A computed tomographic imaging spectrometer (CTIS) disperses the three-dimensional (3-D) datacube (x, y, λ) into two-dimensional (2-D) projections on a focal plane array (FPA). The 3-D datacube is subsequently reconstructed from these 2-D projections using iterative computed tomography algorithms. Conventional designs achieve the 3-D to 2-D mapping by incorporating an optimized disperser. However, these dispersers suffer from the linearity constraint inherent in the first-order grating equation. This constraint means that many of the FPA's pixels are either unilluminated or they are used to image redundant projections; in both cases, they can not be used to increase the datacube's spectral resolution. Here, we outline various hardware improvements that increase the CTIS's spectral resolution by making use of these previously unilluminated or redundant pixels. Specifically, we incorporated a new disperser based on a 2-D grating prism and a division of aperture approach. Included is an optical design analysis of the system, in addition to an experimental characterization of the instrument's performance. Lastly, the new disperser is compared to a conventional disperser to quantify the increased spectral resolution.
This paper will describe methods of measuring all of the components of the Stokes polarization vector for each pixel in a
scene using only one frame of passive optical sensor data, one radar pulse, or one radiometer integration interval. Both
active and passive sensors operating in any waveband from microwave to visible will be considered. For systems
operating in the millimeter wave and terahertz bands, the techniques developed by Dereniak and his students at the
University of Arizona will be discussed. For other wavebands, a technique developed by the author that requires the
coherent reception of two orthogonally-polarized signal components will be presented. This latter method works for both
for both broad-band and narrow-band active or passive signals, but requires focal planes and hardware in the visible and
infrared bands that may be too complicated for many applications. Results of calculations made for the millimeter and
terahertz bands will be presented.
Two imaging systems have been designed and built to function as snapshot imaging spectropolarimeters; one system
made to operate in the visible part of the spectrum, the other for the long wavelength infrared, 8 to 12 microns. The
devices are based on computed tomographic imaging channeled spectropolarimetry (CTICS), a unique technology that
allows both the spectra and the polarization state for all of the wavelength bands in the spectra to be simultaneously
recorded from every spatial position in an image with a single integration period of the imaging system. The devices
contain no moving parts and require no scanning, allowing them to acquire data without the artifacts normally associated
with scanning spectropolarimeters. Details of the two imaging systems will be presented.
A very unique imaging spectopolarimeter for use in the long wave infrared, 8 to 12 microns, is currently being
constructed. The imaging system uses a novel technique first developed at the University of Arizona, which incorporates
channeled spectropolarimetry with a computed tomographic imaging spectrometer (CTIS). The system is especially
noteworthy because it contains no moving parts and operates in a snapshot mode, allowing it to record spectral data as
well as the polarization state of each wavelength band in the spectra from every spatial location in a 2D image in a single
integration period. The paper presents results from the currently constructed longwave infrared snapshot imaging
spectrometer, as well as a description of what will be added to the system to obtain polarization data, and an overview of
the design and operational details of the snapshot imaging spectropolarimeter.
This paper covers the design and construction of a snapshot imaging spectropolarimeter for use in the long wave
infrared, 8 to 12 micron region. This imaging device is unique in the fact that system is nonscanning, contains no
moving parts, and in a single integration period is able to record spectral data as well as the polarization state as a
function of wavelength from every spatial location in a 2D image. The system is based on the Computed Tomographic
Imaging Spectrometer, commonly referred to as CTIS, and has been modified to incorporate components of Channeled
Spectropolarimetry. The paper presents an overview of how both the CTIS and the CTICS (Computed Tomographic
Imaging Channeled Spectropolarimeter) systems work, details on the specific components used in the LWIR system, and
preliminary results from a completed LWIR CTIS system, which is the first of its kind.
This paper is useful for teaching holography workshops in classrooms as well as in makeshift locations such as museums, businesses, and homes. The target audience is very general, young children to adults of any profession, al of whom have no prior experience in making holograms. A typical number of participants is twenty-five, but can vary depending on space and personnel availability. A central original contribution of this paper is the discovery of a new chemical processing regime for the Slavich PFG-03M holographic plates. These silver halide plates have the highest resolution of its kind and some of the world's best holograms have been recorded on it for several decades. Due to its low sensitivity and long developing time, this material has been excluded form use in workshops. Our new processing regime JARB has the following advantages: It (1) increases the sensitivity of PFG-03M emulsion ten-fold without sacrificing resolution; (2) hardens the emulsion during processing without significant shrinkage; (3) has a ten- to twenty-second development time; (4) is quick drying using squeegee and warm air; and (5) allows the finished hologram to be viewable with laser or incandescent light. Other advantages of JARB are (1) low toxicity, (2) low volatility, (3) non-staining, (4) low cost, and (5) long shelf life.
Two fundamental problems have prevented the Leith-Upatnieks Transmission Hologram (LUTH) from popular public display enjoyed by reflection holograms. 1, A laser light source is needed for illumination, which should not exceed five milliwatts in output for the sake of eye safety; and 2, much space is needed behind the hologram for the reconstruction beam. Herein we discuss methods for creating a LUTH display system which is arbitrarily thin regardless of the size of the hologram and arbitrarily bright without safety problems.