Abstract: An optical pickup apparatus is constructed of an objective lens for condensing a light beam emitted from a light source toward an optical recording medium, and a convex lens arranged between the optical recording medium and the objective lens in which a surface thereof upon which the luminous flux projected from the objective lens is incident is a convex spherical surface with a radius of curvature which is a predetermined value, and another surface thereof which is located near and opposite to a surface portion of the optical recording medium which is a plane. With this arrangement, a tolerance with respect to decentering of the convex lens in connection with the optical axis of the objective lens is increased, so that an occurrence of aberration is reduced.

Abstract: There is provided an optical pick-up device capable of eliminating a spherical aberration due to a thickness error of an optical disc. The optical pick-up device includes a convex lens having a flat surface opposed to a surface of an optical recording medium, and having a predetermined refractive index, and an objective lens disposed such that the convex lens is interposed between said optical recording medium and the objective lens. A position-detecting means detects a position relation between the light-incident surface of the optical recording medium and the flat surface of the convex lens, based on first and second detection signals.

Abstract: A disc playback apparatus has an automatics disc changer for selecting one of a plurality of information storage discs at a time. The disc selected by the automatic disc changer is rotated on a turntable by a spindle motor. While the disc is rotating, information contained in the disc is reproduced by a pickup, which transfers the reproduced information to a buffer memory. The information stored in the buffer memory is transferred to and processed by a decoder which decodes and sends the information to a display. The disc playback apparatus includes a controller for monitoring the amount of information stored in the buffer memory and controlling the rotational speed of the disc depending on the amount of information stored in the buffer memory. The rotational speed of the disc is controlled to cause the pickup to transfer the reproduced information to the buffer memory at a maximum rate before the buffer memory becomes full of stored information.

Abstract: An optical recording method and an optical recording apparatus enable recording information on recording tracks substantially corresponding to ideal reference tracks, on an optical recording medium without preformatted tracks. The optical recording medium is scanned by a rotating optical scanning system using a scanning light beam emitted by an external light source to record information on the optical recording medium. Prior to recording the information on the optical recording medium, information recorded on a reference track recording medium provided with ideal reference tracks is reproduced in a tracking control mode to acquire tracking control data and the tracking control data is stored in a waveform memory. In recording information on the optical recording medium, the rotating optical scanning system is controlled on the basis of the previously stored tracking control data so that the scanning spot traces recording tracks corresponding to the ideal reference tracks.

Abstract: An optical pickup is adapted for recording and/or reproducing signals by radiating a light beam from a light source on an optical recording medium via an object lens. The optical pickup includes a light receiving device for receiving a return light from the optical recording medium, and a focusing error detecting unit for detecting an amount of deviation of the focal point along the optical axis. The measurement of a focusing error is based on signals from the light receiving device. The optical pickup further includes an electrostriction device arranged on a path of light outgoing from the light source to the optical recording medium and having a central section and a peripheral section exhibiting a phase difference from each other depending on an applied voltage. Focusing errors may be detected with high accuracy with the optical pickup. A focusing servo device compensates for the focusing error detected by controlling the focal point along the optical axis using a focusing servo device.

Abstract: An optical pickup is adapted for recording and/or reproducing signals by radiating a light beam from a light source on an optical recording medium via an object lens. The optical pickup includes a light receiving device for receiving a return light from the optical recording medium, and a focusing error detecting unit for detecting an amount of deviation of the focal point along the optical axis. The measurement of a focusing error is based on signals from the light receiving device. The optical pickup further includes an electrostriction device arranged on a path of light outgoing from the light source to the optical recording medium and having a central section and a peripheral section exhibiting a phase difference from each other depending on an applied voltage.Focusing errors may be detected with high accuracy with the optical pickup. A focusing servo device compensates for the focusing error detected by controlling the focal point along the optical axis using a focusing servo device.

Abstract: A disc reproducing apparatus such ah as video disc players and compact disc players, etc., surely corrects skew of an optical disc and reproduces recorded information even though the recording density is high. The disc reproducing apparatus has a plate-like transparent member interposed in a focused light path of the light beam so as to tilt the transparent member and cancel any comatic aberration. A light spot correction means having the transparent parallel flat plate and at least a coil and a magnet changing the inclination of the flat plate is arranged in a light path of a light beam, thus comatic aberration due to skew of the optical disc is surely and simply corrected.

