Endoscope objective optical system and endoscope

Abstract

An endoscope objective optical system includes in order from an object side, a first group having a negative refractive power, a second group having a positive refractive power, and a third group having a positive refractive power, focusing from an object point at a long distance to an object point at a short distance is carried out by moving the second group from the object side to an image side, the first group includes a lens having a negative refractive power, the second group includes a lens which is a meniscus lens having a positive refractive power of which a convex surface directed toward the image side, and the third group includes in order from the object side, a lens having a positive refractive power, and a cemented lens of a lens having a positive refractive power and a lens having a negative refractive power, following conditional expressions (1″), (2), and (3) are satisfied, 8<G2f/FL≤17.041  (1″) −0.16<G1f/G2f<−0.04  (2) 0≤(R3−R4)/(R3+R4)<0.2  (3) where, FL denotes a focal length of the overall endoscope objective optical system at the time of a far-point observation, G1f denotes a focal length of the first group, G2f denotes a focal length of the second group, R3 denotes a radius of curvature of an object-side surface of the lens which is a meniscus lens, and R4 denotes a radius of curvature of an image-side surface of the lens which is a meniscus lens.

Dependencies are inferred from the claim text.