The NPS Spectroirradiometer (spectral irradiance meter) incorporates a rotating spectral wedge filter and was developed to measure the spatial distribution of downwelling underwater solar irradiance. Spectral irradiance data in the 402 to 577 nm regime was observed to depths of 130 m under both clear and foggy sky conditions. Diffuse attenuation coefficients, k, for downwelling light at selected wavelength/depth combinations were calculated from the observed spectral irradiances. The downwelling spectral irradiance values obtained ranged from 436 microwatts/sq. cm/nm at 494 nm to .00150 microwatts/sq cm/nm at 577 nm and are numerically comparable to data from other studies of coastal waters. The calculated values for five selected wavelengths, namely 418, 453, 487, 522, and 557 nm, ranged from .097/m at 418 nm to .274/m at 557 nm and are representative values. The results of the measurements indicate that the NPS Spectroirradiometer provides a practical method of determining irradiance distributions.

The use of optical methodology, instrumentation and photonics devices for imaging, vision and optical sensing is of increasing importance in understanding our marine environment. Subsea optics can make an important contribution to the protection and sustainable management of ocean resources and contribute to monitoring the response of marine systems to climate change. This important book provides an authoritative review of key principles, technologies and their applications.The book is divided into three parts. The first part provides a general introduction to the key concepts in subsea optics and imaging, imaging technologies and the development of ocean optics and colour analysis. Part two reviews the use of subsea optics in environmental analysis. An introduction to the concepts of underwater light fields is followed by an overview of coloured dissolved organic matter (CDOM) and an assessment of nutrients in the water column. This section concludes with discussions of the properties of subsea bioluminescence, harmful algal blooms and their impact and finally an outline of optical techniques for studying suspended sediments, turbulence and mixing in the marine environment. Part three reviews subsea optical systems technologies. A general overview of imaging and visualisation using conventional photography and video leads onto advanced techniques like digital holography, laser line-scanning and range-gated imaging as well as their use in controlled observation platforms or global observation networks. This section also outlines techniques like Raman spectroscopy, hyperspectral sensing and imaging, laser Doppler anemometry (LDA) and particle image velocimetry (PIV), optical fibre sensing and LIDAR systems. Finally, a chapter on fluorescence methodologies brings the volume to a close.With its distinguished editor and international team of contributors, Subsea optics and imaging is a standard reference for those researching, developing and using subsea optical technologies as well as environmental scientists and agencies concerned with monitoring the marine environment. - Provides an authoritative review of key principles, technologies and their applications - Outlines the key concepts in subsea optics and imaging, imaging technologies and the development of ocean optics and colour analysis - Reviews the properties of subsea bioluminescence, harmful algal blooms and their impact