An imaging Stokes-vector polarimeter using liquid crystal variable retarders (LCVRs) has
been built and calibrated. Operating in five bands from 450 to
, the polarimeter can
be changed quickly between narrow (12°) and wide
fields of view. The instrument
is designed for studying the effects of differing sky polarization upon the measured
polarization of ground-based objects. LCVRs exhibit variations in retardance with ray
incidence angle and ray position in the aperture. Therefore LCVR-based Stokes
polarimeters exhibit unique calibration challenges not found in other systems. Careful
design and calibration of the instrument has achieved errors within
measurements agree well with previously published data and cloudy data provide
opportunities to explore spatial and spectral variations in sky polarization.
© 2006 Optical Society of America
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