Patent ID: 8009542

Claim:
A holographic information recording and/or reproducing apparatus for use with a holographic information storage medium, the apparatus comprising: a light source to emit light; a first polarization conversion device to form, during a recording mode, a signal beam and a reference beam that are orthogonal polarization to each other from the light emitted from the light source; an optical path forming optical system to separate optical paths of the signal beam and the reference beam so that the signal beam and the reference beam proceed along respective paths, and then, to combine the optical paths thereof; a focus adjustment optical system disposed on an optical path of at least one of the signal beam and the reference beam in the optical path forming optical system, and to vary the position of a focus of at least one of the signal beam and the reference beam in a depth direction of the holographic information storage medium; an objective lens to focus the signal beam and the reference beam within the holographic information storage medium, to thereby form an interference pattern thereof and to record information in the form of the interference pattern on the holographic information storage medium; and a 4f relay system disposed on an optical path between the focus adjustment optical system and the objective lens to maintain a predetermined optical distance between the focus adjustment optical system and the objective lens.