Abstract: Tracking system for guiding an optical beam on tracks on an optical disc, said tracking system comprising a photodetector (A1, A2) for detecting optical beams derived from said optical beam, said photodetector generating a first output signal (A) and a second output signal (B), said tracking system comprising first processing means for generating a first differential signal (PP(DC)) corresponding to the low-frequency part of a difference between said first and second output signals. The tracking system comprises second processing means for generating a tracking error signal (PP(AC/DC)) defined by the addition of said first differential signal (PP(DC)) to a second differential signal (PP?(AC)), said second differential signal corresponding to a fraction of the difference in amplitude of the high-frequency components of said first and second output signals. Use: Optical disc player/writer.

Abstract: A writable optical disc has an information writing track, and a guiding track for introducing a laser beam to the information writing track. The guiding track has prepit information recorded thereon, the prepit information including at least address information of the optical disc. The prepit information is recorded on the guiding track at a position where interference of adjacent guiding tracks with the prepit information is prevented. The information writing track is a groove track, and the guiding track is a land track.

Abstract: An optical pickup apparatus and method are provided. The apparatus and method include a light source unit having a holder in which an optical module having first and second light sources for emitting light having different wavelengths and a grating are installed, an optical path changer for changing a path of the light emitted from the first or second light sources, an object lens for focusing light passing through the optical path changer on a relatively thin disc or a relatively thick disc, and a photodetector unit.

Abstract: An optical pickup which, when a first light reflected by a recording medium is divided into a central light area and first and second peripheral light areas at both sides of the central light area, divides the first light reflected by the recording medium into at least 6 light areas, and the at least 6 light areas are independently detected from first through sixth light-receiving portions of a photodetector. Hence, the photodetector can detect a tracking error signal whose offset generation due to a shift of an objective lens is insensitive and whose offset generation due to an initial photodetector balance deviation is depressed.

Abstract: It is an object to provide a laser module in which the position and the posture of a laser beam source can be adjusted even in a small space so that an optical intensity necessary for recording and reproducing information can be ensured and the laser module is seldom affected by an ambient temperature. It is another object of the present invention to provide an optical pickup device, an optical disk device, a focus error detection method and a tracking error detection method. The laser beam source adjustment member 55 and the laser beam source shift member 56 are attached to the laser beam source 52 so that the lead 51 can penetrate them. Further, FPC 57 is fixed to the lead 51 being soldered. The laser beam source 52 and the laser beam source adjustment member 55 are fixed between the holding plate 54 and the laser beam source shift member 56 being pushed by the pushing spring 53.

Abstract: A signal transmission arrangement includes a signal transmitter and a signal receiver wirelessly communicating with the signal transmitter. The signal transmitter includes a hybrid signal device to hybridize the audio signal with the control signal to form a consolidating signal, a frequency modulator to high-frequency modulate the consolidating signal, wherein the consolidating signal is amplified and sent to the signal receiver in a wireless manner. The signal receiver includes a frequency demodulator to demodulate the consolidating signal and a signal dissociating unit to dissociate the consolidating signal to restore the audio signal and the control signal. Therefore, the signal transmission arrangement provides a low-bit rate coding transmission in control signals, in lieu of the high-bit rate coding transmission which requires the expensive high performance integrated circuit, so as to ensure the quality of the audio signal while being cost effective.

Abstract: The optical disc drive reads and/or writes data from/on an optical disc having an information storage layer. In an optical disc drive 100, light from a light source 3 is focused by a focusing section 1, and each of the peripheral and non-peripheral part of light reflected by the information storage layer is received by a photodetector 4. Then, for each part of light, the drive 100 generates a focus signal and a light quantity signal, and normalizes the focus signal based on the light quantity signal. As a result, it is possible to generate a spherical aberration signal according to a quantity of spherical aberration produced at the focusing position of the light. Hence, the signal is not affected by defocusing and thus it is possible to precisely detect a spherical aberration caused by an uneven thickness of the disc and to detect a spherical aberration with high accuracy.

