Information recording medium, and information reproducing apparatus and method

An information reproducing apparatus for reproducing information recorded on an information recording medium, on which a record mark having a variable length according to first data is formed at a displaced position to which the record mark is displaced, in a direction crossing a reading direction of the record mark, according to a wobble signal obtained by modulating second data in a predetermined modulating method, wherein a first start position at which a head of the first data is recorded is away in the reading direction of the record mark from a second start position at which a head of the second data is recorded by a predetermined constant value, the first start position is a start position of an error correction unit of the first data, the second start position is a start position of an error correction unit of the second data, a first synchronization signal for the first data is recorded at the first start position, and a second synchronization signal for the second data is recorded at the second start position,

• said information reproducing apparatus comprising:
• a reading device for reading the record mark recorded on said information recording medium;
• a read signal generating device for generating a read signal for indicating the variable length of the record mark on the basis of an output signal from said reading device;
• a first data reproducing device for reproducing the first data on the basis of the read signal;
• a wobble signal generating device for generating the wobble signal for indicating the displaced position of the record mark on the basis of the output signal from said reading device;
• a second data reproducing device for reproducing the second data from the generated wobble signal;
• and
• an authenticity judging device for detecting a time difference or a data amount between a head of the reproduced first data and a head of the reproduced second data, comparing the detected time difference or the detected data amount with a time length or a data amount corresponding to the predetermined value, and judging authenticity of said information recording medium on the basis of a comparison result.

An information reproducing method of reproducing information recorded on an information recording medium, on which a record mark having a variable length according to first data is formed at a displaced position to which the record mark is displaced, in a direction crossing a reading direction of the record mark, according to a wobble signal obtained by modulating second data in a predetermined modulating method, wherein a first start position at which a head of the first data is recorded is away in the reading direction of the record mark from a second start position at which a head of the second data is recorded by a predetermined constant value, the first start position is a start position of an error correction unit of the first data, the second start position is a start position of an error correction unit of the second data, a first synchronization signal for the first data is recorded at the first start position, and a second synchronization signal for the second data is recorded at the second start position,

• said information reproducing method comprising:
• a reading process of reading the record mark recorded on said information recording medium;
• a read signal generating process of generating a read signal for indicating the variable length of the record mark on the basis of an output signal in said reading process;
• a first data reproducing process of reproducing the first data on the basis of the read signal;
• a wobble signal generating process of generating the wobble signal for indicating the displaced position of the record mark on the basis of the output signal in said reading process;
• a second data reproducing process of reproducing the second data from the generated wobble signal;
• and
• an authenticity judging process of detecting a time difference or a data amount between a head of the reproduced first data and a head of the reproduced second data, comparing the detected time difference or the detected data amount with a time length or a data amount corresponding to the predetermined value, and judging authenticity of said information recording medium on the basis of a comparison result.