| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens for an optical disk having a numerical aperture of ≥0.75, superior in on-axis aberration, off-axis aberration and eccentric aberration between surfaces and constituted of a bi-aspherical single lens. <P>SOLUTION: The radius of curvature R1 of the apex of the 1st surface 1 of the objective lens 11 satisfies following expressions. (1-D)A<R1<(1+D)A, A=B/C, B=0.85f(n-1), C=n(0.60866-0.11×t/f-0.1272×d/f)×(0.83+0.2× NA), wherein NA is the numerical aperture of the lens, (n) is the refractive index of the lens, (f) is the focal distance of the lens, (t) is the center thickness of the lens and (d) is the thickness of the transmission layer of the optical disk. D is a positive number and is one of following values. D=0.03, 0.04 or 0.05. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
