| 摘要 |
A coupling lens and an optical pickup device are provided to compensate for a color aberration of an objective lens by forming the coupling lens in an aspherical shape. A color aberration compensation coupling lens(30) is arranged at an optical source side of an objective lens, which focuses an optical flux with various wavelengths on an information recording surface of an optical recording medium. Plural annular zones composed of concentrical steps are formed on one surface of the coupling lens around an optical axis. When lambda1 is between 380 and 430 nm and a size d of the step is m1lambda1/(n1-1), where m1 is a real number and n1 is a refractive index of the coupling lens at the wavelength lambda1, a relation, 9.9 <= m1 <= 10.1, is satisfied.
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