Abstract: A method is provided for performing data-writing or data-reading with an optical data storage medium including a substrate. The method includes the following steps. The storage medium is irradiated with light from a light source via an objective lens, so that a light spot is formed on the storage medium. Then, the lens is moved from the focus point to a predetermined defocus point where the light spot has a maximum peak intensity. The defocus point is detected as a minimum depletion point regarding the aberration caused by a thickness error of the substrate.

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: The invention provides a method of adjusting a tracking location in an optical storage device. The method is illustrated as follows. Firstly, the optical pickup head reaches the first tracking location according to a tracking error (TE) signal. Secondly, the optical pickup head is finely moved to an adjusted tracking location where the value of the amplitude of RFRP signal is maximum. The method can avoid wrong tracking location by simply based on the TE signal, then enable the optical pickup head to reach the correct track center and improve the quality of data reading.

Abstract: According to the method, the focusing servo is activated at the zero-crossing point of a focusing error signal FE immediately after the focusing error signal FE has exceeded the first threshold th1 or has dropped below the second threshold th2. The absolute value of the first threshold th1 and the second threshold th2 is reduced each time a predetermined time t is elapsed until the focusing servo is activated.

Abstract: A focusing method of layer jump for an optical storage device to retrieve data from a multi-layer optical disc is disclosed. The optical disc includes first data layer and second data layer. Before layer jump, the focus is on the first data layer, and the second data layer is the target data layer to proceed with layer jump. If layer-jump failure, no matter where the focus is, an auxiliary force is provided to let the lens continuously move along the layer jump direction and prevent the focus from locating between the two data layers. And then, the lens moves along a backward direction to set on the second data layer according to a reference signal.

Abstract: A relative traveling speed detector receives a focus error signal and detects a traveling speed of a pickup relative to a disk. A drive mode determining unit determines a drive mode of the pickup according to the detected relative traveling speed. A drive output generating means generates a focus drive signal for driving the pickup according to the drive mode. The disk drive device is thus capable of reducing the time required to restore a focus servo operation.

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: The invention relates to an apparatus for the reproduction or recording of data or information with a photodetector and digital error signal and evaluation signal processing. The object of the invention is to provide an apparatus for the reproduction or recording of data or information which requires little outlay despite digital evaluation signal processing and a considerable capability of adaptation to different scanning speeds. The invention is based on the principle of enabling digital evaluation signal generation with an analog-to-digital converter known from audio technology, even though the data rate of the data or high-frequency signal requires an analog-to-digital converter for the radio-frequency or for the video signal band. An analog-to-digital converter for the audio frequency band can be used to generate a digital evaluation signal by the analog-to-digital converter having fed to it not the high-frequency signal directly but rather at least one envelope of the high-frequency signal.

Abstract: A tracking control method carries out a tracking control based on a tracking error signal which indicates an error of a beam spot formed on a recording medium by a light beam from a light source with respect to a track. The tracking control method includes detecting a change in a light emission power of the light source, calculating a correction quantity which is used to correct a shift and/or fluctuation of the tracking error signal generated due to the change in the light emission power, and carrying out a correction by adding the correction quantity to the tracking error signal when the change in the light emission power is detected.

Abstract: OPC data record in an optical disk is performed at a plurality of record velocities to obtain a maximum record velocity Vlmax. A rotation number of the optical disk is calculated and set, the rotation number being determined in such a manner that the maximum record velocity Vlmax becomes equal to a linear velocity of the optical disk at a detected record position of the optical disk along the radial direction. The optical disk is rotated under a rotation control that a detected actual revolution number of the optical disk becomes equal to the calculated and set rotation number. It is monitored to check whether the record operation of the optical disk at the maximum record velocity Vlmax is normal. If it is detected that the record operation may become abnormal, the maximum record velocity is lowered by &Dgr;v1.

