Design and analysis of a snapshot imaging spectropolarimeter

Abstract

The subject of this dissertation is the implementation of Computed Tomographic Imaging Channeled Spectropolarimetry (CTICS) in the design and analysis of a short wave infrared (SWIR) system with a 54 x 46 spatial resolution and 70 band spectral resolution from 1.25-1.99 μm for the purpose of object identification and classification. It is the first of its kind to provide imaging spectropolarimetry with no moving parts and snapshot capability. This spectropolarimeter has applications in many fields, such as mining, military reconnaissance, biomedical imaging, and astronomy. First, motivations are provided for building this unique imaging spectropolarimeter by discussing the current applications of such systems, the drawbacks of previous designs, and a review of some the current systems being used. A review of basic concepts on imaging systems, linear algebra, and polarimetry is given as an introduction into the technical details of the design of the system that follow. First, designing the Computed Tomography Imaging Spectrometer (CTIS) and then the channeled spectropolarimetry components. The fusion of these two techniques create the CTICS. An assembled version of the SWIR CTIS is calibrated and reconstructions of various objects demonstrate the capabilities of this portion of the system. The polarimetry components are added and a discussion follows on the method used to extract the new data. Two systems, a polarization state generator (PSG) and rotating retarder fixed analyzer (RRFA) system are built to verify the CTICS accuracy. The final assembled system is presented and testing results are shown. Error analysis on various sources of noise is done. To conclude, a novel sub-Nyquist sampling technique is demonstrated and future work is suggested on a reconstruction technique that will streamline the postprocessing of the images.