Endoscope objective optical system

摘要

An endoscope objective optical system comprises:
a front group having a negative refractive power, a brightness diaphragm, and a back group having a positive refractive power in order from an object side, whereinthe front group is composed of a first group, which is a first lens which is a single lens and a second group, which is a single lens or a cemented lens having a negative refractive power;
1where Iw is a maximum image height in underwater observation, ft is a focal distance of an entire objective optical system in observation in the air, Ia is a maximum image height capable of transmitting a principal ray in the observation in the air, and DL1, RL1a, and fL1 are an outer diameter, a radius of curvature of an object side surface, and a focal distance, respectively of the first lens.

主权项

1. An endoscope objective optical system used for underwater observation comprising:
a front group having a negative refractive power, a brightness diaphragm, and a back group having a positive refractive power in order from an object side, wherein the back group is composed of three groups, all of the three groups having the positive refractive power; the front group is composed of a first group having a negative refractive power and a second group having a negative refractive power; the first group is a first lens which is a single lens; the second group is a single lens or a cemented lens; andconditional expressions below are satisfied:
1