| 摘要 |
PROBLEM TO BE SOLVED: To provide a compact objective lens being a single lens having large NA and including a reflection optical surface, and an optical pickup device and a recording and reproducing device including the objective lens, and capable of making a gap between the objective lens and the recording surface of an optical information recording medium appropriate and coping with a removal disk, and to provide the objective lens hardly causing the deviation of an image-forming position by correcting the deviation of the image-forming position caused by temperature change in use when the objective lens including the reflection optical surface is used as a proximate field optical system. SOLUTION: This objective lens 1 is the single objective lens for performing the recording or the reproducing of the optical information recording medium 10. The lens 1 has a 1st surface 2 being a concave surface, and reflection surfaces 3 and 4, emits luminous flux made incident from the 1st surface through the reflection surfaces, and satisfies following conditions. 0.5<=|R1/f|<=2.0 (R1<0), n>1.4 and t>0.1 mm. R1: the radius of curvature of the 1st surface (the radius of paraxial curvature in the case of an aspherical surface), n: a refractive index in use wavelength, t: a distance expressed in terms of air from the surface of the lens 1 nearest to an image side to an image surface and f: a focal distance in the use wavelength. |
