Abstract: Data read from a disk is input to an RF amplifier. An RF amplifier generates, based on bit data, an RF signal constituted by a plurality of components of mutually different frequencies. The RF amplifier determines a relation between the frequencies and gains on the basis of a control clock and adjusts the gains of respective components in the RF signals on the basis of the relation (equalize-processing). A PLL circuit has a first VCO and first frequency divider to generate a bit clock and generates, on the basis of an output signal of a data slice circuit, a first control voltage for controlling the first VCO. The first control voltage, being passed through a lowpass filter, is converted to a second control voltage for controlling a second VCO. The second VCO has an arrangement and characteristic substantially the same as those of the first VCO.

Abstract: A tracking servo device for use with an optical disc apparatus includes a photodetector unit having a plurality of photodetectors each of which is split in association with the direction of tracks formed on the optical disc, and a tracking error generating unit for finding the difference in outputs from at least two of the photodetectors of the photodetector unit for generating a tracking error signal. The tracking servo device also includes a first correction unit for removing an offset produced in the tracking error signal when the tracking servo is on, and a second correction unit for removing an offset produced in the tracking error signal when the tracking servo is off.

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.

Abstract: A semiconductor integrated circuit device 1 for use in a disk drive has a temperature detection section 9 that detects the temperature inside the semiconductor integrated circuit device 1 to switch a signal TSD between high and low levels when a predetermined temperature is reached, and a delay circuit 11 that receives this signal TSD and a clock from a control section 10 to output signals TSD1 and TSD2.

Abstract: This invention provides an optical head apparatus that is not influenced by the offset component contained in a track deviation signal and the track offset caused by lens shift control. According to an optical head apparatus of this invention, portions of light-receiving regions of a photodetector for detecting a track deviation signal are used as offset component detection light-receiving regions for removing any offset component from a track deviation signal. With this arrangement, the offset component contained in a track deviation signal, i.e., the influence of a lens shift on a tracking error signal, is removed by using light from the region where all the 0th-order diffracted light, 1st-order diffracted light, and −1st-order diffracted light of the light reflected by the optical disk overlap each other.

Abstract: A device for automatically controlling a sled loop gain in an optical disc drive having a sled motor.

Abstract: A high speed optical disc reproducing device includes: a gain amplifier for amplifying data picked-up from an optical disc, with a specific amplification gain and a frequency and boost control unit for outputting a frequency and boost gain control signal under the control of a main control unit in accordance with the kind of pick-up and disc used in the reproducing device. The device also includes a boost filter, which serves the functions of boosting high frequency parts of the output signal of the gain amplifier according to the frequency and boost gain control signal, and a uniform group-delaying section which group-delays all of the frequency areas of the output signal. The device minimizes the signal distortion, caused by the difference in the pick-up and disc characteristics of a high speed optical disc reproducing device.

Abstract: A transfer control system of an information read beam for transferring an information read beam from one recording side to another in an information reader comprising offset error signal generation means for piggybacking a predetermined offset level onto a focus error signal indicating a shift from the focus position of the information read beam to generate an offset error signal in order to shape the beam form of the information read beam for reading record information from an information recording medium having a plurality of laminated recording sides on the recording side. It comprises offset level setting means for setting the predetermined offset level in the offset error signal generation means, transfer signal generation means for generating a transfer signal for forcibly transferring the information read beam, and transfer means for transferring the information read beam from one recording side to another based on the transfer signal.

Abstract: Method for the correction of a tracking error signal during optical scanning of a recording medium in the form of a disc. In the case of MO discs, the Kerr rotation angle is in general very small, so that so-called enhancement is used for processing. This leads to birefringence effects which are thermally induced on the WO disc during the writing process producing a noise level on the track error signal. According to the invention, an optical scanner arrangement is used to determine light intensities from two mutually perpendicular polarization planes. A noise element, which is produced by interfering polarization rotation of the light, in the tracking error signal is compensated by linking the electrical output signals of the scanner arrangement. Applicable both to MO and WO as well as CD audio, CD video and CD-ROM.

