Abstract: A tracking servo apparatus in which reflection light obtained when a laser beam is irradiated onto a recording surface of an optical disc is photoelectrically converted, thereby obtaining a photoelectric conversion signal, a tracking error signal showing a deviation amount of an irradiating position of said laser beam for a track in a disc radial direction on the recording surface is generated by the photoelectric conversion signal, a spherical aberration occurring in an optical system is detected, a level of the tracking error signal is corrected on the basis of the detection result, and the irradiating position of the laser beam is moved in the disc radial direction in accordance with the level-corrected tracking error signal.

Abstract: A disk reproducing apparatus includes a variable gain amplifier (VCA) (32), and the VCA applies a radial push-pull signal including an address signal and an FCM leakage-in signal to a switch (38). The switch outputs only the address signal to a peak-hold circuit (40) on the basis of an FCM mask signal from a mask signal generation circuit (36). The peak-hold circuit generates a peak-hold signal of the address signal so as to be output to a DSP (30), and the DSP controls a gain of the VCA on the basis of the peak-hold signal. Then, the radial push-pull signal in which the gain is controlled on the basis of the address signal is applied to an address detection circuit (42), and the address signal is detected therein.

Abstract: Two sum output signals from two sets of the photodetector elements located symmetrically each other with respect to a light-receiving center of the photodetector of the optical pickup are amplified individually by two amplifiers. A focus error signal is generated in accordance with a difference between respective output levels of the two amplified signals. The gains of the two amplifiers are adjusted in accordance with the focus error signal. A predetermined bias voltage is applied to the focus error signal line in the focus servo control means in accordance with the focus error signal.

Abstract: A servo channel digitally processes the data read from a magnetic media. The channel uses both edges of a system clock to detect peaks and generates position error systems by an area-based automatic gear control loop. By altering the sample delay, the channel digitally, up-samples at higher rates without requiring a higher system clock.

Abstract: A device for amplifying and converting current signals into voltage signals for processing The current signals are delivered by sensors, e.g. optical transducers, magnetical heads. The current signals are first amplified using a current to current amplifier, the amplified current signals are then transported using electrical conductors and eventually amplified using a current to voltage amplifier. The invention may find application in consumer electronic devices, cars, planes, industrial machines.

Abstract: In an optical disc apparatus, a minimum jitter value is established from each jitter value measured in correspondence to a successively changed servo constant, and multiplied by a prescribed ratio so as to set a jitter threshold value. Servo constants corresponding to at least two jitter values substantially equal to the jitter threshold value is established, and an optimum servo constant is set based on this minimum of two servo constants. By doing this, it is possible to quickly and accurately detect the optimum servo constant, and achieve good servo adjustment.

Abstract: A vibration quantity measuring apparatus and method, and a loop design method in which a vibration quantity generated in a focus and tracking loop is accurately measured to optimally design a focus and tracking loop of an optical disc drive. The vibration quantity measuring apparatus includes an error gain adjusting unit which adjusts an amplitude of a focus and tracking error which occurs where a disc rotates, so as to maintain the amplitude of the focus and tracking error constant, a loop gain adjusting unit which compares a closed loop phase of a focus and tracking loop and a predetermined reference closed loop phase, and maintains a constant gain of the focus and tracking loop to compensate for a gain difference of an actuator, and a measuring unit which calculates and outputs a vibration quantity using an error adjusted by the error gain adjusting unit and the loop gain adjusting unit, and an output of a controller which controls a focus and tracking of the disc.

Abstract: A calibration of a loop gain in a digital servo system is presented. The loop gain can be calibrated measuring the response in a control signal generated by the digital servo system when the control signal is replaced by a sum of the control signal and a sinusoidal disturbance. The loop gain can be set to provide a desired gain, for example unity, between the control signal and the sinusoidal disturbance at a cross-over frequency.

Abstract: Push-pull signal is created on the basis of reflected-light detection signals output from four divided light receiving elements that receive a reflection of a recording laser light beam off an optical disk. The push-pull signal is sent to a gain variation circuit. The push-pull signal is normalized by setting the gain of the gain variation circuit to a low level in response to a mark forming section of a recording signal, but to a high level in response to a blank forming section of the recording signal. Wobble detection and pre-pit detection are performed on the basis of the normalized push-pull signal.

