The Sciencetech C230X-Polar variable frequency optical chopper is used with the detectors during the Polarizing Martin Puplett mode. The chopper is positioned in front of the output port just before the detector. The Polarized captures the output at 45^o to the two planes of collimation. This facilitates the retrieval of the Fourier Transform Interferogram during Martin Puplett mode. The optical chopper is designed for high stability and broad range frequency control from 0.5Hz to 100Hz. Price includes servo motor controller and Sci-Chopper Active-X software.