| 摘要 |
The purpose of the present invention is to provide a small objective optical system for an endoscope having good optical performance. The objective optical system for an endoscope comprises, in order from the object side, a first negative lens (L1) that is plano-concave, a second meniscus lens (L2) with the convex surface facing the image side, a third positive meniscus lens (L3) with the convex surface facing the object side, a positive lens group (L4), and a cemented lens with a positive lens (L5) and a negative lens joined to each other. The third positive meniscus lens (L3) moves along an optical axis (AX) to focus the optical system. This objective optical system satisfies the following conditional expression (1): 2.3 ≤ fp/Ih ≤ 5 (1) Where fp represents the focal distance of the positive lens group (L4), and Ih represents the maximum image height in the objective optical system for an endoscope. |
