Abstract: A light emitting portion (1) and an objective lens (3) for collecting a light of the light emitting portion are provided. The light receiving portion (2) is provided in the vicinity of the light emitting portion (1) such that the light can be collected by the objective lens and the light reflected by an optical disk (10) to be an object can be detected. The light emitting portion and the light receiving portion are formed to get in a range of 1.22 &lgr;/NA (beam waist BW) wherein a numerical aperture of the objective lens is represented by NA and a wavelength of the light emitting portion is represented by &lgr; or the light receiving portion is multi-split such that a focal shift of a beam having an astigmatism formed thereon can be detected.

Abstract: An optical scanning device is described which can scan a record carrier by a radiation beam. A dividing element directs radiation reflected from the record carrier to a detection system. The detection system includes at least three detectors. The dividing element has at least three gratings, each forming a sub-beam directed to one of the detectors. The longest dimension of each detector is substantially perpendicular to the bisector of the appertaining sector.

Abstract: An optical disk apparatus is capable of reproducing information from an optical disk 10. The optical disk apparatus mainly includes an illuminating unit which is formed from a semiconductor laser 14, a collimator lens 15, a polarization beam splitter (PBS) 16 and a -wavelength converter 17, as well as an objective lens 18, that focuses a light beam onto the optical disk 10; a two-segment split photo detector 21 which detects the light beam reflected by the optical disk 10; and a signal processing circuit 27 which processes a signal obtained by the two-segment split photo detector 21 to output a signal for reproduction.

Abstract: An optical pick-up device for at least one of recording, reproducing and deleting data on a recording medium includes a light source emitting a light, an objective lens focusing the light from the light source at a predetermined position of a data track of the recording medium and a light receiving element detecting a reflected light from the recording medium. A light receiving means divides the reflected light from the recording medium in a data track direction and detects a part of the reflected light. The reflected light is divided onto the light receiving element into a central component and peripheral components and an original signal is reproduced from at least one of a difference between the peripheral components and the difference between the peripheral components and a central component.

Abstract: An optical pickup device includes at least four light-receiving-surface elements, at least two semiconductor lasers, and an optical system for irradiating a light beam onto an optical recording medium through an objective lens for forming a light spot onto an information recording surface thereof. The optical system guides the return light from the light spot to the four light-receiving-surface elements through the objective. The semiconductor lasers are mounted on a plurality of flat side surfaces of a single heat sink which do not exist on a common virtual plane.

Abstract: A focusing and tracking method and system for use on the read/write head of an optical drive is provided. The focusing and tracking method and system is capable of detecting both the focusing error and the tracking error of the read/write head to thereby control the focusing and tracking of the same during read operation. In particular, this focusing and tracking method and system combines the use of a knife-edge focusing method and a push-pull tracking method respectively for focusing and tracking of the read/write head. A specially designed photo detector is used to obtain both the focusing error signal and the tracking error signal. This allows the focusing and tracking system to be simplified in structural complexity, thereby saving manufacturing cost. Moreover, since the focusing error signal and the tracking error signal are obtained respectively in perpendicular directions, the undesired effect of cross-talk between the two error signals can be avoided.

Abstract: An optical pickup that does not require adjustment of the input/output characteristic of its automatic power control circuit to keep its signal output level at a specific level is proposed. In an optical pickup comprising a light-reception photodiode for converting light reflected from a disk into a current signal, a current-to-voltage converter for converting the current signal outputted from the light-reception photodiode into a voltage signal, a monitoring photodiode for converting part of the light emitted from a semiconductor laser device into a current signal, and an automatic power control circuit for controlling the semiconductor laser device by feedback based on the current signal outputted from the monitoring photodiode, a pair of photodiodes that convert a light signal into a current signal with equal efficiency are used as the light-reception and monitoring photodiodes.

