Optical data recording and reproducing apparatus including non-circular beam spot

摘要

An optical data recording and reproducing apparatus in which a beam spot is made incident upon recording tracks of an optical recording medium, so that the beam reflected from the optical recording medium is detected to obtain a data signal and a tracking error signal. The optical recording medium is a rotatable optical disc having a signal recording surface. The recording tracks include concentrically arranged recording track sectors formed on the signal recording surface of the optical disc and preformat portions provided between the adjacent recording track sectors. A beam shape setting device is provided to shape an image of the beam spot formed on the track sectors into a non-circular shape which is elongated in the circumferential direction of the optical disc.