Patent ID: 8947785
Filing Date: 2015-02-03
Classification: A61B,G02B

Abstract:
1. An endoscope objective lens configured such that focusing from a farthest object to a nearest object is achieved by moving at least one lens group other than a most object-side lens group along an optical axis, wherein one of the at least one lens group that is moved during the focusing is a negative lens group, the negative lens group consists of a cemented lens that is formed by a positive lens and a negative lens cemented together in this order from an object side, wherein a cemented surface of the cemented lens is oriented such that a concave surface faces the object side, and the conditional expressions (1) and (2) below are satisfied: where ft is a focal length of the entire system when the focus is set on the nearest object, fw is a focal length of the entire system when the focus is set on the farthest object, νn is an Abbe number with respect to the d-line of the negative lens forming the cemented lens, and νp is an Abbe number with respect to the d-line of the positive lens forming the cemented lens.