Focusing error detecting device and method of manufacturing the same.

摘要

A focusing error detector comprises a light source (21), a collimator lens (22a) for making parallel the pencil of rays emitted by the light source (21), an objective lens (24a) which focuses the parallel pencil of rays to form a beam spot on a data-recording disc (23) with data tracks and guide tracks formed thereon and which receives the pencil of rays reflected from the data-recording disc (23), an optical system (26) for forming a beam spot from the reflected pencil of rays incident to the objective lens (24a), and an optical detector (27) having a plurality of divided optical sensor blocks (27a, 27b, 27c, 27d) for receiving the formed beam spot so as to detect the focusing error of the beam spot formed on the data-recording disc (23) on the basis of the configuration of the received beam spot.