Abstract: An optical drive device generates a first push-pull signal and a first sum signal based on a light receiving amount in two light receiving areas of which each width in a signal light tangent direction is smaller than a diameter of a spot of signal light, generates a first normalized push-pull signal by normalizing the first push-pull signal by using the first sum signal, and generates a tracking error signal based on the first normalized push-pull signal.

Abstract: A photoreceiver includes: a first light-receiving section divided into two regions by a border extending in a radial direction, and is disposed in a portion where it can receive a +1st order diffraction ray of the main beam from the polarization hologram, so as to detect a spherical aberration; a second light-receiving section is divided into two regions by a border extending in the radial direction, and is disposed in a portion where it can receive a +1st order diffraction ray of the first sub-beam from the polarization hologram, so as to detect a spherical aberration; and a third light-receiving section is divided into two regions by a border extending in the radial direction, and is disposed in a portion where it can receive a +1st order diffraction ray of the second sub-beam from the polarization hologram, so as to detect a spherical aberration.

Abstract: A photodetector detecting reflected light components from an optical medium, the photodetector including a first detector divided into eight sections detecting the reflected light components and converting the light components into electrical signals, a first calculating portion calculating a first tracking error signal from the electrical signals by a differential push-pull method, a second calculating portion calculating a first focusing error signal by an astigmatism method and calculating a second tracking error signal by a differential phase detection method from the electrical signals converted by the first detector; a second detector divided into four sections detecting the reflected light components reflected by the optical recording medium to convert the light components into electrical signals; and a third calculating portion calculating a second focusing error signal by the astigmatism method and calculating a third tracking error signal by the differential phase detection method from the electrica

Abstract: An optical pickup unit comprises a diffraction grating that divides light into at least three luminous fluxes and condenses the three luminous fluxes to apply at least three focusing spots, independent of each other, onto a signal side of a medium. The diffraction grating is divided into at least four regions, a first region, a second region, a third region, and a fourth region.

Abstract: An amplifier circuit and an optical pickup device supporting multi-layered optical discs and hi-speed play mode. The amplifier circuit includes photodiodes 11 to 15; operational amplifiers 21 to 25; feedback resistors 31 to 34; resistors 41 to 45; output terminals 51 to 55; reference voltage sources 56 and 57; a reverse-bias-voltage control circuit 61; and a parasitic-capacitance detecting circuit 65. The reverse-bias-voltage control circuit 61 is connected to the cathodes of the photodiodes 11 to 15. The parasitic-capacitance detecting circuit 65 detects the parasitic capacitance of the photodiode 15. The reverse bias voltage generated in the reverse-bias-voltage control circuit 61 is adjusted according to the detection result by the parasitic-capacitance detecting circuit 65, so that the optical sensitivity of the photodiodes 11 to 14 is maintained at an appropriate value.

Abstract: The present techniques provide methods and systems for alignment of a read head with data tracks on an optical data disk. In embodiments, a multi-pixel detector that is segmented into multiple areas, or detector segments, may be used to detect a pattern in the light reflected from an optical data disk. The detector system may then combine the quantized values from each of the detector segments mathematically to determine the alignment of the read head with a target data track. If the read head drifts to one side or the other, detectors to the side of a center detector may start to pick up energy from the adjacent tracks. If this energy is continuously summed for the detectors on each side, the read head may be centered by balancing the sums from the detectors on each side.

Abstract: A phase error detection apparatus capable of performing offset correction of a tracking error signal accurately even when there is a defect or a non-recorded position on an optical disc. There are provided a phase difference detection circuit (107) which receives two sequences of digital signals, performs phase comparison using a distance between zerocross points of the two sequences of digital signals, and outputs a phase comparison result PCR and a phase comparison completion signal PCC, and an offset control circuit (11) which outputs an offset correction amount for each phase comparison completion signal PCC from the phase difference detection circuit (107), and the offset correction amount ?? is added to the phase comparison result PCR to avoid offset correction in a position where phase comparison is not carried out.

Abstract: A differential phase detector for an optical storage system is set forth. The differential phase detector includes a photodetector circuit arranged to detect light deviations associated with radial errors in the optical storage system. A non-linear equalizer is in communication with the photodetector circuit. The output of the non-linear equalizer is in communication with signal processing circuitry. The signal processing circuitry uses the equalized signals to generate one or more radial error signals.

