Abstract
We have previously reported on coded aperture snapshot spectral imagers (CASSI) that can capture a full frame spectral image in a snapshot. Here we describe the use of CASSI for spectral imaging of a dynamic scene at video rate. We describe significant advances in the design of the optical system, system calibration procedures and reconstruction method. The new optical system uses a double Amici prism to achieve an in-line, direct view configuration, resulting in a substantial improvement in image quality. We describe NeAREst, an algorithm for estimating the instantaneous three-dimensional spatio-spectral data cube from CASSI's two-dimensional array of encoded and compressed measurements. We utilize CASSI's snapshot ability to demonstrate a spectral image video of multi-colored candles with live flames captured at 30 frames per second.
Highlights
A spectral imager measures the intensity of light as a function of wavelength λ at each spatial location (x, y) in an image
The spectral resolution of the data cube depends on the optical transfer function, the pixel width, reconstruction numerical reconstruction effects, the amount of dispersion induced by the double Amici prism, and the size of smallest feature on the coded aperture
Note that coded aperture snapshot spectral imagers (CASSI) could use a charge-coupled device (CCD) with a faster frame rate as long as there is enough light collected in each frame
Summary
A spectral imager measures the intensity of light as a function of wavelength λ at each spatial location (x, y) in an image It acquires a three-dimensional (3D) data cube of spatiospectral information, (x, y, λ ), about the scene being imaged. Tomographic spectral imagers [1] gather a sequence of two-dimensional (2D) spatio-spectral projections of the data cube through a direct view prism on to a detector array. While these techniques are adequate for spectral imaging of static scenes, the temporal scanning can result in spatial and/or spectral artifacts in imaging of dynamic scenes.
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