SYSTEM FOR CONTROLLING THE CHANGE OF READ SIDE FOR AN OPTICAL READER FOR AN INFORMATION CARRIER AND AN OPTICAL READER INCLUDING SUCH SYSTEM

摘要

System for changing the read side on a transparent carrier carrying information recorded on both sides. Reading is carried out by means of an optical device focusing a light beam onto one preselected side, incorporating a feedback loop servomechanism which maintains constant the distance between the optical device and the recorded surface of the disk. The servomechanism is attached or connected by the detection of the high frequency electrical signal representing the recorded information. The system opens the feedback loop when, after the read side change control, the high frequency signal drops below a predetermined threshold. A side jump control pulse imparting an accelerated movement towards the other side to the focusing device is generated synchronously with said loop opening. The high frequency signal again rises above the predetermined threshold when the light beam focusing point reaches the opposite side. At this time, the loop is closed again and a decelerating pulse is generated.