| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent imaging performance from the center to the peripheral of an image in spite of a large aperture diameter. SOLUTION: This objective lens has, successively from an object side, a first light shielding G1 having positive refracting power, a second lens group G2 which includes a negative meniscus lens of which the concave face is directed to an image side and which has negative refracting power, a third lens group G3 which has at least one joint face and has negative refracting power as a whole and a fourth lens group G4 which includes a positive meniscus lens of which the convex face is directed to the image side and a positive combined lens formed by combining a negative lens and a positive lens and has positive refracting power. The focal length of the first lens group G1 , defined as f1 and the distance from the face on the extreme image side of the first lens group G1 to the face on the extreme object side of the second lens group G2 , defined as D1 , are determined to satisfy 1.2<f1 /D1 <2.3 and this objective lens is so formed as to satisfy other conditions. |
