| 摘要 |
An objective lens for a high-density optical recording medium, employed as an objective lens for an optical pickup for converging a luminous flux onto an optical recording medium, comprises, successively from the light source side, a first lens L1 made of a biconvex lens having at least one surface formed as an aspheric, and a second lens L2 made of a planoconvex lens having a convex surface directed onto the light source side, and satisfies the following conditional expressions (1) to (3):where beta2 is the imaging magnification of the second lens L2; NA1 is the numerical aperture of the first lens L1; RMS1 is the RMS of the wavefront aberration of the first lens L1; and lambd is a reference wavelength.
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