Abstract: An optical pickup device includes an objective lens (2), with a numerical aperture (NA) being not less than 1, having a solid immersion lens (1) which is made up by a spherical portion (1a) and a flat portion (1b) parallel to a surface (101a) of an optical disc (101). The component of the reflected light from the optical disc in the polarized state perpendicular to the polarized state of the reflected light which prevails when the distance between the surface of the optical disc and the flat portion of the solid immersion lens is zero is detected. The so detected light intensity is associated with the distance between the optical disc surface and the solid immersion lens to accurately detect the minute gap between the optical disc and the solid immersion lens.

Abstract: A signal recording and/or playback apparatus is disclosed wherein, when near field light is used for recording or playback of an optical disk, dust on the optical disk can be removed effectively. After an optical disk is set in position to a turntable in an apparatus body, before gap control or the like is performed, the optical disk is rotated at a suitable speed so that dust sticking to the optical disk is driven away to the outer circumferential side thereby to clean the signal recording surface of the optical disk. Then, the optical disk is stopped once, and gap control for adjusting the distance or gap between an optical head and the optical disk to a distance with which near field light is produced is performed. Thereafter, it is confirmed whether or not the gap control operates normally, and when the gap control operates normally, the optical disk is rotated to start a recording operation or a playback operation of a signal onto or from the optical disk making use of the near field light.