Abstract: The present invention implements a servo system which can support changes of the higher resonance frequencies of the actuator with a simple configuration at low cost.

Abstract: A low-cost technique to improve the performance of optical disk drives is presented. An algorithm is used to decouple electro-mechanical actuators thus compensating for inaccuracies in the control of the actuators. A similar method can be used to decouple the position sensors. Prior art methods treated cross-coupling between focus, tracking and sled control loops as noise and therefore increased the bandwidth of the system, also increasing the cost of the optical disk drive. The present disclosure actively decouples the control loops using a software algorithm to provide better performing optical disk drives. The cross-coupling effects are measured, a decoupling matrix is determined, and the output of the control laws is modified so as to decouple the actuators.

Abstract: An offset adjusting circuit for an optical disc comprises an offset-adjustment differential operational amplifier having an input terminal to which an output signal of an optical pickup is input and the other input terminal to which a control voltage is applied, an A/D converter that outputs a digital signal based on an output signal of the offset-adjustment differential operational amplifier, and a control voltage adjuster that varies the control voltage applied to the offset-adjustment differential operational amplifier based on the digital signal so as to remove an offset.

Abstract: A disk apparatus according to one aspect of this invention comprises a photodetection unit configured to divisionally detect light reflected by the disk as a plurality of photodetection signals, and a tracking error signal generation unit configured to generate a tracking error signal on the basis of a phase difference between the plurality of photodetection signals detected by the photodetection unit, wherein the tracking error signal generation unit includes an equalization unit configured to equalize waveforms of the plurality of photodetection signals detected by the photodetection unit, and the equalization unit has frequency-gain characteristics that obtain a gain of not less than 15 dB at a frequency corresponding to a shortest pit or mark.

Abstract: An optical disc apparatus has a crosstalk level determining section which, when a track jump is performed without applying a tracking servo, determines whether a crosstalk component is larger than a predetermined level or not. If the crosstalk level determining section determines that the crosstalk component is larger than the predetermined level, a crosstalk correcting section performs a calculation for reducing the crosstalk component. If the crosstalk level determining section determines that the crosstalk component is not larger than the predetermined level, the crosstalk correcting section does not reduce the crosstalk component.

Abstract: A repeatable runout compensator that allows a transducer of a servo system in a storage device employing rotating media to follow the eccentricity on the media is disclosed. In exemplary embodiments, the repeatable runout compensator utilizes error values generated by the servo system, which represent the radial and/or axial eccentricity of the media, to generate an output signal having a sinusoidal waveform that is approximately 180 degrees out of phase with the eccentricities and the harmonics of eccentricities on the media.

Abstract: An information reproducing apparatus(100) is provided with: a focusing device(11a) which makes a signal-reading probe light converge onto an optical recording medium(10); a focus servo device(12) which maintains a focus on a recording layer of the optical recording medium(10) by controlling the focusing device(11a); an offset providing device(14) which provides a predetermined offset to a target value used by the focus servo device(12); and a spherical aberration detecting device(17) which detects a signal indicative of spherical aberration contained in the probe light on the basis of an intensity of a signal reproduced based on a plurality of target values obtained by the offset providing device(14) generated on at least one signal of at least one predetermined spatial frequency recorded on the optical recording medium(10).

Abstract: A displacement detection method in which by reflecting a light beam on a surface of an object to be measured, a displacement of the surface of the object is detected from a change of the reflected light beam due to a change of the displacement of the surface of the object, includes the steps of: causing light beams to be incident upon a substantially identical position on the surface of the object from at least two light sources confronting each other substantially; detecting by position detectors directional changes of the light beams reflected on the surface of the object, respectively; normalizing output signals of the position detectors by luminous intensities received by the position detectors, respectively; and calculating a sum or a difference of the normalized output signals of the position detectors.

