Abstract: A tracking error detecting method comprises the steps of causing intensity distributions of single light introduced into an objective lens to have symmetry with respect to the track direction of an optical recording medium and the direction oblique to the direction perpendicular to the track direction, dividing a light-receiving unit into at least light-receiving units of the track direction and light-receiving units of the direction perpendicular to the track direction and detecting a tracking error signal based on detection signals from the divided light-receiving units.

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.

Abstract: An optical information recording and reproducing apparatus includes a light source for emitting a light beam, a head unit, including an objective lens and a solid immersion lens, that allows a light beam from the light source to reach an optical recording medium as evanescent light, and a photodetector that detects returning light that returns from a bottom surface of the solid immersion lens for detecting a gap and a tilt between the optical recording medium and the solid immersion lens. The photodetector has a first section and a second section, along a direction in which the returning light is moved in the photodetector, when the solid immersion lens is driven in a tracking direction with respect to the optical recording medium. An area of the returning light in the first section and an area of the returning light in the second section is constant, even when the solid immersion lens is driven in the tracking direction.

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: An optical pickup unit for recording information on and/or reproducing information from a multilayer information recording medium including multiple recording surfaces in each of which a guide groove on which the information is to be recorded is spirally formed is disclosed. The optical pickup unit includes a light source, a diffraction element configured to split the light beam emitted from the light source into a main light beam and first and second sub light beams, an objective lens for focusing the main and sub light beams onto a recording surface of the multilayer information recording medium, and multiple light receiving elements each divided into light receiving parts so as to receive the main and sub light beams reflected from the recording surface. The focused first and second sub light beams are disposed at respective positions at least 3/2 tracks away from the focused main light beam on the recording surface.

Abstract: An optical head comprising a light source, objective lens, light splitting means, light receiving element, tracking error signal detection means, and spherical aberration detection means. Light splitting means has six regions divided by a first splitting line parallel to a longitudinal direction of information tracks, and second and third splitting lines perpendicular to the first line. Spherical aberration detection means compares a first focal point shift amount obtained by detecting a light spot size formed by focusing light fluxes, created by laser light passing through two regions between the second and third splitting lines, onto the light receiving element, and a second focal point shift amount obtained by detecting light spot size formed by focusing light fluxes, created by laser light passing through the four regions, on the outer side of second and third splitting lines, generating a spherical aberration error signal for detecting spherical aberration at the objective lens.

Abstract: An image forming apparatus at least includes a photoreceptor, a light emitter, a detector and a controller. The light emitter irradiates the photoreceptor with a laser beam so as to form an electrostatic latent image thereon. The detector detects an incident amount of the laser beam falling on a light receiving portion of the detector on a main scan line. The controller changes at least one of a detection sensitivity of the detector for a laser beam and an emission amount of the laser beam emitted from the light emitter when the incident amount of the laser beam detected by the detector is not greater than a predetermined value.

Abstract: The present invention relates to a drive for accessing an optical record carrier (2) comprising means (4) for determining the type of record carrier, in particular for distinguishing a read-only record carrier from a recordable or rewritable record carrier having a wobbled groove in the lead-in zone, said means comprising: a DPD measuring unit (41) for measuring the differential phase detection (DPD) signal, a PP measuring unit (42) for measuring the push-pull (PP) signal in case no DPD signal could be measured, a wobble locking unit (43) for locking, in case a PP signal could be measured, to the wobble embedded in said wobbled groove using a first and/or a second polarity setting, and an indication unit (44) for generating a first indication signal indicating that the record carrier is a read-only record carrier if a DPD signal could be measured and that the record carrier is a recordable or rewritable record carrier if no DPD signal but a PP signal could be measured and if locking to the wobble has been suc

Abstract: In the first and second light-receiving regions equally divided into two in parallel with the track of the optical disc, the reflected light received from the optical disk is converted into electric signals and fed out by individual light-receiving regions. Then, the light-receiving ratio indicating the ratio of amounts of received light is calculated from the amplitude of the electric signal generated in the first light-receiving region and the amplitude of the electric signal generated in the second light-receiving region. Then, it is determined whether or not an absolute value of the light-receiving ratio is larger than a predetermined vale. When the absolute value is larger, the movement of the objective lens in a radial direction is corrected by incorporating a predetermined correction value.

