A rod integrator holder comprises a wall constituting at least a part of an intermediate
portion interposed between a rod integrator in an illumination optical system or
a holding member for the rod integrator, and an optical member disposed downstream
the rod integrator or a holding member for the optical member. The intermediate
portion tightly closes a space between a light entrance end of the optical member
and a light exit end of the rod integrator against surroundings thereof.
