Information reproducing apparatus and information recording medium

An information reproducing apparatus for reproducing digital information from an information recording medium, on which the digital information is multi-level-recorded by changing a shape of an information pit in correspondence with the digital information by multiple steps, said information reproducing apparatus comprising:

• a detection signal generating device for generating an analog detection signal corresponding to the information pit;
• a sampling device for sampling the generated analog detection signal at a sampling cycle corresponding to a cycle, at which the information pit is formed on said information recording medium, to thereby generate a sampling detection signal;
• an extracting device for extracting a level fluctuating component, which is included in the analog detection signal, out of the generated sampling detection signal;
• a first subtraction signal generating device for subtracting the extracted level fluctuating component from the generated sampling detection signal, to thereby generate a first subtraction signal;
• and
• a reproducing device for reproducing the digital information on the basis of the generated first subtraction signal,
• wherein
• the digital information is multi-level-recorded on said information recording medium by changing respective positions of two edges opposite to each other of each information pit, by multiple steps in correspondence with the digital information,
• a plurality of information pits are formed in a zigzag shape between two tracks adjacent to each other, as for a plurality of tracks formed of the information pits on said information recording medium,
• said detection signal generating device comprises:
• an irradiating device for irradiating a reproducing light beam to reproduce the digital information onto said information recording medium such that an irradiation range of the reproducing light beam includes a plurality of edges on the tracks adjacent to each other;
• and
• a light receiving device for receiving a reflection light of the reproducing light beam from each of the edges on the tracks, to thereby generate the analog detection signal,
• the level fluctuating component is included in the analog detection signal caused by a drift of a position, where each information pit is formed, from a position corresponding to the cycle by which the information pit is to be formed, and
• said reproducing device reproduces the digital information by comparing a level of the first subtraction signal with a plurality of thresholds set in advance in accordance with multiple levels in multi-level recording of the digital information.

An information recording medium, on which digital information having multiple levels is multi-level-recorded by changing a shape of information pit by multiple steps in accordance with the digital information, wherein

• the information pit is shaped in a zigzag shape between two tracks adjacent to each other, each track being formed of a plurality of information pits on said information recording medium,
• positions of two edges opposed to each other of each information pit are respectively changed by multiple steps in correspondence with the multiple levels,
• the information pits have standard edges respectively, which are formed at positions corresponding to a standard level set in advance in the multiple levels and are included simultaneously in an irradiation range of a light beam to reproduce the digital information on said information recording medium, and
• the digital information is reproduced from said information recording medium by detecting the standard edges by using the light beam while a level fluctuating component included in an analog detection signal corresponding to the information pit is cancelled out.