Integrating cavity device for measuring the optical backscattering coefficient in a fluid.

We present the mathematical description, design, and development of an instrument that precisely determines the backscattering coefficient (bb) in water using a custom integrating cavity to collect light scattered in the backward hemisphere-a true bb meter. The design allows us to directly measure bb in a medium while not making any assumptions about the shape of ß(θ) and/or of its scattering particulates. The concave surface of the quartz aperture to the integrating cavity minimizes reflection losses. The output signal is a direct linear function of bb. This bb meter is the first instrument to make a direct measurement of bb with <1% accuracy and it is compatible with several modes of routine oceanic deployment.