Patent ID: 9442283
Filing Date: 2016-09-13
CPC Classification: A61B,G02B

Claim Text:
1. An endoscopic objective lens, consisting essentially of a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power, disposed in order from the object side, wherein: the first lens group is composed of a cemented lens formed of a first lens and a second lens with a concave surface on the image side cemented in order from the object side; the second lens group is composed of a positive single third lens and a cemented lens formed of a fourth lens and a fifth lens, either of which being a positive lens and the other being a negative lens, and having a positive refractive power as a whole, disposed in order from the object side; and the endoscopic objective lens satisfies conditional expressions (1′) and (2) given below: where νd1: Abbe number of the first lens with respect to the d-line, νd2: Abbe number of the second lens with respect to the d-line, R2: radius of curvature of the object side surface of the second lens, and R3: radius of curvature of the image side surface of the second lens.