Method and apparatus for writing information into optical disk and reading it therefrom, and optical disk medium therefor

Abstract

An optical disk for writing data transmitted from a higher rank device is rotated at a constant rate (S,). When the rotational speed of the optical disk reaches a constant rate, data is written or read (S,). At that time, since the data write rate in the innermost circumference side is different from that in the outermost circumference side, whether or not an initial buffer is necessary is judged. When the initial buffer is necessary, data in a capacity corresponding to the data writing/reading rate in the storing region is stored in the buffer (S,). A clock is varied and produced according to the storing region (clock block) into which data is written or from which data is read (S,). Subsequently, data is written or read based on the clock. In the writing or reading, data to be written or read is temporarily stored in a buffer depending upon whether the storing region is on the inner circumference side or outer circumference side of the disk (S,). By virtue of this constitution, realization of writing at a low and constant number of revolutions of the disk simultaneously with writing at a constant writing wavelength can increase the storage capacity per disk.