Patent ID: 7911919

Claim:
An information recording/reproducing device, comprising: a spatial light modulator configured to form a signal light beam containing arbitrary two-dimensional information; a signal light beam irradiation optical system including an optical axis changing portion that changes an incident angle of the signal light beam with respect to a hologram recording medium and configured to irradiate the signal light beam to an arbitrary region of the hologram recording medium; a reference beam irradiation optical system configured to irradiate a reference beam emitted from a same light source as the signal light beam to the region of the hologram recording medium to which the signal light beam is irradiated; and a diffracted beam obtaining portion configured to obtain a diffracted beam from the hologram recording medium, wherein: the signal light beam irradiation optical system and the reference beam irradiation optical system irradiate the signal light beam and the reference beam, respectively, to the arbitrary region of the hologram recording medium to record a first hologram; and the optical axis changing portion changes the incident angle of the signal light beam with respect to the hologram recording medium after the first hologram is recorded, and the signal light beam irradiation optical system and the reference beam irradiation optical system irradiate, respectively, a signal light beam whose incident angle has been changed and a reference beam substantially same as the reference beam used when recording the first hologram to multiplex-record a second hologram, which is different from the first hologram, in a region same as the region in which the first hologram is recorded while the diffracted beam obtaining portion obtains at least a part of a diffracted beam from the first hologram simultaneously.