Abstract: A first optical receiver circuit in an optical receiver IC, which composes an optical disk device, generates a first voltage signal VS1 indicating an amount of light of a laser beam oscillated in a multimode. A second optical receiver circuit generates a second voltage signal VS2 indicating an amount of light of an optical feedback from an optical disk. A binarization circuit extracts a band component corresponding to a predetermined frequency in VS1, and binarizes the band component, thereby obtaining a digital signal. A delay element delays a phase of the digital signal by time equivalent to a phase difference between VS1 and VS2, and outputs the phase delayed signal as a timing signal. A sample hold circuit (S/H) samples and holds the VS2 in synchronization with the timing signal. Further, A LPF eliminates a band component corresponding to the frequency from an output signal of the S/H.

Abstract: An apparatus for detecting a tracking error signal includes an optical detector to receive light beams reflected from an optical disc and having a plurality of detecting regions; and a phase difference extracting unit to extract a phase difference between a pair of optical signals output from the optical detector, wherein the phase difference extracting unit repeatedly moves a first graph representing one optical signal from among the pair of optical signals by a predetermined distance with respect to a second graph representing another optical signal from among the pair of optical signals, the first and second graph represent optical signal values with respect to t-axis, adds differences between optical signal values of the first graph and optical signal values of the second graph corresponding to predetermined positions of the t-axis, the adding differences is repeated for each of the repeatedly moved positions of the first graph, and outputs a moved distance of a position where the added value is smallest

Abstract: An optical disc apparatus includes: a first signal generating portion which generates a first signal that is obtained by processing signal which is output from the photo detecting portion, and which shows a peak in case where a focus position of an objective lens is matched on a recording surface of an optical disc; a second signal generating portion which generates a second signal that is obtained by slicing the first signal at a prescribed level to be digitalized; and a movement stopping portion which stops moving of the objective lens if the second signal is asserted by existence of the recording surface that is a target to be reproduced or to be recorded, then it is negated, and the state to be negated is continued for a prescribed time interval when focus control is performed.

Abstract: The invention provides a tracking control device, a tracking control method, and an optical disc apparatus that enable to stably perform the tracking control, and reduce an influence of stray light from the other layer on the tracking control. A sub push-pull signal correcting section corrects a sub push-pull signal to be generated from returning light of a sub beam in such a manner that a track crossing component of a main push-pull signal to be generated from returning light of a main beam, and a track crossing component of the sub push-pull signal to be generated from the returning light of the sub beam are canceled. A low pass filter reduces a high frequency component of the sub push-pull signal corrected by the sub push-pull signal correcting section. A subtractor subtracts a sub push-pull signal passing the low pass filter from the main push-pull signal to thereby generate a tracking error signal.

Abstract: A DPD tracking error signal detection apparatus includes the following. Four differentiators remove DC components and differentiate four signal with varying differential phases. The signals are then sampled and quantized by four A/D converters, and output to a non-inverting unit and an inverting unit. A phase inverter/compositor then leaves as-is or phase-inverts the output signals, according to a control signal. The non-inverting and the inverting unit each include two Hilbert transformers that phase-shift the output from the A/D converters, two delay units that delay the output of the other A/D converters to match the delay of the Hilbert transformers, two cross-correlators that calculate the cross-correlation between pairs of Hilbert transformers and delay units, and an adding unit that combines the cross-correlator results and outputs the combined result to the phase inverter/compositor.

Abstract: In a multilayer disc has an increased number of recording layers) spaced by spacing from each other, a generation interval between focus error (FE) signals detected from the respective recording layers becomes small. This causes mutual interference between the FE signals and a resulting undesired offset and the like in the signals, leading to a significantly deteriorated quality of the FE signals. To avoid this, in an optical pickup device according to the present invention, detection surfaces are newly added at positions adjacent to the FE signal detection surfaces, a predetermined detection signal obtained from the newly-added detection surfaces is multiplied by a predetermined coefficient value depending on the spacing between the recording layers, and the multiplied signal is subtracted from the original FE signal. As a result, mutual interference between the FE signals can be remarkably reduced.

