Comparison of relative signal-to-noise ratios of different classes of imaging spectrometer

Abstract

The continued development of new and fundamentally different classes of imaging spectrometer has increased both the scope and the complexity of comparisons of their relative signal-to-noise ratios. Although the throughput and multiplex advantages of Fourier-transform spectrometers were established in the early 1950s, the application of this terminology to imaging spectrometers is often ambiguous and has led to some confusion and debate. For comparisons of signal-collection abilities to be useful to a system designer, they must be based on identical requirements and constraints. We present unambiguous definitions of terminology for application to imaging spectrometers and comparisons of signal-collection abilities and signal-to-noise-ratios on a basis that is useful to a systems designer and inclusive of six fundamentally different classes (both traditional and novel) of imaging spectrometers.

Review of snapshot spectral imaging technologies

“…159 Sellar and Boreman, on the other hand, argue that while this appears to be true for the Fellgett advantage, imaging Fourier transform spectrometers (imaging FTS, or IFTS) retain the Jacquinot advantage not because of their higher étendue but because they are able to maintain a longer dwell time on each datacube voxel than alternative technologies can. 38 The authors also provide a convincing case that the Jacquinot advantage can be considered as freedom from the requirement of having an entrance slit, while the Fellgett advantage can be considered as freedom from the requirement of having an exit slit. For filterless snapshot imaging spectrometers, both of the traditional advantages are automatically satisfied: no exit slit is used (Fellgett), and the instrument dwell time on every voxel is equal to the full measurement period (Jacquinot).…”

“…Moreover, it has also been argued that, for scanning instruments at least, the differences in étendue among different technologies is not large. 38 Rather, we try to focus on a more important factor-the portion of datacube voxels that are continuously visible to the instrument. For scanning systems, this portion can be quite low (often <0.01), while filterless snapshot systems can achieve a value of 1 (i.e., all voxels are continuously sensed during the measurement period).…”

On-chip infrared sensors: redefining the benefits of scaling

“…Compared to the "dispersive" type spectrometers, properly designed time-domain "modulated" systems feature the Fellgett or multiplexing advantage, as the input light is concentrated on a single photodetector rather than being split between multiple detectors. As a result, the SNR is enhanced by a factor of square root N for the same integration time, where N is the number of spectral channels or data points 23 . Such time-domain modulation can be implemented via mechanical motion of optical components, for instance in the cases of FTIR spectrometers.…”

Compact and static Fourier transform imaging spectropolarimeters using birefringent elements

“…The CCD is placed on the image plane of the L2 instead of the focal plane. However, since a front slit (S) must be used to limit the field of view, instead of a field stop M, the signal-collection capabilities is relatively lower [38]. …”

“…The precision is expected to be mainly affected by the CCD and photon shot noise. Herein, the windowing model is employed for acquiring data, high signal-collection capability and singnal-to-noise are promised [38,44], which offers a novel solution to the limitations of conventional spectrometers and polarimeters.…”