How can I increase the field of view of my SWIR spectrometer?
Fibers feeding light to the VNIR have a slightly BROADER field of view than the nominal 25 degrees in our specs, while the SWIR fibers have a slightly NARROWER field of view. This means that the VNIR spectrometer may be looking at targets that the SWIR spectrometers can't see if they are only entering the edge of the field. Use of a lens foreoptic, such as the 8-degree lens, is a good way to compensate for this problem.
Different foreoptics will give different quality results, depending on the application:
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A lens is useful for collecting spectra from a distance.
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A bare fiber or an 18-degree tube for is useful for work with visible heterogeneity, like a gravel road or a plant canopy.
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Shiny round things, like apples, with potentially ugly edge effects, lend themselves well to use of the 8-degree foreoptic.
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The one-degree foreoptic is too bulky for up-close work.