An In situ polarized hyperspectral UV-Vis volume scattering function (VSF) instrument (ocean submersible to 300 m) covering the angular range close to 0 degrees and as far as 180 degrees (with ≤2 degree angular resolution) with an ability to measure (at least) horizontal and vertical aspects of linear polarization is proposed herein.
To date, there have been several implementations of VSF instruments that capture a portion of these requirements, but none that completely capture them. The current state of the art instrument for capturing polarized VSF utilizes a single wavelength and a scanning head to capture light intensity at angles along the beam.
Therefore, we propose an innovative instrument design using approximately 180 optical fiber positions laid out in a concentric circle pointing to the small volume of water being measured. Each fiber will feed into a multichannel spectrometer (spectrograph) which can take all the spectra in a single acquisition. This way, spectra at all scattering angles can be collected simultaneously, which greatly reduces the overall measurement time. In additional to the much faster speed, the proposed scheme also offers the following advantages over the current state of the art instrument design:
1) There will be no moving parts outside of the main instrument housing, which makes it easier to be sealed, more robust and portable;
2) Instead of collecting scattered light at different points along the laser beam, the proposed design looks at the same small volume of water.
3) Because the optical path lengths for all scattering angles are the same in the proposed new instrument The overall simple and symmetric geometry (e.g. the identical optical path lengths at different angles) will make calibration easier and improve accuracy.