Abstract: A method for adjusting a tilt of an optical pick-up head includes the steps of: moving the optical pick-up head to a first location and focusing on; obtaining a first focus control power and a first optimum tilt angle at the first location; moving the optical pick-up head to a second location and focusing on; obtaining a second focus control power and a second optimum tilt angle at the second location; calculating an optical sensitivity according to the first and second optimum tilt angles, and the first and second focus control powers; and when the head is moved to a specific location where the tilt of the head is to be adjusted, storing a focus control power corresponding to the specific location, and calculating a tilt angle corresponding to the specific location according to the focus control power and the optical sensitivity so that the tilt of the optical pick-up head can be appropriately adjusted.

Abstract: Provided is an optical pickup apparatus that can be made compact and is capable of producing stable push-pull signals. The optical pickup apparatus includes a light source, an objective lens, a diffraction element, a light-receiving element, and a control-driving section. The diffraction element receives light reflected from an optical recording medium. The light-receiving element receives light beams diffracted by the diffraction element. The light-receiving element has a plurality of light-receiving regions. The light-receiving region produces an output signal responsive to the quantity of the incident light beam. The control-driving section obtains differences among the output signals from a plurality of the light-receiving regions by calculation to derive a push-pull signal, and drives the objective lens under control on the basis of the push-pull signal.

Abstract: An optical disk device has: a detector (11) that converts a reflected light from an optical disk (5) and a reflected light of an incident light from a light source (1) side of a solid immersion lens (4), into electric signals and outputs the signals; a subtracter (15) that computes the output signal of the detector (11) according to a predetermined rule and outputs the result as a tilt detection signal; a CPU (21), an amplifier/phase compensation circuit (16), a switch (17) and an actuator (13) that perform tilt control for controlling tilt of the solid immersion lens (4) with respect to the optical disk (5) using the tilt detection signal; and the CPU (21), a nut (24), a feed screw (25), a decelerator (26) and a stepping motor (27) that perform gap adjustment for changing the gap of the solid immersion lens (4) and optical disk (5), and in the process of adjustment of gap between the solid immersion lens (4) and optical disk (5), the CPU (21) enables tilt control by closing the switch (17) according to the t

Abstract: To provide an optical head device, which can detect an excellent focus error signal for a dual layer optical recording medium, and optical information recording/reproducing device. Reflected light from a dual layer optical recording medium is diffracted by a diffractive optical element divided into four regions, and is received by a photodetector. Optical spots are equivalent to negative first order diffracted light from the four regions of the diffractive optical element, and are received by four dual-divided light receiving sections, respectively, to be used for detection a focus error signal by a Foucault's method. The four dual-divided light receiving sections are provided with positive component light receiving sections for outputting the received light as a positive component of the focus error signal and negative component light receiving sections for outputting the received light as a negative component of the focus error signal, respectively.

Abstract: A disc discriminating method for use in an optical disc drive includes the following steps. Firstly, an optical pickup head of the optical disc drive is controlled to move in a first direction when the optical pickup head is in a track-unlocked state. Then, a tracking error signal and a radio frequency signal are generated. According to the tracking error signal, a tracking error zero crossing signal is obtained. According to the radio frequency signal, a radio frequency zero crossing signal is obtained. According to a phase relation between the tracking error zero crossing signal and the radio frequency zero crossing signal, the disc is discriminated as an on-groove recording disc or an in-groove recording disc.

Abstract: Methods and systems for processing a signal with a corresponding noise profile are disclosed. Aspects of the method may comprise analyzing spectral content of the noise profile. At least one noise harmonic within the signal may be filtered based on said analyzed spectral content. The filtered signal may be limited. The noise profile may comprise a phase noise profile. The signal may comprise at least one of a sinusoidal signal and a noise signal. At least one filter coefficient that is used to filter said at least one noise harmonic may be determined. The filtering may comprise low pass filtering and the limiting may comprise hard-limiting the filtered signal. The signal may be modulated prior to the filtering. The signal may be downconverted prior to the modulating. At least one signal component of the signal may be downconverted.

