Multi-channel, Hyperspectral Spectrograph System using a Volume Phase Holographic Transmissive Grating for In-Water Radiometry
Carol
Johnson, NIST, cjohnson@nist.gov
(Presenting)
Steve
Brown, NIST, swbrown@nist.gov
Dennis
Clark, Marine Optical Consulting, clark.dk@gmail.com
Mike
Feinholz, MLML, feinholz@mlml.calstate.edu
Stephanie
Flora, MLML, twinsf2@gmail.com
Mark
Yarbrough, MLML, yarbrough@mlml.calstate.edu
Determination of the water-leaving spectral radiance using in-water instrumentation requires measurements of the up-welling spectral radiance (Lu) at several depths. If these measurements are separated in time, changes in the measurement conditions result in increased variance in the results. In this project, we will finalize the optical design, incorporate the optics and hardware, characterize, and field test a multi-channel, hyperspectral spectrograph system that uses a volume phase holographic transmissive grating to disperse the light. The system’s optical path will be in a linear configuration to accommodate the optimal housing profile for incorporation into radiometric oceanic autonomous buoys. Two spectrographs are to be designed, one optimized for the blue spectral region and the other for the red. Both will have high spectral resolution (an instrument bandpass of 1 nm to 2 nm with pixel-to-pixel resolution of less than 0.5 nm). The system design is for fiber optical coupling of the radiant flux from six separate input channels; the measurements are synchronized and simultaneous in time because the individual fiber optics illuminate separate sub-areas of the entrance slit (in the vertical dimension), resulting in six spectrally dispersed tracks on the CCD array.
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