Abstract: A method for deriving a tracking error signal based on a first analog detection signal and a second analog detection signal. The method includes summing the first analog detection signal and the second analog detection signal to generate an analog sum signal. An analog delay device is utilized to delay the analog sum signal to be a delay signal. The delay signal is digitalized into a digital delay signal. The first analog detection signal and the second analog detection signal are respectively transformed into a first digital detection signal and a second digital detect signal. The tracking error signal is then generated utilizing a comparing operation among the digital delay signal, the first digital detect signal, and the first digital detect signal.

Abstract: An apparatus for generating tracking error signals including: an optical detection unit having a plurality of divided light receiving elements to allow beams reflected from a recording surface of the optical disks to be incident; a comparator for outputting after comparing the signals from light receiving elements, which correspond to the set group of the optical detection unit, with the reference signals set for the each group; an error correction unit for correcting and outputting errors if there are any errors after mutual comparison with signals of the groups output from the comparator; a phase-difference detection unit for outputting the signals for each group that correspond to a phase-difference after mutual comparison of the signals of the groups output from the error correction unit; a subtractor for mutually subtracting the signals for each group from the phase-difference detection unit and outputting the tracking error signals.

Abstract: An apparatus for recording data on and reproducing data from the disk in which a recording area is divided into sectors, includes a reproducing signal generator for generating a reproducing signal including sum signals V1 and V2 of radial pairs, a sum signal RF_sum, and a push-pull signal RF_pp from an optical signal reflected from the disk, a header area detector for generating a header area signal including a header area from the reproducing signal, a first synchronous signal level detector for detecting a magnitude Ivfo1 of a first synchronous signal in the first header by being synchronized with the header area signal, a second synchronous signal level detector for detecting a magnitude Ivfo3 of a second synchronous signal in the second header by being synchronized with the header area signal, and a balance calculator for calculating the balance of the magnitude Ivfo1 and the magnitude Ivfo3.

Abstract: An optical pickup comprises: first and second semiconductor lasers (11, 14); a hologram element (17) for diffracting light reflected by an optical information recording medium (9 or 12); and a plurality of photodetectors (18-23). The hologram element (17) has two or more different diffraction regions. The plurality of photodetectors (18-23) are provided away from the first and second semiconductor lasers (11, 14) at both sides thereof along an extended line of a line between light emission positions of the first and second semiconductor lasers (11, 14). The diffracted light generated from the light beam of the first wavelength (10) by the hologram element (17) and the diffracted light generated from the light beam of the second wavelength (13) by the hologram element (17) are collected at substantially the same position at one side, and part (18, 19) of the plurality of photodetectors (18-23) are provided at the position.

Abstract: A method and apparatus for tracking error detection in an optical disk reproduction system. The tracking error detecting apparatus generates a tracking error signal as a difference signal of optical detection signals generated by more than two optical detectors positioned along a diagonal line from a track center and includes binarizers which binarize each output of the optical detectors, phase locked loops (PLLs) which generate respective clock signals synchronized with the outputs of each of the binarizers, a phase difference detector which detects a phase difference between the synchronized signals output from the PLLs, and low-pass filters which filter the output of the phase difference detector to output the result as the tracking error signal. The tracking error detecting apparatus generates a tracking error signal which is not dependent on the lengths of pits or marks recorded on an optical disk, enhancing the reliability of the tracking error signal.

Abstract: A track error detection device that removes a phase offset and a phase offset removing method thereof removes an error signal generated by device circuit errors. The device includes an equalizing unit for equalizing the inputted signals A, B, C and D at a level, a comparison unit for quantizing the equalized signals A, B, C and D, and a phase shifting unit for removing phase offsets among the quantized signals A, B, C and D, based on control signals. A system control unit provides the control signals to the phase shifting unit. The track error detection device can remove all types of phase offsets which occur in the track error detection device. The accuracy and reliability of the detected track error signal is thus improved. By adjusting the phases of the quantized signals in the process of removing the phase offsets, power consumption and size of hardware is reduced.