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: An apparatus for recording and/or reproducing information on and/or from a magneto-optical disk including an optical head for projecting a laser beam onto a magneto-optical disk and receiving the laser beam reflected by the disk, an up-down block arranged movably between a lower position and an upper position, an up-down motor for moving said up-down block up and down, a turntable for supporting the disk and a spindle motor secured to said up-down block and having a driving shaft coupled with said turntable for rotating the turntable, a position detecting device for detecting a position of said up-down block to derive a position signal when the up-down block is driven into the upper position, a rotation detecting device for detecting a rotation of said optical information record disk to derive a rotation signal when the optical information record disk is rotated at a predetermined revolving speed, and a control device for initiating a focus control for moving said objective lens and turntable relative to each

Abstract: A stabilization part stabilizes surface vibration of a flexible optical disk along a rotation axis direction of the optical disk by means of pressure difference of air flow created according to Bernoulli's law at a portion on which information writing/reading is performed, provided on a side of the optical disk opposite to a side on which information recording/reproducing is performed. In this case, areas are provide on the upstream side and down stream side along the disk rotation direction of the portion of the optical disk which is stabilized by said stabilization part, said areas of the optical disk not having pressure difference created thereon by the air flow.

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: A calibration method for a control device of an optical storage medium drive includes generating a calibration-driving signal by a signal generator and then generating a sensing signal by a sensor according to the calibration-driving signal, determining whether each period of the sensing signal is suitable, and comparing suitable periods of the sensing signal with corresponding periods of the calibration-driving signal to determine a phase difference between the sensing signal and the calibration-driving signal so as to adjust gain of a control device of the optical storage medium drive according to the phase difference. The calibration method is capable of preventing the influence of unstable sensing signals and promoting the performance of the optical storage medium drive.

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: A digital and analog sound-signal broadcaster includes a turntable controllable by a user in its rotating speed and direction, and a traditional plastic record or a special record to be placed on the turntable. A user can also control music data of a CD to be stored in a dynamic memory chip, broadcasting a variety of special sound effects, bringing forth joy, pleasure and glamorous atmosphere. Thus the digital and analog sound-signal broadcaster can broadcast separately music from a traditional plastic record and that from a CD with easy operation.

Abstract: An optical disk apparatus has a first optical system having an objective lens with a first NA, a second optical system having an objective lens with a second NA lower than the first NA, addition means for adding focus error signals detected by the first and second optical systems, and alignment means for aligning the objective lens in accordance with the addition result of the addition means.

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: A method for detecting the speed of a sledge motor in an optical storage device. In response to a track jumping command, a tracking servo output signal is expanded onto an orthogonal space to obtain simulation parameters corresponding to the tracking servo output signal. A pseudo-tracking servo output signal is generated according to the simulation parameters of the tracking servo output signal. Then, the pseudo-tracking servo output signal is used to compute the speed of the sledge motor.

Abstract: A tracking servo system with a tracking skate detection algorithm is presented. The tracking skate detection algorithm receives a tracking error signal and, takes the absolute value of the tracking error signal and filters the absolute value with a low pass filter. If the filtered signal exceeds a threshold value for a number of cycles exceeding a maximum number, then a tracking skate condition is indicated.

Abstract: An optical disk device capable of preventing the erroneous recording or erroneous deleting on/from other information surfaces different from an information surface in recording during a recording operation to an optical disk having a plurality of layers of recording surfaces. A focus monitor unit monitors for an increase in focus error signals, or a reflection light quantity monitor unit monitors for a reduction in reflection light quantity or detects moved layers of information surfaces during recording. Based on the monitored and detected results, a light intensity control unit lowers the intensity of a light beam to that for reproducing. In addition, the light intensity control unit, when signals are recorded over a plurality of layers of recording surfaces, lowers a light intensity temporarily to that for reproducing and then moves a layer kept track of by the focus of a light beam before a light beam intensity is again raised to that for recording.

Abstract: A disc drive includes a tracking actuator, and determines when the tracking actuator is positioned off a formatted portion of optical media in the disc drive. The optical media includes a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. Tracking control effort is monitored to determine when the tracking actuator is in the off-format condition and whether tracking good or tracking bad is detected within a predetermined time period. An absolute value of the tracking control effort is generated and the absolute value of the tracking control effort is filtered. An off-format condition is indicated if the filtered value of the tracking control effort is not within a predetermined threshold value.

