Apparatus for enabling an autotrack circuit of an optical disc reading apparatus during the positioning of a read beam

摘要

Apparatus for reading a disc-shaped record carrier with a light beam. A radial positioning apparatus controls the radial position of the light beam spot on the information track of a record carrier. A lock-in system is provided for switching the radial positioning apparatus into a tracking mode when the light spot is positioned to coincide with the information track. The direction of relative radial movement between the light spot and the information track is detected and a first control signal is supplied to initiate radial tracking of the information track when the relative radial movement between the reading beam and the information track changes from an outward movement of the light spot over the track to an inward movement of the light spot over the track. At the instant the transition occurs, the radial positioning apparatus is enabled to permit the read spot to follow the information track.