Optical information recording and reproducing apparatus

摘要

An optical record medium has an information record surface on which a plurality of circular arc tracks are arranged such that centers of the circular arc tracks are arranged in a straight line direction. An apparatus for optically recording and reproducing information onto and from the optical record medium is provided with: a rotatable optical system for emitting a light beam onto the circular arc track of the optical record medium which is being moved straight in the straight line direction, while being rotated with an rotational axis perpendicular to the information record surface; a straight moving device for relatively moving the rotatable optical system and the optical record medium to each other in the straight line direction; a detecting device for detecting a displacement amount from the circular arc track at an irradiated position on the information record surface of the light beam, on the basis of a reflection light from the circular arc track of the light beam, and outputting a displacement amount signal indicating the detected displacement amount; a perpendicularly moving device for relatively moving the optical record medium and the rotatable optical system to each other perpendicularly to the straight line direction such that the irradiated position approaches the circular arc track, on the basis of the outputted displacement amount signal; and a recording and reproducing device for recording and reproducing the information onto and from the optical record medium by use of the light beam emitted to the circular arc track.