Abstract: A laser light generating apparatus comprises a light source for generating an exciting light beam, a condenser lens for converging the exciting light beam from the light source, a laser medium for generating a laser light of first wavelength by the radiation of the exciting light beam supplied thereto through the condenser lens, a nonlinear optical crystal element for generating a second laser light by the radiation of the first laser light generated from the laser medium, a pair of reflecting means for constituting a laser resonator together with at least the laser medium and the nonlinear optical crystal element, a deflecting element for deflecting an optical axis of the second laser light emitted from reflecting means provided at the emitting side of the pair of reflecting means, detecting means for detecting a part of a light beam output from reflecting means disposed at the output side of the pair of reflecting means, control means for controlling the light source on the basis of a detected output from t

Abstract: Laser light beams from first and second laser light sources 11 and 12 having different wavelengths are synthesized by a dichroic mirror 16 and irradiated on a magneto-optical disc 20 as a recordable disc and the reflected light is separated into the laser light of the first and second wavelengths. In respect of the laser light of the first wavelength, the phase difference between the P- and S-polarization components produced by the dichroic mirror 16 is compensated by a phase compensation plate 32 and the P-and S-polarization components are separated from each other by a polarization beam splitter 36 so as to be received by photodetector elements 37 and 38, respectively.

Abstract: A control circuit for controlling the position of a head in an optical tape recording/reproducing device having a rotary optical head controls the position of the head at the instant that it faces the tape based upon a desired head position derived from a preceding period in which it was facing the tape. A head position error signal is sampled and added to a sample head position signal during a period when the head is facing the tape and is held during the time the head is not facing the tape. The instant the head begins to face the tape once again, this desired value that has been held is applied to the head in order to reduce the pull-in time of the control circuit and provide more time for information recording/reproduction during the time the rotary optical head is facing the tape.

Abstract: n pairs of light beams are applied to an optical disc to form a plurality of beam spots thereon which are offset by 1/2n of a track pitch p, and n signals which are shifted p/2n in spatial phase are generated from detected output signals indicative of light beams reflected from the beam spots. These n signals are multiplied to produce a tracking control signal whose spatial period is 1/n of the track pitch p. Alternatively, the optical disc has n pairs of wobbling pits or servo pits which are offset by 1/2n of a tracking pitch p are disposed on an optical disc, and the n pairs of servo pits are scanned by a light beam to produce n signals that are shifted p/2n in spatial phase. The tracking control method is effective to effect tracking control on an optical disc whose recording tracks are arranged at a high density that exceeds the spatial cutoff frequency of an optical system of conventional nature used with the tracking control method.

Abstract: An optical recording and/or reproducing apparatus comprising a light beam generator, a photodetector, an optical path forming device for causing a light beam from the light beam generator to impinge upon an optical disc and for guiding the light beam emanating from the optical disc to the photodector, and a signal generating circuit block operative to obtain based on a detection output obtained from the photodetector a first signal representing a tracking condition of the light beam in relation to a record track portion on the optical disc and a second signal different in phase by substantially ninety degrees from the first signal and to produce a tracking error signal which satisfies the following equation:St=Sl/{K.(Sl.sup.2 +S2.sup.2).sup.1/2+S2}where St stands for the tracking error signal, Sl stands for the first signal, S2 stands for the second signal and K stands for a constant equal to or more than 1.

Abstract: An optical recording and/or reproducing apparatus by which a main and two auxiliary light beams are caused to impinge upon a disc. Two auxiliary spots are formed on the disc by two auxiliary light beams to be distant by a quarter of a track pitch from a main spot formed on the disc by the main light beam respectively toward outer peripheral and central portions of the disc. The main and two auxiliary light beams (Lm',Lp',Ln') from the disc are detected respectively by first, second and third photodetecting elements (60,62,64) each divided into two parts to produce first, second and third difference signal (Sm,Sp,Sn) based on respectively detection outputs from two parts of the first photodetecting element, detection outputs from two parts of the second photodetecting element and detection outputs from two parts of the third photodetecting element.

