| 摘要 |
PROBLEM TO BE SOLVED: To provide an objective lens of an endoscope that is suitable for the endoscope, is small, has wide angle, and has high peripheral performance.SOLUTION: This objective lens 1 includes, sequentially from an object side, a brightness diaphragm AS, a positive first group G1, and a positive or negative second group G2. The first group G1 is formed of a positive meniscus single lens L1 having a concave surface on the object side, and the second group G2 is formed of a cemented lens of a biconvex lens L2 and a negative lens L3 sequentially from the object side. Expression (1): 0.04<FL×sinω/(Fb×νd)<0.12 is established. In the expression (1), FL is focal distance of the whole system, ω is half angle of view, Fb is distance from the surface top closest to an image of the second group to a rear side focal position, which is expressed by air conversion length, and νd is Abbe number of a negative lens of the second group. |
