Abstract: Two light sources 2, 3 radiating light beams having different waveforms are simultaneously operated. Reflected beams of these two types of laser beams from an optical recording medium are simultaneously detected by detectors 4, 5. When one of the two types of light beams having different wavelengths is used while being focused on an optical recording medium, the spot diameter of the other non-focused metering beam on the optical recording medium is set larger set larger than that of the one of the two light beams. A reflected light having a larger spot diameter is used to reduce DC offset in a tracking error signal.

Abstract: The spot diameter D3 of a side beam 21 imaged on a disc 5 is set to at least 2.5 times as large as that of a main beam. Via this configuration, an output signal from a detector detecting a reflected light via a side beam, that is, a signal representing a different in the output from photo-detection devices split by split lines in the radial contains a negligible track cross component caused by a beam spot crossing a track. The signal substantially contains a DC offset component alone caused by the shift of an objective lens in the radial direction under tracking control. Thus, by subtracting the output signal of the detector from the push-pull signal of the main beam, a tracking signal substantially containing no DC offset.

Abstract: In a magneto-optical recording disc of the magnetic field modulation recording mode, recording of information for the first time is carried out in an optical modulation mode at a linear velocity which is higher than a reading linear velocity. The time required for recording is reduced while the recorded disc produces satisfactory outputs on playback.

Abstract: An apparatus for generating a modulated magnetic field includes a magnetic head coil and a pair of additional inductive coils. The ratio of the average inductance of the additional inductive coils to the inductance of the head coil is from 2 to 8. The apparatus ensures a magneto-optical recording system of the magnetic field modulation mode having an increased switching speed and a minimized overshoot of recording current.

Abstract: An improved information-modulate magnetic field generating circuit for magneto-optical recording which uses a step-down transformer whose secondary winding has less turns than the primary winding, thus permitting substantial reduction of electric power for driving the magnetic head coil.

Abstract: Magneto-optical recording method for a magneto-optical recording disk using a non-flying magnetic head. The magnetic head produces a magnetic field extending from a primary magnetic pole and returning to an auxiliary magnetic pole while the disk is rotated. The magnetic head is spaced apart from one major surface of the disk such that the primary magnetic pole applies a magnetic field across the disk. Magneto-optical recording is effected in a magnetic field-modulation mode while properly controlling the projected area of the primary magnetic pole and the distance between the magnetic head and the disk surface. A satisfactory C/N is obtained in a consistent manner while jitter is reduced.

Abstract: An optical disk in a cartridge can be identified when loaded in a disk drive system, by changing the openness of a hole in the cartridge to impart at least four types of identifying information, and detecting the openness of the hole by a sensor in the drive system. To establish four different states, two small and large apertures are formed in major walls of the cartridge to define a through window and a shield member is fixedly or slidably mounted between the walls so as to clear or shield a portion or the entirety of the through window.