SMOOTHING OPTICAL ELEMENT AND ILLUMINATION OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To prevent the formation of a shape by the chipping at the edge of an exit end face of a columnar smoothing element which smoothes the intensity distribution of an exit luminous flux by reflecting an incident optical flux at its flank and the foreign matter on the exit end face and to make the F-number of the exit luminous flux larger than the F-number of the incident optical flux. SOLUTION: The smoothing element is composed of a packing section made of glass and a cylindrical hollow section continuous therewith and is so formed as to totally reflect the luminous flux at the flank of the packing section and to reflect the luminous flux at the flank on the inner side of the hollow section as well. The end face of the packing section is formed as an incident end face and the end face of the hollow section as the exit end face, by which the possibility of the occurrence of the chipping at the exit end face and the adhesion of the foreign matter thereto is completely obviated. The F-number of the exit luminous flux is increased by providing the flank with a microstructure to make the reflection angle larger than the incident angle.