Abstract: A mirror support mechanism includes three first supporting members and three second supporting members. Each first supporting member includes a mirror supporting portion that is in contact with and support a corresponding one of three supported surfaces provided on the supported portion with rotational symmetry of 120 degrees around an optical axis, and two first beam portions connected to both sides of the mirror supporting portion. Each second supporting member includes a supporting portion to which ends of two first beam portions adjacent to each other are connected, the ends being not connected to the mirror supporting portion, and two second beam portions connected to both sides of the supporting portion, an end of the second beam portion not connected to the supporting portion being supported by a structure member provided on the rear side of the reflecting mirror.

Abstract: A honeycomb sandwich panel having an absolute value of thermal expansion coefficient smaller than an absolute value of thermal expansion coefficient obtained by using carbon fiber reinforced plastic (CFRP) is provided. The honeycomb sandwich panel includes: a first skin being a plate material made of a low expansion metal being a metal having an absolute value of thermal expansion coefficient smaller than an absolute value of thermal expansion coefficient of CFRP; a second skin being a plate material made of the low expansion metal and arranged to face the first skin; and a core made of CFRP or the low expansion metal, being bonded to the first skin and the second skin and including a plurality of tubular cells each having a hexagonal cross section, the tubular cells being formed adjacently to each other.

Abstract: An optical device can deal with a relative difference in thermal expansion coefficient between a reflecting mirror and a mirror supporting member, and can also support the reflecting mirror with a simpler structure than the conventional one. The optical device includes: a reflecting mirror including a reflecting surface to reflect light, and a supported portion disposed on a rear surface and having three supported surfaces arranged with rotational symmetry of 120 degrees around an optical axis, the rear surface being a surface of the reflecting mirror existing on the contrary side to the reflecting surface; a structural member provided on a rear side of reflecting mirror; and three supporting members, each of the three supporting members including a mirror supporting portion connected to and supporting each of the three supported surfaces, and having two ends connected to the structural member.

Abstract: A honeycomb sandwich panel having an absolute value of thermal expansion coefficient smaller than an absolute value of thermal expansion coefficient obtained by using carbon fiber reinforced plastic (CFRP) is provided. The honeycomb sandwich panel includes: a first skin being a plate material made of a low expansion metal being a metal having an absolute value of thermal expansion coefficient smaller than an absolute value of thermal expansion coefficient of CFRP; a second skin being a plate material made of the low expansion metal and arranged to face the first skin; and a core made of CFRP or the low expansion metal, being bonded to the first skin and the second skin and including a plurality of tubular cells each having a hexagonal cross section, the tubular cells being formed adjacently to each other.

Abstract: An optical device can deal with a relative difference in thermal expansion coefficient between a reflecting mirror and a mirror supporting member, and can also support the reflecting mirror with a simpler structure than the conventional one. The optical device includes: a reflecting mirror including a reflecting surface to reflect light, and a supported portion disposed on a rear surface and having three supported surfaces arranged with rotational symmetry of 120 degrees around an optical axis, the rear surface being a surface of the reflecting mirror existing on the contrary side to the reflecting surface; a structural member provided on a rear side of reflecting mirror; and three supporting members, each of the three supporting members including a mirror supporting portion connected to and supporting each of the three supported surfaces, and having two ends connected to the structural member.