Software field widening of a Fourier-transform spectrometer using a large focal plane array.

Software field widening of a Fourier-transform spectrometer is investigated with a large multielement focal plane array detector. Experimental results are presented that stem from previous work in instrument line-shape correction. Here, pixels with calibrated wavenumber scales are binned to emulate a large-area single-pixel detector. The field of view and the signal-to-noise ratio are accordingly increased. A monochromatic source is used to characterize signal-to-noise ratio gain, and limitations are discussed. This work is motivated by the emergence of affordable infrared integrating cameras, which enable Fourier-transform spectrometers to perform massively parallel spatial sampling.

Hybrid sampling approach for imaging Fourier-transform spectrometry.

A new approach to interferogram sampling is demonstrated for Fourier-transform spectrometry. Sampling of the infrared channel is triggered at equidistant optical path differences while samples are time-referenced with a high-resolution digital clock. This hybrid method exploits the advantages of both time and position-sampling techniques. It minimizes the dataload while allowing a postcorrection scheme to remove sampling errors. It is therefore highly adapted to imaging spectrometers designed for massively parallel spatial sampling. Also, this technique is particularly interesting for spectrometers equipped with an integrating detector, such as a CCD camera, since it can account for the inevitable delay caused by camera integration.

Fast line-shape correction procedure for imaging Fourier-transform spectrometers.

An instrument line-shape correction method adapted to imaging Fourier-transform spectrometers is demonstrated. The method calibrates all pixels on the same spectral grid and permits a direct comparison of the spectral features between pixels such as emission or absorption lines. Computation speed is gained by using matrix line-shape integration formalism rather than properly inverting the line shape of each pixel. A monochromatic source is used to characterize the spectral shift of each pixel, and a line-shape correction scheme is then applied on measured interferograms. This work is motivated by the emergence of affordable infrared CCD cameras that are currently being integrated in imaging Fourier-transform spectrometers.