Abstract: The optical pickup apparatus includes a light emitting means, an optical means, and an optical detection means. The light emitting means emits a single beam. The optical means diffracts the single beam, focuses the optical spot of the diffracted beam on a track, and transmits the diffracted beam to an outside. The optical detection means includes a first optical detection unit on which a central beam having a 0-order diffraction coefficient is focused, and second and third optical detection units on which side beams having ±1 diffraction coefficients are focused, respectively. Each optical detection unit is segmented into a specific number of optical detection areas, and at least one of the optical detection units is provided with an optical detection area on which a tracking error signal used to compensate for tracking offset attributable to optical axis offset of an objective lens is not formed.

Abstract: An optical pickup for recording and/or reproducing data with respect to a multilayer recording medium having a plurality of recording layers, where the optical pickup includes a light source emitting a beam having a predetermined wavelength, a diffraction unit separating the beam emitted from the light source into a main beam and a sub-beam, and a photodetector having a main photodetector detecting a main beam reflected from the multilayer recording medium and a sub-photodetector detecting the sub-beam. In the optical pickup, the main photodetector and sub-photodetector are separated a predetermined distance from each other so that a beam spot formed by the beam reflected from a defocus recording layer is not detected by the sub-photodetector.

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: A system for phase detection in page-based optical data storage involves a number of features that may be used individually or in combination to provide optimizations and to facilitate the heterodyne detection of the modulated readout signal beam. In one aspect, alignment sensors provide signals indicative of angular misalignment between the heterodyne reference beam and the signal beam, and a feedback control system aligns the reference beam with respect to the signal beam. In another aspect, a differential detection approach is utilized. In yet another aspect, a scanning approach is used wherein the reference beam is scanned over approximately a wavelength of phase difference to cause interference fringes to shift over the photodetector pixel array. Each pixel detects the signal at the phase value that cancels out localized variations of the wavefront, thus increasing the tolerance of the system to phase errors and to angular misalignments.

Abstract: A tracking error detection apparatus comprises a photodetector comprising plural photoreceptor elements; zerocross detection circuits for detecting zerocross points at which two sequences of digital signals intersect the center levels of the respective digital signals, which digital signals are generated according to the amounts of light received by the respective photoreceptor elements and are outputted from the photodetector; a phase difference detection circuit for performing phase comparison using a distance between zerocross points of the two sequences of digital signals, and outputting a result of phase comparison; and a low-pass filter for performing band restriction to a signal outputted from the phase difference detection circuit. When a phase difference between the two sequences of digital signals, which is detected by the phase difference detection circuit, is larger than a maximum value of a theoretical tracking error signal, the output from the phase difference detection circuit is limited.

Abstract: An optical recording/reproducing apparatus includes an optical pickup and a signal processor. The optical pickup includes an optical splitting device which splits light emitted from a first light source into a main light beam and sub-light beams which are symmetrical with respect to the main light beam and irradiates the split light beams on a recording medium, and a light detection device which receives the main light beam and the sub-light beams reflected by the recording medium, so as to detect a tracking error signal in a three-beam method and one of a push-pull method and an improved push-pull method.

Abstract: An optical head in which pre-formatted signals may be detected as variations in the amplitude or the phase in the pre-formatted signals are suppressed, and a recording and/or reproducing apparatus employing the optical head, are disclosed. The optical head includes a light source 212, an objective lens 220 for condensing a light beam radiated from the light source 212 on a recording track of an optical recording medium 102, and a photodetector unit 223 for receiving the light beam reflected back from said recording track. The photodetector unit 223 includes a first light receiving section 230b and a second light receiving section 230c.

