FOCUSING ERROR DETECTOR AND OPTICAL DATA DETECTING DEVICE INCORPORATING THE FOCUSING ERROR DETECTOR

摘要

A focusing error detector comprises a light source, a collimator lens for making the pencil of rays emitted by the light source parallel, an objective lens which focuses the parallel pencil of rays to form a beam spot on a datarecording 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.