Abstract: An optical pickup capable of use with disks each having a different thickness, including two optical modules each having a light source having a different wavelength, and a photodetector for receiving reflected light. The optical pickup selects a proper light source out of two light sources each having a different wavelength, according to the type of disk and the information which is to be reproduced, and records/reproduces information stored in the disk under optimum conditions according to the thickness of the disk.

Abstract: An optical pickup which include a light source; an optical path changing portion to change a path of light emitted from the light source; an objective lens to converge the light from the optical path changing portion to form a light spot on a recording surface of a disk; and a photodetector having at least two light-receiving regions, preferably four light-receiving regions in a 2.times.2 matrix, which separately perform photo-electric conversion, for receiving the light which has passed through the optical path changing portion and the objective lens and been reflected from the disk. The light-receiving regions are separated by a predetermined distance, such that a center region of the light is not received by the light-receiving regions.

Abstract: An optical pickup device which is capable of reproducing and recording information from at least two discs having different thicknesses includes a light source, an objective lens provided along the light path from the light source facing the plane of a disc and having a predetermined effective diameter, a beam splitter provided between the objective lens and the light source, a photodetector for detecting the beam split from the light splitter and reflected from the disc, and light controller provided along the light path facing the photodetector lens for controlling the light of the intermediate region between near- and far axis regions of an incident light beam. The optical pickup device is simplified and the manufacturing cost therefor is low. Also, by reducing the spherical aberration effect for the light, discs having different thicknesses can be used in a single disc drive.

Abstract: The disclosure relates to a laser (L) and to at least one detector integrated side by side on one and the same substrate so that the laser emits, through the edge of the device, a light beam along a direction and so that the detector can detect, through the same edge of the device, a beam substantially parallel to this direction of emission. In a system for the optical reading of a recording medium, the light emitted is reflected by the medium to be read to the detector or detectors. A diffraction grating (RZ) that diffracts only diffraction waves with the same sign (positive for example) deflects at least a part of the light to the detector or detectors. Application to the reading of optical disks.

Abstract: A device and system for the reading of a recording medium, which enables the reading of high-density information and the removal of disturbance (or cross-talk) from the information. The invention includes chiefly a reading device carrying out the parallel reading of the information from N pixels of an optical detector array and giving at least two sub-trains of samples in series (X, Y, Z), a cross-talk correction circuit for each sub-train of samples, each sub-train giving a train of cross-talk corrected samples (X', Y', Z'), and an input sequencer giving each correction circuit a train of samples to be corrected (Ys) from a first sub-frame of samples (Y) and samples (XN-1, Z0) from at least one second frame of samples (X,Z). This device and system can be applied to the reading of high-density recording media (magnetic or optical).

Abstract: Small-sized and light-weighted optical pickup apparatus capable of eliminating the effect due to the flaring light rays and performing the signal detection of high reliability is provided.In the apparatus, the quarter-wave (.lambda./4) plate and the reflection-type birefringent prime provided with the deflecting function of deflecting the reflection light rays reflected on the optical information recording medium and the light rays flux separating function of separating the reflected light rays from the outgoing light rays are disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the light-receiving element for receiving the reflection light rays from the optical information recording medium which are defleced and separated by the reflection-type birefringent prism is disposed on a single (same) substrate together with the semiconductor laser.

Abstract: The current invention is directed to an optical storage medium system and a method for adjusting an electrically converted optical signal representing the stored data based upon the environmental or optical disk temperature and/or a heat characteristics of the optical disk.

Abstract: Track detection methods and apparatus for simultaneous electronic monitoring of the locations of multiple adjacent data tracks is provided. A dedicated tracking detector enables both a longer integration time for developing a tracking signal and decreased processing requirements for developing useful tracking information.

Abstract: An optical pickup device which is capable of reproducing and recording information from/onto at least two kinds of discs having different thicknesses includes a light source, an objective lens provided along the light path from the light source facing the plane of a disc and having a predetermined effective diameter, a beam splitter provided between the objective lens and the light source, and a photodetector for detecting the beam split from the light splitter and reflected from the disc, wherein the photodetector has a first detection region and a second detection region provided in the peripheral portion of the first detection region. The optical pickup device is simplified and the manufacturing cost therefor is low. Also, by reducing the spherical aberration effect for the light, discs having different thicknesses can be used for a single disc drive.

