Patent ID: 8727575

Claim:
A light source unit comprising: a light source having a discharge lamp and a converging mirror converging light from the discharge lamp; a light guide on which the light from the light source is incident; and a casing which is made of a metal and which holds the light source and the light guide, wherein: the light guide comprises a liquid core fiber with a light transmitting liquid filled into a cladding, the light source and the light guide are held by a light source holding portion and a light guide holding portion, respectively, in the casing, the casing is equipped with a cylindrical light shielding body which is supported by a support for the light shielding body which is fixed to the casing, and the light shielding body surrounds an optical path extending from the light source to the light guide in an interior of the casing, an infrared cut filter is provided in the light shielding body so as to be located on the optical path from the light source to the light guide, the light shielding body forms a stray light preventing member which prevents stray light generated in the interior of the casing from going out of the casing, a light quantity adjusting member is provided at a position between an opening of the light shielding body on a light guide side and a light incident port of the light guide, and a heat insulating material portion formed of a heat insulating material is interposed between the light shielding body and the light guide holding portion, so that the light shielding body and the light guide holding portion are thermally insulated from each other.