Abstract: A tracking error detection device for an optical disk apparatus comprises a detecting unit which includes at least two detectors and detects a reflected light from a series of pits formed on an optical disk, a phase comparing unit which detects a phase difference of outputs of the at least two detectors, and a low-pass filter which smoothes an output of the phase comparing unit, a cut-off frequency of the low-pass filter being higher than a frequency at which a spectrum of a modulation code recorded in the optical disk becomes ?10 dB and lower than a frequency at which the spectrum of the modulation code recorded in the optical disk becomes ?5 dB.

Abstract: A tracking error signal calculating unit (221) detects a tracking error signal of light with respect to a mark recorded on a wobbled groove in a focused-on state from the light reflected back from the wobbled groove. A pull-in signal calculating unit (225) detects a total light volume signal PI of the mark, recorded on the wobbled groove, from the reflected light. A D-flipflop discriminating circuit (244) compares the phase of a binary coded version of a tracking error signal TE detected by the tracking error signal calculating unit to the phase of a binary coded version of the total light volume signal PI as detected by the pull-in signal calculating unit to discriminate the sorts of the optical discs having the same outer shape and the same optical system but differing in the UTOC recording system.

Abstract: In a configuration in which side beams scan in positions that are offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of an optical disk, a differential signal is generated from push-pull signals of the return lights of the side beams to generate a track-cross signal. In a configuration in which side beams scan in positions that are offset with respect to a main beam by approximately (¼+n)P or (¾+n)P in the radial direction of an optical disk, far-side or near-side light detection results of the return lights of the side beams are processed and computed with respect to a push-pull signal of the return light of the main beam.

Abstract: Provided is an information recording/reproducing apparatus which can perform servo control with a simple circuit structure and can be manufactured at a low cost. Analog output signals from a plurality of separate portions of a photosensor which receive reflected light from an optical disk are converted into one-bit digital outputs using a plurality of ?? conversion circuits; the one-bit output signals of the plurality of ?? conversion circuits are arithmetically operated using an arithmetic circuit to generate an n-bit (n>1) servo error signal. Further, the servo error signal of the arithmetic circuit is converted into an m-bit (m>n) servo error signal by a single decimation filter.

Abstract: The present invention provides an optical pickup device that is resistant to noise in a signal or an RF signal outputted from each light receiving member. Current signals outputted from the light receiving members are converted into voltage signals by I/V converters. The voltage signals are then added up by an adder, and then the added voltage signal is attenuated by an attenuator, so as to obtain an RF signal having the same signal level as the voltage signal outputted from each I/V converter. The RF signal is then transmitted from the optical pickup device to a circuit substrate through a signal line.

Abstract: An optical reproducing apparatus that uses a hologram laser module and is applicable to a DVD Multi drive, wherein five sub spots of light in total that are most suitable to perform the differential push-pull tracking both for DVD-RAM and for DVD-R/RW are irradiated on the disk, respectively, and influence of several sub spots that are unnecessary in recording and reproducing a disk is canceled out by calculation, to realize an optical head that is compatible with the DVD Multi drive using a hologram laser module, and thereby providing a small-size, high-performance optical reproducing apparatus.

Abstract: In a tracking controller for an optical pickup, a photodetector having four light reception parts receives return light from an optical disc and outputs light detection electric signals. Predetermined addition and subtraction operations are performed on the light detection electric signals from the light reception parts. A phase comparator compares phases and outputs a pseudo radial contrast signal. Bringing into tracking servo control is performed based on the pseudo radial contrast signal.

Abstract: According to the present invention, an optical pickup device forms one main spot, a first subspot, and a second subspot by irradiation of light on an optical disk having a groove part and a land part. The optical pickup device includes operation circuits which indicate a deviation between each of the optical spots and a track, and ? detecting means for detecting such an ? value that a difference in absolute value between SPP1 and ?SPP2 falls in a preset range, where an AC amplitude of a push-pull signal of the first subspot is SPP1, and an AC amplitude of a push-pull signal of the second subspot is SPP2, wherein SPP1??SPP2 (? is a constant) is a land/groove discriminating signal. With this, in the optical pickup device for recording and reproducing information on/from the optical disk having a land/groove part, it is possible to generate a land/groove discriminating signal and a tracking error signal without an offset, thereby performing excellent tracking control.

