| 摘要 |
<p>PROBLEM TO BE SOLVED: To constantly maintain the geometrical positional relation of an optical member regardless of temperature change by making the supporting structure of the optical member of an optical system light in weight and simple. SOLUTION: A main mirror 1 which is the optical member is supported by a main mirror supporting part 2 and is coupled with a main mirror base 3. Three frame supporting members 4 are radially extended from the optical axis center or the main mirror 1 by a uniform angle at the main mirror base 3, and a sub-mirror frame 6 is attached at a position opposed to the main mirror 1 through a V-shaped frame 5 fixed by the frame supporting member 4. A sub-mirror 8 is fixed so as to be opposed to the main mirror through a sub- mirror supporting member 7 at the sub-mirror frame 6. The coefficients of the linear expansion of the main mirror base 3, the frame 5 and the sub-mirror frame 6 are equally set asαa=αc=αd, and also the coefficientαb of linear expansion of the frame supporting member 4 is set asαb>αa. Though the temperature change is caused and a change is caused in the dimension of each member, the length and the coefficient of linear expansion of each member are selected so that the change is not caused in an optical distance between the main mirror 1 and the sub-mirror 8.</p> |
