Optical disk apparatus capable of generating clock accurately

An optical disk apparatus (200) for recording and/or reproducing a signal on and/or from an optical disk (100) including a fine clock mark forming a reference for generation of a clock in synchronization with said clock, comprising:

• an optical pickup (102) emitting a laser beam to said optical disk (100) and detecting a reflected beam;
• a fine clock mark detecting circuit (103) producing a fine clock mark detection signal by comparing a fine clock mark signal detected based on said fine clock mark by said optical pickup (102) with reference to a predetermined level;
• and
• a clock producing circuit (104) producing said clock by dividing said fine clock mark detection signal to provide a frequency equal to a predetermined integral submultiple of the input frequency in synchronization with said fine clock mark detection signal, wherein
• said fine clock mark detecting circuit (103) compares a signal component FCMk (a≦k≦n) with reference to a comparison level Lk, and produces said fine clock mark detection signal based on the fact that the compared comparison signal is obtained, assuming that said fine clock mark signal includes signal components of n (n:
• natural number) in number containing said signal component FCMk to be compared and a signal component FCMk−1 compared immediately before comparison of said signal component FCMk, a comparison level Lk−1 is used for said signal component FCMk−1, said signal component FCMk has an amplitude of Pk, and said comparison level Lk is determined based on a weighted average of said comparison level Lk−1 and said amplitude Pk obtained by assigning a larger weight to said comparison level Lk−1 than a weight assigned to said amplitude Pk.