Stray objective optical system and its perspective endoscope

摘要

To provide a high-performance and small oblique-view objective optical system and an oblique-view endoscope including the optical system.SOLUTION: The oblique-view objective optical system comprises, successively from an object side, a front-side lens group having a negative refractive power, an optical path converting element, an aperture stop, and a rear-side lens group having a positive refractive power, in which the front-side lens group is composed of a front-side negative lens; the rear-side lens group is composed of a rear-side positive lens and a cemented lens having a positive refractive power; and the optical system satisfies conditional expression (1): 4.0f2/f12.0, where f2 represents a focal distance of the rear-side positive lens and f represents a focal distance of the overall oblique-view objective optical system.SELECTED DRAWING: Figure 3