Abstract: An optical head comprising a light source, an objective lens, a light splitting means, a light receiving element, a tracking error signal detection means, and a spherical aberration detection means, wherein the light splitting means has six regions that are divided by a first splitting line that is substantially parallel to a longitudinal direction of an information tracks, and by second and third splitting lines perpendicular to the first splitting line.

Abstract: In an optical recording medium having two information recording layers, a highly reliable recording can be conducted in one of the recording layers in the back regardless of the recording state of the other recording layer closer to the side of the disc on which light is incident. A first photodetector 115 detects reflected light from a recording layer 103 in the back when the light is focused thereon. A second photodetector 116 is disposed outside the periphery of the first photodetector 115 and detects reflected light from a recording layer 105 located in front. When recording in the recording layer in the back, the write power is controlled in accordance with the output level of the second photodetector.

Abstract: An unknown optical disc is identified as a CD when an all sum signal value AS-max by a photodetector on a signal surface of the unknown optical disc is larger than an all sum signal value AS-cdref for CD signal surface reference for identifying the CD and the hybrid SACD as a CD based on each CD signal surface thereof, and a focus search driving voltage Y corresponding to the signal surface of the unknown optical disc is lager than a voltage value acquired by a predetermined relational expression between a focus search driving voltage Q corresponding to a DVD signal surface of a reference DVD and a focus search driving voltage R corresponding to a CD signal surface of a reference CD.

Abstract: A tracking error detection apparatus comprises a phase difference detection circuit for receiving two sequences of digital signals, and performing phase comparison using a distance between zerocross points of the two sequences of digital signals to output a result of phase comparison, and an LPF for generating a tracking error signal from the result of phase comparison. The phase difference detection circuit does not carry out phase composition in a position that is not appropriate as a target position to perform phase comparison, and outputs the result of phase comparison as a pulse signal corresponding to one sampling clock. Therefore, even when a disc is played at CAV or a flaw or the like exists on the disc, an accurate tracking error signal can be detected.

Abstract: An optical information apparatus of the present invention includes: an optical pick-up head including: a light source; a diffraction unit; a condensing unit; a beam splitter; a photodetector; and a tracking error signal generator. An optical recording medium has tracks arranged substantially at a constant pitch. An average of a pitch is tp. When a main beam is placed on the track, a first sub-beam and a second sub-beam are placed between the tracks.

Abstract: There is employed a configuration to detect, by making use of an optical pick-up (104) when tracking servo is performed along wobble grooves of an optical disc (102), phase errors between main wobble signal outputted as the result of the fact that reflected light beams corresponding to main spot of the optical disc (102) are received at a main light receiving section (321) of light detecting means (32) and side wobble signals outputted every side spot as the result of the fact reflected light beams corresponding to respective side spots of the optical disc (102) are received at a first sub-light receiving section (322) and a second sub-light receiving section (323) to calculate difference between the both phase errors at a difference calculating circuit (59) to generate, from this difference, a skew signal including inclination direction and inclination quantity of the optical disc (102).

Abstract: An optical reproducing apparatus that uses a hologram laser module and is applicable to a DVD Multi drive, wherein five sub spots of light in total that are most suitable to perform the differential push-pull tracking both for DVD-RAM and for DVD-R/RW are irradiated on the disk, respectively, and influence of several sub spots that are unnecessary in recording and reproducing a disk is canceled out by calculation, to realize an optical head that is compatible with the DVD Multi drive using a hologram laser module, and thereby providing a small-size, high-performance optical reproducing apparatus.