Abstract: An optical pickup includes an optical system in which light from a light source is introduced through an objective lens into an optical recording medium and in which light reflected from the optical recording medium is introduced into a light-receiving unit and an objective lens driving unit for driving the objective lens based on a light output detected at said light-receiving unit. In this optical pickup, a diffraction element is provided between the light source and the objective lens, the diffraction element is provided with at least first and second diffraction areas and the first and second diffraction areas have such grating shapes that ± first-order diffracted lights diffracted are received by the light-receiving unit at the position in which 0-th order light and ± first-order diffracted lights generated from guide grooves of the optical recording medium may not overlap with each other.

Abstract: An optical pickup apparatus comprising: a diffraction grating including a first grating for diffracting a first laser light beam, and a second grating for diffracting a second laser light beam which is shorter in wavelength than the first laser light beam, the diffraction grating being disposed in a common optical path for guiding the first laser light beam and the second laser light beam to an optical disc; and a photo detector including in a first light receiving area, a main light receiving unit, a front sub-light receiving unit, and a rear sub-light receiving unit that receive reflected light beams, which are reflected by the optical disc, of a main beam, of a front sub-beam, and of a rear sub-beam, respectively, the first laser light beam being diffracted by the diffraction grating into the main beam, the front sub-beam formed in front of the main beam, and the rear sub-beam formed at the back of the main beam, wherein the first grating is set such that the front sub-light receiving unit and the rear sub

Abstract: The invention relates to a diffraction grating, a light-receiving element, and an optical head and an optical recording/reproducing apparatus utilizing them and provides a diffraction grating and a light-receiving element capable of detecting a signal of high quality and an optical head and an optical recording/reproducing apparatus utilizing them. A diffraction grating includes a diffracting region which is formed only on a light exit surface and which diffracts and separates first laser light or second laser light emitted by a two-wavelength semiconductor laser to generate a main beam and positive and negative first order sub beams. The depth of concavity formed on the diffracting region is 220 nm. The irregularities are formed such that the pitch length thereof is 22 ?m and such that a convexity thereof has a width of 17.6 ?m. The ratio of the width of the convexity to the pitch length of the irregularities is 0.8.

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: Disclosed are an apparatus and a method for controlling a tracking servo in a near field optics. Gap error signals are detected in a divided state, and a push pull signal is compensated based on the detected gap error signals. A photo detector detecting the gap error signals is divided into two areas such that movement of an image formed on the photo detector can be detected. The push pull signal is compensated by subtracting a value proportional to a difference value between the two gap error signals detected in the photo detector. The difference value between the two gap error signals is proportional to a dc offset component included in the push pull signal. Accordingly, it is possible to simply remove a dc offset included in a push pull signal without largely modifying the near field optics, so that it is possible to exactly perform a tracking servo operation.

Abstract: An optical pickup including: a monolithic laser light-emitting unit for emitting a first laser beam and a second laser beam having mutually different wavelengths; an one-sided spectrally separating unit for spectrally separating the first laser beam and the second laser beam; a polarizing unit for allowing the laser beam passed through the one-sided spectrally separating unit to be introduced to an optical disk side and for reflecting reflected light from the optical disk; an astigmatism unit for imparting astigmatism to the reflected light; and a photodetecting unit in which a first laser reflected light-receiving portion is arranged in such a manner as to be offset from a second laser reflected light-receiving portion, wherein an optical system is constructed such that a long-axis direction of an ellipse indicating a light spot on the optical disk becomes oblique with respect to a tracking direction.

