OPTICAL HEAD DEVICE, OPTICAL INFORMATION APPARATUS, AND INFORMATION PROCESSOR

摘要

PROBLEM TO BE SOLVED: To reduce interference by light of other layers when recording or reproducing information on an optical information medium having three or more recording layers by using light of a wavelength λ1 and to keep an S/N ratio high and excellent when reproducing information from the optical information medium by using light of a wavelength λ2 longer than the wavelength λ1.

SOLUTION: A wavelength selection light shield region 7x is disposed at a position which is between a second beam splitter 6 and a light detector 9 and is a position at least intersecting the center parts of the luminous flux of light of a wavelength λ1 and light of a wavelength λ2, and is formed on a detection hologram 7.

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