Modelling of laser range-measurement of under-water objects in maritime environment

摘要

The paper presents selected issues on laser systems for detection and location of underwater objects. Range detection analysis and simulations include influence of: i) parameters of rangefinder; ii) parameters describing properties of the searched under-water object; iii) parameters of water environment, in particular hydro-meteorological conditions and extinction coefficient, characterizing water transmission properties. This transmission undergoes cyclic and strong changes in time and is strongly area-diversified. In the analyzed regions, average extinction coefficient changes from 0.3 m~(-1) to 2.4 m~(-1), whereas optimal laser wavelength falls into the spectral range of 575-580 nm. The analysis of the background radiation power has shown, that its value varies from several nW to about 25 nW in dependence of the incidence angle of solar radiation. Therefore, in further calculations we assumed the background radiation power equal to its average value of 9 nW. Having already estimated the signal power and the background noise power, signal to noise ratio (SNR) could be determined. The assumption, that the minimal SNR is 17.5 dB, results in the range detection of under-water objects varying from 7 m to 30 m. This range permits effective detecting and position determining of underwater objects like containers or anchor mines.