Abstract: A guide groove is formed without wobbles. The guide groove is periodically modulated with its width. Encrypted data are recorded with marks formed on the record film along the guide groove. Information recorded by periodically modulating the guide groove with its width can be accurately detected by a band pass filter. Thus, rotation control information and address information can be stably reproduced. In addition, since the guide groove is formed without wobbles, a drive device having a pirated disc determination mechanism can reproduce encrypted content as with a ROM disc.

Abstract: A guide groove is formed without wobbles. The guide groove is periodically modulated with its width. Encrypted data are recorded with marks formed on the record film along the guide groove. Information recorded by periodically modulating the guide groove with its width can be accurately detected by a band pass filter. Thus, rotation control information and address information can be stably reproduced. In addition, since the guide groove is formed without wobbles, a drive device having a pirated disc determination mechanism can reproduce encrypted content as with a ROM disc.