Endoscope Objective Optical System

• US 20150359422A1
• Filed: 08/12/2015
• Published: 12/17/2015
• Est. Priority Date: 06/26/2013
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Igarashi, Tsutomu
• Granted Patent: US 9,622,652 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 1/00163 Optical arrangements A61B1/002, A61B1/06 take precedence
• CPC Class Codes: A61B 1/00174 characterised by the viewing angles
• CPC Class Codes: A61B 1/055 having rod-lens arrangements
• CPC Class Codes: A61B 1/307 for the urinary organs, e.g. urethroscopes, cystoscopes
• CPC Class Codes: G02B 23/243 Objectives for endoscopes

Abstract

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, wherein
  • the 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;

1<Iw/ft<1.8

0.6<Ia/Iw<0.95

|DL1/RL1a|<0.4

−3<fL1/ft<−1

where 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.

Claims

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 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; and

conditional expressions below are satisfied;

1<

Iw/ft<

1.8 

 

(1)

0.6<

Ia/Iw<

0.95 

 

(2)

|DL1/RL1a|<

0.4 

 

(3)

−

3<

fL1/ft<

−

1 

 

(4)

where Iw is a maximum image height in the underwater observation, ft is a focal distance of an entire objective optical system in observation in the air, Ia is a maximum image height of a principal ray that is capable of being transmitted through an objective optical system during the observation in the air, DL1 is an outer diameter of the first lens, RL1a is a radius of curvature of an object side surface of the first lens, and fL1 is a focal distance of the first lens.