According to the present disclosure, a first guide unit is provided with a first opening portion through which light in an optical path connecting a first optical element unit and a second optical element unit passes, a second guide unit is provided with a second opening portion through which light in the optical path connecting the first optical element unit and the second optical element unit passes, the first guide unit is provided with a duct for sending air to the first optical element unit, and the air coming out from the first opening portion hits the second optical element unit via the second opening portion.