Design and calibration for a Full-Stokes imaging polarimeter.

Abstract

The design and construction of a Full-Stokes Imaging polarimeter is presented. The device uses a telescope optical system and a polarization state analyzer (PSA) to obtain polarimetric images on a CCD. The PSA employs two liquid crystal variable retarders (LCVR) and a linear polarizer to measure the four Stokes parameters. The Stokes polarimetry method used in this paper is based on the application of six combinations of retardance values on the LCVRs. A well-known method is used to extract all the Stokes vector parameters from this intensity data. Due to experimental errors, a calibration is necessary. The calibration method used in this paper, also calculates the errors in the experimental set-up by fitting the experimental intensity measurements for the calibration samples to a theoretical polarimeter with errors. In this case, we used incident 45° polarized light to control the output polarization, and six calibration samples. The errors calculated in the method include the axes alignment errors and the errors in the retardance values of both LCVRs. The acquisition of Stokes images used a telescope optical system with a CCD camera.