Patent ID: 6674706
Filing Date: 2004-01-06
Classification: G11B

Abstract:
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, said detection signal generating device comprises: an irradiating device for irradiating a reproducing light beam to reproduce the digital information onto one track, which is formed of a plurality of information pits on said information recording medium; and a light receiving device for receiving a reflection light of the reproducing light beam from each of the information pits, to thereby generate the analog detection signal, the level fluctuating component is included in the analog detection signal caused by a drift from a right angle of an angle between (i) an information recording surface, on which the information pit is formed, of said information recording medium and (ii) an optical axis of the reproducing light beam, 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.