PURPOSE: To lessen the reflection loss at end faces to the min. limit and to prevent overheating of the light receiving end of a light guide by connecting this light guide concentrically to an optical rod.

CONSTITUTION: The luminous flux emitted from a light source 5 existing on one side P1 of two pieces of focuses P1, P2' is reflected by a reflector 31a, made incident on the optical rod 32a from its side face, condensed at the other focus P2', passed through the other focus P2' by intersecting therewith, reflected by a reflection film 32a2 formed at the paraboloid 32a1 of revolution of at the front end, and so reflected as to be made into the luminous flux parallel with the central axis of the optical rod 32a. As a result, the parallel luminous fluxes are made incident at incident angle 0 on the light receiving surface of the light guide 22c and the reflection loss at the end face is lessened to the min. limit. Further, the structure is hermetically closed by the reflector 31a and the light guide 22c is not projected into the space arranged with the light source 5. The structure is so formed that the optical rod 32a receives the light and that this light is guided to the light guide 22c and, therefore, there is no possibility of overheating.