Abstract: The optical pickup device according to the present invention includes: a light source which emits a first light at a first wavelength, a second light at a second wavelength and a third light at a third wavelength; an optical path combining unit which combines vectors of the first, second and third light emitted by the light source, and matches optical axes of the first light and the third light; a light collection unit which condenses the light from the optical path combining unit into the optical information storage medium; a diffraction element which diffracts reflected light from the optical information storage medium; a first photo detector, a second photo detector and a third photo detector which receives the diffracted light from the first diffraction element; and a prevention unit formed between the first diffraction element and the first photo detector, the second photo detector and the third photo detector, and which prevents irradiation of + first-order diffracted light diffracted by the first diffr

Abstract: An optical pickup includes: a light source that emits a light beam; an object lens that condenses the light beam on a target recording layer of an optical disk; a lens moving unit; a condensing lens; a hologram element that diffracts, in diffracting a reflected light beam and separating it into reflected zeroth-order and first-order light beams, parts of the reflected first-order light beam in a first direction and sets them as first and second beams, diffracts parts of the reflected first-order light beam in a second direction and sets them as third and fourth beams; and a photodetector that receives the first and second beams and the third and fourth beams and generates light reception signals, and receives interlayer stray light of a part of the light beam reflected by the other recording layers other than the target recording layer and generates a stray light reception signal.

Abstract: An optical pickup apparatus comprising at least: a diffraction grating configured to split first wavelength light into at least a first main beam and first sub-beam, and to split second wavelength light into at least a second main beam and second sub-beam, the diffraction grating including a diffraction surface portion corresponding to the second wavelength light; and a photodetector including a first main light-receiving unit configured to be applied with the first main beam, a first sub-light-receiving unit configured to be applied with the first sub-beam, a second main light-receiving unit configured to be applied with the second main beam, and a second sub-light-receiving unit configured to be applied with the second sub-beam, a distance between the first main light-receiving unit and first sub-light-receiving unit being changed relative to a standardized distance between the first main light-receiving unit and first sub-light-receiving unit.

Abstract: An optical pickup includes: a light source emitting a beam having a predetermined wavelength; a plastic objective lens condensing the emitted beam on an optical disc; a light detector receiving and detecting the beam reflected by the optical disc; an objective-lens driving unit driving the objective lens in the tilt direction to tilt the objective lens; and a tilt-sensitivity sensing unit sensing a tilt sensitivity denoted by ?WLT/??, where ?WLT [?rms] is a coma aberration amount ?? [deg] is a tilt amount at the time of tilting the objective lens, wherein, in the case where the sensed tilt sensitivity is equal to or larger than a predetermined value, tilt is corrected by tilting the objective lens so that signal quality detected by the light detector is improved, and in the case where the sensed tilt sensitivity is smaller than the predetermined value, tilt is not corrected.

Abstract: A method and apparatus for recording/reproducing data is disclosed. The apparatus for recording/reproducing data comprises a diffraction element splitting light diffracted or reflected from a recording medium into a main beam and first and second sub beams, the main beam and the first and second sub beams having no interference from one another; a light-receiving part detecting the main beam and the first and second sub beams; and a controller controlling a position of the diffraction element based on at least one light capacity of the detected beams or the detected position.

Abstract: An optical pickup apparatus, a reproducing apparatus, a recording apparatus, and a tracking error signal generation method are provided. Four light-receiving elements receive stray light of main and sub beams reflected from, out of a plurality of recording layers of the optical disk, the one other than that for effecting recording or reproduction. The four light-receiving elements are disposed individually near every side of the four-part split light-receiving element, of which light-receiving elements are disposed between the two-part split light-receiving elements. Based on stray-light intensity detected by the four light-receiving elements, intensity distribution is calculated for tracking-error signal correction.

Abstract: An optical pickup apparatus is provided with a dividing element having a plurality of regions. The dividing element is capable of dividing a light flux reflected by the optical disc into a plurality of light fluxes having different outgoing directions. Each region of the dividing element and light receiving parts of a light detector are structured such that when a target information recording layer of the optical disc is brought into focus, a light flux reflected from the target information recording layer is focused on the light receiving parts of the light detector, and a light flux reflected from other information recording layer than the target information recording layer is not irradiated onto the light receiving parts of the light detector.

