Patent ID: 6986586

Claim:
A support frame for a thin-film mirror comprising, a) a pan-shaped housing having a pan surface and a hollow wall joined to and surrounding the pan surface, b) the hollow wall having a top mounting surface portion for thin reflecting film, stepped above the pan surface, c) the pan-shaped housing member, including the hollow wall, having the shape of a polygon with the hollow wall having a predetermined number of sides intersecting at a corresponding said predetermined number of corners that define a corresponding said predetermined number of corner angles, d) at least one corner having a corner angle that is less than or equal to 90 degrees, and e) said hollow wall at said at least one corner having a fillet formed as a portion of said hollow wall, said fillet bordering the pan surface and making an obtuse angle with each of the intersecting wall portions at said at least one corner, and said fillet having a fillet top surface formed as a co-planar continuation of the top mounting surface portion of said hollow wall.