Patent ID: 8018801

Claim:
An optical information reproduction device, comprising: an information recording medium that includes a recording unit having a multilayer structure of recording layers capable of recording information three-dimensionally and from which can be reproduced information recorded on one of the recording layers through any of the other recording layer or layers and provided with a track having a specific track pitch, with which information is recorded by forming a plurality of recording marks along the track of the recording unit by a mark length recording method, and when the track direction of the recording marks is assumed to be their longitudinal direction and the direction perpendicular to the track direction is assumed to be their lateral direction, for recording marks located substantially in the same plane, the total area of elongated recording marks, whose longitudinal length is greater than their lateral length, is greater than the total area of recording marks having other than elongated shapes; a first semiconductor laser light source for emitting reproduction light having a wavelength λ 1 , and for emitting recording light with a wavelength of λ 2 different from the wavelength λ 1 ; an objective lens for focusing the reproduction light emitted from the first semiconductor laser light source on the recording unit of the information recording medium, and for focusing the recording light on the recording unit of the information recording medium; and a first photodetector for detecting a reproduction signal from the reflected light from the recording unit, wherein the information recording medium has a track pitch of no more than 1.3 times the wavelength λ 1 of the reproduction light, the first semiconductor laser light source has a characteristic such that it emits the reproduction light in which an amplitude of a polarized light component that is polarized perpendicular to the track direction is greater than that of other polarized light components, and further comprising an optical component that functions so as to convert the state of polarization of the recording light emitted from the first semiconductor laser light source, whereby the amplitude of a polarized light component of the recording light that is polarized perpendicular to the track direction is caused to be greater than that of other polarized light components compared with the state of polarization before the conversion.