Abstract: An optical pickup apparatus reads an information signal recorded on a recording surface of an optical disk along a track by projecting a light beam. Said optical pickup apparatus has: an objective lens for converging said light beam onto said recording surface; an objective lens moving device for moving said objective lens in a radial direction of said optical disk; and a divisional photosensing device for receiving return light reflected by said optical disk, in a plurality of divided regions.

Abstract: The optical pickup device according to the present invention includes: a light source which emits light at first, second and third wavelengths; an optical path combining unit which combines vectors of the light at the first, second and third wavelengths which is emitted by the light source, and matches optical axes of the light at the first wavelength and the light at the third wavelength; a light condensing unit which condenses the light from the optical path combining unit onto the optical information storage medium; a diffraction element which diffracts light at the first, second and third wavelength which is reflected from the optical information storage medium, in a first direction and a second direction respectively; a first photo detector which receives light at the first, second and third wavelength that is diffracted in the first direction by the diffraction element; a second photo detector which receives light at the first and third wavelength that is diffracted in the second direction by the diffra

Abstract: When recording/reproducing an optical disc having a recording layer of multi-layer structure, an unwanted optical beam reflected from a recording layer other than a target layer for recording/reproduction is incident on a photodetector to cause an unwanted disturbance component to leak to a detection signal, giving rise to a degradation in the quality of a tracking control signal. In an optical pickup apparatus, for suppression of the degradation, an optical element is mounted having a diffraction area for diffracting part of the optical beam and light receiving planes for sub-optical beams are provided each of which has a light shielding zone or dead zone of a predetermined width on its central sectioning line.

Abstract: An optical disc apparatus includes a laser diode for emitting a laser light, a beam splitter for dividing the laser light into a main beam and sub beam, a main photodetector for detecting the main beam to output a main push-pull signal, a sub photodetector for detecting the sub beam to output a sub push-pull signal, and a subtracter for calculating the main and sub push-pull signals to output a differential push-pull signal, in which an amplification degree of the sub push-pull signal is adjusted so that a DC offset on the differential push-pull signal is adjusted, even in the case where a laser intensity is varied.

Abstract: A tracking apparatus for an optical information reproduction apparatus includes the following: a photoelectric detector (1) in which a far-field pattern of a light spot converged on a recording medium is formed across a divided light-receiving cell; an arithmetic unit (2) for outputting at least a pair of arithmetic signals from the output of the photoelectric detector (1); a phase comparator (4) for detecting a phase difference between the output signals of the arithmetic unit (2); an absolute value detector (8) for detecting an absolute value of the output signal of the phase comparator (4); a level detector (9) for generating a signal that indicates whether or not a convergence position of the light spot is located off an information track by detecting a predetermined number of times or more the output signal of the absolute value detector (8) has become larger than a predetermined value; a sensitivity detector (10) for detecting and outputting the sensitivity of the level detector (9) by observing the out

Abstract: An optical pickup apparatus includes a semiconductor laser for emitting a laser light, an objective lens for irradiating the light flux emitted from the semiconductor laser onto an optical disc, and a light detector for receiving the light flux reflected from the optical disc. The light detector has a light receiving part that comprises five regions of a region 1, a region 2, a region 3, a region 4 and a region 5.

Abstract: The present invention uses a stationary medium and a stationary optical pickup unit. The stationary optical pickup unit has a laser, which sends a beam of light through an objective lens, which focuses the beam on a point on the track of the stationary medium. The beam is then reflected toward a re-directing surface (e.g., prism) which diverts it to a photodiode array. Instead of the entire optical pickup moving to follow the track as in conventional systems, only the objective lens inside of the optical pickup moves. The position of the objective lens determines where on the information track the laser will reach. Depending upon where the laser beam reaches, the reflected light beam received by the photodetector array changes. This, in turn, affects the amount of light sensed by each photodetector in the array, thereby causing the output of each of the four photodetectors to change each time the objective lens moves.

