DIFFRACTION GRATING AND OPTICAL PICKUP DEVICE USING THE SAME, OPTICAL INFORMATION DEVICE, AND OPTICAL INFORMATION REPRODUCING METHOD

摘要

PROBLEM TO BE SOLVED: To facilitate assembly adjustments in manufacturing of an optical pickup by putting pieces of luminous flux from a plurality of light sources in order on the same optical axis through a simplified optical system.

SOLUTION: The diffraction grating which receives a first beam having a wavelength λ1 and a second beam having a wavelength λ2 to generate a plurality of diffracted light beams has a first grating pattern and a second grating pattern for generating the plurality of diffracted light beams of 0-th order and first order and higher respectively, and the first grating pattern is formed on a surface different from a surface where the second grating pattern is formed. The spatial frequency axis of the first grating pattern is inclined at a predetermined angle θ1 to a reference axis and the spatial frequency axis of the second grating pattern is inclined at a predetermined angle θ2 to the reference axis; and the first grating pattern has higher diffraction grating to the wavelength λ1 than to the wavelength λ2, and the second grating pattern has higher diffraction efficiency to the wavelength λ2 than to the wavelength λ1.

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