Signal detection system for use in an optically operating reproducing apparatus.

摘要

A light beam emitted from a laser light source is made incident upon a video disc by means of an objective lens and a light flux reflected by the disc is made incident upon a light detector (40) arranged in a far field of an information track of the disc. The light detector includes four light receiving regions (41-44) divided in a track direction and a direction perpendicular to the track direction. A first sum (S5) of output signals from diagonally alined two light receiving regions and a second sum (S6) of the remaining two light receiving regions are derived and then a sum signal (S7) and a difference signal (SB) of the first and second sums are formed. The difference signal is sampled by sampling pulses generated at positive going and negative going zero cross points of the sum signal to generate first and second sampled values. A tracking error signal (S29) is obtained by forming a difference between the first (S27)andsecond (S28)sampledvalues.