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Underwater optics: light in the sea
Optics & Laser Technology, Copyright 0
Vol. 29, No. 1, p. I, 1997
1996 published by Elsevier Science Ltd
Printed in Great Britain. All rights reserved 0030-3992197 $17.00 + 0.00
ELSEVlER ADVANCED TECHNOLOGY
Guest editorial Underwater
optics:
light
in the sea
The paper by the Strathclyde University group (McKee et al.) describes the design and construction of an integrated fluorometer/nephelometer/ transmissometer and its use in sea trials for simultaneous measurement of chlorophyll concentration, light attenuation and scattering; while a pan-European group lead by University College, Dublin (Green et al.) outlines the use of a Marine Radiometric Spectrometer (known as MARAS) for simultaneous measurement upwelling and downwelling irradiance. On a different note, the paper by a group at Edinburgh University (Arnott et al.) outlines their use of underwater CCD cameras for flow mapping in particle image velocimetry systems (PIV). To underline the immense range of work covered by underwater optics, the final paper (by Holohan and Dainty at Imperial College) is a speculative, and interesting, presentation of the ideas of using low-order adaptive optics (which are extensively employed in astronomical imaging) in underwater imaging.
On 19 October 1995, a meeting was held at Photonex ‘95, in Kettering, UK to discuss progress in underwater optics and the development of underwater optical sensors. The meeting was organized by the Optics Group of the Applied Optics Division of the Institute of Physics (IOP) and co-sponsored by the Environmental Physics and Instrument Science and Technology Groups of the IOP, the Optical Sensors Collaborative Association and The Society for Underwater Technology (SUT). About a hundred delegates turned up to hear 17 papers describing current advances across a broad spectrum of activity in the application of underwater optics. The quality, content and range of these papers was such that it was felt that the work described should reach a wider audience. In this Special Issue of Optics & Laser Technology, we present a representative selection of those papers. The first thing that strikes the reader of these papers is the breadth of work taking place in Britain and Ireland in underwater optics. The papers included here cover fundamental measurements of the optical properties of the sea, development of new methods of monitoring the optical properties, techniques of measurement of organisms or structures in the sea and the development and application of optical instrumentation. In this respect, the whole gamut of underwater optics is the epitome of multidisciplinary (and multinational) science and engineering. The groups represented here include biologists, oceanographers, physicists, chemists and engineers amongst their number; all interacting and driving in the same direction, towards understanding, working within and using the environment of the sea.
One of the most important and encouraging outcomes of this meeting came from the discussion at the end. Chaired by Mike Wall and including John Tyrer (of Loughborough University) and myself, and attended by about 20 or so of the delegates, the discussion ranged from an appraisal of the technical papers to overwhelming support for further meetings of this type on a regular basis. Considerable activity is taking place in ocean optics; partly by marine biologists whose prime aim is to understand the environment, its properties and the complex interactions within it; partly by engineers in the offshore industry whose objective is to work safely and productively in this environment; and partly by instrumentation scientists whose aim is to develop techniques and devices which will enable others to do their work.
Following the order of presentation at the meeting, we lead with a paper by a research group (Wild-Allen et al.) at the University of Wales, Bangor who have been studying upwelling irradiance and chlorophyll concentrations in the seas near the Canary Islands. A group at DRA Winfrith (Martin et al.) have, in contrast, been looking at the penetration of solar radiation in shallow shelf seas and how this influences the temperature profile and ultimately its effect on sound propagation. Following from this, we present two novel papers describing the use of optical holography for underwater visual inspection and precision measurement (Foster and Watson, Aberdeen University) and its application to the study of plankton size and concentration in aquatic systems (Hobson et al., Brunel University, Aberdeen University, Institute of Oceanographic Sciences and the University Marine Biological Station at Millport).