Abstract: A control system for an optical disc for optical media with a premastered area that cannot be overwritten and a user-writeable area that can be overwritten, comprises a first processor operable to communicate with a second processor via a status register. The first processor sequences and monitors functions performed in the second processor and the second processor issues an interrupt when an error condition is detected in the second processor. The first processor detects the interrupt, and disables detecting further interrupts until the interrupt is serviced. Servicing the interrupt includes recording the error state and changing focus and tracking parameters based on the error condition detected.

Abstract: A write abort algorithm of a tracking and focus servo system that can abort a write operation on an optical disk drive is presented. The write abort algorithm monitors at least one of a tracking error signal or a focus error signal and indicates a write abort status when the tracking error signal or the focus error signal indicates a threshold value. In some embodiments, the write abort algorithms suspends indication of the write abort status in the presence of a defect, suspension of the write abort status occurs more than a predetermined number of times.

Abstract: A tracking and servo system with a one-track jump is disclosed. The one track jump algorithm holds a control signal from the tracking servo system. The one track jump algorithm adds an acceleration control signal to the held control signal for a first period of time, delays for a second period of time, and adds a deceleration control signal to the held control signal for a third period of time. The algorithm then frees the control signal to close tracking on a new track separated by one track from the starting track.

Abstract: An optical disc drive waits to receive a command to perform a function on optical media in the disc drive. The optical media includes a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. Once a command is received, one portion of the disc drive processes the command while another portion of the disc drive monitors the processing of the command and waits until the command is processed. If an error condition is detected while processing the command, the disc drive generates an event request such as a notify event request, a focus event request, a spin event request, and a tracking event request. When an event issues, the disc drive interrupts processing of the command and attempts to recover from the error condition. The state of the disc drive when the requested event was received is saved before attempting to recover from the error condition.

Abstract: A method of controlling a balance of a photodetector capable of increasing light reception efficiency thereof in a compatible optical pickup and an apparatus thereof. The method includes installing first and second light sources in a single module; directing light supplied from the first or second light source and transmitted through a holographic optical element, an optical path changing unit, and an objective lens onto a disk corresponding to each light source, transmitting the light reflected from the disk through the objective lens, and the optical path changing unit to a photodetector, moving the photodetector so that the center of a first one of first and second spots received by the photodetector is concentric with the center of the photodetector; and moving the holographic optical element so that the center of the second received spot from the second light source is concentric with the center of the photodetector.

Abstract: A system and method for handling events issued as a result of error conditions in the operation of an optical disc drive include suspending processing of commanded operations in the disc drive while attempting to recover from the error condition. The recovery attempt can include increasing levels of recovery effort, such as dynamically recalibrating various components in the disc drive. The system can also determine whether a previous notice was received for the same error condition. If so, the system can determine whether excessive recovery attempts have been initiated based criteria such as the time between the notices, and/or the number of notices, for the same error condition. The recovery attempts are aborted when they become excessive. If the recovery attempt is successful, the interrupted operation is resumed at the point where the processing was suspended, such as during a write or read command.

Abstract: A system for determining whether a focus servo system is in focus or out of focus (i.e. open) is disclosed. A sum signal can be compared with a threshold value. If the sum signal is below the threshold value, then a focus open condition (i.e., out-of-focus) can be indicated. In some embodiments, a focus open condition is indicated where the sum signal remains below the threshold value for a predetermined period of time.

Abstract: An off-format condition in a digital tracking servo is presented. An off-format condition detected by low pass filtering a tracking control signal, detecting a DC level over a old level, and indicating the off-format condition if the DC level is above the threshold level for a maximum number of cycles.

Abstract: A method for determining vertical or horizontal operation of optical disk driver is proposed. A feedback signal from a pick-up head of the optical disk driver is sent to a pre-amplifier to generate a focus error signal. The focus error signal is sent to a compensator to generate a compensation voltage. A low-pass filter removes high-frequency components of the compensation voltage to obtain a DC component of the compensation voltage. A comparator compares the DC component of the compensation voltage with a predetermined threshold value to discriminate the vertical or horizontal operation of optical disk driver.

