Automatic gain control method and appartus in optical disk system.

摘要

An amplitude difference between a reproduction signal from a preformat portion of an optical disk and a reproduction signal from a recording portion of user's data is obtained. When the amplitude difference exceeds a predetermined value, a first gain value (5a) which was set for information from the preformat portion is used as a gain value (7a) of an AGC circuit (2) for reproduction and a gain control of the reproduction signal is performed. On the other hand, when the amplitude difference is smaller than the predetermined value, a second gain value (6a) which was set for the user's data is used. Thus, a situation such that a noise and a remaining signal of the user's data which was not erased are erroneously recognized as an inherent reproduction signal can be prevented. A discrimination to see if the data has been recorded in the recording portion of the user's data or not can be also accurately performed.