Patent ID: 7593304

Claim:
A hologram recording/reproducing apparatus, comprising: a recording/reproducing optical system that guides at least one of an information beam and a reference beam to an optical recording medium; a spatial light modulator that is arranged in an optical path of the recording/reproducing optical system, and spatially modulates a beam guided via the recording/reproducing optical system to generate the information beam; a first misalignment detecting unit that detects a first misalignment between the recording/reproducing optical system and the spatial light modulator using a beam for detecting the first misalignment; and a first misalignment correcting unit that corrects the first misalignment based on the first misalignment detected by the first misalignment detecting unit, wherein the spatial light modulator includes a diffracting unit that diffracts the beam for detecting the first misalignment, and the diffracting unit includes an alignment mark that defines two directions that are approximately perpendicular to an optical axis of a recording/reproducing beam.