| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact and high-performance optical pickup lens whose axial chromatic aberration or chromatic aberration of magnification or the like is excellently compensated. SOLUTION: This optical pickup lens is constituted of an SIM lens to form luminous flux from a light source into an image in the vicinity of a recording surface by using reflection performed at least once or more times, and the SIM lens is constituted of a refractive index distribution type lens satisfying a following conditional expression. -3.0<N1/ϕSIM2<3.0 Provided that N1 is the 2nd-order refractive index distribution coefficient of the refractive index distribution type lens, andϕSIM is the power of the SIM lens. Then, N (h)=N0+ N1.h2+N2.h4+N3.h6+N4.h8+... holds. Provided that N (h) is a refractive index at the position (h) of the SIM lens, (h) is the height in a perpendicular direction to an optical axis, N0 is the refractive index on the optical axis, and N1, N2, N3 and N4,... are the 2nd-order, 4th-order, 6th-order and 8th-order,... refractive index distribution coefficients.
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