Abstract: Methods and apparatus are provided for improving optical drive access times using a detector having multiple sensing elements to sense and count disk tracks. The detector may be oriented either radially or tangentially with respect to the disk radius, and either capable of sensing more than one disk location simultaneously or have a length greater than the maximum distance between detectable features of the disk.

Abstract: A disc-thickness-and-warp detecting apparatus includes a light source for emitting rays onto a peripheral portion of an optical disc; a photo-detector having a plurality of photo-detecting portions separated corresponding to the direction of tracks formed on the disc, for detecting rays emitted from the light source and reflected by the disc; an adding circuit for generating a sum-signal by adding the detection-signals from the respective photo-receiving portions; and a subtracting circuit for generating a difference-signal by performing the subtraction of the detection-signals from the respective photo-receiving portions. The apparatus uses such common detecting means to detect the distance between the disc surface and the signal-recording surface and a warp of the disc.

Abstract: An optical information reproducing method, for optically reproducing information recorded on a recording medium, irradiates the recording medium with a laser beam and detects the light returning from the recording medium. When the diffracted light returning from the recording medium is detected, the optical intensity distribution of the diffracted light is detected by a plurality of detectors to produce a plurality of signals, and the signals are calculated to produce a reproduced signal for detecting the information.

Abstract: An optical head device includes a light source for emitting light; an optical system for focusing the light emitted by the light source onto an information medium to form a light spot; a photodetector including a plurality of light detection areas for receiving the light reflected by the information medium and for outputting photocurrents in accordance with the respective amount of the light received; a holographic optical element for diffracting the light reflected by the information medium and for directing the light to the photodetector; and a signal processing circuit section for obtaining a focusing error signal and a tracking error signal for controlling the light spot using the photocurrents. The signal processing circuit section obtains the focusing error signal from the photocurrents which are obtained in accordance with the amount of light of one of .+-.

Abstract: The optical head device disclosed has a light source, a super-resolution filter, an objective lens system a data recording medium, a reconverging lens system, and a photo-detecting system including a photodetector. The super-resolution filter provides a predetermined light intensity distribution with respect to the laser light emitted from the light source. When the data recording medium is a light reflection type, the objective lens system is both for converging the light on the data recording medium and for collecting the light reflected therefrom and, when the same is a light transmission type, the objective lens system comprises a light converging lens for converging the light on the data recording medium and a light collecting lens for collecting the light transmitted through the data recording medium. The objective lens system has a numerical aperture larger for the light collecting than that for the light converging.

Abstract: The present invention provides an optical pick-up device comprising a composite prism in which a prism made of non-axial crystal and a prism made of uniaxial crystal are adhered to each other and a grating, and separating into an extraordinary ray and an ordinary ray by means of the prism made of the uniaxial crystal, and further diffracting each of the extraordinary ray and the ordinary ray to o order ray, + primary ray and - primary ray by means of the grating, and then carrying out an optical detection based on the above mentioned diffracted light.

Abstract: A method and apparatus for high-density reproduction of information recorded on an optical disk by increasing the optical resolution during reproduction. The apparatus focuses an optical beam reflected from the optical disk using a lens, and receives the focused reflected optical beam using a photodetector having an optical area whose width is smaller than the diameter of an optical spot formed thereon. As a result, jitter caused by interfering light, that is, light reflected from the circumference such as a recording portion adjacent to the optical disk, can be solved. Also, high-density reproduction can be performed by increasing the optical resolution during reproduction. The apparatus can be applied to an optical pickup for high-density recording.

