Computed tomography imaging spectrometer

The computed tomography imaging spectrometer (CTIS) is a snapshot (i.e. non-scanning) imaging spectrometer conceived separately by Takayuki Okamoto and Ichirou Yamaguchi at Riken (Japan), and by F. Bulygin and G. Vishnakov in Moscow (Russia).^[1][2][3] The concept was subsequently further developed by Michael Descour, at the time a PhD student at the University of Arizona, under the direction of Prof. Eustace Dereniak.^[4]

The optical layout of a CTIS instrument.

The optical layout of a CTIS instrument is shown at right: a field stop is placed at the image plane of an objective lens, after which a lens collimates the light before it passes through a disperser (such as a grating or prism). Finally, a re-imaging lens maps the dispersed image of the field stop onto a large-format detector array. Shown here is an example in which the device is imaging the university of Arizona's logo, uses a kinoform grating to disperse the transmitted light, and measures a 3 × 3 dispersion pattern on the detector array. After measurement, an algorithm is used to convert the multiplexed (overlapped) two-dimensional data into the three-dimensional datacube (spectrally resolved image). Conceptually, one can consider each of the dispersed images on the detector as a 2D projection of the 3D datacube, in a manner analogous to the way in which X-ray projections measured by medical computed tomography instruments are used to estimate the 3D volume distribution within a patient's body.^[5]

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