An Adaptive Spectroellipsometric Technology for The Remote Ecological Monitoring of The Aquatic Environment

An Adaptive Spectroellipsometric Technology for The Remote Ecological Monitoring of The Aquatic Environment

F. A. Mkrtchyan, V. F. Krapivin, V.I. Kovalev, V.V. Klimov, A. I. Rukovishnikov, and S.P. Golovachev
Institute of Radioengineering and Electronics, Russian Academy of Sciences
1, Vvedensky Square, Fryazino, Moscow Region, 141190, Russia
Tel.: 7+095+5269150, Fax: 7+096+5649060,
Email: sgolovachev@ms.ire.rssi.ru

ABSTRACT
The creation of multichannel polarization optical instrumentation is typical for the real-time ecological control of aquatic environment. It should be mentioned that efficient solution of these multiparametric problems greatly depends on the precision of ellipsometric devices and the possibility of using a wide spectral range. Spectral measurements in an aquatic environment provide an information basis for the application of modern algorithms for the recognition and identification of pollutants.

This report is aimed at elaborating a multichannel spectroellipsometric system that will differ from modern foreign analogues by the use of a new and very promising method of ellipsometric measurements, an original element base of polarization optics and a complex mathematical approach to estimating the quality of a water object subjected to anthropogenic influence. The system will be trainable to the recognition of pollutants of aquatic environment. Also, unlike foreign analogues, the system has no as well as rotating polarization elements. This allows one to increase the signal-to-noise ratio and the long-term stability of measurements, to simplify and reduce the price of multichannel spectroellipsometers.

The Adaptive Identifier
For the first time the combined use of real - time spectrometry measurements and data processing methods has been implemented in an Adaptive Identifier, the main characteristics of which are given in Table 1. For example, modern spectrophotometers provide some spectra per second with a 1% precision and 0.01% response, and measurements of spectra of rotation polarization plane in real time are carried out by spectropolarimeters with high precision. Its creation became possible due to a new approach in the field of polarization optics. An effective elemental base for polarization optics and a method of discrete modulation of the polarization mode have been developed. The application of simple and highly effective polarization switches and sets of silicon photodiodes with arbitrary access to them has essentially simplified the problem of creating compact and cheap polarization - optical devices: spectrophotometers, spectropolarimeters, spectroellipsometers, etc.

A technology of combined use of spectrometry and algorithms of identification and recognition has for the first time allowed the creation of a standard integral complex of instrumental, algorithmic, modular and software tools for the collection and processing of data on the aquatic environment with forecasting and decision - making functions. The Adaptive Identifier has a set of modifications intended for application under different conditions. A stationary version covers the complete set of technical and algorithmic tools providing the real-time measurements. This version can be used if a line power supply with a voltage of 220 V is available. A handheld field version of the Adaptive Identifier provides two applications. If a notebook computer is available under field conditions (in the absence of a line supply), the whole spectrum of the adaptive identifier is realized in a real-time mode. Otherwise, the results of measurements are stored in an of-line storage block and later are processed [1-8].

Table 1. Technical parameters of the Adaptive Identifier

The algorithmic support of the Adaptive Identifier is based on a complex application of recognition and classification of discrete images formed on the basis of 35 spectra registered during a fixed period of time. A time interval of 1 second is usually established and provides about 60 value of brightness for each of the 35 optical channels. The spectra obtained are sources of set of statistical parameters and different characteristics united into vector spaces for their comparison with the standard samples stored on the computer. The technology of this comparison depends on the diversity of identification methods.

The Adaptive Identifier is designed to learn from the measurement of spectral characteristics and the simultaneous independent measurement of the content of chemical elements in the aquatic environment. As a result, a standard bank is formed in the knowledge base, comparison with which provides the solution of the identification problem. The software of the Adaptive Identifier provides different algorithms for the solution of this problem, and cluster analysis is among them.

The Adaptive Identifier can be used in different fields where the quality of water should be estimated or the presence of a particular set of chemical elements should be revealed. The Adaptive Identifier solves these problems by real-time monitoring of the aquatic environment. In the stationary version it allows the tracking of the dynamics of water quality in a stream, and when placed on a ship, it allows the measurement of water parameters along the route.

The functionality of the Adaptive Identifier can be extended by increasing the volume of standards in the knowledge base. The use of a natural light source allows the examination of soils, the indication of oil products on a water surface, the determination of the degree of the pollution of atmospheric air and the estimation of the conditions of other objects of the environment, whose spectral images may change.

The Adaptive Identifier was tested under expeditionary conditions on board of the research vessel "Dmitry Mendeleev" in the Japanese Sea and in central areas of the Pacific Ocean and also during the investigation of aqueous systems of South Vietnam and Siberia (lake Baikal, Angara and Yenisey river) within the framework of the Russian - American and Russian - Vietnamese ecological expeditions.

A Russian - Vietnamese scientific and engineering laboratory has been created within the framework of the cooperation between the RAS, the Russian Academy of Natural Science (RANS) and the Scientific Center for Natural Science and Technologies of Vietnam with the main task being to create a standards base and to prepare the Adaptive Identifier for full - scale production.

References

Aleshin V.A., Klimov V.V., 1992. The Analysis of Optical Inhomo- geneities.- International Symposium " Ecoinformatics Problems". Zwenigorod,1992, pp. 202-203.
Bongard M.M. Problems of Recognition., 1967. Moscow: Nauka.
Aleshin V.A., Klimov V.V., Krapivin V.F., Mkrtchyan F.A. et al., 1998. Remote Sensing of the Water Objects with the Optical Adaptive Identifier.-International Symposium "Ecoinformatics Problems". Moscow, pp. 21-24.
Hong N.S., Chien L.N., Son P., Son K.T., Aleshin V.A., Klimov V.V., Mkrtchyan F.A., 1996. Geoinformatical monitoring and the optical adaptive identificator - Second Hochimihn city conference on mechanics: Abstracts of scientific papers. Institute of Applied Mechanics, pp.28 -29.
Klimov V.V., Kovalev V.I. ,Krapivin V.F., Mkrtchyan F.A., Nitu C., 1999. An expert system to diagnose pollutant spills on the water surface. - В кн : Proceedings of Int.Confer. on Control Systems and Computer Sci.,Buchurest, May, pp.277-283.
Armand N.A., Krapivin V.F., Mkrtchyan F.A., 1987. Methods of Processing Radiophysical Exploration of Environment. Moscow,Nauka, 270 pp( in Russian).
Nitu C. ,Krapivin V.F. ,Bruno A., 2000. Intellegent techniques in ecology. Bucharest, Printech, 150 pp.
Hong N.S., Chien L.N., Son P.,Son K.T., Aleshin V.A., Klimov V.V., Mkrtchyan F.A., 1996. Geoinformatical monitoring and the optical adaptive identifier. Proceedings of the second Hochimihn city conference on mechanics. Institute of Applied Mechanics, pp.180-182.