Abstract: A method and a device for recording and reproducing information utilizing a work function variation of a recording medium, the recording medium being made of a material whose work function can vary according to a structural change thereof caused by the irradiation of an electromagnetic wave or electron beam.

Abstract: A tilt adjustment mechanism for an object lens driving device (4) includes a base (13), a housing (3), a spherical supporting member (14) and adjustment screws (18a, 18b; 18c; 18d). The base (13) holds the object lens driving device (4). The housing (3) is provided with a supporting point (17) for supporting the base (13) and two adjustment points (20a, 20b; 20c; 20d). A straight line interconnecting the supporting point and one of the adjustment points is substantially at right angles with a straight line interconnecting the supporting point and the other of the adjustment points. The surface of the housing (3) facing to the base (13) is formed with a concave portion (17). The supporting member (14) is interposed between the base (13) and the housing (3) so as to be in point contact with the base and the housing. The screw hole (19a; 19c; 19d) is provided in one of the base and the housing.

Abstract: A focusing error detector comprises a light source, a collimator lens for making parallel the pencil of rays emitted by the light source, an objective lens which focuses the parallel pencil of rays to form a beam spot on a data-recording disc with data tracks and guide tracks formed thereon and which receives the pencil of rays reflected from the data-recording disc, an optical system for forming a beam spot from the reflected pencil of rays incident to the objective lens, and an optical detector having a plurality of divided optical sensor blocks for receiving the formed beam spot so as to detect the focusing error of the beam spot formed on the data-recording disc on the basis of the configuration of the received beam spot.