus, initial stable tracking performance can be obtained, and bias of the tracking can be avoided during tracking control by estimating the exact track center value.

Abstract: When a data is recorded to a recording medium, a miserasing preventing circuit determines whether or not a track jump is caused by a shock or a scratch. If it is caused by a shock, such as a quantity of light of an optical pick-up is controlled to change a reproducing state, and then the optical pick-up is moved to the rerecording position to start rerecording. As a result, recorded area is not disturbed, and the rerecording control is not performed by a little dust. Thereby, it can be provided an apparatus with high recording efficiency.

Abstract: A focus control apparatus for a multilayer optical recording medium performs an adequate focus jump on a multilayer optical recording medium. Threshold values are set according to the amount of a level change in a focus error signal of a loaded multilayer optical recording medium, and focus jump control is conducted based on the result of comparison between the level of the focus error signal and the set threshold values.

Abstract: A device for measuring focusing characteristics of an optical pickup and/or an optical disc capable of measuring characteristics of focusing states with high accuracy by a simplified circuit. An arithmetic-logic unit 12d controls an offset supplying circuit 23 for applying an offset voltage to a focusing servo control signal. This arithmetic-logic unit 12d detects an error rate of the playback data in such a state in which the focusing position of the laser light is deviated by a pre-set offset amount. The arithmetic-logic unit 12d sequentially varies the offset voltage to repeat the above processing for detecting the error rate. The arithmetic-logic unit 12d approximates the relationship of the error rate to the offset amount by a quadratic curve based on detected data. The offset amount which minimizes the error rate is found from this equation of approximation.

Abstract: A method and apparatus provides an improved optical storage disk player. An improved method and apparatus for obtaining a tracking error signal for an optical disk player is disclosed which is general across the various data formats found in CD audio disks, CD-ROMs, and digital video disks. The present invention uses a photodetector with at least four active areas to sense the reflected laser beam. A differential amplitude tracking error signal is generated by comparing the signal strength in the different active areas.

Abstract: A polarity switching signal generator able to stably generate a suitable polarity switching signal for inverting the polarity of a tracking error signal, wherein a reference value stored in a reference value storage circuit is updated by a rotational angle indicated by a rotational angle signal at a switching position of a land and groove captured by a capture circuit when an address decode signal is normal and wherein, further, a comparator compares the reference value stored in the reference value storage circuit with the rotational angle indicated by the rotational angle signal and generates a polarity switching signal instructing the switching of the polarity when they match.