OPTICAL PART

PROBLEM TO BE SOLVED: To provide an optical part capable of irradiating the irradiating object part in the comparatively uniform light quantity distribution, capable of reducing the number of reflecting surfaces and capable of reducing a loss by reflection on an interface. SOLUTION: In an optical part composed of a convex lens 1 and the reflecting surface 2 arranged at a prescribed angle with the optical axis of the convex lens, the optical part is constituted in such a way that the reflecting surface has a structure of a large number of recesses/projections of a prism type, this recess/projection structure is a structure that the nonreflective surface and the total reflection surface having an angle of 45 degrees to the optical axis of the convex lens are alternately arranged, and this total reflection surface can totally reflect the parallel light from the convex lens in the right-angles direction to the optical axis. The optical part is formed by arranging the light emitting end of an optical fiber 4 in a focal position of the convex lens.