Abstract: A reading head has odd and even elemental areas for reading corresponding odd and even information segments that alternate to make up a frame of information on a record medium. The odd elemental areas provide a train of sequential odd information segments, each odd segment having cross-talk associated with the neighboring even segments which are on either side thereof when it is read from the record medium. Similarly, the even elemental areas provide a train of even information segments, each even segment having cross-talk associated with the odd segments which neighbored it on either side when it is read from the record medium. To correct for such cross-talk in both signal trains, both are fed to each of two cross-talk correcting circuits. These circuits derive needed adjacent segment information as to the cross-talk producing adjacent segments from one of the trains being fed thereto so as to process the segments of the other train being fed thereto for cross-talk correction.

Abstract: Methods and apparatus are provided for simultaneously reading data from multiple tracks of an optical disk at a high rate. Circuitry is provided for use with a detector matrix to read and buffer data in parallel from the multiple adjacent tracks, while asynchronously providing processed data to a host processor. Circuitry is also provided for electronic tracking of tracks on the optical disk and for reducing cross-talk between adjacent tracks. Circuitry is further provided for correcting phase errors resulting from variations in the linear velocity of the tracks being read, depending upon the radial position of the tracks.

Abstract: Small-sized and light-weighted optical pickup apparatus capable of eliminating the effect due to the flaring light rays and performing the signal detection of high reliability is provided. In the apparatus, the quarter-wave (.lambda./4) plate and the reflection-type birefringent prism provided with the deflecting function of deflecting the reflection light rays reflected on the optical information recording medium and the light rays flux separating function of separating the reflected light rays from the outgoing light rays are disposed in the optical path between the semiconductor laser constructing the optical pickup portion and the objective lens, and the light-receiving element for receiving the reflection light rays from the optical information recording medium which are defleced and separated by the reflection-type birefringent prism is disposed on a single (same) substrate together with the semiconductor laser.

Abstract: An optical pickup for reading information recorded on a recording surface of an optical information storage medium such as a compact disc or a laser video disc has a light beam source for emitting a linear light beam, and an optical system including an objective lens for converging the linear light beam as a linear image on the recording surface and collecting and emitting a light beam reflected from the recording surface.

Abstract: Laser light is focused in an accurate manner on selected layers in a multilayer optical disk recording system by means of an analysis of output electrical signals from a dithered source which results in the production of an electrical signal which is proportional to an amount by which the parts of the system are to be relatively moved in order to achieve the desired focus on one of the layers.

Abstract: An optical pickup provided with a photodetector for detecting a tracking error signal includes a light source for radiating light; an objective lens disposed on an optical path between the light source and a disc which is an optical recording medium for focusing the light radiated from the light source on the optical disc; a diverter for diverting the optical path of reflected light disposed between the light source and the objective lens to prevent the light reflected from the disc from being reflected back to the light source; and a photodetector for receiving the light reflected from the disc and detecting a tracking error signal and a focusing error signal. The photodetector consists of a first photodetector having a plate divided into at least two pieces for detecting light passing through the optical-path diverter converter after being reflected from the disc; and a second photodetector disposed around the objective lens and moving together therewith, and having a plate divided into at least two pieces.

Abstract: There is provided a device for monitoring the light output of a VCSEL and a recording and reproducing optical pick-up adopting the device. The device for monitoring the light output of a VCSEL has a half mirror positioned in front of a VCSEL, for reflecting a portion of the light emitted from the VCSEL, and a monitoring optical detector positioned behind the VCSEL, for detecting the light reflected from the half mirror. The recording and reproducing optical pick-up employing the device includes a VCSEL having a light-emitting surface for emitting light vertically from the light-emitting surface, a light output monitor for monitoring the light output of the VCSEL, an objective lens for concentrating incident light on an optical recording medium to form an optical spot thereon, a light path changer for changing a path of the light reflected from the optical recording medium, and a first optical detector for receiving the reflected light and detecting an error signal and an information signal.