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 layertolayer distance which is measured beforehand. The focus jump is performed by using a lens (143) having a controllable focal distance.

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 device for finding the focus between an optical pickup head and an optical disk by tapping signals from a radio frequency amplifier comprises a high-pass filter for receiving a focus error signal from the radio frequency amplifier and generating a focus error high-pass signal; and a decision circuit that couples to the high-pass filter for receiving the focus error high-pass signal and using a focus zero cross level as a reference for determining a correct focusing point. The focus between the optical pickup head and the optical disk is found when the focus error high-pass signal reaches the positive focus zero cross level or the focus error high-pass signal reaches the negative focus zero cross level.

Abstract: An optical recording apparatus of the present invention has a semiconductor laser 5 for generating a light spot used for information recording, detection means 6 of detecting the aberration amount of the light spot, and control means 7 of controlling the output of the semiconductor laser 5 by use of the detected aberration amount.

Abstract: A method of detecting a crack in a disc loaded on a disc drive and a method of automatically lowering a target speed in response to the detection of a crack in order to stabilize the disc drive. According to the methods, it is automatically determined whether a disc loaded on a disc drive has a crack in a specific mode, and a target speed is automatically changed into a low speed when it is determined that the disc has a crack. Therefore, the crack state of the disc is exactly checked during action of the disc drive, the percentage of error occurrence is decreased, and the probability of damage to the disc is reduced.

Abstract: In case of pulling a focusing servo in a recording surface 2 of an optical disk 1, the focusing servo is pulled in a substrate surface 3 of the optical disk 1, thereafter, a focusing servo pull-in position is allowed to transfer to the recording surface 2 of the optical disk 1 by means of a focusing jump control circuit 12, whereby a focusing servo pull-in operation is made upon the recording surface 2, while an objective lens retreating control circuit 14 outputs a control signal in a direction along which the objective lens 4 is allowed to go away from the optical disk 1 for a predetermined time, and then, another control signal in a direction along which the objective lens 4 is allowed to be close to the optical disk 1 for a predetermined time in the case when an abnormal focusing servo pull-in operation was detected.

Abstract: A disc-shaped information recording medium in which the recording density can be increased to secure a large storage capacity and in which there is no risk of an address section being mistakenly detected by cross-talk from a neighboring track, is disclosed. Specifically, an optical disc of a continuous servo system in which tracking is controlled using a pre-groove and in which information is recorded and/or reproduced with constant angular velocity using clocks of a sole frequency, is disclosed. On the disc is formed a spiral track made up of a data portion for recording data and an address section for recording the management information for recording/reproducing the data. Both a groove and a land are used as a recording/reproducing track. Odd tracks are formed on the land, while even tracks are formed on the groove.

Abstract: An optical device having an irradiated portion formed of an optical recording medium in which a pit is formed on a reflection surface, a semiconductor unit in which a semiconductor laser, a semiconductor structure and a photo-detection element are formed on the same semiconductor substrate, and a converging device for converging a light emitted from the semiconductor laser and irradiating the same of the irradiated portion and further converging a returned light reflected from the irradiated portion. The semiconductor structure is formed near the confocal of the converging device and includes at least three reflection surfaces. The photo-detection element includes a first detection element for receiving a returned light reflected on the second reflection surface and a second detection element for receiving the returned light reflected on the third reflection surface.

Abstract: An optical head device includes a light source for emitting at least one of a coherent beam and a quasi-monochromatic beam; a collection optical system for collecting the beam to an information memory medium having a track which has at least one mark and at least one space; a light detector having a plurality of detection areas for receiving the beam reflected by the information memory medium and outputting a signal in accordance with a light amount of the beam received; and a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals. The tracking error signal generator reduces a difference between a first signal amplitude and a second signal amplitude. The first signal amplitude is an absolute value of a difference between first and second signal levels. The second signal amplitude is an absolute value of a difference between the first and third signal levels.

