Computed Tomography Imaging Spectrometer Research Articles

High-speed spectral imager for imaging transient fluorescence phenomena

We describe fluorescence spectral imaging results with the microscope computed-tomography imaging spectrometer (muCTIS). This imaging spectrometer is capable of recording spatial and spectral data simultaneously. Consequently, muCTIS can be used to image dynamic phenomena. The results presented consist of proof-of-concept imaging results with static targets composed of 6-mum fluorescing microspheres. Image data were collected with integration times of 16 ms, comparable with video-frame-rate integration times. Conversion of raw data acquired by the muCTIS to spatial and spectral data requires postprocessing. The emission spectra were sampled at 10-nm intervals between 420 and 710 nm. The smallest spatial sampling interval presented is 1.7 mum.

Demonstration of a high-speed nonscanning imaging spectrometer

We report results from a field demonstration of a nonscanning high-speed imaging spectrometer [computed-tomography imaging spectrometer (CTIS)] capable of simultaneously recording spatial and spectral information about a rapidly changing scene. High-speed spectral imaging was demonstrated by collection of spectral and spatial snapshots of a missile in flight. This instrument is based on computed-tomography concepts and operates in the visible spectrum (430-710nm). Raw image data were recorded at video frame rate (30frames / s) and an integration time of 2ms. An iterative reconstruction of the spatial and spectral scene information from each raw image took 10s. We present representative missile spectral signatures from the missile firing. The accuracy of the high-speed spectrometer is demonstrated by comparison of extended-source static-scene spectra acquired by a nonimaging reference spectrometer with spectra acquired by use of CTIS imaging of the same static scenes.

Demonstration of a computed-tomography imaging spectrometer using a computer-generated hologram disperser

We have constructed a computed-tomography imaging spectrometer that uses a phase-only computer-generated hologram (CGH) array illuminator as the disperser. This imaging spectrometer collects multiplexed spatial and spectral data simultaneously and can be used for flash spectral imaging. The CGH disperser has been designed to maintain nearly equal spectral diffraction efficiency among a 5 x 5 array of diffraction orders and to minimize diffraction efficiency into higher orders. Reconstruction of the (x, y, lambda) image cube from the raw, two-dimensional data is achieved by computed-tomography techniques. The reconstructed image and spectral-signature data compare favorably with measurements by other spectrometric methods.

Computed-tomography imaging spectrometer: experimental calibration and reconstruction results

A temporally and spatially nonscanning imaging spectrometer is described in terms of computedtomography concepts, specifically the central-slice theorem. A sequence of three transmission sinusoidalphase gratings rotated in 60° increments achieves dispersion in multiple directions and into multiple orders. The dispersed images of the system's field stop are interpreted as two-dimensional projections of a three-dimensional (x, y, λ) object cube. Because of the size of the finite focal-plane array, this imaging spectrometer is an example of a limited-view-angle tomographic system. The imaging spectrometer's point spread function is measured experimentally as a function of wavelength and position in the field of view. Reconstruction of the object cube is then achieved through the maximum-likelihood, expectation-maximization algorithm under the assumption of a Poisson likelihood law. Experimental results indicate that the instrument performs well in the case of broadband and narrow-band emitters.