Abstract: In an information recording/reproducing apparatus constructed of: a buffer for storing therein consecutive recording data in a unit of two dimensional conversion; a coding device for converting the consecutive recording data into a two-dimensional data arrangement arranged by "n" lines and "m" columns corresponding to said unit of data; a recording device for subdividing said two-dimensional data arrangement arranged by "n" lines and "m" columns so as to be read out, and for controlling "m" pieces of light sources in accordance with these data series; and an optical apparatus for converging luminous fluxes from said "m" pieces of light sources so as to form "m" pieces of spots on a disk plane, the recording data is recorded on the disk plane as an optically distringuishable pit group having two-dimensionally extended areas arranged by "n" lines and "m" columns.

Abstract: A packaged integrated information recording system has a plurality of information recording media radially arranged on a disk substrate. Each of the recording media comprises a liquid crystal recording medium including a liquid crystal-polymer composite layer with polymer balls filled in a liquid-crystal phase, stacked on a first electrode layer and a photoelectric sensor including a second electrode layer and a photoconductive layer formed on a transparent substrate. The liquid crystal recording medium and photoelectric sensor are stacked directly, or through an interlayer on each other while the liquid crystal recording layer and photoconductive layer are opposed to each other. The recording media may also be arranged in a row on a film substrate provided with feed holes on both side edges and received in a closable case such that it can be drawn. Alternatively, the recording media on a film substrate may be received in a packaging case having a window openable and closable by a shutter to unroll the film.

Abstract: An optical information reproduction apparatus has a section which scans with an optical beam an optical information recording medium in which information is recorded. The optical beam is modulated according to the information. From this modulated optical beam, the corresponding reproduction signal is generated, then binary-converted. A sampling clock synchronized with this binary-converted reproduction signal is generated. The binary-converted reproduction signal is sampled with the synchronized sampling clock to reproduce the information. The response of the sampling-clock generating section can be switched. This optical information reproduction apparatus enables reliable information reproduction.

Abstract: Ferromagnetic/insulator/ferromagnetic tunneling has been shown to give over 10% change in the junction resistance with H less than 100 Oe, at room temperature but decreases at high dc-bias across the junction. Using such junctions as magnetic sensors or memory elements would have several advantages; it is a trilayer device and does not strongly depend on the thickness of FM electrodes or the tunnel barrier; submicron size is possible with high junction resistance and low power dissipation. The magnitude of the effect is consistent with the simple model of spin-polarized tunneling between ferromagnets.

Abstract: An information recording system including a photoelectric sensor having a semiconductive, photoconductive layer stacked on an electrode, and an information recording medium having an information recording layer stacked on an electrode so that information can be recorded on the information recording layer by an electric field or electric charge. The photoelectric sensor and the information recording medium are disposed to face each other, and information exposure is carried out with a voltage being applied between the two electrodes, thereby enabling information to be recorded on the information recording medium. The photoconductive layer of the photoelectric sensor is capable of amplifying an electric field or electric charge given to the information recording medium, so that the intensity of electric field or the amount of electric charge given to the information recording medium can be increased to a level higher than the light energy actually applied.

Abstract: In an optical pickup using a three beam tracking method a laser light source generates laser beams of a main beam for reading out data from a data recording medium, a movable first guide beam and a movable second guide beam. These three pre-separated laser beams are incident upon the data recording medium and then reflected therefrom. The beam passes through a lens group to read out information recorded in the data recording medium. A light-receiving element receives a part of the reflected beam from the data recording medium for detecting tracking errors. According to this optical pickup having the laser light source generating three separated laser beams, when an azimuth angle in the three beam tracking method changes continuously, phases of the first and the second guide beam with respect to the track are maintained constantly, so that an amplitude of the tracking error signal can be maintained uniformly.

