Brierley - Another variation of this design, disclosed by Brierley in US patent 4,915,502, is shown here. Although Brierley specifically excluded complete rotation in his patent claims, it is estimated that the duty cycle efficiency measuring 4 cm^-1 interferograms by complete rotation would be only 6%. The unwieldy rotating platform would be susceptible to deformation and suffer considerable impedance from air because of the large flat surfaces. Conceptually, Brierley’s patent is the point of departure for a series of innovative interferometer designs.