Abstract: An optical disc drive usable with discs to which data is continuously recorded and discs having a sector format can quickly resume playback signal output after passing imperfection causing potential reading errors, and plays disc with few read errors. A detection signal generator detects DC level fluctuation in the playback signal read from the disc and generates a detection signal tracking the DC level fluctuation. A selector selects a detection signal or a null signal without valid polarity based on the detection signal generated by the detection signal generator and input to the selector. A clamping unit performs a clamping process to suppress DC level fluctuation in the playback signal based on the detection signal when the selection unit selects the detection signal, and does not perform the clamping process when the selection unit selects the null signal. A signal processor performs specific signal processes based on clamping unit output.

Abstract: A signal delay apparatus is provided with; a FIR filter for detecting a leakage signal, which is mixed in a digital detected signal, which is optically obtained from a main truck to be detected in association with the information recorded on a sub truck adjacent to the main truck to be detected, based n a filter coefficient; a coefficient setting unit for generating the above filter coefficient based on the digital detected signal, of which leakage signal is removed, and a digital detected signal, and outputting the generated filter coefficient to the filter; a CPU for controlling the delay amount in the delay with respect to any filter coefficient based on the change of the filter coefficient, which is generated in a predetermined time period and variable delay circuits and for delaying the digital detected signal and the digital detected signal by the controlled delay amount.

Abstract: An optical pickup for high density recording and reproduction, and a reproduction signal detection method, which prevent degradation of a reproduction signal due to shot noise which occurs when a low optical power light is used to form a small light spot for high density reproduction. The optical pickup includes: a light source unit to emit a plurality of light beams, such that a plurality of light spots are formed on a same track of a recording medium; a photodetector to receive and photoelectrically convert the light beams incident through an objective lens and an optical path changer after having been reflected from the recording medium; and a reproduction signal detecting circuit to delay at least one of the detection signals output from the photodetector to remove time gaps between the detection signals, and to sum the delayed detection signal and the remaining detection signals, to detect a reproduction signal. As a result, the reproduction signal with a reduced noise component is detected.

Abstract: A disc player having a prepit detecting circuit which can correctly detect prepits even if phases or amplitude levels of a plurality of read signals read out from a recording disc are deviated from each other. A phase difference between a first read signal and a second read signal read out by first and second reading elements arranged in two regions divided along the direction of recording tracks of a recording disc is detected. A first phase correction read signal is obtained by adjusting the phase of the first read signal by an amount according to the phase difference. A differential value between the first phase correction read signal and the second read signal is outputted as a prepit detection signal.

Abstract: An optical disc which is a rewritable optical disc using a phase change medium or a magneto-optical (MO) medium, or a write once type optical disc using a pigment based medium, and has a track for recording user data, in which a wobble portion waved in a radial direction of the optical disc and a non-wobble portion that is not waved are provided on the track, first sub-information and second sub-information which are data other than the user data are recorded on the track by being overlapped, by using a combination of the wobble portion and the non-wobble portion, in the first sub-information, the length of at least one of the wobble portion and the non-wobble portion is different when a bit takes a logical value “0” and when the bit takes a logical value “1”, and in the second sub-information, the phase of a wave in the wobble portion when a bit takes a logical value “0” is different from the phase of a wave in the wobble portion when the bit takes a logical value “1

Abstract: A meandering groove is formed in a digital disk (10) with a wobble signal that is wobbled to reproduce a clock signal. The wobble signal is read out by an optical head (26). An address detection circuit (40) detects an address signal that is multiplexed with the wobble signal. A PLL oscillation circuit (24) provides a clock signal in synchronization with the wobble signal. Data is modulated by a modulation circuit (16) according to the clock signal and a timing signal based on the address signal, and recorded on the digital disk (10). In reproduction, a RF signal in the wobble signal is converted into a digital signal by an A/D converter (42). The signal is demodulated by a demodulation circuit (44) for data output.

Abstract: An optical disc apparatus prevents erroneous compensation of tilt and minimizes distortion of waveform of the optical and electrical transmitter channel as a whole. For this purpose, a group delay compensator that assures flat frequency characteristic of the gain and can adjust frequency characteristic of group delay is provided to the electrical transmitter of the optical disc apparatus including tilt controller and settings of tilt and group delay are optimized, in the adjustment, to provide minimum jitter of the reproduced signal or minimum code error of data obtained from the reproduced signal.

Abstract: A tracking error generating device which is capable of correctly detecting a phase difference and generating a normal tracking error even when recording marks (or spaces) on an optical disc have short lengths. The tracking error generating device employs, as evaluation target signals, respective output signals of light receiving elements or a signal generated by performing predetermined addition processing on the respective output signals of the light receiving elements, and has a determination circuit for determining whether the evaluation target signals each have a sufficiently large amplitude or time width to generate a tracking error signal, and a selective phase difference supply circuit for selectively supplying a phase difference signal to a smoothing circuit on the basis of a determination result of the determination circuit.

Abstract: An optical pickup compatible with optical discs having different formats. A first light source emits a first light beam suitable for a first format optical disc. An objective lens is optimized for a wavelength of the first light source. Light reflected from the first optical disc provides a reproduction signal. A second light source emits a second light beam suitable for a second format optical disc. A light splitter splits the second light beam and the objective lens focuses the split beams onto the second disc as a main light spot and a sub-light spot. Lights reflected from the main light spot and the sub-light spot are independently detected and then processed to correct for chromatic aberration caused by a difference in the wavelengths of the first and second light beams and/or spherical aberration caused by thickness difference between the first and second format optical discs.

Abstract: Provided are an optical information medium, an optical information recording method and an optical information recording apparatus in which an accurate cross talk can be predicted with a simple structure in a recording mode such as CLV so that a disk having a cross talk reduced can be created.

Abstract: An apparatus for recording first information onto a recording medium, successively to second information that has been already recorded on the recording medium is provided. The first and second information are divided into a plurality of blocks. Each block includes a synchronization signal. This signal is located at a predetermined position in each block. A plurality of pre-pits are pre-formed on the recording medium at intervals of the predetermined length or an integer times the predetermined length. A reference signal with a predetermined frequency is pre-recorded on the recording medium.

Abstract: A recording/reproducing method and apparatus that is capable of driving a recording medium of land/groove recording system using a wobbling signal without a land/groove identification information. The method and apparatus detects the wobbling signal from a recording medium having wobbled land and groove tracks and then multiplies a frequency of the wobbling signal. In the method and apparatus, various control are performed on a basis of a period and a phase of the multiplied wobble signal, so that it becomes unnecessary to switch the polarity of the wobbling signal for the land/groove identification.

Abstract: A recording/reproducing method and apparatus for an optical recording medium that is adapted to accurately detect a wobbling signal from an optical recording medium having recording tracks defined by wobbled grooves independently of a driving condition of the optical recording medium. In the method, a wobbling signal is picked up from a wobbled part of the recording medium. A frequency of a wobbling signal being picked up from the wobbled part is detected, and a frequency band of filtering means for detecting the wobbling signal from the picked-up signal is controlled in accordance with the detected frequency.

Abstract: The present invention relates to a device for reading from and/or writing to optical recording media which has a data slicer for generating a digital output signal from an analogue input signal, a comparison signal generating unit for providing a comparison signal to the data slicer, and a clock generator for generating a clock signal which is matched to the input signal and/or to the output signal. The device optimizes the function of the data slicer independently of the maximum run length in the analogue input signal. The device has a phase comparison device for comparing the digital output signal with the clock signal, which device is connected to an input of the comparison signal generating unit.