Abstract: An optical disc comprises an information recording layer having a record of information as a pit train with a predetermined track pitch and a light-transmissive layer formed on the information recording layer so that the information can be reproduced by a beam of light illuminated through the light-transmissive layer to the information recording layer by an objective lens. The optical disc is characterized in that a relationship of 0.194 (/NA)2 TP×Tmin 0.264 (/NA)2 is satisfied, provided that the track pitch is >TP, a pit shortest length is Tmin, a wavelength of the light beam is and a numerical aperture of the objective lens is NA. The optical disc is characterized in that a pit width is 120 nm or smaller in a range of a track pitch of 0.280 to 0.325 m.

Abstract: A tracking apparatus for a sampled servo system, wherein a tracking servo loop is opened when a jump command is generated by ceasing to supply a tracking error signal to a tracking control circuit, which is instead supplied with a kick pulse to start a track jump operation. Thereafter the tracking control circuit is reset to relay the tracking error signal when a read track is switched causing a change in value of an odd/even determining signal to close the tracking servo loop. Finally a brake pulse is supplied to the tracking control circuit for terminating the track jump operation. This enables an irradiating spot to be stably led into a target track when the track jump operation is switched back to the tracking servo operation even if the track pitch of the disk being read is variable.