Abstract: An optical pickup device includes an irradiating optical system for converging a light beam to form a spot on a recording surface via a light-transmitting layer of an optical recording medium, and a photodetection optical system for converging return light reflected and returned from the spot on a photodetector. The device detects wave aberration and focal error of the light beam. A diffractive optical element is disposed on the optical axis of return light in the photodetection optical system and provided with an annulus. The diffractive optical element annularly extracts, from return light, ray components in the vicinity of a predetermined radius on a pupil on the emitting pupil surface of the irradiating optical system, which is affected by the wave aberration generated in the optical system.

Abstract: An optical pickup, optical recording and/or reproducing apparatus including the same, and a method of realizing a tracking servo that is compatible between different types of optical data storage media. The optical recording and/or reproducing apparatus splits light from a light source into a main beam and four or more sub beams symmetrical with respect to the main beam, which are then emitted on an optical data storage medium, wherein the four or more sub beams include two first sub beams located close to the main beam and two second sub beams located away from the main beam, and detects a tracking error signal by a differential push-pull (DPP) method using detection signals of the main beam and the pair of first sub beams and of the main beam and the pair of second sub beams for ±R/RW and RAM type optical data storage media, respectively.

Abstract: An optical head device includes a light source for emitting light; a collection optical system for collecting the light emitted by the light source to an information memory medium including tracks having prescribed grooves; a light detector having a plurality of detection areas for receiving the light reflected by the information memory medium and outputting a signal in accordance with a light amount of the light received; a tracking error signal generator for receiving the signals output from the light detector and generating a tracking error signal based on the signals; and a light division element for dividing a reflected light reflected by the information memory medium.

Abstract: An optical disc system includes a photo detector circuit of an optical disc drive and a signal processing system. The photo detector circuit is configured to generate at least one information-carrying signal from an optical disc assembly. The signal processing system is coupled to the photo detector circuit to obtain from the at least one information-carrying signal both operational information used to operate the optical disc system and data indicative of presence and/or characteristics of an investigational feature associated with the optical disc assembly. Methods and discs for imaging a biological or medical investigational feature are also provided.

Abstract: Provided is a focus and tracking control method for an optical pick-up apparatus which is used for recording and reproduction of a small-sized optical disc and which can carry out stable focus control and stable tracking control. A focus control method for an optical pick-up apparatus comprising a light source, an objective lens, a light receiving means having divided four light receiving zones and a polarizing means having divided for lattice zones, characterized in that when the reflected light beam is incident upon the four light receiving zones by way of the four lattice zones, focus control is carried out in accordance with a difference signal between the groups, in the radial direction, of the four light receiving zones which are divided into two groups in the radial direction by the division line in parallel with the tangential direction, respectively through the four lattice zones which are divided into two groups in the tangential direction by a division line in parallel with the radial direction.

Abstract: An optical head device includes: an optical element collecting light reflected from a reproduction information layer (a target information layer in an optical information recording medium) and light reflected from information layers adjacent to the reproduction information layer at different positions; a light receiving element obtaining a detection signal from the reflected light collected by this optical element; and arithmetic circuitry obtaining a reproduction signal from this detection signal.

Abstract: An optical pickup apparatus includes a light source module which emits a light beam, a beam splitter which reflects or transmits the light beam emitted from the light source module, an objective lens which focuses the light beam passing through the beam splitter onto a disc, and a photodetector which receives and detects the light beam reflected by the disc, wherein the light source module includes a first light source and a second light source that emit first and second light beams having different wavelengths and are formed into a single module. The optical pickup apparatus further includes a first grating which divides the first light beam emitted from the first light source into three beams of the first light beam and transmits the second light beam emitted from the second light source, and a second grating which transmits the first light beam emitted from the first light source and divides the second light beam emitted from the second light source into three beams of the second light beam.

Abstract: A system provides a signal to an actuator within an optical pickup unit of an optical disk drive. In one implementation, SUM signal data (an output from the quad sensors typically present in the optical pickup unit) is recorded within a SUM table. An error term generator processes the SUM signal data from the SUM table to produce an error term. An actuator control signal generator generates a signal to control movement of the actuator, wherein the signal is a function of a prior actuator position, the error term and an adaptation coefficient, wherein the adaptation coefficient impacts a rate at which the error term is allowed to modify the prior actuator position.

