Patent ID: 7821888

Claim:
An optical disk reproducing apparatus for reproducing data from an optical disk, the optical disk reproducing apparatus comprising: a pickup for irradiating the optical disk with a laser beam; an analog front end for converting light reflected by the optical disk into an electric signal; a binary circuit for converting the electric signal as an output of the analog front end into a binary signal; a first demodulation circuit for demodulating the binary signal as an output of the binary circuit according to a first modulation scheme having a first predetermined limited iteration count of a minimum run length; a second demodulation circuit for demodulating the binary signal as the output of the binary circuit according to a second modulation scheme having the same minimum run length as the first modulation scheme and having a second predetermined limited iteration count of the minimum run length, wherein the first limited iteration count is different from the second limited iteration count; a run length measurement circuit for measuring an iteration count of the minimum run length of the binary signal; a switch for selectively outputting outputs of the first and second demodulation circuits; and a modulation scheme determination circuit for determining which modulation scheme is used for the optical disk, according to the measured iteration count of the minimum run length, and said first and second limited iteration counts, controlling the switch so as to selectively output the output of the first demodulation circuit when data from an optical disk of the first modulation scheme is reproduced, and controlling the switch so as to selectively output the output of the second demodulation circuit when data from an optical disk of the second modulation scheme is reproduced.