A mirror assembly has one or more axes of motion and includes a mirror that is movable and forms an acute angle with a plane orthogonal to its axis of motion. The mirror assembly may include a first reflective mirror surface in the incoming optical path that is movable and forms an acute angle with a plane orthogonal to its axis of motion, and a second reflective mirror surface in the outgoing optical path that is movable and forms an acute angle with a plane orthogonal to its axis of motion and is moveable in a linear translation to scan the mirror in the interferometer in a way to generate a normal interferogram.