Optical recording medium employing an intermittent pattern for guiding tracks and tracking apparatus for the same

摘要

An optical recording medium has a track format with a track pitch smaller than a diffraction limit of a light spot so as to realize an increased capacity and a higher density. A guide groove for tracking purposes is formed along each of the concentrically or spirally formed tracks in a periodic intermittent pattern with respect to a circumferential direction of the optical recording medium. The intermittent patterns of the guide grooves adjoining each other with respect to a radial direction of the optical recording medium are displaced in phase from each other. A light spot of a diameter greater than the track width is projected onto the optical recording medium in rotation and the position of the light spot is servo-controlled in the track width direction in such a manner that a light quantity distribution with respect to the track width direction of a reflected or transmitted light of the light spot diffracted by the selected guide groove maintains its symmetry in the track width direction.