Abstract: Reflected light caused by reflection of a laser beam at a first layer of an optical disc is converted into a main signal. Reflected light caused by reflection of the laser beam at a second layer of the optical disc is converted into a sub signal. An address of a currently-accessed position in the first layer is detected from the main signal. A reference address in the first layer corresponds to a boundary between a signal recorded area and a signal unrecorded area in the second layer. A specified address in the first layer corresponds to a position radially separated from the position at the reference address by an allowable range. A misalignment between tracks on the first and second layers is concluded to be within the allowable range in cases where the sub signal substantially takes a reference level when the detected address reaches the specified address.

Abstract: The present invention discloses an apparatus for generating a TE signal in an optical disc drive. The disclosed apparatus includes a signal generation module, a quality detection module coupled to the signal generation module, and a signal-synthesizing module coupled to the signal generation module and the quality detection module. The signal generation module generates a first and a second candidate TE signal according to a light beam reflected off an optical disc. The quality detection module estimates the signal quality of the first and/or the second candidate TE signal and controls the signal-synthesizing module accordingly. The signal-synthesizing module generates the TE signal according to the first and/or the second candidate TE signal.

Abstract: An optical disc apparatus has: an optical head 400 for emitting a light beam onto a predetermined track of an optical disc 300 before tracking control in order to detect reflected light with a photodetector; an arithmetic circuit 130 for generating measurement signals each indicative of a time-varying change of light received on a respective one of a plurality of light receiving areas of the photodetector; an A/D converter circuit 140 for A/D converting each measurement signal; a microcomputer 190 for determining a correction value based on a difference, in terms of high- and low-frequency components, between measurement signals having been A/D converted; and an adder circuit 180 for adding the correction value to a driving value output from a tracking control circuit 170, so that the driving value is corrected.

Abstract: An optical pickup apparatus which carries out recording/reproduction or deletion of information on an optical disc, including a semiconductor laser device in which at least two light sources are integrated, and a hologram optical element which has a plurality of outgoing light areas that divide light reflected from the optical disc, each light being emitted from the semiconductor laser device; the hologram optical element has division lines which divide the outgoing light areas at a position intersecting with each optical axis of the reflected light. The optical pickup apparatus is able to detect a signal corresponding to a light beam divided almost equally in two, even when any one of the plurality of light sources are operating.

Abstract: A light receiving and emitting integrated device is provided that can be connected to an IC for an optical pickup of the discrete package type, regardless of use of the knife edge method for a focus servo signal. In the light receiving and emitting integrated device, a diffraction grating branches light emitted from a semiconductor laser into three, namely, first to third lights, a hologram element divided into four regions, namely, first to four regions divides the first to third lights reflected by an optical recording medium, and four light receiving segments provided in a light receiving element receive and detect the first light. A focus servo signal can be obtained by the knife edge method using detection outputs of the first light received and detected by the four light receiving segments.

Abstract: In a layer jump and focusing control method, a first focusing error signal is generated according to the differential astigmatism method in a closed-loop focusing control manner when focusing on the first recording layer. A second focusing error signal is generated according to the astigmatic method in an open-loop focusing control manner when a first layer-jumping procedure is performed to shift a focusing position from the first recording layer to the second recording layer. Then, the completion of the first layer-jumping procedure is determined according to the second focusing error signal, for example when the second focusing error signal passes the zero crossing point and exceeds a threshold level. Afterwards, a third focusing error signal is generated according to the differential astigmatism method in a closed-loop focusing control manner when focusing on the second recording layer.