Abstract: A light blocking unit includes a plate-like member which is different from a housing member, and a light blocking portion formed on the plate-like member, for blocking light. A light detector has a light receiving portion for receiving light which is partitioned into four divided regions, by a Y-axis-wise parting line and an X-axis-wise parting line in X-Y coordinates, and outputs photoelectric output signals for the respective divided regions in accordance with intensity of the light received by the respective divided regions of the light receiving portion. Of light beams emitted from a polarization beam splitter, a part of the light beams are blocked by the light blocking unit while the other part of the light beams are not blocked and thus emitted to the light detector excluding a region defined by two sides parallel to the parting lines.

Abstract: An optical pickup has a photo detector which is divided into first, second, third and fourth quadrants, receives a laser beam reflected from an optical disc via an objective lens, and outputs first, second, third and fourth detection signals from the respective quadrants. A system controller controls a memory to store levels (A, B, C and D) of the first, second, third and fourth detection signals after a focus servo section performs a focus operation by shifting the objective lens in a direction perpendicular to the optical disc surface, and then, calculates a ratio of ((A+D)/(B+C)) in a radial direction of the optical disc. The system controller controls the tracking servo section to perform a tracking operation to shift the objective lens in the radial direction based on a correction table which represents a relationship between correction amount of the lens shift and the calculated ratio ((A+D)/(B+C)).

Abstract: An operation mode is arranged to be switched between in recording/reproducing and in adjustment. A switching circuit with a hold circuit therefor is on a light receiving element including an optical pickup having a laser light source emitting a laser beam, an objective lens focusing the laser beam onto a recording layer of a disc, and a light receiving element receiving an optical signal modulated. The light receiving element is operable in an adjustment mode for selecting of the signal of an individual light-receiving surface and for outputting the same. The light receiving element is configured so that the address selection signal line in the adjustment mode may be used also as a sensitivity switching signal line. A compact and highly reliable optical pickup with less signal lines can be provided.

Abstract: A tracking error (TE) signal is formed from a single spot on a photodetector 25 to improve the robustness in optical disc applications having a reduced track-pitch. Reduced track pitches are employed in high data capacity optical disc formats. By using high frequency cross-correlation of a central aperture signal, the differences within the left 21 and right 23 detector halves yield a divergence from the zero crossing that produces a more pronounced tracking signal. The more pronounced tracking signal is insensitive to incoherent cross talk in multi-layer discs.

Abstract: A DSP of the DVD recorder includes a balance value setting portion for determining an appropriate value of a focus balance value ? when information is reproduced from an optical disc so as to record the determined focus balance value ?0 in a balance value storing portion and to set the same in a first amplifier of a focus error signal generating circuit, and a correction executing portion for reading the focus balance value ?0 stored in the balance value storing portion when information is recorded in the optical disc 2 so as to correct the read value to be a focus balance value ?1, which is set in the first amplifier of the focus error signal generating circuit.

Abstract: An optical pickup including a two-wavelength multilaser for generating a tracking error signal and a focusing error signal with high accuracy without light quantity variations which otherwise might be caused by the interference. An optical beam of first wavelength is emitted from first laser light source, and an optical beam of second wavelength longer than the first wavelength is emitted from second laser light source. The optical beams of the first and second wavelength are each split into at least one main optical beam and two sub-optical beams by a grating having, in a single plane, a first grating pattern area for splitting the optical beam of the first wavelength and a second grating pattern area for splitting the optical beam of the second wavelength. The area of the first grating pattern area is larger than the area of the second grating pattern area.

Abstract: A DSP of a DVD recorder includes: a gain setting portion determining appropriate values of a first gain ? and a second gain ? when playback of an optical disc is performed, recording the first gain ? and the second gain ? thus determined in a gain storing portion, and setting them in a main differential amplifier and a sub differential amplifier, respectively; and a correction performing portion reading, when recording on the optical disc is performed, the first gain ? and the second gain ? stored in the gain storing portion, correcting at least one of them, and setting them in the main differential amplifier and the sub differential amplifier, respectively.

