A rod integrator includes a quadrangular prismatic light-guiding member with a
rectangular cross-sectional shape. The light-guiding member guides a light beam
from a first end surface to a second end surface, opposing the first end surface,
while the beam is reflected by the side surfaces so that the beam is output from
the second end surface. The rod integrator includes a tube-shape body having the
first open end portion tightly surrounding the end portion of the light-guiding
member on the side of the second end surface, and having the second open end portion
from which the beam is output while causing the beam from the first end portion
to be reflected by inner mirror surfaces of the tube-shape body. The tube-shape
body is arrangedy in a pinwheel shape. First, second, third, and fourth members,
each of which has a plate shape and a mirror surface on one side, are arranged
on the light-guiding member, such that the tube-shape body has the mirror surfaces
facing inside.
