| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens capable of improving the diffraction efficiency.SOLUTION: The objective lens has a stepwise diffraction structure. The stepwise diffraction structure has a step surface 250 and a side wall surface 260. The step surface 250 is formed so that the surface does not face to an optical axis A in one cycle. The side wall surface 260 is formed to face to the optical axis A. The step surface 250 is inclined by an inclination of Φ [degree] with respect to a plane M perpendicular to the optical axis A. The side wall surface 260 is inclined by an inclination of &thetas; [degree] with respect to the optical axis A. The inclination &thetas; and the inclination Φ satisfies the following formula: 0<&thetas;<Φ and 0<Φ≤60. |
