| 摘要 |
PURPOSE:To correct a temperature drift of an optical head and a circuit, etc. by providing an offset correcting means for generating a control output in the direction for offsetting an offset. CONSTITUTION:The titled device has a means 3 for recording an information signal of two kinds of frequencies to an optical disk, reproducing this information signal, and detecting a frequency and an amplitude value of this reproduced information signal. In this state, based on the frequency and the amplitude value of the reproduced information signal, an offset of a focus servo-means is discriminated. That it to say, in case an offset is generated in a servo-system due to a temperature variation, etc., the offset of the focus servo-system is corrected by detecting a fact that the offset is generated, from a difference of levels of two kinds of frequencies reproduced, and generating a control output in the direction for offsetting its offset. |
