Measurement system for marine animal reflectance functions.

Photonic structures in the skin of pelagic fishes and squids evolved specifically for hiding in the complex light field of the open ocean. To understand the principles under which these structures operate, a detailed characterization of their optical properties is required. An optical scatterometer has been developed to measure one important property, the bidirectional reflectance distribution function (BRDF). The instrument was used to collect reflectance functions from the squid Pterygioteuthis microlampas and fish Sternoptyx sp. Although the animals appear very different to a casual observer, the results reveal interesting similarities in their scattering patterns, suggesting a similar optical strategy for hiding in open water.