Abstract: An optical disk apparatus has an optical head. The optical head emits a light beam onto an optical disk and forms pits in the optical disk, thereby recording a signal. A detector detects the relative inclination between the optical head and the optical disk and generates a signal corresponding to this relative inclination. A beam intensity correction circuit corrects the intensity of the light beam in accordance with the relative inclination to form proper pits. In one embodiment, the intensity of the light beam is increased when the relative inclination is increased.

Abstract: A detecting circuit for detecting an operating center of an actuator of an optical head includes a first comparator for comparing a tracking signal based on a reproduced signal coming from the optical head with a reference voltage approximate to zero voltage level, and a second comparator for comparing the tracking signal of which the DC component is removed with a second reference voltage approximate to zero voltage level. A level inversion of a binary output signal of the first comparator is detected at a level inverting point of a binary output signal of the second comparator. The operating center of the actuator is checked with the detection of the level inversion.

Abstract: An optical disk apparatus has an optical disk for recording data into a recording area on an optical disk and reproducing the recorded data from the recording area. The optical disk is provided at the center with a first section with the same reflectivity as that of the recording area and a second section with a different reflectivity from that of the recording area. A photosensor sense detects the first section and produces a signal representing a reflectivity on the first section. The reflectivity data obtained from the signal level is used for controlling a gain of the servo system according to the reflectivity data.

Abstract: An optical recording/reproducing apparatus has a beam emitting device adapted to emit at least two light beams in directions at a minute angle to each other. The light beams are condensed by a condensing member onto slightly separated two points on a disk and reflected by the disk. The light beams from the disk are polarized to a prism by a polarizing device. The prism refracts the light beams from the polarizing device, thereby increasing the relative angle between the light beams. The refracted light beams are converged by a converging lens on a detector.

Abstract: A light power controlling apparatus contains a semiconductor laser and a photosensor for receiving part of light emitted from the semiconductor laser to produce a corresponding electrical signal. The semiconductor laser is connected to first and second current circuits. The first current circuit averages a voltage signal based on the electrical signal of the photosensor by a first low-pass filter, thereby to have a detected voltage. The detected voltage is compared with a desired voltage by an error amplifier. The error amplifier produces a signal representing a difference between the detected voltage and the desired voltage. The difference signal is integrated by an integrator. According to the integrated signal, the first current circuit supplies a forward current to the semiconductor laser. The second current circuit is set at a peak power value in a modulating mode according to a voltage signal of a peak power setting member.

Abstract: An optical recording and reproducing apparatus includes a first semiconductor laser for emitting a recording laser beam whose intensity is modulated in accordance with an information signal to be recorded and a second semiconductor laser for emitting a reproducing laser beam having a constant intensity. The recording and reproducing semiconductor lasers are commonly mounted in a supporting member which is mounted on a pick-up plate arranged movably in a radial direction of a rotating optical disc. The recording and reproducing laser beams are composed with each other by means of a substantially parallelogram shaped prism having a reflection surface for reflecting the reproducing laser beam and an optical surface upon which the reproducing laser beam is made incident at an incident angle larger than a critical angle and the recording laser beam is made incident at an incident angle near Brewster's angle.

Abstract: In an optical system for synthesizing a plurality of light beams, a first light beam of parallel light rays emitted from a laser beam source is incident on an inclined face of a right angle prism through the prism. A second light beam of parallel light rays emitted from a laser beam source is incident to the inclined face at a predetermined angle of incidence. The first light beam is emitted to the inclined face at an angle of incidence equal to a critical angle so that the first light beam is totally inflected by the inclined face and transmitted in a predetermined direction. The second light beam is refracted at an angle of refraction substantially equal to the Brewster's angle, and then transmitted in a direction which defines a predetermined angular difference with the predetermined direction of the first light beam. A multi-layered film is formed on the inclined face.

Abstract: An FM stereo demodulating circuit comprising a pulse counter detector 1 for generating a pulse train signal including the frequency spectrum of the FM signal, DC biasing means for current biasing the detector output about a midpoint, a subcarrier signal generator 2 and current drivers 8, 10 for generating dual polarity biased subcarrier currents, first and second transistor pairs 3, 4, the emitters of each being connected to one of the current drivers, and the bases of the pairs being cross-connected to one of the biased detector outputs, at least one reference transistor pair whose emitters are connected to a current source 11 and whose collectors are connected to each of the biased detector outputs. The currents entering the cross-connected collectors of the first and second transistor pairs, when referenced against the currents into the emitters of the reference transistor pair, produce signals proportional to the right and left channels of the FM signal.

Abstract: An FM receiver comprising a 90 degree phase shifter 21 of the FM signal and a first multiplier 22 for multiplying the FM signal and the phase shifted signal to produce a main signal L+R and a second multiplier 6 for multiplying the FM signal, the phase shifted signal and a subcarrier wave of 38 kHz to produce a sub-signal L-R.

