FOCUS CONTROLLER

摘要

PURPOSE:To attain stable focus control by starting said control action when a focusing lens and a disk are set close to each other instead when a light beam of a prescribed focused state is set on the surface of a recording material. CONSTITUTION:A start indication signal 16 is supplied to a focus control start indication circuit 20 and a drive signal generating circuit 17. The circuit 17 puts a focusing lens 5 close to a disk 7 at a fixed speed by means of a drive circuit 14 and a drive element 15 according to the signal 16. A comparator 18 compares the reference voltage given from a reference voltage generating circuit 19 with the output of a differential amplifier 11. The output of this comparison is supplied to the circuit 20. The circuit 20 receives the signal 16 from the outside and the output of the comparator 18 and gives a short circuit to a switch 13. Then the focus control is started when the lens 5 gets closer to the disk 7 than the position of the lens 5 set when the light beam of a prescribed focused state is set on the surface of a recording material.