A polarization state generator (PSG) was built to generate light having a degree of linear polarization (DoLP) varying from 0.0005 to 0.4 with 0.0005 uncertainty. The PSG operates by tilting a plane parallel SF11 glass plate in a nearly unpolarized beam. The DoLP of collimated, unpolarized light passing through a plane parallel plate over a defined range of field angles can be calculated from theory, and the PSG was intended to act as a calibration standard based on this calculation. Several effects make the DoLP distribution as a function of field and tilt plate difficult to model to the desired 0.0005 uncertainty: source DoLP and intensity nonuniformity, lens surface diattenuation, and errors in optical alignment. Because of these effects, modeled DoLP was not used as a standard. Instead, DoLP was characterized with repeatability of 0.0005.
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