Abstract: An input signal containing a base line which fluctuates to a great extent is detected or restored by comparing the input signal with reference levels which are shifted in accordance with the fluctuation of base line. The input signal is sampled at a variable sampling rate and an average of sampled values for a predetermined period is derived to produce a profile signal which resembles accurately the fluctuation of the base line. The profile signal thus obtained is added to upper and lower threshold voltages to produce the reference levels which have been corrected in accordance with the fluctuation of the base line of input signal.

Abstract: Disclosed is a frequency converter circuitry having square-law transfer characteristics.In order to reduce undesirable harmonic components of the output signal, the circuitry comprises a plurality of active elements, each being responsive to respective harmonic components and having a characteristic adjusting means, connected in parallel with each other so as to provide an overall input/output transfer function approximating a square-law transfer characteristic.

Abstract: A checking system for checking defects on an optically flat surface of an object to be checked is adapted to spirally scan the surface of the object with a laser beam which is projected from an optical head. The laser beam is reflected from the surface of the object and converted by a photodetector to an electric signal. The level of the electric signal is compared with a reference level to produce a defect signal. The rotation of the object is detected by a position sensor. A counter counts a position signal in response to the defect signal and the contents of the counter is stored, as data representing a defect start position, in a defect position memory. The length data of the defect signal is counted and stored in a defect length memory. Predetermined defect position data is read out of a defect position memory, while defect length data corresponding to the defect position data is read out of the defect length memory.

Abstract: In a system for detecting defects on an optical surface, a disk to be inspected is mounted on a turntable, and is attracted on the surface of the turntable. On the disk is provided an optical head having an objective lens located at its focal point on the surface of the disk. A laser beam emitted from a laser unit is projected through the optical head onto the disk, is reflected on the disk, and is then directed through the optical head to a photo detector. The optical head is moved in the radial direction of the disk as the turntable is rotated, and the disk is helically scanned by the laser beam. Only a defect signal is extracted from an electrical signal generated from the photo detector in a defect signal generator. The defect signal is compared in a data processing unit, and is converted to defect information of different size.

Abstract: A disc drive apparatus for driving a disc selected from discs of various diameters with and without a central hole comprises: a turntable with a hole at the center of rotation thereof; a turntable support for rotatably supporting the turntable; a motor for driving the turntable; a centering member to be detachably inserted in the hole of the turntable and for mounting a disc with a central hole; a plurality of elastic disc support members which are coaxial with the center of rotation of the turntable, which extend from the surface of the turntable, and which form a plurality of annular shapes; centering index marks, disposed on the turntable, for centering a disc without a central hole; a vacuum pump; and suction channels, one end of which is open to the surface of the turntable and the other end of which is connected to the vacuum pump, for fixing on some of the disc support members the disc selected from discs of various diameters with and without a central hole and placed on some of said disc support membe

Abstract: In order to read out information recorded on a disc rotating at a constant angular velocity by means of a pick-up head movably arranged in a disc radius direction, a head position on the disc is detected to obtain a position signal representing a distance from a disc center to the pick-up head, and then a pulse signal having a frequency corresponding to the position signal thus obtained is generated. A detection signal supplied from the pick-up head and the pulse signal are supplied to an AND gate and pulses of the gated out pulse signal are counted by a counter. The number of the counted pulses represents correctly a length of the information recorded on the disc irrespective of position of the information on the disc.

Abstract: A system for focusing an optical head onto a flat surface has a mechanism for moving the optical head in the direction of the optical axis of the head and a mechanism for moving an objective lens in the optical head in the direction of the optical axis of the lens. A laser beam projected from the objective lens of the optical head is reflected on the flat surface, is reflected on the beam splitter, and is introduced into a detector unit. The detector unit thus generates a focusing signal having a level responsive to the distance between the objective lens and the surface. The optical head is lowered by the mechanism for moving the optical head in accordance with the focusing signal when it passes a predetermined point, and is operated to locate the focal point of the objective lens on the surface. Thereafter, the mechanism for moving the optical head becomes inoperative, and the mechanism for moving the objective lens is operated.

Abstract: An apparatus for detecting optically defects in object such as original glass disc for use in manufacturing video and audio discs by projecting a laser light flux onto the object includes an objective lens for focussing the incident laser light flux onto the object as a small light spot, the laser light flux passing through the objective lens at only its central portion. When the object has no defect in the light spot area, the laser light flux is regularly reflected by the object surface, but when the object includes a defect in the light spot area, the light flux is scattered by the defect. The directly reflected and scattered light fluxes are collected by the objective lens and are then separated from each other by means of a small mirror arranged in an optical axis of the directly reflected light flux. The directly reflected and scattered light fluxes thus separated are received by first and second light detectors.