Patent ID: 7480055

Claim:
A two-beam interferometer for measuring radiation using Fourier Transform spectroscopy comprising: a first retro-reflector; a second retro-rellector; a central body; a beamsplitter secured to said central body and arranged in the path of a light beam to split said light beam into two beams, one of said two beams directed toward said first retro-reflector and the other of said two beams directed toward said second retro-reflector, and to recombine beam components from said retro-reflectors to form an interference pattern; a first rigid pendulum rotatable around a first axis of rotation, said first retro-reflector mounted to said first rigid pendulum and spaced from said first axis of rotation; a second rigid pendulum rotatable around a second axis of rotation, said second retro-reflector mounted to said second rigid pendulum and spaced from said second axis of rotation, said first and said second axis of rotation being spaced apart; and a linkage secured to said first and said second rigid pendulums and positioned to constrain the rotation of said first rigid pendulum relative to said second rigid pendulum.