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 includes a light source, an objective lens, light detectors, an optical system, and an error-signal generator. The light-receiving surface of at least one of the light detectors has a width extending in a first direction corresponding to a radial direction of an optical disk, and is formed by first to sixth photoreceptors arrayed along the first direction. The first and second photoreceptors, the third and fourth photoreceptors, and the fifth and sixth photoreceptors are disposed axisymmetrically with respect to a center line extending perpendicularly to the first direction. The error-signal generator generates a focus-error signal using a sum signal of detection signals output from the first and second photoreceptors or a sum signal of detection signals output from the first to fourth photoreceptors in a light spot size method, and generates a tracking-error signal using the other sum signal in a differential compensate push-pull method.

Abstract: An interface device for an optical recording and/or reproducing apparatus for recording and playback of an optical disc, wherein the configuration of an interface circuit between a pickup that reads and writes information from/on the optical disc and a radio frequency (RF) integrated circuit (IC) for signal processing is simplified. To this end, the interface device includes a pickup, an integrated circuit, and a multiplexer. The pickup drives a plurality of laser diodes generating laser signals to record and/or reproduce information on a plurality of discs, respectively, and receives the laser signals reflected from the discs and output photodiode (PD) signals corresponding respectively to the received laser signals. The integrated circuit controls outputs of the laser diodes, and processes the PD signals from the pickup.

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: 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: An optical head includes a hologram which extracts, from a luminous flux of reflected light from an optical disk, at least a first luminous flux branch which does not include the optical axis of the luminous flux; and a photodetector which receives the reflected light from the optical disk and produces signal output, wherein the photodetector has light-receiving areas which receive the first luminous flux branch of reflected light from an optical information recording medium layer targeted for recording or playback out of the plurality of optical information recording medium layers of the optical disk, the light-receiving areas are placed in such a way that the signal output resulting from a light spot formed by the first luminous flux branch of the reflected light from the optical information recording medium layer targeted for recording or playback is practically the same between the first and second photodetection areas, and a boundary line of the light-receiving areas is located in such a position as not

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: Improvements to an optical recording apparatus comprising a laser light source are provided. The improvements include installing a photodiode in an optical path of at least a portion of the laser light beam from the laser light source, and connecting said photodiode to a detection circuit. The photodiode detects the laser light beam and generates a detection signal based on the detected beam. The detection circuit monitors the detection signal and generates an alarm signal if the detection signal indicates a dropout in the laser beam. The alarm signal can trigger an alarm indicator and/or cause a recording process to be halted.

Abstract: In a light receiving amplifier circuit, a dummy amplifier has an identical structure with an IV amplifier except that the dummy amplifier is not connected to a light receiving element and includes a capacitor, i.e., a band limiting capacitor. Further, the capacitor is connected between the collector of the grounded-emitter transistor Tr and GND.

Abstract: The present invention is provided with a detection region for detecting light that is reflected from a first or a second information recording medium and that passes through an optical element. The first information recording medium and the second information recording media are multi-layer disks that have at least two layers, and the detection region includes a detection region (41) for detecting first order and above diffracted light that has a first wavelength, and a detection region (42) for detecting first order and above diffracted light that has a second wavelength.

Abstract: A lens position signal LCE which indicates the discrepancy between the lens and its geometric mid-position is required for coarse tracking of optical storage drives. The prior art is for the lens position signal LCE to be formed in three-beam pick-ups by weighted combination of specific photodetector signals from a primary beam and secondary beam. The only way to ensure that the lens position signal is free of crosstalk caused by the tracking error signal is for the weights to be set correctly. The invention describes methods by means of which the weights can be adjusted automatically and can be matched to the characteristics of the pick-up and of the respective storage medium. The amplitudes of those components in the main and secondary beam signals which are dependent on the tracking error are measured, and the matched weights are determined from them by joint evaluation. Evaluations with synchronous detection and with time integration are described, some of which can be used during writing and reading.

