Abstract: 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 which was set for information from the preformat portion is used as a gain value of an AGC circuit 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 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.

Abstract: In an information recording and reproducing apparatus for recording or reproducing information to/from tracks by irradiating a light spot to an optical disk in which N sectors are included per track and the number of necessary alternating sectors per track is set to M, the apparatus has a track format such that when a desired moving time of the light spot between the adjacent tracks is k times as long as a desired sector passing time of the light spot, M or more alterating sectors are arranged subsequent to the ordinary sectors to record user's data. The light spot jumps between the tracks for a period of time corresponding to k sectors. Thus, the recording of information to a certain track and the subsequent reading check (Read After Write) can be effectively executed at a high speed.

Abstract: When it is detected that the light spot stays in a same track for a time exceeding a predetermined length of time, the light spot is moved to any other track. Thus, the light spot is prevented from staying on a same track for a long time without recording/reproducing data.