Abstract: An apparatus for recording/reproducing holographic data and a method of adjusting a position of a recording layer. While an objective lens focusing first and second lights having different wavelengths on a holographic data storage medium including first and second reflective layers reciprocatingly moves in a direction of an optical axis, a focus movement unit, which moves a focus of the second light in the direction of the optical axis until a time difference between a first detection signal generated when the first light is reflected from the first reflective layer and a second detection signal generated when the second light is reflected from the second reflective layer becomes a value corresponding to a position of a desired recording layer, is controlled to move a focal position of the second light so that the focal position of the second light can be adjusted to the position of a desired recording layer.

Abstract: An optical device diffracts incident light with a hologram element and receives the diffracted light with light receiving faces 20A to 29 on a light receiving element. Reflected sub-beams used for a tracking operation are received with different ones of the light receiving faces depending on the wavelengths of the reflected sub-beams. When first light receiving faces 22, 23, 26, and 27 are receiving an incident beam of a first wavelength, output signals from the first light receiving faces and output signals from the other light receiving faces 24, 25, 28, and 29 are processed to detect an unnecessary light component. The optical device can record and/or reproduce information signals to and/or from optical discs such as DVDs and CDs which need light sources of different wavelengths, without the influence of unnecessary reflected light from the optical discs or without complicating operation of output signals.

Abstract: The optical pickup device includes a semiconductor laser for emitting laser light of 650 nm and 780 nm in wavelengths, a semiconductor laser for emitting laser light of 400 nm in wavelength, and an optical sensor which is provided in sequence with a first light receiving surface divided into four areas in a matrix manner, a second light receiving surface divided into four areas in a matrix manner, and a third light receiving surface divided at least into two areas aligned inline. Reflected light of three beams of 400 nm in wavelength and reflected light of three beams in 780 nm in wavelength are received on the first to third light receiving surfaces respectively, and a main beam of reflected light of 650 nm in wavelength is received on the first light receiving surface on one side out of the three light receiving surfaces.

Abstract: There is provided an optical pickup apparatus and a beam splitter which are capable of suppressing an adverse effect resulting from light reflected by a non-light-condensed layer that is different from a light-condensed layer. In respective TES light-receiving sections, interposed light-receiving elements are disposed so as to be adjacent to first sub beam-receiving elements. The interposed light-receiving elements are disposed away from both of positions where a main beam reflected by a light-condensing recording layer is condensed and where respective sub beams reflected by the light-condensing recording layer are condensed, and disposed so as to be adjacent to the first sub beam-receiving elements. The interposed light-receiving elements receive the main beam reflected by a non-light-condensing recording layer In a compensating section, results of light received by the first sub beam-receiving elements are compensated based on results of light received by the interposed light-receiving elements.

Abstract: A disc-driving apparatus has an optical pickup including an objective lens. The objective lens has an optical axis that is met on a line excluding a central axis of revolution of a disc. The apparatus has storage device that stores plural correction values obtained by detecting fluctuations in amplitude of a tracking error signal with respect to a radial direction of the disc or a quantity of de-tracking with respect to the radial direction thereof. The apparatus has control device that reads the correction value from the storage device and, when the optical pickup is operating, corrects the tracking error signal to conduct servo control based on the corrected tracking error signal.

Abstract: Provided is a focus servo process automatic selecting method. In a related art optical pickup apparatus, only one of AD and DAD is selected and used when a focus servo is performed for disk detection and a focus-on operation. According to the method, servo crosstalk values of the two focus servo processes are compared and a suitable focus servo process is automatically selected, so that an optimum focus servo is realized.

Abstract: By inputting differential signals to transistors Tr21a to Tr21d and Tr22a to Tr21d, an addition operation is performed on the four differential signals, and a filter operation is performed by a capacitor C21 and resistors R21 and R22. An offset of a signal obtained as a result of an addition operation performed on the four differential signals is removed by transistors Tr1 and Tr2.

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.

Abstract: An object of the present invention is to improve a conventional DPD method having a problem that a tracking servo becomes unstable due to a reduction in the accuracy of detecting a phase difference between short mark signals at an edge, in a case where the amplitudes of the short mark signals are very small, or where a readout signal contains large noise. To this end, the present invention provides a method for increasing the contribution ratio of long mark signals to generate a tracking error signal by causing a phase difference pulse to include information on a phase difference, and by causing the area of the pulse to be weighted according to the length of a mark/space adjacent to a concerned edge.