| 摘要 |
PURPOSE: A ring-shaped dispersing prism for multiple overlap recording of a holographic ROM system is provided to change a composition ratio of glass located in a place where a reference beam flows, and to install a ring-shaped dispersing prism type having various refractive indexes, thereby enabling a multiple overlap recording. CONSTITUTION: A laser beam comes down from a top of a holographic ROM disk(S2), and a reference beam comes up from a bottom of the holographic ROM disk(S2), so that the laser beam can be overlapped with the reference beam on the holographic ROM disk(S2) to record data. The reference beam supplied under the holographic ROM disk(S2) is refracted through a ring-shaped dispersing prism(S3), and is incident on the holographic ROM disk(S2).
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