A light source unit is provided which includes a lamp and a reflector for reflecting
rays of light emitted by a light emitting element of the lamp and for focusing
the reflected rays of light. In order to focus on a predetermined focal point the
rays of light emitted by the light emitting element of the lamp and refracted by
a cross-sectional shape of the lamp, the reflector has a concave reflective shape
formed so as to satisfy a predetermined calculation expression. Alternatively,
a reflective surface shape of the reflector may be obtained by shifting portions
of an ellipse and rotating a curve of the shifted portions around the optical axis
of the light source unit.
