Patent ID: 7102832
Filing Date: 2006-09-05
Classification: G02B

Abstract:
1. An apparatus comprising a chopper which includes: a frame having a first coefficient of thermal expansion, having a space therein, and having at least one opening which allows radiation to pass through said space in a first direction; a sheet having a second coefficient of thermal expansion different from said first coefficient of thermal expansion, said sheet being movably disposed within said space in said frame, in a manner so that said sheet can expand and contract relative to said frame in a second direction approximately parallel to said sheet and approximately perpendicular to said first direction, said frame preventing significant movement of said sheet parallel to said first direction with respect to said frame, and said sheet including structure which influences radiation that passes through said sheet in said first direction; wherein said sheet and said frame have cooperating features that maintain said sheet in angular and radial alignment with respect to said frame.