Abstract: A light spot detects a focus offset amount based on an amount of variation of a focus error signal when a light spot passes a boundary between a land section and a groove section adjacent to the land section on an optical disk. Specifically, an amount of variations in the focus error signal at a center of a land section at a time the light spot passes the boundary between the land and the groove adjacent to the land is detected as a focus offset amount, and an amount of variation in the focus error signal at a center of the groove section is detected as a focus offset amount for the groove sections, thereby providing an optical information recording/reproducing device which permits recording/reproducing information on and from a tracking area of an optical disk under just-in-focus conditions without increasing a cost of the device nor being affected by an error due to changes over time or variations in optical disks.

Abstract: A magneto-optical disk apparatus and an adjustment method of a head mechanism are provided for strictly and quickly adjusting a setting position of a magnetic head with respect to an optical axis of an optical head. The adjustment method is executed by the following steps. A magnetic super resolution type magneto-optical disk is mounted to the magneto-optical disk apparatus provided with the optical head and the magnetic head. Then, an external magnetic field from the magnetic head is applied onto the magneto-optical disk as applying a laser beam of a reproduction level onto the magneto-optical disk. Then, a reproduction signal output read from the magneto-optical disk is detected concurrently with the application of the external magnetic field.

Abstract: A detecting system for detecting a rotation angle of a deflecting mirror is disclosed. The detecting system is provided with a laser diode, an objective lens, and a deflection mirror therebetween. The deflection mirror is rotatable about a predetermined rotation axis to change the position, on an optical disc, at which a laser beam emitted by the laser diode is incident. Further, a beam splitter is provided to split the light beam into a first beam directed to the optical disc via the deflection mirror, and a second beam that is directed to a reflection surface of the deflection mirror. The second beam reflected by the reflection member is not directed to the optical disc but received by a detector which determines the rotation angle of the deflection mirror in accordance with the received second beam.

Abstract: An optical disc apparatus includes: a converging section for converging a light beam and irradiating a rotating information medium with the converged light beam; a moving section for moving the converging section, thereby moving a converging point of the converged light beam in a direction perpendicular to an information surface of the information medium; a converging state detection section for generating a focus servo signal which represents a converging state of the light beam on the information medium based on reflected light or transmitted light of the light beam from the information medium; a focus servo control section for controlling the moving section based on the focus servo signal, so that the light beam reaches a predetermined converging state on the information medium; and a focus pull-in section for turning ON the control by the focus servo control section, wherein the focus pull-in section turns ON the control by the focus servo control section in a case where the focus pull-in section determin

Abstract: This invention is applicable to an apparatus using an optical pickup to reproduce information recorded on an optical recording medium. By enabling the automatic setting of reproducing conditions applicable to a mounted optical recording medium so that a plurality of types of optical recording media can be compatibly mounted, the present invention enables recorded information to be reliably reproduced even if the recording medium has a low recording density.

Abstract: Disclosed is a tilt controlling method and apparatus in which an RE 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 the 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: 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 object of the invention is to make it possible to perform, stably in a short time, a focus jump for enabling a focus control on each of a plurality of recording layers of a disc in such a manner that its effect is not absorbed by disturbance or a variation in the movement speed of an objective lens. To attain this object, there are provided means for monitoring the level of a focus error signal, means for rejecting noise from the focus error signal, speed detecting means for detecting a movement speed of an objective lens, and speed control voltage generating means for generating a voltage for controlling the objective lens based on the movement speed detected by the speed detecting means.

Abstract: A storage apparatus rotates an optical recording medium at two or more kinds of rotational speeds. The rotational speed is decreased when a read or write margin becomes less than or equal to a first predetermined value or, when a frequency of generation of a servo abnormality of a tracking servo and/or a focus servo is greater than or equal to a first predetermined frequency. On the other hand, the rotational speed is increased when the read or write margin becomes greater than or equal to a second predetermined value or, when the frequency of generation of the servo abnormality of the tracking servo and/or the focus servo is less than or equal to a second predetermined frequency.