| 摘要 |
An optical system of an optical pick-up including a resin coupling lens and a resin objective lens with NA larger than 0.8, wherein, magnification &bgr; satisfies a condition: −0.13<&bgr;<−0.08, a focal length f of the objective lens satisfies a condition: 1.15<f<1.50, the objective lens has an annular zone structure on at least one surface of the objective lens, and the annular zone structure has a plurality of annular zones and has steps each of which extends in a direction of an optical axis of the objective lens and is formed at a boundary between adjacent ones of the plurality of annular zones to cause a predetermined optical path length difference between a light beam passing inside the boundary and a light beam passing outside the boundary, and the optical system of an optical pick-up satisfies a condition: 0.065 < ( ( ∑ Φ 0.95 - 1.00 ) ( ∑ Φ 0.00 - 1.00 ) × d 0 × n f 2 × ( NA 0.85 ) 4 ) P ave + 1 L < 0.100 where L = L 0 + ( 1 - cos ⁢ ⁢ &thetas; ) L 0 = m ⁢ ⁢ λ n - 1 . |