Abstract: An optical pickup for recording or reproducing information to an optical disk, includes: a first photodetector for detecting a return light from the optical disk, wherein the first photodetector is configured so that the first photodetector is divided into three portions in a radial direction corresponding to a radial direction of the optical disk and light receiving elements at both end portions in the radial direction are divided into three portions in substantially a track direction perpendicular to the radial direction, so that the first photodetector includes a light receiving element at a central portion in the radial direction and the three light receiving portions at each of both the end portions to be seven in total to output a light receiving element signal based on light reception of the return light as a track error signal generation signal.

Abstract: In a dual-channel HD radio receiver, when the broadband filter channel is compromised, the broadband channel is inactivated and the narrowband channel is activated. By mixing the signals of the two channels during the change, undesirable audio artifacts can be minimized.

Abstract: In order to obtain a corrected or compensated focus error signal or track error signal, it is proposed to generate primary and secondary scanning beams incident on adjacent tracks of an optical recording medium and to detect the primary and secondary scanning beams reflected from the optical recording medium in order to derive from them primary-beam and secondary-beam focus error signals or primary-beam and secondary-beam track error signals, which are subsequently normalized in order to obtain the compensated focus error signal or track error signal from the normalized primary-beam and secondary-beam error signals by means of weighted combinations. As a result of the normalization, the corrected or compensated focus error signal or track error signal is generated independently of the reflection properties of the respectively scanned track.

Abstract: In an optical disc device of the present invention, time differences among the focus error signal corresponding to the surface of the optical disc, the focus error signal corresponding to the first reflection layer, and the focus error signal corresponding to the second reflection layer, all of which are obtained through the light receiving element when a relative distance between the objective lens and the optical disc is linearly changed in a focus search of the optical disc are measured. The thickness of the cover layer from the surface of the optical disc to the first reflection layer and the thickness of a cover layer from the surface of the optical disc to the second reflection layer are detected on the basis of these time differences.

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: 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: An optical pickup which can remove birefringence due to the non-uniformity of an optical recording medium by using a polarization beam splitter. The optical pickup includes a light source emitting a laser beam, a beam splitter reflecting part of incident light and straight transmitting the remaining light to change a proceeding path of the incident light, an objective lens focusing the incident light passed through the beam splitter to form a light spot on an optical recording medium, a polarization beam splitter arranged on an optical path between the beam splitter and the objective lens for transmitting light having one polarization and reflecting light having a different polarization.

Abstract: A photo detector for use in an optical pickup apparatus that detects a beam reflected from the disc, and includes a substrate for transmitting one main beam and two sub beams reflected from the optical disc; a liquid crystal for refracting the two sub beams, that are transmitted through the substrate, at different refractive indexes according to the wavelength of a laser beam outputted from the laser diode; an electrode material for supplying power to the liquid crystal; a switch for adjusting the magnitude of an applied voltage to the electrode material; and a photodiode on which the main beam and the refracted sub beams while transmitting the substrate and the liquid crystal are projected, and transformed into electric signals. By refracting the beams refracted from the disc at a proper refractive index, the ±1st-order beams can be projected onto the same position, irrespective of the wavelengths.

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: An apparatus and method has a capable of precisely detecting Land Pre-Pit (LPP) data recorded on an optical medium loaded into an optical drive. The apparatus includes an LPP data detecting unit that detects LPP data, from which a wobble frequency is removed, from a signal reflected from the optical medium; a wobble signal detector that detects a wobble signal from the reflected signal; and an LPP data generator that generates the LPP data recorded on the optical medium, using the detected LPP data and the detected wobble signal.

Abstract: A detection signal S1 outputted from a light reception unit (11A) of detection elements (11) formed by four-division light reception element is added to a detection signal S4 outputted from a light reception unit (11D) so as to obtain an addition signal S14 and a phase difference signal P1 indicating the phase difference between the addition signal S14 and the detection signal S1. Furthermore, a phase difference signal P4 indicating the phase difference between the addition signal S14 and the detection signal S4 is obtained. The phase difference signal P4 is subtracted from the phase difference signal P1 so as to generate a tracking error signal TE1.

