| 摘要 |
PURPOSE:To avoid ill effects due to dew condensation by providing a heater coil at the mobile part of an objective lens and flowing a current to the heater coil according to the detection output of a detector which detects the dew condensation generated at the lens mobile part in order to eliminate the dew condensation at said mobile part. CONSTITUTION:A mobile part 25 is supported movably up and down and rotatably by a main shaft 24 of a fixed part 23 in a housing 12, and an objective lens 19 is provided to the part 25. At the same time, a dew condensation detector 31 is set at a place close to the shaft 24 and a heater coil 33 is wound round a bearing 25a of the part 25. If the dew condensation is produced at the drive mechanism part of the lens 19 and then detected by the detector 31, a heater control circuit 32 receives this detection signal to stop the working of a semiconductor laser drive circuit 37. At the same time, the circuit 32 supplies a current to the coil 33 to generate the heat. This can eliminate the dew condensation of said drive mechanism part. |
