| 摘要 |
An apparatus includes: a light source; a splitting unit that splits a light beam into an information beam and a reference beam; a spatial light modulator that modulates the information beam into a grating binary pattern having bright points and dark points; an irradiation unit that irradiates the reference beam and the information beam onto a hologram recording medium to record information corresponding to each of the regions of the spatial light modulator; a photodetector that detects a signal beam that is diffracted from the hologram recording medium by irradiating the hologram recording medium with a reproduction beam emitted by the light source; and a power detector that detects a difference of powers of signal beams detected by the photodetector at portions in the hologram recording medium corresponding to two of the regions of the spatial light modulator.
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