Proceedings PaperOcean-Optical Measurements Using Acousto-Optic Filtering
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Spectral radiometric, scattering, and absorption measurements have classically been accomplished using grating spectrometers or fixed passband optical filters. Recently, holographic optical elements and linear-geometry detectors have gained popularity in spectrometric instrumentation, thereby eliminating the need for movable mechanical components. Other mechanically-fixed methods of spectral filtering rely upon electro- or acousto-optic interaction in solids or liquids. A system useful for ocean-optical measurements is described which employs an acousto-optic filter under microcomputer control to achieve wavelength tunability from 400-700 nm. This approach allows construction of low-power instrumentation having rapid and programmable control. In addition, output beam collimation is maintained to facilitate measurement over long optical paths. The physical principle of operation is described, various trade-offs discussed, and results presented for seawater containing phytoplankton.