Patent ID: 7585274

Claim:
An optical system for endoscope for use in a distal end portion of an endoscope, comprising: an observation optical system; and a plurality of illumination optical systems which allow light emitted from a light source to diverge, at least one of the plurality of illumination optical systems satisfying the following condition (1): 0≦- df (θ)/ dθ< 0.025, 10°≦θ≦85° (1), wherein θ denotes an angle of emission from a center of the illumination optical system, and f (θ) denotes a spherical light distribution characteristics that is defined by an illuminance distribution at a time when a spherical object is illuminated by the illumination optical system, which is normalized with an illuminance at a time when the angle θ of emission is 0°; and wherein the illumination optical system satisfying the condition (1) satisfies the following condition (7): 0.05≦f(80°)≦0.15 (7), wherein f(80°) is a value of f(θ) at a time when the angle θ of emission is 80°.