Patent ID: 7916610

Claim:
An information recording apparatus for recording information on a multi-layered optical information recording medium consisting of a recording material, which changes quality according to light intensity of an irradiated light, and having an altered layer in which the recording material is already altered and a non-altered layer in which the recording material is not yet altered alternately existing in plurals, the information recording apparatus comprising: a light source to emit a recording light of a predetermined wavelength having coherency; a light path branching unit to branch a light path of the recording light emitted from the light source into a first light path and a second light path; focal position control units, respectively arranged at a post-stage of the light path branching unit, to control focal positions of the recording light in the first light path and the recording light in the second light path; and objective lenses, respectively arranged at a post-stage of the focal position control unit, to collect the recording light in the first light path and the recording light in the second light path on the optical information recording medium; wherein the recording light in the first light path perpendicularly enters the optical information recording medium from a first surface on one side of the optical information recording medium; the recording light in the second light path perpendicularly enters the optical information recording medium from a second surface on the other side of the optical information recording medium; and a hologram corresponding to a standing wave generated by interference between the recording light in the first light path and the recording light in the second light path is recorded as a recording mark; wherein focal depths of the recording light in the first light path and the recording light in the second light path are equal to a thickness of the altered layer and/or non-altered layer.