Abstract: An optical disc drive is used to read and/or write data from/on an optical disc having a data storage layer. The drive corrects electrical offset while reading and/or writing data. The drive updates a correction value based on an electrical offset detected at correcting operation or a value derived using electrical offset values that has been detected and stored, without detecting an electrical offset at correcting operation. Therefore, the optical disc drive can correct the electrical offset less often.

Abstract: A wobble detecting apparatus for an information recording and/or reproducing for an optical disk, includes a wobble detecting unit for detecting a wobble on the basis of a signal from a light receiving element which receives light reflected from the optical disk; an offset voltage generating unit for generating an offset voltage; an adder unit for adding said offset voltage to a control signal to an actuator for the optical disk; an actuator switch for on/off controlling a control signal to said actuator; and a control unit for turning on said actuator for wobble detection to decide whether or not the wobble has been detected by said wobble detecting unit, and if the wobble has not been detected, causing said offset voltage generating unit to generate a positive or negative prescribed voltage to decide further whether or not the wobble has been detected by said wobble detecting unit. In this configuration, the wobble can be detected with high accuracy.

Abstract: A recording and/or reproducing apparatus for an optical disc in which the loop gain variation in tracking servo control can be suppressed to cause the illuminated laser light to follow correctly the recording track center. An optical disc recording/reproducing device 1 detects a traversing signal generated when the laser light traverses a track at the time of tracking servo pull-in and sets the amplification degree of a GCA 4 so that the push-pull signals will be at a predetermined level. The optical disc recording/reproducing device 1 holds the amplitude of the wobbling signals on memory as an initial setting value. On starting the recording or reproduction, the optical disc recording/reproducing device 1 monitors the amplitudes of the wobbling signals during the recording or reproduction to compare the amplitudes to the initial setting value.

Abstract: Comparators compare the amplitudes of a DPD tracking error signal indicating the phase difference between the detection signals supplied from a photodetector, and a PP tracking error signal indicating the level difference between the detection signals with the reference values, respectively. A gain control amplifier mutes a tracking error signal with the maximum amplitude smaller than a reference value.

Abstract: There is provided a disk device including a detector section which generates detection signals according to reflected lights of laser lights emitted on a disk, a removing section which detects detrack components which have failed to detect recording information on the disk from the detection signals and removes and outputs the same from the detection signals, and a processing section which applies a predetermined processing on the basis of signals obtained by removing detrack components from the detection signals, so that erroneous address information on CAPA which has been failed to read or the like can be removed, thereby improving reading accuracy of the disk.

Abstract: A method and apparatus for measuring the eccentricity of an optical disk. The method for measuring the eccentricity of an optical disk in accordance with the present invention comprises the steps of activating tracking servo while the optical disk is rotating, detecting the center value of tracking error signal and setting the center value as a reference value, and detecting the eccentricity of the optical disk by comparing the center value and the tracking error signal received right after the reference value is set. The method in accordance with the present invention precisely measures the eccentricity of an optical disk and adjusts focus and track servo gains and disk rotation speed based upon the measured disk eccentricity, which provides stable data reproduction performance.

Abstract: The correction method of the present invention includes a step for respectively inputting a same-signal pair composed of two signals each having the same signal waveform to two input lines of a normalization circuit, and then adjusting the difference between the values of the two offset signals added to those two input lines to make the output of the normalization circuit fixed or coincide with a predetermined value. The correction method further includes a step for respectively inputting to the two input lines of the normalization circuit a fixed-ratio-signal pair composed of two signals in which the ratio between the amplitudes of waveforms is fixed, and then adjusting each of the two offset signals added to those two input lines while the difference between the values of the two offset signals is maintained as is, to make the output of the normalization circuit fixed or coincide with a predetermined value.

Abstract: The present invention relates to an optical disk apparatus which performs information recording or reproduction into/from an optical disk, and provides an optical disk apparatus which makes the amount of optical pickup movement performed before adjustment of a track error signal suited and enables reduction of a start-up time. When a track error signal is subjected to adjustment, it is previously detected in a signal amplitude detecting circuit 17 whether an optical pickup 1 is located in an area where a required track on an optical disk medium 2 exists or not, and a micro processing unit 6 executes the procedure which uses only the necessary but minimum moving time, even when the optical pickup is required to be moved.

