ILLUMINATION OPTICAL SYSTEM FOR ENDOSCOPE

摘要

PURPOSE: To lessen the light quantity loss in a peripheral region and to improve peripheral luminous intensity distribution by applying antireflection coat having low reflectivity to the rays of a specific incident angle or exit angle on the surface of optical parts. CONSTITUTION: The parallel luminous fluxes emitted at an angle 0 deg. from a light guide 3 are spread by a concave lens 2 around an optical axis 5. The rays emitted from this light guide 3 are refracted at the face 2a of the concave lens 2 and are made incident on the antireflection coat from which the transmitted light is emitted at an angleθto an object plane 4. The max. value of the angleθis the angle of the beam 6 arriving at the point P of the object plane 4 and determines the illumination range of the illumination optical system. The ratio (luminous intensity distribution) to the light quantity in the central part is eventually lowered when the light quantity in the peripheral part where the angleθis large is decreased. The antireflection coat having the low reflectivity to the rays of the specific incident angle or exit angle is, thereupon, applied on the extreme object side surface.