Double-Parallelogram Carriage for Spectrometer Mirrors

A double-parallelogram ("porch swing") carriage mechanism has been devised to provide for free linear motion of one or more retroreflector(s) in a Fourier-transform infrared spectrometer. Mechanisms like this one are particularly well suited for cryogenic high-resolution Fourier transform spectro-meters in which flat mirrors, dihedral mirrors, or corner-cube reflectors are used as retroreflectors. The basic design of this mechanism can also be adapted to a variety of other scanning optical instruments in which linear travel is required.