PROBLEM TO BE SOLVED: To overcome a difficulty in manufacturing a light guide member shaped to have an area of an incident port (incident end face arranged in the light source side) larger than an area of an outgoing port.SOLUTION: A light source optical system comprises: a condensation optical system which has at least one lens and condenses the light made incident from a light source and a light guide rod having an incident port through which the light condensed by the condensation optical system enters, a reflecting inner surface defining a light guide path for the light entering through the incident port, and an outgoing port through which the light guided in the light guide path by being totally reflected on the reflecting inner surface exits. The reflecting inner surface of the light guide rod has a tapered part in which the entire length from the incident port to the outgoing port or a portion thereof from some midpoint thereof to the outgoing port gradually inclines, getting closer to the axial line of the light guide path.SELECTED DRAWING: Figure 2COPYRIGHT: (C)2017,JPO&INPIT
