An optical device (44) includes fluid circulating member link sections
(446) that can link a plurality of fluid circulating members (448). The
fluid circulating member link sections (446) are arranged respectively
between a main tank (445) and an optical device main body (440) and
between a radiator (447) and the optical device main body (440) to allow
the optical device main body (440) to be fitted to and removed from the
main tank (445) and the radiator (447).