Conventional hyperspectral imaging (HSI) techniques are time-sequential and rely on
temporal scanning to capture hyperspectral images. This temporal constraint can limit
the application of HSI to static scenes and platforms, where transient and dynamic
events are not expected during data capture.
The Near-Infrared Image Replicating Imaging Spectrometer (N-IRIS) sensor described
in this thesis enables snapshot HSI in the short-wave infrared (SWIR), without the
requirement for scanning and operates without rejection in polarised light. It operates in
eight wavebands from 1.1μm to 1.7μm with a 2.0° diagonal field-of-view. N-IRIS
produces spectral images directly, without the need for prior topographic or image
reconstruction. Additional benefits include compactness, robustness, static operation,
lower processing overheads, higher signal-to-noise ratio and higher optical throughput
with respect to other HSI snapshot sensors generally.
This thesis covers the IRIS design process from theoretical concepts to quantitative
modelling, culminating in the N-IRIS prototype designed for SWIR imaging. This effort
formed the logical step in advancing from peer efforts, which focussed upon the visible
wavelengths. After acceptance testing to verify optical parameters, empirical laboratory
trials were carried out. This testing focussed on discriminating between common
materials within a controlled environment as proof-of-concept. Significance tests were
used to provide an initial test of N-IRIS capability in distinguishing materials with
respect to using a conventional SWIR broadband sensor.
Motivated by the design and assembly of a cost-effective visible IRIS, an innovative
solution was developed for the problem of chromatic variation in the splitting angle
(CVSA) of Wollaston prisms. CVSA introduces spectral blurring of images. Analytical
theory is presented and is illustrated with an example N-IRIS application where a sixfold
reduction in dispersion is achieved for wavelengths in the region 400nm to 1.7μm,
although the principle is applicable from ultraviolet to thermal-IR wavelengths.
Experimental proof of concept is demonstrated and the spectral smearing of an
achromatised N-IRIS is shown to be reduced by an order of magnitude. These
achromatised prisms can provide benefits to areas beyond hyperspectral imaging, such
as microscopy, laser pulse control and spectrometry