Abstract: A method of adjusting the focus control for an optical storage system where light is reflected from a surface towards a lens. The method includes receiving a reflected light in the form of a spot, dividing the spot into a plurality of areas, generating an adjustment signal based on the relationship between the plurality of areas to determine the variation between the center point of the spot and a desired center point for the spot, combining the adjustment signal with an existing focus error signal to obtain a modified focus error signal, and utilizing the modified focus error signal to control the position of the sensor.

Abstract: A rotation control circuit comprising, a pickup controller configured to amplify an error signal detected by a pickup from an optical disk, and to generate both a low-frequency component in the error signal and a pickup control signal so as to control the pickup, a memory controller configured to generate a memory address control signal in synchronization with a frequency generator signal provided by a disk motor, a memory circuit configured to store the low-frequency component by using the memory address control signal at a specified timing, a compensation signal adder configured to add the low-frequency component to the pickup control signal at another specified timing, and a system controller configured to control operational timing of the memory controller and the compensation signal adder.

Abstract: When first and second read signals generated on the basis of the outputs of electrical signals from a light receiving portion are input to an amplitude correcting circuit, the first and second read signals are added to generate an addition signal. Then the amplitudes of the first and second read signals are corrected for the each RF signal component corresponding to each recording pit, which is contained in the first and second read signals on the basis of the addition signal. Finally, the difference between the first and second read signals is computed to generate a difference signal so that a pre-pit signal will be detected on the basis of the difference signal.

Abstract: A recording and playback apparatus comprises, a drive unit configured to rotate an optical recording medium including a recording track, a recording and playback unit configured to irradiate a light beam on the recording track, and to perform recording and playback of an information detected a reflected light beam by an upside photo detection area and a downside photo detection area bisected in a tangential direction of the recording track, and a recording and playback controller configured to generate a position tracking signal based on the reflected light beam detected by the upside photo detection area and the downside photo detection area, and to compensate a level of the position tracking signal when the position tracking signal and a record mark on the recording track are detected.

Abstract: A method for determining a direct current (DC) level involved in an alternating current signal is provided. The alternating current signal is transmitted from an amplifier to an A/D (analog-to-digital) converter. When any of the extreme values of the alternating current signal is beyond the input range of the A/D converter, the alternating current signal is shifted to make both of the peak and bottom values located within the input range of the A/D converter. Then, the real extreme values are realized according to the shift level(s), the relative peak and bottom values realized after the shifting procedure, and the input range of the A/D converter. Finally, the DC level is determined according to the real peak and bottom values.

Abstract: Methods and systems for controlling a servo are provided. One method includes calculating at least a first switching time to change an amplitude of a command signal to a servo, providing a first amplitude to the servo for the first switching time, and switching the amplitude of the command signal to the servo from the first amplitude to a second amplitude at the first switching time. The second amplitude is the command signal amplitude.

Abstract: A method and an apparatus are provided which are capable of evaluating a state of a signal with a fewer number of samples compared with an error rate. A reproducing signal obtained from a magneto-optical disk is subjected to maximum-likelihood decode in a maximum-likelihood decoder, paths coupling with each other in the maximum-likelihood decode is detected by an evaluation index generation unit and, at the same time, a difference of likelihoods (path metrics) of those paths is obtained to adjust a parameter of a recording and reproducing signal or a control signal of an optical pickup based on the likelihood difference. The parameter is, for example, auto-tracking, a gain of an auto-focusing loop, or an offset value, or a gain value of a reproducing signal, a recording power, or a reproducing power intensity.

Abstract: A gain controlling apparatus includes a pre-amplifier for roughly adjusting a gain of a generation signal, which is generated on the basis of a reception signal from an optical disc; a variable amplifier for finely adjusting the gain on the basis of the roughly adjusted gain by the pre-amplifier; a memory for storing a plurality of values for adjusting the gain generated during a previous occasion of gain adjustment in time series; and a controlling device for controlling the pre-amplifier at a current occasion of gain adjustment on the basis of the respective stored values for adjusting the gain and controlling the variable amplifier, wherein the controlling device comprises a predicting device for predicting a current adjustment value, namely an adjusted value for the gain roughly adjusted at the current occasion by the pre-amplifier, and the controlling device controls the pre-amplifier on the basis of the predicted current adjustment value.

