Endoscope

An endoscope comprising:

• an imaging optical system provided at a distal end of an insertion portion of the endoscope and for observing an object to be observed;
• and
• a plurality of illumination optical systems provided in the insertion portion and for distributing an illuminating light emitted from a light source to the object to be observed,
• wherein at least one of the plurality of illumination optical systems is a first illumination optical system having a convex lens, and at least one of the others is a second illumination optical system having a concave lens,
• wherein the first illumination optical system is directed in a same direction as a direction in which the second illumination optical system is directed, emits the illuminating light in a same direction as a direction in which the second illumination optical system emits the illuminating light, and distributes the illuminating light toward a same field of view as a field of view toward which the second illumination optical system distributes the illuminating light,
• wherein a light distribution characteristic of the first illumination optical system is different from a light distribution characteristic of the second illumination optical system, and
• wherein the following Conditional Expression is satisfied where a spherical light distribution illuminance function of the first illumination optical system is expressed as α(θ)and a spherical light distribution illuminance function of the second illumination optical system is expressed as β(θ):
• α(60°)/β(60°)>2 (1)
• where the spherical light distribution illuminance function α(θ) is a function representing illuminance when a spherical object is illuminated relative to the first illumination optical system, and the function represents illuminance distribution in a range of exit angle θ of the first illumination optical system where the illuminance is set to 1 when the exit angle θ from a center of the first illumination optical system is 0°;
• and
• where a spherical light distribution illuminance function β(θ) is a function representing illuminance when a spherical object is illuminated relative to the second illumination optical system, and the function represents illuminance distribution in a range of exit angle θ of the second illumination optical system where the illuminance is set to 1 when the exit angle θ from a center of the second illumination optical system is 0°.