Abstract: An apparatus for generating tracking error signals including: an optical detection unit having a plurality of divided light receiving elements to allow beams reflected from a recording surface of the optical disks to be incident; a comparator for outputting after comparing the signals from light receiving elements, which correspond to the set group of the optical detection unit, with the reference signals set for the each group; an error correction unit for correcting and outputting errors if there are any errors after mutual comparison with signals of the groups output from the comparator; a phase-difference detection unit for outputting the signals for each group that correspond to a phase-difference after mutual comparison of the signals of the groups output from the error correction unit; a subtractor for mutually subtracting the signals for each group from the phase-difference detection unit and outputting the tracking error signals.

Abstract: A method of and a circuit for providing a playback signal, which is compensated for time delay, from a photodetector having a plurality of outputs. A time difference between a first signal corresponding to a part of the outputs of the photodetector and a second signal corresponding to another part of the outputs of the photodetector is detected and one of the first and second signals is temporally shifted to compensate for a time delay between different outputs of the photodetector. The temporally shifted signal is summed with the other signal to provide a playback signal. Accordingly, the time delay between the outputs of the photodetector is compensated, thereby increasing the degree of modulation of the data playback signal. In addition, distortion or degradation of the signal is suppressed and occurrence of errors in the playback signal is minimized, thereby improving the reliability of the playback signal.

Abstract: An error signal detection method includes detecting light incident through an objective lens after having been reflected and diffracted from a recording medium, as eight light portions in a matrix including four inner light portions and four outer light portions, wherein the rows and columns of the matrix are parallel to the tangential and radial direction of the recording medium, respectively; calculating a first sum signal by summing a detection signal from at least one outer light portion located in a first diagonal direction, and a detection signal from an inner light portion located in a second diagonal direction; calculating second sum signal by summing a detection signal from an inner light portion located in the first diagonal direction, and a detection signal from an outer light portion located in the second diagonal direction; and comparing phases of the first and second sum signals to detect a tilt error signal.

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 method of detecting a servo error, an apparatus therefor, a disk which maintains quantity of a servo error signal, a method of controlling a servo of an apparatus for recording data on and reproducing data from a disk, a method of detecting the tracking error, and a method of detecting tilt error of the apparatus.

Abstract: Part of reflected light from an optical disc enters a diffraction element (10). The ±first-order diffracted light and zero-order diffracted light from the diffraction device (10) travel via a cylindrical lens (11) and a spot lens (12) and enter a photodetector (13). If an objective lens shifts, a beam on the diffraction element (10) also shifts. Therefore, the intensity distribution of a spot of the zero-order diffracted light falling on light-receiving areas (A, B, C, D) of a four-part light-receiving element (13a) becomes bright as a whole, while the intensity distributions of spots of the ±first-order diffracted light falling on light-receiving areas (E, F) of light-receiving elements (13b, 13c) become dark as a whole. Thus, an optical pickup tracking error detecting method and an optical pickup device enabling good tracking control are provided.

Abstract: A circuit for generating tracking error signal using differential phase detection, comprising a quadrant photodetector for receiving optical signal and inducting splitting signal A, splitting signal B, splitting signal C and splitting signal D, two adders for generating group signal (A+C) and group signal (B+D). A plurality of equalizers for receiving, equalizing and amplifying splitting signal A, splitting signal B, splitting signal C, splitting signal D, group signal (A+C) and group signal (B+D). A plurality of phase detectors for receiving the output of equalizers and comparing phase difference of splitting signal A and group signal (A+C), group signal (A+C) and splitting signal B, splitting signal C and group signal (B+D), and group signal (B+D) and splitting signal D, and outputting a plurality of adjustment signals respectively. A circuit for eliminating the phase difference by adding and subtracting some adjustment signals with same phase difference.