Abstract: A servo channel digitally processes the data read from a magnetic media. The channel uses both edges of a system clock to detect peaks and generates position error systems by an area-based automatic gear control loop. By altering the sample delay, the channel digitally, up-samples at higher rates without requiring a higher system clock.

Abstract: In an event of deviation of focusing or tracking from an optimum point, a PLL gain control circuit outputs control signals to decrease the open loop gain of a PLL circuit. In response to the control signals, the PLL circuit decreases the frequency of comparison by a phase detector, decreases the current amount from the constant current circuit, decreases the combined resistance value of a filter circuit, and increases the divisor used by a frequency divider. By these operations, the open loop gain of the PLL circuit decreases from the level adopted during normal operation, and thus the property of the PLL circuit of following the disc playback signal is degraded. This enables generation of an extraction clock kept stable irrespective of a low-reliable disc playback signal. As a result, occurrence of disc read errors is reduced.

Abstract: When a MD is inserted (step S1), AGC is executed for reading the TOC area of the MD 1, and thereafter the information stored in the TOC area of the MD are read to detect the kind and recording capacity, etc. of the MD (step S2, S3). Next, the data relative to the executing position of AGC corresponding to the kind of the detected MD is read out from the memory (step S4). Now, where the MD is of a pre-mastered type, according to the recording capacity, either the first executing position P1 or the second executing position P2 is read as occasion demands. On the other hand, where the MD is of the recordable type, two AGC executing positions of the first executing position R1 in a pit area and the second executing position R2 in a groove area are read out. At each of the executing positions thus read out, the AGC is executed (step S5).

Abstract: An optical head is provided with a beam splitting element which divides a beam reflected by a data recording surface of an optical disc into two beams with generating opposite defocus therebetween, and a pair of light receiving elements which receive the two beams divided by the beam splitting element, respectively, the pair of light receiving elements being arranged substantially on a same plane. A light receiving surface of each of the pair of light receiving elements is divided, by two lines extending in a direction corresponding to a tracking direction on the optical disc, into at least three light receiving areas. A focusing error signal is generated in accordance with outputs of the at least three light receiving areas.

Abstract: A tracking error balance adjustment circuit, and a current control circuit used for a variable gain RF amplifier automatically controlled to output a signal having a predetermined amplitude. The tracking error balance adjustment circuit comprises two separate gain adjusting circuits, each having variable attenuation circuit having first gm amplifier of variable gm type, a second gm amplifier of variable gm type connected to the variable attenuation circuit, and an output circuit connected to the second gm amplifier, comprising an operational amplifier circuit having feedback resistor, wherein the first and second gm amplifiers are differentially controlled commonly by a control current.

Abstract: An optical disc cutting apparatus capable of suppressing an unnecessary deflection component and unnecessary light intensity variation component and manufacturing a optical disc suitable for a high definition, high precision and high density optical disc.

Abstract: In an optical disc playback device, focus and tracking balance amounts are automatically adjusted to specified amounts. An error rate from an error correction circuit for performing error correction of data played back from an optical disk using the optical pickup is then measured, and if the measurement results are a specified threshold value or higher it is determined that the optical disc being played is an inferior disk. The focus and tracking balance amounts are then adjusted to as to reduce the error rate to a minimum level.

Abstract: A servo control apparatus of an optical pickup in which an offset and a gain can be adjustable for each servo control apparatus, and influences caused by changes in environmental conditions and changes with time are reduced without a decrease in operational speed, and increase in size and an increase in cost is disclosed. The servo control apparatus includes a nonvolatile memory for storing compensatory values which correspond to differences of servo characteristics of each servo apparatus and which are measured with the assistance of external measurement instruments, and a compensation portion for compensating an optical pick-up servo signal according to the compensatory values stored in the nonvolatile memory.

Abstract: A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in ±1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by ±1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the ±1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the −1st direction, entering the objective lens.

