The optical engineering of imaging spectrometers based on the Sagnac interferometer.

摘要

This dissertation presents a number of advances in the theory, design, and practice of imaging spectrometers based on the Sagnac interferometer. Imaging spectrometers of this type are placed in the context of a comprehensive system for classification of imaging spectrometers, based on the method by which they obtain spatial discrimination and the method by which they obtain spectral discrimination. The basis of the signal advantage of the interferometric windowing class of imaging spectrometers is established through unambiguous definitions of terminology for application to imaging spectrometers and by comparisons of signal-collection abilities on a basis that is useful to a systems designer and inclusive of both traditional and novel classes of imaging spectrometers. The theoretical basis for the design of Sagnac interferometers for imaging spectrometry is advanced through explanation of the effects of various design parameters upon the performance, including the designs of the beamsplitter coating and the Fourier lens. The inherent field-widened property of the Sagnac and the independence of the interferogram from the position of the source are discussed. The importance of the aspect ratio is explained and the limiting aspect ratios are derived for a range of configurations. An advanced design for a field-portable imaging spectrometer based on the Sagnac interferometer is described. Significant improvements on the current state-of-the-art for this type of instrument are presented, including a processing algorithm that removes constraints on the scan motion and improves the signal-to-noise ratio. Data are presented that demonstrate the signal advantage of this instrument and avenues for future improvements are described.