OBJECTIVE OPTICAL SYSTEM, OPTICAL PICKUP DEVICE, AND OPTICAL INFORMATION RECORDING AND REPRODUCING APPARATUS

摘要

PROBLEM TO BE SOLVED: To reduce manufacturing costs of an objective optical system and an optical pickup device.

SOLUTION: A second diffraction structure having an optical path length ratio δΦB12of light fluxes having wavelengths λ1and λ2different from the optical path length ratio δΦA12in a first diffraction structure is provided in a diffraction optical element and difference between diffraction actions of the first and the second diffraction structures is utilized. Thus, wavelength dependence of spherical aberration of the first diffraction structure in a blue-purple wavelength region can be controlled or decreased. The manufacturing costs of the objective optical system and the optical pickup device can be reduced by constructing the diffraction optical element and a light condensing element by using a single lens.

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