Abstract: An optical pick-up head for reading writing information from on a magneto-optical record medium including a semiconductor laser, a multi-image plane parallel plate for separating an incident light beam emitted by the semiconductor laser from a return light beam reflected by the optical record medium and dividing the return beam transmitted through and refracted by the multi-image plane parallel plate into a plurality of return light beams, and a signal detecting photodetector receiving a plurality of return light beams, wherein the multi-image plane parallel plate is formed by first and second prisms made of birefringent material and is arranged such that major and minor axes of astigmatism introduced by the plane parallel plate are inclined by 45.degree. with respect to an information track.

Abstract: An optical pick-up head for reading writing information from on a magneto-optical record medium including a semiconductor laser, a multi-image plane parallel plate for separating an incident light beam emitted by the semiconductor laser from a return light beam reflected by the optical record medium and dividing the return beam transmitted through and refracted by the multi-image plane parallel plate into a plurality of return light beams, and a signal detecting photodetector receiving a plurality of return light beams, wherein the multi-image plane parallel plate is formed by first and second prisms made of birefringent material and is arranged such that major and minor axes of astigmatism introduced by the plane parallel plate are inclined by 45.degree. with respect to an information track.

Abstract: A polarizing beam splitter for dividing a return light beam reflected by a magneto-optical record medium into two light beams polarized in mutually orthogonal directions, including a main body made of a birefringent crystal and having an incident surface upon which the return light beam is made incident and a reflection surface, and a reflecting member provided on the reflection surface of the main body and formed by a metal film or a stack of dielectric material films. Upon refraction by the incident surface of the main body, the incident light beam is split into ordinary and extraordinary light beams, which are then reflected by the reflection surface of the main body. An optic axis of the main body is set to be parallel with the reflection surface, the ordinary and extraordinary light beams are reflected as they are and emanate from the polarizing beam splitter.

Abstract: A VCO includes an oscillator and a controller for controlling the operation of the oscillator. The oscillator is formed by connecting odd number of stages of delay circuits in a ring form. The controller creates a second control voltage based on an input first control voltage. The second control voltage is set in a symmetrical relation to the first control voltage with respect to an intermediate potential between the power supply and the ground set as a reference. Each of the delay circuits includes an inverter, first and second current control circuits, and first and second current value setting circuits. The inverter includes a first transistor of first conductivity type and a second transistor of second conductivity type to receive and output a signal. The first current control circuit is connected between the first transistor and the ground, for controlling a current flowing in the first transistor when the first transistor is set in the conductive state according to the first control voltage.

Abstract: The present invention is directed to an apparatus using an integrated type pickup as an optical head for writing and reading optical information and capabling of writing data at high speeds. The apparatus includes a laser diode having an active layer at its intermediate position and having one area side held over a surface of a semiconductor substrate with an insulating layer interposed between the semiconductor substrate and the laser diode relative to the active layer. The laser diode has two areas with the active layer as a boundary and a constant potential is applied from a power supply to the insulating layer side of the laser diode and a transistor (laser diode drive unit) is provided to apply a modulation signal to the other area of the laser diode so that the laser diode is driven to modulate its output.

Abstract: In order to measure a phase difference of an opto-magnetic disk having a substrate and a magnetic record layer, linearly polarized light is made incident upon the magnetic layer of the disk from the side of the substrate and light reflected by the disk is received to derive an information signal recorded in the disk, while the opto-magnetic disk is rotated at a usual reproducing speed. A phase compensator arranged in an optical path of the light reflected by the disk is adjusted to change a phase difference introduced by the phase compensator into the light reflected by the disk, while a level of amplitude and/or C/N of the reproduced information signal is monitored. A value of the phase difference introduced by the phase compensator when the amplitude and/or C/N of the reproduced information signal becomes maximum is derived as a measured phase difference of the opto-magnetic disk.

Abstract: A light beam linearly polarized is incident on a substrate for a disc not a right angle, but at an an oblique angle with respect to the substrate surface, while holding constant an angle .kappa. between the plane of polarization of the linearly polarized light and the incident plane, and the intensity of the leaked light passing through an analyzer set in a crossed Nichol state with respect to the linearly polarized light is measured while changing an angle (azimuth angle .PSI.) between the incident plane and a reference line, such as a line extending in the radial direction of the disc substrate. These measured values are compared with the calculated values derived from the theoretical formula for determining the respective magnitudes of the three refractive indices.

Abstract: A structure of an optical pickup. The optical pickup has a substrate used for an optical recording medium. The optical pickup is provided with a device for condensing and radiating a polarized light and a light receiving device for receiving, through an analyzer set in a crossed Nicol state, the reflected light of this substrate or the above mentioned polarized light on the light transmitted side. The amount the C/N (carrier to noise ratio) is reduced or increased based on the substrate may be evaluated by the light amount received by the light receiving device.

Abstract: In the present invention, a discriminating means of recording media is formed in a cartridge containing a magneto-optical type recording media and in a cartridge containing other recording media, a sheltering height of a field applying means is changed according to the loading of each cartridge so that said field applying means is held close to the recording media in the case of the magneto-optical type cartridge while said means is sheltered high in the case of other type cartridge, and at the same time a discriminating means for recording media is provided to perform the signal processing corresponding to the recording media loaded.

Abstract: An apparatus (31) and method for measuring the refractive index of an optical recording medium substrate (34) wherein an angle of incidence of a polarized beam (33) is set at an oblique angle of incidence with the substrate (34), the polarized direction of the polarized beam (33) is varied for the substrate (34) in this state, the transmitted or reflected light beam by the substrate is received by a light receiving means (36) through a light analyzer means (35) in the crossed Nichol state and the received light amount for the polarized angle is measured and is compared with a theoretical formula so that the refractive index in the thickness direction of the substrate can be measured.

Abstract: An optical information recording media substrate made of a plane shaped molded object using thermo-plastic resin possessing optical anisotropy. A light beam is condensed in the direction perpendicular to the plane surface, transmitted through the plane surface and led to a recording media surface on which a recording media is formed. The direction of the optic axis of the light beam is set parallel to that of the plane surface to diminish the deterioration of the C/N ratio of the reproduced signal.