PURPOSE: To decrease the fluctuation in the diffraction efficiency between the facets of a hologram disk disposed with plural pieces of the hologram facets on one face of a substrate by adhering a wavelength plate to at least a part of the other face of the substrate.
CONSTITUTION: The wavelength plate 15 is integrally formed over the entire rear face of the substrate 5 of the hologram disk. The plate 15 is formed of the hologram 15, i.e., the hologram 15 having a function as the wavelength plate. Namely, the hologram disk 10 is formed with the hologram 3 having the intrinsic functions of deflecting (scanning), imaging, and condensing beams on the front face and the hologram 15 having the function of the wavelength plate on the rear face of the substrate 5. The hologram (wavelength plate) 15 for phase shifting is a quarter wave plate (λ/4 plate) for converting linearly polarized light to circularly polarized light. The incident linearly polarized light from the rear face side is circularly polarized by forming the λ/4 plate 15 and the circularly polarized light is eventually entered to the hologram 3. The substantially specified diffraction efficiency by the circularly polarized light is thereby obtd. at all times and the approximately uniform diffraction efficiency is obtd.
YAMAGISHI FUMIO
IKEDA HIROYUKI
INAGAKI YUSHI
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