Measurements and simulations of polarization states of underwater light in clear oceanic waters

Abstract

Polarization states of the underwater light field were measured by a hyperspectral and multiangular polarimeter and a video polarimeter under various atmospheric, surface, and water conditions, as well as solar and viewing geometries, in clear oceanic waters near Port Aransas, Texas. Some of the first comprehensive comparisons were made between the measured polarized light, including the degree and angle of linear polarization and linear Stokes parameters (Q and U), and those from Monte Carlo simulations that used concurrently measured water inherent optical properties and particle volume scattering functions as input. For selected wavelengths in the visible spectrum, measured and model-simulated polarization characteristics were found to be consistent in most cases. Measured degree and angle of linear polarization are found to be largely determined by an in-water single-scattering model. Model simulations suggest that the degree of linear polarization (DoLP) at horizontal viewing directions is highly dependent on the viewing azimuth angle for a low solar elevation. This implies that animals can use the DoLP signal for orientation.

Polaro–cryptic mirror of the lookdown as a biological model for open ocean camouflage

“…The reflective surfaces of some silvery fish are consistent with this vertical mirror strategy (4,5). However, this same scattering environment also produces significant asymmetry in the polarized light fields (6,7). Given the prevalence of polarization-sensitive vision in marine organisms (8)(9)(10)(11)(12), concealment strategies that account for this axial asymmetry are likely to exist, yet to date no quantitative evaluation of polarization camouflage (polaro-crypsis) has been conducted for a living organism.…”

“…We have constructed a division-of-time video polarimeter capable of recording the complete Stokes vector image (6). This polarimeter employs a standard commercial-grade video camera (Sanyo VPC-FH1ABK), combined with a stack of 2.5 × 5.1 cm 2 liquid crystal π-cells (Liquid Crystal Technologies), which act as electronically controlled birefringent wave plates providing half-wave, quarter-wave, and zero-wave retardation states (29).…”

Exploring underwater target detection by imaging polarimetry and correlation techniques

“…The behavior of polarized light in seawater is a topic attracting widespread attention [6][7][8][9].…”

“…Polarization filtering is adapted to underwater target detection and identification [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In this context, combining polarization filtering and a correlation technique is justified because: (i) it is simple to implement, (ii) it is compatible with polarization filtering, and (iii) it allows us for simultaneous detect and identify target objects.…”

Polarization signaling in swordtails alters female mate preference

“…The complex interaction of light with atmospheric and underwater particles leads to predictable polarization backgrounds in terrestrial and aquatic environments (4)(5)(6)(7)(8)(9). In brief, "polarization" refers to the vibrational behavior of the electromagnetic field, with unpolarized light describing photons vibrating in all possible directions (e.g., sunlight before entering our atmosphere) and plane polarized light occurring when one particular orientation is more prevalent (e.g., light interacting with water vapor in our atmosphere).…”