| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical head objective lens which is used for usages having an NA of >=0.70, and capable of satisfactorily correcting an eccentric comatic aberration even though the lens is constituted of a single lens. SOLUTION: The objective lens 20 is a single lens having the NA of >=0.70, for forming a spot on a recording surface 12 through the transparent protecting layer 11 of an optical disk 10 by converging an incident luminous flux. The objective lens 20 is constituted of a single lens, both the 1st and 2nd faces of the lens 20 are aspherical, and the objective lens 20 is set so that fifth-order spherical aberration for mutually cancelling on an axis may be added in the case eccentricity does not exist between the 1st face 21 and the 2nd face 22, and the deterioration of wave aberration due to third-order eccentric coma- aberration caused by the eccentricity of the lens face toward a direction vertical to the optical axis may be compensated by the fifth-order eccentric comatic aberration. |