Abstract: Light receiving elements for receiving a + one-dimensional light divided into four are arranged in the vicinity of a light receiving part for receiving the zero-dimensional light. Some light receiving elements configure the light receiving elements of a first group for receiving the + one-dimensional light forming a focus on the front side of the light receiving surface, and the other light receiving elements configure the light receiving elements of a second group for receiving the + one-dimensional light forming a focus on the rear side of the light receiving surface. A correction value is calculated based on a difference in the outputs of the light receiving elements belonging to the first group and a difference in the outputs of the light receiving elements belonging to the second group, and the focus error signal is corrected using the correction value.

Abstract: An optical pickup includes an optical module that detects an information signal and/or an error signal by radiating light to a recording medium and receives light reflected by the recording medium. The optical module includes a light source; an optical path changer that changes a path of light emitted from the light source; a main photodetector that receives light that is reflected off a recording medium back to the optical module to detect an information signal and/or an error signal; and a hologram element that generates an astigmatism of the light incident onto the optical module. Since most optical elements of the optical pickup except an objective lens are packaged in the optical module, the entire structure of the optical pickup can be simplified and the number of bonding points for fixing the optical elements of the optical pickup on a base can be reduced.

Abstract: A method and apparatus for detecting a signal to determine on-track/off-track and/or a track cross direction, using a detection signal corresponding to a reflected main light beam and detection signals respectively corresponding to reflected first and second sub light beams, and an optical recording and/or reproducing apparatus using the same are provided. When detection signals respectively corresponding to one side portions, in a direction corresponding to a radial direction of the optical information storage medium, of the respective main light beam and first and second sub light beams are referred to as a first main signal, a first sub signal, and a second sub signal, respectively, the method and apparatus include obtaining a first operational signal, which is used to determine on-track/off-track and/or a track cross direction, by performing a subtraction on the combination of the first and second sub signals, and the first main signal.

Abstract: A system for page-based optical data storage includes a sensor array positioned to track a data page when the data page is optically read from or recorded to a storage medium. A servo mechanism is used to position the sensor array. A plurality of alignment points are defined relative to the photodetector pixel array. An alignment arrangement is located at each alignment point. The sensor array further includes servo-feedback signal generation logic operative to drive the servo mechanism based on error signals from the alignment arrangements, thereby aligning the two-dimensional photodetector array with respect to the two-dimensional data page.

Abstract: Methods and systems consistent with the present invention provide broadband subscribers with dynamic, automatic routing information for accessing services offered by a service provider network (35) and/or content provider networks (40, 45). Client software on the subscriber's computer (10) retrieves a file such as an HyperText Markup Language (HTML) document from a predetermined server containing connection-oriented routing information for gaining access to various network services. The client software parses the HTML document and extracts the routing information. The client software then uses this routing information to populate and manipulate the subscriber computer (10) routing table.

Abstract: Disclosed is an apparatus which includes a tracking error detection circuit, for detecting tracking error signal from outputs of a photodetector, a peak/bottom detection circuit for detecting peak and bottom values of the tracking error signal, a difference circuit for finding the difference between a peak value and a bottom value, and a comparator for comparing an output of the difference circuit with a preset reference voltage VR to output a tracking-off signal based on the result of comparison. The comparator outputs the tracking-off signal, indicating the tracking-off of the light beam spot with respect to a track.

Abstract: An optical disk apparatus includes a light emitting unit, a light detecting unit, a tracking error signal generating unit, and a tracking control unit. The light emitting unit emits a single light beam onto an optical disk. The light detecting unit includes at least three light detecting portions, each being configured to receive light reflected off the optical disk and produce corresponding output. The at least three light detecting portions are arranged in a track direction of the optical disk. The tracking error signal generating unit generates at least two types of the tracking error signal using the outputs from the at least three light detecting portions. The tracking control unit performs tracking control on the optical disk on the basis of the tracking error signal.