A chopping secondary mirror system is provided, in which magnetic circuits of a driving motor for causing a secondary mirror to chop about its rotation axis are mounted to the secondary mirror via a driving motor mounting so that the magnetic circuits function as a balancing mass to position the center of gravity of a whole chopping section on said rotation axis. The driving motor mounting is secured to the secondary mirror at the center of the secondary mirror. Leaf springs are used as vibration damping springs of a reaction force compensator.
展开▼
