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1.4
Theory of Operation
Fiber Optic Collection of Reflected/Transmitted Light
Inside the FieldSpec® 3 Spectroradiometer
Visible/Near-Infrared (VNIR)
ASD.Document 600540 Rev. C
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The FieldSpec spectroradiometer measures the optical energy which is
reflected from, absorbed into, or transmitted through a sample. Optical energy
refers to a wavelength range that is greater than just the visible wavelengths,
and is sometimes called electromagnetic radiation or optical radiation.
In its most basic configuration, the spectroradiometer views and detects the
form of radiant energy defined as radiance. With accessories, various set-ups,
and built-in processing of the radiance signal, the FieldSpec
spectroradiometer can measure:
•
spectral reflectance,
•
spectral transmittance,
•
spectral absorbance,
•
spectral radiance, and
•
spectral irradiance.
Optical energy is collected through a bundle of specially formulated optical
fibers, precisely cut, polished, and sealed, for extremely efficient energy
collection. The fibers themselves are of low OH composition providing the
maximum transmission available across the instrument's wavelength range.
The fiber cable sends the spectral radiance into the instrument, where it is
projected onto a holographic diffraction grating. The grating separates and
reflects the wavelength components for independent measurement by the
detectors.
Note:
This discussion assumes that the FieldSpec spectroradiometer has the
hardware to perform a full-range spectrum analysis: VNIR, SWIR1,
and SWIR2.
6
Chapter 1 Introduction
FieldSpec® 3 User Manual
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