OBJECTIVE LENS AND OPTICAL PICKUP SYSTEM

摘要

PROBLEM TO BE SOLVED: To improve a light quantity in a focused spot regarding an objective lens facing an optical recording medium and an optical pickup system provided with the objective lens.

SOLUTION: A magnification m1of the objective lens 5 to a first laser beam and a magnification m2of the objective lens 5 to a second laser beam satisfy 1/30>m1≥0.9×m2. An optical surface 6 has a shape of a non-spherical face and is provided with a center area 61 where a first laser beam and a second laser beam are focused and an outer peripheral area 62 where the first laser beam is focused. In the center area 61, a plurality of annular blaze-type first diffraction structures 65 with an optical axis as a center is provided. A first area 63 of the first diffraction structures 65 faces an outer peripheral side and a second area 64 of the same faces an inner peripheral side. The number of apertures NAP1to the first laser beam passing through only the first area 63 satisfies a following expression 0.35NAC≤NAP1≤0.7NACor 0.73NAC≤NAP1≤0.95NAC.

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