Great strides have been made in recent years in underwater vision, and, as well as outstanding work in improving the performance of TV-based camera systems, we have the significant advances made in range-gated TV systems, scanning beam systems and holographic measurement systems. Underwater optics is a fruitful and exciting area of research activity which is perhaps not gaining the public attention it deserves. It is hoped that the papers in this selection will go some way to redressing the balance and to bringing notice of the significant advances being made to a wider community. JOHN WATXIN
Department of Engineering University of Aberdeen, UK 1
Vol. 29, No. 1, p. I, 1997
1996 published by Elsevier Science Ltd
Printed in Great Britain. All rights reserved 0030-3992197 $17.00 + 0.00
ELSEVlER ADVANCED TECHNOLOGY
Guest editorial Underwater
optics:
light
in the sea
The paper by the Strathclyde University group (McKee et al.) describes the design and construction of an integrated fluorometer/nephelometer/ transmissometer and its use in sea trials for simultaneous measurement of chlorophyll concentration, light attenuation and scattering; while a pan-European group lead by University College, Dublin (Green et al.) outlines the use of a Marine Radiometric Spectrometer (known as MARAS) for simultaneous measurement upwelling and downwelling irradiance. On a different note, the paper by a group at Edinburgh University (Arnott et al.) outlines their use of underwater CCD cameras for flow mapping in particle image velocimetry systems (PIV). To underline the immense range of work covered by underwater optics, the final paper (by Holohan and Dainty at Imperial College) is a speculative, and interesting, presentation of the ideas of using low-order adaptive optics (which are extensively employed in astronomical imaging) in underwater imaging.
On 19 October 1995, a meeting was held at Photonex ‘95, in Kettering, UK to discuss progress in underwater optics and the development of underwater optical sensors. The meeting was organized by the Optics Group of the Applied Optics Division of the Institute of Physics (IOP) and co-sponsored by the Environmental Physics and Instrument Science and Technology Groups of the IOP, the Optical Sensors Collaborative Association and The Society for Underwater Technology (SUT). About a hundred delegates turned up to hear 17 papers describing current advances across a broad spectrum of activity in the application of underwater optics. The quality, content and range of these papers was such that it was felt that the work described should reach a wider audience. In this Special Issue of Optics & Laser Technology, we present a representative selection of those papers. The first thing that strikes the reader of these papers is the breadth of work taking place in Britain and Ireland in underwater optics. The papers included here cover fundamental measurements of the optical properties of the sea, development of new methods of monitoring the optical properties, techniques of measurement of organisms or structures in the sea and the development and application of optical instrumentation. In this respect, the whole gamut of underwater optics is the epitome of multidisciplinary (and multinational) science and engineering. The groups represented here include biologists, oceanographers, physicists, chemists and engineers amongst their number; all interacting and driving in the same direction, towards understanding, working within and using the environment of the sea.
One of the most important and encouraging outcomes of this meeting came from the discussion at the end. Chaired by Mike Wall and including John Tyrer (of Loughborough University) and myself, and attended by about 20 or so of the delegates, the discussion ranged from an appraisal of the technical papers to overwhelming support for further meetings of this type on a regular basis. Considerable activity is taking place in ocean optics; partly by marine biologists whose prime aim is to understand the environment, its properties and the complex interactions within it; partly by engineers in the offshore industry whose objective is to work safely and productively in this environment; and partly by instrumentation scientists whose aim is to develop techniques and devices which will enable others to do their work.
Following the order of presentation at the meeting, we lead with a paper by a research group (Wild-Allen et al.) at the University of Wales, Bangor who have been studying upwelling irradiance and chlorophyll concentrations in the seas near the Canary Islands. A group at DRA Winfrith (Martin et al.) have, in contrast, been looking at the penetration of solar radiation in shallow shelf seas and how this influences the temperature profile and ultimately its effect on sound propagation. Following from this, we present two novel papers describing the use of optical holography for underwater visual inspection and precision measurement (Foster and Watson, Aberdeen University) and its application to the study of plankton size and concentration in aquatic systems (Hobson et al., Brunel University, Aberdeen University, Institute of Oceanographic Sciences and the University Marine Biological Station at Millport).
Great strides have been made in recent years in underwater vision, and, as well as outstanding work in improving the performance of TV-based camera systems, we have the significant advances made in range-gated TV systems, scanning beam systems and holographic measurement systems. Underwater optics is a fruitful and exciting area of research activity which is perhaps not gaining the public attention it deserves. It is hoped that the papers in this selection will go some way to redressing the balance and to bringing notice of the significant advances being made to a wider community. JOHN WATXIN
Department of Engineering University of Aberdeen, UK 1