Abstract: In an apparatus for recording or reproducing signals recorded in tracks on an optical disk, a plurality of main light beams and a plurality of auxiliary light beams are generated and directed so that each of the main light beams impinge on a separate one of the tracks on the optical disk and each of the auxiliary light beams impinge between the tracks, main read light beams, corresponding to the reflections of the main light beams from the disk, and auxiliary read light beams, corresponding to reflections of the auxiliary light beams from the disk, are directed to a photosensor assembly, and the photosensor assembly includes a plurality of sensors for separately sensing each of the main read light beams and the auxiliary read light beams. Each of the sensors is bifurcated to produce a pair of output signals for each sensor.

Abstract: In an optical recording and/or reproducing apparatus a main light beam and at least two auxiliary light beams are caused to impinge upon a disc for recording information thereon or reproducing information therefrom in a manner so that light beam spots formed on the disc by two auxiliary light beams are respectively equidistant from a light beam spot formed on the disc by the main light beam with a space between the auxiliary light beam spots in a radial direction of the disc corresponding to N/2 times a track pitch on the disc and the aforementioned light beams are then guided from the disc to a photosensor comprising a first photodetecting element divided into two parts for detecting the main light beam and a second photodetecting element divided into two parts for detecting both auxiliary light beams.

Abstract: A rotary optical head apparatus comprises a first rotary member carrying an objective lens and a second rotary member carrying an image rotator. The two rotary members are supported for rotation by means of a single common support shaft so that the axes of rotation of the two rotary members coincide with each other with a high degree of accuracy. Consequently, the linearity of a scanning line of a beam spot which is scanned on an optical magnetic tape is ensured with a high degree of accuracy.

Abstract: An apparatus for counting a number of record tracks which an optical head traverses on a basis of a periodical track transverse information INF.sub.TR representing the traverse of the head across the record tracks. The periodical track transverse information INF.sub.TR is derived by sampling information on the record tracks performed discretely on record tracks TR. In the tracks counting apparatus, a tracking signal generating circuit is installed for generating tracking signals V.sub.OP and V.sub.OQ which vary their frequencies and phases so as to follow those of the track transverse information INF.sub.TR. The number of record tracks which the optical head has traversed are counted on the basis of the tracking signals V.sub.OP and V.sub.OQ. The tracking signals V.sub.OP and V.sub.OQ have continuous waveforms so that the number of tracks can accurately be counted even if the only discrete information is derived as the track transverse information INF.sub.TR.

Abstract: An apparatus for recording and reproducing data into/from an optical disc, which includes an optical disc having an optical recording medium into and from which data can be written and erased, a laser diode to write, erase, and read out data into and from the optical disc, and a power setting circuit for sampling and holding a detection output from a photo diode to detect the light emission power of the laser diode, for comparing the value sampled and held with a target value, and for setting the power of laser diode. A light emission power of laser diode in each of the data writing, erasing, and reading modes is controlled by the power setting means. A part of a recording area of the optical disc is provided with an extracting area to sample and hold the detection output from the photo diode.

Abstract: According to a tracking error system of an optical head of the present invention, a pair of beams are irradiated through an objective lens (4) on an optical record medium (5) with a distance of a multiple of an odd number of substantially 1/2 the track pitch thereof, a pair of beams emitted from the optical record medium (5) are respectively introduced into a pair of two-divided photo detection elements (6.sub.1) and (6.sub.2) and a tracking error signal is obtained from a difference between difference outputs between outputs of both detected outputs from the pair of respective two-divided photo detection elements (6.sub.1) and (6.sub.2). Thus, it is possible to remove a DC fluctuation of a tracking error signal caused by the lateral movement of the objective lens (4) and a radial skew of the optical record medium (5).

Abstract: The present invention is, in an optical head tracking error detecting apparatus in which a laser beam from a semiconductor laser element (1) is introduced into a diffraction grating (3), a 0-order beam and .+-.1st-order beams emitted from the diffraction grating (3) are introduced through a beam splitter (4) to an objective lens (5), a 0-order beam and .+-.1st-order beams of converged beams which are introduced into an optical recording medium (6) and reflected on the optical recording medium (6) are passed through the objective lens (5), reflected on the reflection surface of the beam splitter (4), and then introduced into a photodetector (7), a pair of photo-detection outputs corresponding to said .+-.