Abstract: An optical pickup position control device according to the present invention automatically adjusts tracking with precision and in a short time. Two deviation signals, which express deviation of a light beam, projected by a pickup which uses the three-beam method, from a target track of a disk, are digitized by two AD converters. Two high-pass filters extract from the deviation signals AC signals, producing a tracking error signal. Further, two low-pass filters extract from the deviation signals DC signals (offset components). Two other low-pass filters extract from the deviation signals low-band signals containing DC components. Using the various foregoing signals, a control circuit calculates correction values to be applied to two offset correcting circuits and to two gain/balance correcting circuits, and corrections are performed collectively and simultaneously on the basis of these correction values.

Abstract: A tracking method discriminates whether an optical disc loaded in a recording and/or reproduction system is a shallow groove type optical disc or a deep groove type optical disc, and corrects the phase of the tracking error signal detected from the optical disc according to the discrimination result, to then perform a tracking servo control using the corrected result. A tracking apparatus includes an optical signal detector detecting a tracking error signal from an optical disc loaded in a recording and/or reproduction system. A groove type discriminator analyzes the tracking error signal output from the optical signal detector to discriminate a groove type of the loaded optical disc and generates a corresponding control signal. A phase corrector corrects the phase of the tracking error signal output from the optical signal detector according to the control signal applied from the groove type discriminator.

Abstract: An adaptive, discrete-time sliding mode controller (SMC) is disclosed which detects and adapts to gain variations in the controlled plant. The overall control effort is generated by combining a linear control effort with a discrete-time sliding mode control effort generated by switching between gains in order to drive the system's phase states toward a sliding line trajectory. A sliding mode variable &sgr;k defines the position of the system phase states relative to the sliding line. The SMC controller is designed such that the sliding mode variable &sgr;k crosses the sliding line and changes sign at every sample interval. For the nominal plant gain, the SMC controller is also designed such that the magnitude of the sliding mode variable &sgr;k+1=−&sgr;k will remain constant (&sgr;k+1=−&sgr;k) and substantially constrained to |&sgr;k|=&Dgr;/(1+&lgr;) where &Dgr; and &lgr; are predetermined design constants.

Abstract: A tracking control apparatus for effectively compensating for a direct current offset of a tracking error signal when a recording medium having wobbled land and groove tracks is accessed. In the apparatus, a light beam is irradiated onto signal tracks of a recording medium including successively formed wobbled areas or intermittently formed wobbled areas, and a reflective light is detected by a photo detector divided into a plurality of areas. Signals detected by two areas of the photo detector symmetrically divided on a basis of the direction of the track are subtracted to generate a difference signal. Also, signals detected by the two area of the photo detector are added to generate a sum signal. A tracking offset compensating signal is generated based on the difference signal and the sum signal. The tracking error signal is compensated by the tracking offset compensating signal, so that a light beam can accurately trace the signal tracks.

Abstract: A disk recording or playback device first sets a target region, and a pickup is moved toward the disk inner periphery to turn on a sensor switch. The pickup is thereafter reversely moved, and further caused to overrun for a predetermined period of time from the position where the sensor switch is turned off. The pickup is returned after reading the address reached by overrunning. If the address is closer to the disk outer periphery than the target region, the overrun time is decreased, and the movement of the pickup toward the lead-in area is repeated again. When the overrun time becomes not greater than a specified value and if the address then read is closer to the disk outer periphery than the target region, the direction of overrun is reversed toward the disk inner periphery. The overrun time enabling the pickup to reach the target region accurately is saved.

Abstract: A magneto-optical information recording/reproducing apparatus in which a magneto-optical information recording medium at least including a first magnetic film having perpendicular magnetic anisotropy, and a second magnetic film to which information recorded on the first magnetic film is transferred by irradiation of a laser beam, is used so that a readout laser beam is irradiated onto the second magnetic film to thereby readout the information transferred to the second magnetic film. The apparatus includes a 2-split detection circuit for receiving the readout laser beam reflected from the second magnetic film of the recording medium, and a subtraction circuit in which output signals of the two detection elements of the 2-split detection circuit are subtracted from each other to generate a differential signal.