Abstract: With an optical disc device for reproducing information from discs having a recording density different from one another, by means of laser light beams each having a wavelength different from one another, a provision is put in place to prevent data stored on a CD-R disc from being damaged by irradiating a short wavelength laser beam. A method for identifying discs disclosed by the present invention is to find out whether or not a disc in question is CD-R and the like by irradiating long wavelength laser light on the disc while the rotation of the disc is suspended, and otherwise to find out whether or not a disc is DVD and the like by irradiating short wavelength laser light on the disc. Shifting a focusing lens in the light irradiating axis direction of laser light by means of an actuator generates a focus error signal and an all light amount sum signal, the amplitudes of which enable the identification of discs.

Abstract: A near field light emitting element has a first film made of e.g. Al, an intermediate film made of e.g. SiN and a second film made of e.g. Al on an emergent surface of a solid immersion lens made of a high-refractive material. A first hole is made in the first film, and a second hole is made in the second film. The second hole is smaller in area than the first hole.

Abstract: An apparatus operates for recording and reproducing information on and from a recording medium formed with a track and pre-pits. The track has a wobble. The pre-pits are in a predetermined phase relation with the wobble of the track. The apparatus includes a pickup for reproducing a signal from the recording medium. A limiter operates for limiting an amplitude of the signal reproduced by the pickup in response to a limiting level, and thereby processing the signal reproduced by the pickup into a limiting-resultant signal. A filter operates for suppressing components of the limiting-resultant signal, and thereby processing the limiting-resultant signal into a filtering-resultant signal. The components have specified frequencies, and are caused by the pre-pits. The limiting level for the limiter is generated in response to the filtering-resultant signal. A signal caused by the wobble of the groove is extracted from the filtering-resultant signal.