Patent ID: 11487101

Abstract:
The objective lens unit includes, a front lens group having a negative refractive power, a diaphragm, and a rear lens group having a positive refractive power, in order from an object side. The front lens group includes a negative lens having a concave surface facing an image surface side, and a positive lens having a convex surface facing the object side, and the rear lens group includes a positive lens having a convex surface facing the image surface side and a cemented lens in which a positive lens and a negative lens are cemented. The endoscope objective lens unit satisfies −1.6<fF/fR<−1.2 and −1.3<f3/fF<−0.7. Note that fF and fR are focal lengths of the entire system of the front lens group and the rear lens group, and f3 is a focal length of a positive lens, in the rear lens group.