A support unit (20a) for supporting an OPM holder (15a)
so as to be vertical to the laser beam axis is disposed in the lower part of the
OPM holder (15a). A rotary shaft (19) is inserted into the
support unit (20a) and rotary shaft support unit (20b),
and the OPM holder (15a) and DT base (17) are assembled together.
Thus, a rotation support unit (200) is composed. The rotation support unit
has a degree of freedom in the rotating direction of arrow (202). On the
other hand, in the lower part of an RM holder (15b), a support bar
(21) is provided. At the DT base (17), a rotating element (22)
and a rotating element support unit (23) supporting the rotating element
are composed so as to support the support bar. Thus, a slider structure (220)
slidable in the optical axis direction is formed. The slider structure has a degree
of freedom in the direction of arrow (222).