Abstract: An optical pickup head apparatus comprising: a light source; an imaging optics for receiving a linearly polarized light beam emitted from the light source, and converges it on a small spot on an information medium; photodetector units for receiving the light beam being reflected and diffracted at the information medium and output electric signals corresponding to received light quantities; a liquid crystal hologram consisting of a pair of transparent substrates, a liquid crystal sandwiched therebetween through a pair of transparent electrodes, either of the transparent electrodes being formed with a hologram pattern; and a Faraday rotator for rotating a polarized direction of light beam by 45 degrees in a light path leading from the light source to the information medium and, further, rotates the polarized direction of the light beam by 45 degrees in its opposite light path.

Abstract: In an optical pickup, a focus error detector for detecting a focus error of an objective lens for an optical disk includes a focusing lens for focusing the reflected light of the optical disk, a diffraction optical device for diffracting the reflected light focused by the focusing lens into two light rays, two bi-segmented photo-detectors for receiving the two split light rays, respectively, and a circuit for outputting a desired focus error signal from the signal detected from the photo-detectors. The circuit outputs a pure focus error signal without errors created by the deviation of the light amount in the photo-detectors due to the tilt or shift of the reflected light, thereby contributing to the stable operation and miniaturization of the optical pickup.

Abstract: A light emitting unit emits light beams in a direction downwardly oblique from a horizontal direction and a stand-up mirror reflects the light beams so as to deflect them upward. An objective lens converges deflected light beams onto an information recording medium. A lens holder holds the objective lens, and an aperture stop is provided in the lens holder to limit light beams which are then incident on the objective lens. The aperture stop is located higher than a projecting end of a bottom convex surface of the objective lens. A top end of the light emitting unit is located higher than a projecting end of a top convex surface of the objective lens. The lens holder has a shape such that the lens holder may not enter a light path along which the light beams emitted by the light emitting unit and then incident on the stand-up mirror pass. A portion, of the stand-up mirror, which extends lower than a bottom end of mirror surface of the stand-up mirror may be removed from the stand-up mirror.

Abstract: The inventive knife edge method for use in an optical pick-up system capable of detecting a focussing error is comprised of a light source, an optical detector, a knife edge, an objective lens and a differential amplifier. The system is different from the optical pickup system utilizing a conventional knife edge method in that a beam splitter is absent in the inventive system. By eliminating the loss factor stemming from the presence of a beam splitter from the system, it is possible to increase the optical efficiency of the light beam.

Abstract: An optical information reproducing apparatus having an optical recording medium in which information is recorded in a state that it is optically reproduced, and an optical head for reproducing the recorded information from the recording medium while moving relatively to the recording medium. In the apparatus, images are formed on the recording medium by two laser beams emitted from a light source of the optical head, and the difference between the two laser beams transmitted through the recording medium or reflected by the recording medium is detected.

Abstract: A focus error detector for detecting a signal representing a degree of a focus error of an objective lens with respect to an optical disk includes two focusing lenses each for focusing the reflected light of the optical disk by splitting the reflected light into two beams with respect to the optical axis and two photo-detectors for receiving the respectively focused beams, which simplifies necessary components for a beam size method. The two focusing lenses whose focal lengths are different from each other does not necessitate use of a beam splitter, thereby contributing to reduction of necessary components and optimizing the arrangement of the components. Also, the operational stability is secured by removing the sensitivity to the tilt and shift of an optical axis.

Abstract: The invention provides a system in which a photoelectric sensor having a transparent electrode and a photoconductive layer formed on a transparent substrate in this order is opposed to a liquid crystal recording medium having a transparent electrode and a polymer dispersion type of liquid crystal layer formed on a transparent substrate in this order, and voltage is applied between both the electrodes for exposure to image-carrying light, so that the liquid crystals are oriented to record the information.

Abstract: An optical recording and/or reproducing apparatus comprises a light source, a beam splitter located between the light source and an optical recording medium, the beam splitter comprising a first prism and a second prism, a first photosensor for control of light quantity of the light source, and a second photosensor for reproduction of information from the recording medium. The first prism has a first face, a second face, a third face, and a fourth face while the second prism has a fifth face, a sixth face, and a seventh face. The fourth face and the seventh face of the prisms are bonded to each other. The first photosensor is arranged to receive a beam emitted from the light source, entering the first face, reflected by the third face, reflected by the fourth face, reflected by the first face, and then outgoing from the second face.

