Astronomical polarimeter with 2-D detector arrays

Abstract

It is shown how fast (50–100 kHz) piezoelastic modulation of the full Stokes vector can be used in combination with large CCD-type detector arrays with long integration times. The technique is to use an optical demodulation system (replacing the lockin amplifiers in corresponding single-channel detector systems). This allows the CCD detectors to be used with integration times and readout rates as in ordinary photometry. Including an optical phase switch in the system, the effect of the large pixel-to-pixel sensitivity variations can be removed from the recorded polarization images. The beam splitter that suppresses atmospheric noise can be located immediately before the detectors instead of being part of the polarization analyzer.