Mirror support mechanism and optical device

A mirror support mechanism to support a reflecting mirror, the reflecting mirror including a reflecting surface to reflect light and a supported portion being protrusion provided at a center of a rear surface being a surface of the reflecting mirror existing on the contrary side to the reflecting surface, a side surface of the supported portion including three supported surfaces provided with rotational symmetry of 120 degrees around an optical axis, the mirror support mechanism comprising:

• three first supporting members having a hexagonal outer shape in which a side of a first length and a side of a second length are alternately located adjacent to each other in an optical axis perpendicular plane that is a plane perpendicular to the optical axis, each first supporting member including a mirror supporting portion being formed at a center of each side of the first length and being in contact with a corresponding one of the three supported surfaces to support the corresponding supported surface;
• and
• a second supporting member having a hexagonal outer shape in which a side of a third length and a side of a fourth length are alternately located adjacent to each other in the optical axis perpendicular plane, the second supporting member including three supporting portions and three connecting portions, the three supporting portions each being formed at a center of each side of the third length, and being connected to the side of the second length of the first supporting member to support the first supporting member, and the three connecting portions each formed at each side of the fourth length, and being connected to a structure member provided on the rear side of the reflecting mirror.