Abstract: An apparatus and method for providing tracking and focus error signals for controlling an application of a radiation beam to a data track of an optical storage medium. A data signal, indicative of the data stored on the storage medium, may also be provided. One apparatus in accordance with the present invention includes an optical source to generate a radiation beam; a transparent substrate arranged between the optical source and an optical storage medium; and a grating beam splitter formed on a surface of the substrate and having first, second, third and fourth grating elements for separating a return beam reflected and diffracted from the data track into first, second, third and fourth portions, respectively. In other embodiments, more or less than four grating elements and return beam portions could be used. The portions of the return beam are directed onto a detector array.

Abstract: An optical head includes an irradiating device for irradiating a recording medium with a light beam, a separating device disposed in an optical path between the recording medium and the irradiating device, which is provided for separating a portion of the light beam traveling from the irradiating device to the recording medium, and a detecting device for detecting the portion of the beam separated by the separating device, which has a plurality of sensor portions.

Abstract: A focus error detector for detecting a focus error of an objective lens with respect to an optical disk. The focus error detector includes a beam splitter for splitting light reflected from the optical disk. Two critical angle prisms having critical angle reflecting surfaces are included for respectively reflecting the light rays from the beam splitter at the respective critical angles onto two bisectional photo-detectors. The bisectional photo-detector generates detecting signals responsive to the amount of light received. The detecting signals are differentiated and added in a direction offsetting a shift or tilt of the reflected light. Accordingly, only the focus error signal is detected, irrespective of the tilt and shift of the optical axis of the reflected light. Thus, malfunction of an optical pickup is prevented, thereby providing for the uncorrupted recording and reproduction of data.

Abstract: There is provided an optical pickup adapted to read out signals recorded in an optical disk, which is capable of detecting tracking error signals and focusing error signals with good precision even when applied to the SCOOP method, and includes at least three light-emitting parts each capable of emitting laser beam, a detection part provided in association with each of the light-emitting parts for detecting a variation of an output in the light-emitting part associated therewith which is caused by the laser beam reflected by the optical disk, a tracking servo mechanism and a focusing servo mechanism, the servo mechanisms being adapted to be driven in response to signals respectively output by the detection parts for correcting a focusing point of the laser beam, wherein the detection parts each connected to a capacitor and an amplifier sequentially, at least two of the detection parts being each further connected to a rectifier after the amplifier to turn each of the signals respectively output by the detecti

Abstract: A focus error detecting device includes a reflected beam obscurer and a two-division photodetector. The observer obscures a part of the reflected beam. The two-division photodetector includes first and second light receiving sections separated from each other by a division band region which receive the reflected light beam not obscured by the obscurer. A focus error signal is produced based on the output of each light receiving section. Each light receiving section has an array of tapered projections along its edge in the division band region. Alteratively, the light receiving sections have a main part with an edge coincident with an edge of the division band region, and groups of light receiving stripes extending in a direction parallel with the edges of the main part.

Abstract: An optical head includes: a light source for emitting light; first optical element for forming at least three light beams from the light emitted from the light source; second optical element for converging said at least three beams on a storage medium; and a photodetector for receiving said at least three beams reflected by the storage medium to generate electrical outputs in accordance with an intensity of the light beams, the photodetector including; a semiconductor substrate; a light receiving section formed on a surface of the semiconductor substrate for receiving the light beams reflected by the storage medium; a plurality of input terminals for receiving a supply of a predetermined potential; and a plurality of output terminals for outputting electric signals, wherein the light receiving section includes a plurality of light receiving elements for signal detection provided apart from each other on the surface of the semiconductor substrate and a plurality of stray light carrier absorption regions provid