Abstract: An apparatus for writing an optical record carrier (10) according to the invention comprises a write head (21) with a radiation source (22) and an optical system (23) for projecting a scanning spot (24) at the record carrier (10). The write unit (20) further comprises a first detector (25) for generating a first detection signal (Sd1) which is indicative for an intensity of the radiation source (22). It also comprises a second detector (26) for generating a second detection signal (Sd2) which is indicative for an amount of radiation reflected by the record carrier (10). The write unit (20) comprises a supply circuit (27) for modulating the intensity of the radiation source (22) between at least a first and a second value in response to a write signal (Sw). The apparatus according to the invention furthermore comprises a control circuit (30) for controlling the power of the radiation source.

Abstract: An offset measuring unit receives a servo error signal E1 in which a change in an offset caused by a change in an amount of reflection light directly appears and which does not pass through a filter, and measures an offset amount in the servo error signal which is caused by a change in the amount of reflection light. A correction amount calculating unit calculates a correction amount to cancel out the offset amount and outputs the correction amount to an offset correcting circuit for an offset generating period so as to perform correction.

Abstract: A servo channel digitally processes the data read from a magnetic media. The channel uses both edges of a system clock to detect peaks and generates position error systems by an area-based automatic gain control loop. By altering the sample delay, the channel digitally, up-samples at higher rates without requiring a higher system clock.

Abstract: A recording and/or reproducing apparatus for an optical disc in which the loop gain variation in tracking servo control can be suppressed to cause the illuminated laser light to follow correctly the recording track center. An optical disc recording/reproducing device 1 detects a traversing signal generated when the laser light traverses a track at the time of tracking servo pull-in and sets the amplification degree of a GCA 4 so that the push-pull signals will be at a predetermined level. The optical disc recording/reproducing device 1 holds the amplitude of the wobbling signals on memory as an initial setting value. On starting the recording or reproduction, the optical disc recording/reproducing device 1 monitors the amplitudes of the wobbling signals during the recording or reproduction to compare the amplitudes to the initial setting value.

Abstract: A recorded signal reproducing method for an optical recording medium that is adapted to accurately reproduce a signal recorded on the optical recording medium having wobbled tracks. In the method, a signal included in the optical recording medium is picked up and a specified period of signal included the picked-up signal is detected. The picked-up signal is compensated in accordance with the specified period signal.

Abstract: An optical disc device for changing intensities of light beams illuminated on an optical disc. The optical disc device comprises the following elements. A photo detecting device divided into a plurality of photo detectors is used for detecting the reflected light beams illuminated on an optical disc. A plurality of amplifiers is used for changing gains to respectively amplify the output signals of the photo detectors when recording and reproducing on/from the optical disc. A calculating device is used for calculating the output signals of the amplifiers to generate the servo signals. By adding the correction offset signals for correcting the offset voltages of the amplifiers and the photo detectors to the amplifiers, the correction offset signals are amplified. It is, therefore, not necessary to change the correction offset voltages even though the gain of the amplifier is changed and not necessary to change the offset voltage and is independent of the gain-switching of the amplifier.

Abstract: An offset measuring unit receives a servo error signal E1 in which a change in an offset caused by a change in an amount of reflection light directly appears and which does not pass through a filter, and measures an offset amount in the servo error signal which is caused by a change in the amount of reflection light. A correction amount calculating unit calculates a correction amount to cancel out the offset amount and outputs the correction amount to an offset correcting circuit for an offset generating period so as to perform correction.

Abstract: Disclosed is an optical recording and reproducing apparatus comprising a light source directing a light spot toward a recording medium, a detection system detecting light reflected from the recording medium to derive an electrical signal from the reflected light, an information processing circuit modulating the intensity of the light spot according to writing pulses to record information on the recording medium and using the electrical signal to reproduce information from the recording medium, and a tracking servo circuit carrying out tracking servo operation on the basis of the electrical signal and including an extracting circuit connected to a source of extracting pulses having a pulse width at least equal to the writing pulse width so that writing pulse parts contained in the electrical signal are extracted during recording information, whereby a track offset occurring during information recording can be minimized, and the stability of the tracking servo system can be improved.