| 摘要 |
<p>A recording and reproducing apparatus includes a light source (1) to emit a laser beam, an information light beam irradiation unit (2, 4, 6) to irradiate a medium (9) with an information light beam, and a reference light beam irradiation unit (2, 3, 5) to irradiate the medium (9) with a reference light beam so as to form a specific speckle pattern on the medium (9). The reference light beam irradiation unit (2, 3, 5) comprises a diffusion board (5) provided in the way of a light path through which the laser beam is passed and generating the reference light beam, a rotation controller (41) to rotate the diffusion board (5), and an identification information detector (40) to detect identification information previously formed on a surface of the diffusion board (5). The diffusion board (5) comprises a plurality of encode storage regions (51) in which different identification information is formed and a plurality of diffusion pattern generation regions (52) specified by the identification information. A position of the diffusion board (5) is controlled based on the detected identification information such that a desired diffusion pattern generation region comes to a position through which the laser beam is passed while the laser beam is outputted.
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